Skip to main content

Cholesterol-dependent amyloid β production: space for multifarious interactions between amyloid precursor protein, secretases, and cholesterol

Abstract

Amyloid β is considered a key player in the development and progression of Alzheimer’s disease (AD). Many studies investigating the effect of statins on lowering cholesterol suggest that there may be a link between cholesterol levels and AD pathology. Since cholesterol is one of the most abundant lipid molecules, especially in brain tissue, it affects most membrane-related processes, including the formation of the most dangerous form of amyloid β, Aβ42. The entire Aβ production system, which includes the amyloid precursor protein (APP), β-secretase, and the complex of γ-secretase, is highly dependent on membrane cholesterol content. Moreover, cholesterol can affect amyloidogenesis in many ways. Cholesterol influences the stability and activity of secretases, but also dictates their partitioning into specific cellular compartments and cholesterol-enriched lipid rafts, where the amyloidogenic machinery is predominantly localized. The most complicated relationships have been found in the interaction between cholesterol and APP, where cholesterol affects not only APP localization but also the precise character of APP dimerization and APP processing by γ-secretase, which is important for the production of Aβ of different lengths. In this review, we describe the intricate web of interdependence between cellular cholesterol levels, cholesterol membrane distribution, and cholesterol-dependent production of Aβ, the major player in AD.

Background

Numerous pathological processes have been described that may play a role in the etiology of Alzheimer’s disease (AD). Many proteins have been discovered that link AD pathology to cell membrane composition, transport, and dynamics, suggesting a critical role of membranes in brain health. These include phosphatidylinositol-binding clathrin assembly protein (PICALM), sortilin-related receptor 1 (SORL1), clusterin (ApoJ), bridging integrator 1 (BIN1), ATP-binding cassette (ABC) transporters, and ApoE, which is mainly responsible for the intercellular transport of cholesterol in the brain, with the ApoE4 isoform being the most common element associated with the sporadic form of AD [1,2,3,4,5,6]. According to the amyloid hypothesis of AD, altered processing of the amyloid precursor protein (APP) to amyloid β (Aβ) peptides dictates the onset and progression of both familiar (FAD), and the much more prevalent sporadic form of AD [7,8,9]. Among the hallmarks of AD associated with aberrant Aβ formation and aggregation of the most dangerous 42-amino acid long Aβ42, increased reactive oxygen species (ROS) production, mitochondrial dysfunction, calcium dyshomeostasis, and apoptosis have been reported most frequently [8, 10,11,12,13,14]. In addition, endosomal-lysosomal dysregulation [15,16,17,18,19,20,21] and altered autophagy and mitophagy are also associated with increased Aβ production and Aβ42 action [22,23,24,25,26,27].

During the development of AD, the content of cholesterol, cholesterol esters, oxysterols, peroxidized lipids, or ceramides may increase or decrease depending on the brain part, specific membrane, or disease stage [6, 28,29,30,31,32,33,34,35,36,37]. Changes in lipid populations in the brain reflect alterations in lipid synthesis, lipid degradation, lipid clearance, lipid transport, and also the extent of blood–brain barrier (BBB) disruption associated with increased permeability to cholesterol-containing lipid particles. Disruption of BBB integrity caused by elevated plasma cholesterol leads to lipid dyshomeostasis in the brain and links total body cholesterol levels and its regulation to brain health [38,39,40,41].

Cholesterol plays multiple roles in Aβ-mediated AD pathology, and a high-cholesterol diet is associated with AD-related symptoms [39, 41,42,43,44,45,46,47]. However, several studies have found an inverse correlation or no association between cholesterol intake and Aβ production or dementia progression [48,49,50,51]. The inconsistency of results could be due to the use of different experimental designs and AD models, the nonlinear relationship between plasma and brain cholesterol levels, the magnitude of cholesterol changes and differences in monitoring cholesterol as total pool, LDL- or HDL-bound cholesterol, membrane cholesterol, or cholesterol in different parts of the brain. Age, sex, presence of vascular disease, or presence of the risk ApoE4 allele and other AD-related genes may also influence the effects of cholesterol on the disease [48, 50, 52, 53].

One of the most important approaches to studying the role of cholesterol in AD has been the use of statins, which inhibit a key enzyme in cholesterol synthesis, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase. Although many studies showed an ameliorative effect of statins on AD pathology [54,55,56,57,58], the pleiotropy of statin action, which also affects protein prenylation involved in vital cellular and physiological processes, may complicate interpretation of results [59, 60]. However, authors often use alternative methods to lower cholesterol levels, such as the use of methyl-β-cyclodextrin (MβCD), which emphasize the importance of cholesterol in AD. Cholesterol undoubtedly influences Aβ-membrane interactions and its possible toxic effects [61,62,63,64,65,66,67]. Cholesterol levels are also associated with Aβ degradation and clearance, as these mechanisms depend on cholesterol-rich lipid rafts and cholesterol-transporting proteins, including ApoE and ABC pumps [68, 69]. Finally, the presence and amount of cholesterol dictates the mode of APP processing and the resulting amyloid forms that determine the fate of cells and organisms. The present review focuses on the role of cholesterol and cholesterol-dependent membrane rafts in APP processing that determines the amount and forms of amyloid β in the brain.

Cholesterol

Cholesterol pools

Although the human brain represents only 2% of body weight, it contains about 25% of total body cholesterol. Since cholesterol cannot normally pass the BBB, its homeostasis in the brain is regulated mainly by glial cells. During postnatal development, massive cholesterol synthesis in the brain is connected with a brief period after birth when myelination by oligodendrocytes occurs [70, 71]. In adulthood, cholesterol turnover in the neuronal system is relatively slow because most cholesterol is bound in the myelin sheaths [40, 69, 72,73,74]. However, cholesterol turnover is not the same throughout brain tissue [75,76,77]. Therefore, small age- or disease-related changes in cholesterol content in neuronal membranes may appear invisible when all brain tissue is analyzed. While myelin-rich white matter has the slowest cholesterol turnover and glial cells the intermediate, active neurons are characterized by the highest cholesterol metabolism [75, 78]. Although essentially all brain cells are capable of producing cholesterol, the needs of mature neurons are met primarily by astrocytes [38, 77, 79,80,81]. Mature neurons have a limited ability to synthesize cholesterol and rely on a supply of the cholesterol-rich lipoprotein ApoE from astrocytes [79, 82]. Axons in particular lack the ability to synthesize cholesterol, although the soma shows limited cholesterol synthesis in culture [83, 84]. Because axons are often very long, transport of cholesterol from the soma may be insufficient to supply active synaptic membranes. Therefore, local synaptic demand is met by astrocytic ApoE particles released in close proximity to ApoE receptors on the neuronal plasma membrane (PM). This mechanism not only conserves neuronal energy but also provides rapid regulation: ApoE receptors are enriched in the neuronal PM during increased neuronal activity, and on the other hand, excess oxidized cholesterol produced by neurons can rapidly reduce cholesterol synthesis in astrocytes through feedback mechanisms [82, 85]. In remyelination processes, microglia, oligodendrocytes, and neurons play the main role in cholesterol production rather than astrocytes [71, 86]. These observations underscore the fact that cholesterol requirements are saturated by different cell populations locally and depending on the (patho)physiological conditions and ontogenetic stage [38, 70, 71, 76, 77, 80, 86].

There are several cholesterol pools in cells that can be altered in AD. Synthesis of cholesterol in the endoplasmic reticulum (ER) is associated with transport to the Golgi apparatus (GA) and PM [87]. Extracellular (e.c.) cholesterol is bound to cholesterol-rich lipoproteins. In the brain, the ApoE protein of astrocytic origin is the major platform for the organization of lipoproteins that enter the cell by endocytosis [82, 88]. Conversely, the accumulation of sterol molecules in the PM is associated with cholesterol and oxysterol efflux into the ApoE lipoprotein particles, which is assisted by ABC transporters [89,90,91]. Cholesterol can also be released from cholesterol esters concentrated in lipid droplets by the action of ER-resident acyl-CoA cholesterol acyltransferase (ACAT). During aging and neurodegeneration, lipid droplets accumulate in astrocytes and affect cholesterol homeostasis in the cell [89, 92]. Quantitatively, about 1% of cellular cholesterol is converted to esters, while 40% is oxidized. The rest is mainly localized in the PM or exported via the ABC-lipoprotein system [38]. In the PM, cholesterol is predominantly concentrated in lipid rafts. Lipid rafts have been described as PM regions rich in cholesterol and sphingolipids (SL), especially sphingomyelin (SM), and characterized by a specific protein composition [93,94,95,96,97,98]. A higher proportion of saturated and long carbon chains and planar cholesterol molecules results in a less fluid and more rigid liquid-ordered (Lo) phase, which, together with a higher raft thickness, strongly affects the nature of membrane interactions with both peripheral and transmembrane (TM) proteins [99].

Distribution of cholesterol in membrane bilayers

There are seemingly conflicting data and views on the preference of cholesterol for the cytofacial or exofacial leaflet of the membrane [100]. Experimental and theoretical considerations led to the conclusion that cholesterol is enriched in the less fluid outer layer where it interacts with SM [101,102,103,104,105,106,107]. At lower concentrations (15%), most of the cholesterol is captured by SM molecules in the outer leaflet. However, cholesterol content of 33% is sufficient to saturate the SM binding sites, and the cholesterol is evenly distributed [108]. This means that cholesterol distribution is affected by other membrane lipids, which may be different in different tissues, age groups or stages of the disease. Other authors observed preferential accumulation of cholesterol in the cytofacial leaflet [109,110,111,112]. Dynamic redistribution from the exofacial [113] or the cytofacial [114] leaflet may occur after statin or ethanol administration and as a result of changes in polyunsaturated fatty acids (PUFA), aging, or changes in the function of cholesterol transport proteins [109, 113,114,115].

Cholesterol may have a stabilizing effect on the inner membrane leaflet by reducing the bending energy of the inverted hexagonal phase, which consists mainly of cytofacial phosphatidylethanolamine (PE) [116]. The dependence of cholesterol distribution on the length of the hydrocarbon chain of SM was observed in model systems and in erythrocytes. Only the long chain C24 SM, but not the shorter chain C16 SM interdigitated from the outer to the inner monolayer, where it formed hydrophobic holes filled with cholesterol molecules and caused a redistribution of cholesterol from the outer to the inner monolayer [117]. Similar results on the distribution of sterols in the bilayer were obtained in yeast [118]. Thus, the nonuniform localization of SL in exofacial raft patches also leads to cytofacial aggregation of cholesterol in the raft fraction but not in the raft surroundings. However, the rapid cholesterol flip/flop movements and the use of different experimental models make it difficult to draw a definitive conclusion [106, 107]. Because particular membranes in cells, tissues, and organs vary considerably in composition, cholesterol molecules may respond dynamically to the presence of other lipid populations with particularly long saturated or unsaturated fatty chains [107,108,109, 116,117,118,119]. This uncertainty complicates the interpretation of cholesterol effects on Aβ synthesis, and furthermore, only long-term equilibria in cholesterol distribution need to be considered because AD is a long-term pathology.

Oxysterols

In addition to cholesterol, oxysterols (oxidation products of cholesterol) are also involved in the intertwining of Aβ production and cholesterol metabolism [36, 120]. Excess cholesterol in the brain is oxidized to 24-hydroxycholesterol (24-OHC), which, unlike cholesterol itself, exits the brain via the BBB, a process that is in equilibrium with cholesterol synthesis in the brain [75, 121,122,123]. 24-OHC has been shown to be elevated in the brain of AD patients along with plasma-derived 27-hydroxycholesterol (27-OHC), with 24-OHC levels decreasing in the later stages of the disease [30, 88, 124, 125]. Elevated brain oxysterols may trigger neuronal excitotoxicity and neuroinflammation and serve as one of the markers for AD [126, 127]. Cholesterol oxidation leads to membrane thinning and a decrease in membrane order [128], which is accompanied by increased Aβ-membrane association [129]. The flux of 27-OHC from plasma to brain forms is one of the links between AD and hypercholesterolemia [124, 130], while a reduction 27-OHC in serum alleviates symptoms of the disease [131].

However, the role of 24-OHC in brain health remains controversial, as its effects are highly dependent on oxysterol concentration and experimental model [30, 132]. Both oxysterols, but especially 24-OHC, were found to inhibit Aβ synthesis in neurons [133]. It is worth noting that 24-OHC may act as an activator of liver X receptors that induce transcription of cholesterol export pathway genes (ABCA1, ABCG1, ApoE). Importantly, enhanced cholesterol oxidation was associated with decreased cholesterol content and cholesterol-dependent Aβ production [38, 134].

ApoE

ApoE plays a crucial role in cholesterol delivery from astrocytes to neurons and has been found to be involved in AD pathology at many levels in complex ways [135,136,137,138]. Of the three ApoE variants, ApoE4, which contains Arg112/Arg158 instead of Cys112/Cys158 (ApoE2) or Cys112/Arg158 (ApoE3), is associated with AD [139,140,141,142,143,144,145,146]. ApoE4 impairs lipid transport between cells, reduces Aβ clearance, and promotes Aβ aggregation into toxic conformations [136, 142, 147,148,149]. ApoE4 is thought to be less lipidated than ApoE2 and ApoE3 [121, 149, 150]. Thus, ApoE4 does not sufficiently remove cholesterol from the exofacial leaflet of the PM. Accordingly, ApoE4 knock-in mice exhibiting cholesterol-induced amyloid pathology showed a  2-fold increase in cholesterol in the exofacial leaflet compared with wild-type or ApoE3 mice [141]. In human ApoE4-expressing astrocytes derived from induced pluripotent stem cells, accumulation of cholesterol, and higher production but less efficient clearance of Aβ were observed [147]. Moreover, ApoE4 enhanced endosomal dysfunction by decreasing the amount of the Na+/H+ exchanger NHE6 and lowering pH in endosomes where ApoE-bound Aβ and its receptor LRP1 remain trapped, resulting in decreased amyloid clearance [151,152,153].

ABC transporters

ATP-binding cassette (ABC) transporters are responsible for the export of molecules from cells, and their dysregulation leads to degenerative brain disorders [154, 155]. Among the ABC transporters, ABCA1 and, in a lesser extent, ABCG1 and ABCG4 are particularly required for cholesterol efflux because they are responsible for lipidation of ApoE [38, 88, 155,156,157]. Whereas ABCA1 and ABCG1 are localized in astrocytes, ABCG4 is preferentially expressed in neurons, and ABCA7 in microglia [121, 154, 158]. The increase in ABCA1 content in the PM is accompanied by increased cholesterol export and more lipidated apoE particles, and vice versa [149, 159]. However, in cultured astrocytes and neurons, Aβ42 induced an increase in cholesterol synthesis and ABCA1 content but did not result in increased production of lipidated ApoE [160]. Because the function of ABC transporters, ApoE lipidation, cholesterol, and Aβ transport capacity are interconnected, disruption of cholesterol regulation at any level may lead to severe brain dysfunction [154, 161].

Cholesterol changes in AD

The lipid composition of brain tissue has been found to change during aging or AD progression. Age-dependent enrichment of the neuronal PM membrane with cholesterol and SM-dependent lipid rafts was associated with higher Aβ-induced cell injury [162, 163]. Cholesterol content increased in the PM of brain areas characterized by AD-associated damage during aging [29, 35, 164]. Elevated cholesterol and ganglioside GM1 levels were observed in synaptosomes isolated from cortices of AD patients [31], which was associated with increased Aβ generation [165]. In combination with the ApoE4 genotype, increased cholesterol content in the frontal cortex was closely associated with senile plaque formation [28, 166]. The accumulation of cholesterol in mitochondria makes mitochondrial membranes less permeable to cytosolic glutathione, which is associated with increased Aβ-induced oxidative stress [167, 168]. On the other hand, some studies show opposite results. A 30–35% reduction in cholesterol content was observed in the temporal gyrus or hippocampus of AD patients [169, 170], which was associated with a thinning of the bilayer by 0.4 nm [170]. The AD-associated demyelination was also associated with a ~ 12% loss of cholesterol [73]. At this point, it must be emphasized that not only changes in total cholesterol content but also specific changes in different membrane compartments or raft fractions may influence the progression of AD. In addition, cholesterol has many effects on the membrane that influence: (1) membrane thickness and fluidity, (2) interactions of enzymes with substrates and activation of receptors, (3) enzyme activities, and (4) protein sorting and internalization [44, 165, 171, 172]. With respect to AD and as described below, the processing of APP and the formation of Aβ can also be directed by cholesterol content and distribution in the cell [74].

Amyloid β formation

Amyloid β peptide

Aβ is a 37–43 amino acid long peptide, with Aβ40 representing the absolute majority of amyloid products and the ten times rarer Aβ42 known to be the most dangerous form in the brain. All Aβ peptides originate from the amyloid precursor protein, a type I single-span TM protein, which is specifically cleaved by α-, β-, and γ-secretases at distinct sites [173,174,175,176,177,178,179]. Aβ is one of the intrinsically unstable polymers that can adopt different spatial arrangements with varying degrees of toxicity [180, 181]. Thus, Aβ peptides can self-organize into oligomers capable of disrupting the membrane or initiating destructive processes in cells [8, 17, 18, 182,183,184,185,186,187]. The membrane environment, with specific lipids and proteins, co-establishes the extent of amyloid toxicity by creating conditions under which Aβ aggregates into cell-damaging elements. Among lipids, gangliosides GM1, SM, and cholesterol form binding platforms for Aβ [31, 66, 67, 188,189,190,191].

Amyloid precursor protein

The role of APP in nervous system development and function is underpinned by its ability to bind the e.c. matrix and mediate intercellular contacts [192,193,194]. Of the three known isoforms, APP695, which contains 695 amino acids, is most abundant in the brain, where it serves as a precursor for Aβ synthesis. The structure of APP is characterized by a large e.c. glycosylated N-terminus, a single TM α-helix, and a short C-terminal portion [175, 192]. The e.c. part of APP695 consists of the E1 domain (Leu18-Ala190) and the E2 domain (Ser295-Asp500) connected by the acidic domain (AcD) (Fig. 1). The α- and β-secretase cleavage sites are located in the juxtamembrane (j.m.) region connecting the E2 domain to the single TM helix. Both the E1 and E2 domains contain a heparin-binding site that allows the e.c. portion of the molecule to participate in interactions with the e.c. matrix and also in trans interactions with APPs on neighbouring cells [195,196,197,198,199]. A short α-helix, representing an extrinsic anchor of APP, may form at the j.m. region, which is buried in the membrane surface by the hydrophobic sequence Val-Phe-Ala [200,201,202]. Similarly, the C-terminus (the cytosolic APP intracellular domain—AICD) may also be dynamically anchored in the bilayer as an amphipathic helix, which may affect the accessibility of the YENPTY motif required for endosomal sorting or AICD release [200, 201, 203]. The TM domain of APP contains 24–26 amino acids (Asn623/Gly625-Leu648/Lys649) arranged predominantly in a right-handed α-helix depending on the environment [193, 200, 204,205,206,207,208]. Gly633–Gly634 are responsible for the relatively high flexibility of this region, which is required for APP processing, TM domain dimerization, and interactions with cholesterol [204, 206, 209]. Two angles characterize the position of APP in the bilayer. The first describes the overall TM α-helix tilt and the second the hinge angle caused by the glycine Gly633–Gly634 (Fig. 1A). Both angles are affected by the membrane thickness, which in turn affects the flexibility of APP, the stability of the secondary structure, and the accessibility of the cleavage sites for γ-secretase [203, 210, 211].

Fig. 1
figure 1

Amyloid precursor protein. A The extracellular (e.c.) part of APP consists of the E1 domain [containing the N-terminal growth factor-like domain (GFLD) and the copper-binding domain (CuBD)], the acidic region, and the E2 domain. The juxtamembrane (j.m.) region connects the e.c. portion to the transmembrane (TM) segment. The C-terminus is cytosolically aligned at the end of the cytosolic APP intracellular domain (AICD). In the TM domain, glycines G633-634 form a kink that is locally destabilizes the secondary structure. The red lines show the angles characteristic of the orientation of APP in the membrane (see text). B Amino acid sequence of the TM segment and AICD of APP. Cleavage sites for α-, β-, and γ- secretase (including the ε-site) are indicated. Light orange—amino acids buried in the hydrophobic zone of the bilayer, dark orange and red—glycines forming glycine zippers (dimerization motifs). Glycines 37/38 of C99 (after β-cleavage) correspond to G633/634 of APP (A). Adjusted according to [193, 195, 201, 203, 256, 338]

APP processing by secretases

The APP molecule can be cleaved by three proteases, termed α-, β-, and γ-secretases. The α-secretase cleaves APP at the PM extracellularly releasing soluble sAPPα and the C-terminal fragment (CTF) C83. This enzyme belongs to the ADAM (a disintegrin and metalloproteinase) family, in which ADAM10 plays a dominant role in APP cleavage [212, 213]. However, only sequential proteolytic cleavage of APP by β- and γ-secretases leads to the formation of potentially deleterious Αβ peptide fragments. Intramembrane γ-secretase processing of C83 generates the nontoxic P3 peptide and cytosolic AICD with regulatory functions in the cell. The amyloidogenic process begins with APP cleavage by β-secretase, which generates soluble sAPPβ and the membrane-anchored CTF C99. In addition to AICD, sequential γ-secretase activity releases Aβ peptides of varying lengths depending on the position and orientation of the enzyme and substrate [175, 214,215,216].

β-Secretase

The β-secretase is known as β-site APP cleaving enzyme-1 (BACE1), an aspartic protease whose enzymatic activity is highest in the low pH environment of intracellular (i.c.) organelles including the GA and endosomes, where amyloidogenic cleavage predominantly occurs [217,218,219,220,221,222,223,224,225]. Together with other members of the amyloidogenic cascade, part of BACE1 is concentrated in cholesterol-dependent lipid rafts [223, 226], and its enzyme activity is enhanced by cerebrosides, anionic lipids, and especially cholesterol [223]. Furthermore, artificial elevation of BACE1 in rafts led to increased Aβ production, which was reduced after cholesterol depletion, indicating cholesterol regulatory function [54]. The β-secretase cleavage of APP was enhanced after endocytosis of APP from the PM, resulting in coalescence of APP and BACE1-containing rafts in endosomes [227]. Besides endosomes, the GA is also associated with Aβ production. In AD, disruption of GA structure was associated with altered BACE1-APP accumulation in the GA as normal sorting mechanisms failed [228].

γ-Secretase

The complex of γ-secretase consists of four subunits: presenilin (PSEN1/2), anterior pharynx defective (APH-1a/b), nicastrin, and the presenilin enhancer (PEN-2) [174, 221, 229, 230]. Whereas PSEN1 is widely distributed in cellular membranes, including the PM, PSEN2 is preferentially localized in the endosomal network and in the GA, where γ-secretase is localized in lipid rafts [230, 231]. Amyloidogenic processing of C99 by γ-secretase is concentrated in acidic organelles (mainly endosomes), where Aβ peptides can accumulate and form neurotoxic aggregates [8, 177, 218, 232,233,234]. Nicastrin sterically restricts the binding of APP to γ-secretase, so that only after cleavage of the e.c. APP moiety by α- or β-secretase does the active site of the presenilin complex gain access to the truncated substrate by recognizing the j.m. region of C99 [214, 235]. The γ-secretase cleaves the C99 stepwise, starting at the ε-site within the TM domain near the cytoplasmic face of the bilayer (Fig. 1B). Local destabilization of the TM α-helix is necessary for cleavage because the backbone carbonyl carbons must be exposed for nucleophilic attack by water molecules in the active site of the γ-secretase [236, 237]. Interaction of PSEN1 with the TM domain of C99 facilitates unwinding of the α-helix of C99 and transition to the β-sheet, which is the cleavable substrate for the secretase. Depending on the orientation of C99 in the bilayer, three to five cleavages usually follow, leaving mainly 3 but also 4–5 amino acid peptides. If the first ε-cleavage occurs at Aβ48 or 51, the final product is usually Aβ42, while ε-cleavage at Aβ49, 50, or 52 leads to Aβ40, although shorter variants can also be produced [178, 179, 214, 216, 236,237,238,239,240]. While the γ-secretase remains anchored in a stable position, the substrate (C99) shows flexibility that allows sequential peptide cleavage. Lys28 of C99 at the e.c. (or intraluminal) j.m. face blocks the shift of this peptide deeper into the membrane. When mutated to Ala, greater hydrophobicity allows movement of C99 closer to the active secretase and shorter amyloid fragments (Aβ34, 37, 38) are produced [241].

Amyloid precursor protein

APP trafficking and distribution

After synthesis, APP is diverted to the PM, where it undergoes nonamyloidogenic processing by α-secretase. Intracellularly localized Aβ production follows the internalization of APP from the PM [242, 243]. From endosomes, a pool of APP is transported back to the GA with help of SORL1. Depletion of SORL1 blocks transport of APP to the GA and keeps APP in endosomes, where it contributes to endosomal dysfunction and amyloidogenic APP processing instead of PM-localized α-secretase APP cleavage [4, 5, 244]. When APP is mutated at the sorting signal, it remains in the GA, resulting in reduced C99 production in endosomes that do not have a sufficient amount of APP. However, after a prolonged period of time, APP is also processed into C99 in the GA. leading to C99 i.c. accumulation because C99 is not sufficiently degraded in the endosomal-lysosomal compartment [245]. APP trafficking may also be affected by the extent of APP dimerization, as mentioned in the following section.

APP dimerization

APP contains several dimerization motifs, including the E1, E2, and TM domains (Fig. 2) [246,247,248,249,250,251]. Several models for the process of dimerization have been proposed. In any case, the e.c. domains appear to initiate the process and the TM domains can only approach after e.c. domain shedding by β-secretase [250, 252, 253]. Mutations in the TM dimerization glycine motifs do not affect α-secretase processing of APP [212]. The nature of dimerization and spatial orientation of full-length APP differs from cleaved C99, which lacks the e.c. dimerization domains that affect cellular localization and secretase processing. The dimeric status of APP may also be related to the APP-C99 environment, highlighting the importance of the site of Aβ formation. Consequently, the precise shape and position of APP-C99 in the membrane affects the production and length of the amyloid product [198, 247].

Fig. 2
figure 2

APP dimerization. A Dimerization via the E1 domain, which can be supported by heparan sulphate (green) or Cu2+ binding. B Distinct quaternary structure of APP dimer formed by heparan sulphate binding. C Dimerization of APP, triggered by heparan sulphate interaction with the E2 domain. D After shedding the e.c. part of the molecule by β-secretase, the TM domains approach each other and can dimerize. Adjusted according to [196, 198, 199, 250, 252, 255, 256]

Because dimerization through the E1 and E2 domains is supported by e.c. heparan sulfate proteoglycans, the majority of PM-localized APP is in a dimeric form [196, 198, 199, 252, 254, 255]. Heparin-induced e.c. surface APP dimerization at neutral pH contrasts with i.c. accumulation of monomers, resulting from amyloidogenic processing predominant in the acidic endosomal environment [196, 199, 256]. Thus, the full-length APP forms more dimers than the cleaved CTF and the dimeric form is a preferred substrate for PM-located α-secretase [257]. Moreover, removal of the i.c. portion of APP reduces its internalization, and supports its dimerization and non-amyloidogenic processing at the PM [258]. However, dimerization of APP may also be associated with decreased α-secretase processing and increased amyloid production [259,260,261,262]. N-cadherin induced dimerization of the e.c. portion of APP and enhanced β-secretase-mediated cleavage of APP [259]. Dimerization induced by the binding of Cu2+ ions to the E1/E2 domain promoted Aβ generation, but with a lower Aβ42/40 ratio [263]. In contrast to monomers, the APP dimers showed reduced interaction with the sorting proteins SORL1 and LRP1, which interfered with the recycling of APP from the amyloidogenic environment of endosomes to the GA [244]. Increased SORL1 expression resulted in decreased Aβ production, as a greater amount of monomeric APP was transported to the GA and a smaller amount remained in the endosomal fraction in dimeric form as a preferred substrate for amyloidogenesis [264, 265]. At the same time, decreased amount of SORL1 led to accumulation of APP in endosomes and enhancement of the amyloidogenic pathway [264]. In another study, the concentration of APP in the trans-Golgi network (TGN) rather than in endosomes was associated with increased amyloid formation [266]. The authors suggested that APP must pass through the PM and be endocytosed during Aβ generation because most of BACE1 is concentrated in the endosomal compartment. After β-cleavage, C99 is delivered to γ-secretase and its processing occurs mainly in the TGN [266]. Because of the ambiguity of the data, multivalent effects of mutations must be considered, which are often used as a dimerization-modifying factor. In addition, it is necessary to assess the differences between APP and C99 dimerization. Dimerization of TM segments of C99 increases γ-secretase activity and Aβ formation but has no effect on BACE1-mediated APP processing [253]. Because of the different modes of APP-C99 dimerization, the resulting conformations may differ in their interactions with α, β, and γ-secretases [197]. It must be emphasized that both the monomeric and dimeric forms of C99 are substrates for γ-secretase processing, with the initial position for ε-cleavage and the arrest site for the enzyme depending strongly on the dimerization status and TM segment orientation in the bilayer [267]. Finally, not only the membrane position of APP-C99 plays a role in amyloidogenesis, but also its dimeric status and its occurrence in a specific environment enriched in certain secretases, which is a clear indication of the complexity of the process.

C99 dimerization

After APP cleavage by BACE1, the resulting C99 peptide can dimerize through three dimerization-inducing Gly-x-x-x-Gly motifs within the TM region (Fig. 3A) [237, 253, 267]. Computational models showed that the Gly33-x-x-x-Gly37/38 motif plays a major role in stabilizing the C99 dimer [205, 253, 268, 269]. However, Munter et al. emphasized the importance of the Gly29-x-x-x-Gly33 sequence, in which Gly33 is a crucial amino acid [267]. Each of the possible positions of C99 monomers in the dimer provides a distinct orientation to the γ-secretase, and diverse cleavage products are released as different starting ε-sites are recognized. The preferential action of PSEN1 on C99 dimerized through the j.m. Gly25-Gly29 motif leads to an Aβ40 product, whereas the TM dimerization through the Gly33-Gly37 sequence enhances i.c. PSEN2-mediated catalysis through the Aβ48-45-42 pathway [270] (Fig. 3B). TM glycines are known to disrupt the α-helicity and increase local peptide flexibility. In C99, in particular the Gly37-Gly38 pair forms a kink (Fig. 1) that increases the variability of the spatial arrangement of APP-C99 peptides in monomeric or dimeric structures, all of which can affect γ-secretase-mediated peptide processing [236, 247, 269, 271, 272].

Fig. 3
figure 3

Dimerization of C99 and implications for γ-secretase-mediated processing. A Three glycine zippers are located in the TM segment and j.m. region of C99 (G25-x-x-x-G29; G29-x-x-x-G33; G33-x-x-x-G37/G38). Close positioning of the two monomers is required for dimerization. B Shifts and rotations of the TM helices caused by distinct Gly zipper interactions affect (1) the start cleavage site for γ-secretase because different amino acid sequences are exposed to the catalytic site, and (2) the stop of cleavage due to steric hindrance by tightly bound parts of the monomers. If the secretase cannot continue cleavage, longer and more dangerous amyloid β forms (amyloid β42) will be released. Adjusted according to [205, 237, 253, 267,268,269,270]

The dimers of C99 differ not only in the tilt position but, because the monomers can rotate, also in the surface area of the TM segments exposed to γ-secretase. Hence, if the lipid environment, membrane curvature, and bilayer thickness influence APP-C99 dimerization and orientation, they also have a strong impact on the production of Aβ species. In thinner membranes, the C99 dimer has a more open structure with more exposed glycine residues, whereas thicker membranes stabilize the “Gly-in” arrangements; in the thicker membrane, the TM regions are more parallel and the glycine sequences involved in dimerization are closer together than in the thinner membrane [205] (Fig. 4). Thus, membrane thickness, which is inherently different for raft and non-raft regions, as well as for the ER, GA, and PM, directly affects the processing of APP by influencing the association of APP and γ-secretase, γ-secretase activity, the start and end sites of the cleavage, and finally the representation of Aβ species [205, 206, 211]. Mutational studies showed that disruption of glycine zippers did not affect the interaction of APP with secretases, because AICD production remained undisturbed, whereas Aβ formation was reduced. Thus, ε-cleavage is not affected, but the altered orientation of the C99 peptide diminishes the γ-secretase-mediated cleavage system [253]. Due to the steric hindrance, γ-secretase ceases its activity toward C99 dimers earlier and a more dangerous Aβ42 is released, while C99 monomers are more easily cleaved to shorter products (Aβ38), as was shown by disruption of the TM glycine zippers [238, 248, 249, 267]. Apparently, any factor affecting Gly29-x-x-x-Gly33 dimerization, including lipid composition, elevated cholesterol, oxidative stress, or AD-associated mutations in PSEN1 and APP, may influence the site at which γ-secretase leaves the substrate and the variability of Aβ populations [267]. However, mutational studies involving glycine zippers should be taken with caution, as altered amino acid sequence may have a stronger effect on γ-cleavage than dimerization itself, leading to controversial results [215, 238, 249, 271, 273]. In several experiments, monomeric C99 was preferentially processed into longer Aβ42 (increased Aβ42/Aβ40 ratio), while the dimeric form gave rise to less dangerous shorter amyloid forms [251, 274]. Also, instead of glycine zippers, the 43TVIV46 motif in a TM region of C99 was found to be responsible for C99 dimerization [251]. Artificial C99 dimerization via the i.c. C-terminal domains decreased γ-secretase-mediated cleavage and Aβ production [275]. All these observations highlight the importance of the precise monomer orientation and mode of APP-C99 dimerization, as both the e.c. and TM domains of APP play distinct roles in amyloidogenesis.

Fig. 4
figure 4

Membrane thickness and curvature affect the position of APP in the membrane. In thin or curved membranes, the C99/APP TM helices are more tilted than in thicker bilayers, which is associated with different types of dimerization and different γ-secretase-mediated processing. Adjusted according to [205, 206]

Cholesterol-dependent Aβ formation

Lipid rafts as an environment for APP processing

Cholesterol- and SL-rich lipid rafts provide a platform that forms an optimal environment for APP-C99 interaction with β- and γ-secretases and for Aβ production [130, 223, 226, 276]. Only a small but physiologically relevant portion of APP is located in lipid rafts, where the amyloidogenic apparatus of β- and γ-secretase is predominantly localized [72, 277]. Normally, only 10% of APP is palmitoylated and processed by BACE1 in lipid rafts. Artificially increased or decreased APP palmitoylation results in elevated or reduced Aβ production, respectively [278].

All age- or disease-related changes in SM, cholesterol, or unsaturated fatty acids are associated with changes in raft composition and processes related to Aβ formation or Aβ degradation. In aged or AD brains, lipid alterations (especially the decrease in unsaturated fatty acids but also the increase in cholesterol) led to increased raft number and rigidity, accompanied by APP enrichment and enhanced APP-BACE1 association [184, 279,280,281,282,283,284,285].

The relationship between Aβ production and cholesterol

Elevated cholesterol levels along with membrane-associated oxidative stress have been observed in the brain during AD; here, statins may alleviate symptoms of the disease [29, 34, 56, 58, 74, 286, 287]. Simulated cholesterol elevation in the PM of cultured neurons, cell lines, or mouse models caused increased association of APP-C99 with lipid rafts, enlarged endosomal compartment, impaired Aβ degradation, increased APP endocytosis, and Aβ42 secretion [143, 147, 167, 288,289,290,291]. Similarly, inhibition of cholesterol oxidase Cyp46a1 in mouse hippocampus resulted in increased cholesterol in neurons, increased APP recruitment to lipid rafts, Aβ formation, tau phosphorylation, endosomal enlargement, cognitive deficits, and hippocampal atrophy [292]. A shift from Aβ38 to Aβ42 generation was observed after increasing membrane cholesterol, indicating that γ-secretase leaves the substrate earlier [291]. In neurons, 70% cholesterol depletion did not affect α-secretase activity, but Aβ production was diminished, probably as a result of disruption of the APP-C99–β-/γ-secretase interaction [57, 293]. In cell cultures and primary hippocampal neurons, elevated cholesterol promoted APP raft localization, APP endocytosis, and Aβ42 secretion, which was reversible by cholesterol depletion [294, 295]. The APP internalization likely involves both clathrin- and caveolin/flotillin-dependent pathways, with cholesterol always increasing Aβ generation, indicating deleterious effects of disrupted cholesterol homeostasis in the brain [242, 243, 288, 294]. In addition to cholesterol-enhanced Aβ production, C99 accumulation may also represent a burdensome element in cellular pathology, adding to the complexity of cholesterol-mediated effects in AD [296].

The effect of cholesterol on secretases

By forming lipid rafts, cholesterol creates optimal conditions for β- and γ-secretase activity [54, 165, 174, 201, 210, 223, 227, 297,298,299]. Cholesterol makes the active site γ-secretase more compact and supports secretase activity toward C99, which promotes Aβ42 generation [239, 300]. All four parts of the γ-secretase complex contain common TM cholesterol binding motifs CARC or CRAC [239, 301]. Blocking i.c. cholesterol transport impaired both β- and γ-secretase activities in SH-SY5Y cells and primary cortical neurons, where γ-secretase is concentrated in cholesterol-rich endosomal vesicles [230, 231]. Under nonpathological conditions, α-secretase cleavage predominates and is localized in the fluid cholesterol-poor membrane [201, 302, 303]. Moreover, α-secretase activity is inhibited by cholesterol [304]. Furthermore, a reduction of cholesterol content below 60% led to decreased internalization of APP, which was followed by increased association of ADAM10 and APP and nonamyloidogenic cleavage of APP [303]. The sex-specific effect of statins was observed in the model AD Tg2576 mice. Whereas females increased Aβ production by enhancing BACE1 activity, cholesterol lowering had no effect on APP processing in males. This suggests complex relationships between cholesterol levels, statin action (which also affects protein prenylation), and other factors in affected tissues [305]. Increasing dietary and plasma cholesterol levels reduced α- and β-secretase activity and the amount of all APP-derived fragments in an APP gene-targeted mouse model [49]. The authors also suggest that the clearing mechanism, including ApoE, may be more active in elevated cholesterol levels. Thus, the specific lipid and protein background may influence outcome at many levels, indicating considerable complexity of AD pathology.

The effect of cholesterol on APP

In contrast to secretases, APP shows a more dynamic cellular localization. APP has been found in the PM, endocytic compartment, ER and GA. The specific distribution of APP in subcompartments such as mitochondria-associated ER, trans-GA or lipid rafts is closely related to the differential processing of APP [11, 221, 244, 245, 278, 299, 306,307,308]. For amyloidogenic cleavage, APP must colocalize with β- and γ-secretases in the i.c. cholesterol-dependent lipid rafts, whereas outside the rafts APP favors α-secretase-mediated processing [69, 227, 288, 293, 306, 308,309,310,311]. The importance of astrocytic cholesterol bound to ApoE for neuronal Aβ production was highlighted in a study by Wang et al. [81]. When cholesterol synthesis was inhibited in astrocytes, the size and number of lipid rafts in the neuronal PM decreased. And, although the association of β- and γ-secretases with rafts remained unchanged, APP-raft colocalization and Aβ production decreased. Cholesterol deficiency negatively affects endocytosis and BACE1-dependent APP cleavage [297, 311]. Because cholesterol binds to APP and the action of secretases depends on cholesterol, Aβ formation is closely related to cholesterol distribution [202, 229, 258, 293, 312,313,314,315,316]. Some data seem contradictory in the context that APP is better processed by BACE1 after cholesterol depletion when the enzyme leaves the rafts and binds to its substrate, the non-raft APP [169, 317] (Fig. 5). Cholesterol also affects APP dimerization and thus Aβ production [318], as described later. Different experimental conditions and cholesterol manipulations may lead to different results because cholesterol affects not only the distribution, stability, and activity of secretases and APP-C99 but also other raft-dependent processes in the cell.

Fig. 5
figure 5

Effect of cholesterol content on APP processing and Aβ generation. APP is processed by β-secretase (BACE1) predominantly in cholesterol-rich lipid rafts. However, most of APP is localized outside rafts, and only a small fraction of APP is processed via the amyloidogenic pathway. An increase in cholesterol leads to increased raft organization, increased APP-BACE1 association within raft domains, and Aβ production (+ cholesterol). Another model suggests that lowering cholesterol levels may also promote amyloidogenesis (− cholesterol). Low cholesterol level leads to a lower number of rafts and lower amount of BACE1 in the rafts. As a result, BACE1 leaves the raft fraction and encounters its non-raft substrate, APP. Green circles, raft domain; yellow circles, non-raft area

Lowering cholesterol levels usually results in decreased APP-raft association and reduced Aβ formation [81, 243, 288, 294, 319]. However, more subtle alterations in cellular cholesterol levels must also be considered. Redistribution from the cytofacial to the extracellular/intraluminal face of the membrane was associated with decreased γ-secretase-mediated processing of C99 and Aβ production [320]. Furthermore, not only the direction, but also the extent of cholesterol change may affect Aβ production or Aβ degradation. A reduction of cholesterol level of more than 35% was associated with decreased Aβ secretion in CHO cells. However, under less than 25% reduction, Aβ secretion and AD pathology increased that was observed also in hippocampal membranes of rodents or AD patients where disturbation of lipid rafts led to increased APP-BACE1 colocalization outside the rafts and decreased raft-dependent Aβ degradation [169, 317]. It is important to mention here that model systems with increased APP content may lead to biased results because overloaded APP may artificially partition in rafts enriched in β- and γ-secretase [317, 321].

APP binding to cholesterol

The interaction of APP-C99 with cholesterol may support the localization of C99 in lipid rafts where amyloidogenic processing occurs [322]. Computational modeling revealed up to six binding sites for both the α- and β-faces of cholesterol in the APP-C99 structure, which differ in their affinity and interaction dynamics [322]. A simulation model showed two possibilities of C99-cholesterol interaction. In the tight conformation, the smooth α-surface of cholesterol binds tightly to Gly-x-x-x-Gly motifs through van der Waals interactions, whereas in the loose arrangement the rougher β-site faces C99 [202]. The mutual position of cholesterol and APP is stabilized by the H-bond between the cholesterol –OH group and the e.c. oriented amino acids, including Asn27 and Glu22 (Fig. 6). This interaction provides a pH sensor showing the pH dependence of Aβ production [310, 313]. While charged Glu does not reach the bilayer at neutral pH, accepting a proton in acidic environments renders it neutral and incorporates it into the bilayer, where Glu22 interacts with cholesterol and positions it in a specific orientation [310]. In the model of Nierzwicki and Czub, the H-bonding of Glu22 with cholesterol is not observed, but the interaction between Lys16 and Glu22 keeps the j.m. region within the bilayer and in close proximity to the membrane cholesterol, allowing mutual interaction [202].

Fig. 6
figure 6

Interaction of C99 with cholesterol at the luminal/extracellular membrane face. In the j.m. region, both H-bonds and hydrophobic interactions between the cholesterol hydroxyl or aromatic A-ring and surrounding amino acids may be involved, as is indicated by red arrows. The exact arrangement depends on many factors, including the lipid environment, bilayer thickness, pH, and the tertiary and quaternary structure of the peptide. Adjusted according to [202, 310, 315]

By binding to APP, cholesterol promotes the amyloidogenic pathway by impeding the targeting of the cleavage site to α-secretase [313]. Mutation of Lys28 (K28A) disrupts the APP-cholesterol interaction and allows γ-secretase to continue cleavage and produce shorter forms of Aβ instead of the more dangerous longer Aβ40-42 [289]. Besides Lys28, also j.m. Lys16 strengthens cholesterol interaction with APP-C99. Moreover, Lys53 and Lys55 play similar roles at the cytofacial leaflet [315]. The authors conclude that no stable APP-cholesterol dimers persist over time, but various short-lived complexes with low interaction energy exist in the membrane. The exact form and lifetime of such heterodimers depends strongly on pH, membrane thickness (corresponding to the APP-C99-bilayer tilt), the presence of other lipids, and especially on cholesterol concentration or raft localization [315].

Cholesterol and APP-C99 dimerization

A cholesterol content of more than 15% in the lipid raft pool is sufficient to disrupt C99 dimerization and trigger the monomer-dependent γ-processing [200]. This result is also supported by computational modeling [316, 318]. Electron paramagnetic resonance and Förster resonance energy transfer methods showed that C99 monomers bind to cholesterol at physiological concentrations and promote association with rafts and amyloidogenic processing of C99. However, when C99 membrane concentration increases and cholesterol levels are low (e.g. in the endosomal or GA fraction), C99 dimerization may occur, suggesting competition between C99–C99 and C99–cholesterol binding [250]. In molecular dynamics simulations, a low cholesterol content (10%) resulted in a stiffening of the bilayer and stabilization of C99 dimerization. At higher cholesterol levels corresponding to lipid rafts (40%), and especially in the outer membrane leaflet, cholesterol molecules became wedged in the upper part of the dimer and disrupted C99-C99 interactions, leading to C99 monomerization. This was linked to the exposure of the Gly-rich TM motifs to the surrounding cholesterol molecules [318]. From this study, it can be concluded that low cholesterol concentration stabilizes C99 dimers in the rigid membrane, whereas higher cholesterol concentration destabilizes them. In human iPSC-derived neurons and transfected HEK cells, cholesterol competed with APP dimerization, and statin-induced cholesterol reduction enhanced APP dimerization and decreased Aβ production, likely due to obscuring APP amino acids essential for β-secretase action at APP [323]. A complex relationship between cholesterol content, cellular trafficking, APP-BACE–γ-secretase interaction, and endosome-dependent Aβ production was proposed in a model by Feringa and Kant. High ER cholesterol prevents APP dimerization and causes transport of the monomeric APP into the PM. There, cholesterol stimulates raft clustering of APP, β- and γ-secretase, and clathrin-mediated endocytosis leading to amyloidogenic processing of APP to Aβ [324]. At the same time, dimerization of APP is associated with its retention in the ER and reduced maturation and processing of APP [323].

Cholesterol esterification and APP processing

In addition to cholesterol itself, cholesterol esters (CE) formed in the ER might also play a role in amyloidogenesis, because CE levels are correlated with secreted Aβ levels [37]. It has been reported that reducing the amount of CE suppresses AP processing and Aβ production [323, 325, 326]. The reduction in cholesterol esterification results in more cholesterol molecules remaining in the ER. Because the ER cholesterol population represents the reference cholesterol pool, the cell responds by inhibiting cholesterol synthesis and uptake. This leads to reduction of cellular cholesterol amount along with impairment of cholesterol-dependent processes, including β- and γ-secretase activity toward APP-C99 [327]. Decreased synthesis of CE and increased cholesterol content in the ER increases retention of APP in the ER and reduces exposure of APP to β-/γ-secretases and Aβ formation [328]. Although these results are in contrast to the model of Ferringa and Kant (2021), they again illustrate the complexity of cellular processes that depend on cholesterol amount and distribution.

Regulation of cholesterol homeostasis by APP

Importantly, APP itself can serve as a cholesterol-sensitive and regulatory element that reverses the relationship between APP and cholesterol content [329]. In astrocytes responsible for brain cholesterol homeostasis, deletion of the APP gene impaired lipoprotein and Aβ endocytosis, decreased i.c. cholesterol, and activated genes connected with cholesterol synthesis and uptake [330]. APP may affect the function of lipoprotein receptors and vice versa, as both proteins form a functional complex in the PM, secretory, and endosomal compartments [331,332,333]. Increased cholesterol content in the PM supports APP monomerization and internalization, resulting in enhanced i.c. APP processing and AICD release. Because AICD affects the transcription of genes connected with cholesterol metabolism, APP serves in this way as a cholesterol sensor in the cell [200, 201]. In the ER, by binding cholesterol, the C99 pool may contribute to the formation of ER-lipid rafts involved in cholesterol esterification, a process closely associated with cellular sterol homeostasis [334].

Closing remarks

In the last decade, many findings pointed to the importance of a cholesterol-rich environment for β- and γ-secretase-mediated processing of the amyloid precursor protein, APP. All steps of Aβ production, including stability and activity of secretases, their aggregation with substrate, and association with the endosomal compartment and lipid rafts, have been found to be determined by cholesterol levels. However, because so many studies have focused on the role of cholesterol in amyloidogenesis, a variety of inconsistent results have been obtained. This fact suggests that cholesterol plays multiple roles in membrane-associated processes. Many proteins involved in Aβ formation contain different cholesterol-binding sites, so that the binding of cholesterol affects not only their conformation but also their targeting to other members of the machinery and distribution to specific compartments in which other partners are differentially represented.

Nonamyloidogenic α-secretase processing prevails in non-raft plasma membranes, where a significant pool of APP is also located. The opposite is true for β- and γ-secretases, which are concentrated in i.c. compartments (especially endosomes) and in cholesterol-rich lipid rafts. In this context, cholesterol has two essential roles: (1) by direct binding, it affects protein conformation and function, and (2) it establishes specific raft environment. Therefore, any change in cholesterol content may directly or indirectly influence membrane processes, and furthermore, these effects can be contradictory and depend on cholesterol concentration and the presence of other lipids and proteins. The use of different experimental and theoretical models not only leads to controversial results, but also allows us to understand an intricate web of relationships between all the players involved in APP processing. This is well illustrated by the effects of cholesterol alteration on increased APP-β-secretase colocalization after both cholesterol lowering and cholesterol elevation (Fig. 5), underscoring the fact that any disruption of cholesterol homeostasis may exacerbate the onset and progression of AD.

It has been established that APP can exist in monomeric or multiple dimeric forms, which have a strong influence on membrane localization and interaction with secretases. The relationship between the distinct APP and C99 forms, cholesterol, and cholesterol-dependent processing appears to be very complex, as different and conflicting results have been obtained. Both APP-C99 monomers and dimers are suitable substrates for secretases; however, processing may differ in the length of the final amyloid β product, reflecting the different spatial orientation of the substrate and γ-secretase. The dependence of APP cleavage on localization in the plasma membrane or intracellular environment after cholesterol-dependent endocytosis brings up another point where cholesterol is involved in Aβ formation. The involvement of the ER and GA in the amyloid-producing machinery further complicates the understanding of the regulation of amyloidogenesis. Certain forms of APP and C99 are differentially recognized as substrates for inter-organelle transport. The influence of cholesterol on APP-C99 dimerization therefore underscores the complexity of the system, which contains various monomeric or dimeric APP and C99 forms that may be bound to cholesterol and localized to the raft or non-raft membranes of different organelles where different secretases are present. Cholesterol binding to the APP-C99 monomer may attract the peptide to the β-/γ-secretase-rich environment of lipid rafts, whereas the dimeric form may remain longer in the vicinity of β-/γ-secretases in endosomes because the dimer is not recognized by SORL1 for recycling to the TGN. The other source of complexity is due to the specific APP-C99 position and orientation in the membrane, which results in differential exposure of cleavable sites for β-/γ-secretases. Cholesterol can obscure these sites, which are then more accessible in the dimeric state, or it can expose them by disrupting the closed conformation of the dimers. Thus, different interactions of varying importance between cholesterol and APP-C99 have been found, reflecting the application of different models and introducing a great deal of uncertainty into our view of the arrangement. However, the presence of different arrangements provides an explanation for the high sensitivity of APP-C99 processing to more or less significant alterations in the lipid environment, because only minor changes can cause significant conformational shifts and resulting secretase actions.

In summary, cholesterol influences amyloidogenesis at several levels, depending mainly on the nature of its interaction with protein partners. Because a specific lipid environment plays a crucial role in this complex process, all computational models and artificial membrane systems, although very useful in revealing molecular details, provide incomplete data when compared with real neuronal membranes. Unfortunately, no samples of the early stages of AD from affected human brain parts are available for functional analysis of Aβ production. Besides cholesterol, which affects the fluidity and thickness of the bilayer, other lipids or fatty acids may also affect Aβ formation. In particular, PUFA, which reduce membrane rigidity and have heterogeneous molecular shapes, have effects on the protein machinery involved in amyloid production. Monounsaturated oleic acid and ω3 docosahexaenoic acid have been shown to be protective, whereas ω6 PUFA or saturated FA exacerbate the AD pathology [335, 336]. PUFA also enhanced cholesterol-SM association by excluding more cholesterol molecules from bulk membranes into the raft fraction [101, 105, 337].

Consideration of the complexity of the interactions is critical because all simplified models, by their nature, represent only a partial aspect of the problem. However, each partial result helps to untangle the complex web of relationships between molecules responsible for one of the most devastating diseases of our time. In the future, the use of neural stem cells and molecular genetic techniques to manipulate cholesterol levels and other lipids and proteins involved in the APP processing system may help us unravel the intricate web of relationships between Aβ formation and cholesterol distribution.

Availability of data and materials

Not applicable.

References

  1. Guerreiro RJ, Gustafson DR, Hardy J. The genetic architecture of Alzheimer’s disease: beyond APP, PSENs and APOE. Neurobiol Aging. 2012;33:437–56.

    Article  CAS  PubMed  Google Scholar 

  2. Karch CM, Goate AM. Alzheimer’s disease risk genes and mechanisms of disease pathogenesis. Biol Psychiatry. 2015;77:43–51.

    Article  CAS  PubMed  Google Scholar 

  3. Ko YA, Billheimer JT, Lyssenko NN, Kueider-Paisley A, Wolk DA, Arnold SE, Leung YY, Shaw LM, Trojanowski JQ, Kaddurah-Daouk RF, Kling MA, Rader DJ. ApoJ/Clusterin concentrations are determinants of cerebrospinal fluid cholesterol efflux capacity and reduced levels are associated with Alzheimer’s disease. Alzheimers Res Ther. 2022;14:194.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  4. Mishra S, Knupp A, Szabo MP, Williams CA, Kinoshita C, Hailey DW, Wang Y, Andersen OM, Young JE. The Alzheimer’s gene SORL1 is a regulator of endosomal traffic and recycling in human neurons. Cell Mol Life Sci. 2022;79:162.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  5. Muhammad A, Flores I, Zhang H, Yu R, Staniszewski A, Planel E, Herman M, Ho LL, Kreber R, Honig LS, Ganetzky B, Duff K, Arancio O, Small SA. Retromer deficiency observed in Alzheimer’s disease causes hippocampal dysfunction, neurodegeneration, and Abeta accumulation. Proc Natl Acad Sci U S A. 2008;105:7327–32.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  6. van der Kant R, Goldstein LSB, Ossenkoppele R. Amyloid-beta-independent regulators of tau pathology in Alzheimer disease. Nat Rev Neurosci. 2020;21:21–35.

    Article  PubMed  Google Scholar 

  7. Haass C, Selkoe D. If amyloid drives Alzheimer disease, why have anti-amyloid therapies not yet slowed cognitive decline? PLoS Biol. 2022;20: e3001694.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  8. Lee A, Kondapalli C, Virga DM, Lewis TL Jr, Koo SY, Ashok A, Mairet-Coello G, Herzig S, Foretz M, Viollet B, Shaw R, Sproul A, Polleux F. Abeta42 oligomers trigger synaptic loss through CAMKK2-AMPK-dependent effectors coordinating mitochondrial fission and mitophagy. Nat Commun. 2022;13:4444.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  9. Li S, Selkoe DJ. A mechanistic hypothesis for the impairment of synaptic plasticity by soluble Abeta oligomers from Alzheimer’s brain. J Neurochem. 2020;154:583–97.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Ho CL, Kao NJ, Lin CI, Cross TL, Lin SH. Quercetin increases mitochondrial biogenesis and reduces free radicals in neuronal SH-SY5Y cells. Nutrients. 2020;14:3310.

    Article  Google Scholar 

  11. Shang Y, Sun X, Chen X, Wang Q, Wang EJ, Miller E, Xu R, Pieper AA, Qi X. A CHCHD6-APP axis connects amyloid and mitochondrial pathology in Alzheimer’s disease. Acta Neuropathol. 2020;144:911–38.

    Article  Google Scholar 

  12. Shevtsova EF, Angelova PR, Stelmashchuk OA, Esteras N, Vasil’eva NA, Maltsev AV, Shevtsov PN, Shaposhnikov AV, Fisenko VP, Bachurin SO, Abramov AY. Pharmacological sequestration of mitochondrial calcium uptake protects against dementia and beta-amyloid neurotoxicity. Sci Rep. 2022;12:12766.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. Trushina E, Nemutlu E, Zhang S, Christensen T, Camp J, Mesa J, Siddiqui A, Tamura Y, Sesaki H, Wengenack TM, Dzeja PP, Poduslo JF. Defects in mitochondrial dynamics and metabolomic signatures of evolving energetic stress in mouse models of familial Alzheimer’s disease. PLoS ONE. 2012;7: e32737.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  14. Ye X, Sun XQ, Starovoytov V, Cai Q. Parkin-mediated mitophagy in mutant hAPP neurons and Alzheimer’s disease patient brains. Hum Mol Genet. 2015;24:2938–51.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  15. Ba L, Chen XH, Chen YL, Nie Q, Li ZJ, Ding FF, Zhang M. Distinct Rab7-related endosomal-autophagic-lysosomal dysregulation observed in cortex and hippocampus in APPswe/PSEN1dE9 mouse model of Alzheimer’s disease. Chin Med J (Engl). 2017;130:2941–50.

    Article  CAS  PubMed  Google Scholar 

  16. Hung COY, Livesey FJ. Altered gamma-secretase processing of APP disrupts lysosome and autophagosome function in monogenic Alzheimer’s disease. Cell Rep. 2018;25(3647–3660): e3642.

    Google Scholar 

  17. Kelly BL, Ferreira A. beta-Amyloid-induced dynamin 1 degradation is mediated by N-methyl-D-aspartate receptors in hippocampal neurons. J Biol Chem. 2006;281:28079–89.

    Article  CAS  PubMed  Google Scholar 

  18. Kelly BL, Ferreira A. Beta-amyloid disrupted synaptic vesicle endocytosis in cultured hippocampal neurons. Neuroscience. 2007;147:60–70.

    Article  CAS  PubMed  Google Scholar 

  19. Lie PPY, Nixon RA. Lysosome trafficking and signaling in health and neurodegenerative diseases. Neurobiol Dis. 2019;122:94–105.

    Article  CAS  PubMed  Google Scholar 

  20. Nixon RA. Amyloid precursor protein and endosomal-lysosomal dysfunction in Alzheimer’s disease: inseparable partners in a multifactorial disease. FASEB J. 2017;31:2729–43.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Woodruff G, Reyna SM, Dunlap M, Van der Kant R, Callender JA, Young JE, Roberts EA, Goldstein LSB. Defective transcytosis of APP and lipoproteins in human iPSC-derived neurons with familial Alzheimer’s disease mutations. Cell Rep. 2016;17:759–73.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  22. de la Cueva M, Antequera D, Ordonez-Gutierrez L, Wandosell F, Camins A, Carro E, Bartolome F. Amyloid-beta impairs mitochondrial dynamics and autophagy in Alzheimer’s disease experimental models. Sci Rep. 2022;12:10092.

    Article  PubMed  PubMed Central  Google Scholar 

  23. Du F, Yu Q, Yan S, Hu G, Lue LF, Walker DG, Wu L, Yan SF, Tieu K, Yan SS. PINK1 signalling rescues amyloid pathology and mitochondrial dysfunction in Alzheimer’s disease. Brain. 2017;140:3233–51.

    Article  PubMed  PubMed Central  Google Scholar 

  24. Lopez-Toledo G, Silva-Lucero MD, Herrera-Diaz J, Garcia DE, Arias-Montano JA, Cardenas-Aguayo MD. Patient-derived fibroblasts with presenilin-1 mutations, that model aspects of Alzheimer’s disease pathology, constitute a potential object for early diagnosis. Front Aging Neurosci. 2022;14: 921573.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Martin-Maestro P, Gargini R, Perry G, Avila J, Garcia-Escudero V. PARK2 enhancement is able to compensate mitophagy alterations found in sporadic Alzheimer’s disease. Hum Mol Genet. 2016;25:792–806.

    Article  CAS  PubMed  Google Scholar 

  26. Roca-Agujetas V, Barbero-Camps E, de Dios C, Podlesniy P, Abadin X, Morales A, Mari M, Trullas R, Colell A. Cholesterol alters mitophagy by impairing optineurin recruitment and lysosomal clearance in Alzheimer’s disease. Mol Neurodegener. 2021;16:15.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Roca-Agujetas V, de Dios C, Abadin X, Colell A. Upregulation of brain cholesterol levels inhibits mitophagy in Alzheimer disease. Autophagy. 2021;17:1555–7.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  28. Bandaru VV, Troncoso J, Wheeler D, Pletnikova O, Wang J, Conant K, Haughey NJ. ApoE4 disrupts sterol and sphingolipid metabolism in Alzheimer’s but not normal brain. Neurobiol Aging. 2009;30:591–9.

    Article  CAS  PubMed  Google Scholar 

  29. Cutler RG, Kelly J, Storie K, Pedersen WA, Tammara A, Hatanpaa K, Troncoso JC, Mattson MP. Involvement of oxidative stress-induced abnormalities in ceramide and cholesterol metabolism in brain aging and Alzheimer’s disease. Proc Natl Acad Sci U S A. 2004;101:2070–5.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  30. Gamba P, Giannelli S, Staurenghi E, Testa G, Sottero B, Biasi F, Poli G, Leonarduzzi G. The controversial role of 24-S-hydroxycholesterol in Alzheimer’s disease. Antioxidants (Basel). 2021;10:740.

    Article  CAS  PubMed  Google Scholar 

  31. Gylys KH, Fein JA, Yang F, Miller CA, Cole GM. Increased cholesterol in Abeta-positive nerve terminals from Alzheimer’s disease cortex. Neurobiol Aging. 2007;28:8–17.

    Article  CAS  PubMed  Google Scholar 

  32. Kelley AR. Mass spectrometry-based analysis of lipid involvement in Alzheimer’s disease pathology-a review. Metabolites. 2022;12:510.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  33. Kivipelto M, Helkala EL, Hanninen T, Laakso MP, Hallikainen M, Alhainen K, Soininen H, Tuomilehto J, Nissinen A. Midlife vascular risk factors and late-life mild cognitive impairment: a population-based study. Neurology. 2001;56:1683–9.

    Article  CAS  PubMed  Google Scholar 

  34. Lazar AN, Bich C, Panchal M, Desbenoit N, Petit VW, Touboul D, Dauphinot L, Marquer C, Laprevote O, Brunelle A, Duyckaerts C. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging reveals cholesterol overload in the cerebral cortex of Alzheimer disease patients. Acta Neuropathol. 2013;125:133–44.

    Article  CAS  PubMed  Google Scholar 

  35. Mori T, Paris D, Town T, Rojiani AM, Sparks DL, Delledonne A, Crawford F, Abdullah LI, Humphrey JA, Dickson DW, Mullan MJ. Cholesterol accumulates in senile plaques of Alzheimer disease patients and in transgenic APP(sw) mice. J Neuropathol Exp Neurol. 2001;60:778–85.

    Article  CAS  PubMed  Google Scholar 

  36. Popp J, Meichsner S, Kolsch H, Lewczuk P, Maier W, Kornhuber J, Jessen F, Lutjohann D. Cerebral and extracerebral cholesterol metabolism and CSF markers of Alzheimer’s disease. Biochem Pharmacol. 2013;86:37–42.

    Article  CAS  PubMed  Google Scholar 

  37. Puglielli L, Konopka G, Pack-Chung E, Ingano LAM, Berezovska O, Hyman BT, Chang TY, Tanzi RE, Kovacs DM. Acyl-coenzyme A: cholesterol acyltransferase modulates the generation of the amyloid beta-peptide. Nat Cell Biol. 2001;3:905–12.

    Article  CAS  PubMed  Google Scholar 

  38. Dai L, Zou L, Meng L, Qiang G, Yan M, Zhang Z. Cholesterol metabolism in neurodegenerative diseases: molecular mechanisms and therapeutic targets. Mol Neurobiol. 2021;58:2183–201.

    Article  CAS  PubMed  Google Scholar 

  39. Mancini G, Dias C, Lourenco CF, Laranjinha J, de Bem A, Ledo A. A high fat/cholesterol diet recapitulates some Alzheimer’s disease-like features in mice: focus on hippocampal mitochondrial dysfunction. J Alzheimers Dis. 2021;82:1619–33.

    Article  CAS  PubMed  Google Scholar 

  40. Rudge JD. A new hypothesis for Alzheimer’s disease: the lipid invasion model. J Alzheimers Dis Rep. 2022;6:129–61.

    Article  PubMed  PubMed Central  Google Scholar 

  41. Wieckowska-Gacek A, Mietelska-Porowska A, Chutoranski D, Wydrych M, Dlugosz J, Wojda U. Western diet induces impairment of liver-brain axis accelerating neuroinflammation and amyloid pathology in Alzheimer’s Disease. Front Aging Neurosci. 2021;13: 654509.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. An Y, Zhang X, Wang Y, Wang Y, Liu W, Wang T, Qin Z, Xiao R. Longitudinal and nonlinear relations of dietary and Serum cholesterol in midlife with cognitive decline: results from EMCOA study. Mol Neurodegen. 2019;14:51.

    Article  CAS  Google Scholar 

  43. Diaz G, Lengele L, Sourdet S, Soriano G, de Souto BP. Nutrients and amyloid beta status in the brain: a narrative review. Ageing Res Rev. 2022;81: 101728.

    Article  CAS  PubMed  Google Scholar 

  44. Refolo LM, Pappolla MA, Malester B, LaFrancois J, Bryant-Thomas T, Wang R, Tint GS, Sambamurti K, Duff K. Hypercholesterolemia accelerates the Alzheimer’s amyloid pathology in a transgenic mouse model. Neurobiol Dis. 2000;7:321–31.

    Article  CAS  PubMed  Google Scholar 

  45. Solomon A, Kivipelto M, Wolozin B, Zhou JF, Whitmer RA. Midlife serum cholesterol and increased risk of Alzheimer’s and vascular dementia three decades later. Dement Geriatr Cogn Disord. 2009;28:75–80.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  46. Wu MA, Zhai YY, Liang XY, Chen WC, Lin RY, Ma LL, Huang Y, Zhao D, Liang Y, Zhao W, Fang JS, Fang SH, Chen YB, Wang Q, Li WR. Connecting the dots between hypercholesterolemia and Alzheimer’s disease: a potential mechanism based on 27-hydroxycholesterol. Front Neurosci. 2022;16: 842814.

    Article  PubMed  PubMed Central  Google Scholar 

  47. Yang N, Lin K, Zhang J, Wang JP, Meng T, Zhu J, Yang L, Zhou YQ. Amelioration of cholesterol rich diet-induced impaired cognition in AD transgenic mice by an LXR agonist TO901317 is associated with the activation of the LXR-beta-RXR-alpha-ABCA1 transmembrane transport system and improving the composition of lipid raft. Exp Aging Res. 2023;49:214–25.

    Article  Google Scholar 

  48. Ding D, Zhou F, Cao Y, Liang X, Wu W, Xiao Z, Zhao Q, Deng W. Cholesterol profiles and incident cognitive decline among older adults: the Shanghai Aging Study. Age Ageing. 2021;50:472–9.

    Article  PubMed  Google Scholar 

  49. Howland DS, Trusko SP, Savage MJ, Reaume AG, Lang DM, Hirsch JD, Maeda N, Siman R, Greenberg BD, Scott RW, Flood DG. Modulation of secreted beta-amyloid precursor protein and amyloid beta-peptide in brain by cholesterol. J Biol Chem. 1998;273:16576–82.

    Article  CAS  PubMed  Google Scholar 

  50. Mielke MM, Zandi PP, Sjogren M, Gustafson D, Ostling S, Steen B, Skoog I. High total cholesterol levels in late life associated with a reduced risk of dementia. Neurology. 2005;64:1689–95.

    Article  CAS  PubMed  Google Scholar 

  51. Ylilauri MPT, Voutilainen S, Lonnroos E, Mursu J, Virtanen HEK, Koskinen TT, Salonen JT, Tuomainen TP, Virtanen JK. Association of dietary cholesterol and egg intakes with the risk of incident dementia or Alzheimer disease: the Kuopio Ischaemic Heart Disease Risk Factor Study. Am J Clin Nutr. 2017;105:476–84.

    Article  CAS  PubMed  Google Scholar 

  52. Guo Y, Li P, Ma X, Huang X, Liu Z, Ren X, Yang Y, Halm-Lutterodt NV, Yuan L. Association of circulating cholesterol level with cognitive function and mild cognitive impairment in the elderly: a community-based population study. Curr Alzheimer Res. 2020;17:556–65.

    Article  CAS  PubMed  Google Scholar 

  53. Wang CZ, Najm R, Xu Q, Jeong DE, Walker D, Balestra ME, Yoon SY, Yuan HD, Li G, Miller ZA, Miller BL, Malloy MJ, Huang YD. Gain of toxic apolipoprotein E4 effects in human iPSC-derived neurons is ameliorated by a small-molecule structure corrector. Nat Med. 2018;24:647–57.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  54. Cordy JM, Hussain I, Dingwall C, Hooper NM, Turner AJ. Exclusively targeting beta-secretase to lipid rafts by GPI-anchor addition up-regulates beta-site processing of the amyloid precursor protein. Proc Natl Acad Sci U S A. 2003;100:11735–40.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  55. Fassbender K, Simons M, Bergmann C, Stroick M, Lutjohann D, Keller P, Runz H, Kuhl S, Bertsch T, von Bergmann K, Hennerici M, Beyreuther K, Hartmann T. Simvastatin strongly reduces levels of Alzheimer’s disease beta -amyloid peptides Abeta 42 and Abeta 40 in vitro and in vivo. Proc Natl Acad Sci U S A. 2001;98:5856–61.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  56. Jick H, Zornberg GL, Jick SS, Seshadri S, Drachman DA. Statins and the risk of dementia. Lancet. 2000;356:1627–31.

    Article  CAS  PubMed  Google Scholar 

  57. Simons M, Keller P, De Strooper B, Beyreuther K, Dotti CG, Simons K. Cholesterol depletion inhibits the generation of beta-amyloid in hippocampal neurons. Proc Natl Acad Sci U S A. 1998;95:6460–4.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  58. Wolozin B. Cholesterol and the biology of Alzheimer’s disease. Neuron. 2004;41:7–10.

    Article  CAS  PubMed  Google Scholar 

  59. Cordle A, Landreth G. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors attenuate beta-amyloid-induced microglial inflammatory responses. J Neurosci. 2005;25:299–307.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  60. Huang W, Li Z, Zhao L, Zhao W. Simvastatin ameliorate memory deficits and inflammation in clinical and mouse model of Alzheimer’s disease via modulating the expression of miR-106b. Biomed Pharmacother. 2017;92:46–57.

    Article  CAS  PubMed  Google Scholar 

  61. Avdulov NA, Chochina SV, Igbavboa U, Warden CS, Vassiliev AV, Wood WG. Lipid binding to amyloid beta-peptide aggregates: preferential binding of cholesterol as compared with phosphatidylcholine and fatty acids. J Neurochem. 1997;69:1746–52.

    Article  CAS  PubMed  Google Scholar 

  62. Di Scala C, Yahi N, Lelievre C, Garmy N, Chahinian H, Fantini J. Biochemical identification of a linear cholesterol-binding domain within Alzheimer’s beta amyloid peptide. ACS Chem Neurosci. 2013;4:509–17.

    Article  PubMed  Google Scholar 

  63. Henry S, Bercu NB, Bobo C, Cullin C, Molinari M, Lecomte S. Interaction of Abeta(1–42) peptide or their variant with model membrane of different composition probed by infrared nanospectroscopy. Nanoscale. 2018;10:936–40.

    Article  CAS  PubMed  Google Scholar 

  64. Mizuno T, Nakata M, Naiki H, Michikawa M, Wang R, Haass C, Yanagisawa K. Cholesterol-dependent generation of a seeding amyloid beta-protein in cell culture. J Biol Chem. 1999;274:15110–4.

    Article  CAS  PubMed  Google Scholar 

  65. Nicholson AM, Ferreira A. Increased membrane cholesterol might render mature hippocampal neurons more susceptible to beta-amyloid-induced calpain activation and tau toxicity. J Neurosci. 2009;29:4640–51.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  66. Rudajev V, Novotny J. Cholesterol as a key player in amyloid beta-mediated toxicity in Alzheimer’s disease. Front Mol Neurosci. 2022;15: 937056.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  67. Yanagisawa K. Cholesterol and amyloid beta fibrillogenesis. Subcell Biochem. 2005;38:179–202.

    Article  CAS  PubMed  Google Scholar 

  68. Lee CY, Tse W, Smith JD, Landreth GE. Apolipoprotein E promotes beta-amyloid trafficking and degradation by modulating microglial cholesterol levels. J Biol Chem. 2012;287:2032–44.

    Article  CAS  PubMed  Google Scholar 

  69. Maulik M, Westaway D, Jhamandas JH, Kar S. Role of cholesterol in APP metabolism and its significance in Alzheimer’s disease pathogenesis. Mol Neurobiol. 2013;47:37–63.

    Article  CAS  Google Scholar 

  70. Quan G, Xie CL, Dietschy JM, Turley SD. Ontogenesis and regulation of cholesterol metabolism in the central nervous system of the mouse. Dev Brain Res. 2003;146:87–98.

    Article  CAS  Google Scholar 

  71. Berghoff SA, Spieth L, Sun T, Hosang L, Schlaphoff L, Depp C, Duking T, Winchenbach J, Neuber J, Ewers D, Scholz P, van der Meer F, Cantuti-Castelvetri L, Sasmita AO, Meschkat M, Ruhwedel T, Mobius W, Sankowski R, Prinz M, Huitinga I, Sereda MW, Odoardi F, Ischebeck T, Simons M, Stadelmann-Nessler C, Edgar JM, Nave KA, Saher G. Microglia facilitate repair of demyelinated lesions via post-squalene sterol synthesis. Nat Neurosci. 2021;4:47–60.

    Article  Google Scholar 

  72. Allinquant B, Clamagirand C, Potier MC. Role of cholesterol metabolism in the pathogenesis of Alzheimer’s disease. Curr Opin Clin Nutr Metab Care. 2014;17:319–23.

    Article  CAS  PubMed  Google Scholar 

  73. Roher AE, Weiss N, Kokjohn TA, Kuo YM, Kalback W, Anthony J, Watson D, Luehrs DC, Sue L, Walker D, Emmerling M, Goux W, Beach T. Increased A beta peptides and reduced cholesterol and myelin proteins characterize white matter degeneration in Alzheimer’s disease. Biochemistry. 2002;41:11080–90.

    Article  CAS  PubMed  Google Scholar 

  74. Wolozin B. A fluid connection: cholesterol and A beta. Proc Natl Acad Sci U S A. 2001;98:5371–3.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  75. Dietschy JM, Turley SD. Thematic review series: brain lipids. Cholesterol metabolism in the central nervous system during early development and in the mature animal. J Lipid Res. 2004;45:1375–97.

    Article  CAS  PubMed  Google Scholar 

  76. Dietschy JM. Central nervous system: cholesterol turnover, brain development and neurodegeneration. Biol Chem. 2009;390:287–93.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  77. Saher G. Cholesterol metabolism in aging and age-related disorders. Annu Rev Neurosci. 2023;46:59–78.

    Article  CAS  PubMed  Google Scholar 

  78. Xie CL, Lund EG, Turley SD, Russell DW, Dietschy JM. Quantitation of two pathways for cholesterol excretion from the brain in normal mice and mice with neurodegeneration. J Lipid Res. 2003;44:1780–9.

    Article  CAS  PubMed  Google Scholar 

  79. Nieweg K, Schaller H, Pfrieger FW. Marked differences in cholesterol synthesis between neurons and glial cells from postnatal rats. J Neurochem. 2009;109:125–34.

    Article  CAS  PubMed  Google Scholar 

  80. Funfschilling U, Jockusch WJ, Sivakumar N, Mobius W, Corthals K, Li S, Quintes S, Kim Y, Schaap IAT, Rhee JS, Nave KA, Saher G. Critical time window of neuronal cholesterol synthesis during neurite outgrowth. J Neurosci. 2012;32:7632–45.

    Article  PubMed  PubMed Central  Google Scholar 

  81. Wang H, Kulas JA, Wang C, Holtzman DM, Ferris HA, Hansen SB. Regulation of beta-amyloid production in neurons by cholesterol. Proc Natl Acad Sci U S A. 2021;118: e2102191118.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  82. Pfrieger FW. Outsourcing in the brain: do neurons depend on cholesterol delivery by astrocytes? BioEssays. 2003;25:72–8.

    Article  PubMed  Google Scholar 

  83. Vance JE, Pan DB, Campenot RB, Bussiere M, Vance DE. Evidence that the major membrane-lipids, except cholesterol, are made in axons of cultured rat sympathetic neurons. J Neurochem. 1994;62:329–37.

    Article  CAS  PubMed  Google Scholar 

  84. de Chaves EIP, Rusinol AE, Vance DE, Campenot RB, Vance JE. Role of lipoproteins in the delivery of lipids to axons during axonal regeneration. J Biol Chem. 1997;272:30766–73.

    Article  PubMed  Google Scholar 

  85. Hayashi H, Campenot RB, Vance DE, Vance JE. Glial lipoproteins stimulate axon growth of central nervous system neurons in compartmented cultures. J Biol Chem. 2004;279:14009–15.

    Article  CAS  PubMed  Google Scholar 

  86. Berghoff SA, Spieth L, Sun T, Hosang L, Depp C, Sasmita AO, Vasileva MH, Scholz P, Zhao Y, Krueger-Burg D, Wichert S, Brown ER, Michail K, Nave KA, Bonn S, Odoardi F, Rossner M, Ischebeck T, Edgar JM, Saher G. Neuronal cholesterol synthesis is essential for repair of chronically demyelinated lesions in mice. Cell Rep. 2021;37: 109889.

    Article  CAS  PubMed  Google Scholar 

  87. Gatta AT, Wong LH, Sere YY, Calderon-Norena DM, Cockcroft S, Menon AK, Levine TP. A new family of StART domain proteins at membrane contact sites has a role in ER-PM sterol transport. Elife. 2015;4: e07253.

    Article  PubMed  PubMed Central  Google Scholar 

  88. Staurenghi E, Cerrato V, Gamba P, Testa G, Giannelli S, Leoni V, Caccia C, Buffo A, Noble W, Perez-Nievas BG, Leonarduzzi G. Oxysterols present in Alzheimer’s disease brain induce synaptotoxicity by activating astrocytes: A major role for lipocalin-2. Redox Biol. 2021;9: 101837.

    Article  Google Scholar 

  89. Chang TY, Yamauchi Y, Hasan MT, Chang C. Cellular cholesterol homeostasis and Alzheimer’s disease. J Lipid Res. 2017;58:2239–54.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  90. Steck TL, Lange Y. Cell cholesterol homeostasis: Mediation by active cholesterol. Trends Cell Biol. 2010;20:680–7.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  91. Yamauchi Y, Yokoyama S, Chang TY. ABCA1-dependent sterol release: sterol molecule specificity and potential membrane domain for HDL biogenesis. J Lipid Res. 2016;57:77–88.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  92. Farmer BC, Walsh AE, Kluemper JC, Johnson LA. Lipid droplets in neurodegenerative disorders. Front Neurosci. 2020;14:742.

    Article  PubMed  PubMed Central  Google Scholar 

  93. Anderson RG, Jacobson K. A role for lipid shells in targeting proteins to caveolae, rafts, and other lipid domains. Science. 2002;296:1821–5.

    Article  CAS  PubMed  Google Scholar 

  94. Brown RE. Sphingolipid organization in biomembranes: what physical studies of model membranes reveal. J Cell Sci. 1998;111(Pt 1):1–9.

    Article  CAS  PubMed  Google Scholar 

  95. Lingwood D, Simons K. Lipid rafts as a membrane-organizing principle. Science. 2010;327:46–50.

    Article  CAS  PubMed  Google Scholar 

  96. Matousek P, Novotny J, Rudajev V, Svoboda P. Prolonged agonist stimulation does not alter the protein composition of membrane domains in spite of dramatic changes induced in a specific signaling cascade. Cell Biochem Biophys. 2005;42:21–40.

    Article  CAS  PubMed  Google Scholar 

  97. Rudajev V, Novotny J, Hejnova L, Milligan G, Svoboda P. Dominant portion of thyrotropin-releasing hormone receptor is excluded from lipid domains. Detergent-resistant and detergent-sensitive pools of TRH receptor and G(q)alpha/G(11)alpha protein. J Biochem. 2005;138:111–25.

    Article  CAS  PubMed  Google Scholar 

  98. Rushworth JV, Hooper NM. Lipid rafts: linking Alzheimer’s amyloid-beta production, aggregation, and toxicity at neuronal membranes. Int J Alzheimers Dis. 2010;2011: 603052.

    PubMed  PubMed Central  Google Scholar 

  99. Bissig C, Gruenberg J. Lipid sorting and multivesicular endosome biogenesis. Cold Spring Harb Perspect Biol. 2013;5: a016816.

    Article  PubMed  PubMed Central  Google Scholar 

  100. Steck TL, Lange Y. Transverse distribution of plasma membrane bilayer cholesterol: Picking sides. Traffic. 2018;19:750–60.

    Article  CAS  PubMed  Google Scholar 

  101. Engberg O, Hautala V, Yasuda T, Dehio H, Murata M, Slotte JP, Nyholm TKM. The affinity of cholesterol for different phospholipids affects lateral segregation in bilayers. Biophys J. 2016;111:546–56.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  102. Ingolfsson HI, Carpenter TS, Bhatia H, Bremer PT, Marrink SJ, Lightstone FC. Computational lipidomics of the neuronal plasma membrane. Biophys J. 2017;113:2271–80.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  103. Ingolfsson HI, Melo MN, van Eerden FJ, Arnarez C, Lopez CA, Wassenaar TA, Periole X, de Vries AH, Tieleman DP, Marrink SJ. Lipid organization of the plasma membrane. J Am Chem Soc. 2014;136:14554–9.

    Article  CAS  PubMed  Google Scholar 

  104. Liu SL, Sheng R, Jung JH, Wang L, Stec E, O’Connor MJ, Song S, Bikkavilli RK, Winn RA, Lee D, Baek K, Ueda K, Levitan I, Kim KP, Cho W. Orthogonal lipid sensors identify transbilayer asymmetry of plasma membrane cholesterol. Nat Chem Biol. 2017;13:268–74.

    Article  CAS  PubMed  Google Scholar 

  105. Lonnfors M, Doux JP, Killian JA, Nyholm TK, Slotte JP. Sterols have higher affinity for sphingomyelin than for phosphatidylcholine bilayers even at equal acyl-chain order. Biophys J. 2011;100:2633–41.

    Article  PubMed  PubMed Central  Google Scholar 

  106. Marquardt D, Geier B, Pabst G. Asymmetric lipid membranes: towards more realistic model systems. Membranes (Basel). 2015;5:180–96.

    Article  CAS  PubMed  Google Scholar 

  107. Murate M, Kobayashi T. Revisiting transbilayer distribution of lipids in the plasma membrane. Chem Phys Lipids. 2016;194:58–71.

    Article  CAS  PubMed  Google Scholar 

  108. Rivel T, Ramseyer C, Yesylevskyy S. The asymmetry of plasma membranes and their cholesterol content influence the uptake of cisplatin. Sci Rep. 2019;9:5627.

    Article  PubMed  PubMed Central  Google Scholar 

  109. Igbavboa U, Avdulov NA, Schroeder F, Wood WG. Increasing age alters transbilayer fluidity and cholesterol asymmetry in synaptic plasma membranes of mice. J Neurochem. 1996;66:1717–25.

    Article  CAS  PubMed  Google Scholar 

  110. Mondal M, Mesmin B, Mukherjee S, Maxfield FR. Sterols are mainly in the cytoplasmic leaflet of the plasma membrane and the endocytic recycling compartment in CHO cells. Mol Biol Cell. 2009;20:581–8.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  111. Schroeder F, Nemecz G, Wood WG, Joiner C, Morrot G, Ayraut-Jarrier M, Devaux PF. Transmembrane distribution of sterol in the human erythrocyte. Biochim Biophys Acta. 1991;1066:183–92.

    Article  CAS  PubMed  Google Scholar 

  112. Wood WG, Schroeder F, Hogy L, Rao AM, Nemecz G. Asymmetric distribution of a fluorescent sterol in synaptic plasma-membranes—effects of chronic ethanol-consumption. bioch biophys acta. 1990;1025:243–6.

    Article  CAS  Google Scholar 

  113. Kirsch C, Eckert GP, Mueller WE. Statin effects on cholesterol micro-domains in brain plasma membranes. Biochem Pharmacol. 2003;65:843–56.

    Article  CAS  PubMed  Google Scholar 

  114. Burns MP, Igbavboa U, Wang L, Wood WG, Duff K. Cholesterol distribution, not total levels, correlate with altered amyloid precursor protein processing in statin-treated mice. Neuromol Med. 2006;8:319–28.

    Article  CAS  Google Scholar 

  115. Wood WG, Igbavboa U, Muller WE, Eckert GP. Cholesterol asymmetry in synaptic plasma membranes. J Neurochem. 2011;116:684–9.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  116. Giang H, Schick M. How cholesterol could be drawn to the cytoplasmic leaf of the plasma membrane by phosphatidylethanolamine. Biophys J. 2014;107:2337–44.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  117. Courtney KC, Pezeshkian W, Raghupathy R, Zhang C, Darbyson A, Ipsen JH, Ford DA, Khandelia H, Presley JF, Zha X. C24 sphingolipids govern the transbilayer asymmetry of cholesterol and lateral organization of model and live-cell plasma membranes. Cell Rep. 2018;24:1037–49.

    Article  CAS  PubMed  Google Scholar 

  118. Solanko LM, Sullivan DP, Sere YY, Szomek M, Lunding A, Solanko KA, Pizovic A, Stanchev LD, Pomorski TG, Menon AK, Wustner D. Ergosterol is mainly located in the cytoplasmic leaflet of the yeast plasma membrane. Traffic. 2018;19:198–214.

    Article  CAS  PubMed  Google Scholar 

  119. Maekawa M, Fairn GD. Complementary probes reveal that phosphatidylserine is required for the proper transbilayer distribution of cholesterol. J Cell Sci. 2015;128:1422–33.

    Article  CAS  PubMed  Google Scholar 

  120. Leoni V, Shafaati M, Salomon A, Kivipelto M, Bjorkhem I, Wahlund LO. Are the CSF levels of 24S-hydroxycholesterol a sensitive biomarker for mild cognitive impairment? Neurosci Lett. 2006;397:83–7.

    Article  CAS  PubMed  Google Scholar 

  121. Czuba E, Steliga A, Lietzau G, Kowianski P. Cholesterol as a modifying agent of the neurovascular unit structure and function under physiological and pathological conditions. Metab Brain Dis. 2017;32:935–48.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  122. Russell DW, Halford RW, Ramirez DM, Shah R, Kotti T. Cholesterol 24-hydroxylase: an enzy of cholesterol turnover in the brain. Annu Rev Biochem. 2009;78:1017–40.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  123. Wang YQ, Muneton S, Sjovall J, Jovanovic JN, Griffiths WJ. The effect of 24S-hydroxycholesterol on cholesterol homeostasis in neurons: quantitative changes to the cortical neuron proteome. J Proteome Res. 2008;7:1606–14.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  124. Heverin M, Bogdanovic N, Lutjohann D, Bayer T, Pikuleva I, Bretillon L, Diczfalusy U, Winblad B, Bjorkhem I. Changes in the levels of cerebral and extracerebral sterols in the brain of patients with Alzheimer’s disease. J Lipid Res. 2004;45:186–93.

    Article  CAS  PubMed  Google Scholar 

  125. Kao YC, Ho PC, Tu YK, Jou IM, Tsai KJ. Lipids and Alzheimer’s disease. Int J Mol Sci. 2020;21:1505.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  126. Loera-Valencia R, Vazquez-Juarez E, Munoz A, Gerenu G, Gomez-Galan M, Lindskog M, DeFelipe J, Cedazo-Minguez A, Merino-Serrais P. High levels of 27-hydroxycholesterol results in synaptic plasticity alterations in the hippocampus. Sci Rep. 2021;11:3736.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  127. Reitz C. Dyslipidemia and the risk of Alzheimer’s disease. Curr Atheroscler Rep. 2013;15:307.

    Article  PubMed  PubMed Central  Google Scholar 

  128. Wilson KA, Wang L, O’Mara ML. Site of cholesterol oxidation impacts its localization and domain formation in the neuronal plasma membrane. ACS Chem Neurosci. 2021;12:3873–84.

    Article  CAS  PubMed  Google Scholar 

  129. Phan HTT, Hata T, Morita M, Yoda T, Hamada T, Vestergaard MC, Takagi M. The effect of oxysterols on the interaction of Alzheimer’s amyloid beta with model membranes. Biochim Biophys Acta - Biomembr. 2013;1828:2487–95.

    Article  CAS  Google Scholar 

  130. Silva T, Teixeira J, Remiao F, Borges F. Alzheimer’s disease, cholesterol, and statins: the junctions of important metabolic pathways. Angew Chem Int Ed Engl. 2013;52:1110–21.

    Article  CAS  PubMed  Google Scholar 

  131. Sandebring-Matton A, Goikolea J, Bjorkhem I, Paternain L, Kemppainen N, Laatikainen T, Ngandu T, Rinne J, Soininen H, Cedazo-Minguez A, Solomon A, Kivipelto M. 27-Hydroxycholesterol, cognition, and brain imaging markers in the FINGER randomized controlled trial. Alzheimers Res Ther. 2021;13:56.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  132. Pincon A, Thomas MH, Huguet M, Allouche A, Colin JC, Georges A, Derrien A, Lanhers MC, Malaplate-Armand C, Oster T, Corbier C, Pillot T, Olivier JL, Yen FT. Increased susceptibility of dyslipidemic LSR+/− mice to amyloid stress is associated with changes in cortical cholesterol levels. J Alzheimers Dis. 2015;45:195–204.

    Article  CAS  PubMed  Google Scholar 

  133. Brown J 3rd, Theisler C, Silberman S, Magnuson D, Gottardi-Littell N, Lee JM, Yager D, Crowley J, Sambamurti K, Rahman MM, Reiss AB, Eckman CB, Wolozin B. Differential expression of cholesterol hydroxylases in Alzheimer’s disease. J Biol Chem. 2004;279:34674–81.

    Article  CAS  PubMed  Google Scholar 

  134. Hudry E, Van Dam D, Kulik W, De Deyn PP, Stet FS, Ahouansou O, Benraiss A, Delacourte A, Bougneres P, Aubourg P, Cartier N. Adeno-associated virus gene therapy with cholesterol 24-hydroxylase reduces the amyloid pathology before or after the onset of amyloid plaques in mouse models of Alzheimer’s disease. Mol Ther. 2010;18:44–53.

    Article  CAS  PubMed  Google Scholar 

  135. Dolejsi E, Liraz O, Rudajev V, Zimcik P, Dolezal V, Michaelson DM. Apolipoprotein E4 reduces evoked hippocampal acetylcholine release in adult mice. J Neurochem. 2016;136:503–9.

    Article  CAS  PubMed  Google Scholar 

  136. Fernandez CG, Hamby ME, McReynolds ML, Ray WJ. The role of APOE4 in disrupting the homeostatic functions of astrocytes and microglia in aging and Alzheimer’s disease. Front Aging Neurosci. 2019;11:14.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  137. Nunes VS, Cazita PM, Catanozi S, Nakandakare ER, Quintao ECR. Decreased content, rate of synthesis and export of cholesterol in the brain of apoE knockout mice. J Bioenerg Biomembr. 2018;50:283–7.

    Article  CAS  PubMed  Google Scholar 

  138. Oikawa N, Hatsuta H, Murayama S, Suzuki A, Yanagisawa K. Influence of APOE genotype and the presence of Alzheimer’s pathology on synaptic membrane lipids of human brains. J Neurosci Res. 2014;92:641–50.

    Article  CAS  PubMed  Google Scholar 

  139. de Leeuw SM, Kirschner AWT, Lindner K, Rust R, Budny V, Wolski WE, Gavin AC, Nitsch RM, Tackenberg C. APOE2, E3, and E4 differentially modulate cellular homeostasis, cholesterol metabolism, and inflammatory response in isogenic iPSC-derived astrocytes. Stem Cell Rep. 2022;17:110–26.

    Article  Google Scholar 

  140. de Oliveira FF, Chen ES, Smith MC, Bertolucci PHF. Longitudinal lipid profile variations and clinical change in Alzheimer’s disease dementia. Neurosci Lett. 2017;646:36–42.

    Article  PubMed  Google Scholar 

  141. Hayashi H, Igbavboa U, Hamanaka H, Kobayashi M, Fujita SC, Wood WG, Yanagisawa K. Cholesterol is increased in the exofacial leaflet of synaptic plasma membranes of human apolipoprotein E4 knock-in mice. NeuroReport. 2002;13:383–6.

    Article  CAS  PubMed  Google Scholar 

  142. Lanfranco MF, Ng CA, Rebeck GW. ApoE lipidation as a therapeutic target in Alzheimer’s disease. Int J Mol Sci. 2020;21:6336.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  143. Lee SI, Jeong W, Lim H, Cho S, Lee H, Jang Y, Cho J, Bae S, Lin YT, Tsai LH, Moon DW, Seo J. APOE4-carrying human astrocytes oversupply cholesterol to promote neuronal lipid raft expansion and Abeta generation. Stem Cell Rep. 2021;16:2128–37.

    Article  CAS  Google Scholar 

  144. Leoni V, Solomon A, Kivipelto M. Links between ApoE, brain cholesterol metabolism, tau and amyloid beta-peptide in patients with cognitive impairment. Biochem Soc Trans. 2010;38:1021–5.

    Article  CAS  PubMed  Google Scholar 

  145. Schilling S, Tzourio C, Soumare A, Kaffashian S, Dartigues JF, Ancelin ML, Samieri C, Dufouil C, Debette S. Differential associations of plasma lipids with incident dementia and dementia subtypes in the 3C Study: a longitudinal, population-based prospective cohort study. PLoS Med. 2017;14: e1002265.

    Article  PubMed  PubMed Central  Google Scholar 

  146. Wood WG, Li L, Muller WE, Eckert GP. Cholesterol as a causative factor in Alzheimer’s disease: a debatable hypothesis. J Neurochem. 2014;129:559–72.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  147. Lin YT, Seo J, Gao F, Feldman HM, Wen HL, Penney J, Cam HP, Gjoneska E, Raja WK, Cheng J, Rueda R, Kritskiy O, Abdurrob F, Peng Z, Milo B, Yu CJ, Elmsaouri S, Dey D, Ko T, Yankner BA, Tsai LH. APOE4 causes widespread molecular and cellular alterations associated with Alzheimer’s disease phenotypes in human iPSC-derived brain cell types. Neuron. 2018;98:1141–54.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  148. Liu CC, Zhao N, Fu Y, Wang N, Linares C, Tsai CW, Bu G. ApoE4 accelerates early seeding of amyloid pathology. Neuron. 2017;96:1024–32.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  149. Vance JE, Hayashi H. Formation and function of apolipoprotein E-containing lipoproteins in the nervous system. Biochim Biophys Acta - Mol Cell Biol Lipids. 2010;1801:806–18.

    Article  CAS  Google Scholar 

  150. Youmans KL, Tai LM, Nwabuisi-Heath E, Jungbauer L, Kanekiyo T, Gan M, Kim J, Eimer WA, Estus S, Rebeck GW, Weeber EJ, Bu GJ, Yu CJ, LaDu MJ. APOE4-specific changes in A beta accumulation in a new transgenic mouse model of Alzheimer disease. J Biol Chem. 2012;287:41774–86.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  151. Kang DE, Pietrzik CU, Baum L, Chevallier N, Merriam DE, Kounnas MZ, Wagner SL, Troncoso JC, Kawas CH, Katzman R, Koo EH. Modulation of amyloid beta-protein clearance and Alzheimer’s disease susceptibility by the LDL receptor-related protein pathway. J Clin Invest. 2000;106:1159–66.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  152. Prasad H, Rao R. The Na+/H+ exchanger NHE6 modulates endosomal pH to control processing of amyloid precursor protein in a cell culture model of Alzheimer disease. J Biol Chem. 2015;290:5311–27.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  153. Prasad H, Rao R. Amyloid clearance defect in ApoE4 astrocytes is reversed by epigenetic correction of endosomal pH. Proc Natl Acad Sci U S A. 2018;115:E6640–9.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  154. Behl T, Kaur I, Sehgal A, Kumar A, Uddin MS, Bungau S. The interplay of ABC transporters in Abeta translocation and cholesterol metabolism: implicating their roles in Alzheimer’s disease. Mol Neurobiol. 2021;58:1564–82.

    Article  CAS  PubMed  Google Scholar 

  155. Tansley GH, Burgess BL, Bryan MT, Su YA, Hirsch-Reimshagen V, Pearce J, Chan JY, Wilkinson A, Evans J, Naus KE, McIsaac S, Bromley K, Song WH, Yang HC, Wang N, DeMattos RB, Wellington CL. The cholesterol transporter ABCG1 modulates the subcellular distribution and proteolytic processing of beta-amyloid precursor protein. J Lipid Res. 2007;48:1022–34.

    Article  CAS  PubMed  Google Scholar 

  156. Ikonen E. Cellular cholesterol trafficking and compartmentalization. Nat Rev Mol Cell Biol. 2008;9:125–38.

    Article  CAS  PubMed  Google Scholar 

  157. Petrov AM, Kasimov MR, Zefirov AL. Brain cholesterol metabolism and its defects: linkage to neurodegenerative diseases and synaptic dysfunction. Acta Naturae. 2016;8:58–73.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  158. Gamba P, Testa G, Gargiulo S, Staurenghi E, Poli G, Leonarduzzi G. Oxidized cholesterol as the driving force behind the development of Alzheimer’s disease. Front Aging Neurosci. 2015;7:119.

    Article  PubMed  PubMed Central  Google Scholar 

  159. Fan J, Zhao RQ, Parro C, Zhao W, Chou HY, Robert J, Deeb TZ, Raynoschek C, Barichievy S, Engkvist O, Maresca M, Hicks R, Meuller J, Moss SJ, Brandon NJ, Wood MW, Kulic I, Wellington CL. Small molecule inducers of ABCA1 and apoE that act through indirect activation of the LXR pathway. J Lipid Res. 2018;59:830–42.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  160. Azizidoost S, Babaahmadi-Rezaei H, Nazeri Z, Cheraghzadeh M, Kheirollah A. Amyloid beta increases ABCA1 and HMGCR protein expression, and cholesterol synthesis and accumulation in mice neurons and astrocytes. Biochim Biophys Acta Mol Cell Biol Lipids. 2022;1867: 159069.

    Article  CAS  PubMed  Google Scholar 

  161. Rawat V, Wang SW, Sima J, Bar R, Liraz O, Gundimeda U, Parekh T, Chan J, Johansson JO, Tang CR, Chui HC, Harrington MG, Michaelson DM, Yassine HN. ApoE4 alters ABCA1 membrane trafficking in astrocytes. J Neurosci. 2019;39:9611–22.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  162. Ledesma MD, Brugger B, Bunning C, Wieland FT, Dotti CG. Maturation of the axonal plasma membrane requires upregulation of sphingomyelin synthesis and formation of protein-lipid complexes. EMBO J. 1999;18:1761–71.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  163. Malchiodi-Albedi F, Contrusciere V, Raggi C, Fecchi K, Rainaldi G, Paradisi S, Matteucci A, Santini MT, Sargiacomo M, Frank C, Gaudiano MC, Diociaiuti M. Lipid raft disruption protects mature neurons against amyloid oligomer toxicity. Biochim Biophys Acta. 2010;1802:406–15.

    Article  CAS  PubMed  Google Scholar 

  164. Sanchez-Melgar A, Izquierdo-Ramirez PJ, Grinan-Ferre C, Pallas M, Martin M, Albasanz JL. Neuroprotective effects of resveratrol by modifying cholesterol metabolism and Abeta processing in SAMP8 mice. Int J Mol Sci. 2022;23:7580.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  165. Xiong HQ, Callaghan D, Jones A, Walker DG, Lue LF, Beach TG, Sue LI, Woulfe J, Xu HX, Stanimirovic DB, Zhang WD. Cholesterol retention in Alzheimer’s brain is responsible for high beta- and gamma-secretase activities and A beta production. Neurobiol Dis. 2008;29:422–37.

    Article  CAS  PubMed  Google Scholar 

  166. Sparks DL. Coronary artery disease, hypertension, ApoE, and cholesterol: a link to Alzheimer’s disease? Annu N Y Acad Aci. 1997;826:128–46.

    Article  CAS  Google Scholar 

  167. Barbero-Camps E, Roca-Agujetas V, Bartolessis I, de Dios C, Fernandez-Checa JC, Mari M, Morales A, Hartmann T, Colell A. Cholesterol impairs autophagy-mediated clearance of amyloid beta while promoting its secretion. Autophagy. 2018;14:1129–54.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  168. Fernandez A, Llacuna L, Fernandez-Checa JC, Colell A. Mitochondrial cholesterol loading exacerbates amyloid beta peptide-induced inflammation and neurotoxicity. J Neurosci. 2009;29:6394–405.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  169. Ledesma MD, Abad-Rodriguez J, Galvan C, Biondi E, Navarro P, Delacourte A, Dingwall C, Dotti CG. Raft disorganization leads to reduced plasmin activity in Alzheimer’s disease brains. EMBO Rep. 2003;4:1190–6.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  170. Mason RP, Shoemaker WJ, Shajenko L, Chambers TE, Herbette LG. Evidence for changes in the Alzheimer’s disease brain cortical membrane structure mediated by cholesterol. Neurobiol Aging. 1992;3:413–9.

    Article  Google Scholar 

  171. Michal P, Rudajev V, El-Fakahany EE, Dolezal V. Membrane cholesterol content influences binding properties of muscarinic M2 receptors and differentially impacts activation of second messenger pathways. Eur J Pharmacol. 2009;606:50–60.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  172. Randakova A, Dolejsi E, Rudajev V, Zimcik P, Dolezal V, El-Fakahany EE, Jakubik J. Role of membrane cholesterol in differential sensitivity of muscarinic receptor subtypes to persistently bound xanomeline. Neuropharmacology. 2018;133:129–44.

    Article  CAS  PubMed  Google Scholar 

  173. Arbor SC, LaFontaine M, Cumbay M. Amyloid-beta Alzheimer targets—protein processing, lipid rafts, and amyloid-beta pores. Yale J Biol Med. 2016;89:5–21.

    CAS  PubMed  PubMed Central  Google Scholar 

  174. Fraering PC, Ye W, Strub JM, Dolios G, LaVoie MJ, Ostaszewski BL, van Dorsselaer A, Wang R, Selkoe DJ, Wolfe MS. Purification and characterization of the human gamma-secretase complex. Biochemistry. 2004;43:9774–89.

    Article  CAS  PubMed  Google Scholar 

  175. Chen GF, Xu TH, Yan Y, Zhou YR, Jiang Y, Melcher K, Xu HE. Amyloid beta: structure, biology and structure-based therapeutic development. Acta Pharmacol Sin. 2017;38:1205–35.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  176. Chow VW, Mattson MP, Wong PC, Gleichmann M. An overview of APP processing enzymes and products. Neuromolecular Med. 2010;12:1–12.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  177. Kienlen-Campard P, Miolet S, Tasiaux B, Octave JN. Intracellular amyloid-beta 1–42, but not extracellular soluble amyloid-beta peptides, induces neuronal apoptosis. J Biol Chem. 2002;277:15666–70.

    Article  CAS  PubMed  Google Scholar 

  178. Qi-Takahara Y, Morishima-Kawashima M, Tanimura Y, Dolios G, Hirotani N, Horikoshi Y, Kametani F, Maeda M, Saido TC, Wang R, Ihara Y. Longer forms of amyloid beta protein: Implications for the mechanism of intramembrane cleavage by gamma-secretase. J Neurosci. 2005;25:436–45.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  179. Takami M, Nagashima Y, Sano Y, Ishihara S, Morishima-Kawashima M, Funamoto S, Ihara Y. Gamma-secretase: successive tripeptide and tetrapeptide release from the transmembrane domain of beta-carboxyl terminal fragment. J Neurosci. 2009;9:13042–52.

    Article  Google Scholar 

  180. Bucciantini M, Rigacci S, Stefani M. Amyloid aggregation: role of biological membranes and the aggregate-membrane system. J Phys Chem Lett. 2014;5:517–27.

    Article  CAS  PubMed  Google Scholar 

  181. Cecchi C, Stefani M. The amyloid-cell membrane system. The interplay between the biophysical features of oligomers/fibrils and cell membrane defines amyloid toxicity. Biophys Chem. 2013;182:30–43.

    Article  CAS  PubMed  Google Scholar 

  182. Evangelisti E, Cascella R, Becatti M, Marrazza G, Dobson CM, Chiti F, Stefani M, Cecchi C. Binding affinity of amyloid oligomers to cellular membranes is a generic indicator of cellular dysfunction in protein misfolding diseases. Sci Rep. 2016;6:32721.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  183. Evangelisti E, Zampagni M, Cascella R, Becatti M, Fiorillo C, Caselli A, Bagnoli S, Nacmias B, Cecchi C. Plasma membrane injury depends on bilayer lipid composition in Alzheimer’s disease. J Alzheimers Dis. 2014;41:289–300.

    Article  CAS  PubMed  Google Scholar 

  184. Fabelo N, Martin V, Marin R, Moreno D, Ferrer I, Diaz M. Altered lipid composition in cortical lipid rafts occurs at early stages of sporadic Alzheimer’s disease and facilitates APP/BACE1 interactions. Neurobiol Aging. 2014;35:1801–12.

    Article  CAS  PubMed  Google Scholar 

  185. Tonnies E, Trushina E. Oxidative Stress, Synaptic Dysfunction, and Alzheimer’s Disease. J Alzheimers Dis. 2017;57:1105–21.

    Article  PubMed  PubMed Central  Google Scholar 

  186. Williams TL, Day IJ, Serpell LC. The effect of Alzheimer’s A beta aggregation state on the permeation of biomimetic lipid vesicles. Langmuir. 2010;26:17260–8.

    Article  CAS  PubMed  Google Scholar 

  187. Yagi-Utsumi M, Kato K. Conformational variability of amyloid-beta and the morphological diversity of its aggregates. Molecules. 2022;27:4787.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  188. Amaro M, Sachl R, Aydogan G, Mikhalyov II, Vacha R, Hof M. GM1 ganglioside inhibits beta-amyloid oligomerization induced by sphingomyelin. Angew Chem Int Ed Engl. 2016;55:9411–5.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  189. Matsubara T, Nishihara M, Yasumori H, Nakai M, Yanagisawa K, Sato T. Size and shape of amyloid fibrils induced by ganglioside nanoclusters: role of sialyl oligosaccharide in fibril formation. Langmuir. 2017;33:13874–81.

    Article  CAS  PubMed  Google Scholar 

  190. Matsuzaki K. How do membranes initiate Alzheimer’s Disease? Formation of toxic amyloid fibrils by the amyloid beta-protein on ganglioside clusters. Acc Chem Res. 2014;47:2397–404.

    Article  CAS  PubMed  Google Scholar 

  191. Rudajev V, Novotny J. The role of lipid environment in ganglioside GM1-induced amyloid beta aggregation. Membranes. 2020;10:226.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  192. Aydin D, Weyer SW, Muller UC. Functions of the APP gene family in the nervous system: insights from mouse models. Exp Brain Res. 2012;217:423–34.

    Article  CAS  PubMed  Google Scholar 

  193. Dawkins E, Small DH. Insights into the physiological function of the beta-amyloid precursor protein: beyond Alzheimer’s disease. J Neurochem. 2014;129:756–69.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  194. Stahl R, Schilling S, Soba P, Rupp C, Hartmann T, Wagner K, Merdes G, Eggert S, Kins S. Shedding of APP limits its synaptogenic activity and cell adhesion properties. Front Cell Neurosci. 2014;8:410.

    Article  PubMed  PubMed Central  Google Scholar 

  195. Coburger I, Dahms SO, Roeser D, Guhrs KH, Hortschansky P, Than ME. Analysis of the overall structure of the multi-domain amyloid precursor protein (APP). PLoS ONE. 2013;8: e81926.

    Article  PubMed  PubMed Central  Google Scholar 

  196. Lee S, Xue Y, Hu J, Wang Y, Liu X, Demeler B, Ha Y. The E2 domains of APP and APLP1 share a conserved mode of dimerization. Biochemistry. 2011;50:5453–64.

    Article  CAS  PubMed  Google Scholar 

  197. Pfundstein G, Nikonenko AG, Sytnyk V. Amyloid precursor protein (APP) and amyloid beta (A beta) interact with cell adhesion molecules: implications in Alzheimer’s disease and normal physiology. Front Cell Dev Biol. 2022;10: 969547.

    Article  PubMed  PubMed Central  Google Scholar 

  198. Wang YC, Ha Y. The X-ray structure of an antiparaliel dimer of the human amyloid precursor protein E2 domain. Mol Cell. 2004;15:343–53.

    Article  CAS  PubMed  Google Scholar 

  199. Xue Y, Lee S, Ha Y. Crystal structure of amyloid precursor-like protein 1 and heparin complex suggests a dual role of heparin in E2 dimerization. Proc Natl Acad Sci U S A. 2011;108:16229–34.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  200. Beel AJ, Mobley CK, Kim HJ, Tian F, Hadziselimovic A, Jap B, Prestegard JH, Sanders CR. Structural studies of the transmembrane C-terminal domain of the amyloid precursor protein (APP): does APP function as a cholesterol sensor? Biochemistry. 2008;47:9428–46.

    Article  CAS  PubMed  Google Scholar 

  201. Beel AJ, Sakakura M, Barrett PJ, Sanders CR. Direct binding of cholesterol to the amyloid precursor protein: an important interaction in lipid-Alzheimer’s disease relationships? Biochim Biophys Acta. 2010;1801:975–82.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  202. Nierzwicki L, Czub J. Specific binding of cholesterol to the amyloid precursor protein: structure of the complex and driving forces characterized in molecular detail. J Phys Chem Lett. 2015;6:784–90.

    Article  CAS  PubMed  Google Scholar 

  203. Pantelopulos GA, Straub JE, Thirumalai D, Sugita Y. Structure of APP-C99(1–99) and implications for role of extra-membrane domains in function and oligomerization. Biochim Biophys Acta - Biomembr. 2018;1860:1698–708.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  204. Dominguez L, Foster L, Meredith SC, Straub JE, Thirumalai D. Structural heterogeneity in transmembrane amyloid precursor protein homodimer is a consequence of environmental selection. J Am Chem Soc. 2014;136:9619–26.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  205. Dominguez L, Foster L, Straub JE, Thirumalai D. Impact of membrane lipid composition on the structure and stability of the transmembrane domain of amyloid precursor protein. Proc Natl Acad Sci U S A. 2016;113:E5281-5287.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  206. Dominguez L, Meredith SC, Straub JE, Thirumalai D. Transmembrane fragment structures of amyloid precursor protein depend on membrane surface curvature. J Am Chem Soc. 2014;136:854–7.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  207. Gotz A, Scharnagl C. Dissecting conformational changes in APP’s transmembrane domain linked to epsilon-efficiency in familial Alzheimer’s disease. PLoS ONE. 2018;13: e0200077.

    Article  PubMed  PubMed Central  Google Scholar 

  208. Itkin A, Salnikov ES, Aisenbrey C, Raya J, Glattard E, Raussens V, Ruysschaert JM, Bechinger B. Structural characterization of the amyloid precursor protein transmembrane domain and its gamma-cleavage site. ACS Omega. 2017;2:6525–34.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  209. Pester O, Barrett PJ, Hornburg D, Hornburg P, Probstle R, Widmaier S, Kutzner C, Durrbaum M, Kapurniotu A, Sanders CR, Scharnagl C, Langosch D. The backbone dynamics of the amyloid precursor protein transmembrane helix provides a rationale for the sequential cleavage mechanism of gamma-secretase. J Am Chem Soc. 2013;35:1317–29.

    Article  Google Scholar 

  210. Osenkowski P, Ye W, Wang R, Wolfe MS, Selkoe DJ. Direct and potent regulation of gamma-secretase by its lipid microenvironment. J Biol Chem. 2008;283:22529–40.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  211. Winkler E, Kamp F, Scheuring J, Ebke A, Fukumori A, Steiner H. Generation of Alzheimer disease-associated amyloid beta(42/43) peptide by gamma-secretase can be inhibited directly by modulation of membrane thickness. J Biol Chem. 2012;287:21326–34.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  212. Hitschler L, Lang T. The transmembrane domain of the amyloid precursor protein is required for antiamyloidogenic processing by alpha-secretase ADAM10. J Biol Chem. 2022;298: 101911.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  213. Nunan J, Small DH. Regulation of APP cleavage by alpha-, beta- and gamma-secretases. FEBS Lett. 2000;483:6–10.

    Article  CAS  PubMed  Google Scholar 

  214. Bolduc DM, Montagna DR, Seghers MC, Wolfe MS, Selkoe DJ. The amyloid-beta forming tripeptide cleavage mechanism of gamma-secretase. Elife. 2016;5: e17578.

    Article  PubMed  PubMed Central  Google Scholar 

  215. Jung JI, Ran Y, Cruz PE, Rosario AM, Ladd TB, Kukar TL, Koo EH, Felsenstein KM, Golde TE. Complex relationships between substrate sequence and sensitivity to alterations in gamma-secretase processivity induced by gamma-secretase modulators. Biochemistry. 2014;53:1947–57.

    Article  CAS  PubMed  Google Scholar 

  216. Matsumura N, Takami M, Okochi M, Wada-Kakuda S, Fujiwara H, Tagami S, Funamoto S, Ihara Y, Morishima-Kawashima M. gamma-Secretase associated with lipid rafts: multiple interactive pathways in the stepwise processing of beta-carboxyl-terminal fragment. J Biol Chem. 2014;289:5109–21.

    Article  CAS  PubMed  Google Scholar 

  217. Ahmed RR, Holler CJ, Webb RL, Li F, Beckett TL, Murphy MP. BACE1 and BACE2 enzymatic activities in Alzheimer’s disease. J Neurochem. 2010;112:1045–53.

    Article  CAS  PubMed  Google Scholar 

  218. Antonino M, Marmo P, Freites CL, Quassollo GE, Sanchez MF, Lorenzo A, Bignante EA. Abeta assemblies promote amyloidogenic processing of APP and intracellular accumulation of Abeta42 through Go/Gbetagamma signaling. Front Cell Dev Biol. 2022;10: 852738.

    Article  PubMed  PubMed Central  Google Scholar 

  219. Aow J, Huang TR, Thinakaran G, Koo EH. Enhanced cleavage of APP by co-expressed Bace1 alters the distribution of APP and its fragments in neuronal and non-neuronal cells. Mol Neurobiol. 2022;59:3073–90.

    Article  CAS  PubMed  Google Scholar 

  220. Haass C. Take five–BACE and the gamma-secretase quartet conduct Alzheimer’s amyloid beta-peptide generation. EMBO J. 2004;23:483–8.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  221. Haass C, Kaether C, Thinakaran G, Sisodia S. Trafficking and proteolytic processing of APP. Cold Spring Harb Perspect Med. 2012;2: a006270.

    Article  PubMed  PubMed Central  Google Scholar 

  222. Huse JT, Pijak DS, Leslie GJ, Lee VM, Doms RW. Maturation and endosomal targeting of beta-site amyloid precursor protein-cleaving enzyme. The Alzheimer’s disease beta-secretase. J Biol Chem. 2000;275:33729–37.

    Article  CAS  PubMed  Google Scholar 

  223. Kalvodova L, Kahya N, Schwille P, Ehehalt R, Verkade P, Drechsel D, Simons K. Lipids as modulators of proteolytic activity of BACE: involvement of cholesterol, glycosphingolipids, and anionic phospholipids in vitro. J Biol Chem. 2005;280:36815–23.

    Article  CAS  PubMed  Google Scholar 

  224. Park H, Hundley FV, Yu Q, Overmyer KA, Brademan DR, Serrano L, Paulo JA, Paoli JC, Swarup S, Coon JJ, Gygi SP, Harper JW. Spatial snapshots of amyloid precursor protein intramembrane processing via early endosome proteomics. Nat Commun. 2022;13:6112.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  225. Vassar R, Bennett BD, Babu-Khan S, Kahn S, Mendiaz EA, Denis P, Teplow DB, Ross S, Amarante P, Loeloff R, Luo Y, Fisher S, Fuller L, Edenson S, Lile J, Jarosinski MA, Biere AL, Curran E, Burgess T, Louis JC, Collins F, Treanor J, Rogers G, Citron M. beta-secretase cleavage of Alzheimer’s amyloid precursor protein by the transmembrane aspartic protease BACE. Science. 1999;286:735–41.

    Article  CAS  PubMed  Google Scholar 

  226. Riddell DR, Christie G, Hussain I, Dingwall C. Compartmentalization of beta-secretase (Asp2) into low-buoyant density, noncaveolar lipid rafts. Curr Biol. 2001;11:1288–93.

    Article  CAS  PubMed  Google Scholar 

  227. Ehehalt R, Keller P, Haass C, Thiele C, Simons K. Amyloidogenic processing of the Alzheimer beta-amyloid precursor protein depends on lipid rafts. J Cell Biol. 2003;160:113–23.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  228. Fourriere L, Gleeson PA. Amyloid beta production along the neuronal secretory pathway: dangerous liaisons in the Golgi? Traffic. 2021;22:319–27.

    Article  CAS  PubMed  Google Scholar 

  229. Audagnotto M, Lorkowski AK, Dal Peraro M. Recruitment of the amyloid precursor protein by gamma-secretase at the synaptic plasma membrane. Biochem Biophys Res Commun. 2018;498:334–41.

    Article  CAS  PubMed  Google Scholar 

  230. Vetrivel KS, Cheng HP, Lin W, Sakurai T, Li T, Nukina N, Wong PC, Xu HX, Thinakaran G. Association of gamma-secretase with lipid rafts in post-golgi and endosome membranes. J Biol Chem. 2004;279:44945–54.

    Article  CAS  PubMed  Google Scholar 

  231. Runz H, Rietdorf J, Tomic I, de Bernard M, Beyreuther K, Pepperkok R, Hartmann T. Inhibition of intracellular cholesterol transport alters presenilin localization and amyloid precursor protein processing in neuronal cells. J Neurosci. 2002;22:1679–89.

    Article  CAS  PubMed  PubMed Central