Fig. 1

Oligomeric amyloid-β (Aβ) downregulated expression and structure of MHC-I–β₂M complex. A Immunoblot analyses of MHC-I expression levels in Aβ oligomer (oAβ)-treated SH-SY5Y cells (left) The total MHC-I levels were normalized to those of GAPDH (B; n = 4, one-way ANOVA with Tukey’s post-hoc comparisons test) (right). B MHC-I mRNA levels in oAβ-treated SH-SY5Y cells (n = 4, one-way ANOVA with Tukey’s post-hoc comparisons test). C Surface MHC-I was labeled with the W6/32 antibody, analyzed by flow cytometry (n = 4, one-way ANOVA with Tukey’s post-hoc comparisons test). Representative histogram (left) and quantification of fluorescence intensity (right) of surface MHC-I–β₂M complex. D–H Schematic representations of the structural changes in MHC-I–β₂M complex detectable by different antibodies (W6/32 and HC10) and the release of surface β₂M by oAβ-treated SH-SY5Y cells (D). Immunoprecipitation analysis of Aβ-induced structural changes in surface MHC-I–β₂M complex (E; n = 4). The levels of surface MHC-I–β₂M complex (F) and surface-free MHC-I (G) were normalized to total surface MHC-I levels. The levels of released β₂M were normalized to those of total β₂M (H). The data were analyzed by unpaired two-tailed Student’s t-test (F–H). (I, J) Immunoblot analyses of MHC-I levels in oAβ-treated SH-SY5Y cells in the presence or absence of the proteolytic inhibitors lactacystin (LC) and bafilomycin A1 (BFA1); n = 4 (I), or the endocytosis inhibitors chlorpromazine (CPZ) and methyl-β-cyclodextrin (MβCD); n = 4 (J). Total MHC-I levels were normalized to the levels of actin. The data were analyzed by one-way ANOVA with Tukey’s post-hoc comparisons test (I, J). The data are presented as the mean ± SEM (N.S, not significant; *P < 0.05, **P < 0.001, ***P < 0.005)