Fig. 2

Formation of exosomes inside cell. Exosomes are nano-sized vesicles generated from endocytic pathway [5]. They are formed from inward budding of the membrane of multivesicular bodies (MVBs), late endosomes of endocytic pathway, through ESCRT-dependent machinery which involves assortment of ubiquitinated cargo. In addition, different proteins and lipids including CD63 and ceramides mediate exosome biogenesis which known as ESCRT-independent machinery [5, 38]. MVB’s cargo is provided with different sorting molecules located on MVB’s membrane, cytoplasm, and Golgi apparatus. Different Rab-GTPases such as Rab7, Rab11, Rab27, and Rap35 preferentially mediate intracellular trafficking of MVBs. MBVs may back fuse to the plasma membrane and recycle biomolecules to the plasma membrane or present specific biomolecules (such as major histocompatibility complex (MHC) proteins) (1). SNARE and Rab-GTPase (Rab11, Rab27, and Rab35) proteins facilitate the fusion of MVBs with the plasma membrane in order to release exosomes into extracellular environment (2). In degradation pathway, MVBs can fuse with lysosomes for hydrolyzing their cargo (3). EE, early endosome; ER, endoplasmic reticulum; GA, Golgi apparatus; N, nucleus