Fig. 1

The biogenesis of the extracellular vesicle and its structure. a EVs can be divided into three subtypes: exosomes, microvesicles and apoptotic bodies. Exosomes are formed as ILVs in the MVBs. This process requires the involvement of ESCRT components, and it also occurs in ESCRT-independent pathways, including syntenin-, lipids- and tetraspanin-dependent mechanisms and others. After ILVs formation, MVBs are transported to the plasma membrane or the lysosome, which primarily involves some Rab proteins. Finally, MVBs fuse with the plasma membrane with the involvement of SNARE complex, and exosomes are released. Microvesicles are released directly after the outward budding from the plasma membrane, which primarily involves the ESCRT, ARRDC1, lipids, Rho proteins and Ca²⁺. Apoptotic bodies only generate from apoptotic cells and shed from the cell surface. Enveloped viruses that highjack the membranes for release can also be considered as a kind of EV. b The extracellular vesicle is made up of lipid bilayers and enriched in proteins, nucleic acids and lipids