Fig. 1

The process of exosome synthesis. EVs contain a lipid bilayer membrane and two subgroups: ectosomes and exosomes. Ectosomes (diameter: 50 nm to 1 m) are vesicles that pinch off the plasma membrane surface by outward budding. Exosomes are endosome-derived EVs ranging in size from 40 to 160 nm. The formation of exosomes occurs in three steps. (1) The first stage is endocytosis of the cytoplasmic membrane to form early sorting endosomes (ESE). At this stage, material on the cell membrane or around the cell is encapsulated into the ESE. (2) In the second stage, the ESE progressively evolves to the LSE. Furthermore, endosomal limiting membrane endocytosis results in the formation of multivesicular bodies (MVBs) containing several intraluminal vesicles (ILVs). (3) The third step involves the destruction of a portion of the MVB by lysosomes or autophagosomes and the fusing of the remaining MVB with the cell's plasma membrane to release the exosomes