Fig. 1

Exosome biogenesis and internalization mechanisms. Exosomes are surrounded by a phospholipid bilayer comprising various cell surface proteins (including tetraspanins, flotillins, integrins and transmembrane proteins) that mediate the orientation and connection of exosomes. Exosomes carry various biological species, including intracellular proteins, nucleic acids (including DNA and RNA) lipids and metabolites, and regulate the function of target cells by releasing their cargo. Exosome biogenesis begins from the double invagination of the plasma membrane, forming an early endosome and subsequently mature to late endosome. Then, multivesicular bodies (MVBs) form, which contain intraluminal vesicles (ILVs). MVBs can be fated for lysosomal degradation or fusion with the plasma membrane as exocytic vesicle to release exosomes. Exosomes have mainly three ways to communicate with cells: (1) interact with protein or receptor on the membrane, (2) exosome membrane fuses with the cell membrane, and the contents of the exosome are directly delivered into the target cell, and (3) exosomes enter cells through phagocytosis or endocytosis