Fig. 1

The biogenesis and contents of exosomes. The inward budding of the plasma membrane leads to the formation of early endosomes with membrane proteins incorporated. Then the invagination of endosomes and the enclosing of selected cargos including nucleic acids and proteins results in the generation of multivesicular bodies (MVBs), through either ESCRT-dependent or ESCRT-independent mechanisms. Subsequently, these MVBs fuse with plasma membrane and release exosomes into extracellular place. Exosomes release these cargos (proteins, mRNAs, miRNAs, lncRNAs, circRNAs and DNAs) to the recipient cells via mechanisms including a) direct fusion, b) binding with surface proteins, and c) endocytosis