Fig. 1

The formation and regulatory mechanism of exosomes. Exosome biogenesis initiates from the formation of EEs, which derive from the TGN and internalization of membrane microdomains. Then, EEs move into MVBs. During the inward budding of EEs into MVBs, vesicles load different cargoes and form ILVs. In this procedure, the loading of small plasma that contains nearly 100 proteins and 10000 nucleotides with proteins, coding and non-coding RNA, and DNA is a non-random process. Ras-related proteins regulate MVB movement towards cell membrane. MVBs fuse with the plasma membrane, and ILVs released to extracellular space are called exosomes. Exosomes received by recipient cells can be regarded as signalosomes for several biological processes. They can transfer both major histocompatibility complex (MHC) molecule and antigen, thereby involved in antigen presentation and immune regulation. Exosomes can also directly bind cell surface receptors and activate associated pathways. Additionally, exosomes can convey effectors including transcription factors, oncogenes, and infectious particles into recipient cells. Meanwhile, various nucleic acids are contained in extracellular vesicles and can be functionally delivered into recipient cells