Fig. 1

The basic structure and composition of exosomes. Exosomes have a typical lipid bilayer that protects and transfers exosomal bioactive molecules including proteins, lipids and nucleic acids. Exosomes from cells of different types have common proteins that can be used as cell surface markers such as annexins, flotillins, clathrin, Alix, TSG101, integrin and tetraspanins (CD63, CD9, CD81 and CD82). However, exosomes from specific sources have their own special markers, such as MHC-I/II on the surface of exosomes derived from dendritic cells, PD-L1 on the surface of cancer cell-derived exosomes, and adiponectin on the surface of adipocyte-derived exosomes. In addition, specific exosomes secreted by different cells also have their own specific compositions. In general, the proteins in exosomes can be divided into five categories, including signaling proteins (EGFR, HIF-1α, CDC42, PI3K, ARF1, β-Catenin), enzymes (GAPDH, PK, ATPase, PGK, Enolase), cytoskeletal proteins (Actin, Tubulin, Cofilin, profiling, Myosin, Vinmentin, Fibronectin, Meosin, Keratins, Talin), chaperones (HSP70, HSP90, HSP60, HSC70) and MVB making proteins(Alix, Tsg101, Clatherin, ubiquitin). Moreover, exosomes also carry many nucleic acids, including RNA and DNA