Fig. 2

Exosome structure and composition. Exosomes are enriched with lipid rafts, nucleic acids, and proteins. The latter include adhesion molecules, tetraspanins (e.g., CD9, CD63, CD81, and CD82), proteins responsible for membrane transport and fusion (e.g., annexin and Rab GTPase), proteins involved in MVB biogenesis (e.g., Alix and Tsg101), heat shock proteins (e.g., Hsp70 and Hsp90), and cytoskeletal proteins (e.g., actin and tubulin). MHC class I and class II proteins may also be found in exosomes. Alix apoptosis-linked gene-2 interacting protein X, DNA deoxyribonucleic acid, Hsp heat shock protein, MHC major histocompatibility complex, miRNA microRNA, mRNA messenger RNA, MVB multivesicular body, Tsg101 tumor susceptibility gene 101