Exosomes as Emerging Regulators of Immune Responses in Type 2 Diabetes Mellitus

Figure 1

The biogenesis of exosomes and microvesicles. Microvesicles are formed through direct budding from the plasma membrane, while exosomes originate from the endosomal system. The biogenesis of exosomes begins with formation of early-sorting endosomes through endocytosis and plasma membrane invagination. During this process, extracellular materials can enter the endosomes along with cell-surface proteins. These early endosomes mature into late-sorting endosome, which generate intraluminal vesicles (ILVs) by budding inward from the endosomal membrane. These ILVs are the future exosomes. Late-sorting endosomes develop into multivesicular bodies (MVBs) with the accumulation of ILVs. MVBs can be transported to the plasma membrane and release exosomes by exocytosis. Alternatively, MVBs can fuse with autophagosomes or lysosomes and participate in the degradation pathway. The exosomal membrane maintains the same topological orientation as the plasma membrane because of the double invagination process. Exosomes can be taken up by recipient cells through various mechanisms, including endocytosis, receptor-ligand interaction, and direct fusion with the recipient cell membrane.