FIGURE 3.
Various forms of EV fusion with target cells. The different size of the EVs illustrates the parallel processes of ectosomes and exosomes. (A) shows vesicles inducing only signaling upon binding to receptors. In (B) the fusion of single vesicles followed by the integration of the membrane the plasma membrane (PM), induces release of cargo to the cytoplasm. In (C) the EVs, bound to receptors such as those in (A), are internalized in an endosomal cisterna, and the same occurs in (D) for EV groups internalized by phagocytosis or macro-pinocytosis. Upon internalization, the EVs of (C,D) are accumulated within pseudo multi-vesicular bodies (pMVB). Elimination of these structures by ectosomal block and possible fusion with lysosomes do not appear in this Figure. Alternatively, the EV membranes fuse with endosome membrane and the cargos are released in the depth of the cytoplasm. The possible integration of molecules from fused EVs with molecules generated locally to participate in a new generation of EVs is suggested by the word Recycling. Figure reproduced with permission from Meldolesi (2018).