Figure 6.

Schematic representation showing the negative and positive impact of CD9 Fab and CD9 Ab, respectively, on the endocytosis of CD9‐containing extracellular vesicles (EVs). (A, B) CD9 Fab will saturate CD9 proteins present at the surface of cells and EVs, hence interfere with its CD9 function. CD9 Fab can impede the cis/trans‐dimerization of CD9, its oligomerization and/or its interaction with other protein partners and block EV endocytosis (red bar). In contrast, divalent CD9 Ab could cross‐link CD9 proteins associated with host cells and EVs and consequently stimulate the endocytosis on EVs (green arrow). In the latter case, cis‐dimerization/oligomerization of CD9 might organize the components (proteins and lipids) of plasma membrane and/or EV membrane into a specific tetraspanin web (green segment), whose constituents, notably potential adhesion proteins as illustrated would somehow regulate the cell‐EV interaction and promote the endocytosis of EVs