Increasing evidence suggests a critical implication of membrane-associated protease activities in numerous biological processes. ADAM (A Disintegrin and Metalloprotease) proteases, and especially ADAM10, are of particular interest because of the importance of their substrates (EGF receptor, TNF α, Notch, APP…). However, few studies focus on the mechanisms of ADAM10 trafficking. Tetraspanins are a super-family of proteins implicated in numerous biological processes including migration, intercellular interactions, immune response, gamete fusion… One of the most striking features of tetraspanins is their ability to organise multi-molecular complexes called « Tetraspanin Web ». Previous studies in the laboratory have shown that ADAM10 is associated to the « Tetraspanin Web ». Nevertheless, the tetraspanin in direct interaction with ADAM10 that drives its association to the web is not known. In this study, we focused on ADAM10 regulation by tetraspanins. We identified a subfamily of tetraspanins with 8 cysteines in their large extracellular domain that we called TspanC8 (Tspan5, Tspan10, Tspan14, Tspan15, Tspan17 and Tspan33) that can directly interact with ADAM10 and regulate its egress from the endoplasmic reticulum. We have shown that Tspan5, Tspan14, Tspan15 and Tspan33 regulate the surface expression of ADAM10 and that Tspan10 and Tspan17 accumulate ADAM10 in a late endosomal compartment. TspanC8 could also contribute to substrate specificity since Tspan5 and Tspan14 can increase Notch activation when Tspan15 cannot. Drosophila TspanC8 directly interact with the Drosophila ADAM10 ortholog Kuzbanian, increase its accumulation at the cell surface and modulate Notch activation in several developmental contexts. We propose that TspanC8 constitute a new family of Notch regulators with conserved functions in the regulation of ADAM10 trafficking and activity.
