ADAM15 suppresses cell motility by driving integrin α5β1 cell surface expression via Erk inactivation

Abstract

Human ADAM15 is unique among the A disintegrin and metalloprotease domain (ADAM) family because of the integrin binding motif Arg–Gly–Asp (RGD) within its disintegrin domain. Integrin α5β1 has been reported to bind to ADAM15 in an RGD-dependent manner, but the biological significance of the interaction between ADAM15 and α5β1 is unknown. To characterize the effects of ADAM15 on α5β1-mediated cell adhesion and migration and elucidate the potential mechanism, CHO cells which express endogenous integrin α5β1 were transfected with human ADAM15 cDNA. ADAM15 overexpression led to enhanced cell adhesion and decreased migration on fibronectin, which were suppressed by down-regulation of integrin α5. Overexpression of ADAM15 not only increased the cell surface expression of integrin α5 but also resulted in a more clustered staining of α5 on cell surface, while the β1 subunit remained unchanged. Unexpectedly, results from immunoprecipitation and immunofluorescence indicated that ADAM15 and α5β1 integrin did not interact directly in CHO cells. We found that ADAM15 expression decreased the phosphorylation of Erk1/2. Consistently, down-regulation of Erk1/2 phosphorylation by MEK inhibitor PD98059 or siRNA against Erk1/2 enhanced the expression of α5 on cell surface. By using a B16F10 pulmonary metastasis model, we revealed that overexpression of ADAM15 significantly reduced the number of metastatic nodules on the lung. Taken together, this study reveals for the first time that ADAM15 could drive α5 integrin expression on cell surface via down-regulation of phosphorylated Erk1/2. This presents a novel mechanism by which ADAM15 regulates cell-matrix adhesion and migration.