RhoA inhibition activates MMP‐2 via a PI3K dependent mechanism.

Abstract

Basement membrane and interstitial matrix proteolysis are critical early steps in the angiogenic process, and require matrix metalloproteinase (MMP) activation. Skeletal muscle endothelial cells cultured as a monolayer on type I collagen exhibit high levels of stress fibre polymerization and low levels of MMP activity, indicative of a quiescent state. Depolymerization of stress fibres by RhoA inhibition with 10 μM H1152, an inhibitor of Rho kinase, increased cortical actin and MMP-2 activation. We investigated the effect of RhoA inhibition on the localization of membrane type-1 (MT1)-MMP, the activator of MMP-2, and found that H1152 treatment increased cell surface MT1-MMP and caused MT1-MMP localization to areas of strong cortical actin staining. Cortical actin polymerization is hypothesized to involve PI3K and we found that phospho-AKT levels increased as early as 30 min post H1152 exposure and remained elevated for more than 2 hrs. Pretreatment with 10 μM LY294009, an inhibitor of PI3K, abolished the increase in active MMP-2 observed with H1152 treatment alone. These results indicate that inhibition of RhoA, through a PI3K dependent mechanism, increases cell surface MT1-MMP and localizes it to areas of cortical actin polymerization, which facilitates activation of MMP-2. Funded by NSERC.