GPCRs and heterotrimeric G proteins directly regulate membrane type‐1 matrix metalloprotease (1066.6)

Abstract

Matrix metalloproteases (MMPs) mediate the transactivation of epidermal growth factor receptor (EGFR)‐dependent signaling pathways upon stimulation of GPCRs, but mechanisms of GPCR‐stimulated EGFR transactivation are poorly understood. A direct, membrane‐delimited mechanism has not previously been investigated. Several MMPs localize to the plasma membrane, including membrane type‐1 matrix metalloprotease (MT1‐MMP, also known as MMP14). We hypothesized that heterotrimeric G proteins directly activate MT1‐MMP, initiating transactivation of EGFRs via release of heparin‐binding EGF (HB‐EGF). We found that MT1‐MMP is activated by GPCR agonists, GTP, or GTPγS in a concentration and time‐dependent manner in both fibroblast and cardiac myocyte membranes. MT1‐MMP activation does not occur with GMP or ATPγS and is not blunted by Src, PKC or PLC inhibitors. This activation is specific to MT1‐MMP, as shown using siRNA knockdown and a highly selective MT1‐MMP peptide inhibitor, and results in release of HB‐EGF and activation of EGFR. We found a role for G protein βγ subunits, based on use of the selective βγ inhibitor, gallein. MT1‐MMP is thus a previously unrecognized direct GPCR/G protein membrane effector that can produce EGFR transactivation. Further understanding of these mechanisms may define roles for this membrane‐delimited signaling module in pathophysiology and as a therapeutic target.