Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a transmembrane proteinase with an extracellular proteolytic domain and a short cytoplasmic tail. The proteolytic activity of MT1-MMP is inhibited physiologically by tissue inhibitor of matrix metalloproteinase-2 (TIMP-2). TIMP-2 binds to MT1-MMP and the complex is internalized by endocytosis mediated by the cytoplasmic tail of the proteinase. Our extensive preliminary work has shown that binding of TIMP-2 to MT1-MMP rapidly induces ERK1/2 MAP kinase activation, which upregulates cell proliferation and migration. These effects require the cytoplasmic tail but not the proteolytic activity of MT1 -MMP. ? ? We therefore propose to: ? 1. Determine the physiologic significance of ERK1/2 activation generated by TIMP-2 binding to MT1-MMP. For this purpose, wild-type and MT1-MMP knockout mouse embryonic fibroblasts will be used to determine if this signaling mechanism and its resulting biological effects are active in stromal cells expressing physiologic amounts of MT1 -MMP and dependent on the cytoplasmic tail but not the proteolytic activity of the proteinase. ? ? 2. Investigate the molecular mechanism of intracellular signaling by MT1-MMP. We propose to identify proteins that interact with the cytoplasmic tail of MT1-MMP upon TIMP-2 addition, and to characterize the role of endocytosis of the TIMP-2-MT1-MMP complex in the control of MT1-MMP-mediated intracellular signaling. ? ? The results of the proposed research project will elucidate novel mechanisms through which interactions among cell surface proteins generate intracellular signaling that has important roles in the regulation of numerous cell functions. A detailed understanding of these mechanisms can therefore have relevant implications for our comprehension of a variety of physiological and pathological processes, and for the development of pharmacological tools aimed to control them. ? ? ?
