This application seeks to assess a new mechanism for aging-related alterations in cell and tissue function. The proposed studies will determine if our recent discovery and preliminary data regarding a previously unrecognized mechanism for signal transduction---direct, membrane-delimited activation of matrix metalloproteinase 14 (MMP14, also known as MMT1-MMP [membrane type-1 matrix metalloproteinase] by GTP and GTP?S acting via heterotrimeric (???) GTP binding (G) proteins?contribute to such alterations, in particular in cardiac cells and the heart. We find that GTP-promoted activation of MMP14 releases (?sheds?) proteins from the membrane, including heparin binding epidermal growth factor (HB-EGF) and leads to activation of EGF receptors, thus identifying a new mechanism by which G-protein coupled receptor (GPCR)/heterotrimeric G-proteins transactivate receptor tyrosine kinases. Our preliminary data indicate that MMP14 activity and its activation by GTP?S is increased in cardiac cell membranes from aged mice. We propose that this increase in MMP14 activity is a consequence of age-related alterations in the plasma membrane, in particular a loss in caveolin proteins, which scaffold signaling molecules.
The Aims of the studies proposed in this R21 application are to: 1) Define the heterotrimeric G-protein subunit(s) that activate MMP14, the mechanism of its activation by the G-proteins, and of the aging-related increase in MMP14 activity through co-localization with caveolins and loss of caveolin- mediated inhibition of MMP14 and 2) Determine the ability of MMP14 activation by G-proteins to release membrane proteins and activate extracellular proteins, (e.g., soluble MMPs) and to assess the role of MMP14 in aging-related loss in cardiac cell function, including in isolated hearts. Our working hypothesis, which the proposed studies will test, is that MMP14 is part of a GPCR/G-protein/MMP14/MMP14 targets signaling module that is altered in aging as a consequence of aging-related changes in membrane structure. Our preliminary data provide evidence in support of this idea. We believe that those data and our past efforts related to G-protein- mediated signaling and combined efforts of those involved in this project will facilitate success in the proposed studies. In addition, we believe that the results will provide novel information of relevance to biochemical and physiological changes that occur in aging as well as results of interest to multiple disciplines (biochemistry, cell biology, physiology/pathophysiology and pharmacology). Moreover, the findings may also be relevant to other tissues and cell types besides the cardiovascular cells that we will study in the proposed experiments and may identify new targets for the prevention and/or treatment of aging-related disorders.
This proposal will test the hypothesis a membrane on the cell surface, matrix metalloproteinase 14 (MMP14), is regulated by particular proteins within the membrane and that changes in this regulation and MMP14 result in it having increased activity in aging, thereby contributing to altered age-related function of cell in the heart. The studies will examine how MMP14 is regulated and its activity increases in in aging as well as the impact of such an increase on heart muscle cells and collagen-producing cells (fibroblasts) of young and old mice.
| Sriram, Krishna; Insel, Paul A (2018) G Protein-Coupled Receptors as Targets for Approved Drugs: How Many Targets and How Many Drugs? Mol Pharmacol 93:251-258 |
| Busija, Anna R; Patel, Hemal H; Insel, Paul A (2017) Caveolins and cavins in the trafficking, maturation, and degradation of caveolae: implications for cell physiology. Am J Physiol Cell Physiol 312:C459-C477 |
