The enzymes in the family of matrix metalloproteinases (MMPs) are important to regular tissue maintenance by their collective capacity to degrade major tissue molecules and activating growth factors. The MMPs contribute hereby beneficially to normal development and tissue adaptation. Nevertheless, certain MMPs, including MMP-2, have been found at elevated levels and may abnormally degrade tissues in several diseases, such as periodontal disease, arthritis, and cancer. Recent studies by ourselves and other investigators have shown that the major cell adhesion molecule fibronectin is degraded in those diseases and that MMP-2 can efficiently cleave fibronectin. This degradation requires specific binding between fibronectin and a unique subdomain of MMP-2. Since the behavior of cells changes upon exposure to the fibronectin cleavage fragments, such fragments may alter the disease progression. Therefore, understanding the precise mechanism of binding between the two proteins may provide the basis for developing inhibitors that can block MMP-2 degradation of fibronectin. In a collaborative effort that involves investigators from different disciplines and institutions, we will apply molecular biology, biochemical, mass spectrometry, and protein engineering methods to define the precise binding sites for fibronectin and MMP-2. Based on results gained from screening of phage-displayed random peptide libraries, we will design synthetic peptides, which mimic the binding sites, and test their capacity to block both MMP-2 binding and degradation of fibronectin. Introduction of site-specific mutations in binding domains will confirm the binding sites. After precisely mapping the fibronectin cleavage sites and fragments, we will characterize altered periodontal and cancer cell behavior by multiple parameters, MMP expression, and apoptosis in response to contact with a series of recombinant fibronectin cleavage fragments. We will then test the capacity of the inhibitory peptides to rescue cell functions. This experimental strategy should define the specific binding sites for the interactions between MMP-2 and fibronectin and pursues a novel strategy to inhibit degradation of specific molecules by individual MMPs, such as cleavage of fibronectin by MMP-2. Successful inhibition of fibronectin fragmentation could be of significant benefit for the management of both periodontal disease and oral cancer.
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