Enzyme Catalysis and Regulation
Selective Modulation of Matrix Metalloproteinase 9 (MMP-9) Functions via Exosite Inhibition*

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Unregulated activities of the matrix metalloproteinase (MMP) family have been implicated in primary and metastatic tumor growth, angiogenesis, and pathological degradation of extracellular matrix components, such as collagen and laminin. However, clinical trials with small molecule MMP inhibitors have been largely unsuccessful, with a lack of selectivity considered particularly problematic. Enhanced selectivity could be achieved by taking advantage of differences in substrate secondary binding sites (exosites) within the MMP family. In this study, triple-helical substrates and triple-helical transition state analog inhibitors have been utilized to dissect the roles of potential exosites in MMP-9 collagenolytic behavior. Substrate and inhibitor sequences were based on either the α1(V)436–450 collagen region, which is hydrolyzed at the Gly ↓ Val bond selectively by MMP-2 and MMP-9, or the Gly ↓ Leu cleavage site within the consensus interstitial collagen sequence α1(I–III)769–783, which is hydrolyzed by MMP-1, MMP-2, MMP-8, MMP-9, MMP-13, and MT1-MMP. Exosites within the MMP-9 fibronectin II inserts were found to be critical for interactions with type V collagen model substrates and inhibitors and to participate in interactions with an interstitial (types I–III) collagen model inhibitor. A triple-helical peptide incorporating a fibronectin II insert-binding sequence was constructed and found to selectively inhibit MMP-9 type V collagen-based activities compared with interstitial collagen-based activities. This represents the first example of differential inhibition of collagenolytic activities and was achieved via an exosite-binding triple-helical peptide.

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This work was supported, in whole or in part, by National Institutes of Health Grant CA 98799 (to G. B. F. and R. P. H.). This work was also supported by a Glenn/American Federation for Aging Research Scholarship (to J. L. L.-F.), an ASBMB travel award (to J. L. L.-F.), and National Science Foundation IGERT Fellowship CHE-9987603 (to J. K. W.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.