Abstract
Localization of secreted matrix metalloproteinases (MMPs) on the cell surface is required not only for processing of cell surface proteins, but also for controlled degradation of the extracellular matrix (ECM). Our previous study demonstrated that binding of MMP-7 (matrilysin) to cell surface cholesterol sulfate (CS) is essential for the cell membrane-associated proteolytic action of this MMP. In this study, we investigated the role of CS in the MMP-7-catalyzed degradation of protein components of ECM. We found that the degradation of laminin-332 (laminin-5) catalyzed by MMP-7 was accelerated dramatically in the presence of CS, whereas the sulfated lipid inhibited the degradation of casein catalyzed by the protease. The MMP-7-catalyzed degradation of fibronectin was partially inhibited in the presence of low concentrations of CS, whereas it was accelerated significantly at high concentrations of the lipid. Therefore, it is likely that CS alters the substrate preference of MMP-7. We also found that the proteins of which MMP-7-catalyzed degradation were accelerated by CS also had affinities for CS, suggesting that CS facilitates the proteolyses by cross-linking MMP-7 to its substrates. Moreover, MMP-7 tethered to cancer cell surface via CS degraded fibronectin and laminin-332 coated on a culture plate. The degradations of the adhesive proteins led to significant detachment of the cells from the plate. Taken together, our findings provide a novel mechanism in which cell surface CS promotes the proteolytic activities of MMP-7 toward selective substrates in the pericellular ECM, thereby contributing to cancer cell migration and metastasis.
Highlights
Such as morphogenesis, angiogenesis, tissue repair, and tumor invasion [1,2,3,4]
When FN was incubated with matrix metalloproteinases (MMPs)-7 alone, 190- and 150-kDa fragments appeared as the major products, whereas these fragments only transiently appeared, and instead, a 110-kDa fragment appeared when FN was incubated with MMP-7 in the presence of 500 M cholesterol sulfate (CS)
We examined the effects of CS on the catalytic activities of MMP-7 toward protein substrates and found that CS dramatically accelerated MMP-7-catalyzed degradation of Lm332, whereas the lipid inhibited the degradation of casein catalyzed by the MMP
Summary
Such as morphogenesis, angiogenesis, tissue repair, and tumor invasion [1,2,3,4]. It has been suggested that several MMPs proteolytically modulate the biological functions of various cell surface proteins, including growth factor precursors, growth factor receptors, and cell adhesion molecules [4]; such regulation as well as MMP-catalyzed degradation of ECM is important for tumor growth, invasion, metastasis, and progression [5, 6]. To examine the effect of CS on the proteolytic activity of MMP-7, FN, -casein, and Lm332 were incubated with MMP-7 in the presence of various concentrations of CS, and degradation of these proteins was analyzed by SDS-PAGE.
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