Heparan sulfate proteoglycans function in the binding and degradation of vitronectin by fibroblast monolayers
Abstract
Vitronectin, a 75-kDa plasma protein is also found in the extracellular matrix, where it is believed to promote cell adhesion and migration. In addition to its role in adhesion, matrix vitronectin is also believed to function as an opsonin promoting the clearance of thrombin-serpin complexes from the matrix. Vitronectin is cleared from the matrix by receptor-mediated endocytosis followed by lysosomal degradation, suggesting that cells can regulate the levels of vitronectin present in the matrix. However, the mechanism by which plasma vitronectin associates with the extracellular matrix remains unclear. Studies were conducted to define the binding site(s) for vitronectin in fibroblast cell layers. Sodium chlorate, a competitive inhibitor of proteoglycan sulfation, produced a dose-dependent decrease in both binding and degradation of vitronectin. This inhibition was reversible in that removal of chlorate returned both binding and degradation of vitronectin to near control levels within 24 h. The binding of vitronectin to cell layers was not dependent on cells because vitronectin bound directly to isolated matrix. Isolated matrices prepared from cell layers treated with sodium chlorate also exhibited a dose-dependent decrease in v...Continue Reading
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