Vitronectin in the substratum of endothelial cells is cross-linked and phosphorylated.

Vitronectin (VN), previously shown to be a substrate for purified transglutaminases, was demonstrated in this study to be cross-linked when incubated with HUVEC and EAhy926 cells. The cross-linking was calcium-dependent and required that VN be plated at the substratum of the cells. These cells also phosphorylated VN, but in contrast to a previous study demonstrating a cAMP-dependent protein kinase in platelets, the phosphorylation of VN by was decreased with the addition of 1mM cAMP. The cross-linking of VN by endothelial cells demonstrates that the adhesion of these cells to VN is a dynamic process in which the substratum may be enzymatically altered. Furthermore, the modifications of VN by cross-linking and phosphorylation could modulate the functions of VN and influence events such as endothelial cell proliferation and angiogenesis.