Potential role of entactin in hemostasis. Specific interaction of entactin with fibrinogen A alpha and B beta chains.

The interactions between the endothelial basement membrane, platelets, and coagulation factors play essential roles in hemostasis. Entactin is an integral and ubiquitous component of the basement membrane. Experiments were designed to study the interactions between entactin and blood coagulation factors. We have demonstrated, for the first time, that entactin interacts with fibrinogen in a specific manner. Entactin binding sites have been localized to the A alpha and B beta chains of fibrinogen. The binding of entactin to either the A alpha chain or the B beta chain was divalent cation-independent. The binding of 35S-labeled entactin to the immobilized fibrinogen A alpha or B beta chain was concentration-dependent and saturable and could be inhibited by unlabeled entactin, soluble fibrinogen, anti-entactin antiserum, or anti-fibrinogen antiserum. In addition, we have provided evidence that entactin can be cross-linked to itself, and probably also to fibrin(ogen), by transglutaminase. These novel properties, together with its cell binding, chemotactic, and phagocytic promoting activities and ubiquitous distribution in basement membranes, suggest that entactin may play important roles in hemostasis and wound healing.