Locating the active site for angiogenesis and cell proliferation due to fibrin fragment E with a phage epitope display library.

The plasmin-mediated lysis of fibrin present in a wound, or in chronic inflammatory disease, results in the release of fibrin degradation products. One of the two major products is fibrin fragment E, which has been shown to stimulate cell proliferation in many cell types including endothelium, fibroblasts, and smooth muscle cells, and to be angiogenic in the chick chorioallantoic membrane (CAM) system. The activity of fibrin fragment E is dependent on N-terminus thrombin action. Antibodies against fibrin E, which block the cell proliferative activity, were used to locate the active site. Phage epitope display libraries were used to identify the sequence of a peptide, which resembles a region of the N terminus structure. The equivalent synthetic peptide (WTM110) has optimal stimulatory properties at equimolar concentrations to the parent molecule. Such peptide information has therapeutic potential for both stimulating and suppressing angiogenesis and cell proliferation.