DISINTEGRIN INTERACTION WITH ALPHA(V)BETA(3) INTEGRIN ON HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS - EXPRESSION OF LIGAND-INDUCED BINDING-SITEON BETA(3) SUBUNIT

The effect of seven disintegrins (albolabrin, barbourin, bitistatin, e chistatin, eristostatin, flavoridin, and kistrin) and the neurotoxin a nalogue, mambin, on the adhesion of human umbilical vein endothelial c ells (HUVEC) to immobilized vitronectin and fibronectin has been studi ed. Adhesion to vitronectin was significantly inhibited by echistatin, kistrin, flavoridin, and mambin. Echistatin, flavoridin, and kistrin bound with high affinity to immobilized alpha(v) beta(3) in solid phas e assay; other disintegrins bound at a much lower level. Echistatin an d flavoridin had a modest inhibitory effect on HUVEC adhesion to fibro nectin. HUVEC adhered to disintegrins with a high selectivity toward b itistatin, echistatin, flavoridin, kistrin, and mambin. Adhesion of HU VEC to fibronectin and vitronectin resulted in cell spreading, whereas cells adhering to immobilized echistatin remained globular and cells adhering to kistrin showed abnormal morphology. Echistatin and kistrin potently inhibited the binding of monoclonal antibody (Mab) 7E3, whic h recognizes the alpha(v) beta(3) complex, to HUVEC. Echistatin and ki strin also induced the binding to HUVEC of Mab 62, which recognizes th e ligand-induced binding site (LIBS) epitope on the beta(3) subunit, e nhancing HUVEC binding to immobilized Mab 62. Similar results with bot h antibodies were obtained in Chinese hamster ovary cells transfected with alpha(v) beta(3) genes. In conclusion, disintegrin interaction wi th HUVEC appears to be selectively mediated by a;Ps receptors, and it results in an expression of LIBS epitope that may play a role in the r egulation of ligand-binding affinity and intracellular signaling. (C) 1996 Academic Press, Inc.