Contortrostatin, a homodimeric disintegrin, binds to integrin alpha v beta5

Contortrostatin is a homodimeric disintegrin from snake venom. We have show n that contortrostatin binds to integrins alpha IIb beta 3, alpha 5 beta 1, and alpha v beta 3. We now use several criteria to demonstrate the binding of contortrostatin to alpha v beta 5. First, incubation of T24 cells, whic h express alpha v beta 3 and alpha v beta 1, with antibody against alpha v beta 3 failed to completely inhibit adhesion of cells to vitronectin, Howev er, pretreatment of the cells with contortrostatin or the combination of an tibodies against alpha v beta 3 and alpha v beta 3 completely blocked adhes ion to vitronectin. By contrast, either anti-alpha v beta 5 alone or contor trostatin blocked adhesion of an alpha v beta 3-negative T24 subline, Secon d, contortrostatin as well as anti-alpha v beta 5 inhibits invasion of OVCA R-5, which express only alpha v beta 5. Third, contortrostatin binds to pur ified alpha v beta 5 in a saturable manner, Finally, radioligand binding as says yielded a K-d, value of 24 nM for [I-125]contortrostatin binding to al pha v beta 5. This investigation identifies alpha v beta 5 as a binding sit e for contortrostatin, Blockage of alpha v beta 5 by contortrostatin inhibi ts alpha v beta 5-mediated adhesion and invasion. (C) 2000 Academic Press.