NF-KAPPA-B MEDIATES ALPHA-V-BETA-3 INTEGRIN-INDUCED ENDOTHELIAL-CELL SURVIVAL

The alpha(V) beta(3) integrin plays a fundamental role during the angi ogenesis process by inhibiting endothelial cell apoptosis. However, th e mechanism of inhibition is unknown. In this report, we show that int egrin mediated cell survival involves regulation of nuclear factor-kap pa B (NF-kappa B) activity. Different extracellular matrix molecules w ere able to protect rat aorta-derived endothelial cells from apoptosis induced by serum withdrawal. Osteopontin and beta(3) integrin ligatio n rapidly increased NF-kappa B activity as measured by gel shift and r eporter activity. The p65 and p50 subunits were present in the shifted complex. In contrast, collagen type I (a beta(1)-integrin ligand) did not induce NF-kappa B activity. The alpha(V) beta(3) integrin was mos t important for osteopontin-mediated NF-kappa B induction and survival , since adding a neutralizing anti-beta(3) integrin antibody blocked N F-kappa B activity and induced endothelial cell death when cells were plated on osteopontin. NF-kappa B was required for osteopontin-and vit ronectin-induced survival since inhibition of NF-kappa B activity with nonphosphorylatable I kappa B completely blocked the protective effec t of osteopontin and vitronectin. In contrast, NF-kappa B was not requ ired for fibronectin, laminin, and collagen type I-induced survival. A ctivation of NF-kappa B by osteopontin depended on the small GTP-bindi ng protein Ras and the tyrosine kinase Src, since NF-kappa B reporter activity was inhibited by Ras and Src dominant-negative mutants. In co ntrast, inhibition of MEK and PI3-kinase did not affect osteopontin-in duced NF-kappa B activation. These studies identify NF-kappa B as an i mportant signaling molecule in alpha(V) beta(3) integrin-mediated endo thelial cell survival.