MODULATION OF APOPTOTIC CELL-DEATH BY EXTRACELLULAR-MATRIX PROTEINS AND A FIBRONECTIN-DERIVED ANTIADHESIVE PEPTIDE

Cell adhesion to the extracellular matrix (ECM) has been implicated in apoptosis in anchorage-dependent cell types. We recently found that a peptide derived from fibronectin (termed III14-2) inhibits the integr in-mediated cell adhesion to ECM. Using this antiadhesive peptide and a variety of ECM proteins, we show here a critical role of the integri n-ECM protein interaction in apoptotic regulation of human umbilical v ein endothelial cells (HUVEC). HUVEC in suspension underwent apoptosis under the serum-free conditions, as judged by nuclear and DNA fragmen tations, This apoptosis was suppressed to varying degrees when alpha 5 beta 1, alpha v beta 3, and alpha 2 beta 1 integrins were occupied wi th either soluble or immobilized ECM proteins such as fibronectin, vit ronectin, and type I collagen, respectively. Peptide III14-2, which ha d no effect by itself on the HUVEC apoptosis, disrupted the ligation o f alpha 5 beta 1 and alpha v beta 3 but no alpha 2 beta 1 and ultimate ly led the cells to apoptosis, indicating that this antiadhesive pepti de indirectly induces apoptosis by blocking cell survival signals deli vered from alpha 5 beta 1 and alpha v beta 3 integrins. Genistein, a p rotein tyrosine kinase inhibitor, slightly reduced the rescuing effect of fibronectin, whereas sodium orthovanadate and bombesin, which incr ease in the Bevel of protein tyrosine phosphorylation, made HUVEC less susceptible to apoptosis and blocked the effect of peptide III14-2. H UVEC adhesion to fibronectin substrate raised the tyrosine phosphoryla tion level of focal adhesion kinase and the expression of cytoprotecti ve Bcl-2 protein, both of which were reversed by the antiadhesive effe ct of peptide III14-2, Thus, the opposing effects of ECM proteins, inc luding fibronectin and vitronectin, and peptide III14-2 on HUVEC apopt osis appear to be due to the opposing effects of these factors on the signaling pathway which includes tyrosine phosphorylation of FAK and B cl-2 expression. (C) 1998 Academic Press.