INTEGRIN ALPHA(V)BETA(3) DIFFERENTIALLY REGULATES ADHESIVE AND PHAGOCYTIC FUNCTIONS OF THE FIBRONECTIN RECEPTOR ALPHA(5)BETA(1)

The plasma protein fibronectin is an important opsonin in wound repair and host defense. To better understand the process of fibronectin-med iated phagocytosis, we have transfected K562 cells, which endogenously express alpha(5) beta(1), with alpha(v) beta(3). In these transfectan ts, antibodies to alpha(v) beta(3) block phagocytosis of fibronectin-o psonized beads completely, even though half the ingestion occurs throu gh endogenous alpha(5) beta(1) receptors. alpha(5) beta(1)-mediated ad hesion to fibronectin-coated surfaces is unaffected by alpha(v) beta(5 ) ligation. Neither alpha(v) beta(5) nor alpha(M) beta(2) ligation aff ects alpha(5) beta(1)-phagocytic function in transfectants expressing these receptors. Pharmacologic data suggest that alpha(v) beta(5) liga tion suppresses the phagocytic competence of high affinity alpha(5) be ta(1)-receptors through a signal transduction pathway, perhaps involvi ng protein kinase C. In addition to its significance for phagocytosis, alpha(v) beta(3) regulation of alpha(s) beta(1) function may be signi ficant for its roles in cell migration, metastasis, and angiogenesis.