Integrin Differentially Regulates Adhesive and Phagocytic Functions of the Fibronectin Receptor -s/ l

The plasma protein fibronectin is an important opsonin in wound repair and host defense. To better understand the process of fibronectin-mediated phagocytosis, we have transfectod K562 cells, which endogenously express 0~5fll, with a,f13. In these transfectants, antibodies to t~fl3 block phagocytosis of fibronectin-opsonized beads completely, even though half the ingestion occurs through endogenous 0t5/3~ receptors, c~5/31-mediated adhesion to fibronectincoated surfaces is unaffected by c~j33 ligation. Neither av/$5 n o r O/M/~2 ligation affects O~5/~1 phagocytic function in transfectants expressing these receptors. Pharmacologic data suggest that o~v/~3 ligation suppresses the phagocytic competence of high affinity ot5/$1 receptors through a signal transduction pathway, perhaps involving protein kinase C. In addition to its significance for phagocytosis, otv/33 regulation of o~5/31 function may be significant for its roles in cell migration, metastasis,