Solid-phase von Willebrand factor contains a conformationally active RGD motif that mediates endothelial cell adhesion through the αvβ3 receptor

Abstract

The interaction of von Willebrand factor (vWF) with the αvβ3 integrin of human umbilical vein endothelial cells is dependent on the RGD sequence present at residues 1744-1746 of the mature vWF subunit. We compared vWF and its two dimeric fragments, SpIII (residues 1-1365) and SpII (residues 1366-2050), as adhesion substrates. Solid-phase vWF and SpII supported endothelial cell adhesion, whereas SpIII, which contains the glycoprotein (GP) Ib binding domain, did not. Soluble SpII inhibited adhesion to immobilized ligands, whereas soluble vWF did not, suggesting that exposure of the cell attachment domain involves a conformational modification of vWF. Dendroaspin and albolabrin, two RGD-containing peptides of the disintegrin family, were potent inhibitors of cell adhesion to vWF (IC50 ∼15 nmol/L). Complete inhibition of endothelial cell adhesion to vWF was obtained in the presence of F(ab′)2 of monoclonal antibody 9 to vWF, which blocks vWF binding to platelet GPIIb/IIIa. In contrast, monoclonal antibody 713 to vWF, which blocks its binding to platelet GPIb, did not inhibit cell adhesion to vWF. These results indicate that endothelial cell adhesion to vWF is mediated by an RGD-dependent interaction with αvβ3, but does not seem to involve a GPIb-like receptor, and show the importance of the conformation of the RGD sequence. © 1993 by The American Society of Hematology.