Sulfatides inhibit platelet adhesion to von Willebrand factor in flowing blood

Abstract

Sulfatides are sulfated glycosphingolipids present on cell surfaces that bind to adhesive proteins such as von Willebrand factor (VWF), P-selectin, laminin and thrombospondin. Previous studies have localized the sulfatide-binding site of VWF to amino acid residues Gln626-Val646 in the A1 domain. The A1 domain also contains the binding site for platelet glycoprotein Ib (GP Ib), a site that has been reported to be distinct from the sulfatide-binding site. In this study, we analyzed the interaction of sulfatides with VWF and its effect on GP Ib-mediated platelet adhesion under flow conditions. Recombinant VWF A1 domain (rVWF-A1) bound specifically and saturably to sulfatides (half-maximal concentration of ~12.5 μgmL -1), binding that was blocked by dextran sulfate (IC 50 ≈ 100 μgmL -1) but not by heparin at concentrations up to 100 UmL -1. Furthermore, sulfatides (125 μgmL -1) prevented the adhesion of platelets or glycocalicin-coupled polystyrene beads to a rVWF-A1-coated surface under high shear stress. In addition, plasma VWF prebound to a sulfatide-coated surface failed to support subsequent platelet adhesion. These results provide firm evidence that sulfatides bind the VWFA1 domain at a site overlapping the GP Ib-binding site. © 2003 International Society on Thrombosis and Haemostasis.