Sulfatides inhibit platelet adhesion to von Willebrand factor in flowing blood.
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 approximately 12.5 microg mL(-1)), binding that was blocked by dextran sulfate (IC(50) approximately equal to 100 microg mL(-1)) but not by heparin at concentrations up to 100 U mL(-1). Furthermore, sulfatides (125 microg mL(-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 VWF A1 domain at a site overlapping the GP Ib-binding site.
Borthakur
G
G
Division of Hematology, Department of Medicine, University of Texas-Houston Health Science Center, Houston, TX 77030, USA.
Cruz
M A
MA
Dong
J F
JF
McIntire
L
L
Li
F
F
López
J A
JA
Thiagarajan
P
P
D003001:Cloning, Molecular; D006801:Humans; D007700:Kinetics; D010477:Perfusion; D010973:Platelet Adhesiveness / Q000187:drug effects*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011994:Recombinant Proteins / Q000378:metabolism; D013433:Sulfoglycosphingolipids / Q000494:pharmacology*; D020349:Surface Plasmon Resonance; D014841:von Willebrand Factor / Q000378:metabolism*
D019038:Platelet Glycoprotein GPIb-IX Complex; D011994:Recombinant Proteins; D013433:Sulfoglycosphingolipids; C023592:glycocalicin; D014841:von Willebrand Factor