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von Willebrand factor A1 domain can adequately substitute for A3 domain in recruitment of flowing platelets to collagen
Author(s) -
BONNEFOY A.,
ROMIJN R. A.,
VANDERVOORT P. A. H.,
VAN ROMPAEY I.,
VERMYLEN J.,
HOYLAERTS M. F.
Publication year - 2006
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2006.02111.x
Subject(s) - von willebrand factor , chemistry , platelet , microbiology and biotechnology , platelet membrane glycoprotein , biochemistry , biophysics , medicine , glycoprotein , biology
Summary. Background: Binding of von Willebrand factor (VWF) to platelet GPIb α and to collagen is attributed to VWF A1 and A3 domains, respectively. Objectives: Using VWF, VWF lacking A1 (ΔA1‐VWF) or A3 (ΔA3‐VWF) and VWF with defective A3 (H1786A‐VWF), in combination with recombinant A1 (residues 1262–1492) or A3 (residues 1671–1878), fused to glutathione‐S‐transferase (GST‐A1 and GST‐A3), we have re‐investigated the role of A1 in platelet recruitment to surfaces of collagen. Methods and Results: In flow, measurable binding of ΔA3‐VWF occurred to horse tendon, but also to human type III collagen. GST‐A1 and GST‐A3 both competed for binding of ΔA1‐VWF and ΔA3‐VWF to horse tendon collagen fibrils in static conditions and to human collagen III during plasmon surface resonance studies, substantiating overlapping binding sites on both collagens for A1 and A3. Heparin did not affect A3‐mediated binding of VWF and ΔA1‐VWF, but inhibited binding to horse tendon collagen of GST‐A1 and ΔA3‐VWF. Furthermore, A1‐mediated binding to type III collagen of ΔA3‐VWF binding was strongly salt‐sensitive. During perfusions at wall shear rate 2500 s −1 of calcein‐labeled platelets in reconstituted blood, ΔA3‐VWF and H1786A‐VWF triggered platelet binding to horse tendon collagen comparably and as potently as VWF, and to human type III collagen, only fivefold less potently, ΔA1‐VWF being inactive. Additional flow‐controlled interaction studies with ΔA3‐VWF, H1786A‐VWF, the collagen‐VWF antagonist saratin, heparin and the VWF neutralizing antibody 82D6A3 confirmed that H1786A‐VWF binds to collagen exclusively via A1. Conclusion: Hence, in shear forces the VWF A1 domain can assume the role of A3 to trigger substantial platelet recruitment to human collagen fibres.