Abstract Number: OC 09.4
Meeting: ISTH 2021 Congress
Background: The multimeric glycoprotein von Willebrand factor (VWF) plays a critical role in hemostasis by recruiting platelets to sites of vascular injury. VWF dysfunction leads to the bleeding disorder von Willebrand disease (VWD) and hyperactivity of VWF is associated with thrombosis, stroke and myocardial infarction. The VWF-type-C-(VWC)-domain, is one of the most abundant motifs in extracellular proteins but out of VWF’s six C-domains only the structure of C4 was determined.
Aims: Aim of this study was to solve the structure and investigate dynamics of the VWF-C6-domain. Further we investigated the effects of missense single nucleotide polymorphism p.Gly2705Arg.
Methods: The C6-structure was obtained by Nuclear Magnetic Resonance (NMR) and dynamics were investigated by molecular dynamics (MD) simulations. For recombinantly expressed full-length multimers of wtVWF and p.Gly2705Arg binding activities for collagen, glycoprotein (GP)Ibα and GPIIb/IIIa were measured by ELISA. Binding to platelets under flow conditions was investigated by cone and platelet aggregometry (CPA) and light transmission aggregometry (LTA).
Results: The high-resolution NMR structure determination of the isolated C6-domain reveals a VWC-fold containing two β-sheet subdomains connected by a flexible hinge. The canonical VWC-domains generally feature 5 disulfide bonds. The C6-domain lacks the S3 pair.
Recombinant p.Gly2705Arg exhibits a 73% reduced antigen but normal binding to collagen and GPIIb/IIIa under static conditions. GPIbα binding was slightly reduced. In CPA experiments, platelet aggregates showed an increased size in presence of p.Gly2705Arg. GPIbα-mediated platelet agglutination was fully activated by 0.3 mg/ml Ristocetin, while wtVWF requires 0.6 mg/ml.
Conclusions: We provide the first high-resolution structure of VWF-C6 and identified a structural feature unique to C6: The domain is a two-part helical segment broken by the S5 disulfide. SNP variant p.Gly2705Arg, surprisingly, possesses gain-of-function characteristics under flow conditions but also reduces expression/secretion. Thus, in vivo the latter effect most likely dominates, inducing a bleeding phenotype rather than prothrombotic effects.
To cite this abstract in AMA style:Mojzisch A, Chen P-, Kutzki F, Xu E-, Horny K, Simon B, Schneppenheim R, Brehm MA, Wilmanns M, Graeter F, Hennig J. Structure of the von Willebrand Factor C6 Domain and Effect of Variant p.Gly2705Arg [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/structure-of-the-von-willebrand-factor-c6-domain-and-effect-of-variant-p-gly2705arg/. Accessed November 29, 2023.
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