Dataset Information

Assembly of von Willebrand factor tubules with in vivo helical parameters requires A1 domain insertion.

ABSTRACT: The von Willebrand factor (VWF) glycoprotein is stored in tubular form in Weibel-Palade bodies (WPBs) before secretion from endothelial cells into the bloodstream. The organization of VWF in the tubules promotes formation of covalently linked VWF polymers and enables orderly secretion without polymer tangling. Recent studies have described the high-resolution structure of helical tubular cores formed in vitro by the D1D2 and D'D3 amino-terminal protein segments of VWF. Here we show that formation of tubules with the helical geometry observed for VWF in intracellular WPBs requires also the VWA1 (A1) domain. We reconstituted VWF tubules from segments containing the A1 domain and discovered it to be inserted between helical turns of the tubule, altering helical parameters and explaining the increased robustness of tubule formation when A1 is present. The conclusion from this observation is that the A1 domain has a direct role in VWF assembly, along with its known activity in hemostasis after secretion.

SUBMITTER: Javitt G

PROVIDER: S-EPMC10653096 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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Assembly of von Willebrand factor tubules with in vivo helical parameters requires A1 domain insertion.

Javitt Gabriel G Yeshaya Noa N Khmelnitsky Lev L Fass Deborah D

Blood 20221201 26

The von Willebrand factor (VWF) glycoprotein is stored in tubular form in Weibel-Palade bodies (WPBs) before secretion from endothelial cells into the bloodstream. The organization of VWF in the tubules promotes formation of covalently linked VWF polymers and enables orderly secretion without polymer tangling. Recent studies have described the high-resolution structure of helical tubular cores formed in vitro by the D1D2 and D'D3 amino-terminal protein segments of VWF. Here we show that formatio ...[more]

PMID: 36179246

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Project description:Essentials The mechanism for the auto-inhibition of von Willebrand factor (VWF) remains unclear. Hydrogen exchange of two VWF A1 fragments with disparate activities was measured and compared. Discontinuous residues flanking A1 form a structural module that blocks A1 binding to the platelet. Our results suggest a potentially unified model of VWF activation. Click to hear an ISTH Academy presentation on the domain architecture of VWF and activation by elongational flow by Dr Springer SUMMARY: Background How von Willebrand factor (VWF) senses and responds to shear flow remains unclear. In the absence of shear flow, VWF or its fragments can be induced to bind spontaneously to platelet GPIbα. Objectives To elucidate the auto-inhibition mechanism of VWF. Methods Hydrogen-deuterium exchange (HDX) of two recombinant VWF fragments expressed from baby hamster kidney cells were measured and compared. Results The shortA1 protein contains VWF residues 1261-1472 and binds GPIbα with a significantly higher affinity than the longA1 protein that contains VWF residues 1238-1472. Both proteins contain the VWF A1 domain (residues 1272-1458). Many residues in longA1, particularly those in the N- and C-terminal sequences flanking the A1 domain, and in helix α1, loops α1β2 and β3α2, demonstrated markedly reduced HDX compared with their counterparts in shortA1. The HDX-protected region in longA1 overlaps with the GPIbα-binding interface and is clustered with type 2B von Willebrand disease (VWD) mutations. Additional comparison with the HDX of denatured longA1 and ristocetin-bound longA1 indicates the N- and C-terminal sequences flanking the A1 domain form cooperatively an integrated autoinhibitory module (AIM) that interacts with the HDX-protected region. Binding of ristocetin to the C-terminal part of the AIM desorbs the AIM from A1 and enables longA1 binding to GPIbα. Conclusion The discontinuous AIM binds the A1 domain and prevents it from binding to GPIbα, which has significant implications for the pathogenesis of type 2B VWD and the shear-induced activation of VWF activity.

Dataset Information

Assembly of von Willebrand factor tubules with in vivo helical parameters requires A1 domain insertion.

Publications

Assembly of von Willebrand factor tubules with in vivo helical parameters requires A1 domain insertion.

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