von Willebrand factor mutation promotes thrombocytopathy by inhibiting integrin αIIbβ3

J Clin Invest. 2013 Dec;123(12):5071-81. doi: 10.1172/JCI69458. Epub 2013 Nov 25.


von Willebrand disease type 2B (vWD-type 2B) is characterized by gain-of-function mutations in von Willebrand factor (vWF) that enhance its binding to the glycoprotein Ib-IX-V complex on platelets. Patients with vWD-type 2B have a bleeding tendency that is linked to loss of vWF multimers and/or thrombocytopenia. In this study, we uncovered evidence that platelet dysfunction is a third possible mechanism for bleeding tendency. We found that platelet aggregation, secretion, and spreading were diminished due to inhibition of integrin αIIbβ3 in platelets from mice expressing a vWD-type 2B-associated vWF (vWF/p.V1316M), platelets from a patient with the same mutation, and control platelets pretreated with recombinant vWF/p.V1316M. Impaired platelet function coincided with reduced thrombus growth. Further, αIIbβ3 activation and activation of the small GTPase Rap1 were impaired by vWF/p.V1316M following exposure to platelet agonists (thrombin, ADP, or convulxin). Conversely, thrombin- or ADP-induced Ca2+ store release, which is required for αIIbβ3 activation, was normal, indicating that vWF/p.V1316M acts downstream of Ca2+ release and upstream of Rap1. We found normal Syk phosphorylation and PLCγ2 activation following collagen receptor signaling, further implying that vWF/p.V1316M acts directly on or downstream of Ca2+ release. These data indicate that the vWD-type 2B mutation p.V1316M is associated with severe thrombocytopathy, which likely contributes to the bleeding tendency in vWD-type 2B.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Amino Acid Substitution*
  • Animals
  • Blood Platelets / metabolism
  • Calcium Signaling / physiology
  • Hemorrhagic Disorders / etiology*
  • Hemorrhagic Disorders / physiopathology
  • Humans
  • Intracellular Signaling Peptides and Proteins / physiology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mutation, Missense*
  • Phospholipase C gamma / physiology
  • Phosphorylation
  • Platelet Aggregation / genetics*
  • Platelet Glycoprotein GPIIb-IIIa Complex / antagonists & inhibitors*
  • Platelet Glycoprotein GPIIb-IIIa Complex / physiology
  • Point Mutation*
  • Protein Processing, Post-Translational
  • Protein-Tyrosine Kinases / physiology
  • Receptors, Collagen / physiology
  • Recombinant Fusion Proteins / metabolism
  • Syk Kinase
  • rap1 GTP-Binding Proteins / metabolism
  • von Willebrand Disease, Type 2 / blood
  • von Willebrand Disease, Type 2 / genetics*
  • von Willebrand Factor / genetics*
  • von Willebrand Factor / physiology


  • Intracellular Signaling Peptides and Proteins
  • Platelet Glycoprotein GPIIb-IIIa Complex
  • Receptors, Collagen
  • Recombinant Fusion Proteins
  • von Willebrand Factor
  • Adenosine Triphosphate
  • Protein-Tyrosine Kinases
  • SYK protein, human
  • Syk Kinase
  • Syk protein, mouse
  • Phospholipase C gamma
  • rap1 GTP-Binding Proteins