von Willebrand factor mutation promotes thrombocytopathy by inhibiting integrin αIIbβ3.

Abstract

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.

• Authors: Caterina Casari, Eliane Berrou, Marilyne Lebret, Frédéric Adam, Alexandre Kauskot, Régis Bobe, Céline Desconclois, Edith Fressinaud, Olivier D Christophe, Peter J Lenting, Jean-Philippe Rosa, Cécile V Denis, Marijke Bryckaert
• Journal: The Journal of clinical investigation (J Clin Invest) Vol. 123 Issue 12 Pg. 5071-81 (Dec 2013) ISSN: 1558-8238 [Electronic] United States
• PMID: 24270421 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 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

Topics

• Adenosine Triphosphate (metabolism)
• Amino Acid Substitution
• Animals
• Blood Platelets (metabolism)
• Calcium Signaling (physiology)
• Hemorrhagic Disorders (etiology, 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, 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, genetics)
• von Willebrand Factor (genetics, physiology)