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Prepublished online as a Blood First Edition Paper on January 23, 2003; DOI 10.1182/blood-2002-06-1879. This Article Full Text Full Text (PDF) All Versions of this Article: 2002-06-1879v1 101/11/4363    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Rights and Permissions Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Mekrache, M. Articles by Baruch, D. Search for Related Content PubMed PubMed Citation Articles by Mekrache, M. Articles by Baruch, D. Related Collections Hemostasis, Thrombosis, and Vascular Biology Cell Adhesion and Motility Signal Transduction Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  Blood, 1 June 2003, Vol. 101, No. 11, pp. 4363-4371 HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Activation of pp125FAK by type 2B recombinant von Willebrand factor binding to platelet GPIb at a high shear rate occurs independently of IIb3 engagement Médina Mekrache, Christilla Bachelot-Loza, Nadine Ajzenberg, Abdelhafid Saci, Paulette Legendre, and Dominique Baruch From the Institut National de la Santé et de la Recherche Médicale (INSERM) U143, Le Kremlin-Bicetre, France; and INSERM U428, Paris, France. Shear-induced platelet aggregation (SIPA) involves the sequential interaction of von Willebrand factor (VWF) with both glycoprotein Ib (GPIb) and IIb3 receptors. Type 2B recombinant VWF (2B-rVWF), characterized by an increased affinity for GPIb, induces strong SIPA at a high shear rate (4000 s–1). Despite the increased affinity of 2B-rVWF for GPIb, patients with type 2B von Willebrand disease have a paradoxical bleeding disorder, which is not well understood. The purpose of this study was to determine if SIPA induced by 2B-rVWF was associated with IIb3-dependent platelet activation. To this end, we have addressed the influence of 2B-rVWF (Val553Met substitution) on SIPA-dependent variations of tyrosine protein phosphorylation (P-Tyr) and the effect of IIb3 blockers. At a high shear rate, 2B-rVWF induced a strong SIPA, as shown by a 92.7% ± 0.4% disappearance of single platelets (DSP) after 4.5 minutes. In these conditions, increased P-Tyr of proteins migrating at positions 64 kd, 72 kd, and 125 kd were observed. The band at 125 kd was identified as pp125FAK using anti–phospho-FAK antibody. This effect, which required a high level of SIPA (> 70% DSP), was observed at 4000 s–1 but not at 200 s–1. Monoclonal antibodies (MoAbs) 6D1 (anti-GPIb) and 328 (anti-VWF A1 domain), completely abolished SIPA and p125FAK phosphorylation mediated by 2B-rVWF. In contrast, neither RGDS peptide nor MoAb 7E3, both known to block IIb3 engagement, had any effect on SIPA and pp125FAK. The size of aggregates formed at a high shear rate in the presence of 2B-rVWF was decreased by genistein, demonstrating the biologic relevance of pp125FAK. These findings provide a unique mechanism whereby the enhanced interaction of 2B-rVWF with GPIb, without engagement of IIb3, is sufficient to induce SIPA but does not lead to stable thrombus formation. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: P. Nurden, N. Debili, W. Vainchenker, R. Bobe, R. Bredoux, E. Corvazier, R. Combrie, E. Fressinaud, D. Meyer, A. T. Nurden, et al. Impaired megakaryocytopoiesis in type 2B von Willebrand disease with severe thrombocytopenia Blood, October 15, 2006; 108(8): 2587 - 2595. [Abstract] [Full Text] [PDF]

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