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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 (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 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. Social Bookmarking                   What's this? Submitted June 26, 2002 Accepted January 14, 2003 Activation of pp125FAK by type 2B recombinant von Willebrand factor binding to platelet GPIb at high shear rate occurs independently of IIb3 engagement Medina Mekrache, Christilla Bachelot-Loza, Nadine Ajzenberg, Abdelhafid Saci, Paulette Legendre, and Dominique Baruch* INSERM, Unite 143, Kremlin-Bicetre, France INSERM, Unite 428, Paris, France * Corresponding author; email: baruch{at}kb.inserm.fr. Shear-induced platelet aggregation (SIPA) involves the sequential interaction of von Willebrand factor (vWF) with both GPIb and IIb3 receptors. Type 2B recombinant vWF (2B-rvWF), characterized by an increased affinity for GPIb, induces strong SIPA at high shear rate (4,000 sec-1). Despite the increased affinity of 2B-rvWF for GPIb, type 2B von Willebrand disease patients 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 (V553M substitution) on SIPA-dependent variations of tyrosine protein phosphorylation (P-Tyr) and the effect of IIb3 blockers. At high shear rate, 2B-rvWF induced a strong SIPA, as shown by 92.7±0.4% disappearance of single platelets (DSP) after 4.5 min. In these conditions, increased P-Tyr of proteins migrating at position 64, 72 and 125 kDa were observed. The band at 125 kDa was identified as pp125FAK using anti-phospho-FAK antibody. This effect, which required high level of SIPA (>70% DSP), was observed at 4,000 sec-1 but not at 200 sec-1. 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 p125FAK phosphorylation. The size of aggregates formed at high shear rate in the presence of 2B-rvWF was decreased by genistein, demonstrating the biological 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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