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Blood, 1 January 2008, Vol. 111, No. 1, pp. 200-208. Prepublished online as a Blood First Edition Paper on October 4, 2007; DOI 10.1182/blood-2007-01-068957. This Article Full Text Full Text (PDF) Supplemental Figure All Versions of this Article: blood-2007-01-068957v1 111/1/200    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 Hsu, T.-C. Articles by Thompson, A. R. Search for Related Content PubMed PubMed Citation Articles by Hsu, T.-C. Articles by Thompson, A. R. Related Collections Hemostasis, Thrombosis, and Vascular Biology Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY The factor VIII C1 domain contributes to platelet binding Ting-Chang Hsu1, Kathleen P. Pratt1, and Arthur R. Thompson1 1 Puget Sound Blood Center and University of Washington Department of Medicine, Division of Hematology, Seattle Activated factor VIII (FVIIIa) forms a procoagulant complex with factor IXa on negatively charged membranes, including activated platelet surfaces. Membrane attachment involves the FVIII C2 domain; involvement of the adjacent C1 domain has not been established. Binding of recombinant FVIII C1C2 and C2 proteins to platelets was detected by flow cytometry using (1) anti-C2 monoclonal antibody ESH8 followed by a phycoerythrin-labeled secondary antibody; (2) biotinylated C1C2 detected by phycoerythrin-labeled streptavidin, and (3) C1C2 and C2 site-specifically labeled with fluorescein. Highest binding and lowest background were obtained using fluorescein-conjugated proteins. More than 90% of activated platelets bound C1C2, compared with approximately 50% for equimolar C2. Estimates using fluorescent microbeads indicated approximately 7000 C1C2-binding sites per platelet, approximately 1400 for C2, and approximately 3000 for fluorescein-labeled FVIIIa. Unlike C2 or FVIII(a), C1C2 bound to approximately 700 sites/platelet before activation. C1C2 binding to activated platelets appeared independent of von Willebrand factor and was competed effectively by FVIII(a), but only partially by excess C2. Fluorescein-labeled FVIIIa was competed much more effectively by C1C2 than C2 for binding to activated platelets. Two monoclonal antibodies that inhibit C2 binding to membranes competed platelet binding of C2 more effectively than C1C2. Thus, the C1 domain of FVIII contributes to platelet-binding affinity. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: T.-C. Hsu, K. P. Pratt, and A. R. Thompson A FVIII C1 Domain Loop Containing Phe2093 Contributes Affinity to the Binding of Recombinant FVIII C1C2 Proteins to Activated Platelets Blood (ASH Annual Meeting Abstracts), November 16, 2008; 112(11): 3069 - 3069. [Abstract] [Full Text]

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