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Blood, 15 January 2008, Vol. 111, No. 2, pp. 658-665. Prepublished online as a Blood First Edition Paper on October 3, 2007; DOI 10.1182/blood-2007-04-085514. This Article Full Text Full Text (PDF) Supplemental Figure All Versions of this Article: blood-2007-04-085514v1 111/2/658    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 Yin, H. Articles by Du, X. Search for Related Content PubMed PubMed Citation Articles by Yin, H. Articles by Du, X. Related Collections Cell Adhesion and Motility Signal Transduction Hemostasis, Thrombosis, and Vascular Biology Social Bookmarking                   What's this?  Previous Article  |  Table of Contents  |  Next Article  HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY The role of Akt in the signaling pathway of the glycoprotein Ib-IX–induced platelet activation Hong Yin1, Aleksandra Stojanovic1, Nissim Hay1, and Xiaoping Du1 1 Departments of Pharmacology and of Biochemistry and Molecular Genetics, University of Illinois at Chicago The platelet von Willebrand factor (vWF) receptor, glycoprotein Ib-IX (GPIb-IX), mediates platelet adhesion and induces signaling leading to integrin activation. Phosphoinositol 3-kinase (PI3K) is important in GPIb-IX–mediated signaling. PI3K–dependent signaling mechanisms, however, are unclear. We show that GPIb-IX–induced platelet aggregation and stable adhesion under flow were impaired in mouse platelets deficient in PI3K effectors, Akt1 and Akt2, and in human platelets treated with an Akt inhibitor, SH-6. Akt1 and Akt2 play important roles in early GPIb-IX signaling independent of Syk, adenosine diphosphate (ADP), or thromboxane A2 (TXA2), in addition to their recognized roles in ADP- and TXA2–dependent secondary amplification pathways. Knockout of Akt1 or Akt2 diminished platelet spreading on vWF but not on immobilized fibrinogen. Thus, Akt1 and Akt2 are both required only in the GPIb-IX–mediated integrin activation (inside-out signaling). In contrast, PI3K inhibitors abolished platelet spreading on both vWF and fibrinogen, indicating a role for PI3K in integrin outside-in signaling distinct from that in GPIb-IX–mediated inside-out signaling. Furthermore, Akt1- or Akt2-deficiency diminished vWF–induced cGMP elevation, and their inhibitory effects on GPIb-IX–dependent platelet adhesion were reversed by exogenous cGMP. Thus, Akt1 and Akt2 mediate GPIb-IX signaling via the cGMP–dependent signaling pathway. CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this? This article has been cited by other articles: H. Yin, J. Liu, Z. Li, M. C. Berndt, C. A. Lowell, and X. Du Src family tyrosine kinase Lyn mediates VWF/GPIb-IX-induced platelet activation via the cGMP signaling pathway Blood, August 15, 2008; 112(4): 1139 - 1146. [Abstract] [Full Text] [PDF] F.-T. Mu, R. K. Andrews, J. F. Arthur, A. D. Munday, S. L. Cranmer, S. P. Jackson, F. C. Stomski, A. F. Lopez, and M. C. Berndt A functional 14-3-3{zeta}-independent association of PI3-kinase with glycoprotein Ib{alpha}, the major ligand-binding subunit of the platelet glycoprotein Ib-IX-V complex Blood, May 1, 2008; 111(9): 4580 - 4587. [Abstract] [Full Text] [PDF]

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