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Blood, 1 October 2009, Vol. 114, No. 14, pp. 3056-3063.
Prepublished online as a Blood First Edition Paper on July 8, 2009; DOI 10.1182/blood-2008-11-188516.
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Submitted November 7, 2008
Accepted May 14, 2009
Lyn, PKC delta, SHIP-1 interactions regulate GPVI-mediated platelet dense granule secretion
Ramya Chari, Soochong Kim, Swaminathan Murugappan, Archana Sanjay, James L. Daniel, and Satya P. Kunapuli*
Department of Physiology, Temple University School of Medicine, Philadelphia, PA, United States
Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA, United States
Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA, United States
Pharmacology, Temple University School of Medicine, Philadelphia, PA, United States
* Corresponding author; email: spk{at}temple.edu.
Protein Kinase C (PKC ) is expressed in platelets and activated downstream of protease-activated receptors (PAR)s and Glycoprotein VI (GPVI) receptors. We have previously shown that PKC positively regulates PAR-mediated dense granule secretion, whereas it negatively regulates GPVI-mediated dense granule secretion. We further investigated the mechanism of such differential regulation of dense granule release by PKC in platelets. SH2 domain-containing Inositol Phosphatase (SHIP)-1 is phosphorylated on Y1020, a marker for its activation, upon stimulation of human platelets with PAR agonists, SFLLRN and AYPGKF, or GPVI agonist, convulxin. GPVI-mediated SHIP-1 phosphorylation occurred rapidly at 15 sec whereas PAR-mediated phosphorylation was delayed, occurring at 1 min. Lyn and SHIP-1, but not SHIP-2 or Shc, preferentially associated with PKC upon stimulation of platelets with a GPVI agonists, but not with a PAR agonist. In PKC null murine platelets, convulxin-induced SHIP-1 phosphorylation was inhibited. Furthermore, in Lyn null murine platelets, GPVI-mediated phosphorylations on Y1020 of SHIP-1 and Y311 of PKC were inhibited. In murine platelets lacking Lyn, or SHIP-1, GPVI-mediated dense granule secretions are potentiated, whereas PAR-mediated dense granule secretions are inhibited. Therefore, we conclude that Lyn-mediated phosphorylations of PKC and SHIP-1 and their associations negatively regulate GPVI-mediated dense granule secretion in platelets.

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