title: Distinct pathways regulate Syk protein activation downstream of immune tyrosine activation motif (ITAM) and hemITAM receptors in platelets.
abstract: Tyrosine kinase pathways are known to play an important role in the activation of platelets. In particular, the GPVI and CLEC-2 receptors are known to activate Syk upon tyrosine phosphorylation of an immune tyrosine activation motif (ITAM) and hemITAM, respectively. However, unlike GPVI, the CLEC-2 receptor contains only one tyrosine motif in the intracellular domain. The mechanisms by which this receptor activates Syk are not completely understood. In this study, we identified a novel signaling mechanism in CLEC-2-mediated Syk activation. CLEC-2-mediated, but not GPVI-mediated, platelet activation and Syk phosphorylation were abolished by inhibition of PI3K, which demonstrates that PI3K regulates Syk downstream of CLEC-2. Ibrutinib, a Tec family kinase inhibitor, also completely abolished CLEC-2-mediated aggregation and Syk phosphorylation in human and murine platelets. Furthermore, embryos lacking both Btk and Tec exhibited cutaneous edema associated with blood-filled vessels in a typical lymphatic pattern similar to CLEC-2 or Syk-deficient embryos. Thus, our data show, for the first time, that PI3K and Tec family kinases play a crucial role in the regulation of platelet activation and Syk phosphorylation downstream of the CLEC-2 receptor.
authors.affiliation: From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Bhanu Kanth
authors.initials: BK
authors.lastname: Manne
authors.affiliation: From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Rachit
authors.initials: R
authors.lastname: Badolia
authors.affiliation: From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Carol
authors.initials: C
authors.lastname: Dangelmaier
authors.affiliation: the Institute for Physiological Chemistry and Pathobiochemistry, University of Münster, 48149 Münster, Germany.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Eble
authors.affiliation: the Division of Immunobiology, Institution of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, A-1090 Vienna, Austria, and.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Ellmeier
authors.affiliation: the Department of Medicine and Division of Cardiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-5159.
authors.forename: Mark
authors.initials: M
authors.lastname: Kahn
authors.affiliation: From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, spk@temple.edu.
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives; D000077329:Agammaglobulinaemia Tyrosine Kinase; D020816:Amino Acid Motifs; D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D037181:Lectins, C-Type / Q000819:agonists / Q000737:chemistry* / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000819:agonists / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010880:Piperidines; D015539:Platelet Activation / Q000187:drug effects; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000072377:Syk Kinase; D014443:Tyrosine
chemical_list: D000225:Adenine; D000077329:Agammaglobulinaemia Tyrosine Kinase; D002867:Chromones; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D010880:Piperidines; D010980:Platelet Membrane Glycoproteins; D011505:Protein-Tyrosine Kinases; D011720:Pyrazoles; D011743:Pyrimidines; D000072377:Syk Kinase; D014443:Tyrosine; C104778:CLEC2B protein, human; C098341:platelet membrane glycoprotein VI; C551803:ibrutinib; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C089848:Tec protein-tyrosine kinase; C000625949:BTK protein, human; C000606896:SYK protein, human; C000606897:Syk protein, mouse
keywords: Cell Signaling; Platelet; Signal Transduction; Signaling; Thrombosis