title: Distinct role of Pyk2 in mediating thromboxane generation downstream of both G12/13 and integrin αIIbβ3 in platelets.
abstract: Proline-rich tyrosine kinase 2 (Pyk2) is activated by various agonists in platelets. We evaluated the signaling mechanism and the functional role of Pyk2 in platelets by using pharmacological inhibitors and Pyk2-deficient platelets. We found that platelet aggregation and secretion in response to 2-methylthio-ADP (2-MeSADP) and AYPGKF were diminished in the presence of Pyk2 inhibitors or in Pyk2-deficient platelets, suggesting that Pyk2 plays a positive regulatory role in platelet functional responses. It has been shown that ADP-, but not thrombin-induced thromboxane (TxA2) generation depends on integrin signaling. Unlike ADP, thrombin activates G12/13 pathways, and G12/13 pathways can substitute for integrin signaling for TxA2 generation. We found that Pyk2 was activated downstream of both G12/13 and integrin-mediated pathways, and both 2-MeSADP- and AYPGKF-induced TxA2 generation was significantly diminished in Pyk2-deficient platelets. In addition, TxA2 generation induced by co-stimulation of Gi and Gz pathways, which is dependent on integrin signaling, was inhibited by blocking Pyk2. Furthermore, inhibition of 2-MeSADP-induced TxA2 generation by fibrinogen receptor antagonist was not rescued by co-stimulation of G12/13 pathways in the presence of Pyk2 inhibitor. We conclude that Pyk2 is a common signaling effector downstream of both G12/13 and integrin αIIbβ3 signaling, which contributes to thromboxane generation.
authors: Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
authors: Soochong
authors: S
authors: Kim
authors: Lina
authors: L
authors: Cipolla
authors: Gianni
authors: G
authors: Guidetti
authors: Mitsuhiko
authors: M
authors: Okigaki
authors: Jianguo
authors: J
authors: Jin
authors: Mauro
authors: M
authors: Torti
authors: Satya P
authors: SP
authors: Kunapuli
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D051418:Focal Adhesion Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009842:Oligopeptides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013873:Thionucleotides / Q000494:pharmacology; D013928:Thromboxane A2 / Q000096:biosynthesis*; D013997:Time Factors; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D009842:Oligopeptides; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D013873:Thionucleotides; D020032:Tyrphostins; C455901:alanyl-tyrosyl-prolyl-glycyl-lysyl-phenylalanine; C002480:methylthio-ADP; D013928:Thromboxane A2; D000244:Adenosine Diphosphate; D051418:Focal Adhesion Kinase 2; C496053:Ptk2b protein, mouse; D044365:GTP-Binding Protein alpha Subunits, G12-G13
keywords: ADP; G12/13; Integrin; Platelets; Pyk2; Signal Transduction; Thrombin; Thromboxane
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