title: Protein-tyrosine kinase p72syk is activated by thromboxane A2 mimetic U44069 in platelets.
abstract: We show that p72syk is rapidly activated following the stimulation of thromboxane A2 mimetics, U44069 and STA2 in porcine platelets. The activity of p72syk reached a maximum at 10 s and decreased to a basal level within 60 s after 1 microM U44069 stimulation. This activation was enhanced in a dose-dependent manner and completely canceled by the pretreatment of platelet suspension with ONO3708, a specific antagonist of thromboxane A2. Pretreatment of platelets with aspirin as well as apyrase did not affect the activation of p72syk. When both extra- and intra-cellular Ca2+ were depleted, the activation of p72syk was still persistent; in contrast, the deactivation process was completely abrogated even at 120 s after U44069 stimulation. These results suggest that p72syk is a responsible enzyme to the protein-tyrosine phosphorylation events, and that p72syk functions mainly before Ca2+ recruitment in thromboxane A2-stimulated platelets.
authors.affiliation: Department of Biochemistry, Fukui Medical School, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Maeda
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.forename: T
authors.initials: T
authors.lastname: Inazu
authors.forename: C
authors.initials: C
authors.lastname: Yang
authors.forename: G
authors.initials: G
authors.lastname: Nakagawara
authors.forename: H
authors.initials: H
authors.lastname: Yamamura
mesh_terms: D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000187:drug effects*; D047908:Intracellular Signaling Peptides and Proteins; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000187:drug effects*; D013552:Swine; D000072377:Syk Kinase; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D011450:Prostaglandin Endoperoxides, Synthetic; C028429:U 44069; D013928:Thromboxane A2; C037866:STA 2; C049855:ONO 3708; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; D001081:Apyrase; D001241:Aspirin; D002118:Calcium