title: Activation of protein kinase C inhibits hormonal stimulation of the GTPase activity of Gi in human platelets.
abstract: The effect of 12-tetradecanoyl phorbol 13-acetate on the GTPase activity of Gi was investigated. Treatment with TPA did not alter basal GTPase activity of membranes or the stimulatory effect of prostaglandin E1 (putatively via Gs). In contrast, the phorbol ester markedly diminished stimulation of GTPase by agents whose receptors are coupled to Gi such as epinephrine (alpha-adrenergic action), platelet activating factor or thrombin. Pertussis toxin catalyzed ADP-ribosylation was also decreased in membranes from TPA-treated platelets as compared to the controls. It is suggested that the alteration in the hormonal activation of the GTPase activity of Gi is secondary to a perturbation in the receptor-Gi interaction.
authors.affiliation: Instituto de Fisiología Celular, UNAM, México DF, México.
authors.forename: G
authors.initials: G
authors.lastname: Gutiérrez-Venegas
authors.forename: J A
authors.initials: JA
authors.lastname: García-Sáinz
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000527:Alprostadil / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D037342:Pertussis Toxin; D010972:Platelet Activating Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D010972:Platelet Activating Factor; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D011493:Protein Kinase C; D013917:Thrombin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D000527:Alprostadil; D013755:Tetradecanoylphorbol Acetate; D004837:Epinephrine