title: Synergistic phosphorylation of platelet rap1B by SIN-1 and iloprost.
abstract: Human platelets suspended in plasma or buffer were incubated with low concentrations of the nitric oxide (NO)-donor 3-morpholino-syndnonime (SIN-1; 100 nM to 1 microM) and the stable prostacyclin analogue iloprost (50 or 100 pM) and analyzed for cyclic nucleotide levels and protein phosphorylation. SIN-1 and iloprost synergistically stimulated the phosphorylation of rap1B and the 50 kDa vasodilator-stimulated phosphoprotein. SIN-1 stimulated platelet cyclic GMP and cAMP-levels and enhanced the increase in cyclic AMP elicited by iloprost. It was found that the mechanism underlying the synergistic phosphorylation of the 50 kDa protein and rap1B was different: synergistic phosphorylation of the 50 kDa protein seemed to be mediated by activation of both protein kinases A and G, whereas the synergistic rap1B phosphorylation could be attributed entirely to activation of protein kinase A. Measurement of rap1B phosphorylation might be a useful tool to monitor the action of systemically applied prostacyclin-analogues and nitrovasodilators in pharmacological studies.
authors.affiliation: Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Universität München, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Grünberg
authors.forename: E
authors.initials: E
authors.lastname: Negrescu
authors.forename: W
authors.initials: W
authors.lastname: Siess
mesh_terms: D001345:Autoradiography; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004357:Drug Synergism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D016285:Iloprost / Q000494:pharmacology*; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology; D010766:Phosphorylation; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D020668:rap GTP-Binding Proteins
chemical_list: D010975:Platelet Aggregation Inhibitors; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D006152:Cyclic GMP; D016285:Iloprost