Waldmann R, Nieberding M, Walter U
Physiologisch-Chemisches Institut, Universität Würzburg, Federal Republic of Germany.
Eur J Biochem. 1987 Sep 15;167(3):441-8. doi: 10.1111/j.1432-1033.1987.tb13357.x.
Vasodilators such as sodium nitroprusside, nitroglycerin and various prostaglandins are capable of inhibiting platelet aggregation associated with an increase of either cGMP or cAMP. In our studies with intact platelets, prostaglandin E1 and sodium nitroprusside stimulated the phosphorylation of several proteins which could be distinguished from proteins known to be phosphorylated by a calmodulin-regulated protein kinase or by protein kinase C. Prostaglandin E1 (10 microM) or dibutyryl cAMP (2 mM) stimulated the phosphorylation of proteins with apparent relative molecular masses, Mr, of 240,000, 68,000, 50,000, and 22,000 in intact platelets. These proteins were also phosphorylated in response to low concentrations (1-2 microM) of cAMP in a particulate fraction of platelets. In intact platelets, sodium nitroprusside (100 microM) and the 8-bromo derivative of cGMP (2 mM) increased the phosphorylation of one protein of Mr 50,000 which was also phosphorylated in response to low concentrations (1-2 microM) of cGMP in platelet membranes. An additional protein (Mr 24,000) appeared to be phosphorylated to a lesser degree in intact platelets by prostaglandin E1 and sodium nitroprusside. Since the phosphorylation of the protein of Mr 50,000 was stimulated both in intact platelets by cyclic-nucleotide-elevating agents and cyclic nucleotide analogs, as well as in platelet membranes by cyclic nucleotides, this phosphoprotein was analyzed by limited proteolysis, tryptic fingerprinting and phosphoamino acid analysis. These experiments indicated that the 50-kDa proteins phosphorylated by sodium nitroprusside and prostaglandin E1 were identical, and that the peptide of the 50-kDa protein phosphorylated by both agents was also the same as the peptide derived from the 50-kDa protein phosphorylated in platelet membranes by cGMP- and cAMP-dependent protein kinases, respectively. Regulation of protein phosphorylation mediated by cAMP- and cGMP-dependent protein kinases may be the molecular mechanism by which those vasodilators, capable of increasing either cAMP or cGMP, inhibit platelet aggregation.
血管扩张剂，如硝普钠、硝酸甘油和各种前列腺素，能够抑制与cGMP或cAMP增加相关的血小板聚集。在我们对完整血小板的研究中，前列腺素E1和硝普钠刺激了几种蛋白质的磷酸化，这些蛋白质与已知由钙调蛋白调节的蛋白激酶或蛋白激酶C磷酸化的蛋白质不同。前列腺素E1（10 microM）或二丁酰cAMP（2 mM）刺激完整血小板中表观相对分子质量（Mr）为240,000、68,000、50,000和22,000的蛋白质磷酸化。在血小板的微粒部分中，低浓度（1-2 microM）的cAMP也能使这些蛋白质磷酸化。在完整血小板中，硝普钠（100 microM）和cGMP的8-溴衍生物（2 mM）增加了一种Mr为50,000的蛋白质的磷酸化，在血小板膜中，低浓度（1-2 microM）的cGMP也能使该蛋白质磷酸化。另一种蛋白质（Mr 24,000）在完整血小板中似乎被前列腺素E1和硝普钠磷酸化的程度较低。由于Mr为50,000的蛋白质的磷酸化在完整血小板中受到环核苷酸升高剂和环核苷酸类似物的刺激，在血小板膜中受到环核苷酸的刺激，因此通过有限蛋白酶解、胰蛋白酶指纹图谱和磷酸氨基酸分析对这种磷蛋白进行了分析。这些实验表明，硝普钠和前列腺素E1磷酸化的50-kDa蛋白质是相同的，并且两种试剂磷酸化的50-kDa蛋白质的肽段也与分别由cGMP和cAMP依赖性蛋白激酶在血小板膜中磷酸化的50-kDa蛋白质衍生的肽段相同。由cAMP和cGMP依赖性蛋白激酶介导的蛋白质磷酸化调节可能是那些能够增加cAMP或cGMP的血管扩张剂抑制血小板聚集的分子机制。
