Prostaglandin-E1- and Sodium Nitroprusside-Regulated Protein Phosphorylation in Platelets
A variety of agents like ADP, collagen, thrombin, platelet-activating- factor (PAF)* and others activate platelets with a concomitant increase in the phosphorylation of myosin light chain (Mr 20 K) and of a soluble protein with apparent Mr of 44 K 1,2. Certain vasodilators such as cGMP-elevating agents (SNP, nitroglycerin) and cAMP-elevating agents (PGE1 PGI2) are able to inhibit platelet activation and the activation-associated protein phosphorylation 1,2. Since cAK and cGK may mediate the effects of cyclic nucleotide-regulating agents in platelets, we have now compared the vasodilator-regulated protein phosphorylation observed in intact platelets with the cyclic nucleotide stimulated protein phosphorylation found in platelet membranes 3,4. The results show for at least one phosphoprotein that the SNP-and PGE1 -stimulated protein phosphorylation is mediated by cGK and cAK, respectively.
KeywordsProtein Phosphorylation Myosin Light Chain Cyclic Nucleotide Platelet Membrane Inhibit Platelet Activation
cAMP-dependent protein kinase
cGMP-dependent protein kinase
1, 2 discylglycerol
protein kinase C
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