Inhibition of GDP beta S of agonist-activated phospholipase C in human platelets requires cell permeabilization.
The inhibition by guanosine 5'-[beta-thio]diphosphate (GDP beta S) of phospholipase C was compared in intact and saponin-permeabilized human platelets in order to assess whether effects of GDP beta S on phospholipase C activation unrelated to guanine nucleotide binding function were occurring. GDP beta S exhibited no effect on phospholipase C activity, monitored by phosphatidic acid formation, in intact platelets that were unstimulated or stimulated with 0.5 U/ml thrombin or 20 nM ONO-11113 (a stable thromboxane A2 analogue). However, GDP beta S did cause a marked decrease in the activity of phospholipase C in saponin-permeabilized platelets. Thus GDP beta S is a viable tool for studying the role of G-proteins in transducing receptor-mediated activation of phospholipase C in platelets.
Kucera
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GL
Department of Biochemistry, University of Vermont, College of Medicine, Burlington 05405.
Rittenhouse
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SE
D001792:Blood Platelets / Q000166:cytology / Q000201:enzymology*; D002463:Cell Membrane Permeability; D006150:Guanine Nucleotides; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D010712:Phosphatidic Acids / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology*; D013917:Thrombin / Q000494:pharmacology; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
D006150:Guanine Nucleotides; D010712:Phosphatidic Acids; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D013928:Thromboxane A2; C023427:guanosine 5'-O-(2-thiodiphosphate); C037866:STA 2; D010738:Type C Phospholipases; D013917:Thrombin