Alcohol-induced stimulation of phospholipase C in human platelets requires G-protein activation.
In previous studies we have demonstrated that ethanol activates hormone-sensitive phospholipase C in intact human platelets, resulting in the mobilization of intracellular Ca2+ and platelet shape change. The present study aims to localize further this effect of ethanol by examining its interaction with the regulation of phospholipase C in a permeabilized cell system. In platelets permeabilized with a minimal concentration (18 micrograms/ml) of saponin, ethanol by itself did not activate phospholipase C. However, ethanol potentiated the activation of phospholipase C in response to the non-hydrolysable GTP analogue GTP[S] (guanosine 5'-[gamma-thio]triphosphate), an effect similar to that observed with thrombin. Ethanol also potentiated the response to fluoride, which acts directly on G-proteins. Other short-chain alcohols also stimulated phospholipase C in a synergistic manner with GTP[S]. The ability of specific alcohols to stimulate phospholipase C was directly related to their respective lipid-solubilities, as determined by their partition coefficients. Moreover, the potencies of each alcohol correlated with their ability to elicit Ca2+ mobilization and shape change in intact platelets. These effects of ethanol were eliminated by a disruption of receptor-phospholipase C coupling induced by the addition of higher concentrations of saponin. These data indicate that the activation of phospholipase C by ethanol may occur by affecting protein-protein interactions in the signal-transduction complex involving GTP-binding regulatory proteins.
D020001:1-Butanol; D000433:1-Propanol / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D000440:Butanols / Q000494:pharmacology; D002118:Calcium / Q000097:blood; D004790:Enzyme Induction / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000097:blood*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D000432:Methanol / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D010738:Type C Phospholipases / Q000096:biosynthesis* / Q000097:blood
D000440:Butanols; D012503:Saponins; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000431:Ethanol; D006160:Guanosine Triphosphate; D020001:1-Butanol; D000433:1-Propanol; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium; D000432:Methanol