Effects of insulin, pertussis toxin and cholera toxin on protein synthesis and diacylglycerol production in 3T3 fibroblasts: evidence for a G-protein mediated activation of phospholipase C in the insulin signal mechanism.
The rapid increase in protein synthesis that occurs on addition of insulin (1 mU/ml) to stepped-down 3T3 cells was blocked by pre-incubation of the cells with pertussis toxin. Cholera toxin on the other hand stimulated protein synthesis and this effect was insensitive to actinomycin D and inhibited by pre-treatment of the cells with phorbol dibutyrate to deplete cell protein kinase C. Insulin was found to cause a rapid and transient increase in diacylglycerol (DAG) synthesis. The insulin-induced increase in diacylglycerol was blocked by pertussis toxin. Exogenous DAG (10 microM) stimulated protein synthesis within 1 hour. The results suggest that insulin stimulates ribosomal activity through a signal mechanism that involves a G-protein mediated activation of phospholipase C to increase DAG levels.
D000818:Animals; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology*; D004075:Diglycerides / Q000096:biosynthesis*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D005989:Glycerides / Q000096:biosynthesis*; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D037342:Pertussis Toxin; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology; D014316:Tritium; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D004075:Diglycerides; D005989:Glycerides; D007328:Insulin; D010703:Phorbol Esters; D010566:Virulence Factors, Bordetella; D014316:Tritium; D015240:Phorbol 12,13-Dibutyrate; D002772:Cholera Toxin; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins