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Insulin affects the ability of Gi to be ADP-ribosylated but does not elicit its phosphorylation in intact hepatocytes

Pyne, N J and Heyworth, C M and Balfour, N W and Houslay, M D (1989) Insulin affects the ability of Gi to be ADP-ribosylated but does not elicit its phosphorylation in intact hepatocytes. Biochemical and Biophysical Research Communications, 165 (1). pp. 251-256. ISSN 1090-2104

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Abstract

Insulin inhibited the ability of activated pertussis toxin to catalyse the ADP-ribosylation of alpha-Gi in isolated plasma membranes in either the absence of added guanine nucleotides or in the presence of GTP. In contrast, when the non-hydrolysable GTP analogue guanylyl-5'-imido-diphosphate (p[NH]ppG) was added to ribosylation mixtures, to inhibit the action of pertussis toxin in catalysing the ADP-ribosylation of alpha-Gi, then the addition of insulin attenuated the action of p[NH]ppG causing an increase in alpha-Gi ribosylation. Pre treatment of intact hepatocytes with insulin had no effect on the subsequent ability of thiol-preactivated pertussis toxin to cause the ADP-ribosylation of alpha Gi using isolated membranes from such cells. The ability of p[NH]ppG to inhibit forskolin-stimulated adenylate cyclase activity was attenuated in the presence of insulin. Insulin did not cause the phosphorylation of alpha-Gi in either intact hepatocytes or in isolated membranes.