PERTUSSIS TOXIN CATALYZED ADP-RIBOSYLATION OF A 41-KDA G-PROTEIN IMPAIRS INSULIN-STIMULATED GLUCOSE-METABOLISM IN BC3H-1 MYOCYTES

In this study, we examined the effects of pertussis toxin (PT) on the ADP‐ribosylation of guanine nucleotide binding proteins (G‐proteins) and various insulinstimulated processes in cultured BC3H‐1 myocytes. Treatment of intact myocytes with 0.1 μg/ml PT for 24 hours resulted in the complete ribosylation of a 41 kDa protein. The 41 kDa PT substrate was immunoprecipitated with antibodies directed against a synthetic peptide corresponding to a unique sequence in the alpha subunit of Gi‐proteins. PT treatment of intact cells had no effect on insulin receptor binding or internalization. However, PT inhibited insulin‐stimulated glucose transport at all insulin‐concentrations tested (1–100ng/ml). Maximally stimulated glucose transport was reduced by 50% ± 15%. Insulin‐stimulated glucose oxidation was also decreased by 31% ± 8%. The toxin had no significant effect on the basal rates of glucose transport and glucose oxidation. The time course of PT‐induced inhibition on glucose transport correlated with the time course of the “in vivo” ADP‐ribosylation of the 41 kDa protein. The results suggest that a 41 kDa PT‐sensitive G‐protein, identical or very similar to Gi, is involved in the regulation of glucose metabolism by insulin in BC3H‐1 cells. Copyright © 1990 Wiley‐Liss, Inc.