Vanadate, a protein tyrosine phosphatase inhibitor, preserves insulin-stimulated lipogenesis after removal of insulin. To investigate the mechanism of this action of vanadate, lipogenesis was studied in isolated rat adipocytes exposed to vanadate for 60 min followed by insulin for 15 min at 37°C. Vanadate (10–50 μM) prolonged insulin-stimulated lipogenesis. The half-time (t½) of the decay in insulin (0.34 nM)-stimulated lipogenesis after removal of insulin by washing in pH 7.0 followed by pH 7.6 buffer was 21 min in the absence and 59 min in the presence of vanadate. During these conditions, vanadate did not alter insulin binding nor the removal of insulin by the series of washes. In contrast to lipogenesis, the t½ of the decay in insulin receptor tyrosine kinase (IRK) activity, assayed with the artificial substrate Poly[Glu:Tyr] (4:1), was not significantly prolonged by vanadate (6 vs. 6.8 min). However, insulin-stimulated IRK activity was markedly augmented by vanadate to 319 ± 19% of insulin alone, associated with a similar augmentation of phosphotyrosine incorporation into the insulin receptor beta-subunit determined by Western blotting with antiphosphotyrosine antibodies. To determine the relationship between prolongation of lipogenesis and the increase in IRK, adipocytes were exposed to 17.2 nM insulin to activate the IRK to the same extent as insulin (0.34 nM) plus vanadate (maximum activation). During these two conditions, the decay of lipogenesis was similar and after stimulation with 17.2 nM insulin was not prolonged by vanadate. We conclude that vanadate prolongs insulin action at insulin concentrations that do not maximally activate the IRK by augmenting IRK activity.The data suggest that the amplitude of the insulin signal, the IRK, is transduced into duration of response, lipogenesis. Thus activation of receptor above that required for a maximum biological response results in prolongation of action.
Original Articles|
March 01 1994
Vanadate Augments Insulin-Stimulated Insulin Receptor Kinase Activity and Prolongs Insulin Action In Rat Adipocytes: Evidence for Transduction of Amplitude of Signaling into Duration of Response
I George Fantus;
I George Fantus
Protein and Polypeptide Hormone Laboratory, Department of Medicine, Royal Victoria Hospital and McGill University
Montreal, Quebec
Department of Medicine, Mount Sinai Hospital and Banting and Best Diabetes Center, University of Toronto
Toronto, Ontario, Canada
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Ferhaan Ahmad;
Ferhaan Ahmad
Protein and Polypeptide Hormone Laboratory, Department of Medicine, Royal Victoria Hospital and McGill University
Montreal, Quebec
Department of Medicine, Mount Sinai Hospital and Banting and Best Diabetes Center, University of Toronto
Toronto, Ontario, Canada
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Guy Deragon
Guy Deragon
Protein and Polypeptide Hormone Laboratory, Department of Medicine, Royal Victoria Hospital and McGill University
Montreal, Quebec
Department of Medicine, Mount Sinai Hospital and Banting and Best Diabetes Center, University of Toronto
Toronto, Ontario, Canada
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Address correspondence and reprint requests to Dr. I.G. Fantus, Department of Medicine, Mount Sinai Hospital, 600 University Avenue, Suite 780, Toronto, Ontario M5G 1X5, Canada.
Diabetes 1994;43(3):375–383
Article history
Received:
November 23 1992
Revision Received:
November 04 1993
Accepted:
November 04 1993
PubMed:
7508873
Citation
I George Fantus, Ferhaan Ahmad, Guy Deragon; Vanadate Augments Insulin-Stimulated Insulin Receptor Kinase Activity and Prolongs Insulin Action In Rat Adipocytes: Evidence for Transduction of Amplitude of Signaling into Duration of Response. Diabetes 1 March 1994; 43 (3): 375–383. https://doi.org/10.2337/diab.43.3.375
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