Independent Signal-Transduction Pathways for Vanadate and for Insulin in the Activation of Glycogen Synthase and Glycogenesis in Rat Adipocytes

N. Sekar
1999 Endocrinology  
The activating effect of vanadate on glycogenesis and on glycogen synthase (uridine diphosphate-glucose-glycogen glucosyl transferase) activity was studied in rat adipocytes and compared with that of insulin. Using several approaches and specific blockers, we found that vanadate and insulin resemble each other, in the activation of glycogen synthase, in several aspects: both require nonarrested protein phosphatase 1 activity; they are equally suppressed by conditions that elevate cAMP-levels;
more » ... vate cAMP-levels; and both depend on the activation of phosphatidylinositol-3 kinase. The basic differences between them are as follows: 1) vanadate promotes glycogenesis through the activation of a cytosolic protein tyrosine kinase, in an insulin-receptor-independent manner; 2) vanadate elevates glucose-6-phosphate (G-6-P) to a higher level than insulin; 3) vanadate-activated glycogenesis is ac-
doi:10.1210/en.140.3.1125 pmid:10067835 fatcat:35wvei2br5c67aqyfwce65mtjq