Insulin stimulation of glycogen synthesis and glycogen synthase activity is blocked by wortmannin and rapamycin in 3T3-L1 adipocytes: evidence for the involvement of phosphoinositide 3-kinase and p70 ribosomal protein-S6 kinase.
We have investigated the involvement of phosphoinositide (PI) 3-kinase and p70 ribosomal protein-S6 kinase (p70s6k) in mediating insulin stimulation of glycogen synthesis in 3T3-L1 adipocytes using specific inhibitors. Wortmannin inhibited PI 3-kinase activity (IC50 approximately 10 nM), inhibition being complete at 100 nm. Wortmannin (100 nM) completely blocked the ability of insulin to activate glycogen synthase in 3T3-L1 adipocytes and the ability of insulin to stimulate glucose incorporation into glycogen in 3T3-L1 fibroblasts. Rapamycin, which blocks insulin-stimulated activation of p70s6k, decreased insulin activation of glycogen synthase in a dose-dependent manner (IC50 approximately 0.8 ng/ml), with a maximum approx. 75% inhibition of insulin's stimulatory effect. Rapamycin inhibited insulin-stimulated glucose incorporation into glycogen to a similar extent and with similar dose-dependency, while having no effect on insulin-stimulated glucose transport. We conclude that PI 3-kinase and p70s6k are involved in the signalling pathways by which insulin stimulates glycogen synthase in 3T3-L1 adipocytes.
Shepherd
P R
PR
Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, U.K.
Navé
B T
BT
Siddle
K
K
D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology*; D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006003:Glycogen / Q000096:biosynthesis*; D006006:Glycogen Synthase / Q000187:drug effects* / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D007329:Insulin Antagonists / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism; D011090:Polyenes / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; D013268:Stimulation, Chemical; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D006003:Glycogen; D006006:Glycogen Synthase; D007328:Insulin; D007329:Insulin Antagonists; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011090:Polyenes; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; D000077191:Wortmannin