title: Insulin inhibits AMPK activity and phosphorylates AMPK Ser⁴⁸⁵/⁴⁹¹ through Akt in hepatocytes, myotubes and incubated rat skeletal muscle.
abstract: Recent studies have highlighted the importance of an inhibitory phosphorylation site, Ser(485/491), on the α-subunit of AMP-activated protein kinase (AMPK); however, little is known about the regulation of this site in liver and skeletal muscle. We examined whether the inhibitory effects of insulin on AMPK activity may be mediated through the phosphorylation of this inhibitory Ser(485/491) site in hepatocytes, myotubes and incubated skeletal muscle. HepG2 and C2C12 cells were stimulated with or without insulin for 15-min. Similarly, rat extensor digitorum longus (EDL) muscles were treated +/- insulin for 10-min. Insulin significantly increased Ser(485/491) p-AMPK under all conditions, resulting in a subsequent reduction in AMPK activity, ranging from 40% to 70%, despite no change in p-AMPK Thr(172). Akt inhibition both attenuated the increase in Ser(485/491) p-AMPK caused by insulin, and prevented the decrease in AMPK activity. Similarly, the growth factor IGF-1 stimulated Ser(485/491) AMPK phosphorylation, and this too was blunted by inhibition of Akt. Inhibition of the mTOR pathway with rapamycin, however, had no effect on insulin-stimulated Ser(485/491) p-AMPK. These data suggest that insulin and IGF-1 diminish AMPK activity in hepatocytes and muscle, most likely through Akt activation and the inhibitory phosphorylation of Ser(485/491) on its α-subunit.
authors.affiliation: Endocrinology, Diabetes, and Nutrition Section, Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Rudy J
authors.initials: RJ
authors.lastname: Valentine
authors.affiliation: Endocrinology, Diabetes, and Nutrition Section, Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Coughlan
authors.affiliation: Endocrinology, Diabetes, and Nutrition Section, Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Neil B
authors.initials: NB
authors.lastname: Ruderman
authors.affiliation: Endocrinology, Diabetes, and Nutrition Section, Department of Medicine, Boston University School of Medicine, Boston, MA, USA. Electronic address: aksaha@bu.edu.
authors.forename: Asish K
authors.initials: AK
authors.lastname: Saha
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology
chemical_list: D007328:Insulin; D012694:Serine; D007334:Insulin-Like Growth Factor I; C548179:Prkaa1 protein, mouse; C534978:Prkaa2 protein, mouse; C526181:PRKAA2 protein, human; C543928:Prkaa2 protein, rat; D055372:AMP-Activated Protein Kinases; C526180:PRKAA1 protein, human; C568305:Prkaa1 protein, rat; D020123:Sirolimus
keywords: AMPK; Growth factors; Insulin; PKB; Ser(485/491)