title: 5'-AMP-activated protein kinase phosphorylates IRS-1 on Ser-789 in mouse C2C12 myotubes in response to 5-aminoimidazole-4-carboxamide riboside.
abstract: Exercise is known to increase insulin sensitivity and is an effective form of treatment for the hyperglycemia observed in type 2 diabetes. Activation of 5'-AMP-activated protein kinase (AMPK) by 5-aminoimidazole-4-carboxamide riboside (AICAR), exercise, or electrically stimulated contraction leads to increased glucose transport in skeletal muscle. Here we report the first evidence of a direct interaction between AMPK and the most upstream component of the insulin-signaling cascade, insulin receptor substrate-1 (IRS-1). We find that AMPK rapidly phosphorylates IRS-1 on Ser-789 in cell-free assays as well as in mouse C2C12 myotubes incubated with AICAR. In the C2C12 myotubes activation of AMPK by AICAR matched the phosphorylation of IRS-1 on Ser-789. This phosphorylation correlates with a 65% increase in insulin-stimulated IRS-1-associated phosphatidylinositol 3-kinase activity in C2C12 myotubes preincubated with AICAR. The binding of phosphatidylinositol 3-kinase to IRS-1 was not affected by AICAR. These results demonstrate the existence of an interaction between AMPK and early insulin signaling that could be of importance to our understanding of the potentiating effects of exercise on insulin signaling.
authors.affiliation: Diabetes Biology, Novo Nordisk A/S, Novo Alle, 2880 Bagsvaerd, Denmark. snyj@novonordisk.com
authors.forename: S N
authors.initials: SN
authors.lastname: Jakobsen
authors.forename: D G
authors.initials: DG
authors.lastname: Hardie
authors.forename: N
authors.initials: N
authors.lastname: Morrice
authors.forename: H E
authors.initials: HE
authors.lastname: Tornqvist
mesh_terms: D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000737:chemistry*; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D015153:Blotting, Western; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism*; D018482:Muscle, Skeletal; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012263:Ribonucleosides / Q000737:chemistry*; D012694:Serine / Q000737:chemistry*; D015398:Signal Transduction; D013347:Subcellular Fractions; D013997:Time Factors
chemical_list: D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide; D005947:Glucose; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009097:Multienzyme Complexes; D010455:Peptides; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D012263:Ribonucleosides; D012694:Serine; C526292:IRS1 protein, human; C526295:Irs1 protein, mouse; C011651:acadesine