title: Phosphorylation of Ser357 of rat insulin receptor substrate-1 mediates adverse effects of protein kinase C-delta on insulin action in skeletal muscle cells.
abstract: The activation of the protein kinase C (PKC) family of serine/threonine kinases contributes to the modulation of insulin signaling, and the PKC-dependent phosphorylation of insulin receptor substrate (IRS)-1 has been implicated in the development of insulin resistance. Here we demonstrate Ser(357) of rat IRS-1 as a novel PKC-delta-dependent phosphorylation site in skeletal muscle cells upon stimulation with insulin and phorbol ester using Ser(P)(357) antibodies and active and kinase dead mutants of PKC-delta. Phosphorylation of this site was simulated using IRS-1 Glu(357) and shown to reduce insulin-induced tyrosine phosphorylation of IRS-1, to decrease activation of Akt, and to subsequently diminish phosphorylation of glycogen synthase kinase-3. When the phosphorylation was prevented by mutation of Ser(357) to alanine, these effects of insulin were enhanced. When the adjacent Ser(358), present in mouse and rat IRS-1, was mutated to alanine, which is homologous to the human sequence, the insulin-induced phosphorylation of glycogen synthase kinase-3 or tyrosine phosphorylation of IRS-1 was not increased. Moreover, both active PKC-delta and phosphorylation of Ser(357) were shown to be necessary for the attenuation of insulin-stimulated Akt phosphorylation. The phosphorylation of Ser(357) could lead to increased association of PKC-delta to IRS-1 upon insulin stimulation, which was demonstrated with IRS-1 Glu(357). Together, these data suggest that phosphorylation of Ser(357) mediates at least in part the adverse effects of PKC-delta activation on insulin action.
authors.affiliation: Division of Clinical Chemistry and Pathobiochemistry, University of Tuebingen, Tuebingen, Germany.
authors.forename: Rizwana Sanaullah
authors.initials: RS
authors.lastname: Waraich
authors.forename: Cora
authors.initials: C
authors.lastname: Weigert
authors.forename: Hubert
authors.initials: H
authors.lastname: Kalbacher
authors.forename: Anita M
authors.initials: AM
authors.lastname: Hennige
authors.forename: Stefan Z
authors.initials: SZ
authors.lastname: Lutz
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Häring
authors.forename: Erwin D
authors.initials: ED
authors.lastname: Schleicher
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Voelter
authors.forename: Rainer
authors.initials: R
authors.lastname: Lehmann
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D006224:Cricetinae; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D007668:Kidney / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D012694:Serine / Q000737:chemistry*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C526296:Irs1 protein, rat; D012694:Serine; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta