title: ERK1/2 mediates insulin stimulation of Na(+),K(+)-ATPase by phosphorylation of the alpha-subunit in human skeletal muscle cells.
abstract: Insulin stimulates Na(+),K(+)-ATPase activity and induces translocation of Na(+),K(+)-ATPase molecules to the plasma membrane in skeletal muscle. We determined the molecular mechanism by which insulin regulates Na(+),K(+)-ATPase in differentiated primary human skeletal muscle cells (HSMCs). Insulin action on Na(+),K(+)-ATPase was dependent on ERK1/2 in HSMCs. Sequence analysis of Na(+),K(+)-ATPase alpha-subunits revealed several potential ERK phosphorylation sites. Insulin increased ouabain-sensitive (86)Rb(+) uptake and [(3)H]ouabain binding in intact cells. Insulin also increased phosphorylation and plasma membrane content of the Na(+),K(+)-ATPase alpha(1)- and alpha(2)-subunits. Insulin-stimulated Na(+),K(+)-ATPase activation, phosphorylation, and translocation of alpha-subunits to the plasma membrane were abolished by 20 microm PD98059, which is an inhibitor of MEK1/2, an upstream kinase of ERK1/2. Furthermore, inhibitors of phosphatidylinositol 3-kinase (100 nm wortmannin) and protein kinase C (10 microm GF109203X) had similar effects. Notably, insulin-stimulated ERK1/2 phosphorylation was abolished by wortmannin and GF109203X in HSMCs. Insulin also stimulated phosphorylation of alpha(1)- and alpha(2)-subunits on Thr-Pro amino acid motifs, which form specific ERK substrates. Furthermore, recombinant ERK1 and -2 kinases were able to phosphorylate alpha-subunit of purified human Na(+),K(+)-ATPase in vitro. In conclusion, insulin stimulates Na(+),K(+)-ATPase activity and translocation to plasma membrane in HSMCs via phosphorylation of the alpha-subunits by ERK1/2 mitogen-activated protein kinase.
authors.affiliation: Section of Integrative Physiology, Department of Surgical Sciences, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lubna
authors.initials: L
authors.lastname: Al-Khalili
authors.forename: Olga
authors.initials: O
authors.lastname: Kotova
authors.forename: Hiroki
authors.initials: H
authors.lastname: Tsuchida
authors.forename: Ingrid
authors.initials: I
authors.lastname: Ehrén
authors.forename: Eric
authors.initials: E
authors.lastname: Féraille
authors.forename: Anna
authors.initials: A
authors.lastname: Krook
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Chibalin
mesh_terms: D019921:Biotinylation; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010042:Ouabain / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D021122:Protein Subunits; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007328:Insulin; D021122:Protein Subunits; D010042:Ouabain; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase