title: Metabolic and signaling events mediated by cardiotonic steroid ouabain in rat skeletal muscle.
abstract: The cardiac glycoside ouabain initiates a cascade of signaling events through Na+,K+-ATPase, leading to an increase in cell growth and proliferation in different cell types. We explored the effects of ouabain on glucose metabolism in skeletal muscle and clarified the mechanisms of ouabain signal transduction. In rat soleus muscle 200 microM ouabain decreased basal glucose uptake without effect on insulin-stimulated glucose uptake. Ouabain increased glycogen synthesis additively to insulin and this effect was abolished in the presence of a MEK1/2 inhibitor (PD98059) or a c-Src inhibitor (PP2). Ouabain exposure reduced glucose oxidation, and this effect was reversed in the presence of PP2. Incubation with ouabain did not affect intramuscular ATP and its metabolites; however acetyl-CoA carboxylase phosphorylation was reduced, with no effect on AMPK phosphorylation. Insulin-stimulated Akt phosphorylation was not affected by ouabain. Ouabain reduced basal and insulin-stimulated phosphorylation of PKC alpha/beta and delta isoforms, whereas phosphorylation of PKCzeta was unchanged. Ouabain exposure increased interaction of 1- and 2-subunits of Na-pump with c-Src, as assessed by co-immunoprecipitation with c-Src. Phosphorylation of ERK1/2, GSK 3 / and p90rsk activity was increased in response to ouabain, and these effects were prevented in the presence of PD98059 and PP2. In conclusion, the cardiac glycoside ouabain stimulates glycogen synthesis additively to insulin in rat skeletal muscle. This effect is mediated by activation of c-Src-, ERK1/2- p90rsk- and GSK3-dependent signaling pathway.
authors.affiliation: Section of Integrative Physiology, Department of Molecular Medecine and Surgery, Karolinska Institutet, Stockholm Sweden.
authors.forename: O
authors.initials: O
authors.lastname: Kotova
authors.forename: D
authors.initials: D
authors.lastname: Galuska
authors.forename: B
authors.initials: B
authors.lastname: Essén-Gustavsson
authors.forename: A V
authors.initials: AV
authors.lastname: Chibalin
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002301:Cardiac Glycosides / Q000378:metabolism* / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D016391:Genes, src / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000096:biosynthesis; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D066298:In Vitro Techniques; D007328:Insulin / Q000502:physiology; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D011913:Rats, Inbred BB; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C412373:AG 1879; D002301:Cardiac Glycosides; D005419:Flavonoids; D007328:Insulin; D007527:Isoenzymes; D011743:Pyrimidines; D010042:Ouabain; D000255:Adenosine Triphosphate; D006003:Glycogen; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3; D000103:Acetyl-CoA Carboxylase; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one