title: Activation of AMP-activated protein kinase stimulates Na+,K+-ATPase activity in skeletal muscle cells.
abstract: Contraction stimulates Na(+),K(+)-ATPase and AMP-activated protein kinase (AMPK) activity in skeletal muscle. Whether AMPK activation affects Na(+),K(+)-ATPase activity in skeletal muscle remains to be determined. Short term stimulation of rat L6 myotubes with the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), activates AMPK and promotes translocation of the Na(+),K(+)-ATPase α(1)-subunit to the plasma membrane and increases Na(+),K(+)-ATPase activity as assessed by ouabain-sensitive (86)Rb(+) uptake. Cyanide-induced artificial anoxia, as well as a direct AMPK activator (A-769662) also increase AMPK phosphorylation and Na(+),K(+)-ATPase activity. Thus, different stimuli that target AMPK concomitantly increase Na(+),K(+)-ATPase activity. The effect of AICAR on Na(+),K(+)-ATPase in L6 myotubes was attenuated by Compound C, an AMPK inhibitor, as well as siRNA-mediated AMPK silencing. The effects of AICAR on Na(+),K(+)-ATPase were completely abolished in cultured primary mouse muscle cells lacking AMPK α-subunits. AMPK stimulation leads to Na(+),K(+)-ATPase α(1)-subunit dephosphorylation at Ser(18), which may prevent endocytosis of the sodium pump. AICAR stimulation leads to methylation and dephosphorylation of the catalytic subunit of the protein phosphatase (PP) 2A in L6 myotubes. Moreover, AICAR-triggered dephosphorylation of the Na(+),K(+)-ATPase was prevented in L6 myotubes deficient in PP2A-specific protein phosphatase methylesterase-1 (PME-1), indicating a role for the PP2A·PME-1 complex in AMPK-mediated regulation of Na(+),K(+)-ATPase. Thus contrary to the common paradigm, we report AMPK-dependent activation of an energy-consuming ion pumping process. This activation may be a potential mechanism by which exercise and metabolic stress activate the sodium pump in skeletal muscle.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Boubacar
authors.initials: B
authors.lastname: Benziane
authors.forename: Marie
authors.initials: M
authors.lastname: Björnholm
authors.forename: Sergej
authors.initials: S
authors.lastname: Pirkmajer
authors.forename: Reginald L
authors.initials: RL
authors.lastname: Austin
authors.forename: Olga
authors.initials: O
authors.lastname: Kotova
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.forename: Juleen R
authors.initials: JR
authors.lastname: Zierath
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Chibalin
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001713:Biphenyl Compounds; D015153:Blotting, Western; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D015687:Cell Hypoxia; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D008745:Methylation / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011753:Pyrones / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D012265:Ribonucleotides / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013876:Thiophenes / Q000494:pharmacology; D000099221:Protein Kinase C zeta
chemical_list: D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide; D001713:Biphenyl Compounds; D002265:Carboxylic Ester Hydrolases; D011493:Protein Kinase C; D021122:Protein Subunits; D011753:Pyrones; D012265:Ribonucleotides; D000254:Sodium-Potassium-Exchanging ATPase; D013876:Thiophenes; D000099221:Protein Kinase C zeta; C119357:protein phosphatase methylesterase-1; C499075:Atp1a1 protein, rat; C031143:AICA ribonucleotide; C512408:4-hydroxy-3-(4-(2-hydroxyphenyl)phenyl)-6-oxo-7H-thieno(2,3-b)pyridine-5-carbonitrile