title: Differential regulation of eEF2 and p70S6K by AMPKalpha2 in heart.
abstract: Eukaryotic elongation factor 2 (eEF-2) and mammalian target of rapamycin (mTOR)-p70 ribosomal protein S6 kinase (p70S6K) signaling pathways control protein synthesis and are inhibited during myocardial ischemia. Intracellular acidosis and AMP-activated protein kinase (AMPK) activation, both occurring during ischemia, have been proposed to participate in this inhibition. We evaluated the contribution of AMPKα2, the main cardiac AMPK catalytic subunit isoform, in eEF2 and mTOR-p70S6K regulation using AMPKα2 KO mice. Hearts were perfused ex vivo with or without insulin, and then submitted or not to ischemia. Insulin pre-incubation was necessary to activate mTOR-p70S6K and evaluate their subsequent inhibition by ischemia. Ischemia decreased insulin-induced mTOR-p70S6K phosphorylation in WT and AMPKα2 KO mice to a similar extent. This AMPKα2-independent p70S6K inhibition correlated well with the inhibition of PKB/Akt, located upstream of mTOR-p70S6K and can be mimicked in cardiomyocytes by decreasing pH. By contrast, ischemia-induced inhibitory phosphorylation of eEF-2 was drastically reduced in AMPKα2 KO mice. Interestingly, AMPKα2 also played a role under normoxia. Its deletion increased the insulin-induced p70S6K stimulation. This p70S6K over-stimulation was associated with a decrease in inhibitory phosphorylation of Raptor, an mTOR partner identified as an AMPK target. In conclusion, AMPKα2 controls cardiac p70S6K under normoxia and regulates eEF-2 but not the mTOR-p70S6K pathway during ischemia. This challenges the accepted notion that mTOR-p70S6K is inhibited by myocardial ischemia mainly via an AMPK-dependent mechanism.
authors: Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle de Recherche Cardiovasculaire, Avenue Hippocrate, 55, B1.55.05, 1200 Brussels, Belgium.
authors: Bénédicte
authors: B
authors: Demeulder
authors: Elham
authors: E
authors: Zarrinpashneh
authors: Audrey
authors: A
authors: Ginion
authors: Benoit
authors: B
authors: Viollet
authors: Louis
authors: L
authors: Hue
authors: Mark H
authors: MH
authors: Rider
authors: Jean-Louis
authors: JL
authors: Vanoverschelde
authors: Christophe
authors: C
authors: Beauloye
authors: Sandrine
authors: S
authors: Horman
authors: Luc
authors: L
authors: Bertrand
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D017202:Myocardial Ischemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D020652:Peptide Elongation Factor 2 / Q000235:genetics / Q000378:metabolism*; D000076223:Regulatory-Associated Protein of mTOR; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D009124:Muscle Proteins; D020652:Peptide Elongation Factor 2; D000076223:Regulatory-Associated Protein of mTOR; C540162:Rptor protein, mouse; C546843:mTOR protein, mouse; C534978:Prkaa2 protein, mouse; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases