title: 5'-AMP-activated protein kinase is inactivated by adrenergic signalling in adult cardiac myocytes.
abstract: In adult rat cardiac myocytes adrenaline decreased AMPK (AMP-activated protein kinase) activity with a half-time of approximately 4 min, decreased phosphorylation of AMPK (α-Thr172) and decreased phosphorylation of ACC (acetyl-CoA carboxylase). Inactivation of AMPK by adrenaline was through both α1- and β-ARs (adrenergic receptors), but did not involve cAMP or calcium signalling, was not blocked by the PKC (protein kinase C) inhibitor BIM I (bisindoylmaleimide I), by the ERK (extracellular-signal-regulated kinase) cascade inhibitor U0126 or by PTX (pertussis toxin). Adrenaline caused no measurable change in LKB1 activity. Adrenaline decreased AMPK activity through a process that was distinct from AMPK inactivation in response to insulin or PMA. Neither adrenaline nor PMA altered the myocyte AMP:ATP ratio although the adrenaline effect was attenuated by oligomycin and by AICAR (5-amino-4-imidazolecarboxamide-1-β-D-ribofuranoside), agents that mimic 'metabolic stress'. Inactivation of AMPK by adrenaline was abolished by 1 μM okadaic acid suggesting that activation of PP2A (phosphoprotein phosphatase 2A) might mediate the adrenaline effect. However, no change in PP2A activity was detected in myocyte extracts. Adrenaline increased phosphorylation of the AMPK β-subunit in vitro but there was no detectable change in vivo in phosphorylation of previously identified AMPK sites (β-Ser24, β-Ser108 or β-Ser182) suggesting that another site(s) is targeted.
authors.affiliation: *Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London, WC1E 6BT, U.K.
authors.forename: Yugo
authors.initials: Y
authors.lastname: Tsuchiya
authors.forename: Fiona C
authors.initials: FC
authors.lastname: Denison
authors.forename: Richard B
authors.initials: RB
authors.lastname: Heath
authors.forename: David
authors.initials: D
authors.lastname: Carling
authors.forename: David
authors.initials: D
authors.lastname: Saggerson
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000225:Adenine / Q000378:metabolism; D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D004789:Enzyme Activation; D004837:Epinephrine / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism
chemical_list: D007328:Insulin; D011943:Receptors, Adrenergic, beta; D055372:AMP-Activated Protein Kinases; D054648:Protein Phosphatase 2; D000103:Acetyl-CoA Carboxylase; D000225:Adenine; D004837:Epinephrine