Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

RATIONALE: AMP-activated protein kinase (AMPK) is an important regulator of energy balance and signaling in the heart. Mutations affecting the regulatory γ2 subunit have been shown to cause an essentially cardiac-restricted phenotype of hypertrophy and conduction disease, suggesting a specific role for this subunit in the heart. OBJECTIVE: The γ isoforms are highly conserved at their C-termini but have unique N-terminal sequences, and we hypothesized that the N-terminus of γ2 may be involved in conferring substrate specificity or in determining intracellular localization. METHODS AND RESULTS: A yeast 2-hybrid screen of a human heart cDNA library using the N-terminal 273 residues of γ2 as bait identified cardiac troponin I (cTnI) as a putative interactor. In vitro studies showed that cTnI is a good AMPK substrate and that Ser150 is the principal residue phosphorylated. Furthermore, on AMPK activation during ischemia, Ser150 is phosphorylated in whole hearts. Using phosphomimics, measurements of actomyosin ATPase in vitro and force generation in demembraneated trabeculae showed that modification at Ser150 resulted in increased Ca(2+) sensitivity of contractile regulation. Treatment of cardiomyocytes with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) resulted in increased myocyte contractility without changing the amplitude of Ca(2+) transient and prolonged relaxation despite shortening the time constant of Ca(2+) transient decay (tau). Compound C prevented the effect of AICAR on myocyte function. These results suggest that AMPK activation increases myocyte contraction and prolongs relaxation by increasing myofilament Ca(2+) sensitivity. CONCLUSIONS: We conclude that cTnI phosphorylation by AMPK may represent a novel mechanism of regulation of cardiac function.

Original publication

DOI

10.1161/CIRCRESAHA.111.259952

Type

Conference paper

Publication Date

27/04/2012

Volume

110

Pages

1192 - 1201

Keywords

AMP-Activated Protein Kinases, Aminoimidazole Carboxamide, Animals, Calcium Signaling, Enzyme Activation, Enzyme Activators, Heart Ventricles, Humans, Male, Mice, Mice, Inbred C57BL, Myocardial Contraction, Myocytes, Cardiac, Myosins, Phosphorylation, Protein Kinase Inhibitors, Pyrazoles, Pyrimidines, Ribonucleotides, Serine, Time Factors, Troponin I, Two-Hybrid System Techniques, Ventricular Function, Left