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The α 2 ‐Subunit of AMP‐activated Protein Kinase Is a Potent Modulator of Myocardial Diastolic Calcium Homeostasis
Author(s) -
Pohl Ulrich,
Fein Evelyn,
Kameritsch Petra,
Schneider Holger,
Engelhardt Stefan,
Dendorfer Andreas,
Blodow Stephanie
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.969.22
Subject(s) - phospholamban , ampk , medicine , serca , endocrinology , protein kinase a , chemistry , calcium , phosphorylation , biology , atpase , biochemistry , enzyme
Rationale The heterotrimeric enzyme 5′‐adenosine monophosphate‐activated protein kinase (AMPK) is known to have cardioprotective effects which may be partly due to a participation in the control of intracellular calcium concentration. Recently, we described in vascular smooth muscle a dilator role for AMPK which is due to sarcoplasmic reticulum Ca 2+ ‐ATPase (SERCA)‐dependent calcium decrease. The present study elucidates a possible role of AMPK for myocardial diastolic calcium decrease. Objective To investigate, whether AMPK contributes to the regulation of SERCA dependent myocardial diastolic calcium homeostasis via phosphorylation of phospholamban (PLN) and to identify which catalytic subunit of AMPK was involved. Methods and Results Freshly obtained heart slices of wildtype and AMPKα2‐gene‐deficient mice were analyzed by recording contraction amplitudes and relaxation velocities in the presence or absence of the AMPK activator A769662. A769662 (30 μM, 15 min) increased phosphorylation of AMPKThr172 showing effective activation of the enzyme. The AMPK stimulator induced positive inotropic (contraction amplitudes +75%) and lusitropic (relaxation velocity +71%) effects in isolated heart slices (p<0.05 vs controls, n=6–11). The latter corresponded to a significant shortening of the time constant of Ca 2+ ‐transient decay (tau, −25%, Fura2 method, n=15–23) which was similar to the effect observed after stimulation with isoproterenol (100 nM). A second structurally different AMPK activator, PT1 (30 μM), virtually mimicked the A769662‐induced positive inotropy and lusitropy. Western Blots (n=3–9) of freshly isolated, A769662‐stimulated adult mouse cardiomyocytes showed an enhanced phosphorylation of PLN, but exclusively at the regulatory site Thr17, whereas isoproterenol led to increases in phosphorylation of both regulatory sites, PLNSer16 and Thr17. The A769662‐induced effects were blunted in slices and cells isolated from AMPKα2‐gene‐deficient mice while isoproterenol was still effective (n=4–5). Conclusions Our data suggest that AMPK, via its catalytic α2‐subunit, induces phosphorylation of PLNThr17 thereby accelerating diastolic Ca 2+ ‐decrease and increasing relaxation velocity. This novel AMPK‐PLN‐ pathway could serve as a valuable new therapeutic target in failing hearts showing reduced responsiveness to b‐adrenergic stimulation. Support or Funding Information Supported by the DZHK (German Centre for Cardiovascular Research)