casein-kinase-ii and Cardiomyopathy--Hypertrophic

L-type calcium (Ca(2+)) currents conducted by voltage-gated Ca(2+) channel CaV1.2 initiate excitation-contraction coupling in cardiomyocytes. Upon activation of β-adrenergic receptors, phosphorylation of CaV1.2 channels by cAMP-dependent protein kinase (PKA) increases channel activity, thereby allowing more Ca(2+) entry into the cell, which leads to more forceful contraction. In vitro reconstitution studies and in vivo proteomics analysis have revealed that Ser-1700 is a key site of phosphorylation mediating this effect, but the functional role of this amino acid residue in regulation in vivo has remained uncertain. Here we have studied the regulation of calcium current and cell contraction of cardiomyocytes in vitro and cardiac function and homeostasis in vivo in a mouse line expressing the mutation Ser-1700-Ala in the CaV1.2 channel. We found that preventing phosphorylation at this site decreased the basal L-type CaV1.2 current in both neonatal and adult cardiomyocytes. In addition, the incremental increase elicited by isoproterenol was abolished in neonatal cardiomyocytes and was substantially reduced in young adult myocytes. In contrast, cellular contractility was only moderately reduced compared with wild type, suggesting a greater reserve of contractile function and/or recruitment of compensatory mechanisms. Mutant mice develop cardiac hypertrophy by the age of 3-4 mo, and maximal stress-induced exercise tolerance is reduced, indicating impaired physiological regulation in the fight-or-flight response. Our results demonstrate that phosphorylation at Ser-1700 alone is essential to maintain basal Ca(2+) current and regulation by β-adrenergic activation. As a consequence, blocking PKA phosphorylation at this site impairs cardiovascular physiology in vivo, leading to reduced exercise capacity in the fight-or-flight response and development of cardiac hypertrophy.

Topics: Adaptation, Physiological; Adrenergic beta-Agonists; Amino Acid Substitution; Animals; Arrhythmias, Cardiac; Barium; Calcium; Calcium Channels, L-Type; Cardiomyopathy, Hypertrophic; Casein Kinase II; Dihydropyridines; Exercise Tolerance; Heart Failure; Ion Transport; Isoproterenol; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Models, Molecular; Mutation, Missense; Myocardial Contraction; Myocytes, Cardiac; Phosphorylation; Phosphoserine; Point Mutation; Protein Conformation; Protein Processing, Post-Translational; Receptors, Adrenergic, beta; Signal Transduction; Transfection

Cardiac hypertrophy is characterized by transcriptional reprogramming of fetal gene expression, and histone deacetylases (HDACs) are tightly linked to the regulation of those genes. We previously demonstrated that activation of HDAC2, 1 of the class I HDACs, mediates hypertrophy. Here, we show that casein kinase-2α1 (CK2α1)-dependent phosphorylation of HDAC2 S394 is required for the development of cardiac hypertrophy.. Hypertrophic stimuli phosphorylated HDAC2 S394, which was necessary for its enzymatic activation, and therefore the development of hypertrophic phenotypes in rat neonatal cardiomyocytes or in isoproterenol-administered mice hearts. Transgenic mice overexpressing HDAC2 wild type exhibited cardiac hypertrophy, whereas those expressing phosphorylation-resistant HDAC2 S394A did not. Compared with that in age-matched normal human hearts, phosphorylation of HDAC2 S394 was dramatically increased in patients with hypertrophic cardiomyopathy. Hypertrophy-induced phosphorylation of HDAC2 S394 and its enzymatic activity were completely blocked either by CK2 blockers or by CK2α1 short interfering RNA. Hypertrophic stimuli led CK2α1 to be activated, and its chemical inhibitors blocked hypertrophy in both phenylephrine-treated cardiomyocytes and isoproterenol-administered mice. CK2α1-transgenic mice developed hypertrophy, which was attenuated by administration of trichostatin A, an HDAC inhibitor. Overexpression of CK2α1 caused hypertrophy in cardiomyocytes, whereas chemical inhibitors of both CK2 and HDAC as well as HDAC2 S394A blunted it. Hypertrophy in CK2α1-transgenic mice was exaggerated by crossing these mice with wild-type-HDAC2-overexpressing mice. By contrast, however, it was blocked when CK2α1-transgenic mice were crossed with HDAC2 S394A-transgenic mice.. We have demonstrated a novel mechanism in the development of cardiac hypertrophy by which CK2 activates HDAC2 via phosphorylating HDAC2 S394.

Topics: Alanine; Animals; Cardiomegaly; Cardiomyopathy, Hypertrophic; Casein Kinase II; Enzyme Activation; Heart Ventricles; Histone Deacetylase 2; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phosphorylation; Serine