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Alim CC, Ko CY, Mira Hernandez J, Shen EY, Baidar S, Chen‐Izu Y, Bers DM, Bossuyt J. Nitrosylation of cardiac CaMKII at Cys290 mediates mechanical afterload-induced increases in Ca 2+ transient and Ca 2+ sparks. J Physiol 2022; 600:4865-4879. [PMID: 36227145 PMCID: PMC9827875 DOI: 10.1113/jp283427] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 09/30/2022] [Indexed: 01/12/2023] Open
Abstract
Cardiac mechanical afterload induces an intrinsic autoregulatory increase in myocyte Ca2+ dynamics and contractility to enhance contraction (known as the Anrep effect or slow force response). Our prior work has implicated both nitric oxide (NO) produced by NO synthase 1 (NOS1) and calcium/calmodulin-dependent protein kinase II (CaMKII) activity as required mediators of this form of mechano-chemo-transduction. To test whether a single S-nitrosylation site on CaMKIIδ (Cys290) mediates enhanced sarcoplasmic reticulum Ca2+ leak and afterload-induced increases in sarcoplasmic reticulum (SR) Ca2+ uptake and release, we created a novel CRISPR-based CaMKIIδ knock-in (KI) mouse with a Cys to Ala mutation at C290. These CaMKIIδ-C290A-KI mice exhibited normal cardiac morphometry and function, as well as basal myocyte Ca2+ transients (CaTs) and β-adrenergic responses. However, the NO donor S-nitrosoglutathione caused an acute increased Ca2+ spark frequency in wild-type (WT) myocytes that was absent in the CaMKIIδ-C290A-KI myocytes. Using our cell-in-gel system to exert multiaxial three-dimensional mechanical afterload on myocytes during contraction, we found that WT myocytes exhibited an afterload-induced increase in Ca2+ sparks and Ca2+ transient amplitude and rate of decline. These afterload-induced effects were prevented in both cardiac-specific CaMKIIδ knockout and point mutant CaMKIIδ-C290A-KI myocytes. We conclude that CaMKIIδ activation by S-nitrosylation at the C290 site is essential in mediating the intrinsic afterload-induced enhancement of myocyte SR Ca2+ uptake, release and Ca2+ transient amplitude (the Anrep effect). The data also indicate that NOS1 activation is upstream of S-nitrosylation at C290 of CaMKII, and that this molecular mechano-chemo-transduction pathway is beneficial in allowing the heart to increase contractility to limit the reduction in stroke volume when aortic pressure (afterload) is elevated. KEY POINTS: A novel CRISPR-based CaMKIIδ knock-in mouse was created in which kinase activation by S-nitrosylation at Cys290 (C290A) is prevented. How afterload affects Ca2+ signalling was measured in cardiac myocytes that were embedded in a hydrogel that imposes a three-dimensional afterload. This mechanical afterload induced an increase in Ca2+ transient amplitude and decay in wild-type myocytes, but not in cardiac-specific CaMKIIδ knockout or C290A knock-in myocytes. The CaMKIIδ-C290 S-nitrosylation site is essential for the afterload-induced enhancement of Ca2+ transient amplitude and Ca2+ sparks.
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Affiliation(s)
- Chidera C. Alim
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | | | - Juliana Mira Hernandez
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA,Research Group in Veterinary MedicineSchool of Veterinary MedicineUniversity Corporation LasallistaCaldasAntioquiaColombia
| | - Erin Y. Shen
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Sonya Baidar
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Ye Chen‐Izu
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA,Department of Biomedical EngineeringUniversity of CaliforniaDavisCAUSA,Department of Internal Medicine/CardiologyUniversity of CaliforniaDavisCAUSA
| | - Donald M. Bers
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
| | - Julie Bossuyt
- Department of PharmacologyUniversity of CaliforniaDavisCAUSA
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2
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Wright PT, Gorelik J, Harding SE. Electrophysiological Remodeling: Cardiac T-Tubules and ß-Adrenoceptors. Cells 2021; 10:cells10092456. [PMID: 34572106 PMCID: PMC8468945 DOI: 10.3390/cells10092456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 01/09/2023] Open
Abstract
Beta-adrenoceptors (βAR) are often viewed as archetypal G-protein coupled receptors. Over the past fifteen years, investigations in cardiovascular biology have provided remarkable insights into this receptor family. These studies have shifted pharmacological dogma, from one which centralized the receptor to a new focus on structural micro-domains such as caveolae and t-tubules. Important studies have examined, separately, the structural compartmentation of ion channels and βAR. Despite links being assumed, relatively few studies have specifically examined the direct link between structural remodeling and electrical remodeling with a focus on βAR. In this review, we will examine the nature of receptor and ion channel dysfunction on a substrate of cardiomyocyte microdomain remodeling, as well as the likely ramifications for cardiac electrophysiology. We will then discuss the advances in methodologies in this area with a specific focus on super-resolution microscopy, fluorescent imaging, and new approaches involving microdomain specific, polymer-based agonists. The advent of powerful computational modelling approaches has allowed the science to shift from purely empirical work, and may allow future investigations based on prediction. Issues such as the cross-reactivity of receptors and cellular heterogeneity will also be discussed. Finally, we will speculate as to the potential developments within this field over the next ten years.
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Affiliation(s)
- Peter T. Wright
- School of Life & Health Sciences, University of Roehampton, Holybourne Avenue, London SW15 4JD, UK;
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
| | - Julia Gorelik
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
| | - Sian E. Harding
- Cardiac Section, National Heart and Lung Institute (NHLI), Faculty of Medicine, Imperial College London, Hammersmith Campus, Du Cane Road, London W12 0NN, UK;
- Correspondence:
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3
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Syomin F, Osepyan A, Tsaturyan A. Computationally efficient model of myocardial electromechanics for multiscale simulations. PLoS One 2021; 16:e0255027. [PMID: 34293046 PMCID: PMC8297763 DOI: 10.1371/journal.pone.0255027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 07/08/2021] [Indexed: 11/19/2022] Open
Abstract
A model of myocardial electromechanics is suggested. It combines modified and simplified versions of previously published models of cardiac electrophysiology, excitation-contraction coupling, and mechanics. The mechano-calcium and mechano-electrical feedbacks, including the strain-dependence of the propagation velocity of the action potential, are also accounted for. The model reproduces changes in the twitch amplitude and Ca2+-transients upon changes in muscle strain including the slow response. The model also reproduces the Bowditch effect and changes in the twitch amplitude and duration upon changes in the interstimulus interval, including accelerated relaxation at high stimulation frequency. Special efforts were taken to reduce the stiffness of the differential equations of the model. As a result, the equations can be integrated numerically with a relatively high time step making the model suitable for multiscale simulation of the human heart and allowing one to study the impact of myocardial mechanics on arrhythmias.
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Affiliation(s)
- Fyodor Syomin
- Institute of Mechanics, Lomonosov Moscow State University, Moscow, Russia
- * E-mail:
| | - Anna Osepyan
- Institute of Mechanics, Lomonosov Moscow State University, Moscow, Russia
| | - Andrey Tsaturyan
- Institute of Mechanics, Lomonosov Moscow State University, Moscow, Russia
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4
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Zhang H, Zhang S, Wang W, Wang K, Shen W. A Mathematical Model of the Mouse Atrial Myocyte With Inter-Atrial Electrophysiological Heterogeneity. Front Physiol 2020; 11:972. [PMID: 32848887 PMCID: PMC7425199 DOI: 10.3389/fphys.2020.00972] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 07/16/2020] [Indexed: 12/20/2022] Open
Abstract
Biophysically detailed mathematical models of cardiac electrophysiology provide an alternative to experimental approaches for investigating possible ionic mechanisms underlying the genesis of electrical action potentials and their propagation through the heart. The aim of this study was to develop a biophysically detailed mathematical model of the action potentials of mouse atrial myocytes, a popular experimental model for elucidating molecular and cellular mechanisms of arrhythmogenesis. Based on experimental data from isolated mouse atrial cardiomyocytes, a set of mathematical equations for describing the biophysical properties of membrane ion channel currents, intracellular Ca2+ handling, and Ca2+-calmodulin activated protein kinase II and β-adrenergic signaling pathways were developed. Wherever possible, membrane ion channel currents were modeled using Markov chain formalisms, allowing detailed representation of channel kinetics. The model also considered heterogeneous electrophysiological properties between the left and the right atrial cardiomyocytes. The developed model was validated by its ability to reproduce the characteristics of action potentials and Ca2+ transients, matching quantitatively to experimental data. Using the model, the functional roles of four K+ channel currents in atrial action potential were evaluated by channel block simulations, results of which were quantitatively in agreement with existent experimental data. To conclude, this newly developed model of mouse atrial cardiomyocytes provides a powerful tool for investigating possible ion channel mechanisms of atrial electrical activity at the cellular level and can be further used to investigate mechanisms underlying atrial arrhythmogenesis.
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Affiliation(s)
- Henggui Zhang
- Department of Physics and Astronomy, Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom.,Peng Cheng Laboratory, Shenzhen, China
| | - Shanzhuo Zhang
- Department of Physics and Astronomy, Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom.,School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Wei Wang
- Department of Physics and Astronomy, Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom.,Peng Cheng Laboratory, Shenzhen, China.,Shenzhen Key Laboratory of Visual Object Detection and Recognition, Harbin Institute of Technology, Shenzhen, China
| | - Kuanquan Wang
- School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Weijian Shen
- Department of Physics and Astronomy, Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, United Kingdom
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5
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Chung JH, Milani-Nejad N, Davis JP, Weisleder N, Whitson BA, Mohler PJ, Janssen PML. Impact of heart rate on cross-bridge cycling kinetics in failing and nonfailing human myocardium. Am J Physiol Heart Circ Physiol 2019; 317:H640-H647. [PMID: 31347914 DOI: 10.1152/ajpheart.00163.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The force-frequency relationship (FFR) is an important regulatory mechanism that increases the force-generating capacity as well as the contraction and relaxation kinetics in human cardiac muscle as the heart rate increases. In human heart failure, the normally positive FFR often becomes flat, or even negative. The rate of cross-bridge cycling, which has been reported to affect cardiac output, could be potentially dysregulated and contribute to blunted or negative FFR in heart failure. We recently developed and herein use a novel method for measuring the rate of tension redevelopment. This method allows us to obtain an index of the rate of cross-bridge cycling in intact contracting cardiac trabeculae at physiological temperature and assess physiological properties of cardiac muscles while preserving posttranslational modifications representative of those that occur in vivo. We observed that trabeculae from failing human hearts indeed exhibit an impaired FFR and a reduced speed of relaxation kinetics. However, stimulation frequencies in the lower spectrum did not majorly affect cross-bridge cycling kinetics in nonfailing and failing trabeculae when assessed at maximal activation. Trabeculae from failing human hearts had slightly slower cross-bridge kinetics at 3 Hz as well as reduced capacity to generate force upon K+ contracture at this frequency. We conclude that cross-bridge kinetics at maximal activation in the prevailing in vivo heart rates are not majorly impacted by frequency and are not majorly impacted by disease.NEW & NOTEWORTHY In this study, we confirm that cardiac relaxation kinetics are impaired in filing human myocardium and that cross-bridge cycling rate at resting heart rates does not contribute to this impaired relaxation. At high heart rates, failing myocardium cross-bridge rates are slower than in nonfailing myocardium.
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Affiliation(s)
- Jae-Hoon Chung
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Nima Milani-Nejad
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Medical Scientist Training Program and Biomedical Sciences Graduate Program, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Jonathan P Davis
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Noah Weisleder
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Bryan A Whitson
- Department of Surgery, Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Peter J Mohler
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio.,Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, Ohio
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6
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Groban L, Tran QK, Ferrario CM, Sun X, Cheng CP, Kitzman DW, Wang H, Lindsey SH. Female Heart Health: Is GPER the Missing Link? Front Endocrinol (Lausanne) 2019; 10:919. [PMID: 31993020 PMCID: PMC6970950 DOI: 10.3389/fendo.2019.00919] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Accepted: 12/17/2019] [Indexed: 12/20/2022] Open
Abstract
The G Protein-Coupled Estrogen Receptor (GPER) is a novel membrane-bound receptor that mediates non-genomic actions of the primary female sex hormone 17β-estradiol. Studies over the past two decades have elucidated the beneficial actions of this receptor in a number of cardiometabolic diseases. This review will focus specifically on the cardiac actions of GPER, since this receptor is expressed in cardiomyocytes as well as other cells within the heart and most likely contributes to estrogen-induced cardioprotection. Studies outlining the impact of GPER on diastolic function, mitochondrial function, left ventricular stiffness, calcium dynamics, cardiac inflammation, and aortic distensibility are discussed. In addition, recent data using genetic mouse models with global or cardiomyocyte-specific GPER gene deletion are highlighted. Since estrogen loss due to menopause in combination with chronological aging contributes to unique aspects of cardiac dysfunction in women, this receptor may provide novel therapeutic effects. While clinical studies are still required to fully understand the potential for pharmacological targeting of this receptor in postmenopausal women, this review will summarize the evidence gathered thus far on its likely beneficial effects.
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Affiliation(s)
- Leanne Groban
- Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC, United States
- Department of Internal Medicine-Molecular Medicine, Wake Forest School of Medicine, Winston Salem, NC, United States
- *Correspondence: Leanne Groban
| | - Quang-Kim Tran
- Department of Physiology & Pharmacology, Des Moines University College of Osteopathic Medicine, Des Moines, IA, United States
| | - Carlos M. Ferrario
- Department of Surgery, Wake Forest School of Medicine, Winston Salem, NC, United States
- Department of Physiology-Pharmacology, Wake Forest School of Medicine, Winston Salem, NC, United States
| | - Xuming Sun
- Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC, United States
| | - Che Ping Cheng
- Department of Internal Medicine, Cardiovascular Medicine Section, Wake Forest School of Medicine, Winston Salem, NC, United States
| | - Dalane W. Kitzman
- Department of Internal Medicine, Cardiovascular Medicine Section, Wake Forest School of Medicine, Winston Salem, NC, United States
| | - Hao Wang
- Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC, United States
- Department of Internal Medicine-Molecular Medicine, Wake Forest School of Medicine, Winston Salem, NC, United States
| | - Sarah H. Lindsey
- Department of Pharmacology, Tulane University, New Orleans, LA, United States
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7
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Abstract
The transmural heterogeneity of the contractility in ventricular muscle has not been well-studied. Here, we investigated the calcium transient and sarcomere contraction/relaxation in the endocardial (Endo) and epicardial (Epi) myocytes. Endo and Epi myocytes were isolated from C57/BL6 mice by Langendorff perfusion. Ca2+ transient and sarcomere contraction/relaxation were recorded simultaneously at different stimulation frequencies using a dual excitation fluorescence photomultiplier system. We found that the Endo myocytes have higher baseline diastolic calcium, significantly larger calcium transient and stronger sarcomere shortening than Epi myocytes. However, both the rising and decline phases for calcium transient and sarcomere shortening were slower in Endo than in Epi myocytes. When simulation frequency was increased from 1 to 3 Hz, a greater percent increase in the diastole calcium level, Ca2+ transient and sarcomere shortening amplitude has been observed in the Endo myocytes. Accordingly, the frequency-dependent acceleration in the decay rate of calcium transient and sarcomere relaxation was more profound in the Endo than in Epi myocytes. Western blot analysis showed that CaMKII activity was significantly higher in Epi than in Endo myocardium before stimulation. However, this transmural heterogeneity was reversed by rapid pacing. CaMKII inhibition by KN93 diminished the frequency-dependent alterations of Ca2+ transient and sarcomere contraction. Our results suggest that the contractility of ventricular myocytes is heterogeneous. The Endo-myocardium is the major force generating layer in the heart, both at slow and fast heart rate, and the transmural heterogeneity of CaMKII activation plays an important role in the frequency-dependent alterations.
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Affiliation(s)
- Wen Pan
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Ziqi Yang
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Jun Cheng
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Cheng Qian
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Yanggan Wang
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, China.,Medical Research Institute of Wuhan University, Wuhan University, Wuhan, China
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8
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Phosphorylating Titin's Cardiac N2B Element by ERK2 or CaMKIIδ Lowers the Single Molecule and Cardiac Muscle Force. Biophys J 2016; 109:2592-2601. [PMID: 26682816 DOI: 10.1016/j.bpj.2015.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/03/2015] [Accepted: 11/04/2015] [Indexed: 12/28/2022] Open
Abstract
Titin is a large filamentous protein that is responsible for the passive force of the cardiac sarcomere. Titin's force is generated by its I-band region, which includes the cardiac-specific N2B element. The N2B element consists of three immunoglobulin domains, two small unique sequence insertions, and a large 575-residue unique sequence, the N2B-Us. Posttranslational modifications of the N2B element are thought to regulate passive force, but the underlying mechanisms are unknown. Increased passive-force levels characterize diastolic stiffening in heart-failure patients, and it is critical to understand the underlying molecular mechanisms and identify therapeutic targets. Here, we used single-molecule force spectroscopy to study the mechanical effects of the kinases calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ) and extracellular signal-regulated kinase 2 (ERK2) on the single-molecule mechanics of the N2B element. Both CaMKIIδ and ERK2 were found to phosphorylate the N2B element, and single-molecule force spectroscopy revealed an increase in the persistence length (Lp) of the molecule, indicating that the bending rigidity of the molecule was increased. Experiments performed under oxidizing conditions and with a recombinant N2B element that had a simplified domain composition provided evidence that the Lp increase requires the N2B-Us of the N2B element. Mechanical experiments were also performed on skinned myocardium before and after phosphorylation. The results revealed a large (∼30%) passive force reduction caused by CaMKIIδ and a much smaller (∼6%) reduction caused by ERK2. These findings support the notion that the important kinases ERK2 and CaMKIIδ can alter the passive force of myocytes in the heart (although CaMKIIδ appears to be more potent) during physiological and pathophysiological states.
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9
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Li Y, Sirenko S, Riordon DR, Yang D, Spurgeon H, Lakatta EG, Vinogradova TM. CaMKII-dependent phosphorylation regulates basal cardiac pacemaker function via modulation of local Ca2+ releases. Am J Physiol Heart Circ Physiol 2016; 311:H532-44. [PMID: 27402669 DOI: 10.1152/ajpheart.00765.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 06/22/2016] [Indexed: 11/22/2022]
Abstract
Spontaneous beating of the heart pacemaker, the sinoatrial node, is generated by sinoatrial node cells (SANC) due to gradual change of the membrane potential called diastolic depolarization (DD). Spontaneous, submembrane local Ca(2+) releases (LCR) from ryanodine receptors (RyR) occur during late DD and activate an inward Na(+)/Ca(2+)exchange current to boost the DD rate and fire an action potential (AP). Here we studied the extent of basal Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) activation and the role of basal CaMKII-dependent protein phosphorylation in generation of LCRs and regulation of normal automaticity of intact rabbit SANC. The basal level of activated (autophosphorylated) CaMKII in rabbit SANC surpassed that in ventricular myocytes (VM) by approximately twofold, and this was accompanied by high basal level of protein phosphorylation. Specifically, phosphorylation of phospholamban (PLB) at the CaMKII-dependent Thr(17) site was approximately threefold greater in SANC compared with VM, and RyR phosphorylation at CaMKII-dependent Ser(2815) site was ∼10-fold greater in the SA node, compared with that in ventricle. CaMKII inhibition reduced phosphorylation of PLB and RyR, decreased LCR size, increased LCR periods (time from AP-induced Ca(2+) transient to subsequent LCR), and suppressed spontaneous SANC firing. Graded changes in CaMKII-dependent phosphorylation (indexed by PLB phosphorylation at the Thr(17)site) produced by CaMKII inhibition, β-AR stimulation or phosphodiesterase inhibition were highly correlated with changes in SR Ca(2+) replenishment times and LCR periods and concomitant changes in spontaneous SANC cycle lengths (R(2) = 0.96). Thus high basal CaMKII activation modifies the phosphorylation state of Ca(2+) cycling proteins PLB, RyR, L-type Ca(2+) channels (and likely others), adjusting LCR period and characteristics, and ultimately regulates both normal and reserve cardiac pacemaker function.
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Affiliation(s)
- Yue Li
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Syevda Sirenko
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Daniel R Riordon
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Harold Spurgeon
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
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10
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Gattoni S, Røe ÅT, Frisk M, Louch WE, Niederer SA, Smith NP. The calcium-frequency response in the rat ventricular myocyte: an experimental and modelling study. J Physiol 2016; 594:4193-224. [PMID: 26916026 DOI: 10.1113/jp272011] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/22/2016] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS In the majority of species, including humans, increased heart rate increases cardiac contractility. This change is known as the force-frequency response (FFR). The majority of mammals have a positive force-frequency relationship (FFR). In rat the FFR is controversial. We derive a species- and temperature-specific data-driven model of the rat ventricular myocyte. As a measure of the FFR, we test the effects of changes in frequency and extracellular calcium on the calcium-frequency response (CFR) in our model and three altered models. The results show a biphasic peak calcium-frequency response, due to biphasic behaviour of the ryanodine receptor and the combined effect of the rapid calmodulin buffer and the frequency-dependent increase in diastolic calcium. Alterations to the model reveal that inclusion of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated L-type channel and transient outward K(+) current activity enhances the positive magnitude calcium-frequency response, and the absence of CAMKII-mediated increase in activity of the sarco/endoplasmic reticulum Ca(2+) -ATPase induces a negative magnitude calcium-frequency response. ABSTRACT An increase in heart rate affects the strength of cardiac contraction by altering the Ca(2+) transient as a response to physiological demands. This is described by the force-frequency response (FFR), a change in developed force with pacing frequency. The majority of mammals, including humans, have a positive FFR, and cardiac contraction strength increases with heart rate. However, the rat and mouse are exceptions, with the majority of studies reporting a negative FFR, while others report either a biphasic or a positive FFR. Understanding the differences in the FFR between humans and rats is fundamental to interpreting rat-based experimental findings in the context of human physiology. We have developed a novel model of rat ventricular electrophysiology and calcium dynamics, derived predominantly from experimental data recorded under physiological conditions. As a measure of FFR, we tested the effects of changes in stimulation frequency and extracellular calcium concentration on the simulated Ca(2+) transient characteristics and showed a biphasic peak calcium-frequency relationship, consistent with recent observations of a shift from negative to positive FFR when approaching the rat physiological frequency range. We tested the hypotheses that (1) inhibition of Ca(2+) /calmodulin-dependent protein kinase II (CAMKII)-mediated increase in sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) activity, (2) CAMKII modulation of SERCA, L-type channel and transient outward K(+) current activity and (3) Na(+) /K(+) pump dynamics play a significant role in the rat FFR. The results reveal a major role for CAMKII modulation of SERCA in the peak Ca(2+) -frequency response, driven most significantly by the cytosolic calcium buffering system and changes in diastolic Ca(2+) .
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Affiliation(s)
- Sara Gattoni
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK
| | - Åsmund Treu Røe
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Steven A Niederer
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK
| | - Nicolas P Smith
- King's College London, Department of Biomedical Engineering and Imaging Sciences, St. Thomas' Hospital, London, UK.,University of Auckland, Engineering School Block 1, Level 5, 20 Symonds St, Auckland, 101, New Zealand
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11
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Bugenhagen SM, Beard DA. Computational analysis of the regulation of Ca(2+) dynamics in rat ventricular myocytes. Phys Biol 2015; 12:056008. [PMID: 26358004 DOI: 10.1088/1478-3975/12/5/056008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Force-frequency relationships of isolated cardiac myocytes show complex behaviors that are thought to be specific to both the species and the conditions associated with the experimental preparation. Ca(2+) signaling plays an important role in shaping the force-frequency relationship, and understanding the properties of the force-frequency relationship in vivo requires an understanding of Ca(2+) dynamics under physiologically relevant conditions. Ca(2+) signaling is itself a complicated process that is best understood on a quantitative level via biophysically based computational simulation. Although a large number of models are available in the literature, the models are often a conglomeration of components parameterized to data of incompatible species and/or experimental conditions. In addition, few models account for modulation of Ca(2+) dynamics via β-adrenergic and calmodulin-dependent protein kinase II (CaMKII) signaling pathways even though they are hypothesized to play an important regulatory role in vivo. Both protein-kinase-A and CaMKII are known to phosphorylate a variety of targets known to be involved in Ca(2+) signaling, but the effects of these pathways on the frequency- and inotrope-dependence of Ca(2+) dynamics are not currently well understood. In order to better understand Ca(2+) dynamics under physiological conditions relevant to rat, a previous computational model is adapted and re-parameterized to a self-consistent dataset obtained under physiological temperature and pacing frequency and updated to include β-adrenergic and CaMKII regulatory pathways. The necessity of specific effector mechanisms of these pathways in capturing inotrope- and frequency-dependence of the data is tested by attempting to fit the data while including and/or excluding those effector components. We find that: (1) β-adrenergic-mediated phosphorylation of the L-type calcium channel (LCC) (and not of phospholamban (PLB)) is sufficient to explain the inotrope-dependence; and (2) that CaMKII-mediated regulation of neither the LCC nor of PLB is required to explain the frequency-dependence of the data.
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Affiliation(s)
- Scott M Bugenhagen
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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12
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Guilbert A, Lim HJ, Cheng J, Wang Y. CaMKII-dependent myofilament Ca2+ desensitization contributes to the frequency-dependent acceleration of relaxation. Cell Calcium 2015; 58:489-99. [PMID: 26297240 DOI: 10.1016/j.ceca.2015.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 07/06/2015] [Accepted: 08/04/2015] [Indexed: 11/15/2022]
Abstract
BACKGROUND Previous studies suggest that CaMKII activity is required for frequency-dependent acceleration of relaxation (FDAR) in ventricular myocytes. We propose that the underlying mechanism involves CaMKII-dependent regulation of myofilament Ca(2+) sensitivity. METHODS AND RESULTS Cardiac function was measured in mice using murine echo machine. [Ca(2+)]i and sarcomere length were measured by IonOptix Ca(2+) image system. Increasing pacing rate from 0.5 to 4 Hz in left ventricular myocytes induced frequency-dependent myofilament Ca(2+) desensitization (FDMCD) and FDAR. Acute inhibition of PKA or PKC had no effect, whereas CaMKII inhibition abolished both FDMCD and FDAR. Co-immunoprecipitation of CaMKII and troponin I (TnI) has been detected and CaMKII inhibition significantly reduced serine residue phosphorylation of TnI. Finally, chronic inhibition of CaMKII in vivo reduced TnI phosphorylation and abolished both FDAR and FDMCD, leading to impaired diastolic function. CONCLUSIONS Our results suggest that CaMKII-dependent TnI phosphorylation is involved in FDMCD and the consequent FDAR and that CaMKII inhibition removes this mechanism and thus induces diastolic dysfunction.
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Affiliation(s)
| | - Hyun Joung Lim
- Department of Pediatrics, Emory University, Atlanta, USA
| | - Jun Cheng
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan University, China; Department of Pediatrics, Emory University, Atlanta, USA
| | - Yanggan Wang
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan University, China; Department of Pediatrics, Emory University, Atlanta, USA.
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13
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Feridooni HA, Dibb KM, Howlett SE. How cardiomyocyte excitation, calcium release and contraction become altered with age. J Mol Cell Cardiol 2015; 83:62-72. [PMID: 25498213 DOI: 10.1016/j.yjmcc.2014.12.004] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 11/29/2022]
Abstract
Cardiovascular disease is the main cause of death globally, accounting for over 17 million deaths each year. As the incidence of cardiovascular disease rises markedly with age, the overall risk of cardiovascular disease is expected to increase dramatically with the aging of the population such that by 2030 it could account for over 23 million deaths per year. It is therefore vitally important to understand how the heart remodels in response to normal aging for at least two reasons: i) to understand why the aged heart is increasingly susceptible to disease; and ii) since it may be possible to modify treatment of disease in older adults if the underlying substrate upon which the disease first develops is fully understood. It is well known that age modulates cardiac function at the level of the individual cardiomyocyte. Generally, in males, aging reduces cell shortening, which is associated with a decrease in the amplitude of the systolic Ca(2+) transient. This may arise due to a decrease in peak L-type Ca(2+) current. Sarcoplasmic reticulum (SR) Ca(2+) load appears to be maintained during normal aging but evidence suggests that SR function is disrupted, such that the rate of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA)-mediated Ca(2+) removal is reduced and the properties of SR Ca(2+) release in terms of Ca(2+) sparks are altered. Interestingly, Ca(2+) handling is modulated by age to a lesser degree in females. Here we review how cellular contraction is altered as a result of the aging process by considering expression levels and functional properties of key proteins involved in controlling intracellular Ca(2+). We consider how changes in both electrical properties and intracellular Ca(2+) handling may interact to modulate cardiomyocyte contraction. We also reflect on why cardiovascular risk may differ between the sexes by highlighting sex-specific variation in the age-associated remodeling process. This article is part of a Special Issue entitled CV Aging.
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Affiliation(s)
- Hirad A Feridooni
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada.
| | - Katharine M Dibb
- Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK.
| | - Susan E Howlett
- Department of Pharmacology, Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada; Department of Medicine (Geriatric Medicine), Dalhousie University, PO Box 15000, 5850 College St, Halifax, NS B3H 4R2, Canada; Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK.
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Kim JO, Song DW, Kwon EJ, Hong SE, Song HK, Min CK, Kim DH. miR-185 plays an anti-hypertrophic role in the heart via multiple targets in the calcium-signaling pathways. PLoS One 2015; 10:e0122509. [PMID: 25767890 PMCID: PMC4358957 DOI: 10.1371/journal.pone.0122509] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 02/11/2015] [Indexed: 01/15/2023] Open
Abstract
MicroRNA (miRNA) is an endogenous non-coding RNA species that either inhibits RNA translation or promotes degradation of target mRNAs. miRNAs often regulate cellular signaling by targeting multiple genes within the pathways. In the present study, using Gene Set Analysis, a useful bioinformatics tool to identify miRNAs with multiple target genes in the same pathways, we identified miR-185 as a key candidate regulator of cardiac hypertrophy. Using a mouse model, we found that miR-185 was significantly down-regulated in myocardial cells during cardiac hypertrophy induced by transverse aortic constriction. To confirm that miR-185 is an anti-hypertrophic miRNA, genetic manipulation studies such as overexpression and knock-down of miR-185 in neonatal rat ventricular myocytes were conducted. The results showed that up-regulation of miR-185 led to anti-hypertrophic effects, while down-regulation led to pro-hypertrophic effects, suggesting that miR-185 has an anti-hypertrophic role in the heart. Our study further identified Camk2d, Ncx1, and Nfatc3 as direct targets of miR-185. The activity of Nuclear Factor of Activated T-cell (NFAT) and calcium/calmodulin-dependent protein kinase II delta (CaMKIIδ) was negatively regulated by miR-185 as assessed by NFAT-luciferase activity and western blotting. The expression of phospho-phospholamban (Thr-17), a marker of CaMKIIδ activity, was also significantly reduced by miR-185. In conclusion, miR-185 effectively blocked cardiac hypertrophy signaling through multiple targets, rendering it a potential drug target for diseases such as heart failure.
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Affiliation(s)
- Jin Ock Kim
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Dong Woo Song
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Eun Jeong Kwon
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Seong-Eui Hong
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Hong Ki Song
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Choon Kee Min
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
| | - Do Han Kim
- School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea
- * E-mail: (DHK)
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15
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Yaniv Y, Maltsev VA. Numerical Modeling Calcium and CaMKII Effects in the SA Node. Front Pharmacol 2014; 5:58. [PMID: 24744732 PMCID: PMC3978345 DOI: 10.3389/fphar.2014.00058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/16/2014] [Indexed: 11/13/2022] Open
Abstract
Sinoatrial node (SAN) is the primary heart pacemaker which initiates each heartbeat under normal conditions. Numerous experimental data have demonstrated that Ca(2+-) and CaMKII-dependent processes are crucially important for regulation of SAN cells. However, specific mechanisms of this regulation and their relative contribution to pacemaker function remain mainly unknown. Our review summarizes available data and existing numerical modeling approaches to understand Ca(2+) and CaMKII effects on the SAN. Data interpretation and future directions to address the problem are given within the coupled-clock theory, i.e., a modern view on the cardiac pacemaker cell function generated by a system of sarcolemmal and intracellular proteins.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging - National Institutes of Health Baltimore, MD, USA ; Department of Biomedical Engineering, Technion - Israel Institute of Technology Haifa, Israel
| | - Victor A Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging - National Institutes of Health Baltimore, MD, USA
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16
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Mattiazzi A, Kranias EG. The role of CaMKII regulation of phospholamban activity in heart disease. Front Pharmacol 2014; 5:5. [PMID: 24550830 PMCID: PMC3913884 DOI: 10.3389/fphar.2014.00005] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 01/07/2014] [Indexed: 01/06/2023] Open
Abstract
Phospholamban (PLN) is a phosphoprotein in cardiac sarcoplasmic reticulum (SR) that is a reversible regulator of the Ca2+-ATPase (SERCA2a) activity and cardiac contractility. Dephosphorylated PLN inhibits SERCA2a and PLN phosphorylation, at either Ser16 by PKA or Thr17 by Ca2+-calmodulin-dependent protein kinase (CaMKII), reverses this inhibition. Through this mechanism, PLN is a key modulator of SR Ca2+ uptake, Ca2+ load, contractility, and relaxation. PLN phosphorylation is also the main determinant of β1-adrenergic responses in the heart. Although phosphorylation of Thr17 by CaMKII contributes to this effect, its role is subordinate to the PKA-dependent increase in cytosolic Ca2+, necessary to activate CaMKII. Furthermore, the effects of PLN and its phosphorylation on cardiac function are subject to additional regulation by its interacting partners, the anti-apoptotic HAX-1 protein and Gm or the anchoring unit of protein phosphatase 1. Regulation of PLN activity by this multimeric complex becomes even more important in pathological conditions, characterized by aberrant Ca2+-cycling. In this scenario, CaMKII-dependent PLN phosphorylation has been associated with protective effects in both acidosis and ischemia/reperfusion. However, the beneficial effects of increasing SR Ca2+ uptake through PLN phosphorylation may be lost or even become deleterious, when these occur in association with alterations in SR Ca2+ leak. Moreover, a major characteristic in human and experimental heart failure (HF) is depressed SR Ca2+ uptake, associated with decreased SERCA2a levels and dephosphorylation of PLN, leading to decreased SR Ca2+ load and impaired contractility. Thus, the strategy of altering SERCA2a and/or PLN levels or activity to restore perturbed SR Ca2+ uptake is a potential therapeutic tool for HF treatment. We will review here the role of CaMKII-dependent phosphorylation of PLN at Thr17 on cardiac function under physiological and pathological conditions.
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Affiliation(s)
- Alicia Mattiazzi
- Facultad de Medicina, Centro de Investigaciones Cardiovasculares, Conicet La Plata-Universidad Nacional de La Plata La Plata, Argentina
| | - Evangelia G Kranias
- Department of Pharmacology and Cell Biophysics, College of Medicine, University of Cincinnati Cincinnati, OH, USA
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17
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Sikkel MB, Hayward C, MacLeod KT, Harding SE, Lyon AR. SERCA2a gene therapy in heart failure: an anti-arrhythmic positive inotrope. Br J Pharmacol 2014; 171:38-54. [PMID: 24138023 PMCID: PMC3874695 DOI: 10.1111/bph.12472] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Revised: 09/16/2013] [Accepted: 09/24/2013] [Indexed: 01/14/2023] Open
Abstract
Therapeutic options that directly enhance cardiomyocyte contractility in chronic heart failure (HF) therapy are currently limited and do not improve prognosis. In fact, most positive inotropic agents, such as β-adrenoreceptor agonists and PDE inhibitors, which have been assessed in HF patients, cause increased mortality as a result of arrhythmia and sudden cardiac death. Cardiac sarcoplasmic reticulum Ca(2)(+) -ATPase2a (SERCA2a) is a key protein involved in sequestration of Ca(2)(+) into the sarcoplasmic reticulum (SR) during diastole. There is a reduction of SERCA2a protein level and function in HF, which has been successfully targeted via viral transfection of the SERCA2a gene into cardiac tissue in vivo. This has enhanced cardiac contractility and reduced mortality in several preclinical models of HF. Theoretical concerns have been raised regarding the possibility of arrhythmogenic adverse effects of SERCA2a gene therapy due to enhanced SR Ca(2)(+) load and induction of SR Ca(2)(+) leak as a result. Contrary to these concerns, SERCA2a gene therapy in a wide variety of preclinical models, including acute ischaemia/reperfusion, chronic pressure overload and chronic myocardial infarction, has resulted in a reduction in ventricular arrhythmias. The potential mechanisms for this unexpected beneficial effect, as well as mechanisms of enhancement of cardiac contractile function, are reviewed in this article.
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Affiliation(s)
- Markus B Sikkel
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Carl Hayward
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
| | - Kenneth T MacLeod
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Sian E Harding
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
| | - Alexander R Lyon
- Myocardial Function Section, National Heart and Lung Institute, Imperial CollegeLondon, UK
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton HospitalLondon, UK
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Tuncay E, Okatan EN, Vassort G, Turan B. ß-blocker timolol prevents arrhythmogenic Ca²⁺ release and normalizes Ca²⁺ and Zn²⁺ dyshomeostasis in hyperglycemic rat heart. PLoS One 2013; 8:e71014. [PMID: 23923043 PMCID: PMC3726605 DOI: 10.1371/journal.pone.0071014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 06/25/2013] [Indexed: 01/08/2023] Open
Abstract
Defective cardiac mechanical activity in diabetes results from alterations in intracellular Ca(2+) handling, in part, due to increased oxidative stress. Beta-blockers demonstrate marked beneficial effects in heart dysfunction with scavenging free radicals and/or acting as an antioxidant. The aim of this study was to address how β-blocker timolol-treatment of diabetic rats exerts cardioprotection. Timolol-treatment (12-week), one-week following diabetes induction, prevented diabetes-induced depressed left ventricular basal contractile activity, prolonged cellular electrical activity, and attenuated the increase in isolated-cardiomyocyte size without hyperglycemic effect. Both in vivo and in vitro timolol-treatment of diabetic cardiomyocytes prevented the altered kinetic parameters of Ca(2+) transients and reduced Ca(2+) loading of sarcoplasmic reticulum (SR), basal intracellular free Ca(2+) and Zn(2+) ([Ca(2+)]i and [Zn(2+)]i), and spatio-temporal properties of the Ca(2+) sparks, significantly. Timolol also antagonized hyperphosphorylation of cardiac ryanodine receptor (RyR2), and significantly restored depleted protein levels of both RyR2 and calstabin2. Western blot analysis demonstrated that timolol-treatment also significantly normalized depressed levels of some [Ca(2+)]i-handling regulators, such as Na(+)/Ca(2+) exchanger (NCX) and phospho-phospholamban (pPLN) to PLN ratio. Incubation of diabetic cardiomyocytes with 4-mM glutathione exerted similar beneficial effects on RyR2-macromolecular complex and basal levels of both [Ca(2+)]i and [Zn(2+)]i, increased intracellular Zn(2+) hyperphosphorylated RyR2 in a concentration-dependent manner. Timolol also led to a balanced oxidant/antioxidant level in both heart and circulation and prevented altered cellular redox state of the heart. We thus report, for the first time, that the preventing effect of timolol, directly targeting heart, seems to be associated with a normalization of macromolecular complex of RyR2 and some Ca(2+) handling regulators, and prevention of Ca(2+) leak, and thereby normalization of both [Ca(2+)]i and [Zn(2+)]i homeostasis in diabetic rat heart, at least in part by controlling the cellular redox status of hyperglycemic cardiomyocytes.
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Affiliation(s)
- Erkan Tuncay
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Esma N. Okatan
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Guy Vassort
- INSERM U-1046, CHU Arnaud de Villeneuve, Montpellier, France
| | - Belma Turan
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
- * E-mail:
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19
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Carneiro-Júnior MA, Prímola-Gomes TN, Quintão-Júnior JF, Drummond LR, Lavorato VN, Drummond FR, Felix LB, Oliveira EM, Cruz JS, Natali AJ, Mill JG. Regional effects of low-intensity endurance training on structural and mechanical properties of rat ventricular myocytes. J Appl Physiol (1985) 2013; 115:107-15. [DOI: 10.1152/japplphysiol.00041.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We tested the effects of low-intensity endurance training (LIET) on the structural and mechanical properties of right (RV) and left ventricular (LV) myocytes. Male Wistar rats (4 mo old) were randomly divided into control (C, n = 7) and trained (T, n = 7, treadmill running at 50–60% of maximal running speed for 8 wk) groups. Isolated ventricular myocyte dimensions, contractility, Ca2+ transients {intracellular Ca2+ concentration ([Ca2+]i)}, and ventricular [Ca2+]i regulatory proteins were measured. LIET augmented cell length (C, 152.5 ± 2.0 μm vs. T, 162.2 ± 2.1 μm; P < 0.05) and volume (C, 5,162 ± 131 μm3 vs. T, 5,506 ± 132 μm3; P < 0.05) in the LV but not in the RV. LIET increased cell shortening (C, 7.5 ± 0.3% vs. T, 8.6 ± 0.3%; P < 0.05), the [Ca2+]i transient amplitude (C, 2.49 ± 0.06 F/F0 vs. T, 2.82 ± 0.06 F/F0; P < 0.05), the expression of sarcoplasmic reticulum Ca2+-ATPase 2a (C, 1.07 ± 0.13 vs. T, 1.59 ± 0.12; P < 0.05), and the levels of phosphorylated phospholamban at serine 16 (C, 0.99 ± 0.11 vs. T, 1.34 ± 0.10; P < 0.05), and reduced the total phospholamban-to-sarcoplasmic reticulum Ca2+-ATPase 2a ratio (C, 1.19 ± 0.15 vs. T, 0.40 ± 0.16; P < 0.05) in the LV without changing such parameters in the RV. In conclusion, LIET affected the structure and improved the mechanical properties of LV but not of RV myocytes in rats, helping to characterize the functional and morphological changes that accompany the endurance training-induced cardiac remodeling.
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Affiliation(s)
| | - Thales Nicolau Prímola-Gomes
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Judson Fonseca Quintão-Júnior
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Lucas Rios Drummond
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Victor Neiva Lavorato
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Filipe Rios Drummond
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Leonardo Bonato Felix
- Department of Electrical Engineering, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - Edilamar Menezes Oliveira
- School of Physical Education and Sport, Laboratory of Biochemistry and Molecular Biology of the Exercise, University of São Paulo, São Paulo, Brazil; and
| | - Jader Santos Cruz
- Department of Biochemistry and Immunology, Laboratory of Excitable Membranes and Cardiovascular Biology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Antonio José Natali
- Department of Physical Education, Laboratory of Exercise Biology, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil
| | - José Geraldo Mill
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, Espírito Santo, Brazil
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Nitric oxide regulates cardiac intracellular Na⁺ and Ca²⁺ by modulating Na/K ATPase via PKCε and phospholemman-dependent mechanism. J Mol Cell Cardiol 2013; 61:164-71. [PMID: 23612119 PMCID: PMC3981027 DOI: 10.1016/j.yjmcc.2013.04.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 04/11/2013] [Accepted: 04/12/2013] [Indexed: 12/14/2022]
Abstract
In the heart, Na/K-ATPase regulates intracellular Na+ and Ca2 + (via NCX), thereby preventing Na+ and Ca2 + overload and arrhythmias. Here, we test the hypothesis that nitric oxide (NO) regulates cardiac intracellular Na+ and Ca2 + and investigate mechanisms and physiological consequences involved. Effects of both exogenous NO (via NO-donors) and endogenously synthesized NO (via field-stimulation of ventricular myocytes) were assessed in this study. Field stimulation of rat ventricular myocytes significantly increased endogenous NO (18 ± 2 μM), PKCε activation (82 ± 12%), phospholemman phosphorylation (at Ser-63 and Ser-68) and Na/K-ATPase activity (measured by DAF-FM dye, western-blotting and biochemical assay, respectively; p < 0.05, n = 6) and all were abolished by Ca2 +-chelation (EGTA 10 mM) or NOS inhibition l-NAME (1 mM). Exogenously added NO (spermine-NONO-ate) stimulated Na/K-ATPase (EC50 = 3.8 μM; n = 6/grp), via decrease in Km, in PLMWT but not PLMKO or PLM3SA myocytes (where phospholemman cannot be phosphorylated) as measured by whole-cell perforated-patch clamp. Field-stimulation with l-NAME or PKC-inhibitor (2 μM Bis) resulted in elevated intracellular Na+ (22 ± 1.5 and 24 ± 2 respectively, vs. 14 ± 0.6 mM in controls) in SBFI-AM-loaded rat myocytes. Arrhythmia incidence was significantly increased in rat hearts paced in the presence of l-NAME (and this was reversed by l-arginine), as well as in PLM3SA mouse hearts but not PLMWT and PLMKO. We provide physiological and biochemical evidence for a novel regulatory pathway whereby NO activates Na/K-ATPase via phospholemman phosphorylation and thereby limits Na+ and Ca2 + overload and arrhythmias. This article is part of a Special Issue entitled “Na+ Regulation in Cardiac Myocytes”. We tested whether nitric oxide regulates intracellular Na+ and Ca2 + in the heart. Nitric oxide increased Na/K ATPase activity via PKCε-induced phospholemman phosphorylation. Inhibiting nitric oxide pathway resulted in Na+ and Ca2 + overload and contributed to arrhythmia development in the heart.
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Hidalgo CG, Chung CS, Saripalli C, Methawasin M, Hutchinson KR, Tsaprailis G, Labeit S, Mattiazzi A, Granzier HL. The multifunctional Ca(2+)/calmodulin-dependent protein kinase II delta (CaMKIIδ) phosphorylates cardiac titin's spring elements. J Mol Cell Cardiol 2012; 54:90-7. [PMID: 23220127 DOI: 10.1016/j.yjmcc.2012.11.012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 11/22/2012] [Indexed: 10/27/2022]
Abstract
Titin-based passive stiffness is post-translationally regulated by several kinases that phosphorylate specific spring elements located within titin's elastic I-band region. Whether titin is phosphorylated by calcium/calmodulin dependent protein kinase II (CaMKII), an important regulator of cardiac function and disease, has not been addressed. The aim of this work was to determine whether CaMKIIδ, the predominant CaMKII isoform in the heart, phosphorylates titin, and to use phosphorylation assays and mass spectrometry to study which of titin's spring elements might be targeted by CaMKIIδ. It was found that CaMKIIδ phosphorylates titin in mouse LV skinned fibers, that the CaMKIIδ sites can be dephosphorylated by protein phosphatase 1 (PP1), and that under baseline conditions, in both intact isolated hearts and skinned myocardium, about half of the CaMKIIδ sites are phosphorylated. Mass spectrometry revealed that both the N2B and PEVK segments are targeted by CaMKIIδ at several conserved serine residues. Whether phosphorylation of titin by CaMKIIδ occurs in vivo, was tested in several conditions using back phosphorylation assays and phospho-specific antibodies to CaMKIIδ sites. Reperfusion following global ischemia increased the phosphorylation level of CaMKIIδ sites on titin and this effect was abolished by the CaMKII inhibitor KN-93. No changes in the phosphorylation level of the PEVK element were found suggesting that the increased phosphorylation level of titin in IR (ischemia reperfusion) might be due to phosphorylation of the N2B element. The findings of these studies show for the first time that titin can be phosphoryalated by CaMKIIδ, both in vitro and in vivo, and that titin's molecular spring region that determines diastolic stiffness is a target of CaMKIIδ.
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Affiliation(s)
- Carlos G Hidalgo
- Sarver Molecular Cardiovascular Research Program, University of Arizona, Tucson, AZ 85724, USA
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Abstract
Cardiac myocyte function is dependent on the synchronized movements of Ca(2+) into and out of the cell, as well as between the cytosol and sarcoplasmic reticulum. These movements determine cardiac rhythm and regulate excitation-contraction coupling. Ca(2+) cycling is mediated by a number of critical Ca(2+)-handling proteins and transporters, such as L-type Ca(2+) channels (LTCCs) and sodium/calcium exchangers in the sarcolemma, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), ryanodine receptors, and cardiac phospholamban in the sarcoplasmic reticulum. The entry of Ca(2+) into the cytosol through LTCCs activates the release of Ca(2+) from the sarcoplasmic reticulum through ryanodine receptor channels and initiates myocyte contraction, whereas SERCA2a and cardiac phospholamban have a key role in sarcoplasmic reticulum Ca(2+) sequesteration and myocyte relaxation. Excitation-contraction coupling is regulated by phosphorylation of Ca(2+)-handling proteins. Abnormalities in sarcoplasmic reticulum Ca(2+) cycling are hallmarks of heart failure and contribute to the pathophysiology and progression of this disease. Correcting impaired intracellular Ca(2+) cycling is a promising new approach for the treatment of heart failure. Novel therapeutic strategies that enhance myocyte Ca(2+) homeostasis could prevent and reverse adverse cardiac remodeling and improve clinical outcomes in patients with heart failure.
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Wu Y, Luczak ED, Lee EJ, Hidalgo C, Yang J, Gao Z, Li J, Wehrens X, Granzier H, Anderson ME. CaMKII effects on inotropic but not lusitropic force frequency responses require phospholamban. J Mol Cell Cardiol 2012; 53:429-36. [PMID: 22796260 PMCID: PMC3936404 DOI: 10.1016/j.yjmcc.2012.06.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 06/04/2012] [Accepted: 06/29/2012] [Indexed: 11/27/2022]
Abstract
Increasing heart rate enhances cardiac contractility (force frequency relationship, FFR) and accelerates cardiac relaxation (frequency-dependent acceleration of relaxation, FDAR). The positive FFR together with FDAR promotes rapid filling and ejection of blood from the left ventricle (LV) at higher heart rates. Recent studies indicate that the multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is involved in regulating FFR and FDAR. We used isolated perfused mouse hearts to study the mechanisms of FFR and FDAR in different genetic models, including transgenic myocardial CaMKII inhibition (AC3-I) and phospholmban knockout (PLN(-/-)). When the rate was increased from 360 beats/min to 630 beats/min in wild type mouse hearts, the LV developed pressure (LVDP) and the maximum rate of increase in pressure (dP/dt max) increased by 37.6 ± 4.7% and 77.0 ± 8.1%, respectively. However, hearts from AC3-I littermates showed no increase of LVDP and a relatively modest (20.4 ± 3.9%) increase in dP/dt max. PLN(-/-) hearts had a negative FFR, and myocardial AC3-I expression did not change the FFR in PLN(-/-) mice. PLN(-/-) mouse hearts did not exhibit FDAR, while PLN(-/-) mice with myocardial AC3-I expression showed further frequency dependent reductions in cardiac relaxation, suggesting that CaMKII targets in addition to PLN were critical to myocardial relaxation. We incubated a constitutively active form of CaMKII with chemically-skinned myocardium and found that several myofilament proteins were phosphorylated by CaMKII. However, CaMKII did not affect myofilament calcium sensitivity. Our study shows that CaMKII plays an important role in modulating FFR and FDAR in murine hearts and suggest that PLN is a critical target for CaMKII effects on FFR, while CaMKII effects on FDAR partially require PLN-alternative targets.
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Affiliation(s)
- Yiming Wu
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
| | - Elizabeth D Luczak
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
| | - Eun-Jeong Lee
- Department of Physiology, University of Arizona, Tucson, AZ 85724
| | - Carlos Hidalgo
- Department of Physiology, University of Arizona, Tucson, AZ 85724
| | - Jinying Yang
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
| | - Zhan Gao
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
| | - Jingdong Li
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
| | - Xander Wehrens
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX
| | - Henk Granzier
- Department of Physiology, University of Arizona, Tucson, AZ 85724
| | - Mark E Anderson
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA
- Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA
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Sayadi M, Feig M. Role of conformational sampling of Ser16 and Thr17-phosphorylated phospholamban in interactions with SERCA. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:577-85. [PMID: 22959711 DOI: 10.1016/j.bbamem.2012.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Revised: 08/18/2012] [Accepted: 08/21/2012] [Indexed: 11/17/2022]
Abstract
Phosphorylation of phospholamban (PLB) at Ser16 and/ or Thr17 is believed to release its inhibitory effect on sarcoplasmic reticulum calcium ATPase. Ser16 phosphorylation of PLB has been suggested to cause a conformational change that alters the interaction between the enzyme and protein. Using computer simulations, the conformational sampling of Ser16 phosphorylated PLB in implicit membrane environment is compared here with the unphosphorylated PLB system to investigate these conformational changes. The results suggest that conformational changes in the cytoplasmic domain of PLB upon phosphorylation at Ser16 increase the likelihood of unfavorable interactions with SERCA in the E2 state prompting a conformational switch of SERCA from E2 to E1. Phosphorylation of PLB at Thr17 on the other hand does not appear to affect interactions with SERCA significantly suggesting that the mechanism of releasing the inhibitory effect is different between Thr17 phosphorylated and Ser16 phosphorylated PLB.
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Affiliation(s)
- Maryam Sayadi
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
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25
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Duran JM, Taghavi S, Berretta RM, Makarewich CA, Sharp Iii T, Starosta T, Udeshi F, George JC, Kubo H, Houser SR. A characterization and targeting of the infarct border zone in a swine model of myocardial infarction. Clin Transl Sci 2012; 5:416-21. [PMID: 23067355 DOI: 10.1111/j.1752-8062.2012.00432.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
INTRODUCTION Novel therapies for myocardial infarction (MI) involving stem cells, gene therapy, biomaterials, or revascularization strategies have shown promise in animal studies and clinical trials, but results have been limited partially due to the injection of therapeutics into ischemic myocardium that cannot support their mechanism of action. Accurate targeting of therapeutics precisely to the infarct border zone (BZ) may be essential for effective repair of the ischemic heart. METHODS Ischemia-reperfusion MI was induced in Yorkshire swine by inflation of an angioplasty balloon in the left anterior descending coronary artery. Fluorescent microspheres were injected into the BZ under NOGA catheter guidance, and this location was identified grossly then examined by immunohistochemistry and Western analysis. RESULTS Analysis of the infarct zone two hours post-MI revealed a frankly necrotic region devoid of contractile proteins with marked activation of caspase-3. The NOGA-defined BZ closely approximates the grossly-defined BZ and contains intact myocytes and vasculature. Western analysis detected Akt expression and levels of Ca(2+) handling proteins equivalent to that of viable tissues. CONCLUSIONS Histological and Western analysis revealed that NOGA mapping precisely identifies grossly and molecularly defined infarct BZ at a location where there are still viable cells and vessels capable of supporting novel therapeutic strategies.
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Affiliation(s)
- Jason M Duran
- Temple University School of Medicine, Cardiovascular Research Center, Temple University, PA, USA
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26
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Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012; 205:9-25. [PMID: 22463608 DOI: 10.1111/j.1748-1716.2012.02389.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phospholamban (PLN) is a small phosphoprotein closely associated with the cardiac sarcoplasmic reticulum (SR). Dephosphorylated PLN tonically inhibits the SR Ca-ATPase (SERCA2a), while phosphorylation at Ser16 by PKA and Thr17 by Ca(2+) /calmodulin-dependent protein kinase (CaMKII) relieves the inhibition, and this increases SR Ca(2+) uptake. For this reason, PLN is one of the major determinants of cardiac contractility and relaxation. In this review, we attempted to highlight the functional significance of PLN in vertebrate cardiac physiology. We will refer to the huge literature on mammals in order to describe the molecular characteristics of this protein, its interaction with SERCA2a and its role in the regulation of the mechanic and the electric performance of the heart under basal conditions, in the presence of chemical and physical stresses, such as β-adrenergic stimulation, response to stretch, force-frequency relationship and intracellular acidosis. Our aim is to provide the basis to discuss the role of PLN also on the cardiac function of nonmammalian vertebrates, because so far this aspect has been almost neglected. Accordingly, when possible, the literature on PLN will be analysed taking into account the nonuniform cardiac structural and functional characteristics encountered in ectothermic vertebrates, such as the peculiar and variable organization of the SR, the large spectrum of response to stresses and the disaptive absence of crucial proteins (i.e. haemoglobinless and myoglobinless species).
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Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
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27
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Cerra MC, Imbrogno S. Phospholamban and cardiac function: a comparative perspective in vertebrates. Acta Physiol (Oxf) 2012. [DOI: 10.1111/j.1748-1716.2011.02389.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - S. Imbrogno
- Department of Cell Biology; University of Calabria; Arcavacata di Rende (CS); Italy
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28
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Maier LS. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) in the Heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:685-702. [DOI: 10.1007/978-94-007-2888-2_30] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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29
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Moilanen AM, Rysä J, Mustonen E, Serpi R, Aro J, Tokola H, Leskinen H, Manninen A, Levijoki J, Vuolteenaho O, Ruskoaho H. Intramyocardial BNP gene delivery improves cardiac function through distinct context-dependent mechanisms. Circ Heart Fail 2011; 4:483-95. [PMID: 21558448 DOI: 10.1161/circheartfailure.110.958033] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND B-type natriuretic peptide (BNP) is an endogenous peptide produced under physiological and pathological conditions mainly by ventricular myocytes. It has natriuretic, diuretic, blood pressure-lowering, and antifibrotic actions that could mediate cardiorenal protection in cardiovascular diseases. In the present study, we used BNP gene transfer to examine functional and structural effects of BNP on left ventricular (LV) remodeling. METHODS AND RESULTS Human BNP was overexpressed by using adenovirus-mediated gene delivery in normal rat hearts and in hearts during the remodeling process after infarction and in an experimental model of angiotensin II-mediated hypertension. In healthy hearts, BNP gene delivery into the anterior wall of the LV decreased myocardial fibrosis (P<0.01, n=7 to 8) and increased capillary density (P<0.05, n=7 to 8) associated with a 7.3-fold increase in LV BNP peptide levels. Overexpression of BNP improved LV fractional shortening by 22% (P<0.05, n=6 to 7) and ejection fraction by 19% (P<0.05, n=6 to 7) after infarction. The favorable effect of BNP gene delivery on cardiac function after infarction was associated with normalization of cardiac sarcoplasmic reticulum Ca(2+)-ATPase expression and phospholamban Thr17-phosphorylation. BNP gene delivery also improved fractional shortening and ejection fraction in angiotensin II-mediated hypertension as well as decreased myocardial fibrosis and LV collagen III mRNA levels but had no effect on angiogenesis or Ca(2+)-ATPase expression and phospholamban phosphorylation. CONCLUSIONS Local intramyocardial BNP gene delivery improves cardiac function and attenuates adverse postinfarction and angiotensin II-induced remodeling. These results also indicate that myocardial BNP has pleiotropic, context-dependent, favorable actions on cardiac function and suggest that BNP acts locally as a key mechanical load-activated regulator of angiogenesis and fibrosis.
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Affiliation(s)
- Anne-Mari Moilanen
- Institute of Biomedicine, Department of Pharmacology and Toxicology, Biocenter Oulu, Oulu, Finland
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Local control of β-adrenergic stimulation: Effects on ventricular myocyte electrophysiology and Ca(2+)-transient. J Mol Cell Cardiol 2011; 50:863-71. [PMID: 21345340 DOI: 10.1016/j.yjmcc.2011.02.007] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 02/03/2011] [Accepted: 02/09/2011] [Indexed: 11/21/2022]
Abstract
Local signaling domains and numerous interacting molecular pathways and substrates contribute to the whole-cell response of myocytes during β-adrenergic stimulation (βARS). We aimed to elucidate the quantitative contribution of substrates and their local signaling environments during βARS to the canine epicardial ventricular myocyte electrophysiology and calcium transient (CaT). We present a computational compartmental model of βARS and its electrophysiological effects. Novel aspects of the model include localized signaling domains, incorporation of β1 and β2 receptor isoforms, a detailed population-based approach to integrate the βAR and Ca(2+)/Calmodulin kinase (CaMKII) signaling pathways and their effects on a wide range of substrates that affect whole-cell electrophysiology and CaT. The model identifies major roles for phosphodiesterases, adenylyl cyclases, PKA and restricted diffusion in the control of local cAMP levels and shows that activation of specific cAMP domains by different receptor isoforms allows for specific control of action potential and CaT properties. In addition, the model predicts increased CaMKII activity during βARS due to rate-dependent accumulation and increased Ca(2+) cycling. CaMKII inhibition, reduced compartmentation, and selective blockade of β1AR is predicted to reduce the occurrence of delayed afterdepolarizations during βARS. Finally, the relative contribution of each PKA substrate to whole-cell electrophysiology is quantified by comparing simulations with and without phosphorylation of each target. In conclusion, this model enhances our understanding of localized βAR signaling and its whole-cell effects in ventricular myocytes by incorporating receptor isoforms, multiple pathways and a detailed representation of multiple-target phosphorylation; it provides a basis for further studies of βARS under pathological conditions.
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31
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Soltis AR, Saucerman JJ. Synergy between CaMKII substrates and β-adrenergic signaling in regulation of cardiac myocyte Ca(2+) handling. Biophys J 2011; 99:2038-47. [PMID: 20923637 DOI: 10.1016/j.bpj.2010.08.016] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 07/23/2010] [Accepted: 08/04/2010] [Indexed: 01/10/2023] Open
Abstract
Cardiac excitation-contraction coupling is a highly coordinated process that is controlled by protein kinase signaling pathways, including Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and protein kinase A (PKA). Increased CaMKII expression and activity (as occurs during heart failure) destabilizes EC coupling and may lead to sudden cardiac death. To better understand mechanisms of cardiac CaMKII function, we integrated dynamic CaMKII-dependent regulation of key Ca(2+) handling targets with previously validated models of cardiac EC coupling, Ca(2+)/calmodulin-dependent activation of CaMKII, and β-adrenergic activation of PKA. Model predictions are validated against CaMKII-overexpression data from rabbit ventricular myocytes. The model demonstrates how overall changes to Ca(2+) handling during CaMKII overexpression are explained by interactions between individual CaMKII substrates. CaMKII and PKA activities during β-adrenergic stimulation may synergistically facilitate inotropic responses and contribute to a CaMKII-Ca(2+)-CaMKII feedback loop. CaMKII regulated early frequency-dependent acceleration of relaxation and EC coupling gain (which was highly sarcoplasmic reticulum Ca(2+) load-dependent). Additionally, the model identifies CaMKII-dependent ryanodine receptor hyperphosphorylation as a proarrhythmogenic trigger. In summary, we developed a detailed computational model of CaMKII and PKA signaling in cardiac myocytes that provides unique insights into their regulation of normal and pathological Ca(2+) handling.
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Affiliation(s)
- Anthony R Soltis
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
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32
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Kraeutler MJ, Soltis AR, Saucerman JJ. Modeling cardiac β-adrenergic signaling with normalized-Hill differential equations: comparison with a biochemical model. BMC SYSTEMS BIOLOGY 2010; 4:157. [PMID: 21087478 PMCID: PMC2993667 DOI: 10.1186/1752-0509-4-157] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 11/18/2010] [Indexed: 12/11/2022]
Abstract
Background New approaches are needed for large-scale predictive modeling of cellular signaling networks. While mass action and enzyme kinetic approaches require extensive biochemical data, current logic-based approaches are used primarily for qualitative predictions and have lacked direct quantitative comparison with biochemical models. Results We developed a logic-based differential equation modeling approach for cell signaling networks based on normalized Hill activation/inhibition functions controlled by logical AND and OR operators to characterize signaling crosstalk. Using this approach, we modeled the cardiac β1-adrenergic signaling network, including 36 reactions and 25 species. Direct comparison of this model to an extensively characterized and validated biochemical model of the same network revealed that the new model gave reasonably accurate predictions of key network properties, even with default parameters. Normalized Hill functions improved quantitative predictions of global functional relationships compared with prior logic-based approaches. Comprehensive sensitivity analysis revealed the significant role of PKA negative feedback on upstream signaling and the importance of phosphodiesterases as key negative regulators of the network. The model was then extended to incorporate recently identified protein interaction data involving integrin-mediated mechanotransduction. Conclusions The normalized-Hill differential equation modeling approach allows quantitative prediction of network functional relationships and dynamics, even in systems with limited biochemical data.
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Affiliation(s)
- Matthew J Kraeutler
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA
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33
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Al Moamen NJ, Prasad V, Bodi I, Miller ML, Neiman ML, Lasko VM, Alper SL, Wieczorek DF, Lorenz JN, Shull GE. Loss of the AE3 anion exchanger in a hypertrophic cardiomyopathy model causes rapid decompensation and heart failure. J Mol Cell Cardiol 2010; 50:137-46. [PMID: 21056571 DOI: 10.1016/j.yjmcc.2010.10.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/13/2010] [Accepted: 10/24/2010] [Indexed: 02/08/2023]
Abstract
The AE3 Cl(-)/HCO(3)(-) exchanger is abundantly expressed in the sarcolemma of cardiomyocytes, where it mediates Cl(-)-uptake and HCO(3)(-)-extrusion. Inhibition of AE3-mediated Cl(-)/HCO(3)(-) exchange has been suggested to protect against cardiac hypertrophy; however, other studies indicate that AE3 might be necessary for optimal cardiac function. To test these hypotheses we crossed AE3-null mice, which appear phenotypically normal, with a hypertrophic cardiomyopathy mouse model carrying a Glu180Gly mutation in α-tropomyosin (TM180). Loss of AE3 had no effect on hypertrophy; however, survival of TM180/AE3 double mutants was sharply reduced compared with TM180 single mutants. Analysis of cardiac performance revealed impaired cardiac function in TM180 and TM180/AE3 mutants. TM180/AE3 double mutants were more severely affected and exhibited little response to β-adrenergic stimulation, a likely consequence of their more rapid progression to heart failure. Increased expression of calmodulin-dependent kinase II and protein phosphatase 1 and differences in methylation and localization of protein phosphatase 2A were observed, but were similar in single and double mutants. Phosphorylation of phospholamban on Ser16 was sharply increased in both single and double mutants relative to wild-type hearts under basal conditions, leading to reduced reserve capacity for β-adrenergic stimulation of phospholamban phosphorylation. Imaging analysis of isolated myocytes revealed reductions in amplitude and decay of Ca(2+) transients in both mutants, with greater reductions in TM180/AE3 mutants, consistent with the greater severity of their heart failure phenotype. Thus, in the TM180 cardiomyopathy model, loss of AE3 had no apparent anti-hypertrophic effect and led to more rapid decompensation and heart failure.
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Affiliation(s)
- Nabeel J Al Moamen
- Department of Molecular Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
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Li L, Niederer SA, Idigo W, Zhang YH, Swietach P, Casadei B, Smith NP. A mathematical model of the murine ventricular myocyte: a data-driven biophysically based approach applied to mice overexpressing the canine NCX isoform. Am J Physiol Heart Circ Physiol 2010; 299:H1045-63. [PMID: 20656884 DOI: 10.1152/ajpheart.00219.2010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mathematical modeling of Ca(2+) dynamics in the heart has the potential to provide an integrated understanding of Ca(2+)-handling mechanisms. However, many previous published models used heterogeneous experimental data sources from a variety of animals and temperatures to characterize model parameters and motivate model equations. This methodology limits the direct comparison of these models with any particular experimental data set. To directly address this issue, in this study, we present a biophysically based model of Ca(2+) dynamics directly fitted to experimental data collected in left ventricular myocytes isolated from the C57BL/6 mouse, the most commonly used genetic background for genetically modified mice in studies of heart diseases. This Ca(2+) dynamics model was then integrated into an existing mouse cardiac electrophysiology model, which was reparameterized using experimental data recorded at consistent and physiological temperatures. The model was validated against the experimentally observed frequency response of Ca(2+) dynamics, action potential shape, dependence of action potential duration on cycle length, and electrical restitution. Using this framework, the implications of cardiac Na(+)/Ca(2+) exchanger (NCX) overexpression in transgenic mice were investigated. These simulations showed that heterozygous overexpression of the canine cardiac NCX increases intracellular Ca(2+) concentration transient magnitude and sarcoplasmic reticulum Ca(2+) loading, in agreement with experimental observations, whereas acute overexpression of the murine cardiac NCX results in a significant loss of Ca(2+) from the cell and, hence, depressed sarcoplasmic reticulum Ca(2+) load and intracellular Ca(2+) concentration transient magnitude. From this analysis, we conclude that these differences are primarily due to the presence of allosteric regulation in the canine cardiac NCX, which has not been observed experimentally in the wild-type mouse heart.
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Affiliation(s)
- L Li
- Computing Laboratory, University of Oxford and John Radcliffe Hospital, Oxford, United Kingdom
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Role of CaMKIIdelta phosphorylation of the cardiac ryanodine receptor in the force frequency relationship and heart failure. Proc Natl Acad Sci U S A 2010; 107:10274-9. [PMID: 20479242 DOI: 10.1073/pnas.1005843107] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The force frequency relationship (FFR), first described by Bowditch 139 years ago as the observation that myocardial contractility increases proportionally with increasing heart rate, is an important mediator of enhanced cardiac output during exercise. Individuals with heart failure have defective positive FFR that impairs their cardiac function in response to stress, and the degree of positive FFR deficiency correlates with heart failure progression. We have identified a mechanism for FFR involving heart rate dependent phosphorylation of the major cardiac sarcoplasmic reticulum calcium release channel/ryanodine receptor (RyR2), at Ser2814, by calcium/calmodulin-dependent serine/threonine kinase-delta (CaMKIIdelta). Mice engineered with an RyR2-S2814A mutation have RyR2 channels that cannot be phosphorylated by CaMKIIdelta, and exhibit a blunted positive FFR. Ex vivo hearts from RyR2-S2814A mice also have blunted positive FFR, and cardiomyocytes isolated from the RyR2-S2814A mice exhibit impaired rate-dependent enhancement of cytosolic calcium levels and fractional shortening. The cardiac RyR2 macromolecular complexes isolated from murine and human failing hearts have reduced CaMKIIdelta levels. These data indicate that CaMKIIdelta phosphorylation of RyR2 plays an important role in mediating positive FFR in the heart, and that defective regulation of RyR2 by CaMKIIdelta-mediated phosphorylation is associated with the loss of positive FFR in failing hearts.
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Beta-adrenergic receptor signaling in the heart: role of CaMKII. J Mol Cell Cardiol 2009; 48:322-30. [PMID: 19883653 DOI: 10.1016/j.yjmcc.2009.10.016] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 10/20/2009] [Accepted: 10/23/2009] [Indexed: 01/01/2023]
Abstract
The multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) targets a number of Ca(2+) homeostatic proteins and regulates gene transcription. Many of the substrates phosphorylated by CaMKII are also substrates for protein kinase A (PKA), the best known downstream effector of beta-adrenergic receptor (beta-AR) signaling. While PKA and CaMKII are conventionally considered to transduce signals through separate pathways, there is a body of evidence suggesting that CaMKII is activated in response to beta-AR stimulation and that some of the downstream effects of beta-AR stimulation are actually mediated by CaMKII. The signaling pathway through which beta-AR stimulation activates CaMKII, in parallel with or downstream of PKA, is not well-defined. This review considers the evidence for and mechanisms by which CaMKII is activated in response to beta-AR stimulation. In addition the potential role of CaMKII in beta-AR regulation of cardiac function is considered. Notably, although many CaMKII targets (e.g., phospholamban or the ryanodine receptor) are central to the regulation of Ca(2+) handling, and effects of CaMKII on Ca(2+) handling are detectable, inhibition or gene deletion of CaMKII has relatively little effect on the acute physiological contractile response to beta-AR. On the other hand CaMKII expression and activity are increased in heart failure, a pathophysiological condition characterized by chronic stimulation of cardiac beta-ARs. Blockade of beta-ARs is an accepted therapy for treatment of chronic heart failure although the rationale for its beneficial effects in cardiomyocytes is uncertain. There is growing evidence that inhibition or gene deletion of CaMKII also has a significant beneficial impact on the development of heart failure. The possibility that excessive beta-AR stimulation is detrimental because of its effects on CaMKII mediated Ca(2+) handling disturbances (e.g., ryanodine receptor phosphorylation and diastolic SR Ca(2+) leak) is an intriguing hypothesis that merits future consideration.
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Catalucci D, Latronico MVG, Ceci M, Rusconi F, Young HS, Gallo P, Santonastasi M, Bellacosa A, Brown JH, Condorelli G. Akt increases sarcoplasmic reticulum Ca2+ cycling by direct phosphorylation of phospholamban at Thr17. J Biol Chem 2009; 284:28180-28187. [PMID: 19696029 DOI: 10.1074/jbc.m109.036566] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cardiomyocytes adapt to physical stress by increasing their size while maintaining cell function. The serine/threonine kinase Akt plays a critical role in this process of adaptation. We previously reported that transgenic overexpression of an active form of Akt (Akt-E40K) in mice results in increased cardiac contractility and cell size, as well as improved sarcoplasmic reticulum (SR) Ca(2+) handling. Because it is not fully elucidated, we decided to study the molecular mechanism by which Akt-E40K overexpression improves SR Ca(2+) handling. To this end, SR Ca(2+) uptake and the phosphorylation status of phospholamban (PLN) were evaluated in heart extracts from wild-type and Akt-E40K mice and mice harboring inducible and cardiac specific knock-out of phosphatidylinositol-dependent kinase-1, the upstream activator of Akt. Moreover, the effect of Akt was assessed in vitro by overexpressing a mutant Akt targeted preferentially to the SR, and by biochemical assays to evaluate potential interaction with PLN. We found that when activated, Akt interacts with and phosphorylates PLN at Thr(17), the Ca(2+)-calmodulin-dependent kinase IIdelta site, whereas silencing Akt signaling, through the knock-out of phosphatidylinositol-dependent kinase-1, resulted in reduced phosphorylation of PLN at Thr(17). Furthermore, overexpression of SR-targeted Akt in cardiomyocytes improved Ca(2+) handling without affecting cell size. Thus, we describe here a new mechanism whereby the preferential translocation of Akt to the SR is responsible for enhancement of contractility without stimulation of hypertrophy.
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Affiliation(s)
- Daniele Catalucci
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy; Istituto Tecnologie Biomediche, Consiglio Nazionale delle Ricerche, Segrate, Milan 20090, Italy; Division of Cardiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093.
| | | | - Marcello Ceci
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy
| | - Francesca Rusconi
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy; Istituto Tecnologie Biomediche, Consiglio Nazionale delle Ricerche, Segrate, Milan 20090, Italy
| | - Howard S Young
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Paolo Gallo
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy
| | - Marco Santonastasi
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy
| | | | - Joan Heller Brown
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093
| | - Gianluigi Condorelli
- Istituto di Ricovero e Cura a Carattere Scientifico Multimedica, Milan 20138, Italy; Division of Cardiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093; Istituto Tecnologie Biomediche, Consiglio Nazionale delle Ricerche, Segrate, Milan 20090, Italy.
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38
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Koivumäki JT, Takalo J, Korhonen T, Tavi P, Weckström M. Modelling sarcoplasmic reticulum calcium ATPase and its regulation in cardiac myocytes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:2181-2202. [PMID: 19414452 DOI: 10.1098/rsta.2008.0304] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
When developing large-scale mathematical models of physiology, some reduction in complexity is necessarily required to maintain computational efficiency. A prime example of such an intricate cell is the cardiac myocyte. For the predictive power of the cardiomyocyte models, it is vital to accurately describe the calcium transport mechanisms, since they essentially link the electrical activation to contractility. The removal of calcium from the cytoplasm takes place mainly by the Na(+)/Ca(2+) exchanger, and the sarcoplasmic reticulum Ca(2+) ATPase (SERCA). In the present study, we review the properties of SERCA, its frequency-dependent and beta-adrenergic regulation, and the approaches of mathematical modelling that have been used to investigate its function. Furthermore, we present novel theoretical considerations that might prove useful for the elucidation of the role of SERCA in cardiac function, achieving a reduction in model complexity, but at the same time retaining the central aspects of its function. Our results indicate that to faithfully predict the physiological properties of SERCA, we should take into account the calcium-buffering effect and reversible function of the pump. This 'uncomplicated' modelling approach could be useful to other similar transport mechanisms as well.
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Affiliation(s)
- Jussi T Koivumäki
- Division of Biophysics, Department of Physical Sciences, University of Oulu, 90014 Oulu, Finland
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39
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Blayney LM, Lai FA. Ryanodine receptor-mediated arrhythmias and sudden cardiac death. Pharmacol Ther 2009; 123:151-77. [PMID: 19345240 PMCID: PMC2704947 DOI: 10.1016/j.pharmthera.2009.03.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 03/03/2009] [Indexed: 12/25/2022]
Abstract
The cardiac ryanodine receptor-Ca2+ release channel (RyR2) is an essential sarcoplasmic reticulum (SR) transmembrane protein that plays a central role in excitation–contraction coupling (ECC) in cardiomyocytes. Aberrant spontaneous, diastolic Ca2+ leak from the SR due to dysfunctional RyR2 contributes to the formation of delayed after-depolarisations, which are thought to underlie the fatal arrhythmia that occurs in both heart failure (HF) and in catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT is an inherited disorder associated with mutations in either the RyR2 or a SR luminal protein, calsequestrin. RyR2 shows normal function at rest in CPVT but the RyR2 dysfunction is unmasked by physical exercise or emotional stress, suggesting abnormal RyR2 activation as an underlying mechanism. Several potential mechanisms have been advanced to explain the dysfunctional RyR2 observed in HF and CPVT, including enhanced RyR2 phosphorylation status, altered RyR2 regulation at luminal/cytoplasmic sites and perturbed RyR2 intra/inter-molecular interactions. This review considers RyR2 dysfunction in the context of the structural and functional modulation of the channel, and potential therapeutic strategies to stabilise RyR2 function in cardiac pathology.
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Affiliation(s)
- Lynda M Blayney
- Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF144XN, UK.
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40
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Fuller W, Howie J, McLatchie LM, Weber RJ, Hastie CJ, Burness K, Pavlovic D, Shattock MJ. FXYD1 phosphorylation in vitro and in adult rat cardiac myocytes: threonine 69 is a novel substrate for protein kinase C. Am J Physiol Cell Physiol 2009; 296:C1346-55. [PMID: 19339511 DOI: 10.1152/ajpcell.00523.2008] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
FXYD1 (phospholemman), the primary sarcolemmal kinase substrate in the heart, is a regulator of the cardiac sodium pump. We investigated phosphorylation of FXYD1 peptides by purified kinases using HPLC, mass spectrometry, and Edman sequencing, and FXYD1 phosphorylation in cultured adult rat ventricular myocytes treated with PKA and PKC agonists by phosphospecific immunoblotting. PKA phosphorylates serines 63 and 68 (S63 and S68) and PKC phosphorylates S63, S68, and a new site, threonine 69 (T69). In unstimulated myocytes, FXYD1 is approximately 30% phosphorylated at S63 and S68, but barely phosphorylated at T69. S63 and S68 are rapidly dephosphorylated following acute inhibition of PKC in unstimulated cells. Receptor-mediated PKC activation causes sustained phosphorylation of S63 and S68, but transient phosphorylation of T69. To characterize the effect of T69 phosphorylation on sodium pump function, we measured pump currents using whole cell voltage clamping of cultured adult rat ventricular myocytes with 50 mM sodium in the patch pipette. Activation of PKA or PKC increased pump currents (from 2.1 +/- 0.2 pA/pF in unstimulated cells to 2.9 +/- 0.1 pA/pF for PKA and 3.4 +/- 0.2 pA/pF for PKC). Following kinase activation, phosphorylated FXYD1 was coimmunoprecipitated with sodium pump alpha(1)-subunit. We conclude that T69 is a previously undescribed phosphorylation site in FXYD1. Acute T69 phosphorylation elicits stimulation of the sodium pump additional to that induced by S63 and S68 phosphorylation.
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Affiliation(s)
- William Fuller
- The Institute of Cardiovascular Research, Department of Medicine, University of Dundee, Ninewells Hospital, Dundee DD1 9SY, United Kingdom.
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41
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Thiel WH, Chen B, Hund TJ, Koval OM, Purohit A, Song LS, Mohler PJ, Anderson ME. Proarrhythmic defects in Timothy syndrome require calmodulin kinase II. Circulation 2008; 118:2225-34. [PMID: 19001023 DOI: 10.1161/circulationaha.108.788067] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Timothy syndrome (TS) is a disease of excessive cellular Ca(2+) entry and life-threatening arrhythmias caused by a mutation in the primary cardiac L-type Ca(2+) channel (Ca(V)1.2). The TS mutation causes loss of normal voltage-dependent inactivation of Ca(V)1.2 current (I(Ca)). During cellular Ca(2+) overload, the calmodulin-dependent protein kinase II (CaMKII) causes arrhythmias. We hypothesized that CaMKII is a part of the proarrhythmic mechanism in TS. METHODS AND RESULTS We developed an adult rat ventricular myocyte model of TS (G406R) by lentivirus-mediated transfer of wild-type and TS Ca(V)1.2. The exogenous Ca(V)1.2 contained a mutation (T1066Y) conferring dihydropyridine resistance, so we could silence endogenous Ca(V)1.2 with nifedipine and maintain peak I(Ca) at control levels in infected cells. TS Ca(V)1.2-infected ventricular myocytes exhibited the signature voltage-dependent inactivation loss under Ca(2+) buffering conditions, not permissive for CaMKII activation. In physiological Ca(2+) solutions, TS Ca(V)1.2-expressing ventricular myocytes exhibited increased CaMKII activity and a proarrhythmic phenotype that included action potential prolongation, increased I(Ca) facilitation, and afterdepolarizations. Intracellular dialysis of a CaMKII inhibitory peptide, but not a control peptide, reversed increases in I(Ca) facilitation, normalized the action potential, and prevented afterdepolarizations. We developed a revised mathematical model that accounts for CaMKII-dependent and CaMKII-independent effects of the TS mutation. CONCLUSIONS In TS, the loss of voltage-dependent inactivation is an upstream initiating event for arrhythmia phenotypes that are ultimately dependent on CaMKII activation.
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42
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Haghighi K, Chen G, Sato Y, Fan GC, He S, Kolokathis F, Pater L, Paraskevaidis I, Jones WK, Dorn GW, Kremastinos DT, Kranias EG. A human phospholamban promoter polymorphism in dilated cardiomyopathy alters transcriptional regulation by glucocorticoids. Hum Mutat 2008; 29:640-7. [PMID: 18241046 DOI: 10.1002/humu.20692] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Depressed calcium handling by the sarcoplasmic reticulum (SR) Ca-ATPase and its regulator phospholamban (PLN) is a key characteristic of human and experimental heart failure. Accumulating evidence indicates that increases in the relative levels of PLN to Ca-ATPase in failing hearts and resulting inhibition of Ca sequestration during diastole, impairs contractility. Here, we identified a genetic variant in the PLN promoter region, which increases its expression and may serve as a genetic modifier in dilated cardiomyopathy (DCM). The variant AF177763.1:g.203A>C (at position -36 bp relative to the PLN transcriptional start site) was found only in the heterozygous form in 1 out of 296 normal subjects and in 22 out of 381 cardiomyopathy patients (heart failure at age of 18-44 years, ejection fraction=22+/-9%). In vitro analysis, using luciferase as a reporter gene in rat neonatal cardiomyocytes, indicated that the PLN-variant increased activity by 24% compared to the wild type. Furthermore, the g.203A>C substitution altered the specific sequence of the steroid receptor for the glucocorticoid nuclear receptor (GR)/transcription factor in the PLN promoter, resulting in enhanced binding to the mutated DNA site. These findings suggest that the g.203A>C genetic variant in the human PLN promoter may contribute to depressed contractility and accelerate functional deterioration in heart failure.
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Affiliation(s)
- Kobra Haghighi
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267-0575, USA
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43
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Couchonnal LF, Anderson ME. The Role of Calmodulin Kinase II in Myocardial Physiology and Disease. Physiology (Bethesda) 2008; 23:151-9. [DOI: 10.1152/physiol.00043.2007] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates a rich variety of downstream targets in heart. Ca2+ homeostatic proteins are important CaMKII targets that support myocardial excitation-contraction coupling. Under stress conditions, excessive CaMKII activity promotes heart failure and arrhythmias, in part through actions at Ca2+ homeostatic proteins. Here, we briefly review the molecular and cellular physiology of CaMKII in myocardium.
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Affiliation(s)
| | - Mark E. Anderson
- Departments of Internal Medicine and
- Molecular Physiology and Biophysics, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, Iowa,
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44
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Werdich AA, Lima EA, Dzhura I, Singh MV, Li J, Anderson ME, Baudenbacher FJ. Differential effects of phospholamban and Ca2+/calmodulin-dependent kinase II on [Ca2+]i transients in cardiac myocytes at physiological stimulation frequencies. Am J Physiol Heart Circ Physiol 2008; 294:H2352-62. [PMID: 18359893 DOI: 10.1152/ajpheart.01398.2006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In cardiac myocytes, the activity of the Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is hypothesized to regulate Ca(2+) release from and Ca(2+) uptake into the sarcoplasmic reticulum via the phosphorylation of the ryanodine receptor 2 and phospholamban (PLN), respectively. We tested the role of CaMKII and PLN on the frequency adaptation of cytosolic Ca(2+) concentration ([Ca(2+)](i)) transients in nearly 500 isolated cardiac myocytes from transgenic mice chronically expressing a specific CaMKII inhibitor, interbred into wild-type or PLN null backgrounds under physiologically relevant pacing conditions (frequencies from 0.2 to 10 Hz and at 37 degrees C). When compared with that of mice lacking PLN only, the combined chronic CaMKII inhibition and PLN ablation decreased the maximum Ca(2+) release rate by more than 50% at 10 Hz. Although PLN ablation increased the rate of Ca(2+) uptake at all frequencies, its combination with CaMKII inhibition did not prevent a frequency-dependent reduction of the amplitude and the duration of the [Ca(2+)](i) transient. High stimulation frequencies in the physiological range diminished the effects of PLN ablation on the decay time constant and on the maximum decay rate of the [Ca(2+)](i) transient, indicating that the PLN-mediated feedback on [Ca(2+)](i) removal is limited by high stimulation frequencies. Taken together, our results suggest that in isolated mouse ventricular cardiac myocytes, the combined chronic CaMKII inhibition and PLN ablation slowed Ca(2+) release at physiological frequencies: the frequency-dependent decay of the amplitude and shortening of the [Ca(2+)](i) transient occurs independent of chronic CaMKII inhibition and PLN ablation, and the PLN-mediated regulation of Ca(2+) uptake is diminished at higher stimulation frequencies within the physiological range.
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Affiliation(s)
- Andreas A Werdich
- Department of Biomedical Engineering, Vanderbilt University, 6301 Stevenson Center, VU Station B 351631, Nashville, TN 37235-1631, USA
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45
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Zhang YH, Zhang MH, Sears CE, Emanuel K, Redwood C, El-Armouche A, Kranias EG, Casadei B. Reduced phospholamban phosphorylation is associated with impaired relaxation in left ventricular myocytes from neuronal NO synthase-deficient mice. Circ Res 2007; 102:242-9. [PMID: 18007024 DOI: 10.1161/circresaha.107.164798] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Stimulation of nitric oxide (NO) release from the coronary endothelium facilitates myocardial relaxation via a cGMP-dependent reduction in myofilament Ca2+ sensitivity. Recent evidence suggests that NO released by a neuronal NO synthase (nNOS) in the myocardium can also hasten left ventricular relaxation; however, the mechanism underlying these findings is uncertain. Here we show that both relaxation (TR50) and the rate of [Ca2+]i transient decay (tau) are significantly prolonged in field-stimulated or voltage-clamped left ventricular myocytes from nNOS-/- mice and in wild-type myocytes (nNOS+/+) after acute nNOS inhibition. Disabling the sarcoplasmic reticulum abolished the differences in TR50 and tau, suggesting that impaired sarcoplasmic reticulum Ca2+ reuptake may account for the slower relaxation in nNOS-/- mice. In line with these findings, disruption of nNOS (but not of endothelial NOS) decreased phospholamban phosphorylation (P-Ser16 PLN), whereas nNOS inhibition had no effect on TR50 or tau in PLN-/- myocytes. Inhibition of cGMP signaling had no effect on relaxation in either group whereas protein kinase A inhibition abolished the difference in relaxation and PLN phosphorylation by decreasing P-Ser16 PLN and prolonging TR50 in nNOS+/+ myocytes. Conversely, inhibition of type 1 or 2A protein phosphatases shortened TR50 and increased P-Ser16 PLN in nNOS-/- but not in nNOS+/+ myocytes, in agreement with data showing increased protein phosphatase activity in nNOS-/- hearts. Taken together, our findings identify a novel mechanism by which myocardial nNOS promotes left ventricular relaxation by regulating the protein kinase A-mediated phosphorylation of PLN and the rate of sarcoplasmic reticulum Ca2+ reuptake via a cGMP-independent effect on protein phosphatase activity.
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Affiliation(s)
- Yin Hua Zhang
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, United Kingdom
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46
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Janssen PML, Periasamy M. Determinants of frequency-dependent contraction and relaxation of mammalian myocardium. J Mol Cell Cardiol 2007; 43:523-31. [PMID: 17919652 PMCID: PMC2093987 DOI: 10.1016/j.yjmcc.2007.08.012] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 08/13/2007] [Accepted: 08/16/2007] [Indexed: 11/18/2022]
Abstract
An increase in heart rate is the primary mechanism that up-regulates cardiac output during conditions such as exercise and stress. When the heart rate increases, cardiac output increases due to (1) an increased number of beats per time period, and (2) the fact that myocardium generates a higher level of force. In this review, we focus on the underlying mechanisms that are at the basis of frequency-dependent activation of the heart. In addition to increased force development, the kinetics of both cardiac activation and relaxation are faster. This is crucial, as in between successive beats there is less time, and cardiac output can only be maintained if the ventricle can fill adequately. We will discuss the cellular mechanisms that are involved in the regulation of rate-dependent changes in kinetics, with a focus on changes that occur in regulation of the intracellular calcium transient, and the changes in the myofilament responsiveness that occur when the heart rate changes.
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Affiliation(s)
- Paul M L Janssen
- Department of Physiology and Cell Biology, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210-1218, USA.
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47
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Kemi OJ, Ellingsen Ø, Ceci M, Grimaldi S, Smith GL, Condorelli G, Wisløff U. Aerobic interval training enhances cardiomyocyte contractility and Ca2+ cycling by phosphorylation of CaMKII and Thr-17 of phospholamban. J Mol Cell Cardiol 2007; 43:354-61. [PMID: 17689560 PMCID: PMC2995493 DOI: 10.1016/j.yjmcc.2007.06.013] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 06/22/2007] [Accepted: 06/27/2007] [Indexed: 10/23/2022]
Abstract
Cardiac adaptation to aerobic exercise training includes improved cardiomyocyte contractility and calcium handling. Our objective was to determine whether cytosolic calcium/calmodulin-dependent kinase II and its downstream targets are modulated by exercise training. A six-week aerobic interval training program by treadmill running increased maximal oxygen uptake by 35% in adult mice, whereupon left ventricular cardiomyocyte function was studied and myocardial tissue samples were used for biochemical analysis. Cardiomyocytes from trained mice had enhanced contractility and faster relaxation rates, which coincided with larger amplitude and faster decay of the calcium transient, but not increased peak systolic calcium levels. These changes were associated with reduced phospholamban expression relative to sarcoplasmic reticulum calcium ATPase and constitutively increased phosphorylation of phospholamban at the threonine 17, but not at the serine 16 site. Calcium/calmodulin-dependent kinase IIdelta phosphorylation was increased at threonine 287, indicating activation. To investigate the physiological role of calcium/calmodulin-dependent kinase IIdelta phosphorylation, this kinase was blocked specifically by autocamtide-2 related inhibitory peptide II. This maneuver completely abolished training-induced improvements of cardiomyocyte contractility and calcium handling and blunted, but did not completely abolish the training-induced increase in Ca(2+) sensitivity. Also, inhibition of calcium/calmodulin-dependent kinase II reduced the greater frequency-dependent acceleration of relaxation that was observed after aerobic interval training. These observations indicate that calcium/calmodulin-dependent kinase IIdelta contributes significantly to the functional adaptation of the cardiomyocyte to regular exercise training.
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Affiliation(s)
- Ole J. Kemi
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Institute of Biomedical and Life Sciences, University of Glasgow, United Kingdom
- Corresponding author: Ole J. Kemi, Institute of Biomedical and Life Sciences, University of Glasgow, West Medical Building, Glasgow, G12 8QQ, UK. Tel: +44 (0) 1413305962; Fax: +44 (0) 1413302923; , Øyvind Ellingsen, Department of Circulation and Medical Imaging, Olav Kyrres gate 9, NO-7489 Trondheim, Norway. Tel.: +47 73598822; Fax: +47 73598613.
| | - Øyvind Ellingsen
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Cardiology, St. Olavs Hospital, Trondheim, Norway
- Division of Cardiology, Department of Medicine, University of California, San Diego, La Jolla, CA
- Corresponding author: Ole J. Kemi, Institute of Biomedical and Life Sciences, University of Glasgow, West Medical Building, Glasgow, G12 8QQ, UK. Tel: +44 (0) 1413305962; Fax: +44 (0) 1413302923; , Øyvind Ellingsen, Department of Circulation and Medical Imaging, Olav Kyrres gate 9, NO-7489 Trondheim, Norway. Tel.: +47 73598822; Fax: +47 73598613.
| | - Marcello Ceci
- I.R.C.C.S Multimedica, Milan, and Fondazione Parco Scientifico San Raffaele, Rome, Italy
| | - Serena Grimaldi
- I.R.C.C.S Multimedica, Milan, and Fondazione Parco Scientifico San Raffaele, Rome, Italy
| | - Godfrey L. Smith
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Institute of Biomedical and Life Sciences, University of Glasgow, United Kingdom
| | - Gianluigi Condorelli
- Division of Cardiology, Department of Medicine, University of California, San Diego, La Jolla, CA
- I.R.C.C.S Multimedica, Milan, and Fondazione Parco Scientifico San Raffaele, Rome, Italy
| | - Ulrik Wisløff
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Cardiology, St. Olavs Hospital, Trondheim, Norway
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48
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Kim M, Perrino BA. CaM kinase II activation and phospholamban phosphorylation by SNP in murine gastric antrum smooth muscles. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1045-54. [PMID: 17185633 DOI: 10.1152/ajpgi.00203.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Elevations in the intracellular Ca(2+) concentration activate the serine/threonine protein kinase Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II). We tested the hypothesis that increased sarco(endo)plasmic reticulum Ca(2+)-ATPase activity by phospholamban (PLB) phosphorylation contributes to smooth muscle relaxation by elevating the sarcoplasmic reticulum (SR) Ca(2+) load and increasing the frequency of Ca(2+) release events from the SR. We have previously shown that caffeine or sodium nitroprusside (SNP) relaxes murine gastric fundus smooth muscles and increases PLB phosphorylation by CaM kinase II. These findings suggest that an increased SR Ca(2+) load increases the frequency of Ca(2+) transients from the SR and results in PLB phosphorylation by CaM kinase II, contributing to caffeine- or SNP-induced relaxation. The aim of the present study was to investigate the effects of SNP on CaM kinase II and PLB phosphorylation in gastric antrum smooth muscles. SNP or 8-bromo-cGMP decreased the basal tone and amplitudes of spontaneous phasic contractions and activated CaM kinase II. SNP-induced relaxation and CaM kinase II activation were blocked by [1,2,4]oxadizolo-[4,3alpha]quinoxaline-1-one (ODQ) and inhibited by cyclopiazonic acid (CPA) or KN-93. SNP also increased PLBSer(16) and PLBThr(17) phosphorylation. Both PLBSer(16) and Thr(17) phosphorylation were ODQ sensitive. However, only PLBThr(17) phosphorylation was inhibited by CPA or KN-93. These results suggest that CaM kinase II activation and PLB phosphorylation participate in the relaxant effect of SNP on murine gastric antrum smooth muscles through a nitric oxide/guanylyl cyclase/cGMP pathway.
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Affiliation(s)
- Minkyung Kim
- Department of Physiology and Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Anderson Bldg., MS352, Reno, NV 89557, USA
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49
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Zhu W, Woo AYH, Yang D, Cheng H, Crow MT, Xiao RP. Activation of CaMKIIδC Is a Common Intermediate of Diverse Death Stimuli-induced Heart Muscle Cell Apoptosis. J Biol Chem 2007; 282:10833-9. [PMID: 17296607 DOI: 10.1074/jbc.m611507200] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-calmodulin-dependent protein kinase II (CaMKII) is expressed in many mammalian cells, with the delta isoform predominantly expressed in cardiomyocytes. Previous studies have shown that inhibition of CaMKII protects cardiomyocytes against beta(1)-adrenergic receptor-mediated apoptosis. However, it is unclear whether activation of CaMKII is sufficient to cause cardiomyocyte apoptosis and whether CaMKII signaling is important in heart muscle cell apoptosis mediated by other stimuli. Here, we specifically enhanced or suppressed CaMKII activity using adenoviral gene transfer of constitutively active (CA-CaMKII(deltaC)) or dominant negative (DN-CaMKII(deltaC)) mutants of CaMKII(deltaC) in cultured adult rat cardiomyocytes. Expression of CA-CaMKII(deltaC) promoted cardiomyocyte apoptosis that was associated with increased mitochondrial cytochrome c release and attenuated by co-expression of Bcl-X(L). Importantly, isoform-specific suppression of CaMKII(deltaC) with the DN-CaMKII(deltaC) mutant similar to nonselective CaMKII inhibition by the pharmacological inhibitors (KN-93 or AIP) not only prevented CA-CaMKII(deltaC)-mediated apoptosis but also protected cells from multiple death-inducing stimuli. Thus, activation of CaMKII(deltaC) constitutes a common intermediate by which various death-inducing stimuli trigger cardiomyocyte apoptosis via the primary mitochondrial death pathway.
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Affiliation(s)
- Weizhong Zhu
- Laboratory of Cardiovascular Science, Gerontology Research Center, NIA, National Institutes of Health, Baltimore, Maryland 21224
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50
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Yamaguchi N, Meissner G. Does Ca2+/calmodulin-dependent protein kinase deltac activate or inhibit the cardiac ryanodine receptor ion channel? Circ Res 2007; 100:293-5. [PMID: 17307966 DOI: 10.1161/01.res.0000259327.56377.55] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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