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The function and regulation of calsequestrin-2: implications in calcium-mediated arrhythmias. Biophys Rev 2022; 14:329-352. [PMID: 35340602 PMCID: PMC8921388 DOI: 10.1007/s12551-021-00914-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 11/14/2021] [Indexed: 01/09/2023] Open
Abstract
Cardiac arrhythmias are life-threatening events in which the heart develops an irregular rhythm. Mishandling of Ca2+ within the myocytes of the heart has been widely demonstrated to be an underlying mechanism of arrhythmogenesis. This includes altered function of the ryanodine receptor (RyR2)-the primary Ca2+ release channel located to the sarcoplasmic reticulum (SR). The spontaneous leak of SR Ca2+ via RyR2 is a well-established contributor in the development of arrhythmic contractions. This leak is associated with increased channel activity in response to changes in SR Ca2+ load. RyR2 activity can be regulated through several avenues, including interactions with numerous accessory proteins. One such protein is calsequestrin-2 (CSQ2), which is the primary Ca2+-buffering protein within the SR. The capacity of CSQ2 to buffer Ca2+ is tightly associated with the ability of the protein to polymerise in response to changing Ca2+ levels. CSQ2 can itself be regulated through phosphorylation and glycosylation modifications, which impact protein polymerisation and trafficking. Changes in CSQ2 modifications are implicated in cardiac pathologies, while mutations in CSQ2 have been identified in arrhythmic patients. Here, we review the role of CSQ2 in arrhythmogenesis including evidence for the indirect and direct regulation of RyR2 by CSQ2, and the consequences of a loss of functional CSQ2 in Ca2+ homeostasis and Ca2+-mediated arrhythmias. Supplementary Information The online version contains supplementary material available at 10.1007/s12551-021-00914-6.
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Wang Q, Paskevicius T, Filbert A, Qin W, Kim HJ, Chen XZ, Tang J, Dacks JB, Agellon LB, Michalak M. Phylogenetic and biochemical analysis of calsequestrin structure and association of its variants with cardiac disorders. Sci Rep 2020; 10:18115. [PMID: 33093545 PMCID: PMC7582152 DOI: 10.1038/s41598-020-75097-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/08/2020] [Indexed: 12/16/2022] Open
Abstract
Calsequestrin is among the most abundant proteins in muscle sarcoplasmic reticulum and displays a high capacity but a low affinity for Ca2+ binding. In mammals, calsequestrin is encoded by two genes, CASQ1 and CASQ2, which are expressed almost exclusively in skeletal and cardiac muscles, respectively. Phylogenetic analysis indicates that calsequestrin is an ancient gene in metazoans, and that the duplication of the ancestral calsequestrin gene took place after the emergence of the lancelet. CASQ2 gene variants associated with catecholaminergic polymorphic ventricular tachycardia (CPVT) in humans are positively correlated with a high degree of evolutionary conservation across all calsequestrin homologues. The mutations are distributed in diverse locations of the calsequestrin protein and impart functional diversity but remarkably manifest in a similar phenotype in humans.
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Affiliation(s)
- Qian Wang
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Tautvydas Paskevicius
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Alexander Filbert
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB, T6G 2G3, Canada
| | - Wenying Qin
- Institute of Biomedical and Pharmaceutical Sciences, Key Laboratory of Fermentation Engineering, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, Hubei, China
| | - Hyeong Jin Kim
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Xing-Zhen Chen
- Institute of Biomedical and Pharmaceutical Sciences, Key Laboratory of Fermentation Engineering, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, Hubei, China.,Department of Physiology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Jingfeng Tang
- Institute of Biomedical and Pharmaceutical Sciences, Key Laboratory of Fermentation Engineering, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, Hubei, China
| | - Joel B Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB, T6G 2G3, Canada.
| | - Luis B Agellon
- School of Dietetics and Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, H9X 3V9, Canada.
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada. .,Institute of Biomedical and Pharmaceutical Sciences, Key Laboratory of Fermentation Engineering, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, Hubei, China.
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3
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Marchena M, Echebarria B, Shiferaw Y, Alvarez-Lacalle E. Buffering and total calcium levels determine the presence of oscillatory regimes in cardiac cells. PLoS Comput Biol 2020; 16:e1007728. [PMID: 32970668 PMCID: PMC7537911 DOI: 10.1371/journal.pcbi.1007728] [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: 02/11/2020] [Revised: 10/06/2020] [Accepted: 07/07/2020] [Indexed: 12/16/2022] Open
Abstract
Calcium oscillations and waves induce depolarization in cardiac cells which are believed to cause life-threathening arrhythimas. In this work, we study the conditions for the appearance of calcium oscillations in both a detailed subcellular model of calcium dynamics and a minimal model that takes into account just the minimal ingredients of the calcium toolkit. To avoid the effects of homeostatic changes and the interaction with the action potential we consider the somewhat artificial condition of a cell without pacing and with no calcium exchange with the extracellular medium. Both the full subcellular model and the minimal model present the same scenarios depending on the calcium load: two stationary states, one with closed ryanodine receptors (RyR) and most calcium in the cell stored in the sarcoplasmic reticulum (SR), and another, with open RyRs and a depleted SR. In between, calcium oscillations may appear. The robustness of these oscillations is determined by the amount of calsequestrin (CSQ). The lack of this buffer in the SR enhances the appearance of oscillations. The minimal model allows us to relate the stability of the oscillating state to the nullcline structure of the system, and find that its range of existence is bounded by a homoclinic and a Hopf bifurcation, resulting in a sudden transition to the oscillatory regime as the cell calcium load is increased. Adding a small amount of noise to the RyR behavior increases the parameter region where oscillations appear and provides a gradual transition from the resting state to the oscillatory regime, as observed in the subcellular model and experimentally. In cardiac cells, calcium plays a very important role. An increase in calcium levels is the trigger used by the cell to initiate contraction. Besides, calcium modulates several transmembrane currents, affecting the cell transmembrane potential. Thus, dysregulations in calcium handling have been associated with the appearance of arrhythmias. Often, this dysregulation results in the appearance of periodic calcium waves or global oscillations, providing a pro-arrhythmic substrate. In this paper, we study the onset of calcium oscillations in cardiac cells using both a detailed subcellular model of calcium dynamics and a minimal model that takes into account the essential ingredients of the calcium toolkit. Both reproduce the main experimental results and link this behavior with the presence of different steady-state solutions and bifurcations that depend on the total amount of calcium in the cell and in the level of buffering present. We expect that this work will help to clarify the conditions under which calcium oscillations appear in cardiac myocytes and, therefore, will represent a step further in the understanding of the origin of cardiac arrhythmias.
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Affiliation(s)
- Miquel Marchena
- Departament de Física, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
| | - Blas Echebarria
- Departament de Física, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona, Spain
| | - Yohannes Shiferaw
- Physics Department, California State University, Northridge, California 91330, USA
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4
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Ng K, Titus EW, Lieve KV, Roston TM, Mazzanti A, Deiter FH, Denjoy I, Ingles J, Till J, Robyns T, Connors SP, Steinberg C, Abrams DJ, Pang B, Scheinman MM, Bos JM, Duffett SA, van der Werf C, Maltret A, Green MS, Rutberg J, Balaji S, Cadrin-Tourigny J, Orland KM, Knight LM, Brateng C, Wu J, Tang AS, Skanes AC, Manlucu J, Healey JS, January CT, Krahn AD, Collins KK, Maginot KR, Fischbach P, Etheridge SP, Eckhardt LL, Hamilton RM, Ackerman MJ, Noguer FRI, Semsarian C, Jura N, Leenhardt A, Gollob MH, Priori SG, Sanatani S, Wilde AAM, Deo RC, Roberts JD. An International Multicenter Evaluation of Inheritance Patterns, Arrhythmic Risks, and Underlying Mechanisms of CASQ2-Catecholaminergic Polymorphic Ventricular Tachycardia. Circulation 2020; 142:932-947. [PMID: 32693635 PMCID: PMC7484339 DOI: 10.1161/circulationaha.120.045723] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Genetic variants in calsequestrin-2 (CASQ2) cause an autosomal recessive form of catecholaminergic polymorphic ventricular tachycardia (CPVT), although isolated reports have identified arrhythmic phenotypes among heterozygotes. Improved insight into the inheritance patterns, arrhythmic risks, and molecular mechanisms of CASQ2-CPVT was sought through an international multicenter collaboration. METHODS Genotype-phenotype segregation in CASQ2-CPVT families was assessed, and the impact of genotype on arrhythmic risk was evaluated using Cox regression models. Putative dominant CASQ2 missense variants and the established recessive CASQ2-p.R33Q variant were evaluated using oligomerization assays and their locations mapped to a recent CASQ2 filament structure. RESULTS A total of 112 individuals, including 36 CPVT probands (24 homozygotes/compound heterozygotes and 12 heterozygotes) and 76 family members possessing at least 1 presumed pathogenic CASQ2 variant, were identified. Among CASQ2 homozygotes and compound heterozygotes, clinical penetrance was 97.1% and 26 of 34 (76.5%) individuals had experienced a potentially fatal arrhythmic event with a median age of onset of 7 years (95% CI, 6-11). Fifty-one of 66 CASQ2 heterozygous family members had undergone clinical evaluation, and 17 of 51 (33.3%) met diagnostic criteria for CPVT. Relative to CASQ2 heterozygotes, CASQ2 homozygote/compound heterozygote genotype status in probands was associated with a 3.2-fold (95% CI, 1.3-8.0; P=0.013) increased hazard of a composite of cardiac syncope, aborted cardiac arrest, and sudden cardiac death, but a 38.8-fold (95% CI, 5.6-269.1; P<0.001) increased hazard in genotype-positive family members. In vitro turbidity assays revealed that p.R33Q and all 6 candidate dominant CASQ2 missense variants evaluated exhibited filamentation defects, but only p.R33Q convincingly failed to dimerize. Structural analysis revealed that 3 of these 6 putative dominant negative missense variants localized to an electronegative pocket considered critical for back-to-back binding of dimers. CONCLUSIONS This international multicenter study of CASQ2-CPVT redefines its heritability and confirms that pathogenic heterozygous CASQ2 variants may manifest with a CPVT phenotype, indicating a need to clinically screen these individuals. A dominant mode of inheritance appears intrinsic to certain missense variants because of their location and function within the CASQ2 filament structure.
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Affiliation(s)
- Kevin Ng
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
- Cairns Hospital, Queensland, Australia
| | - Erron W. Titus
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, USA
| | - Krystien V. Lieve
- Amsterdam University Medical Centre, University of Amsterdam, Heart Centre, Department of Clinical and Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
| | - Thomas M. Roston
- Heart Rhythm Services, Division of Cardiology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Andrea Mazzanti
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Molecular Cardiology, Istituti Clinici Scientifici Maugeri, Istituto di Ricovero e Cura a Carattere Scientifico and Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Frederick H. Deiter
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, USA
| | - Isabelle Denjoy
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Service de Cardiologie et CNMR Maladies Cardiacques Héréditaires Rares, Hôpital Bichat, Paris, France
| | - Jodie Ingles
- Agnes Ginges Centre for Molecular Cardiology at Centenary Institute, The University of Sydney, Sydney, Australia
| | - Jan Till
- Department of Cardiology, Royal Brompton Hospital, London, United Kingdom
| | - Tomas Robyns
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Department of Cardiovascular Disease, University Hospitals Leuven, Leuven, Belgium
| | - Sean P. Connors
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Memorial University, St. John’s, Newfoundland and Labrador, Canada
| | | | - Dominic J. Abrams
- Inherited Cardiac Arrhythmia Program, Boston Children’s Hospital, Harvard Medical School, Massachusetts, USA
| | - Benjamin Pang
- Arrhythmia Service, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Melvin M. Scheinman
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, University of California San Francisco, San Francisco, California, USA
| | - J. Martijn Bos
- Departments of Cardiovascular Medicine (Division of Heart Rhythm Services), Pediatric and Adolescent Medicine (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, Minnesota, USA
| | - Stephen A. Duffett
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Memorial University, St. John’s, Newfoundland and Labrador, Canada
| | - Christian van der Werf
- Amsterdam University Medical Centre, University of Amsterdam, Heart Centre, Department of Clinical and Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
| | - Alice Maltret
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Service de Cardiologie et CNMR Maladies Cardiacques Héréditaires Rares, Hôpital Bichat, Paris, France
| | - Martin S. Green
- Arrhythmia Service, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Julie Rutberg
- Arrhythmia Service, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Seshadri Balaji
- Department of Pediatrics, Division of Cardiology, Oregon Health & Science University, Portland, Oregon, USA
| | - Julia Cadrin-Tourigny
- Cardiovascular Genetics Center, Montreal Heart Institute, Université de Montréal, Montréal, Canada
| | - Kate M. Orland
- University of Wisconsin-Madison Inherited Arrhythmia Clinic, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Linda M. Knight
- Children’s Healthcare of Atlanta, Sibley Heart Center Cardiology, Atlanta, Georgia, USA
| | - Caitlin Brateng
- Children’s Hospital Colorado, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Jeremy Wu
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
| | - Anthony S. Tang
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
| | - Allan C. Skanes
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
| | - Jaimie Manlucu
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
| | - Jeff S. Healey
- Population Health Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Craig T. January
- University of Wisconsin-Madison Inherited Arrhythmia Clinic, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Andrew D. Krahn
- Heart Rhythm Services, Division of Cardiology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kathryn K. Collins
- Children’s Hospital Colorado, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Kathleen R. Maginot
- Department of Pediatrics, University of Wisconsin School of Medicine & Public Health, Madison, Wisconsin, USA
| | - Peter Fischbach
- Children’s Healthcare of Atlanta, Sibley Heart Center Cardiology, Atlanta, Georgia, USA
| | - Susan P. Etheridge
- Department of Pediatrics, University of Utah, and Primary Children’s Hospital, Salt Lake City, Utah, USA
| | - Lee L. Eckhardt
- University of Wisconsin-Madison Inherited Arrhythmia Clinic, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Robert M. Hamilton
- The Labatt Family Heart Centre (Department of Pediatrics) and Translational Medicine, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada
| | - Michael J. Ackerman
- Departments of Cardiovascular Medicine (Division of Heart Rhythm Services), Pediatric and Adolescent Medicine (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, Minnesota, USA
| | | | - Christopher Semsarian
- Agnes Ginges Centre for Molecular Cardiology at Centenary Institute, The University of Sydney, Sydney, Australia
| | - Natalia Jura
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, USA
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, USA
| | - Antoine Leenhardt
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Service de Cardiologie et CNMR Maladies Cardiacques Héréditaires Rares, Hôpital Bichat, Paris, France
| | - Michael H. Gollob
- Department of Physiology and Department of Medicine, Toronto General Hospital, University of Toronto, Ontario, Canada
| | - Silvia G. Priori
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
- Molecular Cardiology, Istituti Clinici Scientifici Maugeri, Istituto di Ricovero e Cura a Carattere Scientifico and Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Shubhayan Sanatani
- Department of Pediatrics, Children’s Heart Centre, BC Children’s Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Arthur A. M. Wilde
- Amsterdam University Medical Centre, University of Amsterdam, Heart Centre, Department of Clinical and Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam, the Netherlands
- European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart
| | - Rahul C. Deo
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California, USA
- Department of Medicine, University of California San Francisco, San Francisco, California, USA
- One Brave Idea and Division of Cardiovascular Medicine, Brigham and Women’s Hospital, Boston, Massachusetts, USA
- Harvard Medical School, Harvard University, Boston, Massachusetts, USA
| | - Jason D. Roberts
- Section of Cardiac Electrophysiology, Division of Cardiology, Department of Medicine, Western University, London, Ontario, Canada
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5
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Saadeh K, Achercouk Z, Fazmin IT, Nantha Kumar N, Salvage SC, Edling CE, Huang CLH, Jeevaratnam K. Protein expression profiles in murine ventricles modeling catecholaminergic polymorphic ventricular tachycardia: effects of genotype and sex. Ann N Y Acad Sci 2020; 1478:63-74. [PMID: 32713021 DOI: 10.1111/nyas.14426] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/27/2020] [Accepted: 06/15/2020] [Indexed: 12/12/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is associated with mutations in the cardiac ryanodine receptor (RyR2). These result in stress-induced ventricular arrhythmic episodes, with clinical symptoms and prognosis reported more severe in male than female patients. Murine homozygotic RyR2-P2328S (RyR2S/S ) hearts replicate the proarrhythmic CPVT phenotype of abnormal sarcoplasmic reticular Ca2+ leak and disrupted Ca2+ homeostasis. In addition, RyR2S/S hearts show decreased myocardial action potential conduction velocities (CV), all features implicated in arrhythmic trigger and substrate. The present studies explored for independent and interacting effects of RyR2S/S genotype and sex on expression levels of molecular determinants of Ca2+ homeostasis (CASQ2, FKBP12, SERCA2a, NCX1, and CaV 1.2) and CV (NaV 1.5, Connexin (Cx)-43, phosphorylated-Cx43, and TGF-β1) in mice. Expression levels of Ca2+ homeostasis proteins were not altered, hence implicating abnormal RyR2 function alone in disrupted cytosolic Ca2+ homeostasis. Furthermore, altered NaV 1.5, phosphorylated Cx43, and TGF-β1 expression were not implicated in the development of slowed CV. By contrast, decreased Cx43 expression correlated with slowed CV, in female, but not male, RyR2S/S mice. The CV changes may reflect acute actions of the increased cytosolic Ca2+ on NaV 1.5 and Cx43 function.
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Affiliation(s)
- Khalil Saadeh
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Zakaria Achercouk
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Ibrahim T Fazmin
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
| | - Nakulan Nantha Kumar
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Samantha C Salvage
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Charlotte E Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Christopher L-H Huang
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
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6
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Wang Q, Michalak M. Calsequestrin. Structure, function, and evolution. Cell Calcium 2020; 90:102242. [PMID: 32574906 DOI: 10.1016/j.ceca.2020.102242] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/05/2020] [Accepted: 06/06/2020] [Indexed: 12/25/2022]
Abstract
Calsequestrin is the major Ca2+ binding protein in the sarcoplasmic reticulum (SR), serves as the main Ca2+ storage and buffering protein and is an important regulator of Ca2+ release channels in both skeletal and cardiac muscle. It is anchored at the junctional SR membrane through interactions with membrane proteins and undergoes reversible polymerization with increasing Ca2+ concentration. Calsequestrin provides high local Ca2+ at the junctional SR and communicates changes in luminal Ca2+ concentration to Ca2+ release channels, thus it is an essential component of excitation-contraction coupling. Recent studies reveal new insights on calsequestrin trafficking, Ca2+ binding, protein evolution, protein-protein interactions, stress responses and the molecular basis of related human muscle disease, including catecholaminergic polymorphic ventricular tachycardia (CPVT). Here we provide a comprehensive overview of calsequestrin, with recent advances in structure, diverse functions, phylogenetic analysis, and its role in muscle physiology, stress responses and human pathology.
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Affiliation(s)
- Qian Wang
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6H 2S7, Canada
| | - Marek Michalak
- Department of Biochemistry, University of Alberta, Edmonton, AB, T6H 2S7, Canada.
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7
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Rossi D, Gamberucci A, Pierantozzi E, Amato C, Migliore L, Sorrentino V. Calsequestrin, a key protein in striated muscle health and disease. J Muscle Res Cell Motil 2020; 42:267-279. [PMID: 32488451 DOI: 10.1007/s10974-020-09583-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 10/24/2022]
Abstract
Calsequestrin (CASQ) is the most abundant Ca2+ binding protein localized in the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. The genome of vertebrates contains two genes, CASQ1 and CASQ2. CASQ1 and CASQ2 have a high level of homology, but show specific patterns of expression. Fast-twitch skeletal muscle fibers express only CASQ1, both CASQ1 and CASQ2 are present in slow-twitch skeletal muscle fibers, while CASQ2 is the only protein present in cardiomyocytes. Depending on the intraluminal SR Ca2+ levels, CASQ monomers assemble to form large polymers, which increase their Ca2+ binding ability. CASQ interacts with triadin and junctin, two additional SR proteins which contribute to localize CASQ to the junctional region of the SR (j-SR) and also modulate CASQ ability to polymerize into large macromolecular complexes. In addition to its ability to bind Ca2+ in the SR, CASQ appears also to be able to contribute to regulation of Ca2+ homeostasis in muscle cells. Both CASQ1 and CASQ2 are able to either activate and inhibit the ryanodine receptors (RyRs) calcium release channels, likely through their interactions with junctin and triadin. Additional evidence indicates that CASQ1 contributes to regulate the mechanism of store operated calcium entry in skeletal muscle via a direct interaction with the Stromal Interaction Molecule 1 (STIM1). Mutations in CASQ2 and CASQ1 have been identified, respectively, in patients with catecholamine-induced polymorphic ventricular tachycardia and in patients with some forms of myopathy. This review will highlight recent developments in understanding CASQ1 and CASQ2 in health and diseases.
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Affiliation(s)
- Daniela Rossi
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy.
| | - Alessandra Gamberucci
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Enrico Pierantozzi
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Caterina Amato
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Loredana Migliore
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
| | - Vincenzo Sorrentino
- Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena, Via A. Moro, 2, 53100, Siena, Italy
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8
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Chakravarty H, Bal C, Yadav M, Jena N, Bal NC, Sharon A. First Insight on Small Molecules as Cardiac Calsequestrin Stabilizers. ACS OMEGA 2019; 4:11508-11514. [PMID: 31460256 PMCID: PMC6682146 DOI: 10.1021/acsomega.9b01113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 06/19/2019] [Indexed: 06/10/2023]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is caused by mutations of cardiac calsequestrin (CASQ2) that impair its characteristic ability of Ca2+-induced polymerization-depolymerization. However, stabilizing the CASQ2 polymer by pharmacological agents to treat CPVT has not been reported so far. Here, we tested whether small molecules can stabilize CASQ2 polymers. We synthesized 24 glycinate/alaninate/acetate α-pyranone analogs and conducted the CASQ2 depolymerization assay. Most of the molecules of this class of compounds inhibited the depolymerization of the protein upon Ca2+ chelation by ethylene glycol tetraacetic acid. Structure-activity relationship studies revealed that the compounds with the 4-fluoro-phenyl group at the C-6 position of the pyranone ring and open-chain primary amine at C-4 are the most active of the class. This is the first report of an α-pyranone class of compounds with the ability to stabilize CASQ2 polymers and opens up the possibility to target Ca2+-release disorders via modulation of CASQ2 polymerization.
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Affiliation(s)
| | - Chandralata Bal
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
| | - Monika Yadav
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
| | - Nivedita Jena
- KIIT Technology Business Incubator and KIIT School of Biotechnology, KIIT University, Bhubaneswar 751021 India
| | - Naresh C. Bal
- KIIT Technology Business Incubator and KIIT School of Biotechnology, KIIT University, Bhubaneswar 751021 India
| | - Ashoke Sharon
- Department
of Chemistry, Birla Institute of Technology,
Mesra, Ranchi 835215, India
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9
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Shoop S, Maria Z, Campolo A, Rashdan N, Martin D, Lovern P, Lacombe VA. Glial Growth Factor 2 Regulates Glucose Transport in Healthy Cardiac Myocytes and During Myocardial Infarction via an Akt-Dependent Pathway. Front Physiol 2019; 10:189. [PMID: 30971932 PMCID: PMC6445869 DOI: 10.3389/fphys.2019.00189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 02/14/2019] [Indexed: 12/23/2022] Open
Abstract
Neuregulin (NRG), a paracrine factor in myocytes, promotes cardiac development via the ErbB receptors. NRG-1β also improves cardiac function and cell survival after myocardial infarction (MI), although the mechanisms underlying these cardioprotective effects are not well elucidated. Increased glucose uptake has been shown to be cardio-protective during MI. We hypothesized that treatment with a recombinant version of NRG-1β, glial growth factor 2 (GGF2), will enhance glucose transport in the healthy myocardium and during MI. Cardiac myocytes were isolated from MI and healthy adult rats, and subsequently incubated with or without insulin or GGF2. Glucose uptake was measured using a fluorescent D-glucose analog. The translocation of glucose transporter (GLUT) 4 to the cell surface, the rate-limiting step in glucose uptake, was measured using a photolabeled biotinylation assay in isolated myocytes. Similar to insulin, acute in vitro GGF2 treatment increased glucose uptake in healthy cardiac myocytes (by 40 and 49%, respectively, P = 0.002). GGF2 treatment also increased GLUT4 translocation in healthy myocytes by 184% (P < 0.01), while ErbB 2/4 receptor blockade (by afatinib) abolished these effects. In addition, GGF2 treatment enhanced Akt phosphorylation (at both threonine and serine sites, by 75 and 139%, respectively, P = 0.029 and P = 0.01), which was blunted by ErbB 2/4 receptor blockade. GGF2 treatment increased the phosphorylation of AS160 (an Akt effector) by 72% (P < 0.05), as well as the phosphorylation of PDK-1 and PKC (by 118 and 92%, respectively, P < 0.05). During MI, cardiac GLUT4 translocation was downregulated by 44% (P = 0.004) and was partially rescued by both in vitro insulin and GGF2 treatment. Our data demonstrate that acute GGF2 treatment increased glucose transport in cardiac myocytes by activating the ErbB 2/4 receptors and subsequent key downstream effectors (i.e., PDK-1, Akt, AS160, and PKC). These findings highlight novel mechanisms of action of GGF2, which warrant further investigation in patients with heart failure.
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Affiliation(s)
- Shanell Shoop
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States.,Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, United States
| | - Zahra Maria
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States.,Harold Hamm Diabetes Center, University of Oklahoma, Oklahoma City, OK, United States
| | - Allison Campolo
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States.,Harold Hamm Diabetes Center, University of Oklahoma, Oklahoma City, OK, United States
| | - Nabil Rashdan
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States
| | - Dominic Martin
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, United States
| | - Pamela Lovern
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States
| | - Véronique A Lacombe
- Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, United States.,Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, United States.,Harold Hamm Diabetes Center, University of Oklahoma, Oklahoma City, OK, United States
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10
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Abstract
Although the mechanism of sudden cardiac death (SCD) in heart failure is not completely known, genetic variations are known to play key roles in this process. Increasing numbers of mutations and variants are being discovered through genome-wide association studies. The genetic variations involved in the mechanisms of SCD have aroused widespread concern. Comprehensive understanding of the genetic variations involved in SCD may help prevent it. To this end, we briefly reviewed the genetic variations involved in SCD and their associations and interactions, and observed that cardiac ion channels are the core molecules involved in this process. Genetic variations involved in cardiac structure, cardiogenesis and development, cell division and differentiation, and DNA replication and transcription are all speculated to be loci involved in SCD. Additionally, the systems involved in neurohumoral regulation as well as substance and energy metabolism are also potentially responsible for susceptibility to SCD. They form an elaborate network and mutually interact with each other to govern the fate of SCD-susceptible individuals.
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11
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Gergs U, Fahrion CM, Bock P, Fischer M, Wache H, Hauptmann S, Schmitz W, Neumann J. Evidence for a functional role of calsequestrin 2 in mouse atrium. Acta Physiol (Oxf) 2017; 219:669-682. [PMID: 27484853 DOI: 10.1111/apha.12766] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 02/23/2016] [Accepted: 07/30/2016] [Indexed: 12/01/2022]
Abstract
AIM Several genetically modified mice models were studied so far to investigate the role of cardiac calsequestrin (CSQ2) for the contractile function of the ventricle and for the occurrence of ventricular tachycardia. Using a CSQ2 knockout mouse, we wanted to study also the atrial function of CSQ2. METHODS The influence of CSQ2 on atrial function and, for comparison, ventricular function was studied in isolated cardiac preparations and by echocardiography as well as electrocardiography in mice with deletion of CSQ2. RESULTS Using deletion of exon 1, we have successfully generated a constitutive knockout mouse of the calsequestrin 2 gene (CSQ2-/- ). CSQ2 protein was absent in the heart (atrium, ventricle), but also in oesophagus and skeletal muscle of homozygous knockout mice. In 6-month-old CSQ2-/- mice, relative left atrial weight was increased, whereas relative heart weight was unchanged. The staircase phenomena in paced left atrial preparations on force of contraction and the post-rest potentiation were different between wild type and CSQ2-/- indicative for a decreased sarcoplasmic Ca2+ load and supporting an important role of CSQ2 also in the atrium. The incidence of arrhythmias was increased in CSQ2-/- . In 2-year-old CSQ2-/- mice, cardiac hypertrophy and heart failure were noted possibly as a result of chronically increased cytosolic Ca2+ levels. CONCLUSION These data suggest a functional role of CSQ2 not only in the ventricle but also in the atrium of mammalian hearts. Loss of CSQ2 function can cause not only arrhythmias, but also cardiac hypertrophy and heart failure.
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Affiliation(s)
- U. Gergs
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
| | - C. M. Fahrion
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
| | - P. Bock
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
| | - M. Fischer
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
| | - H. Wache
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
| | - S. Hauptmann
- Institut für Pathologie am Krankenhaus Düren gGmbH; Düren Germany
| | - W. Schmitz
- Institut für Pharmakologie und Toxikologie; Universitätsklinikum Münster; Münster Germany
| | - J. Neumann
- Institut für Pharmakologie und Toxikologie; Medizinische Fakultät; Martin-Luther-Universität Halle-Wittenberg; Halle/Saale Germany
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12
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Abstract
Cardiac arrhythmias can follow disruption of the normal cellular electrophysiological processes underlying excitable activity and their tissue propagation as coherent wavefronts from the primary sinoatrial node pacemaker, through the atria, conducting structures and ventricular myocardium. These physiological events are driven by interacting, voltage-dependent, processes of activation, inactivation, and recovery in the ion channels present in cardiomyocyte membranes. Generation and conduction of these events are further modulated by intracellular Ca2+ homeostasis, and metabolic and structural change. This review describes experimental studies on murine models for known clinical arrhythmic conditions in which these mechanisms were modified by genetic, physiological, or pharmacological manipulation. These exemplars yielded molecular, physiological, and structural phenotypes often directly translatable to their corresponding clinical conditions, which could be investigated at the molecular, cellular, tissue, organ, and whole animal levels. Arrhythmogenesis could be explored during normal pacing activity, regular stimulation, following imposed extra-stimuli, or during progressively incremented steady pacing frequencies. Arrhythmic substrate was identified with temporal and spatial functional heterogeneities predisposing to reentrant excitation phenomena. These could arise from abnormalities in cardiac pacing function, tissue electrical connectivity, and cellular excitation and recovery. Triggering events during or following recovery from action potential excitation could thereby lead to sustained arrhythmia. These surface membrane processes were modified by alterations in cellular Ca2+ homeostasis and energetics, as well as cellular and tissue structural change. Study of murine systems thus offers major insights into both our understanding of normal cardiac activity and its propagation, and their relationship to mechanisms generating clinical arrhythmias.
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Affiliation(s)
- Christopher L-H Huang
- Physiological Laboratory and the Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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13
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Maturing human pluripotent stem cell-derived cardiomyocytes in human engineered cardiac tissues. Adv Drug Deliv Rev 2016; 96:110-34. [PMID: 25956564 DOI: 10.1016/j.addr.2015.04.019] [Citation(s) in RCA: 158] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 04/24/2015] [Accepted: 04/25/2015] [Indexed: 12/19/2022]
Abstract
Engineering functional human cardiac tissue that mimics the native adult morphological and functional phenotype has been a long held objective. In the last 5 years, the field of cardiac tissue engineering has transitioned from cardiac tissues derived from various animal species to the production of the first generation of human engineered cardiac tissues (hECTs), due to recent advances in human stem cell biology. Despite this progress, the hECTs generated to date remain immature relative to the native adult myocardium. In this review, we focus on the maturation challenge in the context of hECTs, the present state of the art, and future perspectives in terms of regenerative medicine, drug discovery, preclinical safety testing and pathophysiological studies.
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14
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Novak A, Barad L, Lorber A, Gherghiceanu M, Reiter I, Eisen B, Eldor L, Itskovitz-Eldor J, Eldar M, Arad M, Binah O. Functional abnormalities in iPSC-derived cardiomyocytes generated from CPVT1 and CPVT2 patients carrying ryanodine or calsequestrin mutations. J Cell Mol Med 2015; 19:2006-18. [PMID: 26153920 PMCID: PMC4549051 DOI: 10.1111/jcmm.12581] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 02/17/2015] [Indexed: 01/11/2023] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia characterized by syncope and sudden death occurring during exercise or acute emotion. CPVT is caused by abnormal intracellular Ca2+ handling resulting from mutations in the RyR2 or CASQ2 genes. Because CASQ2 and RyR2 are involved in different aspects of the excitation-contraction coupling process, we hypothesized that these mutations are associated with different functional and intracellular Ca²+ abnormalities. To test the hypothesis we generated induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CM) from CPVT1 and CPVT2 patients carrying the RyR2R420Q and CASQ2D307H mutations, respectively, and investigated in CPVT1 and CPVT2 iPSC-CM (compared to control): (i) The ultrastructural features; (ii) the effects of isoproterenol, caffeine and ryanodine on the [Ca2+]i transient characteristics. Our major findings were: (i) Ultrastructurally, CASQ2 and RyR2 mutated cardiomyocytes were less developed than control cardiomyocytes. (ii) While in control iPSC-CM isoproterenol caused positive inotropic and lusitropic effects, in the mutated cardiomyocytes isoproterenol was either ineffective, caused arrhythmias, or markedly increased diastolic [Ca2+]i. Importantly, positive inotropic and lusitropic effects were not induced in mutated cardiomyocytes. (iii) The effects of caffeine and ryanodine in mutated cardiomyocytes differed from control cardiomyocytes. Our results show that iPSC-CM are useful for investigating the similarities/differences in the pathophysiological consequences of RyR2 versus CASQ2 mutations underlying CPVT1 and CPVT2 syndromes.
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Affiliation(s)
- Atara Novak
- Department of Physiology, Technion, Haifa, Israel.,The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Lili Barad
- Department of Physiology, Technion, Haifa, Israel.,The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Avraham Lorber
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel.,Department of Pediatric Cardiology, Rambam Health Care Campus, Haifa, Israel
| | | | - Irina Reiter
- Department of Physiology, Technion, Haifa, Israel.,The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Binyamin Eisen
- Department of Physiology, Technion, Haifa, Israel.,The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Liron Eldor
- Department of Plastic Surgery, Rambam Health Care Campus, Haifa, Israel
| | - Joseph Itskovitz-Eldor
- The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Michael Eldar
- Leviev Heart Center, Sheba Medical Center, Tel Hashomer and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Michael Arad
- Leviev Heart Center, Sheba Medical Center, Tel Hashomer and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ofer Binah
- Department of Physiology, Technion, Haifa, Israel.,The Rappaport Institute for Research in the Medical Sciences, Technion, Haifa, Israel.,Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
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15
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Zhang JZ, Waddell HMM, Jones PP. Regulation of RYR2 by sarcoplasmic reticulum Ca(2+). Clin Exp Pharmacol Physiol 2015; 42:720-6. [PMID: 25603835 DOI: 10.1111/1440-1681.12364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Revised: 09/17/2014] [Accepted: 10/09/2014] [Indexed: 11/28/2022]
Abstract
Ca(2+) is arguably the most important ion involved in the contraction of the heart. The cardiac ryanodine receptor (RyR2), the major Ca(2+) release channel located in the sarcoplasmic reticulum (SR) membrane, is responsible for releasing the bulk of Ca(2+) required for contraction. Moreover, RyR2 is also crucial for maintaining SR Ca(2+) homeostasis by releasing Ca(2+) from the SR when it becomes overloaded with Ca(2+) . During normal contraction, RyR2 is activated by cytosolic Ca(2+) , whereas during store overload conditions, the opening of RyR2 is governed by SR Ca(2+) . Although the process of the cytosolic control of RyR2 is well established, the molecular mechanism by which SR luminal Ca(2+) regulates RyR2 has only recently been elucidated and remains controversial. In addition to the activation of RyR2, SR luminal Ca(2+) also determines when the RyR2 channel closes. RyR2-mediated Ca(2+) release from the SR does not continue until the SR is completely depleted. Rather, it ceases when SR luminal Ca(2+) falls below a certain level. Given the importance of SR Ca(2+) , it is not surprising that the SR luminal Ca(2+) level is tightly controlled by SR Ca(2+) -buffering proteins. Consequently, the opening and closing of RyR2 is heavily influenced by the presence of such proteins, particularly those associated with RyR2, such as calsequestrin and the histidine-rich Ca(2+) -binding protein. These proteins appear to indirectly alter RyR2 activity by modifying the microdomain SR Ca(2+) level surrounding RyR2.
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Affiliation(s)
- Joe Z Zhang
- Department of Physiology and HeartOtago, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
| | - Helen M M Waddell
- Department of Physiology and HeartOtago, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
| | - Peter P Jones
- Department of Physiology and HeartOtago, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
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16
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Qu Z, Weiss JN. Mechanisms of ventricular arrhythmias: from molecular fluctuations to electrical turbulence. Annu Rev Physiol 2014; 77:29-55. [PMID: 25340965 DOI: 10.1146/annurev-physiol-021014-071622] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Ventricular arrhythmias have complex causes and mechanisms. Despite extensive investigation involving many clinical, experimental, and computational studies, effective biological therapeutics are still very limited. In this article, we review our current understanding of the mechanisms of ventricular arrhythmias by summarizing the state of knowledge spanning from the molecular scale to electrical wave behavior at the tissue and organ scales and how the complex nonlinear interactions integrate into the dynamics of arrhythmias in the heart. We discuss the challenges that we face in synthesizing these dynamics to develop safe and effective novel therapeutic approaches.
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Affiliation(s)
- Zhilin Qu
- Departments of 1Medicine (Cardiology) and
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17
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Peotta VA, Bhandary P, Ogu U, Volk KA, Roghair RD. Reduced blood pressure of CFTR-F508del carriers correlates with diminished arterial reactivity rather than circulating blood volume in mice. PLoS One 2014; 9:e96756. [PMID: 24801204 PMCID: PMC4011854 DOI: 10.1371/journal.pone.0096756] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 04/09/2014] [Indexed: 11/18/2022] Open
Abstract
The F508del mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) is the most common cause of cystic fibrosis (CF). Both CF patients and F508del carriers have decreased blood pressure. While this has been attributed to salt depletion, recent studies have shown F508del expression interferes with smooth muscle cell calcium mobilization. We tested the hypothesis that carriers of the F508del mutation have lower adult blood pressures and reduced aortic contractility without a reduction in circulating blood volume. By radiotelemetry, F508del heterozygous mice had significantly lower arterial pressures than wild-type C57BL/6 controls, with the greatest effect seen at the time of dark-to-light cycle transition (mean difference of 10 mmHg). To replicate the vascular effects of sympathetic arousal, isoproterenol and epinephrine were co-infused, and F508del mice again had significantly reduced arterial pressures. Aortas isolated from F508del heterozygous mice had significantly decreased constriction to noradrenaline (0.9±0.2 versus 2.9±0.7 mN). Inhibition of wild-type CFTR or the inositol triphosphate receptor replicated the phenotype of F508del aortas. CFTR carrier status did not alter circulating blood volume. We conclude the CFTR-F508del mutation decreases aortic contractility and lowers arterial pressures. As a cAMP-activated chloride channel that facilitates calcium mobilization, we speculate wild-type CFTR co-activation during adrenergic receptor stimulation buffers the vasodilatory response to catecholamines, and loss of this compensatory vasoconstrictor tone may contribute to the lower arterial pressures seen in heterozygote carriers of a CFTR-F508del mutation.
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Affiliation(s)
- Veronica A. Peotta
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Prasad Bhandary
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Ugochi Ogu
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Kenneth A. Volk
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Robert D. Roghair
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States of America
- * E-mail:
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18
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Nerbonne JM. Mouse models of arrhythmogenic cardiovascular disease: challenges and opportunities. Curr Opin Pharmacol 2014; 15:107-14. [PMID: 24632325 DOI: 10.1016/j.coph.2014.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Revised: 02/04/2014] [Accepted: 02/05/2014] [Indexed: 12/27/2022]
Abstract
Arrhythmogenic cardiovascular disease is associated with significant morbidity and mortality and, in spite of therapeutic advances, remains an enormous public health burden. The scope of this problem motivates efforts to delineate the molecular, cellular and systemic mechanisms underlying increased arrhythmia risk in inherited and acquired cardiac and systemic disease. The mouse is used increasingly in these efforts owing to the ease with which genetic strategies can be exploited and mechanisms can be probed. The question then arises whether the mouse has proven to be a useful model system to delineate arrhythmogenic cardiovascular disease mechanisms. Rather than trying to provide a definite answer, the goal here is to consider the issues that arise when using mouse models and to highlight the opportunities.
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Affiliation(s)
- Jeanne M Nerbonne
- Department of Developmental Biology, Washington University Medical School, St. Louis, MO 63110, USA; Department of Internal Medicine, Washington University Medical School, St. Louis, MO 63110, USA.
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19
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Kranstuber AL, Del Rio C, Biesiadecki BJ, Hamlin RL, Ottobre J, Gyorke S, Lacombe VA. Advanced glycation end product cross-link breaker attenuates diabetes-induced cardiac dysfunction by improving sarcoplasmic reticulum calcium handling. Front Physiol 2012; 3:292. [PMID: 22934044 PMCID: PMC3429064 DOI: 10.3389/fphys.2012.00292] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 07/04/2012] [Indexed: 01/11/2023] Open
Abstract
Diabetic heart disease is a distinct clinical entity that can progress to heart failure and sudden death. However, the mechanisms responsible for the alterations in excitation-contraction coupling leading to cardiac dysfunction during diabetes are not well known. Hyperglycemia, the landmark of diabetes, leads to the formation of advanced glycation end products (AGEs) on long-lived proteins, including sarcoplasmic reticulum (SR) Ca2+ regulatory proteins. However, their pathogenic role on SR Ca2+ handling in cardiac myocytes is unknown. Therefore, we investigated whether an AGE cross-link breaker could prevent the alterations in SR Ca2+ cycling that lead to in vivo cardiac dysfunction during diabetes. Streptozotocin-induced diabetic rats were treated with alagebrium chloride (ALT-711) for 8 weeks and compared to age-matched placebo-treated diabetic rats and healthy rats. Cardiac function was assessed by echocardiographic examination. Ventricular myocytes were isolated to assess SR Ca2+ cycling by confocal imaging and quantitative Western blots. Diabetes resulted in in vivo cardiac dysfunction and ALT-711 therapy partially alleviated diastolic dysfunction by decreasing isovolumetric relaxation time and myocardial performance index (MPI) (by 27 and 41% vs. untreated diabetic rats, respectively, P < 0.05). In cardiac myocytes, diabetes-induced prolongation of cytosolic Ca2+ transient clearance by 43% and decreased SR Ca2+ load by 25% (P < 0.05); these parameters were partially improved after ALT-711 therapy. SERCA2a and RyR2 protein expression was significantly decreased in the myocardium of untreated diabetic rats (by 64 and 36% vs. controls, respectively, P < 0.05), but preserved in the treated diabetic group compared to controls. Collectively, our results suggest that, in a model of type 1 diabetes, AGE accumulation primarily impairs SR Ca2+ reuptake in cardiac myocytes and that long-term treatment with an AGE cross-link breaker partially normalized SR Ca2+ handling and improved diabetic cardiomyopathy.
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20
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Novak A, Barad L, Lorber A, Itskovitz-Eldor J, Binah O. Modeling Catecholaminergic Polymorphic Ventricular Tachycardia using Induced Pluripotent Stem Cell-derived Cardiomyocytes. Rambam Maimonides Med J 2012; 3:e0015. [PMID: 23908839 PMCID: PMC3678817 DOI: 10.5041/rmmj.10086] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic cardiac disorder characterized by life-threatening arrhythmias induced by physical or emotional stress, in the absence structural heart abnormalities. The arrhythmias may cause syncope or degenerate into cardiac arrest and sudden death which usually occurs during childhood. Recent studies have shown that CPVT is caused by mutations in the cardiac ryanodine receptor type 2 (RyR2) or calsequestrin 2 (CASQ2) genes. Both proteins are key contributors to the intracellular Ca(2+) handling process and play a pivotal role in Ca(2+) release from the sarcoplasmic reticulum to the cytosol during systole. Although the molecular pathogenesis of CPVT is not entirely clear, it was suggested that the CPVT mutations promote excessive sarcoplasmic reticulum Ca(2+) leak, which initiates delayed afterdepolarizations (DADs) and triggered arrhythmias in cardiac myocytes. The recent breakthrough discovery of induced pluripotent stem cells (iPSC) generated from somatic cells (e.g. fibroblasts, keratinocytes) now enables researches to investigate mutated cardiomyocytes generated from the patient's iPSC. To this end, in the present article we review recent studies on CPVT iPSC-derived cardiomyocytes, thus demonstrating in the mutated cells catecholamine-induced DADs and triggered arrhythmias.
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Affiliation(s)
- Atara Novak
- The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel
- The Rappaport Family Institute for Research in the Medical Sciences, Technion - Israel Institute of Technology, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Lili Barad
- The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel
- The Rappaport Family Institute for Research in the Medical Sciences, Technion - Israel Institute of Technology, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Avraham Lorber
- Ruth & Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
- Department of Pediatric Cardiology, Rambam Health Care Campus, Haifa, Israel; and
| | - Joseph Itskovitz-Eldor
- The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
- Department of Obstetrics and Gynecology, Rambam Health Care Campus, Haifa, Israel
| | - Ofer Binah
- The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel
- The Rappaport Family Institute for Research in the Medical Sciences, Technion - Israel Institute of Technology, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
- To whom correspondence should be addressed., E-mail:
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21
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Kochhäuser S, Schulze-Bahr E, Kirchhefer U. Arrhythmia-associated cardiac Ca2+ cycling proteins and gene mutations. Wien Med Wochenschr 2012; 162:292-6. [DOI: 10.1007/s10354-012-0114-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 04/17/2012] [Indexed: 11/30/2022]
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22
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Novak A, Barad L, Zeevi-Levin N, Shick R, Shtrichman R, Lorber A, Itskovitz-Eldor J, Binah O. Cardiomyocytes generated from CPVTD307H patients are arrhythmogenic in response to β-adrenergic stimulation. J Cell Mol Med 2012; 16:468-82. [PMID: 22050625 PMCID: PMC3822924 DOI: 10.1111/j.1582-4934.2011.01476.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sudden cardiac death caused by ventricular arrhythmias is a disastrous event, especially when it occurs in young individuals. Among the five major arrhythmogenic disorders occurring in the absence of a structural heart disease is catecholaminergic polymorphic ventricular tachycardia (CPVT), which is a highly lethal form of inherited arrhythmias. Our study focuses on the autosomal recessive form of the disease caused by the missense mutation D307H in the cardiac calsequestrin gene, CASQ2. Because CASQ2 is a key player in excitation contraction coupling, the derangements in intracellular Ca2+ handling may cause delayed afterdepolarizations (DADs), which constitute the mechanism underlying CPVT. To investigate catecholamine-induced arrhythmias in the CASQ2 mutated cells, we generated for the first time CPVT-derived induced pluripotent stem cells (iPSCs) by reprogramming fibroblasts from skin biopsies of two patients, and demonstrated that the iPSCs carry the CASQ2 mutation. Next, iPSCs were differentiated to cardiomyocytes (iPSCs-CMs), which expressed the mutant CASQ2 protein. The major findings were that the β-adrenergic agonist isoproterenol caused in CPVT iPSCs-CMs (but not in the control cardiomyocytes) DADs, oscillatory arrhythmic prepotentials, after-contractions and diastolic [Ca2+]i rise. Electron microscopy analysis revealed that compared with control iPSCs-CMs, CPVT iPSCs-CMs displayed a more immature phenotype with less organized myofibrils, enlarged sarcoplasmic reticulum cisternae and reduced number of caveolae. In summary, our results demonstrate that the patient-specific mutated cardiomyocytes can be used to study the electrophysiological mechanisms underlying CPVT.
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Affiliation(s)
- Atara Novak
- The Sohnis Family Stem Cells Center, Haifa, Israel
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23
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Abstract
Calsequestrin is the most abundant Ca-binding protein of the specialized endoplasmic reticulum found in muscle, the sarcoplasmic reticulum (SR). Calsequestrin binds Ca with high capacity and low affinity and importantly contributes to the mobilization of Ca during each contraction both in skeletal and cardiac muscle. Surprisingly, mutations in the gene encoding the cardiac isoform of calsequestrin (Casq2) have been associated with an inherited form of ventricular arrhythmia triggered by emotional or physical stress termed catecholaminergic polymorphic ventricular tachycardia (CPVT). Despite normal cardiac contractility and normal resting ECG, CPVT patients present with a high risk of sudden death at a young age. Here, we review recent new insights regarding the role of calsequestrin in genetic and acquired arrhythmia disorders. Mouse models of CPVT have shed light on the pathophysiological mechanism underlying CPVT. Casq2 is not only a Ca-storing protein as initially hypothesized, but it has a far more complex function in Ca handling and regulating SR Ca release channels. The functional importance of Casq2 interactions with other SR proteins and the importance of alterations in Casq2 trafficking are also being investigated. Reports of altered Casq2 trafficking in animal models of acquired heart diseases such as heart failure suggest that Casq2 may contribute to arrhythmia risk beyond genetic forms of Casq2 dysfunction.
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Affiliation(s)
- Michela Faggioni
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0575, USA
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24
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Multiscale modeling of calcium cycling in cardiac ventricular myocyte: macroscopic consequences of microscopic dyadic function. Biophys J 2011; 100:2904-12. [PMID: 21689523 DOI: 10.1016/j.bpj.2011.05.031] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/12/2011] [Accepted: 05/13/2011] [Indexed: 11/22/2022] Open
Abstract
In cardiac ventricular myocytes, calcium (Ca) release occurs at distinct structures (dyads) along t-tubules, where L-type Ca channels (LCCs) appose sarcoplasmic reticulum (SR) Ca release channels (RyR2s). We developed a model of the cardiac ventricular myocyte that simulates local stochastic Ca release processes. At the local Ca release level, the model reproduces Ca spark properties. At the whole-cell level, the model reproduces the action potential, Ca currents, and Ca transients. Changes in microscopic dyadic properties (e.g., during detubulation in heart failure) affect whole-cell behavior in complex ways, which we investigated by simulating changes in the dyadic volume and number of LCCs/RyR2s in the dyad, and effects of calsequestrin (CSQN) as a Ca buffer (CSQN buffer) or a luminal Ca sensor (CSQN regulator). We obtained the following results: 1), Increased dyadic volume and reduced LCCs/RyR2s decrease excitation-contraction coupling gain and cause asynchrony of SR Ca release, and interdyad coupling partially compensates for the reduced synchrony. 2), Impaired CSQN buffer depresses Ca transients without affecting the synchrony of SR Ca release. 3), When CSQN regulator function is impaired, interdyad coupling augments diastolic Ca release activity to form Ca waves and long-lasting Ca release events.
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25
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Kalyanasundaram A, Viatchenko-Karpinski S, Belevych AE, Lacombe VA, Hwang HS, Knollmann BC, Gyorke S, Periasamy M. Functional consequences of stably expressing a mutant calsequestrin (CASQ2D307H) in the CASQ2 null background. Am J Physiol Heart Circ Physiol 2011; 302:H253-61. [PMID: 21984545 DOI: 10.1152/ajpheart.00578.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of calsequestrin (CASQ2) in cardiac sarcoplasmic reticulum (SR) calcium (Ca(2+)) transport has gained significant attention since point mutations in CASQ2 were reported to cause ventricular arrhythmia. In the present study, we have critically evaluated the functional consequences of expressing the CASQ2(D307H) mutant protein in the CASQ2 null mouse. We recently reported that the mutant CASQ2(D307H) protein can be stably expressed in CASQ2 null hearts, and it targets appropriately to the junctional SR (Kalyanasundaram A, Bal NC, Franzini-Armstrong C, Knollmann BC, Periasamy M. J Biol Chem 285: 3076-3083, 2010). In this study, we found that introduction of CASQ2(D307H) protein in the CASQ2 null background partially restored triadin 1 levels, which were decreased in the CASQ2 null mice. Despite twofold expression (relative to wild-type CASQ2), the mutant protein failed to increase SR Ca(2+) load. We also found that the Ca(2+) transient decays slower in the CASQ2 null and CASQ2(D307H) cells. CASQ2(D307H) myocytes, when rhythmically paced and challenged with isoproterenol, exhibit spontaneous Ca(2+) waves similar to CASQ2 null myocytes; however, the stability of Ca(2+) cycling was increased in the CASQ2(D307H) myocytes. In the presence of isoproterenol, Ca(2+)-transient amplitude in CASQ2(D307H) myocytes was significantly decreased, possibly indicating an inherent defect in Ca(2+) buffering capacity and release from the mutant CASQ2 at high Ca(2+) concentrations. We also observed polymorphic ventricular tachycardia in the CASQ2(D307H) mice, although lesser than in the CASQ2 null mice. These data suggest that CASQ2(D307H) point mutation may affect Ca(2+) buffering capacity and Ca(2+) release. We propose that poor interaction between CASQ2(D307H) and triadin 1 could affect ryanodine receptor 2 stability, thereby increasing susceptibility to delayed afterdepolarizations and triggered arrhythmic activity.
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Affiliation(s)
- Anuradha Kalyanasundaram
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, USA
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26
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Abstract
CASQ (calsequestrin) is a Ca2+-buffering protein localized in the muscle SR (sarcoplasmic reticulum); however, it is unknown whether Ca2+ binding to CASQ2 is due to its location inside the SR rich in Ca2+ or due to its preference for Ca2+ over other ions. Therefore a major aim of the present study was to determine how CASQ2 selects Ca2+ over other metal ions by studying monomer folding and subsequent aggregation upon exposure to alkali (monovalent), alkaline earth (divalent) and transition (polyvalent) metals. We additionally investigated how CPVT (catecholaminergic polymorphic ventricular tachycardia) mutations affect CASQ2 structure and its molecular behaviour when exposed to different metal ions. Our results show that alkali and alkaline earth metals can initiate similar molecular compaction (folding), but only Ca2+ can promote CASQ2 to aggregate, suggesting that CASQ2 has a preferential binding to Ca2+ over all other metals. We additionally found that transition metals (having higher co-ordinated bonding ability than Ca2+) can also initiate folding and promote aggregation of CASQ2. These studies led us to suggest that folding and formation of higher-order structures depends on cationic properties such as co-ordinate bonding ability and ionic radius. Among the CPVT mutants studied, the L167H mutation disrupts the Ca2+-dependent folding and, when folding is achieved by Mn2+, L167H can undergo aggregation in a Ca2+-dependent manner. Interestingly, domain III mutants (D307H and P308L) lost their selectivity to Ca2+ and could be aggregated in the presence of Mg2+. In conclusion, these studies suggest that CPVT mutations modify CASQ2 behaviour, including folding, aggregation/polymerization and selectivity towards Ca2+.
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27
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Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease occurring in patients with a structurally normal heart: the disease is characterized by life-threatening arrhythmias elicited by stress and emotion. In 2001, the ryanodine receptor was identified as the gene that is linked to CPVT; shortly thereafter, cardiac calsequestrin was implicated in the recessive form of the same disease. It became clear that abnormalities in intracellular Ca(2+) regulation could profoundly disrupt the electrophysiological properties of the heart. In this article, we discuss the molecular basis of the disease and the pathophysiological mechanisms that are impacting clinical diagnosis and management of affected individuals. As of today, the interaction between basic scientists and clinicians to understand CPVT and identify new therapeutic strategies is one of the most compelling examples of the importance of translational research in cardiology.
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Affiliation(s)
- Silvia G Priori
- Molecular Cardiology Laboratories, IRCCS Fondazione Salvatore Maugeri, Via Maugeri 10/10A, Pavia, Italy.
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28
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Unraveling the secrets of a double life: contractile versus signaling Ca2+ in a cardiac myocyte. J Mol Cell Cardiol 2011; 52:317-22. [PMID: 21600216 DOI: 10.1016/j.yjmcc.2011.05.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 04/27/2011] [Accepted: 05/03/2011] [Indexed: 11/21/2022]
Abstract
No other inorganic molecule known in biology is considered as versatile as Ca(2+). In a vast majority of cell types, Ca(2+) acts as a universal second messenger underlying critical cellular processes varying from gene transcription to cell death. Although the role of Ca(2+) in myocyte contraction has been known for over a century, it was only more recently that this divalent cation has been implicated in mediating reactive signal transduction to promote cardiac hypertrophy. However, it remains unclear how Ca(2+)-dependent signaling pathways are regulated/activated in a cardiac myocyte given the prevailing conditions throughout the cytosol where Ca(2+) concentration oscillates between 100 nM and upwards of 1-2 μM during each contractile cycle. In this review we will examine three hypotheses put forward to explain how Ca(2+) might still function as a hypertrophic signaling molecule in cardiac myocytes and discuss the current literature that supports each of these views. This article is part of a special issue entitled "Local Signaling in Myocytes."
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29
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MacLennan DH, Zvaritch E. Mechanistic models for muscle diseases and disorders originating in the sarcoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:948-64. [DOI: 10.1016/j.bbamcr.2010.11.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 11/11/2010] [Accepted: 11/18/2010] [Indexed: 11/29/2022]
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30
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Song DW, Lee JG, Youn HS, Eom SH, Kim DH. Ryanodine receptor assembly: A novel systems biology approach to 3D mapping. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 105:145-61. [DOI: 10.1016/j.pbiomolbio.2010.09.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Revised: 09/14/2010] [Accepted: 09/28/2010] [Indexed: 10/19/2022]
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31
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Kirchhefer U, Wehrmeister D, Postma AV, Pohlentz G, Mormann M, Kucerova D, Müller FU, Schmitz W, Schulze-Bahr E, Wilde AA, Neumann J. The human CASQ2 mutation K206N is associated with hyperglycosylation and altered cellular calcium handling. J Mol Cell Cardiol 2010; 49:95-105. [DOI: 10.1016/j.yjmcc.2010.03.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 03/04/2010] [Accepted: 03/08/2010] [Indexed: 10/19/2022]
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32
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Hanninen SL, Ronkainen JJ, Leskinen H, Tavi P. Mitochondrial uncoupling downregulates calsequestrin expression and reduces SR Ca2+ stores in cardiomyocytes. Cardiovasc Res 2010; 88:75-82. [DOI: 10.1093/cvr/cvq180] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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33
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Kalyanasundaram A, Bal NC, Franzini-Armstrong C, Knollmann BC, Periasamy M. The calsequestrin mutation CASQ2D307H does not affect protein stability and targeting to the junctional sarcoplasmic reticulum but compromises its dynamic regulation of calcium buffering. J Biol Chem 2009; 285:3076-83. [PMID: 19920148 DOI: 10.1074/jbc.m109.053892] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in cardiac ryanodine receptor (RYR2) and cardiac calsequestrin (CASQ2) genes are linked to catecholaminergic polymorphic ventricular tachycardia, a life-threatening genetic disease. They predispose young individuals to cardiac arrhythmia in the absence of structural abnormalities. One such mutation that changes an aspartic residue to histidine at position 307 in CASQ2 has been linked to catecholaminergic polymorphic ventricular tachycardia. In this study we made a transgenic mouse model expressing the mutant CASQ2(D307H) protein in a CASQ2 null background and investigated if the disease is caused by accelerated degradation of the mutant protein. Our data suggest that the mutant protein can be expressed, is relatively stable, and targets appropriately to the junctional sarcoplasmic reticulum. Moreover, it partially normalizes the ultrastructure of the sarcoplasmic reticulum, which was altered in the CASQ2 null background. In addition, overexpression of the mutant protein does not cause any pathology and/or structural changes in the myocardium. We further demonstrate, using purified protein, that the mutant protein is very stable under chemical and thermal denaturation but shows abnormal Ca(2+) buffering characteristics at high calcium concentrations. In addition, trypsin digestion studies reveal that the mutant protein is more susceptible to protease activity only in the presence of high Ca(2+). These studies collectively suggest that the D307H mutation can compromise the dynamic behavior of CASQ2 including supramolecular rearrangement upon Ca(2+) activation.
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Affiliation(s)
- Anuradha Kalyanasundaram
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
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34
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Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited disease characterized by physical or emotional stress-induced ventricular arrhythmias in the absence of any structural heart disease or QT prolongation. Thus far, mutations in genes encoding the sarcoplasmic reticulum Ca(2+) release channel (RYR2) and the sarcoplasmic reticulum Ca(2+) binding protein cardiac calsequestrin (CASQ2) have been identified in CPVT patients. Here, we review the role of cardiac calsequestrin in health and disease, with a particular focus on how calsequestrin deficiency can cause arrhythmia susceptibility. Clinical implications and a promising new drug therapy for CPVT are discussed.
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Affiliation(s)
- Nagesh Chopra
- Department of Medicine, Division of Cardiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0575, USA
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35
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Beard NA, Wei L, Dulhunty AF. Ca(2+) signaling in striated muscle: the elusive roles of triadin, junctin, and calsequestrin. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:27-36. [PMID: 19434403 DOI: 10.1007/s00249-009-0449-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Revised: 03/22/2009] [Accepted: 03/27/2009] [Indexed: 10/20/2022]
Abstract
This review focuses on molecular interactions between calsequestrin, triadin, junctin and the ryanodine receptor in the lumen of the sarcoplasmic reticulum. These interactions modulate changes in Ca(2+) release in response to changes in the Ca(2+) load within the sarcoplasmic reticulum store in striated muscle and are of fundamental importance to Ca(2+) homeostasis, since massive adaptive changes occur when expression of the proteins is manipulated, while mutations in calsequestrin lead to functional changes which can be fatal. We find that calsequestrin plays a different role in the heart and skeletal muscle, enhancing Ca(2+) release in the heart, but depressing Ca(2+) release in skeletal muscle. We also find that triadin and junctin exert independent influences on the ryanodine receptor in skeletal muscle where triadin alone modifies excitation-contraction coupling, while junctin alone supports functional interactions between calsequestrin and the ryanodine receptor.
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Affiliation(s)
- Nicole A Beard
- Muscle Research Group, John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra, ACT, 2601, Australia
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36
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Wei L, Hanna AD, Beard NA, Dulhunty AF. Unique isoform-specific properties of calsequestrin in the heart and skeletal muscle. Cell Calcium 2009; 45:474-84. [PMID: 19376574 DOI: 10.1016/j.ceca.2009.03.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 02/02/2009] [Accepted: 03/15/2009] [Indexed: 10/20/2022]
Abstract
Calcium signaling in myocytes is dependent on the cardiac ryanodine receptor (RyR2) calcium release channel and the calcium buffering protein in the sarcoplasmic reticulum, cardiac calsequestrin (CSQ2). The overall properties of CSQ2 and its regulation of RyR2 have not been explored in detail or directly compared with skeletal CSQ1 and its regulation of the skeletal RyR1, with physiological ionic strength and Ca(2+) concentrations. We find that there are major differences between the two isoforms under these physiological conditions. Ca(2+) binding to CSQ2 is 50% lower than to CSQ1. Only approximately 30% of CSQ2 is bound to cardiac junctional face membrane (JFM), compared with approximately 70% of CSQ1 and the ratio of CSQ2 to RyR2 is only 50% of the CSQ1/RyR1 ratio. Chemical crosslinking shows that CSQ2 is mostly monomer/dimer, while CSQ1 is mostly polymerized. In single channel lipid bilayer experiments, CSQ2 monomers and/or dimers increase the open probability of both RyR1 and RyR2 channels, while CSQ1 polymers decrease the activity of RyR1. We speculate that CSQ2 facilitates high rates of Ca(2+) release through RyR2 during systole, while CSQ1 curtails RyR1 opening in response to a single action potential to maintain Ca(2+) and allow repeated Ca(2+) release and graded activation with increased stimulation frequency.
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Affiliation(s)
- Lan Wei
- John Curtin School of Medical Research, Australian Capital Territory, Australia
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37
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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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38
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Katz G, Arad M, Eldar M. Catecholaminergic polymorphic ventricular tachycardia from bedside to bench and beyond. Curr Probl Cardiol 2009; 34:9-43. [PMID: 19068246 DOI: 10.1016/j.cpcardiol.2008.09.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a primary electrical myocardial disease characterized by exercise- and stress-related ventricular tachycardia manifested as syncope and sudden death. The disease has a heterogeneous genetic basis, with mutations in the cardiac Ryanodine Receptor channel (RyR2) gene accounting for an autosomal-dominant form (CPVT1) in approximately 50% and mutations in the cardiac calsequestrin gene (CASQ2) accounting for an autosomal-recessive form (CPVT2) in up to 2% of CPVT cases. Both RyR2 and calsequestrin are important participants in the cardiac cellular calcium homeostasis. We review the physiology of the cardiac calcium homeostasis, including the cardiac excitation contraction coupling and myocyte calcium cycling. The pathophysiology of cardiac arrhythmias related to myocyte calcium handling and the effects of different modulators are discussed. The putative derangements in myocyte calcium homeostasis responsible for CPVT, as well as the clinical manifestations and therapeutic options available, are described.
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39
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Abstract
The calcium ion (Ca(2+)) is the simplest and most versatile intracellular messenger known. The discovery of Ca(2+) sparks and a related family of elementary Ca(2+) signaling events has revealed fundamental principles of the Ca(2+) signaling system. A newly appreciated "digital" subsystem consisting of brief, high Ca(2+) concentration over short distances (nanometers to microns) comingles with an "analog" global Ca(2+) signaling subsystem. Over the past 15 years, much has been learned about the theoretical and practical aspects of spark formation and detection. The quest for the spark mechanisms [the activation, coordination, and termination of Ca(2+) release units (CRUs)] has met unexpected challenges, however, and raised vexing questions about CRU operation in situ. Ample evidence shows that Ca(2+) sparks catalyze many high-threshold Ca(2+) processes involved in cardiac and skeletal muscle excitation-contraction coupling, vascular tone regulation, membrane excitability, and neuronal secretion. Investigation of Ca(2+) sparks in diseases has also begun to provide novel insights into hypertension, cardiac arrhythmias, heart failure, and muscular dystrophy. An emerging view is that spatially and temporally patterned activation of the digital subsystem confers on intracellular Ca(2+) signaling an exquisite architecture in space, time, and intensity, which underpins signaling efficiency, stability, specificity, and diversity. These recent advances in "sparkology" thus promise to unify the simplicity and complexity of Ca(2+) signaling in biology.
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Affiliation(s)
- Heping Cheng
- Institute of Molecular Medicine, National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, China.
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40
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Liu N, Rizzi N, Boveri L, Priori SG. Ryanodine receptor and calsequestrin in arrhythmogenesis: what we have learnt from genetic diseases and transgenic mice. J Mol Cell Cardiol 2008; 46:149-59. [PMID: 19027025 DOI: 10.1016/j.yjmcc.2008.10.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 09/22/2008] [Accepted: 10/17/2008] [Indexed: 11/30/2022]
Abstract
The year 2001 has been pivotal for the identification of the molecular bases of catecholaminergic polymorphic ventricular tachycardia (CPVT): a life-threatening genetic disease that predisposes young individuals with normal cardiac structure to cardiac arrest. Interestingly CPVT has been linked to mutations in genes encoding the cardiac ryanodine receptor (RyR2) and cardiac calsequestrin (CASQ2): two fundamental proteins involved in regulation of intracellular Ca(2+) in cardiac myocytes. The critical role of the two proteins in the heart has attracted interests of the scientific community so that networks of investigators have embarked in translational studies to characterize in vitro and in vivo the mutant proteins. Overall in the last seven years the field has substantially advanced but considerable controversies still exist on the consequences of RyR2 and CASQ2 mutations and on the modalities by which they precipitate cardiac arrhythmias. With so many questions that need to be elucidated it is expected that in the near future the field will remain innovative and stimulating. In this review we will outline how research has advanced in the understanding of CPVT and we will present how the observations made have disclosed novel arrhythmogenic cascades that are likely to impact acquired heart diseases.
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Affiliation(s)
- Nian Liu
- Molecular Cardiology, Fondazione Salvatore Maugeri, Pavia, Italy
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41
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Györke S. Molecular basis of catecholaminergic polymorphic ventricular tachycardia. Heart Rhythm 2008; 6:123-9. [PMID: 19121813 DOI: 10.1016/j.hrthm.2008.09.013] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 09/11/2008] [Indexed: 11/27/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant arrhythmia syndrome linked to mutations in the cardiac ryanodine receptor (RyR2) and calsequestrin (CASQ2). RyR2 and CASQ2 are parts of the multimolecular Ca(2+) release channel complex that is present on the sarcoplasmic reticulum (SR) to support myocyte Ca(2+) cycling and contractile activity. Whereas RyR2 operates as a Ca(2+) release channel, the SR Ca(2+) binding protein CASQ2 plays a dual role by serving as a SR Ca(2+) buffer and by regulating RyR2 function. Essential to stable Ca(2+) cycling, SR luminal Ca(2+)-dependent control of RyR2 activity by CASQ2 contributes to RyR2 deactivation and to the development of a temporary refractory state that occurs after each Ca(2+) release. Accumulating evidence suggests that the CPVT mutations act by reducing the extent and shortening the duration of Ca(2+) signaling refractoriness, thereby promoting untimely SR Ca(2+) release and arrhythmogenic delayed afterdepolarizations in cardiac myocytes. Similar mechanisms may apply to arrhythmias during various conditions, including heart failure and ischemic heart disease, associated with acquired defects in components of the Ca(2+) release channel complex.
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Affiliation(s)
- Sandor Györke
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio 43210, USA.
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42
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Weisleder N, Ma J. Altered Ca2+ sparks in aging skeletal and cardiac muscle. Ageing Res Rev 2008; 7:177-88. [PMID: 18272434 DOI: 10.1016/j.arr.2007.12.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 12/17/2007] [Accepted: 12/18/2007] [Indexed: 11/26/2022]
Abstract
Ca2+ sparks are the fundamental units that comprise Ca2+-induced Ca2+ release (CICR) in striated muscle cells. In cardiac muscle, spontaneous Ca2+ sparks underlie the rhythmic CICR activity during heart contraction. In skeletal muscle, Ca2+ sparks remain quiescent during the resting state and are activated in a plastic fashion to accommodate various levels of stress. With aging, the plastic Ca2+ spark signal becomes static in skeletal muscle, whereas loss of CICR control leads to leaky Ca2+ spark activity in aged cardiomyocytes. Ca2+ spark responses reflect the integrated function of the intracellular Ca2+ regulatory machinery centered around the triad or dyad junctional complexes of striated muscles, which harbor the principal molecular players of excitation-contraction coupling. This review highlights the contribution of age-related modification of the Ca2+ release machinery and the effect of membrane structure and membrane cross-talk on the altered Ca2+ spark signaling during aging of striated muscles.
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Abstract
Ventricular arrhythmias deteriorating into sudden cardiac death are a major cause of mortality worldwide. The recent linkage of a genetic form of cardiac arrhythmia to mutations in the gene encoding RyR2 (ryanodine receptor 2) has uncovered an important role of this SR (sarcoplasmic reticulum) calcium release channel in triggering arrhythmias. Mutant RyR2 channels give rise to spontaneous release of calcium (Ca(2+)) from the SR during diastole, which enhances the probability of ventricular arrhythmias. Several molecular mechanisms have been proposed to explain the gain-of-function phenotype observed in mutant RyR2 channels. Despite considerable differences between the models discussed in the present review, each predicts spontaneous diastolic Ca(2+) leak from the SR due to incomplete closure of the RyR2 channel. Enhanced SR Ca(2+) leak is also observed in common structural diseases of the heart, such as heart failure. In heart failure, defective channel regulation in the absence of inherited mutations may also increase SR Ca(2+) leak and initiate cardiac arrhythmias. Therefore inhibition of diastolic Ca(2+) leak through SR Ca(2+) release channels has emerged as a new and promising therapeutic target for cardiac arrhythmias.
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Yan Y, Liu J, Wei C, Li K, Xie W, Wang Y, Cheng H. Bidirectional regulation of Ca2+ sparks by mitochondria-derived reactive oxygen species in cardiac myocytes. Cardiovasc Res 2007; 77:432-41. [DOI: 10.1093/cvr/cvm047] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kirchhefer U, Klimas J, Baba HA, Buchwalow IB, Fabritz L, Hüls M, Matus M, Müller FU, Schmitz W, Neumann J. Triadin is a critical determinant of cellular Ca cycling and contractility in the heart. Am J Physiol Heart Circ Physiol 2007; 293:H3165-74. [PMID: 17890426 DOI: 10.1152/ajpheart.00799.2007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Triadin is involved in the regulation of cardiac excitation-contraction coupling. However, the extent of its contribution to the regulation of sarcoplasmic reticulum (SR) Ca release remains unclear, because overexpression of triadin in single-transgenic mice was associated with the downregulation of its homologous protein, junctin. In the present study, this problem was circumvented by cross-breeding of mice with heart-directed overexpression of triadin and junctin (JxT). This resulted in a stable approximately threefold expression of total triadin but unchanged junctin protein. Transgenic mice exhibited cardiac hypertrophy and structural abnormalities of myofibrils. Measurement of cardiac function by echocardiography and edge detection in myocytes revealed an impaired relaxation in JxT mice. The stimulation of beta-adrenergic receptors resulted in a depressed contractility and an impaired relaxation in catheterized hearts and myocytes of JxT mice. The use of a maximum stimulation frequency (5 Hz) was associated with both a lower shortening and relengthening in isolated myocytes of JxT mice. The contractile effects in JxT myocytes were paralleled by similar changes of the intracellular Ca concentration ([Ca](i)) peak amplitude and Ca transient decay kinetics at basal conditions, under administration of isoproterenol, and with high-frequency stimulation. Finally, we found a higher caffeine-induced [Ca](i) peak amplitude in JxT myocytes. Our data show that the stable expression of triadin, independent of junctin expression, resulted in cardiac hypertrophy, prolonged basal relaxation, a depressed response to beta-adrenergic agonists, and altered Ca transients. Thus the maintenance of triadin expression is essential for normal SR Ca cycling and contractile function.
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Affiliation(s)
- Uwe Kirchhefer
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Münster, Münster, Germany.
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Györke S, Hagen BM, Terentyev D, Lederer WJ. Chain-reaction Ca(2+) signaling in the heart. J Clin Invest 2007; 117:1758-62. [PMID: 17607353 PMCID: PMC1904329 DOI: 10.1172/jci32496] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Mutations in Ca(2+) -handling proteins in the heart have been linked to exercise-induced sudden cardiac death. The best characterized of these have been mutations in the cardiac Ca(2+) release channel known as the ryanodine receptor type 2 (RyR2). RyR2 mutations cause "leaky" channels, resulting in diastolic Ca(2+) leak from the sarcoplasmic reticulum (SR) that can trigger fatal cardiac arrhythmias during stress. In this issue of the JCI, Song et al. show that mutations in the SR Ca(2+)-binding protein calsequestrin 2 (CASQ2) in mice result not only in reduced CASQ2 expression but also in a surprising, compensatory elevation in expression of both the Ca(2+)-binding protein calreticulin and RyR2, culminating in premature Ca(2+) release from cardiac myocytes and stress-induced arrhythmia (see the related article beginning on page 1814). In the context of these findings and other recent reports studying CASQ2 mutations, we discuss how CASQ2 influences the properties of Ca(2+)-dependent regulation of RyR2 and how this contributes to cardiac arrhythmogenesis.
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Affiliation(s)
- Sandor Györke
- Department of Physiology and Cell Biology and OSU Dorothy M Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH, USA
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