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Attachaipanich T, Chattipakorn SC, Chattipakorn N. Cardiovascular toxicities by calcineurin inhibitors: Cellular mechanisms behind clinical manifestations. Acta Physiol (Oxf) 2024; 240:e14199. [PMID: 38984711 DOI: 10.1111/apha.14199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 06/19/2024] [Accepted: 06/25/2024] [Indexed: 07/11/2024]
Abstract
Calcineurin inhibitors (CNI), including cyclosporine A (CsA) and tacrolimus (TAC), are cornerstones of immunosuppressive therapy in solid organ transplant recipients. While extensively recognized for their capacity to induce nephrotoxicity, hypertension, and dyslipidemia, emerging reports suggest potential direct cardiovascular toxicities associated with CNI. Evidence from both in vitro and in vivo studies has demonstrated direct cardiotoxic impact of CNI, manifesting itself as induction of cardiomyocyte apoptosis, enhanced oxidative stress, inflammatory cell infiltration, and cardiac fibrosis. CNI enhances cellular apoptosis through CaSR via activation of the p38 MAPK pathway and deactivation of the ERK pathway, and enhancement of miR-377 axis. Although CNI could attenuate cardiac hypertrophy in certain animal models, CNI concurrently impaired systolic function, enhanced cardiac fibrosis, and increased the risk of heart failure. Evidence from in vivo studies demonstrated that CNI prolong the duration of action potentials through a decrease in potassium current. CNI also exerted direct effects on endothelial cell injury, inducing apoptosis and enhancing oxidative stress. CNI may induce vascular inflammation through TLR4 via MyD88 and TRIF pathways. In addition, CNI affects vascular function by impairing endothelial-dependent vasodilation and promoting vasoconstriction. Clinical studies in transplant patients also revealed an increased incidence of cardiac remodeling. However, the evidence is constrained by the limited number of participants and potential confounding factors. Several studies indicate differing cardiovascular toxicity profiles between CsA and TAC, and these could be potentially due to their different interactions with calcineurin subunits and calcineurin-independent effects. Further studies are needed to clarify these mechanisms to improve cardiovascular outcomes for transplant patients with CNI.
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Affiliation(s)
- Tanawat Attachaipanich
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Siriporn C Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
| | - Nipon Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, Thailand
- Cardiac Electrophysiology Research Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
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2
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Terrar DA. Timing mechanisms to control heart rhythm and initiate arrhythmias: roles for intracellular organelles, signalling pathways and subsarcolemmal Ca 2. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220170. [PMID: 37122228 PMCID: PMC10150226 DOI: 10.1098/rstb.2022.0170] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Rhythms of electrical activity in all regions of the heart can be influenced by a variety of intracellular membrane bound organelles. This is true both for normal pacemaker activity and for abnormal rhythms including those caused by early and delayed afterdepolarizations under pathological conditions. The influence of the sarcoplasmic reticulum (SR) on cardiac electrical activity is widely recognized, but other intracellular organelles including lysosomes and mitochondria also contribute. Intracellular organelles can provide a timing mechanism (such as an SR clock driven by cyclic uptake and release of Ca2+, with an important influence of intraluminal Ca2+), and/or can act as a Ca2+ store involved in signalling mechanisms. Ca2+ plays many diverse roles including carrying electric current, driving electrogenic sodium-calcium exchange (NCX) particularly when Ca2+ is extruded across the surface membrane causing depolarization, and activation of enzymes which target organelles and surface membrane proteins. Heart function is also influenced by Ca2+ mobilizing agents (cADP-ribose, nicotinic acid adenine dinucleotide phosphate and inositol trisphosphate) acting on intracellular organelles. Lysosomal Ca2+ release exerts its effects via calcium/calmodulin-dependent protein kinase II to promote SR Ca2+ uptake, and contributes to arrhythmias resulting from excessive beta-adrenoceptor stimulation. A separate arrhythmogenic mechanism involves lysosomes, mitochondria and SR. Interacting intracellular organelles, therefore, have profound effects on heart rhythms and NCX plays a central role. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Derek A Terrar
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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3
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Abstract
This Review provides an update on ryanodine receptors (RyRs) and their role in human diseases of heart, muscle, and brain. Calcium (Ca2+) is a requisite second messenger in all living organisms. From C. elegans to mammals, Ca2+ is necessary for locomotion, bodily functions, and neural activity. However, too much of a good thing can be bad. Intracellular Ca2+ overload can result in loss of function and death. Intracellular Ca2+ release channels evolved to safely provide large, rapid Ca2+ signals without exposure to toxic extracellular Ca2+. RyRs are intracellular Ca2+ release channels present throughout the zoosphere. Over the past 35 years, our knowledge of RyRs has advanced to the level of atomic-resolution structures revealing their role in the mechanisms underlying the pathogenesis of human disorders of heart, muscle, and brain. Stress-induced RyR-mediated intracellular Ca2+ leak in the heart can promote heart failure and cardiac arrhythmias. In skeletal muscle, RyR1 leak contributes to muscle weakness in inherited myopathies, to age-related loss of muscle function and cancer-associated muscle weakness, and to impaired muscle function in muscular dystrophies, including Duchenne. In the brain, leaky RyR channels contribute to cognitive dysfunction in Alzheimer's disease, posttraumatic stress disorder, and Huntington's disease. Novel therapeutics targeting dysfunctional RyRs are showing promise.
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4
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Elezaby A, Dexheimer R, Sallam K. Cardiovascular effects of immunosuppression agents. Front Cardiovasc Med 2022; 9:981838. [PMID: 36211586 PMCID: PMC9534182 DOI: 10.3389/fcvm.2022.981838] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/30/2022] [Indexed: 11/26/2022] Open
Abstract
Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.
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Affiliation(s)
- Aly Elezaby
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, United States
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, CA, United States
| | - Ryan Dexheimer
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, United States
| | - Karim Sallam
- Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA, United States
- Division of Cardiovascular Medicine, Department of Medicine, Stanford University, Stanford, CA, United States
- *Correspondence: Karim Sallam
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5
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Dridi H, Kushnir A, Zalk R, Yuan Q, Melville Z, Marks AR. Intracellular calcium leak in heart failure and atrial fibrillation: a unifying mechanism and therapeutic target. Nat Rev Cardiol 2020; 17:732-747. [PMID: 32555383 PMCID: PMC8362847 DOI: 10.1038/s41569-020-0394-8] [Citation(s) in RCA: 107] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/06/2020] [Indexed: 12/14/2022]
Abstract
Ca2+ is a fundamental second messenger in all cell types and is required for numerous essential cellular functions, including cardiac and skeletal muscle contraction. The intracellular concentration of free Ca2+ ([Ca2+]) is regulated primarily by ion channels, pumps (ATPases), exchangers and Ca2+-binding proteins. Defective regulation of [Ca2+] is found in a diverse spectrum of pathological states that affect all the major organs. In the heart, abnormalities in the regulation of cytosolic and mitochondrial [Ca2+] occur in heart failure (HF) and atrial fibrillation (AF), two common forms of heart disease and leading contributors to morbidity and mortality. In this Review, we focus on the mechanisms that regulate ryanodine receptor 2 (RYR2), the major sarcoplasmic reticulum (SR) Ca2+-release channel in the heart, how RYR2 becomes dysfunctional in HF and AF, and its potential as a therapeutic target. Inherited RYR2 mutations and/or stress-induced phosphorylation and oxidation of the protein destabilize the closed state of the channel, resulting in a pathological diastolic Ca2+ leak from the SR that both triggers arrhythmias and impairs contractility. On the basis of our increased understanding of SR Ca2+ leak as a shared Ca2+-dependent pathological mechanism in HF and AF, a new class of drugs developed in our laboratory, known as rycals, which stabilize RYR2 channels and prevent Ca2+ leak from the SR, are undergoing investigation in clinical trials.
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Affiliation(s)
- Haikel Dridi
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Alexander Kushnir
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Ran Zalk
- The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Qi Yuan
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Zephan Melville
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Andrew R Marks
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA.
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6
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Yuan M, Meng XW, Ma J, Liu H, Song SY, Chen QC, Liu HY, Zhang J, Song N, Ji FH, Peng K. Dexmedetomidine protects H9c2 cardiomyocytes against oxygen-glucose deprivation/reoxygenation-induced intracellular calcium overload and apoptosis through regulating FKBP12.6/RyR2 signaling. DRUG DESIGN DEVELOPMENT AND THERAPY 2019; 13:3137-3149. [PMID: 31564830 PMCID: PMC6730549 DOI: 10.2147/dddt.s219533] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 08/23/2019] [Indexed: 12/30/2022]
Abstract
Purpose Intracellular calcium ([Ca2+]i) overload is a major cause of cell injury during myocardial ischemia/reperfusion (I/R). Dexmedetomidine (DEX) has been shown to exert anti-inflammatory and organ protective effects. This study aimed to investigate whether pretreatment with DEX could protect H9c2 cardiomyocytes against oxygen-glucose deprivation/reoxygenation (OGD/R) injury through regulating the Ca2+ signaling. Methods H9c2 cardiomyocytes were subjected to OGD for 12 h, followed by 3 h of reoxygenation. DEX was administered 1 h prior to OGD/R. Cell viability, lactate dehydrogenase (LDH) release, level of [Ca2+]i, cell apoptosis, and the expression of 12.6-kd FK506-binding protein/ryanodine receptor 2 (FKBP12.6/RyR2) and caspase-3 were assessed. Results Cells exposed to OGD/R had decreased cell viability, increased LDH release, elevated [Ca2+]i level and apoptosis rate, down-regulated expression of FKBP12.6, and up-regulated expression of phosphorylated-Ser2814-RyR2 and cleaved caspase-3. Pretreatment with DEX significantly blocked the above-mentioned changes, alleviating the OGD/R-induced injury in H9c2 cells. Moreover, knockdown of FKBP12.6 by small interfering RNA abolished the protective effects of DEX. Conclusion This study indicates that DEX pretreatment protects the cardiomyocytes against OGD/R-induced injury by inhibiting [Ca2+]i overload and cell apoptosis via regulating the FKBP12.6/RyR2 signaling. DEX may be used for preventing cardiac I/R injury in the clinical settings.
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Affiliation(s)
- Mei Yuan
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China.,Department of Anesthesiology, Affiliated Suzhou Hospital of Nanjing Medical University, Suzhou, Jiangsu 215008, People's Republic of China
| | - Xiao-Wen Meng
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Jiao Ma
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Hong Liu
- Department of Anesthesiology and Pain Medicine, University of California Davis Health System, Sacramento, CA 95817, USA
| | - Shao-Yong Song
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Qing-Cai Chen
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Hua-Yue Liu
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Juan Zhang
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Nan Song
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Fu-Hai Ji
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
| | - Ke Peng
- Department of Anesthesiology, First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, People's Republic of China
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7
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Pan Z, Ai T, Chang PC, Liu Y, Liu J, Maruyama M, Homsi M, Fishbein MC, Rubart M, Lin SF, Xiao D, Chen H, Chen PS, Shou W, Li BY. Atrial fibrillation and electrophysiology in transgenic mice with cardiac-restricted overexpression of FKBP12. Am J Physiol Heart Circ Physiol 2019; 316:H371-H379. [PMID: 30499712 PMCID: PMC6397388 DOI: 10.1152/ajpheart.00486.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 11/19/2018] [Accepted: 11/19/2018] [Indexed: 12/19/2022]
Abstract
Cardiomyocyte-restricted overexpression of FK506-binding protein 12 transgenic (αMyHC-FKBP12) mice develop spontaneous atrial fibrillation (AF). The aim of the present study is to explore the mechanisms underlying the occurrence of AF in αMyHC-FKBP12 mice. Spontaneous AF was documented by telemetry in vivo and Langendorff-perfused hearts of αMyHC-FKBP12 and littermate control mice in vitro. Atrial conduction velocity was evaluated by optical mapping. The patch-clamp technique was applied to determine the potentially altered electrophysiology in atrial myocytes. Channel protein expression levels were evaluated by Western blot analyses. Spontaneous AF was recorded in four of seven αMyHC-FKBP12 mice but in none of eight nontransgenic (NTG) controls. Atrial conduction velocity was significantly reduced in αMyHC-FKBP12 hearts compared with NTG hearts. Interestingly, the mean action potential duration at 50% but not 90% was significantly prolonged in αMyHC-FKBP12 atrial myocytes compared with their NTG counterparts. Consistent with decreased conduction velocity, average peak Na+ current ( INa) density was dramatically reduced and the INa inactivation curve was shifted by approximately +7 mV in αMyHC-FKBP12 atrial myocytes, whereas the activation and recovery curves were unaltered. The Nav1.5 expression level was significantly reduced in αMyHC-FKBP12 atria. Furthermore, we found increases in atrial Cav1.2 protein levels and peak L-type Ca2+ current density and increased levels of fibrosis in αMyHC-FKBP12 atria. In summary, cardiomyocyte-restricted overexpression of FKBP12 reduces the atrial Nav1.5 expression level and mean peak INa, which is associated with increased peak L-type Ca2+ current and interstitial fibrosis in atria. The combined electrophysiological and structural changes facilitated the development of local conduction block and altered action potential duration and spontaneous AF. NEW & NOTEWORTHY This study addresses a long-standing riddle regarding the role of FK506-binding protein 12 in cardiac physiology. The work provides further evidence that FK506-binding protein 12 is a critical component for regulating voltage-gated sodium current and in so doing has an important role in arrhythmogenic physiology, such as atrial fibrillation.
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Affiliation(s)
- Zhenwei Pan
- Department of Pharmacology, Harbin Medical University, Heilonjiang, China
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Tomohiko Ai
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Po-Cheng Chang
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
- The Second Section of Cardiology, Departments of Medicine, Chang Gung Memorial Hospital and Chang Gung University School of Medicine , Taoyuan , Taiwan
| | - Ying Liu
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
| | - Jijia Liu
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
- The Second Xiangya Hospital, South Central University School of Medicine , China
| | - Mitsunori Maruyama
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Mohamed Homsi
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael C Fishbein
- Department of Pathology and Laboratory Medicine, University of California , Los Angeles, California
| | - Michael Rubart
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
| | - Shien-Fong Lin
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Deyong Xiao
- Fountain Valley Biotechnology, Inc., Dalian Hi-Tech District, Dalian , China
| | - Hanying Chen
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
| | - Peng-Sheng Chen
- Krannert Institute for Cardiology and the Division of Cardiology, Indiana University School of Medicine , Indianapolis, Indiana
| | - Weinian Shou
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
| | - Bai-Yan Li
- Department of Pharmacology, Harbin Medical University, Heilonjiang, China
- Wells Center for Pediatric Research, Indiana University School of Medicine , Indianapolis, Indiana
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8
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Mannhardt I, Eder A, Dumotier B, Prondzynski M, Krämer E, Traebert M, Söhren KD, Flenner F, Stathopoulou K, Lemoine MD, Carrier L, Christ T, Eschenhagen T, Hansen A. Blinded Contractility Analysis in hiPSC-Cardiomyocytes in Engineered Heart Tissue Format: Comparison With Human Atrial Trabeculae. Toxicol Sci 2018; 158:164-175. [PMID: 28453742 PMCID: PMC5837217 DOI: 10.1093/toxsci/kfx081] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) may serve as a new assay for drug testing in a human context, but their validity particularly for the evaluation of inotropic drug effects remains unclear. In this blinded analysis, we compared the effects of 10 indicator compounds with known inotropic effects in electrically stimulated (1.5 Hz) hiPSC-CM-derived 3-dimensional engineered heart tissue (EHT) and human atrial trabeculae (hAT). Human EHTs were prepared from iCell hiPSC-CM, hAT obtained at routine heart surgery. Mean intra-batch variation coefficient in baseline force measurement was 17% for EHT and 49% for hAT. The PDE-inhibitor milrinone did not affect EHT contraction force, but increased force in hAT. Citalopram (selective serotonin reuptake inhibitor), nifedipine (LTCC-blocker) and lidocaine (Na+ channel-blocker) had negative inotropic effects on EHT and hAT. Formoterol (beta-2 agonist) had positive lusitropic but no inotropic effect in EHT, and positive clinotropic, lusitropic, and inotropic effects in hAT. Tacrolimus (calcineurin-inhibitor) had a negative inotropic effect in EHTs, but no effect in hAT. Digoxin (Na+-K+-ATPase-inhibitor) showed a positive inotropic effect only in EHTs, but no effect in hAT probably due to short incubation time. Ryanodine (ryanodine receptor-inhibitor) reduced contraction force in both models. Rolipram and acetylsalicylic acid showed noninterpretable results in hAT. Contraction amplitude and kinetics were more stable over time and less variable in hiPSC-EHTs than hAT. HiPSC-EHT faithfully detected cAMP-dependent and -independent positive and negative inotropic effects, but limited beta-2 adrenergic or PDE3 effects, compatible with an immature CM phenotype.
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Affiliation(s)
- Ingra Mannhardt
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Alexandra Eder
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | | | - Maksymilian Prondzynski
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Elisabeth Krämer
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | | | - Klaus-Dieter Söhren
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Frederik Flenner
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Konstantina Stathopoulou
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Marc D Lemoine
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany.,Department of Cardiology-Electrophysiology, University Heart Center, 20246 Hamburg, Germany
| | - Lucie Carrier
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Torsten Christ
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Thomas Eschenhagen
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - Arne Hansen
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
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9
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Zhao YT, Guo YB, Fan XX, Yang HQ, Zhou P, Chen Z, Yuan Q, Ye H, Ji GJ, Wang SQ. Role of FK506-binding protein in Ca 2+ spark regulation. Sci Bull (Beijing) 2017; 62:1295-1303. [PMID: 36659291 DOI: 10.1016/j.scib.2017.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/06/2017] [Accepted: 09/08/2017] [Indexed: 01/21/2023]
Abstract
The elementary Ca2+ release events, Ca2+ sparks, has been found for a quarter of century. However, the molecular regulation of the spark generator, the ryanodine receptor (RyR) on the sarcoplasmic reticulum, remains obscure. Although each subunit of the RyR homotetramer has a site for FK506-binding protein (FKBP), the role of FKBPs in modifying RyR Ca2+ sparks has been debated for long. One of the reasons behind the controversy is that most previous studies detect spontaneous sparks, where the mixture with out-of-focus events and local wavelets prevents an accurate characterization of Ca2+ sparks. In the present study, we detected Ca2+ sparks triggered by single L-type Ca2+ channels (LCCs) under loose-seal patch clamp conditions in FK506-treated or FKBP12.6 knockout cardiomyocytes. We found that FKBP dissociation both by FK506 and by rapamycin decreased the Ca2+ spark amplitude in ventricular cardiomyocytes. This change was neither due to decreased releasable Ca2+ in the sarcoplasmic reticulum, nor explained by changed RyR sensitivity. Actually FK506 increased the LCC-RyR coupling probability and curtailed the latency for an LCC to trigger a RyR Ca2+ spark. FKBP12.6 knockout had similar effects as FK506/rapamycin treatment, indicating that the decreased spark amplitude was attributable to the dissociation of FKBP12.6 rather than FKBP12. We also explained how decreased amplitude of spontaneous sparks after FKBP dissociation sometimes appears to be increased or unchanged due to inappropriate data processing. Our results provided firm evidence that without the inter-RyR coordination by functional FKBP12.6, the RyR recruitment during a Ca2+ spark would be compromised despite the sensitization of individual RyRs.
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Affiliation(s)
- Yan-Ting Zhao
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Yun-Bo Guo
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Xue-Xin Fan
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Hua-Qian Yang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Peng Zhou
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zheng Chen
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Qi Yuan
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Haihong Ye
- School of Basic Medical Sciences, Beijing Institute for Brain Disorders Center of Schizophrenia, Capital Medical University, Beijing 100069, China
| | - Guang-Ju Ji
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Shi-Qiang Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871, China.
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10
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Zhao YT, Guo YB, Gu L, Fan XX, Yang HQ, Chen Z, Zhou P, Yuan Q, Ji GJ, Wang SQ. Sensitized signalling between L-type Ca2+ channels and ryanodine receptors in the absence or inhibition of FKBP12.6 in cardiomyocytes. Cardiovasc Res 2017; 113:332-342. [PMID: 28077437 DOI: 10.1093/cvr/cvw247] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/03/2016] [Indexed: 12/19/2022] Open
Abstract
Aims The heart contraction is controlled by the Ca2+-induced Ca2+ release (CICR) between L-type Ca2+ channels and ryanodine receptors (RyRs). The FK506-binding protein FKBP12.6 binds to RyR subunits, but its role in stabilizing RyR function has been debated for long. Recent reports of high-resolution RyR structure show that the HD2 domain that binds to the SPRY2 domain of neighbouring subunit in FKBP-bound RyR1 is detached and invisible in FKBP-null RyR2. The present study was to test the consequence of FKBP12.6 absence on the in situ activation of RyR2. Methods and results Using whole-cell patch-clamp combined with confocal imaging, we applied a near threshold depolarization to activate a very small fraction of LCCs, which in turn activated RyR Ca2+ sparks stochastically. FKBP12.6-knockout and FK506/rapamycin treatments increased spark frequency and LCC-RyR coupling fidelity without altering LCC open probability. Neither FK506 nor rapamycin further altered LCC-RyR coupling fidelity in FKBP12.6-knockout cells. In loose-seal patch-clamp experiments, the LCC-RyR signalling kinetics, indexed by the delay for a LCC sparklet to trigger a RyR spark, was accelerated after FKBP12.6 knockout and FK506/rapamycin treatments. These results demonstrated that RyRs became more sensitive to Ca2+ triggers without FKBP12.6. Isoproterenol (1 μM) further accelerated the LCC-RyR signalling in FKBP12.6-knockout cells. The synergistic sensitization of RyRs by catecholaminergic signalling and FKBP12.6 dysfunction destabilized the CICR system, leading to chaotic Ca2+ waves and ventricular arrhythmias. Conclusion FKBP12.6 keeps the RyRs from over-sensitization, stabilizes the potentially regenerative CICR system, and thus may suppress the life-threatening arrhythmogenesis.
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Affiliation(s)
- Yan-Ting Zhao
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
| | - Yun-Bo Guo
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
| | - Lei Gu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Xue-Xin Fan
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
| | - Hua-Qian Yang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
| | - Zheng Chen
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Peng Zhou
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
| | - Qi Yuan
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Guang-Ju Ji
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Shi-Qiang Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
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11
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Munro ML, Jayasinghe I, Wang Q, Quick A, Wang W, Baddeley D, Wehrens XHT, Soeller C. Junctophilin-2 in the nanoscale organisation and functional signalling of ryanodine receptor clusters in cardiomyocytes. J Cell Sci 2016; 129:4388-4398. [PMID: 27802169 PMCID: PMC5201013 DOI: 10.1242/jcs.196873] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/14/2016] [Indexed: 11/20/2022] Open
Abstract
Signalling nanodomains requiring close contact between the plasma membrane and internal compartments, known as 'junctions', are fast communication hubs within excitable cells such as neurones and muscle. Here, we have examined two transgenic murine models probing the role of junctophilin-2, a membrane-tethering protein crucial for the formation and molecular organisation of sub-microscopic junctions in ventricular muscle cells of the heart. Quantitative single-molecule localisation microscopy showed that junctions in animals producing above-normal levels of junctophilin-2 were enlarged, allowing the re-organisation of the primary functional protein within it, the ryanodine receptor (RyR; in this paper, we use RyR to refer to the myocardial isoform RyR2). Although this change was associated with much enlarged RyR clusters that, due to their size, should be more excitable, functionally it caused a mild inhibition in the Ca2+ signalling output of the junctions (Ca2+ sparks). Analysis of the single-molecule densities of both RyR and junctophilin-2 revealed an ∼3-fold increase in the junctophilin-2 to RyR ratio. This molecular rearrangement is compatible with direct inhibition of RyR opening by junctophilin-2 to intrinsically stabilise the Ca2+ signalling properties of the junction and thus the contractile function of the cell.
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Affiliation(s)
- Michelle L Munro
- Department of Physiology, School of Medical Sciences, University of Auckland, 1023, New Zealand
| | - Izzy Jayasinghe
- School of Physics, University of Exeter, Exeter EX4 4QL, UK
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Qiongling Wang
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Ann Quick
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Wei Wang
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - David Baddeley
- Department of Cell Biology, Yale University, New Haven, CT 06520, USA
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), and Pediatrics (Cardiology), Baylor College of Medicine, Houston, TX 77030, USA
| | - Christian Soeller
- Department of Physiology, School of Medical Sciences, University of Auckland, 1023, New Zealand
- School of Physics, University of Exeter, Exeter EX4 4QL, UK
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12
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Wang Y, Tandan S, Hill JA. Calcineurin-dependent ion channel regulation in heart. Trends Cardiovasc Med 2013; 24:14-22. [PMID: 23809405 DOI: 10.1016/j.tcm.2013.05.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/20/2013] [Accepted: 05/21/2013] [Indexed: 02/05/2023]
Abstract
Calcineurin, a serine-threonine-specific, Ca(2+)-calmodulin-activated protein phosphatase, conserved from yeast to humans, plays a key role in regulating cardiac development, hypertrophy, and pathological remodeling. Recent studies demonstrate that calcineurin regulates cardiomyocyte ion channels and receptors in a manner which often entails direct interaction with these target proteins. Here, we review the current state of knowledge of calcineurin-mediated regulation of ion channels in the myocardium with emphasis on the transient outward potassium current (Ito) and L-type calcium current (ICa,L). We go on to discuss unanswered questions that surround these observations and provide perspective on future directions in this exciting field.
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Affiliation(s)
- Yanggan Wang
- Department of Cardiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, China; Department of Pediatrics, Emory University, Atlanta, GA, USA.
| | - Samvit Tandan
- Department of Internal Medicine (Cardiology), University of Texas, Southwestern Medical Center, Dallas, TX, USA
| | - Joseph A Hill
- Department of Internal Medicine (Cardiology), University of Texas, Southwestern Medical Center, Dallas, TX, USA; Department of Molecular Biology, University of Texas, Southwestern Medical Center, Dallas, TX, USA.
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13
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Marx SO, Marks AR. Dysfunctional ryanodine receptors in the heart: new insights into complex cardiovascular diseases. J Mol Cell Cardiol 2013; 58:225-31. [PMID: 23507255 DOI: 10.1016/j.yjmcc.2013.03.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/26/2013] [Accepted: 03/02/2013] [Indexed: 01/07/2023]
Abstract
Calcium dependent signaling is highly regulated in cardiomyocytes and determines the force of cardiac muscle contraction. The cardiac ryanodine receptors (RyR2) play important roles in health and disease. Modulation of RyR2 by phosphorylation is required for sympathetic regulation of cardiac function. Abnormal regulation of RyR2 contributes to heart failure, and atrial and ventricular arrhythmias. RyR2 channels are oxidized, nitrosylated, and hyperphosphorylated by protein kinase A (PKA) in heart failure, resulting in "leaky" channels. These leaky RyR2 channels contribute to depletion of calcium from the sarcoplasmic reticulum, resulting in defective cardiac excitation-contraction coupling. In this review, we discuss both the importance of PKA and calcium/calmodulin-dependent kinase II (CaMKII) regulation of RyR2 in health, and how altered phosphorylation, nitrosylation and oxidation of RyR2 channels lead to cardiac disease. Correcting these defects using either genetic manipulation (knock-in) in mice, or specific and novel small molecules ameliorates the RyR2 dysfunction, reducing the progression to heart failure and the incidence of arrhythmias.
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Affiliation(s)
- Steven O Marx
- Division of Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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14
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FK506 binding proteins: Cellular regulators of intracellular Ca2+ signalling. Eur J Pharmacol 2013; 700:181-93. [DOI: 10.1016/j.ejphar.2012.12.029] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 12/04/2012] [Accepted: 12/18/2012] [Indexed: 02/04/2023]
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15
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Liu Y, Korte FS, Moussavi-Harami F, Yu M, Razumova M, Regnier M, Chin MT. Transcription factor CHF1/Hey2 regulates EC coupling and heart failure in mice through regulation of FKBP12.6. Am J Physiol Heart Circ Physiol 2012; 302:H1860-70. [PMID: 22408025 DOI: 10.1152/ajpheart.00702.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heart failure is a leading cause of morbidity and mortality in Western society. The cardiovascular transcription factor CHF1/Hey2 has been linked to experimental heart failure in mice, but the mechanisms by which it regulates myocardial function remain incompletely understood. The objective of this study was to determine how CHF1/Hey2 affects development of heart failure through examination of contractility in a myocardial knockout mouse model. We generated myocardial-specific knockout mice. At baseline, cardiac function was normal, but, after aortic banding, the conditional knockout mice demonstrated a greater increase in ventricular weight-to-body weight ratio compared with control mice (5.526 vs. 4.664 mg/g) and a significantly decreased ejection fraction (47.8 vs. 72.0% control). Isolated cardiac myocytes from these mice showed decreased calcium transients and fractional shortening after electrical stimulation. To determine the molecular basis for these alterations in excitation-contraction coupling, we first measured total sarcoplasmic reticulum calcium stores and calcium-dependent force generation in isolated muscle fibers, which were normal, suggesting a defect in calcium cycling. Analysis of gene expression demonstrated normal expression of most genes known to be involved in myocardial calcium cycling, with the exception of the ryanodine receptor binding protein FKBP12.6, which was expressed at increased levels in the conditional knockout hearts. Treatment of the isolated knockout myocytes with FK506, which inhibits the association of FKBP12.6 with the ryanodine receptor, restored contractile function. These findings demonstrate that conditional deletion of CHF1/Hey2 in the myocardium leads to abnormalities in calcium handling mediated by FKBP12.6 that predispose to pressure overload-induced heart failure.
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Affiliation(s)
- Yonggang Liu
- Division of Cardiology, Department of Medicine, University of Washington, Seattle, Washington 98109, USA
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16
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Shkryl VM, Blatter LA, Ríos E. Properties of Ca2+ sparks revealed by four-dimensional confocal imaging of cardiac muscle. ACTA ACUST UNITED AC 2012; 139:189-207. [PMID: 22330954 PMCID: PMC3289960 DOI: 10.1085/jgp.201110709] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Parameters (amplitude, width, kinetics) of Ca2+ sparks imaged confocally are affected by errors when the spark source is not in focus. To identify sparks that were in focus, we used fast scanning (LSM 5 LIVE; Carl Zeiss) combined with fast piezoelectric focusing to acquire x–y images in three planes at 1-µm separation (x-y-z-t mode). In 3,000 x–y scans in each of 34 membrane-permeabilized cat atrial cardiomyocytes, 6,906 sparks were detected. 767 sparks were in focus. They had greater amplitude, but their spatial width and rise time were similar compared with all sparks recorded. Their distribution of amplitudes had a mode at ΔF/F0 = 0.7. The Ca2+ release current underlying in-focus sparks was 11 pA, requiring 20 to 30 open channels, a number at the high end of earlier estimates. Spark frequency was greater than in earlier imaging studies of permeabilized ventricular cells, suggesting a greater susceptibility to excitation, which could have functional relevance for atrial cells. Ca2+ release flux peaked earlier than the time of peak fluorescence and then decayed, consistent with significant sarcoplasmic reticulum (SR) depletion. The evolution of fluorescence and release flux were strikingly similar for in-focus sparks of different rise time (T). Spark termination involves both depletion of Ca2+ in the SR and channel closure, which may be synchronized by depletion. The observation of similar flux in sparks of different T requires either that channel closure and other termination processes be independent of the determinants of flux (including [Ca2+]SR) or that different channel clusters respond to [Ca2+]SR with different sensitivity.
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Affiliation(s)
- Vyacheslav M Shkryl
- Department of Molecular Biophysics and Physiology, Section of Cellular Signaling, Rush University, Chicago, IL 60612, USA
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17
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Zissimopoulos S, Seifan S, Maxwell C, Williams AJ, Lai FA. Disparities in the association of the ryanodine receptor and the FK506-binding proteins in mammalian heart. J Cell Sci 2012; 125:1759-69. [PMID: 22328519 DOI: 10.1242/jcs.098012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The FK506-binding proteins (FKBP12 and FKBP12.6; also known as FKBP1A and FKBP1B, respectively) are accessory subunits of the ryanodine receptor (RyR) Ca(2+) release channel. Aberrant RyR2-FKBP12.6 interactions have been proposed to be the underlying cause of channel dysfunction in acquired and inherited cardiac disease. However, the stoichiometry of the RyR2 association with FKBP12 or FKBP12.6 in mammalian heart is currently unknown. Here, we describe detailed quantitative analysis of cardiac stoichiometry between RyR2 and FKBP12 or FKBP12.6 using immunoblotting and [(3)H]ryanodine-binding assays, revealing striking disparities between four mammalian species. In mouse and pig heart, RyR2 is found complexed with both FKBP12 and FKBP12.6, although the former is the most abundant isoform. In rat heart, RyR2 is predominantly associated with FKBP12.6, whereas in rabbit it is associated with FKBP12 only. Co-immunoprecipitation experiments demonstrate RyR2-specific interaction with both FKBP isoforms in native cardiac tissue. Assuming four FKBP-binding sites per RyR2 tetramer, only a small proportion of available sites are occupied by endogenous FKBP12.6. FKBP interactions with RyR2 are very strong and resistant to drug (FK506, rapamycin and cyclic ADPribose) and redox (H(2)O(2) and diamide) treatment. By contrast, the RyR1-FKBP12 association in skeletal muscle is readily disrupted under oxidative conditions. This is the first study to directly assess association of endogenous FKBP12 and FKBP12.6 with RyR2 in native cardiac tissue. Our results challenge the widespread perception that RyR2 associates exclusively with FKBP12.6 to near saturation, with important implications for the role of the FK506-binding proteins in RyR2 pathophysiology and cardiac disease.
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Affiliation(s)
- Spyros Zissimopoulos
- Wales Heart Research Institute, Department of Cardiology, Cardiff University School of Medicine, Cardiff, UK.
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18
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Haizlip KM, Janssen PML. In vitro studies of early cardiac remodeling: impact on contraction and calcium handling. Front Biosci (Schol Ed) 2011; 3:1047-57. [PMID: 21622254 DOI: 10.2741/209] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Cardiac remodeling, hypertrophy, and alterations in calcium signaling are changes of the heart that often lead to failure. After a hypertrophic stimulus, the heart progresses through a state of compensated hypertrophy which over time leads to decompensated hypertrophy or failure. It is at this point that a cardiac transplant is required for survival making early detection imperative. Current experimental systems used to study the remodeling of the heart include in vivo systems (the whole body), isolated organ and sub-organ tissue, and the individual cardiac muscle cells and organelles.. During pathological remodeling there is a derangement in the intracellular calcium handling processes. These derangements are thought to lead to a dysregulation of contractile output. Hence, understanding the mechanism between remodeling and dysregulation is of great interest in the cardiac field and will ultimately help in the development of future treatment and early detection. This review will center on changes in contraction and calcium handling in early cardiac remodeling, with a specific focus on findings in two different in vitro model systems: multicellular and individual cell preparations.
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Affiliation(s)
- Kaylan M Haizlip
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH 43210-1218, USA
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19
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Cannell MB, Kong CHT. Local control in cardiac E-C coupling. J Mol Cell Cardiol 2011; 52:298-303. [PMID: 21586292 DOI: 10.1016/j.yjmcc.2011.04.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 04/12/2011] [Accepted: 04/29/2011] [Indexed: 10/18/2022]
Abstract
The development of local control theories in cardiac excitation-contraction coupling solved a major problem in the calcium-induced calcium release (CICR) hypothesis. Local control explained how regeneration, inherent in the CICR mechanism, might be limited spatially to enable graded Ca release (and force production). The key lies in the stochastic recruitment of individual calcium release units (couplons or CRUs) where adjacent CRUs are partially uncoupled by the distance between them. In the CRU, individual groups of sarcoplasmic reticulum calcium release channels (RyRs) are very close to the surface membrane where calcium influx, controlled by membrane depolarization, leads to high local Ca levels that enable a high speed response from RyRs that have a very low probability to opening at resting Ca levels. However, calcium diffusion from an activated CRU results in adjacent CRUs being exposed to much lower levels of Ca and probability of activation. This effectively uncouples the CRUs and limits overall regenerative gain to enable stability without compromising sensitivity. Nevertheless, it is still unclear how the CRU terminates its release of calcium on the physiological timescale, and possible mechanisms (and problems) are briefly reviewed. We suggest that modulation in RyR gating may serve to control average SR Ca levels to regulate other metabolic functions of the sarco(endo)plasmic reticulum beyond regulating contractility. This article is part of a special issue entitled "Local Signaling in Myocytes."
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Affiliation(s)
- M B Cannell
- School of Physiology & Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
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20
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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: 1.1] [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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21
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Maruyama M, Li BY, Chen H, Xu X, Song LS, Guatimosim S, Zhu W, Yong W, Zhang W, Bu G, Lin SF, Fishbein MC, Lederer WJ, Schild JH, Field LJ, Rubart M, Chen PS, Shou W. FKBP12 is a critical regulator of the heart rhythm and the cardiac voltage-gated sodium current in mice. Circ Res 2011; 108:1042-52. [PMID: 21372286 DOI: 10.1161/circresaha.110.237867] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
RATIONALE FK506 binding protein (FKBP)12 is a known cis-trans peptidyl prolyl isomerase and highly expressed in the heart. Its role in regulating postnatal cardiac function remains largely unknown. METHODS AND RESULTS We generated FKBP12 overexpressing transgenic (αMyHC-FKBP12) mice and cardiomyocyte-restricted FKBP12 conditional knockout (FKBP12(f/f)/αMyHC-Cre) mice and analyzed their cardiac electrophysiology in vivo and in vitro. A high incidence (38%) of sudden death was found in αMyHC-FKBP12 mice. Surface and ambulatory ECGs documented cardiac conduction defects, which were further confirmed by electric measurements and optical mapping in Langendorff-perfused hearts. αMyHC-FKBP12 hearts had slower action potential upstrokes and longer action potential durations. Whole-cell patch-clamp analyses demonstrated an ≈ 80% reduction in peak density of the tetrodotoxin-resistant, voltage-gated sodium current I(Na) in αMyHC-FKBP12 ventricular cardiomyocytes, a slower recovery of I(Na) from inactivation, shifts of steady-state activation and inactivation curves of I(Na) to more depolarized potentials, and augmentation of late I(Na), suggesting that the arrhythmogenic phenotype of αMyHC-FKBP12 mice is attributable to abnormal I(Na). Ventricular cardiomyocytes isolated from FKBP12(f/f)/αMyHC-Cre hearts showed faster action potential upstrokes and a more than 2-fold increase in peak I(Na) density. Dialysis of exogenous recombinant FKBP12 protein into FKBP12-deficient cardiomyocytes promptly recapitulated alterations in I(Na) seen in αMyHC-FKBP12 myocytes. CONCLUSIONS FKBP12 is a critical regulator of I(Na) and is important for cardiac arrhythmogenic physiology. FKPB12-mediated dysregulation of I(Na) may underlie clinical arrhythmias associated with FK506 administration.
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Affiliation(s)
- Mitsunori Maruyama
- Department of Medicine, University School of Medicine, Indianapolis, IN 46202, USA
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22
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Xu H, Ginsburg KS, Hall DD, Zimmermann M, Stein IS, Zhang M, Tandan S, Hill JA, Horne MC, Bers D, Hell JW. Targeting of protein phosphatases PP2A and PP2B to the C-terminus of the L-type calcium channel Ca v1.2. Biochemistry 2010; 49:10298-307. [PMID: 21053940 PMCID: PMC3075818 DOI: 10.1021/bi101018c] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The L-type Ca(2+) channel Ca(v)1.2 forms macromolecular signaling complexes that comprise the β(2) adrenergic receptor, trimeric G(s) protein, adenylyl cyclase, and cAMP-dependent protein kinase (PKA) for efficient signaling in heart and brain. The protein phosphatases PP2A and PP2B are part of this complex. PP2A counteracts increase in Ca(v)1.2 channel activity by PKA and other protein kinases, whereas PP2B can either augment or decrease Ca(v)1.2 currents in cardiomyocytes depending on the precise experimental conditions. We found that PP2A binds to two regions in the C-terminus of the central, pore-forming α(1) subunit of Ca(v)1.2: one region spans residues 1795-1818 and the other residues 1965-1971. PP2B binds immediately downstream of residue 1971. Injection of a peptide that contained residues 1965-1971 and displaced PP2A but not PP2B from endogenous Ca(v)1.2 increased basal and isoproterenol-stimulated L-type Ca(2+) currents in acutely isolated cardiomyocytes. Together with our biochemical data, these physiological results indicate that anchoring of PP2A at this site of Ca(v)1.2 in the heart negatively regulates cardiac L-type currents, likely by counterbalancing basal and stimulated phosphorylation that is mediated by PKA and possibly other kinases.
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Affiliation(s)
- Hui Xu
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA
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Lanner JT, Georgiou DK, Joshi AD, Hamilton SL. Ryanodine receptors: structure, expression, molecular details, and function in calcium release. Cold Spring Harb Perspect Biol 2010; 2:a003996. [PMID: 20961976 DOI: 10.1101/cshperspect.a003996] [Citation(s) in RCA: 566] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Ryanodine receptors (RyRs) are located in the sarcoplasmic/endoplasmic reticulum membrane and are responsible for the release of Ca(2+) from intracellular stores during excitation-contraction coupling in both cardiac and skeletal muscle. RyRs are the largest known ion channels (> 2MDa) and exist as three mammalian isoforms (RyR 1-3), all of which are homotetrameric proteins that interact with and are regulated by phosphorylation, redox modifications, and a variety of small proteins and ions. Most RyR channel modulators interact with the large cytoplasmic domain whereas the carboxy-terminal portion of the protein forms the ion-conducting pore. Mutations in RyR2 are associated with human disorders such as catecholaminergic polymorphic ventricular tachycardia whereas mutations in RyR1 underlie diseases such as central core disease and malignant hyperthermia. This chapter examines the current concepts of the structure, function and regulation of RyRs and assesses the current state of understanding of their roles in associated disorders.
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Affiliation(s)
- Johanna T Lanner
- Baylor College of Medicine, Department of Molecular Physiology and Biophysics, Houston, Texas 77030,USA
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Andersson DC, Marks AR. Fixing ryanodine receptor Ca leak - a novel therapeutic strategy for contractile failure in heart and skeletal muscle. ACTA ACUST UNITED AC 2010; 7:e151-e157. [PMID: 21113427 DOI: 10.1016/j.ddmec.2010.09.009] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A critical component in regulating cardiac and skeletal muscle contractility is the release of Ca(2+) via ryanodine receptor (RyR) Ca(2+) release channels in the sarcoplasmic reticulum (SR). In heart failure and myopathy, the RyR has been found to be excessively phosphorylated or nitrosylated and depleted of the RyR-stabilizing protein calstabin (FK506 binding protein 12/12.6). This remodeling of the RyR channel complex results in an intracellular SR Ca(2+) leak and impaired contractility. Despite recent advances in heart failure treatment, there are still devastatingly high mortality rates with this disease. Moreover, pharmacological treatment for muscle weakness and myopathy is nearly nonexistent. A novel class of RyR-stabilizing drugs, rycals, which reduce Ca(2+) leak by stabilizing the RyR channels due to preservation of the RyR-calstabin interaction, have recently been shown to improve contractile function in both heart and skeletal muscle. This opens up a novel therapeutic strategy for the treatment of contractile failure in the cardiac and skeletal muscle.
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Affiliation(s)
- Daniel C Andersson
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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Ca(2+) release induced by cADP-ribose is mediated by FKBP12.6 proteins in mouse bladder smooth muscle. Cell Calcium 2010; 47:449-57. [PMID: 20451249 DOI: 10.1016/j.ceca.2010.03.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 03/22/2010] [Accepted: 03/26/2010] [Indexed: 12/17/2022]
Abstract
We examined the role and molecular mechanism of cADPR action on Ca(2+) spark properties in mouse bladder smooth muscle. Dialysis of cADPR with patch pipettes increased frequency and amplitude of spontaneous transient out currents (STOCs) to 6.1+/-0.87 currents/min from 1.2+/-0.36 currents/min (control) and to 179.8+/-48.7pA from 36.4+/-22.6pA (control), respectively, in wildtype (WT) cells, and the effects of cADPR on STOCs were significantly blocked by JVT-591, a RYR2 stabilizer. In contrast, no significant changes were observed in FKBP12.6 null cells. Further studies indicated that Ca(2+) spark properties were altered by cADPR in WT but not FKBP12.6 null cells, namely, Ca(2+) spark frequency was increased by about 3.4-fold, peak Ca(2+) (F/F0) increased to 1.72+/-0.57 from 1.56+/-0.13, size increased to 2.86+/-0.26 microM from 1.92+/-0.14 microM, rise time and half-time decay were prolonged 1.6-fold and 2.3-fold, respectively, in WT cells. Furthermore, in the presence of thapsigargin cADPR still altered Ca(2+) spark properties, and cADPR increased F/F0 without affecting Ca(2+) spark decay time in voltage clamping cells. Dissociation studies demonstrated that application of cADPR resulted in significant removal of FKBP12.6 proteins from sarcoplasmic reticulum (SR) microsomes, and that treatment of the RyR2 immunoprecipitation complexes with cADPR or FK506 disrupted the interaction between RyR2 and FKBP12.6. Finally, cADPR altered SR Ca(2+) load in WT myocytes but not in FKBP12.6-null myocytes. Taken together, these results suggest that Ca(2+) release induced by cADPR is mediated by FKBP12.6 proteins in mouse bladder smooth muscle.
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Guo T, Cornea RL, Huke S, Camors E, Yang Y, Picht E, Fruen BR, Bers DM. Kinetics of FKBP12.6 binding to ryanodine receptors in permeabilized cardiac myocytes and effects on Ca sparks. Circ Res 2010; 106:1743-52. [PMID: 20431056 DOI: 10.1161/circresaha.110.219816] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE FK506-binding proteins FKBP12.6 and FKBP12 are associated with cardiac ryanodine receptors (RyR2), and cAMP-dependent protein kinase A (PKA)-dependent phosphorylation of RyR2 was proposed to interrupt FKBP12.6-RyR2 association and activate RyR2. However, the function of FKBP12.6/12 and role of PKA phosphorylation in cardiac myocytes are controversial. OBJECTIVE To directly measure in situ binding of FKBP12.6/12 to RyR2 in ventricular myocytes, with simultaneous Ca sparks measurements as a RyR2 functional index. METHODS AND RESULTS We used permeabilized rat and mouse ventricular myocytes, and fluorescently-labeled FKBP12.6/12. Both FKBP12.6 and FKBP12 concentrate at Z-lines, consistent with RyR2 and Ca spark initiation sites. However, only FKBP12.6 inhibits resting RyR2 activity. Assessment of fluorescent FKBP binding in myocyte revealed a high FKBP12.6-RyR2 affinity (K(d)=0.7+/-0.1 nmol/L) and much lower FKBP12-RyR2 affinity (K(d)=206+/-70 nmol/L). Fluorescence recovery after photobleach confirmed this K(d) difference and showed that it is mediated by k(off). RyR2 phosphorylation by PKA did not alter binding kinetics or affinity of FKBP12.6/12 for RyR2. Using quantitative immunoblots, we determined endogenous [FKBP12] in intact myocytes is approximately 1 micromol/L (similar to [RyR]), whereas [FKBP12.6] is <or=150 nmol/L. CONCLUSIONS Only 10% to 20% of endogenous myocyte RyR2s have FKBP12.6 associated, but virtually all myocyte FKBP12.6 is RyR2-bound (because of very high affinity). FKBP12.6 but not FKBP12 inhibits basal RyR2 activity. PKA-dependent RyR2 phosphorylation has no significant effect on binding of either FKBP12 or 12.6 to RyR2 in myocytes.
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Affiliation(s)
- Tao Guo
- Department of Pharmacology, University of California, Davis, 451 Health Science Dr, Davis, CA 95616, USA
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Role of ryanodine receptor subtypes in initiation and formation of calcium sparks in arterial smooth muscle: comparison with striated muscle. J Biomed Biotechnol 2009; 2009:135249. [PMID: 20029633 PMCID: PMC2793424 DOI: 10.1155/2009/135249] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 09/22/2009] [Indexed: 11/17/2022] Open
Abstract
Calcium sparks represent local, rapid, and transient calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial smooth muscle cells (SMCs), calcium sparks activate calcium-dependent potassium channels causing decrease in the global intracellular [Ca2+] and oppose vasoconstriction. This is in contrast to cardiac and skeletal muscle, where spatial and temporal summation of calcium sparks leads to global increases in intracellular [Ca2+] and myocyte contraction. We summarize the present data on local RyR calcium signaling in arterial SMCs in comparison to striated muscle and muscle-specific differences in coupling between L-type calcium channels and RyRs. Accordingly, arterial SMC Ca(v)1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux though RyRs. Downregulation of RyR2 up to a certain degree is compensated by increased SR calcium content to normalize calcium sparks. This indirect coupling between Ca(v)1.2 and RyR in arterial SMCs is opposite to striated muscle, where triggering of calcium sparks is controlled by rapid and direct cross-talk between Ca(v)1.1/Ca(v)1.2 L-type channels and RyRs. We discuss the role of RyR isoforms in initiation and formation of calcium sparks in SMCs and their possible molecular binding partners and regulators, which differ compared to striated muscle.
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Kise H, Nakamura Y, Hoshiai M, Sugiyama H, Sugita K, Sugiyama A. Cardiac and haemodynamic effects of tacrolimus in the halothane-anaesthetized dog. Basic Clin Pharmacol Toxicol 2009; 106:288-95. [PMID: 19912168 DOI: 10.1111/j.1742-7843.2009.00477.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Tacrolimus (FK506) is a potent immunosuppressant widely used for the treatment of patients with solid organ transplantation and autoimmune diseases. The present study investigated the cardiac, haemodynamic and electrophysiological effects of tacrolimus. Tacrolimus in doses of 0.01 and 0.1 mg/kg was infused over 10 min. with a pause of 20 min. in halothane-anaesthetized dogs under monitoring of plasma drug concentrations (n = 5). Sub-therapeutic dose of 0.01 mg/kg hardly affected any of the cardiovascular variables except that it slightly delayed the repolarization. The clinically relevant dose of 0.1 mg/kg had negative chronotropic, inotropic and dromotropic effects, and lowered blood pressure by 70 +/- 12 mmHg, effects previously ascribed to Ca(2+) channel blocking action. Tacrolimus also delayed the repolarization process in a dose-dependent and reverse use-dependent manner with an increase in electrical vulnerability. The cardiovascular effects of tacrolimus were enhanced after the cessation of drug infusion, despite a decline in the plasma concentrations. In human embryonic kidney 293 cells, however, only supratherapeutic tacrolimus concentrations (>0.1 mumol/l) inhibited hERG K(+) current with a maximum inhibition of 28% at 10 mumol/l, indicating that other mechanisms might have also operated besides direct block of ionic channel function. The present study suggests that tacrolimus has negative chronotropic, inotropic and dromotropic effects in the heart, delays repolarization and lowers blood pressure. Moreover, the monitoring of the actual drug concentration may not necessarily reflect its effects on the cardiovascular system; thus, frequent monitoring of cardiovascular variables may be essential for tacrolimus-treated patients.
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Affiliation(s)
- Hiroaki Kise
- Department of Paediatrics, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan
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29
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Abstract
Puffs and sparks are localized intracellular Ca(2+) elevations that arise from the cooperative activity of Ca(2+)-regulated inositol 1,4,5-trisphosphate receptors and ryanodine receptors clustered at Ca(2+) release sites on the surface of the endoplasmic reticulum or the sarcoplasmic reticulum. While the synchronous gating of Ca(2+)-regulated Ca(2+) channels can be mediated entirely though the buffered diffusion of intracellular Ca(2+), interprotein allosteric interactions also contribute to the dynamics of ryanodine receptor (RyR) gating and Ca(2+) sparks. In this article, Markov chain models of Ca(2+) release sites are used to investigate how the statistics of Ca(2+) spark generation and termination are related to the coupling of RyRs via local [Ca(2+)] changes and allosteric interactions. Allosteric interactions are included in a manner that promotes the synchronous gating of channels by stabilizing neighboring closed-closed and/or open-open channel pairs. When the strength of Ca(2+)-mediated channel coupling is systematically varied (e.g., by changing the Ca(2+) buffer concentration), simulations that include synchronizing allosteric interactions often exhibit more robust Ca(2+) sparks; however, for some Ca(2+) coupling strengths the sparks are less robust. We find no evidence that the distribution of spark durations can be used to distinguish between allosteric interactions that stabilize closed channel pairs, open channel pairs, or both in a balanced fashion. On the other hand, the changes in spark duration, interspark interval, and frequency observed when allosteric interactions that stabilize closed channel pairs are gradually removed from simulations are qualitatively different than the changes observed when open or both closed and open channel pairs are stabilized. Thus, our simulations clarify how changes in spark statistics due to pharmacological washout of the accessory proteins mediating allosteric coupling may indicate the type of synchronizing allosteric interactions exhibited by physically coupled RyRs. We also investigate the validity of a mean-field reduction applicable to the dynamics of a ryanodine receptor cluster coupled via local [Ca(2+)] and allosteric interactions. In addition to facilitating parameter studies of the effect of allosteric coupling on spark statistics, the derivation of the mean-field model establishes the correct functional form for cooperativity factors representing the coupled gating of RyRs. This mean-field formulation is well suited for use in computationally efficient whole cell simulations of excitation-contraction coupling.
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Xiao J, Tian X, Jones PP, Bolstad J, Kong H, Wang R, Zhang L, Duff HJ, Gillis AM, Fleischer S, Kotlikoff M, Copello JA, Chen SRW. Removal of FKBP12.6 does not alter the conductance and activation of the cardiac ryanodine receptor or the susceptibility to stress-induced ventricular arrhythmias. J Biol Chem 2007; 282:34828-38. [PMID: 17921453 DOI: 10.1074/jbc.m707423200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 12.6-kDa FK506-binding protein (FKBP12.6) is considered to be a key regulator of the cardiac ryanodine receptor (RyR2), but its precise role in RyR2 function is complex and controversial. In the present study we investigated the impact of FKBP12.6 removal on the properties of the RyR2 channel and the propensity for spontaneous Ca(2+) release and the occurrence of ventricular arrhythmias. Single channel recordings in lipid bilayers showed that FK506 treatment of recombinant RyR2 co-expressed with or without FKBP12.6 or native canine RyR2 did not induce long-lived subconductance states. [(3)H]Ryanodine binding studies revealed that coexpression with or without FKBP12.6 or treatment with or without FK506 did not alter the sensitivity of RyR2 to activation by Ca(2+) or caffeine. Furthermore, single cell Ca(2+) imaging analyses demonstrated that HEK293 cells co-expressing RyR2 and FKBP12.6 or expressing RyR2 alone displayed the same propensity for spontaneous Ca(2+) release or store overload-induced Ca(2+) release (SOICR). FK506 increased the amplitude and decreased the frequency of SOICR in HEK293 cells expressing RyR2 with or without FKBP12.6, indicating that the action of FK506 on SOICR is independent of FKBP12.6. As with recombinant RyR2, the conductance and ligand-gating properties of single RyR2 channels from FKBP12.6-null mice were indistinguishable from those of single wild type channels. Moreover, FKBP12.6-null mice did not exhibit enhanced susceptibility to stress-induced ventricular arrhythmias, in contrast to previous reports. Collectively, our results demonstrate that the loss of FKBP12.6 has no significant effect on the conduction and activation of RyR2 or the propensity for spontaneous Ca(2+) release and stress-induced ventricular arrhythmias.
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Affiliation(s)
- Jianmin Xiao
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Biophysics, University of Calgary, Calgary, AB, T2N 4N1, Canada
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Wongcharoen W, Chen YC, Chen YJ, Chen SY, Yeh HI, Lin CI, Chen SA. Aging increases pulmonary veins arrhythmogenesis and susceptibility to calcium regulation agents. Heart Rhythm 2007; 4:1338-49. [PMID: 17905341 DOI: 10.1016/j.hrthm.2007.06.023] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Accepted: 06/26/2007] [Indexed: 11/16/2022]
Abstract
BACKGROUND Aging and pulmonary veins (PVs) play a critical role in the pathophysiology of atrial fibrillation. Abnormal Ca(2+) regulation and ryanodine receptors are known to contribute to PV arrhythmogenesis. OBJECTIVE The purpose of this study was to investigate whether aging alters PV electrophysiology, Ca(2+) regulation proteins, and responses to rapamycin, FK-506, ryanodine, and ouabain. METHODS Conventional microelectrodes were used to record action potential and contractility in isolated PV tissue samples in 15 young (age 3 months) and 16 aged (age 3 years) rabbits before and after drug administration. Expression of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a), ryanodine receptor, and Na(+)/Ca(2+) exchanger was evaluated by western blot. RESULTS Aged PVs had larger amplitude of delayed afterdepolarizations, greater depolarized resting membrane potential, longer action potential duration, and higher incidence of action potential alternans and contractile alternans with increased expression of Na(+)/Ca(2+) exchanger and ryanodine receptor and decreased expression of SERCA2a. Rapamycin (1,10,100 nM), FK-506 (0.01, 0.1, 1 microM), ryanodine (0.1, 1 microM), and ouabain (0.1, 1 microM) concentration-dependently increased PV spontaneous rates and the incidence of delayed afterdepolarizations in young and aged PVs. Compared with results in young PVs, rapamycin and FK-506 in aged PVs increased PV spontaneous rates to a greater extent and exhibited a larger delayed afterdepolarization amplitude. In PVs without spontaneous activity, rapamycin and FK-506 induced spontaneous activity only in aged PVs, but ryanodine and ouabain induced spontaneous activity in both young and aged PVs. CONCLUSION Aging increases PV arrhythmogenesis via abnormal Ca(2+) regulation. These findings support the concept that ryanodine receptor dysfunction may result in high PV arrhythmogenesis and aging-related arrhythmogenic vulnerability.
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Abstract
Regulation of Calcium (Ca) cycling by the sarcoplasmic reticulum (SR) underlies the control of cardiac contraction during excitation-contraction (E-C) coupling. Moreover, alterations in E-C coupling occurring in cardiac hypertrophy and heart failure are characterized by abnormal Ca-cycling through the SR network. A large body of evidence points to the central role of: a) SERCA and its regulator phospholamban (PLN) in the modulation of cardiac relaxation; b) calsequestrin in the regulation of SR Ca-load; and c) the ryanodine receptor (RyR) Ca-channel in the control of SR Ca-release. The levels or activity of these key Ca-handling proteins are altered in cardiomyopathies, and these changes have been linked to the deteriorated cardiac function and remodeling. Furthermore, genetic variants in these SR Ca-cycling proteins have been identified, which may predispose to heart failure or fatal arrhythmias. This chapter concentrates on the pivotal role of SR Ca-cycling proteins in health and disease with specific emphasis on their recently reported genetic modifiers.
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Abstract
Triggered activity in cardiac muscle and intracellular Ca2+ have been linked in the past. However, today not only are there a number of cellular proteins that show clear Ca2+ dependence but also there are a number of arrhythmias whose mechanism appears to be linked to Ca2+-dependent processes. Thus we present a systematic review of the mechanisms of Ca2+ transport (forward excitation-contraction coupling) in the ventricular cell as well as what is known for other cardiac cell types. Second, we review the molecular nature of the proteins that are involved in this process as well as the functional consequences of both normal and abnormal Ca2+ cycling (e.g., Ca2+ waves). Finally, we review what we understand to be the role of Ca2+ cycling in various forms of arrhythmias, that is, those associated with inherited mutations and those that are acquired and resulting from reentrant excitation and/or abnormal impulse generation (e.g., triggered activity). Further solving the nature of these intricate and dynamic interactions promises to be an important area of research for a better recognition and understanding of the nature of Ca2+ and arrhythmias. Our solutions will provide a more complete understanding of the molecular basis for the targeted control of cellular calcium in the treatment and prevention of such.
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Affiliation(s)
- Henk E D J Ter Keurs
- Department of Medicine, Physiology and Biophysics, University of Calgary, Alberta, Canada
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34
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Dulhunty AF, Beard NA, Pouliquin P, Casarotto MG. Agonists and antagonists of the cardiac ryanodine receptor: Potential therapeutic agents? Pharmacol Ther 2007; 113:247-63. [PMID: 17055586 DOI: 10.1016/j.pharmthera.2006.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 08/16/2006] [Indexed: 10/24/2022]
Abstract
This review addresses the potential use of the intracellular ryanodine receptor (RyR) Ca(2+) release channel as a therapeutic target in heart disease. Heart disease encompasses a wide range of conditions with the major contributors to mortality and morbidity being ischaemic heart disease and heart failure (HF). In addition there are many rare, but devastating conditions, some of which are either genetically linked to the RyR and its regulatory proteins or involve drug-induced modification of the proteins. The defects in Ca(2+) signalling vary with the nature of the heart disease and the stage in its progress and therefore specific corrections require different modifications of Ca(2+) signalling. Compounds that activate the RyR are potential inotropic agents to increase the Ca(2+) transient and strength of contraction. Compounds that reduce RyR activity are potentially useful in conditions where excess RyR activity initiates arrhythmias, or depletes the Ca(2+) store, as in end stage HF. It has recently been discovered that the cardio-protective action of the drug JTV519 can be attributed partly to its ability to stabilise the interaction between the RyR and the 12.6 kDa binding protein for the commonly used immunosuppressive drug FK506 (FKBP12.6, known as tacrolimus). This has established the credibility of the RyR as a therapeutic target. We explore the possibility that mutations causing the rare RyR-linked arrhythmias will open the door to identification of novel RyR-based therapeutic agents. The use of regulatory binding sites within the RyR complex or on its associated proteins as templates for drug design is discussed.
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Affiliation(s)
- Angela F Dulhunty
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, P.O. Box 334, ACT, 2601, Australia
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35
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Katra RP, Oya T, Hoeker GS, Laurita KR. Ryanodine receptor dysfunction and triggered activity in the heart. Am J Physiol Heart Circ Physiol 2006; 292:H2144-51. [PMID: 17189349 DOI: 10.1152/ajpheart.00924.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Arrhythmogenesis has been increasingly linked to cardiac ryanodine receptor (RyR) dysfunction. However, the mechanistic relationship between abnormal RyR function and arrhythmogenesis in the heart is not clear. We hypothesize that, under abnormal RyR conditions, triggered activity will be caused by spontaneous calcium release (SCR) events that depend on transmural heterogeneities of calcium handling. We performed high-resolution optical mapping of intracellular calcium and transmembrane potential in the canine left ventricular wedge preparation (n = 28). Rapid pacing was used to initiate triggered activity under normal and abnormal RyR conditions induced by FKBP12.6 dissociation and beta-adrenergic stimulation (20-150 microM rapamycin, 0.2 microM isoproterenol). Under abnormal RyR conditions, almost all preparations experienced SCRs and triggered activity, in contrast to control, rapamycin, or isoproterenol conditions alone. Furthermore, under abnormal RyR conditions, complex arrhythmias (monomorphic and polymorphic tachycardia) were commonly observed. After washout of rapamycin and isoproterenol, no triggered activity was observed. Surprisingly, triggered activity and SCRs occurred preferentially near the epicardium but not the endocardium (P < 0.01). Interestingly, the occurrence of triggered activity and SCR events could not be explained by cytoplasmic calcium levels, but rather by fast calcium reuptake kinetics. These data suggest that, under abnormal RyR conditions, triggered activity is caused by multiple SCR events that depend on the faster calcium reuptake kinetics near the epicardium. Furthermore, multiple regions of SCR may be a mechanism for multifocal arrhythmias associated with RyR dysfunction.
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Affiliation(s)
- Rodolphe P Katra
- MetroHealth Campus, Case Western Reserve University, 2500 MetroHealth Drive, Cleveland, OH 44109-1998, USA
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McCarron JG, Chalmers S, Bradley KN, MacMillan D, Muir TC. Ca2+ microdomains in smooth muscle. Cell Calcium 2006; 40:461-93. [PMID: 17069885 DOI: 10.1016/j.ceca.2006.08.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 08/23/2006] [Indexed: 02/03/2023]
Abstract
In smooth muscle, Ca(2+) controls diverse activities including cell division, contraction and cell death. Of particular significance in enabling Ca(2+) to perform these multiple functions is the cell's ability to localize Ca(2+) signals to certain regions by creating high local concentrations of Ca(2+) (microdomains), which differ from the cytoplasmic average. Microdomains arise from Ca(2+) influx across the plasma membrane or release from the sarcoplasmic reticulum (SR) Ca(2+) store. A single Ca(2+) channel can create a microdomain of several micromolar near (approximately 200 nm) the channel. This concentration declines quickly with peak rates of several thousand micromolar per second when influx ends. The high [Ca(2+)] and the rapid rates of decline target Ca(2+) signals to effectors in the microdomain with rapid kinetics and enable the selective activation of cellular processes. Several elements within the cell combine to enable microdomains to develop. These include the brief open time of ion channels, localization of Ca(2+) by buffering, the clustering of ion channels to certain regions of the cell and the presence of membrane barriers, which restrict the free diffusion of Ca(2+). In this review, the generation of microdomains arising from Ca(2+) influx across the plasma membrane and the release of the ion from the SR Ca(2+) store will be discussed and the contribution of mitochondria and the Golgi apparatus as well as endogenous modulators (e.g. cADPR and channel binding proteins) will be considered.
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Affiliation(s)
- John G McCarron
- Department of Physiology and Pharmacology, University of Strathclyde, SIPBS, Glasgow, UK.
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Ozkanlar Y, Nishijima Y, da Cunha D, Hamlin RL. Acute effects of tacrolimus (FK506) on left ventricular mechanics. Pharmacol Res 2006; 52:307-12. [PMID: 15975821 DOI: 10.1016/j.phrs.2005.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2005] [Revised: 05/06/2005] [Accepted: 05/13/2005] [Indexed: 11/17/2022]
Abstract
Tacrolimus (FK506) is a macrolide antibiotic used to minimize transplant rejections. Several macrolides affect ventricular function, but the effects of tacrolimus are unknown. This study evaluated acute effects of escalating doses of tacrolimus on heart rate (HR), left ventricular inotropy, lusitropy, preload (end-diastolic short axis radius on a 2D directed M-mode echocardiogram), and afterload (product of end-diastolic radius and diastolic arterial pressure divided by end-diastolic wall thickness) in anesthetized dogs. Tacrolimus at 0.025 mg kg(-1) increased HR and inotropy with continued escalation up to a dose of 0.1 mg kg(-1) (p<0.01). Conversely, tacrolimus at 0.025 mg kg(-1) decreased lusitropy and preload, which never achieved steady states (p<0.05). Afterload tended to increase between doses of 0.0125 and 0.025 mg kg(-1), and tended to decrease at higher doses, achieving baseline at a dose of 0.1 mg kg(-1). Tacrolimus significantly prolonged the QT interval (QTc) between doses of 0.0125 (p<0.05) and 0.1mg kg(-1) (p<0.001). These effects are consistent with altered calcium kinetics leading to increased cytosolic calcium. Tacrolimus at a clinically relevant dose of 0.1 mg kg(-1) possesses profound, acute effects on left ventricular mechanics, suggesting that cardiovascular monitoring may be necessary in tacrolimus-treated patients. Potential adverse effects include myocardial stiffness, transient increase in systemic arterial pressure, and tendency for ventricular arrhythmia.
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Affiliation(s)
- Yunusemre Ozkanlar
- Department of Veterinary Internal Medicine, Ataturk University, Ilica, Erzurum 25700, Turkey.
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Boyden PA, ter Keurs H. Would modulation of intracellular Ca2+ be antiarrhythmic? Pharmacol Ther 2005; 108:149-79. [PMID: 16038982 DOI: 10.1016/j.pharmthera.2005.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Accepted: 03/22/2005] [Indexed: 01/10/2023]
Abstract
Under several types of conditions, reversal of steps of excitation-contraction coupling (RECC) can give rise to nondriven electrical activity. In this review we explore those conditions for several cardiac cell types (SA, atrial, Purkinje, ventricular cells). We find that abnormal spontaneous Ca2+ release from intracellular Ca2+ stores, aberrant Ca2+ influx from sarcolemmal channels or abnormal Ca2+ surges in nonuniform muscle can be the initiators of the RECC. Often, with such increases in Ca2+, spontaneous Ca2+ waves occur and lead to membrane depolarizations. Because the change in membrane voltage is produced by Ca2+-dependent changes in ion channel function, we also review here what is known about the molecular interaction of Ca2+ and several Ca2+-dependent processes, including the intracellular Ca2+ release channels implicated in the genetic basis of some forms of human arrhythmias. Finally, we review what is known about the effectiveness of several agents in modifying such Ca2+-dependent arrhythmias.
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Affiliation(s)
- Penelope A Boyden
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, NY 10032, USA.
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Wang K, Tu Y, Rappel WJ, Levine H. Excitation-contraction coupling gain and cooperativity of the cardiac ryanodine receptor: a modeling approach. Biophys J 2005; 89:3017-25. [PMID: 16126827 PMCID: PMC1366799 DOI: 10.1529/biophysj.105.058958] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 08/05/2005] [Indexed: 11/18/2022] Open
Abstract
During calcium-induced calcium-release, the ryanodine receptor (RyR) opens and releases large amounts of calcium from the sarcoplasmic reticulum into the cytoplasm of the myocyte. Recent experiments have suggested that cooperativity between the four monomers comprising the RyR plays an important role in the dynamics of the overall receptor. Furthermore, this cooperativity can be affected by the binding of FK506 binding protein, and hence, modulated by adrenergic stimulation through the phosphorylating action of protein kinase A. This has important implications for heart failure, where it has been hypothesized that RyR hyperphosphorylation, resulting in a loss of cooperativity, can lead to a persistent leak and a reduced sarcoplasmic-reticula content. In this study, we construct a theoretical model that examines the cooperativity via the assumption of an allosteric interaction between the four subunits. We find that the level of cooperativity, regulated by the binding of FK506 binding-protein, can have a dramatic effect on the excitation-contraction coupling gain and that this gain exhibits a clear maximum. These findings are compared to currently available data from different species and allows for an evaluation of the aforementioned heart-failure scenario.
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Affiliation(s)
- Kai Wang
- Department of Physics and Center for Theoretical Biological Physics, University of California at San Diego, La Jolla, CA, USA
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Fritz N, Macrez N, Mironneau J, Jeyakumar LH, Fleischer S, Morel JL. Ryanodine receptor subtype 2 encodes Ca2+ oscillations activated by acetylcholine via the M2 muscarinic receptor/cADP-ribose signalling pathway in duodenum myocytes. J Cell Sci 2005; 118:2261-70. [PMID: 15870112 DOI: 10.1242/jcs.02344] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this study, we characterized the signalling pathway activated by acetylcholine that encodes Ca2+ oscillations in rat duodenum myocytes. These oscillations were observed in intact myocytes after removal of external Ca2+, in permeabilized cells after abolition of the membrane potential and in the presence of heparin (an inhibitor of inositol 1,4,5-trisphosphate receptors) but were inhibited by ryanodine, indicating that they are dependent on Ca2+ release from intracellular stores through ryanodine receptors. Ca2+ oscillations were selectively inhibited by methoctramine (a M2 muscarinic receptor antagonist). The M2 muscarinic receptor-activated Ca2+ oscillations were inhibited by 8-bromo cyclic adenosine diphosphoribose and inhibitors of adenosine diphosphoribosyl cyclase (ZnCl2 and anti-CD38 antibody). Stimulation of ADP-ribosyl cyclase activity by acetylcholine was evaluated in permeabilized cells by measuring the production of cyclic guanosine diphosphoribose (a fluorescent compound), which resulted from the cyclization of nicotinamide guanine dinucleotide. As duodenum myocytes expressed the three subtypes of ryanodine receptors, an antisense strategy revealed that the ryanodine receptor subtype 2 alone was required to initiate the Ca2+ oscillations induced by acetylcholine and also by cyclic adenosine diphosphoribose and rapamycin (a compound that induced uncoupling between 12/12.6 kDa FK506-binding proteins and ryanodine receptors). Inhibition of cyclic adenosine diphosphoribose-induced Ca2+ oscillations, after rapamycin treatment, confirmed that both compounds interacted with the ryanodine receptor subtype 2. Our findings show for the first time that the M2 muscarinic receptor activation triggered Ca2+ oscillations in duodenum myocytes by activation of the cyclic adenosine diphosphoribose/FK506-binding protein/ryanodine receptor subtype 2 signalling pathway.
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Affiliation(s)
- Nicolas Fritz
- Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017, Université Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France
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Abstract
Intracellular calcium release channels are present on sarcoplasmic and endoplasmic reticuli (SR, ER) of all cell types. There are two classes of these channels: ryanodine receptors (RyR) and inositol 1,4,5-trisphosphate receptors (IP3R). RyRs are required for excitation-contraction (EC) coupling in striated (cardiac and skeletal) muscles. RyRs are made up of macromolecular signaling complexes that contain large cytoplasmic domains, which serve as scaffolds for proteins that regulate the function of the channel. These regulatory proteins include calstabin1/calstabin2 (FKBP12/FKBP12.6), a 12/12.6 kDa subunit that stabilizes the closed state of the channel and prevents aberrant calcium leak from the SR. Kinases and phosphatases are targeted to RyR2 channels and modulate RyR2 function in response to extracellular signals. In the classic fight or flight stress response, phosphorylation of RyR channels by protein kinase A reduces the affinity for calstabin and activates the channels leading to increased SR calcium release. In heart failure, a cardiac insult causes a mismatch between blood supply and metabolic demands of organs. The chronically activated fight or flight response leads to leaky channels, altered calcium signaling, and contractile dysfunction and cardiac arrhythmias.
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Affiliation(s)
- Xander H T Wehrens
- Department of Physiology and Cellular Biophysics, Center for Molecular Cardiology, Department of Medicine, Columbia University College of Physicians and Surgeons, New York 10032, USA.
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42
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Yoshihara S, Satoh H, Saotome M, Katoh H, Terada H, Watanabe H, Hayashi H. Modification of sarcoplasmic reticulum (SR) Ca2+release by FK506 induces defective excitation-contraction coupling only when SR Ca2+recycling is disturbed. Can J Physiol Pharmacol 2005; 83:357-66. [PMID: 15877110 DOI: 10.1139/y05-020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined whether the effects of FK506-binding protein dissociation from sarcoplasmic reticulum (SR) Ca2+release channels on excitation-contraction (EC) coupling changed when SR Ca2+reuptake and (or) the trans-sarcolemmal Ca2+extrusion were altered. The steady-state twitch Ca2+transient (CaT), cell shortening, post-rest caffeine-induced CaT, and Ca2+sparks were measured in rat ventricular myocytes using laser-scanning confocal microscopy. In the normal condition, 50 µmol FK506/L significantly increased steady-state CaT, cell shortening, and post-rest caffeine-induced CaT. When the cells were solely perfused with thapsigargin, FK506 did not reduce any of the states, but when low [Ca2+]0(0.1 mmol/L) was perfused additionally, FK506 reduced CaT and cell shortening, and accelerated the reduction of post-rest caffeine-induced CaT. FK506 significantly increased Ca2+spark frequency in the normal condition, whereas it mainly prolonged duration of individual Ca2+sparks under the combination of thapsigargin and low [Ca2+]0perfusion. Modification of SR Ca2+release by FK506 impaired EC coupling only when released Ca2+could not be taken back into the SR and was readily extruded to the extracellular space. Our findings could partly explain the controversy regarding the contribution of FK506-binding protein dissociation to defective EC coupling.Key words: FK506, ryanodine receptor, sarcoplasmic reticulum Ca2+-ATPase, Na+/Ca2+exchange, excitation-contraction coupling
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Affiliation(s)
- Shu Yoshihara
- Division of Cardiology, Internal Medicine III, Hamamatsu University of School of Medicine, Japan
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43
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Fauconnier J, Lacampagne A, Rauzier JM, Fontanaud P, Frapier JM, Sejersted OM, Vassort G, Richard S. Frequency-dependent and proarrhythmogenic effects of FK-506 in rat ventricular cells. Am J Physiol Heart Circ Physiol 2005; 288:H778-86. [PMID: 15471978 DOI: 10.1152/ajpheart.00542.2004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
FK-506, a widely used immunosuppressant, has caused a few clinical cases with QT prolongation and torsades de pointe at high blood concentration. The proarrhytmogenic potential of FK-506 was investigated in single rat ventricular cells using the whole cell clamp method to record action potentials (APs) and ionic currents. Fluorescence measurements of Ca2+ transients were performed with indo-1 AM using a multiphotonic microscope. FK-506 (25 μmol/l) hyperpolarized the resting membrane potential (RMP; −3 mV) and prolonged APs (AP duration at 90% repolarization increased by 21%) at 0.1 Hz. Prolongation was enhanced by threefold at 3.3 Hz, and early afterdepolarizations (EADs) occurred in 59% of cells. EADs were prevented by stronger intracellular Ca2+ buffering (EGTA: 10 vs. 0.5 mmol/l in the patch pipette) or replacement of extracellular Na+ by Li+, which abolishes Na+/Ca2+ exchange [Na+/Ca2+ exchanger current ( INaCa)]. In indo-1-loaded cells, FK-506 generated doublets of Ca2+ transients associated with increased diastolic Ca2+ in one-half of the cells. FK-506 reversibly decreased the L-type Ca2+ current ( ICaL) by 25%, although high-frequency-dependent facilitation of ICaL persisted, and decreased three distinct K+ currents: delayed rectifier K+ current ( IK; >80%), transient outward K+ current (<20%), and inward rectifier K+ current ( IK1; >40%). A shift in the reversal potential of IK1 (−5 mV) accounted for RMP hyperpolarization. Numerical simulations, reproducing all experimental effects of FK-506, and the use of nifedipine showed that frequency-dependent facilitation of ICaL plays a role in the occurrence of EADs. In conclusion, the effects of FK-506 on the cardiac AP are more complex than previously reported and include inhibitions of IK1 and ICaL. Alterations in Ca2+ release and INaCa may contribute to FK-506-induced AP prolongation and EADs in addition to the permissive role of ICaL facilitation at high rates of stimulation.
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Affiliation(s)
- Jérémy Fauconnier
- Physiolpatholgie Cardiovascularie, Institut National de la Santé et de la Recherche Médicale U-637, Université Montpellier 1, Montpellier, France
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44
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Lehnart SE, Wehrens XHT, Marks AR. Calstabin deficiency, ryanodine receptors, and sudden cardiac death. Biochem Biophys Res Commun 2004; 322:1267-79. [PMID: 15336974 DOI: 10.1016/j.bbrc.2004.08.032] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Indexed: 11/28/2022]
Abstract
Altered cardiac ryanodine receptor (RyR2) function has an important role in heart failure and genetic forms of arrhythmias. RyR2 constitutes the major intracellular Ca2+ release channel in the cardiac sarcoplasmic reticulum (SR). The peptidyl-prolyl isomerase calstabin2 (FKBP12.6) is a component of the RyR2 macromolecular signaling complex. Calstabin2 binding to RyR2 is regulated by PKA phosphorylation of Ser2809 in RyR2. PKA phosphorylation of RyR2 decreases the binding affinity for calstabin2 and increases RyR2 open probability and sensitivity to Ca2+-dependent activation. In heart failure, a majority of studies have found that RyR2 becomes chronically PKA hyper-phosphorylated which depletes calstabin2 from the channel complex. Calstabin2 dissociation causes a diastolic SR Ca2+ leak contributing to depressed intracellular Ca2+ cycling and decreased cardiac contractility. Missense mutations linked to genetic forms of exercise-induced arrhythmias and sudden cardiac death also cause decreased calstabin2-binding affinity and leaky RyR2 channels. We review the importance of calstabin2 for RyR2 function and excitation-contraction coupling, and discuss new observations that implicate dysregulation of calstabin2 binding as a central mechanism for abnormal calcium cycling in heart failure and triggered arrhythmias.
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Affiliation(s)
- Stephan E Lehnart
- Department of Physiology and Cellular Biophysics, Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, 630W 168th Street, P&S 9-401, New York, NY 10032, USA.
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45
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Gómez AM, Schuster I, Fauconnier J, Prestle J, Hasenfuss G, Richard S. FKBP12.6 overexpression decreases Ca2+ spark amplitude but enhances [Ca2+]i transient in rat cardiac myocytes. Am J Physiol Heart Circ Physiol 2004; 287:H1987-93. [PMID: 15271664 DOI: 10.1152/ajpheart.00409.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ryanodine receptors/Ca2+-release channels (RyR2) from the sarcoplasmic reticulum (SR) provide the Ca2+ required for contraction at each cardiac twitch. RyR2 are regulated by a variety of proteins, including the immunophilin FK506 binding protein (FKBP12.6). FKBP12.6 seems to be important for coupled gating of RyR2 and its deficit and alteration may be involved in heart failure. The role of FKBP12.6 on Ca2+ release has not been analyzed directly, but rather it was inferred from the effects of immunophilins, such us FK506 and rapamycin, which, among other effects, dissociates FKBP12.6 from the RyR2. Here, we investigated directly the effects of FKBP12.6 on local (Ca2+ sparks) and global {intracellular Ca2+ concentration ([Ca2+]i) transients} Ca2+ release in single rat cardiac myocytes. The FKBP12.6 gene was transfected in single myocytes using the adenovirus technique with a reporter gene strategy based on green fluorescent protein (GFP) to check out the success of transfections. Control myocytes were transfected with only GFP (Ad-GFP). Rhod-2 was used as the Ca2+ indicator, and cells were viewed with a confocal microscope. We found that overexpression of FKBP12.6 decreases the occurrence, amplitude, duration, and width of spontaneous Ca2+ sparks. FK506 had diametrically opposed effects. However, overexpression of FKBP12.6 increased the [Ca2+]i transient amplitude and accelerated its decay in field-stimulated cells. The associated cell shortening was increased. SR Ca2+ load, estimated by rapid caffeine application, was increased. In conclusion, FKBP12.6 overexpression decreases spontaneous Ca2+ sparks but increases [Ca2+]i transients, in relation with enhanced SR Ca2+ load, therefore improving excitation-contraction coupling.
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Affiliation(s)
- Ana M Gómez
- Institut National de la Santé et de la Recherche Médicale U-637, Centre Hospitalier Universitaire Arnaud de Villeneuve, 34295 Montpellier, France
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46
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Van Acker K, Bultynck G, Rossi D, Sorrentino V, Boens N, Missiaen L, De Smedt H, Parys JB, Callewaert G. The 12 kDa FK506-binding protein, FKBP12, modulates the Ca(2+)-flux properties of the type-3 ryanodine receptor. J Cell Sci 2004; 117:1129-37. [PMID: 14970260 DOI: 10.1242/jcs.00948] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have characterised the functional regulation of the type-3 ryanodine receptor by the 12 kDa FK506-binding protein. Wild-type type-3 ryanodine receptor and mutant type-3 ryanodine receptor in which the critical valine at position 2322 in the central 12 kDa FK506-binding protein binding site was substituted by aspartate, were stably expressed in human embryonic kidney cells. In contrast to the wild-type receptor, the mutant receptor was strongly impaired in binding to immobilised glutathione S-transferase 12 kDa FK506-binding protein. Caffeine-induced 45Ca(2+)-efflux was markedly increased in cells expressing mutant type-3 ryanodine receptor whereas the maximal-releasable Ca2+ was not affected. Confocal Ca2+ imaging provided clear evidence for a much higher sensitivity of the mutant receptor, which showed global Ca2+ release at about 20-fold lower caffeine concentrations than the wild-type receptor. Spontaneous Ca2+ sparks were observed in both wild-type- and mutant-expressing cells but the number of sparking cells was about 1.5-fold higher in the mutant group, suggesting that the degree of FK506 binding controls the stability of the closed state of ryanodine receptor channels. Furthermore, overexpression of 12 kDa FK506-binding protein decreased the number of sparking cells in the wild-type-expressing cells whereas it did not affect the number of sparking cells in cells expressing the mutant receptor. Concerning spark properties, the amplitude and duration of Ca2+ sparks mediated by mutant channels were significantly reduced in comparison to wild-type channels. This suggests that functional coupling between different mutant type-3 ryanodine receptor channels in a cluster is impaired. Our findings show for the first time that the central binding site for the 12 kDa FK506-binding protein of type-3 ryanodine receptor, encompassing the critical valine proline motif, plays a crucial role in the modulation of the Ca2+ release properties of the type-3 ryanodine receptor channel, including the regulation of both global Ca2+ responses and spontaneous Ca2+ sparks.
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Affiliation(s)
- Kristel Van Acker
- Laboratorium voor Fysiologie, Campus Gasthuisberg O/N, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
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47
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Loughrey CM, Seidler T, Miller SLW, Prestle J, MacEachern KE, Reynolds DF, Hasenfuss G, Smith GL. Over-expression of FK506-binding protein FKBP12.6 alters excitation-contraction coupling in adult rabbit cardiomyocytes. J Physiol 2004; 556:919-34. [PMID: 14966299 PMCID: PMC1665006 DOI: 10.1113/jphysiol.2003.057166] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study investigated the function of FK506-binding protein (FKBP12.6) using adenoviral-mediated gene transfer to over-express FKBP12.6 (Ad-FKBP12.6) in adult rabbit ventricular cardiomyocytes. Infection with a beta-galactosidase-expressing adenovirus (Ad-LacZ) was used as a control. Peak-systolic intracellular [Ca(2+)] (measured with Fura-2) was higher in the Ad-FKBP12.6 group compared to Ad-LacZ (1 Hz field stimulation at 37 degrees C). The amplitude of caffeine-induced Ca(2+) release was also greater, indicating a higher SR Ca(2+) content in the Ad-FKBP12.6 group. Voltage clamp experiments indicated that FKBP12.6 over-expression did not change L-type Ca(2+) current amplitude or Ca(2+) efflux rates via the Na(+)-Ca(2+) exchanger. Ca(2+) transients comparable to those after Ad-FKBP12.6 transfection could be obtained by enhancing SR Ca(2+) content of Ad-LacZ infected cells with periods of high frequency stimulation. Line-scan confocal microscopy (Fluo-3 fluorescence) of intact cardiomyocytes stimulated at 0.5 Hz (20-21 degrees C) revealed a higher degree of synchronicity of SR Ca(2+) release and fewer non-responsive Ca(2+) release sites in the Ad-FKBP12.6 group compared to control. Ca(2+) spark morphology was measured in beta-escin-permeabilized cardiomyocytes at a free [Ca(2+)](i) of 150 nm. The average values of the spark parameters (amplitude, duration, width and frequency) were reduced in the Ad-FKBP12.6 group. Increasing [Ca(2+)](i) to 400 nm caused coherent propagating Ca(2+) waves in the Ad-FKBP12.6 group but only limited Ca(2+) release events were recorded in the control group. These data indicate that FKBP12.6 over-expression enhances Ca(2+) transient amplitude predominately by increasing SR Ca(2+) content. Moreover, there is also evidence that FKBP12.6 can enhance the coupling between SR Ca(2+) release sites independently of SR content.
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Affiliation(s)
- C M Loughrey
- Institute of Comparative Medicine, University of Glasgow Veterinary School, University of Glasgow, Glasgow G61 1QH, UK
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48
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Tavi P, Pikkarainen S, Ronkainen J, Niemelä P, Ilves M, Weckström M, Vuolteenaho O, Bruton J, Westerblad H, Ruskoaho H. Pacing-induced calcineurin activation controls cardiac Ca2+ signalling and gene expression. J Physiol 2004; 554:309-20. [PMID: 14565991 PMCID: PMC1664772 DOI: 10.1113/jphysiol.2003.053579] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Accepted: 10/16/2003] [Indexed: 12/19/2022] Open
Abstract
Calcineurin, a Ca(2+)-calmodulin-dependent protein phosphatase (PP2B) is one of the links between Ca(2+) signals and regulation of gene transcription in cardiac muscle. We studied the Ca(2+) signal specificity of calcineurin activation experimentally and with modelling. In the rat atrial preparation, an increase in pacing frequency increased nuclear activity of the calcineurin-sensitive transcription factor, nuclear factor of activated T-cells (NFAT), 2-fold in a cyclosporin A (CsA)-sensitive manner. In line with this, modelling results predicted that the frequency of cardiac Ca(2+) transients encodes the stimulus for calcineurin activation. We further observed experimentally that calcineurin inhibition by CsA modulated Ca(2+) release in a Ca(2+)-dependent manner. CsA had no effect on [Ca(2+)](i) at a pacing frequency of 1 Hz but it significantly suppressed the amplitude of Ca(2+) transients, systolic [Ca(2+)](i) and time averaged [Ca(2+)](i) at 6 Hz. Calcineurin had a differential role in the expression of immediate-early genes B-type natriuretic peptide (BNP) and c-fos. CsA inhibited the pacing-induced BNP gene expression, whereas pacing alone had no effect on the expression of c-fos. However, in the presence of CsA, c-fos mRNA levels were significantly augmented by increased pacing frequency. These results show that frequency-dependent calcineurin activation has a specific role in [Ca(2+)](i) regulation and gene expression, constantly recruited by varying cardiac Ca(2+) signals.
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Affiliation(s)
- Pasi Tavi
- Department of Physiology, Biocentre Oulu, University of Oulu, Finland.
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49
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Wang YX, Zheng YM, Mei QB, Wang QS, Collier ML, Fleischer S, Xin HB, Kotlikoff MI. FKBP12.6 and cADPR regulation of Ca2+ release in smooth muscle cells. Am J Physiol Cell Physiol 2003; 286:C538-46. [PMID: 14592808 DOI: 10.1152/ajpcell.00106.2003] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intracellular Ca2+ release through ryanodine receptors (RyRs) plays important roles in smooth muscle excitation-contraction coupling, but the underlying regulatory mechanisms are poorly understood. Here we show that FK506 binding protein of 12.6 kDa (FKBP12.6) associates with and regulates type 2 RyRs (RyR2) in tracheal smooth muscle. FKBP12.6 binds to RyR2 but not other RyR or inositol 1,4,5-trisphosphate receptors, and FKBP12, known to bind to and modulate skeletal RyRs, does not associate with RyR2. When dialyzed into tracheal myocytes, cyclic ADP-ribose (cADPR) alters spontaneous Ca2+ release at lower concentrations and produces macroscopic Ca2+ release at higher concentrations; neurotransmitter-evoked Ca2+ release is also augmented by cADPR. These actions are mediated through FKBP12.6 because they are inhibited by molar excess of recombinant FKBP12.6 and are not observed in myocytes from FKBP12.6-knockout mice. We also report that force development in FKBP12.6-null mice, observed as a decrease in the concentration/tension relationship of isolated trachealis segments, is impaired. Taken together, these findings point to an important role of the FKBP12.6/RyR2 complex in stochastic (spontaneous) and receptor-mediated Ca2+ release in smooth muscle.
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Affiliation(s)
- Yong-Xiao Wang
- Center for Cardiovascular Sciences, Albany Medical College, Albany, New York 12208, USA.
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50
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Su Z, Sugishita K, Li F, Ritter M, Barry WH. Effects of FK506 on [Ca2+]i differ in mouse and rabbit ventricular myocytes. J Pharmacol Exp Ther 2003; 304:334-41. [PMID: 12490609 DOI: 10.1124/jpet.102.041210] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
FK506 binding proteins (FKBPs 12 and 12.6) interact with ryanodine receptor (RyR) and modulate its functions. FK506 binds to and reverses effects of FKBP on RyR, thus increasing RyR sensitivity to Ca2+, decreasing RyR cooperativity, and increasing RyR open probability. FK506 would thus be expected to have an effect on excitation-contraction coupling, but which of these FK506 effects predominates and how the [Ca2+]i transient would be altered are difficult to predict. FK506 has been reported to increase the [Ca2+]i transient in rat myocytes, but effects in other species have not been described. We compared the effects of FK506 on [Ca2+]i transients, L-type Ca2+ channel and Na/Ca exchange currents, membrane potential, and sarcoplasmic reticulum (SR) Ca2+ content in adult mouse and rabbit ventricular myocytes (VM). FK506 (10 microM) increased the [Ca2+]i transient in mouse VM (656 +/- 116 to 945 +/- 144 nM, p < 0.001) but decreased the amplitude of [Ca2+]i transients in rabbit VM (627 +/- 61 to 401 +/- 37 nM, p < 0.001). Similar effects were observed with rapamycin. The effects of FK506 and rapamycin on [Ca2+]i transients in VM of both species were reversible upon washout. FK506 did not alter SR Ca2+ content in mouse VM (0.79 +/- 0.1 versus 0.78 +/- 0.1 pC/pF) but reduced the SR Ca2+ content in rabbit VM (0.43 +/- 0.05 versus 0.30 +/- 0.04 pC/pF, P < 0.05) [pC = the integral (pA. s) of the caffeine-induced inward I(Na/Ca) normalized by cell capacitance (pF)]. FK506 had no effects on membrane potential, I(Ca,L) and outward I(Na/Ca) in either mouse or rabbit VM. These results indicate that alteration of the functions of RyR by FK506-mediated dissociation of FKBP from RyR has different species-dependent effects on SR Ca2+ load and thus [Ca2+]i transients. This difference may result from the fact that [Na+]i is low in rabbit myocytes, allowing extrusion by Na+/Ca2+ exchange of Ca2+ released by FK506-induced dissociation of FKBP12.6 from SR RyR.
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Affiliation(s)
- Zhi Su
- Cardiology Division, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA
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