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Le Ribeuz H, Masson B, Capuano V, Dutheil M, Gooroochurn H, Boët A, Ghigna MR, De Montpreville V, Girerd B, Lambert M, Mercier O, Chung WK, Humbert M, Montani D, Antigny F. SUR1 as a New Therapeutic Target for Pulmonary Arterial Hypertension. Am J Respir Cell Mol Biol 2022; 66:539-554. [PMID: 35175177 DOI: 10.1165/rcmb.2021-0180oc] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Mutations in ABCC8 have been identified in pulmonary arterial hypertension (PAH). ABCC8 encodes SUR1, a regulatory subunit of the ATP-sensitive-potassium channel Kir6.2. However, the pathophysiological role of the SUR1/Kir6.2 channel in PAH is unknown. We hypothesized that activation of SUR1 could be a novel potential target for PAH. We analysed the expression of SUR1/Kir6.2 in the lungs and pulmonary artery (PA) in human PAH or experimental pulmonary hypertension (PH). The contribution of SUR1 in human or rat PA tone was evaluated, and we measured the consequences of in vivo activation of SUR1 in control and PH rats. SUR1 and Kir6.2 protein expression was not reduced in the lungs or human pulmonary arterial endothelial cells and smooth muscle cells (hPAECs and hPASMCs) from PAH or experimentally induced PH. We showed that pharmacological activation of SUR1 by 3 different SUR1 activators (diazoxide, VU0071063, and NN414) leads to PA relaxation. Conversely, the inhibition of SUR1/Kir6.2 channels causes PA constriction. In vivo, long- and short-term activation of SUR1 with diazoxide reversed monocrotaline-induced PH in rats. Additionally, in vivo diazoxide application (short protocol) reduced the severity of PH in chronic-hypoxia rats. Moreover, 3 weeks of diazoxide exposure in control rats had no cardiovascular effects. Finally, in vivo, activation of SUR1 with NN414 reduced monocrotaline-induced PH in rats. In PAH and experimental PH, the expression of SUR1/Kir6.2 was still presented. In vivo pharmacological SUR1 activation by two different molecules alleviated experimental PH, providing proof-of-concept that SUR1 activation should be considered for PAH and evaluated more thoroughly.
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Affiliation(s)
| | | | | | - Mary Dutheil
- INSERM U999, 130034, Le Plessis Robinson, France
| | | | - Angèle Boët
- INSERM U999, 130034, Le Plessis Robinson, France
| | - Maria-Rosa Ghigna
- INSERM UMR_S 999, Hôpital Marie Lannelongue, Le Plessis-Robinson, France.,School of Medicine, Université Paris-Sud / Université Paris Saclay, Le Kremlin-Bicêtre, France
| | | | - Barbara Girerd
- INSERM U999, 130034, pneumolgie, Le Plessis Robinson, France
| | - Mélanie Lambert
- INSERM UMR_S 999, Pulmonary Hypertension: Pathophysiology and Novel Therapies, Hôpital Marie Lannelongue, Le Plessis-Robinson, France
| | - Olaf Mercier
- INSERM U999, 130034, Thoracic Surgery , Le Plessis Robinson, France
| | - Wendy K Chung
- Departments of Pediatrics and Medicine Columbia University, New York, New York, United States
| | - Marc Humbert
- INSERM U999, 130034, Le Plessis Robinson, France
| | - David Montani
- CHU de Bicetre, Service de Pneumologie, Le Kremlin Bicetre, France.,INSERM UMRS 999, Hôpital Marie Lannelongue, Le plessis robinson, France
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2
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Huang Y, Hu D, Huang C, Nichols CG. Genetic Discovery of ATP-Sensitive K + Channels in Cardiovascular Diseases. Circ Arrhythm Electrophysiol 2020; 12:e007322. [PMID: 31030551 DOI: 10.1161/circep.119.007322] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ATP-sensitive K+ (KATP) channels are hetero-octameric protein complexes comprising 4 pore-forming (Kir6.x) subunits and 4 regulatory sulfonylurea receptor (SURx) subunits. They are prominent in myocytes, pancreatic β cells, and neurons and link cellular metabolism with membrane excitability. Using genetically modified animals and genomic analysis in patients, recent studies have implicated certain ATP-sensitive K+ channel subtypes in physiological and pathological processes in a variety of cardiovascular diseases. In this review, we focus on the causal relationship between ATP-sensitive K+ channel activity and pathophysiology in the cardiovascular system, particularly from the perspective of genetic changes in human and animal models.
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Affiliation(s)
- Yan Huang
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Congxin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University; Cardiovascular Research Institute, Wuhan University, PR China (Y.H., D.H., C.H.).,Hubei Key Laboratory of Cardiology, Wuhan, PR China (Y.H., D.H., C.H.)
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases and Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO (C.G.N.)
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3
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Bohnen MS, Ma L, Zhu N, Qi H, McClenaghan C, Gonzaga-Jauregui C, Dewey FE, Overton JD, Reid JG, Shuldiner AR, Baras A, Sampson KJ, Bleda M, Hadinnapola C, Haimel M, Bogaard HJ, Church C, Coghlan G, Corris PA, Eyries M, Gibbs JSR, Girerd B, Houweling AC, Humbert M, Guignabert C, Kiely DG, Lawrie A, MacKenzie Ross RV, Martin JM, Montani D, Peacock AJ, Pepke-Zaba J, Soubrier F, Suntharalingam J, Toshner M, Treacy CM, Trembath RC, Vonk Noordegraaf A, Wharton J, Wilkins MR, Wort SJ, Yates K, Gräf S, Morrell NW, Krishnan U, Rosenzweig EB, Shen Y, Nichols CG, Kass RS, Chung WK. Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension. CIRCULATION. GENOMIC AND PRECISION MEDICINE 2018; 11:e002087. [PMID: 30354297 PMCID: PMC6206877 DOI: 10.1161/circgen.118.002087] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 08/01/2018] [Indexed: 11/16/2022]
Abstract
BACKGROUND In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, because of mutations in KCNK3, was identified as a genetic cause and pharmacological target. METHODS Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult-onset group I PAH patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult-onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis. RESULTS We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes SUR1 (sulfonylurea receptor 1)-a regulatory subunit of the ATP-sensitive potassium channel. We observed loss of ATP-sensitive potassium channel function for all ABCC8 variants evaluated and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide. CONCLUSIONS Novel and rare missense variants in ABCC8 are associated with PAH. Identified ABCC8 mutations decreased ATP-sensitive potassium channel function, which was pharmacologically recovered.
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Affiliation(s)
- Michael S. Bohnen
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Lijiang Ma
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Na Zhu
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Hongjian Qi
- Dept of Applied Physics & Applied Mathematics, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Conor McClenaghan
- Dept of Cell Biology & Physiology, and the Centre for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Washington University in St Louis, St Louis, MO
| | | | | | - John D. Overton
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Jeffrey G. Reid
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Alan R. Shuldiner
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Aris Baras
- Regeneron Genetics Center, Regeneron Pharmaceuticals Inc. Tarrytown, NY
| | - Kevin J. Sampson
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Marta Bleda
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Charaka Hadinnapola
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Matthias Haimel
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | | | - Colin Church
- Golden Jubilee National Hospital, Glasgow, Scotland
| | | | - Paul A. Corris
- Newcastle University & The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
| | - Mélanie Eyries
- Dépt de génétique, hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, and UMR_S 1166-ICAN, INSERM, UPMC Sorbonne Universités, Paris, France
| | - J. Simon R. Gibbs
- National Heart & Lung Institute, Imperial College London, United Kingdom
| | - Barbara Girerd
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | - Marc Humbert
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | - Christophe Guignabert
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | - Allan Lawrie
- Dept of Infection, Immunity & Cardiovascular Disease, University of Sheffield
| | | | - Jennifer M. Martin
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - David Montani
- Université Paris-Sud, Faculté de Médecine, Université Paris-Saclay, AP-HP, Centre de référence de l’hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
| | | | | | - Florent Soubrier
- Dépt de génétique, hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, and UMR_S 1166-ICAN, INSERM, UPMC Sorbonne Universités, Paris, France
| | | | - Mark Toshner
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
- Papworth Hospital, Cambridge
| | - Carmen M. Treacy
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Richard C. Trembath
- Division of Genetics & Molecular Medicine, King’s College, London, Hammersmith Campus, London
| | | | - John Wharton
- Dept of Medicine, Imperial College London, Hammersmith Campus, London
| | - Martin R. Wilkins
- Dept of Medicine, Imperial College London, Hammersmith Campus, London
| | - Stephen J. Wort
- National Heart & Lung Institute, Imperial College London, United Kingdom
- Royal Brompton Hospital, London, United Kingdom
| | - Katherine Yates
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Stefan Gräf
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
- Dept of Haematology, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Nicholas W. Morrell
- Dept of Medicine, University of Cambridge, Addenbrookes Hospital, Hills Road, Cambridge, United Kingdom
| | - Usha Krishnan
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Erika B. Rosenzweig
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
| | - Yufeng Shen
- Dept of Applied Physics & Applied Mathematics, Columbia University, New York, NY
- Dept of Systems Biology, Columbia University, New York, NY
| | - Colin G. Nichols
- Dept of Cell Biology & Physiology, and the Centre for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Washington University in St Louis, St Louis, MO
| | - Robert S. Kass
- Dept of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY
| | - Wendy K. Chung
- Dept of Pediatrics, College of Physicians & Surgeons, Columbia University, New York, NY
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4
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Watanabe Y, Kishimoto T, Miki T, Seino S, Nakaya H, Matsumoto A. Ectopic overexpression of Kir6.1 in the mouse heart impacts on the life expectancy. Sci Rep 2018; 8:11723. [PMID: 30082733 PMCID: PMC6078942 DOI: 10.1038/s41598-018-30175-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 07/24/2018] [Indexed: 12/28/2022] Open
Abstract
We recently reported the reduced ATP-sensitive potassium (KATP) channel activities in the transgenic mouse heart overexpressing the vascular type KATP channel pore-forming subunit (Kir6.1). Although dysfunction of cardiac KATP channel has been nominated as a cause of cardiomyopathy in human, these transgenic mice looked normal as wild-type (WT) during the experiment period (~20 weeks). Extended observation period revealed unexpected deaths beginning from 30 weeks and about 50% of the transgenic mice died by 55 weeks. Surface ECG recordings from the transgenic mice at rest demonstrated the normal sinus rhythm and the regular ECG complex as well as the control WT mice except for prolonged QT interval. However, the stress ECG test with noradrenaline revealed abnormal intraventricular conduction delay and arrhythmogeneity in the transgenic mouse. Fibrotic changes in the heart tissue were remarkable in aged transgenic mice, and the cardiac fibrosis developed progressively at least from the age of 30 weeks. Gene expression analyses revealed the differentiation of cardiac fibroblasts to myofibroblasts with elevated cytokine expressions was initiated way in advance before the fibrotic changes and the upregulation of BNP in the ventricle. In sum, Kir6.1TG mice provide an electro-pathological disease concept originated from KATP channel dysfunction.
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Affiliation(s)
- Yasuhiro Watanabe
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takashi Kishimoto
- Department of Molecular Pathology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Takashi Miki
- Department of Medical Physiology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Haruaki Nakaya
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Akio Matsumoto
- Department of Pharmacology, Graduate School of Medicine, Chiba University, Chiba, Japan.
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6
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Nichols CG. Adenosine Triphosphate-Sensitive Potassium Currents in Heart Disease and Cardioprotection. Card Electrophysiol Clin 2016; 8:323-35. [PMID: 27261824 DOI: 10.1016/j.ccep.2016.01.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The subunit makeup of the family of adenosine triphosphate-sensitive potassium channel (KATP) channels is more complex and labile than thought. The growing association of Kir6.1 and SUR2 variants with specific cardiovascular electrical and contractile derangements and the clear association with Cantu syndrome establish the importance of appropriate activity in normal function of the heart and vasculature. Further studies of such patients will reveal new mutations in KATP subunits and perhaps in proteins that regulate KATP synthesis, trafficking, or location, all of which may ultimately benefit therapeutically from the unique pharmacology of KATP channels.
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Affiliation(s)
- Colin G Nichols
- Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO 63110, USA.
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Fatima N, Cohen DC, Sukumar G, Sissung TM, Schooley JF, Haigney MC, Claycomb WC, Cox RT, Dalgard CL, Bates SE, Flagg TP. Histone deacetylase inhibitors modulate KATP subunit transcription in HL-1 cardiomyocytes through effects on cholesterol homeostasis. Front Pharmacol 2015; 6:168. [PMID: 26321954 PMCID: PMC4534802 DOI: 10.3389/fphar.2015.00168] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/27/2015] [Indexed: 11/29/2022] Open
Abstract
Histone deacetylase inhibitors (HDIs) are under investigation for the treatment of a number of human health problems. HDIs have proven therapeutic value in refractory cases of cutaneous T-cell lymphoma. Electrocardiographic ST segment morphological changes associated with HDIs were observed during development. Because ST segment morphology is typically linked to changes in ATP sensitive potassium (KATP) channel activity, we tested the hypothesis that HDIs affect cardiac KATP channel subunit expression. Two different HDIs, romidepsin and trichostatin A, caused ~20-fold increase in SUR2 (Abcc9) subunit mRNA expression in HL-1 cardiomyocytes. The effect was specific for the SUR2 subunit as neither compound causes a marked change in SUR1 (Abcc8) expression. Moreover, the effect was cell specific as neither HDI markedly altered KATP subunit expression in MIN6 pancreatic β-cells. We observe significant enrichment of the H3K9Ac histone mark specifically at the SUR2 promoter consistent with the conclusion that chromatin remodeling at this locus plays a role in increasing SUR2 gene expression. Unexpectedly, however, we also discovered that HDI-dependent depletion of cellular cholesterol is required for the observed effects on SUR2 expression. Taken together, the data in the present study demonstrate that KATP subunit expression can be epigenetically regulated in cardiomyocytes, defines a role for cholesterol homeostasis in mediating epigenetic regulation and suggests a potential molecular basis for the cardiac effects of the HDIs.
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Affiliation(s)
- Naheed Fatima
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Devin C Cohen
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Gauthaman Sukumar
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Tristan M Sissung
- Developmental Therapeutic Branch, National Cancer Institute, National Institutes of Health Bethesda, MD, USA
| | - James F Schooley
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Mark C Haigney
- Department of Medicine, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - William C Claycomb
- Department of Biochemistry and Molecular Biology, LSU Health Sciences Center New Orleans, LA, USA
| | - Rachel T Cox
- Department of Biochemistry, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Clifton L Dalgard
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
| | - Susan E Bates
- Developmental Therapeutic Branch, National Cancer Institute, National Institutes of Health Bethesda, MD, USA
| | - Thomas P Flagg
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences Bethesda, MD, USA
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Zhang HX, Silva JR, Lin YW, Verbsky JW, Lee US, Kanter EM, Yamada KA, Schuessler RB, Nichols CG. Heterogeneity and function of K(ATP) channels in canine hearts. Heart Rhythm 2013; 10:1576-83. [PMID: 23871704 DOI: 10.1016/j.hrthm.2013.07.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Indexed: 01/08/2023]
Abstract
BACKGROUND The concept that pore-forming Kir6.2 and regulatory SUR2A subunits form cardiac ATP-sensitive potassium (K(ATP)) channels is challenged by recent reports that SUR1 is predominant in mouse atrial K(ATP) channels. OBJECTIVE To assess SUR subunit composition of K(ATP) channels and consequence of K(ATP) activation for action potential duration (APD) in dog hearts. METHODS Patch-clamp techniques were used on isolated dog cardiomyocytes to investigate K(ATP) channel properties. Dynamic current clamp, by injection of a linear K(+) conductance to simulate activation of the native current, was used to study the consequences of K(ATP) activation on APD. RESULTS Metabolic inhibitor (MI)-activated current was not significantly different from pinacidil (SUR2A-specific)-activated current, and both currents were larger than diazoxide (SUR1-specific)-activated current in both the atrium and the ventricle. Mean K(ATP) conductance (activated by MI) did not differ significantly between chambers, although, within the ventricle, both MI-induced and pinacidil-induced currents tended to decrease from the epicardium to the endocardium. Dynamic current-clamp results indicate that myocytes with longer baseline APDs are more susceptible to injected K(ATP) current, a result reproduced in silico by using a canine action potential model (Hund-Rudy) to simulate epicardial and endocardial myocytes. CONCLUSIONS Even a small fraction of K(ATP) activation significantly shortens APD in a manner that depends on existing heterogeneity in K(ATP) current and APD.
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Affiliation(s)
- Hai Xia Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
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Abstract
ATP-sensitive potassium (KATP) channels were first discovered in the heart 30 years ago. Reconstitution of KATP channel activity by coexpression of members of the pore-forming inward rectifier gene family (Kir6.1, KCNJ8, and Kir6.2 KCNJ11) with sulfonylurea receptors (SUR1, ABCC8, and SUR2, ABCC9) of the ABCC protein subfamily has led to the elucidation of many details of channel gating and pore properties. In addition, the essential roles of Kir6.x and SURx subunits in generating cardiac and vascular KATP(2) and the detrimental consequences of genetic deletions or mutations in mice have been recognized. However, despite this extensive body of knowledge, there has been a paucity of defined roles of KATP subunits in human cardiovascular diseases, although there are reports of association of a single Kir6.1 variant with the J-wave syndrome in the ECG, and 2 isolated studies have reported association of loss of function mutations in SUR2 with atrial fibrillation and heart failure. Two new studies convincingly demonstrate that mutations in the SUR2 gene are associated with Cantu syndrome, a complex multi-organ disorder characterized by hypertrichosis, craniofacial dysmorphology, osteochondrodysplasia, patent ductus arteriosus, cardiomegaly, pericardial effusion, and lymphoedema. This realization of previously unconsidered consequences provides significant insight into the roles of the KATP channel in the cardiovascular system and suggests novel therapeutic possibilities.
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Affiliation(s)
- Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases and Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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10
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Functional roles of KATP channel subunits in metabolic inhibition. J Mol Cell Cardiol 2013; 62:90-8. [PMID: 23624089 DOI: 10.1016/j.yjmcc.2013.04.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Revised: 03/11/2013] [Accepted: 04/15/2013] [Indexed: 11/23/2022]
Abstract
ATP-sensitive potassium channel (KATP) activation can drastically shorten action potential duration (APD) in metabolically compromised myocytes. We showed previously that SUR1 with Kir6.2 forms the functional channel in mouse atria while Kir6.2 and SUR2A predominate in ventricles. SUR1 is more sensitive to metabolic stress than SUR2A, raising the possibility that KATP in atria and ventricles may respond differently to metabolic stress. Action potential duration (APD) and calcium transient duration (CaTD) were measured simultaneously in both atria and ventricles by optical mapping of the posterior surface of Langendorff-perfused hearts from C57BL wild-type (WT; n=11), Kir6.2(-/-) (n=5), and SUR1(-/-) (n=6) mice during metabolic inhibition (MI, 0mM glucose+2mM sodium cyanide). After variable delay, MI led to significant shortening of APD in WT hearts. On average, atrial APD shortened by 60.5 ± 2.7% at 13.1 ± 2.1 min (n=6, p<0.01) after onset of MI. Ventricular APD shortening (56.4 ± 10.0% shortening at 18.2 ± 1.8 min) followed atrial APD shortening. In SUR1(-/-) hearts (n=6), atrial APD shortening was abolished, but ventricular shortening (65.0 ± 15.4% at 25.33 ± 4.48 min, p<0.01) was unaffected. In Kir6.2(-/-) hearts, two disparate responses to MI were observed; 3 of 5 hearts displayed slight shortening of APD in the ventricles (24 ± 3%, p<0.05) and atria (39.0 ± 1.9%, p<0.05) but this shortening occurred later and to much less extent than in WT (p<0.05). Marked prolongation of ventricular APD was observed in the remaining hearts (327% and 489% prolongation) and was associated with occurrence of ventricular tachyarrhythmias. The results confirm that Kir6.2 contributes to APD shortening in both atria and ventricle during metabolic stress, and that SUR1 is required for atrial APD shortening while SUR2A is required for ventricular APD shortening. Importantly, the results show that the presence of SUR1-dependent KATP in the atria results in the action potential being more susceptible to metabolically driven shortening than the ventricle.
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11
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Toib A, Zhang HX, Broekelmann TJ, Hyrc KL, Guo Q, Chen F, Remedi MS, Nichols CG. Cardiac specific ATP-sensitive K+ channel (KATP) overexpression results in embryonic lethality. J Mol Cell Cardiol 2012; 53:437-45. [PMID: 22796573 PMCID: PMC3423334 DOI: 10.1016/j.yjmcc.2012.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 06/23/2012] [Accepted: 07/02/2012] [Indexed: 11/26/2022]
Abstract
Transgenic mice overexpressing SUR1 and gain of function Kir6.2[∆N30, K185Q] K(ATP) channel subunits, under cardiac α-myosin heavy chain (αMHC) promoter control, demonstrate arrhythmia susceptibility and premature death. Pregnant mice, crossed to carry double transgenic progeny, which harbor high levels of both overexpressed subunits, exhibit the most extreme phenotype and do not deliver any double transgenic pups. To explore the fetal lethality and embryonic phenotype that result from K(ATP) overexpression, wild type (WT) and K(ATP) overexpressing embryonic cardiomyocytes were isolated, cultured and voltage-clamped using whole cell and excised patch clamp techniques. Whole mount embryonic imaging, Hematoxylin and Eosin (H&E) and α smooth muscle actin (αSMA) immunostaining were used to assess anatomy, histology and cardiac development in K(ATP) overexpressing and WT embryos. Double transgenic embryos developed in utero heart failure and 100% embryonic lethality by 11.5 days post conception (dpc). K(ATP) currents were detectable in both WT and K(ATP)-overexpressing embryonic cardiomyocytes, starting at early stages of cardiac development (9.5 dpc). In contrast to adult cardiomyocytes, WT and K(ATP)-overexpressing embryonic cardiomyocytes exhibit basal and spontaneous K(ATP) current, implying that these channels may be open and active under physiological conditions. At 9.5 dpc, live double transgenic embryos demonstrated normal looping pattern, although all cardiac structures were collapsed, probably representing failed, non-contractile chambers. In conclusion, K(ATP) channels are present and active in embryonic myocytes, and overexpression causes in utero heart failure and results in embryonic lethality. These results suggest that the K(ATP) channel may have an important physiological role during early cardiac development.
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Affiliation(s)
- Amir Toib
- Department of Pediatrics, St. Louis, MO, 63110, USA.
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12
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Miura M, Hattori T, Murai N, Nagano T, Nishio T, Boyden PA, Shindoh C. Regional increase in extracellular potassium can be arrhythmogenic due to nonuniform muscle contraction in rat ventricular muscle. Am J Physiol Heart Circ Physiol 2012; 302:H2301-9. [PMID: 22447939 DOI: 10.1152/ajpheart.01161.2011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In the ischemic myocardium, extracellular potassium ([K(+)](o)) increases to ≥20 mmol/l. To determine how lethal arrhythmias occur during ischemia, we investigated whether the increased spatial pattern of [K(+)](o), i.e., a regional or a global increase, affects the incidence of arrhythmias. Force, sarcomere length, membrane potential, and nonuniform intracellular Ca(2+) ([Ca(2+)](i)) were measured in rat ventricular trabeculae. A "regional" or "global" increase in [K(+)](o) was produced by exposing a restricted region of muscle to a jet of 30 mmol/l KCl or by superfusing trabeculae with a solution containing 30 mmol/l KCl, respectively. The increase in [Ca(2+)](i) (Ca(CW)) during Ca(2+) waves was measured (24°C, 3.0 mmol/l [Ca(2+)](o)). A regional increase in [K(+)](o) caused nonuniform [Ca(2+)](i) and contraction. In the presence of isoproterenol, the regional increase in [K(+)](o) induced sustained arrhythmias in 10 of 14 trabeculae, whereas the global increase did not induce such arrhythmias. During sustained arrhythmias, Ca(2+) surged within the jet-exposed region. In the absence of isoproterenol, the regional increase in [K(+)](o) increased Ca(CW), whereas the global increase decreased it. This increase in Ca(CW) with the regional increase in [K(+)](o) was not suppressed by 100 μmol/l streptomycin, whereas it was suppressed by 1) a combination of 10 μmol/l cilnidipine and 3 μmol/l SEA0400; 2) 20 mmol/l 2,3-butanedione monoxime; and 3) 10 μmol/l blebbistatin. A regional but not a global increase in [K(+)](o) induces sustained arrhythmias, probably due to nonuniform excitation-contraction coupling. The same mechanism may underlie arrhythmias during ischemia.
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Affiliation(s)
- Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
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Barajas-Martínez H, Hu D, Ferrer T, Onetti CG, Wu Y, Burashnikov E, Boyle M, Surman T, Urrutia J, Veltmann C, Schimpf R, Borggrefe M, Wolpert C, Ibrahim BB, Sánchez-Chapula JA, Winters S, Haïssaguerre M, Antzelevitch C. Molecular genetic and functional association of Brugada and early repolarization syndromes with S422L missense mutation in KCNJ8. Heart Rhythm 2011; 9:548-55. [PMID: 22056721 DOI: 10.1016/j.hrthm.2011.10.035] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 10/30/2011] [Indexed: 12/18/2022]
Abstract
BACKGROUND Adenosine triphosphate (ATP)-sensitive potassium cardiac channels consist of inward-rectifying channel subunits Kir6.1 or Kir6.2 (encoded by KCNJ8 or KCNJ11) and the sulfonylurea receptor subunits SUR2A (encoded by ABCC9). OBJECTIVE To examine the association of mutations in KCNJ8 with Brugada syndrome (BrS) and early repolarization syndrome (ERS) and to elucidate the mechanism underlying the gain of function of ATP-sensitive potassium channel current. METHODS Direct sequencing of KCNJ8 and other candidate genes was performed on 204 BrS and ERS probands and family members. Whole-cell and inside-out patch-clamp methods were used to study mutated channels expressed in TSA201 cells. RESULTS The same missense mutation, p.Ser422Leu (c.1265C>T) in KCNJ8, was identified in 3 BrS and 1 ERS probands but was absent in 430 alleles from ethnically matched healthy controls. Additional genetic variants included CACNB2b-D601E. Whole-cell patch-clamp studies showed a 2-fold gain of function of glibenclamide-sensitive ATP-sensitive potassium channel current when KCNJ8-S422L was coexpressed with SUR2A-wild type. Inside-out patch-clamp evaluation yielded a significantly greater half maximal inhibitory concentration for ATP in the mutant channels (785.5 ± 2 vs 38.4 ± 3 μM; n = 5; P <.01), pointing to incomplete closing of the ATP-sensitive potassium channels under normoxic conditions. Patients with a CACNB2b-D601E polymorphism displayed longer QT/corrected QT intervals, likely owing to their effect to induce an increase in L-type calcium channel current (I(Ca-L)). CONCLUSIONS Our results support the hypothesis that KCNJ8 is a susceptibility gene for BrS and ERS and point to S422L as a possible hotspot mutation. Our findings suggest that the S422L-induced gain of function in ATP-sensitive potassium channel current is due to reduced sensitivity to intracellular ATP.
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Affiliation(s)
- Hector Barajas-Martínez
- Molecular Genetics Department, Masonic Medical Research Laboratory, Utica, New York 13501, USA
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Nicorandil normalizes prolonged repolarisation in the first transgenic rabbit model with Long-QT syndrome 1 both in vitro and in vivo. Eur J Pharmacol 2010; 650:309-16. [PMID: 20959120 DOI: 10.1016/j.ejphar.2010.10.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 10/05/2010] [Accepted: 10/06/2010] [Indexed: 01/08/2023]
Abstract
Transgenic rabbits expressing loss-of-function pore mutants of the human gene KCNQ1 (K(v)LQT1-Y315S) have a Long QT-Syndrome 1 (LQT1) phenotype. We evaluated for the first time the effect of nicorandil, an opener of ATP-sensitive potassium channels, and of isoproterenol on cardiac action potential duration and heart rate dependent dispersion of repolarisation in transgenic LQT1 rabbits. In vivo LQT1 and littermate control were subjected to transvenous electrophysiological studies; in vitro monophasic action potentials were recorded from explanted Langendorff-perfused hearts. In vivo ventricular effective refractory periods (VERP) at the right ventricular base were significantly prolonged in LQT1 as compared to littermate control, resulting in a more pronounced VERP dispersion in LQT1. This difference in VERP dispersion between LQT1 and littermate control disappeared after infusion of nicorandil. In vitro, mean action potential durations (APD(75) and APD(90)) of LQT1 were significantly prolonged compared to littermate control at baseline. Nicorandil decreased APD(75) and APD(90) in LQT1 and littermate control at all stimulated heart rates. After adding nicorandil, the APD(90) at all hearts rates and the APD(75) at high heart rates were no longer different. Dispersion of repolarisation (∆APD(75) and ∆APD(90)) was heart rate dependently decreased after nicorandil at all tested stimulation cycle lengths only in LQT1. We demonstrated phenotypic differences of LQT1 and littermate control in vivo and in vitro. Nicorandil 20μmol/l improved repolarisation abnormalities and heterogeneities in transgenic LQT1 rabbits.
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Flagg TP, Enkvetchakul D, Koster JC, Nichols CG. Muscle KATP channels: recent insights to energy sensing and myoprotection. Physiol Rev 2010; 90:799-829. [PMID: 20664073 DOI: 10.1152/physrev.00027.2009] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are present in the surface and internal membranes of cardiac, skeletal, and smooth muscle cells and provide a unique feedback between muscle cell metabolism and electrical activity. In so doing, they can play an important role in the control of contractility, particularly when cellular energetics are compromised, protecting the tissue against calcium overload and fiber damage, but the cost of this protection may be enhanced arrhythmic activity. Generated as complexes of Kir6.1 or Kir6.2 pore-forming subunits with regulatory sulfonylurea receptor subunits, SUR1 or SUR2, the differential assembly of K(ATP) channels in different tissues gives rise to tissue-specific physiological and pharmacological regulation, and hence to the tissue-specific pharmacological control of contractility. The last 10 years have provided insights into the regulation and role of muscle K(ATP) channels, in large part driven by studies of mice in which the protein determinants of channel activity have been deleted or modified. As yet, few human diseases have been correlated with altered muscle K(ATP) activity, but genetically modified animals give important insights to likely pathological roles of aberrant channel activity in different muscle types.
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Affiliation(s)
- Thomas P Flagg
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Raeis V, Philip-Couderc P, Roatti A, Habre W, Sierra J, Kalangos A, Beghetti M, Baertschi AJ. Central Venous Hypoxemia Is a Determinant of Human Atrial ATP-Sensitive Potassium Channel Expression. Hypertension 2010; 55:1186-92. [DOI: 10.1161/hypertensionaha.109.148767] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Véronique Raeis
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Pierre Philip-Couderc
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Angela Roatti
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Walid Habre
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Jorge Sierra
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Afksendyios Kalangos
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Maurice Beghetti
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
| | - Alex J. Baertschi
- From the Departments of Neuroscience (V.R., P.P.-C., A.R., A.J.B.), Anaesthesia (W.H.), Surgery (J.S., A.K.), and Child and Adolescent (M.B.), University of Geneva, Geneva, Switzerland
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Glukhov AV, Flagg TP, Fedorov VV, Efimov IR, Nichols CG. Differential K(ATP) channel pharmacology in intact mouse heart. J Mol Cell Cardiol 2010; 48:152-60. [PMID: 19744493 PMCID: PMC2813353 DOI: 10.1016/j.yjmcc.2009.08.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 08/13/2009] [Accepted: 08/29/2009] [Indexed: 11/29/2022]
Abstract
Classically, cardiac sarcolemmal K(ATP) channels have been thought to be composed of Kir6.2 (KCNJ11) and SUR2A (ABCC9) subunits. However, the evidence is strong that SUR1 (sulfonylurea receptor type 1, ABCC8) subunits are also expressed in the heart and that they play a significant functional role in the atria. To examine this further, we have assessed the effects of isotype-specific potassium channel-opening drugs, diazoxide (specific to SUR1>SUR2A) and pinacidil (SUR2A>SUR1), in intact hearts from wild-type mice (WT, n=6), SUR1(-/-) (n=6), and Kir6.2(-/-) mice (n=5). Action potential durations (APDs) in both atria and ventricles were estimated by optical mapping of the posterior surface of Langendorff-perfused hearts. To confirm the atrial effect of both openers, isolated atrial preparations were mapped in both WT (n=4) and SUR1(-/-) (n=3) mice. The glass microelectrode technique was also used to validate optical action potentials. In WT hearts, diazoxide (300 microM) decreased APD in atria (from 33.8+/-1.9 ms to 24.2+/-1.1 ms, p<0.001) but was without effect in ventricles (APD 60.0+/-7.6 ms vs. 60.8+/-7.5 ms, respectively, NS), consistent with an atrial-specific role for SUR1. The absence of SUR1 resulted in loss of efficacy of diazoxide in SUR1(-/-) atria (APD 36.8+/-1.9 ms vs. 36.8+/-2.8 ms, respectively, NS). In contrast, pinacidil (300 microM) significantly decreased ventricular APD in both WT and SUR1(-/-) hearts (from 60.0+/-7.6 ms to 29.8+/-3.5 ms in WT, p<0.001, and from 63.5+/-2.1 ms to 24.8+/-3.8 ms in SUR1(-/-), p<0.001), but did not decrease atrial APD in either WT or SUR1(-/-) hearts. Glibenclamide (10 microM) reversed the effect of pinacidil in ventricles and restored APD to control values. The absence of Kir6.2 subunits in Kir6.2(-/-) hearts resulted in loss of efficacy of both openers (APD 47.2+/-2.2 ms vs. 47.6+/-2.1 ms and 50.8+/-2.4 ms, and 90.6+/-5.7 ms vs. 93.2+/-6.5 ms and 117.3+/-6.4 ms, for atria and ventricle in control versus diazoxide and pinacidil, respectively). Collectively, these results indicate that in the same mouse heart, significant differential K(ATP) pharmacology in atria and ventricles, resulting from SUR1 predominance in forming the atrial channel, leads to differential effects of potassium channel openers on APD in the two chambers.
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Affiliation(s)
- Alexey V. Glukhov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Thomas P. Flagg
- Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO, 63110
| | - Vadim V. Fedorov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Igor R. Efimov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO, 63110
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Cardiac sarcolemmal K(ATP) channels: Latest twists in a questing tale! J Mol Cell Cardiol 2009; 48:71-5. [PMID: 19607836 DOI: 10.1016/j.yjmcc.2009.07.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 06/23/2009] [Accepted: 07/06/2009] [Indexed: 11/24/2022]
Abstract
Reconstitution of K(ATP) channel activity from coexpression of members of the pore-forming inward rectifier gene family (Kir6.1, KCNJ8, and Kir6.2 KCNJ11) with sulfonylurea receptors (SUR1, ABCC8, and SUR2, ABCC9) of the ABCC protein sub-family, has led to the elucidation of many details of channel gating and pore properties, as well as the essential roles of Kir6.2 and SUR2 subunits in generating cardiac ventricular K(ATP). However, despite this extensive body of knowledge, there remain significant holes in our understanding of the physiological role of the cardiac K(ATP) channel, and surprising new findings keep emerging. Recent findings from genetically modified animals include the apparent insensitivity of cardiac sarcolemmal channels to nucleotide levels, and unenvisioned complexities of the subunit make-up of the cardiac channels. This topical review focuses on these new findings and considers their implications.
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19
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Flagg TP, Kurata HT, Masia R, Caputa G, Magnuson MA, Lefer DJ, Coetzee WA, Nichols CG. Differential structure of atrial and ventricular KATP: atrial KATP channels require SUR1. Circ Res 2008; 103:1458-65. [PMID: 18974387 DOI: 10.1161/circresaha.108.178186] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The isoform-specific structure of the ATP-sensitive potassium (K(ATP)) channel endows it with differential fundamental properties, including physiological activation and pharmacology. Numerous studies have convincingly demonstrated that the pore-forming Kir6.2 (KCNJ11) and regulatory SUR2A (ABCC9) subunits are essential elements of the sarcolemmal K(ATP) channel in cardiac ventricular myocytes. Using a novel antibody directed against the COOH terminus of SUR1 (ABCC8), we show that this K(ATP) subunit is also expressed in mouse myocardium and is the dominant SUR isoform in the atrium. This suggests differential sarcolemmal K(ATP) composition in atria and ventricles, and, to test this, K(ATP) currents were measured in isolated atrial and ventricular myocytes from wild-type and SUR1(-/-) animals. K(ATP) conductance is essentially abolished in SUR1(-/-) atrial myocytes but is normal in SUR1(-/-) ventricular myocytes. Furthermore, pharmacological properties of wild-type atrial K(ATP) match closely the properties of heterologously expressed SUR1/Kir6.2 channels, whereas ventricular K(ATP) properties match those of heterologously expressed SUR2A/Kir6.2 channels. Collectively, the data demonstrate a previously unappreciated K(ATP) channel heterogeneity: SUR1 is an essential component of atrial, but not ventricular, K(ATP) channels. Differential molecular make-up of the 2 channels underlies differential pharmacology, with important implications when considering sulfonylurea therapy or dissecting the role of cardiac K(ATP) pharmacologically, as well as for understanding of the role of diazoxide in preconditioning.
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Affiliation(s)
- Thomas P Flagg
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
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20
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Kung FL, Tsai JL, Lee CH, Lou KL, Tang CY, Liou HH, Lu KL, Chen YH, Wang WJ, Tsai MC. Effects of sodium azide, barium ion, d-amphetamine and procaine on inward rectifying potassium channel 6.2 expressed in Xenopus oocytes. J Formos Med Assoc 2008; 107:600-8. [PMID: 18678543 DOI: 10.1016/s0929-6646(08)60177-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/PURPOSE Inward rectifying potassium channel 6.2 (Kir6.2DelataC26 channel) is closely related to ATP-sensitive potassium channels. Whether sodium azide, barium ion, d-amphetamine or procaine acts directly on the Kir6.2DeltaC26 channel remains unclear. We studied the effects of these compounds on Kir6.2DeltaC26 channel expressed in Xenopus oocytes. METHODS The coding sequence of a truncated form of mouse Kir6.2 (GenBank accession number NP_034732.1), Kir6.2(1-364) (i.e. Kir6.2DeltaC26), was subcloned into the pET20b(+) vector. Plasmid containing the correct T7 promoter-Kir6.2(1-364) cDNA fragment [Kir6.2/pET20b(+)] was then subject to NotI digestion to generate the templates for in vitro run-off transcriptions. The channel was expressed in Xenopus laevis oocytes. Two-electrode voltage clamping was used to measure the effects of sodium azide, barium ion, d-amphetamine and procaine on Kir6.2DeltaC26 channel current. RESULTS Sodium azide activated and barium ion and d-amphetamine inhibited the Kir6.2DeltaC26 channel. Procaine did not have any significant effect on the Kir6.2DeltaC26 channel. CONCLUSION Kir6.2DeltaC26 channel expressed in Xenopus oocytes can be used as a pharmacological tool for the study of inward rectifying potassium channels.
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Affiliation(s)
- Fan-Lu Kung
- School of Pharmacy, College of Medicine, National Taiwan University, Taipei, Taiwan
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Billman GE. The cardiac sarcolemmal ATP-sensitive potassium channel as a novel target for anti-arrhythmic therapy. Pharmacol Ther 2008; 120:54-70. [PMID: 18708091 DOI: 10.1016/j.pharmthera.2008.07.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 07/14/2008] [Indexed: 12/25/2022]
Affiliation(s)
- George E Billman
- Department of Physiology and Cell Biology, The Ohio State University, 1645 Neil Avenue, Columbus, OH 43210-1218, USA.
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