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Zhong L, Yan Z, Jiang D, Weng KC, Ouyang Y, Zhang H, Lin X, Xiao C, Yang H, Yao J, Kang X, Wang C, Huang C, Shen B, Chung SK, Jiang ZH, Zhu W, Neher E, Silva JR, Hou P. Targeting the I Ks Channel PKA Phosphorylation Axis to Restore Its Function in High-Risk LQT1 Variants. Circ Res 2024; 135:722-738. [PMID: 39166328 PMCID: PMC11392204 DOI: 10.1161/circresaha.124.325009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Revised: 08/05/2024] [Accepted: 08/09/2024] [Indexed: 08/22/2024]
Abstract
BACKGROUND The KCNQ1+KCNE1 (IKs) potassium channel plays a crucial role in cardiac adaptation to stress, in which β-adrenergic stimulation phosphorylates the IKs channel through the cyclic adenosine monophosphate (cAMP)/PKA (protein kinase A) pathway. Phosphorylation increases the channel current and accelerates repolarization to adapt to an increased heart rate. Variants in KCNQ1 can cause long-QT syndrome type 1 (LQT1), and those with defective cAMP effects predispose patients to the highest risk of cardiac arrest and sudden death. However, the molecular connection between IKs channel phosphorylation and channel function, as well as why high-risk LQT1 mutations lose cAMP sensitivity, remain unclear. METHODS Regular patch clamp and voltage clamp fluorometry techniques were utilized to record pore opening and voltage sensor movement of wild-type and mutant KCNQ1/IKs channels. The clinical phenotypic penetrance of each LQT1 mutation was analyzed as a metric for assessing their clinical risk. The patient-specific-induced pluripotent stem-cell model was used to test mechanistic findings in physiological conditions. RESULTS By systematically elucidating mechanisms of a series of LQT1 variants that lack cAMP sensitivity, we identified molecular determinants of IKs channel regulation by phosphorylation. These key residues are distributed across the N-terminus of KCNQ1 extending to the central pore region of IKs. We refer to this pattern as the IKs channel PKA phosphorylation axis. Next, by examining LQT1 variants from clinical databases containing 10 579 LQT1 carriers, we found that the distribution of the most high-penetrance LQT1 variants extends across the IKs channel PKA phosphorylation axis, demonstrating its clinical relevance. Furthermore, we found that a small molecule, ML277, which binds at the center of the phosphorylation axis, rescues the defective cAMP effects of multiple high-risk LQT1 variants. This finding was then tested in high-risk patient-specific induced pluripotent stem cell-derived cardiomyocytes, where ML277 remarkably alleviates the beating abnormalities. CONCLUSIONS Our findings not only elucidate the molecular mechanism of PKA-dependent IKs channel phosphorylation but also provide an effective antiarrhythmic strategy for patients with high-risk LQT1 variants.
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Affiliation(s)
- Ling Zhong
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Zhenzhen Yan
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Dexiang Jiang
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Kuo-Chan Weng
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO (K.-C.W., J.R.S.)
| | - Yue Ouyang
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Hangyu Zhang
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Xiaoqing Lin
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Chenxin Xiao
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University (H.Y.)
| | - Jing Yao
- State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, TaiKang Center for Life and Medical Sciences, Frontier Science Center for Immunology and Metabolism, Wuhan University, China (J.Y.)
| | - Xinjiang Kang
- Key Laboratory of Medical Electrophysiology, Ministry of Education of China, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease and the Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China (X.K.)
- Department of Neurosurgery, the Affiliated Hospital of Southwest Medical University, Luzhou, China (X.K.)
- College of Life Sciences, Liaocheng University, China (X.K.)
| | - Changhe Wang
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Department of Neurology, First Affiliated Hospital, Neuroscience Research Center, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, China (C.W.)
| | - Chen Huang
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Bing Shen
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Sookja Kim Chung
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Zhi-Hong Jiang
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Wandi Zhu
- Cardiovascular Medicine Division and Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (W.Z.)
| | - Erwin Neher
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
| | - Jonathan R Silva
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO (K.-C.W., J.R.S.)
| | - Panpan Hou
- Dr. Neher's Biophysics Laboratory for Innovative Drug Discovery, State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Taipa, Macao SAR, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
- Macau University of Science and Technology Zhuhai MUST Science and Technology Research Institute. Zhuhai, Guangdong, China (L.Z., Z.Y., D.J., Y.O., H.Z., X.L., C.X., C.H., B.S., S.K.C., Z.-H.J., E.N., P.H.)
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Zhao Z, Zang X, Niu K, Song W, Wang X, Mügge A, Aweimer A, Hamdani N, Zhou X, Zhao Y, Akin I, El-Battrawy I. Impacts of gene variants on drug effects-the foundation of genotype-guided pharmacologic therapy for long QT syndrome and short QT syndrome. EBioMedicine 2024; 103:105108. [PMID: 38653189 PMCID: PMC11041837 DOI: 10.1016/j.ebiom.2024.105108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 03/20/2024] [Accepted: 03/24/2024] [Indexed: 04/25/2024] Open
Abstract
The clinical significance of optimal pharmacotherapy for inherited arrhythmias such as short QT syndrome (SQTS) and long QT syndrome (LQTS) has been increasingly recognised. The advancement of gene technology has opened up new possibilities for identifying genetic variations and investigating the pathophysiological roles and mechanisms of genetic arrhythmias. Numerous variants in various genes have been proven to be causative in genetic arrhythmias. Studies have demonstrated that the effectiveness of certain drugs is specific to the patient or genotype, indicating the important role of gene-variants in drug response. This review aims to summarize the reported data on the impact of different gene-variants on drug response in SQTS and LQTS, as well as discuss the potential mechanisms by which gene-variants alter drug response. These findings may provide valuable information for future studies on the influence of gene variants on drug efficacy and the development of genotype-guided or precision treatment for these diseases.
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Affiliation(s)
- Zhihan Zhao
- Heart Center of Henan Provincial People's Hospital, Central China Fuwai Hospital, Central China Fuwai Hospital of Zhengzhou University, Zhengzhou, Henan, 450003, China
| | - Xiaobiao Zang
- Heart Center of Henan Provincial People's Hospital, Central China Fuwai Hospital, Central China Fuwai Hospital of Zhengzhou University, Zhengzhou, Henan, 450003, China
| | - Kerun Niu
- Department of Orthopaedic, Henan Provincial People's Hospital; Zhengzhou University People's Hospital, Zhengzhou, Henan, 450003, China
| | - Weifeng Song
- Heart Center of Henan Provincial People's Hospital, Central China Fuwai Hospital, Central China Fuwai Hospital of Zhengzhou University, Zhengzhou, Henan, 450003, China
| | - Xianqing Wang
- Heart Center of Henan Provincial People's Hospital, Central China Fuwai Hospital, Central China Fuwai Hospital of Zhengzhou University, Zhengzhou, Henan, 450003, China
| | - Andreas Mügge
- Department of Cardiology and Angiology, Bergmannsheil University Hospitals, Ruhr University of Bochum, 44789, Bochum, Germany
| | - Assem Aweimer
- Institute of Physiology, Department of Cellular and Translational Physiology, Medical Faculty and Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany
| | - Nazha Hamdani
- Institute of Physiology, Department of Cellular and Translational Physiology, Medical Faculty and Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany
- HCEMM-Cardiovascular Research Group, Department of Pharmacology and Pharmacotherapy, University of Budapest, Budapest, Hungary
- Department of Physiology, Cardiovascular Research Institute Maastricht University Maastricht, Maastricht, the Netherlands
| | - Xiaobo Zhou
- Cardiology, Angiology, Haemostaseology, and Medical Intensive Care, Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Heidelberg/Mannheim, Medical Centre Mannheim, Heidelberg University, Germany
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, Sichuan, China
| | - Yonghui Zhao
- Heart Center of Henan Provincial People's Hospital, Central China Fuwai Hospital, Central China Fuwai Hospital of Zhengzhou University, Zhengzhou, Henan, 450003, China
| | - Ibrahim Akin
- Cardiology, Angiology, Haemostaseology, and Medical Intensive Care, Medical Centre Mannheim, Medical Faculty Mannheim, Heidelberg University, Germany
- German Center for Cardiovascular Research (DZHK) Partner Site Heidelberg/Mannheim, Medical Centre Mannheim, Heidelberg University, Germany
| | - Ibrahim El-Battrawy
- Department of Cardiology and Angiology, Bergmannsheil University Hospitals, Ruhr University of Bochum, 44789, Bochum, Germany
- Institute of Physiology, Department of Cellular and Translational Physiology, Medical Faculty and Institut für Forschung und Lehre (IFL), Molecular and Experimental Cardiology, Ruhr University Bochum, Bochum, Germany
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Alam KA, Svalastoga P, Martinez A, Glennon JC, Haavik J. Potassium channels in behavioral brain disorders. Molecular mechanisms and therapeutic potential: A narrative review. Neurosci Biobehav Rev 2023; 152:105301. [PMID: 37414376 DOI: 10.1016/j.neubiorev.2023.105301] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 06/26/2023] [Accepted: 06/30/2023] [Indexed: 07/08/2023]
Abstract
Potassium channels (K+-channels) selectively control the passive flow of potassium ions across biological membranes and thereby also regulate membrane excitability. Genetic variants affecting many of the human K+-channels are well known causes of Mendelian disorders within cardiology, neurology, and endocrinology. K+-channels are also primary targets of many natural toxins from poisonous organisms and drugs used within cardiology and metabolism. As genetic tools are improving and larger clinical samples are being investigated, the spectrum of clinical phenotypes implicated in K+-channels dysfunction is rapidly expanding, notably within immunology, neurosciences, and metabolism. K+-channels that previously were considered to be expressed in only a few organs and to have discrete physiological functions, have recently been found in multiple tissues and with new, unexpected functions. The pleiotropic functions and patterns of expression of K+-channels may provide additional therapeutic opportunities, along with new emerging challenges from off-target effects. Here we review the functions and therapeutic potential of K+-channels, with an emphasis on the nervous system, roles in neuropsychiatric disorders and their involvement in other organ systems and diseases.
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Affiliation(s)
| | - Pernille Svalastoga
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway; Children and Youth Clinic, Haukeland University Hospital, Bergen, Norway
| | | | - Jeffrey Colm Glennon
- Conway Institute for Biomolecular and Biomedical Research, School of Medicine, University College Dublin, Dublin, Ireland.
| | - Jan Haavik
- Department of Biomedicine, University of Bergen, Norway; Division of Psychiatry, Haukeland University Hospital, Norway.
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Zou X, Wu X, Sampson KJ, Colecraft HM, Larsson HP, Kass RS. Pharmacological rescue of specific long QT variants of KCNQ1/KCNE1 channels. Front Physiol 2022; 13:902224. [PMID: 36505078 PMCID: PMC9726718 DOI: 10.3389/fphys.2022.902224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 11/02/2022] [Indexed: 11/24/2022] Open
Abstract
The congenital Long QT Syndrome (LQTS) is an inherited disorder in which cardiac ventricular repolarization is delayed and predisposes patients to cardiac arrhythmias and sudden cardiac death. LQT1 and LQT5 are LQTS variants caused by mutations in KCNQ1 or KCNE1 genes respectively. KCNQ1 and KCNE1 co-assemble to form critical IKS potassium channels. Beta-blockers are the standard of care for the treatment of LQT1, however, doing so based on mechanisms other than correcting the loss-of-function of K+ channels. ML277 and R-L3 are compounds that enhance IKS channels and slow channel deactivation in a manner that is dependent on the stoichiometry of KCNE1 subunits in the assembled channels. In this paper, we used expression of IKS channels in Chinese hamster ovary (CHO) cells and Xenopus oocytes to study the potential of these two drugs (ML277 and R-L3) for the rescue of LQT1 and LQT5 mutant channels. We focused on the LQT1 mutation KCNQ1-S546L, and two LQT5 mutations, KCNE1-L51H and KCNE1-G52R. We found ML277 and R-L3 potentiated homozygote LQTS mutations in the IKS complexes-KCNE1-G52R and KCNE1-L51H and in heterogeneous IKS channel complexes which mimic heterogeneous expression of mutations in patients. ML277 and R-L3 increased the mutant IKS current amplitude and slowed current deactivation, but not in wild type (WT) IKS. We obtained similar results in the LQT1 mutant (KCNQ1 S546L/KCNE1) with ML277 and R-L3. ML277 and R-L3 had a similar effect on the LQT1 and LQT5 mutants, however, ML277 was more effective than R-L3 in this modulation. Importantly we found that not all LQT5 mutants expressed with KCNQ1 resulted in channels that are potentiated by these drugs as the KCNE1 mutant D76N inhibited drug action when expressed with KCNQ1. Thus, our work shows that by directly studying the treatment of LQT1 and LQT5 mutations with ML277 and R-L3, we will understand the potential utility of these activators as options in specific LQTS therapeutics.
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Affiliation(s)
- Xinle Zou
- Department of Molecular Pharmacology & Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, United States
| | - Kevin J. Sampson
- Department of Molecular Pharmacology & Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Henry M. Colecraft
- Department of Molecular Pharmacology & Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - H. Peter Larsson
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, United States
| | - Robert S. Kass
- Department of Molecular Pharmacology & Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States,*Correspondence: Robert S. Kass,
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Homma K. The Pathological Mechanisms of Hearing Loss Caused by KCNQ1 and KCNQ4 Variants. Biomedicines 2022; 10:biomedicines10092254. [PMID: 36140355 PMCID: PMC9496569 DOI: 10.3390/biomedicines10092254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 11/29/2022] Open
Abstract
Deafness-associated genes KCNQ1 (also associated with heart diseases) and KCNQ4 (only associated with hearing loss) encode the homotetrameric voltage-gated potassium ion channels Kv7.1 and Kv7.4, respectively. To date, over 700 KCNQ1 and over 70 KCNQ4 variants have been identified in patients. The vast majority of these variants are inherited dominantly, and their pathogenicity is often explained by dominant-negative inhibition or haploinsufficiency. Our recent study unexpectedly identified cell-death-inducing cytotoxicity in several Kv7.1 and Kv7.4 variants. Elucidation of this cytotoxicity mechanism and identification of its modifiers (drugs) have great potential for aiding the development of a novel pharmacological strategy against many pathogenic KCNQ variants. The purpose of this review is to disseminate this emerging pathological role of Kv7 variants and to underscore the importance of experimentally characterizing disease-associated variants.
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Affiliation(s)
- Kazuaki Homma
- Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; ; Tel.: +1-312-503-5344
- The Hugh Knowles Center for Clinical and Basic Science in Hearing and Its Disorders, Northwestern University, Evanston, IL 60608, USA
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Chen L, Peng G, Comollo TW, Zou X, Sampson KJ, Larsson HP, Kass RS. Two small-molecule activators share similar effector sites in the KCNQ1 channel pore but have distinct effects on voltage sensor movements. Front Physiol 2022; 13:903050. [PMID: 35957984 PMCID: PMC9359618 DOI: 10.3389/fphys.2022.903050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
ML277 and R-L3 are two small-molecule activators of KCNQ1, the pore-forming subunit of the slowly activating potassium channel IKs. KCNQ1 loss-of-function mutations prolong cardiac action potential duration and are associated with long QT syndrome, which predispose patients to lethal ventricular arrhythmia. ML277 and R-L3 enhance KCNQ1 current amplitude and slow deactivation. However, the presence of KCNE1, an auxiliary subunit of IKs channels, renders the channel insensitive to both activators. We found that ML277 effects are dependent on several residues in the KCNQ1 pore domain. Some of these residues are also necessary for R-L3 effects. These residues form a putative hydrophobic pocket located between two adjacent KCNQ1 subunits, where KCNE1 subunits are thought to dwell, thus providing an explanation for how KCNE1 renders the IKs channel insensitive to these activators. Our experiments showed that the effect of R-L3 on voltage sensor movement during channel deactivation was much more prominent than that of ML277. Simulations using a KCNQ1 kinetic model showed that the effects of ML277 and R-L3 could be reproduced through two different effects on channel gating: ML277 enhances KCNQ1 channel function through a pore-dependent and voltage sensor-independent mechanism, while R-L3 affects both channel pore and voltage sensor.
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Affiliation(s)
- Lei Chen
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Gary Peng
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Thomas W. Comollo
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Xinle Zou
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Kevin J. Sampson
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - H. Peter Larsson
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, United States
| | - Robert S. Kass
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States,*Correspondence: Robert S. Kass,
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Haverinen J, Hassinen M, Vornanen M. Effect of Channel Assembly (KCNQ1 or KCNQ1 + KCNE1) on the Response of Zebrafish IKs Current to IKs Inhibitors and Activators. J Cardiovasc Pharmacol 2022; 79:670-677. [PMID: 35377576 DOI: 10.1097/fjc.0000000000001230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/15/2022] [Indexed: 11/26/2022]
Abstract
ABSTRACT In cardiac myocytes, the slow component of the delayed rectifier K+ current (IKs) ensures repolarization of action potential during beta-adrenergic activation or when other repolarizing K+ currents fail. As a key factor of cardiac repolarization, IKs should be present in model species used for cardiovascular drug screening, preferably with pharmacological characteristics similar to those of the human IKs. To this end, we investigated the effects of inhibitors and activators of the IKs on KCNQ1 and KCNQ1 + KCNE1 channels of the zebrafish, an important model species, in Chinese hamster ovary cells. Inhibitors of IKs, chromanol 293B and HMR-1556, inhibited zebrafish IKs channels with approximately similar potency as that of mammalian IKs. Chromanol 293B concentration for half-maximal inhibition (IC50) of zebrafish IKs was at 13.1 ± 5.8 and 13.4 ± 2.8 µM for KCNQ1 and KCNQ1+KCNE1 channels, respectively. HMR-1556 was a more potent inhibitor of zebrafish IKs channels with IC50 = 0.1 ± 0.1 µM and 1.5 ± 0.8 µM for KCNQ1 and KCNQ1 + KCNE1 channels, respectively. R-L3 and mefenamic acid, generally identified as IKs activators, both inhibited zebrafish IKs. R-L3 almost completely inhibited the current generated by KCNQ1 and KCNQ1 + KCNE1 channels with similar potency (IC50 1.1 ± 0.4 and 1.0 ± 0.4 µM, respectively). Mefenamic acid partially blocked zebrafish KCNQ1 (IC50 = 9.5 ± 4.8 µM) and completely blocked KCNQ1 + KCNE1 channels (IC50 = 3.3 ± 1.8 µM). Although zebrafish IKs channels respond to IKs inhibitors in the same way as mammalian IKs channels, their response to activators is atypical, probably because of the differences in the binding domain of KCNE1 to KCNQ1. Therefore, care must be taken when translating the results from zebrafish to humans.
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Affiliation(s)
- Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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8
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A benzodiazepine activator locks K v7.1 channels open by electro-mechanical uncoupling. Commun Biol 2022; 5:301. [PMID: 35365746 PMCID: PMC8976019 DOI: 10.1038/s42003-022-03229-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/22/2022] [Indexed: 01/18/2023] Open
Abstract
Loss-of-function mutations in Kv7.1 often lead to long QT syndrome (LQTS), a cardiac repolarization disorder associated with arrhythmia and subsequent sudden cardiac death. The discovery of agonistic IKs modulators may offer a new potential strategy in pharmacological treatment of this disorder. The benzodiazepine derivative (R)-L3 potently activates Kv7.1 channels and shortens action potential duration, thus may represent a starting point for drug development. However, the molecular mechanisms underlying modulation by (R)-L3 are still unknown. By combining alanine scanning mutagenesis, non-canonical amino acid incorporation, voltage-clamp electrophysiology and fluorometry, and in silico protein modelling, we show that (R)-L3 not only stimulates currents by allosteric modulation of the pore domain but also alters the kinetics independently from the pore domain effects. We identify novel (R)-L3-interacting key residues in the lower S4-segment of Kv7.1 and observed an uncoupling of the outer S4 segment with the inner S5, S6 and selectivity filter segments.
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9
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Kv7 Channels in Cyclic-Nucleotide Dependent Relaxation of Rat Intra-Pulmonary Artery. Biomolecules 2022; 12:biom12030429. [PMID: 35327621 PMCID: PMC8946781 DOI: 10.3390/biom12030429] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 12/22/2022] Open
Abstract
Pulmonary hypertension is treated with drugs that stimulate cGMP or cAMP signalling. Both nucleotides can activate Kv7 channels, leading to smooth muscle hyperpolarisation, reduced Ca2+ influx and relaxation. Kv7 activation by cGMP contributes to the pulmonary vasodilator action of nitric oxide, but its contribution when dilation is evoked by the atrial natriuretic peptide (ANP) sensitive guanylate cyclase, or cAMP, is unknown. Small vessel myography was used to investigate the ability of Kv7 channel blockers to interfere with pulmonary artery relaxation when cyclic nucleotide pathways were stimulated in different ways. The pan-Kv7 blockers, linopirdine and XE991, caused substantial inhibition of relaxation evoked by NO donors and ANP, as well as endothelium-dependent dilators, the guanylate cyclase stimulator, riociguat, and the phosphodiesterase-5 inhibitor, sildenafil. Maximum relaxation was reduced without a change in sensitivity. The blockers had relatively little effect on cAMP-mediated relaxation evoked by forskolin, isoprenaline or treprostinil. The Kv7.1-selective blocker, HMR1556, had no effect on cGMP or cAMP-dependent relaxation. Western blot analysis demonstrated the presence of Kv7.1 and Kv7.4 proteins, while selective activators of Kv7.1 and Kv7.4 homomeric channels, but not Kv7.5, caused pulmonary artery relaxation. It is concluded that Kv7.4 channels contribute to endothelium-dependent dilation and the effects of drugs that act by stimulating cGMP, but not cAMP, signalling.
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10
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Sanguinetti MC, Seebohm G. Physiological Functions, Biophysical Properties, and Regulation of KCNQ1 (K V7.1) Potassium Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1349:335-353. [PMID: 35138621 DOI: 10.1007/978-981-16-4254-8_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
KCNQ1 (KV7.1) K+ channels are expressed in multiple tissues, including the heart, pancreas, colon, and inner ear. The gene encoding the KCNQ1 protein was discovered by a positional cloning effort to determine the genetic basis of long QT syndrome, an inherited ventricular arrhythmia that can cause sudden death. Mutations in KCNQ1 can also cause other types of arrhythmia (i.e., short QT syndrome, atrial fibrillation) and the gene may also have a role in diabetes and certain cancers. KCNQ1 α-subunits can partner with accessory β-subunits (KCNE1-KCNE5) to form K+-selective channels that have divergent biophysical properties. In the heart, KCNQ1 α-subunits coassemble with KCNE1 β-subunits to form channels that conduct IKs, a very slowly activating delayed rectifier K+ current. KV7.1 channels are highly regulated by PIP2, calmodulin, and phosphorylation, and rich pharmacology includes blockers and gating modulators. Recent biophysical studies and a cryo-EM structure of the KCNQ1-calmodulin complex have provided new insights into KV7.1 channel function, and how interactions between KCNQ1 and KCNE subunits alter the gating properties of heteromultimeric channels.
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Affiliation(s)
| | - Guiscard Seebohm
- Cellular Electrophysiology and Molecular Biology, Institute for Genetics of Heart Diseases, University Hospital Münster, Münster, Germany
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11
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Eldstrom J, McAfee DA, Dou Y, Wang Y, Fedida D. ML277 regulates KCNQ1 single-channel amplitudes and kinetics, modified by voltage sensor state. J Gen Physiol 2021; 153:212696. [PMID: 34636894 PMCID: PMC8515649 DOI: 10.1085/jgp.202112969] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/16/2021] [Accepted: 09/15/2021] [Indexed: 11/25/2022] Open
Abstract
KCNQ1 is a pore-forming K+ channel subunit critically important to cardiac repolarization at high heart rates. (2R)-N-[4-(4-methoxyphenyl)-2-thiazolyl]-1-[(4-methylphenyl)sulfonyl]-2 piperidinecarboxamide, or ML277, is an activator of this channel that rescues function of pathophysiologically important mutant channel complexes in human induced pluripotent stem cell–derived cardiomyocytes, and that therefore may have therapeutic potential. Here we extend our understanding of ML277 actions through cell-attached single-channel recordings of wild-type and mutant KCNQ1 channels with voltage sensor domains fixed in resting, intermediate, and activated states. ML277 has profound effects on KCNQ1 single-channel kinetics, eliminating the flickering nature of the openings, converting them to discrete opening bursts, and increasing their amplitudes approximately threefold. KCNQ1 single-channel behavior after ML277 treatment most resembles IO state-locked channels (E160R/R231E) rather than AO state channels (E160R/R237E), suggesting that at least during ML277 treatment, KCNQ1 does not frequently visit the AO state. Introduction of KCNE1 subunits reduces the effectiveness of ML277, but some enhancement of single-channel openings is still observed.
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Affiliation(s)
- Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Donald A McAfee
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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12
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Kojima T, Wasano K, Takahashi S, Homma K. Cell death-inducing cytotoxicity in truncated KCNQ4 variants associated with DFNA2 hearing loss. Dis Model Mech 2021; 14:272416. [PMID: 34622280 PMCID: PMC8628632 DOI: 10.1242/dmm.049015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 09/22/2021] [Indexed: 01/30/2023] Open
Abstract
KCNQ4 encodes the homotetrameric voltage-dependent potassium ion channel Kv7.4, and is the causative gene for autosomal dominant nonsyndromic sensorineural hearing loss, DFNA2. Dominant-negative inhibition accounts for the observed dominant inheritance of many DFNA2-associated KCNQ4 variants. In addition, haploinsufficiency has been presumed as the pathological mechanism for truncated Kv7.4 variants lacking the C-terminal tetramerization region, as they are unlikely to exert a dominant-negative inhibitory effect. Such truncated Kv7.4 variants should result in relatively mild hearing loss when heterozygous; however, this is not always the case. In this study, we characterized Kv7.4Q71fs (c.211delC), Kv7.4W242X (c.725G>A) and Kv7.4A349fs (c.1044_1051del8) in heterologous expression systems and found that expression of these truncated Kv7.4 variants induced cell death. We also found similar cell death-inducing cytotoxic effects in truncated Kv7.1 (KCNQ1) variants, suggesting that the generality of our findings could account for the dominant inheritance of many, if not most, truncated Kv7 variants. Moreover, we found that the application of autophagy inducers can ameliorate the cytotoxicity, providing a novel insight for the development of alternative therapeutic strategies for Kv7.4 variants. Summary: Expression of truncated KCNQ4 variants lacking the C-terminal tetramerization domain results in cell-death inducing cytotoxicity, providing novel insight into the development of alternative therapeutic strategies for DFNA2 hearing loss.
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Affiliation(s)
- Takashi Kojima
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.,Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan
| | - Koichiro Wasano
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.,Laboratory of Auditory Disorders, Division of Hearing and Balance Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, 2-5-1 Higashigaoka, Meguro, Tokyo 152-8902, Japan
| | - Satoe Takahashi
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Kazuaki Homma
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.,The Hugh Knowles Center for Clinical and Basic Science in Hearing and Its Disorders, Northwestern University, Evanston, IL 60608, USA
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13
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Naffaa MM, Al-Ewaidat OA. Ligand modulation of KCNQ-encoded (K V7) potassium channels in the heart and nervous system. Eur J Pharmacol 2021; 906:174278. [PMID: 34174270 DOI: 10.1016/j.ejphar.2021.174278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/06/2021] [Accepted: 06/18/2021] [Indexed: 10/21/2022]
Abstract
KCNQ-encoded (KV7) potassium channels are diversely distributed in the human tissues, associated with many physiological processes and pathophysiological conditions. These channels are increasingly used as drug targets for treating diseases. More selective and potent molecules on various types of the KV7 channels are desirable for appropriate therapies. The recent knowledge of the structure and function of human KCNQ-encoded channels makes it more feasible to achieve these goals. This review discusses the role and mechanism of action of many molecules in modulating the function of the KCNQ-encoded potassium channels in the heart and nervous system. The effects of these compounds on KV7 channels help to understand their involvement in many diseases, and to search for more selective and potent ligands to be used in the treatment of many disorders such as various types of cardiac arrhythmias, epilepsy, and pain.
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Affiliation(s)
- Moawiah M Naffaa
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
| | - Ola A Al-Ewaidat
- Faculty of Medicine, The University of Jordan, Amman, 11942, Jordan
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14
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Modulating the voltage sensor of a cardiac potassium channel shows antiarrhythmic effects. Proc Natl Acad Sci U S A 2021; 118:2024215118. [PMID: 33990467 DOI: 10.1073/pnas.2024215118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cardiac arrhythmias are the most common cause of sudden cardiac death worldwide. Lengthening the ventricular action potential duration (APD), either congenitally or via pathologic or pharmacologic means, predisposes to a life-threatening ventricular arrhythmia, Torsade de Pointes. IKs (KCNQ1+KCNE1), a slowly activating K+ current, plays a role in action potential repolarization. In this study, we screened a chemical library in silico by docking compounds to the voltage-sensing domain (VSD) of the IKs channel. Here, we show that C28 specifically shifted IKs VSD activation in ventricle to more negative voltages and reversed the drug-induced lengthening of APD. At the same dosage, C28 did not cause significant changes of the normal APD in either ventricle or atrium. This study provides evidence in support of a computational prediction of IKs VSD activation as a potential therapeutic approach for all forms of APD prolongation. This outcome could expand the therapeutic efficacy of a myriad of currently approved drugs that may trigger arrhythmias.
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15
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Borgini M, Mondal P, Liu R, Wipf P. Chemical modulation of Kv7 potassium channels. RSC Med Chem 2021; 12:483-537. [PMID: 34046626 PMCID: PMC8128042 DOI: 10.1039/d0md00328j] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 01/10/2023] Open
Abstract
The rising interest in Kv7 modulators originates from their ability to evoke fundamental electrophysiological perturbations in a tissue-specific manner. A large number of therapeutic applications are, in part, based on the clinical experience with two broad-spectrum Kv7 agonists, flupirtine and retigabine. Since precise molecular structures of human Kv7 channel subtypes in closed and open states have only very recently started to emerge, computational studies have traditionally been used to analyze binding modes and direct the development of more potent and selective Kv7 modulators with improved safety profiles. Herein, the synthetic and medicinal chemistry of small molecule modulators and the representative biological properties are summarized. Furthermore, new therapeutic applications supported by in vitro and in vivo assay data are suggested.
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Affiliation(s)
- Matteo Borgini
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Pravat Mondal
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Ruiting Liu
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
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16
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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17
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Mondejar-Parreño G, Perez-Vizcaino F, Cogolludo A. Kv7 Channels in Lung Diseases. Front Physiol 2020; 11:634. [PMID: 32676036 PMCID: PMC7333540 DOI: 10.3389/fphys.2020.00634] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/18/2020] [Indexed: 12/23/2022] Open
Abstract
Lung diseases constitute a global health concern causing disability. According to WHO in 2016, respiratory diseases accounted for 24% of world population mortality, the second cause of death after cardiovascular diseases. The Kv7 channels family is a group of voltage-dependent K+ channels (Kv) encoded by KCNQ genes that are involved in various physiological functions in numerous cell types, especially, cardiac myocytes, smooth muscle cells, neurons, and epithelial cells. Kv7 channel α-subunits are regulated by KCNE1–5 ancillary β-subunits, which modulate several characteristics of Kv7 channels such as biophysical properties, cell-location, channel trafficking, and pharmacological sensitivity. Kv7 channels are mainly expressed in two large groups of lung tissues: pulmonary arteries (PAs) and bronchial tubes. In PA, Kv7 channels are expressed in pulmonary artery smooth muscle cells (PASMCs); while in the airway (trachea, bronchus, and bronchioles), Kv7 channels are expressed in airway smooth muscle cells (ASMCs), airway epithelial cells (AEPs), and vagal airway C-fibers (VACFs). The functional role of Kv7 channels may vary depending on the cell type. Several studies have demonstrated that the impairment of Kv7 channel has a strong impact on pulmonary physiology contributing to the pathophysiology of different respiratory diseases such as cystic fibrosis, asthma, chronic obstructive pulmonary disease, chronic coughing, lung cancer, and pulmonary hypertension. Kv7 channels are now recognized as playing relevant physiological roles in many tissues, which have encouraged the search for Kv7 channel modulators with potential therapeutic use in many diseases including those affecting the lung. Modulation of Kv7 channels has been proposed to provide beneficial effects in a number of lung conditions. Therefore, Kv7 channel openers/enhancers or drugs acting partly through these channels have been proposed as bronchodilators, expectorants, antitussives, chemotherapeutics and pulmonary vasodilators.
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Affiliation(s)
- Gema Mondejar-Parreño
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Francisco Perez-Vizcaino
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
| | - Angel Cogolludo
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.,Ciber Enfermedades Respiratorias (Ciberes), Madrid, Spain.,Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Madrid, Spain
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18
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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19
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Tariq S, Khalid M, Raza AR, Rubab SL, Morais SFDA, Khan MU, Tahir MN, Braga AAC. Experimental and computational investigations of new indole derivatives: A combined spectroscopic, SC-XRD, DFT/TD-DFT and QTAIM analysis. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2020.127803] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Maguy A, Kucera JP, Wepfer JP, Forest V, Charpentier F, Li J. KCNQ1 Antibodies for Immunotherapy of Long QT Syndrome Type 2. J Am Coll Cardiol 2020; 75:2140-2152. [DOI: 10.1016/j.jacc.2020.02.067] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/04/2020] [Accepted: 02/25/2020] [Indexed: 02/02/2023]
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21
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Synthesis and structural analysis of novel indole derivatives by XRD, spectroscopic and DFT studies. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.127438] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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22
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Hou P, Shi J, White KM, Gao Y, Cui J. ML277 specifically enhances the fully activated open state of KCNQ1 by modulating VSD-pore coupling. eLife 2019; 8:e48576. [PMID: 31329101 PMCID: PMC6684268 DOI: 10.7554/elife.48576] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/22/2019] [Indexed: 12/16/2022] Open
Abstract
Upon membrane depolarization, the KCNQ1 potassium channel opens at the intermediate (IO) and activated (AO) states of the stepwise voltage-sensing domain (VSD) activation. In the heart, KCNQ1 associates with KCNE1 subunits to form IKs channels that regulate heart rhythm. KCNE1 suppresses the IO state so that the IKs channel opens only to the AO state. Here, we tested modulations of human KCNQ1 channels by an activator ML277 in Xenopus oocytes. It exclusively changes the pore opening properties of the AO state without altering the IO state, but does not affect VSD activation. These observations support a distinctive mechanism responsible for the VSD-pore coupling at the AO state that is sensitive to ML277 modulation. ML277 provides insights and a tool to investigate the gating mechanism of KCNQ1 channels, and our study reveals a new strategy for treating long QT syndrome by specifically enhancing the AO state of native IKs currents.
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Affiliation(s)
- Panpan Hou
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | - Jingyi Shi
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | - Kelli McFarland White
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
| | | | - Jianmin Cui
- Department of Biomedical EngineeringWashington UniversitySt. LouisUnited States
- Center for the Investigation of Membrane Excitability DisordersWashington UniversitySt. LouisUnited States
- Cardiac Bioelectricity and Arrhythmia CenterWashington UniversitySt. LouisUnited States
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23
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Amarelle L, Katzen J, Shigemura M, Welch LC, Cajigas H, Peteranderl C, Celli D, Herold S, Lecuona E, Sznajder JI. Cardiac glycosides decrease influenza virus replication by inhibiting cell protein translational machinery. Am J Physiol Lung Cell Mol Physiol 2019; 316:L1094-L1106. [PMID: 30892074 DOI: 10.1152/ajplung.00173.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cardiac glycosides (CGs) are used primarily for cardiac failure and have been reported to have other effects, including inhibition of viral replication. Here we set out to study mechanisms by which CGs as inhibitors of the Na-K-ATPase decrease influenza A virus (IAV) replication in the lungs. We found that CGs inhibit influenza virus replication in alveolar epithelial cells by decreasing intracellular potassium, which in turn inhibits protein translation, independently of viral entry, mRNA transcription, and protein degradation. These effects were independent of the Src signaling pathway and intracellular calcium concentration changes. We found that short-term treatment with ouabain prevented IAV replication without cytotoxicity. Rodents express a Na-K-ATPase-α1 resistant to CGs. Thus we utilized Na-K-ATPase-α1-sensitive mice, infected them with high doses of influenza virus, and observed a modest survival benefit when treated with ouabain. In summary, we provide evidence that the inhibition of the Na-K-ATPase by CGs decreases influenza A viral replication by modulating the cell protein translational machinery and results in a modest survival benefit in mice.
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Affiliation(s)
- Luciano Amarelle
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois.,Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República , Montevideo , Uruguay
| | - Jeremy Katzen
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois.,Pulmonary, Allergy, and Critical Care Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania , Philadelphia, Pennsylvania
| | - Masahiko Shigemura
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Lynn C Welch
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Héctor Cajigas
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Christin Peteranderl
- Department of Internal Medicine II, University of Giessen and Marburg Lung Center , Giessen , Germany
| | - Diego Celli
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Susanne Herold
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois.,Department of Internal Medicine II, University of Giessen and Marburg Lung Center , Giessen , Germany
| | - Emilia Lecuona
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
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24
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Gollasch M, Welsh DG, Schubert R. Perivascular adipose tissue and the dynamic regulation of K v 7 and K ir channels: Implications for resistant hypertension. Microcirculation 2018; 25. [PMID: 29211322 DOI: 10.1111/micc.12434] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 11/30/2017] [Indexed: 12/20/2022]
Abstract
Resistant hypertension is defined as high blood pressure that remains uncontrolled despite treatment with at least three antihypertensive drugs at adequate doses. Resistant hypertension is an increasingly common clinical problem in older age, obesity, diabetes, sleep apnea, and chronic kidney disease. Although the direct vasodilator minoxidil was introduced in the early 1970s, only recently has this drug been shown to be particularly effective in a subgroup of patients with treatment-resistant or uncontrolled hypertension. This pharmacological approach is interesting from a mechanistic perspective as minoxidil is the only clinically used K+ channel opener today, which targets a subclass of K+ channels, namely KATP channels in VSMCs. Beside KATP channels, two other classes of VSMC K+ channels could represent novel effective targets for treatment of resistant hypertension, namely Kv 7 (KCNQ) and inward rectifier potassium (Kir 2.1) channels. Interestingly, these channels are unique among VSMC potassium channels. First, both have been implicated in the control of microvascular tone by perivascular adipose tissue. Second, they exhibit biophysical properties strongly controlled and regulated by membrane voltage, but not intracellular calcium. This review focuses on Kv 7 (Kv 7.1-5) and Kir (Kir 2.1) channels in VSMCs as potential novel drug targets for treatment of resistant hypertension, particularly in comorbid conditions such as obesity and metabolic syndrome.
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Affiliation(s)
- Maik Gollasch
- Medical Clinic for Nephrology and Internal Intensive Care, Charité Campus Virchow Klinikum, Experimental and Clinical Research Center (ECRC) - a joint cooperation between the Charité - University Medicine Berlin and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Donald G Welsh
- Department of Physiology and Pharmacology, Western University, London, ON, Canada
| | - Rudolf Schubert
- Centre for Biomedicine and Medical Technology Mannheim (CBTM), Research Division Cardiovascular Physiology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
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25
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Qiu B, Wang Y, Li C, Guo H, Xu Y. Utility of the JT Peak Interval and the JT Area in Determining the Proarrhythmic Potential of QT-Shortening Agents. J Cardiovasc Pharmacol Ther 2018; 24:160-171. [PMID: 30092655 DOI: 10.1177/1074248418791999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Drug-induced long QT increases the risk of ventricular tachyarrhythmia known as torsades de pointes (TdP). Many biomarkers have been used to predict TdP. At present, however, there are few biomarkers for arrhythmias induced by QT-shortening drugs. The objective of the present study was to identify the best biomarkers for predicting arrhythmias caused by the 4 potassium channel openers ICA-105574, NS-1643, R-L3, and pinacidil. Our results showed that, at higher concentrations, all 4 potassium channel openers induced ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff-perfused guinea pig hearts, but not in rabbit hearts. The electrocardiography parameters were measured including QT/QTc, JT peak, Tp-e interval, JT area, short-term beat-to-beat QT interval variability (STV), and index of cardiac electrophysiological balance (iCEB). We found that the potassium channel openers at test concentrations shortened the QT/QTc and the JT peak interval and increased the JT area. Nevertheless, even at proarrhythmic concentrations, they did not always change STV, Tp-e, or iCEB. Receiver operating characteristic curve analysis showed that the JT peak interval representing the early repolarization phase and the JT area reflecting the dispersion of ventricular repolarization were the best predictors of VT/VF. Action potential recordings in guinea pig papillary muscle revealed that except for pinacidil, the potassium channel openers shortened APD30 in a concentration-dependent manner. They also evoked early or delayed afterdepolarizations at fast pacing rates. Patch-clamp recordings in guinea pig ventricular cardiomyocytes showed that the potassium channel openers enhanced the total outward currents during the early phase of action potential repolarization, especially at proarrhythmic concentrations. We concluded that the JT peak interval and the JT area are surrogate biomarkers identifying the risk of proarrhythmia associated with the administration of QT-shortening agents. The acceleration of early-phase repolarization and the increased dispersion of ventricular repolarization may contribute to the occurrence of arrhythmias.
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Affiliation(s)
- Bo Qiu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China.,Hebei General Hospital, Shijiazhuang, China
| | - Yuhong Wang
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Beijing Union Medical College, Beijing, China
| | - Congxin Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
| | - Huicai Guo
- Department of Toxicology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, Hebei, China.,The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei, China
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26
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Larsson JE, Larsson HP, Liin SI. KCNE1 tunes the sensitivity of K V7.1 to polyunsaturated fatty acids by moving turret residues close to the binding site. eLife 2018; 7:37257. [PMID: 30014849 PMCID: PMC6080945 DOI: 10.7554/elife.37257] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 07/15/2018] [Indexed: 12/23/2022] Open
Abstract
The voltage-gated potassium channel KV7.1 and the auxiliary subunit KCNE1 together form the cardiac IKs channel, which is a proposed target for future anti-arrhythmic drugs. We previously showed that polyunsaturated fatty acids (PUFAs) activate KV7.1 via an electrostatic mechanism. The activating effect was abolished when KV7.1 was co-expressed with KCNE1, as KCNE1 renders PUFAs ineffective by promoting PUFA protonation. PUFA protonation reduces the potential of PUFAs as anti-arrhythmic compounds. It is unknown how KCNE1 promotes PUFA protonation. Here, we found that neutralization of negatively charged residues in the S5-P-helix loop of KV7.1 restored PUFA effects on KV7.1 co-expressed with KCNE1 in Xenopus oocytes. We propose that KCNE1 moves the S5-P-helix loop of KV7.1 towards the PUFA-binding site, which indirectly causes PUFA protonation, thereby reducing the effect of PUFAs on KV7.1. This mechanistic understanding of how KCNE1 alters KV7.1 pharmacology is essential for development of drugs targeting the IKs channel.
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Affiliation(s)
- Johan E Larsson
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, United States
| | - Sara I Liin
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
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27
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Barrese V, Stott JB, Greenwood IA. KCNQ-Encoded Potassium Channels as Therapeutic Targets. Annu Rev Pharmacol Toxicol 2018; 58:625-648. [DOI: 10.1146/annurev-pharmtox-010617-052912] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | | | - Iain A. Greenwood
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, United Kingdom;, ,
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28
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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29
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Haick JM, Byron KL. Novel treatment strategies for smooth muscle disorders: Targeting Kv7 potassium channels. Pharmacol Ther 2016; 165:14-25. [PMID: 27179745 DOI: 10.1016/j.pharmthera.2016.05.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Smooth muscle cells provide crucial contractile functions in visceral, vascular, and lung tissues. The contractile state of smooth muscle is largely determined by their electrical excitability, which is in turn influenced by the activity of potassium channels. The activity of potassium channels sustains smooth muscle cell membrane hyperpolarization, reducing cellular excitability and thereby promoting smooth muscle relaxation. Research over the past decade has indicated an important role for Kv7 (KCNQ) voltage-gated potassium channels in the regulation of the excitability of smooth muscle cells. Expression of multiple Kv7 channel subtypes has been demonstrated in smooth muscle cells from viscera (gastrointestinal, bladder, myometrial), from the systemic and pulmonary vasculature, and from the airways of the lung, from multiple species, including humans. A number of clinically used drugs, some of which were developed to target Kv7 channels in other tissues, have been found to exert robust effects on smooth muscle Kv7 channels. Functional studies have indicated that Kv7 channel activators and inhibitors have the ability to relax and contact smooth muscle preparations, respectively, suggesting a wide range of novel applications for the pharmacological tool set. This review summarizes recent findings regarding the physiological functions of Kv7 channels in smooth muscle, and highlights potential therapeutic applications based on pharmacological targeting of smooth muscle Kv7 channels throughout the body.
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Affiliation(s)
- Jennifer M Haick
- Department of Molecular Pharmacology & Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA
| | - Kenneth L Byron
- Department of Molecular Pharmacology & Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, USA.
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30
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Wu W, Sanguinetti MC. Molecular Basis of Cardiac Delayed Rectifier Potassium Channel Function and Pharmacology. Card Electrophysiol Clin 2016; 8:275-84. [PMID: 27261821 DOI: 10.1016/j.ccep.2016.01.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Human cardiomyocytes express 3 distinct types of delayed rectifier potassium channels. Human ether-a-go-go-related gene (hERG) channels conduct the rapidly activating current IKr; KCNQ1/KCNE1 channels conduct the slowly activating current IKs; and Kv1.5 channels conduct an ultrarapid activating current IKur. Here the authors provide a general overview of the mechanistic and structural basis of ion selectivity, gating, and pharmacology of the 3 types of cardiac delayed rectifier potassium ion channels. Most blockers bind to S6 residues that line the central cavity of the channel, whereas activators interact with the channel at 4 symmetric binding sites outside the cavity.
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Affiliation(s)
- Wei Wu
- Department of Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112, USA
| | - Michael C Sanguinetti
- Department of Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, 95 South 2000 East, Salt Lake City, UT 84112, USA.
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31
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Chapter Five - Ubiquitination of Ion Channels and Transporters. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:161-223. [DOI: 10.1016/bs.pmbts.2016.02.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Abstract
BACKGROUND The impact of volatile anesthetics on patients with inherited long QT syndrome (LQTS) is not well understood. This is further complicated by the different genotypes underlying LQTS. No studies have reported on the direct effects of volatile anesthetics on specific LQTS-associated mutations. We investigated the effects of isoflurane on a common LQTS type 1 mutation, A341V, with an unusually severe phenotype. METHODS Whole cell potassium currents (IKs) were recorded from HEK293 and HL-1 cells transiently expressing/coexpressing wild-type KCNQ1 (α-subunit), mutant KCNQ1, wild-type KCNE1 (β-subunit), and fusion KCNQ1 + KCNE1. Current was monitored in the absence and presence of clinically relevant concentration of isoflurane (0.54 ± 0.05 mM, 1.14 vol %). Computer simulations determined the resulting impact on the cardiac action potential. RESULTS Isoflurane had significantly greater inhibitory effect on A341V + KCNE1 (62.2 ± 3.4%, n = 8) than on wild-type KCNQ1 + KCNE1 (40.7 ± 4.5%; n = 9) in transfected HEK293 cells. Under heterozygous conditions, isoflurane inhibited A341V + KCNQ1 + KCNE1 by 65.2 ± 3.0% (n = 13) and wild-type KCNQ1 + KCNE1 (2:1 ratio) by 32.0 ± 4.5% (n = 11). A341V exerted a dominant negative effect on IKs. Similar differential effects of isoflurane were also observed in experiments using the cardiac HL-1 cells. Mutations of the neighboring F340 residue significantly attenuated the effects of isoflurane, and fusion proteins revealed the modulatory effect of KCNE1. Action potential simulations revealed a stimulation frequency-dependent effect of A341V. CONCLUSIONS The LQTS-associated A341V mutation rendered the IKs channel more sensitive to the inhibitory effects of isoflurane compared to wild-type IKs in transfected cell lines; F340 is a key residue for anesthetic action.
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33
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Polyunsaturated fatty acid analogs act antiarrhythmically on the cardiac IKs channel. Proc Natl Acad Sci U S A 2015; 112:5714-9. [PMID: 25901329 DOI: 10.1073/pnas.1503488112] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polyunsaturated fatty acids (PUFAs) affect cardiac excitability. Kv7.1 and the β-subunit KCNE1 form the cardiac IKs channel that is central for cardiac repolarization. In this study, we explore the prospects of PUFAs as IKs channel modulators. We report that PUFAs open Kv7.1 via an electrostatic mechanism. Both the polyunsaturated acyl tail and the negatively charged carboxyl head group are required for PUFAs to open Kv7.1. We further show that KCNE1 coexpression abolishes the PUFA effect on Kv7.1 by promoting PUFA protonation. PUFA analogs with a decreased pKa value, to preserve their negative charge at neutral pH, restore the sensitivity to open IKs channels. PUFA analogs with a positively charged head group inhibit IKs channels. These different PUFA analogs could be developed into drugs to treat cardiac arrhythmias. In support of this possibility, we show that PUFA analogs act antiarrhythmically in embryonic rat cardiomyocytes and in isolated perfused hearts from guinea pig.
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34
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Nakajo K, Kubo Y. KCNQ1 channel modulation by KCNE proteins via the voltage-sensing domain. J Physiol 2015; 593:2617-25. [PMID: 25603957 DOI: 10.1113/jphysiol.2014.287672] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/14/2015] [Indexed: 12/16/2022] Open
Abstract
The gating of the KCNQ1 potassium channel is drastically regulated by auxiliary subunit KCNE proteins. KCNE1, for example, slows the activation kinetics of KCNQ1 by two orders of magnitude. Like other voltage-gated ion channels, the opening of KCNQ1 is regulated by the voltage-sensing domain (VSD; S1-S4 segments). Although it has been known that KCNE proteins interact with KCNQ1 via the pore domain, some recent reports suggest that the VSD movement may be altered by KCNE. The altered VSD movement of KCNQ1 by KCNE proteins has been examined by site-directed mutagenesis, the scanning cysteine accessibility method (SCAM), voltage clamp fluorometry (VCF) and gating charge measurements. These accumulated data support the idea that KCNE proteins interact with the VSDs of KCNQ1 and modulate the gating of the KCNQ1 channel. In this review, we will summarize recent findings and current views of the KCNQ1 modulation by KCNE via the VSD. In this context, we discuss our recent findings that KCNE1 may alter physical interactions between the S4 segment (VSD) and the S5 segment (pore domain) of KCNQ1. Based on these findings from ourselves and others, we propose a hypothetical mechanism for how KCNE1 binding alters the VSD movement and the gating of the channel.
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Affiliation(s)
- Koichi Nakajo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDA), Hayama, Kanagawa, 240-0115, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDA), Hayama, Kanagawa, 240-0115, Japan
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35
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Zhou P, Zhang Y, Xu H, Chen F, Chen X, Li X, Pi X, Wang L, Zhan L, Nan F, Gao Z. P-retigabine: an N-propargyled retigabine with improved brain distribution and enhanced antiepileptic activity. Mol Pharmacol 2014; 87:31-8. [PMID: 25319542 DOI: 10.1124/mol.114.095190] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Retigabine (RTG, [ethyl N-[2-amino-4-[(4-fluorophenyl)methyl]amino] phenyl] carbamate]) is a first-in-class antiepileptic drug that acts by potentiating neuronal KCNQ potassium channels; however, it has less than optimal brain distribution. In this study, we report that P-RTG (ethyl N-[2-amino-4-((4-fluorobenzyl)(prop-2-ynyl)amino)phenyl]carbamate), an RTG derivative that incorporates a propargyl group at the N position of the RTG linker, exhibits an inverted brain distribution compared with RTG. The brain-to-plasma concentration ratio of P-RTG increased to 2.30 compared with 0.16 for RTG. However, the structural modification did not change the drug's potentiation potency, subtype selectivity, or RTG molecular determinants on KCNQ channels. In addition, in cultured hippocampal neurons, P-RTG exhibited a similar capability as RTG for suppressing both induced and spontaneous action potential firing. Notably, P-RTG antiepileptic activity in the maximal electroshock (MES)-induced mouse seizure model was significantly enhanced to a value 2.5 times greater than that of RTG. Additionally, the neurotoxicity of P-RTG in the rotarod test was comparable with that of RTG. Collectively, our results indicate that the incorporation of a propargyl group significantly improves the RTG brain distribution, supporting P-RTG as a promising antiepileptic drug candidate. The strategy for improving brain-to-plasma distribution of RTG might be applicable for the drug development of other central nervous system diseases.
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Affiliation(s)
- Pingzheng Zhou
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Yangming Zhang
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Haiyan Xu
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Fei Chen
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xueqin Chen
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xiaoying Li
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xiaoping Pi
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Lipeng Wang
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Li Zhan
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Fajun Nan
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Zhaobing Gao
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
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Choi SH, Lee BH, Kim HJ, Jung SW, Kim HS, Shin HC, Lee JH, Kim HC, Rhim H, Hwang SH, Ha TS, Kim HJ, Cho H, Nah SY. Ginseng gintonin activates the human cardiac delayed rectifier K+ channel: involvement of Ca2+/calmodulin binding sites. Mol Cells 2014; 37:656-63. [PMID: 25234465 PMCID: PMC4179134 DOI: 10.14348/molcells.2014.0087] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 07/25/2014] [Accepted: 08/11/2014] [Indexed: 02/07/2023] Open
Abstract
Gintonin, a novel, ginseng-derived G protein-coupled lysophosphatidic acid (LPA) receptor ligand, elicits [Ca(2+)]i transients in neuronal and non-neuronal cells via pertussis toxin-sensitive and pertussis toxin-insensitive G proteins. The slowly activating delayed rectifier K(+) (I(Ks)) channel is a cardiac K(+) channel composed of KCNQ1 and KCNE1 subunits. The C terminus of the KCNQ1 channel protein has two calmodulin-binding sites that are involved in regulating I(Ks) channels. In this study, we investigated the molecular mechanisms of gintonin-mediated activation of human I(Ks) channel activity by expressing human I(Ks) channels in Xenopus oocytes. We found that gintonin enhances IKs channel currents in concentration- and voltage-dependent manners. The EC50 for the I(Ks) channel was 0.05 ± 0.01 μg/ml. Gintonin-mediated activation of the I(Ks) channels was blocked by an LPA1/3 receptor antagonist, an active phospholipase C inhibitor, an IP3 receptor antagonist, and the calcium chelator BAPTA. Gintonin-mediated activation of both the I(Ks) channel was also blocked by the calmodulin (CaM) blocker calmidazolium. Mutations in the KCNQ1 [Ca(2+)]i/CaM-binding IQ motif sites (S373P, W392R, or R539W)blocked the action of gintonin on I(Ks) channel. However, gintonin had no effect on hERG K(+) channel activity. These results show that gintonin-mediated enhancement of I(Ks) channel currents is achieved through binding of the [Ca(2+)]i/CaM complex to the C terminus of KCNQ1 subunit.
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Affiliation(s)
- Sun-Hye Choi
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Byung-Hwan Lee
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Hyeon-Joong Kim
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Seok-Won Jung
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Hyun-Sook Kim
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Ho-Chul Shin
- Department of Pharmacology and Toxicology, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea
| | - Jun-Hee Lee
- Department of Physical Therapy, College of Health Science, Cheongju University, Cheongju 360-764, Korea
| | - Hyoung-Chun Kim
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chuncheon 200-701, Korea
| | - Hyewhon Rhim
- Life Science Division, Korea Institute of Science and Technology, Seoul 136-791, Korea
| | - Sung-Hee Hwang
- Department of Pharmaceutical Engineering College of Health Sciences Sangji University, Wonju 220-702, Korea
| | - Tal soo Ha
- Department of Biomedical Science, Daegu University, Gyeonsan 712-714, Korea
| | - Hyun-Ji Kim
- Department of Physiology and Samsung Biomedical Research Institute, School of Medicine, Sungkyunkwan University, Suwon 440-746, Korea
| | - Hana Cho
- Department of Physiology and Samsung Biomedical Research Institute, School of Medicine, Sungkyunkwan University, Suwon 440-746, Korea
| | - Seung-Yeol Nah
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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38
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Jing L, Brownson K, Patwardhan A. Role of slow delayed rectifying potassium current in dynamics of repolarization and electrical memory in swine ventricles. J Physiol Sci 2014; 64:185-93. [PMID: 24682806 PMCID: PMC10717138 DOI: 10.1007/s12576-014-0310-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 03/03/2014] [Indexed: 01/26/2023]
Abstract
Dynamics of repolarization, quantified as restitution and electrical memory, impact conduction stability. Relatively less is known about role of slow delayed rectifying potassium current, I(Ks), in dynamics of repolarization and memory compared to the rapidly activating current I(Kr). Trans-membrane potentials were recorded from right ventricular tissues from pigs during reduction (chromanol 293B) and increases in I(Ks) (mefenamic acid). A novel pacing protocol was used to explicitly control diastolic intervals to quantify memory. Restitution hysteresis, a consequence of memory, increased after chromanol 293B (loop thickness and area increased 27 and 38 %) and decreased after mefenamic acid (52 and 53 %). Standard and dynamic restitutions showed an increase in average slope after chromanol 293B and a decrease after mefenamic acid. Increase in slope and memory are hypothesized to have opposite effects on electrical stability; therefore, these results suggest that reduction and enhancement of I(Ks) likely also have offsetting components that affect stability.
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Affiliation(s)
- Linyuan Jing
- Department of Biomedical Engineering, University of Kentucky, Lexington, KY USA
| | - Kathleen Brownson
- Department of Biomedical Engineering, University of Kentucky, Lexington, KY USA
| | - Abhijit Patwardhan
- Department of Biomedical Engineering, University of Kentucky, Lexington, KY USA
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Stott JB, Jepps TA, Greenwood IA. KV7 potassium channels: a new therapeutic target in smooth muscle disorders. Drug Discov Today 2014; 19:413-24. [DOI: 10.1016/j.drudis.2013.12.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 10/21/2013] [Accepted: 12/04/2013] [Indexed: 12/23/2022]
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Choi SH, Lee BH, Kim HJ, Jung SW, Hwang SH, Nah SY. Differential effects of ginsenoside metabolites on slowly activating delayed rectifier K(+) and KCNQ1 K(+) channel currents. J Ginseng Res 2013; 37:324-31. [PMID: 24198658 PMCID: PMC3818959 DOI: 10.5142/jgr.2013.37.324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/27/2013] [Accepted: 05/27/2013] [Indexed: 11/18/2022] Open
Abstract
Channels formed by the co-assembly of the KCNQ1 subunit and the mink (KCNE1) subunit underline the slowly activating delayed rectifier K+ channels (IKs) in the heart. This K+ channel is one of the main pharmacological targets for the development of drugs against cardiovascular disease. Panax ginseng has been shown to exhibit beneficial cardiovascular effects. In a previous study, we showed that ginsenoside Rg3 activates human KCNQ1 K+ channel currents through interactions with the K318 and V319 residues. However, little is known about the effects of ginsenoside metabolites on KCNQ1 K+ alone or the KCNQ1 + KCNE1 K+ (IKs) channels. In the present study, we examined the effect of protopanaxatriol (PPT) and compound K (CK) on KCNQ1 K+ and IKs channel activity expressed in Xenopus oocytes. PPT more strongly inhibited the IKs channel currents than the currents of KCNQ1 K+ alone in concentration- and voltage-dependent manners. The IC50 values on IKs and KCNQ1 alone currents for PPT were 5.18±0.13 and 10.04±0.17 μM, respectively. PPT caused a leftward shift in the activation curve of IKs channel activity, but minimally affected KCNQ1 alone. CK exhibited slight inhibition on IKs and KCNQ1 alone K+ channel currents. These results indicate that ginsenoside metabolites show limited effects on IKs channel activity, depending on the structure of the ginsenoside metabolites.
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Affiliation(s)
- Sun-Hye Choi
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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Hayashi M, Novak I. Molecular basis of potassium channels in pancreatic duct epithelial cells. Channels (Austin) 2013; 7:432-41. [PMID: 23962792 PMCID: PMC4042478 DOI: 10.4161/chan.26100] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K+ channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K+ channels in pancreatic duct cells, including KCNN4 (KCa3.1), KCNMA1 (KCa1.1), KCNQ1 (Kv7.1), KCNH2 (Kv11.1), KCNH5 (Kv10.2), KCNT1 (KCa4.1), KCNT2 (KCa4.2), and KCNK5 (K2P5.1). We will give an overview of K+ channels with respect to their electrophysiological and pharmacological characteristics and regulation, which we know from other cell types, preferably in epithelia, and, where known, their identification and functions in pancreatic ducts and in adenocarcinoma cells. We conclude by pointing out some outstanding questions and future directions in pancreatic K+ channel research with respect to the physiology of secretion and pancreatic pathologies, including pancreatitis, cystic fibrosis, and cancer, in which the dysregulation or altered expression of K+ channels may be of importance.
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Affiliation(s)
- Mikio Hayashi
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
| | - Ivana Novak
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
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K+ channels regulate ENaC expression via changes in promoter activity and control fluid clearance in alveolar epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1818:1682-90. [PMID: 22406554 DOI: 10.1016/j.bbamem.2012.02.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 02/16/2012] [Accepted: 02/22/2012] [Indexed: 12/21/2022]
Abstract
Active Na+ absorption by alveolar ENaC is the main driving force of liquid clearance at birth and lung edema resorption in adulthood. We have demonstrated previously that long-term modulation of KvLQT1 and KATP K+ channel activities exerts sustained control in Na+ transport through the regulation of ENaC expression in primary alveolar type II (ATII) cells. The goal of the present study was: 1) to investigate the role of the alpha-ENaC promoter, transfected in the A549 alveolar cell line, in the regulation of ENaC expression by K+ channels, and 2) to determine the physiological impact of K+ channels and ENaC modulation on fluid clearance in ATII cells. KvLQT1 and KATP channels were first identified in A549 cells by PCR and Western blotting. We showed, for the first time, that KvLQT1 activation by R-L3 (applied for 24 h) increased alpha-ENaC expression, similarly to KATP activation by pinacidil. Conversely, pharmacological KvLQT1 and KATP inhibition or silencing with siRNAs down-regulated alpha-ENaC expression. Furthermore, K+ channel blockers significantly decreased alpha-ENaC promoter activity. Our results indicated that this decrease in promoter activity could be mediated, at least in part, by the repressor activity of ERK1/2. Conversely, KvLQT1 and KATP activation dose-dependently enhanced alpha-ENaC promoter activity. Finally, we noted a physiological impact of changes in K+ channel functions on ERK activity, alpha-, beta-, gamma-ENaC subunit expression and fluid absorption through polarized ATII cells. In summary, our results disclose that K+ channels regulate alpha-ENaC expression by controlling its promoter activity and thus affect the alveolar function of fluid clearance.
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Dynamic subunit stoichiometry confers a progressive continuum of pharmacological sensitivity by KCNQ potassium channels. Proc Natl Acad Sci U S A 2013; 110:8732-7. [PMID: 23650380 DOI: 10.1073/pnas.1300684110] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Voltage-gated KCNQ1 (Kv7.1) potassium channels are expressed abundantly in heart but they are also found in multiple other tissues. Differential coassembly with single transmembrane KCNE beta subunits in different cell types gives rise to a variety of biophysical properties, hence endowing distinct physiological roles for KCNQ1-KCNEx complexes. Mutations in either KCNQ1 or KCNE1 genes result in diseases in brain, heart, and the respiratory system. In addition to complexities arising from existence of five KCNE subunits, KCNE1 to KCNE5, recent studies in heterologous systems suggest unorthodox stoichiometric dynamics in subunit assembly is dependent on KCNE expression levels. The resultant KCNQ1-KCNE channel complexes may have a range of zero to two or even up to four KCNE subunits coassembling per KCNQ1 tetramer. These findings underscore the need to assess the selectivity of small-molecule KCNQ1 modulators on these different assemblies. Here we report a unique small-molecule gating modulator, ML277, that potentiates both homomultimeric KCNQ1 channels and unsaturated heteromultimeric (KCNQ1)4(KCNE1)n (n < 4) channels. Progressive increase of KCNE1 or KCNE3 expression reduces efficacy of ML277 and eventually abolishes ML277-mediated augmentation. In cardiomyocytes, the slowly activating delayed rectifier potassium current, or IKs, is believed to be a heteromultimeric combination of KCNQ1 and KCNE1, but it is not entirely clear whether IKs is mediated by KCNE-saturated KCNQ1 channels or by channels with intermediate stoichiometries. We found ML277 effectively augments IKs current of cultured human cardiomyocytes and shortens action potential duration. These data indicate that unsaturated heteromultimeric (KCNQ1)4(KCNE1)n channels are present as components of IKs and are pharmacologically distinct from KCNE-saturated KCNQ1-KCNE1 channels.
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Veeraraghavan R, Larsen AP, Torres NS, Grunnet M, Poelzing S. Potassium channel activators differentially modulate the effect of sodium channel blockade on cardiac conduction. Acta Physiol (Oxf) 2013; 207:280-9. [PMID: 22913299 DOI: 10.1111/j.1748-1716.2012.02481.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/02/2012] [Accepted: 07/30/2012] [Indexed: 11/29/2022]
Abstract
AIMS Diminished repolarization reserve contributes to the arrhythmogenic substrate in many disease states. Pharmacological activation of K(+) channels has been suggested as a potential antiarrhythmic therapy in such conditions. Having previously demonstrated that I(K1) and I(Kr) can modulate cardiac conduction, we tested here the effects of pharmacological I(KATP) and I(Ks) activation on cardiac conduction and its dependence on the sodium current (I(Na)). METHODS AND RESULTS Bath electrocardiograms (ECGs) recorded from Langendorff-perfused guinea pig ventricles revealed QRS prolongation during I(KATP) activation by pinacidil but not during I(Ks) activation by R-L3 relative to control. In contrast, when I(Na) was partially blocked by flecainide, R-L3 but not pinacidil prolonged the QRS relative to flecainide alone. Conduction velocity (θ) was quantified by optical mapping during epicardial pacing. Both longitudinal (θ(L)) and transverse (θ(T)) θ were reduced by pinacidil (by 10 ± 1 and 9 ± 3%, respectively) and R-L3 (by 11 ± 2% and 15 ± 4%, respectively). Flecainide decreased θ(L) by 33 ± 4% and θ(T) by 36 ± 5%. Whereas pinacidil did not further slow θ relative to flecainide alone, R-L3 decreased both θ(L) and θ(T). CONCLUSION Pharmacological activation of I(KATP) and I(Ks) slows cardiac conduction; however, they demonstrate diverse effects on θ dependence on I(Na) blockade. These findings may have significant implications for the use of K(+) channel activators as antiarrhythmic drugs and for patients with Na(+) channel abnormalities or being treated with Na(+) channel blockers.
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Affiliation(s)
- R. Veeraraghavan
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | - A. P. Larsen
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | - N. S. Torres
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
| | | | - S. Poelzing
- Nora Eccles Harrison Cardiovascular Research and Training Institute; University of Utah; Salt Lake City; UT; USA
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Corici C, Kohajda Z, Kristóf A, Horváth A, Virág L, Szél T, Nagy N, Szakonyi Z, Fülöp F, Muntean DM, Varró A, Jost N. L-364,373 (R-L3) enantiomers have opposite modulating effects on IKs in mammalian ventricular myocytes. Can J Physiol Pharmacol 2013; 91:586-92. [PMID: 23889560 DOI: 10.1139/cjpp-2012-0407] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activators of the slow delayed rectifier K⁺ current (IKs) have been suggested as promising tools for suppressing ventricular arrhythmias due to prolongation of repolarization. Recently, L-364,373 (R-L3) was nominated to activate IKs in myocytes from several species; however, in some studies, it failed to activate IKs. One later study suggested opposite modulating effects from the R-L3 enantiomers as a possible explanation for this discrepancy. Therefore, we analyzed the effect of the RL-3 enantiomers on IKs in ventricular mammalian myocytes, by applying standard microelectrode and whole-cell patch-clamp techniques at 37 °C. We synthesized 2 substances, ZS_1270B (right) and ZS_1271B (left), the 2 enantiomers of R-L3. In rabbit myocytes, ZS_1270B enhanced the IKs tail current by approximately 30%, whereas ZS_1271B reduced IKs tails by 45%. In guinea pig right ventricular preparations, ZS_1270B shortened APD90 (action potential duration measured at 90% repolarization) by 12%, whereas ZS_1271B lengthened it by approximately 15%. We concluded that R-L3 enantiomers in the same concentration range indeed have opposite modulating effects on IKs, which may explain why the racemic drug R-L3 previously failed to activate IKs. ZS_1270B is a potent IKs activator, therefore, this substance is appropriate to test whether IKs activators are ideal tools to suppress ventricular arrhythmias originating from prolongation of action potentials.
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Affiliation(s)
- Claudia Corici
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, H-6701 Szeged, Hungary
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Zheng Y, Zhu X, Zhou P, Lan X, Xu H, Li M, Gao Z. Hexachlorophene is a potent KCNQ1/KCNE1 potassium channel activator which rescues LQTs mutants. PLoS One 2012; 7:e51820. [PMID: 23251633 PMCID: PMC3520906 DOI: 10.1371/journal.pone.0051820] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 11/06/2012] [Indexed: 12/22/2022] Open
Abstract
The voltage-gated KCNQ1 potassium channel is expressed in cardiac tissues, and coassembly of KCNQ1 with an auxiliary KCNE1 subunit mediates a slowly activating current that accelerates the repolarization of action potential in cardiomyocytes. Mutations of KCNQ1 genes that result in reduction or loss of channel activity cause prolongation of repolarization during action potential, thereby causing long QT syndrome (LQTs). Small molecule activators of KCNQ1/KCNE1 are useful both for understanding the mechanism of the complex activity and for developing therapeutics for LQTs. In this study we report that hexachlorophene (HCP), the active component of the topical anti-infective prescription drug pHisoHex, is a KCNQ1/KCNE1 activator. HCP potently increases the current amplitude of KCNQ1/KCNE1 expressed by stabilizing the channel in an open state with an EC50 of 4.61±1.29 μM. Further studies in cardiomyocytes showed that HCP significantly shortens the action potential duration at 1 μM. In addition, HCP is capable of rescuing the loss of function of the LQTs mutants caused by either impaired activation gating or phosphatidylinositol-4,5-bisphosphate (PIP2) binding affinity. Our results indicate HCP is a novel KCNQ1/KCNE1 activator and may be a useful tool compound for the development of LQTs therapeutics.
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Affiliation(s)
- Yueming Zheng
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xuejing Zhu
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Pingzheng Zhou
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xi Lan
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Haiyan Xu
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Min Li
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- Department of Neuroscience, High Throughput Biology Center and Johns Hopkins Ion Channel Center, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail: (ML); (ZG)
| | - Zhaobing Gao
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- * E-mail: (ML); (ZG)
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Chadha PS, Zunke F, Davis AJ, Jepps TA, Linders JTM, Schwake M, Towart R, Greenwood IA. Pharmacological dissection of K(v)7.1 channels in systemic and pulmonary arteries. Br J Pharmacol 2012; 166:1377-87. [PMID: 22251082 DOI: 10.1111/j.1476-5381.2012.01863.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to characterize the functional impact of KCNQ1-encoded voltage-dependent potassium channels (K(v)7.1) in the vasculature. EXPERIMENTAL APPROACH Mesenteric arteries, intrapulmonary arteries and thoracic aortae were isolated from adult rats. K(v)7.1 channel expression was established by fluorescence immunocytochemistry. Wire myography determined functionality of these channels in response to selective blockers and activators. Xenopus oocytes expressing K(v)7.1 channels were used to assess the effectiveness of selective K(v)7.1 channel blockers. KEY RESULTS K(v)7.1 channels were identified in arterial myocytes by immunocytochemistry. K(v)7.1 blockers HMR1556, L-768,673 (10 µM) and JNJ39490282 (JNJ282; 1 µM) had no contractile effects in arteries, whereas the pan-K(v)7 channel blocker linopirdine (10 µM) evoked robust contractions. Application of two compounds purported to activate K(v)7.1 channels, L-364 373 (R-L3) and mefenamic acid, relaxed mesenteric arteries preconstricted by methoxamine. These responses were reversed by HMR1556 or L-768,673 but not JNJ282. Similar effects were observed in the thoracic aorta and intrapulmonary arteries. CONCLUSIONS AND IMPLICATIONS In contrast to previous assumptions, K(v)7.1 channels expressed in arterial myocytes are functional ion channels. Although these channels do not appear to contribute to resting vascular tone, K(v)7.1 activators were effective vasorelaxants.
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Affiliation(s)
- Preet S Chadha
- Division of Biomedical Sciences: Ion Channels and Cell Signalling Group, St George's, University of London, London, UK
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Identification of (R)-N-(4-(4-methoxyphenyl)thiazol-2-yl)-1-tosylpiperidine-2-carboxamide, ML277, as a novel, potent and selective K(v)7.1 (KCNQ1) potassium channel activator. Bioorg Med Chem Lett 2012; 22:5936-41. [PMID: 22910039 DOI: 10.1016/j.bmcl.2012.07.060] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 07/11/2012] [Accepted: 07/16/2012] [Indexed: 11/21/2022]
Abstract
A high-throughput screen utilizing a depolarization-triggered thallium influx through KCNQ1 channels was developed and used to screen the MLSMR collection of over 300,000 compounds. An iterative medicinal chemistry approach was initiated and from this effort, ML277 was identified as a potent activator of KCNQ1 channels (EC(50)=260 nM). ML277 was shown to be highly selective against other KCNQ channels (>100-fold selectivity versus KCNQ2 and KCNQ4) as well as against the distantly related hERG potassium channel.
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49
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Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel. Proc Natl Acad Sci U S A 2012; 109:11866-71. [PMID: 22745159 DOI: 10.1073/pnas.1205266109] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as I(Ks) and I(Kr). The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of I(Kr) by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if I(Ks) is reduced. Using a unique specific chemical activator for I(Kr) that has a primary effect of causing a right shift of V(1/2) for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an I(Kr) chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent.
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Jia S, Lian J, Guo D, Xue X, Patel C, Yang L, Yuan Z, Ma A, Yan GX. Modulation of the late sodium current by ATX-II and ranolazine affects the reverse use-dependence and proarrhythmic liability of IKr blockade. Br J Pharmacol 2012; 164:308-16. [PMID: 21182492 DOI: 10.1111/j.1476-5381.2010.01181.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Drug-induced torsades de pointes (TdP) often occurs during bradycardia due to reverse use-dependence. We tested the hypothesis that inhibition or enhancement of late sodium current (I(Na,L) ) could modulate the drug-induced reverse use-dependence in QT and T(p-e) (an index of dispersion of repolarization), and therefore the liability for TdP. EXPERIMENTAL APPROACH Arterially perfused rabbit left ventricular wedge preparations were used. Action potentials from the endocardium were recorded simultaneously with a transmural ECG. The effects of Anemonia sulcata toxin (ATX-II) (an I(Na,L) enhancer), d,l-sotalol, clarithromycin and ranolazine (an I(Na,L) blocker) on rate-dependent changes in QT, T(p-e) and proarrhythmic events were tested, either alone or in combination. Rate-dependent QT and T(p-e) slopes and TdP score (a combined index of TdP liability) were calculated at control and during drug infusion. KEY RESULTS ATX-II (30 nM) and sotalol (300 µM) caused a marked increase in QT and T(p-e) intervals, steeper QT-basic cycle length (BCL) and T(p-e) -BCL slopes (i.e. reverse use-dependence), and TdP. Addition of ranolazine (15 µM) to ATX-II or sotalol significantly attenuated QT-BCL, T(p-e) -BCL slopes and the increased TdP scores. In contrast, clarithromycin (100 µM) moderately prolonged QT and T(p-e) without causing R-on-T extrasystole or TdP, but addition of ATX-II (1 nM) to clarithromycin markedly amplified the QT-BCL and T(p-e) -BCL slopes and further increased TdP score. CONCLUSION AND IMPLICATIONS Modulation of I(Na,L) altered drug-induced reverse use-dependence related to QT as well as T(p-e) , indicating that inhibition of I(Na,L) can markedly reduce the TdP liability of agents that prolong QT intervals.
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Affiliation(s)
- Shaobin Jia
- The First Hospital, Xi'An Jiaotong University, Xi'An, China
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