1
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Lu H, Ding W, Xiao H, Dai M, Xue Y, Jia Z, Guo J, Wu M, Shen B, Zhao R. Association of the P441L KCNQ1 variant with severity of long QT syndrome and risk of cardiac events. Front Cardiovasc Med 2022; 9:922335. [PMID: 36386331 PMCID: PMC9659898 DOI: 10.3389/fcvm.2022.922335] [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: 04/17/2022] [Accepted: 09/12/2022] [Indexed: 11/27/2022] Open
Abstract
Dysfunction of potassium voltage-gated channel subfamily Q member 1 (KCNQ1) is a primary cause of long QT syndrome type 1 (LQT1). Here, we report a missense mutation P441L in KCNQ1 C-terminus of a 37-year-old woman with severe LQT1 phenotype. Variant P441L transporting to the plasma membrane and interacting with KCNE1 were both markedly decreased, leading to potassium efflux disorder and eventually LQT1. Mutations between the C-terminal helix A and helix B of KCNQ1 have linked with low cardiac event risk, however, we firstly find variant P441L causing a severe LQT1 phenotype with a high risk of cardiac events.
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Affiliation(s)
- Haoyang Lu
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Wen Ding
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Hui Xiao
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Manyu Dai
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Yangcheng Xue
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Zhuoran Jia
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Jie Guo
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Mengzuo Wu
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Bing Shen
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
- Bing Shen,
| | - Ren Zhao
- Department of Cardiovascular Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, China
- *Correspondence: Ren Zhao,
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2
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Blandin CE, Gravez BJ, Hatem SN, Balse E. Remodeling of Ion Channel Trafficking and Cardiac Arrhythmias. Cells 2021; 10:cells10092417. [PMID: 34572065 PMCID: PMC8468138 DOI: 10.3390/cells10092417] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/08/2021] [Accepted: 09/11/2021] [Indexed: 01/08/2023] Open
Abstract
Both inherited and acquired cardiac arrhythmias are often associated with the abnormal functional expression of ion channels at the cellular level. The complex machinery that continuously traffics, anchors, organizes, and recycles ion channels at the plasma membrane of a cardiomyocyte appears to be a major source of channel dysfunction during cardiac arrhythmias. This has been well established with the discovery of mutations in the genes encoding several ion channels and ion channel partners during inherited cardiac arrhythmias. Fibrosis, altered myocyte contacts, and post-transcriptional protein changes are common factors that disorganize normal channel trafficking during acquired cardiac arrhythmias. Channel availability, described notably for hERG and KV1.5 channels, could be another potent arrhythmogenic mechanism. From this molecular knowledge on cardiac arrhythmias will emerge novel antiarrhythmic strategies.
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Affiliation(s)
- Camille E. Blandin
- INSERM, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition—UNITE 1166, Sorbonne Université, EQUIPE 3, F-75013 Paris, France; (C.E.B.); (B.J.G.); (S.N.H.)
| | - Basile J. Gravez
- INSERM, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition—UNITE 1166, Sorbonne Université, EQUIPE 3, F-75013 Paris, France; (C.E.B.); (B.J.G.); (S.N.H.)
| | - Stéphane N. Hatem
- INSERM, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition—UNITE 1166, Sorbonne Université, EQUIPE 3, F-75013 Paris, France; (C.E.B.); (B.J.G.); (S.N.H.)
- ICAN—Institute of Cardiometabolism and Nutrition, Institute of Cardiology, Pitié-Salpêtrière Hospital, Sorbonne University, F-75013 Paris, France
| | - Elise Balse
- INSERM, Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition—UNITE 1166, Sorbonne Université, EQUIPE 3, F-75013 Paris, France; (C.E.B.); (B.J.G.); (S.N.H.)
- Correspondence:
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3
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Needham PG, Guerriero CJ, Brodsky JL. Chaperoning Endoplasmic Reticulum-Associated Degradation (ERAD) and Protein Conformational Diseases. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033928. [PMID: 30670468 DOI: 10.1101/cshperspect.a033928] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Misfolded proteins compromise cellular homeostasis. This is especially problematic in the endoplasmic reticulum (ER), which is a high-capacity protein-folding compartment and whose function requires stringent protein quality-control systems. Multiprotein complexes in the ER are able to identify, remove, ubiquitinate, and deliver misfolded proteins to the 26S proteasome for degradation in the cytosol, and these events are collectively termed ER-associated degradation, or ERAD. Several steps in the ERAD pathway are facilitated by molecular chaperone networks, and the importance of ERAD is highlighted by the fact that this pathway is linked to numerous protein conformational diseases. In this review, we discuss the factors that constitute the ERAD machinery and detail how each step in the pathway occurs. We then highlight the underlying pathophysiology of protein conformational diseases associated with ERAD.
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Affiliation(s)
- Patrick G Needham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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4
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Capera J, Serrano-Novillo C, Navarro-Pérez M, Cassinelli S, Felipe A. The Potassium Channel Odyssey: Mechanisms of Traffic and Membrane Arrangement. Int J Mol Sci 2019; 20:ijms20030734. [PMID: 30744118 PMCID: PMC6386995 DOI: 10.3390/ijms20030734] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/06/2019] [Accepted: 02/08/2019] [Indexed: 12/29/2022] Open
Abstract
Ion channels are transmembrane proteins that conduct specific ions across biological membranes. Ion channels are present at the onset of many cellular processes, and their malfunction triggers severe pathologies. Potassium channels (KChs) share a highly conserved signature that is necessary to conduct K⁺ through the pore region. To be functional, KChs require an exquisite regulation of their subcellular location and abundance. A wide repertoire of signatures facilitates the proper targeting of the channel, fine-tuning the balance that determines traffic and location. These signature motifs can be part of the secondary or tertiary structure of the protein and are spread throughout the entire sequence. Furthermore, the association of the pore-forming subunits with different ancillary proteins forms functional complexes. These partners can modulate traffic and activity by adding their own signatures as well as by exposing or masking the existing ones. Post-translational modifications (PTMs) add a further dimension to traffic regulation. Therefore, the fate of a KCh is not fully dependent on a gene sequence but on the balance of many other factors regulating traffic. In this review, we assemble recent evidence contributing to our understanding of the spatial expression of KChs in mammalian cells. We compile specific signatures, PTMs, and associations that govern the destination of a functional channel.
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Affiliation(s)
- Jesusa Capera
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain.
| | - Clara Serrano-Novillo
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain.
| | - María Navarro-Pérez
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain.
| | - Silvia Cassinelli
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain.
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, 08028 Barcelona, Spain.
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5
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Balse E, Boycott HE. Ion Channel Trafficking: Control of Ion Channel Density as a Target for Arrhythmias? Front Physiol 2017; 8:808. [PMID: 29089904 PMCID: PMC5650974 DOI: 10.3389/fphys.2017.00808] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/02/2017] [Indexed: 12/20/2022] Open
Abstract
The shape of the cardiac action potential (AP) is determined by the contributions of numerous ion channels. Any dysfunction in the proper function or expression of these ion channels can result in a change in effective refractory period (ERP) and lead to arrhythmia. The processes underlying the correct targeting of ion channels to the plasma membrane are complex, and have not been fully characterized in cardiac myocytes. Emerging evidence highlights ion channel trafficking as a potential causative factor in certain acquired and inherited arrhythmias, and therapies which target trafficking as opposed to pore block are starting to receive attention. In this review we present the current evidence for the mechanisms which underlie precise control of cardiac ion channel trafficking and targeting.
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Affiliation(s)
- Elise Balse
- Unité de Recherche sur les Maladies Cardiovasculaires, le Métabolisme et la Nutrition, Faculté de Médecine Pitié-Salpêtrière, Sorbonne Universités, UPMC Univ. Paris VI, Inserm, UMRS 1166, Université Pierre et Marie Curie, Paris, France
| | - Hannah E. Boycott
- Department of Cardiovascular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
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6
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Nishimura M, Ueda M, Ebata R, Utsuno E, Ishii T, Matsushita K, Ohara O, Shimojo N, Kobayashi Y, Nomura F. A novel KCNQ1 nonsense variant in the isoform-specific first exon causes both jervell and Lange-Nielsen syndrome 1 and long QT syndrome 1: a case report. BMC MEDICAL GENETICS 2017; 18:66. [PMID: 28595573 PMCID: PMC5465588 DOI: 10.1186/s12881-017-0430-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 05/30/2017] [Indexed: 01/08/2023]
Abstract
Background According to previous KCNQ1 (potassium channel, voltage gated, KQT-like subfamily, member 1) gene screening studies, missense variants, but not nonsense or frame-shift variants, cause the majority of long QT syndrome (LQTS; Romano-Ward syndrome [RWS]) 1 cases. Several missense variants are reported to cause RWS by a dominant-negative mechanism, and some KCNQ1 variants can cause both Jervell and Lange-Nielsen Syndrome (JLNS; in an autosomal recessive manner) and LQTS1 (in an autosomal dominant manner), while other KCNQ1 variants cause only JLNS. The human KCNQ1 gene is known to have two transcript isoforms (kidney isoform and pancreas isoform), and both isoforms can form a functional cardiac potassium channel. Case presentation Here, we report a novel nonsense KCNQ1 variant causing not only JLNS, but also significant QTc prolongation identical to RWS in an autosomal dominant manner. Our case study supports that haploinsufficiency in the KCNQ1 gene is causative of significant QTc prolongation identical to RWS. Interestingly, the nonsense variant (NM_000218.2:c.115G > T [p.Glu39X]) locates in exon 1a of KCNQ1, which is a kidney-isoform specific exon. The variant is located closer to the N-terminus than previously identified nonsense or frame-shift variants. Conclusion To the best of our knowledge, this is the first report showing that a nonsense variant in exon 1a of KCNQ1, which is the kidney-isoform specific exon, causes JLNS. Our findings may be informative to the genetic pathogenesis of RWS and JLNS caused by KCNQ1 variants. Electronic supplementary material The online version of this article (doi:10.1186/s12881-017-0430-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Motoi Nishimura
- Division of Clinical Genetics, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan. .,Division of Laboratory Medicine, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan.
| | - Marehiko Ueda
- Department of Cardiovascular Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Ryota Ebata
- Department of Pediatrics, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Emi Utsuno
- Division of Clinical Genetics, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Takuma Ishii
- Kawaguchi Kogyo General Hospital, 1-18-10, Sakae-cho, Kawaguchi, Saitama, 332-0017, Japan
| | - Kazuyuki Matsushita
- Division of Clinical Genetics, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan.,Division of Laboratory Medicine, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Osamu Ohara
- Kazusa DNA Reaearch Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba, 292-0818, Japan
| | - Naoki Shimojo
- Department of Pediatrics, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Yoshio Kobayashi
- Department of Cardiovascular Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
| | - Fumio Nomura
- Division of Clinical Genetics, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan.,Divisions of Clinical Mass Spectrometry and Clinical Genetics, Chiba University Hospital, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture, 260-8670, Japan
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7
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Wang S, Li L, Tao R, Gao Y. Ion channelopathies associated genetic variants as the culprit for sudden unexplained death. Forensic Sci Int 2017; 275:128-137. [PMID: 28363160 DOI: 10.1016/j.forsciint.2017.03.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 02/23/2017] [Accepted: 03/13/2017] [Indexed: 11/29/2022]
Abstract
Forensic identification of sudden unexplained death (SUD) has always been a ticklish issue because it used to be defined as sudden death without a conclusive diagnosis after autopsy. However, benefiting from the developments in genome research, a growing body of evidence points to the importance of ion channelopathies associated genetic variants in the pathogenesis of SUD. Genetic diagnosis of the deceased is also a new trend in epidemiological studies, for it enables the undertaking for preventive approach in individuals with high risks. In this review, we briefly discuss the molecular structure of ion channels and the role of genetic variants in regulating their functions as well as the diverse mechanisms underlying the ion channelopathies at gene level.
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Affiliation(s)
- Shouyu Wang
- Department of Forensic Medicine, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Lijuan Li
- Department of Forensic Medicine, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Ruiyang Tao
- Department of Forensic Medicine, Medical College of Soochow University, Suzhou 215123, Jiangsu, China
| | - Yuzhen Gao
- Department of Forensic Medicine, Medical College of Soochow University, Suzhou 215123, Jiangsu, China.
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8
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Wu J, Ding WG, Horie M. Molecular pathogenesis of long QT syndrome type 1. J Arrhythm 2016; 32:381-388. [PMID: 27761162 PMCID: PMC5063268 DOI: 10.1016/j.joa.2015.12.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/16/2015] [Accepted: 12/17/2015] [Indexed: 01/08/2023] Open
Abstract
Long QT syndrome type 1 (LQT1) is a subtype of a congenital cardiac syndrome caused by mutation in the KCNQ1 gene, which encodes the α-subunit of the slow component of delayed rectifier K+ current (IKs) channel. Arrhythmias in LQT1 are characterized by prolongation of the QT interval on ECG, as well as the occurrence of life-threatening cardiac events, frequently triggered by adrenergic stimuli (e.g., physical or emotional stress). During the past two decades, much advancement has been made in understanding the molecular pathogenesis underlying LQT1. Uncovering the genotype-phenotype correlations in LQT1 is of clinical importance to better understand the gene-specific differences that may influence the propensity for developing life-threatening arrhythmias under specific conditions. Elucidation of these mechanisms will also help to improve the diagnosis and management of this cardiac disorder based on gene-specific considerations. This review describes the current medical consensus and recent developments regarding the molecular pathogenesis of LQT1 and provides a novel insight into the adrenergic regulation of this disease.
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Affiliation(s)
- Jie Wu
- Department of Pharmacology, School of Basic Medical Sciences, Xi’an Jiaotong University Health Science Center, 710061, Xi׳an, China
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu 520-2192, Japan
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Wei-Guang Ding
- Department of Physiology, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu 520-2192, Japan
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9
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Abstract
Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia.
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Affiliation(s)
- Lei Chen
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Kevin J Sampson
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Robert S Kass
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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10
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Cellular mechanisms underlying the increased disease severity seen for patients with long QT syndrome caused by compound mutations in KCNQ1. Biochem J 2014; 462:133-42. [PMID: 24912595 DOI: 10.1042/bj20140425] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The KCNQ1 (potassium voltage-gated channel, KQT-like subfamily, member 1) gene encodes the Kv7.1 potassium channel which forms a complex with KCNE1 (potassium voltage-gated channel Isk-related family member 1) in the human heart to produce the repolarizing IKs (slow delayed rectifier potassium current). Mutations in KCNQ1 can perturb IKs function and cause LQT1 (long QT syndrome type 1). In LQT1, compound mutations are relatively common and are associated with increased disease severity. LQT1 compound mutations have been shown to increase channel dysfunction, but whether other disease mechanisms, such as defective channel trafficking, contribute to the increase in arrhythmic risk has not been determined. Using an imaging-based assay we investigated the effects of four compound heterozygous mutations (V310I/R594Q, A341V/P127T, T391I/Q530X and A525T/R518X), one homozygous mutation (W248F) and one novel compound heterozygous mutation (A178T/K422fs39X) (where fs denotes frameshift) on channel trafficking. By analysing the effects in the equivalent of a homozygous, heterozygous and compound heterozygous condition, we identify three different types of behaviour. A341V/P127T and W248F/W248F had no effect, whereas V310I/R594Q had a moderate, but not compound, effect on channel trafficking. In contrast, T391I/Q530X, A525T/R518X and A178T/K422fs39X severely disrupted channel trafficking when expressed in compound form. In conclusion, we have characterized the disease mechanisms for six LQT1 compound mutations and report that, for four of these, defective channel trafficking underlies the severe clinical phenotype.
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11
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Macri V, Mahida SN, Zhang ML, Sinner MF, Dolmatova EV, Tucker NR, McLellan M, Shea MA, Milan DJ, Lunetta KL, Benjamin EJ, Ellinor PT. A novel trafficking-defective HCN4 mutation is associated with early-onset atrial fibrillation. Heart Rhythm 2014; 11:1055-1062. [PMID: 24607718 DOI: 10.1016/j.hrthm.2014.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Indexed: 01/08/2023]
Abstract
BACKGROUND Atrial fibrillation (AF) is the most common arrhythmia, and a recent genome-wide association study identified the hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) as a novel AF susceptibility locus. HCN4 encodes for the cardiac pacemaker channel, and HCN4 mutations are associated with familial sinus bradycardia and AF. OBJECTIVE The purpose of this study was to determine whether novel variants in the coding region of HCN4 contribute to the susceptibility for AF. METHODS We sequenced the coding region of HCN4 for novel variants from 527 cases with early-onset AF from the Massachusetts General Hospital AF Study and 443 referents from the Framingham Heart Study. We used site-directed mutagenesis, cellular electrophysiology, immunocytochemistry, and confocal microscopy to functionally characterize novel variants. RESULTS We found the frequency of novel coding HCN4 variants was 2-fold greater for individuals with AF (7 variants) compared to the referents (3 variants). We determined that of the 7 novel HCN4 variants in our AF cases, 1 (p.Pro257Ser, located in the amino-terminus adjacent to the first transmembrane spanning domain) did not traffic to cell membrane, whereas the remaining 6 were not functionally different from wild type. In addition, the 3 novel variants in our referents did not alter function compared to wild-type. Coexpression studies showed that the p.Pro257Ser mutant channel failed to colocalize with the wild-type HCN4 channel on the cell membrane. CONCLUSION Our findings are consistent with HCN4 haploinsufficiency as the likely mechanism for early-onset AF in the p.Pro257Ser carrier.
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Affiliation(s)
- Vincenzo Macri
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Saagar N Mahida
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Michael L Zhang
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Moritz F Sinner
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Department of Medicine I, University Hospital Grosshadern, Ludwig-Maximilians University, Munich, Germany.,National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA
| | - Elena V Dolmatova
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Nathan R Tucker
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Micheal McLellan
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Marisa A Shea
- Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - David J Milan
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Kathryn L Lunetta
- Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA.,Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA.,National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA
| | - Emelia J Benjamin
- Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA.,Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA.,National Heart, Lung, and Blood Institute's and Boston University's Framingham Heart Study, Framingham, Massachusetts, USA.,Preventive Medicine Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA.,Cardiology Section, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Patrick T Ellinor
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA.,Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, Massachusetts, USA
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12
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A Molecular Mechanism for Adrenergic-Induced Long QT Syndrome. J Am Coll Cardiol 2014; 63:819-27. [DOI: 10.1016/j.jacc.2013.08.1648] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 08/05/2013] [Accepted: 08/26/2013] [Indexed: 11/19/2022]
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13
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Iron-deficiency anaemia, gastric hyperplasia, and elevated gastrin levels due to potassium channel dysfunction in the Jervell and Lange-Nielsen Syndrome. Cardiol Young 2013; 23:325-34. [PMID: 22805636 DOI: 10.1017/s1047951112001060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
AIM We investigated extra-cardiac clinical symptoms and signs in the rare Jervell and Lange-Nielsen Syndrome, characterised by impaired KCNQ1 function, a gene essential for gastric acid secretion. METHODS All Swedish Jervell and Lange-Nielsen cases with double KCNQ1 mutations (14 cases) were investigated by medical record review, an interview, and were offered laboratory testing for iron-deficiency anaemia and gastrointestinal markers. RESULTS A history of iron-deficiency anaemia in 12 of 14 patients and subjective gastrointestinal symptoms in 13 of 14 patients was revealed. Previous endoscopy in five cases had revealed no case of coeliac or inflammatory bowel disease but three cases of mucosal hyperplasia/dysplasia. Current signs of anaemia or iron substitution were present in 9 of 12 tested cases. Elevated levels of gastrin in seven of nine cases, pepsinogen in six of seven cases, and faecal calprotectin in nine of nine cases were present. A significant correlation between elevated gastrin levels and concurrent iron-deficiency and/or anaemia was revealed (p-value 0.039). CONCLUSIONS A high frequency of extra-cardiac clinical symptoms and previous medical investigations was found. We propose that the Jervell and Lange-Nielsen Syndrome phenotypically includes gastrointestinal symptoms/signs and secondary iron-deficiency anaemia owing to hypochlorhydria on the basis of KCNQ1 mutations. The resultant elevated gastrin level is a potential risk factor for later gastrointestinal cancer. Clinical monitoring with regard to developing anaemia and hypergastrinaemia should be considered in the Jervell and Lange-Nielsen Syndrome.
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14
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Friedrichs S, Malan D, Sasse P. Modeling long QT syndromes using induced pluripotent stem cells: Current progress and future challenges. Trends Cardiovasc Med 2013; 23:91-8. [DOI: 10.1016/j.tcm.2012.09.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 09/07/2012] [Accepted: 09/08/2012] [Indexed: 01/27/2023]
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15
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Zaklyazminskaya EV, Abriel H. Prevalence of Significant Genetic Variants in Congenital Long QT Syndrome is Largely Underestimated. Front Pharmacol 2012; 3:72. [PMID: 22557970 PMCID: PMC3338122 DOI: 10.3389/fphar.2012.00072] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 04/06/2012] [Indexed: 11/17/2022] Open
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16
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Winbo A, Stattin EL, Diamant UB, Persson J, Jensen SM, Rydberg A. Prevalence, mutation spectrum, and cardiac phenotype of the Jervell and Lange-Nielsen syndrome in Sweden. Europace 2012; 14:1799-806. [PMID: 22539601 DOI: 10.1093/europace/eus111] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
AIMS To explore the national prevalence, mutation spectrum, cardiac phenotype, and outcome of the uncommon Jervell and Lange-Nielsen syndrome (JLNS), associated with a high risk of sudden cardiac death. METHODS AND RESULTS A national inventory of clinical JLNS cases was performed. Genotype and area of origin were ascertained in index families. Retrospective clinical data were collected from medical records and interviews. We identified 19 cases in 13 Swedish families. A JLNS prevalence >1:200 000 was revealed (five living cases <10 years of age). The mutation spectrum consisted of eight KCNQ1 mutations, whereof p.R518X in 12/24 alleles. Geographic clustering of four mutations (20/24 alleles) and similarities to Norway's mutation spectrum were seen. A high prevalence of heterozygotes was suggested. Three paediatric cases on β-blockers since birth were as yet asymptomatic. Seven symptomatic cases had suffered an aborted cardiac arrest and four had died suddenly. QTc prolongation was significantly longer in symptomatic cases (mean 605 ± 62 vs. 518 ± 50 ms, P = 0.016). β-Blockers reduced, but did not abolish, cardiac events in any previously symptomatic case. β-Blocker type, dosage, and compliance probably affect outcome significantly. Implantable cardioverter-defibrillator therapy (ICD, n = 6) was associated with certain complications; however, no case of sudden death. CONCLUSION Founder effects could explain 83% of the Swedish JLNS mutation spectrum and probably contribute to the high JLNS prevalence found in preadolescent Swedish children. Due to the severe cardiac phenotype in JLNS, the importance of stringent β-blocker therapy and compliance, and consideration of ICD implantation in the case of therapy failure is stressed.
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Affiliation(s)
- Annika Winbo
- Division of Pediatrics, Department of Clinical Sciences, Pediatrics, Umeå University, 90185 Umeå, Sweden.
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Readthrough of long-QT syndrome type 1 nonsense mutations rescues function but alters the biophysical properties of the channel. Biochem J 2012; 443:635-42. [DOI: 10.1042/bj20111912] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The nonsense mutations R518X-KCNQ1 and Q530X-KCNQ1 cause LQT1 (long-QT syndrome type 1) and result in a complete loss of IKs channel function. In the present study we attempted to rescue the function of these mutants, in HEK (human embryonic kidney)-293 cells, by promoting readthrough of their PTCs (premature termination codons) using the pharmacological agents G-418, gentamicin and PTC124. Gentamicin and G-418 acted to promote full-length channel protein expression from R518X at 100 μM and from Q530X at 1 mM. In contrast, PTC124 did not, at any dose tested, induce readthrough of either mutant. G-418 (1 mM) treatment also acted to significantly (P<0.05) increase current density and peak-tail current density, at +80 mV for R518X, but not Q530X, to 58±11% and 82±17% of the wild-type level respectively. However, the biophysical properties of the currents produced from R518X, while similar, were not identical with wild-type as the voltage-dependence of activation was significantly (P<0.05) shifted by +25 mV. Overall, these findings indicate that although functional rescue of LQT1 nonsense mutations is possible, it is dependent on the degree of readthrough achieved and the effect on channel function of the amino acid substituted for the PTC. Such considerations will determine the success of future therapies.
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Abstract
The coordinated generation and propagation of action potentials within cardiomyocytes creates the intrinsic electrical stimuli that are responsible for maintaining the electromechanical pump function of the human heart. The synchronous opening and closing of cardiac Na(+), Ca(2+), and K(+) channels corresponds with the activation and inactivation of inward depolarizing (Na(+) and Ca(2+)) and outward repolarizing (K(+)) currents that underlie the various phases of the cardiac action potential (resting, depolarization, plateau, and repolarization). Inherited mutations in pore-forming α subunits and accessory β subunits of cardiac K(+) channels can perturb the atrial and ventricular action potential and cause various cardiac arrhythmia syndromes, including long QT syndrome, short QT syndrome, Brugada syndrome, and familial atrial fibrillation. In this Review, we summarize the current understanding of the molecular and cellular mechanisms that underlie K(+)-channel-mediated arrhythmia syndromes. We also describe translational advances that have led to the emerging role of genetic testing and genotype-specific therapy in the diagnosis and clinical management of individuals who harbor pathogenic mutations in genes that encode α or β subunits of cardiac K(+) channels.
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Shimizu W, Horie M. Phenotypic Manifestations of Mutations in Genes Encoding Subunits of Cardiac Potassium Channels. Circ Res 2011; 109:97-109. [DOI: 10.1161/circresaha.110.224600] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Since 1995, when a potassium channel gene,
hERG
(human ether-à-go-go-related gene), now referred to as
KCNH2
, encoding the rapid component of cardiac delayed rectifier potassium channels was identified as being responsible for type 2 congenital long-QT syndrome, a number of potassium channel genes have been shown to cause different types of inherited cardiac arrhythmia syndromes. These include congenital long-QT syndrome, short-QT syndrome, Brugada syndrome, early repolarization syndrome, and familial atrial fibrillation. Genotype-phenotype correlations have been investigated in some inherited arrhythmia syndromes, and as a result, gene-specific risk stratification and gene-specific therapy and management have become available, particularly for patients with congenital long-QT syndrome. In this review article, the molecular structure and function of potassium channels, the clinical phenotype due to potassium channel gene mutations, including genotype-phenotype correlations, and the diverse mechanisms underlying the potassium channel gene–related diseases will be discussed.
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Affiliation(s)
- Wataru Shimizu
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
| | - Minoru Horie
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
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20
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The EGFP/hERG fusion protein alter the electrophysiological properties of hERG channels in HEK293 cells. Cell Biol Int 2011; 35:193-9. [PMID: 21143190 DOI: 10.1042/cbi20100022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
EGFP (enhanced green fluorescent protein) tagged to either the N (amino)-terminus [EGFP/hERG (human ether-a-go-go-related gene)] or C (carboxyl)-terminus (hERG/EGFP) of hERG channel is used to study mutant channel protein trafficking for several years. However, it has been reported that the process can alter hERG channel properties. The aim of the study was to determine whether EGFP tagged to N-terminus of hERG channels would alter the cellular localizations and the electrophysiological properties of hERG channels compared with untagged hERG channels. The hERG channels tagged with or without EGFP were transiently expressed in HEK (human embryonic kidney) 293 cells using a lipofectamine method. HEK 293 cells expressing pCDNA3-hERG or pEGFP-hERG were double immunolabelled with anti-hERG and anti-calnexin (an ER marker protein) followed with FITC- and TRITC (tetramethylrhodamine β-isothiocyanate)-labelled secondary antibodies, respectively. Confocal laser scanning microscope was used to observe the cellular localization of EGFP-tagged hERG channels and untagged hERG channels. Patch-clamp technique was used to record whole cell currents. We found that the EGFP/hERG fusion protein and untagged hERG channels were both expressed not only on the cell surface membrane but also in the cytoplasm of HEK293 cells. The EGFP/hERG appeared to influence the hERG channel gating properties, including reduction of the peak tail current density, more rapid inactivation process, faster recovery from inactivation and faster deactivation kinetics compared with untagged hERG channels. Our results suggest that the EGFP/hERG channel alter the electrophysiological properties of hERG channel, but it does not seem to alter the cellular location of hERG channels. Thus, EGFP tagging to N-terminus might be used for research of subcellular location of hERG channels but not for the channel electrophysiological properties.
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Andersen MN, Olesen SP, Rasmussen HB. Kv7.1 surface expression is regulated by epithelial cell polarization. Am J Physiol Cell Physiol 2011; 300:C814-24. [DOI: 10.1152/ajpcell.00390.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The potassium channel KV7.1 is expressed in the heart where it contributes to the repolarization of the cardiac action potential. In addition, KV7.1 is expressed in epithelial tissues where it plays a role in salt and water transport. Mutations in the kcnq1 gene can lead to long QT syndrome and deafness, and several mutations have been described as trafficking mutations. To learn more about the basic mechanisms that regulate KV7.1 surface expression, we have investigated the trafficking of KV7.1 during the polarization process of the epithelial cell line Madin-Darby Canine Kidney (MDCK) using a modified version of the classical calcium switch. We discovered that KV7.1 exhibits a very dynamic localization pattern during the calcium switch. When MDCK cells are kept in low calcium medium, KV7.1 is mainly observed at the plasma membrane. During the first hours of the switch, KV7.1 is removed from the plasma membrane and an intracellular accumulation in the endoplasmic reticulum (ER) is observed. The channel is retained in the ER until the establishment of the lateral membranes at which point KV7.1 is released from the ER and moves to the plasma membrane. Our data furthermore suggest that while the removal of KV7.1 from the cell surface and its accumulation in the ER could involve activation of protein kinase C, the subsequent release of KV7.1 from the ER depends on phosphoinositide 3-kinase (PI3K) activation. In conclusion, our results demonstrate that KV7.1 surface expression is regulated by signaling mechanisms involved in epithelial cell polarization in particular signaling cascades involving protein kinase C and PI3K.
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Affiliation(s)
- Martin N. Andersen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Søren-Peter Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hanne B. Rasmussen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, The Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
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Aidery P, Kisselbach J, Schweizer PA, Becker R, Katus HA, Thomas D. Biophysical properties of mutant KCNQ1 S277L channels linked to hereditary long QT syndrome with phenotypic variability. Biochim Biophys Acta Mol Basis Dis 2011; 1812:488-94. [PMID: 21241800 DOI: 10.1016/j.bbadis.2011.01.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 01/06/2011] [Accepted: 01/10/2011] [Indexed: 01/02/2023]
Abstract
Hereditary long QT syndrome (LQTS) is associated with ventricular torsade de pointes tachyarrhythmias and sudden cardiac death. Mutations in a cardiac voltage-gated potassium channel, KCNQ1, induce the most frequent variant of LQTS. We identified a KCNQ1 missense mutation, KCNQ1 S277L, in a patient presenting with recurrent syncope triggered by emotional stress (QTc=528ms). This mutation is located in the conserved S5 transmembrane region of the KCNQ1 channel. Using in vitro electrophysiological testing in the Xenopus oocyte expression system, the S277L mutation was found to be non-functional and to suppress wild type currents in dominant-negative fashion in the presence and in the absence of the regulatory ß-subunit, KCNE1. In addition, expression of S277L and wild type KCNQ1 with KCNE1 resulted in a shift of the voltage-dependence of activation by -8.7mV compared to wild type I(Ks), indicating co-assembly of mutant and wild type subunits. The electrophysiological phenotype corresponds well with the severe clinical phenotype of the index patient. However, investigation of family members revealed three patients that exhibit asymptomatic QT interval prolongation (QTc=493-518ms). In conclusion, this study emphasizes the value of biophysical testing to provide mechanistic evidence for pathogenicity of ion channel mutations identified in LQTS patients. The inconsistent association of the KCNQ1 S277L mutation with the clinical presentation suggests that additional genetic, epigenetic, or environmental factors play a role in defining the individual clinical LQTS phenotype.
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Affiliation(s)
- Parwez Aidery
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg, Germany
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23
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Harkcom WT, Abbott GW. Emerging concepts in the pharmacogenomics of arrhythmias: ion channel trafficking. Expert Rev Cardiovasc Ther 2010; 8:1161-73. [PMID: 20670193 DOI: 10.1586/erc.10.89] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Continuous, rhythmic beating of the heart requires exquisite control of expression, localization and function of cardiac ion channels - the foundations of the cardiac myocyte action potential. Disruption of any of these processes can alter the shape of the action potential, predisposing to cardiac arrhythmias. These arrhythmias can manifest in a variety of ways depending on both the channels involved and the type of disruption (i.e., gain or loss of function). As much as 1% of the population of developed countries is affected by cardiac arrhythmia each year, and a detailed understanding of the mechanism of each arrhythmia is crucial to developing and prescribing the proper therapies. Many of the antiarrhythmic drugs currently on the market were developed before the underlying cause of the arrhythmia was known, and as a result lack specificity, causing side effects. The majority of the available drugs target the conductance of cardiac ion channels, either by blocking or enhancing current through the channel. In recent years, however, it has become apparent that specific targeting of ion channel conductance may not be the most effective means for treatment. Here we review increasing evidence that suggests defects in ion channel trafficking play an important role in the etiology of arrhythmias, and small molecule approaches to correct trafficking defects will likely play an important role in the future of arrhythmia treatment.
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Affiliation(s)
- William T Harkcom
- Department of Pharmacology, Weill Medical College of Cornell University, 520 E 70th Street, New York, NY 10021, USA
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Labro AJ, Boulet IR, Timmermans JP, Ottschytsch N, Snyders DJ. The rate-dependent biophysical properties of the LQT1 H258R mutant are counteracted by a dominant negative effect on channel trafficking. J Mol Cell Cardiol 2009; 48:1096-104. [PMID: 19913547 DOI: 10.1016/j.yjmcc.2009.10.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 10/28/2009] [Accepted: 10/28/2009] [Indexed: 01/17/2023]
Abstract
The long QT syndrome (LQTS) is a cardiac disorder caused by a prolonged ventricular repolarization. The co-assembly of the pore-forming human KCNQ1 alpha-subunits with the modulating hKCNE1 beta-subunits generates I(Ks)in vivo, explaining why mutations in the hKCNQ1 gene underlie the LQT1 form of congenital LQT. Here we describe the functional defects of the LQT1 mutation H258R located in the S4-S5 linker, a segment important for channel gating. Mutant subunits with this arginine substitution generated no or barely detectable currents in a homotetrameric condition, but did generate I(Ks)-like currents in association with hKCNE1. Compared to the WT hKCNQ1/hKCNE1 complex, the H258R/hKCNE1 complex displayed accelerated activation kinetics, slowed channel closure and a hyperpolarizing shift of the voltage-dependence of activation, thus predicting an increased K(+) current. However, current density analysis combined with subcellular localization indicated that the H258R subunit exerted a dominant negative effect on channel trafficking to the plasma membrane. The co-expression hKCNQ1/H258R/hKCNE1, mimicking the heterozygous state of a patient, displayed similar properties. During repetitive stimulation the mutant yielded more current compared to WT at 1 Hz but this effect was counteracted by the trafficking defect at faster frequencies. These rate-dependent effects may be relevant given the larger contribution of I(Ks) to the "repolarization reserve" at higher action potential rates. The combination of complex kinetics that counteract the trafficking problem represents a particular mechanism underlying LQT1.
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Affiliation(s)
- Alain J Labro
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp (UA), Universiteitsplein 1, 2610 Antwerp, Belgium
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25
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Hedley PL, Jørgensen P, Schlamowitz S, Wangari R, Moolman-Smook J, Brink PA, Kanters JK, Corfield VA, Christiansen M. The genetic basis of long QT and short QT syndromes: A mutation update. Hum Mutat 2009; 30:1486-511. [DOI: 10.1002/humu.21106] [Citation(s) in RCA: 318] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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26
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Ruan Y, Liu N, Napolitano C, Priori SG. Therapeutic strategies for long-QT syndrome: does the molecular substrate matter? Circ Arrhythm Electrophysiol 2009; 1:290-7. [PMID: 19808421 DOI: 10.1161/circep.108.795617] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Yanfei Ruan
- Molecular Cardiology Fondazione Salvatore Maugeri, University of Pavia, Pavia, Italy
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27
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Yang T, Chung SK, Zhang W, Mullins JGL, McCulley CH, Crawford J, MacCormick J, Eddy CA, Shelling AN, French JK, Yang P, Skinner JR, Roden DM, Rees MI. Biophysical properties of 9 KCNQ1 mutations associated with long-QT syndrome. Circ Arrhythm Electrophysiol 2009; 2:417-26. [PMID: 19808498 DOI: 10.1161/circep.109.850149] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Inherited long-QT syndrome is characterized by prolonged QT interval on the ECG, syncope, and sudden death caused by ventricular arrhythmia. Causative mutations occur mostly in cardiac potassium and sodium channel subunit genes. Confidence in mutation pathogenicity is usually reached through family genotype-phenotype tracking, control population studies, molecular modeling, and phylogenetic alignments; however, biophysical testing offers a higher degree of validating evidence. METHODS AND RESULTS By using in vitro electrophysiological testing of transfected mutant and wild-type long-QT syndrome constructs into Chinese hamster ovary cells, we investigated the biophysical properties of 9 KCNQ1 missense mutations (A46T, T265I, F269S, A302V, G316E, F339S, R360G, H455Y, and S546L) identified in a New Zealand-based long-QT syndrome screening program. We demonstrate through electrophysiology and molecular modeling that 7 of the missense mutations have profound pathological dominant-negative loss-of-function properties, confirming their likely disease-causing nature. This supports the use of these mutations in diagnostic family screening. Two mutations (A46T, T265I) show suggestive evidence of pathogenicity within the experimental limits of biophysical testing, indicating that these variants are disease-causing via delayed- or fast-activation kinetics. Further investigation of the A46T family has revealed an inconsistent cosegregation of the variant with the clinical phenotype. CONCLUSIONS Electrophysiological characterization should be used to validate long-QT syndrome pathogenicity of novel missense channelopathies. When such results are inconclusive, great care should be taken with genetic counseling and screening of such families, and alternative disease-causing mechanisms should be considered.
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Affiliation(s)
- Tao Yang
- Department of Medicine and Pharmacology, Oates Institute for Experimental Therapeutics, Vanderbilt University School of Medicine, Nashville, Tenn, USA
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Pan N, Sun J, Lv C, Li H, Ding J. A hydrophobicity-dependent motif responsible for surface expression of cardiac potassium channel. Cell Signal 2009; 21:349-55. [DOI: 10.1016/j.cellsig.2008.11.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 11/09/2008] [Accepted: 11/10/2008] [Indexed: 01/01/2023]
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Congenital long QT syndrome caused by the F275S KCNQ1 mutation: mechanism of impaired channel function. Biochem Biophys Res Commun 2009; 380:127-31. [PMID: 19167356 DOI: 10.1016/j.bbrc.2009.01.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Accepted: 01/13/2009] [Indexed: 01/22/2023]
Abstract
Congenital long QT syndrome is characterized by a prolongation of ventricular repolarization and recurrent episodes of life-threatening ventricular tachyarrhythmias, often leading to sudden death. We previously identified a missense mutation F275S located within the S5 transmembrane domain of the KCNQ1 ion channel in a Chinese family with long QT syndrome. We used oocyte expression of the KCNQ1 polypeptide to study the effects of the F275S mutation on channel properties. Expression of the F275 mutant, or co-expression with the wild-type S275 polypeptide, significantly decreased channel current amplitudes. Moreover, the F275S substitution decreased the rates of channel activation and deactivation. In transfected HEK293 cells fluorescence microscopy revealed that the F275S mutation perturbed the subcelluar localization of the ion channel. These results indicate that the F275S KCNQ1 mutation leads to impaired polypeptide trafficking that in turn leads to reduction of channel ion currents and altered gating kinetics.
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Funada A, Hayashi K, Ino H, Fujino N, Uchiyama K, Sakata K, Masuta E, Sakamoto Y, Tsubokawa T, Yamagishi M. Assessment of QT intervals and prevalence of short QT syndrome in Japan. Clin Cardiol 2008; 31:270-4. [PMID: 18543308 DOI: 10.1002/clc.20208] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Long QT syndrome causes ventricular tachyarrhythmias and sudden death. Recently, a short QT interval has also been shown to be associated with an increased risk of tachyarrhythmia and sudden death. However, the prevalence of short QT syndrome is not well-known. HYPOTHESIS The aim of this study was to assess the distribution of corrected QT intervals (QTc) and prevalence of short QT syndrome. METHODS This study comprised 12,149 consecutive subjects who received a consultation at Kanazawa University Hospital, Kanazawa, Japan, and had an electrocardiogram (ECG) between February 2003 and May 2004. Of these subjects, 1,165 subjects were excluded because of inappropriate ECGs, while the remaining 10,984 subjects had their last-recorded ECGs analyzed. RESULTS The QTc values showed a nearly normal distribution (408 +/- 25 msec(1/2)), and were significantly longer in females (412 +/- 24 msec(1/2)) than in males (404 +/- 25 msec(1/2)) (p < 0.05). Among 5,511 males, 69 subjects (1.25%) exhibited QTc < 354 msec(1/2) (2 standard deviations [SDs] below the mean in males), and among 5,473 females, 89 subjects (1.63%) exhibited QTc < 364 msec(1/2) (2 SDs below the mean in females). Only 3 subjects (0.03% in all subjects and 0.05% in males) exhibited QTc < 300 msec(1/2), however, none had clinical symptoms of short QT syndrome. CONCLUSIONS Short QT syndrome may be very rare.
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Affiliation(s)
- Akira Funada
- Division of Cardiovascular Medicine, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.
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Patel C, Antzelevitch C. Pharmacological approach to the treatment of long and short QT syndromes. Pharmacol Ther 2008; 118:138-51. [PMID: 18378319 DOI: 10.1016/j.pharmthera.2008.02.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Accepted: 02/05/2008] [Indexed: 12/30/2022]
Abstract
Inherited channelopathies have received increasing attention in recent years. The past decade has witnessed impressive progress in our understanding of the molecular and cellular basis of arrhythmogenesis associated with inherited channelopathies. An imbalance in ionic forces induced by these channelopathies affects the duration of ventricular repolarization and amplifies the intrinsic electrical heterogeneity of the myocardium, creating an arrhythmogenic milieu. Today, many of the channelopathies have been linked to mutations in specific genes encoding either components of ion channels or membrane or regulatory proteins. Many of the channelopathies are genetically heterogeneous with a variable degree of expression of the disease. Defining the molecular basis of channelopathies can have a profound impact on patient management, particularly in cases in which genotype-specific pharmacotherapy is available. The long QT syndrome (LQTS) is one of the first identified and most studied channelopathies where abnormal prolongation of ventricular repolarization predisposes an individual to life threatening ventricular arrhythmia called Torsade de Pointes. On the other hand of the spectrum, molecular defects favoring premature repolarization lead to Short QT syndrome (SQTS), a recently described inherited channelopathy. Both of these channelopathies are associated with a high risk of sudden cardiac death due to malignant ventricular arrhythmia. Whereas pharmacological therapy is first line treatment for LQTS, defibrillators are considered as primary treatment for SQTS. This review provides a comprehensive review of the molecular genetics, clinical features, genotype-phenotype correlations and genotype-specific approach to pharmacotherapy of these two mirror-image channelopathies, SQTS and LQTS.
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Lowe JS, Palygin O, Bhasin N, Hund TJ, Boyden PA, Shibata E, Anderson ME, Mohler PJ. Voltage-gated Nav channel targeting in the heart requires an ankyrin-G dependent cellular pathway. ACTA ACUST UNITED AC 2008; 180:173-86. [PMID: 18180363 PMCID: PMC2213608 DOI: 10.1083/jcb.200710107] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Voltage-gated Nav channels are required for normal electrical activity in neurons, skeletal muscle, and cardiomyocytes. In the heart, Nav1.5 is the predominant Nav channel, and Nav1.5-dependent activity regulates rapid upstroke of the cardiac action potential. Nav1.5 activity requires precise localization at specialized cardiomyocyte membrane domains. However, the molecular mechanisms underlying Nav channel trafficking in the heart are unknown. In this paper, we demonstrate that ankyrin-G is required for Nav1.5 targeting in the heart. Cardiomyocytes with reduced ankyrin-G display reduced Nav1.5 expression, abnormal Nav1.5 membrane targeting, and reduced Na+ channel current density. We define the structural requirements on ankyrin-G for Nav1.5 interactions and demonstrate that loss of Nav1.5 targeting is caused by the loss of direct Nav1.5–ankyrin-G interaction. These data are the first report of a cellular pathway required for Nav channel trafficking in the heart and suggest that ankyrin-G is critical for cardiac depolarization and Nav channel organization in multiple excitable tissues.
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Affiliation(s)
- John S Lowe
- Department of Internal Medicine, Division of Cardiology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
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Chung SK, MacCormick JM, McCulley CH, Crawford J, Eddy CA, Mitchell EA, Shelling AN, French JK, Skinner JR, Rees MI. Long QT and Brugada syndrome gene mutations in New Zealand. Heart Rhythm 2007; 4:1306-14. [PMID: 17905336 DOI: 10.1016/j.hrthm.2007.06.022] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 06/21/2007] [Indexed: 11/23/2022]
Abstract
BACKGROUND Genetic testing in long QT syndrome (LQTS) is moving from research into clinical practice. We have recently piloted a molecular genetics program in a New Zealand research laboratory with a view to establishing a clinical diagnostic service. OBJECTIVE This study sought to report the spectrum of LQTS and Brugada mutations identified by a pilot LQTS gene testing program in New Zealand. METHODS Eighty-four consecutive index cases referred for LQT gene testing, from New Zealand and Australia, were evaluated. The coding sequence and splice sites of 5 LQTS genes (KCNQ1, HERG, SCN5A, KCNE1, and KCNE2) were screened for genomic variants by transgenomics denaturing high-performance liquid chromatography (dHPLC) system and automated DNA sequencing. RESULTS Forty-five LQTS mutations were identified in 43 patients (52% of the cohort): 25 KCNQ1 mutations (9 novel), 13 HERG mutations (7 novel), and 7 SCN5A mutations (2 novel). Forty patients had LQTS, and 3 had Brugada syndrome. Mutations were identified in 14 patients with resuscitated sudden cardiac death: 4 KCNQ1, 5 HERG, 5 SCN5A. In 17 cases there was a family history of sudden cardiac death in a first-degree relative: 8 KCNQ1, 6 HERG, 2 SCN5A, and 1 case with mutations in both KCNQ1 and HERG. CONCLUSION The spectrum of New Zealand LQTS and Brugada mutations is similar to previous studies. The high proportion of novel mutations (40%) dictates a need to confirm pathogenicity for locally prevalent mutations. Careful screening selection criteria, cellular functional analysis of novel mutations, and development of locally relevant control sample cohorts will all be essential to establishing regional diagnostic services.
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MESH Headings
- Adolescent
- Adult
- Brugada Syndrome/diagnosis
- Brugada Syndrome/genetics
- Cardiopulmonary Resuscitation
- Child
- Child, Preschool
- Chromosome Deletion
- DNA Mutational Analysis
- Death, Sudden, Cardiac/etiology
- Death, Sudden, Cardiac/prevention & control
- ERG1 Potassium Channel
- Ether-A-Go-Go Potassium Channels/genetics
- Female
- Genetic Predisposition to Disease/genetics
- Genetic Variation/genetics
- Humans
- INDEL Mutation/genetics
- Infant
- KCNQ1 Potassium Channel/genetics
- Long QT Syndrome/diagnosis
- Long QT Syndrome/genetics
- Male
- Middle Aged
- Muscle Proteins/genetics
- Mutation, Missense/genetics
- NAV1.5 Voltage-Gated Sodium Channel
- New Zealand
- Open Reading Frames/genetics
- Pilot Projects
- Polymerase Chain Reaction
- Polymorphism, Single Nucleotide/genetics
- Potassium Channels, Voltage-Gated/genetics
- RNA Splice Sites/genetics
- Risk Factors
- Sequence Analysis, DNA
- Sequence Analysis, Protein
- Sodium Channels/genetics
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Affiliation(s)
- Seo-Kyung Chung
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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Aizawa Y, Ueda K, Scornik F, Cordeiro JM, Wu Y, Desai M, Guerchicoff A, Nagata Y, Iesaka Y, Kimura A, Hiraoka M, Antzelevitch C. A novel mutation in KCNQ1 associated with a potent dominant negative effect as the basis for the LQT1 form of the long QT syndrome. J Cardiovasc Electrophysiol 2007; 18:972-7. [PMID: 17655673 PMCID: PMC2085492 DOI: 10.1111/j.1540-8167.2007.00889.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Long QT Syndrome (LQTS) is an inherited disorder characterized by prolonged QT intervals and life-threatening polymorphic ventricular tachyarrhythmias. LQT1 caused by KCNQ1 mutations is the most common form of LQTS. METHODS AND RESULTS Patients diagnosed with LQTS were screened for disease-associated mutations in KCNQ1, KCNH2, KCNE1, KCNE2, KCNJ2, and SCN5A. A novel mutation was identified in KCNQ1 caused by a three-base deletion at the position 824-826, predicting a deletion of phenylalanine at codon 275 in segment 5 of KCNQ1 (DeltaF275). Wild-type (WT) and DeltaF275-KCNQ1 constructs were generated and transiently transfected together with a KCNE1 construct in CHO-K1 cells to characterize the properties of the slowly activating delayed rectifier current (IKs) using conventional whole-cell patch-clamp techniques. Cells transfected with WT-KCNQ1 and KCNE1 (1:1.3 molar ratio) produced slowly activating outward current with the characteristics of IKs. Tail current density measured at -40 mV following a two-second step to +60 mV was 381.3 +/- 62.6 pA/pF (n = 11). Cells transfected with DeltaF275-KCNQ1 and KCNE1 exhibited essentially no current. (Tail current density: 0.8 +/- 2.1 pA/pF, n = 11, P = 0.00001 vs WT). Cotransfection of WT- and DeltaF275- KCNQ1 (50/50), along with KCNE1, produced little to no current (tail current density: 10.3 +/- 3.5 pA/pF, n = 11, P = 0.00001 vs WT alone), suggesting a potent dominant negative effect. Immunohistochemistry showed normal membrane trafficking of DeltaF275-KCNQ1. CONCLUSION Our data suggest that a DeltaF275 mutation in KCNQ1 is associated with a very potent dominant negative effect leading to an almost complete loss of function of IKs and that this defect underlies a LQT1 form of LQTS.
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Affiliation(s)
- Yoshiyasu Aizawa
- Masonic Medical Research Laboratory, Utica, NY, USA
- Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kazuo Ueda
- Tokyo Medical and Dental University, Tokyo, Japan
| | | | | | - Yuesheng Wu
- Masonic Medical Research Laboratory, Utica, NY, USA
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Schmitt N, Calloe K, Nielsen NH, Buschmann M, Speckmann EJ, Schulze-Bahr E, Schwarz M. The novel C-terminal KCNQ1 mutation M520R alters protein trafficking. Biochem Biophys Res Commun 2007; 358:304-10. [PMID: 17482572 DOI: 10.1016/j.bbrc.2007.04.127] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 04/19/2007] [Indexed: 11/17/2022]
Abstract
The long QT-syndrome is characterized by a prolongation of the QT-interval and tachyarrhythmias causing syncopes and sudden death. We identified the missense mutation M520R in the calmodulin binding domain of the Kv7.1 channel from a German family with long QT-syndrome. Heterologous expression of the mutant did not reveal any whole-cell currents independent of the auxiliary subunit KCNE1. Co-expression of the wild-type Kv7.1 channels and the mutant showed that the mutant did not have a dominant negative effect. In immunocytochemical assays of transfected COS-1 cells wild-type Kv7.1 showed an immunopositive labeling of the plasma membrane. For M520R no plasma membrane staining was visible, instead a strong signal in the ER was observed. These results indicate that the LQT1 mutation M520R leads to ER-retention and dysfunctional trafficking of the mutant channel resulting in haploinsufficiency.
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Affiliation(s)
- Nicole Schmitt
- Department of Biomedical Sciences, The Danish National Research Foundation Centre for Cardiac Arrhythmia, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
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Jost N, Papp JG, Varró A. Slow delayed rectifier potassium current (IKs) and the repolarization reserve. Ann Noninvasive Electrocardiol 2007; 12:64-78. [PMID: 17286653 PMCID: PMC6931982 DOI: 10.1111/j.1542-474x.2007.00140.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The aim of this review is to present the properties of the slow component of the delayed rectifier potassium current (IKs) in the human ventricle. The review gives a detailed description of the physiology, molecular biology and pharmacology of the IKs current, including kinetic properties, genetic structures, agonists and antagonists. The authors also present the role of the IKs current in the human cardiac repolarization focusing on several pathophysiological situations, such as the LQT syndrome and the Torsade de Pointes arrhythmia.
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Affiliation(s)
- Norbert Jost
- Division of Cardiovascular Pharmacology, Hungarian Academy of Sciences, University of Szeged, Szeged, Hungary
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37
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Kamada F, Kure S, Kudo T, Suzuki Y, Oshima T, Ichinohe A, Kojima K, Niihori T, Kanno J, Narumi Y, Narisawa A, Kato K, Aoki Y, Ikeda K, Kobayashi T, Matsubara Y. A novel KCNQ4 one-base deletion in a large pedigree with hearing loss: implication for the genotype-phenotype correlation. J Hum Genet 2006; 51:455-460. [PMID: 16596322 DOI: 10.1007/s10038-006-0384-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Accepted: 01/23/2006] [Indexed: 10/24/2022]
Abstract
Autosomal-dominant, nonsyndromic hearing impairment is clinically and genetically heterogeneous. We encountered a large Japanese pedigree in which nonsyndromic hearing loss was inherited in an autosomal-dominant fashion. A genome-wide linkage study indicated linkage to the DFNA2 locus on chromosome 1p34. Mutational analysis of KCNQ4 encoding a potassium channel revealed a novel one-base deletion in exon 1, c.211delC, which generated a profoundly truncated protein without transmembrane domains (p.Q71fsX138). Previously, six missense mutations and one 13-base deletion, c.211_223del, had been reported in KCNQ4. Patients with the KCNQ4 missense mutations had younger-onset and more profound hearing loss than patients with the 211_223del mutation. In our current study, 12 individuals with the c.211delC mutation manifested late-onset and pure high-frequency hearing loss. Our results support the genotype-phenotype correlation that the KCNQ4 deletions are associated with later-onset and milder hearing impairment than the missense mutations. The phenotypic difference may be caused by the difference in pathogenic mechanisms: haploinsufficiency in deletions and dominant-negative effect in missense mutations.
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Affiliation(s)
- Fumiaki Kamada
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
- 21st COE Program "Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation", Tohoku University, Sendai, Japan
| | - Shigeo Kure
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan.
- 21st COE Program "Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation", Tohoku University, Sendai, Japan.
| | - Takayuki Kudo
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Yoichi Suzuki
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Takeshi Oshima
- Department of Otorhinolaryngology, Head and Neck Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Akiko Ichinohe
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Kanako Kojima
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Tetsuya Niihori
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Junko Kanno
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Yoko Narumi
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Ayumi Narisawa
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
| | - Kumi Kato
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
- 21st COE Program "Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation", Tohoku University, Sendai, Japan
| | - Yoko Aoki
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
- 21st COE Program "Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation", Tohoku University, Sendai, Japan
| | - Katsuhisa Ikeda
- Department of Otorhinolaryngology, Head and Neck Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Toshimitsu Kobayashi
- Department of Otorhinolaryngology, Head and Neck Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Yoichi Matsubara
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan
- 21st COE Program "Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation", Tohoku University, Sendai, Japan
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Priori SG, Napolitano C, Cerrone M. Experimental therapy of genetic arrhythmias: disease-specific pharmacology. Handb Exp Pharmacol 2006:267-86. [PMID: 16610348 DOI: 10.1007/3-540-29715-4_10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The integration between molecular biology and clinical practice requires the achievement of fundamental steps to link basic science to diagnosis and management of patients. In the last decade, the study of genetic bases of human diseases has achieved several milestones, and it is now possible to apply the knowledge that stems from the identification of the genetic substrate of diseases to clinical practice. The first step along the process of linking molecular biology to clinical medicine is the identification of the genetic bases of inherited diseases. After this important goal is achieved, it becomes possible to extend research to understand the functional impairments of mutant protein(s) and to link them to clinical manifestations (genotype-phenotype correlation). In genetically heterogeneous diseases, it may be possible to identify locus-specific risk stratification and management algorithms. Finally, the most ambitious step in the study of genetic disease is to discover a novel pharmacological therapy targeted at correcting the inborn defect (locus-specific therapy) or even to "cure" the DNA abnormality by replacing the defective gene with gene therapy. At present, this curative goal has been successful only for very few diseases. In the field of inherited arrhythmogenic diseases, several genes have been discovered, and genetics is now emerging as a source of information contributing not only to a better diagnosis but also to risk stratification and management of patients. The functional characterization of mutant proteins has opened new perspectives about the possibility of performing gene-specific or mutation-specific therapy. In this chapter, we will briefly summarize the genetic bases of inherited arrhythmogenic conditions and we will point out how the information derived from molecular genetics has influenced the "optimal use of traditional therapies" and has paved the way to the development of gene-specific therapy.
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Affiliation(s)
- S G Priori
- Molecular Cardiology Laboratories, IRCCS Fondazione Salvatore Maugeri, Via Ferrata 8, 27100 Pavia, Italy.
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Napolitano C, Bloise R, Priori SG. Gene-specific therapy for inherited arrhythmogenic diseases. Pharmacol Ther 2005; 110:1-13. [PMID: 16168489 DOI: 10.1016/j.pharmthera.2005.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 08/01/2005] [Indexed: 11/26/2022]
Abstract
In the last few years, major advancement has been made in the understanding of the genetic basis of inherited arrhythmogenic diseases. Interestingly, the information obtained with the application of molecular genetics to these diseases is now influencing their clinical management, allowing gene-specific risk stratification and gene-specific management. The first attempt for a gene-specific therapy was made in 1995 with the use of mexiletine in long-QT syndrome (LQTS) patients with mutations in the SCN5A gene. Since then, several investigators have proposed novel therapeutic approaches based on the identification of the functional consequences of genetic mutations. In some instances, these novel therapies have already been introduced in clinical practice, and data are being collected to establish their long-term efficacy. In this review, we will summarize the current understanding of the molecular bases of inherited arrhythmias, with a specific focus toward discussing the most recent advancements toward the development of gene-specific therapies.
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Gouas L, Nicaud V, Berthet M, Forhan A, Tiret L, Balkau B, Guicheney P. Association of KCNQ1, KCNE1, KCNH2 and SCN5A polymorphisms with QTc interval length in a healthy population. Eur J Hum Genet 2005; 13:1213-22. [PMID: 16132053 DOI: 10.1038/sj.ejhg.5201489] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The QT interval (QT) reflects cardiac ventricular repolarization and varies according to various known factors such as heart rate, gender and age. Nevertheless, a high intrasubject stability of the QT-RR pattern also suggests that a genetic component contributes to individual QT length. To determine whether single nucleotide polymorphisms (SNPs) in genes encoding cardiac ion channels were associated with the heart-rate corrected QT (QTc) length, we analyzed two groups of 200 subjects presenting the shortest and the longest QTc from a cohort of 2,008 healthy subjects. A total of 17 polymorphisms were genotyped; they were all in the Hardy-Weinberg equilibrium in both groups. Neither allele nor haplotype frequencies of the 10 KCNQ1 SNPs showed a significant difference between the two groups. In contrast, KCNH2 2690 C (K897T) and SCN5A 5457 T (D1819D) minor alleles were significantly more frequent in the group with the shortest QTc interval, whereas KCNE1 253 A (D85N), SCN5A 1673 G (H558R) and 1141-3 A minor alleles were significantly more frequent in the group with the longest QTc interval. Interestingly, an interaction was also found between the KCNH2 2690 A>C SNP and the KCNQ1 2031+ 932 A>G SNP suggesting that the effect of the KCNH2 2690 C allele on QTc length may occur within a particular genetic background. This suggests that genetic determinants located in KCNQ1, KCNE1, KCNH2 and SCN5A influence QTc length in healthy individuals and may represent risk factors for arrhythmias or cardiac sudden death in patients with cardiovascular diseases.
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Affiliation(s)
- Laetitia Gouas
- INSERM U582, Institut de Myologie, IFR 14, UPMC, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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Gong Q, Keeney DR, Molinari M, Zhou Z. Degradation of Trafficking-defective Long QT Syndrome Type II Mutant Channels by the Ubiquitin-Proteasome Pathway. J Biol Chem 2005; 280:19419-25. [PMID: 15760896 DOI: 10.1074/jbc.m502327200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Mutations in the human ether-a-go-go-related gene (hERG) cause chromosome 7-linked long QT syndrome type II (LQT2). We have shown previously that LQT2 mutations lead to endoplasmic reticulum (ER) retention and rapid degradation of mutant hERG proteins. In this study we examined the role of the ubiquitin-proteasome pathway in the degradation of the LQT2 mutation Y611H. We showed that proteasome inhibitors N-acetyl-L-leucyl-L-leucyl-L-norleucinal and lactacystin but not lysosome inhibitor leupeptin inhibited the degradation of Y611H mutant channels. In addition, ER mannosidase I inhibitor kifunensine and down-regulation of EDEM (ER degradation-enhancing alpha-mannosidase-like protein) also suppressed the degradation of Y611H mutant channels. Proteasome inhibition but not mannosidase inhibition led to the accumulation of full-length hERG protein in the cytosol. The hERG protein accumulated in the cytosol was deglycosylated. Proteasome inhibition also resulted in the accumulation of polyubiquitinated hERG channels. These results suggest that the degradation of LQT2 mutant channels is mediated by the cytosolic proteasome in a process that involves mannose trimming, polyubiquitination, and deglycosylation of mutant channels.
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Affiliation(s)
- Qiuming Gong
- Division of Molecular Medicine, Department of Medicine, Oregon Health and Science University, Portland, Oregon 97239, USA
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Park KH, Piron J, Dahimene S, Mérot J, Baró I, Escande D, Loussouarn G. Impaired KCNQ1-KCNE1 and phosphatidylinositol-4,5-bisphosphate interaction underlies the long QT syndrome. Circ Res 2005; 96:730-9. [PMID: 15746441 DOI: 10.1161/01.res.0000161451.04649.a8] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nearly a hundred different KCNQ1 mutations have been reported as leading to the cardiac long QT syndrome, characterized by prolonged QT interval, syncopes, and sudden death. We have previously shown that phosphatidylinositol-4,5-bisphosphate (PIP2) regulates the KCNQ1-KCNE1 complex. In the present study, we show that PIP2 affinity is reduced in three KCNQ1 mutant channels (R243H, R539W, and R555C) associated with the long QT syndrome. In giant excised patches, direct application of PIP2 on the cytoplasmic face of the three mutant channels counterbalances the loss of function. Reintroduction of a positive charge by application of methanethiosulfonate ethylammonium on the cytoplasmic face of R555C mutant channels also restores channel activity. The channel affinity for a soluble analog of PIP2 is decreased in the three mutant channels. By using a model that describes the KCNQ1-KCNE1 channel behavior and by fitting the relationship between the kinetics of deactivation and the current amplitude obtained in whole-cell experiments, we estimated the PIP2 binding and dissociation rates on wild-type and mutant channels. The dissociation rate of the three mutants was higher than for the wild-type channel, suggesting a decreased affinity for PIP2. PIP2 binding was magnesium-dependent, and the PIP2-dependent equilibrium constant in the absence of magnesium was higher with the wild-type than with the mutant channels. Altogether, our data suggest that a reduced PIP2 affinity of KCNQ1 mutants can lead to the long QT syndrome.
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Affiliation(s)
- Kyu-Ho Park
- L'Institut du Thorax, INSERM U533, Faculté de Médecine, Nantes, France
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