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Campagna N, Wall E, Lee K, Guo J, Li W, Yang T, Baranchuk A, El-Diasty M, Zhang S. Differential Effects of Remdesivir and Lumacaftor on Homomeric and Heteromeric hERG Channels. Mol Pharmacol 2023; 104:164-173. [PMID: 37419691 DOI: 10.1124/molpharm.123.000708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/31/2023] [Accepted: 06/08/2023] [Indexed: 07/09/2023] Open
Abstract
The human ether-a-go-go-related gene (hERG) encodes for the pore-forming subunit of the channel that conducts the rapidly activating delayed K+ current (IKr) in the heart. The hERG channel is important for cardiac repolarization, and reduction of its expression in the plasma membrane due to mutations causes long QT syndrome type 2 (LQT2). As such, promoting hERG membrane expression is a strategy to rescue mutant channel function. In the present study, we applied patch clamp, western blots, immunocytochemistry, and quantitative reverse transcription polymerase chain reaction techniques to investigate the rescue effects of two drugs, remdesivir and lumacaftor, on trafficking-defective mutant hERG channels. As our group has recently reported that the antiviral drug remdesivir increases wild-type (WT) hERG current and surface expression, we studied the effects of remdesivir on trafficking-defective LQT2-causing hERG mutants G601S and R582C expressed in HEK293 cells. We also investigated the effects of lumacaftor, a drug used to treat cystic fibrosis, that promotes CFTR protein trafficking and has been shown to rescue membrane expression of some hERG mutations. Our results show that neither remdesivir nor lumacaftor rescued the current or cell-surface expression of homomeric mutants G601S and R582C. However, remdesivir decreased while lumacaftor increased the current and cell-surface expression of heteromeric channels formed by WT hERG and mutant G601S or R582C hERG. We concluded that drugs can differentially affect homomeric WT and heteromeric WT+G601S (or WT+R582C) hERG channels. These findings extend our understanding of drug-channel interaction and may have clinical implications for patients with hERG mutations. SIGNIFICANCE STATEMENT: Various naturally occurring mutations in a cardiac potassium channel called hERG can impair channel function by decreasing cell-surface channel expression, resulting in cardiac electrical disturbances and even sudden cardiac death. Promotion of cell-surface expression of mutant hERG channels represents a strategy to rescue channel function. This work demonstrates that drugs such as remdesivir and lumacaftor can differently affect homomeric and heteromeric mutant hERG channels, which have biological and clinical implications.
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Affiliation(s)
- Noah Campagna
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Erika Wall
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Kevin Lee
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Jun Guo
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Wentao Li
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Tonghua Yang
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Adrian Baranchuk
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Mohammad El-Diasty
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
| | - Shetuan Zhang
- Department of Biomedical and Molecular Sciences (N.C., E.W., K.L., J.G., W.L., T.Y., S.Z.); Division of Cardiology, Department of Medicine (A.B.); and Division of Cardiac Surgery, Department of Surgery (M.E.-D.), Queen's University, Kingston, Ontario, Canada
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Alameh M, Oliveira-Mendes BR, Kyndt F, Rivron J, Denjoy I, Lesage F, Schott JJ, De Waard M, Loussouarn G. A need for exhaustive and standardized characterization of ion channels activity. The case of K V11.1. Front Physiol 2023; 14:1132533. [PMID: 36860515 PMCID: PMC9968853 DOI: 10.3389/fphys.2023.1132533] [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: 12/27/2022] [Accepted: 01/30/2023] [Indexed: 02/16/2023] Open
Abstract
hERG, the pore-forming subunit of the rapid component of the delayed rectifier K+ current, plays a key role in ventricular repolarization. Mutations in the KCNH2 gene encoding hERG are associated with several cardiac rhythmic disorders, mainly the Long QT syndrome (LQTS) characterized by prolonged ventricular repolarization, leading to ventricular tachyarrhythmias, sometimes progressing to ventricular fibrillation and sudden death. Over the past few years, the emergence of next-generation sequencing has revealed an increasing number of genetic variants including KCNH2 variants. However, the potential pathogenicity of the majority of the variants remains unknown, thus classifying them as variants of uncertain significance or VUS. With diseases such as LQTS being associated with sudden death, identifying patients at risk by determining the variant pathogenicity, is crucial. The purpose of this review is to describe, on the basis of an exhaustive examination of the 1322 missense variants, the nature of the functional assays undertaken so far and their limitations. A detailed analysis of 38 hERG missense variants identified in Long QT French patients and studied in electrophysiology also underlies the incomplete characterization of the biophysical properties for each variant. These analyses lead to two conclusions: first, the function of many hERG variants has never been looked at and, second, the functional studies done so far are excessively heterogeneous regarding the stimulation protocols, cellular models, experimental temperatures, homozygous and/or the heterozygous condition under study, a context that may lead to conflicting conclusions. The state of the literature emphasizes how necessary and important it is to perform an exhaustive functional characterization of hERG variants and to standardize this effort for meaningful comparison among variants. The review ends with suggestions to create a unique homogeneous protocol that could be shared and adopted among scientists and that would facilitate cardiologists and geneticists in patient counseling and management.
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Affiliation(s)
- Malak Alameh
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France,Labex ICST, INSERM, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d’Azur, Valbonne, France
| | - Barbara Ribeiro Oliveira-Mendes
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France,*Correspondence: Barbara Ribeiro Oliveira-Mendes,
| | - Florence Kyndt
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France
| | - Jordan Rivron
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France
| | - Isabelle Denjoy
- Service de Cardiologie et CNMR Maladies Cardiaques Héréditaires Rares, Hôpital Bichat, Paris, France
| | - Florian Lesage
- Labex ICST, INSERM, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d’Azur, Valbonne, France
| | - Jean-Jacques Schott
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France
| | - Michel De Waard
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France,Labex ICST, INSERM, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d’Azur, Valbonne, France
| | - Gildas Loussouarn
- CNRS, INSERM, l’institut du thorax, Nantes Université, CHU Nantes, Nantes, France
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Kozek KA, Glazer AM, Ng CA, Blackwell D, Egly CL, Vanags LR, Blair M, Mitchell D, Matreyek KA, Fowler DM, Knollmann BC, Vandenberg JI, Roden DM, Kroncke BM. High-throughput discovery of trafficking-deficient variants in the cardiac potassium channel K V11.1. Heart Rhythm 2020; 17:2180-2189. [PMID: 32522694 DOI: 10.1016/j.hrthm.2020.05.041] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 05/27/2020] [Accepted: 05/31/2020] [Indexed: 01/09/2023]
Abstract
BACKGROUND KCHN2 encodes the KV11.1 potassium channel responsible for IKr, a major repolarization current during the cardiomyocyte action potential. Variants in KCNH2 that lead to decreased IKr have been associated with long QT syndrome type 2 (LQT2). The mechanism of LQT2 is most often induced loss of KV11.1 trafficking to the cell surface. Accurately discriminating between variants with normal and abnormal trafficking would aid in understanding the deleterious nature of these variants; however, the volume of reported nonsynonymous KCNH2 variants precludes the use of conventional methods for functional study. OBJECTIVE The purpose of this study was to report a high-throughput, multiplexed screening method for KCNH2 genetic variants capable of measuring the cell surface abundance of hundreds of missense variants in the resulting KV11.1 channel. METHODS We developed a method to quantitate KV11.1 variant trafficking on a pilot region of 11 residues in the S5 helix. RESULTS We generated trafficking scores for 220 of 231 missense variants in the pilot region. For 5 of 5 variants, high-throughput trafficking scores validated when tested in single variant flow cytometry and confocal microscopy experiments. We further explored these results with planar patch electrophysiology and found that loss-of-trafficking variants do not produce IKr. Conversely, but expectedly, some variants that traffic normally were still functionally compromised. CONCLUSION We describe a new method for detecting KV11.1 trafficking-deficient variants in a multiplexed assay. This new method accurately generated trafficking data for variants in KV11.1 and is extendable both to all residues in KV11.1 and to other cell surface proteins.
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Affiliation(s)
- Krystian A Kozek
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Andrew M Glazer
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Chai-Ann Ng
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Daniel Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Christian L Egly
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Loren R Vanags
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Marcia Blair
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Devyn Mitchell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Kenneth A Matreyek
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | - Douglas M Fowler
- Department of Genome Sciences, University of Washington, Seattle, Washington; Department of Bioengineering, University of Washington, Seattle, Washington
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Dan M Roden
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee.
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Truitt R, Mu A, Corbin EA, Vite A, Brandimarto J, Ky B, Margulies KB. Increased Afterload Augments Sunitinib-Induced Cardiotoxicity in an Engineered Cardiac Microtissue Model. JACC Basic Transl Sci 2018; 3:265-276. [PMID: 30062212 PMCID: PMC6059907 DOI: 10.1016/j.jacbts.2017.12.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 12/22/2017] [Accepted: 12/22/2017] [Indexed: 12/17/2022]
Abstract
Sunitinib, a multitargeted oral tyrosine kinase inhibitor, used widely to treat solid tumors, results in hypertension in up to 47% and left ventricular dysfunction in up to 19% of treated individuals. The relative contribution of afterload toward inducing cardiac dysfunction with sunitinib treatment remains unknown. We created a preclinical model of sunitinib cardiotoxicity using engineered microtissues that exhibited cardiomyocyte death, decreases in force generation, and spontaneous beating at clinically relevant doses. Simulated increases in afterload augmented sunitinib cardiotoxicity in both rat and human microtissues, which suggest that antihypertensive therapy may be a strategy to prevent left ventricular dysfunction in patients treated with sunitinib.
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Key Words
- 2D, 2-dimensional
- 3D, 3-dimensional
- AICAR, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside
- AMPK, adenosine monophosphate-activated protein kinase
- ATP, adenosine triphosphate
- CCCP, carbonyl cyanide m-chlorophenyl hydrazine
- CMT, cardiac microtissue
- DMSO, dimethyl sulfoxide
- EDTA, ethylenediamine tetraacetic acid
- Hu-iPS-CM, human induced pluripotent stem cell cardiomyocyte
- LV, left ventricle
- NRVM, neonatal rat ventricular myocyte
- PDMS, polydimethylsiloxane
- RPMI, Roswell Park Memorial Institute medium
- TMRM, tetramethylrhodamine
- afterload
- apoptosis
- cardiotoxicity
- huMSC, human mesenchymal stem cell
- iPS-CM, induced pluripotent stem cell-derived cardiomyocyte
- sunitinib
- tissue engineering
- toxicology
- tyrosine kinase inhibitors
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Affiliation(s)
- Rachel Truitt
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Anbin Mu
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Elise A. Corbin
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
- Department of Mechanical Engineering and Applied Mechanics, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Alexia Vite
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jeffrey Brandimarto
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Bonnie Ky
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
- Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Kenneth B. Margulies
- Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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Lin EC, Moungey BM, Lim E, Concannon SP, Anderson CL, Kyle JW, Makielski JC, Balijepalli SY, January CT. Mouse ERG K(+) channel clones reveal differences in protein trafficking and function. J Am Heart Assoc 2014; 3:e001491. [PMID: 25497881 PMCID: PMC4338741 DOI: 10.1161/jaha.114.001491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background The mouse ether‐a‐go‐go‐related gene 1a (mERG1a, mKCNH2) encodes mERG K+ channels in mouse cardiomyocytes. The mERG channels and their human analogue, hERG channels, conduct IKr. Mutations in hERG channels reduce IKr to cause congenital long‐QT syndrome type 2, mostly by decreasing surface membrane expression of trafficking‐deficient channels. Three cDNA sequences were originally reported for mERG channels that differ by 1 to 4 amino acid residues (mERG‐London, mERG‐Waterston, and mERG‐Nie). We characterized these mERG channels to test the postulation that they would differ in their protein trafficking and biophysical function, based on previous findings in long‐QT syndrome type 2. Methods and Results The 3 mERG and hERG channels were expressed in HEK293 cells and neonatal mouse cardiomyocytes and were studied using Western blot and whole‐cell patch clamp. We then compared our findings with the recent sequencing results in the Welcome Trust Sanger Institute Mouse Genomes Project (WTSIMGP). Conclusions First, the mERG‐London channel with amino acid substitutions in regions of highly ordered structure is trafficking deficient and undergoes temperature‐dependent and pharmacological correction of its trafficking deficiency. Second, the voltage dependence of channel gating would be different for the 3 mERG channels. Third, compared with the WTSIMGP data set, the mERG‐Nie clone is likely to represent the wild‐type mouse sequence and physiology. Fourth, the WTSIMGP analysis suggests that substrain‐specific sequence differences in mERG are a common finding in mice. These findings with mERG channels support previous findings with hERG channel structure–function analyses in long‐QT syndrome type 2, in which sequence changes in regions of highly ordered structure are likely to result in abnormal protein trafficking.
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Affiliation(s)
- Eric C Lin
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Brooke M Moungey
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Evi Lim
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Sarah P Concannon
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Corey L Anderson
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - John W Kyle
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Jonathan C Makielski
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Sadguna Y Balijepalli
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
| | - Craig T January
- Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison, WI (E.C.L., B.M.M., E.L., S.P.C., C.L.A., J.W.K., J.C.M., S.Y.B., C.T.J.)
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Mechanistic basis for type 2 long QT syndrome caused by KCNH2 mutations that disrupt conserved arginine residues in the voltage sensor. J Membr Biol 2013; 246:355-64. [PMID: 23546015 DOI: 10.1007/s00232-013-9539-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 03/19/2013] [Indexed: 01/24/2023]
Abstract
KCNH2 encodes the Kv11.1 channel, which conducts the rapidly activating delayed rectifier K+ current (I Kr) in the heart. KCNH2 mutations cause type 2 long QT syndrome (LQT2), which increases the risk for life-threatening ventricular arrhythmias. LQT2 mutations are predicted to prolong the cardiac action potential (AP) by reducing I Kr during repolarization. Kv11.1 contains several conserved basic amino acids in the fourth transmembrane segment (S4) of the voltage sensor that are important for normal channel trafficking and gating. This study sought to determine the mechanism(s) by which LQT2 mutations at conserved arginine residues in S4 (R531Q, R531W or R534L) alter Kv11.1 function. Western blot analyses of HEK293 cells transiently expressing R531Q, R531W or R534L suggested that only R534L inhibited Kv11.1 trafficking. Voltage-clamping experiments showed that R531Q or R531W dramatically altered Kv11.1 current (I Kv11.1) activation, inactivation, recovery from inactivation and deactivation. Coexpression of wild type (to mimic the patients' genotypes) mostly corrected the changes in I Kv11.1 activation and inactivation, but deactivation kinetics were still faster. Computational simulations using a human ventricular AP model showed that accelerating deactivation rates was sufficient to prolong the AP, but these effects were minimal compared to simply reducing I Kr. These are the first data to demonstrate that coexpressing wild type can correct activation and inactivation dysfunction caused by mutations at a critical voltage-sensing residue in Kv11.1. We conclude that some Kv11.1 mutations might accelerate deactivation to cause LQT2 but that the ventricular AP duration is much more sensitive to mutations that decrease I Kr. This likely explains why most LQT2 mutations are nonsense or trafficking-deficient.
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Balijepalli SY, Lim E, Concannon SP, Chew CL, Holzem KE, Tester DJ, Ackerman MJ, Delisle BP, Balijepalli RC, January CT. Mechanism of loss of Kv11.1 K+ current in mutant T421M-Kv11.1-expressing rat ventricular myocytes: interaction of trafficking and gating. Circulation 2012; 126:2809-18. [PMID: 23136156 DOI: 10.1161/circulationaha.112.118018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Type 2 long QT syndrome involves mutations in the human ether a-go-go-related gene (hERG or KCNH2). T421M, an S1 domain mutation in the Kv11.1 channel protein, was identified in a resuscitated patient. We assessed its biophysical, protein trafficking, and pharmacological mechanisms in adult rat ventricular myocytes. METHODS AND RESULTS Isolated adult rat ventricular myocytes were infected with wild-type (WT)-Kv11.1- and T421M-Kv11.1-expressing adenovirus and analyzed with the use of patch clamp, Western blot, and confocal imaging techniques. Expression of WT-Kv11.1 or T421M-Kv11.1 produced peak tail current (I(Kv11.1)) of 8.78±1.18 and 1.91±0.22 pA/pF, respectively. Loss of mutant I(Kv11.1) resulted from (1) a partially trafficking-deficient channel protein with reduced cell surface expression and (2) altered channel gating with a positive shift in the voltage dependence of activation and altered kinetics of activation and deactivation. Coexpression of WT+T421M-Kv11.1 resulted in heterotetrameric channels that remained partially trafficking deficient with only a minimal increase in peak I(Kv11.1) density, whereas the voltage dependence of channel gating became WT-like. In the adult rat ventricular myocyte model, both WT-Kv11.1 and T421M-Kv11.1 channels responded to β-adrenergic stimulation by increasing I(Kv11.1). CONCLUSIONS The T421M-Kv11.1 mutation caused a loss of I(Kv11.1) through interactions of abnormal protein trafficking and channel gating. Furthermore, for coexpressed WT+T421M-Kv11.1 channels, different dominant-negative interactions govern protein trafficking and ion channel gating, and these are likely to be reflected in the clinical phenotype. Our results also show that WT and mutant Kv11.1 channels responded to β-adrenergic stimulation.
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Braam SR, Tertoolen L, Casini S, Matsa E, Lu HR, Teisman A, Passier R, Denning C, Gallacher DJ, Towart R, Mummery CL. Repolarization reserve determines drug responses in human pluripotent stem cell derived cardiomyocytes. Stem Cell Res 2012; 10:48-56. [PMID: 23089628 DOI: 10.1016/j.scr.2012.08.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/24/2012] [Accepted: 08/28/2012] [Indexed: 11/17/2022] Open
Abstract
Unexpected induction of arrhythmias in the heart is still one of the major risks of new drugs despite recent improvements in cardiac safety assays. Here we address this in a novel emerging assay system. Eleven reference compounds were administrated to spontaneously beating clusters of cardiomyocytes from human pluripotent stem cells (hPSC-CM) and the responses determined using multi-electrode arrays. Nine showed clear dose-dependence effects on field potential (FP) duration. Of these, the Ca(2+) channel blockers caused profound shortening of action potentials, whereas the classical hERG blockers, like dofetilide and d,l-sotalol, induced prolongation, as expected. Unexpectedly, two potent blockers of the slow component of the delayed rectifier potassium current (I(Ks)), HMR1556 and JNJ303, had only minor effects on the extracellular FP of wild-type hPSC-CM despite evidence of functional I(Ks) channels. These compounds were therefore re-evaluated under conditions that mimicked reduced "repolarization reserve," a parameter reflecting the capacity of cardiomyocytes to repolarize and a strong risk factor for the development of ventricular arrhythmias. Strikingly, in both pharmacological and genetic models of diminished repolarization reserve, HMR1556 and JNJ03 strongly increased the FP duration. These profound effects indicate that I(Ks) plays an important role in limiting action potential prolongation when repolarization reserve is attenuated. The findings have important clinical implications and indicate that enhanced sensitization to repolarization-prolonging compounds through pharmacotherapy or genetic predisposition should be taken into account when assessing drug safety.
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Affiliation(s)
- S R Braam
- Pluriomics BV, Leiden, The Netherlands.
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Song W, Shou W. Cardiac sodium channel Nav1.5 mutations and cardiac arrhythmia. Pediatr Cardiol 2012; 33:943-9. [PMID: 22460359 PMCID: PMC3393812 DOI: 10.1007/s00246-012-0303-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 03/09/2012] [Indexed: 12/19/2022]
Abstract
As a major cardiac voltage-gated sodium channel isoform in the heart, the Nav1.5 channel is essential for cardiac action potential initiation and subsequent propagation throughout the heart. Mutations of Nav1.5 have been linked to a variety of cardiac diseases such as long QT syndrome (LQTs), Brugada syndrome, cardiac conduction defect, atrial fibrillation, and dilated cardiomyopathy. The mutagenesis approach and heterologous expression systems are most frequently used to study the function of this channel. This review focuses primarily on recent findings of Nav1.5 mutations associated with type 3 long QT syndrome (LQT3) in particular. Understanding the functional changes of the Nav1.5 mutation may offer critical insight into the mechanism of long QT3 syndrome. In addition, this review provides the updated information on the current progress of using various experimental model systems to study primarily the long QT3 syndrome.
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Affiliation(s)
- Weihua Song
- Department of Pediatrics, Riley Heart Research Center, Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA
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Kinoshita K, Yamaguchi Y, Nishide K, Kimoto K, Nonobe Y, Fujita A, Asano K, Tabata T, Mori H, Inoue H, Hata Y, Fukurotani K, Nishida N. A novel missense mutation causing a G487R substitution in the S2-S3 loop of human ether-à-go-go-related gene channel. J Cardiovasc Electrophysiol 2012; 23:1246-53. [PMID: 22764740 DOI: 10.1111/j.1540-8167.2012.02383.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION Mutations of human ether-à-go-go-related gene (hERG), which encodes a cardiac K(+) channel responsible for the acceleration of the repolarizing phase of an action potential and the prevention of premature action potential regeneration, often cause severe arrhythmic disorders. We found a novel missense mutation of hERG that results in a G487R substitution in the S2-S3 loop of the channel subunit [hERG(G487R)] from a family and determined whether this mutant gene could induce an abnormality in channel function. METHODS AND RESULTS We made whole-cell voltage-clamp recordings from HEK-293T cells transfected with wild-type hERG [hERG(WT)], hERG(G487R), or both. We measured hERG channel-mediated current as the "tail" of a depolarization-elicited current. The current density of the tail current and its voltage- and time-dependences were not different among all the cell groups. The time-courses of deactivation, inactivation, and recovery from inactivation and their voltage-dependences were not different among all the cell groups. Furthermore, we performed immunocytochemical analysis using an anti-hERG subunit antibody. The ratio of the immunoreactivity of the plasma membrane to that of the cytoplasm was not different between cells transfected with hERG(WT), hERG(G487R), or both. CONCLUSION hERG(G487R) can produce functional channels with normal gating kinetics and cell-surface expression efficiency with or without the aid of hERG(WT). Therefore, neither the heterozygous nor homozygous inheritance of hERG(G487R) is thought to cause severe cardiac disorders. hERG(G487R) would be a candidate for a rare variant or polymorphism of hERG with an amino acid substitution in the unusual region of the channel subunit.
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Affiliation(s)
- Koshi Kinoshita
- Department of Legal Medicine Second, Graduate School of Medical and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
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Park DS, Fishman GI. Forever young: induced pluripotent stem cells as models of inherited arrhythmias. Circulation 2012; 125:3055-6. [PMID: 22647977 DOI: 10.1161/circulationaha.112.114165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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Davis RP, van den Berg CW, Casini S, Braam SR, Mummery CL. Pluripotent stem cell models of cardiac disease and their implication for drug discovery and development. Trends Mol Med 2011; 17:475-84. [PMID: 21703926 DOI: 10.1016/j.molmed.2011.05.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 05/02/2011] [Accepted: 05/05/2011] [Indexed: 12/13/2022]
Abstract
Recent advances in pluripotent stem cell biology now make it possible to generate human cardiomyocytes in vitro from both healthy individuals and from patients with cardiac abnormalities. This offers unprecedented opportunities to study cardiac disease development 'in a dish' and establish novel platforms for drug discovery, either to prevent disease progression or to reverse it. In this review paper, we discuss some of the genetic diseases that affect the heart and illustrate how these new paradigms could assist our understanding of cardiac pathogenesis and aid in drug discovery. In particular, we highlight the limitations of other commonly used model systems in predicting the consequences of drug exposure on the human heart.
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Affiliation(s)
- Richard P Davis
- Department of Anatomy and Embryology, Leiden University Medical Center, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
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