1
|
Crespo-García T, Cámara-Checa A, Dago M, Rubio-Alarcón M, Rapún J, Tamargo J, Delpón E, Caballero R. Regulation of cardiac ion channels by transcription factors: Looking for new opportunities of druggable targets for the treatment of arrhythmias. Biochem Pharmacol 2022; 204:115206. [PMID: 35963339 DOI: 10.1016/j.bcp.2022.115206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/04/2022] [Accepted: 08/05/2022] [Indexed: 11/29/2022]
Abstract
Cardiac electrical activity is governed by different ion channels that generate action potentials. Acquired or inherited abnormalities in the expression and/or function of ion channels usually result in electrophysiological changes that can cause cardiac arrhythmias. Transcription factors (TFs) control gene transcription by binding to specific DNA sequences adjacent to target genes. Linkage analysis, candidate-gene screening within families, and genome-wide association studies have linked rare and common genetic variants in the genes encoding TFs with genetically-determined cardiac arrhythmias. Besides its critical role in cardiac development, recent data demonstrated that they control cardiac electrical activity through the direct regulation of the expression and function of cardiac ion channels in adult hearts. This narrative review summarizes some studies showing functional data on regulation of the main human atrial and ventricular Na+, Ca2+, and K+ channels by cardiac TFs such as Pitx2c, Tbx20, Tbx5, Zfhx3, among others. The results have improved our understanding of the mechanisms regulating cardiac electrical activity and may open new avenues for therapeutic interventions in cardiac acquired or inherited arrhythmias through the identification of TFs as potential drug targets. Even though TFs have for a long time been considered as 'undruggable' targets, advances in structural biology have led to the identification of unique pockets in TFs amenable to be targeted with small-molecule drugs or peptides that are emerging as novel therapeutic drugs.
Collapse
Affiliation(s)
- T Crespo-García
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - A Cámara-Checa
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - M Dago
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - M Rubio-Alarcón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - J Rapún
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - J Tamargo
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | - E Delpón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain.
| | - R Caballero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| | -
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, 28040 Madrid, Spain
| |
Collapse
|
2
|
Ríos-Pérez EB, Liu F, Stevens-Sostre WA, Eichel CA, Silignavong J, Robertson GA. A stable cell line inducibly expressing hERG1a/1b heteromeric channels. J Pharmacol Toxicol Methods 2021; 110:107081. [PMID: 34058320 DOI: 10.1016/j.vascn.2021.107081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 04/07/2021] [Accepted: 05/20/2021] [Indexed: 11/24/2022]
Abstract
Heterologously expressed hERG channels represent a mainstay of in vitro drug safety screens intended to mitigate risk of cardiac IKr block and sudden cardiac death. This is true even as more channel types are adopted as part of the Comprehensive in vitro Proarrhythmia Assay (CiPA) intended to elevate specificity and thus enhance throughput of promising lead drugs. Until now, hERG1a homomeric channels have been used as a proxy for IKr despite a wealth of evidence showing that hERG1a/1b heteromers better represent native channels in terms of protein abundance and channel biophysical and pharmacological properties. Past efforts to create a stable hERG1a/1b cell line were met with unpredictable silencing of hERG1b expression despite stable integration of the gene into the HEK293 cell genome. Here we report a new cell line stably expressing hERG1a, with hERG1b reliably controlled by an inducible promoter sensitive to doxycycline. Co-immunoprecipitation, Western blot analysis and patch-clamp electrophysiology confirm the heteromeric composition of the expressed channels. Association with hERG1b was found to promote hERG1a protein levels and enhance membrane current levels. Optimal conditions for drug screening and experimental investigation were achieved at 24 h exposure to 100 ng/ml doxycycline. Differences in pharmacological sensitivity between homomeric and heteromeric channels were observed for dofetilide and ebastine, but not fluoxetine, as evaluated by their IC50 values. Using these values in the O'Hara-Rudy-CiPA in silico model revealed discrepancies in pro-arrhythmia risk, implying the hERG1a homomeric platform overestimates risk for these two drugs. Dofetilide block was use-dependent and faster for hERG1a/1b than hERG1a channels, whereas ebastine showed considerable block at rest and had a slower progression for hERG1a/1b channels. The hERG1a/1b cell line thus represents an advanced model for contemporary drug safety screening assays such as CiPA that employ IC50 values to estimate risk of proarrhythmia in computational models of ventricular cardiomyocytes. This novel technology fulfills an unmet need to enhance specificity and foster a safe yet expanded drug development pipeline.
Collapse
Affiliation(s)
- Erick B Ríos-Pérez
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Fang Liu
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Whitney A Stevens-Sostre
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Catherine A Eichel
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Jonathan Silignavong
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Gail A Robertson
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America.
| |
Collapse
|
3
|
Filatova TS, Abramochkin DV, Pavlova NS, Pustovit KB, Konovalova OP, Kuzmin VS, Dobrzynski H. Repolarizing potassium currents in working myocardium of Japanese quail: a novel translational model for cardiac electrophysiology. Comp Biochem Physiol A Mol Integr Physiol 2021; 255:110919. [DOI: 10.1016/j.cbpa.2021.110919] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/06/2021] [Accepted: 02/06/2021] [Indexed: 12/14/2022]
|
4
|
Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
Collapse
Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| |
Collapse
|
5
|
Orvos P, Kohajda Z, Szlovák J, Gazdag P, Árpádffy-Lovas T, Tóth D, Geramipour A, Tálosi L, Jost N, Varró A, Virág L. Evaluation of Possible Proarrhythmic Potency: Comparison of the Effect of Dofetilide, Cisapride, Sotalol, Terfenadine, and Verapamil on hERG and Native IKr Currents and on Cardiac Action Potential. Toxicol Sci 2020; 168:365-380. [PMID: 30561737 DOI: 10.1093/toxsci/kfy299] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The proarrhythmic potency of drugs is usually attributed to the IKr current block. During safety pharmacology testing analysis of IKr in cardiomyocytes was replaced by human ether-a-go-go-related gene (hERG) test using automated patch-clamp systems in stable transfected cell lines. Aim of this study was to compare the effect of proarrhythmic compounds on hERG and IKr currents and on cardiac action potential. The hERG current was measured by using both automated and manual patch-clamp methods on HEK293 cells. The native ion currents (IKr, INaL, ICaL) were recorded from rabbit ventricular myocytes by manual patch-clamp technique. Action potentials in rabbit ventricular muscle and undiseased human donor hearts were studied by conventional microelectrode technique. Dofetilide, cisapride, sotalol, terfenadine, and verapamil blocked hERG channels at 37°C with an IC50 of 7 nM, 18 nM, 343 μM, 165 nM, and 214 nM, respectively. Using manual patch-clamp, the IC50 values of sotalol and terfenadine were 78 µM and 31 nM, respectively. The IC50 values calculated from IKr measurements at 37°C were 13 nM, 26 nM, 52 μM, 54 nM, and 268 nM, respectively. Cisapride, dofetilide, and sotalol excessively lengthened, terfenadine, and verapamil did not influence the action potential duration. Terfenadine significantly inhibited INaL and moderately ICaL, verapamil blocked only ICaL. Automated hERG assays may over/underestimate proarrhythmic risk. Manual patch-clamp has substantially higher sensitivity to certain drugs. Action potential studies are also required to analyze complex multichannel effects. Therefore, manual patch-clamp and action potential experiments should be a part of preclinical safety tests.
Collapse
Affiliation(s)
- Péter Orvos
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine.,Department of Ophthalmology, University of Szeged, Szeged H-6720, Hungary
| | - Zsófia Kohajda
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged H-6720, Hungary
| | - Jozefina Szlovák
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine
| | - Péter Gazdag
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine
| | | | - Dániel Tóth
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine
| | - Amir Geramipour
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine
| | | | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged H-6720, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged H-6720, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged H-6720, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged H-6720, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine.,MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged H-6720, Hungary.,Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged H-6720, Hungary
| |
Collapse
|
6
|
Yang PC, DeMarco KR, Aghasafari P, Jeng MT, Dawson JRD, Bekker S, Noskov SY, Yarov-Yarovoy V, Vorobyov I, Clancy CE. A Computational Pipeline to Predict Cardiotoxicity: From the Atom to the Rhythm. Circ Res 2020; 126:947-964. [PMID: 32091972 DOI: 10.1161/circresaha.119.316404] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RATIONALE Drug-induced proarrhythmia is so tightly associated with prolongation of the QT interval that QT prolongation is an accepted surrogate marker for arrhythmia. But QT interval is too sensitive a marker and not selective, resulting in many useful drugs eliminated in drug discovery. OBJECTIVE To predict the impact of a drug from the drug chemistry on the cardiac rhythm. METHODS AND RESULTS In a new linkage, we connected atomistic scale information to protein, cell, and tissue scales by predicting drug-binding affinities and rates from simulation of ion channel and drug structure interactions and then used these values to model drug effects on the hERG channel. Model components were integrated into predictive models at the cell and tissue scales to expose fundamental arrhythmia vulnerability mechanisms and complex interactions underlying emergent behaviors. Human clinical data were used for model framework validation and showed excellent agreement, demonstrating feasibility of a new approach for cardiotoxicity prediction. CONCLUSIONS We present a multiscale model framework to predict electrotoxicity in the heart from the atom to the rhythm. Novel mechanistic insights emerged at all scales of the system, from the specific nature of proarrhythmic drug interaction with the hERG channel, to the fundamental cellular and tissue-level arrhythmia mechanisms. Applications of machine learning indicate necessary and sufficient parameters that predict arrhythmia vulnerability. We expect that the model framework may be expanded to make an impact in drug discovery, drug safety screening for a variety of compounds and targets, and in a variety of regulatory processes.
Collapse
Affiliation(s)
- Pei-Chi Yang
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis
| | - Kevin R DeMarco
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis
| | - Parya Aghasafari
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis
| | - Mao-Tsuen Jeng
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis
| | - John R D Dawson
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis.,Biophysics Graduate Group (J.R.D.D.), University of California Davis
| | - Slava Bekker
- Department of Science and Engineering, American River College, Sacramento, CA (S.B.)
| | - Sergei Y Noskov
- Faculty of Science, Centre for Molecular Simulations and Department of Biological Sciences, University of Calgary, Alberta, Canada (S.Y.N.)
| | - Vladimir Yarov-Yarovoy
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis
| | - Igor Vorobyov
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis.,Department of Pharmacology (I.V., C.E.C.), University of California Davis
| | - Colleen E Clancy
- From the Department of Physiology and Membrane Biology (P.-C.Y., K.R.D., P.A., M.-T.J., J.R.D.D., V.Y.-Y., I.V., C.E.C.), University of California Davis.,Department of Pharmacology (I.V., C.E.C.), University of California Davis
| |
Collapse
|
7
|
Cernuda B, Fernandes CT, Allam SM, Orzillo M, Suppa G, Chia Chang Z, Athanasopoulos D, Buraei Z. The molecular determinants of R-roscovitine block of hERG channels. PLoS One 2019; 14:e0217733. [PMID: 31479461 PMCID: PMC6719874 DOI: 10.1371/journal.pone.0217733] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 08/17/2019] [Indexed: 02/06/2023] Open
Abstract
Human ether-à-go-go-related gene (Kv11.1, or hERG) is a potassium channel that conducts the delayed rectifier potassium current (IKr) during the repolarization phase of cardiac action potentials. hERG channels have a larger pore than other K+channels and can trap many unintended drugs, often resulting in acquired LQTS (aLQTS). R-roscovitine is a cyclin-dependent kinase (CDK) inhibitor that induces apoptosis in colorectal, breast, prostate, multiple myeloma, other cancer cell lines, and tumor xenografts, in micromolar concentrations. It is well tolerated in phase II clinical trials. R-roscovitine inhibits open hERG channels but does not become trapped in the pore. Two-electrode voltage clamp recordings from Xenopus oocytes expressing wild-type (WT) or hERG pore mutant channels (T623A, S624A, Y652A, F656A) demonstrated that compared to WT hERG, T623A, Y652A, and F656A inhibition by 200 μM R-roscovitine was ~ 48%, 29%, and 73% weaker, respectively. In contrast, S624A hERG was inhibited more potently than WT hERG, with a ~ 34% stronger inhibition. These findings were further supported by the IC50 values, which were increased for T623A, Y652A and F656A (by ~5.5, 2.75, and 42 fold respectively) and reduced 1.3 fold for the S624A mutant. Our data suggest that while T623, Y652, and F656 are critical for R-roscovitine-mediated inhibition, S624 may not be. Docking studies further support our findings. Thus, R-roscovitine’s relatively unique features, coupled with its tolerance in clinical trials, could guide future drug screens.
Collapse
Affiliation(s)
- Bryan Cernuda
- Department of Biology, Pace University, New York, NY, United States of America
| | | | - Salma Mohamed Allam
- Department of Biology, Pace University, New York, NY, United States of America
| | - Matthew Orzillo
- Department of Biology, Pace University, New York, NY, United States of America
| | - Gabrielle Suppa
- Department of Biology, Pace University, New York, NY, United States of America
| | - Zuleen Chia Chang
- Department of Biology, Pace University, New York, NY, United States of America
| | | | - Zafir Buraei
- Department of Biology, Pace University, New York, NY, United States of America
- * E-mail:
| |
Collapse
|
8
|
Lainez S, Doray A, Hancox JC, Cannell MB. Regulation of Kv4.3 and hERG potassium channels by KChIP2 isoforms and DPP6 and response to the dual K + channel activator NS3623. Biochem Pharmacol 2018; 150:120-130. [PMID: 29378180 PMCID: PMC5906734 DOI: 10.1016/j.bcp.2018.01.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/22/2018] [Indexed: 12/14/2022]
Abstract
Transient outward potassium current (Ito) contributes to early repolarization of many mammalian cardiac action potentials, including human, whilst the rapid delayed rectifier K+ current (IKr) contributes to later repolarization. Fast Ito channels can be produced from the Shal family KCNDE gene product Kv4.3s, although accessory subunits including KChIP2.x and DPP6 are also needed to produce a near physiological Ito. In this study, the effect of KChIP2.1 & KChIP2.2 (also known as KChIP2b and KChIP2c respectively), alone or in conjunction with the accessory subunit DPP6, on both Kv4.3 and hERG were evaluated. A dual Ito and IKr activator, NS3623, has been recently proposed to be beneficial in heart failure and the action of NS3623 on the two channels was also investigated. Whole-cell patch-clamp experiments were performed at 33 ± 1 °C on HEK293 cells expressing Kv4.3 or hERG in the absence or presence of these accessory subunits. Kv4.3 current magnitude was augmented by co-expression with either KChIP2.2 or KChIP2.1 and KChIP2/DPP6 with KChIP2.1 producing a greater effect than KChIP2.2. Adding DPP6 removed the difference in Kv4.3 augmentation between KChIP2.1 and KChIP2.2. The inactivation rate and recovery from inactivation were also altered by KChIP2 isoform co-expression. In contrast, hERG (Kv11.1) current was not altered by co-expression with KChIP2.1, KChIP2.2 or DPP6. NS3623 increased Kv4.3 amplitude to a similar extent with and without accessory subunit co-expression, however KChIP2 isoforms modulated the compound’s effect on inactivation time course. The agonist effect of NS3623 on hERG channels was not affected by KChIP2.1, KChIP2.2 or DPP6 co-expression.
Collapse
Affiliation(s)
- Sergio Lainez
- School of Physiology, Pharmacology and Neuroscience, Faculty of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Adélaïde Doray
- School of Physiology, Pharmacology and Neuroscience, Faculty of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, Faculty of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
| | - Mark B Cannell
- School of Physiology, Pharmacology and Neuroscience, Faculty of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
| |
Collapse
|
9
|
Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
Collapse
Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| |
Collapse
|
10
|
Liu L, Tian J, Lu C, Chen X, Fu Y, Xu B, Zhu C, Sun Y, Zhang Y, Zhao Y, Li Y. Electrophysiological Characteristics of the LQT2 Syndrome Mutation KCNH2-G572S and Regulation by Accessory Protein KCNE2. Front Physiol 2016; 7:650. [PMID: 28082916 PMCID: PMC5187237 DOI: 10.3389/fphys.2016.00650] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/12/2016] [Indexed: 01/18/2023] Open
Abstract
Mutations in hERG cause long QT syndrome type 2 which is characterized by a prolonged QT interval on electrocardiogram and predisposition to life-threatening ventricular tachyarrhythmia, syncope, and sudden death. hERG-G572S induces trafficking defects of hERG channel protein from Golgi to the plasma membrane and results in a dominant negative suppression of hERG current density. As an accessory β subunit, KCNE2 promotes hERG migration from Golgi to cellular membrane. In this study, we investigated the rescue effect of KCNE2 in a G572S mutation of hERG. Transfection was performed into HEK293 cells. Patch clamp technique, western blotting analyses and confocal microscopic examination were used. Results showed that KCNE2 had a significantly enhanced effect on G572S mutation current. The increase of current was largest at KCNH2:KCNE2 of 1:3. Confocal images showed co-expressing G572S and KCNE2 could cause a substantial up-regulated membrane protein (155 kDa) expression. Expression of membrane protein accumulated markedly with increasing ratio of KCNH2:KCNE2. G572S defective mutant could be restored by both KCNE2 and lower temperature (27°C), which suggested that the lower temperature could be the favorable circumstances for the rescue function of KCNE2. In this study, we successfully set up “the action potential” on the HEK 293 cells by genetically engineered to express Kir2.1, Nav1.5, and Kv11.1, wherein on reaching over an excitation threshold by current injection. The results suggested that KCNE2 could shorten action potential duration which was prolonged by G572S. These findings described electrophysiological characteristics of the LQT2 syndrome mutation KCNH2-G572S and regulation by accessory protein KCNE2, and provided a clue about LQT2 and relative rescue mechanism.
Collapse
Affiliation(s)
- Li Liu
- Department of Cardiology, General Hospital of People's Liberation ArmyBeijing, China; The Third Department of Internal Medicine, Beijing Municipal Corps Hospital of Chinese People's Armed Police ForceBeijing, China
| | - Jinwen Tian
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Caiyi Lu
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Xi Chen
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Yicheng Fu
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Bin Xu
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Chao Zhu
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Yanmei Sun
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Yu Zhang
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Ying Zhao
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| | - Yang Li
- Department of Cardiology, General Hospital of People's Liberation Army Beijing, China
| |
Collapse
|
11
|
Zhang Y, Colenso CK, El Harchi A, Cheng H, Witchel HJ, Dempsey CE, Hancox JC. Interactions between amiodarone and the hERG potassium channel pore determined with mutagenesis and in silico docking. Biochem Pharmacol 2016; 113:24-35. [PMID: 27256139 PMCID: PMC4959829 DOI: 10.1016/j.bcp.2016.05.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 05/27/2016] [Indexed: 02/04/2023]
Abstract
The antiarrhythmic drug amiodarone delays cardiac repolarisation through inhibition of hERG-encoded potassium channels responsible for the rapid delayed rectifier potassium current (IKr). This study aimed to elucidate molecular determinants of amiodarone binding to the hERG channel. Whole-cell patch-clamp recordings were made at 37 °C of ionic current (IhERG) carried by wild-type (WT) or mutant hERG channels expressed in HEK293 cells. Alanine mutagenesis and ligand docking were used to investigate the roles of pore cavity amino-acid residues in amiodarone binding. Amiodarone inhibited WT outward IhERG tails with a half-maximal inhibitory concentration (IC50) of ∼45 nM, whilst inward IhERG tails in a high K+ external solution ([K+]e) of 94 mM were blocked with an IC50 of 117.8 nM. Amiodarone’s inhibitory action was contingent upon channel gating. Alanine-mutagenesis identified multiple residues directly or indirectly involved in amiodarone binding. The IC50 for the S6 aromatic Y652A mutation was increased to ∼20-fold that of WT IhERG, similar to the pore helical mutant S624A (∼22-fold WT control). The IC50 for F656A mutant IhERG was ∼17-fold its corresponding WT control. Computational docking using a MthK-based hERG model differentiated residues likely to interact directly with drug and those whose Ala mutation may affect drug block allosterically. The requirements for amiodarone block of aromatic residues F656 and Y652 within the hERG pore cavity are smaller than for other high affinity IhERG inhibitors, with relative importance to amiodarone binding of the residues investigated being S624A ∼ Y652A > F656A > V659A > G648A > T623A.
Collapse
Affiliation(s)
- Yihong Zhang
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Charlotte K Colenso
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Aziza El Harchi
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Hongwei Cheng
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Harry J Witchel
- Brighton and Sussex Medical School, University of Sussex, Falmer BN1 9PX, UK
| | - Chris E Dempsey
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| | - Jules C Hancox
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| |
Collapse
|
12
|
Cotranslational association of mRNA encoding subunits of heteromeric ion channels. Proc Natl Acad Sci U S A 2016; 113:4859-64. [PMID: 27078096 DOI: 10.1073/pnas.1521577113] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oligomers of homomeric voltage-gated potassium channels associate early in biogenesis as the nascent proteins emerge from the polysome. Less is known about how proteins emerging from different polysomes associate to form hetero-oligomeric channels. Here, we report that alternate mRNA transcripts encoding human ether-à-go-go-related gene (hERG) 1a and 1b subunits, which assemble to produce ion channels mediating cardiac repolarization, are physically associated during translation. We show that shRNA specifically targeting either hERG 1a or 1b transcripts reduced levels of both transcripts, but only when they were coexpressed heterologously. Both transcripts could be copurified with an Ab against the nascent hERG 1a N terminus. This interaction occurred even when translation of 1b was prevented, indicating the transcripts associate independent of their encoded proteins. The association was also demonstrated in cardiomyocytes, where levels of both hERG transcripts were reduced by either 1a or 1b shRNA, but native KCNE1 and ryanodine receptor 2 (RYR2) transcripts were unaffected. Changes in protein levels and membrane currents mirrored changes in transcript levels, indicating the targeted transcripts were undergoing translation. The physical association of transcripts encoding different subunits provides the spatial proximity required for nascent proteins to interact during biogenesis, and may represent a general mechanism facilitating assembly of heteromeric protein complexes involved in a range of biological processes.
Collapse
|
13
|
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.
Collapse
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.
| |
Collapse
|
14
|
Romero L, Trenor B, Yang PC, Saiz J, Clancy CE. In silico screening of the impact of hERG channel kinetic abnormalities on channel block and susceptibility to acquired long QT syndrome. J Mol Cell Cardiol 2015; 87:271-82. [DOI: 10.1016/j.yjmcc.2015.08.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
15
|
Pedersen PJ, Thomsen KB, Olander ER, Hauser F, Tejada MDLA, Poulsen KL, Grubb S, Buhl R, Calloe K, Klaerke DA. Molecular Cloning and Functional Expression of the Equine K+ Channel KV11.1 (Ether à Go-Go-Related/KCNH2 Gene) and the Regulatory Subunit KCNE2 from Equine Myocardium. PLoS One 2015; 10:e0138320. [PMID: 26376488 PMCID: PMC4574097 DOI: 10.1371/journal.pone.0138320] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 08/28/2015] [Indexed: 11/18/2022] Open
Abstract
The KCNH2 and KCNE2 genes encode the cardiac voltage-gated K+ channel KV11.1 and its auxiliary β subunit KCNE2. KV11.1 is critical for repolarization of the cardiac action potential. In humans, mutations or drug therapy affecting the KV11.1 channel are associated with prolongation of the QT intervals on the ECG and increased risk of ventricular tachyarrhythmia and sudden cardiac death—conditions known as congenital or acquired Long QT syndrome (LQTS), respectively. In horses, sudden, unexplained deaths are a well-known problem. We sequenced the cDNA of the KCNH2 and KCNE2 genes using RACE and conventional PCR on mRNA purified from equine myocardial tissue. Equine KV11.1 and KCNE2 cDNA had a high homology to human genes (93 and 88%, respectively). Equine and human KV11.1 and KV11.1/KCNE2 were expressed in Xenopus laevis oocytes and investigated by two-electrode voltage-clamp. Equine KV11.1 currents were larger compared to human KV11.1, and the voltage dependence of activation was shifted to more negative values with V1/2 = -14.2±1.1 mV and -17.3±0.7, respectively. The onset of inactivation was slower for equine KV11.1 compared to the human homolog. These differences in kinetics may account for the larger amplitude of the equine current. Furthermore, the equine KV11.1 channel was susceptible to pharmacological block with terfenadine. The physiological importance of KV11.1 was investigated in equine right ventricular wedge preparations. Terfenadine prolonged action potential duration and the effect was most pronounced at slow pacing. In conclusion, these findings indicate that horses could be disposed to both congenital and acquired LQTS.
Collapse
Affiliation(s)
- Philip Juul Pedersen
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Kirsten Brolin Thomsen
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Emma Rie Olander
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Frank Hauser
- Center for Functional and Comparative Insect Genomics, Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Maria de los Angeles Tejada
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Kristian Lundgaard Poulsen
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Soren Grubb
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Rikke Buhl
- Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Kirstine Calloe
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
- * E-mail:
| | - Dan Arne Klaerke
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| |
Collapse
|
16
|
Fermini B, Hancox JC, Abi-Gerges N, Bridgland-Taylor M, Chaudhary KW, Colatsky T, Correll K, Crumb W, Damiano B, Erdemli G, Gintant G, Imredy J, Koerner J, Kramer J, Levesque P, Li Z, Lindqvist A, Obejero-Paz CA, Rampe D, Sawada K, Strauss DG, Vandenberg JI. A New Perspective in the Field of Cardiac Safety Testing through the Comprehensive In Vitro Proarrhythmia Assay Paradigm. ACTA ACUST UNITED AC 2015; 21:1-11. [PMID: 26170255 DOI: 10.1177/1087057115594589] [Citation(s) in RCA: 198] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 06/11/2015] [Indexed: 12/31/2022]
Abstract
For the past decade, cardiac safety screening to evaluate the propensity of drugs to produce QT interval prolongation and Torsades de Pointes (TdP) arrhythmia has been conducted according to ICH S7B and ICH E14 guidelines. Central to the existing approach are hERG channel assays and in vivo QT measurements. Although effective, the present paradigm carries a risk of unnecessary compound attrition and high cost, especially when considering costly thorough QT (TQT) studies conducted later in drug development. The C: omprehensive I: n Vitro P: roarrhythmia A: ssay (CiPA) initiative is a public-private collaboration with the aim of updating the existing cardiac safety testing paradigm to better evaluate arrhythmia risk and remove the need for TQT studies. It is hoped that CiPA will produce a standardized ion channel assay approach, incorporating defined tests against major cardiac ion channels, the results of which then inform evaluation of proarrhythmic actions in silico, using human ventricular action potential reconstructions. Results are then to be confirmed using human (stem cell-derived) cardiomyocytes. This perspective article reviews the rationale, progress of, and challenges for the CiPA initiative, if this new paradigm is to replace existing practice and, in time, lead to improved and widely accepted cardiac safety testing guidelines.
Collapse
Affiliation(s)
| | - Jules C Hancox
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - Najah Abi-Gerges
- Translational Safety, Drug Safety and Metabolism, Innovative Medicines and Early Development, AstraZeneca R&D, Macclesfield, UK AnaBios Corporation, San Diego, CA, USA
| | - Matthew Bridgland-Taylor
- Discovery Sciences, Innovative Medicines and Early Development, AstraZeneca R&D, Macclesfield, UK
| | | | - Thomas Colatsky
- Division of Applied Regulatory Science, CDER, US Food and Drug Administration, Silver Spring, MD, USA
| | | | | | - Bruce Damiano
- Global Safety Pharmacology, Discovery Sciences, Janssen Research & Development LLC, Spring House, PA, USA
| | - Gul Erdemli
- Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Inc, Cambridge, MA, USA
| | - Gary Gintant
- Department of Integrative Pharmacology, Integrated Sciences & Technology, AbbVie, North Chicago, IL, USA
| | - John Imredy
- Department of Safety Assessment, Merck & Co, Kenilworth, NJ, USA
| | - John Koerner
- Division of Cardiovascular and Renal Products, CDER, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | - James Kramer
- ChanTest, A Charles River Company, Cleveland, OH, USA
| | - Paul Levesque
- Bristol Myers Squibb Research & Development, Princeton, NJ, USA
| | - Zhihua Li
- Division of Applied Regulatory Science, CDER, US Food and Drug Administration, Silver Spring, MD, USA
| | | | | | - David Rampe
- Preclinical Safety, Sanofi, Bridgewater, NJ, USA
| | - Kohei Sawada
- Global Cardiovascular Assessment, Eisai Co., Ltd., Ibaraki, Japan
| | - David G Strauss
- Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, St Vincent's Clinical School, University of NSW, Darlinghurst, NSW, Australia
| |
Collapse
|
17
|
The interaction between delayed rectifier channel alpha-subunits does not involve hetero-tetramer formation. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:973-81. [PMID: 25790957 DOI: 10.1007/s00210-015-1108-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/17/2015] [Indexed: 12/20/2022]
Abstract
We have previously reported a physiologically relevant interaction between KCNQ1 (Q1) and KCNH2 (H2). While the H2 C-terminus has been suggested to play a role, so far, no more detailed information regarding the interaction site is available. The methods used in the study are cell culture, PCR for mutagenesis, patch clamp for ion current recordings, co-immunoprecipitation for determination of protein interaction. Co-expression of Q1 and H2 resulted in an increase of I H2 (tails after +50 mV; Q1 + H2, 36 ± 6 pA/pF; H2, 14 ± 2 pA/pF; n = 10; 12; P < 0.05). Upon expressing a non-conductive (dominant-negative) Q1-pore mutation (dnQ1), there was still an increase in I H2 (tails after +50 mV; H2 + dnQ1, 24 ± 4 pA/pF; n = 10; P < 0.05) making the pore region unlikely as an interaction site. Experiments using the KCNH2-pore blocking agent quinidine supported these findings. If Q1 and H2 formed hetero-tetramers, steric changes within the pore should change the quinidine half-inhibitory concentrations (IC50). However, I H2 sensitivity did not significantly change in the presence or absence of Q1 (IC50 341 ± 63 vs. 611 ± 293 nmol/L, respectively, P = n.s.), providing further evidence that the pore is not a likely H2-Q1 interaction site. To obtain further insights into the role of intra-cytoplasmic structures, we used both C- and N-terminally truncated mutant H2 proteins. Both H2 mutants co-immunoprecipitated with Q1, suggesting no specific role of C- or N-termini. Accordingly, rather than these, the transmembrane domains of the α-subunits appear relevant for the interaction. Our results largely exclude the formation of hetero-tetramers between H2 and Q1 comprising the pore region or H2 C- or N-termini.
Collapse
|
18
|
Zhang KP, Yang BF, Li BX. Translational toxicology and rescue strategies of the hERG channel dysfunction: biochemical and molecular mechanistic aspects. Acta Pharmacol Sin 2014; 35:1473-84. [PMID: 25418379 PMCID: PMC4261120 DOI: 10.1038/aps.2014.101] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/20/2014] [Indexed: 01/08/2023] Open
Abstract
The human ether-à-go-go related gene (hERG) potassium channel is an obligatory anti-target for drug development on account of its essential role in cardiac repolarization and its close association with arrhythmia. Diverse drugs have been removed from the market owing to their inhibitory activity on the hERG channel and their contribution to acquired long QT syndrome (LQTS). Moreover, mutations that cause hERG channel dysfunction may induce congenital LQTS. Recently, an increasing number of biochemical and molecular mechanisms underlying hERG-associated LQTS have been reported. In fact, numerous potential biochemical and molecular rescue strategies are hidden within the biogenesis and regulating network. So far, rescue strategies of hERG channel dysfunction and LQTS mainly include activators, blockers, and molecules that interfere with specific links and other mechanisms. The aim of this review is to discuss the rescue strategies based on hERG channel toxicology from the biochemical and molecular perspectives.
Collapse
Affiliation(s)
- Kai-ping Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-feng Yang
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| | - Bao-xin Li
- Department of Pharmacology, Harbin Medical University, Harbin, China
- The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China (Key Laboratory of Cardiovascular Research, Ministry of Education), China
| |
Collapse
|
19
|
Long Y, Chen W, Lin Z, Sun H, Xia M, Zheng W, Li Z. Inhibition of HERG potassium channels by domiphen bromide and didecyl dimethylammonium bromide. Eur J Pharmacol 2014; 737:202-9. [PMID: 24846011 DOI: 10.1016/j.ejphar.2014.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 04/23/2014] [Accepted: 05/07/2014] [Indexed: 10/25/2022]
Abstract
Domiphen bromide and didecyl dimethylammonium bromide were widely used environmental chemicals with potent activity on blockade of human ether-a-go-go related gene (HERG) channels. But the mechanism of their action is not clear. The kinetics of block of HERG channels by domiphen bromide and didecyl dimethylammonium bromide was studied in order to characterize the inhibition of HERG currents by these quaternary ammonium compounds (QACs). Domiphen bromide and didecyl dimethylammonium bromide inhibited HERG channel currents in a dose-dependent manner with IC50 values of 9nM and 5nM, respectively. Block of HERG channel by domiphen bromide and didecyl dimethylammonium bromide was voltage-dependent and use-dependent. Domiphen bromide and didecyl dimethylammonium bromide caused substantial negative shift of the activation curves, accelerated activated process, but had no effects on the deactivation and reactivation processes. The docking models implied that these two compounds bound to PAS domain of HERG channels and inhibited its function. Our data demonstrated that domiphen bromide and didecyl dimethylammonium bromide blocked the HERG channel with a preference for the activated channel state.
Collapse
Affiliation(s)
- Yan Long
- Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Kaiyuan Road 190, Guangzhou Science Park, Guangzhou 510530, China
| | - Wanjuan Chen
- The School of Life Sciences, Anhui University, Hefei 230027, China
| | - Zuoxian Lin
- Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Kaiyuan Road 190, Guangzhou Science Park, Guangzhou 510530, China
| | - Hongmao Sun
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA
| | - Menghang Xia
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Zheng
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zhiyuan Li
- Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Kaiyuan Road 190, Guangzhou Science Park, Guangzhou 510530, China.
| |
Collapse
|
20
|
Rodriguez-Menchaca AA, Ferrer T, Navarro-Polanco RA, Sanchez-Chapula JA, Moreno-Galindo EG. Impact of the whole-cell patch-clamp configuration on the pharmacological assessment of the hERG channel: Trazodone as a case example. J Pharmacol Toxicol Methods 2014; 69:237-44. [DOI: 10.1016/j.vascn.2013.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 12/03/2013] [Accepted: 12/31/2013] [Indexed: 11/28/2022]
|
21
|
Romero L, Trenor B, Yang PC, Saiz J, Clancy CE. In silico screening of the impact of hERG channel kinetic abnormalities on channel block and susceptibility to acquired long QT syndrome. J Mol Cell Cardiol 2014; 72:126-37. [PMID: 24631769 DOI: 10.1016/j.yjmcc.2014.02.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/27/2014] [Accepted: 02/28/2014] [Indexed: 01/08/2023]
Abstract
Accurate diagnosis of predisposition to long QT syndrome is crucial for reducing the risk of cardiac arrhythmias. In recent years, drug-induced provocative tests have proved useful to unmask some latent mutations linked to cardiac arrhythmias. In this study we expanded this concept by developing a prototype for a computational provocative screening test to reveal genetic predisposition to acquired long-QT syndrome (aLQTS). We developed a computational approach to reveal the pharmacological properties of IKr blocking drugs that are most likely to cause aLQTS in the setting of subtle alterations in IKr channel gating that would be expected to result from benign genetic variants. We used the model to predict the most potentially lethal combinations of kinetic anomalies and drug properties. In doing so, we also implicitly predicted ideal inverse therapeutic properties of K channel openers that would be expected to remedy a specific defect. We systematically performed "in silico mutagenesis" by altering discrete kinetic transition rates of the Fink et al. Markov model of human IKr channels, corresponding to activation, inactivation, deactivation and recovery from inactivation of IKr channels. We then screened and identified the properties of IKr blockers that caused acquired long QT and therefore unmasked mutant phenotypes for mild, moderate and severe variants. Mutant IKr channels were incorporated into the O'Hara et al. human ventricular action potential (AP) model and subjected to simulated application of a wide variety of IKr-drug interactions in order to identify the characteristics that selectively exacerbate the AP duration (APD) differences between wild-type and IKr mutated cells. Our results show that drugs with disparate affinities to conformation states of the IKr channel are key to amplify variants underlying susceptibility to acquired long QT syndrome, an effect that is especially pronounced at slow frequencies. Finally, we developed a mathematical formulation of the M54T MiRP1 latent mutation and simulated a provocative test. In this setting, application of dofetilide dramatically amplified the predicted QT interval duration in the M54T hMiRP1 mutation compared to wild-type.
Collapse
Affiliation(s)
- Lucia Romero
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano (I3BH), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain.
| | - Beatriz Trenor
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano (I3BH), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain.
| | - Pei-Chi Yang
- Department of Pharmacology, University of California, Davis, Genome Building Rm 3503, Davis, CA 95616-8636, USA.
| | - Javier Saiz
- Instituto de Investigación Interuniversitario en Bioingeniería y Tecnología Orientada al Ser Humano (I3BH), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain.
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome Building Rm 3503, Davis, CA 95616-8636, USA.
| |
Collapse
|
22
|
Abstract
Abnormal functioning of cardiac ion channels can disrupt cardiac myocyte action potentials and thus cause potentially lethal cardiac arrhythmias. Ion channel dysfunction has been observed at all stages in channel ontogeny, from biogenesis to regulation, and arises from genetic or environmental factors, or both. Acquired arrhythmias - including those that are drug induced - are more common than solely inherited arrhythmias but, in some cases, also contain an identifiable genetic component. This interplay between the pharmacology and genetics - known as 'pharmacogenetics' - of cardiac ion channels and the systems that impact them presents both challenges and opportunities to academics, pharmaceutical companies and clinicians seeking to develop and utilize therapies for cardiac rhythm disorders. In this review, we discuss ion channel pharmacogenetics in the context of both causation and treatment of cardiac arrhythmias, focusing on the long QT syndromes.
Collapse
Affiliation(s)
- Geoffrey W Abbott
- Weill Medical College of Cornell University, Greenberg Division of Cardiology, Department of Medicine and Department of Pharmacology, 520 East 70th Street, New York, NY 10021, USA.
| | | |
Collapse
|
23
|
Mechakra A, Vincent Y, Chevalier P, Millat G, Ficker E, Jastrzebski M, Poulin H, Pouliot V, Chahine M, Christé G. The variant hERG/R148W associated with LQTS is a mutation that reduces current density on co-expression with the WT. Gene 2013; 536:348-56. [PMID: 24334129 DOI: 10.1016/j.gene.2013.11.072] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 11/08/2013] [Accepted: 11/26/2013] [Indexed: 10/25/2022]
Abstract
BACKGROUND A variant of the ether-à-go-go related channel (hERG), p.Arg148Trp (R148W) was found at heterozygous state in two infants who died from sudden infant death syndrome (SIDS), one with documented prolonged QTc and Torsade de Pointes (TdP), and in an adult woman with QTc >500 ms, atrioventricular block and TdP. This variant was previously reported in cases of severe ventricular arrhythmia but very rarely in control subjects. Its classification as mutation or polymorphism awaited electrophysiological characterization. METHODS The properties of this N-terminal, proximal domain, hERG variant were explored in Xenopus oocytes injected with the same amount of RNA encoding for either hERG/WT or hERG/R148W or their equimolar mixture. The human ventricular cell (TNNP) model was used to test the effects of changes in hERG current. RESULTS R148W alone produced a current similar to the WT (369 ± 76 nA (mean ± SEM), n=13 versus 342 ± 55 nA in WT, n=13), while the co-expression of 1/2 WT+1/2 R148W lowered the current by 29% versus WT (243 ± 35 nA, n=13, p<0.05). The voltage dependencies of steady-state activation and inactivation were not changed in the variant alone or in co-expression with the WT. The time constants of fast recovery from inactivation and of fast and slow deactivation analyzed between -120 and +20 mV were not changed. The voltage-dependent distribution of the current amplitudes among fast-, slow- and non-deactivating fractions was unaltered. A 6.6% increase in APD90 from 323.5 ms to 345 ms was observed using the human cardiac ventricular myocyte model. CONCLUSIONS Such a decrease in hERG current as evidenced here when co-expressing the hERG/R148W variant with the WT may have predisposed to the observed long QT syndrome and associated TdP. Therefore, the heterozygous carriers of hERG/R148W may be at risk of cardiac sudden death.
Collapse
Affiliation(s)
- Asma Mechakra
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France
| | - Yohann Vincent
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France
| | - Philippe Chevalier
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France; Unité de Rythmologie, Centre National de Référence des Troubles du Rythme d'Origine Héréditaire, Hôpital Cardiovasculaire et Pneumologique L. Pradel, Hospices Civils de Lyon, Lyon F-69003, France
| | - Gilles Millat
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France; Laboratoire de Cardiogénétique, Centre de Biologie Est, Hospices Civils de Lyon, Lyon F-69003, France
| | | | - Marek Jastrzebski
- Department of Cardiology and Hypertension, University Hospital, Kracow, Poland
| | - Hugo Poulin
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Valérie Pouliot
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Mohamed Chahine
- Le Centre de Recherche en neuroscience, Institut Universitaire en Santé Mentale de Québec and Department of Medicine, Laval University, Québec, Canada
| | - Georges Christé
- Laboratoire de Neurocardiologie, EA4612, Université Lyon 1, Lyon F-69003, France.
| |
Collapse
|
24
|
Du C, El Harchi A, Zhang H, Hancox JC. Modification by KCNE1 variants of the hERG potassium channel response to premature stimulation and to pharmacological inhibition. Physiol Rep 2013; 1:e00175. [PMID: 24400172 PMCID: PMC3871485 DOI: 10.1002/phy2.175] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/02/2013] [Accepted: 11/04/2013] [Indexed: 01/08/2023] Open
Abstract
human Ether-à-go-go-Related Gene (hERG) encodes the pore-forming subunit of cardiac rapid delayed rectifier K(+) current (I Kr) channels, which play important roles in ventricular repolarization, in protecting the myocardium from unwanted premature stimuli, and in drug-induced Long QT Syndrome (LQTS). KCNE1, a small transmembrane protein, can coassemble with hERG. However, it is not known how KCNE1 variants influence the channel's response to premature stimuli or if they influence the sensitivity of hERG to pharmacological inhibition. Accordingly, whole-cell patch-clamp measurements of hERG current (I hERG) were made at 37°C from hERG channels coexpressed with either wild-type (WT) KCNE1 or with one of three KCNE1 variants (A8V, D76N, and D85N). Under both conventional voltage clamp and ventricular action potential (AP) clamp, the amplitude of I hERG was smaller for A8V, D76N, and D85N KCNE1 + hERG than for WT KCNE1 + hERG. Using paired AP commands, with the second AP waveform applied at varying time intervals following the first to mimic premature ventricular excitation, the response of I hERG carried by each KCNE1 variant was reduced compared to that with WT KCNE1 + hERG. The I hERG blocking potency of the antiarrhythmic drug quinidine was similar between WT KCNE1 and the three KCNE1 variants. However, the I hERG inhibitory potency of the antibiotic clarithromycin and of the prokinetic drug cisapride was altered by KCNE1 variants. These results demonstrate that naturally occurring KCNE1 variants can reduce the response of hERG channels to premature excitation and also alter the sensitivity of hERG channels to inhibition by some drugs linked to acquired LQTS.
Collapse
Affiliation(s)
- Chunyun Du
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol Bristol, BS8 1TD, U.K
| | - Aziza El Harchi
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol Bristol, BS8 1TD, U.K
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, University of Manchester Manchester, M13 9PL, U.K
| | - Jules C Hancox
- School of Physiology and Pharmacology and Cardiovascular Research Laboratories, Medical Sciences Building, University of Bristol Bristol, BS8 1TD, U.K
| |
Collapse
|
25
|
Abstract
Congenital long QT syndrome (LQTS) is a genetically heterogeneous group of heritable disorders of myocardial repolarization linked by the shared clinical phenotype of QT prolongation on electrocardiogram and an increased risk of potentially life-threatening cardiac arrhythmias. At the molecular level, mutations in 15 distinct LQTS-susceptibility genes that encode ion channel pore-forming α-subunits and accessory β-subunits central to the electromechanical function of the heart have been implicated in its pathogenesis. Over the past 2 decades, our evolving understanding of the electrophysiological mechanisms by which specific genetic substrates perturb the cardiac action potential has translated into vastly improved approaches to the diagnosis, risk stratification, and treatment of patients with LQTS. In this review, we describe how our understanding of the molecular underpinnings of LQTS has yielded numerous clinically meaningful genotype-phenotype correlations and how these insights have translated into genotype- and phenotype-guided approaches to the clinical management of LQTS.
Collapse
Affiliation(s)
| | - Michael J. Ackerman
- Departments of Medicine (Division of Cardiovascular Diseases), Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| |
Collapse
|
26
|
Xu J, Yu P, Yang Q, Meng JN, Shan JJ, You QD, Tang YQ. Antiarrhythmic Efficacy of CPUY11018 Under Pathological Conditions. Drug Dev Res 2013. [DOI: 10.1002/ddr.21060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jing Xu
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Peng Yu
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Qian Yang
- Department of Medicinal Chemistry; China Pharmaceutical University; Nanjing; China
| | - Jia-ning Meng
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Jiao-jiao Shan
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| | - Qi-dong You
- Department of Medicinal Chemistry; China Pharmaceutical University; Nanjing; China
| | - Yi-qun Tang
- Research Division of Pharmacology; China Pharmaceutical University; Nanjing; China
| |
Collapse
|
27
|
Cardiac ion channels and mechanisms for protection against atrial fibrillation. Rev Physiol Biochem Pharmacol 2013; 162:1-58. [PMID: 21987061 DOI: 10.1007/112_2011_3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Atrial fibrillation (AF) is recognised as the most common sustained cardiac arrhythmia in clinical practice. Ongoing drug development is aiming at obtaining atrial specific effects in order to prevent pro-arrhythmic, devastating ventricular effects. In principle, this is possible due to a different ion channel composition in the atria and ventricles. The present text will review the aetiology of arrhythmias with focus on AF and include a description of cardiac ion channels. Channels that constitute potentially atria-selective targets will be described in details. Specific focus is addressed to the recent discovery that Ca(2+)-activated small conductance K(+) channels (SK channels) are important for the repolarisation of atrial action potentials. Finally, an overview of current pharmacological treatment of AF is included.
Collapse
|
28
|
Long Y, Lin Z, Xia M, Zheng W, Li Z. Mechanism of HERG potassium channel inhibition by tetra-n-octylammonium bromide and benzethonium chloride. Toxicol Appl Pharmacol 2013; 267:155-66. [PMID: 23313619 DOI: 10.1016/j.taap.2012.12.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 12/12/2012] [Accepted: 12/28/2012] [Indexed: 10/27/2022]
Abstract
Tetra-n-octylammonium bromide and benzethonium chloride are synthetic quaternary ammonium salts that are widely used in hospitals and industries for the disinfection and surface treatment and as the preservative agent. Recently, the activities of HERG channel inhibition by these compounds have been found to have potential risks to induce the long QT syndrome and cardiac arrhythmia, although the mechanism of action is still elusive. This study was conducted to investigate the mechanism of HERG channel inhibition by these compounds by using whole-cell patch clamp experiments in a CHO cell line stably expressing HERG channels. Tetra-n-octylammonium bromide and benzethonium chloride exhibited concentration-dependent inhibitions of HERG channel currents with IC(50) values of 4nM and 17nM, respectively, which were also voltage-dependent and use-dependent. Both compounds shifted the channel activation I-V curves in a hyperpolarized direction for 10-15mV and accelerated channel activation and inactivation processes by 2-fold. In addition, tetra-n-octylammonium bromide shifted the inactivation I-V curve in a hyperpolarized direction for 24.4mV and slowed the rate of channel deactivation by 2-fold, whereas benzethonium chloride did not. The results indicate that tetra-n-octylammonium bromide and benzethonium chloride are open-channel blockers that inhibit HERG channels in the voltage-dependent, use-dependent and state-dependent manners.
Collapse
Affiliation(s)
- Yan Long
- Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China
| | | | | | | | | |
Collapse
|
29
|
Gillie DJ, Novick SJ, Donovan BT, Payne LA, Townsend C. Development of a high-throughput electrophysiological assay for the human ether-à-go-go related potassium channel hERG. J Pharmacol Toxicol Methods 2013; 67:33-44. [DOI: 10.1016/j.vascn.2012.10.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 10/02/2012] [Accepted: 10/18/2012] [Indexed: 01/03/2023]
|
30
|
Abbott GW. KCNE genetics and pharmacogenomics in cardiac arrhythmias: much ado about nothing? Expert Rev Clin Pharmacol 2013; 6:49-60. [PMID: 23272793 PMCID: PMC4917007 DOI: 10.1586/ecp.12.76] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Voltage-gated ion channels respond to changes in membrane potential with conformational shifts that either facilitate or stem the movement of charged ions across the cell membrane. This controlled movement of ions is particularly important for the action potentials of excitable cells such as cardiac myocytes and therefore essential for timely beating of the heart. Inherited mutations in ion channel genes and in the genes encoding proteins that regulate them can cause lethal cardiac arrhythmias either by direct channel disruption or by altering interactions with therapeutic drugs, the best-understood example of both these scenarios being long QT syndrome (LQTS). Unsurprisingly, mutations in the genes encoding ion channel pore-forming α subunits underlie the large majority (~90%) of identified cases of inherited LQTS. Given that inherited LQTS is comparatively rare in itself (~0.04% of the US population), is pursuing study of the remaining known and unknown LQTS-associated genes subject to the law of diminishing returns? Here, with a particular focus on the KCNE family of single transmembrane domain K(+) channel ancillary subunits, the significance to cardiac pharmacogenetics of ion channel regulatory subunits is discussed.
Collapse
Affiliation(s)
- Geoffrey W Abbott
- Department of Pharmacology, Department of Physiology & Biophysics, University of California, Irvine, CA, USA.
| |
Collapse
|
31
|
Saito S, Nakatsuka K, Takahashi K, Fukuta N, Imagawa T, Ohta T, Tominaga M. Analysis of transient receptor potential ankyrin 1 (TRPA1) in frogs and lizards illuminates both nociceptive heat and chemical sensitivities and coexpression with TRP vanilloid 1 (TRPV1) in ancestral vertebrates. J Biol Chem 2012; 287:30743-54. [PMID: 22791718 DOI: 10.1074/jbc.m112.362194] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient receptor potential ankyrin 1 (TRPA1) and TRP vanilloid 1 (V1) perceive noxious temperatures and chemical stimuli and are involved in pain sensation in mammals. Thus, these two channels provide a model for understanding how different genes with similar biological roles may influence the function of one another during the course of evolution. However, the temperature sensitivity of TRPA1 in ancestral vertebrates and its evolutionary path are unknown as its temperature sensitivities vary among different vertebrate species. To elucidate the functional evolution of TRPA1, TRPA1s of the western clawed (WC) frogs and green anole lizards were characterized. WC frog TRPA1 was activated by heat and noxious chemicals that activate mammalian TRPA1. These stimuli also activated native sensory neurons and elicited nocifensive behaviors in WC frogs. Similar to mammals, TRPA1 was functionally co-expressed with TRPV1, another heat- and chemical-sensitive nociceptive receptor, in native sensory neurons of the WC frog. Green anole TRPA1 was also activated by heat and noxious chemical stimulation. These results suggest that TRPA1 was likely a noxious heat and chemical receptor and co-expressed with TRPV1 in the nociceptive sensory neurons of ancestral vertebrates. Conservation of TRPV1 heat sensitivity throughout vertebrate evolution could have changed functional constraints on TRPA1 and influenced the functional evolution of TRPA1 regarding temperature sensitivity, whereas conserving its noxious chemical sensitivity. In addition, our results also demonstrated that two mammalian TRPA1 inhibitors elicited different effect on the TRPA1s of WC frogs and green anoles, which can be utilized to clarify the structural bases for inhibition of TRPA1.
Collapse
Affiliation(s)
- Shigeru Saito
- Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institute of Natural Sciences, Okazaki, Aichi, 444-8787, Japan.
| | | | | | | | | | | | | |
Collapse
|
32
|
Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
Collapse
Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| |
Collapse
|
33
|
Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel. Proc Natl Acad Sci U S A 2012; 109:11866-71. [PMID: 22745159 DOI: 10.1073/pnas.1205266109] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as I(Ks) and I(Kr). The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of I(Kr) by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if I(Ks) is reduced. Using a unique specific chemical activator for I(Kr) that has a primary effect of causing a right shift of V(1/2) for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an I(Kr) chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent.
Collapse
|
34
|
Jonsson MKB, van der Heyden MAG, van Veen TAB. Deciphering hERG channels: molecular basis of the rapid component of the delayed rectifier potassium current. J Mol Cell Cardiol 2012; 53:369-74. [PMID: 22742967 DOI: 10.1016/j.yjmcc.2012.06.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 06/07/2012] [Accepted: 06/19/2012] [Indexed: 12/23/2022]
Abstract
The rapid component of the delayed rectifier potassium current (I(Kr)), encoded by the ether-a-go-go-related gene (ERG1, officially denominated as KCNH2), is a major contributor to repolarization in the mammalian heart. Acute (e.g. drug-induced) and chronic (e.g. inherited genetic disorder) disruptions of this current can lead to prolongation of the action potential and potentiate occurrence of lethal arrhythmias. Many cardiac and non-cardiac drugs show high affinity for the I(Kr) channel and it is therefore extensively studied during safety pharmacology. The unique biophysical and pharmacological properties of the I(Kr) channel are largely recapitulated by expressing the human variant (hERG1a) in overexpressing systems. hERG1a channels are tetramers consisting of four 1159 amino acid long proteins and have electrophysiological properties similar, but not identical, to native I(Kr). In the search for an explanation to the discrepancies between I(Kr) and hERG1a channels, two alternative hERG1 proteins have been found. Alternative transcription of hERG1 leads to a protein with a 56 amino acid shorter N-terminus, known as hERG1b. hERG1b can form channels alone or coassemble with hERG1a. Alternative splicing leads to an alternate C-terminus and a protein known as hERGuso. hERGuso and hERG1b regulate hERG1a channel trafficking, functional expression and channel kinetics. Expression of hERGuso leads to a reduced number of channels at the plasma membrane and thereby reduces current density. On the contrary, co-assembly with hERG1b alters channel kinetics resulting in more available channels and a larger current. These findings have implication for understanding mechanisms of disease, acute and chronic drug effects, and potential gender differences.
Collapse
Affiliation(s)
- Malin K B Jonsson
- Department of Medical Physiology, Division Heart and Lungs, University Medical Center Utrecht, Utrecht, The Netherlands.
| | | | | |
Collapse
|
35
|
Valenzuela C, Moreno C, de la Cruz A, Macías Á, Prieto Á, González T. Stereoselective Interactions between Local Anesthetics and Ion Channels. Chirality 2012; 24:944-50. [DOI: 10.1002/chir.22051] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 02/14/2012] [Accepted: 02/28/2012] [Indexed: 11/06/2022]
Affiliation(s)
- Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| | - Cristina Moreno
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| | - Alicia de la Cruz
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| | - Álvaro Macías
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| | - Ángela Prieto
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| | - Teresa González
- Instituto de Investigaciones Biomédicas Alberto Sols; Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid; Madrid; Spain
| |
Collapse
|
36
|
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.
Collapse
|
37
|
Abstract
KCNE2, originally designated MinK-related peptide 1 (MiRP1), belongs to a five-strong family of potassium channel ancillary (β) subunits that, despite the diminutive size of the family and its members, has loomed large in the field of ion channel physiology. KCNE2 dictates K (+) channel gating, conductance, α subunit composition, trafficking and pharmacology, and also modifies functional properties of monovalent cation-nonselective HCN channels. The Kcne2 (-/-) mouse exhibits cardiac arrhythmia and hypertrophy, achlorhydria, gastric neoplasia, hypothyroidism, alopecia, stunted growth and choroid plexus epithelial dysfunction, illustrating the breadth and depth of the influence of KCNE2, mutations which are also associated with human cardiac arrhythmias. Here, the modus operandi and physiological roles of this potent regulator of membrane excitability and ion secretion are reviewed with particular emphasis on the ability of KCNE2 to shape the electrophysiological landscape of both excitable and non-excitable cells.
Collapse
Affiliation(s)
- Geoffrey W Abbott
- Departments of Pharmacology and Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA.
| |
Collapse
|
38
|
The voltage-gated channel accessory protein KCNE2: multiple ion channel partners, multiple ways to long QT syndrome. Expert Rev Mol Med 2011; 13:e38. [DOI: 10.1017/s1462399411002092] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The single-pass transmembrane protein KCNE2 or MIRP1 was once thought to be the missing accessory protein that combined with hERG to fully recapitulate the cardiac repolarising current IKr. As a result of this role, it was an easy next step to associate mutations in KCNE2 to long QT syndrome, in which there is delayed repolarisation of the heart. Since that time however, KCNE2 has been shown to modify the behaviour of several other channels and currents, and its role in the heart and in the aetiology of long QT syndrome has become less clear. In this article, we review the known interactions of the KCNE2 protein and the resulting functional effects, and the effects of mutations in KCNE2 and their clinical role.
Collapse
|
39
|
Schuster AM, Glassmeier G, Bauer CK. Strong Activation of ether-à-go-go-Related Gene 1 K+ Channel Isoforms by NS1643 in Human Embryonic Kidney 293 and Chinese Hamster Ovary Cells. Mol Pharmacol 2011; 80:930-42. [DOI: 10.1124/mol.111.071621] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
|
40
|
Zhang YH, Colenso CK, Sessions RB, Dempsey CE, Hancox JC. The hERG K(+) channel S4 domain L532P mutation: characterization at 37°C. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2477-87. [PMID: 21777565 PMCID: PMC3245891 DOI: 10.1016/j.bbamem.2011.07.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/28/2011] [Accepted: 07/06/2011] [Indexed: 11/10/2022]
Abstract
hERG (human Ether-à-go-go Related Gene) is responsible for ion channels mediating rapid delayed rectifier potassium current, IKr, which is key to cardiac action potential repolarization. Gain-of-function hERG mutations give rise to the SQT1 variant of the Short QT Syndrome (SQTS). Reggae mutant zebrafish, with a S4 zERG mutation (Leucine499Proline; L499P), display arrhythmic features analogous to those seen in the SQTS. The affected S4 domain ERG residue is highly conserved. This study was executed to determine how the homologous hERG mutation (L532P) influences channel function at 37 °C. Whole-cell measurements of current (IhERG) were made from HEK 293 cells expressing WT or L532P hERG. The half maximal activation voltage (V0.5) of L532P IhERG was positively shifted by ~+36 mV compared to WT IhERG; however at negative voltages a pronounced L532P IhERG was observed. Both activation and deactivation time-courses were accelerated for L532P IhERG. The inactivation V0.5 for L532P IhERG was shifted by ~+32 mV. Under action potential (AP) voltage-clamp, L532P IhERG exhibited a dome-shaped current peaking at ~+16 mV, compared to ~−31 mV for WT-IhERG. The L532P mutation produced an ~ 5-fold increase in the IC50 for dronedarone inhibition of IhERG. Homology modeling indicated that the L532 residue within the S4 helix lies closely apposed to the S5 region of an adjacent hERG subunit. Alterations to the S4 domain structure and, potentially, to interactions between adjacent hERG subunits are likely to account for the functional effects of this mutation.
Collapse
Affiliation(s)
- Yi H Zhang
- University of Bristol, University Walk, Bristol BS8 1TD, UK
| | | | | | | | | |
Collapse
|
41
|
Abstract
Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. This brief review addresses issues relevant to the dynamics of the rotors responsible for functional reentry and VF. It also makes an attempt to summarize present-day knowledge of the manner in which the dynamic interplay between inward and outward transmembrane currents and the heterogeneous cardiac structure establish a substrate for the initiation and maintenance of rotors and VF. The fragmentary nature of our current understanding of ionic VF mechanisms does not even allow an approach toward a "Theory of VF". Yet some hope is provided by recently obtained insight into the roles played in VF by some of the sarcolemmal ion channels that control the excitation-recovery process. For example, strong evidence supports the idea that the interplay between the rapid-inward sodium current and the inward-rectifier potassium current controls rotor formation, as well as rotor stability and frequency. Solid evidence also exists for an involvement of L-type calcium current in the control of rotor frequency and in determining VF-to-ventricular tachycardia conversion. Less clear, however, is whether or not time dependent outward currents through voltage-gated potassium channels affect the fibrillatory process. Hopefully, taking advantage of currently available approaches of structural, molecular and cellular biology, together with computational and imaging techniques, will afford us the opportunity to further advance knowledge on VF mechanisms.
Collapse
Affiliation(s)
- Sami F Noujaim
- Department of Pharmacology and Institute for Cardiovascular Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | | | | |
Collapse
|
42
|
Takahara A, Wagatsuma H, Aritomi S, Konda T, Akie Y, Nakamura Y, Sugiyama A. Measurements of cardiac ion channel subunits in the chronic atrioventricular block dog. J Pharmacol Sci 2011; 116:132-5. [PMID: 21512305 DOI: 10.1254/jphs.11019sc] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The chronic atrioventricular block (CAVB) dog has been widely used as an in vivo proarrhythmia model. mRNA levels of K(+) and Ca(2+) channels in the isolated ventricular tissues from normal and CAVB dogs were assayed using a real-time PCR. The mRNA levels of KvLQT1 and MiRP1 were significantly less in the CAVB heart compared with those in the intact heart, whereas no significant difference was detected in the mRNA levels of other K(+)- or Ca(2+)-channel subunits. Adaptation against chronic bradycardia-related pathophysiology may have decreased the mRNA levels of cardiac K(+) channels, which may partly explain the arrhythmogenic property of this model.
Collapse
Affiliation(s)
- Akira Takahara
- Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan.
| | | | | | | | | | | | | |
Collapse
|
43
|
DU C, EL HARCHI A, ZHANG Y, ORCHARD C, HANCOX J. Pharmacological Inhibition of the hERG Potassium Channel Is Modulated by Extracellular But Not Intracellular Acidosis. J Cardiovasc Electrophysiol 2011; 22:1163-70. [DOI: 10.1111/j.1540-8167.2011.02060.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
44
|
Hayashi K, Fujino N, Ino H, Uchiyama K, Sakata K, Konno T, Masuta E, Funada A, Sakamoto Y, Tsubokawa T, Hodatsu A, Yasuda T, Kanaya H, Kim MY, Kupershmidt S, Higashida H, Yamagishi M. A KCR1 variant implicated in susceptibility to the long QT syndrome. J Mol Cell Cardiol 2011; 50:50-7. [DOI: 10.1016/j.yjmcc.2010.10.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 11/25/2022]
|
45
|
Saiz J, Gomis-Tena J, Monserrat M, Ferrero JM, Cardona K, Chorro J. Effects of the Antiarrhythmic Drug Dofetilide on Transmural Dispersion of Repolarization in Ventriculum. A Computer Modeling Study. IEEE Trans Biomed Eng 2011; 58:43-53. [DOI: 10.1109/tbme.2010.2077292] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
46
|
Toyoda F, Ding WG, Zankov DP, Omatsu-Kanbe M, Isono T, Horie M, Matsuura H. Characterization of the Rapidly Activating Delayed Rectifier Potassium Current, I Kr, in HL-1 Mouse Atrial Myocytes. J Membr Biol 2010; 235:73-87. [DOI: 10.1007/s00232-010-9257-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Accepted: 04/29/2010] [Indexed: 10/19/2022]
|
47
|
Abstract
Since the first discovery of Kvbeta-subunits more than 15 years ago, many more ancillary Kv channel subunits were characterized, for example, KChIPs, KCNEs, and BKbeta-subunits. The ancillary subunits are often integral parts of native Kv channels, which, therefore, are mostly multiprotein complexes composed of voltage-sensing and pore-forming Kvalpha-subunits and of ancillary or beta-subunits. Apparently, Kv channels need the ancillary subunits to fulfill their many different cell physiological roles. This is reflected by the large structural diversity observed with ancillary subunit structures. They range from proteins with transmembrane segments and extracellular domains to purely cytoplasmic proteins. Ancillary subunits modulate Kv channel gating but can also have a great impact on channel assembly, on channel trafficking to and from the cellular surface, and on targeting Kv channels to different cellular compartments. The importance of the role of accessory subunits is further emphasized by the number of mutations that are associated in both humans and animals with diseases like hypertension, epilepsy, arrhythmogenesis, periodic paralysis, and hypothyroidism. Interestingly, several ancillary subunits have in vitro enzymatic activity; for example, Kvbeta-subunits are oxidoreductases, or modulate enzymatic activity, i.e., KChIP3 modulates presenilin activity. Thus different modes of beta-subunit association and of functional impact on Kv channels can be delineated, making it difficult to extract common principles underlying Kvalpha- and beta-subunit interactions. We critically review present knowledge on the physiological role of ancillary Kv channel subunits and their effects on Kv channel properties.
Collapse
Affiliation(s)
- Olaf Pongs
- Institut für Neurale Signalverarbeitung, Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg-Eppendorf, Universität Hamburg, Hamburg, Germany.
| | | |
Collapse
|
48
|
Ehrlich JR. Cardiac delayed rectifiers--together as one? A patho-physiologically relevant interaction between IKr and IKs. Heart Rhythm 2010; 7:981-2. [PMID: 20398798 DOI: 10.1016/j.hrthm.2010.04.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Indexed: 01/30/2023]
|
49
|
Abstract
Drug-induced long QT syndrome is a cardiac safety issue that all drugs seeking approval must currently address, in part via in vitro electrophysiological testing of the drug's effects on the function of the human Ether-à-go-go Related Gene (hERG) potassium channel. This regulatory strategy has also been scientifically successful, in that these in vitro assays are cheaper and faster than are many other surrogates for arrhythmogenic risk, including QT prolongation in humans and action potential prolongation in cardiomyocytes. In some ways hERG assays are also more sensitive to the underlying repolarization anomalies that lead to the risk of the Torsades de pointes arrhythmia. In addition, the higher throughput of hERG assays combined with advances in our understanding of the molecular structures underlying this pathophysiology have led to new approaches in the medicinal chemistry of "designing out" hERG liability from lead compounds. While generally effectual, hERG screening produces some false positives: drugs with an apparent liability that are known not to be clinically arrhythmogenic. New technologies continue to be developed to improve hERG screening, while further insights into the molecular pharmacology of hERG and cardiac repolarization are providing avenues to mitigate and make sense of the lack of torsadogenic specificity in extant hERG assays.
Collapse
Affiliation(s)
- Harry J Witchel
- Medical Research Building, Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton, UK.
| |
Collapse
|
50
|
Grunnet M. Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle? Acta Physiol (Oxf) 2010; 198 Suppl 676:1-48. [PMID: 20132149 DOI: 10.1111/j.1748-1716.2009.02072.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.
Collapse
Affiliation(s)
- M Grunnet
- NeuroSearch A/S, Ballerup, and Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Denmark.
| |
Collapse
|