1
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Bassetto CAZ, Costa F, Guardiani C, Bezanilla F, Giacomello A. Noncanonical electromechanical coupling paths in cardiac hERG potassium channel. Nat Commun 2023; 14:1110. [PMID: 36849440 PMCID: PMC9971164 DOI: 10.1038/s41467-023-36730-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 02/15/2023] [Indexed: 03/01/2023] Open
Abstract
Voltage-gated potassium channels are involved in many physiological processes such as nerve impulse transmission, the heartbeat, and muscle contraction. However, for many of them the molecular determinants of the gating mechanism remain elusive. Here, using a combination of theoretical and experimental approaches, we address this problem focusing on the cardiac hERG potassium channel. Network analysis of molecular dynamics trajectories reveals the presence of a kinematic chain of residues that couples the voltage sensor domain to the pore domain and involves the S4/S1 and S1/S5 subunit interfaces. Mutagenesis experiments confirm the role of these residues and interfaces in the activation and inactivation mechanisms. Our findings demonstrate the presence of an electromechanical transduction path crucial for the non-domain-swapped hERG channel gating that resembles the noncanonical path identified in domain-swapped K+ channels.
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Affiliation(s)
- Carlos A Z Bassetto
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Flavio Costa
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
| | - Carlo Guardiani
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, USA.
- Centro Interdisciplinario de Neurociencias, Facultad de Ciencias, Universidad de Valparaiso, Valparaiso, Chile.
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy.
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2
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Shan M, Jiang C, Qin L, Cheng G. A Review of Computational Methods in Predicting hERG Channel Blockers. ChemistrySelect 2022. [DOI: 10.1002/slct.202201221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mengyi Shan
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
| | - Chen Jiang
- QuanMin RenZheng (HangZhou) Technology Co. Ltd. China
| | - Lu‐Ping Qin
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
| | - Gang Cheng
- School of Pharmaceutical Sciences Zhejiang Chinese Medical University Hangzhou 310053 People's Republic of China
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3
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El Harchi A, Butler AS, Zhang Y, Dempsey CE, Hancox JC. The macrolide drug erythromycin does not protect the hERG channel from inhibition by thioridazine and terfenadine. Physiol Rep 2020; 8:e14385. [PMID: 32147975 PMCID: PMC7061092 DOI: 10.14814/phy2.14385] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/07/2020] [Accepted: 02/10/2020] [Indexed: 12/25/2022] Open
Abstract
The macrolide antibiotic erythromycin has been associated with QT interval prolongation and inhibition of the hERG-encoded channels responsible for the rapid delayed rectifier K+ current I(Kr ). It has been suggested that low concentrations of erythromycin may have a protective effect against hERG block and associated drug-induced arrhythmia by reducing the affinity of the pore-binding site for high potency hERG inhibitors. This study aimed to explore further the notion of a potentially protective effect of erythromycin. Whole-cell patch-clamp experiments were performed in which hERG-expressing mammalian (Human Embryonic Kidney; HEK) cells were preincubated with low to moderate concentrations of erythromycin (3 or 30 µM) prior to whole-cell patch clamp recordings of hERG current (IhERG ) at 37°C. In contrast to a previous report, exposure to low concentrations of erythromycin did not reduce pharmacological sensitivity of hERG to the antipsychotic thioridazine and antihistamine terfenadine. The IC50 value for IhERG tail inhibition by terfenadine was decreased by ~32-fold in the presence of 3 µM erythromycin (p < .05 vs. no preincubation). Sensitivity to thioridazine remained unchanged (p > .05 vs. no preincubation). The effects of low concentrations of erythromycin were investigated for a series of pore blocking drugs, and the results obtained were consistent with additive and/or synergistic effects. Experiments with the externally acting blocker BeKm-1 on WT hERG and a pore mutant (F656V) were used to explore the location of the binding site for erythromycin. Our data are inconsistent with the use of erythromycin for the management of drug-induced QT prolongation.
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Affiliation(s)
- Aziza El Harchi
- School of Physiology and Pharmacology and Neuroscience, Biomedical Sciences Building, The University of Bristol, University Walk, Bristol, UK
| | - Andrew S Butler
- School of Physiology and Pharmacology and Neuroscience, Biomedical Sciences Building, The University of Bristol, University Walk, Bristol, UK
| | - Yihong Zhang
- School of Physiology and Pharmacology and Neuroscience, Biomedical Sciences Building, The University of Bristol, University Walk, Bristol, UK
| | - Christopher E Dempsey
- School of Biochemistry, Biomedical Sciences Building, The University of Bristol, University Walk, Bristol, UK
| | - Jules C Hancox
- School of Physiology and Pharmacology and Neuroscience, Biomedical Sciences Building, The University of Bristol, University Walk, Bristol, UK
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4
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Butler A, Helliwell MV, Zhang Y, Hancox JC, Dempsey CE. An Update on the Structure of hERG. Front Pharmacol 2020; 10:1572. [PMID: 32038248 PMCID: PMC6992539 DOI: 10.3389/fphar.2019.01572] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 12/04/2019] [Indexed: 01/22/2023] Open
Abstract
The human voltage-sensitive K+ channel hERG plays a fundamental role in cardiac action potential repolarization, effectively controlling the QT interval of the electrocardiogram. Inherited loss- or gain-of-function mutations in hERG can result in dangerous “long” (LQTS) or “short” QT syndromes (SQTS), respectively, and the anomalous susceptibility of hERG to block by a diverse range of drugs underlies an acquired LQTS. A recent open channel cryo-EM structure of hERG should greatly advance understanding of the molecular basis of hERG channelopathies and drug-induced LQTS. Here we describe an update of recent research that addresses the nature of the particular gated state of hERG captured in the new structure, and the insight afforded by the structure into the molecular basis for high affinity drug block of hERG, the binding of hERG activators and the molecular basis of hERG's peculiar gating properties. Interpretation of the pharmacology of natural SQTS mutants in the context of the structure is a promising approach to understanding the molecular basis of hERG inactivation, and the structure suggests how voltage-dependent changes in the membrane domain may be transmitted to an extracellular “turret” to effect inactivation through aromatic side chain motifs that are conserved throughout the KCNH family of channels.
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Affiliation(s)
- Andrew Butler
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, Bristol, United Kingdom
| | - Matthew V Helliwell
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, Bristol, United Kingdom
| | - Yihong Zhang
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, Medical Sciences Building, Bristol, United Kingdom
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5
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Gunay BC, Yurtsever M, Durdagi S. Elucidation of interaction mechanism of hERG1 potassium channel with scorpion toxins BeKm-1 and BmTx3b. J Mol Graph Model 2019; 96:107504. [PMID: 31901677 DOI: 10.1016/j.jmgm.2019.107504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 11/10/2019] [Accepted: 11/25/2019] [Indexed: 12/20/2022]
Abstract
The human ether-a-go-go related gene 1 (hERG1) K+ channels play crucial role in the heart, different regions of brain, endocrine cells, smooth muscle cells, and numerous tumor cells. It is known that the inherited mutations of hERG1 gene may lead to the disorder of cardiac repolarization (i.e., long QT syndrome (LQTS)), which may result in sudden cardiac death. It is known that K+ ion channels involved in signaling pathways lead to cell proliferation or apoptosis and some specific toxins were investigated for diverse therapeutic applications on targeting the hERG1 K+ channel. Thus, investigation of channel/toxin interactions mechanisms in atomic level is an important topic for the development of toxin-based therapeutics. Thus, in this work, the interaction mechanisms of two toxins named as BeKm-1 and BmTx3b with the closed-state hERG1 channel have been studied by using different molecular modeling techniques including protein-protein docking and molecular dynamics (MD) simulations. The crucial residues of toxins in channel interactions have been elucidated. It is found that R1, K6, K18, R20, K23 and R27 residues in BeKm-1 and F1, K7, K19, K20 and K28 in BmTx3b are the important residues involved in the strong interactions with the closed-state hERG1 K+ channel. The results of this study can be used by medicinal chemists in the designing of diverse therapeutic applications of natural or synthetic peptides targeting the closed state hERG1 K+ channels.
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Affiliation(s)
- Beril Colak Gunay
- Department of Chemistry, Istanbul Technical University, Istanbul, 34469, Turkey; Computational Biology and Molecular Simulations Laboratory, Department of Biophysics, School of Medicine, Bahcesehir University, Istanbul, 34353, Turkey
| | - Mine Yurtsever
- Department of Chemistry, Istanbul Technical University, Istanbul, 34469, Turkey.
| | - Serdar Durdagi
- Computational Biology and Molecular Simulations Laboratory, Department of Biophysics, School of Medicine, Bahcesehir University, Istanbul, 34353, Turkey.
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Helliwell MV, Zhang Y, El Harchi A, Du C, Hancox JC, Dempsey CE. Structural implications of hERG K + channel block by a high-affinity minimally structured blocker. J Biol Chem 2018; 293:7040-7057. [PMID: 29545312 PMCID: PMC5936838 DOI: 10.1074/jbc.ra117.000363] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 02/06/2018] [Indexed: 11/29/2022] Open
Abstract
Cardiac potassium channels encoded by human ether-à-go-go–related gene (hERG) are major targets for structurally diverse drugs associated with acquired long QT syndrome. This study characterized hERG channel inhibition by a minimally structured high-affinity hERG inhibitor, Cavalli-2, composed of three phenyl groups linked by polymethylene spacers around a central amino group, chosen to probe the spatial arrangement of side chain groups in the high-affinity drug-binding site of the hERG pore. hERG current (IhERG) recorded at physiological temperature from HEK293 cells was inhibited with an IC50 of 35.6 nm with time and voltage dependence characteristic of blockade contingent upon channel gating. Potency of Cavalli-2 action was markedly reduced for attenuated inactivation mutants located near (S620T; 54-fold) and remote from (N588K; 15-fold) the channel pore. The S6 Y652A and F656A mutations decreased inhibitory potency 17- and 75-fold, respectively, whereas T623A and S624A at the base of the selectivity filter also decreased potency (16- and 7-fold, respectively). The S5 helix F557L mutation decreased potency 10-fold, and both F557L and Y652A mutations eliminated voltage dependence of inhibition. Computational docking using the recent cryo-EM structure of an open channel hERG construct could only partially recapitulate experimental data, and the high dependence of Cavalli-2 block on Phe-656 is not readily explainable in that structure. A small clockwise rotation of the inner (S6) helix of the hERG pore from its configuration in the cryo-EM structure may be required to optimize Phe-656 side chain orientations compatible with high-affinity block.
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Affiliation(s)
- Matthew V Helliwell
- From the Schools of Biochemistry and.,Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Yihong Zhang
- Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Aziza El Harchi
- Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Chunyun Du
- Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jules C Hancox
- Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
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7
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Leipold E, Ullrich F, Thiele M, Tietze AA, Terlau H, Imhof D, Heinemann SH. Subtype-specific block of voltage-gated K+ channels by μ-conopeptides. Biochem Biophys Res Commun 2017; 482:1135-1140. [DOI: 10.1016/j.bbrc.2016.11.170] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 11/30/2016] [Indexed: 12/19/2022]
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8
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Pearlstein RA, Dickson CJ, Hornak V. Contributions of the membrane dipole potential to the function of voltage-gated cation channels and modulation by small molecule potentiators. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:177-194. [PMID: 27836643 DOI: 10.1016/j.bbamem.2016.11.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 10/28/2016] [Accepted: 11/06/2016] [Indexed: 01/27/2023]
Abstract
The membrane dipole potential (Ψd) constitutes one of three electrical potentials generated by cell membranes. Ψd arises from the unfavorable parallel alignment of phospholipid and water dipoles, and varies in magnitude both longitudinally and laterally across the bilayer according to membrane composition and phospholipid packing density. In this work, we propose that dynamic counter-balancing between Ψd and the transmembrane potential (ΔΨm) governs the conformational state transitions of voltage-gated ion channels. Ψd consists of 1) static outer, and dynamic inner leaflet components (Ψd(extra) and Ψd(intra), respectively); and 2) a transmembrane component (ΔΨd(inner-outer)), ariing from differences in intra- and extracellular leaflet composition. Ψd(intra), which transitions between high and low energy states (Ψd(intra, high) and Ψd(intra, low)) as a function of channel conformation, is transduced by the pore domain. ΔΨd(inner-outer) is transduced by the voltage-sensing (VS) domain in summation with ΔΨm. Potentiation of voltage-gated ion channels is of interest for the treatment of cardiac, neuronal, and other disorders arising from inherited/acquired ion channel dysfunction. Potentiators are widely believed to alter the rates and voltage-dependencies of channel gating transitions by binding to pockets in the membrane-facing and other regions of ion channel targets. Here, we propose that potentiators alter Ψd(intra) and/or Ψd(extra), thereby increasing or decreasing the energy barriers governing channel gating transitions. We used quantum mechanical and molecular dynamics (MD) simulations to predict the overall Ψd-modulating effects of a series of published positive hERG potentiators partitioned into model DOPC bilayers. Our findings suggest a strong correlation between the magnitude of Ψd-lowering and positive hERG potentiation across the series.
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Affiliation(s)
- Robert A Pearlstein
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA.
| | - Callum J Dickson
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA
| | - Viktor Hornak
- Global Discovery Chemistry, Computer-Aided Drug Discovery, Novartis Institutes for BioMedical Research, 181 Mass Ave., Cambridge, MA 02139, USA
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9
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Ng CA, Gravel AE, Perry MD, Arnold AA, Marcotte I, Vandenberg JI. Tyrosine Residues from the S4-S5 Linker of Kv11.1 Channels Are Critical for Slow Deactivation. J Biol Chem 2016; 291:17293-302. [PMID: 27317659 DOI: 10.1074/jbc.m116.729392] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 01/24/2023] Open
Abstract
Slow deactivation of Kv11.1 channels is critical for its function in the heart. The S4-S5 linker, which joins the voltage sensor and pore domains, plays a critical role in this slow deactivation gating. Here, we use NMR spectroscopy to identify the membrane-bound surface of the S4S5 linker, and we show that two highly conserved tyrosine residues within the KCNH subfamily of channels are membrane-associated. Site-directed mutagenesis and electrophysiological analysis indicates that Tyr-542 interacts with both the pore domain and voltage sensor residues to stabilize activated conformations of the channel, whereas Tyr-545 contributes to the slow kinetics of deactivation by primarily stabilizing the transition state between the activated and closed states. Thus, the two tyrosine residues in the Kv11.1 S4S5 linker play critical but distinct roles in the slow deactivation phenotype, which is a hallmark of Kv11.1 channels.
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Affiliation(s)
- Chai-Ann Ng
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst and the St. Vincent's Clinical School, University of New South Wales, Victoria Street, Darlinghurst, New South Wales 2010, Australia and
| | - Andrée E Gravel
- the Department of Chemistry, Université du Québec à Montréal, Montreal H3C 3P8, Québec, Canada
| | - Matthew D Perry
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst and the St. Vincent's Clinical School, University of New South Wales, Victoria Street, Darlinghurst, New South Wales 2010, Australia and
| | - Alexandre A Arnold
- the Department of Chemistry, Université du Québec à Montréal, Montreal H3C 3P8, Québec, Canada
| | - Isabelle Marcotte
- the Department of Chemistry, Université du Québec à Montréal, Montreal H3C 3P8, Québec, Canada
| | - Jamie I Vandenberg
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst and the St. Vincent's Clinical School, University of New South Wales, Victoria Street, Darlinghurst, New South Wales 2010, Australia and
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10
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Perry MD, Ng CA, Phan K, David E, Steer K, Hunter MJ, Mann SA, Imtiaz M, Hill AP, Ke Y, Vandenberg JI. Rescue of protein expression defects may not be enough to abolish the pro-arrhythmic phenotype of long QT type 2 mutations. J Physiol 2016; 594:4031-49. [PMID: 26958806 DOI: 10.1113/jp271805] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 02/25/2016] [Indexed: 01/28/2023] Open
Abstract
KEY POINTS Most missense long QT syndrome type 2 (LQTS2) mutations result in Kv11.1 channels that show reduced levels of membrane expression. Pharmacological chaperones that rescue mutant channel expression could have therapeutic potential to reduce the risk of LQTS2-associated arrhythmias and sudden cardiac death, but only if the mutant Kv11.1 channels function normally (i.e. like WT channels) after membrane expression is restored. Fewer than half of mutant channels exhibit relatively normal function after rescue by low temperature. The remaining rescued missense mutant Kv11.1 channels have perturbed gating and/or ion selectivity characteristics. Co-expression of WT subunits with gating defective missense mutations ameliorates but does not eliminate the functional abnormalities observed for most mutant channels. For patients with mutations that affect gating in addition to expression, it may be necessary to use a combination therapy to restore both normal function and normal expression of the channel protein. ABSTRACT In the heart, Kv11.1 channels pass the rapid delayed rectifier current (IKr ) which plays critical roles in repolarization of the cardiac action potential and in the suppression of arrhythmias caused by premature stimuli. Over 500 inherited mutations in Kv11.1 are known to cause long QT syndrome type 2 (LQTS2), a cardiac electrical disorder associated with an increased risk of life threatening arrhythmias. Most missense mutations in Kv11.1 reduce the amount of channel protein expressed at the membrane and, as a consequence, there has been considerable interest in developing pharmacological agents to rescue the expression of these channels. However, pharmacological chaperones will only have clinical utility if the mutant Kv11.1 channels function normally after membrane expression is restored. The aim of this study was to characterize the gating phenotype for a subset of LQTS2 mutations to assess what proportion of mutations may be suitable for rescue. As an initial screen we used reduced temperature to rescue expression defects of mutant channels expressed in Xenopus laevis oocytes. Over half (∼56%) of Kv11.1 mutants exhibited functional gating defects that either dramatically reduced the amount of current contributing to cardiac action potential repolarization and/or reduced the amount of protective current elicited in response to premature depolarizations. Our data demonstrate that if pharmacological rescue of protein expression defects is going to have clinical utility in the treatment of LQTS2 then it will be important to assess the gating phenotype of LQTS2 mutations before attempting rescue.
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Affiliation(s)
- Matthew D Perry
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
| | - Chai Ann Ng
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
| | - Kevin Phan
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
| | - Erikka David
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia
| | - Kieran Steer
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,Faculty of Science, McGill University, Montreal, Quebec, Canada
| | - Mark J Hunter
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia
| | - Stefan A Mann
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
| | - Mohammad Imtiaz
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
| | - Ying Ke
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Molecular Cardiology and Biophysics Division, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, NSW, 2052, Australia
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11
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Molecular Modeling and Its Applications in Protein Engineering. Synth Biol (Oxf) 2016. [DOI: 10.1007/978-3-319-22708-5_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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12
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Kanters JK, Skibsbye L, Hedley PL, Dembic M, Liang B, Hagen CM, Eschen O, Grunnet M, Christiansen M, Jespersen T. Combined gating and trafficking defect in Kv11.1 manifests as a malignant long QT syndrome phenotype in a large Danish p.F29L founder family. Scandinavian Journal of Clinical and Laboratory Investigation 2015; 75:699-709. [PMID: 26403377 DOI: 10.3109/00365513.2015.1091090] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Congenital long QT syndrome (LQTS) is a hereditary cardiac channelopathy characterized by delayed ventricular repolarization, syncope, torsades de pointes and sudden cardiac death. Thirty-three members of five apparently 'unrelated' Danish families carry the KCNH2:c.87C> A; p.F29L founder mutation. METHODS AND RESULTS Linkage disequilibrium mapping with microsatellites around KCNH2 enabled us to estimate the age of the founder mutation to be approximately 22 generations, corresponding to around 550 years. Neighbouring-Joining analysis disclosed one early and three later nodes. The median QTc time of the carriers was 490 ms (range: 415-589 ms) and no difference was seen between the different branches of the family. The mutation is malignant with a penetrance of 73%. Ten F29L carriers received implantable defibrillators (ICDs) (median age at implant 20 years), and of those four individuals experienced eight appropriate shocks. Patch-clamp analysis in HEK 293 cells, performed at 34°C disclosed a loss-of-function phenotype with fast deactivation, reduced steady-state inactivation current density and a positive voltage shift in inactivation. Western blotting of HEK 293 cells transfected with KCNH2:WT and KCNH2:c.87C> A revealed a reduced fraction of fully glycosylated hERG:p.F29L suggesting that this mutation results in defective trafficking. CONCLUSION The altered channel gating kinetics in combination with defective trafficking of mutated channels is expected to result in reduced repolarizing current density and, thus, a LQTS phenotype.
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Affiliation(s)
- Jørgen K Kanters
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark.,b Department of Cardiology , Herlev and Gentofte Hospitals , Denmark
| | - Lasse Skibsbye
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark
| | - Paula L Hedley
- c Department for Congenital Disorders , Statens Serum Institut , Denmark.,d MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University , Aarhus , Denmark
| | - Maja Dembic
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark.,c Department for Congenital Disorders , Statens Serum Institut , Denmark
| | - Bo Liang
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark
| | - Christian M Hagen
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark.,c Department for Congenital Disorders , Statens Serum Institut , Denmark
| | - Ole Eschen
- e Department of Cardiology , Center for Cardiovascular Research, Aalborg Sygehus, Aarhus University Hospital , Aarhus , Denmark
| | - Morten Grunnet
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark
| | - Michael Christiansen
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark.,c Department for Congenital Disorders , Statens Serum Institut , Denmark
| | - Thomas Jespersen
- a Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences , University of Copenhagen , Denmark
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13
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Computational investigations of hERG channel blockers: New insights and current predictive models. Adv Drug Deliv Rev 2015; 86:72-82. [PMID: 25770776 DOI: 10.1016/j.addr.2015.03.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/13/2015] [Accepted: 03/04/2015] [Indexed: 01/08/2023]
Abstract
Identification of potential human Ether-a-go-go Related-Gene (hERG) potassium channel blockers is an essential part of the drug development and drug safety process in pharmaceutical industries or academic drug discovery centers, as they may lead to drug-induced QT prolongation, arrhythmia and Torsade de Pointes. Recent reports also suggest starting to address such issues at the hit selection stage. In order to prioritize molecules during the early drug discovery phase and to reduce the risk of drug attrition due to cardiotoxicity during pre-clinical and clinical stages, computational approaches have been developed to predict the potential hERG blockage of new drug candidates. In this review, we will describe the current in silico methods developed and applied to predict and to understand the mechanism of actions of hERG blockers, including ligand-based and structure-based approaches. We then discuss ongoing research on other ion channels and hERG polymorphism susceptible to be involved in LQTS and how systemic approaches can help in the drug safety decision.
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14
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Schmidtke P, Ciantar M, Theret I, Ducrot P. Dynamics of hERG Closure Allow Novel Insights into hERG Blocking by Small Molecules. J Chem Inf Model 2014; 54:2320-33. [DOI: 10.1021/ci5001373] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Peter Schmidtke
- Institut de Recherches Servier, 125 Chemin de Ronde, 87290 Croissy-sur-Seine, France
- Discngine, 33 Rue du Faubourg Saint-Antoine, 75011 Paris, France
| | - Marine Ciantar
- Institut de Recherches Servier, 125 Chemin de Ronde, 87290 Croissy-sur-Seine, France
| | - Isabelle Theret
- Institut de Recherches Servier, 125 Chemin de Ronde, 87290 Croissy-sur-Seine, France
| | - Pierre Ducrot
- Institut de Recherches Servier, 125 Chemin de Ronde, 87290 Croissy-sur-Seine, France
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15
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Insight into the molecular interaction between the cyclic nucleotide-binding homology domain and the eag domain of the hERG channel. FEBS Lett 2014; 588:2782-8. [PMID: 24931372 DOI: 10.1016/j.febslet.2014.05.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 05/14/2014] [Accepted: 05/27/2014] [Indexed: 12/18/2022]
Abstract
The gating of the hERG channel is regulated by its eag domain through molecular interaction with either the cyclic nucleotide-binding homology domain (CNBHD) or the linker between transmembrane segments 4 and 5. Our NMR study on the purified CNBHD demonstrated that it contains nine β-strands and does not bind cAMP. We show that the eag domain binds to the CBND through an interface containing several disease-associated mutations. The N-terminal cap domain and R56 in the eag domain are important for the interaction with the CNBHD. Residues from the CNBHD that were affected by the interaction with the eag domain were also identified. A R56Q mutation does not cause major structural changes in the eag domain and showed reduced interaction with the CNBHD.
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16
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Perry MD, Wong S, Ng CA, Vandenberg JI. Hydrophobic interactions between the voltage sensor and pore mediate inactivation in Kv11.1 channels. ACTA ACUST UNITED AC 2014; 142:275-88. [PMID: 23980196 PMCID: PMC3753607 DOI: 10.1085/jgp.201310975] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Kv11.1 channels are critical for the maintenance of a normal heart rhythm. The flow of potassium ions through these channels is controlled by two voltage-regulated gates, termed "activation" and "inactivation," located at opposite ends of the pore. Crucially in Kv11.1 channels, inactivation gating occurs much more rapidly, and over a distinct range of voltages, compared with activation gating. Although it is clear that the fourth transmembrane segments (S4), within each subunit of the tetrameric channel, are important for controlling the opening and closing of the activation gate, their role during inactivation gating is much less clear. Here, we use rate equilibrium free energy relationship (REFER) analysis to probe the contribution of the S4 "voltage-sensor" helix during inactivation of Kv11.1 channels. Contrary to the important role that charged residues play during activation gating, it is the hydrophobic residues (Leu529, Leu530, Leu532, and Val535) that are the key molecular determinants of inactivation gating. Within the context of an interconnected multi-domain model of Kv11.1 inactivation gating, our REFER analysis indicates that the S4 helix and the S4-S5 linker undergo a conformational rearrangement shortly after that of the S5 helix and S5P linker, but before the S6 helix. Combining REFER analysis with double mutant cycle analysis, we provide evidence for a hydrophobic interaction between residues on the S4 and S5 helices. Based on a Kv11.1 channel homology model, we propose that this hydrophobic interaction forms the basis of an intersubunit coupling between the voltage sensor and pore domain that is an important mediator of inactivation gating.
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Affiliation(s)
- Matthew D Perry
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia
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17
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Ng CA, Ke Y, Perry MD, Tan PS, Hill AP, Vandenberg JI. C-terminal β9-strand of the cyclic nucleotide-binding homology domain stabilizes activated states of Kv11.1 channels. PLoS One 2013; 8:e77032. [PMID: 24204727 PMCID: PMC3808384 DOI: 10.1371/journal.pone.0077032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 09/06/2013] [Indexed: 12/25/2022] Open
Abstract
Kv11.1 potassium channels are important for regulation of the normal rhythm of the heartbeat. Reduced activity of Kv11.1 channels causes long QT syndrome type 2, a disorder that increases the risk of cardiac arrhythmias and sudden cardiac arrest. Kv11.1 channels are members of the KCNH subfamily of voltage-gated K+ channels. However, they also share many similarities with the cyclic nucleotide gated ion channel family, including having a cyclic nucleotide-binding homology (cNBH) domain. Kv11.1 channels, however, are not directly regulated by cyclic nucleotides. Recently, crystal structures of the cNBH domain from mEAG and zELK channels, both members of the KCNH family of voltage-gated potassium channels, revealed that a C-terminal β9-strand in the cNBH domain occupied the putative cyclic nucleotide-binding site thereby precluding binding of cyclic nucleotides. Here we show that mutations to residues in the β9-strand affect the stability of the open state relative to the closed state of Kv11.1 channels. We also show that disrupting the structure of the β9-strand reduces the stability of the inactivated state relative to the open state. Clinical mutations located in this β9-strand result in reduced trafficking efficiency, which suggests that binding of the C-terminal β9-strand to the putative cyclic nucleotide-binding pocket is also important for assembly and trafficking of Kv11.1 channels.
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Affiliation(s)
- Chai Ann Ng
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Ying Ke
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Matthew D. Perry
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Peter S. Tan
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Adam P. Hill
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Jamie I. Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
- * E-mail:
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18
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Wan X, Lu Y, Chen X, Xiong J, Zhou Y, Li P, Xia B, Li M, Zhu MX, Gao Z. Bimodal voltage dependence of TRPA1: mutations of a key pore helix residue reveal strong intrinsic voltage-dependent inactivation. Pflugers Arch 2013; 466:1273-87. [PMID: 24092046 PMCID: PMC4062818 DOI: 10.1007/s00424-013-1345-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 12/03/2022]
Abstract
Transient receptor potential A1 (TRPA1) is implicated in somatosensory processing and pathological pain sensation. Although not strictly voltage-gated, ionic currents of TRPA1 typically rectify outwardly, indicating channel activation at depolarized membrane potentials. However, some reports also showed TRPA1 inactivation at high positive potentials, implicating voltage-dependent inactivation. Here we report a conserved leucine residue, L906, in the putative pore helix, which strongly impacts the voltage dependency of TRPA1. Mutation of the leucine to cysteine (L906C) converted the channel from outward to inward rectification independent of divalent cations and irrespective to stimulation by allyl isothiocyanate. The mutant, but not the wild-type channel, displayed exclusively voltage-dependent inactivation at positive potentials. The L906C mutation also exhibited reduced sensitivity to inhibition by TRPA1 blockers, HC030031 and ruthenium red. Further mutagenesis of the leucine to all natural amino acids individually revealed that most substitutions at L906 (15/19) resulted in inward rectification, with exceptions of three amino acids that dramatically reduced channel activity and one, methionine, which mimicked the wild-type channel. Our data are plausibly explained by a bimodal gating model involving both voltage-dependent activation and inactivation of TRPA1. We propose that the key pore helix residue, L906, plays an essential role in responding to the voltage-dependent gating.
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Affiliation(s)
- Xia Wan
- Department of Clinical Pharmacology, the First Affiliated Hospital, Chongqing Medical University, Chongqing, China
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19
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Colenso CK, Sessions RB, Zhang YH, Hancox JC, Dempsey CE. Interactions between voltage sensor and pore domains in a hERG K+ channel model from molecular simulations and the effects of a voltage sensor mutation. J Chem Inf Model 2013; 53:1358-70. [PMID: 23672495 DOI: 10.1021/ci4000739] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The hERG K(+) channel is important for establishing normal electrical activity in the human heart. The channel's unique gating response to membrane potential changes indicates specific interactions between voltage sensor and pore domains that are poorly understood. In the absence of a crystal structure we constructed a homology model of the full hERG membrane domain and performed 0.5 μs molecular dynamics (MD) simulations in a hydrated membrane. The simulations identify potential interactions involving residues at the extracellular surface of S1 in the voltage sensor and at the N-terminal end of the pore helix in the hERG model. In addition, a diffuse interface involving hydrophobic residues on S4 (voltage sensor) and pore domain S5 of an adjacent subunit was stable during 0.5 μs of simulation. To assess the ability of the model to give insight into the effects of channel mutation we simulated a hERG mutant that contains a Leu to Pro substitution in the voltage sensor S4 helical segment (hERG L532P). Consistent with the retention of gated K(+) conductance, the L532P mutation was accommodated in the S4 helix with little disruption of helical structure. The mutation reduced the extent of interaction across the S4-S5 interface, suggesting a structural basis for the greatly enhanced deactivation rate in hERG L532P. The study indicates that pairwise comparison of wild-type and mutated channel models is a useful approach to interpreting functional data where uncertainty in model structures exist.
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Affiliation(s)
- Charlotte K Colenso
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
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20
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Perry MD, Ng CA, Vandenberg JI. Pore helices play a dynamic role as integrators of domain motion during Kv11.1 channel inactivation gating. J Biol Chem 2013; 288:11482-91. [PMID: 23471968 DOI: 10.1074/jbc.m113.461442] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteins that form ion-selective pores in the membrane of cells are integral to many rapid signaling processes, including regulating the rhythm of the heartbeat. In potassium channels, the selectivity filter is critical for both endowing an exquisite selectivity for potassium ions, as well as for controlling the flow of ions through the pore. Subtle rearrangements in the complex hydrogen-bond network that link the selectivity filter to the surrounding pore helices differentiate conducting (open) from nonconducting (inactivated) conformations of the channel. Recent studies suggest that beyond the selectivity filter, inactivation involves widespread rearrangements of the channel protein. Here, we use rate equilibrium free energy relationship analysis to probe the structural changes that occur during selectivity filter gating in Kv11.1 channels, at near atomic resolution. We show that the pore helix plays a crucial dynamic role as a bidirectional interface during selectivity filter gating. We also define the molecular bases of the energetic coupling between the pore helix and outer helix of the pore domain that occurs early in the transition from open to inactivated states, as well as the coupling between the pore helix and inner helix late in the transition. Our data demonstrate that the pore helices are more than just static structural elements supporting the integrity of the selectivity filter; instead they play a crucial dynamic role during selectivity filter gating.
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Affiliation(s)
- Matthew D Perry
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
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21
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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.
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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
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22
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Ng CA, Torres AM, Pagès G, Kuchel PW, Vandenberg JI. Insights into hERG K+ channel structure and function from NMR studies. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:71-9. [DOI: 10.1007/s00249-012-0808-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 03/07/2012] [Accepted: 03/13/2012] [Indexed: 01/09/2023]
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23
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Ng CA, Perry MD, Tan PS, Hill AP, Kuchel PW, Vandenberg JI. The S4-S5 linker acts as a signal integrator for HERG K+ channel activation and deactivation gating. PLoS One 2012; 7:e31640. [PMID: 22359612 PMCID: PMC3280985 DOI: 10.1371/journal.pone.0031640] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 01/10/2012] [Indexed: 01/07/2023] Open
Abstract
Human ether-à-go-go-related gene (hERG) K(+) channels have unusual gating kinetics. Characterised by slow activation/deactivation but rapid inactivation/recovery from inactivation, the unique gating kinetics underlie the central role hERG channels play in cardiac repolarisation. The slow activation and deactivation kinetics are regulated in part by the S4-S5 linker, which couples movement of the voltage sensor domain to opening of the activation gate at the distal end of the inner helix of the pore domain. It has also been suggested that cytosolic domains may interact with the S4-S5 linker to regulate activation and deactivation kinetics. Here, we show that the solution structure of a peptide corresponding to the S4-S5 linker of hERG contains an amphipathic helix. The effects of mutations at the majority of residues in the S4-S5 linker of hERG were consistent with the previously identified role in coupling voltage sensor movement to the activation gate. However, mutations to Ser543, Tyr545, Gly546 and Ala548 had more complex phenotypes indicating that these residues are involved in additional interactions. We propose a model in which the S4-S5 linker, in addition to coupling VSD movement to the activation gate, also contributes to interactions that stabilise the closed state and a separate set of interactions that stabilise the open state. The S4-S5 linker therefore acts as a signal integrator and plays a crucial role in the slow deactivation kinetics of the channel.
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Affiliation(s)
- Chai Ann Ng
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Molecular Biosciences, University of Sydney, Sydney, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Matthew D. Perry
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Peter S. Tan
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Adam P. Hill
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
| | - Philip W. Kuchel
- School of Molecular Biosciences, University of Sydney, Sydney, New South Wales, Australia
- Mechanistic Systems-biology NMR Group, Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore, Singapore
| | - Jamie I. Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Molecular Biosciences, University of Sydney, Sydney, New South Wales, Australia
- St Vincent's Clinical School, University of New South Wales, New South Wales, Australia
- * E-mail:
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24
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Ferrer T, Cordero-Morales JF, Arias M, Ficker E, Medovoy D, Perozo E, Tristani-Firouzi M. Molecular coupling in the human ether-a-go-go-related gene-1 (hERG1) K+ channel inactivation pathway. J Biol Chem 2011; 286:39091-9. [PMID: 21908602 PMCID: PMC3234734 DOI: 10.1074/jbc.m111.292060] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Revised: 09/05/2011] [Indexed: 01/30/2023] Open
Abstract
Emerging evidence suggests that K(+) channel inactivation involves coupling between residues in adjacent regions of the channel. Human ether-a-go-go-related gene-1 (hERG1) K(+) channels undergo a fast inactivation gating process that is crucial for maintaining electrical stability in the heart. The molecular mechanisms that drive inactivation in hERG1 channels are unknown. Using alanine scanning mutagenesis, we show that a pore helix residue (Thr-618) that points toward the S5 segment is critical for normal inactivation gating. Amino acid substitutions at position 618 modulate the free energy of inactivation gating, causing enhanced or reduced inactivation. Mutation of an S5 residue that is predicted to be adjacent to Thr-618 (W568L) abolishes inactivation and alters ion selectivity. The introduction of the Thr-618-equivalent residue in Kv1.5 enhances inactivation. Molecular dynamic simulations of the Kv1.2 tetramer reveal van der Waals coupling between hERG1 618- and 568-equivalent residues and a significant increase in interaction energies when threonine is introduced at the 618-equivalent position. We propose that coupling between the S5 segment and pore helix may participate in the inactivation process in hERG1 channels.
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Affiliation(s)
- Tania Ferrer
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112
| | | | - Marcelo Arias
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112
| | - Eckhard Ficker
- the Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio 44109
| | - David Medovoy
- the Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, and
| | - Eduardo Perozo
- the Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637, and
| | - Martin Tristani-Firouzi
- From the Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112
- the Division of Pediatric Cardiology, University of Utah, Salt Lake City, Utah 84113
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25
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Gayen S, Li Q, Kang C. The solution structure of the S4-S5 linker of the hERG potassium channel. J Pept Sci 2011; 18:140-5. [DOI: 10.1002/psc.1427] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 09/15/2011] [Accepted: 09/22/2011] [Indexed: 11/09/2022]
Affiliation(s)
- Shovanlal Gayen
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); Singapore 138669 Singapore
| | - Qingxin Li
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); Singapore 138669 Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre; Agency for Science, Technology and Research (A*STAR); Singapore 138669 Singapore
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26
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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.
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Affiliation(s)
- Yi H Zhang
- University of Bristol, University Walk, Bristol BS8 1TD, UK
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27
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Boukharta L, Keränen H, Stary-Weinzinger A, Wallin G, de Groot BL, Åqvist J. Computer Simulations of Structure–Activity Relationships for hERG Channel Blockers. Biochemistry 2011; 50:6146-56. [DOI: 10.1021/bi200173n] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lars Boukharta
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Henrik Keränen
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Göran Wallin
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Bert L. de Groot
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Johan Åqvist
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
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28
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de la Peña P, Alonso-Ron C, Machín A, Fernández-Trillo J, Carretero L, Domínguez P, Barros F. Demonstration of physical proximity between the N terminus and the S4-S5 linker of the human ether-a-go-go-related gene (hERG) potassium channel. J Biol Chem 2011; 286:19065-75. [PMID: 21474444 DOI: 10.1074/jbc.m111.238899] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Potassium channels encoded by the human ether-à-go-go-related gene (hERG) contribute to cardiac repolarization as a result of their characteristic gating properties. The hERG channel N terminus acts as a crucial determinant in gating. It is also known that the S4-S5 linker couples the voltage-sensing machinery to the channel gate. Moreover, this linker has been repeatedly proposed as an interaction site for the distal portion of the N terminus controlling channel gating, but direct evidence for such an interaction is still lacking. In this study, we used disulfide bond formation between pairs of engineered cysteines to demonstrate the close proximity between the beginning of the N terminus and the S4-S5 linker. Currents from channels with introduced cysteines were rapidly and strongly attenuated by an oxidizing agent, this effect being maximal for cysteine pairs located around amino acids 3 and 542 of the hERG sequence. The state-dependent modification of the double-mutant channels, but not the single-cysteine mutants, and the ability to readily reverse modification with the reducing agent dithiothreitol indicate that a disulfide bond is formed under oxidizing conditions, locking the channels in a non-conducting state. We conclude that physical interactions between the N-terminal-most segment of the N terminus and the S4-S5 linker constitute an essential component of the hERG gating machinery, thus providing a molecular basis for previous data and indicating an important contribution of these cytoplasmic domains in controlling its unusual gating and hence determining its physiological role in setting the electrical behavior of cardiac and other cell types.
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Affiliation(s)
- Pilar de la Peña
- Department of Biochemistry and Molecular Biology, University of Oviedo, 33006 Oviedo, Spain
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Mapping the sequence of conformational changes underlying selectivity filter gating in the K(v)11.1 potassium channel. Nat Struct Mol Biol 2010; 18:35-41. [PMID: 21170050 DOI: 10.1038/nsmb.1966] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2010] [Accepted: 10/18/2010] [Indexed: 11/08/2022]
Abstract
The potassium channel selectivity filter both discriminates between K(+) and sodium ions and contributes to gating of ion flow. Static structures of conducting (open) and nonconducting (inactivated) conformations of this filter are known; however, the sequence of protein rearrangements that connect these two states is not. We show that closure of the selectivity filter gate in the human K(v)11.1 K(+) channel (also known as hERG, for ether-a-go-go-related gene), a key regulator of the rhythm of the heartbeat, is initiated by K(+) exit, followed in sequence by conformational rearrangements of the pore domain outer helix, extracellular turret region, voltage sensor domain, intracellular domains and pore domain inner helix. In contrast to the simple wave-like sequence of events proposed for opening of ligand-gated ion channels, a complex spatial and temporal sequence of widespread domain motions connect the open and inactivated states of the K(v)11.1 K(+) channel.
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Functional effects of a missense mutation in HERG associated with type 2 long QT syndrome. Heart Rhythm 2010; 8:463-70. [PMID: 21109023 DOI: 10.1016/j.hrthm.2010.11.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 11/11/2010] [Indexed: 12/13/2022]
Abstract
BACKGROUND Long QT syndrome (LQTS) is characterized by a prolonged QT interval that can lead to severe ventricular arrhythmias (torsades de pointes) and sudden death. Congenital LQTS type 2 (LQT2) is due to loss-of-function mutations in the KCNH2 gene encoding Kv11.1 channels responsible for the rapid component of the delayed rectifier current. OBJECTIVE The purpose of this study was to determine the functional properties of the LQT2-associated mutation p.E637G found in a Spanish family. METHODS Wild-type (WT) and p.E637G Kv11.1 channels were transiently transfected in Chinese hamster ovary cells, and currents were recorded using the patch-clamp technique. RESULTS The p.E637G channels lost inward rectification and K(+) selectivity, generating small but measurable slowly activating, noninactivating currents. These important alterations were corrected neither by cotransfection with WT channels nor by incubation at low temperatures or with pharmacological chaperones. As a consequence of its effects on channel gating, the mutation significantly reduced the outward repolarizing current during the action potential (AP), resulting in a marked lengthening of the duration of a simulated human ventricular AP. CONCLUSION We have identified and characterized an LQT2-associated mutation that through removal of C-type inactivation and reduction of K(+) selectivity causes the QT prolongation observed in the patients carrying the mutation. Moreover, the results obtained demonstrate the importance of the glutamic acid at position 637 for the inactivation process and K(+) selectivity of Kv11.1 channels.
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Subbotina J, Yarov-Yarovoy V, Lees-Miller J, Durdagi S, Guo J, Duff HJ, Noskov SY. Structural refinement of the hERG1 pore and voltage-sensing domains with ROSETTA-membrane and molecular dynamics simulations. Proteins 2010; 78:2922-34. [PMID: 20740484 PMCID: PMC2939218 DOI: 10.1002/prot.22815] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The hERG1 gene (Kv11.1) encodes a voltage-gated potassium channel. Mutations in this gene lead to one form of the Long QT Syndrome (LQTS) in humans. Promiscuous binding of drugs to hERG1 is known to alter the structure/function of the channel leading to an acquired form of the LQTS. Expectably, creation and validation of reliable 3D model of the channel have been a key target in molecular cardiology and pharmacology for the last decade. Although many models were built, they all were limited to pore domain. In this work, a full model of the hERG1 channel is developed which includes all transmembrane segments. We tested a template-driven de-novo design with ROSETTA-membrane modeling using side-chain placements optimized by subsequent molecular dynamics (MD) simulations. Although backbone templates for the homology modeled parts of the pore and voltage sensors were based on the available structures of KvAP, Kv1.2 and Kv1.2-Kv2.1 chimera channels, the missing parts are modeled de-novo. The impact of several alignments on the structure of the S4 helix in the voltage-sensing domain was also tested. Herein, final models are evaluated for consistency to the reported structural elements discovered mainly on the basis of mutagenesis and electrophysiology. These structural elements include salt bridges and close contacts in the voltage-sensor domain; and the topology of the extracellular S5-pore linker compared with that established by toxin foot-printing and nuclear magnetic resonance studies. Implications of the refined hERG1 model to binding of blockers and channels activators (potent new ligands for channel activations) are discussed.
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Affiliation(s)
- Julia Subbotina
- Institute for Biocomplexity and Informatics, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | | | - James Lees-Miller
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Serdar Durdagi
- Institute for Biocomplexity and Informatics, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Jiqing Guo
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Henry J. Duff
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sergei Yu. Noskov
- Institute for Biocomplexity and Informatics, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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Trigger-specific risk factors and response to therapy in long QT syndrome type 2. Heart Rhythm 2010; 7:1797-805. [PMID: 20850565 DOI: 10.1016/j.hrthm.2010.09.011] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Accepted: 09/10/2010] [Indexed: 11/22/2022]
Abstract
BACKGROUND Cardiac events in patients with long QT syndrome type 2 (LQT2) are predominately associated with sudden arousal. However, exercise-induced events also occur in this population. OBJECTIVE The purpose of this study was to test the hypothesis that risk factors show a trigger-specific association with cardiac events in LQT2 patients. METHODS The study population consisted of 634 genetically confirmed LQT2 patients from the U.S. portion of the International LQTS Registry. Multivariate Cox proportional hazards regression analysis was used to determine the independent contribution of clinical and genetic risk factors to the first occurrence of trigger-specific cardiac events, categorized as arousal, exercise-induced, and nonarousal/nonexercise, from birth through age 40 years. RESULTS Study patients experienced 204 cardiac events during follow-up, of which 44% were associated with arousal triggers, 13% with exercise activity, and 43% with nonexercise/nonarousal triggers. Risk factors for arousal-triggered cardiac events included gender (female:male > 13 years: hazard ratio [HR] 9.10, P < .001) and the presence of pore-loop mutations (HR 2.19, P = .009). In contrast, non-pore-loop transmembrane mutations were the predominant risk factor for exercise-triggered events (HR 6.84, P < .001), whereas gender was not a significant risk factor for this endpoint. Nonexercise/nonarousal events were associated with heterogeneous causes. Risk factors for this endpoint included gender, mutation location and type, and prolonged QTc (≥ 500 m) Beta-blocker therapy was associated with a pronounced reduction in the risk for exercise-triggered events (HR 0.29, P < .01) but had a nonsignificant effect on the risk for arousal and nonexercise/nonarousal events. CONCLUSION The study findings suggest that management of patients with the LQT2 genotype should use a trigger-specific approach to risk assessment and medical therapy.
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Chartrand É, Arnold AA, Gravel A, Jenna S, Marcotte I. Potential role of the membrane in hERG channel functioning and drug-induced long QT syndrome. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1651-62. [DOI: 10.1016/j.bbamem.2010.05.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 04/21/2010] [Accepted: 05/17/2010] [Indexed: 11/16/2022]
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Perry M, Sanguinetti M, Mitcheson J. Revealing the structural basis of action of hERG potassium channel activators and blockers. J Physiol 2010; 588:3157-67. [PMID: 20643767 DOI: 10.1113/jphysiol.2010.194670] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Human ether-á-go-go related gene (hERG) potassium (K(+)) channels play a critical role in cardiac action potential repolarization. This is due, in large part, to the unique gating properties of these channels, which are characterized by relatively slow activation and an unusually fast and voltage-dependent inactivation. A large number of structurally diverse compounds bind to hERG and carry an unacceptably high risk of causing arrhythmias. On the other hand, drugs that increase hERG current may, at least in principle, prove useful for treatment of long QT syndrome. A few blockers have been shown to increase hERG current at potentials close to the threshold for channel activation--a process referred to as facilitation. More recently, a novel group of hERG channel activators have been identified that slow deactivation and/or attenuate inactivation. Structural determinants for the action of two different types of activators have been identified. These compounds bind at sites that are distinct from each other and also separate from the binding site of high affinity blockers. They reveal not only novel ways of chemically manipulating hERG channel function, but also interactions between structural domains that are critical to normal activation and inactivation gating.
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Affiliation(s)
- Matthew Perry
- University of Utah, Department of Physiology, Nora Eccles Harrison Cardiovascular Research & Training Institute, 95 South 2000 East, Salt Lake City,UT 84112, USA
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Es-Salah-Lamoureux Z, Fougere R, Xiong PY, Robertson GA, Fedida D. Fluorescence-tracking of activation gating in human ERG channels reveals rapid S4 movement and slow pore opening. PLoS One 2010; 5:e10876. [PMID: 20526358 PMCID: PMC2878317 DOI: 10.1371/journal.pone.0010876] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Accepted: 05/07/2010] [Indexed: 01/24/2023] Open
Abstract
Background hERG channels are physiologically important ion channels which mediate cardiac repolarization as a result of their unusual gating properties. These are very slow activation compared with other mammalian voltage-gated potassium channels, and extremely rapid inactivation. The mechanism of slow activation is not well understood and is investigated here using fluorescence as a direct measure of S4 movement and pore opening. Methods and Findings Tetramethylrhodamine-5-maleimide (TMRM) fluorescence at E519 has been used to track S4 voltage sensor movement, and channel opening and closing in hERG channels. Endogenous cysteines (C445 and C449) in the S1–S2 linker bound TMRM, which caused a 10 mV hyperpolarization of the V½ of activation to −27.5±2.0 mV, and showed voltage-dependent fluorescence signals. Substitution of S1–S2 linker cysteines with valines allowed unobstructed recording of S3–S4 linker E519C and L520C emission signals. Depolarization of E519C channels caused rapid initial fluorescence quenching, fit with a double Boltzmann relationship, F-VON, with V½,1 = −37.8±1.7 mV, and V½,2 = 43.5±7.9 mV. The first phase, V½,1, was ∼20 mV negative to the conductance-voltage relationship measured from ionic tail currents (G-V½ = −18.3±1.2 mV), and relatively unchanged in a non-inactivating E519C:S620T mutant (V½ = −34.4±1.5 mV), suggesting the fast initial fluorescence quenching tracked S4 voltage sensor movement. The second phase of rapid quenching was absent in the S620T mutant. The E519C fluorescence upon repolarization (V½ = −20.6±1.2, k = 11.4 mV) and L520C quenching during depolarization (V½ = −26.8±1.0, k = 13.3 mV) matched the respective voltage dependencies of hERG ionic tails, and deactivation time constants from −40 to −110 mV, suggesting they detected pore-S4 rearrangements related to ionic current flow during pore opening and closing. Conclusion The data indicate: 1) that rapid environmental changes occur at the outer end of S4 in hERG channels that underlie channel activation gating, and 2) that secondary slower changes reflect channel pore opening during sustained depolarizations, and channel closing upon repolarization. 3) No direct evidence was obtained of conformational changes related to inactivation from fluorophores attached at the outer end of S4.
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Affiliation(s)
- Zeineb Es-Salah-Lamoureux
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Robert Fougere
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Ping Yu Xiong
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gail A. Robertson
- Department of Physiology, University of Wisconsin-Madison School of Medicine, Madison, Wisconsin, United States of America
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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Stary A, Wacker SJ, Boukharta L, Zachariae U, Karimi-Nejad Y, Aqvist J, Vriend G, de Groot BL. Toward a consensus model of the HERG potassium channel. ChemMedChem 2010; 5:455-67. [PMID: 20104563 DOI: 10.1002/cmdc.200900461] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Malfunction of hERG potassium channels, due to inherited mutations or inhibition by drugs, can cause long QT syndrome, which can lead to life-threatening arrhythmias. A three-dimensional structure of hERG is a prerequisite to understand the molecular basis of hERG malfunction. To achieve a consensus model, we carried out an extensive analysis of hERG models based on various alignments of helix S5. We analyzed seven models using a combination of conventional geometry/packing/normality validation methods as well as molecular dynamics simulations and molecular docking. A synthetic test set with the X-ray crystal structure of K(v)1.2 with artificially shifted S5 sequences modeled into the structure served as a reference case. We docked the known hERG inhibitors (+)-cisapride, (S)-terfenadine, and MK-499 into the hERG models and simulation snapshots. None of the single analyses unambiguously identified a preferred model, but the combination of all three revealed that there is only one model that fulfils all quality criteria. This model is confirmed by a recent mutation scanning experiment (P. Ju, G. Pages, R. P. Riek, P. C. Chen, A. M. Torres, P. S. Bansal, S. Kuyucak, P. W. Kuchel, J. I. Vandenberg, J. Biol. Chem. 2009, 284, 1000-1008). We expect the modeled structure to be useful as a basis both for computational studies of channel function and kinetics as well as the design of experiments.
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Affiliation(s)
- Anna Stary
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
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Transfer of rolf S3-S4 linker to HERG eliminates activation gating but spares inactivation. Biophys J 2009; 97:1323-34. [PMID: 19720020 DOI: 10.1016/j.bpj.2009.05.060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 05/20/2009] [Accepted: 05/28/2009] [Indexed: 02/03/2023] Open
Abstract
Studies in Shaker, a voltage-dependent potassium channel, suggest a coupling between activation and inactivation. This coupling is controversial in hERG, a fast-inactivating voltage-dependent potassium channel. To address this question, we transferred to hERG the S3-S4 linker of the voltage-independent channel, rolf, to selectively disrupt the activation process. This chimera shows an intact voltage-dependent inactivation process consistent with a weak coupling, if any, between both processes. Kinetic models suggest that the chimera presents only an open and an inactivated states, with identical transition rates as in hERG. The lower sensitivity of the chimera to BeKm-1, a hERG preferential closed-state inhibitor, also suggests that the chimera presents mainly open and inactivated conformations. This chimera allows determining the mechanism of action of hERG blockers, as exemplified by the test on ketoconazole.
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PD-118057 contacts the pore helix of hERG1 channels to attenuate inactivation and enhance K+ conductance. Proc Natl Acad Sci U S A 2009; 106:20075-80. [PMID: 19892732 DOI: 10.1073/pnas.0906597106] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human ether-a-go-go-related gene 1 (hERG1) K(+) channels mediate repolarization of cardiac action potentials. Unintended block of hERG1 channels by some drugs can prolong the QT interval and induce arrhythmia. Recently, hERG1 channel agonists were discovered and, based on their mechanisms of action can be classified into two types. RPR260243 [(3R,4R)-4-[3-(6-methoxy-quinolin-4-yl)-3-oxo-propyl]-1-[3-(2,3,5 trifluorophenyl)-prop-2-ynyl]-piperidine-3-carboxylic acid], a type 1 agonist, binds to residues located near the intracellular end of S5 and S6 transmembrane segments and activates hERG1 channels by a dual mechanism of slowed deactivation and attenuated P-type inactivation. As defined here, type 2 agonists such as PD-118057 [2-(4-[2-(3,4-dichloro-phenyl)-ethyl]-phenylamino)-benzoic acid] attenuate inactivation but do not slow deactivation. At 10 muM, PD-118057 shifted the half-point for inactivation of wild-type hERG1 channels by +19 mV and increased peak outward current by 136%. Scanning mutagenesis and functional characterization of 44 mutant channels expressed in Xenopus oocytes was used to identify the major structural determinants of the binding site for PD-118057. Single mutations of residues in the pore helix (F619) or the S6 segment (L646) of hERG1 eliminated agonist activity. Mutation of a nearby residues in the S6 segment (C643, M645) enhanced drug activity, presumably by reducing steric hindrance for drug binding. Molecular modeling indicates that PD-118057 binds to a hydrophobic pocket formed by L646 of one hERG1 subunit and F619 of an adjacent subunit. We conclude that direct interaction of PD-118057 with the pore helix attenuates fast P-type inactivation and increases open probability of hERG1 channels.
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Pages G, Torres AM, Ju P, Bansal PS, Alewood PF, Kuchel PW, Vandenberg JI. Structure of the pore-helix of the hERG K+ channel. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:111-20. [DOI: 10.1007/s00249-009-0433-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 02/19/2009] [Accepted: 02/23/2009] [Indexed: 10/21/2022]
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