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Thomson KL, Jiang C, Richardson E, Westphal DS, Burkard T, Wolf CM, Vatta M, Harrison SM, Ingles J, Bezzina CR, Kroncke BM, Vandenberg JI, Ng CA. Clinical interpretation of KCNH2 variants using a robust PS3/BS3 functional patch-clamp assay. HGG Adv 2024; 5:100270. [PMID: 38219013 PMCID: PMC10840334 DOI: 10.1016/j.xhgg.2024.100270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/15/2024] Open
Abstract
Long QT syndrome (LQTS), caused by the dysfunction of cardiac ion channels, increases the risk of sudden death in otherwise healthy young people. For many variants in LQTS genes, there is insufficient evidence to make a definitive genetic diagnosis. We have established a robust functional patch-clamp assay to facilitate classification of missense variants in KCNH2, one of the key LQTS genes. A curated set of 30 benign and 30 pathogenic missense variants were used to establish the range of normal and abnormal function. The extent to which variants reduced protein function was quantified using Z scores, the number of standard deviations from the mean of the normalized current density of the set of benign variant controls. A Z score of -2 defined the threshold for abnormal loss of function, which corresponds to 55% wild-type function. More extreme Z scores were observed for variants with a greater loss-of-function effect. We propose that the Z score for each variant can be used to inform the application and weighting of abnormal and normal functional evidence criteria (PS3 and BS3) within the American College of Medical Genetics and Genomics variant classification framework. The validity of this approach was demonstrated using a series of 18 KCNH2 missense variants detected in a childhood onset LQTS cohort, where the level of function assessed using our assay correlated to the Schwartz score (a scoring system used to quantify the probability of a clinical diagnosis of LQTS) and the length of the corrected QT (QTc) interval.
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Affiliation(s)
- Kate L Thomson
- Oxford Genetics Laboratories, Churchill Hospital, Oxford, UK
| | - Connie Jiang
- Faculty of Medicine and Health, UNSW Sydney, Kensington, NSW, Australia; Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Ebony Richardson
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, VIC, Australia
| | - Dominik S Westphal
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine and Health, Technical University of Munich, Munich, Germany; Department of Internal Medicine I, Klinikum Rechts der Isar, School of Medicine and Health, Technical University of Munich, Munich, Germany; European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart
| | - Tobias Burkard
- Department of Congenital Heart Disease and Pediatric Cardiology, German Heart Center Munich, Technical University of Munich, School of Medicine and Health, Munich, Germany
| | - Cordula M Wolf
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart; Department of Congenital Heart Disease and Pediatric Cardiology, German Heart Center Munich, Technical University of Munich, School of Medicine and Health, Munich, Germany; DZHK (German Centre for Cardiovascular Research), partner site Munich Heart Alliance, Munich, Germany
| | | | | | - Jodie Ingles
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, VIC, Australia
| | - Connie R Bezzina
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart; Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, University of Amsterdam, Amsterdam UMC, Amsterdam, the Netherlands
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
| | - Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
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TeBay C, Vandenberg JI. The real-world incidence of severe QT prolongation in patients taking antipsychotic drugs. Heart Rhythm 2024; 21:329-330. [PMID: 38231169 DOI: 10.1016/j.hrthm.2023.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 11/09/2023] [Accepted: 11/10/2023] [Indexed: 01/18/2024]
Affiliation(s)
- Clifford TeBay
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, New South Wales, Australia
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, New South Wales, Australia.
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O’Neill MJ, Ng CA, Aizawa T, Sala L, Bains S, Denjoy I, Winbo A, Ullah R, Shen Q, Tan CY, Kozek K, Vanags LR, Mitchell DW, Shen A, Wada Y, Kashiwa A, Crotti L, Dagradi F, Musu G, Spazzolini C, Neves R, Bos JM, Giudicessi JR, Bledsoe X, Lancaster M, Glazer AM, Roden DM, Leenhardt A, Salem JE, Earle N, Stiles R, Agee T, Johnson CN, Horie M, Skinner J, Extramiana F, Ackerman MJ, Schwartz PJ, Ohno S, Vandenberg JI, Kroncke BM. Prognostic Value of Multiplexed Assays of Variant Effect and Automated Patch-clamping for KCNH2-LQTS Risk Stratification. medRxiv 2024:2024.02.01.24301443. [PMID: 38370760 PMCID: PMC10871451 DOI: 10.1101/2024.02.01.24301443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Background Long QT syndrome (LQTS) is a lethal arrhythmia condition, frequently caused by rare loss-of-function variants in the cardiac potassium channel encoded by KCNH2. Variant-based risk stratification is complicated by heterogenous clinical data, incomplete penetrance, and low-throughput functional data. Objective To test the utility of variant-specific features, including high-throughput functional data, to predict cardiac events among KCNH2 variant heterozygotes. Methods We quantified cell-surface trafficking of 18,323 variants in KCNH2 and recorded potassium current densities for 506 KCNH2 variants. Next, we deeply phenotyped 1150 KCNH2 missense variant patients, including ECG features, cardiac event history (528 total cardiac events), and mortality. We then assessed variant functional, in silico, structural, and LQTS penetrance data to stratify event-free survival for cardiac events in the study cohort. Results Variant-specific current density (HR 0.28 [0.13-0.60]) and estimates of LQTS penetrance incorporating MAVE data (HR 3.16 [1.59-6.27]) were independently predictive of severe cardiac events when controlling for patient-specific features. Risk prediction models incorporating these data significantly improved prediction of 20 year cardiac events (AUC 0.79 [0.75-0.82]) over patient-only covariates (QTc and sex) (AUC 0.73 [0.70-0.77]). Conclusion We show that high-throughput functional data, and other variant-specific features, meaningfully contribute to both diagnosis and prognosis of a clinically actionable monogenic disease.
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Affiliation(s)
- Matthew J. O’Neill
- Vanderbilt University School of Medicine, Medical Scientist Training Program, Nashville, TN, USA
- These authors contributed equally
| | - Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
- These authors contributed equally
| | - Takanori Aizawa
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine Kyoto, Japan
| | - Luca Sala
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
| | - Sahej Bains
- Department of Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, MN, USA
| | - Isabelle Denjoy
- Department of Cardiovascular Medicine, Hôpital Bichat, APHP, Université de Paris Cité, Paris, France
| | - Annika Winbo
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Rizwan Ullah
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Qianyi Shen
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Chek-Ying Tan
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Krystian Kozek
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Loren R. Vanags
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Devyn W. Mitchell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Alex Shen
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Yuko Wada
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Asami Kashiwa
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine Kyoto, Japan
| | - Lia Crotti
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
- Department of Medicine and Surgery, University Milano Bicocca, Milan, Italy
| | - Federica Dagradi
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
| | - Giulia Musu
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
| | - Carla Spazzolini
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
| | - Raquel Neves
- Department of Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, MN, USA
| | - J. Martijn Bos
- Department of Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, MN, USA
| | - John R. Giudicessi
- Department of Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, MN, USA
| | - Xavier Bledsoe
- Vanderbilt University School of Medicine, Medical Scientist Training Program, Nashville, TN, USA
| | - Megan Lancaster
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andrew M. Glazer
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Dan M. Roden
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Antoine Leenhardt
- Department of Cardiovascular Medicine, Hôpital Bichat, APHP, Université de Paris Cité, Paris, France
| | - Joe-Elie Salem
- Department of Cardiovascular Medicine, Hôpital Bichat, APHP, Université de Paris Cité, Paris, France
| | - Nikki Earle
- Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Rachael Stiles
- Department of Cardiology, Waikato Hospital, Hamilton, New Zealand
| | - Taylor Agee
- Department of Chemistry, Mississippi State University, Starkville, MS 39759, USA
| | | | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Jonathan Skinner
- Sydney Children’s Hospital Network, University of Sydney, Sydney, Australia
| | - Fabrice Extramiana
- Department of Cardiovascular Medicine, Hôpital Bichat, APHP, Université de Paris Cité, Paris, France
| | - Michael J. Ackerman
- Department of Molecular Pharmacology & Experimental Therapeutics (Windland Smith Rice Sudden Death Genomics Laboratory), Mayo Clinic, Rochester, MN, USA
| | - Peter J. Schwartz
- IRCCS, Istituto Auxologico Italiano, Center for Cardiac Arrhythmias of Genetic Origin and Laboratory of Cardiovascular Genetics, Milano, Italy
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Jamie I. Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Brett M. Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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Ma JG, O’Neill MJ, Richardson E, Thomson KL, Ingles J, Muhammad A, Solus JF, Davogustto G, Anderson KC, Benjamin Shoemaker M, Stergachis AB, Floyd BJ, Dunn K, Parikh VN, Chubb H, Perrin MJ, Roden DM, Vandenberg JI, Ng CA, Glazer AM. Multi-site validation of a functional assay to adjudicate SCN5A Brugada Syndrome-associated variants. medRxiv 2023:2023.12.19.23299592. [PMID: 38196587 PMCID: PMC10775332 DOI: 10.1101/2023.12.19.23299592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Brugada Syndrome (BrS) is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in the cardiac sodium channel gene, SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging and ~79% of SCN5A missense variants in ClinVar are currently classified as Variants of Uncertain Significance (VUS). An in vitro SCN5A-BrS automated patch clamp assay was generated for high-throughput functional studies of NaV1.5. The assay was independently studied at two separate research sites - Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute - revealing strong correlations, including peak INa density (R2=0.86). The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. The assay accurately distinguished benign controls (24/25) from pathogenic controls (23/24). Odds of Pathogenicity values derived from the experimental results yielded 0.042 for normal function (BS3 criterion) and 24.0 for abnormal function (PS3 criterion), resulting in up to strong evidence for both ACMG criteria. The calibrated assay was then used to study SCN5A VUS observed in four families with BrS and other arrhythmia phenotypes associated with SCN5A loss-of-function. The assay revealed loss-of-function for three of four variants, enabling reclassification to likely pathogenic. This validated APC assay provides clinical-grade functional evidence for the reclassification of current VUS and will aid future SCN5A-BrS variant classification.
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Affiliation(s)
- Joanne G. Ma
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | | | - Ebony Richardson
- Clinical Genomics Laboratory, Centre for Population Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia and Murdoch Children Research Institute, Melbourne, Australia
| | - Kate L. Thomson
- Oxford Genetics Laboratories, Churchill Hospital, Oxford, UK
| | - Jodie Ingles
- Clinical Genomics Laboratory, Centre for Population Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia and Murdoch Children Research Institute, Melbourne, Australia
| | - Ayesha Muhammad
- Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Joseph F. Solus
- Vanderbilt Center for Arrhythmia Research and Therapeutics (VanCART), Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Giovanni Davogustto
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Katherine C. Anderson
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - M. Benjamin Shoemaker
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andrew B. Stergachis
- University of Washington School of Medicine, Department of Medicine, Seattle, WA, USA
| | - Brendan J. Floyd
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Stanford, CA, USA
| | - Kyla Dunn
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Stanford, CA, USA
| | - Victoria N. Parikh
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Stanford, CA, USA
| | - Henry Chubb
- Stanford Center for Inherited Cardiovascular Disease, Stanford University School of Medicine, Stanford, CA, USA
| | - Mark J. Perrin
- Department of Genomic Medicine, Royal Melbourne Hospital, Victoria, Australia
| | - Dan M. Roden
- Vanderbilt Center for Arrhythmia Research and Therapeutics (VanCART), Departments of Medicine, Pharmacology, and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jamie I. Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Andrew M. Glazer
- Vanderbilt Center for Arrhythmia Research and Therapeutics (VanCART), Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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Heitmann S, Vandenberg JI, Hill AP. Assessing drug safety by identifying the axis of arrhythmia in cardiomyocyte electrophysiology. eLife 2023; 12:RP90027. [PMID: 38079357 PMCID: PMC10712948 DOI: 10.7554/elife.90027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023] Open
Abstract
Many classes of drugs can induce fatal cardiac arrhythmias by disrupting the electrophysiology of cardiomyocytes. Safety guidelines thus require all new drugs to be assessed for pro-arrhythmic risk prior to conducting human trials. The standard safety protocols primarily focus on drug blockade of the delayed-rectifier potassium current (IKr). Yet the risk is better assessed using four key ion currents (IKr, ICaL, INaL, IKs). We simulated 100,000 phenotypically diverse cardiomyocytes to identify the underlying relationship between the blockade of those currents and the emergence of ectopic beats in the action potential. We call that relationship the axis of arrhythmia. It serves as a yardstick for quantifying the arrhythmogenic risk of any drug from its profile of multi-channel block alone. We tested it on 109 drugs and found that it predicted the clinical risk labels with an accuracy of 88.1-90.8%. Pharmacologists can use our method to assess the safety of novel drugs without resorting to animal testing or unwieldy computer simulations.
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Affiliation(s)
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research InstituteDarlinghurstAustralia
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South WalesSydneyAustralia
| | - Adam P Hill
- Victor Chang Cardiac Research InstituteDarlinghurstAustralia
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South WalesSydneyAustralia
- Victor Chang Cardiac Research Institute Innovation CentreDarlinghurstAustralia
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Zeng YC, Sobti M, Quinn A, Smith NJ, Brown SHJ, Vandenberg JI, Ryan RM, O'Mara ML, Stewart AG. Structural basis of promiscuous substrate transport by Organic Cation Transporter 1. Nat Commun 2023; 14:6374. [PMID: 37821493 PMCID: PMC10567722 DOI: 10.1038/s41467-023-42086-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 09/29/2023] [Indexed: 10/13/2023] Open
Abstract
Organic Cation Transporter 1 (OCT1) plays a crucial role in hepatic metabolism by mediating the uptake of a range of metabolites and drugs. Genetic variations can alter the efficacy and safety of compounds transported by OCT1, such as those used for cardiovascular, oncological, and psychological indications. Despite its importance in drug pharmacokinetics, the substrate selectivity and underlying structural mechanisms of OCT1 remain poorly understood. Here, we present cryo-EM structures of full-length human OCT1 in the inward-open conformation, both ligand-free and drug-bound, indicating the basis for its broad substrate recognition. Comparison of our structures with those of outward-open OCTs provides molecular insight into the alternating access mechanism of OCTs. We observe that hydrophobic gates stabilize the inward-facing conformation, whereas charge neutralization in the binding pocket facilitates the release of cationic substrates. These findings provide a framework for understanding the structural basis of the promiscuity of drug binding and substrate translocation in OCT1.
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Affiliation(s)
- Yi C Zeng
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
- School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia.
| | - Meghna Sobti
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Ada Quinn
- Australian Institute of Bioengineering and Nanotechnology, University of Queensland, Brisbane, QLD, Australia
| | - Nicola J Smith
- School of Biomedical Sciences, Faculty of Medicine & Health, UNSW Sydney, Kensington, NSW, Australia
| | - Simon H J Brown
- School of Chemistry and Molecular Bioscience, Molecular Horizons, and Australian Research Council Centre for Cryo-electron Microscopy of Membrane Proteins, University of Wollongong, Wollongong, NSW, Australia
| | - Jamie I Vandenberg
- School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
- Molecular Cardiology and Biophysics Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Megan L O'Mara
- Australian Institute of Bioengineering and Nanotechnology, University of Queensland, Brisbane, QLD, Australia
| | - Alastair G Stewart
- Molecular, Structural and Computational Biology Division, The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
- School of Clinical Medicine, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia.
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Thorpe J, Perry MD, Contreras O, Hurley E, Parker G, Harvey RP, Hill AP, Vandenberg JI. Development of a robust induced pluripotent stem cell atrial cardiomyocyte differentiation protocol to model atrial arrhythmia. Stem Cell Res Ther 2023; 14:183. [PMID: 37501071 PMCID: PMC10373292 DOI: 10.1186/s13287-023-03405-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 06/27/2023] [Indexed: 07/29/2023] Open
Abstract
BACKGROUND Atrial fibrillation is the most common arrhythmia syndrome and causes significant morbidity and mortality. Current therapeutics, however, have limited efficacy. Notably, many therapeutics shown to be efficacious in animal models have not proved effective in humans. Thus, there is a need for a drug screening platform based on human tissue. The aim of this study was to develop a robust protocol for generating atrial cardiomyocytes from human-induced pluripotent stem cells. METHODS A novel protocol for atrial differentiation, with optimized timing of retinoic acid during mesoderm formation, was compared to two previously published methods. Each differentiation method was assessed for successful formation of a contractile syncytium, electrical properties assayed by optical action potential recordings and multi-electrode array electrophysiology, and response to the G-protein-gated potassium channel activator, carbamylcholine. Atrial myocyte monolayers, derived using the new differentiation protocol, were further assessed for cardiomyocyte purity, gene expression, and the ability to form arrhythmic rotors in response to burst pacing. RESULTS Application of retinoic acid at day 1 of mesoderm formation resulted in a robust differentiation of atrial myocytes with contractile syncytium forming in 16/18 differentiations across two cell lines. Atrial-like myocytes produced have shortened action potentials and field potentials, when compared to standard application of retinoic acid at the cardiac mesoderm stage. Day 1 retinoic acid produced atrial cardiomyocytes are also carbamylcholine sensitive, indicative of active Ikach currents, which was distinct from ventricular myocytes and standard retinoic addition in matched differentiations. A current protocol utilizing reduced Activin A and BMP4 can produce atrial cardiomyocytes with equivalent functionality but with reduced robustness of differentiation; only 8/17 differentiations produced a contractile syncytium. The day 1 retinoic acid protocol was successfully applied to 6 iPSC lines (3 male and 3 female) without additional optimization or modification. Atrial myocytes produced could also generate syncytia with rapid conduction velocities, > 40 cm s-1, and form rotor style arrhythmia in response to burst pacing. CONCLUSIONS This method combines an enhanced atrial-like phenotype with robustness of differentiation, which will facilitate further research in human atrial arrhythmia and myopathies, while being economically viable for larger anti-arrhythmic drug screens.
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Affiliation(s)
- Jordan Thorpe
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- Department of Pharmacology, School of Biomedical Sciences, University of New South Wales, Sydney, Australia
| | - Osvaldo Contreras
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia
| | - Emily Hurley
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | - George Parker
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | - Richard P Harvey
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia.
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia.
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia.
- School of Clinical Medicine, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia.
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8
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Lee W, Ng B, Mangala MM, Perry MD, Subbiah RN, Vandenberg JI, Hill AP. Action Potential Morphology Accurately Predicts Proarrhythmic Risk for Drugs With Potential to Prolong Cardiac Repolarization. Circ Arrhythm Electrophysiol 2023:e011574. [PMID: 37334695 DOI: 10.1161/circep.122.011574] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
BACKGROUND Drug-induced or acquired long QT syndrome occurs as a result of the unintended disruption of cardiac repolarization due to drugs that block cardiac ion channels. These side effects have been responsible for the withdrawal of a range of drugs from market and are a common reason for termination of the development of new drugs in the preclinical stage. Existing approaches to risk prediction are expensive and overly sensitive meaning that recently there have been renewed efforts, largely driven by the comprehensive proarrhythmic assay initiative, to develop more accurate methods for allocation of proarrhythmic risk. METHODS In this study, we aimed to quantify changes in the morphology of the repolarization phase of the cardiac action potential as an indicator of proarrhythmia, supposing that these shape changes might precede the emergence of ectopic depolarizations that trigger arrhythmia. To do this, we describe a new method of quantifying action potential morphology by measuring the radius of curvature of the repolarization phase both in simulated action potentials, as well as in action potentials measured from induced pluripotent stem cell-derived cardiomyocytes. Features derived from the curvature signal were used as inputs for logistic regressions to predict proarrhythmic risk. RESULTS Optimal risk classifiers based on morphology were able to correctly classify risk to drugs in the comprehensive proarrhythmic assay initiative panels with very high accuracy (0.9375) and outperformed conventional metrics based on action potential duration at 90% repolarization, triangulation, and charge movement (qNet). CONCLUSIONS Analysis of action potential morphology in response to proarrhythmic drugs improves prediction of torsadogenic risk. Furthermore, morphology metrics can be measured directly from the action potential, potentially eliminating the burden of undertaking complex screens of potency and drug-binding kinetics against multiple cardiac ion channels. As such, this method has the potential to improve and streamline regulatory assessment of proarrhythmia in preclinical drug development.
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Affiliation(s)
- William Lee
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
| | - Ben Ng
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
| | - Melissa M Mangala
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- Department of Pharmacology, School of Medical Sciences, The University of New South Wales, Sydney, Australia (M.D.P.)
| | - Rajesh N Subbiah
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Darlinghurst (B.N., M.M.M., M.D.P., R.N.S., J.I.V., A.P.H.)
- School of Clinical Medicine, Faculty of Medicine and Health (W.L., B.N., M.M.M., R.N.S., J.I.V., A.P.H.)
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9
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Copier JS, Bootsma M, Ng CA, Wilde AAM, Bertels RA, Bikker H, Christiaans I, van der Crabben SN, Hol JA, Koopmann TT, Knijnenburg J, Lommerse AAJ, van der Smagt JJ, Bezzina CR, Vandenberg JI, Verkerk AO, Barge-Schaapveld DQCM, Lodder EM. Reclassification of a likely pathogenic Dutch founder variant in KCNH2; implications of reduced penetrance. Hum Mol Genet 2023; 32:1072-1082. [PMID: 36269083 PMCID: PMC10026256 DOI: 10.1093/hmg/ddac261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 10/03/2022] [Accepted: 10/14/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Variants in KCNH2, encoding the human ether a-go-go (hERG) channel that is responsible for the rapid component of the cardiac delayed rectifier K+ current (IKr), are causal to long QT syndrome type 2 (LQTS2). We identified eight index patients with a new variant of unknown significance (VUS), KCNH2:c.2717C > T:p.(Ser906Leu). We aimed to elucidate the biophysiological effect of this variant, to enable reclassification and consequent clinical decision-making. METHODS A genotype-phenotype overview of the patients and relatives was created. The biophysiological effects were assessed independently by manual-, and automated calibrated patch clamp. HEK293a cells expressing (i) wild-type (WT) KCNH2, (ii) KCNH2-p.S906L alone (homozygous, Hm) or (iii) KCNH2-p.S906L in combination with WT (1:1) (heterozygous, Hz) were used for manual patching. Automated patch clamp measured the variants function against known benign and pathogenic variants, using Flp-In T-rex HEK293 KCNH2-variant cell lines. RESULTS Incomplete penetrance of LQTS2 in KCNH2:p.(Ser906Leu) carriers was observed. In addition, some patients were heterozygous for other VUSs in CACNA1C, PKP2, RYR2 or AKAP9. The phenotype of carriers of KCNH2:p.(Ser906Leu) ranged from asymptomatic to life-threatening arrhythmic events. Manual patch clamp showed a reduced current density by 69.8 and 60.4% in KCNH2-p.S906L-Hm and KCNH2-p.S906L-Hz, respectively. The time constant of activation was significantly increased with 80.1% in KCNH2-p.S906L-Hm compared with KCNH2-WT. Assessment of KCNH2-p.S906L-Hz by calibrated automatic patch clamp assay showed a reduction in current density by 35.6%. CONCLUSION The reduced current density in the KCNH2-p.S906L-Hz indicates a moderate loss-of-function. Combined with the reduced penetrance and variable phenotype, we conclude that KCNH2:p.(Ser906Leu) is a low penetrant likely pathogenic variant for LQTS2.
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Affiliation(s)
- Jaël S Copier
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Marianne Bootsma
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 Leiden, The Netherlands
| | - Chai A Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Arthur A M Wilde
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Robin A Bertels
- Department of Paediatric Cardiology, Leiden University Medical Center, Willem-Alexander Children's Hospital, Albinusdreef 2, 2333 Leiden, Netherlands
| | - Hennie Bikker
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
- Human Genetics, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Imke Christiaans
- Department of Clinical Genetics, University Medical Centre Groningen, 9713GZ Groningen, The Netherlands
| | - Saskia N van der Crabben
- Human Genetics, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Janna A Hol
- Erasmus MC, Clinical Genetics, Doctor Molewaterplein 40, 3015 Rotterdam, The Netherlands
| | - Tamara T Koopmann
- Clinical Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 Leiden, The Netherlands
| | - Jeroen Knijnenburg
- Clinical Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 Leiden, The Netherlands
| | - Aafke A J Lommerse
- Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, 2300 Leiden, The Netherlands
| | - Jasper J van der Smagt
- Clinical Genetics, University Medical Center Utrecht, Lundlaan 6, Utrecht, The Netherlands
| | - Connie R Bezzina
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
- School of Clinical Medicine, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Arie O Verkerk
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
- Medical Biology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | | | - Elisabeth M Lodder
- Experimental Cardiology, Amsterdam UMC location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Amsterdam Cardiovascular Sciences, Heart Failure & Arrhythmias, Amsterdam, The Netherlands
- European Reference Network for Rare, Low Prevalence and Complex Diseases of the Heart: ERN GUARD-Heart'
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10
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Tardo DT, Peck M, Subbiah R, Vandenberg JI, Hill AP. The diagnostic role of T wave morphology biomarkers in congenital and acquired long QT syndrome: A systematic review. Ann Noninvasive Electrocardiol 2022; 28:e13015. [PMID: 36345173 PMCID: PMC9833360 DOI: 10.1111/anec.13015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 10/12/2022] [Indexed: 11/11/2022] Open
Abstract
INTRODUCTION QTc prolongation is key in diagnosing long QT syndrome (LQTS), however 25%-50% with congenital LQTS (cLQTS) demonstrate a normal resting QTc. T wave morphology (TWM) can distinguish cLQTS subtypes but its role in acquired LQTS (aLQTS) is unclear. METHODS Electronic databases were searched using the terms "LQTS," "long QT syndrome," "QTc prolongation," "prolonged QT," and "T wave," "T wave morphology," "T wave pattern," "T wave biomarkers." Whole text articles assessing TWM, independent of QTc, were included. RESULTS Seventeen studies met criteria. TWM measurements included T-wave amplitude, duration, magnitude, Tpeak-Tend, QTpeak, left and right slope, center of gravity (COG), sigmoidal and polynomial classifiers, repolarizing integral, morphology combination score (MCS) and principal component analysis (PCA); and vectorcardiographic biomarkers. cLQTS were distinguished from controls by sigmoidal and polynomial classifiers, MCS, QTpeak, Tpeak-Tend, left slope; and COG x axis. MCS detected aLQTS more significantly than QTc. Flatness, asymmetry and notching, J-Tpeak; and Tpeak-Tend correlated with QTc in aLQTS. Multichannel block in aLQTS was identified by early repolarization (ERD30% ) and late repolarization (LRD30% ), with ERD reflecting hERG-specific blockade. Cardiac events were predicted in cLQTS by T wave flatness, notching, and inversion in leads II and V5 , left slope in lead V6 ; and COG last 25% in lead I. T wave right slope in lead I and T-roundness achieved this in aLQTS. CONCLUSION Numerous TWM biomarkers which supplement QTc assessment were identified. Their diagnostic capabilities include differentiation of genotypes, identification of concealed LQTS, differentiating aLQTS from cLQTS; and determining multichannel versus hERG channel blockade.
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Affiliation(s)
- Daniel T. Tardo
- Cardiac Electrophysiology LaboratoryVictor Chang Cardiac Research InstituteDarlinghurstNew South WalesAustralia,Department of CardiologySt. Vincent's HospitalDarlinghurstNew South WalesAustralia,School of MedicineUniversity of Notre Dame AustraliaDarlinghurstNew South WalesAustralia
| | - Matthew Peck
- Cardiac Electrophysiology LaboratoryVictor Chang Cardiac Research InstituteDarlinghurstNew South WalesAustralia
| | - Rajesh N. Subbiah
- Cardiac Electrophysiology LaboratoryVictor Chang Cardiac Research InstituteDarlinghurstNew South WalesAustralia,Department of CardiologySt. Vincent's HospitalDarlinghurstNew South WalesAustralia,St. Vincent's Clinical School, Faculty of MedicineUniversity of New South WalesSydneyNew South WalesAustralia
| | - Jamie I. Vandenberg
- Cardiac Electrophysiology LaboratoryVictor Chang Cardiac Research InstituteDarlinghurstNew South WalesAustralia,St. Vincent's Clinical School, Faculty of MedicineUniversity of New South WalesSydneyNew South WalesAustralia
| | - Adam. P. Hill
- Cardiac Electrophysiology LaboratoryVictor Chang Cardiac Research InstituteDarlinghurstNew South WalesAustralia,St. Vincent's Clinical School, Faculty of MedicineUniversity of New South WalesSydneyNew South WalesAustralia
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11
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Bursill CA, Smith NJ, Palpant N, Tan I, Sunde M, Harvey RP, Lewis B, Figtree GA, Vandenberg JI. Don't Turn Off the Tap! The Importance of Discovery Science to the Australian Cardiovascular Sector and Improving Clinical Outcomes Into the Future. Heart Lung Circ 2022; 31:1321-1332. [PMID: 35961820 DOI: 10.1016/j.hlc.2022.06.669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/01/2022] [Accepted: 06/10/2022] [Indexed: 10/15/2022]
Abstract
Despite significant advances in interventional and therapeutic approaches, cardiovascular disease (CVD) remains the leading cause of death and mortality. To lower this health burden, cardiovascular discovery scientists need to play an integral part in the solution. Successful clinical translation is achieved when built upon a strong foundational understanding of the disease mechanisms involved. Changes in the Australian funding landscape, to place greater emphasis on translation, however, have increased job insecurity for discovery science researchers and especially early-mid career researchers. To highlight the importance of discovery science in cardiovascular research, this review compiles six science stories in which fundamental discoveries, often involving Australian researchers, has led to or is advancing to clinical translation. These stories demonstrate the importance of the role of discovery scientists and the need for their work to be prioritised now and in the future. Australia needs to keep discovery scientists supported and fully engaged within the broader cardiovascular research ecosystem so they can help realise the next game-changing therapy or diagnostic approach that diminishes the burden of CVD on society.
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Affiliation(s)
- Christina A Bursill
- Vascular Research Centre, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia; Faculty of Health and Medical Research, The University of Adelaide, Adelaide, SA, Australia; Australian Research Council (ARC) Centre of Excellence for Nanoscale BioPhotonics (CNBP).
| | - Nicola J Smith
- School of Medical Sciences, Faculty of Medicine and Health, UNSW Sydney, Sydney, NSW, Australia
| | - Nathan Palpant
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, Australia
| | - Isabella Tan
- Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Melbourne, Vic, Australia; The George Institute of Global Health, Sydney, NSW, Australia
| | - Margaret Sunde
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW, Australia
| | - Richard P Harvey
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia; St Vincent's Clinical School, UNSW Sydney, Sydney, NSW, Australia; School of Biotechnology and Biomolecular Science, UNSW Sydney, Sydney, NSW, Australia
| | - Benjamin Lewis
- Vascular Research Centre, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, SA, Australia
| | - Gemma A Figtree
- Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia; St Vincent's Clinical School, UNSW Sydney, Sydney, NSW, Australia
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12
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Jiang C, Richardson E, Farr J, Hill AP, Ullah R, Kroncke BM, Harrison SM, Thomson KL, Ingles J, Vandenberg JI, Ng CA. A calibrated functional patch-clamp assay to enhance clinical variant interpretation in KCNH2-related long QT syndrome. Am J Hum Genet 2022; 109:1199-1207. [PMID: 35688147 PMCID: PMC9300752 DOI: 10.1016/j.ajhg.2022.05.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 05/03/2022] [Indexed: 01/09/2023] Open
Abstract
Modern sequencing technologies have revolutionized our detection of gene variants. However, in most genes, including KCNH2, the majority of missense variants are currently classified as variants of uncertain significance (VUSs). The aim of this study was to investigate the utility of an automated patch-clamp assay for aiding clinical variant classification in KCNH2. The assay was designed according to recommendations proposed by the Clinical Genome Sequence Variant Interpretation Working Group. Thirty-one variants (17 pathogenic/likely pathogenic, 14 benign/likely benign) were classified internally as variant controls. They were heterozygously expressed in Flp-In HEK293 cells for assessing the effects of variants on current density and channel gating in order to determine the sensitivity and specificity of the assay. All 17 pathogenic variant controls had reduced current density, and 13 of 14 benign variant controls had normal current density, which enabled determination of normal and abnormal ranges for applying evidence of moderate or supporting strength for VUS reclassification. Inclusion of functional assay evidence enabled us to reclassify 6 out of 44 KCNH2 VUSs as likely pathogenic. The high-throughput patch-clamp assay can provide moderate-strength evidence for clinical interpretation of clinical KCNH2 variants and demonstrates the value of developing automated patch-clamp assays for functional characterization of ion channel gene variants.
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Affiliation(s)
- Connie Jiang
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; Faculty of Medicine and Health, UNSW Sydney, Kensington, NSW, Australia
| | - Ebony Richardson
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, Australia
| | - Jessica Farr
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Computer Science and Engineering, UNSW Sydney, Kensington, NSW, Australia
| | - Adam P Hill
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Rizwan Ullah
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | | | - Kate L Thomson
- Oxford Medical Genetics Laboratories, Churchill Hospital, Oxford, UK
| | - Jodie Ingles
- Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, Australia; Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, Australia
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
| | - Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
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13
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Ng CA, Ullah R, Farr J, Hill AP, Kozek KA, Vanags LR, Mitchell DW, Kroncke BM, Vandenberg JI. A massively parallel assay accurately discriminates between functionally normal and abnormal variants in a hotspot domain of KCNH2. Am J Hum Genet 2022; 109:1208-1216. [PMID: 35688148 PMCID: PMC9300756 DOI: 10.1016/j.ajhg.2022.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 05/03/2022] [Indexed: 01/09/2023] Open
Abstract
Many genes, including KCNH2, contain "hotspot" domains associated with a high density of variants associated with disease. This has led to the suggestion that variant location can be used as evidence supporting classification of clinical variants. However, it is not known what proportion of all potential variants in hotspot domains cause loss of function. Here, we have used a massively parallel trafficking assay to characterize all single-nucleotide variants in exon 2 of KCNH2, a known hotspot for variants that cause long QT syndrome type 2 and an increased risk of sudden cardiac death. Forty-two percent of KCNH2 exon 2 variants caused at least 50% reduction in protein trafficking, and 65% of these trafficking-defective variants exerted a dominant-negative effect when co-expressed with a WT KCNH2 allele as assessed using a calibrated patch-clamp electrophysiology assay. The massively parallel trafficking assay was more accurate (AUC of 0.94) than bioinformatic prediction tools (REVEL and CardioBoost, AUC of 0.81) in discriminating between functionally normal and abnormal variants. Interestingly, over half of variants in exon 2 were found to be functionally normal, suggesting a nuanced interpretation of variants in this "hotspot" domain is necessary. Our massively parallel trafficking assay can provide this information prospectively.
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Affiliation(s)
- Chai-Ann Ng
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Rizwan Ullah
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jessica Farr
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Computer Science and Engineering, UNSW Sydney, Kensington, NSW, Australia
| | - Adam P Hill
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia
| | - Krystian A Kozek
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Loren R Vanags
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Devyn W Mitchell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; School of Clinical Medicine, UNSW Sydney, Darlinghurst, NSW, Australia.
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14
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Peters S, Thompson BA, Perrin M, James P, Zentner D, Kalman JM, Vandenberg JI, Fatkin D. Arrhythmic Phenotypes Are a Defining Feature of Dilated Cardiomyopathy-Associated SCN5A Variants: A Systematic Review. Circ Genom Precis Med 2022; 15:e003432. [PMID: 34949099 DOI: 10.1161/circgen.121.003432] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Variants in the SCN5A gene, that encodes the cardiac sodium channel, Nav1.5, are associated with a highly arrhythmogenic form of dilated cardiomyopathy (DCM). Our aim was to review the phenotypes, natural history, functional effects, and treatment outcomes of DCM-associated rare SCN5A variants. METHODS A systematic review of reported DCM-associated rare SCN5A variants was undertaken using PubMed and Embase. RESULTS Eighteen SCN5A rare variants in 29 families with DCM (173 affected individuals) were identified. Eleven variants had undergone experimental evaluation, with 7 of these resulting in increased sustained current flow during the action potential (eg, increased window current) and at resting membrane potentials (eg, creation of a new gating pore current). These variants were located in transmembrane voltage-sensing domains and had a consistent phenotype characterized by frequent multifocal narrow and broad complex ventricular premature beats (VPB; 72% of affected relatives), ventricular arrhythmias (33%), atrial arrhythmias (32%), sudden cardiac death (13%), and DCM (56%). This VPB-predominant phenotype was not seen with 1 variant that increased late sodium current, or with variants that reduced peak current density or had mixed effects. In the latter groups, affected individuals mainly showed sinus node dysfunction, conduction defects, and atrial arrhythmias, with infrequent VPB and ventricular arrhythmias. DCM did not occur in the absence of arrhythmias for any variant. Twelve studies (23 total patients) reported treatment success in the VPB-predominant cardiomyopathy using sodium channel-blocking drug therapy. CONCLUSIONS SCN5A variants can present with a diverse spectrum of primary arrhythmic features. A majority of DCM-associated variants cause a multifocal VPB-predominant cardiomyopathy that is reversible with sodium channel blocking drug therapy. Early recognition of the distinctive phenotype and prompt genetic testing to identify variant carriers are needed. Our findings have implications for interpretation and management of SCN5A variants found in DCM patients with and without arrhythmias.
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Affiliation(s)
- Stacey Peters
- Department of Cardiology (S.P., M.P., D.Z., J.M.K.), Royal Melbourne Hospital
- Department of Genomic Medicine (S.P., B.A.T., M.P., P.J., D.Z.), Royal Melbourne Hospital
- Department of Medicine, University of Melbourne (S.P., P.J., D.Z., J.M.K.)
| | - Bryony A Thompson
- Department of Genomic Medicine (S.P., B.A.T., M.P., P.J., D.Z.), Royal Melbourne Hospital
- Department of Pathology (B.A.T.), Royal Melbourne Hospital
| | - Mark Perrin
- Department of Genomic Medicine (S.P., B.A.T., M.P., P.J., D.Z.), Royal Melbourne Hospital
| | - Paul James
- Department of Genomic Medicine (S.P., B.A.T., M.P., P.J., D.Z.), Royal Melbourne Hospital
- Department of Medicine, University of Melbourne (S.P., P.J., D.Z., J.M.K.)
- Familial Cancer Centre, Peter MacCallum Centre, Melbourne, Victoria (P.J.)
| | - Dominica Zentner
- Department of Genomic Medicine (S.P., B.A.T., M.P., P.J., D.Z.), Royal Melbourne Hospital
- Department of Medicine, University of Melbourne (S.P., P.J., D.Z., J.M.K.)
| | - Jonathan M Kalman
- Department of Medicine, University of Melbourne (S.P., P.J., D.Z., J.M.K.)
| | - Jamie I Vandenberg
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute (J.I.V., D.F.)
- St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney (J.I.V., D.F.)
| | - Diane Fatkin
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute (J.I.V., D.F.)
- St. Vincent's Clinical School, Faculty of Medicine, UNSW Sydney (J.I.V., D.F.)
- Cardiology Department, St. Vincent's Hospital, Sydney, New South Wales, Australia (D.F.)
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15
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TeBay C, McArthur JR, Mangala M, Kerr N, Heitmann S, Perry MD, Windley MJ, Vandenberg JI, Hill AP. Pathophysiological metabolic changes associated with disease modify the proarrhythmic risk profile of drugs with potential to prolong repolarisation. Br J Pharmacol 2021; 179:2631-2646. [PMID: 34837219 DOI: 10.1111/bph.15757] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 11/16/2021] [Accepted: 11/18/2021] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Hydroxychloroquine, chloroquine and azithromycin are three drugs that were proposed to treat COVID-19. While concern already existed around their proarrhythmic potential there is little data regarding how altered physiological states encountered in patients such as febrile state, electrolyte imbalances or acidosis might change their risk profiles. EXPERIMENTAL APPROACH Potency of hERG block was measured using high-throughput electrophysiology in the presence of variable environmental factors. These potencies informed simulations to predict population risk profiles. Effects on cardiac repolarisation were verified in human induced pluripotent stem cell-derived cardiomyocytes from multiple individuals. KEY RESULTS Chloroquine and hydroxychloroquine blocked hERG with IC50 of 1.47±0.07 μM and 3.78±0.17 μM respectively, indicating proarrhythmic risk at concentrations effective against SARS-CoV-2 in vitro. Hypokalaemia and hypermagnesemia increased potency of chloroquine and hydroxychloroquine, indicating increased proarrhythmic risk. Acidosis significantly reduced potency of all drugs, whereas increased temperature decreased potency of chloroquine and hydroxychloroquine against hERG but increased potency for azithromycin. In silico simulations demonstrated that proarrhythmic risk was increased by female sex, hypokalaemia and heart failure, and identified specific genetic backgrounds associated with emergence of arrhythmia. CONCLUSION AND IMPLICATIONS Our study demonstrates how proarrhythmic risk can be exacerbated by metabolic changes and pre-existing disease. More broadly, the study acts as a blueprint for how high-throughput in vitro screening, combined with in silico simulations can help guide both preclinical screening and clinical management of patients in relation to drugs with potential to prolong repolarisation.
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Affiliation(s)
- Clifford TeBay
- Victor Chang Cardiac Research Institute, Sydney, Australia
| | - Jeffrey R McArthur
- Victor Chang Cardiac Research Institute, Sydney, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Australia
| | - Melissa Mangala
- Victor Chang Cardiac Research Institute, Sydney, Australia.,St. Vincent's Clinical school, UNSW Sydney, Sydney, Australia
| | - Nicholas Kerr
- Victor Chang Cardiac Research Institute, Sydney, Australia.,St. Vincent's Clinical school, UNSW Sydney, Sydney, Australia
| | | | - Matthew D Perry
- Victor Chang Cardiac Research Institute, Sydney, Australia.,School of Medical Sciences, UNSW Sydney, Sydney, Australia
| | - Monique J Windley
- Victor Chang Cardiac Research Institute, Sydney, Australia.,St. Vincent's Clinical school, UNSW Sydney, Sydney, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Sydney, Australia.,St. Vincent's Clinical school, UNSW Sydney, Sydney, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Sydney, Australia.,St. Vincent's Clinical school, UNSW Sydney, Sydney, Australia
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16
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Ng CA, Vandenberg JI. When it takes two to get one into trouble. Heart Rhythm 2021; 19:293-294. [PMID: 34687922 DOI: 10.1016/j.hrthm.2021.10.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 10/18/2021] [Indexed: 11/04/2022]
Affiliation(s)
- Chai-Ann Ng
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia, and St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia, and St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia.
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17
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Ng CA, Farr J, Young P, Windley MJ, Perry MD, Hill AP, Vandenberg JI. Heterozygous KCNH2 variant phenotyping using Flp-In HEK293 and high-throughput automated patch clamp electrophysiology. Biol Methods Protoc 2021; 6:bpab003. [PMID: 33884304 PMCID: PMC8046900 DOI: 10.1093/biomethods/bpab003] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/10/2021] [Accepted: 03/16/2021] [Indexed: 11/13/2022] Open
Abstract
KCNH2 is one of the 59 medically actionable genes recommended by the American College of Medical Genetics for reporting of incidental findings from clinical genomic sequencing. However, half of the reported KCNH2 variants in the ClinVar database are classified as variants of uncertain significance. In the absence of strong clinical phenotypes, there is a need for functional phenotyping to help decipher the significance of variants identified incidentally. Here, we report detailed methods for assessing the molecular phenotype of any KCNH2 missense variant. The key components of the assay include quick and cost-effective generation of a bi-cistronic vector to co-express Wild-type (WT) and any KCNH2 variant allele, generation of stable Flp-In HEK293 cell lines and high-throughput automated patch clamp electrophysiology analysis of channel function. Stable cell lines take 3–4 weeks to produce and can be generated in bulk, which will then allow up to 30 variants to be phenotyped per week after 48 h of channel expression. This high-throughput functional genomics assay will enable a much more rapid assessment of the extent of loss of function of any KCNH2 variant.
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Affiliation(s)
- Chai-Ann Ng
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales 2010, Australia
| | - Jessica Farr
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,School of Computer Science and Engineering, UNSW Sydney, Kensington, New South Wales 2052, Australia
| | - Paul Young
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Monique J Windley
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales 2010, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales 2010, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales 2010, Australia
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18
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Heitmann S, Shpak A, Vandenberg JI, Hill AP. Arrhythmogenic effects of ultra-long and bistable cardiac action potentials. PLoS Comput Biol 2021; 17:e1008683. [PMID: 33591969 PMCID: PMC7909657 DOI: 10.1371/journal.pcbi.1008683] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 02/26/2021] [Accepted: 01/08/2021] [Indexed: 12/04/2022] Open
Abstract
Contemporary accounts of the initiation of cardiac arrhythmias typically rely on after-depolarizations as the trigger for reentrant activity. The after-depolarizations are usually triggered by calcium entry or spontaneous release within the cells of the myocardium or the conduction system. Here we propose an alternative mechanism whereby arrhythmias are triggered autonomously by cardiac cells that fail to repolarize after a normal heartbeat. We investigated the proposal by representing the heart as an excitable medium of FitzHugh-Nagumo cells where a proportion of cells were capable of remaining depolarized indefinitely. As such, those cells exhibit bistable membrane dynamics. We found that heterogeneous media can tolerate a surprisingly large number of bistable cells and still support normal rhythmic activity. Yet there is a critical limit beyond which the medium is persistently arrhythmogenic. Numerical analysis revealed that the critical threshold for arrhythmogenesis depends on both the strength of the coupling between cells and the extent to which the abnormal cells resist repolarization. Moreover, arrhythmogenesis was found to emerge preferentially at tissue boundaries where cells naturally have fewer neighbors to influence their behavior. These findings may explain why atrial fibrillation typically originates from tissue boundaries such as the cuff of the pulmonary vein. Cardiac fibrillation is a medical condition where normal heart function is compromised as electrical activity becomes disordered. How fibrillation arises spontaneously is not fully understood. It is generally thought to be triggered by premature depolarization of the cardiac action potential in one or more cells. Those premature beats, known as after-depolarizations, subsequently initiate a self-sustaining rotor in the otherwise normal heart tissue. In this study, we propose an alternative mechanism whereby arrhythmias are initiated by cardiac cells that fail to repolarize of their own accord but still operate normally when embedded in functional heart tissue. We find that such cells can act as focal ectopic sources under appropriate conditions of inter-cellular coupling. Moreover, those cells are more prone to initiating arrhythmia when they are located on natural tissue boundaries. This may explain why atrial fibrillation typically originates from the site where the pulmonary vein attaches to the wall of the heart.
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Affiliation(s)
- Stewart Heitmann
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- * E-mail:
| | - Anton Shpak
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- Victor Chang Cardiac Research Institute Innovation Centre, Darlinghurst, NSW, Australia
| | - Jamie I. Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- St Vincent’s Clinical School, UNSW Sydney, Kensington, NSW, Australia
| | - Adam P. Hill
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- Victor Chang Cardiac Research Institute Innovation Centre, Darlinghurst, NSW, Australia
- St Vincent’s Clinical School, UNSW Sydney, Kensington, NSW, Australia
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19
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Perry MD, Ng CA, Mangala MM, Ng TYM, Hines AD, Liang W, Xu MJO, Hill AP, Vandenberg JI. Pharmacological activation of IKr in models of long QT Type 2 risks overcorrection of repolarization. Cardiovasc Res 2021; 116:1434-1445. [PMID: 31628797 DOI: 10.1093/cvr/cvz247] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/21/2019] [Accepted: 10/09/2019] [Indexed: 12/11/2022] Open
Abstract
AIMS Current treatment for congenital long QT syndrome Type 2 (cLQTS2), an electrical disorder that increases the risk of life-threatening cardiac arrhythmias, is aimed at reducing the incidence of arrhythmia triggers (beta-blockers) or terminating the arrhythmia after onset (implantable cardioverter-defibrillator). An alternative strategy is to target the underlying disease mechanism, which is reduced rapid delayed rectifier current (IKr) passed by Kv11.1 channels. Small molecule activators of Kv11.1 have been identified but the extent to which these can restore normal cardiac signalling in cLQTS2 backgrounds remains unclear. Here, we examined the ability of ICA-105574, an activator of Kv11.1 that impairs transition to the inactivated state, to restore function to heterozygous Kv11.1 channels containing either inactivation enhanced (T618S, N633S) or expression deficient (A422T) mutations. METHODS AND RESULTS ICA-105574 effectively restored Kv11.1 current from heterozygous inactivation enhanced or expression defective mutant channels in heterologous expression systems. In a human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) model of cLQTS2 containing the expression defective Kv11.1 mutant A422T, cardiac repolarization, estimated from the duration of calcium transients in isolated cells and the rate corrected field potential duration (FPDc) in culture monolayers of cells, was significantly prolonged. The Kv11.1 activator ICA-105574 was able to reverse the prolonged repolarization in a concentration-dependent manner. However, at higher doses, ICA-105574 produced a shortening of the FPDc compared to controls. In vitro and in silico analysis suggests that this overcorrection occurs as a result of a temporal redistribution of the peak IKr to much earlier in the plateau phase of the action potential, which results in early repolarization. CONCLUSION Kv11.1 activators, which target the primary disease mechanism, provide a possible treatment option for cLQTS2, with the caveat that there may be a risk of overcorrection that could itself be pro-arrhythmic.
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Affiliation(s)
- Matthew D Perry
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
| | - Chai-Ann Ng
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
| | - Melissa M Mangala
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Timothy Y M Ng
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
| | - Adam D Hines
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,Queensland Brain Institute, The University of Queensland, St. Lucia 4072, Queensland, Australia
| | - Whitney Liang
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Michelle J O Xu
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, New South Wales, Australia
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20
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Ballouz S, Mangala MM, Perry MD, Heitmann S, Gillis JA, Hill AP, Vandenberg JI. Co-expression of calcium and hERG potassium channels reduces the incidence of proarrhythmic events. Cardiovasc Res 2020; 117:2216-2227. [PMID: 33002116 DOI: 10.1093/cvr/cvaa280] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/25/2020] [Accepted: 09/17/2020] [Indexed: 01/02/2023] Open
Abstract
AIMS Cardiac electrical activity is extraordinarily robust. However, when it goes wrong it can have fatal consequences. Electrical activity in the heart is controlled by the carefully orchestrated activity of more than a dozen different ion conductances. While there is considerable variability in cardiac ion channel expression levels between individuals, studies in rodents have indicated that there are modules of ion channels whose expression co-vary. The aim of this study was to investigate whether meta-analytic co-expression analysis of large-scale gene expression datasets could identify modules of co-expressed cardiac ion channel genes in human hearts that are of functional importance. METHODS AND RESULTS Meta-analysis of 3653 public human RNA-seq datasets identified a strong correlation between expression of CACNA1C (L-type calcium current, ICaL) and KCNH2 (rapid delayed rectifier K+ current, IKr), which was also observed in human adult heart tissue samples. In silico modelling suggested that co-expression of CACNA1C and KCNH2 would limit the variability in action potential duration seen with variations in expression of ion channel genes and reduce susceptibility to early afterdepolarizations, a surrogate marker for proarrhythmia. We also found that levels of KCNH2 and CACNA1C expression are correlated in human-induced pluripotent stem cell-derived cardiac myocytes and the levels of CACNA1C and KCNH2 expression were inversely correlated with the magnitude of changes in repolarization duration following inhibition of IKr. CONCLUSION Meta-analytic approaches of multiple independent human gene expression datasets can be used to identify gene modules that are important for regulating heart function. Specifically, we have verified that there is co-expression of CACNA1C and KCNH2 ion channel genes in human heart tissue, and in silico analyses suggest that CACNA1C-KCNH2 co-expression increases the robustness of cardiac electrical activity.
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Affiliation(s)
- Sara Ballouz
- Garvan-Weizmann Centre for Cellular Genomics, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst NSW 2010, Australia.,University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, One Bungtown Road, NY 11724, USA
| | - Melissa M Mangala
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Matthew D Perry
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Stewart Heitmann
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Jesse A Gillis
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, One Bungtown Road, NY 11724, USA
| | - Adam P Hill
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Jamie I Vandenberg
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
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21
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Kozek KA, Glazer AM, Ng CA, Blackwell D, Egly CL, Vanags LR, Blair M, Mitchell D, Matreyek KA, Fowler DM, Knollmann BC, Vandenberg JI, Roden DM, Kroncke BM. High-throughput discovery of trafficking-deficient variants in the cardiac potassium channel K V11.1. Heart Rhythm 2020; 17:2180-2189. [PMID: 32522694 DOI: 10.1016/j.hrthm.2020.05.041] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 05/27/2020] [Accepted: 05/31/2020] [Indexed: 01/09/2023]
Abstract
BACKGROUND KCHN2 encodes the KV11.1 potassium channel responsible for IKr, a major repolarization current during the cardiomyocyte action potential. Variants in KCNH2 that lead to decreased IKr have been associated with long QT syndrome type 2 (LQT2). The mechanism of LQT2 is most often induced loss of KV11.1 trafficking to the cell surface. Accurately discriminating between variants with normal and abnormal trafficking would aid in understanding the deleterious nature of these variants; however, the volume of reported nonsynonymous KCNH2 variants precludes the use of conventional methods for functional study. OBJECTIVE The purpose of this study was to report a high-throughput, multiplexed screening method for KCNH2 genetic variants capable of measuring the cell surface abundance of hundreds of missense variants in the resulting KV11.1 channel. METHODS We developed a method to quantitate KV11.1 variant trafficking on a pilot region of 11 residues in the S5 helix. RESULTS We generated trafficking scores for 220 of 231 missense variants in the pilot region. For 5 of 5 variants, high-throughput trafficking scores validated when tested in single variant flow cytometry and confocal microscopy experiments. We further explored these results with planar patch electrophysiology and found that loss-of-trafficking variants do not produce IKr. Conversely, but expectedly, some variants that traffic normally were still functionally compromised. CONCLUSION We describe a new method for detecting KV11.1 trafficking-deficient variants in a multiplexed assay. This new method accurately generated trafficking data for variants in KV11.1 and is extendable both to all residues in KV11.1 and to other cell surface proteins.
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Affiliation(s)
- Krystian A Kozek
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Andrew M Glazer
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Chai-Ann Ng
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Daniel Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Christian L Egly
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Loren R Vanags
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Marcia Blair
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Devyn Mitchell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Kenneth A Matreyek
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | - Douglas M Fowler
- Department of Genome Sciences, University of Washington, Seattle, Washington; Department of Bioengineering, University of Washington, Seattle, Washington
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; St Vincent's Clinical School, UNSW Sydney, Darlinghurst, New South Wales, Australia
| | - Dan M Roden
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Brett M Kroncke
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee.
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22
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Lee W, Windley MJ, Perry MD, Vandenberg JI, Hill AP. Protocol-Dependent Differences in IC 50 Values Measured in Human Ether-Á-Go-Go-Related Gene Assays Occur in a Predictable Way and Can Be Used to Quantify State Preference of Drug Binding. Mol Pharmacol 2019; 95:537-550. [PMID: 30770456 DOI: 10.1124/mol.118.115220] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 02/10/2019] [Indexed: 12/22/2022] Open
Abstract
Current guidelines around preclinical screening for drug-induced arrhythmias require the measurement of the potency of block of voltage-gated potassium channel subtype 11.1 (Kv11.1) as a surrogate for risk. A shortcoming of this approach is that the measured IC50 of Kv11.1 block varies widely depending on the voltage protocol used in electrophysiological assays. In this study, we aimed to investigate the factors that contribute to these differences and to identify whether it is possible to make predictions about protocol-dependent block that might facilitate the comparison of potencies measured using different assays. Our data demonstrate that state preferential binding, together with drug-binding kinetics and trapping, is an important determinant of the protocol dependence of Kv11.1 block. We show for the first time that differences in IC50 measured between protocols occurs in a predictable way, such that machine-learning algorithms trained using a selection of simple voltage protocols can indeed predict protocol-dependent potency. Furthermore, we also show that the preference of a drug for binding to the open versus the inactivated state of Kv11.1 can also be inferred from differences in IC50 values measured between protocols. Our work therefore identifies how state preferential drug binding is a major determinant of the protocol dependence of IC50 values measured in preclinical Kv11.1 assays. It also provides a novel method for quantifying the state dependence of Kv11.1 drug binding that will facilitate the development of more complete models of drug binding to Kv11.1 and improve our understanding of proarrhythmic risk associated with compounds that block Kv11.1.
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Affiliation(s)
- William Lee
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Monique J Windley
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute (W.L., M.J.W., M.D.P., J.I.V., A.P.H.) and St Vincent's Clinical School (W.L., M.J.W., M.D.P., J.I.V., A.P.H.), University of New South Wales, Darlinghurst, New South Wales, Australia
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23
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Munawar S, Windley MJ, Tse EG, Todd MH, Hill AP, Vandenberg JI, Jabeen I. Experimentally Validated Pharmacoinformatics Approach to Predict hERG Inhibition Potential of New Chemical Entities. Front Pharmacol 2018; 9:1035. [PMID: 30333745 PMCID: PMC6176658 DOI: 10.3389/fphar.2018.01035] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/27/2018] [Indexed: 12/17/2022] Open
Abstract
The hERG (human ether-a-go-go-related gene) encoded potassium ion (K+) channel plays a major role in cardiac repolarization. Drug-induced blockade of hERG has been a major cause of potentially lethal ventricular tachycardia termed Torsades de Pointes (TdPs). Therefore, we presented a pharmacoinformatics strategy using combined ligand and structure based models for the prediction of hERG inhibition potential (IC50) of new chemical entities (NCEs) during early stages of drug design and development. Integrated GRid-INdependent Descriptor (GRIND) models, and lipophilic efficiency (LipE), ligand efficiency (LE) guided template selection for the structure based pharmacophore models have been used for virtual screening and subsequent hERG activity (pIC50) prediction of identified hits. Finally selected two hits were experimentally evaluated for hERG inhibition potential (pIC50) using whole cell patch clamp assay. Overall, our results demonstrate a difference of less than ±1.6 log unit between experimentally determined and predicted hERG inhibition potential (IC50) of the selected hits. This revealed predictive ability and robustness of our models and could help in correctly rank the potency order (lower μM to higher nM range) against hERG.
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Affiliation(s)
- Saba Munawar
- Research Center for Modeling and Simulation, National University of Science and Technology, Islamabad, Pakistan.,Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | | | - Edwin G Tse
- School of Chemistry, The University of Sydney, Sydney, NSW, Australia
| | - Matthew H Todd
- School of Chemistry, The University of Sydney, Sydney, NSW, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | | | - Ishrat Jabeen
- Research Center for Modeling and Simulation, National University of Science and Technology, Islamabad, Pakistan
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24
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Windley MJ, Lee W, Vandenberg JI, Hill AP. The Temperature Dependence of Kinetics Associated with Drug Block of hERG Channels Is Compound-Specific and an Important Factor for Proarrhythmic Risk Prediction. Mol Pharmacol 2018; 94:760-769. [DOI: 10.1124/mol.117.111534] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 05/02/2018] [Indexed: 01/08/2023] Open
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Beattie KA, Hill AP, Bardenet R, Cui Y, Vandenberg JI, Gavaghan DJ, de Boer TP, Mirams GR. Sinusoidal voltage protocols for rapid characterisation of ion channel kinetics. J Physiol 2018; 596:1813-1828. [PMID: 29573276 PMCID: PMC5978315 DOI: 10.1113/jp275733] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 02/19/2018] [Indexed: 12/21/2022] Open
Abstract
Key points Ion current kinetics are commonly represented by current–voltage relationships, time constant–voltage relationships and subsequently mathematical models fitted to these. These experiments take substantial time, which means they are rarely performed in the same cell. Rather than traditional square‐wave voltage clamps, we fitted a model to the current evoked by a novel sum‐of‐sinusoids voltage clamp that was only 8 s long. Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions. The new model predicts the current under traditional square‐wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically relevant series of action potential clamps is predicted extremely well. The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell–cell variability in current kinetics for the first time.
Abstract Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics – the voltage‐dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fitted a mathematical model to currents evoked by a novel 8 second sinusoidal voltage clamp in CHO cells overexpressing hERG1a. The model was then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step voltage clamps, and also a novel voltage clamp comprising a collection of physiologically relevant action potentials. We demonstrate that we can make predictive cell‐specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell–cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches. Ion current kinetics are commonly represented by current–voltage relationships, time constant–voltage relationships and subsequently mathematical models fitted to these. These experiments take substantial time, which means they are rarely performed in the same cell. Rather than traditional square‐wave voltage clamps, we fitted a model to the current evoked by a novel sum‐of‐sinusoids voltage clamp that was only 8 s long. Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions. The new model predicts the current under traditional square‐wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically relevant series of action potential clamps is predicted extremely well. The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell–cell variability in current kinetics for the first time.
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Affiliation(s)
- Kylie A Beattie
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, OX1 3QD, UK.,Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Adam P Hill
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Sydney, NSW, 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, NSW, 2010, Australia
| | - Rémi Bardenet
- CNRS & CRIStAL, Université de Lille, 59651 Villeneuve d'Ascq, Lille, France
| | - Yi Cui
- Safety Evaluation and Risk Management, Global Clinical Safety and Pharmacovigilance, GlaxoSmithKline, Uxbridge, UB11 1BS, UK
| | - Jamie I Vandenberg
- Department of Molecular Cardiology and Biophysics, Victor Chang Cardiac Research Institute, Sydney, NSW, 2010, Australia.,St Vincent's Clinical School, UNSW Sydney, Darlinghurst, NSW, 2010, Australia
| | - David J Gavaghan
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, OX1 3QD, UK
| | - Teun P de Boer
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Gary R Mirams
- Centre for Mathematical Medicine & Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
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26
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Lau C, Hunter MJ, Stewart A, Perozo E, Vandenberg JI. Never at rest: insights into the conformational dynamics of ion channels from cryo-electron microscopy. J Physiol 2018; 596:1107-1119. [PMID: 29377132 PMCID: PMC5878226 DOI: 10.1113/jp274888] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 12/27/2017] [Indexed: 01/04/2023] Open
Abstract
The tightly regulated opening and closure of ion channels underlies the electrical signals that are vital for a wide range of physiological processes. Two decades ago the first atomic level view of ion channel structures led to a detailed understanding of ion selectivity and conduction. In recent years, spectacular developments in the field of cryo-electron microscopy have resulted in cryo-EM superseding crystallography as the technique of choice for determining near-atomic resolution structures of ion channels. Here, we will review the recent developments in cryo-EM and its specific application to the study of ion channel gating. We will highlight the advantages and disadvantages of the current technology and where the field is likely to head in the next few years.
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Affiliation(s)
- Carus Lau
- Victor Chang Cardiac Research InstituteDarlinghurstNSW2010Australia
- St Vincent's Clinical SchoolUniversity of NSWDarlinghurstNSW2010Australia
| | - Mark J. Hunter
- Victor Chang Cardiac Research InstituteDarlinghurstNSW2010Australia
| | - Alastair Stewart
- Victor Chang Cardiac Research InstituteDarlinghurstNSW2010Australia
- St Vincent's Clinical SchoolUniversity of NSWDarlinghurstNSW2010Australia
| | - Eduardo Perozo
- Department of Biochemistry and Molecular BiologyUniversity of ChicagoChicagoIL60637USA
| | - Jamie I. Vandenberg
- Victor Chang Cardiac Research InstituteDarlinghurstNSW2010Australia
- St Vincent's Clinical SchoolUniversity of NSWDarlinghurstNSW2010Australia
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27
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Beattie KA, Hill AP, Bardenet R, Cui Y, Vandenberg JI, Gavaghan DJ, de Boer TP, Mirams GR. Sinusoidal Voltage Protocols for Rapid Characterisation of Ion Channel Kinetics. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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28
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Lee W, Windley MJ, Vandenberg JI, Hill AP. In Vitro and In Silico Risk Assessment in Acquired Long QT Syndrome: The Devil Is in the Details. Front Physiol 2017; 8:934. [PMID: 29201009 PMCID: PMC5696636 DOI: 10.3389/fphys.2017.00934] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 11/03/2017] [Indexed: 12/16/2022] Open
Abstract
Acquired long QT syndrome, mostly as a result of drug block of the Kv11. 1 potassium channel in the heart, is characterized by delayed cardiac myocyte repolarization, prolongation of the T interval on the ECG, syncope and sudden cardiac death due to the polymorphic ventricular arrhythmia Torsade de Pointes (TdP). In recent years, efforts are underway through the Comprehensive in vitro proarrhythmic assay (CiPA) initiative, to develop better tests for this drug induced arrhythmia based in part on in silico simulations of pharmacological disruption of repolarization. However, drug binding to Kv11.1 is more complex than a simple binary molecular reaction, meaning simple steady state measures of potency are poor surrogates for risk. As a result, there is a plethora of mechanistic detail describing the drug/Kv11.1 interaction—such as drug binding kinetics, state preference, temperature dependence and trapping—that needs to be considered when developing in silico models for risk prediction. In addition to this, other factors, such as multichannel pharmacological profile and the nature of the ventricular cell models used in simulations also need to be considered in the search for the optimum in silico approach. Here we consider how much of mechanistic detail needs to be included for in silico models to accurately predict risk and further, how much of this detail can be retrieved from protocols that are practical to implement in high throughout screens as part of next generation of preclinical in silico drug screening approaches?
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Affiliation(s)
- William Lee
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Monique J Windley
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Adam P Hill
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
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29
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Beattie KA, Bardenet R, Louttit JB, Vandenberg JI, Hill AP, Gavaghan DJ, de Boer TP, Mirams GR. Mathematical Modelling of hERG Channel Kinetics Using Sinusoidal Voltage Protocols. J Pharmacol Toxicol Methods 2017. [DOI: 10.1016/j.vascn.2017.09.089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
There have been tremendous advances in the diagnosis and treatment of heart disease over the last 50 years. Nevertheless, it remains the number one cause of death. About half of heart-related deaths occur suddenly, and in about half of these cases the person was unaware that they had underlying heart disease. Genetic heart disease accounts for only approximately 2% of sudden cardiac deaths, but as it typically occurs in younger people it has been a particular focus of activity in our quest to not only understand the underlying mechanisms of cardiac arrhythmogenesis but also develop better strategies for earlier detection and prevention. In this brief review, we will highlight trends in the recent literature focused on sudden cardiac death in genetic heart diseases and how these studies are contributing to a broader understanding of sudden death in the community.
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Affiliation(s)
- Jamie I Vandenberg
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia.,Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Matthew D Perry
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia.,Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Adam P Hill
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia.,Victor Chang Cardiac Research Institute, Darlinghurst, Australia
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Vandenberg JI, Perozo E, Allen TW. Towards a Structural View of Drug Binding to hERG K + Channels. Trends Pharmacol Sci 2017; 38:899-907. [PMID: 28711156 DOI: 10.1016/j.tips.2017.06.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 06/09/2017] [Accepted: 06/14/2017] [Indexed: 01/10/2023]
Abstract
The human ether-a-go-go-related gene (hERG) K+ channel is of great medical and pharmaceutical relevance. Inherited mutations in hERG result in congenital long-QT syndrome which is associated with a markedly increased risk of cardiac arrhythmia and sudden death. hERG K+ channels are also remarkably susceptible to block by a wide range of drugs, which in turn can cause drug-induced long-QT syndrome and an increased risk of sudden death. The recent determination of the near-atomic resolution structure of the hERG K+ channel, using single-particle cryo-electron microscopy (cryo-EM), provides tremendous insights into how these channels work. It also suggests a way forward in our quest to understand why these channels are so promiscuous with respect to drug binding.
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Affiliation(s)
- Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW 2010, Australia.
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, VIC 3001, Australia
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32
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Phan K, Ng CA, David E, Shishmarev D, Kuchel PW, Vandenberg JI, Perry MD. The S1 helix critically regulates the finely tuned gating of Kv11.1 channels. J Biol Chem 2017; 292:7688-7705. [PMID: 28280240 DOI: 10.1074/jbc.m117.779298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 02/26/2017] [Indexed: 11/06/2022] Open
Abstract
Congenital mutations in the cardiac Kv11.1 channel can cause long QT syndrome type 2 (LQTS2), a heart rhythm disorder associated with sudden cardiac death. Mutations act either by reducing protein expression at the membrane and/or by perturbing the intricate gating properties of Kv11.1 channels. A number of clinical LQTS2-associated mutations have been reported in the first transmembrane segment (S1) of Kv11.1 channels, but the role of this region of the channel is largely unexplored. In part, this is due to problems defining the extent of the S1 helix, as a consequence of its low sequence homology with other Kv family members. Here, we used NMR spectroscopy and electrophysiological characterization to show that the S1 of Kv11.1 channels extends seven helical turns, from Pro-405 to Phe-431, and is flanked by unstructured loops. Functional analysis suggests that pre-S1 loop residues His-402 and Tyr-403 play an important role in regulating the kinetics and voltage dependence of channel activation and deactivation. Multiple residues within the S1 helix also play an important role in fine-tuning the voltage dependence of activation, regulating slow deactivation, and modulating C-type inactivation of Kv11.1 channels. Analyses of LQTS2-associated mutations in the pre-S1 loop or S1 helix of Kv11.1 channels demonstrate perturbations to both protein expression and most gating transitions. Thus, S1 region mutations would reduce both the action potential repolarizing current passed by Kv11.1 channels in cardiac myocytes, as well as the current passed in response to premature depolarizations that normally helps protect against the formation of ectopic beats.
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Affiliation(s)
- Kevin Phan
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Chai Ann Ng
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Erikka David
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010
| | - Dmitry Shishmarev
- the School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Philip W Kuchel
- the School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Jamie I Vandenberg
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010.,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
| | - Matthew D Perry
- From the Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales 2010, .,the St. Vincent's Clinical School, University of New South Wales, New South Wales 2052, and
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33
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Windley MJ, Abi-Gerges N, Fermini B, Hancox JC, Vandenberg JI, Hill AP. Measuring kinetics and potency of hERG block for CiPA. J Pharmacol Toxicol Methods 2017; 87:99-107. [PMID: 28192183 DOI: 10.1016/j.vascn.2017.02.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 01/25/2017] [Accepted: 02/07/2017] [Indexed: 12/20/2022]
Abstract
INTRODUCTION The Comprehensive in vitro Proarrhythmic Assay (CiPA) aims to update current cardiac safety testing to better evaluate arrhythmic risk. A central theme of CiPA is the use of in silico approaches to risk prediction incorporating models of drug binding to hERG. To parameterize these models, accurate in vitro measurement of potency and kinetics of block is required. The Ion Channel Working Group was tasked with: i) selecting a protocol that could measure kinetics of block and was easily implementable on automated platforms for future rollout in industry and ii) acquiring a reference dataset using the standardized protocol. METHODS Data were acquired using a 'step depolarisation' protocol using manual patch-clamp at ambient temperature. RESULTS Potency, kinetics and trapping characteristics of hERG block for the CiPA training panel of twelve drugs were measured. Timecourse of block and trapping characteristics could be reliably measured if the time constant for onset of block was between ~500ms and ~15s. Seven drugs, however had time courses of block faster than this cut-off. DISCUSSION Here we describe the implementation of the standardized protocol for measurement of kinetics and potency of hERG block for CiPA. The results highlight the challenges in identifying a single protocol to measure hERG block over a range of kinetics. The dataset from this study is being used by the In Silico Working Group to develop models of drug binding for risk prediction and is freely available as a 'gold standard' ambient temperature dataset to evaluate variability across high throughput platforms.
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Affiliation(s)
- Monique J Windley
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Sydney, NSW 2010, Australia; St. Vincent's Clinical School, University of New South Wales, Sydney, NSW 2052, Australia
| | | | - Bernard Fermini
- Coyne Scientific, LLC, 58 Edgewood Ave NE Atlanta, GA 30303, USA
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, UK
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Sydney, NSW 2010, Australia; St. Vincent's Clinical School, University of New South Wales, Sydney, NSW 2052, Australia
| | - Adam P Hill
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Sydney, NSW 2010, Australia; St. Vincent's Clinical School, University of New South Wales, Sydney, NSW 2052, Australia.
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34
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Hill AP, Mann SA, Imtiaz MS, Perry MD, Vandenberg JI. Using Clinical Datasets to Optimize Models of Human Ventricular Electrophysiology: Implications for In Silico Drug Screening. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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35
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Chiamvimonvat N, Chen-Izu Y, Clancy CE, Deschenes I, Dobrev D, Heijman J, Izu L, Qu Z, Ripplinger CM, Vandenberg JI, Weiss JN, Koren G, Banyasz T, Grandi E, Sanguinetti MC, Bers DM, Nerbonne JM. Potassium currents in the heart: functional roles in repolarization, arrhythmia and therapeutics. J Physiol 2017; 595:2229-2252. [PMID: 27808412 DOI: 10.1113/jp272883] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/11/2016] [Indexed: 12/19/2022] Open
Abstract
This is the second of the two White Papers from the fourth UC Davis Cardiovascular Symposium Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias (3-4 March 2016), a biennial event that brings together leading experts in different fields of cardiovascular research. The theme of the 2016 symposium was 'K+ channels and regulation', and the objectives of the conference were severalfold: (1) to identify current knowledge gaps; (2) to understand what may go wrong in the diseased heart and why; (3) to identify possible novel therapeutic targets; and (4) to further the development of systems biology approaches to decipher the molecular mechanisms and treatment of cardiac arrhythmias. The sessions of the Symposium focusing on the functional roles of the cardiac K+ channel in health and disease, as well as K+ channels as therapeutic targets, were contributed by Ye Chen-Izu, Gideon Koren, James Weiss, David Paterson, David Christini, Dobromir Dobrev, Jordi Heijman, Thomas O'Hara, Crystal Ripplinger, Zhilin Qu, Jamie Vandenberg, Colleen Clancy, Isabelle Deschenes, Leighton Izu, Tamas Banyasz, Andras Varro, Heike Wulff, Eleonora Grandi, Michael Sanguinetti, Donald Bers, Jeanne Nerbonne and Nipavan Chiamvimonvat as speakers and panel discussants. This article summarizes state-of-the-art knowledge and controversies on the functional roles of cardiac K+ channels in normal and diseased heart. We endeavour to integrate current knowledge at multiple scales, from the single cell to the whole organ levels, and from both experimental and computational studies.
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Affiliation(s)
- Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, Genome and Biomedical Science Facility, Rm 2303, Davis, CA, 95616, USA
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44109, USA.,Heart and Vascular Research Center, MetroHealth Medical Center, Cleveland, OH, 44109, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Leighton Izu
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Zhilin Qu
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
| | - James N Weiss
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Gideon Koren
- Cardiovascular Research Center, Rhode Island Hospital and the Cardiovascular Institute, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Tamas Banyasz
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research & Training Institute, Salt Lake City, UT, 84112, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jeanne M Nerbonne
- Departments of Developmental Biology and Internal Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, 63110, USA
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Abstract
The sudden unexpected death of a child is a devastating event. One of the first questions a family will ask is “Why did this happen?” In some cases, the answer may become obvious during a postmortem examination, but in up to 40% of cases, the postmortem is negative (Bagnall et al, 2016). In the last 1–2 decades, an improved understanding of the genetic basis of the primary arrhythmia syndromes, the major cause of sudden unexplained death in children with structurally normal hearts, has greatly enhanced our ability to make a postmortem diagnosis (Van Norstrand & Ackerman, 2010). Establishing an accurate genetic diagnosis can not only answer the parents' question as to why did this happen to my child, but is invaluable for cascade screening of all family members to identify other individuals harbouring the same mutation and who therefore may be at risk of sudden cardiac death. However, even after screening for all of the established genes associated with primary arrhythmia syndromes, up to two thirds of unexplained cardiac deaths will remain unsolved. Such was the case for a family of Sudanese origin with a highly malignant form of exercise‐induced arrhythmias, originally reported by Bhuiyan et al (2007).
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Affiliation(s)
- Matthew D Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Jamie I Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
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37
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Grandi E, Sanguinetti MC, Bartos DC, Bers DM, Chen-Izu Y, Chiamvimonvat N, Colecraft HM, Delisle BP, Heijman J, Navedo MF, Noskov S, Proenza C, Vandenberg JI, Yarov-Yarovoy V. Potassium channels in the heart: structure, function and regulation. J Physiol 2016; 595:2209-2228. [PMID: 27861921 DOI: 10.1113/jp272864] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 07/18/2016] [Indexed: 12/22/2022] Open
Abstract
This paper is the outcome of the fourth UC Davis Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias Symposium, a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2016 symposium was 'K+ Channels and Regulation'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies and challenges on the topic of cardiac K+ channels. This paper summarizes the topics of formal presentations and informal discussions from the symposium on the structural basis of voltage-gated K+ channel function, as well as the mechanisms involved in regulation of K+ channel gating, expression and membrane localization. Given the critical role for K+ channels in determining the rate of cardiac repolarization, it is hardly surprising that essentially every aspect of K+ channel function is exquisitely regulated in cardiac myocytes. This regulation is complex and highly interrelated to other aspects of myocardial function. K+ channel regulatory mechanisms alter, and are altered by, physiological challenges, pathophysiological conditions, and pharmacological agents. An accompanying paper focuses on the integrative role of K+ channels in cardiac electrophysiology, i.e. how K+ currents shape the cardiac action potential, and how their dysfunction can lead to arrhythmias, and discusses K+ channel-based therapeutics. A fundamental understanding of K+ channel regulatory mechanisms and disease processes is fundamental to reveal new targets for human therapy.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, 84112, USA
| | - Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA.,Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, KY, 40536, USA
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Sergei Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado - Anschutz Medical Campus, Denver, CO, 80045, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, CA, 95616, USA
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38
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Mann SA, Imtiaz M, Winbo A, Rydberg A, Perry MD, Couderc JP, Polonsky B, McNitt S, Zareba W, Hill AP, Vandenberg JI. Convergence of models of human ventricular myocyte electrophysiology after global optimization to recapitulate clinical long QT phenotypes. J Mol Cell Cardiol 2016; 100:25-34. [DOI: 10.1016/j.yjmcc.2016.09.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/11/2016] [Accepted: 09/19/2016] [Indexed: 12/15/2022]
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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40
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Immanuel SA, Sadrieh A, Baumert M, Couderc JP, Zareba W, Hill AP, Vandenberg JI. T-wave morphology can distinguish healthy controls from LQTS patients. Physiol Meas 2016; 37:1456-73. [PMID: 27510854 DOI: 10.1088/0967-3334/37/9/1456] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Long QT syndrome (LQTS) is an inherited disorder associated with prolongation of the QT/QTc interval on the surface electrocardiogram (ECG) and a markedly increased risk of sudden cardiac death due to cardiac arrhythmias. Up to 25% of genotype-positive LQTS patients have QT/QTc intervals in the normal range. These patients are, however, still at increased risk of life-threatening events compared to their genotype-negative siblings. Previous studies have shown that analysis of T-wave morphology may enhance discrimination between control and LQTS patients. In this study we tested the hypothesis that automated analysis of T-wave morphology from Holter ECG recordings could distinguish between control and LQTS patients with QTc values in the range 400-450 ms. Holter ECGs were obtained from the Telemetric and Holter ECG Warehouse (THEW) database. Frequency binned averaged ECG waveforms were obtained and extracted T-waves were fitted with a combination of 3 sigmoid functions (upslope, downslope and switch) or two 9th order polynomial functions (upslope and downslope). Neural network classifiers, based on parameters obtained from the sigmoid or polynomial fits to the 1 Hz and 1.3 Hz ECG waveforms, were able to achieve up to 92% discrimination between control and LQTS patients and 88% discrimination between LQTS1 and LQTS2 patients. When we analysed a subgroup of subjects with normal QT intervals (400-450 ms, 67 controls and 61 LQTS), T-wave morphology based parameters enabled 90% discrimination between control and LQTS patients, compared to only 71% when the groups were classified based on QTc alone. In summary, our Holter ECG analysis algorithms demonstrate the feasibility of using automated analysis of T-wave morphology to distinguish LQTS patients, even those with normal QTc, from healthy controls.
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Affiliation(s)
- S A Immanuel
- Mark Cowley Lidwill Research Program in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, Australia. Department of Electrical and Electronics Engineering, University of Adelaide, Adelaide, Australia
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41
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Hill AP, Perry MD, Abi-Gerges N, Couderc JP, Fermini B, Hancox JC, Knollmann BC, Mirams GR, Skinner J, Zareba W, Vandenberg JI. Computational cardiology and risk stratification for sudden cardiac death: one of the grand challenges for cardiology in the 21st century. J Physiol 2016; 594:6893-6908. [PMID: 27060987 PMCID: PMC5134408 DOI: 10.1113/jp272015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 03/16/2016] [Indexed: 12/25/2022] Open
Abstract
Risk stratification in the context of sudden cardiac death has been acknowledged as one of the major challenges facing cardiology for the past four decades. In recent years, the advent of high performance computing has facilitated organ-level simulation of the heart, meaning we can now examine the causes, mechanisms and impact of cardiac dysfunction in silico. As a result, computational cardiology, largely driven by the Physiome project, now stands at the threshold of clinical utility in regards to risk stratification and treatment of patients at risk of sudden cardiac death. In this white paper, we outline a roadmap of what needs to be done to make this translational step, using the relatively well-developed case of acquired or drug-induced long QT syndrome as an exemplar case.
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Affiliation(s)
- Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Matthew D Perry
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Najah Abi-Gerges
- AnaBios Corporation, 3030 Bunker Hill St., San Diego, CA, 92109, USA
| | | | - Bernard Fermini
- Global Safety Pharmacology, Pfizer Inc, MS8274-1347 Eastern Point Road, Groton, CT, 06340, USA
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Bjorn C Knollmann
- Vanderbilt University School of Medicine, 1285 Medical Research Building IV, Nashville, Tennessee, 37232, USA
| | - Gary R Mirams
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Jon Skinner
- Cardiac Inherited Disease Group, Starship Hospital, Auckland, New Zealand
| | - Wojciech Zareba
- University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.,St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2052, Australia
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42
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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43
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Windley MJ, Mann SA, Vandenberg JI, Hill AP. Temperature Effects on Kinetics of KV11.1 Drug Block Have Important Consequences for In Silico Proarrhythmic Risk Prediction. Mol Pharmacol 2016; 90:1-11. [PMID: 27190211 DOI: 10.1124/mol.115.103127] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 05/11/2016] [Indexed: 01/08/2023] Open
Abstract
Drug block of voltage-gated potassium channel subtype 11.1 human ether-a-go-go related gene (Kv11.1) (hERG) channels, encoded by the KCNH2 gene, is associated with reduced repolarization of the cardiac action potential and is the predominant cause of acquired long QT syndrome that can lead to fatal cardiac arrhythmias. Current safety guidelines require that potency of KV11.1 block is assessed in the preclinical phase of drug development. However, not all drugs that block KV11.1 are proarrhythmic, meaning that screening on the basis of equilibrium measures of block can result in high attrition of potentially low-risk drugs. The basis of the next generation of drug-screening approaches is set to be in silico risk prediction, informed by in vitro mechanistic descriptions of drug binding, including measures of the kinetics of block. A critical issue in this regard is characterizing the temperature dependence of drug binding. Specifically, it is important to address whether kinetics relevant to physiologic temperatures can be inferred or extrapolated from in vitro data gathered at room temperature in high-throughout systems. Here we present the first complete study of the temperature-dependent kinetics of block and unblock of a proarrhythmic drug, cisapride, to KV11.1. Our data highlight a complexity to binding that manifests at higher temperatures and can be explained by accumulation of an intermediate, non-blocking encounter-complex. These results suggest that for cisapride, physiologically relevant kinetic parameters cannot be simply extrapolated from those measured at lower temperatures; rather, data gathered at physiologic temperatures should be used to constrain in silico models that may be used for proarrhythmic risk prediction.
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Affiliation(s)
- Monique J Windley
- Computational Cardiology, Victor Chang Cardiac Research Institute, Darlinghurst, Australia (M.J.W., S.A.M., J.I.V., A.P.H.); and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia (S.A.M., J.I.V., A.P.H.)
| | - Stefan A Mann
- Computational Cardiology, Victor Chang Cardiac Research Institute, Darlinghurst, Australia (M.J.W., S.A.M., J.I.V., A.P.H.); and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia (S.A.M., J.I.V., A.P.H.)
| | - Jamie I Vandenberg
- Computational Cardiology, Victor Chang Cardiac Research Institute, Darlinghurst, Australia (M.J.W., S.A.M., J.I.V., A.P.H.); and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia (S.A.M., J.I.V., A.P.H.)
| | - Adam P Hill
- Computational Cardiology, Victor Chang Cardiac Research Institute, Darlinghurst, Australia (M.J.W., S.A.M., J.I.V., A.P.H.); and St. Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia (S.A.M., J.I.V., A.P.H.)
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44
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Vandenberg JI, Hill AP. An 'alternans' way to quantify arrhythmogenic substrates. J Physiol 2016; 594:2375-6. [PMID: 27126416 DOI: 10.1113/jp271838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 12/23/2015] [Indexed: 11/08/2022] Open
Affiliation(s)
- Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of NSW, Victoria Street, Darlinghurst, NSW, 2010, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, University of NSW, Victoria Street, Darlinghurst, NSW, 2010, Australia
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45
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Hodkinson EC, Neijts M, Sadrieh A, Imtiaz MS, Baumert M, Subbiah RN, Hayward CS, Boomsma D, Willemsen G, Vandenberg JI, Hill AP, De Geus E. Heritability of ECG Biomarkers in the Netherlands Twin Registry Measured from Holter ECGs. Front Physiol 2016; 7:154. [PMID: 27199769 PMCID: PMC4850154 DOI: 10.3389/fphys.2016.00154] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 04/11/2016] [Indexed: 11/17/2022] Open
Abstract
Introduction: The resting ECG is the most commonly used tool to assess cardiac electrophysiology. Previous studies have estimated heritability of ECG parameters based on these snapshots of the cardiac electrical activity. In this study we set out to determine whether analysis of heart rate specific data from Holter ECGs allows more complete assessment of the heritability of ECG parameters. Methods and Results: Holter ECGs were recorded from 221 twin pairs and analyzed using a multi-parameter beat binning approach. Heart rate dependent estimates of heritability for QRS duration, QT interval, Tpeak–Tend and Theight were calculated using structural equation modeling. QRS duration is largely determined by environmental factors whereas repolarization is primarily genetically determined. Heritability estimates of both QT interval and Theight were significantly higher when measured from Holter compared to resting ECGs and the heritability estimate of each was heart rate dependent. Analysis of the genetic contribution to correlation between repolarization parameters demonstrated that covariance of individual ECG parameters at different heart rates overlap but at each specific heart rate there was relatively little overlap in the genetic determinants of the different repolarization parameters. Conclusions: Here we present the first study of heritability of repolarization parameters measured from Holter ECGs. Our data demonstrate that higher heritability can be estimated from the Holter than the resting ECG and reveals rate dependence in the genetic—environmental determinants of the ECG that has not previously been tractable. Future applications include deeper dissection of the ECG of participants with inherited cardiac electrical disease.
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Affiliation(s)
- Emily C Hodkinson
- Molecular Cardiology and Biophysics, Victor Chang Cardiac Research InstituteDarlinghurst, NSW, Australia; St Vincent's Clinical School, University of New South WalesSydney, NSW, Australia
| | - Melanie Neijts
- Department of Biological Psychology, EMGO+ Institute, VU University and VU Medical Center Amsterdam, Netherlands
| | - Arash Sadrieh
- Molecular Cardiology and Biophysics, Victor Chang Cardiac Research InstituteDarlinghurst, NSW, Australia; St Vincent's Clinical School, University of New South WalesSydney, NSW, Australia
| | - Mohammad S Imtiaz
- Molecular Cardiology and Biophysics, Victor Chang Cardiac Research InstituteDarlinghurst, NSW, Australia; St Vincent's Clinical School, University of New South WalesSydney, NSW, Australia
| | - Mathias Baumert
- School of Electrical and Electronic Engineering, University of Adelaide Adelaide, SA, Australia
| | - Rajesh N Subbiah
- St Vincent's Clinical School, University of New South Wales Sydney, NSW, Australia
| | | | - Dorret Boomsma
- Department of Biological Psychology, EMGO+ Institute, VU University and VU Medical Center Amsterdam, Netherlands
| | - Gonneke Willemsen
- Department of Biological Psychology, EMGO+ Institute, VU University and VU Medical Center Amsterdam, Netherlands
| | - Jamie I Vandenberg
- Molecular Cardiology and Biophysics, Victor Chang Cardiac Research InstituteDarlinghurst, NSW, Australia; St Vincent's Clinical School, University of New South WalesSydney, NSW, Australia
| | - Adam P Hill
- Molecular Cardiology and Biophysics, Victor Chang Cardiac Research InstituteDarlinghurst, NSW, Australia; St Vincent's Clinical School, University of New South WalesSydney, NSW, Australia
| | - Eco De Geus
- Department of Biological Psychology, EMGO+ Institute, VU University and VU Medical Center Amsterdam, Netherlands
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46
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Christensen AH, Chatelain FC, Huttner IG, Olesen MS, Soka M, Feliciangeli S, Horvat C, Santiago CF, Vandenberg JI, Schmitt N, Olesen SP, Lesage F, Fatkin D. The two-pore domain potassium channel, TWIK-1, has a role in the regulation of heart rate and atrial size. J Mol Cell Cardiol 2016; 97:24-35. [PMID: 27103460 DOI: 10.1016/j.yjmcc.2016.04.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/11/2016] [Accepted: 04/14/2016] [Indexed: 12/24/2022]
Abstract
The two-pore domain potassium (K(+)) channel TWIK-1 (or K2P1.1) contributes to background K(+) conductance in diverse cell types. TWIK-1, encoded by the KCNK1 gene, is present in the human heart with robust expression in the atria, however its physiological significance is unknown. To evaluate the cardiac effects of TWIK-1 deficiency, we studied zebrafish embryos after knockdown of the two KCNK1 orthologues, kcnk1a and kcnk1b. Knockdown of kcnk1a or kcnk1b individually caused bradycardia and atrial dilation (p<0.001 vs. controls), while ventricular stroke volume was preserved. Combined knockdown of both kcnk1a and kcnk1b resulted in a more severe phenotype, which was partially reversed by co-injection of wild-type human KCNK1 mRNA, but not by a dominant negative variant of human KCNK1 mRNA. To determine whether genetic variants in KCNK1 might cause atrial fibrillation (AF), we sequenced protein-coding regions in two independent cohorts of patients (373 subjects) and identified three non-synonymous variants, p.R171H, p.I198M and p.G236S, that were all located in highly conserved amino acid residues. In transfected mammalian cells, zebrafish and wild-type human TWIK-1 channels had a similar cellular distribution with predominant localization in the endosomal compartment. Two-electrode voltage-clamp experiments using Xenopus oocytes showed that both zebrafish and wild-type human TWIK-1 channels produced K(+) currents that are sensitive to external K(+) concentration as well as acidic pH. There were no effects of the three KCNK1 variants on cellular localization, current amplitude or reversal potential at pH7.4 or pH6. Our data indicate that TWIK-1 has a highly conserved role in cardiac function and is required for normal heart rate and atrial morphology. Despite the functional importance of TWIK-1 in the atrium, genetic variation in KCNK1 is not a common primary cause of human AF.
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Affiliation(s)
- Alex Hørby Christensen
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Franck C Chatelain
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia-Antipolis, Sophia-Antipolis, Valbonne, France
| | - Inken G Huttner
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Morten Salling Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Magdalena Soka
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Sylvain Feliciangeli
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia-Antipolis, Sophia-Antipolis, Valbonne, France
| | - Claire Horvat
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Celine F Santiago
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Søren-Peter Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Florian Lesage
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, and Université de Nice Sophia-Antipolis, Sophia-Antipolis, Valbonne, France
| | - Diane Fatkin
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia; Cardiology Department, St Vincent's Hospital, Darlinghurst, New South Wales, Australia.
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47
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Perry MD, Ng CA, Mann SA, Sadrieh A, Imtiaz M, Hill AP, Vandenberg JI. Getting to the heart of hERG K(+) channel gating. J Physiol 2016; 593:2575-85. [PMID: 25820318 DOI: 10.1113/jp270095] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/13/2015] [Indexed: 12/24/2022] Open
Abstract
Potassium ion channels encoded by the human ether-a-go-go related gene (hERG) form the ion-conducting subunit of the rapid delayed rectifier potassium current (IKr ). Although hERG channels exhibit a widespread tissue distribution they play a particularly important role in the heart. There has been considerable interest in hERG K(+) channels for three main reasons. First, they have very unusual gating kinetics, most notably rapid and voltage-dependent inactivation coupled to slow deactivation, which has led to the suggestion that they may play a specific role in the suppression of arrhythmias. Second, mutations in hERG are the cause of 30-40% of cases of congenital long QT syndrome (LQTS), the commonest inherited primary arrhythmia syndrome. Third, hERG is the molecular target for the vast majority of drugs that cause drug-induced LQTS, the commonest cause of drug-induced arrhythmias and cardiac death. Drug-induced LQTS has now been reported for a large range of both cardiac and non-cardiac drugs, in which this side effect is entirely undesired. In recent years there have been comprehensive reviews published on hERG K(+) channels (Vandenberg et al. 2012) and we will not re-cover this ground. Rather, we focus on more recent work on the structural basis and dynamics of hERG gating with an emphasis on how the latest developments may facilitate translational research in the area of stratifying risk of arrhythmias.
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Affiliation(s)
- Matthew D Perry
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Chai-Ann Ng
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Stefan A Mann
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Arash Sadrieh
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Mohammad Imtiaz
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, University of NSW, Darlinghurst, NSW 2010, Australia
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Mann SA, Vandenberg JI, Hill AP. Sudden Infant Death and Modulation of Late Sodium Current by Hypoxia, Investigated in Induced Pluripotent Stem Cells. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Heide J, Zhang F, Bigos KL, Mann SA, Carr VJ, Shannon Weickert C, Green MJ, Weinberger DR, Vandenberg JI. Differential Response to Risperidone in Schizophrenia Patients by KCNH2 Genotype and Drug Metabolizer Status. Am J Psychiatry 2016; 173:53-9. [PMID: 26481172 DOI: 10.1176/appi.ajp.2015.14050653] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Antipsychotic drugs target dopamine and serotonin receptors as well as Kv11.1 potassium channels encoded by KCNH2. Variable patient responses and a wide range of side effects, however, limit their efficacy. Slow metabolizer status and gene variants in KCNH2 associated with increased expression of Kv11.1-3.1, an alternatively spliced isoform of Kv11.1, are correlated with improved responses to antipsychotic medications. Here, the authors test the hypothesis that these effects may be influenced by differential drug binding to Kv11.1 channel isoforms. METHOD Drug block of Kv11.1 isoforms was tested in cellular electrophysiology assays. The effects of drug metabolism and KCNH2 genotypes on clinical responses were assessed in patients enrolled in the multicenter Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE). RESULTS Risperidone caused greater in vitro block of the alternatively spliced Kv11.1-3.1 isoform than full-length Kv11.1-1A channels, whereas its metabolite paliperidone and other atypical antipsychotics have similar potencies for the two isoforms. In the CATIE study (N=362), patients with genotypes associated with increased Kv11.1-3.1 expression (N=52) showed a better treatment response to risperidone compared with other drugs, but this association was dependent on metabolism status. Patients with KCNH2 risk genotypes and slow metabolizer status (approximately 7% of patients) showed marked improvement in symptoms when treated with risperidone compared with patients with fast metabolizer status or without the KCNH2 risk genotypes. CONCLUSIONS These data support the hypothesis that Kv11.1 channels play a role in the therapeutic action of antipsychotic drugs, particularly risperidone, and further highlight the promise of optimizing response with genotype-guided therapy for schizophrenia patients.
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Affiliation(s)
- Juliane Heide
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Fengyu Zhang
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Kristin L Bigos
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Stefan A Mann
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Vaughan J Carr
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Cynthia Shannon Weickert
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Melissa J Green
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Daniel R Weinberger
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
| | - Jamie I Vandenberg
- From the Victor Chang Cardiac Research Institute, Darlinghurst, Australia; St. Vincent's Clinical School, University of New South Wales, Darlinghurst; the Schizophrenia Research Institute, Darlinghurst; the Lieber Institute for Brain Development, Baltimore; the Department of Psychiatry and Behavioral Sciences, the Department of Neurology, the Department of Neuroscience, the Institute of Genetic Medicine, and the Department of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore; the School of Psychiatry, University of New South Wales, Randwick; the Research Unit for Schizophrenia Epidemiology, University of New South Wales, Darlinghurst; and Neuroscience Research Australia, Randwick
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Lee W, Mann SA, Windley MJ, Imtiaz MS, Vandenberg JI, Hill AP. In silico assessment of kinetics and state dependent binding properties of drugs causing acquired LQTS. Prog Biophys Mol Biol 2015; 120:89-99. [PMID: 26713558 DOI: 10.1016/j.pbiomolbio.2015.12.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 11/06/2015] [Accepted: 12/16/2015] [Indexed: 11/24/2022]
Abstract
The Kv11.1 or hERG potassium channel is responsible for one of the major repolarising currents (IKr) in cardiac myocytes. Drug binding to hERG can result in reduction in IKr, action potential prolongation, acquired long QT syndrome and fatal cardiac arrhythmias. The current guidelines for pre-clinical assessment of drugs in development is based on the measurement of the drug concentration that causes 50% current block, i.e., IC50. However, drugs with the same apparent IC50 may have very different kinetics of binding and unbinding, as well as different affinities for the open and inactivated states of Kv11.1. Therefore, IC50 measurements may not reflect the true risk of drug induced arrhythmias. Here we have used an in silico approach to test the hypothesis that drug binding kinetics and differences in state-dependent affinity will influence the extent of cardiac action potential prolongation independent of apparent IC50 values. We found, in general that drugs with faster overall kinetics and drugs with higher affinity for the open state relative to the inactivated state cause more action potential prolongation. These characteristics of drug-hERG interaction are likely to be more arrhythmogenic but cannot be predicted by IC50 measurement alone. Our results suggest that the pre-clinical assessment of Kv11.1-drug interactions should include descriptions of the kinetics and state dependence of drug binding. Further, incorporation of this information into sophisticated in silico models should be able to better predict arrhythmia risk and therefore more accurately assess safety of new drugs in development.
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Affiliation(s)
- William Lee
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, NSW 2052, Australia
| | - Stefan A Mann
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, NSW 2052, Australia
| | - Monique J Windley
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia
| | - Mohammad S Imtiaz
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, NSW 2052, Australia
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, NSW 2052, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, NSW 2052, Australia.
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