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Chan M, Sahakyan H, Eldstrom J, Sastre D, Wang Y, Dou Y, Pourrier M, Vardanyan V, Fedida D. A generic binding pocket for small molecule IKs activators at the extracellular inter-subunit interface of KCNQ1 and KCNE1 channel complexes. eLife 2023; 12:RP87038. [PMID: 37707495 PMCID: PMC10501768 DOI: 10.7554/elife.87038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023] Open
Abstract
The cardiac IKs ion channel comprises KCNQ1, calmodulin, and KCNE1 in a dodecameric complex which provides a repolarizing current reserve at higher heart rates and protects from arrhythmia syndromes that cause fainting and sudden death. Pharmacological activators of IKs are therefore of interest both scientifically and therapeutically for treatment of IKs loss-of-function disorders. One group of chemical activators are only active in the presence of the accessory KCNE1 subunit and here we investigate this phenomenon using molecular modeling techniques and mutagenesis scanning in mammalian cells. A generalized activator binding pocket is formed extracellularly by KCNE1, the domain-swapped S1 helices of one KCNQ1 subunit and the pore/turret region made up of two other KCNQ1 subunits. A few residues, including K41, A44 and Y46 in KCNE1, W323 in the KCNQ1 pore, and Y148 in the KCNQ1 S1 domain, appear critical for the binding of structurally diverse molecules, but in addition, molecular modeling studies suggest that induced fit by structurally different molecules underlies the generalized nature of the binding pocket. Activation of IKs is enhanced by stabilization of the KCNQ1-S1/KCNE1/pore complex, which ultimately slows deactivation of the current, and promotes outward current summation at higher pulse rates. Our results provide a mechanistic explanation of enhanced IKs currents by these activator compounds and provide a map for future design of more potent therapeutically useful molecules.
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Affiliation(s)
- Magnus Chan
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Harutyun Sahakyan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular BiologyYerevanArmenia
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Daniel Sastre
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Marc Pourrier
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
| | - Vitya Vardanyan
- Molecular Neuroscience Group, Institute of Molecular BiologyYerevanArmenia
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British ColumbiaVancouverCanada
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2
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Abrahamyan A, Eldstrom J, Sahakyan H, Karagulyan N, Mkrtchyan L, Karapetyan T, Sargsyan E, Kneussel M, Nazaryan K, Schwarz JR, Fedida D, Vardanyan V. Mechanism of external K+ sensitivity of KCNQ1 channels. J Gen Physiol 2023; 155:213880. [PMID: 36809486 PMCID: PMC9960071 DOI: 10.1085/jgp.202213205] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/20/2022] [Accepted: 01/31/2023] [Indexed: 02/23/2023] Open
Abstract
KCNQ1 voltage-gated K+ channels are involved in a wide variety of fundamental physiological processes and exhibit the unique feature of being markedly inhibited by external K+. Despite the potential role of this regulatory mechanism in distinct physiological and pathological processes, its exact underpinnings are not well understood. In this study, using extensive mutagenesis, molecular dynamics simulations, and single-channel recordings, we delineate the molecular mechanism of KCNQ1 modulation by external K+. First, we demonstrate the involvement of the selectivity filter in the external K+ sensitivity of the channel. Then, we show that external K+ binds to the vacant outermost ion coordination site of the selectivity filter inducing a diminution in the unitary conductance of the channel. The larger reduction in the unitary conductance compared to whole-cell currents suggests an additional modulatory effect of external K+ on the channel. Further, we show that the external K+ sensitivity of the heteromeric KCNQ1/KCNE complexes depends on the type of associated KCNE subunits.
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Affiliation(s)
- Astghik Abrahamyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Harutyun Sahakyan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Nare Karagulyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Liana Mkrtchyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Tatev Karapetyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Ernest Sargsyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Matthias Kneussel
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - Karen Nazaryan
- Laboratory of Computational Modeling of Biological Processes, Institute of Molecular Biology of National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
| | - Jürgen R Schwarz
- Institute for Molecular Neurogenetics, Center for Molecular Neurobiology Hamburg , Hamburg, Germany
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia , Vancouver, BC, Canada
| | - Vitya Vardanyan
- Molecular Neuroscience Group, Institute of Molecular Biology, National Academy of Sciences of the Republic of Armenia , Yerevan, Armenia
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3
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Dellin M, Rohrbeck I, Asrani P, Schreiber JA, Ritter N, Glorius F, Wünsch B, Budde T, Temme L, Strünker T, Stallmeyer B, Tüttelmann F, Meuth SG, Spehr M, Matschke J, Steinbicker A, Gatsogiannis C, Stoll R, Strutz-Seebohm N, Seebohm G. The second PI(3,5)P 2 binding site in the S0 helix of KCNQ1 stabilizes PIP 2-at the primary PI1 site with potential consequences on intermediate-to-open state transition. Biol Chem 2023; 404:241-254. [PMID: 36809224 DOI: 10.1515/hsz-2022-0247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 12/13/2022] [Indexed: 02/23/2023]
Abstract
The Phosphatidylinositol 3-phosphate 5-kinase Type III PIKfyve is the main source for selectively generated phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), a known regulator of membrane protein trafficking. PI(3,5)P2 facilitates the cardiac KCNQ1/KCNE1 channel plasma membrane abundance and therewith increases the macroscopic current amplitude. Functional-physical interaction of PI(3,5)P2 with membrane proteins and its structural impact is not sufficiently understood. This study aimed to identify molecular interaction sites and stimulatory mechanisms of the KCNQ1/KCNE1 channel via the PIKfyve-PI(3,5)P2 axis. Mutational scanning at the intracellular membrane leaflet and nuclear magnetic resonance (NMR) spectroscopy identified two PI(3,5)P2 binding sites, the known PIP2 site PS1 and the newly identified N-terminal α-helix S0 as relevant for functional PIKfyve effects. Cd2+ coordination to engineered cysteines and molecular modeling suggest that repositioning of S0 stabilizes the channel s open state, an effect strictly dependent on parallel binding of PI(3,5)P2 to both sites.
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Affiliation(s)
- Maurice Dellin
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
| | - Ina Rohrbeck
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
| | - Purva Asrani
- Faculty of Chemistry and Biochemistry, Biomolecular NMR Spectroscopy and RUBiospek|NMR, Ruhr University of Bochum, Universitätsstraße 150, D-44780, Bochum, Germany
| | - Julian A Schreiber
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
- Institut für Pharmazeutische und Medizinische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149, Münster, Germany
| | - Nadine Ritter
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Frank Glorius
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149, Münster, Germany
| | - Bernhard Wünsch
- Institut für Pharmazeutische und Medizinische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149, Münster, Germany
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Thomas Budde
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
- Institute of Physiology I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
| | - Louisa Temme
- Institut für Pharmazeutische und Medizinische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149, Münster, Germany
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Timo Strünker
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
- Centre of Reproductive Medicine and Andrology, University Hospital Münster, University of Münster, Domagkstraße 11, D-48149, Münster, Germany
- Cells in Motion Interfaculty Centre, University of Münster, Münster, Germany
| | - Birgit Stallmeyer
- Institute of Reproductive Genetics, University of Münster, Vesaliusweg 12-14, D-48149, Münster, Germany
| | - Frank Tüttelmann
- Institute of Reproductive Genetics, University of Münster, Vesaliusweg 12-14, D-48149, Münster, Germany
| | - Sven G Meuth
- Department of Neurology, Heinrich Heine University Düsseldorf, Moorenstraße 5, D-40225, Düsseldorf, Germany
| | - Marc Spehr
- Department of Chemosensation, Institute for Biology II, RWTH Aachen University, Worringerweg 3, D-52074, Aachen, Germany
| | - Johann Matschke
- Institute of Cell Biology (Cancer Research), University Hospital Essen, University of Duisburg-Essen, D-45147, Essen, Germany
| | - Andrea Steinbicker
- Goethe University Frankfurt and University Hospital Frankfurt, Theodor-Stern-Kai 7, D-60590, Frankfurt, Germany
| | - Christos Gatsogiannis
- Institute for Medical Physics and Biophysics and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Münster, Busso-Peus Strasse 10, D-48149, Germany
| | - Raphael Stoll
- Faculty of Chemistry and Biochemistry, Biomolecular NMR Spectroscopy and RUBiospek|NMR, Ruhr University of Bochum, Universitätsstraße 150, D-44780, Bochum, Germany
| | - Nathalie Strutz-Seebohm
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
| | - Guiscard Seebohm
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Robert-Koch Str. 45, D-48149, Münster, Germany
- GRK 2515, Chemical biology of ion channels (Chembion), Westfälische Wilhelms-Universität Münster, Münster, Germany
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4
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Chen L, Peng G, Comollo TW, Zou X, Sampson KJ, Larsson HP, Kass RS. Two small-molecule activators share similar effector sites in the KCNQ1 channel pore but have distinct effects on voltage sensor movements. Front Physiol 2022; 13:903050. [PMID: 35957984 PMCID: PMC9359618 DOI: 10.3389/fphys.2022.903050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
ML277 and R-L3 are two small-molecule activators of KCNQ1, the pore-forming subunit of the slowly activating potassium channel IKs. KCNQ1 loss-of-function mutations prolong cardiac action potential duration and are associated with long QT syndrome, which predispose patients to lethal ventricular arrhythmia. ML277 and R-L3 enhance KCNQ1 current amplitude and slow deactivation. However, the presence of KCNE1, an auxiliary subunit of IKs channels, renders the channel insensitive to both activators. We found that ML277 effects are dependent on several residues in the KCNQ1 pore domain. Some of these residues are also necessary for R-L3 effects. These residues form a putative hydrophobic pocket located between two adjacent KCNQ1 subunits, where KCNE1 subunits are thought to dwell, thus providing an explanation for how KCNE1 renders the IKs channel insensitive to these activators. Our experiments showed that the effect of R-L3 on voltage sensor movement during channel deactivation was much more prominent than that of ML277. Simulations using a KCNQ1 kinetic model showed that the effects of ML277 and R-L3 could be reproduced through two different effects on channel gating: ML277 enhances KCNQ1 channel function through a pore-dependent and voltage sensor-independent mechanism, while R-L3 affects both channel pore and voltage sensor.
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Affiliation(s)
- Lei Chen
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Gary Peng
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Thomas W. Comollo
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Xinle Zou
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - Kevin J. Sampson
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States
| | - H. Peter Larsson
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, United States
| | - Robert S. Kass
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians & Surgeons of Columbia University Irving Medical Center, New York, NY, United States,*Correspondence: Robert S. Kass,
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5
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Wu X, Larsson HP. Insights into Cardiac IKs (KCNQ1/KCNE1) Channels Regulation. Int J Mol Sci 2020; 21:ijms21249440. [PMID: 33322401 PMCID: PMC7763278 DOI: 10.3390/ijms21249440] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/05/2020] [Accepted: 12/09/2020] [Indexed: 12/19/2022] Open
Abstract
The delayed rectifier potassium IKs channel is an important regulator of the duration of the ventricular action potential. Hundreds of mutations in the genes (KCNQ1 and KCNE1) encoding the IKs channel cause long QT syndrome (LQTS). LQTS is a heart disorder that can lead to severe cardiac arrhythmias and sudden cardiac death. A better understanding of the IKs channel (here called the KCNQ1/KCNE1 channel) properties and activities is of great importance to find the causes of LQTS and thus potentially treat LQTS. The KCNQ1/KCNE1 channel belongs to the superfamily of voltage-gated potassium channels. The KCNQ1/KCNE1 channel consists of both the pore-forming subunit KCNQ1 and the modulatory subunit KCNE1. KCNE1 regulates the function of the KCNQ1 channel in several ways. This review aims to describe the current structural and functional knowledge about the cardiac KCNQ1/KCNE1 channel. In addition, we focus on the modulation of the KCNQ1/KCNE1 channel and its potential as a target therapeutic of LQTS.
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6
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Xu Parks X, Qudsi H, Braun C, Lopes CMB. The auxiliary subunit KCNE1 regulates KCNQ1 channel response to sustained calcium-dependent PKC activation. PLoS One 2020; 15:e0237591. [PMID: 32833978 PMCID: PMC7446858 DOI: 10.1371/journal.pone.0237591] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 07/29/2020] [Indexed: 11/18/2022] Open
Abstract
The slow cardiac delayed rectifier current (IKs) is formed by KCNQ1 and KCNE1 subunits and is one of the major repolarizing currents in the heart. Decrease of IKs currents either due to inherited mutations or pathological remodeling is associated with increased risk for cardiac arrhythmias and sudden death. Ca2+-dependent PKC isoforms (cPKC) are chronically activated in heart disease and diabetes. Recently, we found that sustained stimulation of the calcium-dependent PKCβII isoform leads to decrease in KCNQ1 subunit membrane localization and KCNQ1/KCNE1 channel activity, although the role of KCNE1 in this regulation was not explored. Here, we show that the auxiliary KCNE1 subunit expression is necessary for channel internalization. A mutation in a KCNE1 phosphorylation site (KCNE1(S102A)) abolished channel internalization in both heterologous expression systems and cardiomyocytes. Altogether, our results suggest that KCNE1(S102) phosphorylation by PKCβII leads to KCNQ1/KCNE1 channel internalization in response to sustained PKC stimulus, while leaving KCNQ1 homomeric channels in the membrane. This preferential internalization is expected to have strong impact on cardiac repolarization. Our results suggest that KCNE1(S102) is an important anti-arrhythmic drug target to prevent IKs pathological remodeling leading to cardiac arrhythmias.
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Affiliation(s)
- Xiaorong Xu Parks
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America
| | - Haani Qudsi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America
| | - Chen Braun
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America
| | - Coeli M. B. Lopes
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States of America
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7
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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8
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Taylor KC, Kang PW, Hou P, Yang ND, Kuenze G, Smith JA, Shi J, Huang H, White KM, Peng D, George AL, Meiler J, McFeeters RL, Cui J, Sanders CR. Structure and physiological function of the human KCNQ1 channel voltage sensor intermediate state. eLife 2020; 9:e53901. [PMID: 32096762 PMCID: PMC7069725 DOI: 10.7554/elife.53901] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 02/24/2020] [Indexed: 12/14/2022] Open
Abstract
Voltage-gated ion channels feature voltage sensor domains (VSDs) that exist in three distinct conformations during activation: resting, intermediate, and activated. Experimental determination of the structure of a potassium channel VSD in the intermediate state has previously proven elusive. Here, we report and validate the experimental three-dimensional structure of the human KCNQ1 voltage-gated potassium channel VSD in the intermediate state. We also used mutagenesis and electrophysiology in Xenopus laevisoocytes to functionally map the determinants of S4 helix motion during voltage-dependent transition from the intermediate to the activated state. Finally, the physiological relevance of the intermediate state KCNQ1 conductance is demonstrated using voltage-clamp fluorometry. This work illuminates the structure of the VSD intermediate state and demonstrates that intermediate state conductivity contributes to the unusual versatility of KCNQ1, which can function either as the slow delayed rectifier current (IKs) of the cardiac action potential or as a constitutively active epithelial leak current.
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Affiliation(s)
- Keenan C Taylor
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Po Wei Kang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Panpan Hou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Nien-Du Yang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
| | - Jarrod A Smith
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Hui Huang
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Kelli McFarland White
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Dungeng Peng
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical CenterNashvilleUnited States
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of MedicineChicagoUnited States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
- Department of Bioinformatics, Vanderbilt University Medical CenterNashvilleUnited States
| | - Robert L McFeeters
- Department of Chemistry, University of Alabama in HuntsvilleHuntsvilleUnited States
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Vanderbilt University Medical CenterNashvilleUnited States
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9
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Chen J, Liu Z, Creagh J, Zheng R, McDonald TV. Physical and functional interaction sites in cytoplasmic domains of KCNQ1 and KCNE1 channel subunits. Am J Physiol Heart Circ Physiol 2019; 318:H212-H222. [PMID: 31834838 DOI: 10.1152/ajpheart.00459.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The cardiac potassium IKs current is carried by a channel complex formed from α-subunits encoded by KCNQ1 and β-subunits encoded by KCNE1. Deleterious mutations in either gene are associated with hereditary long QT syndrome. Interactions between the transmembrane domains of the α- and β-subunits determine the activation kinetics of IKs. A physical and functional interaction between COOH termini of the proteins has also been identified that impacts deactivation rate and voltage dependence of activation. We sought to explore the specific physical interactions between the COOH termini of the subunits that confer such control. Hydrogen/deuterium exchange coupled to mass spectrometry narrowed down the region of interaction to KCNQ1 residues 352-374 and KCNE1 residues 70-81, and provided evidence of secondary structure within these segments. Key mutations of residues in these regions tended to shift voltage dependence of activation toward more depolarizing voltages. Double-mutant cycle analysis then revealed energetic coupling between KCNQ1-I368 and KCNE1-D76 during channel activation. Our results suggest that the proximal COOH-terminal regions of KCNQ1 and KCNE1 participate in a physical and functional interaction during channel opening that is sensitive to perturbation and may explain the clustering of long QT mutations in the region.NEW & NOTEWORTHY Interacting ion channel subunits KCNQ1 and KCNE1 have received intense investigation due to their critical importance to human cardiovascular health. This work uses physical (hydrogen/deuterium exchange with mass spectrometry) and functional (double-mutant cycle analyses) studies to elucidate precise and important areas of interaction between the two proteins in an area that has eluded structural definition of the complex. It highlights the importance of pathogenic mutations in these regions.
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Affiliation(s)
- Jerri Chen
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, New York.,Department of Anesthesiology, Columbia University Medical Center, New York, New York
| | - Zhenning Liu
- Department of Emergency Medicine, Shengjing Hospital of China Medical University, Shenyang, China
| | - John Creagh
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, New York
| | - Renjian Zheng
- Department of Anesthesiology, Columbia University Medical Center, New York, New York
| | - Thomas V McDonald
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, New York.,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York.,Department of Cardiovascular Sciences, Morsani College of Medicine, University of South Florida, Tampa, Florida
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10
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The membrane protein KCNQ1 potassium ion channel: Functional diversity and current structural insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183148. [PMID: 31825788 DOI: 10.1016/j.bbamem.2019.183148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 11/15/2019] [Accepted: 12/04/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Ion channels play crucial roles in cellular biology, physiology, and communication including sensory perception. Voltage-gated potassium (Kv) channels execute their function by sensor activation, pore-coupling, and pore opening leading to K+ conductance. SCOPE OF REVIEW This review focuses on a voltage-gated K+ ion channel KCNQ1 (Kv 7.1). Firstly, discussing its positioning in the human ion chanome, and the role of KCNQ1 in the multitude of cellular processes. Next, we discuss the overall channel architecture and current structural insights on KCNQ1. Finally, the gating mechanism involving members of the KCNE family and its interaction with non-KCNE partners. MAJOR CONCLUSIONS KCNQ1 executes its important physiological functions via interacting with KCNE1 and non-KCNE1 proteins/molecules: calmodulin, PIP2, PKA. Although, KCNQ1 has been studied in great detail, several aspects of the channel structure and function still remain unexplored. This review emphasizes the structural and biophysical studies of KCNQ1, its interaction with KCNE1 and non-KCNE1 proteins and focuses on several seminal findings showing the role of VSD and the pore domain in the channel activation and gating properties. GENERAL SIGNIFICANCE KCNQ1 mutations can result in channel defects and lead to several diseases including atrial fibrillation and long QT syndrome. Therefore, a thorough structure-function understanding of this channel complex is essential to understand its role in both normal and disease biology. Moreover, unraveling the molecular mechanisms underlying the regulation of this channel complex will help to find therapeutic strategies for several diseases.
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11
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Kuenze G, Duran AM, Woods H, Brewer KR, McDonald EF, Vanoye CG, George AL, Sanders CR, Meiler J. Upgraded molecular models of the human KCNQ1 potassium channel. PLoS One 2019; 14:e0220415. [PMID: 31518351 PMCID: PMC6743773 DOI: 10.1371/journal.pone.0220415] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 07/15/2019] [Indexed: 11/29/2022] Open
Abstract
The voltage-gated potassium channel KCNQ1 (KV7.1) assembles with the KCNE1 accessory protein to generate the slow delayed rectifier current, IKS, which is critical for membrane repolarization as part of the cardiac action potential. Loss-of-function (LOF) mutations in KCNQ1 are the most common cause of congenital long QT syndrome (LQTS), type 1 LQTS, an inherited genetic predisposition to cardiac arrhythmia and sudden cardiac death. A detailed structural understanding of KCNQ1 is needed to elucidate the molecular basis for KCNQ1 LOF in disease and to enable structure-guided design of new anti-arrhythmic drugs. In this work, advanced structural models of human KCNQ1 in the resting/closed and activated/open states were developed by Rosetta homology modeling guided by newly available experimentally-based templates: X. leavis KCNQ1 and various resting voltage sensor structures. Using molecular dynamics (MD) simulations, the capacity of the models to describe experimentally established channel properties including state-dependent voltage sensor gating charge interactions and pore conformations, PIP2 binding sites, and voltage sensor–pore domain interactions were validated. Rosetta energy calculations were applied to assess the utility of each model in interpreting mutation-evoked KCNQ1 dysfunction by predicting the change in protein thermodynamic stability for 50 experimentally characterized KCNQ1 variants with mutations located in the voltage-sensing domain. Energetic destabilization was successfully predicted for folding-defective KCNQ1 LOF mutants whereas wild type-like mutants exhibited no significant energetic frustrations, which supports growing evidence that mutation-induced protein destabilization is an especially common cause of KCNQ1 dysfunction. The new KCNQ1 Rosetta models provide helpful tools in the study of the structural basis for KCNQ1 function and can be used to generate hypotheses to explain KCNQ1 dysfunction.
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Affiliation(s)
- Georg Kuenze
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Amanda M. Duran
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Hope Woods
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Eli Fritz McDonald
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Carlos G. Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Alfred L. George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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12
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Policarová M, Novotný T, Bébarová M. Impaired Adrenergic/Protein Kinase A Response of Slow Delayed Rectifier Potassium Channels as a Long QT Syndrome Motif: Importance and Unknowns. Can J Cardiol 2019; 35:511-522. [DOI: 10.1016/j.cjca.2018.11.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 11/20/2018] [Accepted: 11/20/2018] [Indexed: 12/29/2022] Open
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13
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Yao H, Ji CC, Cheng YJ, Chen XM, Liu LJ, Fan J, Wu SH. Mutation in KCNE1 associated to early repolarization syndrome by modulation of slowly activating delayed rectifier K + current. Exp Cell Res 2018; 363:315-320. [DOI: 10.1016/j.yexcr.2018.01.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/11/2018] [Accepted: 01/20/2018] [Indexed: 01/13/2023]
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14
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Jalily Hasani H, Ahmed M, Barakat K. A comprehensive structural model for the human KCNQ1/KCNE1 ion channel. J Mol Graph Model 2017; 78:26-47. [PMID: 28992529 DOI: 10.1016/j.jmgm.2017.09.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 09/25/2017] [Accepted: 09/26/2017] [Indexed: 10/18/2022]
Abstract
The voltage-gated KCNQ1/KCNE1 potassium ion channel complex, forms the slow delayed rectifier (IKs) current in the heart, which plays an important role in heart signaling. The importance of KCNQ1/KCNE1 channel's function is further implicated by the linkage between loss-of-function and gain-of-function mutations in KCNQ1 or KCNE1, and long QT syndromes, congenital atrial fibrillation, and short QT syndrome. Also, KCNQ1/KCNE1 channels are an off-target for many non-cardiovascular drugs, leading to fatal cardiac irregularities. One solution to address and study the mentioned aspects of KCNQ1/KNCE1 channel would be the structural studies using a validated and accurate model. Along the same line in this study, we have used several top-notch modeling approaches to build a structural model for the open state of KCNQ1 protein, which is both accurate and compatible with available experimental data. Next, we included the KCNE1 protein components using data-driven protein-protein docking simulations, encompassing a 4:2 stoichiometry to complete the picture of the channel complex formed by these two proteins. All the protein systems generated through these processes were refined by long Molecular Dynamics simulations. The refined models were analyzed extensively to infer data about the interaction of KCNQ1 channel with its accessory KCNE1 beta subunits.
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Affiliation(s)
- Horia Jalily Hasani
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Marawan Ahmed
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Khaled Barakat
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada; Li Ka Shing Institute of Virology, University of Alberta, Edmonton, Alberta, Canada; Li Ka Shing Applied Virology Institute, University of Alberta, Edmonton, Alberta, Canada.
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15
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Westhoff M, Murray CI, Eldstrom J, Fedida D. Photo-Cross-Linking of I Ks Demonstrates State-Dependent Interactions between KCNE1 and KCNQ1. Biophys J 2017; 113:415-425. [PMID: 28746852 DOI: 10.1016/j.bpj.2017.06.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 05/26/2017] [Accepted: 06/02/2017] [Indexed: 01/09/2023] Open
Abstract
The slow delayed rectifier potassium current (IKs) is a key repolarizing current during the cardiac action potential. It consists of four KCNQ1 α-subunits and up to four KCNE1 β-subunits, which are thought to reside within external clefts of the channel. The interaction of KCNE1 with KCNQ1 dramatically delays opening of the channel but the mechanisms by which this occur are not yet fully understood. Here, we have used unnatural amino acid photo-cross-linking to investigate the dynamic interactions that occur between KCNQ1 and KCNE1 during activation gating. The unnatural amino acid p-Benzoylphenylalanine was successfully incorporated into two residues within the transmembrane domain of KCNE1: F56 and F57. UV-induced cross-linking suggested that F56Bpa interacts with KCNQ1 in the open state, whereas F57Bpa interacts predominantly in resting channel conformations. When UV was applied at progressively more depolarized preopen holding potentials, cross-linking of F57Bpa with KCNQ1 was slowed, which indicates that KCNE1 is displaced within the channel's cleft early during activation, or that conformational changes in KCNQ1 alter its interaction with KCNE1. In E1R/R4E KCNQ1, a mutant with constitutively activated voltage sensors, F56Bpa and F57Bpa KCNE1 were cross-linked in open and closed states, respectively, which suggests that their actions are mediated mainly by modulation of KCNQ1 pore function.
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Affiliation(s)
- Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher I Murray
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
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16
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KCNE1 and KCNE3 modulate KCNQ1 channels by affecting different gating transitions. Proc Natl Acad Sci U S A 2017; 114:E7367-E7376. [PMID: 28808020 DOI: 10.1073/pnas.1710335114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
KCNE β-subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with the α-subunit KCNQ1 to generate the slowly activating, voltage-dependent potassium current (IKs) in the heart that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach, and kidney, KCNE3 coassembles with KCNQ1 to form K+ channels that are voltage-independent K+ channels in the physiological voltage range and important for controlling water and salt secretion and absorption. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by mutations or phosphatidylinositol 4,5-bisphosphate depletion, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 affects the S4 movement and only affects the gate in KCNQ1 if an intact S4-to-gate coupling is present. Further, we show that a triple mutation in the middle of the transmembrane (TM) segment of KCNE3 introduces KCNE1-like effects on the second S4 movement and the gate. In addition, we show that differences in two residues at the external end of the KCNE TM segments underlie differences in the effects of the different KCNEs on the first S4 movement and the voltage sensor-to-gate coupling.
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17
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Gating mechanisms underlying deactivation slowing by two KCNQ1 atrial fibrillation mutations. Sci Rep 2017; 7:45911. [PMID: 28383569 PMCID: PMC5382920 DOI: 10.1038/srep45911] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/03/2017] [Indexed: 01/13/2023] Open
Abstract
KCNQ1 is a voltage-gated potassium channel that is modulated by the beta-subunit KCNE1 to generate IKs, the slow delayed rectifier current, which plays a critical role in repolarizing the cardiac action potential. Two KCNQ1 gain-of-function mutations that cause a genetic form of atrial fibrillation, S140G and V141M, drastically slow IKs deactivation. However, the underlying gating alterations remain unknown. Voltage clamp fluorometry (VCF) allows simultaneous measurement of voltage sensor movement and current through the channel pore. Here, we use VCF and kinetic modeling to determine the effects of mutations on channel voltage-dependent gating. We show that in the absence of KCNE1, S140G, but not V141M, directly slows voltage sensor movement, which indirectly slows current deactivation. In the presence of KCNE1, both S140G and V141M slow pore closing and alter voltage sensor-pore coupling, thereby slowing current deactivation. Our results suggest that KCNE1 can mediate changes in pore movement and voltage sensor-pore coupling to slow IKs deactivation and provide a key step toward developing mechanism-based therapies.
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18
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Bohnen MS, Peng G, Robey SH, Terrenoire C, Iyer V, Sampson KJ, Kass RS. Molecular Pathophysiology of Congenital Long QT Syndrome. Physiol Rev 2017; 97:89-134. [PMID: 27807201 PMCID: PMC5539372 DOI: 10.1152/physrev.00008.2016] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ion channels represent the molecular entities that give rise to the cardiac action potential, the fundamental cellular electrical event in the heart. The concerted function of these channels leads to normal cyclical excitation and resultant contraction of cardiac muscle. Research into cardiac ion channel regulation and mutations that underlie disease pathogenesis has greatly enhanced our knowledge of the causes and clinical management of cardiac arrhythmia. Here we review the molecular determinants, pathogenesis, and pharmacology of congenital Long QT Syndrome. We examine mechanisms of dysfunction associated with three critical cardiac currents that comprise the majority of congenital Long QT Syndrome cases: 1) IKs, the slow delayed rectifier current; 2) IKr, the rapid delayed rectifier current; and 3) INa, the voltage-dependent sodium current. Less common subtypes of congenital Long QT Syndrome affect other cardiac ionic currents that contribute to the dynamic nature of cardiac electrophysiology. Through the study of mutations that cause congenital Long QT Syndrome, the scientific community has advanced understanding of ion channel structure-function relationships, physiology, and pharmacological response to clinically employed and experimental pharmacological agents. Our understanding of congenital Long QT Syndrome continues to evolve rapidly and with great benefits: genotype-driven clinical management of the disease has improved patient care as precision medicine becomes even more a reality.
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Affiliation(s)
- M S Bohnen
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - G Peng
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - S H Robey
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - C Terrenoire
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - V Iyer
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - K J Sampson
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
| | - R S Kass
- Department of Pharmacology, Columbia University Medical Center, New York, New York; and The New York Stem Cell Foundation Research Institute, New York, New York
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19
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Solé L, Roig SR, Vallejo-Gracia A, Serrano-Albarrás A, Martínez-Mármol R, Tamkun MM, Felipe A. The C-terminal domain of Kv1.3 regulates functional interactions with the KCNE4 subunit. J Cell Sci 2016; 129:4265-4277. [PMID: 27802162 DOI: 10.1242/jcs.191650] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 09/29/2016] [Indexed: 12/23/2022] Open
Abstract
The voltage-dependent K+ channel Kv1.3 (also known as KCNA3), which plays crucial roles in leukocytes, physically interacts with KCNE4. This interaction inhibits the K+ currents because the channel is retained within intracellular compartments. Thus, KCNE subunits are regulators of K+ channels in the immune system. Although the canonical interactions of KCNE subunits with Kv7 channels are under intensive investigation, the molecular determinants governing the important Kv1.3- KCNE4 association in the immune system are unknown. Our results suggest that the tertiary structure of the C-terminal domain of Kv1.3 is necessary and sufficient for such an interaction. However, this element is apparently not involved in modulating Kv1.3 gating. Furthermore, the KCNE4-dependent intracellular retention of the channel, which negatively affects the activity of Kv1.3, is mediated by two independent and additive mechanisms. First, KCNE4 masks the YMVIEE signature at the C-terminus of Kv1.3, which is crucial for the surface targeting of the channel. Second, we identify a potent endoplasmic reticulum retention motif in KCNE4 that further limits cell surface expression. Our results define specific molecular determinants that play crucial roles in the physiological function of Kv1.3 in leukocytes.
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Affiliation(s)
- Laura Solé
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain.,Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Sara R Roig
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain
| | - Albert Vallejo-Gracia
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain
| | - Antonio Serrano-Albarrás
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain
| | - Ramón Martínez-Mármol
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain.,Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Michael M Tamkun
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Avda. Diagonal 643, Barcelona 08028, Spain
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20
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Cui J. Voltage-Dependent Gating: Novel Insights from KCNQ1 Channels. Biophys J 2016; 110:14-25. [PMID: 26745405 DOI: 10.1016/j.bpj.2015.11.023] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 11/16/2015] [Accepted: 11/17/2015] [Indexed: 11/26/2022] Open
Abstract
Gating of voltage-dependent cation channels involves three general molecular processes: voltage sensor activation, sensor-pore coupling, and pore opening. KCNQ1 is a voltage-gated potassium (Kv) channel whose distinctive properties have provided novel insights on fundamental principles of voltage-dependent gating. 1) Similar to other Kv channels, KCNQ1 voltage sensor activation undergoes two resolvable steps; but, unique to KCNQ1, the pore opens at both the intermediate and activated state of voltage sensor activation. The voltage sensor-pore coupling differs in the intermediate-open and the activated-open states, resulting in changes of open pore properties during voltage sensor activation. 2) The voltage sensor-pore coupling and pore opening require the membrane lipid PIP2 and intracellular ATP, respectively, as cofactors, thus voltage-dependent gating is dependent on multiple stimuli, including the binding of intracellular signaling molecules. These mechanisms underlie the extraordinary KCNE1 subunit modification of the KCNQ1 channel and have significant physiological implications.
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Affiliation(s)
- Jianmin Cui
- Department of Biomedical Engineering, Cardiac Bioelectricity and Arrhythmia Center and Center for the Investigation of Membrane Excitability Disorders, Washington University, St. Louis, Missouri.
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21
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Abstract
Cardiac delayed rectifier potassium channels conduct outward potassium currents during the plateau phase of action potentials and play pivotal roles in cardiac repolarization. These include IKs, IKr and the atrial specific IKur channels. In this article, we will review their molecular identities and biophysical properties. Mutations in the genes encoding delayed rectifiers lead to loss- or gain-of-function phenotypes, disrupt normal cardiac repolarization and result in various cardiac rhythm disorders, including congenital Long QT Syndrome, Short QT Syndrome and familial atrial fibrillation. We will also discuss the prospect of using delayed rectifier channels as therapeutic targets to manage cardiac arrhythmia.
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Affiliation(s)
- Lei Chen
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Kevin J Sampson
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA
| | - Robert S Kass
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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22
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Abstract
KCNE β-subunits assemble with and modulate the properties of voltage-gated K(+) channels. In the colon, stomach, and kidney, KCNE3 coassembles with the α-subunit KCNQ1 to form K(+) channels important for K(+) and Cl(-) secretion that appear to be voltage-independent. How KCNE3 subunits turn voltage-gated KCNQ1 channels into apparent voltage-independent KCNQ1/KCNE3 channels is not completely understood. Different mechanisms have been proposed to explain the effect of KCNE3 on KCNQ1 channels. Here, we use voltage clamp fluorometry to determine how KCNE3 affects the voltage sensor S4 and the gate of KCNQ1. We find that S4 moves in KCNQ1/KCNE3 channels, and that inward S4 movement closes the channel gate. However, KCNE3 shifts the voltage dependence of S4 movement to extreme hyperpolarized potentials, such that in the physiological voltage range, the channel is constitutively conducting. By separating S4 movement and gate opening, either by a mutation or PIP2 depletion, we show that KCNE3 directly affects the S4 movement in KCNQ1. Two negatively charged residues of KCNE3 (D54 and D55) are found essential for the effect of KCNE3 on KCNQ1 channels, mainly exerting their effects by an electrostatic interaction with R228 in S4. Our results suggest that KCNE3 primarily affects the voltage-sensing domain and only indirectly affects the gate.
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23
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Abbott GW. KCNE1 and KCNE3: The yin and yang of voltage-gated K(+) channel regulation. Gene 2015; 576:1-13. [PMID: 26410412 DOI: 10.1016/j.gene.2015.09.059] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 09/03/2015] [Accepted: 09/22/2015] [Indexed: 12/20/2022]
Abstract
The human KCNE gene family comprises five genes encoding single transmembrane-spanning ion channel regulatory subunits. The primary function of KCNE subunits appears to be regulation of voltage-gated potassium (Kv) channels, and the best-understood KCNE complexes are with the KCNQ1 Kv α subunit. Here, we review the often opposite effects of KCNE1 and KCNE3 on Kv channel biology, with an emphasis on regulation of KCNQ1. Slow-activating IKs channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways. Because of their contrasting effects on KCNQ1 function, KCNE1 and KCNE3 have proved invaluable tools in the mechanistic understanding of how channel gating can be manipulated, and each may also provide a window into novel insights and new therapeutic opportunities in K(+) channel pharmacology. Finally, findings from studies of Kcne1(-/-) and Kcne3(-/-) mouse lines serve to illustrate the complexity of KCNE biology and KCNE-linked disease states.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Dept. of Pharmacology and Dept. of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA; 360 Medical Surge II, Dept. of Pharmacology, School of Medicine, University of California, Irvine, CA 92697, USA.
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24
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Moreno C, Oliveras A, de la Cruz A, Bartolucci C, Muñoz C, Salar E, Gimeno JR, Severi S, Comes N, Felipe A, González T, Lambiase P, Valenzuela C. A new KCNQ1 mutation at the S5 segment that impairs its association with KCNE1 is responsible for short QT syndrome. Cardiovasc Res 2015; 107:613-23. [PMID: 26168993 DOI: 10.1093/cvr/cvv196] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 06/26/2015] [Indexed: 11/12/2022] Open
Abstract
AIMS KCNQ1 and KCNE1 encode Kv7.1 and KCNE1, respectively, the pore-forming and the accessory subunits of the slow delayed rectifier potassium current, IKs. KCNQ1 mutations are associated with long and short QT syndrome. The aim of this study was to characterize the biophysical and cellular phenotype of a KCNQ1 missense mutation, F279I, found in a 23-year-old man with a corrected QT interval (QTc) of 356 ms and a family history of sudden cardiac death. METHODS AND RESULTS Experiments were performed using perforated patch-clamp, western blot, co-immunoprecipitation, biotinylation, and immunocytochemistry techniques in HEK293, COS7 cells and in cardiomyocytes transfected with WT Kv7.1/KCNE1 or F279I Kv7.1/KCNE1 channels. In the absence of KCNE1, F279I Kv7.1 current exhibited a lesser degree of inactivation than WT Kv7.1. Also, functional analysis of F279I Kv7.1 in the presence of KCNE1 revealed a negative shift in the activation curve and an acceleration of the activation kinetics leading to a gain of function in IKs. The co-assembly between F279I Kv7.1 channels and KCNE1 was markedly decreased compared with WT Kv7.1 channels, as revealed by co-immunoprecipitation and Föster Resonance Energy Transfer experiments. All these effects contribute to the increase of IKs when channels incorporate F279I Kv7.1 subunits, as shown by a computer model simulation of these data that predicts a shortening of the action potential (AP) consistent with the patient phenotype. CONCLUSION The F279I mutation induces a gain of function of IKs due to an impaired gating modulation of Kv7.1 induced by KCNE1, leading to a shortening of the cardiac AP.
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Affiliation(s)
- Cristina Moreno
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, C/Arturo Duperier 4, Madrid 28029, Spain
| | - Anna Oliveras
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Alicia de la Cruz
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, C/Arturo Duperier 4, Madrid 28029, Spain
| | - Chiara Bartolucci
- Cellular and Molecular Engineering Laboratory 'S. Cavalcanti', Department of Electrical, Electronic and Information Engineering 'Guglielmo Marconi', University of Bologna, Bologna, Italy
| | - Carmen Muñoz
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca de Murcia, Murcia, Spain
| | - Eladia Salar
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca de Murcia, Murcia, Spain
| | - Juan R Gimeno
- Department of Cardiology, Hospital Universitario Virgen de la Arrixaca de Murcia, Murcia, Spain
| | - Stefano Severi
- Cellular and Molecular Engineering Laboratory 'S. Cavalcanti', Department of Electrical, Electronic and Information Engineering 'Guglielmo Marconi', University of Bologna, Bologna, Italy
| | - Nuria Comes
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Teresa González
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, C/Arturo Duperier 4, Madrid 28029, Spain
| | - Pier Lambiase
- Department of Cardiac Electrophysiology, The Heart Hospital, Institute of Cardiovascular Science, University College London, London, UK
| | - Carmen Valenzuela
- Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, C/Arturo Duperier 4, Madrid 28029, Spain
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25
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Polyunsaturated fatty acid analogs act antiarrhythmically on the cardiac IKs channel. Proc Natl Acad Sci U S A 2015; 112:5714-9. [PMID: 25901329 DOI: 10.1073/pnas.1503488112] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polyunsaturated fatty acids (PUFAs) affect cardiac excitability. Kv7.1 and the β-subunit KCNE1 form the cardiac IKs channel that is central for cardiac repolarization. In this study, we explore the prospects of PUFAs as IKs channel modulators. We report that PUFAs open Kv7.1 via an electrostatic mechanism. Both the polyunsaturated acyl tail and the negatively charged carboxyl head group are required for PUFAs to open Kv7.1. We further show that KCNE1 coexpression abolishes the PUFA effect on Kv7.1 by promoting PUFA protonation. PUFA analogs with a decreased pKa value, to preserve their negative charge at neutral pH, restore the sensitivity to open IKs channels. PUFA analogs with a positively charged head group inhibit IKs channels. These different PUFA analogs could be developed into drugs to treat cardiac arrhythmias. In support of this possibility, we show that PUFA analogs act antiarrhythmically in embryonic rat cardiomyocytes and in isolated perfused hearts from guinea pig.
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26
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Liin SI, Barro-Soria R, Larsson HP. The KCNQ1 channel - remarkable flexibility in gating allows for functional versatility. J Physiol 2015; 593:2605-15. [PMID: 25653179 DOI: 10.1113/jphysiol.2014.287607] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 01/30/2015] [Indexed: 12/12/2022] Open
Abstract
The KCNQ1 channel (also called Kv7.1 or KvLQT1) belongs to the superfamily of voltage-gated K(+) (Kv) channels. KCNQ1 shares several general features with other Kv channels but also displays a fascinating flexibility in terms of the mechanism of channel gating, which allows KCNQ1 to play different physiological roles in different tissues. This flexibility allows KCNQ1 channels to function as voltage-independent channels in epithelial tissues, whereas KCNQ1 function as voltage-activated channels with very slow kinetics in cardiac tissues. This flexibility is in part provided by the association of KCNQ1 with different accessory KCNE β-subunits and different modulators, but also seems like an integral part of KCNQ1 itself. The aim of this review is to describe the main mechanisms underlying KCNQ1 flexibility.
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Affiliation(s)
- Sara I Liin
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
| | - Rene Barro-Soria
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
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27
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Nakajo K, Kubo Y. KCNQ1 channel modulation by KCNE proteins via the voltage-sensing domain. J Physiol 2015; 593:2617-25. [PMID: 25603957 DOI: 10.1113/jphysiol.2014.287672] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/14/2015] [Indexed: 12/16/2022] Open
Abstract
The gating of the KCNQ1 potassium channel is drastically regulated by auxiliary subunit KCNE proteins. KCNE1, for example, slows the activation kinetics of KCNQ1 by two orders of magnitude. Like other voltage-gated ion channels, the opening of KCNQ1 is regulated by the voltage-sensing domain (VSD; S1-S4 segments). Although it has been known that KCNE proteins interact with KCNQ1 via the pore domain, some recent reports suggest that the VSD movement may be altered by KCNE. The altered VSD movement of KCNQ1 by KCNE proteins has been examined by site-directed mutagenesis, the scanning cysteine accessibility method (SCAM), voltage clamp fluorometry (VCF) and gating charge measurements. These accumulated data support the idea that KCNE proteins interact with the VSDs of KCNQ1 and modulate the gating of the KCNQ1 channel. In this review, we will summarize recent findings and current views of the KCNQ1 modulation by KCNE via the VSD. In this context, we discuss our recent findings that KCNE1 may alter physical interactions between the S4 segment (VSD) and the S5 segment (pore domain) of KCNQ1. Based on these findings from ourselves and others, we propose a hypothetical mechanism for how KCNE1 binding alters the VSD movement and the gating of the channel.
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Affiliation(s)
- Koichi Nakajo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDA), Hayama, Kanagawa, 240-0115, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi, 444-8585, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDA), Hayama, Kanagawa, 240-0115, Japan
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28
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Zaydman MA, Kasimova MA, McFarland K, Beller Z, Hou P, Kinser HE, Liang H, Zhang G, Shi J, Tarek M, Cui J. Domain-domain interactions determine the gating, permeation, pharmacology, and subunit modulation of the IKs ion channel. eLife 2014; 3:e03606. [PMID: 25535795 PMCID: PMC4381907 DOI: 10.7554/elife.03606] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 11/19/2014] [Indexed: 01/22/2023] Open
Abstract
Voltage-gated ion channels generate electrical currents that control muscle
contraction, encode neuronal information, and trigger hormonal release.
Tissue-specific expression of accessory (β) subunits causes these channels to
generate currents with distinct properties. In the heart, KCNQ1 voltage-gated
potassium channels coassemble with KCNE1 β-subunits to generate the
IKs current (Barhanin et al.,
1996; Sanguinetti et al., 1996),
an important current for maintenance of stable heart rhythms. KCNE1 significantly
modulates the gating, permeation, and pharmacology of KCNQ1 (Wrobel et al., 2012; Sun et
al., 2012; Abbott, 2014). These
changes are essential for the physiological role of IKs (Silva and Rudy, 2005); however, after 18 years
of study, no coherent mechanism explaining how KCNE1 affects KCNQ1 has emerged. Here
we provide evidence of such a mechanism, whereby, KCNE1 alters the state-dependent
interactions that functionally couple the voltage-sensing domains (VSDs) to the
pore. DOI:http://dx.doi.org/10.7554/eLife.03606.001 Cells are surrounded by a membrane that prevents charged molecules from flowing
directly into or out of the cell. Instead ions move through channel proteins within
the cell membrane. Most ion channel proteins are selective and only allow one or a
few types of ion to cross. Ion channels can also be ‘gated’, and have a
central pore that can open or close to allow or stop the flow of selected ions. This
gating can be affected by the channel sensing changes in conditions, such as changes
in the voltage across the cell membrane. Research conducted more than half a century ago—before the discovery of
channel proteins—led to a mathematical model of the flow of potassium ions
across a membrane in response to changes in voltage. This model made a number of
assumptions, many of which are still widely accepted. However, Zaydman et al. have
now called into question some of the assumptions of this model. Based on the original model, it has been long assumed that the voltage-sensing
domains that open or close the central pore in response to changes in voltage must be
fully activated to allow the channel to open. It had also been assumed that the
voltage-sensing domains do not affect the flow of ions once the channel is open.
Zaydman et al. have now shown that these assumptions are not valid for a specific
voltage-gated potassium channel called KCNQ1. Instead, this ion channel opens when
its voltage-sensing domains are either partially or fully activated. Zaydman found
that the intermediate-open and activated-open states had different preferences for
passing various types of ion; therefore, the gating of the channel and the flow of
ions through the open channel are both dependent on the state of the voltage-sensing
domains. This is in direct contrast to what had previously been assumed. The original model cannot reproduce the gating of KCNQ1, nor can any other
established model. Therefore, Zaydman et al. devised a new model to understand how
the interactions between different states of the voltage-sensing domains and the pore
lead to gating. Zaydman et al. then used their model to address how another protein
called KCNE1 is able to alter properties of the KCNQ1 channel. KCNE1 is a protein that is expressed in the heart muscle cell and mutations affecting
KCNQ1 or KCNE1 have been associated with potentially fatal heart conditions. Based on
the assumptions of the original model, it had been difficult to understand how KCNE1
was able to affect different properties of the KCNQ1 channel. Thus, for nearly 20
years it has been debated whether KCNE1 primarily affects the activation of the
voltage-sensing domains or the opening of the pore. Zaydman et al. found instead that
KCNE1 alters the interactions between the voltage-sensing domains and the pore, which
prevented the intermediate-open state and modified the properties of the
activated-open state. This mechanism provides one of the most complete explanations
for the action of the KCNE1 protein. DOI:http://dx.doi.org/10.7554/eLife.03606.002
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Affiliation(s)
- Mark A Zaydman
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Marina A Kasimova
- Theory, Modeling, and Simulations, UMR 7565, Université de Lorraine, Nancy, France
| | - Kelli McFarland
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Zachary Beller
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Panpan Hou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Holly E Kinser
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Hongwu Liang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Guohui Zhang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
| | - Mounir Tarek
- Theory, Modeling, and Simulations, UMR 7565, Université de Lorraine, Nancy, France
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, United States
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29
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Gourgy-Hacohen O, Kornilov P, Pittel I, Peretz A, Attali B, Paas Y. Capturing distinct KCNQ2 channel resting states by metal ion bridges in the voltage-sensor domain. ACTA ACUST UNITED AC 2014; 144:513-27. [PMID: 25385787 PMCID: PMC4242811 DOI: 10.1085/jgp.201411221] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Although crystal structures of various voltage-gated K(+) (Kv) and Na(+) channels have provided substantial information on the activated conformation of the voltage-sensing domain (VSD), the topology of the VSD in its resting conformation remains highly debated. Numerous studies have investigated the VSD resting state in the Kv Shaker channel; however, few studies have explored this issue in other Kv channels. Here, we investigated the VSD resting state of KCNQ2, a K(+) channel subunit belonging to the KCNQ (Kv7) subfamily of Kv channels. KCNQ2 can coassemble with the KCNQ3 subunit to mediate the IM current that regulates neuronal excitability. In humans, mutations in KCNQ2 are associated with benign neonatal forms of epilepsy or with severe epileptic encephalopathy. We introduced cysteine mutations into the S4 transmembrane segment of the KCNQ2 VSD and determined that external application of Cd(2+) profoundly reduced the current amplitude of S4 cysteine mutants S195C, R198C, and R201C. Based on reactivity with the externally accessible endogenous cysteine C106 in S1, we infer that each of the above S4 cysteine mutants forms Cd(2+) bridges to stabilize a channel closed state. Disulfide bonds and metal bridges constrain the S4 residues S195, R198, and R201 near C106 in S1 in the resting state, and experiments using concatenated tetrameric constructs indicate that this occurs within the same VSD. KCNQ2 structural models suggest that three distinct resting channel states have been captured by the formation of different S4-S1 Cd(2+) bridges. Collectively, this work reveals that residue C106 in S1 can be very close to several N-terminal S4 residues for stabilizing different KCNQ2 resting conformations.
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Affiliation(s)
- Orit Gourgy-Hacohen
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Polina Kornilov
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ilya Pittel
- The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Asher Peretz
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Bernard Attali
- Department of Physiology and Pharmacology, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yoav Paas
- The Mina and Everard Goodman Faculty of Life Sciences, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel
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30
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Xu Y, Wang Y, Meng XY, Zhang M, Jiang M, Cui M, Tseng GN. Building KCNQ1/KCNE1 channel models and probing their interactions by molecular-dynamics simulations. Biophys J 2014; 105:2461-73. [PMID: 24314077 DOI: 10.1016/j.bpj.2013.09.058] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/10/2013] [Accepted: 09/11/2013] [Indexed: 10/25/2022] Open
Abstract
The slow delayed rectifier (I(KS)) channel is composed of KCNQ1 (pore-forming) and KCNE1 (auxiliary) subunits, and functions as a repolarization reserve in the human heart. Design of I(KS)-targeting anti-arrhythmic drugs requires detailed three-dimensional structures of the KCNQ1/KCNE1 complex, a task made possible by Kv channel crystal structures (templates for KCNQ1 homology-modeling) and KCNE1 NMR structures. Our goal was to build KCNQ1/KCNE1 models and extract mechanistic information about their interactions by molecular-dynamics simulations in an explicit lipid/solvent environment. We validated our models by confirming two sets of model-generated predictions that were independent from the spatial restraints used in model-building. Detailed analysis of the molecular-dynamics trajectories revealed previously unrecognized KCNQ1/KCNE1 interactions, whose relevance in I(KS) channel function was confirmed by voltage-clamp experiments. Our models and analyses suggest three mechanisms by which KCNE1 slows KCNQ1 activation: by promoting S6 bending at the Pro hinge that closes the activation gate; by promoting a downward movement of gating charge on S4; and by establishing a network of electrostatic interactions with KCNQ1 on the extracellular surface that stabilizes the channel in a pre-open activated state. Our data also suggest how KCNE1 may affect the KCNQ1 pore conductance.
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Affiliation(s)
- Yu Xu
- Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia
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31
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Cui G, Rahman KS, Infield DT, Kuang C, Prince CZ, McCarty NA. Three charged amino acids in extracellular loop 1 are involved in maintaining the outer pore architecture of CFTR. ACTA ACUST UNITED AC 2014; 144:159-79. [PMID: 25024266 PMCID: PMC4113900 DOI: 10.1085/jgp.201311122] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Disease-associated mutation of charged amino acids in extracellular loop 1 of CFTR may reduce chloride flow by damaging the outer pore architecture. The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) bears six extracellular loops (ECL1–6); ECL1 is the site of several mutations associated with CF. Mutation R117H has been reported to reduce current amplitude, whereas D110H, E116K, and R117C/L/P may impair channel stability. We hypothesized that these amino acids might not be directly involved in ion conduction and permeation but may contribute to stabilizing the outer vestibule architecture in CFTR. We used cRNA injected oocytes combined with electrophysiological techniques to test this hypothesis. Mutants bearing cysteine at these sites were not functionally modified by extracellular MTS reagents and were blocked by GlyH-101 similarly to WT-CFTR. These results suggest that these three residues do not contribute directly to permeation in CFTR. In contrast, mutants D110R-, E116R-, and R117A-CFTR exhibited instability of the open state and significantly shortened burst duration compared with WT-CFTR and failed to be locked into the open state by AMP-PNP (adenosine 5′-(β,γ-imido) triphosphate); charge-retaining mutants showed mainly the full open state with comparably longer open burst duration. These interactions suggest that these ECL1 residues might be involved in maintaining the outer pore architecture of CFTR. A CFTR homology model suggested that E116 interacts with R104 in both the closed and open states, D110 interacts with K892 in the fully closed state, and R117 interacts with E1126 in the open state. These interactions were confirmed experimentally. The results suggest that D110, E116, and R117 may contribute to stabilizing the architecture of the outer pore of CFTR by interactions with other charged residues.
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Affiliation(s)
- Guiying Cui
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Kazi S Rahman
- Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332 Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332
| | - Daniel T Infield
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Christopher Kuang
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Chengyu Z Prince
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322
| | - Nael A McCarty
- Division of Pulmonary, Allergy and Immunology, Cystic Fibrosis, and Sleep, Department of Pediatrics, Center for Cystic Fibrosis and Airways Disease Research, Emory+Children's Pediatric Research Center, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, GA 30322 Parker H. Petit Institute for Bioengineering and Bioscience and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332
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Eckey K, Wrobel E, Strutz-Seebohm N, Pott L, Schmitt N, Seebohm G. Novel Kv7.1-phosphatidylinositol 4,5-bisphosphate interaction sites uncovered by charge neutralization scanning. J Biol Chem 2014; 289:22749-22758. [PMID: 24947509 DOI: 10.1074/jbc.m114.589796] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Kv7.1 to Kv7.5 α-subunits belong to the family of voltage-gated potassium channels (Kv). Assembled with the β-subunit KCNE1, Kv7.1 conducts the slowly activating potassium current IKs, which is one of the major currents underlying repolarization of the cardiac action potential. A known regulator of Kv7 channels is the lipid phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 increases the macroscopic current amplitude by stabilizing the open conformation of 7.1/KCNE1 channels. However, knowledge about the exact nature of the interaction is incomplete. The aim of this study was the identification of the amino acids responsible for the interaction between Kv7.1 and PIP2. We generated 13 charge neutralizing point mutations at the intracellular membrane border and characterized them electrophysiologically in complex with KCNE1 under the influence of diC8-PIP2. Electrophysiological analysis of corresponding long QT syndrome mutants suggested impaired PIP2 regulation as the cause for channel dysfunction. To clarify the underlying structural mechanism of PIP2 binding, molecular dynamics simulations of Kv7.1/KCNE1 complexes containing two PIP2 molecules in each subunit at specific sites were performed. Here, we identified a subset of nine residues participating in the interaction of PIP2 and Kv7.1/KCNE1. These residues may form at least two binding pockets per subunit, leading to the stabilization of channel conformations upon PIP2 binding.
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Affiliation(s)
- Karina Eckey
- Department of Biochemistry I-Cation Channel Group, Ruhr University Bochum, 44801 Bochum, Germany; International Graduate School of Neuroscience, Ruhr University Bochum, 44801 Bochum, Germany; Ruhr University Bochum Research School, and Ruhr University Bochum, 44801 Bochum, Germany
| | - Eva Wrobel
- IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and
| | - Nathalie Strutz-Seebohm
- IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and
| | - Lutz Pott
- Institute of Physiology, Ruhr University Bochum, 44801 Bochum, Germany
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, 1165 Copenhagen, Denmark
| | - Guiscard Seebohm
- International Graduate School of Neuroscience, Ruhr University Bochum, 44801 Bochum, Germany; Ruhr University Bochum Research School, and Ruhr University Bochum, 44801 Bochum, Germany; IfGH-Myocellular Electrophysiology, Department of Cardiovascular Medicine, University Hospital of Münster, 48149 Münster, Germany, and.
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33
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Nakajo K, Kubo Y. Steric hindrance between S4 and S5 of the KCNQ1/KCNE1 channel hampers pore opening. Nat Commun 2014; 5:4100. [PMID: 24920132 DOI: 10.1038/ncomms5100] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 05/13/2014] [Indexed: 01/06/2023] Open
Abstract
In voltage-gated K(+) channels, membrane depolarization induces an upward movement of the voltage-sensing domains (VSD) that triggers pore opening. KCNQ1 is a voltage-gated K(+) channel and its gating behaviour is substantially modulated by auxiliary subunit KCNE proteins. KCNE1, for example, markedly shifts the voltage dependence of KCNQ1 towards the positive direction and slows down the activation kinetics. Here we identify two phenylalanine residues on KCNQ1, Phe232 on S4 (VSD) and Phe279 on S5 (pore domain) to be responsible for the gating modulation by KCNE1. Phe232 collides with Phe279 during the course of the VSD movement and hinders KCNQ1 channel from opening in the presence of KCNE1. This steric hindrance caused by the bulky amino-acid residues destabilizes the open state and thus shifts the voltage dependence of KCNQ1/KCNE1 channel.
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Affiliation(s)
- Koichi Nakajo
- 1] Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan [2] Department of Physiological Sciences, Hayama, Kanagawa 240-0193, Japan
| | - Yoshihiro Kubo
- 1] Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan [2] Department of Physiological Sciences, Hayama, Kanagawa 240-0193, Japan
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KCNE1 divides the voltage sensor movement in KCNQ1/KCNE1 channels into two steps. Nat Commun 2014; 5:3750. [PMID: 24769622 PMCID: PMC4019390 DOI: 10.1038/ncomms4750] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 03/28/2014] [Indexed: 11/09/2022] Open
Abstract
The functional properties of KCNQ1 channels are highly dependent on associated KCNE β subunits. Mutations in KCNQ1 or KCNE subunits can cause congenital channelopathies, such as deafness, cardiac arrhythmias, and epilepsy. The mechanism by which KCNE1 beta subunits slow the kinetics of KCNQ1 channels is a matter of current controversy. Here we show that KCNQ1/KCNE1 channel activation occurs in two steps: first, mutually independent voltage sensor movements in the four KCNQ1 subunits generate the main gating charge movement and underlie the initial delay in the activation time course of KCNQ1/KCNE1 currents. Second, a slower and concerted conformational change of all four voltage sensors and the gate, which opens the KCNQ1/KCNE1 channel. Our data show that KCNE1 divides the voltage sensor movement into two steps with widely different voltage dependences and kinetics. The two voltage sensor steps in KCNQ1/KCNE1 channels can be pharmacologically isolated and further separated by a disease-causing mutation.
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Dvir M, Peretz A, Haitin Y, Attali B. Recent molecular insights from mutated IKS channels in cardiac arrhythmia. Curr Opin Pharmacol 2013; 15:74-82. [PMID: 24721657 DOI: 10.1016/j.coph.2013.12.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/04/2013] [Accepted: 12/06/2013] [Indexed: 12/19/2022]
Abstract
Co-assembly of KCNQ1 with KCNE1 generates the IKS potassium current that is vital for the proper repolarization of the cardiac action potential. Mutations in either KCNQ1 or KCNE1 genes lead to life-threatening cardiac arrhythmias causing long QT syndrome, short QT syndrome, sinus bradycardia and atrial fibrillation. Findings emerging from recent studies are beginning to provide a picture of how gain-of-function and loss-of-function mutations are associated with pleiotropic cardiac phenotypes in the clinics. In this review, we discuss recent molecular insights obtained from mutations altering different structural modules of the channel complex that are essential for proper IKS function. We present the possible molecular mechanisms underlying mutations impairing the voltage sensing functions, as well as those altering the channel regulation by phosphatidylinositol-4,5-bisphosphate, calmodulin and protein kinase A. We also discuss the significance of diseased IKS channels for adequate pharmacological targeting of cardiac arrhythmias.
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Affiliation(s)
- Meidan Dvir
- Department of Physiology & Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Asher Peretz
- Department of Physiology & Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Yoni Haitin
- Department of Physiology & Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Bernard Attali
- Department of Physiology & Pharmacology, The Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel.
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Wang Y, Zhang M, Xu Y, Jiang M, Zankov DP, Cui M, Tseng GN. Probing the structural basis for differential KCNQ1 modulation by KCNE1 and KCNE2. ACTA ACUST UNITED AC 2013. [PMID: 23183700 PMCID: PMC3514736 DOI: 10.1085/jgp.201210847] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
KCNE1 associates with KCNQ1 to increase its current amplitude and slow the activation gating process, creating the slow delayed rectifier channel that functions as a “repolarization reserve” in human heart. The transmembrane domain (TMD) of KCNE1 plays a key role in modulating KCNQ1 pore conductance and gating kinetics, and the extracellular juxtamembrane (EJM) region plays a modulatory role by interacting with the extracellular surface of KCNQ1. KCNE2 is also expressed in human heart and can associate with KCNQ1 to suppress its current amplitude and slow the deactivation gating process. KCNE1 and KCNE2 share the transmembrane topology and a high degree of sequence homology in TMD and surrounding regions. The structural basis for their distinctly different effects on KCNQ1 is not clear. To address this question, we apply cysteine (Cys) scanning mutagenesis to TMDs and EJMs of KCNE1 and KCNE2. We analyze the patterns of functional perturbation to identify high impact positions, and probe disulfide formation between engineered Cys side chains on KCNE subunits and native Cys on KCNQ1. We also use methanethiosulfonate reagents to probe the relationship between EJMs of KCNE subunits and KCNQ1. Our data suggest that the TMDs of both KCNE subunits are at about the same location but interact differently with KCNQ1. In particular, the much closer contact of KCNE2 TMD with KCNQ1, relative to that of KCNE1, is expected to impact the allosteric modulation of KCNQ1 pore conductance and may explain their differential effects on the KCNQ1 current amplitude. KCNE1 and KCNE2 also differ in the relationship between their EJMs and KCNQ1. Although the EJM of KCNE1 makes intimate contacts with KCNQ1, there appears to be a crevice between KCNQ1 and KCNE2. This putative crevice may perturb the electrical field around the voltage-sensing domain of KCNQ1, contributing to the differential effects of KCNE2 versus KCNE1 on KCNQ1 gating kinetics.
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Affiliation(s)
- Yuhong Wang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA
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Hoosien M, Ahearn ME, Myerburg RJ, Pham TV, Miller TE, Smets MJ, Baumbach-Reardon L, Young ML, Farooq A, Bishopric NH. Dysfunctional potassium channel subunit interaction as a novel mechanism of long QT syndrome. Heart Rhythm 2013; 10:728-37. [PMID: 23291057 PMCID: PMC4770260 DOI: 10.1016/j.hrthm.2012.12.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Indexed: 01/02/2023]
Abstract
BACKGROUND The slowly-activating delayed rectifier current IKs contributes to repolarization of the cardiac action potential, and is composed of a pore-forming α-subunit, KCNQ1, and a modulatory β-subunit, KCNE1. Mutations in either subunit can cause long QT syndrome, a potentially fatal arrhythmic disorder. How KCNE1 exerts its extensive control over the kinetics of IKs remains unresolved OBJECTIVE To evaluate the impact of a novel KCNQ1 mutation on IKs channel gating and kinetics METHODS KCNQ1 mutations were expressed in Xenopus oocytes in the presence and absence of KCNE1. Voltage clamping and MODELLER software were used to characterize and model channel function. Mutant and wt genes were cloned into FLAG, Myc and HA expression vectors to achieve differential epitope tagging, and expressed in HEK293 cells for immunohistochemical localization and surface biotinylation assay. RESULTS We identified 2 adjacent mutations, S338F and F339S, in the KCNQ1 S6 domain in unrelated probands. The novel KCNQ1 S338F mutation segregated with prolonged QT interval and torsade de pointes; the second variant, F339S, was associated with fetal bradycardia and prolonged QT interval, but no other clinical events. S338F channels expressed in Xenopus oocytes had slightly increased peak conductance relative to wild type, with a more positive activation voltage. F339S channels conducted minimal current. Unexpectedly, S338F currents were abolished by co-expression with intact WT KCNE1 or its C-terminus (aa63-129), despite normal membrane trafficking and surface co-localization of KCNQ1 S338F and wt KCNE1. Structural modeling indicated that the S338F mutation specifically alters the interaction between the S6 domain of one KCNQ1 subunit and the S4-S5 linker of another, inhibiting voltage-induced movement synergistically with KCNE1 binding. CONCLUSIONS A novel KCNQ1 mutation specifically impaired channel function in the presence of KCNE1. Our structural model shows that this mutation effectively immobilizes voltage gating by an inhibitory interaction that is additive with that of KCNE1. Our findings illuminate a previously unreported mechanism for LQTS, and validate recent theoretical models of the closed state of the KCNQ1:KCNE1 complex.
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Affiliation(s)
- Michael Hoosien
- Department of Medicine, University of Miami Miller School of Medicine
| | - Mary Ellen Ahearn
- Department of Medicine, University of Miami Miller School of Medicine
- Department of Neurology, University of Miami Miller School of Medicine
| | - Robert J. Myerburg
- Department of Medicine, University of Miami Miller School of Medicine
- Department of Physiology, University of Miami Miller School of Medicine
| | - Thai V. Pham
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine
| | - Todd E. Miller
- Department of Medicine, University of Miami Miller School of Medicine
| | - Marcel J. Smets
- Department of Medicine, University of Miami Miller School of Medicine
| | - Lisa Baumbach-Reardon
- Department of Neurology, University of Miami Miller School of Medicine
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine
| | - Ming-Lon Young
- Department of Pediatrics, University of Miami Miller School of Medicine
| | - Amjad Farooq
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine
| | - Nanette H. Bishopric
- Department of Medicine, University of Miami Miller School of Medicine
- Department of Pediatrics, University of Miami Miller School of Medicine
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine
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Wrobel E, Tapken D, Seebohm G. The KCNE Tango - How KCNE1 Interacts with Kv7.1. Front Pharmacol 2012; 3:142. [PMID: 22876232 PMCID: PMC3410610 DOI: 10.3389/fphar.2012.00142] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/29/2012] [Indexed: 12/23/2022] Open
Abstract
The classical tango is a dance characterized by a 2/4 or 4/4 rhythm in which the partners dance in a coordinated way, allowing dynamic contact. There is a surprising similarity between the tango and how KCNE β-subunits "dance" to the fast rhythm of the cell with their partners from the Kv channel family. The five KCNE β-subunits interact with several members of the Kv channels, thereby modifying channel gating via the interaction of their single transmembrane-spanning segment, the extracellular amino terminus, and/or the intracellular carboxy terminus with the Kv α-subunit. Best studied is the molecular basis of interactions between KCNE1 and Kv7.1, which, together, supposedly form the native cardiac I(Ks) channel. Here we review the current knowledge about functional and molecular interactions of KCNE1 with Kv7.1 and try to summarize and interpret the tango of the KCNEs.
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Affiliation(s)
- Eva Wrobel
- Cation Channel Group, Department of Biochemistry I, Faculty of Chemistry and Biochemistry, Ruhr University Bochum Bochum, Germany
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Gofman Y, Shats S, Attali B, Haliloglu T, Ben-Tal N. How does KCNE1 regulate the Kv7.1 potassium channel? Model-structure, mutations, and dynamics of the Kv7.1-KCNE1 complex. Structure 2012; 20:1343-52. [PMID: 22771213 DOI: 10.1016/j.str.2012.05.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 05/29/2012] [Accepted: 05/29/2012] [Indexed: 11/15/2022]
Abstract
The voltage-gated potassium channel Kv7.1 and its auxiliary subunit KCNE1 are expressed in the heart and give rise to the major repolarization current. The interaction of Kv7.1 with the single transmembrane helix of KCNE1 considerably slows channel activation and deactivation, raises single-channel conductance, and prevents slow voltage-dependent inactivation. We built a Kv7.1-KCNE1 model-structure. The model-structure agrees with previous disulfide mapping studies and enables us to derive molecular interpretations of electrophysiological recordings that we obtained for two KCNE1 mutations. An elastic network analysis of Kv7.1 fluctuations in the presence and absence of KCNE1 suggests a mechanistic perspective on the known effects of KCNE1 on Kv7.1 function: slow deactivation is attributed to the low mobility of the voltage-sensor domains upon KCNE1 binding, abolishment of voltage-dependent inactivation could result from decreased fluctuations in the external vestibule, and amalgamation of the fluctuations in the pore region is associated with enhanced ion conductivity.
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Affiliation(s)
- Yana Gofman
- Department of Biochemistry and Molecular Biology, Tel-Aviv University, 69978 Tel-Aviv, Israel
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Sun X, Zaydman MA, Cui J. Regulation of Voltage-Activated K(+) Channel Gating by Transmembrane β Subunits. Front Pharmacol 2012; 3:63. [PMID: 22529812 PMCID: PMC3328208 DOI: 10.3389/fphar.2012.00063] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 03/29/2012] [Indexed: 01/15/2023] Open
Abstract
Voltage-activated K+ (KV) channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. KV channels contain a central pore-gate domain (PGD) surrounded by four voltage-sensing domains (VSDs). The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many KV channels are heteromeric protein complexes containing auxiliary β subunits. These β subunits modulate channel expression and activity to increase functional diversity and render tissue specific phenotypes. This review focuses on the KV β subunits that contain transmembrane (TM) segments including the KCNE family and the β subunits of large conductance, Ca2+- and voltage-activated K+ (BK) channels. These TM β subunits affect the voltage-dependent activation of KV α subunits. Experimental and computational studies have described the structural location of these β subunits in the channel complexes and the biophysical effects on VSD activation, PGD opening, and VSD–PGD coupling. These results reveal some common characteristics and mechanistic insights into KV channel modulation by TM β subunits.
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Affiliation(s)
- Xiaohui Sun
- Department of Biomedical Engineering, Washington University Saint Louis, MO, USA
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Chen J, Angeletti R, McDonald TV, Xiao H. Binding interface of cardiac potassium channel proteins identified by hydrogen deuterium exchange of synthetic peptides. Anal Bioanal Chem 2012; 403:1303-9. [PMID: 22392372 DOI: 10.1007/s00216-012-5857-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/03/2012] [Accepted: 02/08/2012] [Indexed: 10/28/2022]
Abstract
Three synthetic peptides, derived from the human potassium channel proteins Ether-a-go-go-related gene (HERG), KCNQ1, and KCNE1, were investigated by hydrogen deuterium exchange coupled with electron-transfer dissociation mass spectrometry at single residue resolution. Each amino acid residue in the first half of the HERG peptide incorporated deuterons with a higher rate than those in the second half of the peptide, consistent with the nuclear magnetic resonance structure of this peptide, with amino acids 1-10 being a flexible coil, whereas amino acids 11-24 are a stable amphipathic helix. The binding interface of KCNQ1 and KCNE1 was determined by comparing the difference of sequential fragment ions before and after binding. The residues determined to be involved in binding were consistent with a cysteine cross-linking study and confirmed by double mutant cycle analysis.
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Affiliation(s)
- Jerri Chen
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Nakajo K, Nishino A, Okamura Y, Kubo Y. KCNQ1 subdomains involved in KCNE modulation revealed by an invertebrate KCNQ1 orthologue. ACTA ACUST UNITED AC 2012; 138:521-35. [PMID: 22042987 PMCID: PMC3206303 DOI: 10.1085/jgp.201110677] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
KCNQ1 channels are voltage-gated potassium channels that are widely expressed in various non-neuronal tissues, such as the heart, pancreas, and intestine. KCNE proteins are known as the auxiliary subunits for KCNQ1 channels. The effects and functions of the different KCNE proteins on KCNQ1 modulation are various; the KCNQ1–KCNE1 ion channel complex produces a slowly activating potassium channel that is crucial for heartbeat regulation, while the KCNE3 protein makes KCNQ1 channels constitutively active, which is important for K+ and Cl− transport in the intestine. The mechanisms by which KCNE proteins modulate KCNQ1 channels have long been studied and discussed; however, it is not well understood how different KCNE proteins exert considerably different effects on KCNQ1 channels. Here, we approached this point by taking advantage of the recently isolated Ci-KCNQ1, a KCNQ1 homologue from marine invertebrate Ciona intestinalis. We found that Ci-KCNQ1 alone could be expressed in Xenopus laevis oocytes and produced a voltage-dependent potassium current, but that Ci-KCNQ1 was not properly modulated by KCNE1 and totally unaffected by coexpression of KCNE3. By making chimeras of Ci-KCNQ1 and human KCNQ1, we determined several amino acid residues located in the pore region of human KCNQ1 involved in KCNE1 modulation. Interestingly, though, these amino acid residues of the pore region are not important for KCNE3 modulation, and we subsequently found that the S1 segment plays an important role in making KCNQ1 channels constitutively active by KCNE3. Our findings indicate that different KCNE proteins use different domains of KCNQ1 channels, and that may explain why different KCNE proteins give quite different outcomes by forming a complex with KCNQ1 channels.
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Affiliation(s)
- Koichi Nakajo
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan.
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Chan PJ, Osteen JD, Xiong D, Bohnen MS, Doshi D, Sampson KJ, Marx SO, Karlin A, Kass RS. Characterization of KCNQ1 atrial fibrillation mutations reveals distinct dependence on KCNE1. ACTA ACUST UNITED AC 2012; 139:135-44. [PMID: 22250012 PMCID: PMC3269792 DOI: 10.1085/jgp.201110672] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The I(Ks) potassium channel, critical to control of heart electrical activity, requires assembly of α (KCNQ1) and β (KCNE1) subunits. Inherited mutations in either I(Ks) channel subunit are associated with cardiac arrhythmia syndromes. Two mutations (S140G and V141M) that cause familial atrial fibrillation (AF) are located on adjacent residues in the first membrane-spanning domain of KCNQ1, S1. These mutations impair the deactivation process, causing channels to appear constitutively open. Previous studies suggest that both mutant phenotypes require the presence of KCNE1. Here we found that despite the proximity of these two mutations in the primary protein structure, they display different functional dependence in the presence of KCNE1. In the absence of KCNE1, the S140G mutation, but not V141M, confers a pronounced slowing of channel deactivation and a hyperpolarizing shift in voltage-dependent activation. When coexpressed with KCNE1, both mutants deactivate significantly slower than wild-type KCNQ1/KCNE1 channels. The differential dependence on KCNE1 can be correlated with the physical proximity between these positions and KCNE1 as shown by disulfide cross-linking studies: V141C forms disulfide bonds with cysteine-substituted KCNE1 residues, whereas S140C does not. These results further our understanding of the structural relationship between KCNE1 and KCNQ1 subunits in the I(Ks) channel, and provide mechanisms for understanding the effects on channel deactivation underlying these two atrial fibrillation mutations.
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Affiliation(s)
- Priscilla J Chan
- Department of Pharmacology, Columbia University Medical Center, New York, NY 10032, USA
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The voltage-gated channel accessory protein KCNE2: multiple ion channel partners, multiple ways to long QT syndrome. Expert Rev Mol Med 2011; 13:e38. [DOI: 10.1017/s1462399411002092] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The single-pass transmembrane protein KCNE2 or MIRP1 was once thought to be the missing accessory protein that combined with hERG to fully recapitulate the cardiac repolarising current IKr. As a result of this role, it was an easy next step to associate mutations in KCNE2 to long QT syndrome, in which there is delayed repolarisation of the heart. Since that time however, KCNE2 has been shown to modify the behaviour of several other channels and currents, and its role in the heart and in the aetiology of long QT syndrome has become less clear. In this article, we review the known interactions of the KCNE2 protein and the resulting functional effects, and the effects of mutations in KCNE2 and their clinical role.
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Girmatsion Z, Biliczki P, Takac I, Schwerthelm C, Hohnloser SH, Ehrlich JR. N-terminal arginines modulate plasma-membrane localization of Kv7.1/KCNE1 channel complexes. PLoS One 2011; 6:e26967. [PMID: 22073228 PMCID: PMC3208574 DOI: 10.1371/journal.pone.0026967] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 10/06/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND AND OBJECTIVE The slow delayed rectifier current (I(Ks)) is important for cardiac action potential termination. The underlying channel is composed of Kv7.1 α-subunits and KCNE1 β-subunits. While most evidence suggests a role of KCNE1 transmembrane domain and C-terminus for the interaction, the N-terminal KCNE1 polymorphism 38G is associated with reduced I(Ks) and atrial fibrillation (a human arrhythmia). Structure-function relationship of the KCNE1 N-terminus for I(Ks) modulation is poorly understood and was subject of this study. METHODS We studied N-terminal KCNE1 constructs disrupting structurally important positively charged amino-acids (arginines) at positions 32, 33, 36 as well as KCNE1 constructs that modify position 38 including an N-terminal truncation mutation. Experimental procedures included molecular cloning, patch-clamp recording, protein biochemistry, real-time-PCR and confocal microscopy. RESULTS All KCNE1 constructs physically interacted with Kv7.1. I(Ks) resulting from co-expression of Kv7.1 with non-atrial fibrillation '38S' was greater than with any other construct. Ionic currents resulting from co-transfection of a KCNE1 mutant with arginine substitutions ('38G-3xA') were comparable to currents evoked from cells transfected with an N-terminally truncated KCNE1-construct ('Δ1-38'). Western-blots from plasma-membrane preparations and confocal images consistently showed a greater amount of Kv7.1 protein at the plasma-membrane in cells co-transfected with the non-atrial fibrillation KCNE1-38S than with any other construct. CONCLUSIONS The results of our study indicate that N-terminal arginines in positions 32, 33, 36 of KCNE1 are important for reconstitution of I(Ks). Furthermore, our results hint towards a role of these N-terminal amino-acids in membrane representation of the delayed rectifier channel complex.
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Affiliation(s)
- Zenawit Girmatsion
- Division of Cardiology, Section of Electrophysiology, JW Goethe-University, Frankfurt, Germany
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Mikuni I, Torres CG, Bienengraeber MW, Kwok WM. Partial restoration of the long QT syndrome associated KCNQ1 A341V mutant by the KCNE1 β-subunit. Biochim Biophys Acta Gen Subj 2011; 1810:1285-93. [PMID: 21854832 DOI: 10.1016/j.bbagen.2011.07.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 07/19/2011] [Accepted: 07/29/2011] [Indexed: 12/27/2022]
Abstract
BACKGROUND The A341V mutation in the pore-forming KCNQ1 subunit of the slowly activating delayed-rectifier potassium current (IKs) underlies a common form of the long QT syndrome, and is associated with an unusually severe phenotype. However, there is controversy regarding the underlying mechanism responsible for the clinically observed phenotype. We investigated the biophysical characteristics of A341V in a cardiac environment by utilizing a cardiac cell line, and in particular the impact of the KCNE1 β-subunit. METHODS Whole-cell current were recorded from transiently transfected HL-1 cells, a cardiac cell line. Mutant KCNQ1 and KCNE1 were constructed by site-directed mutagenesis. RESULTS The A341V mutant resulted in a non-functional channel when expressed alone. When co-expressed with wild type KCNE1, A341V produced a slowly activating current, with a smaller current density, slower rates of activation, and a depolarized shift in its activation curve compared to the wild type KCNQ1+KCNE1. Confocal microscopy confirmed the surface expression of GFP-tagged A341V, suggesting a functionally defective protein. A T58A mutation in KCNE1 abolished functional restoration of A341V. Under heterozygous conditions, the expression of A341V+KCNQ1+KCNE1 reduced but did not abolish the electrophysiological changes observed in A341V+KCNE1. A dominant negative effect of A341V was also observed. Action potential simulations revealed that the A341V mutation is arrhythmogenic. CONCLUSIONS The KCNE1 β-subunit partially rescued the non-functional A341V mutant, with electrophysiological properties distinct from the wild type IKs. GENERAL SIGNIFICANCE The severity of the A341V phenotype may be due to a combination of a significant suppression of the IKs with altered biophysical characteristics.
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Affiliation(s)
- Ikuomi Mikuni
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Strutz-Seebohm N, Pusch M, Wolf S, Stoll R, Tapken D, Gerwert K, Attali B, Seebohm G. Structural basis of slow activation gating in the cardiac I Ks channel complex. Cell Physiol Biochem 2011; 27:443-52. [PMID: 21691061 DOI: 10.1159/000329965] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2011] [Indexed: 12/18/2022] Open
Abstract
Accessory β-subunits of the KCNE gene family modulate the function of various cation channel α-subunits by the formation of heteromultimers. Among the most dramatic changes of biophysical properties of a voltage-gated channel by KCNEs are the effects of KCNE1 on KCNQ1 channels. KCNQ1 and KCNE1 are believed to form nativeI(Ks) channels. Here, we characterize molecular determinants of KCNE1 interaction with KCNQ1 channels by scanning mutagenesis, double mutant cycle analysis, and molecular dynamics simulations. Our findings suggest that KCNE1 binds to the outer face of the KCNQ1 channel pore domain, modifies interactions between voltage sensor, S4-S5 linker and the pore domain, leading to structural modifications of the selectivity filter and voltage sensor domain. Molecular dynamics simulations suggest a stable interaction of the KCNE1 transmembrane α-helix with the pore domain S5/S6 and part of the voltage sensor domain S4 of KCNQ1 in a putative pre-open channel state. Formation of this state may induce slow activation gating, the pivotal characteristic of native cardiac I(Ks) channels. This new KCNQ1-KCNE1 model may become useful for dynamic modeling of disease-associated mutant I(Ks) channels.
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Wu D, Pan H, Delaloye K, Cui J. KCNE1 remodels the voltage sensor of Kv7.1 to modulate channel function. Biophys J 2011; 99:3599-608. [PMID: 21112284 DOI: 10.1016/j.bpj.2010.10.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 10/07/2010] [Accepted: 10/12/2010] [Indexed: 01/28/2023] Open
Abstract
The KCNE1 auxiliary subunit coassembles with the Kv7.1 channel and modulates its properties to generate the cardiac I(Ks) current. Recent biophysical evidence suggests that KCNE1 interacts with the voltage-sensing domain (VSD) of Kv7.1. To investigate the mechanism of how KCNE1 affects the VSD to alter the voltage dependence of channel activation, we perturbed the VSD of Kv7.1 by mutagenesis and chemical modification in the absence and presence of KCNE1. Mutagenesis of S4 in Kv7.1 indicates that basic residues in the N-terminal half (S4-N) and C-terminal half (S4-C) of S4 are important for stabilizing the resting and activated states of the channel, respectively. KCNE1 disrupts electrostatic interactions involving S4-C, specifically with the lower conserved glutamate in S2 (Glu(170) or E2). Likewise, Trp scanning of S4 shows that mutations to a cluster of residues in S4-C eliminate current in the presence of KCNE1. In addition, KCNE1 affects S4-N by enhancing MTS accessibility to the top of the VSD. Consistent with the structure of Kv channels and previous studies on the KCNE1-Kv7.1 interaction, these results suggest that KCNE1 alters the interactions of S4 residues with the surrounding protein environment, possibly by changing the protein packing around S4, thereby affecting the voltage dependence of Kv7.1.
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Affiliation(s)
- Dick Wu
- Department of Biomedical Engineering, and Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri, USA
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Van Horn WD, Vanoye CG, Sanders CR. Working model for the structural basis for KCNE1 modulation of the KCNQ1 potassium channel. Curr Opin Struct Biol 2011; 21:283-91. [PMID: 21296569 DOI: 10.1016/j.sbi.2011.01.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 01/03/2011] [Accepted: 01/04/2011] [Indexed: 12/19/2022]
Abstract
The voltage-gated potassium channel KCNQ1 (Kv7.1) is modulated by KCNE1 (minK) to generate the I(Ks) current crucial to heartbeat. Defects in either protein result in serious cardiac arrhythmias. Recently developed structural models of the open and closed state KCNQ1/KCNE1 complexes offer a compelling explanation for how KCNE1 slows channel opening and provides a platform from which to refine and test hypotheses for other aspects of KCNE1 modulation. These working models were developed using an integrative approach based on results from nuclear magnetic resonance spectroscopy, electrophysiology, biochemistry, and computational methods-an approach that can be applied iteratively for model testing and revision. We present a critical review of these structural models, illustrating the strengths and challenges of the integrative approach.
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Affiliation(s)
- Wade D Van Horn
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-8725, USA
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