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Fedida D, Sastre D, Dou Y, Westhoff M, Eldstrom J. Evaluating sequential and allosteric activation models in IKs channels with mutated voltage sensors. J Gen Physiol 2024; 156:e202313465. [PMID: 38294435 PMCID: PMC10829594 DOI: 10.1085/jgp.202313465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 11/30/2023] [Accepted: 01/03/2024] [Indexed: 02/01/2024] Open
Abstract
The ion-conducting IKs channel complex, important in cardiac repolarization and arrhythmias, comprises tetramers of KCNQ1 α-subunits along with 1-4 KCNE1 accessory subunits and calmodulin regulatory molecules. The E160R mutation in individual KCNQ1 subunits was used to prevent activation of voltage sensors and allow direct determination of transition rate data from complexes opening with a fixed number of 1, 2, or 4 activatable voltage sensors. Markov models were used to test the suitability of sequential versus allosteric models of IKs activation by comparing simulations with experimental steady-state and transient activation kinetics, voltage-sensor fluorescence from channels with two or four activatable domains, and limiting slope currents at negative potentials. Sequential Hodgkin-Huxley-type models approximately describe IKs currents but cannot explain an activation delay in channels with only one activatable subunit or the hyperpolarizing shift in the conductance-voltage relationship with more activatable voltage sensors. Incorporating two voltage sensor activation steps in sequential models and a concerted step in opening via rates derived from fluorescence measurements improves models but does not resolve fundamental differences with experimental data. Limiting slope current data that show the opening of channels at negative potentials and very low open probability are better simulated using allosteric models of activation with one transition per voltage sensor, which implies that movement of all four sensors is not required for IKs conductance. Tiered allosteric models with two activating transitions per voltage sensor can fully account for IKs current and fluorescence activation kinetics in constructs with different numbers of activatable voltage sensors.
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Affiliation(s)
- David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Daniel Sastre
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Maartje Westhoff
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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2
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Scheyer MW, Campbell C, William PL, Hussain M, Begum A, Fonseca SE, Asare IK, Dabney P, Dabney-Smith C, Lorigan GA, Sahu ID. Electron paramagnetic resonance spectroscopic characterization of the human KCNE3 protein in lipodisq nanoparticles for structural dynamics of membrane proteins. Biophys Chem 2023; 301:107080. [PMID: 37531799 DOI: 10.1016/j.bpc.2023.107080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/07/2023] [Accepted: 07/24/2023] [Indexed: 08/04/2023]
Abstract
One of the major challenges in solubilization of membrane proteins is to find the optimal physiological environment for their biophysical studies. EPR spectroscopy is a powerful biophysical technique for studying the structural and dynamic properties of macromolecules. However, the challenges in the membrane protein sample preparation and flexible motion of the spin label limit the utilization of EPR spectroscopy to a majority of membrane protein systems in a physiological membrane-bound state. Recently, lipodisq nanoparticles or styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) have emerged as a membrane mimetic system for investigating the structural studies of membrane proteins. However, its detail characterization for membrane protein studies is still poorly understood. Recently, we characterized the potassium channel membrane protein KCNQ1 voltage sensing domain (KCNQ1-VSD) and KCNE1 reconstituted into lipodisq nanoparticles using EPR spectroscopy. In this study, the potassium channel accessory protein KCNE3 containing flexible N- and C-termini was encapsulated into proteoliposomes and lipodisq nanoparticles and characterized for studying its structural and dynamic properties using nitroxide based site-directed spin labeling EPR spectroscopy. CW-EPR lineshape analysis data indicated an increase in spectral line broadenings with the addition of the styrene-maleic acid (SMA) polymer which approaches close to the rigid limit providing a homogeneous stabilization of the protein-lipid complex. Similarly, EPR DEER measurements indicated an enhanced quality of distance measurements with an increase in the phase memory time (Tm) values upon incorporation of the sample into lipodisq nanoparticles, when compared to proteoliposomes. These results agree with the solution NMR structural structure of the KCNE3 and EPR studies of other membrane proteins in lipodisq nanoparticles. This study along with our earlier studies will provide the reference characterization data that will provide benefit to the membrane protein researchers for studying structural dynamics of challenging membrane proteins.
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Affiliation(s)
- Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Patrick L William
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Mustakim Hussain
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Afsana Begum
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | | | - Isaac K Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Peyton Dabney
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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3
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Hiniesto-Iñigo I, Castro-Gonzalez LM, Corradi V, Skarsfeldt MA, Yazdi S, Lundholm S, Nikesjö J, Noskov SY, Bentzen BH, Tieleman DP, Liin SI. Endocannabinoids enhance hK V7.1/KCNE1 channel function and shorten the cardiac action potential and QT interval. EBioMedicine 2023; 89:104459. [PMID: 36796231 PMCID: PMC9958262 DOI: 10.1016/j.ebiom.2023.104459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 01/11/2023] [Accepted: 01/18/2023] [Indexed: 02/15/2023] Open
Abstract
BACKGROUND Genotype-positive patients who suffer from the cardiac channelopathy Long QT Syndrome (LQTS) may display a spectrum of clinical phenotypes, with often unknown causes. Therefore, there is a need to identify factors influencing disease severity to move towards an individualized clinical management of LQTS. One possible factor influencing the disease phenotype is the endocannabinoid system, which has emerged as a modulator of cardiovascular function. In this study, we aim to elucidate whether endocannabinoids target the cardiac voltage-gated potassium channel KV7.1/KCNE1, which is the most frequently mutated ion channel in LQTS. METHODS We used two-electrode voltage clamp, molecular dynamics simulations and the E4031 drug-induced LQT2 model of ex-vivo guinea pig hearts. FINDINGS We found a set of endocannabinoids that facilitate channel activation, seen as a shifted voltage-dependence of channel opening and increased overall current amplitude and conductance. We propose that negatively charged endocannabinoids interact with known lipid binding sites at positively charged amino acids on the channel, providing structural insights into why only specific endocannabinoids modulate KV7.1/KCNE1. Using the endocannabinoid ARA-S as a prototype, we show that the effect is not dependent on the KCNE1 subunit or the phosphorylation state of the channel. In guinea pig hearts, ARA-S was found to reverse the E4031-prolonged action potential duration and QT interval. INTERPRETATION We consider the endocannabinoids as an interesting class of hKV7.1/KCNE1 channel modulators with putative protective effects in LQTS contexts. FUNDING ERC (No. 850622), Canadian Institutes of Health Research, Canada Research Chairs and Compute Canada, Swedish National Infrastructure for Computing.
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Affiliation(s)
- Irene Hiniesto-Iñigo
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Laura M Castro-Gonzalez
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Valentina Corradi
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Mark A Skarsfeldt
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Samira Yazdi
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Siri Lundholm
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Johan Nikesjö
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Bo Hjorth Bentzen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Sara I Liin
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.
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Campbell C, Faleel FDM, Scheyer MW, Haralu S, Williams PL, Carbo WD, Wilson-Taylor AS, Patel NH, Sanders CR, Lorigan GA, Sahu ID. Comparing the structural dynamics of the human KCNE3 in reconstituted micelle and lipid bilayered vesicle environments. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183974. [PMID: 35716725 DOI: 10.1016/j.bbamem.2022.183974] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 05/12/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
KCNE3 is a single transmembrane protein of the KCNE family that modulates the function and trafficking of several voltage-gated potassium channels, including KCNQ1. Structural studies of KCNE3 have been previously conducted in a wide range of model membrane mimics. However, it is important to assess the impact of the membrane mimics used on the observed conformation and dynamics. In this study, we have optimized a method for the reconstitution of the KCNE3 into POPC/POPG lipid bilayer vesicles for electron paramagnetic resonance (EPR) spectroscopy. Our CD spectroscopic data suggested that the degree of regular secondary structure for KCNE3 protein reconstituted into lipid bilayered vesicle is significantly higher than in DPC detergent micelles. Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labeling (SDSL) was used to probe the structural dynamics of S49C, M59C, L67C, V85C, and S101C mutations of KCNE3 in both DPC micelles and in POPC/POPG lipid bilayered vesicles. Our CW-EPR power saturation data suggested that the site S74C is buried inside the lipid bilayered membrane while the site V85C is located outside the membrane, in contrast to DPC micelle results. These results suggest that the KCNE3 micelle structures need to be refined using data obtained in the lipid bilayered vesicles in order to ascertain the native structure of KCNE3. This work will provide guidelines for detailed structural studies of KCNE3 in a more native membrane environment and comparing the lipid bilayer results to the isotropic bicelle structure and to the KCNQ1-bound cryo-EM structure.
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Affiliation(s)
- Conner Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | | | - Matthew W Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Samuel Haralu
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Patrick L Williams
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - William David Carbo
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | | | - Nima H Patel
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN, United States of America
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, United States of America
| | - Indra D Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY, United States of America; Department of Chemistry and Biochemistry, Miami University, Oxford, OH, United States of America.
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5
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Asare IK, Galende AP, Garcia AB, Cruz MF, Moura ACM, Campbell CC, Scheyer M, Alao JP, Alston S, Kravats AN, Sanders CR, Lorigan GA, Sahu ID. Investigating Structural Dynamics of KCNE3 in Different Membrane Environments Using Molecular Dynamics Simulations. MEMBRANES 2022; 12:membranes12050469. [PMID: 35629795 PMCID: PMC9147993 DOI: 10.3390/membranes12050469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/21/2022] [Accepted: 04/21/2022] [Indexed: 11/27/2022]
Abstract
KCNE3 is a potassium channel accessory transmembrane protein that regulates the function of various voltage-gated potassium channels such as KCNQ1. KCNE3 plays an important role in the recycling of potassium ion by binding with KCNQ1. KCNE3 can be found in the small intestine, colon, and in the human heart. Despite its biological significance, there is little information on the structural dynamics of KCNE3 in native-like membrane environments. Molecular dynamics (MD) simulations are a widely used as a tool to study the conformational dynamics and interactions of proteins with lipid membranes. In this study, we have utilized all-atom molecular dynamics simulations to characterize the molecular motions and the interactions of KCNE3 in a bilayer composed of: a mixture of POPC and POPG lipids (3:1), POPC alone, and DMPC alone. Our MD simulation results suggested that the transmembrane domain (TMD) of KCNE3 is less flexible and more stable when compared to the N- and C-termini of KCNE3 in all three membrane environments. The conformational flexibility of N- and C-termini varies across these three lipid environments. The MD simulation results further suggested that the TMD of KCNE3 spans the membrane width, having residue A69 close to the center of the lipid bilayers and residues S57 and S82 close to the lipid bilayer membrane surfaces. These results are consistent with previous biophysical studies of KCNE3. The outcomes of these MD simulations will help design biophysical experiments and complement the experimental data obtained on KCNE3 to obtain a more detailed understanding of its structural dynamics in the native membrane environment.
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Affiliation(s)
- Isaac K. Asare
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Alberto Perez Galende
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Andres Bastidas Garcia
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Mateo Fernandez Cruz
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Anna Clara Miranda Moura
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Conner C. Campbell
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Matthew Scheyer
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - John Paul Alao
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
| | - Steve Alston
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
| | - Andrea N. Kravats
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
| | - Charles R. Sanders
- Center for Structural Biology, Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA;
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
- Correspondence: (G.A.L.); (I.D.S.); Tel.: +1-(513)-529-2813 (G.A.L.); +1-(270)-789-5597 (I.D.S.)
| | - Indra D. Sahu
- Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA; (I.K.A.); (A.P.G.); (A.B.G.); (M.F.C.); (A.C.M.M.); (C.C.C.); (M.S.); (S.A.)
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; (J.P.A.); (A.N.K.)
- Correspondence: (G.A.L.); (I.D.S.); Tel.: +1-(513)-529-2813 (G.A.L.); +1-(270)-789-5597 (I.D.S.)
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6
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Keely SJ, Barrett KE. Intestinal secretory mechanisms and diarrhea. Am J Physiol Gastrointest Liver Physiol 2022; 322:G405-G420. [PMID: 35170355 PMCID: PMC8917926 DOI: 10.1152/ajpgi.00316.2021] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 01/31/2023]
Abstract
One of the primary functions of the intestinal epithelium is to transport fluid and electrolytes to and from the luminal contents. Under normal circumstances, absorptive and secretory processes are tightly regulated such that absorption predominates, thereby enabling conservation of the large volumes of water that pass through the intestine each day. However, in conditions of secretory diarrhea, this balance becomes dysregulated, so that fluid secretion, driven primarily by Cl- secretion, overwhelms absorptive capacity, leading to increased loss of water in the stool. Secretory diarrheas are common and include those induced by pathogenic bacteria and viruses, allergens, and disruptions to bile acid homeostasis, or as a side effect of many drugs. Here, we review the cellular and molecular mechanisms by which Cl- and fluid secretion in the intestine are regulated, how these mechanisms become dysregulated in conditions of secretory diarrhea, currently available and emerging therapeutic approaches, and how new strategies to exploit intestinal secretory mechanisms are successfully being used in the treatment of constipation.
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Affiliation(s)
- Stephen J Keely
- School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland, University of Medicine and Health Sciences, Dublin, Ireland
| | - Kim E Barrett
- Department of Medicine, School of Medicine, University of California San Diego, La Jolla, California
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, California
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7
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Sepela RJ, Stewart RG, Valencia LA, Thapa P, Wang Z, Cohen BE, Sack JT. The AMIGO1 adhesion protein activates Kv2.1 voltage sensors. Biophys J 2022; 121:1395-1416. [PMID: 35314141 PMCID: PMC9072587 DOI: 10.1016/j.bpj.2022.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 11/11/2021] [Accepted: 03/16/2022] [Indexed: 11/30/2022] Open
Abstract
Kv2 voltage-gated potassium channels are modulated by amphoterin-induced gene and open reading frame (AMIGO) neuronal adhesion proteins. Here, we identify steps in the conductance activation pathway of Kv2.1 channels that are modulated by AMIGO1 using voltage-clamp recordings and spectroscopy of heterologously expressed Kv2.1 and AMIGO1 in mammalian cell lines. AMIGO1 speeds early voltage-sensor movements and shifts the gating charge-voltage relationship to more negative voltages. The gating charge-voltage relationship indicates that AMIGO1 exerts a larger energetic effect on voltage-sensor movement than is apparent from the midpoint of the conductance-voltage relationship. When voltage sensors are detained at rest by voltage-sensor toxins, AMIGO1 has a greater impact on the conductance-voltage relationship. Fluorescence measurements from voltage-sensor toxins bound to Kv2.1 indicate that with AMIGO1, the voltage sensors enter their earliest resting conformation, yet this conformation is less stable upon voltage stimulation. We conclude that AMIGO1 modulates the Kv2.1 conductance activation pathway by destabilizing the earliest resting state of the voltage sensors.
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Affiliation(s)
- Rebecka J Sepela
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Robert G Stewart
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Luis A Valencia
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Zeming Wang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Bruce E Cohen
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California; Division of Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, California; Department of Anesthesiology and Pain Medicine, University of California, Davis, California.
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8
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Eldstrom J, McAfee DA, Dou Y, Wang Y, Fedida D. ML277 regulates KCNQ1 single-channel amplitudes and kinetics, modified by voltage sensor state. J Gen Physiol 2021; 153:212696. [PMID: 34636894 PMCID: PMC8515649 DOI: 10.1085/jgp.202112969] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/16/2021] [Accepted: 09/15/2021] [Indexed: 11/25/2022] Open
Abstract
KCNQ1 is a pore-forming K+ channel subunit critically important to cardiac repolarization at high heart rates. (2R)-N-[4-(4-methoxyphenyl)-2-thiazolyl]-1-[(4-methylphenyl)sulfonyl]-2 piperidinecarboxamide, or ML277, is an activator of this channel that rescues function of pathophysiologically important mutant channel complexes in human induced pluripotent stem cell–derived cardiomyocytes, and that therefore may have therapeutic potential. Here we extend our understanding of ML277 actions through cell-attached single-channel recordings of wild-type and mutant KCNQ1 channels with voltage sensor domains fixed in resting, intermediate, and activated states. ML277 has profound effects on KCNQ1 single-channel kinetics, eliminating the flickering nature of the openings, converting them to discrete opening bursts, and increasing their amplitudes approximately threefold. KCNQ1 single-channel behavior after ML277 treatment most resembles IO state-locked channels (E160R/R231E) rather than AO state channels (E160R/R237E), suggesting that at least during ML277 treatment, KCNQ1 does not frequently visit the AO state. Introduction of KCNE1 subunits reduces the effectiveness of ML277, but some enhancement of single-channel openings is still observed.
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Affiliation(s)
- Jodene Eldstrom
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Donald A McAfee
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Ying Dou
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Yundi Wang
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada
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9
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Synergistic effect between the KCNQ1 haplotype and alcohol consumption on the development of type 2 diabetes mellitus in Korean cohorts. Sci Rep 2021; 11:21796. [PMID: 34750480 PMCID: PMC8575903 DOI: 10.1038/s41598-021-01399-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 10/05/2021] [Indexed: 11/27/2022] Open
Abstract
Potassium voltage-gated channel subfamily Q member 1 (KCNQ1) is one of the strongest susceptibility genes for type 2 diabetes mellitus (T2DM). Association studies between KCNQ1 genetic variants and T2DM have been reported. The multifactorial disease T2DM is caused by interactions between genetic susceptibility and environmental factors. In this study, we examined the associations between the KCNQ1 haplotype, which consists of the major alleles rs3852528, rs11024175, and rs2237892 (ht: ACC), and environmental factors such as alcohol consumption, which are related to the risk of T2DM, in two independent Korean populations. Data from health examination studies, i.e., HEXA (n = 50,357 subjects) and the Ansung–Ansan community-based Korean cohort study (n = 7603), were analyzed. In both cohorts, fasting blood glucose levels were significantly increased in moderate-to-heavy drinkers and carriers of the homozygous ACC haplotype. A significant association between the KCNQ1 haplotype and alcohol consumption in the risk of diabetes was observed in the HEXA (OR 1.587; 95% CI 1.128–2.234) and Ansung–Ansan (OR 2.165; 95% CI 1.175–3.989) cohorts compared with abstainers not carrying the KCNQ1 haplotype. Associations of the KCNQ1 haplotype with alcohol consumption and β-cell function were observed in the Ansung–Ansan cohort. Moderate-to-heavy drinkers with the ACC haplotype had lower fasting insulin levels and mean 60 min insulinogenic index (IGI60) compared with light drinkers and abstainers not carrying the ACC haplotype. These findings indicate that KCNQ1 variants play a synergistic role with alcohol consumption in the development of T2DM and impaired β-cell function.
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Chen L, He Y, Wang X, Ge J, Li H. Ventricular voltage-gated ion channels: Detection, characteristics, mechanisms, and drug safety evaluation. Clin Transl Med 2021; 11:e530. [PMID: 34709746 PMCID: PMC8516344 DOI: 10.1002/ctm2.530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 02/06/2023] Open
Abstract
Cardiac voltage-gated ion channels (VGICs) play critical roles in mediating cardiac electrophysiological signals, such as action potentials, to maintain normal heart excitability and contraction. Inherited or acquired alterations in the structure, expression, or function of VGICs, as well as VGIC-related side effects of pharmaceutical drug delivery can result in abnormal cellular electrophysiological processes that induce life-threatening cardiac arrhythmias or even sudden cardiac death. Hence, to reduce possible heart-related risks, VGICs must be acknowledged as important targets in drug discovery and safety studies related to cardiac disease. In this review, we first summarize the development and application of electrophysiological techniques that are employed in cardiac VGIC studies alone or in combination with other techniques such as cryoelectron microscopy, optical imaging and optogenetics. Subsequently, we describe the characteristics, structure, mechanisms, and functions of various well-studied VGICs in ventricular myocytes and analyze their roles in and contributions to both physiological cardiac excitability and inherited cardiac diseases. Finally, we address the implications of the structure and function of ventricular VGICs for drug safety evaluation. In summary, multidisciplinary studies on VGICs help researchers discover potential targets of VGICs and novel VGICs in heart, enrich their knowledge of the properties and functions, determine the operation mechanisms of pathological VGICs, and introduce groundbreaking trends in drug therapy strategies, and drug safety evaluation.
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Affiliation(s)
- Lulan Chen
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Yue He
- Department of CardiologyShanghai Xuhui District Central Hospital & Zhongshan‐xuhui HospitalShanghaiChina
| | - Xiangdong Wang
- Institute of Clinical Science, Zhongshan HospitalFudan UniversityShanghaiChina
| | - Junbo Ge
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Hua Li
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
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11
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A second S4 movement opens hyperpolarization-activated HCN channels. Proc Natl Acad Sci U S A 2021; 118:2102036118. [PMID: 34504015 DOI: 10.1073/pnas.2102036118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2021] [Indexed: 11/18/2022] Open
Abstract
Rhythmic activity in pacemaker cells, as in the sino-atrial node in the heart, depends on the activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. As in depolarization-activated K+ channels, the fourth transmembrane segment S4 functions as the voltage sensor in hyperpolarization-activated HCN channels. But how the inward movement of S4 in HCN channels at hyperpolarized voltages couples to channel opening is not understood. Using voltage clamp fluorometry, we found here that S4 in HCN channels moves in two steps in response to hyperpolarizations and that the second S4 step correlates with gate opening. We found a mutation in sea urchin HCN channels that separate the two S4 steps in voltage dependence. The E356A mutation in S4 shifts the main S4 movement to positive voltages, but channel opening remains at negative voltages. In addition, E356A reveals a second S4 movement at negative voltages that correlates with gate opening. Cysteine accessibility and molecular models suggest that the second S4 movement opens up an intracellular crevice between S4 and S5 that would allow radial movement of the intracellular ends of S5 and S6 to open HCN channels.
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12
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Nickerson AJ, Rajendran VM. Flupirtine enhances NHE-3-mediated Na + absorption in rat colon via an ENS-dependent mechanism. Am J Physiol Gastrointest Liver Physiol 2021; 321:G185-G199. [PMID: 34132108 PMCID: PMC8410105 DOI: 10.1152/ajpgi.00158.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/11/2021] [Accepted: 06/11/2021] [Indexed: 01/31/2023]
Abstract
Recent studies in our lab have shown that the KV7 channel activator, flupirtine, inhibits colonic epithelial Cl- secretion through effects on submucosal neurons of the enteric nervous system (ENS). We hypothesized that flupirtine would also stimulate Na+ absorption as a result of reduced secretory ENS input to the epithelium. To test this hypothesis, unidirectional 22Na+ fluxes were measured under voltage-clamped conditions. Pharmacological approaches using an Ussing-style recording chamber combined with immunofluorescence microscopy techniques were used to determine the effect of flupirtine on active Na+ transport in the rat colon. Flupirtine stimulated electroneutral Na+ absorption in partially seromuscular-stripped colonic tissues, while simultaneously inhibiting short-circuit current (ISC; i.e., Cl- secretion). Both of these effects were attenuated by pretreatment with the ENS inhibitor, tetrodotoxin. The Na+/H+ exchanger isoform 3 (NHE-3)-selective inhibitor, S3226, significantly inhibited flupirtine-stimulated Na+ absorption, whereas the NHE-2-selective inhibitor HOE-694 did not. NHE-3 localization near the apical membranes of surface epithelial cells was also more apparent in flupirtine-treated colon versus control. Flupirtine did not alter epithelial Na+ channel (ENaC)-mediated Na+ absorption in distal colonic tissues obtained from hyperaldosteronaemic rats and had no effect in the normal ileum but did stimulate Na+ absorption in the proximal colon. Finally, the parallel effects of flupirtine on ISC (Cl- secretion) and Na+ absorption were significantly correlated with each other. Together, these data indicate that flupirtine stimulates NHE-3-dependent Na+ absorption, likely as a result of reduced stimulatory input to the colonic epithelium by submucosal ENS neurons.NEW & NOTEWORTHY We present a novel mechanism regarding regulation of epithelial ion transport by enteric neurons. Activation of neuronal KV7 K+ channels markedly stimulates Na+ absorption and inhibits Cl- secretion across the colonic epithelium. This may be useful in developing new treatments for diarrheal disorders, such as irritable bowel syndrome with diarrhea (IBS-D).
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Affiliation(s)
- Andrew J Nickerson
- Departments of Physiology, Pharmacology and Neuroscience, West Virginia University School of Medicine, Morgantown, West Virginia
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Vazhaikkurichi M Rajendran
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
- Department of Medicine, West Virginia University School of Medicine, Morgantown, West Virginia
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13
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Wu X, Perez ME, Noskov SY, Larsson HP. A general mechanism of KCNE1 modulation of KCNQ1 channels involving non-canonical VSD-PD coupling. Commun Biol 2021; 4:887. [PMID: 34285340 PMCID: PMC8292421 DOI: 10.1038/s42003-021-02418-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 07/05/2021] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated KCNQ1 channels contain four separate voltage-sensing domains (VSDs) and a pore domain (PD). KCNQ1 expressed alone opens when the VSDs are in an intermediate state. In cardiomyocytes, KCNQ1 co-expressed with KCNE1 opens mainly when the VSDs are in a fully activated state. KCNE1 also drastically slows the opening of KCNQ1 channels and shifts the voltage dependence of opening by >40 mV. We here show that mutations of conserved residues at the VSD-PD interface alter the VSD-PD coupling so that the mutant KCNQ1/KCNE1 channels open in the intermediate VSD state. Using recent structures of KCNQ1 and KCNE beta subunits in different states, we present a mechanism by which KCNE1 rotates the VSD relative to the PD and affects the VSD-PD coupling of KCNQ1 channels in a non-canonical way, forcing KCNQ1/KCNE1 channels to open in the fully-activated VSD state. This would explain many of the KCNE1-induced effects on KCNQ1 channels.
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Affiliation(s)
- Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Marta E Perez
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Sergei Yu Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - H Peter Larsson
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, USA.
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14
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Cowgill J, Chanda B. Mapping Electromechanical Coupling Pathways in Voltage-Gated Ion Channels: Challenges and the Way Forward. J Mol Biol 2021; 433:167104. [PMID: 34139217 PMCID: PMC8579740 DOI: 10.1016/j.jmb.2021.167104] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/07/2021] [Accepted: 06/10/2021] [Indexed: 01/06/2023]
Abstract
Inter- and intra-molecular allosteric interactions underpin regulation of activity in a variety of biological macromolecules. In the voltage-gated ion channel superfamily, the conformational state of the voltage-sensing domain regulates the activity of the pore domain via such long-range allosteric interactions. Although the overall structure of these channels is conserved, allosteric interactions between voltage-sensor and pore varies quite dramatically between the members of this superfamily. Despite the progress in identifying key residues and structural interfaces involved in mediating electromechanical coupling, our understanding of the biophysical mechanisms remains limited. Emerging new structures of voltage-gated ion channels in various conformational states will provide a better three-dimensional view of the process but to conclusively establish a mechanism, we will also need to quantitate the energetic contribution of various structural elements to this process. Using rigorous unbiased metrics, we want to compare the efficiency of electromechanical coupling between various sub-families in order to gain a comprehensive understanding. Furthermore, quantitative understanding of the process will enable us to correctly parameterize computational approaches which will ultimately enable us to predict allosteric activation mechanisms from structures. In this review, we will outline the challenges and limitations of various experimental approaches to measure electromechanical coupling and highlight the best practices in the field.
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Affiliation(s)
- John Cowgill
- Department of Anesthesiology, Washington University, St. Louis, MO 63110, United States; Center for Investigations of Membrane Excitability Disorders (CIMED), Washington University, St. Louis, MO 63110, United States
| | - Baron Chanda
- Department of Anesthesiology, Washington University, St. Louis, MO 63110, United States; Center for Investigations of Membrane Excitability Disorders (CIMED), Washington University, St. Louis, MO 63110, United States.
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15
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Nickerson AJ, Rottgen TS, Rajendran VM. Activation of KCNQ (K V7) K + channels in enteric neurons inhibits epithelial Cl - secretion in mouse distal colon. Am J Physiol Cell Physiol 2021; 320:C1074-C1087. [PMID: 33852365 PMCID: PMC8285638 DOI: 10.1152/ajpcell.00536.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 03/30/2021] [Accepted: 03/30/2021] [Indexed: 12/14/2022]
Abstract
Voltage-gated Kv7 (KCNQ family) K+ channels are expressed in many neuronal populations and play an important role in regulating membrane potential by generating a hyperpolarizing K+ current and decreasing cell excitability. However, the role of KV7 channels in the neural regulation of intestinal epithelial Cl- secretion is not known. Cl- secretion in mouse distal colon was measured as a function of short-circuit current (ISC), and pharmacological approaches were used to test the hypothesis that activation of KV7 channels in enteric neurons would inhibit epithelial Cl- secretion. Flupirtine, a nonselective KV7 activator, inhibited basal Cl- secretion in mouse distal colon and abolished or attenuated the effects of drugs that target various components of enteric neurotransmission, including tetrodotoxin (NaV channel blocker), veratridine (NaV channel activator), nicotine (nicotinic acetylcholine receptor agonist), and hexamethonium (nicotinic antagonist). In contrast, flupritine did not block the response to epithelium-targeted agents VIP (endogenous VPAC receptor ligand) or carbachol (nonselective cholinergic agonist). Flupirtine inhibited Cl- secretion in both full-thickness and seromuscular-stripped distal colon (containing the submucosal, but not myenteric plexus) but generated no response in epithelial T84 cell monolayers. KV7.2 and KV7.3 channel proteins were detected by immunofluorescence in whole mount preparations of the submucosa from mouse distal colon. ICA 110381 (KV7.2/7.3 specific activator) inhibited Cl- secretion comparably to flupirtine. We conclude that KV7 channel activators inhibit neurally driven Cl- secretion in the colonic epithelium and may therefore have therapeutic benefit in treating pathologies associated with hyperexcitable enteric nervous system, such as irritable bowel syndrome with diarrhea (IBS-D).
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Affiliation(s)
- Andrew J Nickerson
- Departments of Physiology, Pharmacology and Neuroscience, West Virginia University School of Medicine, Morgantown, West Virginia
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Trey S Rottgen
- Departments of Physiology, Pharmacology and Neuroscience, West Virginia University School of Medicine, Morgantown, West Virginia
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Vazhaikkurichi M Rajendran
- Department of Biochemistry, West Virginia University School of Medicine, Morgantown, West Virginia
- Department of Medicine, West Virginia University School of Medicine, Morgantown, West Virginia
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16
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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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17
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Ahmad N, Shah SA, Abdul Gafor AH, Abdul Murad NA, Kamaruddin MA, Abd Jalal N, Ismail N, Alias MR, Jamal R. Gene-environment interaction in chronic kidney disease among people with type 2 diabetes from The Malaysian Cohort project: a case-control study. Diabet Med 2020; 37:1890-1901. [PMID: 32012348 DOI: 10.1111/dme.14257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/28/2020] [Indexed: 01/05/2023]
Abstract
AIM To examine the possible gene-environment interactions between 32 single nucleotide polymorphisms and environmental factors that could modify the probability of chronic kidney disease. METHODS A case-control study was conducted involving 600 people with type 2 diabetes (300 chronic kidney disease cases, 300 controls) who participated in The Malaysian Cohort project. Retrospective subanalysis was performed on the chronic kidney disease cases to assess chronic kidney disease progression from the recruitment phase. We genotyped 32 single nucleotide polymorphisms using mass spectrometry. The probability of chronic kidney disease and predicted rate of newly detected chronic kidney disease progression were estimated from the significant gene-environment interaction analyses. RESULTS Four single nucleotide polymorphisms (eNOS rs2070744, PPARGC1A rs8192678, KCNQ1 rs2237895 and KCNQ1 rs2283228) and five environmental factors (age, sex, smoking, waist circumference and HDL) were significantly associated with chronic kidney disease. Gene-environment interaction analyses revealed significant probabilities of chronic kidney disease for sex (PPARGC1A rs8192678), smoking (eNOS rs2070744, PPARGC1A rs8192678 and KCNQ1 rs2237895), waist circumference (eNOS rs2070744, PPARGC1A rs8192678, KCNQ1 rs2237895 and KCNQ1 rs2283228) and HDL (eNOS rs2070744 and PPARGC1A rs8192678). Subanalysis indicated that the rate of newly detected chronic kidney disease progression was 133 cases per 1000 person-years (95% CI: 115, 153), with a mean follow-up period of 4.78 (SD 0.73) years. There was a significant predicted rate of newly detected chronic kidney disease progression in gene-environment interactions between KCNQ1 rs2283228 and two environmental factors (sex and BMI). CONCLUSIONS Our findings suggest that the gene-environment interactions of eNOS rs2070744, PPARGC1A rs8192678, KCNQ1 rs2237895 and KCNQ1 rs2283228 with specific environmental factors could modify the probability for chronic kidney disease.
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Affiliation(s)
- N Ahmad
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
- Epidemiology and Statistics Unit, Department of Community Health, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - S A Shah
- Epidemiology and Statistics Unit, Department of Community Health, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - A H Abdul Gafor
- Nephrology Unit, Department of Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - N A Abdul Murad
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - M A Kamaruddin
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - N Abd Jalal
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | | | - M R Alias
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
| | - R Jamal
- UKM Medical Molecular Biology Institute (UMBI), Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Cheras, Kuala Lumpur, Malaysia
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18
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Kuenze G, Vanoye CG, Desai RR, Adusumilli S, Brewer KR, Woods H, McDonald EF, Sanders CR, George AL, Meiler J. Allosteric mechanism for KCNE1 modulation of KCNQ1 potassium channel activation. eLife 2020; 9:57680. [PMID: 33095155 PMCID: PMC7584456 DOI: 10.7554/elife.57680] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 09/28/2020] [Indexed: 01/04/2023] Open
Abstract
The function of the voltage-gated KCNQ1 potassium channel is regulated by co-assembly with KCNE auxiliary subunits. KCNQ1-KCNE1 channels generate the slow delayed rectifier current, IKs, which contributes to the repolarization phase of the cardiac action potential. A three amino acid motif (F57-T58-L59, FTL) in KCNE1 is essential for slow activation of KCNQ1-KCNE1 channels. However, how this motif interacts with KCNQ1 to control its function is unknown. Combining computational modeling with electrophysiological studies, we developed structural models of the KCNQ1-KCNE1 complex that suggest how KCNE1 controls KCNQ1 activation. The FTL motif binds at a cleft between the voltage-sensing and pore domains and appears to affect the channel gate by an allosteric mechanism. Comparison with the KCNQ1-KCNE3 channel structure suggests a common transmembrane-binding mode for different KCNEs and illuminates how specific differences in the interaction of their triplet motifs determine the profound differences in KCNQ1 functional modulation by KCNE1 versus KCNE3.
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Affiliation(s)
- Georg Kuenze
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States.,Institute for Drug Discovery, Leipzig University, Leipzig, Germany
| | - Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Reshma R Desai
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Sneha Adusumilli
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Kathryn R Brewer
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Biochemistry, Vanderbilt University, Nashville, United States
| | - Hope Woods
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Eli F McDonald
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States
| | - Charles R Sanders
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Biochemistry, Vanderbilt University, Nashville, United States
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University, Nashville, United States.,Department of Chemistry, Vanderbilt University, Nashville, United States.,Institute for Drug Discovery, Leipzig University, Leipzig, Germany.,Department of Pharmacology, Vanderbilt University, Nashville, United States
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19
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Hu B, Zeng WP, Li X, Al-Sheikh U, Chen SY, Ding J. A conserved arginine/lysine-based motif promotes ER export of KCNE1 and KCNE2 to regulate KCNQ1 channel activity. Channels (Austin) 2020; 13:483-497. [PMID: 31679457 PMCID: PMC6833972 DOI: 10.1080/19336950.2019.1685626] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
KCNE β-subunits play critical roles in modulating cardiac voltage-gated potassium channels. Among them, KCNE1 associates with KCNQ1 channel to confer a slow-activated IKs current, while KCNE2 functions as a dominant negative modulator to suppress the current amplitude of KCNQ1. Any anomaly in these channels will lead to serious myocardial diseases, such as the long QT syndrome (LQTS). Trafficking defects of KCNE1 have been reported to account for the pathogenesis of LQT5. However, the molecular mechanisms underlying KCNE forward trafficking remain elusive. Here, we describe an arginine/lysine-based motif ([R/K](S)[R/K][R/K]) in the proximal C-terminus regulating the endoplasmic reticulum (ER) export of KCNE1 and KCNE2 in HEK293 cells. Notably, this motif is highly conserved in the KCNE family. Our results indicate that the forward trafficking of KCNE2 controlled by the motif (KSKR) is essential for suppressing the cell surface expression and current amplitude of KCNQ1. Unlike KCNE2, the motif (RSKK) in KCNE1 plays important roles in modulating the gating of KCNQ1 in addition to mediating the ER export of KCNE1. Furthermore, truncations of the C-terminus did not reduce the apparent affinity of KCNE2 for KCNQ1, demonstrating that the rigid C-terminus of KCNE2 may not physically interact with KCNQ1. In contrast, the KCNE1 C-terminus is critical for its interaction with KCNQ1. These results contribute to the understanding of the mechanisms of KCNE1 and KCNE2 membrane targeting and how they coassemble with KCNQ1 to regulate the channels activity.
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Affiliation(s)
- Bin Hu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Wen-Ping Zeng
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xia Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Umar Al-Sheikh
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - San-You Chen
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China.,CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, China
| | - Jiuping Ding
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
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20
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Wang Y, Eldstrom J, Fedida D. Gating and Regulation of KCNQ1 and KCNQ1 + KCNE1 Channel Complexes. Front Physiol 2020; 11:504. [PMID: 32581825 PMCID: PMC7287213 DOI: 10.3389/fphys.2020.00504] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 04/24/2020] [Indexed: 12/20/2022] Open
Abstract
The IKs channel complex is formed by the co-assembly of Kv7.1 (KCNQ1), a voltage-gated potassium channel, with its β-subunit, KCNE1 and the association of numerous accessory regulatory molecules such as PIP2, calmodulin, and yotiao. As a result, the IKs potassium current shows kinetic and regulatory flexibility, which not only allows IKs to fulfill physiological roles as disparate as cardiac repolarization and the maintenance of endolymph K+ homeostasis, but also to cause significant disease when it malfunctions. Here, we review new areas of understanding in the assembly, kinetics of activation and inactivation, voltage-sensor pore coupling, unitary events and regulation of this important ion channel complex, all of which have been given further impetus by the recent solution of cryo-EM structural representations of KCNQ1 alone and KCNQ1+KCNE3. Recently, the stoichiometric ratio of KCNE1 to KCNQ1 subunits has been confirmed to be variable up to a ratio of 4:4, rather than fixed at 2:4, and we will review the results and new methodologies that support this conclusion. Significant advances have been made in understanding differences between KCNQ1 and IKs gating using voltage clamp fluorimetry and mutational analysis to illuminate voltage sensor activation and inactivation, and the relationship between voltage sensor translation and pore domain opening. We now understand that the KCNQ1 pore can open with different permeabilities and conductance when the voltage sensor is in partially or fully activated positions, and the ability to make robust single channel recordings from IKs channels has also revealed the complicated pore subconductance architecture during these opening steps, during inactivation, and regulation by 1−4 associated KCNE1 subunits. Experiments placing mutations into individual voltage sensors to drastically change voltage dependence or prevent their movement altogether have demonstrated that the activation of KCNQ1 alone and IKs can best be explained using allosteric models of channel gating. Finally, we discuss how the intrinsic gating properties of KCNQ1 and IKs are highly modulated through the impact of intracellular signaling molecules and co-factors such as PIP2, protein kinase A, calmodulin and ATP, all of which modulate IKs current kinetics and contribute to diverse IKs channel complex function.
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Affiliation(s)
- Yundi Wang
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada
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21
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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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22
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Di Lollo V, Canciello A, Orsini M, Bernabò N, Ancora M, Di Federico M, Curini V, Mattioli M, Russo V, Mauro A, Cammà C, Barboni B. Transcriptomic and computational analysis identified LPA metabolism, KLHL14 and KCNE3 as novel regulators of Epithelial-Mesenchymal Transition. Sci Rep 2020; 10:4180. [PMID: 32144311 PMCID: PMC7060278 DOI: 10.1038/s41598-020-61017-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 02/17/2020] [Indexed: 12/15/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT) is a complex biological program between physiology and pathology. Here, amniotic epithelial cells (AEC) were used as in vitro model of transiently inducible EMT in order to evaluate the transcriptional insights underlying this process. Therefore, RNA-seq was used to identify the differentially expressed genes and enrichment analyses were carried out to assess the intracellular pathways involved. As a result, molecules exclusively expressed in AEC that experienced EMT (GSTA1-1 and GSTM3) or when this process is inhibited (KLHL14 and KCNE3) were identified. Lastly, the network theory was used to obtain a computational model able to recognize putative controller genes involved in the induction and in the prevention of EMT. The results suggested an opposite role of lysophosphatidic acid (LPA) synthesis and degradation enzymes in the regulation of EMT process. In conclusion, these molecules may represent novel EMT regulators and also targets for developing new therapeutic strategies.
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Affiliation(s)
- V Di Lollo
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy. .,Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy.
| | - A Canciello
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy.
| | - M Orsini
- Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - N Bernabò
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - M Ancora
- Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - M Di Federico
- Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - V Curini
- Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - M Mattioli
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - V Russo
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - A Mauro
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - C Cammà
- Molecular biology and genomic Unit, Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise "G. Caporale", Teramo, Italy
| | - B Barboni
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
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23
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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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24
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Sun J, MacKinnon R. Structural Basis of Human KCNQ1 Modulation and Gating. Cell 2019; 180:340-347.e9. [PMID: 31883792 DOI: 10.1016/j.cell.2019.12.003] [Citation(s) in RCA: 154] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/25/2019] [Accepted: 12/04/2019] [Indexed: 01/04/2023]
Abstract
KCNQ1, also known as Kv7.1, is a voltage-dependent K+ channel that regulates gastric acid secretion, salt and glucose homeostasis, and heart rhythm. Its functional properties are regulated in a tissue-specific manner through co-assembly with beta subunits KCNE1-5. In non-excitable cells, KCNQ1 forms a complex with KCNE3, which suppresses channel closure at negative membrane voltages that otherwise would close it. Pore opening is regulated by the signaling lipid PIP2. Using cryoelectron microscopy (cryo-EM), we show that KCNE3 tucks its single-membrane-spanning helix against KCNQ1, at a location that appears to lock the voltage sensor in its depolarized conformation. Without PIP2, the pore remains closed. Upon addition, PIP2 occupies a site on KCNQ1 within the inner membrane leaflet, which triggers a large conformational change that leads to dilation of the pore's gate. It is likely that this mechanism of PIP2 activation is conserved among Kv7 channels.
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Affiliation(s)
- Ji Sun
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics and Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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25
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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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26
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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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27
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Nakajo K. Gating modulation of the KCNQ1 channel by KCNE proteins studied by voltage-clamp fluorometry. Biophys Physicobiol 2019; 16:121-126. [PMID: 31236320 PMCID: PMC6587909 DOI: 10.2142/biophysico.16.0_121] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/01/2019] [Indexed: 01/22/2023] Open
Abstract
The KCNQ1 channel is a voltage-dependent potassium channel and is ubiquitously expressed throughout the human body including the heart, lung, kidney, pancreas, intestine and inner ear. Gating properties of the KCNQ1 channel are modulated by KCNE auxiliary subunits. For example, the KCNQ1-KCNE1 channel produces a slowly-activating potassium current, while KCNE3 makes KCNQ1 a voltage-independent, constitutively open channel. Thus, physiological functions of KCNQ1 channels are greatly dependent on the type of KCNE protein that is co-expressed in that organ. It has long been debated how the similar single transmembrane KCNE proteins produce quite different gating behaviors. Recent applications of voltage-clamp fluorometry (VCF) for the KCNQ1 channel have shed light on this question. The VCF is a quite sensitive method to detect structural changes of membrane proteins and is especially suitable for tracking the voltage sensor domains of voltage-gated ion channels. In this short review, I will introduce how the VCF technique can be applied to detect structural changes and what have been revealed by the recent VCF applications to the gating modulation of KCNQ1 channels by KCNE proteins.
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Affiliation(s)
- Koichi Nakajo
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University, Shimotsuke, Tochigi 329-0498, Japan
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28
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Law CL, Sanders CR. NMR resonance assignments and secondary structure of a mutant form of the human KCNE1 channel accessory protein that exhibits KCNE3-like function. BIOMOLECULAR NMR ASSIGNMENTS 2019; 13:143-147. [PMID: 30603955 PMCID: PMC6440842 DOI: 10.1007/s12104-018-09867-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 12/13/2018] [Indexed: 06/09/2023]
Abstract
KCNQ1 (Q1) is a voltage-gated potassium channel that is modulated by members of the KCNE family, the best-characterized being KCNE1 (E1) and KCNE3 (E3). The Q1/E1 complex generates a channel with delayed activation and increased conductance. This complex is expressed in cardiomyocytes where it provides the IKs current that is critical for the repolarization phase of the cardiac action potential. The Q1/E3 complex, on the other hand, is expressed in epithelial cells of the colon and stomach, where it serves as a constitutively active leak channel to help maintain water and ion homeostasis. Studies show the single transmembrane segments (TMS) present in both E1 and E3 are essential to their distinct functions. More specifically, residues FTL located near the middle of the E1 TMS are essential for the delayed activation of Q1, while the corresponding TVG sites in E3 are critical for constitutive activation of the channel. Swapping these three residues leads to the switching of the functional properties for both Q1/E1FTL→TVG and Q1/E3TVG→FTL complexes. This work details the backbone assignments and chemical shifts for the E1FTL→TVG mutant, as determined using a suite of 3D NMR experiments along with specific and inverse amino acid isotopic labeling. The completed assignments can be used, in conjunction with other NMR experiments, to generate a 3D structure of E1FTL→TVG. The results of TALOS-N analysis of the chemical shifts are reported here. The E1FTL→TVG structure will be compared to the already available E1 and E3 structures to determine the roles that their TMS triplet motifs play in each protein to dictate their distinct channel-modulatory functions.
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Affiliation(s)
- Cheryl L Law
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, 37240-7917, USA
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, 37240-7917, USA.
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29
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Abstract
The highly structurally similar drugs flupirtine and retigabine have been regarded as safe and effective for many years but lately they turned out to exert intolerable side effects. While the twin molecules share the mode of action, both stabilize the open state of voltage-gated potassium channels, the form and severity of adverse effects is different. The analgesic flupirtine caused drug-induced liver injury in rare but fatal cases, whereas prolonged use of the antiepileptic retigabine led to blue tissue discoloration. Because the adverse effects seem unrelated to the mode of action, it is likely, that both drugs that occupied important therapeutic niches, could be replaced. Reasons for the clinically relevant toxicity will be clarified and future substitutes for these drugs presented in this review.
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30
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Larsson JE, Larsson HP, Liin SI. KCNE1 tunes the sensitivity of K V7.1 to polyunsaturated fatty acids by moving turret residues close to the binding site. eLife 2018; 7:37257. [PMID: 30014849 PMCID: PMC6080945 DOI: 10.7554/elife.37257] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 07/15/2018] [Indexed: 12/23/2022] Open
Abstract
The voltage-gated potassium channel KV7.1 and the auxiliary subunit KCNE1 together form the cardiac IKs channel, which is a proposed target for future anti-arrhythmic drugs. We previously showed that polyunsaturated fatty acids (PUFAs) activate KV7.1 via an electrostatic mechanism. The activating effect was abolished when KV7.1 was co-expressed with KCNE1, as KCNE1 renders PUFAs ineffective by promoting PUFA protonation. PUFA protonation reduces the potential of PUFAs as anti-arrhythmic compounds. It is unknown how KCNE1 promotes PUFA protonation. Here, we found that neutralization of negatively charged residues in the S5-P-helix loop of KV7.1 restored PUFA effects on KV7.1 co-expressed with KCNE1 in Xenopus oocytes. We propose that KCNE1 moves the S5-P-helix loop of KV7.1 towards the PUFA-binding site, which indirectly causes PUFA protonation, thereby reducing the effect of PUFAs on KV7.1. This mechanistic understanding of how KCNE1 alters KV7.1 pharmacology is essential for development of drugs targeting the IKs channel.
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Affiliation(s)
- Johan E Larsson
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, United States
| | - Sara I Liin
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
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31
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Wulf M, Pless SA. High-Sensitivity Fluorometry to Resolve Ion Channel Conformational Dynamics. Cell Rep 2018; 22:1615-1626. [DOI: 10.1016/j.celrep.2018.01.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 12/01/2017] [Accepted: 01/10/2018] [Indexed: 10/18/2022] Open
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