1
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Liu Z, Wang F, Yuan H, Tian F, Yang C, Hu F, Liu Y, Tang M, Ping M, Kang C, Luo T, Yang G, Hu M, Gao Z, Li P. An LQT2-related mutation in the voltage-sensing domain is involved in switching the gating polarity of hERG. BMC Biol 2024; 22:29. [PMID: 38317233 DOI: 10.1186/s12915-024-01833-0] [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: 02/14/2023] [Accepted: 01/23/2024] [Indexed: 02/07/2024] Open
Abstract
BACKGROUND Cyclic Nucleotide-Binding Domain (CNBD)-family channels display distinct voltage-sensing properties despite sharing sequence and structural similarity. For example, the human Ether-a-go-go Related Gene (hERG) channel and the Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channel share high amino acid sequence similarity and identical domain structures. hERG conducts outward current and is activated by positive membrane potentials (depolarization), whereas HCN conducts inward current and is activated by negative membrane potentials (hyperpolarization). The structural basis for the "opposite" voltage-sensing properties of hERG and HCN remains unknown. RESULTS We found the voltage-sensing domain (VSD) involves in modulating the gating polarity of hERG. We identified that a long-QT syndrome type 2-related mutation within the VSD, K525N, mediated an inwardly rectifying non-deactivating current, perturbing the channel closure, but sparing the open state and inactivated state. K525N rescued the current of a non-functional mutation in the pore helix region (F627Y) of hERG. K525N&F627Y switched hERG into a hyperpolarization-activated channel. The reactivated inward current induced by hyperpolarization mediated by K525N&F627Y can be inhibited by E-4031 and dofetilide quite well. Moreover, we report an extracellular interaction between the S1 helix and the S5-P region is crucial for modulating the gating polarity. The alanine substitution of several residues in this region (F431A, C566A, I607A, and Y611A) impaired the inward current of K525N&F627Y. CONCLUSIONS Our data provide evidence that a potential cooperation mechanism in the extracellular vestibule of the VSD and the PD would determine the gating polarity in hERG.
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Affiliation(s)
- Zhipei Liu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Feng Wang
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Hui Yuan
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Fuyun Tian
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Chuanyan Yang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Fei Hu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yiyao Liu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Meiqin Tang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Meixuan Ping
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chunlan Kang
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Ting Luo
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang, 550025, China
| | - Guimei Yang
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
| | - Mei Hu
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, 528401, China
| | - Zhaobing Gao
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China.
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China.
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Ping Li
- School of Pharmacy, Zunyi Medical University, Zunyi, 563000, China.
- Zhongshan Institute for Drug Discovery, Zhongshan, 528400, China.
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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2
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Costa F, Ocello R, Guardiani C, Giacomello A, Masetti M. Integrated Approach Including Docking, MD Simulations, and Network Analysis Highlights the Action Mechanism of the Cardiac hERG Activator RPR260243. J Chem Inf Model 2023; 63:4888-4899. [PMID: 37504578 PMCID: PMC10428221 DOI: 10.1021/acs.jcim.3c00596] [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: 04/19/2023] [Indexed: 07/29/2023]
Abstract
hERG is a voltage-gated potassium channel involved in the heart contraction whose defections are associated with the cardiac arrhythmia Long QT Syndrome type 2. The activator RPR260243 (RPR) represents a possible candidate to pharmacologically treat LQTS2 because it enhances the opening of the channel. However, the molecular detail of its action mechanism remains quite elusive. Here, we address the problem using a combination of docking, molecular dynamics simulations, and network analysis. We show that the drug preferably binds at the interface between the voltage sensor and the pore, enhancing the canonical activation path and determining a whole-structure rearrangement of the channel that slightly impairs inactivation.
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Affiliation(s)
- Flavio Costa
- Dipartimento
di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, via Eudossiana 18, 00184 Rome, Italy
| | - Riccardo Ocello
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum−Università di Bologna, via Belmeloro 6, 40126 Bologna, Italy
| | - Carlo Guardiani
- Dipartimento
di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, via Eudossiana 18, 00184 Rome, Italy
| | - Alberto Giacomello
- Dipartimento
di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, via Eudossiana 18, 00184 Rome, Italy
| | - Matteo Masetti
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum−Università di Bologna, via Belmeloro 6, 40126 Bologna, Italy
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3
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Van Theemsche KM, Heymans JG, Popovic NZ, Martinez-Morales E, Snyders DJ, Labro AJ. Offsetting Voltage-Dependent Kv1.5 Channel Opening Through Charged Residue Substitutions on Top of the First Transmembrane Segment. Bioelectricity 2022. [DOI: 10.1089/bioe.2022.0005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kenny M. Van Theemsche
- Department of Basic and Applied Medical Sciences, Faculty of Medicine, Ghent University, Ghent, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Joni G. Heymans
- Department of Basic and Applied Medical Sciences, Faculty of Medicine, Ghent University, Ghent, Belgium
| | - Nikola Z. Popovic
- Department of Basic and Applied Medical Sciences, Faculty of Medicine, Ghent University, Ghent, Belgium
| | | | - Dirk J. Snyders
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Alain J. Labro
- Department of Basic and Applied Medical Sciences, Faculty of Medicine, Ghent University, Ghent, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
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4
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Zimmermann MT. Molecular Modeling is an Enabling Approach to Complement and Enhance Channelopathy Research. Compr Physiol 2022; 12:3141-3166. [PMID: 35578963 DOI: 10.1002/cphy.c190047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hundreds of human membrane proteins form channels that transport necessary ions and compounds, including drugs and metabolites, yet details of their normal function or how function is altered by genetic variants to cause diseases are often unknown. Without this knowledge, researchers are less equipped to develop approaches to diagnose and treat channelopathies. High-resolution computational approaches such as molecular modeling enable researchers to investigate channelopathy protein function, facilitate detailed hypothesis generation, and produce data that is difficult to gather experimentally. Molecular modeling can be tailored to each physiologic context that a protein may act within, some of which may currently be difficult or impossible to assay experimentally. Because many genomic variants are observed in channelopathy proteins from high-throughput sequencing studies, methods with mechanistic value are needed to interpret their effects. The eminent field of structural bioinformatics integrates techniques from multiple disciplines including molecular modeling, computational chemistry, biophysics, and biochemistry, to develop mechanistic hypotheses and enhance the information available for understanding function. Molecular modeling and simulation access 3D and time-dependent information, not currently predictable from sequence. Thus, molecular modeling is valuable for increasing the resolution with which the natural function of protein channels can be investigated, and for interpreting how genomic variants alter them to produce physiologic changes that manifest as channelopathies. © 2022 American Physiological Society. Compr Physiol 12:3141-3166, 2022.
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Affiliation(s)
- Michael T Zimmermann
- Bioinformatics Research and Development Laboratory, Genomic Sciences and Precision Medicine Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Clinical and Translational Sciences Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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5
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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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6
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Structural basis of gating modulation of Kv4 channel complexes. Nature 2021; 599:158-164. [PMID: 34552243 PMCID: PMC8566240 DOI: 10.1038/s41586-021-03935-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 08/19/2021] [Indexed: 11/08/2022]
Abstract
Modulation of voltage-gated potassium (Kv) channels by auxiliary subunits is central to the physiological function of channels in the brain and heart1,2. Native Kv4 tetrameric channels form macromolecular ternary complexes with two auxiliary β-subunits—intracellular Kv channel-interacting proteins (KChIPs) and transmembrane dipeptidyl peptidase-related proteins (DPPs)—to evoke rapidly activating and inactivating A-type currents, which prevent the backpropagation of action potentials1–5. However, the modulatory mechanisms of Kv4 channel complexes remain largely unknown. Here we report cryo-electron microscopy structures of the Kv4.2–DPP6S–KChIP1 dodecamer complex, the Kv4.2–KChIP1 and Kv4.2–DPP6S octamer complexes, and Kv4.2 alone. The structure of the Kv4.2–KChIP1 complex reveals that the intracellular N terminus of Kv4.2 interacts with its C terminus that extends from the S6 gating helix of the neighbouring Kv4.2 subunit. KChIP1 captures both the N and the C terminus of Kv4.2. In consequence, KChIP1 would prevent N-type inactivation and stabilize the S6 conformation to modulate gating of the S6 helices within the tetramer. By contrast, unlike the reported auxiliary subunits of voltage-gated channel complexes, DPP6S interacts with the S1 and S2 helices of the Kv4.2 voltage-sensing domain, which suggests that DPP6S stabilizes the conformation of the S1–S2 helices. DPP6S may therefore accelerate the voltage-dependent movement of the S4 helices. KChIP1 and DPP6S do not directly interact with each other in the Kv4.2–KChIP1–DPP6S ternary complex. Thus, our data suggest that two distinct modes of modulation contribute in an additive manner to evoke A-type currents from the native Kv4 macromolecular complex. Cryo-electron microscopy structures of the voltage-gated potassium channel Kv4.2 alone and in complex with auxiliary subunits (DPP6S and/or KChIP1) reveal the distinct mechanisms of these two different subunits in modulating channel activity.
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7
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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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8
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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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9
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Clark MD, Contreras GF, Shen R, Perozo E. Electromechanical coupling in the hyperpolarization-activated K + channel KAT1. Nature 2020; 583:145-149. [PMID: 32461693 PMCID: PMC7747229 DOI: 10.1038/s41586-020-2335-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 03/16/2020] [Indexed: 12/30/2022]
Abstract
Voltage-gated potassium (Kv) channels orchestrate electrical signaling and control cell volume by gating in response to either membrane depolarization or hyperpolarization. Yet, while all voltage-sensing domains transduce transmembrane electric field changes by a common mechanism involving the outward or inward translocation of gating charges1–3, the general determinants of channel gating polarity remain poorly understood4. Here, we suggest a molecular mechanism for electromechanical coupling and gating polarity in non-domain-swapped Kv channels based on the cryo-EM structure of KAT1, the hyperpolarization-activated Kv channel from Arabidopsis thaliana. KAT1 displays a depolarized voltage sensor, which interacts with a closed pore domain directly via two interfaces and indirectly via an intercalated phospholipid. Functional evaluation of KAT1 structure-guided mutants at the sensor-pore interfaces suggests a mechanism in which direct interaction between the sensor and C-linker hairpin in the adjacent pore subunit is the primary determinant of gating polarity. We suggest that a ~5–7 Å inward motion of the S4 sensor helix can underlie a direct-coupling mechanism, driving a conformational reorientation of the C-linker and ultimately opening the activation gate formed by the S6 intracellular bundle. This direct-coupling mechanism contrasts with allosteric mechanisms proposed for hyperpolarization-activated cyclic nucleotide-gated (HCN) channels5, and may represent an unexpected link between depolarization and hyperpolarization-activated channels.
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Affiliation(s)
- Michael David Clark
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Gustavo F Contreras
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, USA.
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10
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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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11
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Barros F, de la Peña P, Domínguez P, Sierra LM, Pardo LA. The EAG Voltage-Dependent K + Channel Subfamily: Similarities and Differences in Structural Organization and Gating. Front Pharmacol 2020; 11:411. [PMID: 32351384 PMCID: PMC7174612 DOI: 10.3389/fphar.2020.00411] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 03/18/2020] [Indexed: 12/17/2022] Open
Abstract
EAG (ether-à-go-go or KCNH) are a subfamily of the voltage-gated potassium (Kv) channels. Like for all potassium channels, opening of EAG channels drives the membrane potential toward its equilibrium value for potassium, thus setting the resting potential and repolarizing action potentials. As voltage-dependent channels, they switch between open and closed conformations (gating) when changes in membrane potential are sensed by a voltage sensing domain (VSD) which is functionally coupled to a pore domain (PD) containing the permeation pathway, the potassium selectivity filter, and the channel gate. All Kv channels are tetrameric, with four VSDs formed by the S1-S4 transmembrane segments of each subunit, surrounding a central PD with the four S5-S6 sections arranged in a square-shaped structure. Structural information, mutagenesis, and functional experiments, indicated that in "classical/Shaker-type" Kv channels voltage-triggered VSD reorganizations are transmitted to PD gating via the α-helical S4-S5 sequence that links both modules. Importantly, these Shaker-type channels share a domain-swapped VSD/PD organization, with each VSD contacting the PD of the adjacent subunit. In this case, the S4-S5 linker, acting as a rigid mechanical lever (electromechanical lever coupling), would lead to channel gate opening at the cytoplasmic S6 helices bundle. However, new functional data with EAG channels split between the VSD and PD modules indicate that, in some Kv channels, alternative VSD/PD coupling mechanisms do exist. Noticeably, recent elucidation of the architecture of some EAG channels, and other relatives, showed that their VSDs are non-domain swapped. Despite similarities in primary sequence and predicted structural organization for all EAG channels, they show marked kinetic differences whose molecular basis is not completely understood. Thus, while a common general architecture may establish the gating system used by the EAG channels and the physicochemical coupling of voltage sensing to gating, subtle changes in that common structure, and/or allosteric influences of protein domains relatively distant from the central gating machinery, can crucially influence the gating process. We consider here the latest advances on these issues provided by the elucidation of eag1 and erg1 three-dimensional structures, and by both classical and more recent functional studies with different members of the EAG subfamily.
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Affiliation(s)
- Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Oviedo, Spain
| | - Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Oviedo, Spain
| | - Pedro Domínguez
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Oviedo, Spain
| | - Luisa Maria Sierra
- Departamento de Biología Funcional (Area de Genética), Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Universidad de Oviedo, Oviedo, Spain
| | - Luis A. Pardo
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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12
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Malak OA, Abderemane-Ali F, Wei Y, Coyan FC, Pontus G, Shaya D, Marionneau C, Loussouarn G. Up-regulation of voltage-gated sodium channels by peptides mimicking S4-S5 linkers reveals a variation of the ligand-receptor mechanism. Sci Rep 2020; 10:5852. [PMID: 32246066 PMCID: PMC7125111 DOI: 10.1038/s41598-020-62615-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 03/12/2020] [Indexed: 11/09/2022] Open
Abstract
Prokaryotic NaV channels are tetramers and eukaryotic NaV channels consist of a single subunit containing four domains. Each monomer/domain contains six transmembrane segments (S1-S6), S1-S4 being the voltage-sensor domain and S5-S6 the pore domain. A crystal structure of NaVMs, a prokaryotic NaV channel, suggests that the S4-S5 linker (S4-S5L) interacts with the C-terminus of S6 (S6T) to stabilize the gate in the open state. However, in several voltage-gated potassium channels, using specific S4-S5L-mimicking peptides, we previously demonstrated that S4-S5L/S6T interaction stabilizes the gate in the closed state. Here, we used the same strategy on another prokaryotic NaV channel, NaVSp1, to test whether equivalent peptides stabilize the channel in the open or closed state. A NaVSp1-specific S4-S5L peptide, containing the residues supposed to interact with S6T according to the NaVMs structure, induced both an increase in NaVSp1 current density and a negative shift in the activation curve, consistent with S4-S5L stabilizing the open state. Using this approach on a human NaV channel, hNaV1.4, and testing 12 hNaV1.4 S4-S5L peptides, we identified four activating S4-S5L peptides. These results suggest that, in eukaryotic NaV channels, the S4-S5L of DI, DII and DIII domains allosterically modulate the activation gate and stabilize its open state.
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Affiliation(s)
- Olfat A Malak
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, California, 94945, USA
| | - Fayal Abderemane-Ali
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Cardiovascular Research Institute, University of California, San Francisco, California, 941158-9001, USA
| | - Yue Wei
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.,Department of Cardiology, Shanghai Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fabien C Coyan
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - Gilyane Pontus
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - David Shaya
- Cardiovascular Research Institute, University of California, San Francisco, California, 941158-9001, USA
| | - Céline Marionneau
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France
| | - Gildas Loussouarn
- Université de Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France.
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13
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Catacuzzeno L, Sforna L, Franciolini F. Voltage-dependent gating in K channels: experimental results and quantitative models. Pflugers Arch 2019; 472:27-47. [PMID: 31863286 DOI: 10.1007/s00424-019-02336-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 12/18/2022]
Abstract
Voltage-dependent K channels open and close in response to voltage changes across the cell membrane. This voltage dependence was postulated to depend on the presence of charged particles moving through the membrane in response to voltage changes. Recording of gating currents originating from the movement of these particles fully confirmed this hypothesis, and gave substantial experimental clues useful for the detailed understanding of the process. In the absence of structural information, the voltage-dependent gating was initially investigated using discrete Markov models, an approach only capable of providing a kinetic and thermodynamic comprehension of the process. The elucidation of the crystal structure of the first voltage-dependent channel brought in a dramatic change of pace in the understanding of channel gating, and in modeling the underlying processes. It was now possible to construct quantitative models using molecular dynamics, where all the interactions of each individual atom with the surroundings were taken into account, and its motion predicted by Newton's laws. Unfortunately, this modeling is computationally very demanding, and in spite of the advances in simulation procedures and computer technology, it is still limited in its predictive ability. To overcome these limitations, several groups have developed more macroscopic voltage gating models. Their approaches understandably require a number of approximations, which must however be physically well justified. One of these models, based on the description of the voltage sensor as a Brownian particle, that we have recently developed, is able to simultaneously describe the behavior of a single voltage sensor and to predict the macroscopic gating current originating from a population of sensors. The basics of this model are here described, and a typical application using the Kv1.2/2.1 chimera channel structure is also presented.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
| | - Luigi Sforna
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy.
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14
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Malak OA, Gluhov GS, Grizel AV, Kudryashova KS, Sokolova OS, Loussouarn G. Voltage-dependent activation in EAG channels follows a ligand-receptor rather than a mechanical-lever mechanism. J Biol Chem 2019; 294:6506-6521. [PMID: 30808709 DOI: 10.1074/jbc.ra119.007626] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/21/2019] [Indexed: 01/08/2023] Open
Abstract
Ether-a-go-go family (EAG) channels play a major role in many physiological processes in humans, including cardiac repolarization and cell proliferation. Cryo-EM structures of two of them, KV10.1 and human ether-a-go-go-related gene (hERG or KV11.1), have revealed an original nondomain-swapped structure, suggesting that the mechanism of voltage-dependent gating of these two channels is quite different from the classical mechanical-lever model. Molecular aspects of hERG voltage-gating have been extensively studied, indicating that the S4-S5 linker (S4-S5L) acts as a ligand binding to the S6 gate (S6 C-terminal part, S6T) and stabilizes it in a closed state. Moreover, the N-terminal extremity of the channel, called N-Cap, has been suggested to interact with S4-S5L to modulate channel voltage-dependent gating, as N-Cap deletion drastically accelerates hERG channel deactivation. In this study, using COS-7 cells, site-directed mutagenesis, electrophysiological measurements, and immunofluorescence confocal microscopy, we addressed whether these two major mechanisms of voltage-dependent gating are conserved in KV10.2 channels. Using cysteine bridges and S4-S5L-mimicking peptides, we show that the ligand/receptor model is conserved in KV10.2, suggesting that this model is a hallmark of EAG channels. Truncation of the N-Cap domain, Per-Arnt-Sim (PAS) domain, or both in KV10.2 abolished the current and altered channel trafficking to the membrane, unlike for the hERG channel in which N-Cap and PAS domain truncations mainly affected channel deactivation. Our results suggest that EAG channels function via a conserved ligand/receptor model of voltage gating, but that the N-Cap and PAS domains have different roles in these channels.
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Affiliation(s)
- Olfat A Malak
- From the INSERM, CNRS, l'Institut du Thorax, Université de Nantes, 44007 Nantes, France
| | - Grigory S Gluhov
- the Moscow M.V. Lomonosov State University, Moscow 119234, Russia
| | - Anastasia V Grizel
- the Saint Petersburg State University, Saint Petersburg 199034, Russia, and
| | - Kseniya S Kudryashova
- the Moscow M.V. Lomonosov State University, Moscow 119234, Russia.,the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of Russian Academy of Sciences, Moscow 117997, Russia
| | - Olga S Sokolova
- the Moscow M.V. Lomonosov State University, Moscow 119234, Russia
| | - Gildas Loussouarn
- From the INSERM, CNRS, l'Institut du Thorax, Université de Nantes, 44007 Nantes, France,
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15
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Barros F, Pardo LA, Domínguez P, Sierra LM, de la Peña P. New Structures and Gating of Voltage-Dependent Potassium (Kv) Channels and Their Relatives: A Multi-Domain and Dynamic Question. Int J Mol Sci 2019; 20:ijms20020248. [PMID: 30634573 PMCID: PMC6359393 DOI: 10.3390/ijms20020248] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/30/2018] [Accepted: 01/07/2019] [Indexed: 12/15/2022] Open
Abstract
Voltage-dependent potassium channels (Kv channels) are crucial regulators of cell excitability that participate in a range of physiological and pathophysiological processes. These channels are molecular machines that display a mechanism (known as gating) for opening and closing a gate located in a pore domain (PD). In Kv channels, this mechanism is triggered and controlled by changes in the magnitude of the transmembrane voltage sensed by a voltage-sensing domain (VSD). In this review, we consider several aspects of the VSD–PD coupling in Kv channels, and in some relatives, that share a common general structure characterized by a single square-shaped ion conduction pore in the center, surrounded by four VSDs located at the periphery. We compile some recent advances in the knowledge of their architecture, based in cryo-electron microscopy (cryo-EM) data for high-resolution determination of their structure, plus some new functional data obtained with channel variants in which the covalent continuity between the VSD and PD modules has been interrupted. These advances and new data bring about some reconsiderations about the use of exclusively a classical electromechanical lever model of VSD–PD coupling by some Kv channels, and open a view of the Kv-type channels as allosteric machines in which gating may be dynamically influenced by some long-range interactional/allosteric mechanisms.
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Affiliation(s)
- Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006 Oviedo, Asturias, Spain.
| | - Luis A Pardo
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany.
| | - Pedro Domínguez
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006 Oviedo, Asturias, Spain.
| | - Luisa Maria Sierra
- Departamento de Biología Funcional (Area de Genética), Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, 33006 Oviedo, Asturias, Spain.
| | - Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006 Oviedo, Asturias, Spain.
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16
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de la Peña P, Domínguez P, Barros F. Functional characterization of Kv11.1 (hERG) potassium channels split in the voltage-sensing domain. Pflugers Arch 2018; 470:1069-1085. [PMID: 29572566 PMCID: PMC6013512 DOI: 10.1007/s00424-018-2135-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 02/26/2018] [Accepted: 02/28/2018] [Indexed: 12/20/2022]
Abstract
Voltage-dependent KCNH family potassium channel functionality can be reconstructed using non-covalently linked voltage-sensing domain (VSD) and pore modules (split channels). However, the necessity of a covalent continuity for channel function has not been evaluated at other points within the two functionally independent channel modules. We find here that by cutting Kv11.1 (hERG, KCNH2) channels at the different loops linking the transmembrane spans of the channel core, not only channels split at the S4–S5 linker level, but also those split at the intracellular S2–S3 and the extracellular S3–S4 loops, yield fully functional channel proteins. Our data indicate that albeit less markedly, channels split after residue 482 in the S2–S3 linker resemble the uncoupled gating phenotype of those split at the C-terminal end of the VSD S4 transmembrane segment. Channels split after residues 514 and 518 in the S3–S4 linker show gating characteristics similar to those of the continuous wild-type channel. However, breaking the covalent link at this level strongly accelerates the voltage-dependent accessibility of a membrane impermeable methanethiosulfonate reagent to an engineered cysteine at the N-terminal region of the S4 transmembrane helix. Thus, besides that of the S4–S5 linker, structural integrity of the intracellular S2–S3 linker seems to constitute an important factor for proper transduction of VSD rearrangements to opening and closing the cytoplasmic gate. Furthermore, our data suggest that the short and probably rigid characteristics of the extracellular S3–S4 linker are not an essential component of the Kv11.1 voltage sensing machinery.
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Affiliation(s)
- Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006, Oviedo, Asturias, Spain.
| | - Pedro Domínguez
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006, Oviedo, Asturias, Spain
| | - Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006, Oviedo, Asturias, Spain.
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17
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Deyawe A, Kasimova MA, Delemotte L, Loussouarn G, Tarek M. Studying Kv Channels Function using Computational Methods. Methods Mol Biol 2018; 1684:321-341. [PMID: 29058202 DOI: 10.1007/978-1-4939-7362-0_24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In recent years, molecular modeling techniques, combined with MD simulations, provided significant insights on voltage-gated (Kv) potassium channels intrinsic properties. Among the success stories are the highlight of molecular level details of the effects of mutations, the unraveling of several metastable intermediate states, and the influence of a particular lipid, PIP2, in the stability and the modulation of Kv channel function. These computational studies offered a detailed view that could not have been reached through experimental studies alone. With the increase of cross disciplinary studies, numerous experiments provided validation of these computational results, which endows an increase in the reliability of molecular modeling for the study of Kv channels. This chapter offers a description of the main techniques used to model Kv channels at the atomistic level.
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Affiliation(s)
- Audrey Deyawe
- Structure et Réactivité des Systèmes Moléculaires Complexes, CNRS, Université de Lorraine, Nancy, France
| | - Marina A Kasimova
- Structure et Réactivité des Systèmes Moléculaires Complexes, CNRS, Université de Lorraine, Nancy, France
| | - Lucie Delemotte
- Structure et Réactivité des Systèmes Moléculaires Complexes, CNRS, Université de Lorraine, Nancy, France
| | - Gildas Loussouarn
- L'institut du thorax, Inserm, CNRS, Université de Nantes, Nantes, France
| | - Mounir Tarek
- Structure et Réactivité des Systèmes Moléculaires Complexes, CNRS, Université de Lorraine, Nancy, France.
- CNRS, Unité Mixte de Recherches 7565, Université de Lorraine, Boulevard des Aiguillettes, BP 70239, 54506, Vandoeuvre-lès-Nancy, France.
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18
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de la Peña P, Domínguez P, Barros F. Gating mechanism of Kv11.1 (hERG) K + channels without covalent connection between voltage sensor and pore domains. Pflugers Arch 2017; 470:517-536. [PMID: 29270671 PMCID: PMC5805800 DOI: 10.1007/s00424-017-2093-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 11/17/2017] [Accepted: 11/28/2017] [Indexed: 12/20/2022]
Abstract
Kv11.1 (hERG, KCNH2) is a voltage-gated potassium channel crucial in setting the cardiac rhythm and the electrical behaviour of several non-cardiac cell types. Voltage-dependent gating of Kv11.1 can be reconstructed from non-covalently linked voltage sensing and pore modules (split channels), challenging classical views of voltage-dependent channel activation based on a S4–S5 linker acting as a rigid mechanical lever to open the gate. Progressive displacement of the split position from the end to the beginning of the S4–S5 linker induces an increasing negative shift in activation voltage dependence, a reduced zg value and a more negative ΔG0 for current activation, an almost complete abolition of the activation time course sigmoid shape and a slowing of the voltage-dependent deactivation. Channels disconnected at the S4–S5 linker near the S4 helix show a destabilization of the closed state(s). Furthermore, the isochronal ion current mode shift magnitude is clearly reduced in the different splits. Interestingly, the progressive modifications of voltage dependence activation gating by changing the split position are accompanied by a shift in the voltage-dependent availability to a methanethiosulfonate reagent of a Cys introduced at the upper S4 helix. Our data demonstrate for the first time that alterations in the covalent connection between the voltage sensor and the pore domains impact on the structural reorganizations of the voltage sensor domain. Also, they support the hypothesis that the S4–S5 linker integrates signals coming from other cytoplasmic domains that constitute either an important component or a crucial regulator of the gating machinery in Kv11.1 and other KCNH channels.
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Affiliation(s)
- Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006, Oviedo, Asturias, Spain.
| | - Pedro Domínguez
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006, Oviedo, Asturias, Spain
| | - Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus de El Cristo, Universidad de Oviedo, 33006, Oviedo, Asturias, Spain.
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19
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hERG S4-S5 linker acts as a voltage-dependent ligand that binds to the activation gate and locks it in a closed state. Sci Rep 2017; 7:113. [PMID: 28273916 PMCID: PMC5427910 DOI: 10.1038/s41598-017-00155-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 02/08/2017] [Indexed: 12/27/2022] Open
Abstract
Delayed-rectifier potassium channels (hERG and KCNQ1) play a major role in cardiac repolarization. These channels are formed by a tetrameric pore (S5–S6) surrounded by four voltage sensor domains (S1-S4). Coupling between voltage sensor domains and the pore activation gate is critical for channel voltage-dependence. However, molecular mechanisms remain elusive. Herein, we demonstrate that covalently binding, through a disulfide bridge, a peptide mimicking the S4-S5 linker (S4-S5L) to the channel S6 C-terminus (S6T) completely inhibits hERG. This shows that channel S4-S5L is sufficient to stabilize the pore activation gate in its closed state. Conversely, covalently binding a peptide mimicking S6T to the channel S4-S5L prevents its inhibiting effect and renders the channel almost completely voltage-independent. This shows that the channel S4-S5L is necessary to stabilize the activation gate in its closed state. Altogether, our results provide chemical evidence that S4-S5L acts as a voltage-controlled ligand that binds S6T to lock the channel in a closed state, elucidating the coupling between voltage sensors and the gate in delayed rectifier potassium channels and potentially other voltage-gated channels.
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20
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Taylor KC, Sanders CR. Regulation of KCNQ/Kv7 family voltage-gated K + channels by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:586-597. [PMID: 27818172 DOI: 10.1016/j.bbamem.2016.10.023] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 10/24/2016] [Accepted: 10/31/2016] [Indexed: 12/19/2022]
Abstract
Many years of studies have established that lipids can impact membrane protein structure and function through bulk membrane effects, by direct but transient annular interactions with the bilayer-exposed surface of protein transmembrane domains, and by specific binding to protein sites. Here, we focus on how phosphatidylinositol 4,5-bisphosphate (PIP2) and polyunsaturated fatty acids (PUFAs) impact ion channel function and how the structural details of the interactions of these lipids with ion channels are beginning to emerge. We focus on the Kv7 (KCNQ) subfamily of voltage-gated K+ channels, which are regulated by both PIP2 and PUFAs and play a variety of important roles in human health and disease. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Keenan C Taylor
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN, USA; Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
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21
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Wollberg J, Bähring R. Intra- and Intersubunit Dynamic Binding in Kv4.2 Channel Closed-State Inactivation. Biophys J 2016; 110:157-75. [PMID: 26745419 DOI: 10.1016/j.bpj.2015.10.046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/02/2015] [Accepted: 10/14/2015] [Indexed: 12/28/2022] Open
Abstract
We studied the kinetics and structural determinants of closed-state inactivation (CSI) in Kv4.2 channels, considering a multistep process and the possibility that both intra- and intersubunit dynamic binding (i.e., loss and restoration of physical contact) may occur between the S4-S5 linker, including the initial S5 segment (S4S5), and the S6 gate. We expressed Kv4.2 channels in Xenopus oocytes and measured the onset of low-voltage inactivation under two-electrode voltage clamp. Indicative of a transitory state, the onset kinetics were best described by a double-exponential function. To examine the involvement of individual S4S5 and S6 amino acid residues in dynamic binding, we studied S4S5 and S6 single alanine mutants and corresponding double mutants. Both transitory and steady-state inactivation were modified by these mutations, and we quantified the mutational effects based on apparent affinities for the respective inactivated states. Double-mutant cycle analyses revealed strong functional coupling of the S6 residues V404 and I412 to all tested S4S5 residues. To examine whether dynamic S4S5/S6 binding occurs within individual α-subunits or between neighboring α-subunits, we performed a double-mutant cycle analysis with Kv4.2 tandem-dimer constructs. The constructs carried either an S4S5/S6 double mutation in the first α-subunit and no mutation in the second (concatenated) α-subunit or an S4S5 point mutation in the first α-subunit and an S6 point mutation in the second α-subunit. Our results support the notion that CSI in Kv4.2 channels is a multistep process that involves dynamic binding both within individual α-subunits and between neighboring α-subunits.
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Affiliation(s)
- Jessica Wollberg
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Robert Bähring
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.
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22
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Abstract
BK channels are universal regulators of cell excitability, given their exceptional unitary conductance selective for K(+), joint activation mechanism by membrane depolarization and intracellular [Ca(2+)] elevation, and broad expression pattern. In this chapter, we discuss the structural basis and operational principles of their activation, or gating, by membrane potential and calcium. We also discuss how the two activation mechanisms interact to culminate in channel opening. As members of the voltage-gated potassium channel superfamily, BK channels are discussed in the context of archetypal family members, in terms of similarities that help us understand their function, but also seminal structural and biophysical differences that confer unique functional properties.
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Affiliation(s)
- A Pantazis
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States
| | - R Olcese
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, United States.
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23
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Li Y, Ng HQ, Li Q, Kang C. Structure of the Cyclic Nucleotide-Binding Homology Domain of the hERG Channel and Its Insight into Type 2 Long QT Syndrome. Sci Rep 2016; 6:23712. [PMID: 27025590 PMCID: PMC4812329 DOI: 10.1038/srep23712] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 03/14/2016] [Indexed: 01/09/2023] Open
Abstract
The human ether-à-go-go related gene (hERG) channel is crucial for the cardiac action potential by contributing to the fast delayed-rectifier potassium current. Mutations in the hERG channel result in type 2 long QT syndrome (LQT2). The hERG channel contains a cyclic nucleotide-binding homology domain (CNBHD) and this domain is required for the channel gating though molecular interactions with the eag domain. Here we present solution structure of the CNBHD of the hERG channel. The structural study reveals that the CNBHD adopts a similar fold to other KCNH channels. It is self-liganded and it contains a short β-strand that blocks the nucleotide-binding pocket in the β-roll. Folding of LQT2-related mutations in this domain was shown to be affected by point mutation. Mutations in this domain can cause protein aggregation in E. coli cells or induce conformational changes. One mutant-R752W showed obvious chemical shift perturbation compared with the wild-type, but it still binds to the eag domain. The helix region from the N-terminal cap domain of the hERG channel showed unspecific interactions with the CNBHD.
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Affiliation(s)
- Yan Li
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Hui Qi Ng
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Qingxin Li
- Institute of Chemical &Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
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Canine CNGA3 Gene Mutations Provide Novel Insights into Human Achromatopsia-Associated Channelopathies and Treatment. PLoS One 2015; 10:e0138943. [PMID: 26407004 PMCID: PMC4583268 DOI: 10.1371/journal.pone.0138943] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 09/06/2015] [Indexed: 12/27/2022] Open
Abstract
Cyclic nucleotide-gated (CNG) ion channels are key mediators underlying signal transduction in retinal and olfactory receptors. Genetic defects in CNGA3 and CNGB3, encoding two structurally related subunits of cone CNG channels, lead to achromatopsia (ACHM). ACHM is a congenital, autosomal recessive retinal disorder that manifests by cone photoreceptor dysfunction, severely reduced visual acuity, impaired or complete color blindness and photophobia. Here, we report the first canine models for CNGA3-associated channelopathy caused by R424W or V644del mutations in the canine CNGA3 ortholog that accurately mimic the clinical and molecular features of human CNGA3-associated ACHM. These two spontaneous mutations exposed CNGA3 residues essential for the preservation of channel function and biogenesis. The CNGA3-R424W results in complete loss of cone function in vivo and channel activity confirmed by in vitro electrophysiology. Structural modeling and molecular dynamics (MD) simulations revealed R424-E306 salt bridge formation and its disruption with the R424W mutant. Reversal of charges in a CNGA3-R424E-E306R double mutant channel rescued cGMP-activated currents uncovering new insights into channel gating. The CNGA3-V644del affects the C-terminal leucine zipper (CLZ) domain destabilizing intersubunit interactions of the coiled-coil complex in the MD simulations; the in vitro experiments showed incompetent trimeric CNGA3 subunit assembly consistent with abnormal biogenesis of in vivo channels. These newly characterized large animal models not only provide a valuable system for studying cone-specific CNG channel function in health and disease, but also represent prime candidates for proof-of-concept studies of CNGA3 gene replacement therapy for ACHM patients.
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25
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Lörinczi É, Gómez-Posada JC, de la Peña P, Tomczak AP, Fernández-Trillo J, Leipscher U, Stühmer W, Barros F, Pardo LA. Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains. Nat Commun 2015; 6:6672. [PMID: 25818916 PMCID: PMC4389246 DOI: 10.1038/ncomms7672] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 02/18/2015] [Indexed: 12/25/2022] Open
Abstract
Voltage-gated channels open paths for ion permeation upon changes in membrane potential, but how voltage changes are coupled to gating is not entirely understood. Two modules can be recognized in voltage-gated potassium channels, one responsible for voltage sensing (transmembrane segments S1 to S4), the other for permeation (S5 and S6). It is generally assumed that the conversion of a conformational change in the voltage sensor into channel gating occurs through the intracellular S4–S5 linker that provides physical continuity between the two regions. Using the pathophysiologically relevant KCNH family, we show that truncated proteins interrupted at, or lacking the S4–S5 linker produce voltage-gated channels in a heterologous model that recapitulate both the voltage-sensing and permeation properties of the complete protein. These observations indicate that voltage sensing by the S4 segment is transduced to the channel gate in the absence of physical continuity between the modules. The pore of voltage-gated ion channels opens in response to membrane depolarization sensed by a separate voltage-sensing domain. Here, Lörinczi et al. show that, contrary to assumptions, no physical linker is required to transmit changes from the voltage-sensing to the permeation domain of KCNH channels.
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Affiliation(s)
- Éva Lörinczi
- Department of Molecular Biology of Neuronal Signals, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Juan Camilo Gómez-Posada
- Department of Molecular Biology of Neuronal Signals, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Pilar de la Peña
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006 Oviedo, Spain
| | - Adam P Tomczak
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Jorge Fernández-Trillo
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Ulrike Leipscher
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Walter Stühmer
- Department of Molecular Biology of Neuronal Signals, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany.,Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, 37073 Göttingen, Germany
| | - Francisco Barros
- Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, Edificio Santiago Gascón, Campus de El Cristo, 33006 Oviedo, Spain
| | - Luis A Pardo
- Oncophysiology Group, Max Planck Institute of Experimental Medicine, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
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26
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Liin SI, Barro-Soria R, Larsson HP. The KCNQ1 channel - remarkable flexibility in gating allows for functional versatility. J Physiol 2015; 593:2605-15. [PMID: 25653179 DOI: 10.1113/jphysiol.2014.287607] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 01/30/2015] [Indexed: 12/12/2022] Open
Abstract
The KCNQ1 channel (also called Kv7.1 or KvLQT1) belongs to the superfamily of voltage-gated K(+) (Kv) channels. KCNQ1 shares several general features with other Kv channels but also displays a fascinating flexibility in terms of the mechanism of channel gating, which allows KCNQ1 to play different physiological roles in different tissues. This flexibility allows KCNQ1 channels to function as voltage-independent channels in epithelial tissues, whereas KCNQ1 function as voltage-activated channels with very slow kinetics in cardiac tissues. This flexibility is in part provided by the association of KCNQ1 with different accessory KCNE β-subunits and different modulators, but also seems like an integral part of KCNQ1 itself. The aim of this review is to describe the main mechanisms underlying KCNQ1 flexibility.
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Affiliation(s)
- Sara I Liin
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
| | - Rene Barro-Soria
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
| | - H Peter Larsson
- Department of Physiology and Biophysics, University of Miami, Miami, FL 33136, USA
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27
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Abstract
Antibody drugs have become an increasingly significant component of the therapeutic landscape. Their success has been driven by some of their unique properties, in particular their very high specificity and selectivity, in contrast to the off-target liabilities of small molecules (SMs). Antibodies can bring additional functionality to the table with their ability to interact with the immune system, and this can be further manipulated with advances in antibody engineering. This review summarizes what antibody therapeutics have achieved to date and what opportunities and challenges lie ahead. The target landscape for large molecules (LMs) versus SMs and some of the challenges for antibody drug development are discussed. Effective penetration of membrane barriers and intracellular targeting is one challenge, particularly across the highly resistant blood-brain barrier. The expanding pipeline of antibody-drug conjugates offers the potential to combine SM and LM modalities in a variety of creative ways, and antibodies also offer exciting potential to build bi- and multispecific molecules. The ability to pursue more challenging targets can also be further exploited but highlights the need for earlier screening in functional cell-based assays. I discuss how this might be addressed given the practical constraints imposed by high-throughput screening sample type and process differences in antibody primary screening.
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Affiliation(s)
- Alison J. Smith
- Department of Antibody Discovery and Protein Engineering, MedImmune Ltd, Cambridge, UK
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28
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Functional heterogeneity of the four voltage sensors of a human L-type calcium channel. Proc Natl Acad Sci U S A 2014; 111:18381-6. [PMID: 25489110 DOI: 10.1073/pnas.1411127112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Excitation-evoked Ca(2+) influx is the fastest and most ubiquitous chemical trigger for cellular processes, including neurotransmitter release, muscle contraction, and gene expression. The voltage dependence and timing of Ca(2+) entry are thought to be functions of voltage-gated calcium (CaV) channels composed of a central pore regulated by four nonidentical voltage-sensing domains (VSDs I-IV). Currently, the individual voltage dependence and the contribution to pore opening of each VSD remain largely unknown. Using an optical approach (voltage-clamp fluorometry) to track the movement of the individual voltage sensors, we discovered that the four VSDs of CaV1.2 channels undergo voltage-evoked conformational rearrangements, each exhibiting distinct voltage- and time-dependent properties over a wide range of potentials and kinetics. The voltage dependence and fast kinetic components in the activation of VSDs II and III were compatible with the ionic current properties, suggesting that these voltage sensors are involved in CaV1.2 activation. This view is supported by an obligatory model, in which activation of VSDs II and III is necessary to open the pore. When these data were interpreted in view of an allosteric model, where pore opening is intrinsically independent but biased by VSD activation, VSDs II and III were each found to supply ∼50 meV (∼2 kT), amounting to ∼85% of the total energy, toward stabilizing the open state, with a smaller contribution from VSD I (∼16 meV). VSD IV did not appear to participate in channel opening.
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29
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Conservation analysis of residues in the S4-S5 linker and the terminal part of the S5-P-S6 pore modulus in Kv and HCN channels: flexible determinants for the electromechanical coupling. Pflugers Arch 2014; 467:2069-79. [PMID: 25398373 DOI: 10.1007/s00424-014-1647-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 11/03/2014] [Indexed: 12/22/2022]
Abstract
Protein mobility is important to achieve protein function. Intrinsic flexibility associated with motion underlies this important issue and the analysis of side chain flexibility gives insights to understand it. In this work, the S5-P-S6 pore modulus (PM) of members of Kv and HCN channels was examined by a combination of sequence alignment, residue composition analysis, and intrinsic side chain flexibility. The PM sequences were organized as a database that was used to reveal and correlate the functional diversity of each analyzed family. Specifically, we focused our attention on the crucial role of the S4-S5 linker and its well-described interaction with the S6 T during the electromechanical coupling. Our analysis suggests the presence of a Gly-hinge in the middle of the S4-S5 linkers. This apparent Gly-hinge links a flexible N-terminal segment with a rigid C-terminal one, although in Kv7 channels, the latter segment is even more flexible. Instead, HCN channels exhibit a putative Thr-hinge and is rich in aromatic residues, in consequence, their linker is more rigid. Concerning S6, we confirm the presence of the two flexible kinks previously described and we provide the complete segmental flexibility profiles for the different families. Our results are discussed in terms of the relation between residue composition, conservation, and local conformational flexibility. This provides important insights to understand and differentiate the characteristic gating properties of these channels as well as their implications in cell physiology.
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30
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Martinez-Morales E, Snyders DJ, Labro AJ. Mutations in the S6 gate isolate a late step in the activation pathway and reduce 4-AP sensitivity in shaker K(v) channel. Biophys J 2014; 106:134-44. [PMID: 24411245 DOI: 10.1016/j.bpj.2013.11.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 10/28/2013] [Accepted: 11/12/2013] [Indexed: 01/12/2023] Open
Abstract
Kv channels detect changes in the membrane potential via their voltage-sensing domains (VSDs) that control the status of the S6 bundle crossing (BC) gate. The movement of the VSDs results in a transfer of the S4 gating charges across the cell membrane but only the last 10-20% of the total gating charge movement is associated with BC gate opening, which involves cooperative transition(s) in the subunits. Substituting the proline residue P475 in the S6 of the Shaker channel by a glycine or alanine causes a considerable shift in the voltage-dependence of the cooperative transition(s) of BC gate opening, effectively isolating the late gating charge component from the other gating charge that originates from earlier VSD movements. Interestingly, both mutations also abolished Shaker's sensitivity to 4-aminopyridine, which is a pharmacological tool to isolate the late gating charge component. The alanine substitution (that would promote a α-helical configuration compared to proline) resulted in the largest separation of both gating charge components; therefore, BC gate flexibility appears to be important for enabling the late cooperative step of channel opening.
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Affiliation(s)
- Evelyn Martinez-Morales
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, University of Antwerp, Antwerp, Belgium
| | - Dirk J Snyders
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, University of Antwerp, Antwerp, Belgium
| | - Alain J Labro
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, University of Antwerp, Antwerp, Belgium.
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31
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Randich AM, Cuello LG, Wanderling SS, Perozo E. Biochemical and structural analysis of the hyperpolarization-activated K(+) channel MVP. Biochemistry 2014; 53:1627-36. [PMID: 24490868 PMCID: PMC3985891 DOI: 10.1021/bi4014243] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
In
contrast to the majority of voltage-gated ion channels, hyperpolarization-activated
channels remain closed at depolarizing potentials and are activated
at hyperpolarizing potentials. The basis for this reverse polarity
is thought to be a result of differences in the way the voltage-sensing
domain (VSD) couples to the pore domain. In the absence of structural
data, the molecular mechanism of this reverse polarity coupling remains
poorly characterized. Here we report the characterization of the structure
and local dynamics of the closed activation gate (lower S6 region)
of MVP, a hyperpolarization-activated potassium channel from Methanococcus jannaschii, by electron paramagnetic resonance
(EPR) spectroscopy. We show that a codon-optimized version of MVP
has high expression levels in Escherichia coli, is
purified as a stable tetramer, and exhibits expected voltage-dependent
activity when reconstituted in liposomes. EPR analysis of the mid
to lower S6 region revealed positions exhibiting strong spin–spin
coupling, indicating that the activation gate of MVP is closed at
0 mV. A comparison of local environmental parameters along the activation
gate for MVP and KcsA indicates that MVP adopts a different closed
conformation. These structural details set the stage for future evaluations
of reverse electromechanical coupling in MVP.
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Affiliation(s)
- Amelia M Randich
- Department of Biochemistry and Molecular Biology, The University of Chicago , Chicago, Illinois 60637, United States
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32
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Tian C, Zhu R, Zhu L, Qiu T, Cao Z, Kang T. Potassium Channels: Structures, Diseases, and Modulators. Chem Biol Drug Des 2013; 83:1-26. [DOI: 10.1111/cbdd.12237] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Chuan Tian
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| | - Ruixin Zhu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Lixin Zhu
- Department of Pediatrics; Digestive Diseases and Nutrition Center; The State University of New York at Buffalo; Buffalo NY 14226 USA
| | - Tianyi Qiu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Zhiwei Cao
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Tingguo Kang
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
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33
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French RJ, Finol-Urdaneta RK. Open-state stabilization in Kv channels: voltage-sensor relaxation and pore propping by a bound ion. ACTA ACUST UNITED AC 2012; 140:463-7. [PMID: 23071264 PMCID: PMC3483110 DOI: 10.1085/jgp.201210901] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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34
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Loussouarn G, Tarek M. Mechanisms of Ion Channels Voltage-Dependency: All about Molecular Sensors, Gates, Levers, Locks, and Grease. Front Pharmacol 2012; 3:174. [PMID: 23060794 PMCID: PMC3459010 DOI: 10.3389/fphar.2012.00174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 09/11/2012] [Indexed: 11/13/2022] Open
Affiliation(s)
- Gildas Loussouarn
- Institut National de la Santé et de la Recherche Médicale, UMR1087 Nantes, France ; Centre National de la Recherche Scientifique, UMR 6291 Nantes, France ; L'institut du Thorax, L'UNAM Université, Université de Nantes Nantes, France
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35
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Zhang J, Qu X, Covarrubias M, Germann MW. Insight into the modulation of Shaw2 Kv channels by general anesthetics: structural and functional studies of S4-S5 linker and S6 C-terminal peptides in micelles by NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:595-601. [PMID: 23031574 DOI: 10.1016/j.bbamem.2012.09.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 09/23/2012] [Accepted: 09/24/2012] [Indexed: 12/20/2022]
Abstract
The modulation of the Drosophila Shaw2 Kv channel by 1-alkanols and inhaled anesthetics is correlated with the involvement of the S4-S5 linker and C-terminus of S6, and consistent with stabilization of the channel's closed state. Structural analysis of peptides from S4-S5 (L45) and S6 (S6c), by nuclear magnetic resonance and circular dichroism spectroscopy supports that an α-helical conformation was adopted by L45, while S6c was only in an unstable/dynamic partially folded α-helix in dodecylphosphocholine micelles. Solvent accessibility and paramagnetic probing of L45 revealed that L45 lies parallel to the surface of micelles with charged and polar residues pointing towards the solution while hydrophobic residues are buried inside the micelles. Chemical shift perturbation introduced by 1-butanol on residues Gln320, Thr321, Phe322 and Arg323 of L45, as well as Thr423 and Gln424 of S6c indicates possible anesthetic binding sites on these two important components in the channel activation apparatus. Diffusion measurements confirmed the association of L45, S6c and 1-butanol with micelles which suggests the capability of 1-butanol to influence a possible interaction of L45 and S6c in the micelle environment.
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Affiliation(s)
- Jin Zhang
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
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36
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Labro AJ, Snyders DJ. Being flexible: the voltage-controllable activation gate of kv channels. Front Pharmacol 2012; 3:168. [PMID: 22993508 PMCID: PMC3440756 DOI: 10.3389/fphar.2012.00168] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 08/26/2012] [Indexed: 12/16/2022] Open
Abstract
Kv channels form voltage-dependent potassium selective pores in the outer cell membrane and are composed out of four α-subunits, each having six membrane-spanning α-helices (S1–S6). The α-subunits tetramerize such that the S5–S6 pore domains co-assemble into a centrally located K+ pore which is surrounded by four operational voltage-sensing domains (VSD) that are each formed by the S1–S4 segments. Consequently, each subunit is capable of responding to changes in membrane potential and dictates whether the pore should be conductive or not. K+ permeation through the pore can be sealed off by two separate gates in series: (a) at the inner S6 bundle crossing (BC gate) and (b) at the level of the selectivity filter (SF gate) located at the extracellular entrance of the pore. Within the last years a general consensus emerged that a direct communication between the S4S5-linker and the bottom part of S6 (S6c) constitutes the coupling with the VSD thus making the BC gate the main voltage-controllable activation gate. While the BC gate listens to the VSD, the SF changes its conformation depending on the status of the BC gate. Through the eyes of an entering K+ ion, the operation of the BC gate apparatus can be compared with the iris-like motion of the diaphragm from a camera whereby its diameter widens. Two main gating motions have been proposed to create this BC gate widening: (1) tilting of the helix whereby the S6 converts from a straight α-helix to a tilted one or (2) swiveling of the S6c whereby the S6 remains bent. Such motions require a flexible hinge that decouples the pre- and post-hinge segment. Roughly at the middle of the S6 there exists a highly conserved glycine residue and a tandem proline motif that seem to fulfill the role of a gating hinge which allows for tilting/swiveling/rotations of the post-hinge S6 segment. In this review we delineate our current view on the operation of the BC gate for controlling K+ permeation in Kv channels.
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Affiliation(s)
- Alain J Labro
- Department of Biomedical Sciences, University of Antwerp Antwerp, Belgium
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37
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Blunck R, Batulan Z. Mechanism of electromechanical coupling in voltage-gated potassium channels. Front Pharmacol 2012; 3:166. [PMID: 22988442 PMCID: PMC3439648 DOI: 10.3389/fphar.2012.00166] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 08/24/2012] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion - sodium, calcium, or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv) undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt, and vertical displacement in order to bring 3-4e(+) each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy, and molecular dynamics simulations. Evidently, the S4-S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i) an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii) insight as to how the voltage sensor and pore domain influence one another; and (iii) theoretical predictions on the movement of the cytosolic face of the Kv channels during gating.
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Affiliation(s)
- Rikard Blunck
- Groupe d’étude des protéines membranairesMontreal, QC, Canada
- Department of Physiology, Université de MontréalMontreal, QC, Canada
- Department of Physics, Université de MontréalMontreal, QC, Canada
| | - Zarah Batulan
- Groupe d’étude des protéines membranairesMontreal, QC, Canada
- Department of Physiology, Université de MontréalMontreal, QC, Canada
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