1
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Todorovic J, Swapna I, Suma A, Carnevale V, Zakon H. Dual mechanisms contribute to enhanced voltage dependence of an electric fish potassium channel. Biophys J 2024; 123:2097-2109. [PMID: 38429925 DOI: 10.1016/j.bpj.2024.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 01/31/2024] [Accepted: 02/27/2024] [Indexed: 03/03/2024] Open
Abstract
The voltage dependence of different voltage-gated potassium channels, described by the voltage at which half of the channels are open (V1/2), varies over a range of 80 mV and is influenced by factors such as the number of positive gating charges and the identity of the hydrophobic amino acids in the channel's voltage sensor (S4). Here we explore by experimental manipulations and molecular dynamics simulation the contributions of two derived features of an electric fish potassium channel (Kv1.7a) that is among the most voltage-sensitive Shaker family potassium channels known. These are a patch of four contiguous negatively charged glutamates in the S3-S4 extracellular loop and a glutamate in the S3b helix. We find that these negative charges affect V1/2 by separate, complementary mechanisms. In the closed state, the S3-S4 linker negative patch reduces the membrane surface charge biasing the channel to enter the open state while, upon opening, the negative amino acid in the S3b helix faces the second (R2) gating charge of the voltage sensor electrostatically biasing the channel to remain in the open state. This work highlights two evolutionary novelties that illustrate the potential influence of negatively charged amino acids in extracellular loops and adjacent helices to voltage dependence.
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Affiliation(s)
- Jelena Todorovic
- Department of Neuroscience, The University of Texas, Austin, Texas
| | - Immani Swapna
- Department of Neuroscience, The University of Texas, Austin, Texas
| | - Antonio Suma
- Institute for Computational Molecular Science, College of Science and Technology & Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia, Pennsylvania
| | - Vincenzo Carnevale
- Institute for Computational Molecular Science, College of Science and Technology & Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia, Pennsylvania
| | - Harold Zakon
- Department of Neuroscience, The University of Texas, Austin, Texas; Department of Integrative Biology, The University of Texas, Austin, Texas.
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2
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Rayaprolu V, Miettinen HM, Baker WD, Young VC, Fisher M, Mueller G, Rankin WO, Kelley JT, Ratzan WJ, Leong LM, Davisson JA, Baker BJ, Kohout SC. Hydrophobic residues in S1 modulate enzymatic function and voltage sensing in voltage-sensing phosphatase. J Gen Physiol 2024; 156:e202313467. [PMID: 38771271 PMCID: PMC11109755 DOI: 10.1085/jgp.202313467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 12/13/2023] [Accepted: 05/07/2024] [Indexed: 05/22/2024] Open
Abstract
The voltage-sensing domain (VSD) is a four-helix modular protein domain that converts electrical signals into conformational changes, leading to open pores and active enzymes. In most voltage-sensing proteins, the VSDs do not interact with one another, and the S1-S3 helices are considered mainly scaffolding, except in the voltage-sensing phosphatase (VSP) and the proton channel (Hv). To investigate its contribution to VSP function, we mutated four hydrophobic amino acids in S1 to alanine (F127, I131, I134, and L137), individually or in combination. Most of these mutations shifted the voltage dependence of activity to higher voltages; however, not all substrate reactions were the same. The kinetics of enzymatic activity were also altered, with some mutations significantly slowing down dephosphorylation. The voltage dependence of VSD motions was consistently shifted to lower voltages and indicated a second voltage-dependent motion. Additionally, none of the mutations broke the VSP dimer, indicating that the S1 impact could stem from intra- and/or intersubunit interactions. Lastly, when the same mutations were introduced into a genetically encoded voltage indicator, they dramatically altered the optical readings, making some of the kinetics faster and shifting the voltage dependence. These results indicate that the S1 helix in VSP plays a critical role in tuning the enzyme's conformational response to membrane potential transients and influencing the function of the VSD.
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Affiliation(s)
- Vamseedhar Rayaprolu
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Heini M. Miettinen
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William D. Baker
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Victoria C. Young
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, USA
| | - Matthew Fisher
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Gwendolyn Mueller
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William O. Rankin
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - John T. Kelley
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William J. Ratzan
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Lee Min Leong
- Division of Bio-Medical Science and Technology, KIST School, Brain Science Institute, Korea Institute of Science and Technology (KIST), Korea University of Science and Technology (UST), Seoul, South Korea
| | - Joshua A. Davisson
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Bradley J. Baker
- Division of Bio-Medical Science and Technology, KIST School, Brain Science Institute, Korea Institute of Science and Technology (KIST), Korea University of Science and Technology (UST), Seoul, South Korea
| | - Susy C. Kohout
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, USA
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3
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Rayaprolu V, Miettinen HM, Baker W, Young VC, Fisher M, Mueller G, Rankin WO, Kelley JJ, Ratzan W, Leong LM, Davisson JA, Baker BJ, Kohout SC. S1 hydrophobic residues modulate voltage sensing phosphatase enzymatic function and voltage sensing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.27.573443. [PMID: 38234747 PMCID: PMC10793425 DOI: 10.1101/2023.12.27.573443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
The voltage sensing domain (VSD) is a four-helix modular protein domain that converts electrical signals into conformational changes, leading to open pores and active enzymes. In most voltage sensing proteins, the VSDs do not interact with one another and the S1-S3 helices are considered mainly as scaffolding. The two exceptions are the voltage sensing phosphatase (VSP) and the proton channel (Hv). VSP is a voltage-regulated enzyme and Hvs are channels that only have VSDs. To investigate the S1 contribution to VSP function, we individually mutated four hydrophobic amino acids in S1 to alanine (F127, I131, I134 and L137). We also combined these mutations to generate quadruple mutation designated S1-Q. Most of these mutations shifted the voltage dependence of activity to higher voltages though interestingly, not all substrate reactions were the same. The kinetics of enzymatic activity were also altered with some mutations significantly slowing down dephosphorylation. The voltage dependence of VSD motions were consistently shifted to lower voltages and indicated a second voltage dependent motion. Co-immunoprecipitation demonstrated that none of the mutations broke the VSP dimer indicating that the S1 impact could stem from intrasubunit and/or intersubunit interactions. Lastly, when the same alanine mutations were introduced into a genetically encoded voltage indicator, they dramatically altered the optical readings, making some of the kinetics faster and shifting the voltage dependence. These results indicate that the S1 helix in VSP plays a critical role in tuning the enzymes conformational response to membrane potential transients and influencing the function of the VSD.
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4
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González-González MA, Conde SV, Latorre R, Thébault SC, Pratelli M, Spitzer NC, Verkhratsky A, Tremblay MÈ, Akcora CG, Hernández-Reynoso AG, Ecker M, Coates J, Vincent KL, Ma B. Bioelectronic Medicine: a multidisciplinary roadmap from biophysics to precision therapies. Front Integr Neurosci 2024; 18:1321872. [PMID: 38440417 PMCID: PMC10911101 DOI: 10.3389/fnint.2024.1321872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/10/2024] [Indexed: 03/06/2024] Open
Abstract
Bioelectronic Medicine stands as an emerging field that rapidly evolves and offers distinctive clinical benefits, alongside unique challenges. It consists of the modulation of the nervous system by precise delivery of electrical current for the treatment of clinical conditions, such as post-stroke movement recovery or drug-resistant disorders. The unquestionable clinical impact of Bioelectronic Medicine is underscored by the successful translation to humans in the last decades, and the long list of preclinical studies. Given the emergency of accelerating the progress in new neuromodulation treatments (i.e., drug-resistant hypertension, autoimmune and degenerative diseases), collaboration between multiple fields is imperative. This work intends to foster multidisciplinary work and bring together different fields to provide the fundamental basis underlying Bioelectronic Medicine. In this review we will go from the biophysics of the cell membrane, which we consider the inner core of neuromodulation, to patient care. We will discuss the recently discovered mechanism of neurotransmission switching and how it will impact neuromodulation design, and we will provide an update on neuronal and glial basis in health and disease. The advances in biomedical technology have facilitated the collection of large amounts of data, thereby introducing new challenges in data analysis. We will discuss the current approaches and challenges in high throughput data analysis, encompassing big data, networks, artificial intelligence, and internet of things. Emphasis will be placed on understanding the electrochemical properties of neural interfaces, along with the integration of biocompatible and reliable materials and compliance with biomedical regulations for translational applications. Preclinical validation is foundational to the translational process, and we will discuss the critical aspects of such animal studies. Finally, we will focus on the patient point-of-care and challenges in neuromodulation as the ultimate goal of bioelectronic medicine. This review is a call to scientists from different fields to work together with a common endeavor: accelerate the decoding and modulation of the nervous system in a new era of therapeutic possibilities.
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Affiliation(s)
- María Alejandra González-González
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, United States
- Department of Pediatric Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Silvia V. Conde
- iNOVA4Health, NOVA Medical School, Faculdade de Ciências Médicas, NOVA University, Lisbon, Portugal
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Stéphanie C. Thébault
- Laboratorio de Investigación Traslacional en salud visual (D-13), Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Marta Pratelli
- Neurobiology Department, Kavli Institute for Brain and Mind, UC San Diego, La Jolla, CA, United States
| | - Nicholas C. Spitzer
- Neurobiology Department, Kavli Institute for Brain and Mind, UC San Diego, La Jolla, CA, United States
| | - Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
- Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China
- International Collaborative Center on Big Science Plan for Purinergic Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, Vilnius, Lithuania
| | - Marie-Ève Tremblay
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Department of Molecular Medicine, Université Laval, Québec City, QC, Canada
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada
| | - Cuneyt G. Akcora
- Department of Computer Science, University of Central Florida, Orlando, FL, United States
| | | | - Melanie Ecker
- Department of Biomedical Engineering, University of North Texas, Denton, TX, United States
| | | | - Kathleen L. Vincent
- Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, TX, United States
| | - Brandy Ma
- Stanley H. Appel Department of Neurology, Houston Methodist Hospital, Houston, TX, United States
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5
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Bibollet H, Kramer A, Bannister RA, Hernández-Ochoa EO. Advances in Ca V1.1 gating: New insights into permeation and voltage-sensing mechanisms. Channels (Austin) 2023; 17:2167569. [PMID: 36642864 PMCID: PMC9851209 DOI: 10.1080/19336950.2023.2167569] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 01/09/2023] [Indexed: 01/17/2023] Open
Abstract
The CaV1.1 voltage-gated Ca2+ channel carries L-type Ca2+ current and is the voltage-sensor for excitation-contraction (EC) coupling in skeletal muscle. Significant breakthroughs in the EC coupling field have often been close on the heels of technological advancement. In particular, CaV1.1 was the first voltage-gated Ca2+ channel to be cloned, the first ion channel to have its gating current measured and the first ion channel to have an effectively null animal model. Though these innovations have provided invaluable information regarding how CaV1.1 detects changes in membrane potential and transmits intra- and inter-molecular signals which cause opening of the channel pore and support Ca2+ release from the sarcoplasmic reticulum remain elusive. Here, we review current perspectives on this topic including the recent application of functional site-directed fluorometry.
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Affiliation(s)
- Hugo Bibollet
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Audra Kramer
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Roger A. Bannister
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Erick O. Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, USA
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6
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Zhao C, Webster PD, De Angeli A, Tombola F. Mechanically-primed voltage-gated proton channels from angiosperm plants. Nat Commun 2023; 14:7515. [PMID: 37980353 PMCID: PMC10657467 DOI: 10.1038/s41467-023-43280-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 11/06/2023] [Indexed: 11/20/2023] Open
Abstract
Voltage-gated and mechanically-gated ion channels are distinct classes of membrane proteins that conduct ions across gated pores and are turned on by electrical or mechanical stimuli, respectively. Here, we describe an Hv channel (a.k.a voltage-dependent H+ channel) from the angiosperm plant A. thaliana that gates with a unique modality as it is turned on by an electrical stimulus only after exposure to a mechanical stimulus, a process that we call priming. The channel localizes in the vascular tissue and has homologs in vascular plants. We find that mechanical priming is not required for activation of non-angiosperm Hvs. Guided by AI-generated structural models of plant Hv homologs, we identify a set of residues playing a crucial role in mechanical priming. We propose that Hvs from angiosperm plants require priming because of a network of hydrophilic/charged residues that locks the channels in a silent resting conformation. Mechanical stimuli destabilize the network allowing the conduction pathway to turn on. In contrast to many other channels and receptors, Hv proteins are not thought to possess mechanisms such as inactivation or desensitization. Our findings demonstrate that angiosperm Hv channels are electrically silent until a mechanical stimulation turns on their voltage-dependent activity.
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Affiliation(s)
- Chang Zhao
- Department of Physiology and Biophysics, University of California, Irvine, CA, 92697, USA
| | - Parker D Webster
- Department of Physiology and Biophysics, University of California, Irvine, CA, 92697, USA
| | - Alexis De Angeli
- IPSiM, University of Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France.
| | - Francesco Tombola
- Department of Physiology and Biophysics, University of California, Irvine, CA, 92697, USA.
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7
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Kalienkova V, Peter MF, Rheinberger J, Paulino C. Structures of a sperm-specific solute carrier gated by voltage and cAMP. Nature 2023; 623:202-209. [PMID: 37880361 PMCID: PMC10620091 DOI: 10.1038/s41586-023-06629-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/08/2023] [Indexed: 10/27/2023]
Abstract
The newly characterized sperm-specific Na+/H+ exchanger stands out by its unique tripartite domain composition1,2. It unites a classical solute carrier unit with regulatory domains usually found in ion channels, namely, a voltage-sensing domain and a cyclic-nucleotide binding domain1,3, which makes it a mechanistic chimera and a secondary-active transporter activated strictly by membrane voltage. Our structures of the sea urchin SpSLC9C1 in the absence and presence of ligands reveal the overall domain arrangement and new structural coupling elements. They allow us to propose a gating model, where movements in the voltage sensor indirectly cause the release of the exchanging unit from a locked state through long-distance allosteric effects transmitted by the newly characterized coupling helices. We further propose that modulation by its ligand cyclic AMP occurs by means of disruption of the cytosolic dimer interface, which lowers the energy barrier for S4 movements in the voltage-sensing domain. As SLC9C1 members have been shown to be essential for male fertility, including in mammals2,4,5, our structure represents a potential new platform for the development of new on-demand contraceptives.
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Affiliation(s)
- Valeria Kalienkova
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Martin F Peter
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands
- Biochemistry Center, Heidelberg University, Heidelberg, Germany
| | - Jan Rheinberger
- Biochemistry Center, Heidelberg University, Heidelberg, Germany
| | - Cristina Paulino
- Groningen Biomolecular Sciences and Biotechnology, University of Groningen, Groningen, The Netherlands.
- Biochemistry Center, Heidelberg University, Heidelberg, Germany.
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8
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Catacuzzeno L, Conti F, Franciolini F. Fifty years of gating currents and channel gating. J Gen Physiol 2023; 155:e202313380. [PMID: 37410612 PMCID: PMC10324510 DOI: 10.1085/jgp.202313380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023] Open
Abstract
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Franco Conti
- Department of Physics, University of Genova, Genova, Italy
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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9
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Cong S, Zhang J, Pan F, Pan L, Zhang A, Ma J. Research progress on ion channels and their molecular regulatory mechanisms in the human sperm flagellum. FASEB J 2023; 37:e23052. [PMID: 37352114 DOI: 10.1096/fj.202300756r] [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: 04/17/2023] [Revised: 06/06/2023] [Accepted: 06/09/2023] [Indexed: 06/25/2023]
Abstract
The ion channels in sperm tail play an important role in triggering key physiological reactions, e.g., progressive motility, hyperactivation, required for successful fertilization. Among them, CatSper and KSper have been shown to be important ion channels for the transport of Ca2+ and K+ . Moreover, the voltage-gated proton channel Hv1, the sperm-specific sodium-hydrogen exchanger (sNHE), the epithelial sodium channel (ENaC), members of the temperature-sensitive TRP channel family, and the cystic fibrosis transmembrane regulator (CFTR) are also found in the flagellum. This review focuses on the latest advances in ion channels located at the flagellum, describes how they affect sperm physiological function, and summarizes some primary mutual regulation mechanism between ion channels, including PH, membrane potential, and cAMP. These ion channels may be promising targets for clinical application in infertility.
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Affiliation(s)
- Shengnan Cong
- Obstetrics and Gynecology Department, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Jingjing Zhang
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Feng Pan
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Lianjun Pan
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Aixia Zhang
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Jiehua Ma
- Obstetrics and Gynecology Department, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
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10
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Kostritskii AY, Machtens JP. Domain- and state-specific shape of the electric field tunes voltage sensing in voltage-gated sodium channels. Biophys J 2023; 122:1807-1821. [PMID: 37077046 PMCID: PMC10209041 DOI: 10.1016/j.bpj.2023.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/27/2023] [Accepted: 04/12/2023] [Indexed: 04/21/2023] Open
Abstract
The ability to sense transmembrane voltage underlies most physiological roles of voltage-gated sodium (Nav) channels. Whereas the key role of their voltage-sensing domains (VSDs) in channel activation is well established, the molecular underpinnings of voltage coupling remain incompletely understood. Voltage-dependent energetics of the activation process can be described in terms of the gating charge that is defined by coupling of charged residues to the external electric field. The shape of the electric field within VSDs is therefore crucial for the activation of voltage-gated ion channels. Here, we employed molecular dynamics simulations of cardiac Nav1.5 and bacterial NavAb, together with our recently developed tool g_elpot, to gain insights into the voltage-sensing mechanisms of Nav channels via high-resolution quantification of VSD electrostatics. In contrast to earlier low-resolution studies, we found that the electric field within VSDs of Nav channels has a complex isoform- and domain-specific shape, which prominently depends on the activation state of a VSD. Different VSDs vary not only in the length of the region where the electric field is focused but also differ in their overall electrostatics, with possible implications in the diverse ion selectivity of their gating pores. Due to state-dependent field reshaping, not only translocated basic but also relatively immobile acidic residues contribute significantly to the gating charge. In the case of NavAb, we found that the transition between structurally resolved activated and resting states results in a gating charge of 8e, which is noticeably lower than experimental estimates. Based on the analysis of VSD electrostatics in the two activation states, we propose that the VSD likely adopts a deeper resting state upon hyperpolarization. In conclusion, our results provide an atomic-level description of the gating charge, demonstrate diversity in VSD electrostatics, and reveal the importance of electric-field reshaping for voltage sensing in Nav channels.
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Affiliation(s)
- Andrei Y Kostritskii
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany; Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany.
| | - Jan-Philipp Machtens
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany; Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany.
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11
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Treptow W. Allosteric Modulation of Membrane Proteins by Small Low-Affinity Ligands. J Chem Inf Model 2023; 63:2047-2057. [PMID: 36933226 DOI: 10.1021/acs.jcim.2c01542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
Abstract
Membrane proteins may respond to a variety of ligands under an applied external stimulus. These ligands include small low-affinity molecules that account for functional effects in the mM range. Understanding the modulation of protein function by low-affinity ligands requires characterizing their atomic-level interactions under dilution, challenging the current resolution of theoretical and experimental routines. Part of the problem derives from the fact that small low-affinity ligands may interact with multiple sites of a membrane protein in a highly degenerate manner to a degree that it is better conceived as a partition phenomenon, hard to track at the molecular interface of the protein. Looking for new developments in the field, we rely on the classic two-state Boltzmann model to devise a novel theoretical description of the allosteric modulation mechanism of membrane proteins in the presence of small low-affinity ligands and external stimuli. Free energy stability of the partition process and its energetic influence on the protein coupling with the external stimulus are quantified. The outcome is a simple formulation that allows the description of the equilibrium shifts of the protein in terms of the grand-canonical partition function of the ligand at dilute concentrations. The model's predictions of the spatial distribution and response probability shift across a variety of ligand concentrations, and thermodynamic conjugates can be directly compared to macroscopic measurements, making it especially useful to interpret experimental data at the atomic level. Illustration and discussion of the theory is shown in the context of general anesthetics and voltage-gated channels for which structural data are available.
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Affiliation(s)
- Werner Treptow
- Laboratório de Biologia Teórica e Computacional (LBTC), Universidade de Brasília, Distrito Federal, Brasília CEP 70904-970, Brasil
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12
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Duran-Urriago A, Marzen S. Not so optimal: The evolution of mutual information in potassium voltage-gated channels. PLoS One 2023; 18:e0264424. [PMID: 36735679 PMCID: PMC9897580 DOI: 10.1371/journal.pone.0264424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 02/10/2022] [Indexed: 02/04/2023] Open
Abstract
Potassium voltage-gated (Kv) channels need to detect and respond to rapidly changing ionic concentrations in their environment. With an essential role in regulating electric signaling, they would be expected to be optimal sensors that evolved to predict the ionic concentrations. To explore these assumptions, we use statistical mechanics in conjunction with information theory to model how animal Kv channels respond to changes in potassium concentrations in their environment. By measuring mutual information in representative Kv channel types across a variety of environments, we find two things. First, under weak conditions, there is a gating charge that maximizes mutual information with the environment. Second, as Kv channels evolved, they have moved towards decreasing mutual information with the environment. This either suggests that Kv channels do not need to act as sensors of their environment or that Kv channels have other functionalities that interfere with their role as sensors of their environment.
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Affiliation(s)
| | - Sarah Marzen
- W. M. Keck Science Department, Pitzer, Scripps, and Claremont McKenna Colleges, Claremont, CA, United States of America
- * E-mail:
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13
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Kudaibergenova M, Guo J, Khan HM, Lees-Miller J, Mousaei M, Miranda W, Ngo VA, Noskov SY, Tieleman DP, Duff HJ. The voltage-sensing domain of a hERG1 mutant is a cation-selective channel. Biophys J 2022; 121:4585-4599. [PMID: 36815709 PMCID: PMC9748372 DOI: 10.1016/j.bpj.2022.10.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 06/29/2022] [Accepted: 10/24/2022] [Indexed: 11/24/2022] Open
Abstract
A cationic leak current known as an "omega current" may arise from mutations of the first charged residue in the S4 of the voltage sensor domains of sodium and potassium voltage-gated channels. The voltage-sensing domains (VSDs) in these mutated channels act as pores allowing nonspecific passage of cations, such as Li+, K+, Cs+, and guanidinium. Interestingly, no omega currents have been previously detected in the nonswapped voltage-gated potassium channels such as the human-ether-a-go-go-related (hERG1), hyperpolarization-activated cyclic nucleotide-gated, and ether-a-go-go channels. In this work, we discovered a novel omega current by mutating the first charged residue of the S4 of the hERG1, K525 to serine. To characterize this omega current, we used various probes, including the hERG1 pore domain blocker, dofetilide, to show that the omega current does not require cation flux via the canonical pore domain. In addition, the omega flux does not cross the conventional selectivity filter. We also show that the mutated channel (K525S hERG1) conducts guanidinium. These data are indicative of the formation of an omega current channel within the VSD. Using molecular dynamics simulations with replica-exchange umbrella sampling simulations of the wild-type hERG1 and the K525S hERG1, we explored the molecular underpinnings governing the cation flow in the VSD of the mutant. We also show that the wild-type hERG1 may form water crevices supported by the biophysical surface accessibility data. Overall, our multidisciplinary study demonstrates that the VSD of hERG1 may act as a cation-selective channel wherein a mutation of the first charged residue in the S4 generates an omega current. Our simulation uncovers the atomistic underpinning of this mechanism.
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Affiliation(s)
- Meruyert Kudaibergenova
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Jiqing Guo
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - Hanif M Khan
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - James Lees-Miller
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - Mahdi Mousaei
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Williams Miranda
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Van A Ngo
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.
| | - Henry J Duff
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
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14
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David D, Bentulila Z, Tauber M, Ben-Chaim Y. G Protein-Coupled Receptors Regulated by Membrane Potential. Int J Mol Sci 2022; 23:ijms232213988. [PMID: 36430466 PMCID: PMC9696401 DOI: 10.3390/ijms232213988] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/09/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are involved in a vast majority of signal transduction processes. Although they span the cell membrane, they have not been considered to be regulated by the membrane potential. Numerous studies over the last two decades have demonstrated that several GPCRs, including muscarinic, adrenergic, dopaminergic, and glutamatergic receptors, are voltage regulated. Following these observations, an effort was made to elucidate the molecular basis for this regulatory effect. In this review, we will describe the advances in understanding the voltage dependence of GPCRs, the suggested molecular mechanisms that underlie this phenomenon, and the possible physiological roles that it may play.
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15
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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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16
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Abstract
In neurosecretion, allosteric communication between voltage sensors and Ca2+ binding in BK channels is crucially involved in damping excitatory stimuli. Nevertheless, the voltage-sensing mechanism of BK channels is still under debate. Here, based on gating current measurements, we demonstrate that two arginines in the transmembrane segment S4 (R210 and R213) function as the BK gating charges. Significantly, the energy landscape of the gating particles is electrostatically tuned by a network of salt bridges contained in the voltage sensor domain (VSD). Molecular dynamics simulations and proton transport experiments in the hyperpolarization-activated R210H mutant suggest that the electric field drops off within a narrow septum whose boundaries are defined by the gating charges. Unlike Kv channels, the charge movement in BK appears to be limited to a small displacement of the guanidinium moieties of R210 and R213, without significant movement of the S4.
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17
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Catacuzzeno L, Franciolini F. The 70-year search for the voltage sensing mechanism of ion channels. J Physiol 2022; 600:3227-3247. [PMID: 35665931 PMCID: PMC9545881 DOI: 10.1113/jp282780] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 04/25/2022] [Indexed: 01/10/2023] Open
Abstract
This retrospective on the voltage‐sensing mechanisms and gating models of ion channels begins in 1952 with the charged gating particles postulated by Hodgkin and Huxley, viewed as charges moving across the membrane and controlling its permeability to Na+ and K+ ions. Hodgkin and Huxley postulated that their movement should generate small and fast capacitive currents, which were recorded 20 years later as gating currents. In the early 1980s, several voltage‐dependent channels were cloned and found to share a common architecture: four homologous domains or subunits, each displaying six transmembrane α‐helical segments, with the fourth segment (S4) displaying four to seven positive charges invariably separated by two non‐charged residues. This immediately suggested that this segment was serving as the voltage sensor of the channel (the molecular counterpart of the charged gating particle postulated by Hodgkin and Huxley) and led to the development of the sliding helix model. Twenty years later, the X‐ray crystallographic structures of many voltage‐dependent channels allowed investigation of their gating by molecular dynamics. Further understanding of how channels gate will benefit greatly from the acquisition of high‐resolution structures of each of their relevant functional or structural states. This will allow the application of molecular dynamics and other approaches. It will also be key to investigate the energetics of channel gating, permitting an understanding of the physical and molecular determinants of gating. The use of multiscale hierarchical approaches might finally prove to be a rewarding strategy to overcome the limits of the various single approaches to the study of channel gating.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Italy
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18
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Edmond MA, Hinojo-Perez A, Wu X, Perez Rodriguez ME, Barro-Soria R. Distinctive mechanisms of epilepsy-causing mutants discovered by measuring S4 movement in KCNQ2 channels. eLife 2022; 11:77030. [PMID: 35642783 PMCID: PMC9197397 DOI: 10.7554/elife.77030] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 05/31/2022] [Indexed: 01/10/2023] Open
Abstract
Neuronal KCNQ channels mediate the M-current, a key regulator of membrane excitability in the central and peripheral nervous systems. Mutations in KCNQ2 channels cause severe neurodevelopmental disorders, including epileptic encephalopathies. However, the impact that different mutations have on channel function remains poorly defined, largely because of our limited understanding of the voltage-sensing mechanisms that trigger channel gating. Here, we define the parameters of voltage sensor movements in wt-KCNQ2 and channels bearing epilepsy-associated mutations using cysteine accessibility and voltage clamp fluorometry (VCF). Cysteine modification reveals that a stretch of eight to nine amino acids in the S4 becomes exposed upon voltage sensing domain activation of KCNQ2 channels. VCF shows that the voltage dependence and the time course of S4 movement and channel opening/closing closely correlate. VCF reveals different mechanisms by which different epilepsy-associated mutations affect KCNQ2 channel voltage-dependent gating. This study provides insight into KCNQ2 channel function, which will aid in uncovering the mechanisms underlying channelopathies.
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Affiliation(s)
- Michaela A Edmond
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
| | - Andy Hinojo-Perez
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
| | - Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, United States
| | - Marta E Perez Rodriguez
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, United States
| | - Rene Barro-Soria
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
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19
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Ruiz-Fernández AR, Campos L, Gutierrez-Maldonado SE, Núñez G, Villanelo F, Perez-Acle T. Nanosecond Pulsed Electric Field (nsPEF): Opening the Biotechnological Pandora’s Box. Int J Mol Sci 2022; 23:ijms23116158. [PMID: 35682837 PMCID: PMC9181413 DOI: 10.3390/ijms23116158] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/23/2022] [Accepted: 05/23/2022] [Indexed: 02/04/2023] Open
Abstract
Nanosecond Pulsed Electric Field (nsPEF) is an electrostimulation technique first developed in 1995; nsPEF requires the delivery of a series of pulses of high electric fields in the order of nanoseconds into biological tissues or cells. They primary effects in cells is the formation of membrane nanopores and the activation of ionic channels, leading to an incremental increase in cytoplasmic Ca2+ concentration, which triggers a signaling cascade producing a variety of effects: from apoptosis up to cell differentiation and proliferation. Further, nsPEF may affect organelles, making nsPEF a unique tool to manipulate and study cells. This technique is exploited in a broad spectrum of applications, such as: sterilization in the food industry, seed germination, anti-parasitic effects, wound healing, increased immune response, activation of neurons and myocites, cell proliferation, cellular phenotype manipulation, modulation of gene expression, and as a novel cancer treatment. This review thoroughly explores both nsPEF’s history and applications, with emphasis on the cellular effects from a biophysics perspective, highlighting the role of ionic channels as a mechanistic driver of the increase in cytoplasmic Ca2+ concentration.
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Affiliation(s)
- Alvaro R. Ruiz-Fernández
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
- Correspondence: (A.R.R.-F.); (T.P.-A.)
| | - Leonardo Campos
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Sebastian E. Gutierrez-Maldonado
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Gonzalo Núñez
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
| | - Felipe Villanelo
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
| | - Tomas Perez-Acle
- Computational Biology Lab, Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Fundación Ciencia & Vida, Santiago 7780272, Chile; (L.C.); (S.E.G.-M.); (G.N.); (F.V.)
- Facultad de Ingeniería y Tecnología, Universidad San Sebastian, Bellavista 7, Santiago 8420524, Chile
- Correspondence: (A.R.R.-F.); (T.P.-A.)
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20
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Bavan S, Goodkin HP, Papazian DM. Altered Closed State Inactivation Gating in Kv4.2 Channels Results in Developmental and Epileptic Encephalopathies in Human Patients. Hum Mutat 2022; 43:1286-1298. [PMID: 35510384 DOI: 10.1002/humu.24396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 04/27/2022] [Accepted: 05/01/2022] [Indexed: 11/06/2022]
Abstract
Kv4.2 subunits, encoded by KCND2, serve as the pore-forming components of voltage-gated, inactivating ISA K+ channels expressed in the brain. ISA channels inactivate without opening in response to subthreshold excitatory input, temporarily increasing neuronal excitability, the back propagation of action potentials, and Ca2+ influx into dendrites, thereby regulating mechanisms of spike timing-dependent synaptic plasticity. As previously described, a de novo variant in Kv4.2, p.Val404Met, is associated with an infant-onset developmental and epileptic encephalopathy (DEE) in monozygotic twin boys. The p.Val404Met variant enhances inactivation directly from closed states, but dramatically impairs inactivation after channel opening. We now report the identification of a closely related, novel, de novo variant in Kv4.2, p.Val402Leu, in a boy with an early-onset pharmacoresistant epilepsy that evolved to an epileptic aphasia syndrome (Continuous Spike Wave during Sleep Syndrome). Like p.Val404Met, the p.Val402Leu variant increases the rate of inactivation from closed states, but significantly slows inactivation after the pore opens. Although quantitatively the p.Val402Leu mutation alters channel kinetics less dramatically than p.Val404Met, our results strongly support the conclusion that p.Val402Leu and p.Val404Met cause the clinical features seen in the affected individuals and underscore the importance of closed state inactivation in ISA channels in normal brain development and function. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Selvan Bavan
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095-1571.,Labcorp Drug Development, Huntingdon, PE28 4HS, UK
| | - Howard P Goodkin
- Departments of Neurology and Pediatrics, University of Virginia School of Medicine, Charlottesville, VA, 22903
| | - Diane M Papazian
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095-1571
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21
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Tan XF, Bae C, Stix R, Fernández-Mariño AI, Huffer K, Chang TH, Jiang J, Faraldo-Gómez JD, Swartz KJ. Structure of the Shaker Kv channel and mechanism of slow C-type inactivation. SCIENCE ADVANCES 2022; 8:eabm7814. [PMID: 35302848 PMCID: PMC8932672 DOI: 10.1126/sciadv.abm7814] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 01/26/2022] [Indexed: 06/14/2023]
Abstract
Voltage-activated potassium (Kv) channels open upon membrane depolarization and proceed to spontaneously inactivate. Inactivation controls neuronal firing rates and serves as a form of short-term memory and is implicated in various human neurological disorders. Here, we use high-resolution cryo-electron microscopy and computer simulations to determine one of the molecular mechanisms underlying this physiologically crucial process. Structures of the activated Shaker Kv channel and of its W434F mutant in lipid bilayers demonstrate that C-type inactivation entails the dilation of the ion selectivity filter and the repositioning of neighboring residues known to be functionally critical. Microsecond-scale molecular dynamics trajectories confirm that these changes inhibit rapid ion permeation through the channel. This long-sought breakthrough establishes how eukaryotic K+ channels self-regulate their functional state through the plasticity of their selectivity filters.
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Affiliation(s)
- Xiao-Feng Tan
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Chanhyung Bae
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Robyn Stix
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Ana I. Fernández-Mariño
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kate Huffer
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
- Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Tsg-Hui Chang
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jiansen Jiang
- Laboratory of Membrane Proteins and Structural Biology and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - José D. Faraldo-Gómez
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kenton J. Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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22
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Montnach J, Blömer LA, Lopez L, Filipis L, Meudal H, Lafoux A, Nicolas S, Chu D, Caumes C, Béroud R, Jopling C, Bosmans F, Huchet C, Landon C, Canepari M, De Waard M. In vivo spatiotemporal control of voltage-gated ion channels by using photoactivatable peptidic toxins. Nat Commun 2022; 13:417. [PMID: 35058427 PMCID: PMC8776733 DOI: 10.1038/s41467-022-27974-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 12/20/2021] [Indexed: 12/11/2022] Open
Abstract
Photoactivatable drugs targeting ligand-gated ion channels open up new opportunities for light-guided therapeutic interventions. Photoactivable toxins targeting ion channels have the potential to control excitable cell activities with low invasiveness and high spatiotemporal precision. As proof-of-concept, we develop HwTxIV-Nvoc, a UV light-cleavable and photoactivatable peptide that targets voltage-gated sodium (NaV) channels and validate its activity in vitro in HEK293 cells, ex vivo in brain slices and in vivo on mice neuromuscular junctions. We find that HwTxIV-Nvoc enables precise spatiotemporal control of neuronal NaV channel function under all conditions tested. By creating multiple photoactivatable toxins, we demonstrate the broad applicability of this toxin-photoactivation technology.
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Affiliation(s)
- Jérôme Montnach
- l'institut du thorax, INSERM, CNRS, UNIV NANTES, F-44007, Nantes, France
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
| | - Laila Ananda Blömer
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
- Laboratoire Interdisciplinaire de Physique, Université Grenoble Alpes, CNRS UMR 5588, 38402, St Martin d'Hères, cedex, France
| | - Ludivine Lopez
- l'institut du thorax, INSERM, CNRS, UNIV NANTES, F-44007, Nantes, France
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
- Smartox Biotechnology, 6 rue des Platanes, F-38120, Saint-Egrève, France
| | - Luiza Filipis
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
- Laboratoire Interdisciplinaire de Physique, Université Grenoble Alpes, CNRS UMR 5588, 38402, St Martin d'Hères, cedex, France
| | - Hervé Meudal
- Center for Molecular Biophysics, CNRS, rue Charles Sadron, CS 80054, Orléans, 45071, France
| | - Aude Lafoux
- Therassay Platform, IRS2-Université de Nantes, Nantes, France
| | - Sébastien Nicolas
- l'institut du thorax, INSERM, CNRS, UNIV NANTES, F-44007, Nantes, France
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
| | - Duong Chu
- Queen's University Faculty of Medicine, Kingston, ON, Canada
| | - Cécile Caumes
- Smartox Biotechnology, 6 rue des Platanes, F-38120, Saint-Egrève, France
| | - Rémy Béroud
- Smartox Biotechnology, 6 rue des Platanes, F-38120, Saint-Egrève, France
| | - Chris Jopling
- Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094, Montpellier, France
| | - Frank Bosmans
- Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| | - Corinne Huchet
- Therassay Platform, IRS2-Université de Nantes, Nantes, France
| | - Céline Landon
- Center for Molecular Biophysics, CNRS, rue Charles Sadron, CS 80054, Orléans, 45071, France
| | - Marco Canepari
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France
- Laboratoire Interdisciplinaire de Physique, Université Grenoble Alpes, CNRS UMR 5588, 38402, St Martin d'Hères, cedex, France
| | - Michel De Waard
- l'institut du thorax, INSERM, CNRS, UNIV NANTES, F-44007, Nantes, France.
- Laboratory of Excellence Ion Channels, Science & Therapeutics, F-06560, Valbonne, France.
- Smartox Biotechnology, 6 rue des Platanes, F-38120, Saint-Egrève, France.
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23
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Qiuju H, Jianlong Z, Qi W, Zhifa L, Ding W, Xiaofang S, Yingjun X. Epilepsy Combined With Multiple Gene Heterozygous Mutation. Front Pediatr 2022; 10:763642. [PMID: 35299674 PMCID: PMC8921529 DOI: 10.3389/fped.2022.763642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 01/26/2022] [Indexed: 11/16/2022] Open
Abstract
The fast pace of gene discovery has resulted in groundbreaking advances in the field of epilepsy genetics. Clinical testing using comprehensive gene panels, exomes, or genomes is now increasingly available and has significantly increased the diagnostic yield for early-onset epilepsies and enabled precision medicine approaches. In this paper, we report a case of epilepsy in a pedigree. The proband had heterozygous mutations in KCNC1 (NM_001112741.1:c.959G>A, p. Arg320His), CAPN3 (NM_000070.2:c.526G>A, p. Val176Met), and NEFH (NM_021076.3:c. 2595 delC, p. Lys866Argfs*51). Sanger sequencing verification was consistent with the results of whole-exome sequencing. The KCNC1 mutation was a de novo mutation, and the CAPN3 and NEFH mutations were inherited from their father and mother, respectively. Based on the American College of Medical Genetics and Genomics (ACMG) guidelines, a heterozygous mutation was found for APOB (NM_000384.2: c.10579C > T, p. Arg3527Trp). The heterozygous mutation at this site was inherent in the pedigree. Coexpression analysis indicated that heterozygous mutations of KCNC1, CAPN3, NEFH, and APOB were closely related to the clinical phenotypes of the patient, and the clinical phenotypic heterogeneity of the disease may be the result of the interaction of multiple genes.
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Affiliation(s)
- He Qiuju
- Department of Obstetrics and Gynaecology, Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Zhuang Jianlong
- Prenatal Diagnosis Center, Quanzhou Women's and Children's Hospital, Quanzhou, China
| | - Wen Qi
- Department of Obstetrics and Gynaecology, Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Department of Clinical Medicine, The Third Clinical School of Guangzhou Medical University, Guangzhou, China
| | - Li Zhifa
- Gastrointestinal Surgery, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Wang Ding
- Department of Obstetrics and Gynaecology, Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Sun Xiaofang
- Department of Obstetrics and Gynaecology, Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Xie Yingjun
- Department of Obstetrics and Gynaecology, Key Laboratory for Major Obstetric Diseases of Guangdong Province, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.,Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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24
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Hirazawa K, Tateyama M, Kubo Y, Shimomura T. Phosphoinositide regulates dynamic movement of the S4 voltage sensor in the second repeat in two-pore channel 3. J Biol Chem 2021; 297:101425. [PMID: 34800436 PMCID: PMC8665364 DOI: 10.1016/j.jbc.2021.101425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 11/11/2021] [Accepted: 11/15/2021] [Indexed: 11/24/2022] Open
Abstract
The two-pore channels (TPCs) are voltage-gated cation channels consisting of single polypeptides with two repeats of a canonical 6-transmembrane unit. TPCs are known to be regulated by various physiological signals such as membrane voltage and phosphoinositide (PI). The fourth helix in the second repeat (second S4) plays a major role in detecting membrane voltage, whereas the first repeat contains a PI binding site. Therefore, each of these stimuli is detected by a unique repeat to regulate the gating of the TPC central pore. How these various stimuli regulate the dynamic structural rearrangement of the TPC molecule remain unknown. Here, we found that PI binding to the first repeat in TPC3 regulates the movement of the distally located second S4 helix, showing that the PI-binding signal is not confined to the pore gate but also transmitted to the voltage sensor. Using voltage clamp fluorometry, measurement of gating charges, and Cys-accessibility analysis, we observed that PI binding significantly potentiates the voltage dependence of the movement of the second S4 helix. Notably, voltage clamp fluorometry analysis revealed that the voltage-dependent movement of the second S4 helix occurred in two phases, of which the second phase corresponds to the transfer of the gating charges. This movement was observed in the voltage range where gate-opening occurs and was potentiated by PI. In conclusion, this regulation of the second S4 helix by PI indicates a tight inter-repeat coupling within TPC3, a feature which might be conserved among TPC family members to integrate various physiological signals.
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Affiliation(s)
- Kiichi Hirazawa
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies, Hayama, Japan
| | - Michihiro Tateyama
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies, Hayama, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies, Hayama, Japan
| | - Takushi Shimomura
- Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies, Hayama, Japan.
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25
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Priest MF, Lee EE, Bezanilla F. Tracking the movement of discrete gating charges in a voltage-gated potassium channel. eLife 2021; 10:58148. [PMID: 34779404 PMCID: PMC8635975 DOI: 10.7554/elife.58148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/08/2021] [Indexed: 01/18/2023] Open
Abstract
Positively charged amino acids respond to membrane potential changes to drive voltage sensor movement in voltage-gated ion channels, but determining the displacements of voltage sensor gating charges has proven difficult. We optically tracked the movement of the two most extracellular charged residues (R1 and R2) in the Shaker potassium channel voltage sensor using a fluorescent positively charged bimane derivative (qBBr) that is strongly quenched by tryptophan. By individually mutating residues to tryptophan within the putative pathway of gating charges, we observed that the charge motion during activation is a rotation and a tilted translation that differs between R1 and R2. Tryptophan-induced quenching of qBBr also indicates that a crucial residue of the hydrophobic plug is linked to the Cole-Moore shift through its interaction with R1. Finally, we show that this approach extends to additional voltage-sensing membrane proteins using the Ciona intestinalis voltage-sensitive phosphatase (CiVSP).
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Affiliation(s)
- Michael F Priest
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Elizabeth El Lee
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Francisco Bezanilla
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States.,Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, United States
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26
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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27
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Li X, Zheng Y, Li S, Nair U, Sun C, Zhao C, Lu J, Zhang VW, Maljevic S, Petrou S, Lin J. Kv3.1 channelopathy: a novel loss-of-function variant and the mechanistic basis of its clinical phenotypes. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:1397. [PMID: 34733949 PMCID: PMC8506712 DOI: 10.21037/atm-21-1885] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 08/11/2021] [Indexed: 11/26/2022]
Abstract
Background KCNC1 encodes Kv3.1, a subunit of the Kv3 voltage-gated potassium channels. It is predominantly expressed in inhibitory GABAergic interneurons and cerebellar neurons. Kv3.1 channelopathy has been linked to a variety of human diseases including epilepsy, developmental delay, and ataxia. Characterization of structural and functional disturbances of this channel, and its relationship to a heterogenous group of clinical phenotypes, is a current topic of research. We herein characterize the clinical phenotype as well as the functional and structural consequences of the novel KCNC1 p.R317S variant. We further set out to explore the mechanistic basis for the spectrum of KCNC1 related channelopathies. Methods Variant was identified via whole-exome sequencing and its functional impact was determined using two-electrode voltage clamp recordings in Xenopus laevis oocytes. Homolog modeling and in silico structural analysis were performed on the p.R317S variant and other KCNC1 related variants. Results We identified a novel loss-of-function KCNC1 variant c.949C>A (p.R317S) presenting with symptoms similar to myoclonic epilepsy and ataxia due to potassium channel (MEAK), but with distinct radiological features. Functional analysis in the Xenopus laevis oocyte’s expression system revealed that the current amplitudes were significantly decreased in the p.R317S variant compared to the wild type, indicating a dominant-negative effect. Atomic structural analysis of the KCNC1 related variants provided a possible mechanistic explanation for the heterogeneity in the clinical spectrum. Conclusions We have identified the p.R317S loss-of-function variant in the KCNC1 gene, expanded the spectrum of potassium channelopathy and provided mechanistic insights into KCNC1 related disorders.
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Affiliation(s)
- Xiaoyang Li
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China.,Department of Neurology, University of North Carolina, Chapel Hill, USA
| | - Yongsheng Zheng
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | | | - Umesh Nair
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia
| | - Chong Sun
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jiahong Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | | | - Snezana Maljevic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia
| | - Jie Lin
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
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28
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Thapa P, Stewart R, Sepela RJ, Vivas O, Parajuli LK, Lillya M, Fletcher-Taylor S, Cohen BE, Zito K, Sack JT. EVAP: A two-photon imaging tool to study conformational changes in endogenous Kv2 channels in live tissues. J Gen Physiol 2021; 153:212666. [PMID: 34581724 PMCID: PMC8480965 DOI: 10.1085/jgp.202012858] [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: 01/03/2021] [Accepted: 09/03/2021] [Indexed: 12/29/2022] Open
Abstract
A primary goal of molecular physiology is to understand how conformational changes of proteins affect the function of cells, tissues, and organisms. Here, we describe an imaging method for measuring the conformational changes of the voltage sensors of endogenous ion channel proteins within live tissue, without genetic modification. We synthesized GxTX-594, a variant of the peptidyl tarantula toxin guangxitoxin-1E, conjugated to a fluorophore optimal for two-photon excitation imaging through light-scattering tissue. We term this tool EVAP (Endogenous Voltage-sensor Activity Probe). GxTX-594 targets the voltage sensors of Kv2 proteins, which form potassium channels and plasma membrane–endoplasmic reticulum junctions. GxTX-594 dynamically labels Kv2 proteins on cell surfaces in response to voltage stimulation. To interpret dynamic changes in fluorescence intensity, we developed a statistical thermodynamic model that relates the conformational changes of Kv2 voltage sensors to degree of labeling. We used two-photon excitation imaging of rat brain slices to image Kv2 proteins in neurons. We found puncta of GxTX-594 on hippocampal CA1 neurons that responded to voltage stimulation and retain a voltage response roughly similar to heterologously expressed Kv2.1 protein. Our findings show that EVAP imaging methods enable the identification of conformational changes of endogenous Kv2 voltage sensors in tissue.
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Affiliation(s)
- Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Robert Stewart
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Rebecka J Sepela
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Oscar Vivas
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Laxmi K Parajuli
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Mark Lillya
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Sebastian Fletcher-Taylor
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Bruce E Cohen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA.,Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Karen Zito
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA
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29
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Cui J. BK Channel Gating Mechanisms: Progresses Toward a Better Understanding of Variants Linked Neurological Diseases. Front Physiol 2021; 12:762175. [PMID: 34744799 PMCID: PMC8567085 DOI: 10.3389/fphys.2021.762175] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 10/01/2021] [Indexed: 12/21/2022] Open
Abstract
The large conductance Ca2+-activated potassium (BK) channel is activated by both membrane potential depolarization and intracellular Ca2+ with distinct mechanisms. Neural physiology is sensitive to the function of BK channels, which is shown by the discoveries of neurological disorders that are associated with BK channel mutations. This article reviews the molecular mechanisms of BK channel activation in response to voltage and Ca2+ binding, including the recent progress since the publication of the atomistic structure of the whole BK channel protein, and the neurological disorders associated with BK channel mutations. These results demonstrate the unique mechanisms of BK channel activation and that these mechanisms are important factors in linking BK channel mutations to neurological disorders.
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Affiliation(s)
- Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, MO, United States
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30
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Voltage sensor movements of Ca V1.1 during an action potential in skeletal muscle fibers. Proc Natl Acad Sci U S A 2021; 118:2026116118. [PMID: 34583989 DOI: 10.1073/pnas.2026116118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2021] [Indexed: 11/18/2022] Open
Abstract
The skeletal muscle L-type Ca2+ channel (CaV1.1) works primarily as a voltage sensor for skeletal muscle action potential (AP)-evoked Ca2+ release. CaV1.1 contains four distinct voltage-sensing domains (VSDs), yet the contribution of each VSD to AP-evoked Ca2+ release remains unknown. To investigate the role of VSDs in excitation-contraction coupling (ECC), we encoded cysteine substitutions on each S4 voltage-sensing segment of CaV1.1, expressed each construct via in vivo gene transfer electroporation, and used in cellulo AP fluorometry to track the movement of each CaV1.1 VSD in skeletal muscle fibers. We first provide electrical measurements of CaV1.1 voltage sensor charge movement in response to an AP waveform. Then we characterize the fluorescently labeled channels' VSD fluorescence signal responses to an AP and compare them with the waveforms of the electrically measured charge movement, the optically measured free myoplasmic Ca2+, and the calculated rate of Ca2+ release from the sarcoplasmic reticulum for an AP, the physiological signal for skeletal muscle fiber activation. A considerable fraction of the fluorescence signal for each VSD occurred after the time of peak Ca2+ release, and even more occurred after the earlier peak of electrically measured charge movement during an AP, and thus could not directly reflect activation of Ca2+ release or charge movement, respectively. However, a sizable fraction of the fluorometric signals for VSDs I, II, and IV, but not VSDIII, overlap the rising phase of charge moved, and even more for Ca2+ release, and thus could be involved in voltage sensor rearrangements or Ca2+ release activation.
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31
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Pipatpolkai T, Quetschlich D, Stansfeld PJ. From Bench to Biomolecular Simulation: Phospholipid Modulation of Potassium Channels. J Mol Biol 2021; 433:167105. [PMID: 34139216 PMCID: PMC8361781 DOI: 10.1016/j.jmb.2021.167105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 06/09/2021] [Accepted: 06/10/2021] [Indexed: 12/05/2022]
Abstract
Potassium (K+) ion channels are crucial in numerous cellular processes as they hyperpolarise a cell through K+ conductance, returning a cell to its resting potential. K+ channel mutations result in multiple clinical complications such as arrhythmia, neonatal diabetes and migraines. Since 1995, the regulation of K+ channels by phospholipids has been heavily studied using a range of interdisciplinary methods such as cellular electrophysiology, structural biology and computational modelling. As a result, K+ channels are model proteins for the analysis of protein-lipid interactions. In this review, we will focus on the roles of lipids in the regulation of K+ channels, and how atomic-level structures, along with experimental techniques and molecular simulations, have helped guide our understanding of the importance of phospholipid interactions.
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Affiliation(s)
- Tanadet Pipatpolkai
- Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK; Department of Physiology Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Daniel Quetschlich
- Department of Biochemistry, South Parks Road, Oxford OX1 3QU, UK; Department of Chemistry, South Parks Road, Oxford OX1 3QZ, UK
| | - Phillip J Stansfeld
- School of Life Sciences & Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
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32
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Exploring the Conformational Changes Induced by Nanosecond Pulsed Electric Fields on the Voltage Sensing Domain of a Ca 2+ Channel. MEMBRANES 2021; 11:membranes11070473. [PMID: 34206827 PMCID: PMC8303878 DOI: 10.3390/membranes11070473] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/11/2021] [Accepted: 06/13/2021] [Indexed: 12/21/2022]
Abstract
Nanosecond Pulsed Electric Field (nsPEF or Nano Pulsed Stimulation, NPS) is a technology that delivers a series of pulses of high-voltage electric fields during a short period of time, in the order of nanoseconds. The main consequence of nsPEF upon cells is the formation of nanopores, which is followed by the gating of ionic channels. Literature is conclusive in that the physiological mechanisms governing ion channel gating occur in the order of milliseconds. Hence, understanding how these channels can be activated by a nsPEF would be an important step in order to conciliate fundamental biophysical knowledge with improved nsPEF applications. To get insights on both the kinetics and thermodynamics of ion channel gating induced by nsPEF, in this work, we simulated the Voltage Sensing Domain (VSD) of a voltage-gated Ca2+ channel, inserted in phospholipidic membranes with different concentrations of cholesterol. We studied the conformational changes of the VSD under a nsPEF mimicked by the application of a continuous electric field lasting 50 ns with different intensities as an approach to reveal novel mechanisms leading to ion channel gating in such short timescales. Our results show that using a membrane with high cholesterol content, under an nsPEF of 50 ns and E→ = 0.2 V/nm, the VSD undergoes major conformational changes. As a whole, our work supports the notion that membrane composition may act as an allosteric regulator, specifically cholesterol content, which is fundamental for the response of the VSD to an external electric field. Moreover, changes on the VSD structure suggest that the gating of voltage-gated Ca2+ channels by a nsPEF may be due to major conformational changes elicited in response to the external electric field. Finally, the VSD/cholesterol-bilayer under an nsPEF of 50 ns and E→ = 0.2 V/nm elicits a pore formation across the VSD suggesting a new non-reported effect of nsPEF into cells, which can be called a “protein mediated electroporation”.
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33
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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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34
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Bertagna F, Lewis R, Silva SRP, McFadden J, Jeevaratnam K. Effects of electromagnetic fields on neuronal ion channels: a systematic review. Ann N Y Acad Sci 2021; 1499:82-103. [PMID: 33945157 DOI: 10.1111/nyas.14597] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 02/09/2021] [Accepted: 03/12/2021] [Indexed: 12/18/2022]
Abstract
Many aspects of chemistry and biology are mediated by electromagnetic field (EMF) interactions. The central nervous system (CNS) is particularly sensitive to EMF stimuli. Studies have explored the direct effect of different EMFs on the electrical properties of neurons in the last two decades, particularly focusing on the role of voltage-gated ion channels (VGCs). This work aims to systematically review published evidence in the last two decades detailing the effects of EMFs on neuronal ion channels as per the PRISM guidelines. Following a predetermined exclusion and inclusion criteria, 22 papers were included after searches on three online databases. Changes in calcium homeostasis, attributable to the voltage-gated calcium channels, were found to be the most commonly reported result of EMF exposure. EMF effects on the neuronal landscape appear to be diverse and greatly dependent on parameters, such as the field's frequency, exposure time, and intrinsic properties of the irradiated tissue, such as the expression of VGCs. Here, we systematically clarify how neuronal ion channels are particularly affected and differentially modulated by EMFs at multiple levels, such as gating dynamics, ion conductance, concentration in the membrane, and gene and protein expression. Ion channels represent a major transducer for EMF-related effects on the CNS.
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Affiliation(s)
- Federico Bertagna
- Leverhulme Quantum Biology Doctoral Training Centre, University of Surrey, Guildford, Surrey, UK.,School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
| | - Rebecca Lewis
- Leverhulme Quantum Biology Doctoral Training Centre, University of Surrey, Guildford, Surrey, UK.,School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
| | - S Ravi P Silva
- Leverhulme Quantum Biology Doctoral Training Centre, University of Surrey, Guildford, Surrey, UK.,Advanced Technology Institute, University of Surrey, Guildford, Surrey, UK
| | - Johnjoe McFadden
- Leverhulme Quantum Biology Doctoral Training Centre, University of Surrey, Guildford, Surrey, UK.,School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
| | - Kamalan Jeevaratnam
- Leverhulme Quantum Biology Doctoral Training Centre, University of Surrey, Guildford, Surrey, UK.,School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
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35
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Abstract
Voltage gated ion channels (VGICs) shape the electrical character of cells by undergoing structural changes in response to membrane depolarization. High-resolution techniques have provided a wealth of data on individual VGIC structures, but the conformational changes of endogenous channels in live cell membranes have remained unexplored. Here, we describe methods for imaging structural changes of voltage-gated K+ channels in living cells, using peptidyl toxins labeled with fluorophores that report specific protein conformations. These Endogenous Voltage-sensor Activity Probes (EVAPs) enable study of both VGIC allostery and function in the context of endogenous live-cell membranes under different physiological states. In this chapter, we describe methods for the synthesis, imaging, and analysis of dynamic EVAPs, which can report K+ channel activity in complex tissue preparations via 2-photon excitation microscopy, and environment-sensitive EVAPs, which report voltage-dependent conformational changes at the VGIC-toxin interface. The methods here present the utility of current EVAPs and lay the groundwork for the development of other probes that act by similar mechanisms. EVAPs can be correlated with electrophysiology, offering insight into the molecular details of endogenous channel function and allostery in live cells. This enables investigation of conformational changes of channels in their native, functional states, putting structures and models into a context of live-cell membranes. The expansive array of state-dependent ligands and optical probes should enable probes more generally for investigating the molecular motions of endogenous proteins.
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Affiliation(s)
- Robert Stewart
- Department of Physiology & Membrane Biology, University of California, Davis, CA, United States
| | - Bruce E Cohen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, United States; Division of Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
| | - Jon T Sack
- Department of Physiology & Membrane Biology, University of California, Davis, CA, United States; Department of Anesthesiology & Pain Medicine, University of California, Davis, CA, United States.
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36
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Silverå Ejneby M, Gromova A, Ottosson NE, Borg S, Estrada-Mondragón A, Yazdi S, Apostolakis P, Elinder F, Delemotte L. Resin-acid derivatives bind to multiple sites on the voltage-sensor domain of the Shaker potassium channel. J Gen Physiol 2021; 153:211862. [PMID: 33683319 PMCID: PMC7944402 DOI: 10.1085/jgp.202012676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 11/30/2020] [Accepted: 01/27/2021] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated potassium (KV) channels can be opened by negatively charged resin acids and their derivatives. These resin acids have been proposed to attract the positively charged voltage-sensor helix (S4) toward the extracellular side of the membrane by binding to a pocket located between the lipid-facing extracellular ends of the transmembrane segments S3 and S4. By contrast to this proposed mechanism, neutralization of the top gating charge of the Shaker KV channel increased resin-acid-induced opening, suggesting other mechanisms and sites of action. Here, we explore the binding of two resin-acid derivatives, Wu50 and Wu161, to the activated/open state of the Shaker KV channel by a combination of in silico docking, molecular dynamics simulations, and electrophysiology of mutated channels. We identified three potential resin-acid-binding sites around S4: (1) the S3/S4 site previously suggested, in which positively charged residues introduced at the top of S4 are critical to keep the compound bound, (2) a site in the cleft between S4 and the pore domain (S4/pore site), in which a tryptophan at the top of S6 and the top gating charge of S4 keeps the compound bound, and (3) a site located on the extracellular side of the voltage-sensor domain, in a cleft formed by S1-S4 (the top-VSD site). The multiple binding sites around S4 and the anticipated helical-screw motion of the helix during activation make the effect of resin-acid derivatives on channel function intricate. The propensity of a specific resin acid to activate and open a voltage-gated channel likely depends on its exact binding dynamics and the types of interactions it can form with the protein in a state-specific manner.
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Affiliation(s)
- Malin Silverå Ejneby
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Arina Gromova
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Nina E Ottosson
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Stina Borg
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | | | - Samira Yazdi
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Panagiotis Apostolakis
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Fredrik Elinder
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
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37
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Bassetto CA, Carvalho-de-Souza JL, Bezanilla F. Molecular basis for functional connectivity between the voltage sensor and the selectivity filter gate in Shaker K + channels. eLife 2021; 10:63077. [PMID: 33620313 PMCID: PMC7943188 DOI: 10.7554/elife.63077] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 02/22/2021] [Indexed: 01/18/2023] Open
Abstract
In Shaker K+ channels, the S4-S5 linker couples the voltage sensor (VSD) and pore domain (PD). Another coupling mechanism is revealed using two W434F-containing channels: L361R:W434F and L366H:W434F. In L361R:W434F, W434F affects the L361R VSD seen as a shallower charge-voltage (Q-V) curve that crosses the conductance-voltage (G-V) curve. In L366H:W434F, L366H relieves the W434F effect converting a non-conductive channel in a conductive one. We report a chain of residues connecting the VSD (S4) to the selectivity filter (SF) in the PD of an adjacent subunit as the molecular basis for voltage sensor selectivity filter gate (VS-SF) coupling. Single alanine substitutions in this region (L409A, S411A, S412A, or F433A) are enough to disrupt the VS-SF coupling, shown by the absence of Q-V and G-V crossing in L361R:W434F mutant and by the lack of ionic conduction in the L366H:W434F mutant. This residue chain defines a new coupling between the VSD and the PD in voltage-gated channels.
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Affiliation(s)
- Carlos Az Bassetto
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States
| | - João Luis Carvalho-de-Souza
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States.,Department of Anesthesiology, University of Arizona, Tucson, United States
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States.,Centro Interdisciplinario de Neurociencias, Facultad de Ciencias, Universidad de Valparaiso, Valparaiso, Chile
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38
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Abstract
Potassium channels are present in every living cell and essential to setting up a stable, non-zero transmembrane electrostatic potential which manifests the off-equilibrium livelihood of the cell. They are involved in other cellular activities and regulation, such as the controlled release of hormones, the activation of T-cells for immune response, the firing of action potential in muscle cells and neurons, etc. Pharmacological reagents targeting potassium channels are important for treating various human diseases linked to dysfunction of the channels. High-resolution structures of these channels are very useful tools for delineating the detailed chemical basis underlying channel functions and for structure-based design and optimization of their pharmacological and pharmaceutical agents. Structural studies of potassium channels have revolutionized biophysical understandings of key concepts in the field - ion selectivity, conduction, channel gating, and modulation, making them multi-modality targets of pharmacological regulation. In this chapter, I will select a few high-resolution structures to illustrate key structural insights, proposed allostery behind channel functions, disagreements still open to debate, and channel-lipid interactions and co-evolution. The known structural consensus allows the inference of conserved molecular mechanisms shared among subfamilies of K+ channels and makes it possible to develop channel-specific pharmaceutical agents.
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Affiliation(s)
- Qiu-Xing Jiang
- Laboratory of Molecular Physiology and Biophysics and the Cryo-EM Center, Hauptmann-Woodward Medical Research Institute, Buffalo, NY, USA.
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL, USA.
- Departments of Materials Design and Invention and Physiology and Biophysics, University of Buffalo (SUNY), Buffalo, NY, USA.
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39
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Abstract
Aberrant function or expression of potassium channels can be underlying in pathologies such as cardiac arrhythmia, diabetes mellitus, hypertension, preterm birth, and various types of cancer. The expression of potassium channels is altered in many types of diseases. Also, we have previously shown that natural polyphenols, such as resveratrol, and selective synthetic modulators of potassium channels, like pinacidil, can alter their function and lead to the desired outcome. Therefore, targeting potassium channels with substance, which has an influence on their function, is promising access to cancer, diabetes mellitus, preterm birth, or hypertension therapy. In this chapter, we could discuss strategies for targeting different types of potassium channels as potential targets for synthetic and natural molecules therapy.
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40
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Garcia K, Guerrero-Galán C, Frank HER, Haider MZ, Delteil A, Conéjéro G, Lambilliotte R, Fizames C, Sentenac H, Zimmermann SD. Fungal Shaker-like channels beyond cellular K+ homeostasis: A role in ectomycorrhizal symbiosis between Hebeloma cylindrosporum and Pinus pinaster. PLoS One 2020; 15:e0242739. [PMID: 33216794 PMCID: PMC7678990 DOI: 10.1371/journal.pone.0242739] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 11/07/2020] [Indexed: 01/04/2023] Open
Abstract
Potassium (K+) acquisition, translocation and cellular homeostasis are mediated by various membrane transport systems in all organisms. We identified and described an ion channel in the ectomycorrhizal fungus Hebeloma cylindrosporum (HcSKC) that harbors features of animal voltage-dependent Shaker-like K+ channels, and investigated its role in both free-living hyphae and symbiotic conditions. RNAi lines affected in the expression of HcSKC were produced and used for in vitro mycorrhizal assays with the maritime pine as host plant, under standard or low K+ conditions. The adaptation of H. cylindrosporum to the downregulation of HcSKC was analyzed by qRT-PCR analyses for other K+-related transport proteins: the transporters HcTrk1, HcTrk2, and HcHAK, and the ion channels HcTOK1, HcTOK2.1, and HcTOK2.2. Downregulated HcSKC transformants displayed greater K+ contents at standard K+ only. In such conditions, plants inoculated with these transgenic lines were impaired in K+ nutrition. Taken together, these results support the hypothesis that the reduced expression of HcSKC modifies the pool of fungal K+ available for the plant and/or affects its symbiotic transfer to the roots. Our study reveals that the maintenance of K+ transport in H. cylindrosporum, through the regulation of HcSKC expression, is required for the K+ nutrition of the host plant.
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Affiliation(s)
- Kevin Garcia
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, California, United States of America
| | | | - Hannah E. R. Frank
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, California, United States of America
| | | | - Amandine Delteil
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
| | - Geneviève Conéjéro
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
- Plateforme Histocytologie et Imagerie Cellulaire Végétale, INRA-CIRAD Montpellier, France
| | - Raphaël Lambilliotte
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
| | - Cécile Fizames
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
| | - Hervé Sentenac
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
| | - Sabine D. Zimmermann
- BPMP, Université de Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France
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41
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Yang F, Xu L, Lee BH, Xiao X, Yarov‐Yarovoy V, Zheng J. An Unorthodox Mechanism Underlying Voltage Sensitivity of TRPV1 Ion Channel. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2000575. [PMID: 33101845 PMCID: PMC7578911 DOI: 10.1002/advs.202000575] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 08/05/2020] [Indexed: 05/10/2023]
Abstract
While the capsaicin receptor transient receptor potential vanilloid 1 (TRPV1) channel is a polymodal nociceptor for heat, capsaicin, and protons, the channel's responses to each of these stimuli are profoundly regulated by membrane potential, damping or even prohibiting its response at negative voltages and amplifying its response at positive voltages. Therefore, voltage sensitivity of TRPV1 is anticipated to play an important role in shaping pain responses. How voltage regulates TRPV1 activation remains unknown. Here, it is shown that voltage sensitivity does not originate from the S4 segment like classic voltage-gated ion channels; instead, outer pore acidic residues directly partake in voltage-sensitive activation, with their negative charges collectively constituting the observed gating charges. Outer pore gating-charge movement is titratable by extracellular pH and is allosterically coupled to channel activation, likely by influencing the upper gate in the ion selectivity filter. Elucidating this unorthodox voltage-gating process provides a mechanistic foundation for understanding TRPV1 polymodal gating and opens the door to novel approaches regulating channel activity for pain management.
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Affiliation(s)
- Fan Yang
- Department of Biophysics, and Kidney Disease Center of the First Affiliated HospitalZhejiang University School of Medicine866 Yuhangtang RoadHangzhouZhejiang310058China
- Department of Physiology and Membrane BiologyUniversity of California, DavisOne Shields AvenueDavisCA95616USA
| | - Lizhen Xu
- Department of Biophysics, and Kidney Disease Center of the First Affiliated HospitalZhejiang University School of Medicine866 Yuhangtang RoadHangzhouZhejiang310058China
| | - Bo Hyun Lee
- Department of Physiology and Membrane BiologyUniversity of California, DavisOne Shields AvenueDavisCA95616USA
| | - Xian Xiao
- Department of Physiology and Membrane BiologyUniversity of California, DavisOne Shields AvenueDavisCA95616USA
- School of Life Sciences, Westlake Institute for Advanced StudyWestlake UniversityShilongshan Road No. 18, Xihu DistrictHangzhouZhejiang310064China
| | - Vladimir Yarov‐Yarovoy
- Department of Physiology and Membrane BiologyUniversity of California, DavisOne Shields AvenueDavisCA95616USA
| | - Jie Zheng
- Department of Physiology and Membrane BiologyUniversity of California, DavisOne Shields AvenueDavisCA95616USA
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42
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Fletcher-Taylor S, Thapa P, Sepela RJ, Kaakati R, Yarov-Yarovoy V, Sack JT, Cohen BE. Distinguishing Potassium Channel Resting State Conformations in Live Cells with Environment-Sensitive Fluorescence. ACS Chem Neurosci 2020; 11:2316-2326. [PMID: 32579336 DOI: 10.1021/acschemneuro.0c00276] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Ion channels are polymorphic membrane proteins whose high-resolution structures offer images of individual conformations, giving us starting points for identifying the complex and transient allosteric changes that give rise to channel physiology. Here, we report live-cell imaging of voltage-dependent structural changes of voltage-gated Kv2.1 channels using peptidyl tarantula toxins labeled with an environment-sensitive fluorophore, whose spectral shifts enable identification of voltage-dependent conformation changes in the resting voltage sensing domain (VSD) of the channel. We synthesize a new environment-sensitive, far-red fluorophore, julolidine phenoxazone (JP) azide, and conjugate it to tarantula toxin GxTX to characterize Kv2.1 VSD allostery during membrane depolarization. JP has an inherent response to the polarity of its immediate surroundings, offering site-specific structural insight into each channel conformation. Using voltage-clamp spectroscopy to collect emission spectra as a function of membrane potential, we find that they vary with toxin labeling site, the presence of Kv2 channels, and changes in membrane potential. With a high-affinity conjugate in which the fluorophore itself interacts closely with the channel, the emission shift midpoint is 50 mV more negative than the Kv2.1 gating current midpoint. This suggests that substantial conformational changes at the toxin-channel interface are associated with early gating charge transitions and these are not concerted with VSD motions at more depolarized potentials. These fluorescent probes enable study of conformational changes that can be correlated with electrophysiology, putting channel structures and models into a context of live-cell membranes and physiological states.
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43
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Hsieh JY, Ulrich BN, Issa FA, Lin MCA, Brown B, Papazian DM. Infant and adult SCA13 mutations differentially affect Purkinje cell excitability, maturation, and viability in vivo. eLife 2020; 9:57358. [PMID: 32644043 PMCID: PMC7386905 DOI: 10.7554/elife.57358] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 07/08/2020] [Indexed: 12/23/2022] Open
Abstract
Mutations in KCNC3, which encodes the Kv3.3 K+ channel, cause spinocerebellar ataxia 13 (SCA13). SCA13 exists in distinct forms with onset in infancy or adulthood. Using zebrafish, we tested the hypothesis that infant- and adult-onset mutations differentially affect the excitability and viability of Purkinje cells in vivo during cerebellar development. An infant-onset mutation dramatically and transiently increased Purkinje cell excitability, stunted process extension, impaired dendritic branching and synaptogenesis, and caused rapid cell death during cerebellar development. Reducing excitability increased early Purkinje cell survival. In contrast, an adult-onset mutation did not significantly alter basal tonic firing in Purkinje cells, but reduced excitability during evoked high frequency spiking. Purkinje cells expressing the adult-onset mutation matured normally and did not degenerate during cerebellar development. Our results suggest that differential changes in the excitability of cerebellar neurons contribute to the distinct ages of onset and timing of cerebellar degeneration in infant- and adult-onset SCA13.
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Affiliation(s)
- Jui-Yi Hsieh
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States.,Interdepartmental PhD Program in Molecular, Cellular, and Integrative Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Brittany N Ulrich
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States.,Interdepartmental PhD Program in Molecular, Cellular, and Integrative Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Fadi A Issa
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Meng-Chin A Lin
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Brandon Brown
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Diane M Papazian
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States.,Interdepartmental PhD Program in Molecular, Cellular, and Integrative Physiology, David Geffen School of Medicine at UCLA, Los Angeles, United States.,Brain Research Institute, UCLA, Los Angeles, United States.,Molecular Biology Institute, UCLA, Los Angeles, United States
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44
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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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45
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Groome JR, Bayless-Edwards L. Roles for Countercharge in the Voltage Sensor Domain of Ion Channels. Front Pharmacol 2020; 11:160. [PMID: 32180723 PMCID: PMC7059764 DOI: 10.3389/fphar.2020.00160] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 02/07/2020] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated ion channels share a common structure typified by peripheral, voltage sensor domains. Their S4 segments respond to alteration in membrane potential with translocation coupled to ion permeation through a central pore domain. The mechanisms of gating in these channels have been intensely studied using pioneering methods such as measurement of charge displacement across a membrane, sequencing of genes coding for voltage-gated ion channels, and the development of all-atom molecular dynamics simulations using structural information from prokaryotic and eukaryotic channel proteins. One aspect of this work has been the description of the role of conserved negative countercharges in S1, S2, and S3 transmembrane segments to promote sequential salt-bridge formation with positively charged residues in S4 segments. These interactions facilitate S4 translocation through the lipid bilayer. In this review, we describe functional and computational work investigating the role of these countercharges in S4 translocation, voltage sensor domain hydration, and in diseases resulting from countercharge mutations.
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Affiliation(s)
- James R. Groome
- Department of Biological Sciences, Idaho State University, Pocatello, ID, United States
| | - Landon Bayless-Edwards
- Department of Biological Sciences, Idaho State University, Pocatello, ID, United States
- Oregon Health and Sciences University School of Medicine, Portland, OR, United States
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46
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Shi YP, Thouta S, Claydon TW. Modulation of hERG K + Channel Deactivation by Voltage Sensor Relaxation. Front Pharmacol 2020; 11:139. [PMID: 32184724 PMCID: PMC7059196 DOI: 10.3389/fphar.2020.00139] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 01/31/2020] [Indexed: 12/17/2022] Open
Abstract
The hERG (human-ether-à-go-go-related gene) channel underlies the rapid delayed rectifier current, Ikr, in the heart, which is essential for normal cardiac electrical activity and rhythm. Slow deactivation is one of the hallmark features of the unusual gating characteristics of hERG channels, and plays a crucial role in providing a robust current that aids repolarization of the cardiac action potential. As such, there is significant interest in elucidating the underlying mechanistic determinants of slow hERG channel deactivation. Recent work has shown that the hERG channel S4 voltage sensor is stabilized following activation in a process termed relaxation. Voltage sensor relaxation results in energetic separation of the activation and deactivation pathways, producing a hysteresis, which modulates the kinetics of deactivation gating. Despite widespread observation of relaxation behaviour in other voltage-gated K+ channels, such as Shaker, Kv1.2 and Kv3.1, as well as the voltage-sensing phosphatase Ci-VSP, the relationship between stabilization of the activated voltage sensor by the open pore and voltage sensor relaxation in the control of deactivation has only recently begun to be explored. In this review, we discuss present knowledge and questions raised related to the voltage sensor relaxation mechanism in hERG channels and compare structure-function aspects of relaxation with those observed in related ion channels. We focus discussion, in particular, on the mechanism of coupling between voltage sensor relaxation and deactivation gating to highlight the insight that these studies provide into the control of hERG channel deactivation gating during their physiological functioning.
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Affiliation(s)
- Yu Patrick Shi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Samrat Thouta
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Thomas W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
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47
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Resting state structure of the hyperdepolarization activated two-pore channel 3. Proc Natl Acad Sci U S A 2020; 117:1988-1993. [PMID: 31924746 DOI: 10.1073/pnas.1915144117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Voltage-gated ion channels endow membranes with excitability and the means to propagate action potentials that form the basis of all neuronal signaling. We determined the structure of a voltage-gated sodium channel, two-pore channel 3 (TPC3), which generates ultralong action potentials. TPC3 is distinguished by activation only at extreme membrane depolarization (V50 ∼ +75 mV), in contrast to other TPCs and NaV channels that activate between -20 and 0 mV. We present electrophysiological evidence that TPC3 voltage activation depends only on voltage sensing domain 2 (VSD2) and that each of the three gating arginines in VSD2 reduces the activation threshold. The structure presents a chemical basis for sodium selectivity, and a constricted gate suggests a closed pore consistent with extreme voltage dependence. The structure, confirmed by our electrophysiology, illustrates the configuration of a bona fide resting state voltage sensor, observed without the need for any inhibitory ligand, and independent of any chemical or mutagenic alteration.
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48
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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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49
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Kasimova MA, Tewari D, Cowgill JB, Ursuleaz WC, Lin JL, Delemotte L, Chanda B. Helix breaking transition in the S4 of HCN channel is critical for hyperpolarization-dependent gating. eLife 2019; 8:e53400. [PMID: 31774399 PMCID: PMC6904216 DOI: 10.7554/elife.53400] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 11/19/2019] [Indexed: 12/19/2022] Open
Abstract
In contrast to most voltage-gated ion channels, hyperpolarization- and cAMP gated (HCN) ion channels open on hyperpolarization. Structure-function studies show that the voltage-sensor of HCN channels are unique but the mechanisms that determine gating polarity remain poorly understood. All-atom molecular dynamics simulations (~20 μs) of HCN1 channel under hyperpolarization reveals an initial downward movement of the S4 voltage-sensor but following the transfer of last gating charge, the S4 breaks into two sub-helices with the lower sub-helix becoming parallel to the membrane. Functional studies on bipolar channels show that the gating polarity strongly correlates with helical turn propensity of the substituents at the breakpoint. Remarkably, in a proto-HCN background, the replacement of breakpoint serine with a bulky hydrophobic amino acid is sufficient to completely flip the gating polarity from inward to outward-rectifying. Our studies reveal an unexpected mechanism of inward rectification involving a linker sub-helix emerging from HCN S4 during hyperpolarization.
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Affiliation(s)
- Marina A Kasimova
- Science for Life Laboratory, Department of Applied PhysicsKTH Royal Institute of TechnologyStockholmSweden
| | - Debanjan Tewari
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
| | - John B Cowgill
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Graduate program in BiophysicsUniversity of WisconsinMadisonUnited States
| | | | - Jenna L Lin
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Graduate program in BiophysicsUniversity of WisconsinMadisonUnited States
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied PhysicsKTH Royal Institute of TechnologyStockholmSweden
| | - Baron Chanda
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Department of Biomolecular ChemistryUniversity of Wisconsin-MadisonMadisonUnited States
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Myotonia in a patient with a mutation in an S4 arginine residue associated with hypokalaemic periodic paralysis and a concomitant synonymous CLCN1 mutation. Sci Rep 2019; 9:17560. [PMID: 31772215 PMCID: PMC6879752 DOI: 10.1038/s41598-019-54041-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
The sarcolemmal voltage gated sodium channel NaV1.4 conducts the key depolarizing current that drives the upstroke of the skeletal muscle action potential. It contains four voltage-sensing domains (VSDs) that regulate the opening of the pore domain and ensuing permeation of sodium ions. Mutations that lead to increased NaV1.4 currents are found in patients with myotonia or hyperkalaemic periodic paralysis (HyperPP). Myotonia is also caused by mutations in the CLCN1gene that result in loss-of-function of the skeletal muscle chloride channel ClC-1. Mutations affecting arginine residues in the fourth transmembrane helix (S4) of the NaV1.4 VSDs can result in a leak current through the VSD and hypokalemic periodic paralysis (HypoPP), but these have hitherto not been associated with myotonia. We report a patient with an Nav1.4 S4 arginine mutation, R222Q, presenting with severe myotonia without fulminant paralytic episodes. Other mutations affecting the same residue, R222W and R222G, have been found in patients with HypoPP. We show that R222Q channels have enhanced activation, consistent with myotonia, but also conduct a leak current. The patient carries a concomitant synonymous CLCN1 variant that likely worsens the myotonia and potentially contributes to the amelioration of muscle paralysis. Our data show phenotypic variability for different mutations affecting the same S4 arginine that have implications for clinical therapy.
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