1
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Okochi Y, Jinno Y, Okamura Y. Dimerization is required for the glycosylation of S1-S2 linker of sea urchin voltage-gated proton channel Hv1. Biophys J 2024:S0006-3495(24)00493-4. [PMID: 39086135 DOI: 10.1016/j.bpj.2024.07.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/08/2024] [Accepted: 07/25/2024] [Indexed: 08/02/2024] Open
Abstract
Multimerization of ion channels is essential for establishing the ion-selective pathway and tuning the gating regulated by membrane potential, second messengers, and temperature. Voltage-gated proton channel, Hv1, consists of voltage-sensor domain and coiled-coil domain. Hv1 forms dimer, whereas voltage-dependent channel activity is self-contained in monomer unlike many ion channels, which assemble to form ion-conductive pathways among multiple subunits. Dimerization of Hv1 is necessary for cooperative gating, but other roles of dimerization in physiological aspects are still largely unclear. In this study, we show that dimerization of Hv1 takes place in ER. Sea urchin Hv1 (Strongylocentrotus purpuratus Hv1: SpHv1) was glycosylated in the consensus sequence for N-linked glycosylation within the S1-S2 extracellular loop. However, glycosylation was not observed in the monomeric SpHv1 that lacks the coiled-coil domain. A version of mHv1 in which the S1-S2 loop was replaced by that of SpHv1 showed glycosylation and its monomeric form was not glycosylated. Tandem dimer of monomeric SpHv1 underwent glycosylation, suggesting that dimerization of Hv1 is required for glycosylation. Moreover, when monomeric Hv1 has a dilysine motif in the C-terminal end, which is known to act as a retrieval signal from Golgi to ER, prolonging the time of residency in ER, it was glycosylated. Overall, our results suggest that monomeric SpHv1 does not stay long in ER, thereby escaping glycosylation, while the dimerization causes the proteins to stay longer in ER. Thus, the findings highlight the novel significance of dimerization of Hv1: regulation of biogenesis and maturation of the proteins in intracellular compartments.
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Affiliation(s)
- Yoshifumi Okochi
- Integrative Physiology, Graduate School of Medicine, Osaka University, Suita, Japan.
| | - Yuka Jinno
- Integrative Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yasushi Okamura
- Integrative Physiology, Graduate School of Medicine, Osaka University, Suita, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.
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2
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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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3
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Papp F, Toombes GES, Pethő Z, Bagosi A, Feher A, Almássy J, Borrego J, Kuki Á, Kéki S, Panyi G, Varga Z. Multiple mechanisms contribute to fluorometry signals from the voltage-gated proton channel. Commun Biol 2022; 5:1131. [PMID: 36289443 PMCID: PMC9606259 DOI: 10.1038/s42003-022-04065-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 09/30/2022] [Indexed: 11/30/2022] Open
Abstract
Voltage-clamp fluorometry (VCF) supplies information about the conformational changes of voltage-gated proteins. Changes in the fluorescence intensity of the dye attached to a part of the protein that undergoes a conformational rearrangement upon the alteration of the membrane potential by electrodes constitute the signal. The VCF signal is generated by quenching and dequenching of the fluorescence as the dye traverses various local environments. Here we studied the VCF signal generation, using the Hv1 voltage-gated proton channel as a tool, which shares a similar voltage-sensor structure with voltage-gated ion channels but lacks an ion-conducting pore. Using mutagenesis and lipids added to the extracellular solution we found that the signal is generated by the combined effects of lipids during movement of the dye relative to the plane of the membrane and by quenching amino acids. Our 3-state model recapitulates the VCF signals of the various mutants and is compatible with the accepted model of two major voltage-sensor movements. Fluorometry signals indicating conformational change in an ion channel are generated by quenching amino acids and lipid effects during movement of the dye relative to the plane of the membrane.
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Affiliation(s)
- Ferenc Papp
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Gilman E. S. Toombes
- grid.94365.3d0000 0001 2297 5165Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Dr., MSC 3701, Bethesda, MD 20892-3701 USA
| | - Zoltán Pethő
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary ,grid.5949.10000 0001 2172 9288Institut für Physiologie II, Robert-Koch-Str. 27b, 48149 Münster, Germany
| | - Adrienn Bagosi
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Adam Feher
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - János Almássy
- grid.7122.60000 0001 1088 8582Department of Physiology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Jesús Borrego
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Ákos Kuki
- grid.7122.60000 0001 1088 8582Department of Applied Chemistry, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Sándor Kéki
- grid.7122.60000 0001 1088 8582Department of Applied Chemistry, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Gyorgy Panyi
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
| | - Zoltan Varga
- grid.7122.60000 0001 1088 8582Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, Debrecen, H-4032 Hungary
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4
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Han S, Peng S, Vance J, Tran K, Do N, Bui N, Gui Z, Wang S. Structural dynamics determine voltage and pH gating in human voltage-gated proton channel. eLife 2022; 11:73093. [PMID: 35244539 PMCID: PMC8926398 DOI: 10.7554/elife.73093] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 02/24/2022] [Indexed: 11/25/2022] Open
Abstract
Voltage-gated proton (Hv) channels are standalone voltage sensors without separate ion conductive pores. They are gated by both voltage and transmembrane proton gradient (i.e., ∆pH), serving as acid extruders in most cells. Like the canonical voltage sensors, Hv channels are a bundle of four helices (named S1 –S4), with the S4 segment carrying three positively charged Arg residues. Extensive structural and electrophysiological studies on voltage-gated ion channels, in general, agree on an outwards movement of the S4 segment upon activating voltage, but the real-time conformational transitions are still unattainable. With purified human voltage-gated proton (hHv1) channels reconstituted in liposomes, we have examined its conformational dynamics, including the S4 segment at different voltage and pHs using single-molecule fluorescence resonance energy transfer (smFRET). Here, we provide the first glimpse of real-time conformational trajectories of the hHv1 voltage sensor and show that both voltage and pH gradient shift the conformational dynamics of the S4 segment to control channel gating. Our results indicate that the S4 segment transits among three major conformational states and only the transitions between the inward and outward conformations are highly dependent on voltage and pH. Altogether, we propose a kinetic model that explains the mechanisms underlying voltage and pH gating in Hv channels, which may also serve as a general framework for understanding the voltage sensing and gating in other voltage-gated ion channels.
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Affiliation(s)
- Shuo Han
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Sophia Peng
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Joshua Vance
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Kimberly Tran
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Nhu Do
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Nauy Bui
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Zhenhua Gui
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
| | - Shizhen Wang
- Department of Cell Biology and Biophysics, University of Missouri-Kansas City, Kansas City, United States
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5
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Guidelli R. The common features of tetrameric ion channels and the role of electrostatic interactions. Electrochem commun 2020. [DOI: 10.1016/j.elecom.2020.106866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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6
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Guidelli R, Becucci L, Aloisi G. Role of the time dependence of Boltzmann open probability in voltage-gated proton channels. Bioelectrochemistry 2020; 134:107520. [PMID: 32279034 DOI: 10.1016/j.bioelechem.2020.107520] [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: 12/12/2019] [Revised: 03/24/2020] [Accepted: 03/25/2020] [Indexed: 11/28/2022]
Abstract
The modeling and simulation of experimental families of current-time (I-t) curves of dimeric voltage-gated proton channels and of proton-conducting voltage sensing domains (VSDs) with a minimum of free parameters requires the movement of protons to be controlled by the rate of increase of the Boltzmann open probability p over time in passing from the holding to the depolarizing potential. Families of I-t curves of protomers and proton-conducting VSDs can be satisfactorily fitted by the use of a single free parameter expressing the rate constant kp for the increase of p over time. Families of I-t curves of dimeric Hv1 channels can be fitted by a model that assumes an initial proton current I1 flowing along the two monomeric units, while they are still operating separately; I1 is gradually replaced by a slower and more potential-dependent current I2 flowing when the two monomers start operating jointly under the control of the coiled-coil domain. Here too, p is assumed to increase over time with a rate constant kp that doubles in passing from I1 to I2, with fit requiring three free parameters. Chord conductance yields erroneously high gating charges when fitted by the Boltzmann function, differently from slope conductance.
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Affiliation(s)
- Rolando Guidelli
- Department of Chemistry "Ugo Schiff", Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy.
| | - Lucia Becucci
- Department of Chemistry "Ugo Schiff", Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy
| | - Giovanni Aloisi
- Department of Chemistry "Ugo Schiff", Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy
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7
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Jardin C, Chaves G, Musset B. Assessing Structural Determinants of Zn 2+ Binding to Human H V1 via Multiple MD Simulations. Biophys J 2020; 118:1221-1233. [PMID: 31972155 DOI: 10.1016/j.bpj.2019.12.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 12/20/2019] [Accepted: 12/27/2019] [Indexed: 01/02/2023] Open
Abstract
Voltage-gated proton channels (HV1) are essential for various physiological tasks but are strongly inhibited by Zn2+ cations. Some determinants of Zn2+ binding have been elucidated experimentally and in computational studies. However, the results have always been interpreted under the assumption that Zn2+ binds to monomeric HV1 despite evidence that HV1 expresses as a dimer and that the dimer has a higher affinity for zinc than the monomer and experimental data that suggest coordination in the dimer interface. The results of former studies are also controversial, e.g., supporting either one single or two binding sites. Some structural determinants of the binding are still elusive. We performed a series of molecular dynamics simulations to address different structures of the human proton channel, the monomer and two plausible dimer conformations, to compare their respective potential to interact with and bind Zn2+ via the essential histidines. The series consisted of several copies of the system to generate independent trajectories and increase the significance compared to a single simulation. The amount of time simulated totals 29.9 μs for 126 simulations of systems comprising ∼59,000 to ∼187,000 atoms. Our approach confirms the existence of two binding sites in monomeric and dimeric human HV1. The dimer interface is more efficient for attracting and binding Zn2+ via the essential histidines than the monomer or a dimer with the histidines in the periphery. The higher affinity is due to the residues in the dimer interface that create an attractive electrostatic potential funneling the zinc cations toward the binding sites.
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Affiliation(s)
- Christophe Jardin
- Institute of Physiology and Pathophysiology, Klinikum Nuremberg Medical School, Paracelsus Medical University, Nuremberg, Germany
| | - Gustavo Chaves
- Institute of Physiology and Pathophysiology, Klinikum Nuremberg Medical School, Paracelsus Medical University, Nuremberg, Germany
| | - Boris Musset
- Institute of Physiology and Pathophysiology, Klinikum Nuremberg Medical School, Paracelsus Medical University, Nuremberg, Germany.
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8
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DeCoursey TE. Voltage and pH sensing by the voltage-gated proton channel, H V1. J R Soc Interface 2018; 15:20180108. [PMID: 29643227 PMCID: PMC5938591 DOI: 10.1098/rsif.2018.0108] [Citation(s) in RCA: 47] [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: 02/12/2018] [Accepted: 03/19/2018] [Indexed: 12/15/2022] Open
Abstract
Voltage-gated proton channels are unique ion channels, membrane proteins that allow protons but no other ions to cross cell membranes. They are found in diverse species, from unicellular marine life to humans. In all cells, their function requires that they open and conduct current only under certain conditions, typically when the electrochemical gradient for protons is outwards. Consequently, these proteins behave like rectifiers, conducting protons out of cells. Their activity has electrical consequences and also changes the pH on both sides of the membrane. Here we summarize what is known about the way these proteins sense the membrane potential and the pH inside and outside the cell. Currently, it is hypothesized that membrane potential is sensed by permanently charged arginines (with very high pKa) within the protein, which results in parts of the protein moving to produce a conduction pathway. The mechanism of pH sensing appears to involve titratable side chains of particular amino acids. For this purpose their pKa needs to be within the operational pH range. We propose a 'counter-charge' model for pH sensing in which electrostatic interactions within the protein are selectively disrupted by protonation of internally or externally accessible groups.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, 1750 West Harrison, Chicago, IL 60612, USA
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9
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DeCoursey TE, Morgan D, Musset B, Cherny VV. Insights into the structure and function of HV1 from a meta-analysis of mutation studies. J Gen Physiol 2017; 148:97-118. [PMID: 27481712 PMCID: PMC4969798 DOI: 10.1085/jgp.201611619] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 06/30/2016] [Indexed: 01/26/2023] Open
Abstract
The voltage-gated proton channel (HV1) is a widely distributed, proton-specific ion channel with unique properties. Since 2006, when genes for HV1 were identified, a vast array of mutations have been generated and characterized. Accessing this potentially useful resource is hindered, however, by the sheer number of mutations and interspecies differences in amino acid numbering. This review organizes all existing information in a logical manner to allow swift identification of studies that have characterized any particular mutation. Although much can be gained from this meta-analysis, important questions about the inner workings of HV1 await future revelation.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Deri Morgan
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
| | - Boris Musset
- Institut für Physiologie, PMU Klinikum Nürnberg, 90419 Nürnberg, Germany
| | - Vladimir V Cherny
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612
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10
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DeCoursey TE. The intimate and controversial relationship between voltage-gated proton channels and the phagocyte NADPH oxidase. Immunol Rev 2017; 273:194-218. [PMID: 27558336 DOI: 10.1111/imr.12437] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
One of the most fascinating and exciting periods in my scientific career entailed dissecting the symbiotic relationship between two membrane transporters, the Nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase complex and voltage-gated proton channels (HV 1). By the time I entered this field, there had already been substantial progress toward understanding NADPH oxidase, but HV 1 were known only to a tiny handful of cognoscenti around the world. Having identified the first proton currents in mammalian cells in 1991, I needed to find a clear function for these molecules if the work was to become fundable. The then-recent discoveries of Henderson, Chappell, and colleagues in 1987-1988 that led them to hypothesize interactions of both molecules during the respiratory burst of phagocytes provided an excellent opportunity. In a nutshell, both transporters function by moving electrical charge across the membrane: NADPH oxidase moves electrons and HV 1 moves protons. The consequences of electrogenic NADPH oxidase activity on both membrane potential and pH strongly self-limit this enzyme. Fortunately, both consequences specifically activate HV 1, and HV 1 activity counteracts both consequences, a kind of yin-yang relationship. Notwithstanding a decade starting in 1995 when many believed the opposite, these are two separate molecules that function independently despite their being functionally interdependent in phagocytes. The relationship between NADPH oxidase and HV 1 has become a paradigm that somewhat surprisingly has now extended well beyond the phagocyte NADPH oxidase - an industrial strength producer of reactive oxygen species (ROS) - to myriad other cells that produce orders of magnitude less ROS for signaling purposes. These cells with their seven NADPH oxidase (NOX) isoforms provide a vast realm of mechanistic obscurity that will occupy future studies for years to come.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL, USA
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11
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Rodriguez JD, Haq S, Bachvaroff T, Nowak KF, Nowak SJ, Morgan D, Cherny VV, Sapp MM, Bernstein S, Bolt A, DeCoursey TE, Place AR, Smith SME. Identification of a vacuolar proton channel that triggers the bioluminescent flash in dinoflagellates. PLoS One 2017; 12:e0171594. [PMID: 28178296 PMCID: PMC5298346 DOI: 10.1371/journal.pone.0171594] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 01/23/2017] [Indexed: 11/19/2022] Open
Abstract
In 1972, J. Woodland Hastings and colleagues predicted the existence of a proton selective channel (HV1) that opens in response to depolarizing voltage across the vacuole membrane of bioluminescent dinoflagellates and conducts protons into specialized luminescence compartments (scintillons), thereby causing a pH drop that triggers light emission. HV1 channels were subsequently identified and demonstrated to have important functions in a multitude of eukaryotic cells. Here we report a predicted protein from Lingulodinium polyedrum that displays hallmark properties of bona fide HV1, including time-dependent opening with depolarization, perfect proton selectivity, and characteristic ΔpH dependent gating. Western blotting and fluorescence confocal microscopy of isolated L. polyedrum scintillons immunostained with antibody to LpHV1 confirm LpHV1's predicted organellar location. Proteomics analysis demonstrates that isolated scintillon preparations contain peptides that map to LpHV1. Finally, Zn2+ inhibits both LpHV1 proton current and the acid-induced flash in isolated scintillons. These results implicate LpHV1 as the voltage gated proton channel that triggers bioluminescence in L. polyedrum, confirming Hastings' hypothesis. The same channel likely mediates the action potential that communicates the signal along the tonoplast to the scintillon.
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Affiliation(s)
- Juan D. Rodriguez
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Saddef Haq
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
| | - Tsvetan Bachvaroff
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
| | - Kristine F. Nowak
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Scott J. Nowak
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Deri Morgan
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois, United States of America
| | - Vladimir V. Cherny
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois, United States of America
| | - Maredith M. Sapp
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Steven Bernstein
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Andrew Bolt
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
| | - Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois, United States of America
| | - Allen R. Place
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
| | - Susan M. E. Smith
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, Georgia, United States of America
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12
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Abstract
The main properties of the voltage-gated proton channel (HV1) are described in this review, along with what is known about how the channel protein structure accomplishes its functions. Just as protons are unique among ions, proton channels are unique among ion channels. Their four transmembrane helices sense voltage and the pH gradient and conduct protons exclusively. Selectivity is achieved by the unique ability of H3O(+) to protonate an Asp-Arg salt bridge. Pathognomonic sensitivity of gating to the pH gradient ensures HV1 channel opening only when acid extrusion will result, which is crucial to most of its biological functions. An exception occurs in dinoflagellates in which influx of H(+) through HV1 triggers the bioluminescent flash. Pharmacological interventions that promise to ameliorate cancer, asthma, brain damage in ischemic stroke, Alzheimer's disease, autoimmune diseases, and numerous other conditions await future progress.
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Affiliation(s)
- Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, 1750 West Harrison, Chicago IL, 60612 USA
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13
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DeCoursey TE, Hosler J. Philosophy of voltage-gated proton channels. J R Soc Interface 2014; 11:20130799. [PMID: 24352668 PMCID: PMC3899857 DOI: 10.1098/rsif.2013.0799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/22/2013] [Indexed: 02/02/2023] Open
Abstract
In this review, voltage-gated proton channels are considered from a mainly teleological perspective. Why do proton channels exist? What good are they? Why did they go to such lengths to develop several unique hallmark properties such as extreme selectivity and ΔpH-dependent gating? Why is their current so minuscule? How do they manage to be so selective? What is the basis for our belief that they conduct H(+) and not OH(-)? Why do they exist in many species as dimers when the monomeric form seems to work quite well? It is hoped that pondering these questions will provide an introduction to these channels and a way to logically organize their peculiar properties as well as to understand how they are able to carry out some of their better-established biological functions.
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Affiliation(s)
- Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, 1750 West Harrison, Chicago, IL 60612, USA
| | - Jonathan Hosler
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216, USA
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