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DeCoursey TE. Transcendent Aspects of Proton Channels. Annu Rev Physiol 2024; 86:357-377. [PMID: 37931166 PMCID: PMC10938948 DOI: 10.1146/annurev-physiol-042222-023242] [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] [Indexed: 11/08/2023]
Abstract
A handful of biological proton-selective ion channels exist. Some open at positive or negative membrane potentials, others open at low or high pH, and some are light activated. This review focuses on common features that result from the unique properties of protons. Proton conduction through water or proteins differs qualitatively from that of all other ions. Extraordinary proton selectivity is needed to ensure that protons permeate and other ions do not. Proton selectivity arises from a proton pathway comprising a hydrogen-bonded chain that typically includes at least one titratable amino acid side chain. The enormously diverse functions of proton channels in disparate regions of the phylogenetic tree can be summarized by considering the chemical and electrical consequences of proton flux across membranes. This review discusses examples of cells in which proton efflux serves to increase pHi, decrease pHo, control the membrane potential, generate action potentials, or compensate transmembrane movement of electrical charge.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, Chicago, Illinois, USA;
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2
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Kariev AM, Green ME. Water, Protons, and the Gating of Voltage-Gated Potassium Channels. MEMBRANES 2024; 14:37. [PMID: 38392664 PMCID: PMC10890431 DOI: 10.3390/membranes14020037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 01/17/2024] [Accepted: 01/23/2024] [Indexed: 02/24/2024]
Abstract
Ion channels are ubiquitous throughout all forms of life. Potassium channels are even found in viruses. Every cell must communicate with its surroundings, so all cells have them, and excitable cells, in particular, especially nerve cells, depend on the behavior of these channels. Every channel must be open at the appropriate time, and only then, so that each channel opens in response to the stimulus that tells that channel to open. One set of channels, including those in nerve cells, responds to voltage. There is a standard model for the gating of these channels that has a section of the protein moving in response to the voltage. However, there is evidence that protons are moving, rather than protein. Water is critical as part of the gating process, although it is hard to see how this works in the standard model. Here, we review the extensive evidence of the importance of the role of water and protons in gating these channels. Our principal example, but by no means the only example, will be the Kv1.2 channel. Evidence comes from the effects of D2O, from mutations in the voltage sensing domain, as well as in the linker between that domain and the gate, and at the gate itself. There is additional evidence from computations, especially quantum calculations. Structural evidence comes from X-ray studies. The hydration of ions is critical in the transfer of ions in constricted spaces, such as the gate region and the pore of a channel; we will see how the structure of the hydrated ion fits with the structure of the channel. In addition, there is macroscopic evidence from osmotic experiments and streaming current measurements. The combined evidence is discussed in the context of a model that emphasizes the role of protons and water in gating these channels.
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Affiliation(s)
- Alisher M Kariev
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY 10031, USA
| | - Michael E Green
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY 10031, USA
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3
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Peña-Pichicoi A, Fernández M, Navarro-Quezada N, Alvear-Arias JJ, Carrillo CA, Carmona EM, Garate J, Lopez-Rodriguez AM, Neely A, Hernández-Ochoa EO, González C. N-terminal region is responsible for mHv1 channel activity in MDSCs. Front Pharmacol 2023; 14:1265130. [PMID: 37915407 PMCID: PMC10616795 DOI: 10.3389/fphar.2023.1265130] [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: 07/22/2023] [Accepted: 09/25/2023] [Indexed: 11/03/2023] Open
Abstract
Voltage-gated proton channels (Hv1) are important regulators of the immunosuppressive function of myeloid-derived suppressor cells (MDSCs) in mice and have been proposed as a potential therapeutic target to alleviate dysregulated immunosuppression in tumors. However, till date, there is a lack of evidence regarding the functioning of the Hvcn1 and reports on mHv1 isoform diversity in mice and MDSCs. A computational prediction has suggested that the Hvcn1 gene may express up to six transcript variants, three of which are translated into distinct N-terminal isoforms of mHv1: mHv1.1 (269 aa), mHv1.2 (269 + 42 aa), and mHv1.3 (269 + 4 aa). To validate this prediction, we used RT-PCR on total RNA extracted from MDSCs, and the presence of all six predicted mRNA variances was confirmed. Subsequently, the open-reading frames (ORFs) encoding for mHv1 isoforms were cloned and expressed in Xenopus laevis oocytes for proton current recording using a macro-patch voltage clamp. Our findings reveal that all three isoforms are mammalian mHv1 channels, with distinct differences in their activation properties. Specifically, the longest isoform, mHv1.2, displays a right-shifted conductance-voltage (GV) curve and slower opening kinetics, compared to the mid-length isoform, mHv1.3, and the shortest canonical isoform, mHv1.1. While mHv1.3 exhibits a V0.5 similar to that of mHv1.1, mHv1.3 demonstrates significantly slower activation kinetics than mHv1.1. These results suggest that isoform gating efficiency is inversely related to the length of the N-terminal end. To further explore this, we created the truncated mHv1.2 ΔN20 construct by removing the first 20 amino acids from the N-terminus of mHv1.2. This construct displayed intermediate activation properties, with a V0.5 value lying intermediate of mHv1.1 and mHv1.2, and activation kinetics that were faster than that of mHv1.2 but slower than that of mHv1.1. Overall, these findings indicate that alternative splicing of the N-terminal exon in mRNA transcripts encoding mHv1 isoforms is a regulatory mechanism for mHv1 function within MDSCs. While MDSCs have the capability to translate multiple Hv1 isoforms with varying gating properties, the Hvcn1 gene promotes the dominant expression of mHv1.1, which exhibits the most efficient gating among all mHv1 isoforms.
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Affiliation(s)
- Antonio Peña-Pichicoi
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Miguel Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Nieves Navarro-Quezada
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Juan J. Alvear-Arias
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Christian A. Carrillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Emerson M. Carmona
- Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Jose Garate
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
- Facultad de Ingeniería y Tecnología, Universidad San Sebastián, Santiago, Chile
| | | | - Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
| | - Erick O. Hernández-Ochoa
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso, Chile
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, United States
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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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Chaves G, Jardin C, Derst C, Musset B. Voltage-Gated Proton Channels in the Tree of Life. Biomolecules 2023; 13:1035. [PMID: 37509071 PMCID: PMC10377628 DOI: 10.3390/biom13071035] [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: 05/14/2023] [Revised: 06/14/2023] [Accepted: 06/21/2023] [Indexed: 07/30/2023] Open
Abstract
With a single gene encoding HV1 channel, proton channel diversity is particularly low in mammals compared to other members of the superfamily of voltage-gated ion channels. Nonetheless, mammalian HV1 channels are expressed in many different tissues and cell types where they exert various functions. In the first part of this review, we regard novel aspects of the functional expression of HV1 channels in mammals by differentially comparing their involvement in (1) close conjunction with the NADPH oxidase complex responsible for the respiratory burst of phagocytes, and (2) in respiratory burst independent functions such as pH homeostasis or acid extrusion. In the second part, we dissect expression of HV channels within the eukaryotic tree of life, revealing the immense diversity of the channel in other phylae, such as mollusks or dinoflagellates, where several genes encoding HV channels can be found within a single species. In the last part, a comprehensive overview of the biophysical properties of a set of twenty different HV channels characterized electrophysiologically, from Mammalia to unicellular protists, is given.
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Affiliation(s)
- Gustavo Chaves
- Center of Physiology, Pathophysiology and Biophysics, The Nuremberg Location, Paracelsus Medical University, 90419 Nuremberg, Germany
| | - Christophe Jardin
- Center of Physiology, Pathophysiology and Biophysics, The Nuremberg Location, Paracelsus Medical University, 90419 Nuremberg, Germany
| | - Christian Derst
- Center of Physiology, Pathophysiology and Biophysics, The Nuremberg Location, Paracelsus Medical University, 90419 Nuremberg, Germany
| | - Boris Musset
- Center of Physiology, Pathophysiology and Biophysics, The Nuremberg Location, Paracelsus Medical University, 90419 Nuremberg, Germany
- Center of Physiology, Pathophysiology and Biophysics, The Salzburg Location, Paracelsus Medical University, 5020 Salzburg, Austria
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6
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Han S, Applewhite S, DeCata J, Jones S, Cummings J, Wang S. Arachidonic acid reverses cholesterol and zinc inhibition of human voltage-gated proton channels. J Biol Chem 2023:104918. [PMID: 37315791 PMCID: PMC10344949 DOI: 10.1016/j.jbc.2023.104918] [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: 03/21/2023] [Revised: 05/08/2023] [Accepted: 06/09/2023] [Indexed: 06/16/2023] Open
Abstract
Unlike other members of the voltage-gated ion channel superfamily, voltage-gated proton (Hv) channels are solely composed of voltage sensor domains without separate ion-conducting pores. Due to their unique dependence on both voltage and transmembrane pH gradients, Hv channels normally open to mediate proton efflux. Multiple cellular ligands were also found to regulate the function of Hv channels, including Zn2+, cholesterol, polyunsaturated arachidonic acid, and albumin. Our previous work showed that Zn2+ and cholesterol inhibit the human voltage-gated proton channel hHv1 by stabilizing its S4 segment at resting state conformations. Released from phospholipids by phospholipase A2 in cells upon infection or injury, arachidonic acid regulates the function of many ion channels, including hHv1. In the present work, we examined the effects of arachidonic acid on purified hHv1 channels using liposome flux assays and revealed underlying structural mechanisms using single-molecule Fluorescence Resonance Energy Transfer (smFRET). Our data indicated that arachidonic acid strongly activates hHv1 channels by promoting transitions of the S4 segment towards opening or 'pre-opening' conformations. Moreover, we found that arachidonic acid even activates hHv1 channels inhibited by Zn2+ and cholesterol, providing a biophysical mechanism to activate hHv1 channels in non-excitable cells upon infection or injury.
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Affiliation(s)
- Shuo Han
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA
| | - Sarah Applewhite
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA
| | - Jenna DeCata
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA
| | - Samuel Jones
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA
| | - John Cummings
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA
| | - Shizhen Wang
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110 USA.
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Korpos É, Papp F. New 'kids' on the voltage-gated proton channel block. FEBS J 2023; 290:970-973. [PMID: 36315610 DOI: 10.1111/febs.16670] [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: 10/07/2022] [Accepted: 10/25/2022] [Indexed: 02/17/2023]
Abstract
So far one gene for Hv1 has been detected in studied species. The work presented by Chaves et al. in The FEBS Journal reported an 'Unexpected expansion of the voltage-gated proton channel family'. They searched for proton channel candidates and found three sequences in the genome of Aplysia californica (Ac), which were named AcHv1, AcHv2 and AcHv3. Based on electrophysiological experiments, AcHv1 and AcHv2 are voltage-gated channels. While AcHv1 behaves like Hv1 in other species, that is, it is voltage and pH-dependent, it can be inhibited by zinc and conducts protons outwardly, AcHv2 conducts protons inwards at symmetrical pH. AcHv3 constantly leaks protons, and its C-terminal part contains several cytoplasmic retention motifs. Through carefully designed and carried out electrophysiological experiments, Chaves et al. determined the biophysical parameters of all three proton channels, such as the voltage and the pH dependence, the threshold-voltage, the gating charge and the time constants of activation and inactivation. Comment on: https://doi.org/10.1111/febs.16617.
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Affiliation(s)
- Éva Korpos
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Hungary.,MTA-DE Cell Biology and Signalling Research Group, Faculty of Medicine, University of Debrecen, Hungary
| | - Ferenc Papp
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Hungary
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8
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Chaves G, Derst C, Jardin C, Franzen A, Musset B. Voltage-gated proton channels in polyneopteran insects. FEBS Open Bio 2022; 12:523-537. [PMID: 34986517 PMCID: PMC8804609 DOI: 10.1002/2211-5463.13361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/04/2021] [Accepted: 01/04/2022] [Indexed: 11/17/2022] Open
Abstract
Voltage‐gated proton channels (HV1) are expressed in eukaryotes, including basal hexapods and polyneopteran insects. However, currently, there is little known about HV1 channels in insects. A characteristic aspartate (Asp) that functions as the proton selectivity filter (SF) and the RxWRxxR voltage‐sensor motif are conserved structural elements in HV1 channels. By analysing Transcriptome Shotgun Assembly (TSA) databases, we found 33 polyneopteran species meeting these structural requirements. Unexpectedly, an unusual natural variation Asp to glutamate (Glu) at SF was found in Phasmatodea and Mantophasmatodea. Additionally, we analysed the expression and function of HV1 in the phasmatodean stick insect Extatosoma tiaratum (Et). EtHV1 is strongly expressed in nervous tissue and shows pronounced inward proton conduction. This is the first study of a natural occurring Glu within the SF of a functional HV1 and might be instrumental in uncovering the physiological function of HV1 in insects.
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Affiliation(s)
- Gustavo Chaves
- Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Nuremberg, Germany
| | - Christian Derst
- Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Nuremberg, Germany
| | - Christophe Jardin
- Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Nuremberg, Germany
| | - Arne Franzen
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, Forschungszentrum Jülich, Germany
| | - Boris Musset
- Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Nuremberg, Germany.,Center of Physiology, Pathophysiology and Biophysics, Paracelsus Medical University, Salzburg, Austria
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Sokolov VS, Cherny VV, Ayuyan AG, DeCoursey TE. Analysis of an electrostatic mechanism for ΔpH dependent gating of the voltage-gated proton channel, H V1, supports a contribution of protons to gating charge. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2021; 1862:148480. [PMID: 34363792 PMCID: PMC8432343 DOI: 10.1016/j.bbabio.2021.148480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/23/2021] [Accepted: 08/02/2021] [Indexed: 11/23/2022]
Abstract
Voltage-gated proton channels (HV1) resemble the voltage-sensing domain of other voltage-gated ion channels, but differ in containing the conduction pathway. Essential to the functions of HV1 channels in many cells and species is a unique feature called ΔpH dependent gating. The pH on both sides of the membrane strictly regulates the voltage range of channel opening, generally resulting in exclusively outward proton current. Two types of mechanisms could produce ΔpH dependent gating. The "countercharge" mechanism proposes that protons destabilize salt bridges between amino acids in the protein that stabilize specific gating configurations (closed or open). An "electrostatic" mechanism proposes that protons bound to the channel alter the electrical field sensed by the protein. Obligatory proton binding within the membrane electrical field would contribute to measured gating charge. Estimations on the basis of the electrostatic model explain ΔpH dependent gating, but quantitative modeling requires calculations of the electric field inside the protein which, in turn, requires knowledge of its structure. We conclude that both mechanisms operate and contribute to ΔpH dependent gating of HV1.
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Affiliation(s)
- Valerij S Sokolov
- Frumkin Institute of Physical Chemistry and Electrochemistry of Russian Academy of Sciences, Moscow 119071, Russia
| | - Vladimir V Cherny
- Department of Physiology & Biophysics, Rush University, Chicago, IL 60612, USA
| | - Artem G Ayuyan
- Department of Physiology & Biophysics, Rush University, Chicago, IL 60612, USA
| | - Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, Chicago, IL 60612, USA.
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Cherny VV, Musset B, Morgan D, Thomas S, Smith SME, DeCoursey TE. Engineered high-affinity zinc binding site reveals gating configurations of a human proton channel. J Gen Physiol 2021; 152:152076. [PMID: 32902579 PMCID: PMC7537347 DOI: 10.1085/jgp.202012664] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/10/2020] [Indexed: 11/23/2022] Open
Abstract
The voltage-gated proton channel (HV1) is a voltage sensor that also conducts protons. The singular ability of protons to penetrate proteins complicates distinguishing closed and open channels. When we replaced valine with histidine at position 116 in the external vestibule of hHV1, current was potently inhibited by externally applied Zn2+ in a construct lacking the two His that bind Zn2+ in WT channels. High-affinity binding with profound effects at 10 nM Zn2+ at pHo 7 suggests additional groups contribute. We hypothesized that Asp185, which faces position 116 in our closed-state model, contributes to Zn2+ chelation. Confirming this prediction, V116H/D185N abolished Zn2+ binding. Studied in a C-terminal truncated monomeric construct, V116H channels activated rapidly. Anomalously, Zn2+ slowed activation, producing a time constant independent of both voltage and Zn2+ concentration. We hypothesized that slow turn-on of H+ current in the presence of Zn2+ reflects the rate of Zn2+ unbinding from the channel, analogous to drug-receptor dissociation reactions. This behavior in turn suggests that the affinity for Zn2+ is greater in the closed state of hHV1. Supporting this hypothesis, pulse pairs revealed a rapid component of activation whose amplitude decreased after longer intervals at negative voltages as closed channels bound Zn2+. The lower affinity of Zn2+ in open channels is consistent with the idea that structural rearrangements within the transmembrane region bring Arg205 near position 116, electrostatically expelling Zn2+. This phenomenon provides direct evidence that Asp185 opposes position 116 in closed channels and that Arg205 moves between them when the channel opens.
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Affiliation(s)
| | - Boris Musset
- Institut für Physiologie und Pathophysiologie, Paracelsus Medizinische Privatuniversität, Nürnberg, Germany
| | - Deri Morgan
- Department of Physiology & Biophysics, Rush University, Chicago IL
| | - Sarah Thomas
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA
| | - Susan M E Smith
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA
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11
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Bondar AN. Proton-Binding Motifs of Membrane-Bound Proteins: From Bacteriorhodopsin to Spike Protein S. Front Chem 2021; 9:685761. [PMID: 34136464 PMCID: PMC8203321 DOI: 10.3389/fchem.2021.685761] [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: 03/26/2021] [Accepted: 05/18/2021] [Indexed: 11/13/2022] Open
Abstract
Membrane-bound proteins that change protonation during function use specific protein groups to bind and transfer protons. Knowledge of the identity of the proton-binding groups is of paramount importance to decipher the reaction mechanism of the protein, and protonation states of prominent are studied extensively using experimental and computational approaches. Analyses of model transporters and receptors from different organisms, and with widely different biological functions, indicate common structure-sequence motifs at internal proton-binding sites. Proton-binding dynamic hydrogen-bond networks that are exposed to the bulk might provide alternative proton-binding sites and proton-binding pathways. In this perspective article I discuss protonation coupling and proton binding at internal and external carboxylate sites of proteins that use proton transfer for function. An inter-helical carboxylate-hydroxyl hydrogen-bond motif is present at functionally important sites of membrane proteins from archaea to the brain. External carboxylate-containing H-bond clusters are observed at putative proton-binding sites of protonation-coupled model proteins, raising the question of similar functionality in spike protein S.
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Affiliation(s)
- Ana-Nicoleta Bondar
- Freie Universität Berlin, Department of Physics, Theoretical Molecular Biophysics Group, Berlin, Germany
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12
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Hofschröer V, Najder K, Rugi M, Bouazzi R, Cozzolino M, Arcangeli A, Panyi G, Schwab A. Ion Channels Orchestrate Pancreatic Ductal Adenocarcinoma Progression and Therapy. Front Pharmacol 2021; 11:586599. [PMID: 33841132 PMCID: PMC8025202 DOI: 10.3389/fphar.2020.586599] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 10/30/2020] [Indexed: 02/06/2023] Open
Abstract
Pancreatic ductal adenocarcinoma is a devastating disease with a dismal prognosis. Therapeutic interventions are largely ineffective. A better understanding of the pathophysiology is required. Ion channels contribute substantially to the "hallmarks of cancer." Their expression is dysregulated in cancer, and they are "misused" to drive cancer progression, but the underlying mechanisms are unclear. Ion channels are located in the cell membrane at the interface between the intracellular and extracellular space. They sense and modify the tumor microenvironment which in itself is a driver of PDAC aggressiveness. Ion channels detect, for example, locally altered proton and electrolyte concentrations or mechanical stimuli and transduce signals triggered by these microenvironmental cues through association with intracellular signaling cascades. While these concepts have been firmly established for other cancers, evidence has emerged only recently that ion channels are drivers of PDAC aggressiveness. Particularly, they appear to contribute to two of the characteristic PDAC features: the massive fibrosis of the tumor stroma (desmoplasia) and the efficient immune evasion. Our critical review of the literature clearly shows that there is still a remarkable lack of knowledge with respect to the contribution of ion channels to these two typical PDAC properties. Yet, we can draw parallels from ion channel research in other fibrotic and inflammatory diseases. Evidence is accumulating that pancreatic stellate cells express the same "profibrotic" ion channels. Similarly, it is at least in part known which major ion channels are expressed in those innate and adaptive immune cells that populate the PDAC microenvironment. We explore potential therapeutic avenues derived thereof. Since drugs targeting PDAC-relevant ion channels are already in clinical use, we propose to repurpose those in PDAC. The quest for ion channel targets is both motivated and complicated by the fact that some of the relevant channels, for example, KCa3.1, are functionally expressed in the cancer, stroma, and immune cells. Only in vivo studies will reveal which arm of the balance we should put our weights on when developing channel-targeting PDAC therapies. The time is up to explore the efficacy of ion channel targeting in (transgenic) murine PDAC models before launching clinical trials with repurposed drugs.
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Affiliation(s)
| | - Karolina Najder
- Institute of Physiology II, University of Münster, Münster, Germany
| | - Micol Rugi
- Institute of Physiology II, University of Münster, Münster, Germany
| | - Rayhana Bouazzi
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Florence, Italy
| | - Marco Cozzolino
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, Section of Internal Medicine, University of Florence, Florence, Italy
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Albrecht Schwab
- Institute of Physiology II, University of Münster, Münster, Germany
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13
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Taylor KC, Kang PW, Hou P, Yang ND, Kuenze G, Smith JA, Shi J, Huang H, White KM, Peng D, George AL, Meiler J, McFeeters RL, Cui J, Sanders CR. Structure and physiological function of the human KCNQ1 channel voltage sensor intermediate state. eLife 2020; 9:e53901. [PMID: 32096762 PMCID: PMC7069725 DOI: 10.7554/elife.53901] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 02/24/2020] [Indexed: 12/14/2022] Open
Abstract
Voltage-gated ion channels feature voltage sensor domains (VSDs) that exist in three distinct conformations during activation: resting, intermediate, and activated. Experimental determination of the structure of a potassium channel VSD in the intermediate state has previously proven elusive. Here, we report and validate the experimental three-dimensional structure of the human KCNQ1 voltage-gated potassium channel VSD in the intermediate state. We also used mutagenesis and electrophysiology in Xenopus laevisoocytes to functionally map the determinants of S4 helix motion during voltage-dependent transition from the intermediate to the activated state. Finally, the physiological relevance of the intermediate state KCNQ1 conductance is demonstrated using voltage-clamp fluorometry. This work illuminates the structure of the VSD intermediate state and demonstrates that intermediate state conductivity contributes to the unusual versatility of KCNQ1, which can function either as the slow delayed rectifier current (IKs) of the cardiac action potential or as a constitutively active epithelial leak current.
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Affiliation(s)
- Keenan C Taylor
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Po Wei Kang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Panpan Hou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Nien-Du Yang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
| | - Jarrod A Smith
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Hui Huang
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
| | - Kelli McFarland White
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Dungeng Peng
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical CenterNashvilleUnited States
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of MedicineChicagoUnited States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Departments of Chemistry and Pharmacology, Vanderbilt UniversityNashvilleUnited States
- Department of Bioinformatics, Vanderbilt University Medical CenterNashvilleUnited States
| | - Robert L McFeeters
- Department of Chemistry, University of Alabama in HuntsvilleHuntsvilleUnited States
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University in St. LouisSt. LouisUnited States
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt UniversityNashvilleUnited States
- Center for Structural Biology, Vanderbilt UniversityNashvilleUnited States
- Department of Medicine, Vanderbilt University Medical CenterNashvilleUnited States
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14
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Hydrophobic gasket mutation produces gating pore currents in closed human voltage-gated proton channels. Proc Natl Acad Sci U S A 2019; 116:18951-18961. [PMID: 31462498 PMCID: PMC6754559 DOI: 10.1073/pnas.1905462116] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A large family of membrane proteins, voltage-gated ion channels, regulate a vast array of physiological functions in essentially all life forms. How these molecules sense membrane potential and respond by creating ionic conduction is incompletely understood. The voltage sensors of these channels contain a “hydrophobic gasket,” a ring of hydrophobic amino acids near the center of the membrane, separating internal and external aqueous solutions. Although voltage-gated proton channels, HV1, resemble voltage-sensing domains of other channels, they differ fundamentally. On depolarization, HV1 conducts protons, whereas other voltage sensors open a physically distinct pore. We identify Val109, Phe150, Val177, and Val178 as the hHV1 hydrophobic gasket. Replacement with less hydrophobic amino acids accelerated channel opening and caused proton-selective leak through closed channels. The hydrophobic gasket (HG), a ring of hydrophobic amino acids in the voltage-sensing domain of most voltage-gated ion channels, forms a constriction between internal and external aqueous vestibules. Cationic Arg or Lys side chains lining the S4 helix move through this “gating pore” when the channel opens. S4 movement may occur during gating of the human voltage-gated proton channel, hHV1, but proton current flows through the same pore in open channels. Here, we replaced putative HG residues with less hydrophobic residues or acidic Asp. Substitution of individuals, pairs, or all 3 HG positions did not impair proton selectivity. Evidently, the HG does not act as a secondary selectivity filter. However, 2 unexpected functions of the HG in HV1 were discovered. Mutating HG residues independently accelerated channel opening and compromised the closed state. Mutants exhibited open–closed gating, but strikingly, at negative voltages where “normal” gating produces a nonconducting closed state, the channel leaked protons. Closed-channel proton current was smaller than open-channel current and was inhibited by 10 μM Zn2+. Extreme hyperpolarization produced a deeper closed state through a weakly voltage-dependent transition. We functionally identify the HG as Val109, Phe150, Val177, and Val178, which play a critical and exclusive role in preventing H+ influx through closed channels. Molecular dynamics simulations revealed enhanced mobility of Arg208 in mutants exhibiting H+ leak. Mutation of HG residues produces gating pore currents reminiscent of several channelopathies.
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15
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Boonamnaj P, Sompornpisut P. Effect of Ionization State on Voltage-Sensor Structure in Resting State of the Hv1 Channel. J Phys Chem B 2019; 123:2864-2873. [DOI: 10.1021/acs.jpcb.9b00634] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Panisak Boonamnaj
- Center of Excellence in Computational Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Pornthep Sompornpisut
- Center of Excellence in Computational Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
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16
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Branda MM, Guérin DMA. Alkalinization of Icosahedral Non-enveloped Viral Capsid Interior Through Proton Channeling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:181-199. [DOI: 10.1007/978-3-030-14741-9_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Gating currents indicate complex gating of voltage-gated proton channels. Proc Natl Acad Sci U S A 2018; 115:9057-9059. [PMID: 30135099 DOI: 10.1073/pnas.1813013115] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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18
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Mishra AK, Kumar A, Swain DK, Yadav S, Nigam R. Insights into pH regulatory mechanisms in mediating spermatozoa functions. Vet World 2018; 11:852-858. [PMID: 30034181 PMCID: PMC6048093 DOI: 10.14202/vetworld.2018.852-858] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/17/2018] [Indexed: 12/18/2022] Open
Abstract
Regulation of pH in spermatozoa is a complex and dynamic process as sperm cells encounter different pH gradients during their journey from testes to the site of fertilization in female genital tract. The precise regulations of pH in sperm cells regulate the sperm functions such as motility, hyperactivity, capacitation, and acrosome reaction. Electrophysiological, pharmacological, and molecular studies have revealed the presence of different ion channels and exchanger systems which regulate intracellular pH in sperm cells as well as regulate sperm functions. Recent studies also have shown the potential involvement of pH in the regulation of fertility competence of sperm cells, and alterations in pH have shown to impede sperm functions. This mini-review discusses the probable mechanisms involved in pH regulation in sperm cells and how pH is involved in regulation of various sperm functions.
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Affiliation(s)
- Abhishek Kumar Mishra
- College of Biotechnology, U.P. Pandit Deendayal Upadhayaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go Anusandhan Sansthan, Mathura - 281 001, Uttar Pradesh, India
| | - Akshay Kumar
- Department of Gynaecology and Obstetrics, College of Veterinary Sciences and Animal Husbandry, U.P. Pandit Deendayal Upadhayaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go Anusandhan Sansthan, Mathura - 281 001, Uttar Pradesh, India
| | - Dilip Kumar Swain
- Department of Physiology, College of Veterinary Sciences and Animal Husbandry, U.P. Pandit Deendayal Upadhayaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go Anusandhan Sansthan, Mathura - 281 001, Uttar Pradesh, India
| | - Sarvajeet Yadav
- Department of Physiology, College of Veterinary Sciences and Animal Husbandry, U.P. Pandit Deendayal Upadhayaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go Anusandhan Sansthan, Mathura - 281 001, Uttar Pradesh, India
| | - Rajesh Nigam
- College of Biotechnology, U.P. Pandit Deendayal Upadhayaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go Anusandhan Sansthan, Mathura - 281 001, Uttar Pradesh, India
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19
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Kigundu G, Cooper JL, Smith SME. H v 1 Proton Channels in Dinoflagellates: Not Just for Bioluminescence? J Eukaryot Microbiol 2018; 65:928-933. [PMID: 29698585 PMCID: PMC7167071 DOI: 10.1111/jeu.12627] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 04/11/2018] [Accepted: 04/15/2018] [Indexed: 01/08/2023]
Abstract
Bioluminescence in dinoflagellates is controlled by HV1 proton channels. Database searches of dinoflagellate transcriptomes and genomes yielded hits with sequence features diagnostic of all confirmed HV1, and show that HV1 is widely distributed in the dinoflagellate phylogeny including the basal species Oxyrrhis marina. Multiple sequence alignments followed by phylogenetic analysis revealed three major subfamilies of HV1 that do not correlate with presence of theca, autotrophy, geographic location, or bioluminescence. These data suggest that most dinoflagellates express a HV1 which has a function separate from bioluminescence. Sequence evidence also suggests that dinoflagellates can contain more than one HV1 gene.
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Affiliation(s)
- Gabriel Kigundu
- Department of Molecular and Cellular Biology, Kennesaw State University, 370 Paulding Avenue MD 1202, Kennesaw, Georgia, 30144
| | - Jennifer L Cooper
- Department of Molecular and Cellular Biology, Kennesaw State University, 370 Paulding Avenue MD 1202, Kennesaw, Georgia, 30144
| | - Susan M E Smith
- Department of Molecular and Cellular Biology, Kennesaw State University, 370 Paulding Avenue MD 1202, Kennesaw, Georgia, 30144
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20
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Cherny VV, Morgan D, Thomas S, Smith SME, DeCoursey TE. Histidine 168 is crucial for ΔpH-dependent gating of the human voltage-gated proton channel, hH V1. J Gen Physiol 2018; 150:851-862. [PMID: 29743300 PMCID: PMC5987877 DOI: 10.1085/jgp.201711968] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 03/27/2018] [Indexed: 01/28/2023] Open
Abstract
Voltage-gated proton channels open appropriately in myriad physiological situations because their gating is powerfully modulated by both pHo and pHi. Cherny et al. serendipitously identify a histidine at the inner end of the S3 helix that is required for the response to pHi. We recently identified a voltage-gated proton channel gene in the snail Helisoma trivolvis, HtHV1, and determined its electrophysiological properties. Consistent with early studies of proton currents in snail neurons, HtHV1 opens rapidly, but it unexpectedly exhibits uniquely defective sensitivity to intracellular pH (pHi). The H+ conductance (gH)-V relationship in the voltage-gated proton channel (HV1) from other species shifts 40 mV when either pHi or pHo (extracellular pH) is changed by 1 unit. This property, called ΔpH-dependent gating, is crucial to the functions of HV1 in many species and in numerous human tissues. The HtHV1 channel exhibits normal pHo dependence but anomalously weak pHi dependence. In this study, we show that a single point mutation in human hHV1—changing His168 to Gln168, the corresponding residue in HtHV1—compromises the pHi dependence of gating in the human channel so that it recapitulates the HtHV1 response. This location was previously identified as a contributor to the rapid gating kinetics of HV1 in Strongylocentrotus purpuratus. His168 mutation in human HV1 accelerates activation but accounts for only a fraction of the species difference. H168Q, H168S, or H168T mutants exhibit normal pHo dependence, but changing pHi shifts the gH-V relationship on average by <20 mV/unit. Thus, His168 is critical to pHi sensing in hHV1. His168, located at the inner end of the pore on the S3 transmembrane helix, is the first residue identified in HV1 that significantly impairs pH sensing when mutated. Because pHo dependence remains intact, the selective erosion of pHi dependence supports the idea that there are distinct internal and external pH sensors. Although His168 may itself be a pHi sensor, the converse mutation, Q229H, does not normalize the pHi sensitivity of the HtHV1 channel. We hypothesize that the imidazole group of His168 interacts with nearby Phe165 or other parts of hHV1 to transduce pHi into shifts of voltage-dependent gating.
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Affiliation(s)
| | - Deri Morgan
- Department of Physiology & Biophysics, Rush University, Chicago, IL
| | - Sarah Thomas
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA
| | - Susan M E Smith
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA
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21
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Zhang J, Chen X, Xue Y, Gamper N, Zhang X. Beyond voltage-gated ion channels: Voltage-operated membrane proteins and cellular processes. J Cell Physiol 2018; 233:6377-6385. [PMID: 29667735 DOI: 10.1002/jcp.26555] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 02/20/2018] [Indexed: 12/26/2022]
Abstract
Voltage-gated ion channels were believed to be the only voltage-sensitive proteins in excitable (and some non-excitable) cells for a long time. Emerging evidence indicates that the voltage-operated model is shared by some other transmembrane proteins expressed in both excitable and non-excitable cells. In this review, we summarize current knowledge about voltage-operated proteins, which are not classic voltage-gated ion channels as well as the voltage-dependent processes in cells for which single voltage-sensitive proteins have yet to be identified. Particularly, we will focus on the following. (1) Voltage-sensitive phosphoinositide phosphatases (VSP) with four transmembrane segments homologous to the voltage sensor domain (VSD) of voltage-gated ion channels; VSPs are the first family of proteins, other than the voltage-gated ion channels, for which there is sufficient evidence for the existence of the VSD domain; (2) Voltage-gated proton channels comprising of a single voltage-sensing domain and lacking an identified pore domain; (3) G protein coupled receptors (GPCRs) that mediate the depolarization-evoked potentiation of Ca2+ mobilization; (4) Plasma membrane (PM) depolarization-induced but Ca2+ -independent exocytosis in neurons. (5) Voltage-dependent metabolism of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P2 , PIP2 ) in the PM. These recent discoveries expand our understanding of voltage-operated processes within cellular membranes.
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Affiliation(s)
- Jianping Zhang
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Xingjuan Chen
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.,Beijing Key Laboratory of Diabetes Prevention and Research, Lu He Hospital, Capital Medical University, Beijing, China
| | - Yucong Xue
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Nikita Gamper
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Xuan Zhang
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
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22
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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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23
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Bennett AL, Ramsey IS. CrossTalk opposing view: proton transfer in Hv1 utilizes a water wire, and does not require transient protonation of a conserved aspartate in the S1 transmembrane helix. J Physiol 2017; 595:6797-6799. [PMID: 29023730 DOI: 10.1113/jp274553] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Ashley L Bennett
- Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Ian Scott Ramsey
- Virginia Commonwealth University School of Medicine, Richmond, VA, USA
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24
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Wright BJ, Bickham-Wright U, Yoshino TP, Jackson MB. H+ channels in embryonic Biomphalaria glabrata cell membranes: Putative roles in snail host-schistosome interactions. PLoS Negl Trop Dis 2017; 11:e0005467. [PMID: 28319196 PMCID: PMC5373640 DOI: 10.1371/journal.pntd.0005467] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 03/30/2017] [Accepted: 03/07/2017] [Indexed: 01/19/2023] Open
Abstract
The human blood fluke Schistosoma mansoni causes intestinal schistosomiasis, a widespread neglected tropical disease. Infection of freshwater snails Biomphalaria spp. is an essential step in the transmission of S. mansoni to humans, although the physiological interactions between the parasite and its obligate snail host that determine success or failure are still poorly understood. In the present study, the B. glabrata embryonic (Bge) cell line, a widely used in vitro model for hemocyte-like activity, was used to investigate membrane properties, and assess the impact of larval transformation proteins (LTP) on identified ion channels. Whole-cell patch clamp recordings from Bge cells demonstrated that a Zn2+-sensitive H+ channel serves as the dominant plasma membrane conductance. Moreover, treatment of Bge cells with Zn2+ significantly inhibited an otherwise robust production of reactive oxygen species (ROS), thus implicating H+ channels in the regulation of this immune function. A heat-sensitive component of LTP appears to target H+ channels, enhancing Bge cell H+ current over 2-fold. Both Bge cells and B. glabrata hemocytes express mRNA encoding a hydrogen voltage-gated channel 1 (HVCN1)-like protein, although its function in hemocytes remains to be determined. This study is the first to identify and characterize an H+ channel in non-neuronal cells of freshwater molluscs. Importantly, the involvement of these channels in ROS production and their modulation by LTP suggest that these channels may function in immune defense responses against larval S. mansoni.
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Affiliation(s)
- Brandon J. Wright
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Utibe Bickham-Wright
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Timothy P. Yoshino
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Meyer B. Jackson
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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25
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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: 24] [Impact Index Per Article: 3.4] [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
- * E-mail:
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26
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Kim J, Song JH. Inhibitory effects of antihistamines, diphenhydramine and chlorpheniramine, on proton currents in BV2 microglial cells. Eur J Pharmacol 2017; 798:122-128. [PMID: 28131782 DOI: 10.1016/j.ejphar.2017.01.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 01/02/2017] [Accepted: 01/25/2017] [Indexed: 02/08/2023]
Abstract
Microglial NADPH oxidase is a major source of toxic reactive oxygen species produced during chronic neuroinflammation. Voltage-gated proton channel (HV1) functions to maintain the intense activity of NADPH oxidase, and channel inhibition alleviates the pathology of neurodegenerative diseases such as ischemic stroke and multiple sclerosis associated with oxidative neuroinflammation. Antagonists of histamine H1 receptors have beneficial effects against microglia-mediated oxidative stress and neurotoxicity. We examined the effects of the H1 antihistamines, diphenhydramine and chlorpheniramine, on proton currents in BV2 microglial cells recorded using the whole-cell patch clamp technique. Diphenhydramine and chlorpheniramine reduced the proton currents with almost the same potency, yielding IC50 values of 42 and 43μM, respectively. Histamine did not affect proton currents, excluding the involvement of histamine receptors in their action. Neither drug shifted the voltage-dependence of activation or the reversal potential of the proton currents, even though diphenhydramine slowed the activation and deactivation kinetics. The inhibitory effects of the two antihistamines on proton currents could be utilized to develop therapeutic agents for neurodegenerative diseases and other diseases associated with HV1 proton channel abnormalities.
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Affiliation(s)
- Jiwon Kim
- Department of Pharmacology, College of Medicine, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 06974, Republic of Korea
| | - Jin-Ho Song
- Department of Pharmacology, College of Medicine, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 06974, Republic of Korea.
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