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Zhang L, Wu X, Cao X, Rao K, Hong L. Trp207 regulation of voltage-dependent activation of human H v1 proton channel. J Biol Chem 2024; 300:105674. [PMID: 38272234 PMCID: PMC10875263 DOI: 10.1016/j.jbc.2024.105674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/08/2024] [Accepted: 01/13/2024] [Indexed: 01/27/2024] Open
Abstract
In voltage-gated Na+ and K+ channels, the hydrophobicity of noncharged residues in the S4 helix has been shown to regulate the S4 movement underlying the process of voltage-sensing domain (VSD) activation. In voltage-gated proton channel Hv1, there is a bulky noncharged tryptophan residue located at the S4 transmembrane segment. This tryptophan remains entirely conserved across all Hv1 members but is not seen in other voltage-gated ion channels, indicating that the tryptophan contributes different roles in VSD activation. The conserved tryptophan of human voltage-gated proton channel Hv1 is Trp207 (W207). Here, we showed that W207 modifies human Hv1 voltage-dependent activation, and small residues replacement at position 207 strongly perturbs Hv1 channel opening and closing, and the size of the side chain instead of the hydrophobic group of W207 regulates the transition between closed and open states of the channel. We conclude that the large side chain of tryptophan controls the energy barrier during the Hv1 VSD transition.
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Affiliation(s)
- Lu Zhang
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Xin Wu
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Xinyu Cao
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Khushi Rao
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | - Liang Hong
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, USA; Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA.
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2
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Fernández M, Alvear-Arias JJ, Carmona EM, Carrillo C, Pena-Pichicoi A, Hernandez-Ochoa EO, Neely A, Alvarez O, Latorre R, Garate JA, Gonzalez C. Trapping Charge Mechanism in Hv1 Channels ( CiHv1). Int J Mol Sci 2023; 25:426. [PMID: 38203601 PMCID: PMC10779229 DOI: 10.3390/ijms25010426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/16/2023] [Accepted: 12/20/2023] [Indexed: 01/12/2024] Open
Abstract
The majority of voltage-gated ion channels contain a defined voltage-sensing domain and a pore domain composed of highly conserved amino acid residues that confer electrical excitability via electromechanical coupling. In this sense, the voltage-gated proton channel (Hv1) is a unique protein in that voltage-sensing, proton permeation and pH-dependent modulation involve the same structural region. In fact, these processes synergistically work in concert, and it is difficult to separate them. To investigate the process of Hv1 voltage sensor trapping, we follow voltage-sensor movements directly by leveraging mutations that enable the measurement of Hv1 channel gating currents. We uncover that the process of voltage sensor displacement is due to two driving forces. The first reveals that mutations in the selectivity filter (D160) located in the S1 transmembrane interact with the voltage sensor. More hydrophobic amino acids increase the energy barrier for voltage sensor activation. On the other hand, the effect of positive charges near position 264 promotes the formation of salt bridges between the arginines of the voltage sensor domain, achieving a stable conformation over time. Our results suggest that the activation of the Hv1 voltage sensor is governed by electrostatic-hydrophobic interactions, and S4 arginines, N264 and selectivity filter (D160) are essential in the Ciona-Hv1 to understand the trapping of the voltage sensor.
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Affiliation(s)
- Miguel Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
| | - Juan J. Alvear-Arias
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
| | - Emerson M. Carmona
- Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
| | - Christian Carrillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
| | - Antonio Pena-Pichicoi
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
| | - Erick O. Hernandez-Ochoa
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2351319, Chile; (M.F.); (J.J.A.-A.); (C.C.); (A.P.-P.); (A.N.); (O.A.); (R.L.)
| | - Jose A. Garate
- Facultad de Ingeniería, Arquitectura y Diseño, Universidad San Sebastian, Santiago 7780272, Chile
| | - Carlos Gonzalez
- Millennium Nucleus in NanoBioPhysics, Universidad de Valparaíso, Valparaíso 2351319, Chile
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
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Hellmold N, Eberwein M, Phan MHT, Kümmel S, Einsle O, Deobald D, Adrian L. Dehalococcoides mccartyi strain CBDB1 takes up protons from the cytoplasm to reductively dehalogenate organohalides indicating a new modus of proton motive force generation. Front Microbiol 2023; 14:1305108. [PMID: 38192294 PMCID: PMC10772276 DOI: 10.3389/fmicb.2023.1305108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 12/07/2023] [Indexed: 01/10/2024] Open
Abstract
Proton translocation across the cytoplasmic membrane is a vital process for all organisms. Dehalococcoides strains are strictly anaerobic organohalide respiring bacteria that lack quinones and cytochromes but express a large membrane-bound protein complex (OHR complex) proposed to generate a proton gradient. However, its functioning is unclear. By using a dehalogenase-based enzyme activity assay with deuterium-labelled water in various experimental designs, we obtained evidence that the halogen atom of the halogenated electron acceptor is substituted with a proton from the cytoplasm. This suggests that the protein complex couples exergonic electron flux through the periplasmic subunits of the OHR complex to the endergonic transport of protons from the cytoplasm across the cytoplasmic membrane against the proton gradient to the halogenated electron acceptor. Using computational tools, we located two proton-conducting half-channels in the AlphaFold2-predicted structure of the OmeB subunit of the OHR complex, converging in a highly conserved arginine residue that could play a proton gatekeeper role. The cytoplasmic proton half-channel in OmeB is connected to a putative proton-conducting path within the reductive dehalogenase subunit. Our results indicate that the reductive dehalogenase and its halogenated substrate serve as both electron and proton acceptors, providing insights into the proton translocation mechanism within the OHR complex and contributing to a better understanding of energy conservation in D. mccartyi strains. Our results reveal a very simple mode of energy conservation in anaerobic bacteria, showing that proton translocation coupled to periplasmic electron flow might have importance also in other microbial processes and biotechnological applications.
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Affiliation(s)
- Nadine Hellmold
- Department Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany
| | - Marie Eberwein
- Department Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany
| | - My Hanh Thi Phan
- Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Steffen Kümmel
- Department Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany
| | - Oliver Einsle
- Institute of Biochemistry, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany
| | - Darja Deobald
- Department Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany
| | - Lorenz Adrian
- Department Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany
- Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
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Korneenko TV, Pestov NB, Nevzorov IA, Daks AA, Trachuk KN, Solopova ON, Barlev NA. At the Crossroads of the cGAS-cGAMP-STING Pathway and the DNA Damage Response: Implications for Cancer Progression and Treatment. Pharmaceuticals (Basel) 2023; 16:1675. [PMID: 38139802 PMCID: PMC10747911 DOI: 10.3390/ph16121675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 11/21/2023] [Accepted: 11/21/2023] [Indexed: 12/24/2023] Open
Abstract
The evolutionary conserved DNA-sensing cGAS-STING innate immunity pathway represents one of the most important cytosolic DNA-sensing systems that is activated in response to viral invasion and/or damage to the integrity of the nuclear envelope. The key outcome of this pathway is the production of interferon, which subsequently stimulates the transcription of hundreds of genes. In oncology, the situation is complex because this pathway may serve either anti- or pro-oncogenic roles, depending on context. The prevailing understanding is that when the innate immune response is activated by sensing cytosolic DNA, such as DNA released from ruptured micronuclei, it results in the production of interferon, which attracts cytotoxic cells to destroy tumors. However, in tumor cells that have adjusted to significant chromosomal instability, particularly in relapsed, treatment-resistant cancers, the cGAS-STING pathway often supports cancer progression, fostering the epithelial-to-mesenchymal transition (EMT). Here, we review this intricate pathway in terms of its association with cancer progression, giving special attention to pancreatic ductal adenocarcinoma and gliomas. As the development of new cGAS-STING-modulating small molecules and immunotherapies such as oncolytic viruses involves serious challenges, we highlight several recent fundamental discoveries, such as the proton-channeling function of STING. These discoveries may serve as guiding lights for potential pharmacological advancements.
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Affiliation(s)
- Tatyana V. Korneenko
- Group of Cross-Linking Enzymes, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Nikolay B. Pestov
- Group of Cross-Linking Enzymes, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
- Institute of Biomedical Chemistry, Moscow 119121, Russia
- Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products, Moscow 108819, Russia
| | - Ivan A. Nevzorov
- Institute of Cytology, Tikhoretsky ave 4, St-Petersburg 194064, Russia
| | - Alexandra A. Daks
- Institute of Cytology, Tikhoretsky ave 4, St-Petersburg 194064, Russia
| | - Kirill N. Trachuk
- Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products, Moscow 108819, Russia
| | - Olga N. Solopova
- Research Institute of Experimental Diagnostics and Tumor Therapy, Blokhin National Medical Research Center of Oncology, Moscow 115478, Russia
| | - Nickolai A. Barlev
- Institute of Biomedical Chemistry, Moscow 119121, Russia
- Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products, Moscow 108819, Russia
- Institute of Cytology, Tikhoretsky ave 4, St-Petersburg 194064, Russia
- Institute of Translational Medicine and Biotechnology, Sechenov First Moscow State Medical University, Moscow 119991, Russia
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5
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Renfeld ZV, Chernykh AM, Baskunov BP, Gaidina AS, Myasoedova NM, Egorova AD, Moiseeva OV, Gorina SY, Kolomytseva MP. Unusual Oligomeric Laccase-like Oxidases from Ascomycete Curvularia geniculata VKM F-3561 Polymerizing Phenylpropanoids and Phenolic Compounds under Neutral Environmental Conditions. Microorganisms 2023; 11:2698. [PMID: 38004710 PMCID: PMC10673308 DOI: 10.3390/microorganisms11112698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/26/2023] [Accepted: 11/01/2023] [Indexed: 11/26/2023] Open
Abstract
The unique oligomeric alkaliphilic laccase-like oxidases of the ascomycete C. geniculata VKM F-3561 (with molecular masses about 1035 and 870 kDa) were purified and characterized for the first time. The ability of the enzymes to oxidize phenylpropanoids and phenolic compounds under neutral environmental conditions with the formation of previously unknown di-, tri-, and tetrameric products of transformation was shown. The possibility to obtain industrially valuable compounds (dihydroxybenzyl alcohol and hydroxytyrosol) from caffeic acid using laccase-like oxidases of C. geniculata VKM F-3561 has been shown. Complete nucleotide sequence of the laccase gene, which is expressed at the peak of alkaliphilic laccase activity of the fungus, and its promoter region were determined. Based on the phylogenetic analysis of the nucleotide sequence, the nearest relationship of the isolated laccase gene with similar genes of fungi of the genera Alternaria, Bipolaris, and Cochliobolus was shown. Homologous model of the laccase structure was predicted and a proton channel was found, which was presumably responsible for the accumulation and transport of protons to T2/T3-copper center in the alkaliphilic laccase molecule and providing the functional activity of the enzyme in the neutral alkaline environment conditions.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Marina P. Kolomytseva
- G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Federal Research Center “Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences”, Prosp. Nauki 5, 142290 Pushchino, Russia; (Z.V.R.); (A.M.C.); (B.P.B.); (A.D.E.); (O.V.M.); (S.Y.G.)
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6
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Yang C, Tian F, Hu M, Kang C, Ping M, Liu Y, Hu M, Xu H, Yu Y, Gao Z, Li P. Characterization of the role of TMEM175 in an in vitro lysosomal H + fluxes model. FEBS J 2023; 290:4641-4659. [PMID: 37165739 DOI: 10.1111/febs.16814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/06/2023] [Accepted: 05/09/2023] [Indexed: 05/12/2023]
Abstract
Lysosome acidification is a dynamic equilibrium of H+ influx and efflux across the membrane, which is crucial for cell physiology. The vacuolar H+ ATPase (V-ATPase) is responsible for the H+ influx or refilling of lysosomes. TMEM175 was identified as a novel H+ permeable channel on lysosomal membranes, and it plays a critical role in lysosome acidification. However, how TMEM175 participates in lysosomal acidification remains unknown. Here, we present evidence that TMEM175 regulates lysosomal H+ influx and efflux in enlarged lysosomes isolated from COS1 treated with vacuolin-1. By utilizing the whole-endolysosome patch-clamp recording technique, a series of integrated lysosomal H+ influx and efflux signals in a ten-of-second time scale under the physiological pH gradient (luminal pH 4.60, and cytosolic pH 7.20) was recorded from this in vitro system. Lysosomal H+ fluxes constitute both the lysosomal H+ refilling and releasing, and they are asymmetrical processes with distinct featured kinetics for each of the H+ fluxes. Lysosomal H+ fluxes are entirely abolished when TMEM175 losses of function in the F39V mutant and is blocked by the antagonist (2-GBI). Meanwhile, lysosomal H+ fluxes are modulated by the pH-buffering capacity of the lumen and the lysosomal glycosylated membrane proteins, lysosome-associated membrane protein 1 (LAMP1). We propose that the TMEM175-mediated lysosomal H+ fluxes model would provide novel thoughts for studying the pathology of Parkinson's disease and lysosome storage disorders.
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Affiliation(s)
- Chuanyan Yang
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Fuyun Tian
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
| | - Mei Hu
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Pharmacology Laboratory, Zhongshan Hospital, Guangzhou University of Chinese Medicine, China
| | - Chunlan Kang
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China
| | - Meixuan Ping
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yiyao Liu
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
| | - Meiqin Hu
- Department of Molecular, Cellular, and Developmental Biology, The University of Michigan, Ann Arbor, Michigan, USA
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, The University of Michigan, Ann Arbor, Michigan, USA
| | - Ye Yu
- Department of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Zhaobing Gao
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Ping Li
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China
- University of Chinese Academy of Sciences, Beijing, China
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7
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Tang T, Jian B, Liu Z. Transmembrane Protein 175, a Lysosomal Ion Channel Related to Parkinson's Disease. Biomolecules 2023; 13:biom13050802. [PMID: 37238672 DOI: 10.3390/biom13050802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/14/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
Lysosomes are membrane-bound organelles with an acidic lumen and are traditionally characterized as a recycling center in cells. Lysosomal ion channels are integral membrane proteins that form pores in lysosomal membranes and allow the influx and efflux of essential ions. Transmembrane protein 175 (TMEM175) is a unique lysosomal potassium channel that shares little sequence similarity with other potassium channels. It is found in bacteria, archaea, and animals. The prokaryotic TMEM175 consists of one six-transmembrane domain that adopts a tetrameric architecture, while the mammalian TMEM175 is comprised of two six-transmembrane domains that function as a dimer in lysosomal membranes. Previous studies have demonstrated that the lysosomal K+ conductance mediated by TMEM175 is critical for setting membrane potential, maintaining pH stability, and regulating lysosome-autophagosome fusion. AKT and B-cell lymphoma 2 regulate TMEM175's channel activity through direct binding. Two recent studies reported that the human TMEM175 is also a proton-selective channel under normal lysosomal pH (4.5-5.5) as the K+ permeation dramatically decreased at low pH while the H+ current through TMEM175 greatly increased. Genome-wide association studies and functional studies in mouse models have established that TMEM175 is implicated in the pathogenesis of Parkinson's disease, which sparks more research interests in this lysosomal channel.
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Affiliation(s)
- Tuoxian Tang
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Boshuo Jian
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun 130012, China
| | - Zhenjiang Liu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun 130012, China
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Szanto TG, Feher A, Korpos E, Gyöngyösi A, Kállai J, Mészáros B, Ovari K, Lányi Á, Panyi G, Varga Z. 5-Chloro-2-Guanidinobenzimidazole (ClGBI) Is a Non-Selective Inhibitor of the Human H V1 Channel. Pharmaceuticals (Basel) 2023; 16:ph16050656. [PMID: 37242439 DOI: 10.3390/ph16050656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 04/13/2023] [Accepted: 04/24/2023] [Indexed: 05/28/2023] Open
Abstract
5-chloro-2-guanidinobenzimidazole (ClGBI), a small-molecule guanidine derivative, is a known effective inhibitor of the voltage-gated proton (H+) channel (HV1, Kd ≈ 26 μM) and is widely used both in ion channel research and functional biological assays. However, a comprehensive study of its ion channel selectivity determined by electrophysiological methods has not been published yet. The lack of selectivity may lead to incorrect conclusions regarding the role of hHv1 in physiological or pathophysiological responses in vitro and in vivo. We have found that ClGBI inhibits the proliferation of lymphocytes, which absolutely requires the functioning of the KV1.3 channel. We, therefore, tested ClGBI directly on hKV1.3 using a whole-cell patch clamp and found an inhibitory effect similar in magnitude to that seen on hHV1 (Kd ≈ 72 μM). We then further investigated ClGBI selectivity on the hKV1.1, hKV1.4-IR, hKV1.5, hKV10.1, hKV11.1, hKCa3.1, hNaV1.4, and hNaV1.5 channels. Our results show that, besides HV1 and KV1.3, all other off-target channels were inhibited by ClGBI, with Kd values ranging from 12 to 894 μM. Based on our comprehensive data, ClGBI has to be considered a non-selective hHV1 inhibitor; thus, experiments aiming at elucidating the significance of these channels in physiological responses have to be carefully evaluated.
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Affiliation(s)
- Tibor G Szanto
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Adam Feher
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Eva Korpos
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- ELKH-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Adrienn Gyöngyösi
- Department of Immunology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Judit Kállai
- ELKH-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Immunology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Beáta Mészáros
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Krisztian Ovari
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Árpád Lányi
- Department of Immunology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Gyorgy Panyi
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- ELKH-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Zoltan Varga
- Department of Biophysics & Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
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9
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Teng B, Kaplan J, Liang Z, Chyung KS, Goldschen-Ohm MP, Liman ER. Zinc activation of OTOP proton channels identifies structural elements of the gating apparatus. eLife 2023; 12:85317. [PMID: 37053086 PMCID: PMC10101688 DOI: 10.7554/elife.85317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 03/27/2023] [Indexed: 04/14/2023] Open
Abstract
Otopetrin proteins (OTOPs) form proton-selective ion channels that are expressed in diverse cell types where they mediate detection of acids or regulation of pH. In vertebrates there are three family members: OTOP1 is required for formation of otoconia in the vestibular system and it forms the receptor for sour taste, while the functions of OTOP2 and OTOP3 are not yet known. Importantly, the gating mechanisms of any of the OTOP channels are not well understood. Here, we show that zinc (Zn2+), as well as other transition metals including copper (Cu2+), potently activates murine OTOP3 (mOTOP3). Zn2+ pre-exposure increases the magnitude of mOTOP3 currents to a subsequent acid stimulus by as much as 10-fold. In contrast, mOTOP2 currents are insensitive to activation by Zn2+. Swapping the extracellular tm 11-12 linker between mOTOP3 and mOTOP2 was sufficient to eliminate Zn2+ activation of mOTOP3 and confer Zn2+ activation on mOTOP2. Mutation to alanine of H531 and E535 within the tm 11-12 linker and H234 and E238 within the 5-6 linker reduced or eliminated activation of mOTOP3 by Zn2+, indicating that these residues likely contribute to the Zn2+ activating site. Kinetic modeling of the data is consistent with Zn2+ stabilizing the opn2+en state of the channel, competing with H+ for activation of the channels. These results establish the tm 11-12 and tm 5-6 linkers as part of the gating apparatus of OTOP channels and a target for drug discovery. Zn2+ is an essential micronutrient and its activation of OTOP channels will undoubtedly have important physiological sequelae.
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Affiliation(s)
- Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Joshua Kaplan
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Kevin Saejin Chyung
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | | | - Emily Ruth Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
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10
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Grund TN, Kabashima Y, Kusumoto T, Wu D, Welsch S, Sakamoto J, Michel H, Safarian S. The cryoEM structure of cytochrome bd from C. glutamicum provides novel insights into structural properties of actinobacterial terminal oxidases. Front Chem 2023; 10:1085463. [PMID: 36688035 PMCID: PMC9846854 DOI: 10.3389/fchem.2022.1085463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 12/12/2022] [Indexed: 01/05/2023] Open
Abstract
Cytochromes bd are essential for microaerobic respiration of many prokaryotes including a number of human pathogens. These enzymes catalyze the reduction of molecular oxygen to water using quinols as electron donors. Their importance for prokaryotic survival and the absence of eukaryotic homologs make these enzyme ideal targets for antimicrobial drugs. Here, we determined the cryoEM structure of the menaquinol-oxidizing cytochrome bd-type oxygen reductase of the facultative anaerobic Actinobacterium Corynebacterium glutamicum at a resolution of 2.7 Å. The obtained structure adopts the signature pseudosymmetrical heterodimeric architecture of canonical cytochrome bd oxidases formed by the core subunits CydA and CydB. No accessory subunits were identified for this cytochrome bd homolog. The two b-type hemes and the oxygen binding heme d are organized in a triangular geometry with a protein environment around these redox cofactors similar to that of the closely related cytochrome bd from M. tuberculosis. We identified oxygen and a proton conducting channels emerging from the membrane space and the cytoplasm, respectively. Compared to the prototypical enzyme homolog from the E. coli, the most apparent difference is found in the location and size of the proton channel entry site. In canonical cytochrome bd oxidases quinol oxidation occurs at the highly flexible periplasmic Q-loop located in the loop region between TMHs six and seven. An alternative quinol-binding site near heme b 595 was previously identified for cytochrome bd from M. tuberculosis. We discuss the relevance of the two quinol oxidation sites in actinobacterial bd-type oxidases and highlight important differences that may explain functional and electrochemical differences between C. glutamicum and M. tuberculosis. This study expands our current understanding of the structural diversity of actinobacterial and proteobacterial cytochrome bd oxygen reductases and provides deeper insights into the unique structural and functional properties of various cytochrome bd variants from different phylae.
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Affiliation(s)
- Tamara N. Grund
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Yoshiki Kabashima
- Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Fukuoka, Japan
| | - Tomoichirou Kusumoto
- Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Fukuoka, Japan
| | - Di Wu
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Junshi Sakamoto
- Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Fukuoka, Japan
| | - Hartmut Michel
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
| | - Schara Safarian
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt, Germany,Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand,Fraunhofer Institute for Translational Medicine and Pharmacology ITMP Frankfurt, Frankfurt, Germany,*Correspondence: Schara Safarian,
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11
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Ma J, Gao X, Li Y, DeCoursey TE, Shull GE, Wang HS. The HVCN1 voltage-gated proton channel contributes to pH regulation in canine ventricular myocytes. J Physiol 2022; 600:2089-2103. [PMID: 35244217 PMCID: PMC9058222 DOI: 10.1113/jp282126] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 02/24/2022] [Indexed: 11/09/2022] Open
Abstract
KEY POINTS Intracellular pH (pHi ) regulation is crucial for cardiac function, as acidification depresses contractility and causes arrhythmias. H+ ions are generated in cardiomyocytes from metabolic processes and particularly from CO2 hydration, which has been shown to facilitate CO2 -venting from mitochondria. Currently, the NHE1 Na+ /H+ exchanger is viewed as the dominant H+ -extrusion mechanism in cardiac muscle. We show that the HVCN1 voltage-gated proton channel is present and functional in canine ventricular myocytes, and that HVCN1 and NHE1 both contribute to pHi regulation. HVCN1 provides an energetically-efficient mechanism of H+ -extrusion that would not cause Na+ -loading, which can cause pathology, and that could contribute to transport-mediated CO2 disposal. These results provide a major advance in our understanding of pHi regulation in cardiac muscle. ABSTRACT Regulation of intracellular pH (pHi ) in cardiomyocytes is crucial for cardiac function; however, currently known mechanisms for direct or indirect extrusion of acid from cardiomyocytes seem insufficient for energetically-efficient extrusion of the massive H+ loads generated under in vivo conditions. In cardiomyocytes, voltage-sensitive H+ channel activity mediated by the HVCN1 proton channel would be a highly efficient means of disposing of H+ , while avoiding Na+ -loading, as occurs during direct acid extrusion via Na+ /H+ exchange or indirect acid extrusion via Na+ -HCO3 - cotransport. PCR and immunoblotting demonstrated expression of HVCN1 mRNA and protein in canine heart. Patch clamp analysis of canine ventricular myocytes revealed a voltage-gated H+ current that was highly H+ -selective. The current was blocked by external Zn2+ and the HVCN1 blocker 5-chloro-2-guanidinobenzimidazole (ClGBI). Both the gating and Zn2+ blockade of the current were strongly influenced by the pH gradient across the membrane. All characteristics of the observed current were consistent with the known hallmarks of HVCN1-mediated H+ current. Inhibition of HVCN1 and the NHE1 Na+ /H+ exchanger, singly and in combination, showed that either mechanism is largely sufficient to maintain pHi in beating cardiomyocytes, but that inhibition of both activities causes rapid acidification. These results show that HVCN1 is expressed in canine ventricular myocytes and provides a major H+ -extrusion activity, with a capacity similar to that of NHE1. In the beating heart in vivo, this activity would allow Na+ -independent extrusion of H+ during each action potential and, when functionally coupled with anion transport mechanisms, could facilitate transport-mediated CO2 disposal. Abstract figure legend The HVCN1 proton channel is expressed in canine ventricular myocytes and contributes to H+ extrusion. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Jianyong Ma
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Xiaoqian Gao
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Yutian Li
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, Chicago, Illinois, 60612, USA
| | - Gary E Shull
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
| | - Hong-Sheng Wang
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA
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12
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Teng B, Kaplan JP, Liang Z, Krieger Z, Tu YH, Burendei B, Ward AB, Liman ER. Structural motifs for subtype-specific pH-sensitive gating of vertebrate otopetrin proton channels. eLife 2022; 11:77946. [PMID: 35920807 PMCID: PMC9348849 DOI: 10.7554/elife.77946] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 07/19/2022] [Indexed: 01/05/2023] Open
Abstract
Otopetrin (OTOP) channels are proton-selective ion channels conserved among vertebrates and invertebrates, with no structural similarity to other ion channels. There are three vertebrate OTOP channels (OTOP1, OTOP2, and OTOP3), of which one (OTOP1) functions as a sour taste receptor. Whether extracellular protons gate OTOP channels, in addition to permeating them, was not known. Here, we compare the functional properties of the three murine OTOP channels using patch-clamp recording and cytosolic pH microfluorimetry. We find that OTOP1 and OTOP3 are both steeply activated by extracellular protons, with thresholds of pHo <6.0 and 5.5, respectively, and kinetics that are pH-dependent. In contrast, OTOP2 channels are broadly active over a large pH range (pH 5 pH 10) and carry outward currents in response to extracellular alkalinization (>pH 9.0). Strikingly, we could change the pH-sensitive gating of OTOP2 and OTOP3 channels by swapping extracellular linkers that connect transmembrane domains. Swaps of extracellular linkers in the N domain, comprising transmembrane domains 1-6, tended to change the relative conductance at alkaline pH of chimeric channels, while swaps within the C domain, containing transmembrane domains 7-12, tended to change the rates of OTOP3 current activation. We conclude that members of the OTOP channel family are proton-gated (acid-sensitive) proton channels and that the gating apparatus is distributed across multiple extracellular regions within both the N and C domains of the channels. In addition to the taste system, OTOP channels are expressed in the vertebrate vestibular and digestive systems. The distinct gating properties we describe may allow them to subserve varying cell-type specific functions in these and other biological systems.
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Affiliation(s)
- Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Joshua P Kaplan
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Zachary Krieger
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States
| | - Yu-Hsiang Tu
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUnited States
| | - Batuujin Burendei
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Emily R Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
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13
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Yan T, Liu S, Xu J, Sun H, Yu S, Liu J. Unimolecular Helix-Based Transmembrane Nanochannel with a Smallest Luminal Cavity of 1 Å Expressing High Proton Selectivity and Transport Activity. Nano Lett 2021; 21:10462-10468. [PMID: 34860025 DOI: 10.1021/acs.nanolett.1c03858] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Natural protein channels have evolved with exquisite structures to transport ions selectively and rapidly. Learning from nature to construct biomimetic artificial channels is always challenging. Herein we present a unimolecular transmembrane proton channel by quinoline-derived helix, which exhibited highly selective and ultrafast proton transport behaviors. This helix-based channel possesses a small luminal cavity of 1 Å in diameter, which could efficiently reject the permeation of cations, anions or water molecules but only permits the translocation of protons owing to the size effect. The proton flow rate exceeded 107 H+ s-1 channel-1 and reached the same magnitude with gramicidin A. Mechanism investigation revealed that the directionally arrayed NH-chain inside the synthetic channel played a pivotal role during the proton flux. This work not only presented a helix-based channel with the smallest observable nanopore, but also unveiled an unexplored pathway for realizing efficient transport of protons via the consecutive NH-chain.
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Affiliation(s)
- Tengfei Yan
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Shengda Liu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Jiayun Xu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Hongcheng Sun
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Shuangjiang Yu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
| | - Junqiu Liu
- College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 311121, China
- College of Chemistry, State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China
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14
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Panzer S, Zhang C, Konte T, Bräuer C, Diemar A, Yogendran P, Yu-Strzelczyk J, Nagel G, Gao S, Terpitz U. Modified Rhodopsins From Aureobasidium pullulans Excel With Very High Proton-Transport Rates. Front Mol Biosci 2021; 8:750528. [PMID: 34790700 PMCID: PMC8591190 DOI: 10.3389/fmolb.2021.750528] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/16/2021] [Indexed: 11/19/2022] Open
Abstract
Aureobasidium pullulans is a black fungus that can adapt to various stressful conditions like hypersaline, acidic, and alkaline environments. The genome of A. pullulans exhibits three genes coding for putative opsins ApOps1, ApOps2, and ApOps3. We heterologously expressed these genes in mammalian cells and Xenopus oocytes. Localization in the plasma membrane was greatly improved by introducing additional membrane trafficking signals at the N-terminus and the C-terminus. In patch-clamp and two-electrode-voltage clamp experiments, all three proteins showed proton pump activity with maximal activity in green light. Among them, ApOps2 exhibited the most pronounced proton pump activity with current amplitudes occasionally extending 10 pA/pF at 0 mV. Proton pump activity was further supported in the presence of extracellular weak organic acids. Furthermore, we used site-directed mutagenesis to reshape protein functions and thereby implemented light-gated proton channels. We discuss the difference to other well-known proton pumps and the potential of these rhodopsins for optogenetic applications.
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Affiliation(s)
- Sabine Panzer
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Chong Zhang
- Department of Neurophysiology, Physiological Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Tilen Konte
- Faculty of Medicine, Institute of Biochemistry, University of Ljubljana, Ljubljana, Slovenia
| | - Celine Bräuer
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Anne Diemar
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Parathy Yogendran
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Jing Yu-Strzelczyk
- Department of Neurophysiology, Physiological Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Georg Nagel
- Department of Neurophysiology, Physiological Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Shiqiang Gao
- Department of Neurophysiology, Physiological Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
| | - Ulrich Terpitz
- Department of Biotechnology and Biophysics, Theodor-Boveri-Institute, Julius Maximilian University of Wuerzburg, Wuerzburg, Germany
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15
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Abstract
The Hv1 proton channel is an unusual voltage-gated ion channel with atypical architecture and stoichiometry. While functional as a monomer, Hv1 is usually expressed as a dimer of two voltage-sensing domains (VSDs). How the two VSDs arrange relative to each other is a matter of debate and the functional impact of VSD–VSD interactions is only partly understood. We show that the Hv1 dimer interface is formed by the S1 and S4 transmembrane segments of the VSD. We find this S1–S4 dimer interface to be a strong regulator of Hv1 gating. This interface therefore constitutes a promising target for the development of allosteric modulators for this class of channels critical for pH regulation and immunity. The voltage-gated proton channel Hv1 is a member of the voltage-gated ion channel superfamily, which stands out in design: It is a dimer of two voltage-sensing domains (VSDs), each containing a pore pathway, a voltage sensor (S4), and a gate (S1) and forming its own ion channel. Opening of the two channels in the dimer is cooperative. Part of the cooperativity is due to association between coiled-coil domains that extend intracellularly from the S4s. Interactions between the transmembrane portions of the subunits may also contribute, but the nature of transmembrane packing is unclear. Using functional analysis of a mutagenesis scan, biochemistry, and modeling, we find that the subunits form a dimer interface along the entire length of S1, and also have intersubunit contacts between S1 and S4. These interactions exert a strong effect on gating, in particular on the stability of the open state. Our results suggest that gating in Hv1 is tuned by extensive VSD–VSD interactions between the gates and voltage sensors of the dimeric channel.
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16
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Wobig L, Wolfenstetter T, Fechner S, Bönigk W, Körschen HG, Jikeli JF, Trötschel C, Feederle R, Kaupp UB, Seifert R, Berger TK. A family of hyperpolarization-activated channels selective for protons. Proc Natl Acad Sci U S A 2020; 117:13783-91. [PMID: 32467169 DOI: 10.1073/pnas.2001214117] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Proton (H+) channels are special: They select protons against other ions that are up to a millionfold more abundant. Only a few proton channels have been identified so far. Here, we identify a family of voltage-gated "pacemaker" channels, HCNL1, that are exquisitely selective for protons. HCNL1 activates during hyperpolarization and conducts protons into the cytosol. Surprisingly, protons permeate through the channel's voltage-sensing domain, whereas the pore domain is nonfunctional. Key to proton permeation is a methionine residue that interrupts the series of regularly spaced arginine residues in the S4 voltage sensor. HCNL1 forms a tetramer and thus contains four proton pores. Unlike classic HCN channels, HCNL1 is not gated by cyclic nucleotides. The channel is present in zebrafish sperm and carries a proton inward current that acidifies the cytosol. Our results suggest that protons rather than cyclic nucleotides serve as cellular messengers in zebrafish sperm. Through small modifications in two key functional domains, HCNL1 evolutionarily adapted to a low-Na+ freshwater environment to conserve sperm's ability to depolarize.
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17
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Teng B, Wilson CE, Tu YH, Joshi NR, Kinnamon SC, Liman ER. Cellular and Neural Responses to Sour Stimuli Require the Proton Channel Otop1. Curr Biol 2019; 29:3647-3656.e5. [PMID: 31543453 DOI: 10.1016/j.cub.2019.08.077] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/08/2019] [Accepted: 08/30/2019] [Indexed: 11/24/2022]
Abstract
The sense of taste allows animals to sample chemicals in the environment prior to ingestion. Of the five basic tastes, sour, the taste of acids, had remained among the most mysterious. Acids are detected by type III taste receptor cells (TRCs), located in taste buds across the tongue and palate epithelium. The first step in sour taste transduction is believed to be entry of protons into the cell cytosol, which leads to cytosolic acidification and the generation of action potentials. The proton-selective ion channel Otop1 is expressed in type III TRCs and is a candidate sour receptor. Here, we tested the contribution of Otop1 to taste cell and gustatory nerve responses to acids in mice in which Otop1 was genetically inactivated (Otop1-KO mice). We first show that Otop1 is required for the inward proton current in type III TRCs from different parts of the tongue that are otherwise molecularly heterogeneous. We next show that in type III TRCs from Otop1-KO mice, intracellular pH does not track with extracellular pH and that moderately acidic stimuli do not elicit trains of action potentials, as they do in type III TRCs from wild-type mice. Moreover, gustatory nerve responses in Otop1-KO mice were severely and selectively attenuated for acidic stimuli, including citric acid and HCl. These results establish that the Otop1 proton channel plays a critical role in acid detection in the mouse gustatory system, evidence that it is a bona fide sour taste receptor.
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18
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Ratanayotha A, Kawai T, Okamura Y. Real-time functional analysis of Hv1 channel in neutrophils: a new approach from zebrafish model. Am J Physiol Regul Integr Comp Physiol 2019; 316:R819-R831. [PMID: 30943046 DOI: 10.1152/ajpregu.00326.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Voltage-gated proton channel (Hv1) has been studied in various immune cells, including neutrophils. However, most studies have taken an in vitro approach using isolated cells or primary cultured cells of mammals; therefore, limited evidence is available on the function of Hv1 in a physiological context. In this study, we have developed the in vivo system that enables real-time functional analysis of Hv1 using zebrafish embryos (Danio rerio). Hvcn1-deficiency (hvcn1-/-) in zebrafish completely abolished voltage-gated proton current, which is typically observed in wild-type neutrophils. Importantly, hvcn1-deficiency significantly reduced reactive oxygen species production and calcium response of zebrafish neutrophils, comparable to the results observed in mammalian models. These findings verify zebrafish Hv1 (DrHv1) as the primary contributor for native Hv1-derived proton current in neutrophils and suggest the conserved function of Hv1 in the immune cells across vertebrate animals. Taking advantage of Hv1 zebrafish model, we compared real-time behaviors of neutrophils between wild-type and hvcn1-/- zebrafish in response to tissue injury and acute bacterial infection. Notably, we observed a significant increase in the number of phagosomes in hvcn1-/- neutrophils, raising a possible link between Hv1 and phagosomal maturation. Furthermore, survival analysis of zebrafish larvae potentially supports a protective role of Hv1 in the innate immune response against systemic bacterial infection. This study represents the influence of Hv1 on neutrophil behaviors and highlights the benefits of in vivo approach toward the understanding of Hv1 in a physiological context.
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Affiliation(s)
- Adisorn Ratanayotha
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University , Suita, Osaka , Japan
| | - Takafumi Kawai
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University , Suita, Osaka , Japan
| | - Yasushi Okamura
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University , Suita, Osaka , Japan
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19
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Suzuki Y, Morimoto YV, Oono K, Hayashi F, Oosawa K, Kudo S, Nakamura S, Mullineaux CW. Effect of the MotA(M206I) Mutation on Torque Generation and Stator Assembly in the Salmonella H + -Driven Flagellar Motor. J Bacteriol 2019; 201. [PMID: 30642987 DOI: 10.1128/jb.00727-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/03/2019] [Indexed: 12/20/2022] Open
Abstract
The bacterial flagellar motor is composed of a rotor and a dozen stators and converts the ion flux through the stator into torque. Each stator unit alternates in its attachment to and detachment from the rotor even during rotation. In some species, stator assembly depends on the input energy, but it remains unclear how an electrochemical potential across the membrane (e.g., proton motive force [PMF]) or ion flux is involved in stator assembly dynamics. Here, we focused on pH dependence of a slow motile MotA(M206I) mutant of Salmonella The MotA(M206I) motor produces torque comparable to that of the wild-type motor near stall, but its rotation rate is considerably decreased as the external load is reduced. Rotation assays of flagella labeled with 1-μm beads showed that the rotation rate of the MotA(M206I) motor is increased by lowering the external pH whereas that of the wild-type motor is not. Measurements of the speed produced by a single stator unit using 1-μm beads showed that the unit speed of the MotA(M206I) is about 60% of that of the wild-type and that a decrease in external pH did not affect the MotA(M206I) unit speed. Analysis of the subcellular stator localization revealed that the number of functional stators is restored by lowering the external pH. The pH-dependent improvement of stator assembly was observed even when the PMF was collapsed and proton transfer was inhibited. These results suggest that MotA-Met206 is responsible for not only load-dependent energy coupling between the proton influx and rotation but also pH-dependent stator assembly.IMPORTANCE The bacterial flagellar motor is a rotary nanomachine driven by the electrochemical transmembrane potential (ion motive force). About 10 stators (MotA/MotB complexes) are docked around a rotor, and the stator recruitment depends on the load, ion motive force, and coupling ion flux. The MotA(M206I) mutation slows motor rotation and decreases the number of docked stators in Salmonella We show that lowering the external pH improves the assembly of the mutant stators. Neither the collapse of the ion motive force nor a mutation mimicking the proton-binding state inhibited stator localization to the motor. These results suggest that MotA-Met206 is involved in torque generation and proton translocation and that stator assembly is stabilized by protonation of the stator.
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20
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Zhao R, Kennedy K, De Blas GA, Orta G, Pavarotti MA, Arias RJ, de la Vega-Beltrán JL, Li Q, Dai H, Perozo E, Mayorga LS, Darszon A, Goldstein SAN. Role of human Hv1 channels in sperm capacitation and white blood cell respiratory burst established by a designed peptide inhibitor. Proc Natl Acad Sci U S A 2018; 115:E11847-56. [PMID: 30478045 DOI: 10.1073/pnas.1816189115] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Using a de novo peptide inhibitor, Corza6 (C6), we demonstrate that the human voltage-gated proton channel (hHv1) is the main pathway for H+ efflux that allows capacitation in sperm and permits sustained reactive oxygen species (ROS) production in white blood cells (WBCs). C6 was identified by a phage-display strategy whereby ∼1 million novel peptides were fabricated on an inhibitor cysteine knot (ICK) scaffold and sorting on purified hHv1 protein. Two C6 peptides bind to each dimeric channel, one on the S3-S4 loop of each voltage sensor domain (VSD). Binding is cooperative with an equilibrium affinity (K d) of ∼1 nM at -50 mV. As expected for a VSD-directed toxin, C6 inhibits by shifting hHv1 activation to more positive voltages, slowing opening and speeding closure, effects that diminish with membrane depolarization.
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21
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Lee M, Bai C, Feliks M, Alhadeff R, Warshel A. On the control of the proton current in the voltage-gated proton channel Hv1. Proc Natl Acad Sci U S A 2018; 115:10321-6. [PMID: 30254162 DOI: 10.1073/pnas.1809766115] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The nature of the action of voltage-activated proton transport proteins is a conundrum of great current interest. Here we approach this issue by exploring the action of Hv1, a voltage-gated proton channel found in different cells in humans and other organisms. Our study focuses on evaluating the free energy of transporting a proton through the channel, as well as the effect of the proton transfer through D112, in both the closed and open channel conformations. It is found that D112 allows a transported proton to bypass the electrostatic barrier of the open channel, while not being able to help in passing the barrier in the closed form. This reflects the change in position of the gating arginine residues relative to D112, upon voltage activation. Significantly, the effect of D112 accounts for the observed trend in selectivity by overcoming the electrostatic barrier at its highest point. Thus, the calculations provide a structure/function correlation for the Hv1 system. The present work also clarifies that the action of Hv1 is not controlled by a Grotthuss mechanism but, as is always the case, by the protein electrostatic potential at the rate-limiting barriers.
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22
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Zhang Q, Padayatti PS, Leung JH. Proton-Translocating Nicotinamide Nucleotide Transhydrogenase: A Structural Perspective. Front Physiol 2017; 8:1089. [PMID: 29312000 PMCID: PMC5742237 DOI: 10.3389/fphys.2017.01089] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/11/2017] [Indexed: 01/07/2023] Open
Abstract
Nicotinamide nucleotide transhydrogenase (TH) is an enzyme complex in animal mitochondria and bacteria that utilizes the electrochemical proton gradient across membranes to drive the production of NADPH. The enzyme plays an important role in maintaining the redox balance of cells with implications in aging and a number of human diseases. TH exists as a homodimer with each protomer containing a proton-translocating transmembrane domain and two soluble nucleotide binding domains that mediate hydride transfer between NAD(H) and NADP(H). The three-domain architecture of TH is conserved across species but polypeptide composition differs substantially. The complex domain coupling mechanism of TH is not fully understood despite extensive biochemical and structural characterizations. Herein the progress is reviewed, focusing mainly on structural findings from 3D crystallization of isolated soluble domains and more recently of the transmembrane domain and the holo-enzyme from Thermus thermophilus. A structural perspective and impeding challenges in further elucidating the mechanism of TH are discussed.
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Affiliation(s)
- Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Pius S Padayatti
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Josephine H Leung
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
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23
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DeCoursey TE. CrossTalk proposal: Proton permeation through H V 1 requires transient protonation of a conserved aspartate in the S1 transmembrane helix. J Physiol 2017; 595:6793-6795. [PMID: 29023793 DOI: 10.1113/jp274495] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Thomas E DeCoursey
- Department of Physiology and Biophysics, Rush University, Chicago, IL, 60612, USA
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24
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Thomaston JL, Woldeyes RA, Nakane T, Yamashita A, Tanaka T, Koiwai K, Brewster AS, Barad BA, Chen Y, Lemmin T, Uervirojnangkoorn M, Arima T, Kobayashi J, Masuda T, Suzuki M, Sugahara M, Sauter NK, Tanaka R, Nureki O, Tono K, Joti Y, Nango E, Iwata S, Yumoto F, Fraser JS, DeGrado WF. XFEL structures of the influenza M2 proton channel: Room temperature water networks and insights into proton conduction. Proc Natl Acad Sci U S A 2017; 114:13357-62. [PMID: 28835537 DOI: 10.1073/pnas.1705624114] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The M2 proton channel of influenza A is a drug target that is essential for the reproduction of the flu virus. It is also a model system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in "wires" inside the channel pore have been proposed to play a role in both the conduction of protons to the four gating His37 residues and the stabilization of multiple positive charges within the channel. To visualize the solvent in the pore of the channel at room temperature while minimizing the effects of radiation damage, data were collected to a resolution of 1.4 Å using an X-ray free-electron laser (XFEL) at three different pH conditions: pH 5.5, pH 6.5, and pH 8.0. Data were collected on the Inwardopen state, which is an intermediate that accumulates at high protonation of the His37 tetrad. At pH 5.5, a continuous hydrogen-bonded network of water molecules spans the vertical length of the channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH 5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The number of ordered pore waters decreases at pH 6.5 and 8.0, where the Inwardopen state is less stable. These studies provide a graphical view of the response of water to a change in charge within a restricted channel environment.
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25
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Bkaily G, Jacques D. Na +-H + exchanger and proton channel in heart failure associated with Becker and Duchenne muscular dystrophies. Can J Physiol Pharmacol 2017; 95:1213-1223. [PMID: 28727929 DOI: 10.1139/cjpp-2017-0265] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Cardiomyopathy is found in patients with Duchenne (DMD) and Becker (BMD) muscular dystrophies, which are linked muscle diseases caused by mutations in the dystrophin gene. Dystrophin defects are not limited to DMD but are also present in mild BMD. The hereditary cardiomyopathic hamster of the UM-X7.1 strain is a particular experimental model of heart failure (HF) leading to early death in muscular dystrophy (dystrophin deficiency and sarcoglycan mutation) and heart disease (δ-sarcoglycan deficiency and dystrophin mutation) in human DMD. Using this model, our previous work showed a defect in intracellular sodium homeostasis before the appearance of any apparent biochemical and histological defects. This was attributed to the continual presence of the fetal slow sodium channel, which was also found to be active in human DMD. Due to muscular intracellular acidosis, the intracellular sodium overload in DMD and BMD was also due to sodium influx through the sodium-hydrogen exchanger NHE-1. Lifetime treatment with an NHE-1 inhibitor prevented intracellular Na+ overload and early death due to HF. Our previous work also showed that another proton transporter, the voltage-gated proton channel (Hv1), exists in many cell types including heart cells and skeletal muscle fibers. The Hv1 could be indirectly implicated in the beneficial effect of blocking NHE-1.
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Affiliation(s)
- Ghassan Bkaily
- Department of Anatomy and Cell Biology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Danielle Jacques
- Department of Anatomy and Cell Biology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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26
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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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27
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Padayatti PS, Leung JH, Mahinthichaichan P, Tajkhorshid E, Ishchenko A, Cherezov V, Soltis SM, Jackson JB, Stout CD, Gennis RB, Zhang Q. Critical Role of Water Molecules in Proton Translocation by the Membrane-Bound Transhydrogenase. Structure 2017. [PMID: 28648609 DOI: 10.1016/j.str.2017.05.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The nicotinamide nucleotide transhydrogenase (TH) is an integral membrane enzyme that uses the proton-motive force to drive hydride transfer from NADH to NADP+ in bacteria and eukaryotes. Here we solved a 2.2-Å crystal structure of the TH transmembrane domain (Thermus thermophilus) at pH 6.5. This structure exhibits conformational changes of helix positions from a previous structure solved at pH 8.5, and reveals internal water molecules interacting with residues implicated in proton translocation. Together with molecular dynamics simulations, we show that transient water flows across a narrow pore and a hydrophobic "dry" region in the middle of the membrane channel, with key residues His42α2 (chain A) being protonated and Thr214β (chain B) displaying a conformational change, respectively, to gate the channel access to both cytoplasmic and periplasmic chambers. Mutation of Thr214β to Ala deactivated the enzyme. These data provide new insights into the gating mechanism of proton translocation in TH.
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Affiliation(s)
- Pius S Padayatti
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Josephine H Leung
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Paween Mahinthichaichan
- Department of Biochemistry, University of Illinois Urbana-Champaign, Champaign, IL 61801, USA
| | - Emad Tajkhorshid
- Department of Biochemistry, University of Illinois Urbana-Champaign, Champaign, IL 61801, USA
| | - Andrii Ishchenko
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA
| | - Vadim Cherezov
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA; Laboratory for Structural Biology of GPCRs, Moscow Institute of Physics and Technology, Dolgoprudny 141701, Russia
| | - S Michael Soltis
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - J Baz Jackson
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - C David Stout
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Robert B Gennis
- Department of Biochemistry, University of Illinois Urbana-Champaign, Champaign, IL 61801, USA
| | - Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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28
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Mignot T, Nöllmann M. New insights into the function of a versatile class of membrane molecular motors from studies of Myxococcus xanthus surface (gliding) motility. Microb Cell 2017; 4:98-100. [PMID: 28357395 PMCID: PMC5349195 DOI: 10.15698/mic2017.03.563] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cell motility is a central function of living cells, as it empowers colonization
of new environmental niches, cooperation, and development of multicellular
organisms. This process is achieved by complex yet precise energy-consuming
machineries in both eukaryotes and bacteria. Bacteria move on surfaces using
extracellular appendages such as flagella and pili but also by a less-understood
process called gliding motility. During this process, rod-shaped bacteria move
smoothly along their long axis without any visible morphological changes besides
occasional bending. For this reason, the molecular mechanism of gliding motility
and its origin have long remained a complete mystery. An important breakthrough
in the understanding of gliding motility came from single cell and genetic
studies in the delta-proteobacterium Myxococcus xanthus. These
early studies revealed, for the first time, the existence of bacterial Focal
Adhesion complexes (FA). FAs are formed at the bacterial pole and rapidly move
towards the opposite cell pole. Their attachment to the underlying surface is
linked to cell propulsion, in a process similar to the rearward translocation of
actomyosin complexes in Apicomplexans. The protein machinery that forms at FAs
was shown to contain up to seventeen proteins predicted to localize in all
layers of the bacterial cell envelope, the cytosolic face, the inner membrane
(IM), the periplasmic space and the outer membrane (OM). Among these proteins, a
proton-gated channel at the inner membrane was identified as the molecular
motor. Thus, thrust generation requires the transduction of traction forces
generated at the inner membrane through the cell envelope beyond the rigid
barrier of the bacterial peptidoglycan.
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Affiliation(s)
- Tâm Mignot
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS -Aix Marseille University UMR7283, 31 chemin Joseph Aiguier, 13009 Marseille, France
| | - Marcelo Nöllmann
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Montpellier University, 29 rue de Navacelles, 34090 Montpellier, France
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29
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Wang J, Li F, Ma C. Recent progress in designing inhibitors that target the drug-resistant M2 proton channels from the influenza A viruses. Biopolymers 2016; 104:291-309. [PMID: 25663018 DOI: 10.1002/bip.22623] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/24/2015] [Indexed: 12/15/2022]
Abstract
Influenza viruses are the causative agents for seasonal influenza, which results in thousands of deaths and millions of hospitalizations each year. Moreover, sporadic transmission of avian or swan influenza viruses to humans often leads to an influenza pandemic, as there is no preimmunity in the human body to fight against such novel strains. The metastable genome of the influenza viruses, coupled with the reassortment of different strains from a wide range of host origins, leads to the continuous evolution of the influenza virus diversity. Such characteristics of influenza viruses present a grand challenge in devising therapeutic strategies to combat influenza virus infection. This review summarizes recent progress in designing small molecule inhibitors that target the drug-resistant influenza A virus M2 proton channels and highlights the contribution of mechanistic studies of proton conductance to drug discovery. The lessons learned throughout the course of M2 drug discovery might provide insights for designing inhibitors that target other therapeutically important ion channels.
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Affiliation(s)
- Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721.,BIO5 Institute, University of Arizona, Tucson, AZ, 85721
| | - Fang Li
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721
| | - Chunlong Ma
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721
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30
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Thomaston JL, DeGrado WF. Crystal structure of the drug-resistant S31N influenza M2 proton channel. Protein Sci 2016; 25:1551-4. [PMID: 27082171 DOI: 10.1002/pro.2937] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 04/11/2016] [Accepted: 04/12/2016] [Indexed: 01/23/2023]
Abstract
The M2 protein is a small proton channel found in the influenza A virus that is necessary for viral replication. The M2 channel is the target of a class of drugs called the adamantanes, which block the channel pore and prevent the virus from replicating. In recent decades mutations have arisen in M2 that prevent the adamantanes from binding to the channel pore, with the most prevalent of these mutations being S31N. Here we report the first crystal structure of the S31N mutant crystallized using lipidic cubic phase crystallization techniques and solved to 1.59 Å resolution. The Asn31 residues point directly into the center of the channel pore and form a hydrogen-bonded network that disrupts the drug-binding site. Ordered waters in the channel pore form a continuous hydrogen bonding network from Gly34 to His37.
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Affiliation(s)
- Jessica L Thomaston
- Department of Pharmaceutical Chemistry, University of California San Francisco, 555 Mission Bay Blvd. (S) Room 452V, San Francisco, California, 94158
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California San Francisco, 555 Mission Bay Blvd. (S) Room 452V, San Francisco, California, 94158
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31
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Ye W, Chang RB, Bushman JD, Tu YH, Mulhall EM, Wilson CE, Cooper AJ, Chick WS, Hill-Eubanks DC, Nelson MT, Kinnamon SC, Liman ER. The K+ channel KIR2.1 functions in tandem with proton influx to mediate sour taste transduction. Proc Natl Acad Sci U S A 2016; 113:E229-38. [PMID: 26627720 DOI: 10.1073/pnas.1514282112] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Sour taste is detected by a subset of taste cells on the tongue and palate epithelium that respond to acids with trains of action potentials. Entry of protons through a Zn(2+)-sensitive proton conductance that is specific to sour taste cells has been shown to be the initial event in sour taste transduction. Whether this conductance acts in concert with other channels sensitive to changes in intracellular pH, however, is not known. Here, we show that intracellular acidification generates excitatory responses in sour taste cells, which can be attributed to block of a resting K(+) current. We identify KIR2.1 as the acid-sensitive K(+) channel in sour taste cells using pharmacological and RNA expression profiling and confirm its contribution to sour taste with tissue-specific knockout of the Kcnj2 gene. Surprisingly, acid sensitivity is not conferred on sour taste cells by the specific expression of Kir2.1, but by the relatively small magnitude of the current, which makes the cells exquisitely sensitive to changes in intracellular pH. Consistent with a role of the K(+) current in amplifying the sensory response, entry of protons through the Zn(2+)-sensitive conductance produces a transient block of the KIR2.1 current. The identification in sour taste cells of an acid-sensitive K(+) channel suggests a mechanism for amplification of sour taste and may explain why weak acids that produce intracellular acidification, such as acetic acid, taste more sour than strong acids.
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32
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Li Q, Shen R, Treger JS, Wanderling SS, Milewski W, Siwowska K, Bezanilla F, Perozo E. Resting state of the human proton channel dimer in a lipid bilayer. Proc Natl Acad Sci U S A 2015; 112:E5926-35. [PMID: 26443860 PMCID: PMC4640771 DOI: 10.1073/pnas.1515043112] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The voltage-gated proton channel Hv1 plays a critical role in the fast proton translocation that underlies a wide range of physiological functions, including the phagocytic respiratory burst, sperm motility, apoptosis, and metastatic cancer. Both voltage activation and proton conduction are carried out by a voltage-sensing domain (VSD) with strong similarity to canonical VSDs in voltage-dependent cation channels and enzymes. We set out to determine the structural properties of membrane-reconstituted human proton channel (hHv1) in its resting conformation using electron paramagnetic resonance spectroscopy together with biochemical and computational methods. We evaluated existing structural templates and generated a spectroscopically constrained model of the hHv1 dimer based on the Ci-VSD structure at resting state. Mapped accessibility data revealed deep water penetration through hHv1, suggesting a highly focused electric field, comprising two turns of helix along the fourth transmembrane segment. This region likely contains the H(+) selectivity filter and the conduction pore. Our 3D model offers plausible explanations for existing electrophysiological and biochemical data, offering an explicit mechanism for voltage activation based on a one-click sliding helix conformational rearrangement.
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Affiliation(s)
- Qufei Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Jeremy S Treger
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Sherry S Wanderling
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Wieslawa Milewski
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Klaudia Siwowska
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637
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33
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Chen Z, Peng Y, Liu F, Le Z, Zhu J, Shen G, Zhang D, Wen M, Xiao S, Liu CP, Lu Y, Li H. Hierarchical Nanostructured WO3 with Biomimetic Proton Channels and Mixed Ionic-Electronic Conductivity for Electrochemical Energy Storage. Nano Lett 2015; 15:6802-8. [PMID: 26406938 DOI: 10.1021/acs.nanolett.5b02642] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Protein channels in biologic systems can effectively transport ions such as proton (H(+)), sodium (Na(+)), and calcium (Ca(+)) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO3 (h-WO3) which can conduct both protons and electrons. This mixed protonic-electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from h-WO3 nanorods. Such a unique h-WO3 contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the h-WO3 with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50,000 cycles without capacitance decay), thus providing a new platform for a broad range of applications.
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Affiliation(s)
- Zheng Chen
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
| | - Yiting Peng
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
- Shanghai University of Electric Power , Shanghai 200090, China
| | - Fang Liu
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
| | - Zaiyuan Le
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
| | - Jian Zhu
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University , Shanghai 200234, China
| | - Gurong Shen
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
| | - Dieqing Zhang
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University , Shanghai 200234, China
| | - Meicheng Wen
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University , Shanghai 200234, China
| | - Shuning Xiao
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University , Shanghai 200234, China
| | - Chi-Ping Liu
- Department of Materials Science and Engineering, University of California , Los Angeles, California 90095, United States
| | - Yunfeng Lu
- Department of Chemical and Biomolecular Engineering, University of California , Los Angeles, California 90095, United States
| | - Hexing Li
- Shanghai University of Electric Power , Shanghai 200090, China
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34
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Okochi Y, Aratani Y, Adissu HA, Miyawaki N, Sasaki M, Suzuki K, Okamura Y. The voltage-gated proton channel Hv1/VSOP inhibits neutrophil granule release. J Leukoc Biol 2015; 99:7-19. [PMID: 25990245 DOI: 10.1189/jlb.3hi0814-393r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 03/19/2015] [Indexed: 01/09/2023] Open
Abstract
Neutrophil granule exocytosis is crucial for host defense and inflammation. Neutrophils contain 4 types of granules, the exocytotic release of which is differentially regulated. This exocytosis is known to be driven by diverse mediators, including calcium and nucleotides, but the precise molecular mechanism remains largely unknown. We show in the present study that voltage-gated proton (Hv) channels are necessary for the proper release of azurophilic granules in neutrophils. On activation of NADPH oxidase by PMA and IgG, neutrophils derived from Hvcn1 gene knockout mouse exhibited greater secretion of MPO and elastase than WT cells. In contrast, release of LTF enriched in specific granules was not enhanced in these cells. The excess release of azurophilic granules in Hv1/VSOP-deficient neutrophils was suppressed by inhibiting NADPH oxidase activity and, in part, by valinomycin, a potassium ionophore. In addition, Hv1/VSOP-deficient mice exhibited more severe lung inflammation after intranasal Candida albicans infection than WT mice. These findings suggest that the Hv channel acts to specifically dampen the release of azurophilic granules through, in part, the suppression of increased positive charges at the plasma membrane accompanied by the activation of NADPH oxidase in neutrophils.
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Affiliation(s)
- Yoshifumi Okochi
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Yasuaki Aratani
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Hibret A Adissu
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Nana Miyawaki
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Mari Sasaki
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Kazuo Suzuki
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Yasushi Okamura
- *Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Kanagawa, Japan; Physiology & Experimental Medicine, Hospital for Sick Children, Ontario, Canada; Department of Bioactive Molecules and Bacteriology, National Institute of Infectious Diseases, Tokyo, Japan; and Inflammation Program, Department of Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan; and Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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35
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Abstract
The identification of the HVCN1 gene, encoding the only mammalian voltage-gated proton channel, prompted a number of studies on how proton channels affect cellular functions. As their expression is mainly restricted to immune cells, it is not surprising that proton channels regulate different aspects of immune responses. In this review, I will examine the current knowledge of voltage-gated proton channels in both innate and adaptive responses and assess the remaining outstanding questions.
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Affiliation(s)
- Melania Capasso
- Centre for Cancer and Inflammation, Barts Cancer Institute, Queen Mary University of London, London, UK
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36
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Nakamura S, Minamino T, Kami-Ike N, Kudo S, Namba K. Effect of the MotB(D33N) mutation on stator assembly and rotation of the proton-driven bacterial flagellar motor. Biophysics (Nagoya-shi) 2014; 10:35-41. [PMID: 27493496 PMCID: PMC4629662 DOI: 10.2142/biophysics.10.35] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 05/28/2014] [Indexed: 01/21/2023] Open
Abstract
The bacterial flagellar motor generates torque by converting the energy of proton translocation through the transmembrane proton channel of the stator complex formed by MotA and MotB. The MotA/B complex is thought to be anchored to the peptidoglycan (PG) layer through the PG-binding domain of MotB to act as the stator. The stator units dynamically associate with and dissociate from the motor during flagellar motor rotation, and an electrostatic interaction between MotA and a rotor protein FliG is required for efficient stator assembly. However, the association and dissociation mechanism of the stator units still remains unclear. In this study, we analyzed the speed fluctuation of the flagellar motor of Salmonella enterica wild-type cells carrying a plasmid encoding a nonfunctional stator complex, MotA/B(D33N), which lost the proton conductivity. The wild-type motor rotated stably but the motor speed fluctuated considerably when the expression level of MotA/B(D33N) was relatively high compared to MotA/B. Rapid accelerations and decelerations were frequently observed. A quantitative analysis of the speed fluctuation and a model simulation suggested that the MotA/B(D33N) stator retains the ability to associate with the motor at a low affinity but dissociates more rapidly than the MotA/B stator. We propose that the stator dissociation process depends on proton translocation through the proton channel.
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Affiliation(s)
- Shuichi Nakamura
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Tohru Minamino
- Graduate School of Frontier Bioscience, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Nobunori Kami-Ike
- Graduate School of Frontier Bioscience, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Seishi Kudo
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Keiichi Namba
- Graduate School of Frontier Bioscience, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan; Riken Quantitative Biology Center, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
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37
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Castillo DJ, Nakamura S, Morimoto YV, Che YS, Kami-Ike N, Kudo S, Minamino T, Namba K. The C-terminal periplasmic domain of MotB is responsible for load-dependent control of the number of stators of the bacterial flagellar motor. Biophysics (Nagoya-shi) 2013; 9:173-81. [PMID: 27493556 PMCID: PMC4629673 DOI: 10.2142/biophysics.9.173] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 12/07/2013] [Indexed: 12/29/2022] Open
Abstract
The bacterial flagellar motor is made of a rotor and stators. In Salmonella it is thought that about a dozen MotA/B complexes are anchored to the peptidoglycan layer around the motor through the C-terminal peptidoglycan-binding domain of MotB to become active stators as well as proton channels. MotB consists of 309 residues, forming a single transmembrane helix (30–50), a stalk (51–100) and a C-terminal peptidoglycan-binding domain (101–309). Although the stalk is dispensable for torque generation by the motor, it is required for efficient motor performance. Residues 51 to 72 prevent premature proton leakage through the proton channel prior to stator assembly into the motor. However, the role of residues 72–100 remains unknown. Here, we analyzed the torque-speed relationship of the MotB(Δ72–100) motor. At a low speed near stall, this mutant motor produced torque at the wild-type level. Unlike the wild-type motor, however, torque dropped off drastically by slight decrease in external load and then showed a slow exponential decay over a wide range of load by its further reduction. Since it is known that the stator is a mechano-sensor and that the number of active stators changes in a load-dependent manner, we interpreted this unusual torque-speed relationship as anomaly in load-dependent control of the number of active stators. The results suggest that residues 72–100 of MotB is required for proper load-dependent control of the number of active stators around the rotor.
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Affiliation(s)
- David J Castillo
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shuichi Nakamura
- Department of Applied Physics, Tohoku University, 6-6-05 Aoba, Aramakiaza, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Yusuke V Morimoto
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan; Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
| | - Yong-Suk Che
- Department of Frontier Bioscience, Hosei University, 3-7-2 Kajino-cho, Koganei, Tokyo 184-8584, Japan
| | - Nobunori Kami-Ike
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Seishi Kudo
- Department of Applied Physics, Tohoku University, 6-6-05 Aoba, Aramakiaza, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Tohru Minamino
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Keiichi Namba
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan; Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
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38
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Zhou HX. Mechanistic insight into the h(2)o/d (2)o isotope effect in the proton transport of the influenza virus m2 protein. J Membr Biol 2011; 244:93-6. [PMID: 22041938 PMCID: PMC3237009 DOI: 10.1007/s00232-011-9402-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 10/15/2011] [Indexed: 11/27/2022]
Abstract
The M2 proton channel is essential for the replication of the flu virus and is a known drug target. The functional mechanism of channel activation and conductance is key to both the basic biology of viral replication and the design of drugs that can withstand mutations. A quantitative model was previously developed for calculating the rate of proton transport through the M2 channel. The permeant proton was assumed to diffuse to the pore, obligatorily bind to the His37 tetrad, and then dissociate and be released to either side of the tetrad. Here the model is used to calculate the effect of a change in solvent from H(2)O to D(2)O on the rate of proton transport. The solvent substitution affects two parameters in the model: the proton diffusion constant and the pK (a) for proton binding to the His37 tetrad. When the known effects on these two parameters are included, the deuterium isotope effect calculated from the model is in quantitatively agreement with experimental results. This strict test of the theoretical model provides strong support for the hypothesis that the permeant proton obligatorily binds to and then unbinds from the His37 tetrad. This putatively essential role of the His37 tetrad in the functional mechanism of the M2 channel makes it a promising target for designing mutation-tolerant drugs.
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Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, USA.
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39
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Pielak RM, Chou JJ. Solution NMR structure of the V27A drug resistant mutant of influenza A M2 channel. Biochem Biophys Res Commun 2010; 401:58-63. [PMID: 20833142 PMCID: PMC3215091 DOI: 10.1016/j.bbrc.2010.09.008] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 09/04/2010] [Indexed: 10/19/2022]
Abstract
The M2 protein of influenza A virus forms a proton-selective channel that is required for viral replication. It is the target of the anti-influenza drugs, amantadine and rimantadine. Widespread drug resistant mutants, however, has greatly compromised the effectiveness of these drugs. Here, we report the solution NMR structure of the highly pathogenic, drug resistant mutant V27A. The structure reveals subtle structural differences from wildtype that maybe linked to drug resistance. The V27A mutation significantly decreases hydrophobic packing between the N-terminal ends of the transmembrane helices, which explains the looser, more dynamic tetrameric assembly. The weakened channel assembly can resist drug binding either by destabilizing the rimantadine-binding pocket at Asp44, in the case of the allosteric inhibition model, or by reducing hydrophobic contacts with amantadine in the pore, in the case of the pore-blocking model. Moreover, the V27A structure shows a substantially increased channel opening at the N-terminal end, which may explain the faster proton conduction observed for this mutant. Furthermore, due to the high quality NMR data recorded for the V27A mutant, we were able to determine the structured region connecting the channel domain to the C-terminal amphipathic helices that was not determined in the wildtype structure. The new structural data show that the amphipathic helices are packed much more closely to the channel domain and provide new insights into the proton transfer pathway.
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Affiliation(s)
- Rafal M. Pielak
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
- Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA 02115, USA
| | - James J. Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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40
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Abstract
The history of research on voltage-gated proton channels is recounted, from their proposed existence in dinoflagellates by Hastings in 1972 and their demonstration in snail neurons by Thomas and Meech in 1982 to the discovery in 2006 (after a decade of controversy) of genes that unequivocally code for proton channels. Voltage-gated proton channels are perfectly selective for protons, conduct deuterons half as well, and the conductance is strongly temperature dependent. These properties are consistent with a conduction mechanism involving hydrogen-bonded-chain transfer, in which the selectivity filter is a titratable amino acid residue. Channel opening is regulated stringently by pH such that only outward current is normally activated. Main functions of proton channels include acid extrusion from cells and charge compensation for the electrogenic activity of the phagocyte NADPH oxidase. Genetic approaches hold the promise of rapid progress in the near future.
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Affiliation(s)
- T E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, 1750 W. Harrison, Chicago, Illinois 60612, USA.
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41
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Petheo GL, Girardin NC, Goossens N, Molnár GZ, Demaurex N. Role of nucleotides and phosphoinositides in the stability of electron and proton currents associated with the phagocytic NADPH oxidase. Biochem J 2006; 400:431-8. [PMID: 16842239 PMCID: PMC1698601 DOI: 10.1042/bj20060578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 07/07/2006] [Accepted: 07/14/2006] [Indexed: 11/17/2022]
Abstract
The phagocytic NADPH oxidase (phox) moves electrons across cell membranes to kill microbes. The activity of this lethal enzyme is tightly regulated, but the mechanisms that control phox inactivation are poorly understood for lack of appropriate assays. The phox generates measurable electron currents, I(e), that are associated with inward proton currents, I(H). To study the inactivation of the phox and of its associated proton channel, we determined which soluble factors can stabilize I(e) (induced by the addition of NADPH) and I(H) (initiated by small depolarizing voltage steps) in inside-out patches from PMA-activated human eosinophils. I(e) decayed rapidly in the absence of nucleotides (tau approximately 6 min) and was maximally stabilized by the combined addition of 5 mM ATP and 50 microM of the non-hydrolysable GTP analogue GTP[S] (guanosine 5'-[gamma-thio]triphosphate) (tau approximately 57 min), but not by either ATP or GTP[S] alone. I(H) also decayed rapidly and was stabilized by the ATP/GTP[S] mixture, but maximal stabilization of I(H) required further addition of 25 muM PI(3,4)P2 (phosphoinositide 3,4-bisphosphate) to the cytosolic side of the patch. PI(3,4)P2 had no effect on I(e) and its stabilizing effect on I(H) could not be mimicked by other phosphoinositides. Reducing the ATP concentration below millimolar levels decreased I(H) stability, an effect that was not prevented by phosphatase inhibitors but by the non-hydrolysable ATP analogue ATP[S] (adenosine 5'-[gamma-thio]triphosphate). Our data indicate that the assembled phox complex is very stable in eosinophil membranes if both ATP and GTP[S] are present, but inactivates within minutes if one of the nucleotides is removed. Stabilization of the phox-associated proton channel in a highly voltage-sensitive conformation does not appear to involve phosphorylation but ATP binding, and requires not only ATP and GTP[S] but also PI(3,4)P2, a protein known to anchor the cytosolic phox subunit p47(phox) to the plasma membrane.
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Key Words
- cytochrome
- eosinophil
- nadph oxidase
- patch-clamp
- proton channel
- phosphoinositide
- atp[s], adenosine 5′-[γ-thio]triphosphate
- cgd, chronic granulomatous disease
- dpi, diphenyleneiodonium
- gap, gtpase-activating protein
- gtp[s], guanosine 5′-[γ-thio]triphosphate
- hv1/vsop, voltage-gated hydrogen channel 1/voltage sensor domain-only protein
- pi(3,4)p2, phosphoinositide 3,4-bisphosphate
- pip, phosphoinositide phosphate
- px domain, phox homology domain
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Affiliation(s)
- Gábor L Petheo
- Department of Cell Physiology and Metabolism, University of Geneva Medical School, 1 Michel-Servet, CH-1211 Geneva 4, Switzerland.
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42
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Abstract
The voltage sensor of the Shaker potassium channel is comprised mostly of positively charged residues in the putative fourth transmembrane segment, S4 (Aggarwal, S.K., and R. MacKinnon. 1996. Neuron. 16:1169-1177; Seoh, S.-A., D. Sigg, D.M. Papazian, and F. Bezanilla. 1996. Neuron. 16:1159-1167). Movement of the voltage sensor in response to a change in the membrane potential was examined indirectly by measuring how the accessibilities of residues in and around the sensor change with voltage. Each basic residue in the S4 segment was individually replaced with a histidine. If the histidine tag is part of the voltage sensor, then the gating charge displaced by the voltage sensor will include the histidine charge. Accessibility of the histidine to the bulk solution was therefore monitored as pH-dependent changes in the gating currents evoked by membrane potential pulses. Histidine scanning mutagenesis has several advantages over other similar techniques. Since histidine accessibility is detected by labeling with solution protons, very confined local environments can be resolved and labeling introduces minimal interference of voltage sensor motion. After histidine replacement of either residue K374 or R377, there was no titration of the gating currents with internal or external pH, indicating that these residues do not move in the transmembrane electric field or that they are always inaccessible. Histidine replacement of residues R365, R368, and R371, on the other hand, showed that each of these residues traverses entirely from internal exposure at hyperpolarized potentials to external exposure at depolarized potentials. This translocation enables the histidine to transport protons across the membrane in the presence of a pH gradient. In the case of 371H, depolarization drives the histidine to a position that forms a proton pore. Kinetic models of titrateable voltage sensors that account for proton transport and conduction are presented. Finally, the results presented here are incorporated into existing information to propose a model of voltage sensor movement and structure.
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Affiliation(s)
- Dorine M. Starace
- Department of Physiology and Department of Anesthesiology, University of California Los Angeles School of Medicine, Los Angeles, California 90095
| | - Francisco Bezanilla
- Department of Physiology and Department of Anesthesiology, University of California Los Angeles School of Medicine, Los Angeles, California 90095
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43
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DeCoursey TE, Cherny VV, Zhou W, Thomas LL. Simultaneous activation of NADPH oxidase-related proton and electron currents in human neutrophils. Proc Natl Acad Sci U S A 2000; 97:6885-9. [PMID: 10823889 PMCID: PMC18770 DOI: 10.1073/pnas.100047297] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Generation of reactive oxygen species by the NADPH oxidase complex is an important bactericidal weapon of phagocytes. Phorbol myristate acetate (PMA) is a potent agonist for this "respiratory burst" in human neutrophils. Although stoichiometric H(+) efflux occurs during the respiratory burst, efforts to stimulate voltage-gated H(+) channels by PMA in whole-cell patch-clamped phagocytes have been unsuccessful. We have used a modification of the permeabilized-patch configuration that allows control of intracellular pH and preserves second-messenger pathways. Using this method, we show that PMA dramatically enhances and alters voltage-gated proton currents in human neutrophils. PMA produced four alterations in H(+) current properties, each of which increases the H(+) current at any given voltage: (i) a 40-mV negative shift in the H(+) conductance-voltage (g(H)-V) relationship; (ii) faster activation [smaller activation time constant (tau(act))] during depolarizing pulses; (iii) slower deactivation [larger deactivation time constant (tau(tail))] on repolarization; and (iv) a larger maximum H(+) conductance (g(H, max)). Inward current that directly reflects electron transport by NADPH oxidase was also activated by PMA stimulation. The identity of this electron current was confirmed by its sensitivity to diphenylene iodinium, an inhibitor of NADPH oxidase. Diphenylene iodinium also reversed the slowing of tau(tail) with a time course paralleling the inhibition of electron current. However, the amplitudes of H(+) and electron currents activated by PMA were not correlated. A complex interaction between NADPH oxidase and voltage-gated proton channels is indicated. The data suggest that PMA stimulation modulates preexisting H(+) channels rather than inducing a new H(+) channel.
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Affiliation(s)
- T E DeCoursey
- Departments of Molecular Biophysics and Physiology and Immunology/Microbiology, Rush Presbyterian St. Luke's Medical Center, Chicago, IL 60612, USA.
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