1
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Kawai T, Morioka S, Miyata H, Andriani RT, Akter S, Toma G, Nakagawa T, Oyama Y, Iida-Norita R, Sasaki J, Watanabe M, Sakimura K, Ikawa M, Sasaki T, Okamura Y. The significance of electrical signals in maturing spermatozoa for phosphoinositide regulation through voltage-sensing phosphatase. Nat Commun 2024; 15:7289. [PMID: 39181879 PMCID: PMC11344830 DOI: 10.1038/s41467-024-51755-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 08/14/2024] [Indexed: 08/27/2024] Open
Abstract
Voltage-sensing phosphatase (VSP) exhibits voltage-dependent phosphatase activity toward phosphoinositides. VSP generates a specialized phosphoinositide environment in mammalian sperm flagellum. However, the voltage-sensing mechanism of VSP in spermatozoa is not yet characterized. Here, we found that VSP is activated during sperm maturation, indicating that electric signals in immature spermatozoa are essential. Using a heterologous expression system, we show the voltage-sensing property of mouse VSP (mVSP). The voltage-sensing threshold of mVSP is approximately -30 mV, which is sensitive enough to activate mVSP in immature spermatozoa. We also report several knock-in mice in which we manipulate the voltage-sensitivity or electrochemical coupling of mVSP. Notably, the V312R mutant, with a minor voltage-sensitivity change, exhibits abnormal sperm motility after, but not before, capacitation. Additionally, the V312R mutant shows a significant change in the acyl-chain profile of phosphoinositide. Our findings suggest that electrical signals during sperm maturation are crucial for establishing the optimal phosphoinositide environment in spermatozoa.
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Affiliation(s)
- Takafumi Kawai
- Graduate School of Medicine, Osaka University, Suita, Japan.
| | - Shin Morioka
- Department of Biochemical Pathophysiology/Lipid Biology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Haruhiko Miyata
- Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | | | - Sharmin Akter
- Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Physiology, Bangladesh Agricultural University, Mymensingh, Bangladesh
| | - Gabriel Toma
- Center for Medical Research and Education, Osaka University, Suita, Japan
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Tatsuya Nakagawa
- Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Yuki Oyama
- Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Rie Iida-Norita
- Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Junko Sasaki
- Department of Biochemical Pathophysiology/Lipid Biology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | | | - Kenji Sakimura
- Brain Research Institute, Niigata University, Niigata, Japan
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Suita, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Takehiko Sasaki
- Department of Biochemical Pathophysiology/Lipid Biology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yasushi Okamura
- Graduate School of Medicine, Osaka University, Suita, Japan
- Graduate School of Frontier Bioscience, Osaka University, Suita, Japan
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2
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Yu Y, Zhang L, Li B, Fu Z, Brohawn SG, Isacoff EY. Coupling sensor to enzyme in the voltage sensing phosphatase. Nat Commun 2024; 15:6409. [PMID: 39080263 PMCID: PMC11289409 DOI: 10.1038/s41467-024-50319-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 07/03/2024] [Indexed: 08/02/2024] Open
Abstract
Voltage-sensing phosphatases (VSPs) dephosphorylate phosphoinositide (PIP) signaling lipids in response to membrane depolarization. VSPs possess an S4-containing voltage sensor domain (VSD), resembling that of voltage-gated cation channels, and a lipid phosphatase domain (PD). The mechanism by which voltage turns on enzyme activity is unclear. Structural analysis and modeling suggest several sites of VSD-PD interaction that could couple voltage sensing to catalysis. Voltage clamp fluorometry reveals voltage-driven rearrangements in three sites implicated earlier in enzyme activation-the VSD-PD linker, gating loop and R loop-as well as the N-terminal domain, which has not yet been explored. N-terminus mutations perturb both rearrangements in the other segments and enzyme activity. Our results provide a model for a dynamic assembly by which S4 controls the catalytic site.
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Affiliation(s)
- Yawei Yu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Lin Zhang
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Baobin Li
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
- Zhongshan Hospital, Institute for Translational Brain Research, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
| | - Zhu Fu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Stephen G Brohawn
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
- The California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California, USA
| | - Ehud Y Isacoff
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA.
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA.
- The California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California, USA.
- MBIB Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
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3
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Rayaprolu V, Miettinen HM, Baker WD, Young VC, Fisher M, Mueller G, Rankin WO, Kelley JT, Ratzan WJ, Leong LM, Davisson JA, Baker BJ, Kohout SC. Hydrophobic residues in S1 modulate enzymatic function and voltage sensing in voltage-sensing phosphatase. J Gen Physiol 2024; 156:e202313467. [PMID: 38771271 PMCID: PMC11109755 DOI: 10.1085/jgp.202313467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 12/13/2023] [Accepted: 05/07/2024] [Indexed: 05/22/2024] Open
Abstract
The voltage-sensing domain (VSD) is a four-helix modular protein domain that converts electrical signals into conformational changes, leading to open pores and active enzymes. In most voltage-sensing proteins, the VSDs do not interact with one another, and the S1-S3 helices are considered mainly scaffolding, except in the voltage-sensing phosphatase (VSP) and the proton channel (Hv). To investigate its contribution to VSP function, we mutated four hydrophobic amino acids in S1 to alanine (F127, I131, I134, and L137), individually or in combination. Most of these mutations shifted the voltage dependence of activity to higher voltages; however, not all substrate reactions were the same. The kinetics of enzymatic activity were also altered, with some mutations significantly slowing down dephosphorylation. The voltage dependence of VSD motions was consistently shifted to lower voltages and indicated a second voltage-dependent motion. Additionally, none of the mutations broke the VSP dimer, indicating that the S1 impact could stem from intra- and/or intersubunit interactions. Lastly, when the same mutations were introduced into a genetically encoded voltage indicator, they dramatically altered the optical readings, making some of the kinetics faster and shifting the voltage dependence. These results indicate that the S1 helix in VSP plays a critical role in tuning the enzyme's conformational response to membrane potential transients and influencing the function of the VSD.
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Affiliation(s)
- Vamseedhar Rayaprolu
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Heini M. Miettinen
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William D. Baker
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Victoria C. Young
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, USA
| | - Matthew Fisher
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Gwendolyn Mueller
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William O. Rankin
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - John T. Kelley
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - William J. Ratzan
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Lee Min Leong
- Division of Bio-Medical Science and Technology, KIST School, Brain Science Institute, Korea Institute of Science and Technology (KIST), Korea University of Science and Technology (UST), Seoul, South Korea
| | - Joshua A. Davisson
- Department of Cell Biology and Neuroscience, Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA
| | - Bradley J. Baker
- Division of Bio-Medical Science and Technology, KIST School, Brain Science Institute, Korea Institute of Science and Technology (KIST), Korea University of Science and Technology (UST), Seoul, South Korea
| | - Susy C. Kohout
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, USA
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4
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Rühl P, Nair AG, Gawande N, Dehiwalage SNCW, Münster L, Schönherr R, Heinemann SH. An Ultrasensitive Genetically Encoded Voltage Indicator Uncovers the Electrical Activity of Non-Excitable Cells. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2307938. [PMID: 38526185 PMCID: PMC11132041 DOI: 10.1002/advs.202307938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 02/10/2024] [Indexed: 03/26/2024]
Abstract
Most animal cell types are classified as non-excitable because they do not generate action potentials observed in excitable cells, such as neurons and muscle cells. Thus, resolving voltage signals in non-excitable cells demands sensors with exceptionally high voltage sensitivity. In this study, the ultrabright, ultrasensitive, and calibratable genetically encoded voltage sensor rEstus is developed using structure-guided engineering. rEstus is most sensitive in the resting voltage range of non-excitable cells and offers a 3.6-fold improvement in brightness change for fast voltage spikes over its precursor ASAP3. Using rEstus, it is uncovered that the membrane voltage in several non-excitable cell lines (A375, HEK293T, MCF7) undergoes spontaneous endogenous alterations on a second to millisecond timescale. Correlation analysis of these optically recorded voltage alterations provides a direct, real-time readout of electrical cell-cell coupling, showing that visually connected A375 and HEK293T cells are also largely electrically connected, while MCF7 cells are only weakly coupled. The presented work provides enhanced tools and methods for non-invasive voltage imaging in living cells and demonstrates that spontaneous endogenous membrane voltage alterations are not limited to excitable cells but also occur in a variety of non-excitable cell types.
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Affiliation(s)
- Philipp Rühl
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Anagha G Nair
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Namrata Gawande
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Sassrika N C W Dehiwalage
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Lukas Münster
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Roland Schönherr
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
| | - Stefan H Heinemann
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, D-07745, Jena, Germany
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5
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Rayaprolu V, Miettinen HM, Baker W, Young VC, Fisher M, Mueller G, Rankin WO, Kelley JJ, Ratzan W, Leong LM, Davisson JA, Baker BJ, Kohout SC. S1 hydrophobic residues modulate voltage sensing phosphatase enzymatic function and voltage sensing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.27.573443. [PMID: 38234747 PMCID: PMC10793425 DOI: 10.1101/2023.12.27.573443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
The voltage sensing domain (VSD) is a four-helix modular protein domain that converts electrical signals into conformational changes, leading to open pores and active enzymes. In most voltage sensing proteins, the VSDs do not interact with one another and the S1-S3 helices are considered mainly as scaffolding. The two exceptions are the voltage sensing phosphatase (VSP) and the proton channel (Hv). VSP is a voltage-regulated enzyme and Hvs are channels that only have VSDs. To investigate the S1 contribution to VSP function, we individually mutated four hydrophobic amino acids in S1 to alanine (F127, I131, I134 and L137). We also combined these mutations to generate quadruple mutation designated S1-Q. Most of these mutations shifted the voltage dependence of activity to higher voltages though interestingly, not all substrate reactions were the same. The kinetics of enzymatic activity were also altered with some mutations significantly slowing down dephosphorylation. The voltage dependence of VSD motions were consistently shifted to lower voltages and indicated a second voltage dependent motion. Co-immunoprecipitation demonstrated that none of the mutations broke the VSP dimer indicating that the S1 impact could stem from intrasubunit and/or intersubunit interactions. Lastly, when the same alanine mutations were introduced into a genetically encoded voltage indicator, they dramatically altered the optical readings, making some of the kinetics faster and shifting the voltage dependence. These results indicate that the S1 helix in VSP plays a critical role in tuning the enzymes conformational response to membrane potential transients and influencing the function of the VSD.
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6
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Guo SC, Shen R, Roux B, Dinner AR. Dynamics of activation in the voltage-sensing domain of Ciona intestinalis phosphatase Ci-VSP. Nat Commun 2024; 15:1408. [PMID: 38360718 PMCID: PMC10869754 DOI: 10.1038/s41467-024-45514-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 01/25/2024] [Indexed: 02/17/2024] Open
Abstract
The Ciona intestinalis voltage-sensing phosphatase (Ci-VSP) is a membrane protein containing a voltage-sensing domain (VSD) that is homologous to VSDs from voltage-gated ion channels responsible for cellular excitability. Previously published crystal structures of Ci-VSD in putative resting and active conformations suggested a helical-screw voltage sensing mechanism in which the S4 helix translocates and rotates to enable exchange of salt-bridge partners, but the microscopic details of the transition between the resting and active conformations remained unknown. Here, by combining extensive molecular dynamics simulations with a recently developed computational framework based on dynamical operators, we elucidate the microscopic mechanism of the resting-active transition at physiological membrane potential. Sparse regression reveals a small set of coordinates that distinguish intermediates that are hidden from electrophysiological measurements. The intermediates arise from a noncanonical helical-screw mechanism in which translocation, rotation, and side-chain movement of the S4 helix are only loosely coupled. These results provide insights into existing experimental and computational findings on voltage sensing and suggest ways of further probing its mechanism.
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Affiliation(s)
- Spencer C Guo
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA
- James Franck Institute, The University of Chicago, Chicago, IL, 60637, USA
| | - Rong Shen
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Benoît Roux
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA.
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.
| | - Aaron R Dinner
- Department of Chemistry, The University of Chicago, Chicago, IL, 60637, USA.
- James Franck Institute, The University of Chicago, Chicago, IL, 60637, USA.
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.
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7
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Kuwabara MF, Haddad BG, Lenz-Schwab D, Hartmann J, Longo P, Huckschlag BM, Fuß A, Questino A, Berger TK, Machtens JP, Oliver D. Elevator-like movements of prestin mediate outer hair cell electromotility. Nat Commun 2023; 14:7145. [PMID: 37932294 PMCID: PMC10628124 DOI: 10.1038/s41467-023-42489-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 10/12/2023] [Indexed: 11/08/2023] Open
Abstract
The outstanding acuity of the mammalian ear relies on cochlear amplification, an active mechanism based on the electromotility (eM) of outer hair cells. eM is a piezoelectric mechanism generated by little-understood, voltage-induced conformational changes of the anion transporter homolog prestin (SLC26A5). We used a combination of molecular dynamics (MD) simulations and biophysical approaches to identify the structural dynamics of prestin that mediate eM. MD simulations showed that prestin samples a vast conformational landscape with expanded (ES) and compact (CS) states beyond previously reported prestin structures. Transition from CS to ES is dominated by the translational-rotational movement of prestin's transport domain, akin to elevator-type substrate translocation by related solute carriers. Reversible transition between CS and ES states was supported experimentally by cysteine accessibility scanning, cysteine cross-linking between transport and scaffold domains, and voltage-clamp fluorometry (VCF). Our data demonstrate that prestin's piezoelectric dynamics recapitulate essential steps of a structurally conserved ion transport cycle.
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Affiliation(s)
- Makoto F Kuwabara
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Bassam G Haddad
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany
| | - Dominik Lenz-Schwab
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Julia Hartmann
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Piersilvio Longo
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany
| | - Britt-Marie Huckschlag
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Anneke Fuß
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Annalisa Questino
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Thomas K Berger
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany
| | - Jan-Philipp Machtens
- Institute of Biological Information Processing (IBI-1), Molekular- und Zellphysiologie, and JARA-HPC, Forschungszentrum Jülich, Jülich, Germany.
- Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany.
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037, Marburg, Germany.
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps University, Marburg, Germany.
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, Marburg, Germany.
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8
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Catacuzzeno L, Conti F, Franciolini F. Fifty years of gating currents and channel gating. J Gen Physiol 2023; 155:e202313380. [PMID: 37410612 PMCID: PMC10324510 DOI: 10.1085/jgp.202313380] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/12/2023] [Accepted: 06/02/2023] [Indexed: 07/08/2023] Open
Abstract
We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.
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Affiliation(s)
- Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Franco Conti
- Department of Physics, University of Genova, Genova, Italy
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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9
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Abstract
The genetically encoded fluorescent sensors convert chemical and physical signals into light. They are powerful tools for the visualisation of physiological processes in living cells and freely moving animals. The fluorescent protein is the reporter module of a genetically encoded biosensor. In this study, we first review the history of the fluorescent protein in full emission spectra on a structural basis. Then, we discuss the design of the genetically encoded biosensor. Finally, we briefly review several major types of genetically encoded biosensors that are currently widely used based on their design and molecular targets, which may be useful for the future design of fluorescent biosensors.
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Affiliation(s)
- Minji Wang
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
| | - Yifan Da
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
| | - Yang Tian
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
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10
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Paixao IC, Mizutani N, Matsuda M, Andriani RT, Kawai T, Nakagawa A, Okochi Y, Okamura Y. Role of K364 next to the active site cysteine in voltage-dependent phosphatase activity of Ci-VSP. Biophys J 2023:S0006-3495(23)00038-3. [PMID: 36680342 DOI: 10.1016/j.bpj.2023.01.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 10/16/2022] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
Voltage-sensing phosphatase (VSP) consists of the voltage sensor domain (VSD) similar to that of voltage-gated ion channels and the cytoplasmic phosphatase region with remarkable similarity to the phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Membrane depolarization activates VSD, leading to dephosphorylation of three species of phosphoinositides (phosphatidylinositol phosphates (PIPs)), PI(3,4,5)P3, PI(4,5)P2, and PI(3,4)P2. VSP dephosphorylates 3- and 5-phosphate of PIPs, unlike PTEN, which shows rigid 3-phosphate specificity. In this study, a bioinformatics search showed that some mammals have VSP orthologs with amino acid diversity in the active center motif, Cx5R, which is highly conserved among protein tyrosine phosphatases and PTEN-related phosphatases; lysine next to the active site cysteine in the Cx5R motif was substituted for methionine in VSP orthologs of Tasmanian devil, koala, and prairie deer mouse, and leucine in opossum. Since lysine at the corresponding site in PTEN is known to be critical for enzyme activities, we attempted to address the significance of amino acid diversity among VSP orthologs at this site. K364 was changed to different amino acids in sea squirt VSP (Ci-VSP), and voltage-dependent phosphatase activity in Xenopus oocyte was studied using fluorescent probes for PI(4,5)P2 and PI(3,4)P2. All mutants retained both 5-phosphatase and 3-phosphatase activity, indicating that lysine at this site is dispensable for 3-phosphatase activity, unlike PTEN. Notably, K364M mutant showed increased activity both of 5-phosphatase and 3-phosphatase compared with the wild type (WT). It also showed slower kinetics of voltage sensor motion. Malachite green assay of K364M mutant did not show significant difference of phosphatase activity from WT, suggesting tighter interaction between substrate binding and voltage sensing. Mutation corresponding to K364M in the zebrafish VSP led to enhanced voltage-dependent dephosphorylation of PI(4,5)P2. Further studies will provide clues to understanding of substrate preference in PIPs phosphatases as well as to customization of a molecular tool.
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Affiliation(s)
- Ian Costa Paixao
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Natsuki Mizutani
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Makoto Matsuda
- Department Oncogene Research, Research Institute for Microbial Diseases, Osaka University, Suita, Japan; Laboratory for Supramolecular Crystallography, Institute for Protein Research, Osaka University, Suita, Japan
| | - Rizki Tsari Andriani
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan; Graduate School of Medicine, Osaka University JSPS International Research Fellow, Suita, Japan
| | - Takafumi Kawai
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Atsushi Nakagawa
- Laboratory for Supramolecular Crystallography, Institute for Protein Research, Osaka University, Suita, Japan
| | - Yoshifumi Okochi
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan.
| | - Yasushi Okamura
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Japan.
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11
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Mechanism of voltage gating in the voltage-sensing phosphatase Ci-VSP. Proc Natl Acad Sci U S A 2022; 119:e2206649119. [PMID: 36279472 PMCID: PMC9636939 DOI: 10.1073/pnas.2206649119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conformational changes in voltage-sensing domains (VSDs) are driven by the transmembrane electric field acting on the protein charges. Yet, the overall energetics and detailed mechanism of this process are not fully understood. Here, we determined free energy and displacement charge landscapes as well as the major conformations visited during a complete functional gating cycle in the isolated VSD of the phosphatase Ci-VSP (Ci-VSD) comprising four transmembrane helices (segments S1 to S4). Molecular dynamics simulations highlight the extent of S4 movements. In addition to the crystallographically determined activated “Up” and resting “Down” states, the simulations predict two Ci-VSD conformations: a deeper resting state (“down-minus”) and an extended activated (“up-plus”) state. These additional conformations were experimentally probed via systematic cysteine mutagenesis with metal-ion bridges and the engineering of proton conducting mutants at hyperpolarizing voltages. The present results show that these four states are visited sequentially in a stepwise manner during voltage activation, each step translocating one arginine or the equivalent of ∼1
e
0
across the membrane electric field, yielding a transfer of ∼3
e
0
charges in total for the complete process.
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12
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Mizutani N, Kawanabe A, Jinno Y, Narita H, Yonezawa T, Nakagawa A, Okamura Y. Interaction between S4 and the phosphatase domain mediates electrochemical coupling in voltage-sensing phosphatase (VSP). Proc Natl Acad Sci U S A 2022; 119:e2200364119. [PMID: 35733115 PMCID: PMC9245683 DOI: 10.1073/pnas.2200364119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 05/13/2022] [Indexed: 11/18/2022] Open
Abstract
Voltage-sensing phosphatase (VSP) consists of a voltage sensor domain (VSD) and a cytoplasmic catalytic region (CCR), which is similar to phosphatase and tensin homolog (PTEN). How the VSD regulates the innate enzyme component of VSP remains unclear. Here, we took a combined approach that entailed the use of electrophysiology, fluorometry, and structural modeling to study the electrochemical coupling in Ciona intestinalis VSP. We found that two hydrophobic residues at the lowest part of S4 play an essential role in the later transition of VSD-CCR coupling. Voltage clamp fluorometry and disulfide bond locking indicated that S4 and its neighboring linker move as one helix (S4-linker helix) and approach the hydrophobic spine in the CCR, a structure located near the cell membrane and also conserved in PTEN. We propose that the hydrophobic spine operates as a hub for translating an electrical signal into a chemical one in VSP.
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Affiliation(s)
- Natsuki Mizutani
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Akira Kawanabe
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yuka Jinno
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hirotaka Narita
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Tomoko Yonezawa
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Atsushi Nakagawa
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yasushi Okamura
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
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13
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Priest MF, Lee EE, Bezanilla F. Tracking the movement of discrete gating charges in a voltage-gated potassium channel. eLife 2021; 10:58148. [PMID: 34779404 PMCID: PMC8635975 DOI: 10.7554/elife.58148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/08/2021] [Indexed: 01/18/2023] Open
Abstract
Positively charged amino acids respond to membrane potential changes to drive voltage sensor movement in voltage-gated ion channels, but determining the displacements of voltage sensor gating charges has proven difficult. We optically tracked the movement of the two most extracellular charged residues (R1 and R2) in the Shaker potassium channel voltage sensor using a fluorescent positively charged bimane derivative (qBBr) that is strongly quenched by tryptophan. By individually mutating residues to tryptophan within the putative pathway of gating charges, we observed that the charge motion during activation is a rotation and a tilted translation that differs between R1 and R2. Tryptophan-induced quenching of qBBr also indicates that a crucial residue of the hydrophobic plug is linked to the Cole-Moore shift through its interaction with R1. Finally, we show that this approach extends to additional voltage-sensing membrane proteins using the Ciona intestinalis voltage-sensitive phosphatase (CiVSP).
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Affiliation(s)
- Michael F Priest
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Elizabeth El Lee
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Francisco Bezanilla
- Committee on Neurobiology and Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States.,Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, United States
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14
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Timsit Y, Grégoire SP. Towards the Idea of Molecular Brains. Int J Mol Sci 2021; 22:ijms222111868. [PMID: 34769300 PMCID: PMC8584932 DOI: 10.3390/ijms222111868] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 02/06/2023] Open
Abstract
How can single cells without nervous systems perform complex behaviours such as habituation, associative learning and decision making, which are considered the hallmark of animals with a brain? Are there molecular systems that underlie cognitive properties equivalent to those of the brain? This review follows the development of the idea of molecular brains from Darwin’s “root brain hypothesis”, through bacterial chemotaxis, to the recent discovery of neuron-like r-protein networks in the ribosome. By combining a structural biology view with a Bayesian brain approach, this review explores the evolutionary labyrinth of information processing systems across scales. Ribosomal protein networks open a window into what were probably the earliest signalling systems to emerge before the radiation of the three kingdoms. While ribosomal networks are characterised by long-lasting interactions between their protein nodes, cell signalling networks are essentially based on transient interactions. As a corollary, while signals propagated in persistent networks may be ephemeral, networks whose interactions are transient constrain signals diffusing into the cytoplasm to be durable in time, such as post-translational modifications of proteins or second messenger synthesis. The duration and nature of the signals, in turn, implies different mechanisms for the integration of multiple signals and decision making. Evolution then reinvented networks with persistent interactions with the development of nervous systems in metazoans. Ribosomal protein networks and simple nervous systems display architectural and functional analogies whose comparison could suggest scale invariance in information processing. At the molecular level, the significant complexification of eukaryotic ribosomal protein networks is associated with a burst in the acquisition of new conserved aromatic amino acids. Knowing that aromatic residues play a critical role in allosteric receptors and channels, this observation suggests a general role of π systems and their interactions with charged amino acids in multiple signal integration and information processing. We think that these findings may provide the molecular basis for designing future computers with organic processors.
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Affiliation(s)
- Youri Timsit
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM110, 13288 Marseille, France
- Research Federation for the Study of Global Ocean Systems Ecology and Evolution, FR2022/Tara GOSEE, 3 rue Michel-Ange, 75016 Paris, France
- Correspondence:
| | - Sergeant-Perthuis Grégoire
- Institut de Mathématiques de Jussieu—Paris Rive Gauche (IMJ-PRG), UMR 7586, CNRS-Université Paris Diderot, 75013 Paris, France;
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15
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Tsutsui H, Mizutani N, Okamura Y. Engineering voltage sensing phosphatase (VSP). Methods Enzymol 2021; 654:85-114. [PMID: 34120726 DOI: 10.1016/bs.mie.2021.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Voltage sensing phosphatase (VSP), consists of a voltage sensor domain (VSD) like that found in voltage-gated ion channels and a phosphoinositide (PIP) phosphatase region exhibiting remarkable structural similarity to a tumor suppressor enzyme, PTEN. Membrane depolarization activates the enzyme activity through tight coupling between the VSD and enzyme region. The VSD of VSP has a unique nature; it is a self-contained module that can be transferred to other proteins, conferring voltage sensitivity. Thanks to this nature, numerous versions of gene-encoded voltage indicators (GEVIs) have been developed through combination of a fluorescent protein with the VSD of VSP. In addition, VSP itself can also serve as a tool to alter PIP levels in cells. Cellular levels of PIPs, PI(4,5)P2 in particular, can be acutely and transiently reduced using a simple voltage protocol after heterologous expression of VSP. Recent progress in our understanding of the molecular structure and mechanisms underlying VSP facilitates optimization of its molecular properties for its use as a molecular tool.
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Affiliation(s)
- Hidekazu Tsutsui
- School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Nomi, Ishikawa, Japan.
| | - Natsuki Mizutani
- Graduate School of Medicine, Japan Advanced Institute of Science and Technology (JAIST), Osaka University, Suita, Osaka, Japan
| | - Yasushi Okamura
- Graduate School of Medicine, Japan Advanced Institute of Science and Technology (JAIST), Osaka University, Suita, Osaka, Japan.
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16
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Chen C, Ulbrich MH. Zinc-Finger-Mediated Labeling Reveals the Stoichiometry of Membrane Proteins. ACS NANO 2020; 14:4134-4140. [PMID: 32208669 DOI: 10.1021/acsnano.9b08865] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Characterizing interactions of proteins is pivotal for understanding their function. Recently, single-molecule imaging-based methods have proven useful for directly testing the stoichiometry of multi-subunit protein complexes. A limiting factor is the labeling of proteins with multiple spectrally discernible tags and low background. Here, we describe the use of zinc-finger (ZF)-mediated protein labeling for single-molecule imaging studies in living cells. A DNA-binding ZF is fused to the protein of interest and labeled by a DNA probe carrying the specific ZF binding sequence and an organic dye. Nonspecific binding is minimized by injecting the DNA/dye conjugate into the cell. With a reproducible labeling efficiency of 20%, we developed an approach to deduce the multiplicity of the subunits in a protein complex from the overall degree of labeling. We were able to confirm the fixed 2:2 assembly of the NMDA receptor in a three-color single-molecule imaging setup and reject alternative stoichiometries. Due to the modular design and small size of ZF proteins, this approach will allow the analysis of more complicated protein interaction patterns to understand the assembly rules for large protein complexes.
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Affiliation(s)
- Changsheng Chen
- School of Life Sciences, Co-innovation Center of Neuroregeneration, Key Laboratory of Neurogeneration of Jiangsu and MOE, Nantong University, 226019 Jiangsu, China
- Internal Medicine IV, Department of Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
- Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Maximilian H Ulbrich
- Internal Medicine IV, Department of Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
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17
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Papp F, Lomash S, Szilagyi O, Babikow E, Smith J, Chang TH, Bahamonde MI, Toombes GES, Swartz KJ. TMEM266 is a functional voltage sensor regulated by extracellular Zn 2. eLife 2019; 8:42372. [PMID: 30810529 PMCID: PMC6392501 DOI: 10.7554/elife.42372] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/13/2019] [Indexed: 12/15/2022] Open
Abstract
Voltage-activated ion channels contain S1-S4 domains that sense membrane voltage and control opening of ion-selective pores, a mechanism that is crucial for electrical signaling. Related S1-S4 domains have been identified in voltage-sensitive phosphatases and voltage-activated proton channels, both of which lack associated pore domains. hTMEM266 is a protein of unknown function that is predicted to contain an S1-S4 domain, along with partially structured cytoplasmic termini. Here we show that hTMEM266 forms oligomers, undergoes both rapid (µs) and slow (ms) structural rearrangements in response to changes in voltage, and contains a Zn2+ binding site that can regulate the slow conformational transition. Our results demonstrate that the S1-S4 domain in hTMEM266 is a functional voltage sensor, motivating future studies to identify cellular processes that may be regulated by the protein. The ability of hTMEM266 to respond to voltage on the µs timescale may be advantageous for designing new genetically encoded voltage indicators.
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Affiliation(s)
- Ferenc Papp
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.,MTA-DE-NAP B Ion Channel Structure-Function Research Group, Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Suvendu Lomash
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Orsolya Szilagyi
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Erika Babikow
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Jaime Smith
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Tsg-Hui Chang
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Maria Isabel Bahamonde
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Gilman Ewan Stephen Toombes
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Kenton Jon Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
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18
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Kannan M, Vasan G, Pieribone VA. Optimizing Strategies for Developing Genetically Encoded Voltage Indicators. Front Cell Neurosci 2019; 13:53. [PMID: 30863283 PMCID: PMC6399427 DOI: 10.3389/fncel.2019.00053] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 02/04/2019] [Indexed: 01/23/2023] Open
Abstract
Genetically encoded optical indicators of neuronal activity enable unambiguous recordings of input-output activity patterns from identified cells in intact circuits. Among them, genetically encoded voltage indicators (GEVIs) offer additional advantages over calcium indicators as they are direct sensors of membrane potential and can adeptly report subthreshold events and hyperpolarization. Here, we outline the major GEVI designs and give an account of properties that need to be carefully optimized during indicator engineering. While designing the ideal GEVI, one should keep in mind aspects such as membrane localization, signal size, signal-to-noise ratio, kinetics and voltage dependence of optical responses. Using ArcLight and derivatives as prototypes, we delineate how a probe should be optimized for the former properties and developed along other areas in a need-based manner. Finally, we present an overview of the GEVI engineering process and lend an insight into their discovery, delivery and diagnosis.
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Affiliation(s)
- Madhuvanthi Kannan
- The John B. Pierce Laboratory, New Haven, CT, United States.,Department of Cellular and Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Ganesh Vasan
- The John B. Pierce Laboratory, New Haven, CT, United States.,Department of Cellular and Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Vincent A Pieribone
- The John B. Pierce Laboratory, New Haven, CT, United States.,Department of Cellular and Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Neuroscience, Yale School of Medicine, Yale University, New Haven, CT, United States
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19
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Kruse M, Kohout SC, Hille B. Reinterpretation of the substrate specificity of the voltage-sensing phosphatase during dimerization. J Gen Physiol 2019; 151:258-263. [PMID: 30622132 PMCID: PMC6363406 DOI: 10.1085/jgp.201812260] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/17/2018] [Indexed: 11/23/2022] Open
Abstract
Ciona intestinalis voltage-sensing phosphatase (VSP) has lipid 5- and 3-phosphatase activity, but 3-phosphatase is evident only at high VSP concentrations. Using kinetic modeling including endogenous lipid metabolizing enzymes and VSP phosphatase activities, Kruse et al. show how apparent activation of 3-phosphatase at high concentrations arises. Voltage-sensing phosphatases (VSPs) cleave both 3- and 5-phosphates from inositol phospholipids in response to membrane depolarization. When low concentrations of Ciona intestinalis VSP are expressed in Xenopus laevis oocytes, the 5-phosphatase reaction can be observed during large membrane depolarizations. When higher concentrations are expressed, the 5-phosphatase activity is observed with smaller depolarizations, and the 3-phosphatase activity is revealed with strong depolarization. Here we ask whether this apparent induction of 3-phosphatase activity is attributable to the dimerization that has been reported when VSP is expressed at higher concentrations. Using a simple kinetic model, we show that these enzymatic phenomena can be understood as an emergent property of a voltage-dependent enzyme with invariant substrate selectivity operating in the context of endogenous lipid-metabolizing enzymes present in oocytes. Thus, a switch of substrate specificity with dimerization need not be invoked to explain the appearance of 3-phosphatase activity at high VSP concentrations.
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Affiliation(s)
- Martin Kruse
- Department of Biology and Program in Neuroscience, Bates College, Lewiston, ME
| | - Susy C Kohout
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA
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20
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Okamura Y, Kawanabe A, Kawai T. Voltage-Sensing Phosphatases: Biophysics, Physiology, and Molecular Engineering. Physiol Rev 2019; 98:2097-2131. [PMID: 30067160 DOI: 10.1152/physrev.00056.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Voltage-sensing phosphatase (VSP) contains a voltage sensor domain (VSD) similar to that in voltage-gated ion channels, and a phosphoinositide phosphatase region similar to phosphatase and tensin homolog deleted on chromosome 10 (PTEN). The VSP gene is conserved from unicellular organisms to higher vertebrates. Membrane depolarization induces electrical driven conformational rearrangement in the VSD, which is translated into catalytic enzyme activity. Biophysical and structural characterization has revealed details of the mechanisms underlying the molecular functions of VSP. Coupling between the VSD and the enzyme is tight, such that enzyme activity is tuned in a graded fashion to the membrane voltage. Upon VSP activation, multiple species of phosphoinositides are simultaneously altered, and the profile of enzyme activity depends on the history of the membrane potential. VSPs have been the obvious candidate link between membrane potential and phosphoinositide regulation. However, patterns of voltage change regulating VSP in native cells remain largely unknown. This review addresses the current understanding of the biophysical biochemical properties of VSP and provides new insight into the proposed functions of VSP.
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Affiliation(s)
- Yasushi Okamura
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Akira Kawanabe
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
| | - Takafumi Kawai
- Department of Physiology, Laboratory of Integrative Physiology, Graduate School of Medicine, Osaka University , Osaka , Japan ; and Graduate School of Frontier Biosciences, Osaka University , Osaka , Japan
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21
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OKAMURA Y, OKOCHI Y. Molecular mechanisms of coupling to voltage sensors in voltage-evoked cellular signals. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2019; 95:111-135. [PMID: 30853698 PMCID: PMC6541726 DOI: 10.2183/pjab.95.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 01/07/2019] [Indexed: 06/09/2023]
Abstract
The voltage sensor domain (VSD) has long been studied as a unique domain intrinsic to voltage-gated ion channels (VGICs). Within VGICs, the VSD is tightly coupled to the pore-gate domain (PGD) in diverse ways suitable for its specific function in each physiological context, including action potential generation, muscle contraction and relaxation, hormone and neurotransmitter secretion, and cardiac pacemaking. However, some VSD-containing proteins lack a PGD. Voltage-sensing phosphatase contains a cytoplasmic phosphoinositide phosphatase with similarity to phosphatase and tensin homolog (PTEN). Hv1, a voltage-gated proton channel, also lacks a PGD. Within Hv1, the VSD operates as a voltage sensor, gate, and pore for both proton sensing and permeation. Hv1 has a C-terminal coiled coil that mediates dimerization for cooperative gating. Recent progress in the structural biology of VGICs and VSD proteins provides insights into the principles of VSD coupling conserved among these proteins as well as the hierarchy of protein organization for voltage-evoked cell signaling.
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Affiliation(s)
- Yasushi OKAMURA
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
- Graduate School of Frontier Bioscience, Osaka University, Suita, Japan
| | - Yoshifumi OKOCHI
- Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Japan
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22
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Kawanabe A, Hashimoto M, Nishizawa M, Nishizawa K, Narita H, Yonezawa T, Jinno Y, Sakata S, Nakagawa A, Okamura Y. The hydrophobic nature of a novel membrane interface regulates the enzyme activity of a voltage-sensing phosphatase. eLife 2018; 7:41653. [PMID: 30484774 PMCID: PMC6298786 DOI: 10.7554/elife.41653] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 11/28/2018] [Indexed: 01/24/2023] Open
Abstract
Voltage-sensing phosphatases (VSP) contain a voltage sensor domain (VSD) similar to that of voltage-gated ion channels but lack a pore-gate domain. A VSD in a VSP regulates the cytoplasmic catalytic region (CCR). However, the mechanisms by which the VSD couples to the CCR remain elusive. Here we report a membrane interface (named ‘the hydrophobic spine’), which is essential for the coupling of the VSD and CCR. Our molecular dynamics simulations suggest that the hydrophobic spine of Ciona intestinalis VSP (Ci-VSP) provides a hinge-like motion for the CCR through the loose membrane association of the phosphatase domain. Electrophysiological experiments indicate that the voltage-dependent phosphatase activity of Ci-VSP depends on the hydrophobicity and presence of an aromatic ring in the hydrophobic spine. Analysis of conformational changes in the VSD and CCR suggests that the VSP has two states with distinct enzyme activities and that the second transition depends on the hydrophobic spine.
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Affiliation(s)
- Akira Kawanabe
- Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Masaki Hashimoto
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | | | | | - Hirotaka Narita
- Institute for Protein Research, Osaka University, Osaka, Japan
| | - Tomoko Yonezawa
- Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yuka Jinno
- Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Souhei Sakata
- Department of Physiology, Division of Life Sciences, Faculty of Medicine, Osaka Medical College, Osaka, Japan
| | | | - Yasushi Okamura
- Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Osaka, Japan.,Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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23
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Rayaprolu V, Royal P, Stengel K, Sandoz G, Kohout SC. Dimerization of the voltage-sensing phosphatase controls its voltage-sensing and catalytic activity. J Gen Physiol 2018; 150:683-696. [PMID: 29695412 PMCID: PMC5940254 DOI: 10.1085/jgp.201812064] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 03/28/2018] [Indexed: 01/27/2023] Open
Abstract
The Ciona intestinalis voltage-sensing phosphatase (Ci-VSP) was not thought to multimerize. Rayaprolu et al. show that Ci-VSP exists as a dimer and that this interaction lowers the voltage dependence of activation and alters substrate specificity. Multimerization is a key characteristic of most voltage-sensing proteins. The main exception was thought to be the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP). In this study, we show that multimerization is also critical for Ci-VSP function. Using coimmunoprecipitation and single-molecule pull-down, we find that Ci-VSP stoichiometry is flexible. It exists as both monomers and dimers, with dimers favored at higher concentrations. We show strong dimerization via the voltage-sensing domain (VSD) and weak dimerization via the phosphatase domain. Using voltage-clamp fluorometry, we also find that VSDs cooperate to lower the voltage dependence of activation, thus favoring the activation of Ci-VSP. Finally, using activity assays, we find that dimerization alters Ci-VSP substrate specificity such that only dimeric Ci-VSP is able to dephosphorylate the 3-phosphate from PI(3,4,5)P3 or PI(3,4)P2. Our results indicate that dimerization plays a significant role in Ci-VSP function.
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Affiliation(s)
- Vamseedhar Rayaprolu
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT
| | - Perrine Royal
- Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Medicale, iBV, Université Côte d'Azur, Valbonne, France.,Laboratory of Excellence, Ion Channel Science and Therapeutics, Nice, France
| | - Karen Stengel
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT
| | - Guillaume Sandoz
- Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Medicale, iBV, Université Côte d'Azur, Valbonne, France.,Laboratory of Excellence, Ion Channel Science and Therapeutics, Nice, France
| | - Susy C Kohout
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT
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24
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Zhang J, Chen X, Xue Y, Gamper N, Zhang X. Beyond voltage-gated ion channels: Voltage-operated membrane proteins and cellular processes. J Cell Physiol 2018; 233:6377-6385. [PMID: 29667735 DOI: 10.1002/jcp.26555] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 02/20/2018] [Indexed: 12/26/2022]
Abstract
Voltage-gated ion channels were believed to be the only voltage-sensitive proteins in excitable (and some non-excitable) cells for a long time. Emerging evidence indicates that the voltage-operated model is shared by some other transmembrane proteins expressed in both excitable and non-excitable cells. In this review, we summarize current knowledge about voltage-operated proteins, which are not classic voltage-gated ion channels as well as the voltage-dependent processes in cells for which single voltage-sensitive proteins have yet to be identified. Particularly, we will focus on the following. (1) Voltage-sensitive phosphoinositide phosphatases (VSP) with four transmembrane segments homologous to the voltage sensor domain (VSD) of voltage-gated ion channels; VSPs are the first family of proteins, other than the voltage-gated ion channels, for which there is sufficient evidence for the existence of the VSD domain; (2) Voltage-gated proton channels comprising of a single voltage-sensing domain and lacking an identified pore domain; (3) G protein coupled receptors (GPCRs) that mediate the depolarization-evoked potentiation of Ca2+ mobilization; (4) Plasma membrane (PM) depolarization-induced but Ca2+ -independent exocytosis in neurons. (5) Voltage-dependent metabolism of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P2 , PIP2 ) in the PM. These recent discoveries expand our understanding of voltage-operated processes within cellular membranes.
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Affiliation(s)
- Jianping Zhang
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Xingjuan Chen
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.,Beijing Key Laboratory of Diabetes Prevention and Research, Lu He Hospital, Capital Medical University, Beijing, China
| | - Yucong Xue
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Nikita Gamper
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
| | - Xuan Zhang
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
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25
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Zhao R, Li N, Xu J, Li W, Fang X. Quantitative single-molecule study of TGF-β/Smad signaling. Acta Biochim Biophys Sin (Shanghai) 2018; 50:51-59. [PMID: 29190315 DOI: 10.1093/abbs/gmx121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 11/03/2017] [Indexed: 12/31/2022] Open
Abstract
TGF-β/Smad signaling pathway triggers diverse cellular responses among different cell types and environmental conditions. Quantitative analysis of protein-protein interactions involved in TGF-β/Smad signaling is demanded for understanding the molecular mechanism of this signaling pathway. Live-cell single-molecule microcopy with high spatiotemporal resolution is a new tool to monitor key molecular events in a real-time manner. In this review, we mainly presented the recent work on the quantitative characterization of TGF-β/Smad signaling proteins by single-molecule method, and showed how it enabled us to obtain new insights about this canonical signaling process.
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Affiliation(s)
- Rong Zhao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Nan Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiachao Xu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenhui Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaohong Fang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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26
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Abstract
Fluorescent protein-based biosensors are indispensable molecular tools for life science research. The invention and development of high-fidelity biosensors for a particular molecule or molecular event often catalyze important scientific breakthroughs. Understanding the structural and functional organization of brain activities remain a subject for which optical sensors are in desperate need and of growing interest. Here, we review genetically encoded fluorescent sensors for imaging neuronal activities with a focus on the design principles and optimizations of various sensors. New bioluminescent sensors useful for deep-tissue imaging are also discussed. By highlighting the protein engineering efforts and experimental applications of these sensors, we can consequently analyze factors influencing their performance. Finally, we remark on how future developments can fill technological gaps and lead to new discoveries.
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Affiliation(s)
- Zhijie Chen
- California Institute for Quantitative Biosciences, QB3, University of California, Berkeley, CA 94720, USA
| | - Tan M. Truong
- Center for Membrane and Cell Physiology, and Biomedical Sciences (BIMS) Graduate Program, University of Virginia, Charlottesville, VA 22908, USA
| | - Hui-wang Ai
- Center for Membrane and Cell Physiology, and Biomedical Sciences (BIMS) Graduate Program, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
- Correspondence:
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27
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Savalli N, Pantazis A, Sigg D, Weiss JN, Neely A, Olcese R. The α2δ-1 subunit remodels CaV1.2 voltage sensors and allows Ca2+ influx at physiological membrane potentials. J Gen Physiol 2017; 148:147-59. [PMID: 27481713 PMCID: PMC4969795 DOI: 10.1085/jgp.201611586] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/30/2016] [Indexed: 12/30/2022] Open
Abstract
Voltage-sensing domains (VSDs) in voltage-gated calcium channels sense the potential difference across membranes and interact with the pore to open it. Savalli et al. find that the accessory subunit α2δ-1 increases the sensitivity of VSDs I–III and also their efficiency of coupling to the pore. Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel’s voltage dependence. The accessory α2δ-1 subunit is known to facilitate CaV1.2 voltage-dependent activation, but the underlying mechanism is unknown. In this study, using voltage clamp fluorometry, we track the activation of the four individual VSDs in a human L-type CaV1.2 channel consisting of α1C and β3 subunits. We find that, without α2δ-1, the channel complex displays a right-shifted voltage dependence such that currents mainly develop at nonphysiological membrane potentials because of very weak VSD–pore interactions. The presence of α2δ-1 facilitates channel activation by increasing the voltage sensitivity (i.e., the effective charge) of VSDs I–III. Moreover, the α2δ-1 subunit also makes VSDs I–III more efficient at opening the channel by increasing the coupling energy between VSDs II and III and the pore, thus allowing Ca influx within the range of physiological membrane potentials.
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Affiliation(s)
- Nicoletta Savalli
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | | | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Neely
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
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28
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Sakata S, Matsuda M, Kawanabe A, Okamura Y. Domain-to-domain coupling in voltage-sensing phosphatase. Biophys Physicobiol 2017; 14:85-97. [PMID: 28744425 PMCID: PMC5515349 DOI: 10.2142/biophysico.14.0_85] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 05/10/2017] [Indexed: 01/12/2023] Open
Abstract
Voltage-sensing phosphatase (VSP) consists of a transmembrane voltage sensor and a cytoplasmic enzyme region. The enzyme region contains the phosphatase and C2 domains, is structurally similar to the tumor suppressor phosphatase PTEN, and catalyzes the dephosphorylation of phosphoinositides. The transmembrane voltage sensor is connected to the phosphatase through a short linker region, and phosphatase activity is induced upon membrane depolarization. Although the detailed molecular characteristics of the voltage sensor domain and the enzyme region have been revealed, little is known how these two regions are coupled. In addition, it is important to know whether mechanism for coupling between the voltage sensor domain and downstream effector function is shared among other voltage sensor domain-containing proteins. Recent studies in which specific amino acid sites were genetically labeled using a fluorescent unnatural amino acid have enabled detection of the local structural changes in the cytoplasmic region of Ciona intestinalis VSP that occur with a change in membrane potential. The results of those studies provide novel insight into how the enzyme activity of the cytoplasmic region of VSP is regulated by the voltage sensor domain.
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Affiliation(s)
- Souhei Sakata
- Department of Physiology, Division of Life Sciences, Faculty of Medicine, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan
| | - Makoto Matsuda
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Akira Kawanabe
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yasushi Okamura
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.,Graduate School of Frontier Bioscience, Osaka University
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29
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Pathak MM, Tran T, Hong L, Joós B, Morris CE, Tombola F. The Hv1 proton channel responds to mechanical stimuli. J Gen Physiol 2016; 148:405-418. [PMID: 27799320 PMCID: PMC5089936 DOI: 10.1085/jgp.201611672] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/22/2016] [Indexed: 12/21/2022] Open
Abstract
The voltage-gated proton channel, Hv1, is expressed in tissues throughout the body and plays important roles in pH homeostasis and regulation of NADPH oxidase. Hv1 operates in membrane compartments that experience strong mechanical forces under physiological or pathological conditions. In microglia, for example, Hv1 activity is potentiated by cell swelling and causes an increase in brain damage after stroke. The channel complex consists of two proton-permeable voltage-sensing domains (VSDs) linked by a cytoplasmic coiled-coil domain. Here, we report that these VSDs directly respond to mechanical stimuli. We find that membrane stretch facilitates Hv1 channel opening by increasing the rate of activation and shifting the steady-state activation curve to less depolarized potentials. In the presence of a transmembrane pH gradient, membrane stretch alone opens the channel without the need for strong depolarizations. The effect of membrane stretch persists for several minutes after the mechanical stimulus is turned off, suggesting that the channel switches to a "facilitated" mode in which opening occurs more readily and then slowly reverts to the normal mode observed in the absence of membrane stretch. Conductance simulations with a six-state model recapitulate all the features of the channel's response to mechanical stimulation. Hv1 mechanosensitivity thus provides a mechanistic link between channel activation in microglia and brain damage after stroke.
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Affiliation(s)
- Medha M Pathak
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697
| | - Truc Tran
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697
| | - Liang Hong
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697
| | - Béla Joós
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | | | - Francesco Tombola
- Department of Physiology and Biophysics, University of California, Irvine, CA 92697
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30
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Abstract
Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels.
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Affiliation(s)
- Carlos A Villalba-Galea
- a Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy & Health Sciences , University of the Pacific , Stockton , CA , USA
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31
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Rosasco MG, Gordon SE, Bajjalieh SM. Characterization of the Functional Domains of a Mammalian Voltage-Sensitive Phosphatase. Biophys J 2016; 109:2480-2491. [PMID: 26682807 DOI: 10.1016/j.bpj.2015.11.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 10/27/2015] [Accepted: 11/03/2015] [Indexed: 12/12/2022] Open
Abstract
Voltage-sensitive phosphatases (VSPs) are proteins that directly couple changes in membrane electrical potential to inositol lipid phosphatase activity. VSPs thus couple two signaling pathways that are critical for cellular functioning. Although a number of nonmammalian VSPs have been characterized biophysically, mammalian VSPs are less well understood at both the physiological and biophysical levels. In this study, we aimed to address this gap in knowledge by determining whether the VSP from mouse, Mm-VSP, is expressed in the brain and contains a functional voltage-sensing domain (VSD) and a phosphatase domain. We report that Mm-VSP is expressed in neurons and is developmentally regulated. To address whether the functions of the VSD and phosphatase domain are retained in Mm-VSP, we took advantage of the modular nature of these domains and expressed each independently as a chimeric protein in a heterologous expression system. We found that the Mm-VSP VSD, fused to a viral potassium channel, was able to drive voltage-dependent gating of the channel pore. The Mm-VSP phosphatase domain, fused to the VSD of a nonmammalian VSP, was also functional: activation resulted in PI(4,5)P2 depletion that was sufficient to inhibit the PI(4,5)P2-regulated KCNQ2/3 channels. While testing the functionality of the VSD and phosphatase domain, we observed slight differences between the activities of Mm-VSP-based chimeras and those of nonmammalian VSPs. Although the properties of VSP chimeras may not completely reflect the properties of native VSPs, the differences we observed in voltage-sensing and phosphatase activity provide a starting point for future experiments to investigate the function of Mm-VSP and other mammalian VSPs. In conclusion, our data reveal that both the VSD and the lipid phosphatase domain of Mm-VSP are functional, indicating that Mm-VSP likely plays an important role in mouse neurophysiology.
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Affiliation(s)
- Mario G Rosasco
- Department of Pharmacology, University of Washington, Seattle, Washington; Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Sandra M Bajjalieh
- Department of Pharmacology, University of Washington, Seattle, Washington.
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32
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Latty SL, Felce JH, Weimann L, Lee SF, Davis SJ, Klenerman D. Referenced Single-Molecule Measurements Differentiate between GPCR Oligomerization States. Biophys J 2016; 109:1798-806. [PMID: 26536257 PMCID: PMC4643199 DOI: 10.1016/j.bpj.2015.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 08/25/2015] [Accepted: 09/08/2015] [Indexed: 11/24/2022] Open
Abstract
The extent to which Rhodopsin family G-protein-coupled receptors (GPCRs) form invariant oligomers is contentious. Recent single-molecule fluorescence imaging studies mostly argue against the existence of constitutive receptor dimers and instead suggest that GPCRs only dimerize transiently, if at all. However, whether or not even transient dimers exist is not always clear due to difficulties in unambiguously distinguishing genuine interactions from chance colocalizations, particularly with respect to short-lived events. Previous single-molecule studies have depended critically on calculations of chance colocalization rates and/or comparison with unfixed control proteins whose diffusional behavior may or may not differ from that of the test receptor. Here, we describe a single-molecule imaging assay that 1) utilizes comparisons with well-characterized control proteins, i.e., the monomer CD86 and the homodimer CD28, and 2) relies on cell fixation to limit artifacts arising from differences in the distribution and diffusion of test proteins versus these controls. The improved assay reliably reports the stoichiometry of the Glutamate-family GPCR dimer, γ-amino butyric acid receptor b2, whereas two Rhodopsin-family GPCRs, β2-adrenergic receptor and mCannR2, exhibit colocalization levels comparable to those of CD86 monomers, strengthening the case against invariant GPCR oligomerization.
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Affiliation(s)
- Sarah L Latty
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - James H Felce
- Radcliffe Department of Clinical Medicine and Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Laura Weimann
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Steven F Lee
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Simon J Davis
- Radcliffe Department of Clinical Medicine and Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
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33
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Simple scheme of lipid enzyme can explain complex lives of phosphoinositides. Proc Natl Acad Sci U S A 2016; 113:7012-4. [DOI: 10.1073/pnas.1607427113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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34
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Grafting voltage and pharmacological sensitivity in potassium channels. Cell Res 2016; 26:935-45. [PMID: 27174053 DOI: 10.1038/cr.2016.57] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 03/04/2016] [Accepted: 03/29/2016] [Indexed: 11/08/2022] Open
Abstract
A classical voltage-gated ion channel consists of four voltage-sensing domains (VSDs). However, the roles of each VSD in the channels remain elusive. We developed a GVTDT (Graft VSD To Dimeric TASK3 channels that lack endogenous VSDs) strategy to produce voltage-gated channels with a reduced number of VSDs. TASK3 channels exhibit a high host tolerance to VSDs of various voltage-gated ion channels without interfering with the intrinsic properties of the TASK3 selectivity filter. The constructed channels, exemplified by the channels grafted with one or two VSDs from Kv7.1 channels, exhibit classical voltage sensitivity, including voltage-dependent opening and closing. Furthermore, the grafted Kv7.1 VSD transfers the potentiation activity of benzbromarone, an activator that acts on the VSDs of the donor channels, to the constructed channels. Our study indicates that one VSD is sufficient to voltage-dependently gate the pore and provides new insight into the roles of VSDs.
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35
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Kim DM, Nimigean CM. Voltage-Gated Potassium Channels: A Structural Examination of Selectivity and Gating. Cold Spring Harb Perspect Biol 2016; 8:a029231. [PMID: 27141052 PMCID: PMC4852806 DOI: 10.1101/cshperspect.a029231] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Voltage-gated potassium channels play a fundamental role in the generation and propagation of the action potential. The discovery of these channels began with predictions made by early pioneers, and has culminated in their extensive functional and structural characterization by electrophysiological, spectroscopic, and crystallographic studies. With the aid of a variety of crystal structures of these channels, a highly detailed picture emerges of how the voltage-sensing domain reports changes in the membrane electric field and couples this to conformational changes in the activation gate. In addition, high-resolution structural and functional studies of K(+) channel pores, such as KcsA and MthK, offer a comprehensive picture on how selectivity is achieved in K(+) channels. Here, we illustrate the remarkable features of voltage-gated potassium channels and explain the mechanisms used by these machines with experimental data.
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Affiliation(s)
- Dorothy M Kim
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York 10065
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medical College, New York, New York 10065
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36
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Design and development of genetically encoded fluorescent sensors to monitor intracellular chemical and physical parameters. Biophys Rev 2016; 8:121-138. [PMID: 28510054 PMCID: PMC4884202 DOI: 10.1007/s12551-016-0195-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 03/09/2016] [Indexed: 01/26/2023] Open
Abstract
Over the past decades many researchers have made major contributions towards the development of genetically encoded (GE) fluorescent sensors derived from fluorescent proteins. GE sensors are now used to study biological phenomena by facilitating the measurement of biochemical behaviors at various scales, ranging from single molecules to single cells or even whole animals. Here, we review the historical development of GE fluorescent sensors and report on their current status. We specifically focus on the development strategies of the GE sensors used for measuring pH, ion concentrations (e.g., chloride and calcium), redox indicators, membrane potential, temperature, pressure, and molecular crowding. We demonstrate that these fluroescent protein-based sensors have a shared history of concepts and development strategies, and we highlight the most original concepts used to date. We believe that the understanding and application of these various concepts will pave the road for the development of future GE sensors and lead to new breakthroughs in bioimaging.
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37
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Priest M, Bezanilla F. Functional Site-Directed Fluorometry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 869:55-76. [PMID: 26381940 DOI: 10.1007/978-1-4939-2845-3_4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Initially developed in the mid-1990s to examine the conformational changes of the canonical Shaker voltage-gated potassium channel, functional site-directed fluorometry has since been expanded to numerous other voltage-gated and ligand-gated ion channels as well as transporters, pumps, and other integral membrane proteins. The power of functional site-directed fluorometry, also known as voltage-clamp fluorometry, lies in its ability to provide information on the conformational changes in a protein in response to changes in its environment with high temporal resolution while simultaneously monitoring the function of that protein. Over time, applications of site-directed fluorometry have expanded to examine the interactions of ion channels with modulators ranging from membrane potential to ligands to accessory protein subunits to lipids. In the future, the range of questions answerable by functional site-directed fluorometry and its interpretive power should continue to improve, making it an even more powerful technique for dissecting the conformational dynamics of ion channels and other membrane proteins.
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Affiliation(s)
- Michael Priest
- Department of Biochemistry and Molecular Biology and Committee on Neurobiology, University of Chicago, Gordon Center for Integrative Science W229M, 929 East 57th Street, 60637, Chicago, IL, USA.
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology and Committee on Neurobiology, University of Chicago, Gordon Center for Integrative Science W229M, 929 East 57th Street, 60637, Chicago, IL, USA.
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38
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Allosteric substrate switching in a voltage-sensing lipid phosphatase. Nat Chem Biol 2016; 12:261-7. [PMID: 26878552 PMCID: PMC4798927 DOI: 10.1038/nchembio.2022] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 12/31/2015] [Indexed: 11/29/2022]
Abstract
Allostery provides a critical control over enzyme activity, biasing the catalytic site between inactive and active states. We find the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), which modifies phosphoinositide signaling lipids (PIPs), to have not one but two sequential active states with distinct substrate specificities, whose occupancy is allosterically controlled by sequential conformations of the voltage sensing domain (VSD). Using fast FRET reporters of PIPs to monitor enzyme activity and voltage clamp fluorometry to monitor conformational changes in the VSD, we find that Ci-VSP switches from inactive to a PIP3-preferring active state when the VSD undergoes an initial voltage sensing motion and then into a second PIP2-preferring active state when the VSD activates fully. This novel 2-step allosteric control over a dual specificity enzyme enables voltage to shape PIP concentrations in time, and provides a mechanism for the complex modulation of PIP-regulated ion channels, transporters, cell motility and endo/exocytosis.
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39
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Abstract
Hv1 is a voltage-gated proton-selective channel that plays critical parts in host defense, sperm motility, and cancer progression. Hv1 contains a conserved voltage-sensor domain (VSD) that is shared by a large family of voltage-gated ion channels, but it lacks a pore domain. Voltage sensitivity and proton conductivity are conferred by a unitary VSD that consists of four transmembrane helices. The architecture of Hv1 differs from that of cation channels that form a pore in the center among multiple subunits (as in most cation channels) or homologous repeats (as in voltage-gated sodium and calcium channels). Hv1 forms a dimer in which a cytoplasmic coiled coil underpins the two protomers and forms a single, long helix that is contiguous with S4, the transmembrane voltage-sensing segment. The closed-state structure of Hv1 was recently solved using X-ray crystallography. In this article, we discuss the gating mechanism of Hv1 and focus on cooperativity within dimers and their sensitivity to metal ions.
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Affiliation(s)
- Yasushi Okamura
- Department of Integrative Physiology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; , ,
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40
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Storace D, Rad MS, Han Z, Jin L, Cohen LB, Hughes T, Baker BJ, Sung U. Genetically Encoded Protein Sensors of Membrane Potential. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:493-509. [PMID: 26238066 DOI: 10.1007/978-3-319-17641-3_20] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Organic voltage-sensitive dyes offer very high spatial and temporal resolution for imaging neuronal function. However these dyes suffer from the drawbacks of non-specificity of cell staining and low accessibility of the dye to some cell types. Further progress in imaging activity is expected from the development of genetically encoded fluorescent sensors of membrane potential. Cell type specificity of expression of these fluorescent protein (FP) voltage sensors can be obtained via several different mechanisms. One is cell type specificity of infection by individual virus subtypes. A second mechanism is specificity of promoter expression in individual cell types. A third, depends on the offspring of transgenic animals with cell type specific expression of cre recombinase mated with an animal that has the DNA for the FP voltage sensor in all of its cells but its expression is dependent on the recombinase activity. Challenges remain. First, the response time constants of many of the new FP voltage sensors are slower (2-10 ms) than those of organic dyes. This results in a relatively small fractional fluorescence change, ΔF/F, for action potentials. Second, the largest signal presently available is only ~40% for a 100 mV depolarization and many of the new probes have signals that are substantially smaller. Large signals are especially important when attempting to detect fast events because the shorter measurement interval results in a relatively small number of detected photons and therefore a relatively large shot noise (see Chap. 1). Another kind of challenge has occurred when attempts were made to transition from one species to another or from one cell type to another or from cell culture to in vivo measurements.Several laboratories have recently described a number of novel FP voltage sensors. Here we attempt to critically review the current status of these developments in terms of signal size, time course, and in vivo function.
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Affiliation(s)
- Douglas Storace
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, 06520, USA
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Interrogation of the intersubunit interface of the open Hv1 proton channel with a probe of allosteric coupling. Sci Rep 2015; 5:14077. [PMID: 26365828 PMCID: PMC4568520 DOI: 10.1038/srep14077] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 08/14/2015] [Indexed: 12/15/2022] Open
Abstract
The Hv1 voltage-gated proton channel is a dimeric complex consisting of two voltage-sensing domains (VSDs), each containing a gated proton permeation pathway. Dimerization is controlled by a cytoplasmic coiled-coil domain. The transitions from the closed to the open state in the two VSDs are known to occur cooperatively; however, the underlying mechanism is poorly understood. Intersubunit interfaces play a critical role in allosteric processes; but, such interfaces have not been determined in the open Hv1 channel. Here we show that 2-guanidinothiazole derivatives block the two Hv1 VSDs in a cooperative way, and use one of the compounds as a probe of allosteric coupling between open subunits. We find that the extracellular ends of the first transmembrane segments of the VSDs form the intersubunit interface that mediates coupling between binding sites, while the coiled-coil domain does not directly participate in the process. We also find strong evidence that the channel’s proton selectivity filter controls blocker binding cooperativity.
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Kubota T, Lacroix JJ, Bezanilla F, Correa AM. Probing α-3(10) transitions in a voltage-sensing S4 helix. Biophys J 2015; 107:1117-1128. [PMID: 25185547 DOI: 10.1016/j.bpj.2014.07.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 07/10/2014] [Accepted: 07/22/2014] [Indexed: 01/24/2023] Open
Abstract
The S4 helix of voltage sensor domains (VSDs) transfers its gating charges across the membrane electrical field in response to changes of the membrane potential. Recent studies suggest that this process may occur via the helical conversion of the entire S4 between α and 310 conformations. Here, using LRET and FRET, we tested this hypothesis by measuring dynamic changes in the transmembrane length of S4 from engineered VSDs expressed in Xenopus oocytes. Our results suggest that the native S4 from the Ciona intestinalis voltage-sensitive phosphatase (Ci-VSP) does not exhibit extended and long-lived 310 conformations and remains mostly α-helical. Although the S4 of NavAb displays a fully extended 310 conformation in x-ray structures, its transplantation in the Ci-VSP VSD scaffold yielded similar results as the native Ci-VSP S4. Taken together, our study does not support the presence of long-lived extended α-to-310 helical conversions of the S4 in Ci-VSP associated with voltage activation.
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Affiliation(s)
- Tomoya Kubota
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois
| | - Jérôme J Lacroix
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois.
| | - Ana M Correa
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois.
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Rjasanow A, Leitner MG, Thallmair V, Halaszovich CR, Oliver D. Ion channel regulation by phosphoinositides analyzed with VSPs-PI(4,5)P2 affinity, phosphoinositide selectivity, and PI(4,5)P2 pool accessibility. Front Pharmacol 2015; 6:127. [PMID: 26150791 PMCID: PMC4472987 DOI: 10.3389/fphar.2015.00127] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/05/2015] [Indexed: 11/13/2022] Open
Abstract
The activity of many proteins depends on the phosphoinositide (PI) content of the membrane. E.g., dynamic changes of the concentration of PI(4,5)P2 are cellular signals that regulate ion channels. The susceptibility of a channel to such dynamics depends on its affinity for PI(4,5)P2. Yet, measuring affinities for endogenous PIs has not been possible directly, but has relied largely on the response to soluble analogs, which may not quantitatively reflect binding to native lipids. Voltage-sensitive phosphatases (VSPs) turn over PI(4,5)P2 to PI(4)P when activated by depolarization. In combination with voltage-clamp electrophysiology VSPs are useful tools for rapid and reversible depletion of PI(4,5)P2. Because cellular PI(4,5)P2 is resynthesized rapidly, steady state PI(4,5)P2 changes with the degree of VSP activation and thus depends on membrane potential. Here we show that titration of endogenous PI(4,5)P2 with Ci-VSP allows for the quantification of relative PI(4,5)P2 affinities of ion channels. The sensitivity of inward rectifier and voltage-gated K+ channels to Ci-VSP allowed for comparison of PI(4,5)P2 affinities within and across channel subfamilies and detected changes of affinity in mutant channels. The results also reveal that VSPs are useful only for PI effectors with high binding specificity among PI isoforms, because PI(4,5)P2 depletion occurs at constant overall PI level. Thus, Kir6.2, a channel activated by PI(4,5)P2 and PI(4)P was insensitive to VSP. Surprisingly, despite comparable PI(4,5)P2 affinity as determined by Ci-VSP, the Kv7 and Kir channel families strongly differed in their sensitivity to receptor-mediated depletion of PI(4,5)P2. While Kv7 members were highly sensitive to activation of PLC by Gq-coupled receptors, Kir channels were insensitive even when PI(4,5)P2 affinity was lowered by mutation. We hypothesize that different channels may be associated with distinct pools of PI(4,5)P2 that differ in their accessibility to PLC and VSPs.
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Affiliation(s)
- Alexandra Rjasanow
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Germany ; Institute of Physiology, University of Freiburg Freiburg, Germany
| | - Michael G Leitner
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Germany
| | - Veronika Thallmair
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Germany
| | - Christian R Halaszovich
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Germany
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, Germany
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St-Pierre F, Chavarha M, Lin MZ. Designs and sensing mechanisms of genetically encoded fluorescent voltage indicators. Curr Opin Chem Biol 2015; 27:31-8. [PMID: 26079047 DOI: 10.1016/j.cbpa.2015.05.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/04/2015] [Indexed: 11/24/2022]
Abstract
Neurons tightly regulate the electrical potential difference across the plasma membrane with millivolt accuracy and millisecond resolution. Membrane voltage dynamics underlie the generation of an impulse, the transduction of impulses from one end of the neuron to the other, and the release of neurotransmitters. Imaging these voltage dynamics in multiple neurons simultaneously is therefore crucial for understanding how neurons function together within circuits in intact brains. Genetically encoded fluorescent voltage sensors have long been desired to report voltage in defined subsets of neurons with optical readout. In this review, we discuss the diverse strategies used to design and optimize protein-based voltage sensors, and highlight the chemical mechanisms by which different classes of reporters sense voltage. To guide neuroscientists in choosing an appropriate sensor for their applications, we also describe operating trade-offs of each class of voltage indicators.
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Affiliation(s)
- François St-Pierre
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Mariya Chavarha
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Michael Z Lin
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA.
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Voltage Sensing in Membranes: From Macroscopic Currents to Molecular Motions. J Membr Biol 2015; 248:419-30. [PMID: 25972106 DOI: 10.1007/s00232-015-9805-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/24/2015] [Indexed: 01/06/2023]
Abstract
Voltage-sensing domains (VSDs) are integral membrane protein units that sense changes in membrane electric potential, and through the resulting conformational changes, regulate a specific function. VSDs confer voltage-sensitivity to a large superfamily of membrane proteins that includes voltage-gated Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] ,and H[Formula: see text] selective channels, hyperpolarization-activated cyclic nucleotide-gated channels, and voltage-sensing phosphatases. VSDs consist of four transmembrane segments (termed S1 through S4). Their most salient structural feature is the highly conserved positions for charged residues in their sequences. S4 exhibits at least three conserved triplet repeats composed of one basic residue (mostly arginine) followed by two hydrophobic residues. These S4 basic side chains participate in a state-dependent internal salt-bridge network with at least four acidic residues in S1-S3. The signature of voltage-dependent activation in electrophysiology experiments is a transient current (termed gating or sensing current) upon a change in applied membrane potential as the basic side chains in S4 move across the membrane electric field. Thus, the unique structural features of the VSD architecture allow for competing requirements: maintaining a series of stable transmembrane conformations, while allowing charge motion, as briefly reviewed here.
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Castle PM, Zolman KD, Kohout SC. Voltage-sensing phosphatase modulation by a C2 domain. Front Pharmacol 2015; 6:63. [PMID: 25904865 PMCID: PMC4389355 DOI: 10.3389/fphar.2015.00063] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/10/2015] [Indexed: 11/13/2022] Open
Abstract
The voltage-sensing phosphatase (VSP) is the first example of an enzyme controlled by changes in membrane potential. VSP has four distinct regions: the transmembrane voltage-sensing domain (VSD), the inter-domain linker, the cytosolic catalytic domain, and the C2 domain. The VSD transmits the changes in membrane potential through the inter-domain linker activating the catalytic domain which then dephosphorylates phosphatidylinositol phosphate (PIP) lipids. The role of the C2, however, has not been established. In this study, we explore two possible roles for the C2: catalysis and membrane-binding. The Ci-VSP crystal structures show that the C2 residue Y522 lines the active site suggesting a contribution to catalysis. When we mutated Y522 to phenylalanine, we found a shift in the voltage dependence of activity. This suggests hydrogen bonding as a mechanism of action. Going one step further, when we deleted the entire C2 domain, we found voltage-dependent enzyme activity was no longer detectable. This result clearly indicates the entire C2 is necessary for catalysis as well as for modulating activity. As C2s are known membrane-binding domains, we tested whether the VSP C2 interacts with the membrane. We probed a cluster of four positively charged residues lining the top of the C2 and suggested by previous studies to interact with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] (Kalli et al., 2014). Neutralizing those positive charges significantly shifted the voltage dependence of activity to higher voltages. We tested membrane binding by depleting PI(4,5)P2 from the membrane using the 5HT2C receptor and found that the VSD motions as measured by voltage clamp fluorometry (VCF) were not changed. These results suggest that if the C2 domain interacts with the membrane to influence VSP function it may not occur exclusively through PI(4,5)P2. Together, this data advances our understanding of the VSP C2 by demonstrating a necessary and critical role for the C2 domain in VSP function.
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Affiliation(s)
- Paul M Castle
- Department of Cell Biology and Neuroscience, Montana State University Bozeman, MT, USA
| | - Kevin D Zolman
- Department of Cell Biology and Neuroscience, Montana State University Bozeman, MT, USA
| | - Susy C Kohout
- Department of Cell Biology and Neuroscience, Montana State University Bozeman, MT, USA
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Akemann W, Song C, Mutoh H, Knöpfel T. Route to genetically targeted optical electrophysiology: development and applications of voltage-sensitive fluorescent proteins. NEUROPHOTONICS 2015; 2:021008. [PMID: 26082930 PMCID: PMC4465821 DOI: 10.1117/1.nph.2.2.021008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 12/11/2014] [Indexed: 06/04/2023]
Abstract
The invention of membrane voltage protein indicators widens the reach of optical voltage imaging in cell physiology, most notably neurophysiology, by enabling membrane voltage recordings from genetically defined cell types in chronic and life-long preparations. While the last years have seen a dramatic improvement in the technical performance of these indicators, concomitant innovations in optogenetics, optical axon tracing, and high-speed digital microscopy are beginning to fulfill the age-old vision of an all-optical analysis of neuronal circuits, reaching beyond the limits of traditional electrode-based recordings. We will present our personal account of the development of protein voltage indicators from the pioneering days to the present state, including their applications in neurophysiology that has inspired our own work for more than a decade.
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Affiliation(s)
- Walther Akemann
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
- Institute of Biology, CNRS UMR 8197, École Normale Supérieure, 46 rue d’Ulm, 75005 Paris, France
| | - Chenchen Song
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
| | - Hiroki Mutoh
- Hamamatsu University School of Medicine, Department of Neurophysiology, Shizuoka 431-3192, Japan
| | - Thomas Knöpfel
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
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48
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A specialized molecular motion opens the Hv1 voltage-gated proton channel. Nat Struct Mol Biol 2015; 22:283-290. [PMID: 25730777 PMCID: PMC4385474 DOI: 10.1038/nsmb.2978] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 01/30/2015] [Indexed: 12/22/2022]
Abstract
The Hv1 proton channel is unique among voltage-gated channels for containing the pore and gate within its voltage-sensing domain. Pore opening has been proposed to include assembly of the selectivity filter between an arginine (R3) of segment S4 and an aspartate (D1) of segment S1. We determined whether gating involves motion of S1, using Ciona intestinalis Hv1. We found that channel opening is concomitant with solution access to the pore-lining face of S1, from the cytoplasm to deep inside the pore. Voltage- and patch-clamp fluorometry showed that this involves a motion of S1 relative to its surroundings. S1 motion and the S4 motion that precedes it are each influenced by residues on the other helix, thus suggesting a dynamic interaction between S1 and S4. Our findings suggest that the S1 of Hv1 has specialized to function as part of the channel's gate.
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49
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Berger TK, Isacoff EY. Fluorescent labeling for patch-clamp fluorometry (PCF) measurements of real-time protein motion in ion channels. Methods Mol Biol 2015; 1266:93-106. [PMID: 25560069 DOI: 10.1007/978-1-4939-2272-7_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Understanding the function of ion channels is a major goal of molecular neurophysiology. While standard electrophysiological methods are invaluable tools to investigate the gating of ion channels, the structural rearrangements that mediate the way a channel senses physiological signals and opens and closes its gates cannot be measured electrically in a direct way. Here, we describe a method, based on site-specific labeling of a channel of interest with an environmentally sensitive fluorophore, which makes it possible to monitor conformational changes of ion channels in biological membranes in real time.
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Affiliation(s)
- Thomas K Berger
- Research Center Caesar, Ludwig-Erhard-Allee 2, 53175, Bonn, Germany,
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50
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Giraldez T. Let's twist (the S4) again. Biophys J 2014; 107:1035-1037. [PMID: 25185537 DOI: 10.1016/j.bpj.2014.07.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 07/17/2014] [Accepted: 07/22/2014] [Indexed: 01/01/2023] Open
Affiliation(s)
- Teresa Giraldez
- Department of Physiology, School of Medicine & Centre for Biomedical Research of the Canary Islands (CIBICAN), University de La Laguna, La Laguna, Santa Cruz de Tenerife, Spain.
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