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Ott S, Xu S, Lee N, Hong I, Anns J, Suresh DD, Zhang Z, Zhang X, Harion R, Ye W, Chandramouli V, Jesuthasan S, Saheki Y, Claridge-Chang A. Kalium channelrhodopsins effectively inhibit neurons. Nat Commun 2024; 15:3480. [PMID: 38658537 PMCID: PMC11043423 DOI: 10.1038/s41467-024-47203-w] [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: 08/02/2023] [Accepted: 03/18/2024] [Indexed: 04/26/2024] Open
Abstract
The analysis of neural circuits has been revolutionized by optogenetic methods. Light-gated chloride-conducting anion channelrhodopsins (ACRs)-recently emerged as powerful neuron inhibitors. For cells or sub-neuronal compartments with high intracellular chloride concentrations, however, a chloride conductance can have instead an activating effect. The recently discovered light-gated, potassium-conducting, kalium channelrhodopsins (KCRs) might serve as an alternative in these situations, with potentially broad application. As yet, KCRs have not been shown to confer potent inhibitory effects in small genetically tractable animals. Here, we evaluated the utility of KCRs to suppress behavior and inhibit neural activity in Drosophila, Caenorhabditis elegans, and zebrafish. In direct comparisons with ACR1, a KCR1 variant with enhanced plasma-membrane trafficking displayed comparable potency, but with improved properties that include reduced toxicity and superior efficacy in putative high-chloride cells. This comparative analysis of behavioral inhibition between chloride- and potassium-selective silencing tools establishes KCRs as next-generation optogenetic inhibitors for in vivo circuit analysis in behaving animals.
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Affiliation(s)
- Stanislav Ott
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Sangyu Xu
- Institute for Molecular and Cell Biology, A*STAR Agency for Science, Technology and Research, Singapore, Singapore
| | - Nicole Lee
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Ivan Hong
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Jonathan Anns
- Institute for Molecular and Cell Biology, A*STAR Agency for Science, Technology and Research, Singapore, Singapore
- School of Biological Sciences and Institute for Life Sciences, University of Southampton, Southampton, UK
| | - Danesha Devini Suresh
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Zhiyi Zhang
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Xianyuan Zhang
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Raihanah Harion
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Weiying Ye
- Department of Pharmacy, National University of Singapore, Singapore, Singapore
| | - Vaishnavi Chandramouli
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Suresh Jesuthasan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Adam Claridge-Chang
- Program in Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore, Singapore.
- Institute for Molecular and Cell Biology, A*STAR Agency for Science, Technology and Research, Singapore, Singapore.
- Department of Pharmacy, National University of Singapore, Singapore, Singapore.
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2
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Bi X, Beck C, Gong Y. A kinetic-optimized CoChR variant with enhanced high-frequency spiking fidelity. Biophys J 2022; 121:4166-4178. [PMID: 36151721 PMCID: PMC9675021 DOI: 10.1016/j.bpj.2022.09.024] [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: 01/19/2022] [Revised: 07/09/2022] [Accepted: 09/21/2022] [Indexed: 11/22/2022] Open
Abstract
Channelrhodopsins are a promising toolset for noninvasive optical manipulation of genetically identifiable neuron populations. Existing channelrhodopsins have generally suffered from a trade-off between two desired properties: fast channel kinetics and large photocurrent. Such a trade-off hinders spatiotemporally precise optogenetic activation during both one-photon and two-photon photostimulation. Furthermore, the simultaneous use of spectrally separated genetically encoded indicators and channelrhodopsins has generally suffered from non-negligible crosstalk in photocurrent or fluorescence. These limitations have hindered crosstalk-free dual-channel experiments needed to establish relationships between multiple neural populations. Recent large-scale transcriptome sequencing revealed one potent optogenetic actuator, the channelrhodopsin from species Chloromonas oogama (CoChR), which possessed high cyan light-driven photocurrent but slow channel kinetics. We rationally designed and engineered a kinetic-optimized CoChR variant that was faster than native CoChR while maintaining large photocurrent amplitude. When expressed in cultured hippocampal pyramidal neurons, our CoChR variant improved high-frequency spiking fidelity under one-photon illumination. Our CoChR variant's blue-shifted excitation spectrum enabled simultaneous cyan photostimulation and red calcium imaging with negligible photocurrent crosstalk.
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Affiliation(s)
- Xiaoke Bi
- Department of Biomedical Engineering, Duke University, Durham, North Carolina.
| | - Connor Beck
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
| | - Yiyang Gong
- Department of Biomedical Engineering, Duke University, Durham, North Carolina.
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3
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Idzhilova OS, Smirnova GR, Petrovskaya LE, Kolotova DA, Ostrovsky MA, Malyshev AY. Cationic Channelrhodopsin from the Alga Platymonas subcordiformis as a Promising Optogenetic Tool. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1327-1334. [PMID: 36509722 DOI: 10.1134/s0006297922110116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The progress in optogenetics largely depends on the development of light-activated proteins as new molecular tools. Using cultured hippocampal neurons, we compared the properties of two light-activated cation channels - classical channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) and recently described channelrhodopsin isolated from the alga Platymonas subcordiformis (PsChR2). PsChR2 ensured generation of action potentials by neurons when activated by the pulsed light stimulation with the frequencies up to 40-50 Hz, while the upper limit for CrChR2 was 20-30 Hz. An important advantage of PsChR2 compared to classical channelrhodopsin CrChR2 is the blue shift of its excitation spectrum, which opens the possibility for its application in all-optical electrophysiology experiments that require the separation of the maxima of the spectra of channelrhodopsins used for the stimulation of neurons and the maxima of the excitation spectra of various red fluorescent probes. We compared the response (generation of action potentials) of neurons expressing CrChR2 and PsChR2 to light stimuli at 530 and 550 nm commonly used for the excitation of red fluorescent probes. The 530-nm light was significantly (3.7 times) less efficient in the activation of neurons expressing PsChR2 vs. CrChR2-expressing neurons. The light at 550 nm, even at the maximal used intensity, failed to stimulate neurons expressing either of the studied opsins. This indicates that the PsChR2 channelrhodopsin from the alga P. subcordiformis is a promising optogenetic tool, both in terms of its frequency characteristics and possibility of its application for neuronal stimulation with a short-wavelength (blue, 470 nm) light accompanied by simultaneous recording of various physiological processes using fluorescent probes.
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Affiliation(s)
- Olga S Idzhilova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, 117485, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Gulnur R Smirnova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, 117485, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Lada E Petrovskaya
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - Darya A Kolotova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, 117485, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Mikhail A Ostrovsky
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia
| | - Alexey Y Malyshev
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, 117485, Russia.
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4
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Govorunova EG, Sineshchekov OA, Brown LS, Spudich JL. Biophysical characterization of light-gated ion channels using planar automated patch clamp. Front Mol Neurosci 2022; 15:976910. [PMID: 36017077 PMCID: PMC9396214 DOI: 10.3389/fnmol.2022.976910] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 07/21/2022] [Indexed: 01/09/2023] Open
Abstract
Channelrhodopsins (ChRs) are proteins that guide phototaxis in protists and exhibit light-gated channel conductance when their genes are heterologously expressed in mammalian cells. ChRs are widely used as molecular tools to control neurons and cardiomyocytes with light (optogenetics). Cation- and anion-selective ChRs (CCRs and ACRs, respectively) enable stimulation and inhibition of neuronal activity by depolarization and hyperpolarization of the membrane, respectively. More than 400 natural ChR variants have been identified so far, and high-throughput polynucleotide sequencing projects add many more each year. However, electrophysiological characterization of new ChRs lags behind because it is mostly done by time-consuming manual patch clamp (MPC). Here we report using a high-throughput automated patch clamp (APC) platform, SyncroPatch 384i from Nanion Technologies, for ChR research. We find that this instrument can be used for determination of the light intensity dependence and current-voltage relationships in ChRs and discuss its advantages and limitations.
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Affiliation(s)
- Elena G. Govorunova
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, United States
| | - Oleg A. Sineshchekov
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, United States
| | - Leonid S. Brown
- Biophysics Interdepartmental Group, Department of Physics, University of Guelph, Guelph, ON, Canada
| | - John L. Spudich
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX, United States
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Abstract
Optogenetic actuators enable highly precise spatiotemporal interrogation of biological processes at levels ranging from the subcellular to cells, circuits and behaving organisms. Although their application in neuroscience has traditionally focused on the control of spiking activity at the somatodendritic level, the scope of optogenetic modulators for direct manipulation of presynaptic functions is growing. Presynaptically localized opsins combined with light stimulation at the terminals allow light-mediated neurotransmitter release, presynaptic inhibition, induction of synaptic plasticity and specific manipulation of individual components of the presynaptic machinery. Here, we describe presynaptic applications of optogenetic tools in the context of the unique cell biology of axonal terminals, discuss their potential shortcomings and outline future directions for this rapidly developing research area.
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6
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Paez Segala MG, Looger LL. Optogenetics. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00092-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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7
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Sineshchekov OA, Govorunova EG, Li H, Wang Y, Melkonian M, Wong GKS, Brown LS, Spudich JL. Conductance Mechanisms of Rapidly Desensitizing Cation Channelrhodopsins from Cryptophyte Algae. mBio 2020; 11:e00657-20. [PMID: 32317325 PMCID: PMC7175095 DOI: 10.1128/mbio.00657-20] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 03/26/2020] [Indexed: 01/14/2023] Open
Abstract
Channelrhodopsins guide algal phototaxis and are widely used as optogenetic probes for control of membrane potential with light. "Bacteriorhodopsin-like" cation channelrhodopsins (BCCRs) from cryptophytes differ in primary structure from other CCRs, lacking usual residues important for their cation conductance. Instead, the sequences of BCCR match more closely those of rhodopsin proton pumps, containing residues responsible for critical proton transfer reactions. We report 19 new BCCRs which, together with the earlier 6 known members of this family, form three branches (subfamilies) of a phylogenetic tree. Here, we show that the conductance mechanisms in two subfamilies differ with respect to involvement of the homolog of the proton donor in rhodopsin pumps. Two BCCRs from the genus Rhodomonas generate photocurrents that rapidly desensitize under continuous illumination. Using a combination of patch clamp electrophysiology, absorption, Raman spectroscopy, and flash photolysis, we found that the desensitization is due to rapid accumulation of a long-lived nonconducting intermediate of the photocycle with unusually blue-shifted absorption with a maximum at 330 nm. These observations reveal diversity within the BCCR family and contribute to deeper understanding of their independently evolved cation channel function.IMPORTANCE Cation channelrhodopsins, light-gated channels from flagellate green algae, are extensively used as optogenetic photoactivators of neurons in research and recently have progressed to clinical trials for vision restoration. However, the molecular mechanisms of their photoactivation remain poorly understood. We recently identified cryptophyte cation channelrhodopsins, structurally different from those of green algae, which have separately evolved to converge on light-gated cation conductance. This study reveals diversity within this new protein family and describes a subclade with unusually rapid desensitization that results in short transient photocurrents in continuous light. Such transient currents have not been observed in the green algae channelrhodopsins and are potentially useful in optogenetic protocols. Kinetic UV-visible (UV-vis) spectroscopy and photoelectrophysiology reveal that the desensitization is caused by rapid accumulation of a nonconductive photointermediate in the photochemical reaction cycle. The absorption maximum of the intermediate is 330 nm, the shortest wavelength reported in any rhodopsin, indicating a novel chromophore structure.
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Affiliation(s)
- Oleg A Sineshchekov
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, Texas, USA
| | - Elena G Govorunova
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, Texas, USA
| | - Hai Li
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, Texas, USA
| | - Yumei Wang
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, Texas, USA
| | - Michael Melkonian
- Institute for Plant Sciences, Department of Biology, University of Cologne, Cologne, Germany
- Central Collection of Algal Cultures, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Gane K-S Wong
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
- Beijing Genomics Institute-Shenzhen, Shenzhen, China
| | - Leonid S Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | - John L Spudich
- Center for Membrane Biology, Department of Biochemistry & Molecular Biology, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, Texas, USA
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8
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Greotti E, Pozzan T. Live Mitochondrial or Cytosolic Calcium Imaging Using Genetically-encoded Cameleon Indicator in Mammalian Cells. Bio Protoc 2020; 10:e3504. [PMID: 33654731 DOI: 10.21769/bioprotoc.3504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/16/2019] [Accepted: 12/17/2019] [Indexed: 02/04/2023] Open
Abstract
Calcium (Ca2+) imaging aims at investigating the dynamic changes in live cells of its concentration ([Ca2+]) in different pathophysiological conditions. Ca2+ is an ubiquitous and versatile intracellular signal that modulates a large variety of cellular functions thanks to a cell type-specific toolkit and a complex subcellular compartmentalization. Many Ca2+ sensors are presently available (chemical and genetically encoded) that can be specifically targeted to different cellular compartments. Using these probes, it is now possible to monitor Ca2+ dynamics of living cells not only in the cytosol but also within specific organelles. The choice of a specific sensor depends on the experimental design and the spatial and temporal resolution required. Here we describe the use of novel Förster resonance energy transfer (FRET)-based fluorescent Ca2+ probes to dynamically and quantitatively monitor the changes in cytosolic and mitochondrial [Ca2+] in a variety of cell types and experimental conditions. FRET-based sensors have the enormous advantage of being ratiometric, a feature that makes them particularly suitable for quantitative and in vivo applications.
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Affiliation(s)
- Elisa Greotti
- Neuroscience Institute, National Research Council (CNR), 35131 Padua, Italy.,Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy
| | - Tullio Pozzan
- Neuroscience Institute, National Research Council (CNR), 35131 Padua, Italy.,Department of Biomedical Sciences, University of Padua, 35131 Padua, Italy.,Venetian Institute of Molecular Medicine (VIMM), 35129 Padua, Italy
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9
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10
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Ingram TGJ, King JL, Crowder NA. Divisive Inhibition Prevails During Simultaneous Optogenetic Activation of All Interneuron Subtypes in Mouse Primary Visual Cortex. Front Neural Circuits 2019; 13:40. [PMID: 31191259 PMCID: PMC6546973 DOI: 10.3389/fncir.2019.00040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 05/08/2019] [Indexed: 01/02/2023] Open
Abstract
The mouse primary visual cortex (V1) has become an important brain area for exploring how neural circuits process information. Optogenetic tools have helped to outline the connectivity of a local V1 circuit comprising excitatory pyramidal neurons and several genetically-defined inhibitory interneuron subtypes that express parvalbumin, somatostatin, or vasoactive intestinal peptide. Optogenetic modulation of individual interneuron subtypes can alter the visual responsiveness of pyramidal neurons with distinct forms of inhibition and disinhibition. However, different interneuron subtypes have potentially opposing actions, and the potency of their effects relative to each other remains unclear. Therefore, in this study we simultaneously optogenetically activated all interneuron subtypes during visual processing to explore whether any single inhibitory effect would predominate. This aggregate interneuron activation consistently inhibited pyramidal neurons in a divisive manner, which was essentially identical to the pattern of inhibition produced by activating parvalbumin-expressing interneurons alone.
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Affiliation(s)
- Tony G J Ingram
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada
| | - Jillian L King
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada
| | - Nathan A Crowder
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada
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11
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Mukherjee S, Hegemann P, Broser M. Enzymerhodopsins: novel photoregulated catalysts for optogenetics. Curr Opin Struct Biol 2019; 57:118-126. [PMID: 30954887 DOI: 10.1016/j.sbi.2019.02.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 12/22/2022]
Abstract
Enzymerhodopsins are a recently discovered class of natural rhodopsin-based photoreceptors with light-regulated enzyme activity. Currently, three different types of these fusion proteins with an N-terminal type-1 rhodopsin and a C-terminal enzyme domain have been identified, but their physiological relevance is mostly unknown. Among these, histidine kinase rhodopsins (HKR) are photo-regulated two-component-like signaling systems that trigger a phosphorylation cascade, whereas rhodopsin phosphodiesterase (RhoPDE) or rhodopsin guanylyl cyclase (RhGC) show either light-activated hydrolysis or production of cyclic nucleotides. RhGC, the best characterized enzymerhodopsin, is involved in the phototaxis of fungal zoospores and allows for optically controlled production of cyclic nucleotides in different cell-types. These photoreceptors have great optogenetic potential and possess several advantages over the hitherto existing tools to manipulate cyclic-nucleotide dynamics in living cells.
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Affiliation(s)
- Shatanik Mukherjee
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Germany.
| | - Peter Hegemann
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Germany
| | - Matthias Broser
- Institute for Biology, Experimental Biophysics, Humboldt-Universität zu Berlin, Germany.
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12
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Brown J, Behnam R, Coddington L, Tervo DGR, Martin K, Proskurin M, Kuleshova E, Park J, Phillips J, Bergs ACF, Gottschalk A, Dudman JT, Karpova AY. Expanding the Optogenetics Toolkit by Topological Inversion of Rhodopsins. Cell 2018; 175:1131-1140.e11. [PMID: 30343901 DOI: 10.1016/j.cell.2018.09.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 06/30/2018] [Accepted: 09/13/2018] [Indexed: 12/17/2022]
Abstract
Targeted manipulation of activity in specific populations of neurons is important for investigating the neural circuit basis of behavior. Optogenetic approaches using light-sensitive microbial rhodopsins have permitted manipulations to reach a level of temporal precision that is enabling functional circuit dissection. As demand for more precise perturbations to serve specific experimental goals increases, a palette of opsins with diverse selectivity, kinetics, and spectral properties will be needed. Here, we introduce a novel approach of "topological engineering"-inversion of opsins in the plasma membrane-and demonstrate that it can produce variants with unique functional properties of interest for circuit neuroscience. In one striking example, inversion of a Channelrhodopsin variant converted it from a potent activator into a fast-acting inhibitor that operates as a cation pump. Our findings argue that membrane topology provides a useful orthogonal dimension of protein engineering that immediately permits as much as a doubling of the available toolkit.
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Affiliation(s)
- Jennifer Brown
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Reza Behnam
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Luke Coddington
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - D G R Tervo
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Kathleen Martin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Mikhail Proskurin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Department of Neuroscience, Johns Hopkins University Medical School, Baltimore, MD 21205, USA
| | - Elena Kuleshova
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences, Moscow 117485, Russia
| | - Junchol Park
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - James Phillips
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Amelie C F Bergs
- Buchmann Institute for Molecular Life Sciences, Goethe-University D-60438 Frankfurt, Germany; Institute for Biophysical Chemistry, Goethe-University, D-60438 Frankfurt, Germany; International Max-Planck Research School in Structure and Function of Biological Membranes, Max-Planck-Institute of Biophysics, D-60438 Frankfurt, Germany
| | - Alexander Gottschalk
- Buchmann Institute for Molecular Life Sciences, Goethe-University D-60438 Frankfurt, Germany; Institute for Biophysical Chemistry, Goethe-University, D-60438 Frankfurt, Germany
| | - Joshua T Dudman
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
| | - Alla Y Karpova
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
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13
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Shin M, Copeland JM, Venton BJ. Drosophila as a Model System for Neurotransmitter Measurements. ACS Chem Neurosci 2018; 9:1872-1883. [PMID: 29411967 DOI: 10.1021/acschemneuro.7b00456] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Drosophila melanogaster, the fruit fly, is an important, simple model organism for studying the effects of genetic mutations on neuronal activity and behavior. Biologists use Drosophila for neuroscience studies because of its genetic tractability, complex behaviors, well-known and simple neuroanatomy, and many orthologues to human genes. Neurochemical measurements in Drosophila are challenging due to the small size of the central nervous system. Recently, methods have been developed to measure real-time neurotransmitter release and clearance in both larvae and adults using electrochemistry. These studies have characterized dopamine, serotonin, and octopamine release in both wild type and genetic mutant flies. Tissue content measurements are also important, and separations are predominantly used. Capillary electrophoresis, with either electrochemical, laser-induced fluorescence, or mass spectrometry detection, facilitates tissue content measurements from single, isolated Drosophila brains or small samples of hemolymph. Neurochemical studies in Drosophila have revealed that flies have functioning transporters and autoreceptors, that their metabolism is different than in mammals, and that flies have regional, life stage, and sex differences in neurotransmission. Future studies will develop smaller electrodes, expand optical imaging techniques, explore physiological stimulations, and use advanced genetics to target single neuron release or study neurochemical changes in models of human diseases.
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Affiliation(s)
- Mimi Shin
- Department of Chemistry and Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia 22901, United States
| | - Jeffrey M. Copeland
- Department of Chemistry and Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia 22901, United States
- Department of Biology, Eastern Mennonite University, Harrisonburg, Virginia 22802, United States
| | - B. Jill Venton
- Department of Chemistry and Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia 22901, United States
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14
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Sun S, Schaffer DV. Engineered viral vectors for functional interrogation, deconvolution, and manipulation of neural circuits. Curr Opin Neurobiol 2018; 50:163-170. [PMID: 29614429 PMCID: PMC5984719 DOI: 10.1016/j.conb.2017.12.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 11/27/2017] [Accepted: 12/16/2017] [Indexed: 12/19/2022]
Abstract
Optimization of traditional replication-competent viral tracers has granted access to immediate synaptic partners of target neuronal populations, enabling the dissection of complex brain circuits into functional neural pathways. The excessive virulence of most conventional tracers, however, impedes their utility in revealing and genetically perturbing cellular function on long time scales. As a promising alternative, the natural capacity of adeno-associated viral (AAV) vectors to safely mediate persistent and robust gene expression has stimulated strong interest in adapting them for sparse neuronal labeling and physiological studies. Furthermore, increasingly refined engineering strategies have yielded novel AAV variants with enhanced target specificity, transduction, and retrograde trafficking in the CNS. These potent vectors offer new opportunities for characterizing the identity and connectivity of single neurons within immense networks and modulating their activity via robust delivery of functional genetic tools.
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Affiliation(s)
- Sabrina Sun
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA
| | - David V Schaffer
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, USA; Department of Bioengineering, University of California, Berkeley, CA, USA; The Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.
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15
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Abstract
Channelrhodopsin-2 (ChR2) is a light-sensitive ion channel widely used in optogenetics. Photoactivation triggers a trans-to-cis isomerization of a covalently bound retinal. Ensuing conformational changes open a cation-selective channel. We explore the structural dynamics in the early photocycle leading to channel opening by classical (MM) and quantum mechanical (QM) molecular simulations. With QM/MM simulations, we generated a protein-adapted force field for the retinal chromophore, which we validated against absorption spectra. In a 4-µs MM simulation of a dark-adapted ChR2 dimer, water entered the vestibules of the closed channel. Retinal all-trans to 13-cis isomerization, simulated with metadynamics, triggered a major restructuring of the charge cluster forming the channel gate. On a microsecond time scale, water penetrated the gate to form a membrane-spanning preopen pore between helices H1, H2, H3, and H7. This influx of water into an ion-impermeable preopen pore is consistent with time-resolved infrared spectroscopy and electrophysiology experiments. In the retinal 13-cis state, D253 emerged as the proton acceptor of the Schiff base. Upon proton transfer from the Schiff base to D253, modeled by QM/MM simulations, we obtained an early-M/P2390-like intermediate. Rapid rotation of the unprotonated Schiff base toward the cytosolic side effectively prevents its reprotonation from the extracellular side. From MM and QM simulations, we gained detailed insight into the mechanism of ChR2 photoactivation and early events in pore formation. By rearranging the network of charges and hydrogen bonds forming the gate, water emerges as a key player in light-driven ChR2 channel opening.
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Affiliation(s)
- Albert Ardevol
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
- Department of Physics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
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16
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Abstract
Microbial rhodopsins (MRs) are a large family of photoactive membrane proteins, found in microorganisms belonging to all kingdoms of life, with new members being constantly discovered. Among the MRs are light-driven proton, cation and anion pumps, light-gated cation and anion channels, and various photoreceptors. Due to their abundance and amenability to studies, MRs served as model systems for a great variety of biophysical techniques, and recently found a great application as optogenetic tools. While the basic aspects of microbial rhodopsins functioning have been known for some time, there is still a plenty of unanswered questions. This chapter presents and summarizes the available knowledge, focusing on the functional and structural studies.
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Affiliation(s)
- Ivan Gushchin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
| | - Valentin Gordeliy
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia.
- University of Grenoble Alpes, CEA, CNRS, IBS, Grenoble, France.
- Institute of Complex Systems (ICS), ICS-6: Structural Biochemistry, Research Centre Jülich, Jülich, Germany.
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17
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Delbeke J, Hoffman L, Mols K, Braeken D, Prodanov D. And Then There Was Light: Perspectives of Optogenetics for Deep Brain Stimulation and Neuromodulation. Front Neurosci 2017; 11:663. [PMID: 29311765 PMCID: PMC5732983 DOI: 10.3389/fnins.2017.00663] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/14/2017] [Indexed: 12/12/2022] Open
Abstract
Deep Brain Stimulation (DBS) has evolved into a well-accepted add-on treatment for patients with severe Parkinsons disease as well as for other chronic neurological conditions. The focal action of electrical stimulation can yield better responses and it exposes the patient to fewer side effects compared to pharmaceuticals distributed throughout the body toward the brain. On the other hand, the current practice of DBS is hampered by the relatively coarse level of neuromodulation achieved. Optogenetics, in contrast, offers the perspective of much more selective actions on the various physiological structures, provided that the stimulated cells are rendered sensitive to the action of light. Optogenetics has experienced tremendous progress since its first in vivo applications about 10 years ago. Recent advancements of viral vector technology for gene transfer substantially reduce vector-associated cytotoxicity and immune responses. This brings about the possibility to transfer this technology into the clinic as a possible alternative to DBS and neuromodulation. New paths could be opened toward a rich panel of clinical applications. Some technical issues still limit the long term use in humans but realistic perspectives quickly emerge. Despite a rapid accumulation of observations about patho-physiological mechanisms, it is still mostly serendipity and empiric adjustments that dictate clinical practice while more efficient logically designed interventions remain rather exceptional. Interestingly, it is also very much the neuro technology developed around optogenetics that offers the most promising tools to fill in the existing knowledge gaps about brain function in health and disease. The present review examines Parkinson's disease and refractory epilepsy as use cases for possible optogenetic stimulation therapies.
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Affiliation(s)
- Jean Delbeke
- LCEN3, Department of Neurology, Institute of Neuroscience, Ghent University, Ghent, Belgium
| | | | - Katrien Mols
- Neuroscience Research Flanders, Leuven, Belgium.,Life Science and Imaging, Imec, Leuven, Belgium
| | | | - Dimiter Prodanov
- Neuroscience Research Flanders, Leuven, Belgium.,Environment, Health and Safety, Imec, Leuven, Belgium
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18
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Dagnew R, Lin YY, Agatep J, Cheng M, Jann A, Quach V, Monroe M, Singh G, Minasyan A, Hakimian J, Kee T, Cushman J, Walwyn W. CerebraLux: a low-cost, open-source, wireless probe for optogenetic stimulation. NEUROPHOTONICS 2017; 4:045001. [PMID: 29057282 PMCID: PMC5635269 DOI: 10.1117/1.nph.4.4.045001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 08/30/2017] [Indexed: 06/07/2023]
Abstract
The use of optogenetics to activate or inhibit neurons is an important toolbox for neuroscientists. Several optogenetic devices are in use. These range from wired systems where the optoprobe is physically connected to the light source by a tether, to wireless systems that are remotely controlled. There are advantages and disadvantages of both; the wired systems are lightweight but limit movement due to the tether, and wireless systems allow unrestricted movement but may be heavier than wired systems. Both systems can be expensive to install and use. We have developed a low cost, wireless optogenetic probe, CerebraLux, built from off-the-shelf components. CerebraLux consists of two separable units; an optical component consisting of the baseplate holding the fiber-optic in place and an electronic component consisting of a light-emitting diode, custom-printed circuit board, an infrared receiver, microcontroller, and a rechargeable, lightweight lithium polymer battery. The optical component (0.5 g) is mounted on the head permanently, whereas the electronic component (2.3 g) is removable and is applied for each experiment. We describe the device, provide all designs and specifications, the methods to manufacture and use the device in vivo, and demonstrate feasibility in a mouse behavioral paradigm.
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Affiliation(s)
- Robel Dagnew
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Yin-Ying Lin
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Jerikko Agatep
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Michael Cheng
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Andrew Jann
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Viola Quach
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Michelle Monroe
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Ganeev Singh
- University of California, David Geffen School of Medicine, Department of Psychiatry and Biobehavioral Sciences, Los Angeles, California, United States
| | - Ani Minasyan
- University of California, David Geffen School of Medicine, Department of Psychiatry and Biobehavioral Sciences, Los Angeles, California, United States
| | - Joshua Hakimian
- University of California, David Geffen School of Medicine, Department of Psychiatry and Biobehavioral Sciences, Los Angeles, California, United States
| | - Theodore Kee
- University of California, Department of Bioengineering, Los Angeles, California, United States
| | - Jesse Cushman
- University of California, Department of Psychology, Los Angeles, California, United States
| | - Wendy Walwyn
- University of California, David Geffen School of Medicine, Department of Psychiatry and Biobehavioral Sciences, Los Angeles, California, United States
- University of California, Brain Research Institute, Los Angeles, California, United States
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19
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Long-term expression of melanopsin and channelrhodopsin causes no gross alterations in the dystrophic dog retina. Gene Ther 2017; 24:735-741. [PMID: 28880021 DOI: 10.1038/gt.2017.63] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 07/05/2017] [Accepted: 07/10/2017] [Indexed: 01/25/2023]
Abstract
Several preclinical studies have investigated the potential of algal channelrhodopsin and human melanopsin as optogenetic tools for vision restoration. In the present study, we assessed the potentially deleterious effects of long-term expression of these optogenes on the diseased retina in a large animal model of retinal degeneration, the RPE65-deficient Briard dog model of Leber congenital amaurosis. Intravitreal injection of adeno-associated virus vectors expressing channelrhodopsin and melanopsin had no effect on retinal thickness over a 16-month period post injection. Our data support the safety of the optogenetic approach for the treatment of blindness.
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20
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Govorunova EG, Sineshchekov OA, Li H, Spudich JL. Microbial Rhodopsins: Diversity, Mechanisms, and Optogenetic Applications. Annu Rev Biochem 2017; 86:845-872. [PMID: 28301742 PMCID: PMC5747503 DOI: 10.1146/annurev-biochem-101910-144233] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Microbial rhodopsins are a family of photoactive retinylidene proteins widespread throughout the microbial world. They are notable for their diversity of function, using variations of a shared seven-transmembrane helix design and similar photochemical reactions to carry out distinctly different light-driven energy and sensory transduction processes. Their study has contributed to our understanding of how evolution modifies protein scaffolds to create new protein chemistry, and their use as tools to control membrane potential with light is fundamental to optogenetics for research and clinical applications. We review the currently known functions and present more in-depth assessment of three functionally and structurally distinct types discovered over the past two years: (a) anion channelrhodopsins (ACRs) from cryptophyte algae, which enable efficient optogenetic neural suppression; (b) cryptophyte cation channelrhodopsins (CCRs), structurally distinct from the green algae CCRs used extensively for neural activation and from cryptophyte ACRs; and
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Affiliation(s)
- Elena G Govorunova
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - Oleg A Sineshchekov
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - Hai Li
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
| | - John L Spudich
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030; , , ,
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21
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Illuminating developmental biology through photochemistry. Nat Chem Biol 2017; 13:587-598. [PMID: 28514427 DOI: 10.1038/nchembio.2369] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 03/22/2017] [Indexed: 01/06/2023]
Abstract
Developmental biology has been continually shaped by technological advances, evolving from a descriptive science into one immersed in molecular and cellular mechanisms. Most recently, genome sequencing and 'omics' profiling have provided developmental biologists with a wealth of genetic and biochemical information; however, fully translating this knowledge into functional understanding will require new experimental capabilities. Photoactivatable probes have emerged as particularly valuable tools for investigating developmental mechanisms, as they can enable rapid, specific manipulations of DNA, RNA, proteins, and cells with spatiotemporal precision. In this Perspective, we describe optochemical and optogenetic systems that have been applied in multicellular organisms, insights gained through the use of these probes, and their current limitations. We also suggest how chemical biologists can expand the reach of photoactivatable technologies and bring new depth to our understanding of organismal development.
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22
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Grimm C, Vierock J, Hegemann P, Wietek J. Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins. J Vis Exp 2017. [PMID: 28570519 DOI: 10.3791/55497] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Over the past decade, channelrhodopsins became indispensable in neuroscientific research where they are used as tools to non-invasively manipulate electrical processes in target cells. In this context, ion selectivity of a channelrhodopsin is of particular importance. This article describes the investigation of chloride selectivity for a recently identified anion-conducting channelrhodopsin of Proteomonas sulcata via electrophysiological patch-clamp recordings on HEK293 cells. The experimental procedure for measuring light-gated photocurrents demands a fast switchable - ideally monochromatic - light source coupled into the microscope of an otherwise conventional patch-clamp setup. Preparative procedures prior to the experiment are outlined involving preparation of buffered solutions, considerations on liquid junction potentials, seeding and transfection of cells, and pulling of patch pipettes. The actual recording of current-voltage relations to determine the reversal potentials for different chloride concentrations takes place 24 h to 48 h after transfection. Finally, electrophysiological data are analyzed with respect to theoretical considerations of chloride conduction.
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Affiliation(s)
- Christiane Grimm
- Experimental Biophysics, Institute of Biology, Humboldt-Universität zu Berlin
| | - Johannes Vierock
- Experimental Biophysics, Institute of Biology, Humboldt-Universität zu Berlin
| | - Peter Hegemann
- Experimental Biophysics, Institute of Biology, Humboldt-Universität zu Berlin
| | - Jonas Wietek
- Experimental Biophysics, Institute of Biology, Humboldt-Universität zu Berlin;
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23
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Hempel CM, Werley CA, Dempsey GT, Gerber DJ. Targeting neuronal function for CNS drug discovery. DRUG DISCOVERY TODAY. TECHNOLOGIES 2017. [PMID: 28647082 DOI: 10.1016/j.ddtec.2017.03.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is a pressing need for new and more effective treatments for central nervous system (CNS) disorders. A large body of evidence now suggests that alterations in synaptic transmission and neuronal excitability represent underlying factors for many neurological and psychiatric diseases. However, it has been challenging to target these complex functional domains for therapeutic discovery using traditional neuronal assay methods. Here we review advances in neuronal screening technologies and cellular model systems that enable phenotypic screening of neuronal function as a basis for novel CNS drug discovery approaches.
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Affiliation(s)
- Chris M Hempel
- Q-State Biosciences, 179 Sidney Street, Cambridge, MA 02139, USA
| | | | - Graham T Dempsey
- Q-State Biosciences, 179 Sidney Street, Cambridge, MA 02139, USA
| | - David J Gerber
- Q-State Biosciences, 179 Sidney Street, Cambridge, MA 02139, USA.
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