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Piatkevich KD, Boyden ES. Optogenetic control of neural activity: The biophysics of microbial rhodopsins in neuroscience. Q Rev Biophys 2023; 57:e1. [PMID: 37831008 DOI: 10.1017/s0033583523000033] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Optogenetics, the use of microbial rhodopsins to make the electrical activity of targeted neurons controllable by light, has swept through neuroscience, enabling thousands of scientists to study how specific neuron types contribute to behaviors and pathologies, and how they might serve as novel therapeutic targets. By activating a set of neurons, one can probe what functions they can initiate or sustain, and by silencing a set of neurons, one can probe the functions they are necessary for. We here review the biophysics of these molecules, asking why they became so useful in neuroscience for the study of brain circuitry. We review the history of the field, including early thinking, early experiments, applications of optogenetics, pre-optogenetics targeted neural control tools, and the history of discovering and characterizing microbial rhodopsins. We then review the biophysical attributes of rhodopsins that make them so useful to neuroscience - their classes and structure, their photocycles, their photocurrent magnitudes and kinetics, their action spectra, and their ion selectivity. Our hope is to convey to the reader how specific biophysical properties of these molecules made them especially useful to neuroscientists for a difficult problem - the control of high-speed electrical activity, with great precision and ease, in the brain.
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Affiliation(s)
- Kiryl D Piatkevich
- School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Edward S Boyden
- McGovern Institute and Koch Institute, Departments of Brain and Cognitive Sciences, Media Arts and Sciences, and Biological Engineering, K. Lisa Yang Center for Bionics and Center for Neurobiological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Cambridge, MA, USA
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2
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Miranda JG, Schleicher WE, Wells KL, Ramirez DG, Landgrave SP, Benninger RKP. Dynamic changes in β-cell [Ca 2+] regulate NFAT activation, gene transcription, and islet gap junction communication. Mol Metab 2022; 57:101430. [PMID: 34979329 PMCID: PMC8804269 DOI: 10.1016/j.molmet.2021.101430] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 12/28/2021] [Accepted: 12/29/2021] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE Diabetes occurs because of insufficient insulin secretion due to β-cell dysfunction within the islet of Langerhans. Elevated glucose levels trigger β-cell membrane depolarization, action potential generation, and slow sustained free-Ca2+ ([Ca2+]) oscillations, which trigger insulin release. Nuclear factor of activated T-cell (NFAT) is a transcription factor, which is regulated by the increases in [Ca2+] and calceineurin (CaN) activation. NFAT regulation links cell activity with gene transcription in many systems and regulates proliferation and insulin granule biogenesis within the β-cell. However, the link between the regulation of β-cell electrical activity and oscillatory [Ca2+] dynamics with NFAT activation and downstream transcription is poorly understood. Here, we tested whether dynamic changes to β-cell electrical activity and [Ca2+] regulate NFAT activation and downstream transcription. METHODS In cell lines, mouse islets, and human islets, including those from donors with type 2 diabetes, we applied both agonists/antagonists of ion channels together with optogenetics to modulate β-cell electrical activity. We measured the dynamics of [Ca2+] and NFAT activation as well as performed whole transcriptome and functional analyses. RESULTS Both glucose-induced membrane depolarization and optogenetic stimulation triggered NFAT activation as well as increased the transcription of NFAT targets and intermediate early genes (IEGs). Importantly, slow, sustained [Ca2+] oscillation conditions led to NFAT activation and downstream transcription. In contrast, in human islets from donors with type2 diabetes, NFAT activation by glucose was diminished, but rescued upon pharmacological stimulation of electrical activity. NFAT activation regulated GJD2 expression and increased Cx36 gap junction permeability upon elevated oscillatory [Ca2+] dynamics. However, it is unclear if NFAT directly binds the GJD2 gene to regulate expression. CONCLUSIONS This study provides an insight into the specific patterns of electrical activity that regulate NFAT activation, gene transcription, and islet function. In addition, it provides information on how these factors are disrupted in diabetes.
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Affiliation(s)
- Jose G Miranda
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora CO, 80045, USA
| | - Wolfgang E Schleicher
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora CO, 80045, USA
| | - Kristen L Wells
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - David G Ramirez
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora CO, 80045, USA
| | - Samantha P Landgrave
- Program in Cell Biology, Stem Cell and Development, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Richard K P Benninger
- Department of Bioengineering, University of Colorado Anschutz Medical Campus, Aurora CO, 80045, USA; Program in Cell Biology, Stem Cell and Development, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA; Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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3
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Walther F, Feind D, Vom Dahl C, Müller CE, Kukaj T, Sattler C, Nagel G, Gao S, Zimmer T. Action potentials in Xenopus oocytes triggered by blue light. J Gen Physiol 2020; 152:151581. [PMID: 32211871 PMCID: PMC7201882 DOI: 10.1085/jgp.201912489] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 02/24/2020] [Indexed: 11/20/2022] Open
Abstract
Voltage-gated sodium (Na+) channels are responsible for the fast upstroke of the action potential of excitable cells. The different α subunits of Na+ channels respond to brief membrane depolarizations above a threshold level by undergoing conformational changes that result in the opening of the pore and a subsequent inward flux of Na+. Physiologically, these initial membrane depolarizations are caused by other ion channels that are activated by a variety of stimuli such as mechanical stretch, temperature changes, and various ligands. In the present study, we developed an optogenetic approach to activate Na+ channels and elicit action potentials in Xenopus laevis oocytes. All recordings were performed by the two-microelectrode technique. We first coupled channelrhodopsin-2 (ChR2), a light-sensitive ion channel of the green alga Chlamydomonas reinhardtii, to the auxiliary β1 subunit of voltage-gated Na+ channels. The resulting fusion construct, β1-ChR2, retained the ability to modulate Na+ channel kinetics and generate photosensitive inward currents. Stimulation of Xenopus oocytes coexpressing the skeletal muscle Na+ channel Nav1.4 and β1-ChR2 with 25-ms lasting blue-light pulses resulted in rapid alterations of the membrane potential strongly resembling typical action potentials of excitable cells. Blocking Nav1.4 with tetrodotoxin prevented the fast upstroke and the reversal of the membrane potential. Coexpression of the voltage-gated K+ channel Kv2.1 facilitated action potential repolarization considerably. Light-induced action potentials were also obtained by coexpressing β1-ChR2 with either the neuronal Na+ channel Nav1.2 or the cardiac-specific isoform Nav1.5. Potential applications of this novel optogenetic tool are discussed.
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Affiliation(s)
- Florian Walther
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Dominic Feind
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Vom Dahl
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christoph Emanuel Müller
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Taulant Kukaj
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Christian Sattler
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
| | - Georg Nagel
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Shiqiang Gao
- Institute of Physiology-Neurophysiology, Biocentre, Julius-Maximilians-University, Wuerzburg, Germany
| | - Thomas Zimmer
- Institute of Physiology II, University Hospital Jena, Friedrich Schiller University, Jena, Germany
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4
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Mattingly M, Weineck K, Costa J, Cooper RL. Hyperpolarization by activation of halorhodopsin results in enhanced synaptic transmission: Neuromuscular junction and CNS circuit. PLoS One 2018; 13:e0200107. [PMID: 29969493 PMCID: PMC6029800 DOI: 10.1371/journal.pone.0200107] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 06/19/2018] [Indexed: 12/22/2022] Open
Abstract
Optogenetics offers a unique method to regulate the activity of select neural circuits. However, the electrophysiological consequences of targeted optogenetic manipulation upon the entire circuit remain poorly understood. Analysis of the sensory-CNS-motor circuit in Drosophila larvae expressing eHpHR and ChR2-XXL revealed unexpected patterns of excitability. Optical stimulation of motor neurons targeted to express eNpHR resulted in inhibition followed by excitation of body wall contraction with repetitive stimulation in intact larvae. In situ preparations with direct electrophysiological measures showed an increased responsiveness to excitatory synaptic activity induced by sensory stimulation within a functional neural circuit. To ensure proper function of eNpHR and ChR2-XXL they were expressed in body wall muscle and direct electrophysiological measurements were obtained. Under eNpHR induced hyperpolarization the muscle remained excitable with increased amplitude of excitatory postsynaptic synaptic potentials. Theoretical models to explain the observations are presented. This study aids in increasing the understanding of the varied possible influences with light activated proteins within intact neural circuits.
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Affiliation(s)
- Matthew Mattingly
- Department of Biology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Kristin Weineck
- Department of Biology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States of America
- Goethe University Frankfurt am Main, Frankfurt, Germany
| | - Jennifer Costa
- Department of Biology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Robin L. Cooper
- Department of Biology and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky, United States of America
- * E-mail:
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5
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Rorsman NJG, Ta CM, Garnett H, Swietach P, Tammaro P. Defining the ionic mechanisms of optogenetic control of vascular tone by channelrhodopsin-2. Br J Pharmacol 2018; 175:2028-2045. [PMID: 29486056 PMCID: PMC5979753 DOI: 10.1111/bph.14183] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 01/16/2018] [Accepted: 02/14/2018] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Optogenetic control of electromechanical coupling in vascular smooth muscle cells (VSMCs) is emerging as a powerful research tool with potential applications in drug discovery and therapeutics. However, the precise ionic mechanisms involved in this control remain unclear. EXPERIMENTAL APPROACH Cell imaging, patch-clamp electrophysiology and muscle tension recordings were used to define these mechanisms over a wide range of light stimulations. KEY RESULTS Transgenic mice expressing a channelrhodopsin-2 variant [ChR2(H134R)] selectively in VSMCs were generated. Isolated VSMCs obtained from these mice demonstrated blue light-induced depolarizing whole-cell currents. Fine control of artery tone was attained by varying the intensity of the light stimulus. This arterial response was sufficient to overcome the endogenous, melanopsin-mediated, light-evoked, arterial relaxation observed in the presence of contractile agonists. Ca2+ entry through voltage-gated Ca2+ channels, and opening of plasmalemmal depolarizing channels (TMEM16A and TRPM) and intracellular IP3 receptors were involved in the ChR2(H134R)-dependent arterial response to blue light at intensities lower than ~0.1 mW·mm-2 . Light stimuli of greater intensity evoked a significant Ca2+ influx directly through ChR2(H134R) and produced marked intracellular alkalinization of VSMCs. CONCLUSIONS AND IMPLICATIONS We identified the range of light intensity allowing optical control of arterial tone, primarily by means of endogenous channels and without substantial alteration to intracellular pH. Within this range, mice expressing ChR2(H134R) in VSMCs are a powerful experimental model for achieving accurate and tuneable optical voltage-clamp of VSMCs and finely graded control of arterial tone, offering new approaches to the discovery of vasorelaxant drugs.
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Affiliation(s)
- Nils J G Rorsman
- Department of PharmacologyUniversity of OxfordOxfordUK
- OXION Initiative in Ion Channels and DiseaseUniversity of OxfordOxfordUK
| | - Chau M Ta
- Department of PharmacologyUniversity of OxfordOxfordUK
| | | | - Pawel Swietach
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Paolo Tammaro
- Department of PharmacologyUniversity of OxfordOxfordUK
- OXION Initiative in Ion Channels and DiseaseUniversity of OxfordOxfordUK
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Martín R, Ferrero JJ, Collado-Alsina A, Aguado C, Luján R, Torres M, Sánchez-Prieto J. Bidirectional modulation of glutamatergic synaptic transmission by metabotropic glutamate type 7 receptors at Schaffer collateral-CA1 hippocampal synapses. J Physiol 2018; 596:921-940. [PMID: 29280494 DOI: 10.1113/jp275371] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 12/21/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Neurotransmitter release is inhibited by metabotropic glutamate type 7 (mGlu7 ) receptors that reduce Ca2+ influx, yet synapses lacking this receptor also produce weaker release, suggesting that mGlu7 receptors may also prime synaptic vesicles for release. Prolonged activation of mGlu7 receptors with the agonist l-AP4 first reduces and then enhances the amplitude of EPSCs through a presynaptic effect. The inhibitory response is blocked by pertussis toxin, while the potentiating response is prevented by a phospholipase C inhibitor (U73122) and an inhibitor of diacylglycerol (DAG) binding (calphostin C), suggesting that this receptor also couples to pathways that generate DAG. Release potentiation is associated with an increase in the number of synaptic vesicles close to the plasma membrane, which was dependent on the Munc13-2 and RIM1α proteins. The Glu7 receptors activated by the glutamate released following high frequency stimulation provoke a bidirectional modulation of synaptic transmission. ABSTRACT Neurotransmitter release is driven by Ca2+ influx at synaptic boutons that acts on synaptic vesicles ready to undergo exocytosis. Neurotransmitter release is inhibited when metabotropic glutamate type 7 (mGlu7 ) receptors provoke a reduction in Ca2+ influx, although the reduced release from synapses lacking this receptor suggests that they may also prime synaptic vesicles for release. These mGlu7 receptors activate phospholipase C (PLC) and generate inositol trisphosphate, which in turn releases Ca2+ from intracellular stores and produces diacylglycerol (DAG), an activator of proteins containing DAG-binding domains such as Munc13 and protein kinase C (PKC). However, the full effects of mGlu7 receptor signalling on synaptic transmission are unclear. We found that prolonged activation of mGlu7 receptors with the agonist l-AP4 first reduces and then enhances the amplitude of EPSCs, a presynaptic effect that changes the frequency but not the amplitude of the mEPSCs and the paired pulse ratio. Pertussis toxin blocks the inhibitory response, while the PLC inhibitor U73122, and the inhibitor of DAG binding calphostin C, prevent receptor mediated potentiation. Moreover, this DAG-dependent potentiation of the release machinery brings more synaptic vesicles closer to the active zone plasma membrane in a Munc13-2- and RIM1α-dependent manner. Electrically evoked release of glutamate that activates mGlu7 receptors also bidirectionally modulates synaptic transmission. In these conditions, potentiation now occurs rapidly and it overcomes any inhibition, such that potentiation prevails unless it is suppressed with the PLC inhibitor U73122.
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Affiliation(s)
- Ricardo Martín
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - José Javier Ferrero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - Andrea Collado-Alsina
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Magdalena Torres
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - José Sánchez-Prieto
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, 28040, Madrid, Spain.,Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
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Shen W, Nikolic L, Meunier C, Pfrieger F, Audinat E. An autocrine purinergic signaling controls astrocyte-induced neuronal excitation. Sci Rep 2017; 7:11280. [PMID: 28900295 PMCID: PMC5595839 DOI: 10.1038/s41598-017-11793-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 08/29/2017] [Indexed: 12/30/2022] Open
Abstract
Astrocyte-derived gliotransmitters glutamate and ATP modulate neuronal activity. It remains unclear, however, how astrocytes control the release and coordinate the actions of these gliotransmitters. Using transgenic expression of the light-sensitive channelrhodopsin 2 (ChR2) in astrocytes, we observed that photostimulation reliably increases action potential firing of hippocampal pyramidal neurons. This excitation relies primarily on a calcium-dependent glutamate release by astrocytes that activates neuronal extra-synaptic NMDA receptors. Remarkably, our results show that ChR2-induced Ca2+ increase and subsequent glutamate release are amplified by ATP/ADP-mediated autocrine activation of P2Y1 receptors on astrocytes. Thus, neuronal excitation is promoted by a synergistic action of glutamatergic and autocrine purinergic signaling in astrocytes. This new mechanism may be particularly relevant for pathological conditions in which ATP extracellular concentration is increased and acts as a major danger signal.
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Affiliation(s)
- Weida Shen
- Inserm U1128, Paris Descartes University, 75006, Paris, France
| | | | - Claire Meunier
- Inserm U1128, Paris Descartes University, 75006, Paris, France
| | - Frank Pfrieger
- Institute of Cellular and Integrative Neurosciences, CNRS UPR 3212, University of Strasbourg, 67084, Strasbourg, France
| | - Etienne Audinat
- Inserm U1128, Paris Descartes University, 75006, Paris, France.
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Dhammika Bandara HM, Hua Z, Zhang M, Pauff SM, Miller SC, Colby Davie EA, Kobertz WR. Palladium-Mediated Synthesis of a Near-Infrared Fluorescent K + Sensor. J Org Chem 2017; 82:8199-8205. [PMID: 28664732 PMCID: PMC5715468 DOI: 10.1021/acs.joc.7b00845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Potassium (K+) exits electrically excitable cells during normal and pathophysiological activity. Currently, K+-sensitive electrodes and electrical measurements are the primary tools to detect K+ fluxes. Here, we describe the synthesis of a near-IR, oxazine fluorescent K+ sensor (KNIR-1) with a dissociation constant suited for detecting changes in intracellular and extracellular K+ concentrations. KNIR-1 treatment of cells expressing voltage-gated K+ channels enabled the visualization of intracellular K+ depletion upon channel opening and restoration of cytoplasmic K+ after channel closing.
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Affiliation(s)
- H. M. Dhammika Bandara
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Zhengmao Hua
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Mei Zhang
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Steven M. Pauff
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Stephen C. Miller
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Elizabeth A. Colby Davie
- Department of Natural Sciences, Assumption College, 500 Salisbury Street, Worcester MA 01609, United States
| | - William R. Kobertz
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
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9
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Li Q, Ni RR, Hong H, Goh KY, Rossi M, Fast VG, Zhou L. Electrophysiological Properties and Viability of Neonatal Rat Ventricular Myocyte Cultures with Inducible ChR2 Expression. Sci Rep 2017; 7:1531. [PMID: 28484220 PMCID: PMC5431527 DOI: 10.1038/s41598-017-01723-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 04/03/2017] [Indexed: 11/25/2022] Open
Abstract
Channelrhodopsin-2 (ChR2)-based optogenetic technique has been increasingly applied to cardiovascular research. However, the potential effects of ChR2 protein overexpression on cardiomyocytes are not completely understood. The present work aimed to examine how the doxycycline-inducible lentiviral-mediated ChR2 expression may affect cell viability and electrophysiological property of neonatal rat ventricular myocyte (NRVM) cultures. Primary NVRMs were infected with lentivirus containing ChR2 or YFP gene and subjected to cytotoxicity analysis. ChR2-expressing cultures were then paced electrically or optically with a blue light-emitting diode, with activation spread recorded simultaneously using optical mapping. Results showed that ChR2 could be readily transduced to NRVMs by the doxycycline-inducible lentiviral system; however, high-level ChR2 (but not YFP) expression was associated with substantial cytotoxicity, which hindered optical pacing. Application of bromodeoxyuridine significantly reduced cell damage, allowing stimulation with light. Simultaneous optical Vm mapping showed that conduction velocity, action potential duration, and dVm/dtmax were similar in ChR2-expressing and control cultures. Finally, the ChR2-expressing cultures could be optically paced at multiple sites, with significantly reduced overall activation time. In summary, we demonstrated that inducible lentiviral-mediated ChR2 overexpression might cause cytotoxicity in NRVM cultures, which could be alleviated without impairing electrophysiological function, allowing simultaneous optical pacing and Vm mapping.
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Affiliation(s)
- Qince Li
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, 1900 University Blvd, Birmingham, 35294, Alabama, USA.,Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA
| | - Rong Ruby Ni
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, 1900 University Blvd, Birmingham, 35294, Alabama, USA.,Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA
| | - Huixian Hong
- Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA
| | - Kah Yong Goh
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, 1900 University Blvd, Birmingham, 35294, Alabama, USA.,Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA
| | - Michael Rossi
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd, Birmingham, 35294, Alabama, USA
| | - Vladimir G Fast
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd, Birmingham, 35294, Alabama, USA. .,Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA.
| | - Lufang Zhou
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, 1900 University Blvd, Birmingham, 35294, Alabama, USA. .,Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd, Birmingham, 35294, Alabama, USA. .,Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA. .,Comprehensive Cardiovascular Center, University of Alabama at Birmingham, Birmingham, 35294, Alabama, USA.
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Abstract
After the discovery of Channelrhodopsin, a light-gated ion channel, only a few people saw the diverse range of applications for such a protein. Now, more than 10 years later Channelrhodopsins have become widely accepted as the ultimate tool to control the membrane potential of excitable cells via illumination. The demand for more application-specific Channelrhodopsin variants started a race between protein engineers to design improved variants. Even though many engineered variants have undisputable advantages compared to wild-type variants, many users are alienated by the tremendous amount of new variants and their perplexing names. Here, we review new variants whose efficacy has already been proven in neurophysiological experiments, or variants which are likely to extend the optogenetic toolbox. Variants are described based on their mechanistic and operational properties in terms of expression, kinetics, ion selectivity, and wavelength responsivity.
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Affiliation(s)
- Jonas Wietek
- Experimental Biophysics, Humboldt University Berlin, Invalidenstrasse 42, 10115, Berlin, Germany
| | - Matthias Prigge
- Department of Neurobiology, Weizmann Institute of Science, Herzel 234, 76100, Rehovot, Israel.
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11
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Distinct roles for GABA across multiple timescales in mammalian circadian timekeeping. Proc Natl Acad Sci U S A 2015; 112:E3911-9. [PMID: 26130805 DOI: 10.1073/pnas.1420753112] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The suprachiasmatic nuclei (SCN), the central circadian pacemakers in mammals, comprise a multiscale neuronal system that times daily events. We use recent advances in graphics processing unit computing to generate a multiscale model for the SCN that resolves cellular electrical activity down to the timescale of individual action potentials and the intracellular molecular events that generate circadian rhythms. We use the model to study the role of the neurotransmitter GABA in synchronizing circadian rhythms among individual SCN neurons, a topic of much debate in the circadian community. The model predicts that GABA signaling has two components: phasic (fast) and tonic (slow). Phasic GABA postsynaptic currents are released after action potentials, and can both increase or decrease firing rate, depending on their timing in the interspike interval, a modeling hypothesis we experimentally validate; this allows flexibility in the timing of circadian output signals. Phasic GABA, however, does not significantly affect molecular timekeeping. The tonic GABA signal is released when cells become very excited and depolarized; it changes the excitability of neurons in the network, can shift molecular rhythms, and affects SCN synchrony. We measure which neurons are excited or inhibited by GABA across the day and find GABA-excited neurons are synchronized by-and GABA-inhibited neurons repelled from-this tonic GABA signal, which modulates the synchrony in the SCN provided by other signaling molecules. Our mathematical model also provides an important tool for circadian research, and a model computational system for the many multiscale projects currently studying brain function.
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12
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Optical control of neuronal excitation and inhibition using a single opsin protein, ChR2. Sci Rep 2013; 3:3110. [PMID: 24173561 PMCID: PMC3813941 DOI: 10.1038/srep03110] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 10/14/2013] [Indexed: 12/11/2022] Open
Abstract
The effect of electrical stimulation on neuronal membrane potential is frequency dependent. Low frequency electrical stimulation can evoke action potentials, whereas high frequency stimulation can inhibit action potential transmission. Optical stimulation of channelrhodopsin-2 (ChR2) expressed in neuronal membranes can also excite action potentials. However, it is unknown whether optical stimulation of ChR2-expressing neurons produces a transition from excitation to inhibition with increasing light pulse frequencies. Here we report optical inhibition of motor neuron and muscle activity in vivo in the cooled sciatic nerves of Thy1-ChR2-EYFP mice. We also demonstrate all-optical single-wavelength control of neuronal excitation and inhibition without co-expression of inhibitory and excitatory opsins. This all-optical system is free from stimulation-induced electrical artifacts and thus provides a new approach to investigate mechanisms of high frequency inhibition in neuronal circuits in vivo and in vitro.
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Yawo H, Asano T, Sakai S, Ishizuka T. Optogenetic manipulation of neural and non-neural functions. Dev Growth Differ 2013; 55:474-90. [PMID: 23550617 DOI: 10.1111/dgd.12053] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 02/25/2013] [Accepted: 02/26/2013] [Indexed: 01/22/2023]
Abstract
Optogenetic manipulation of the neuronal activity enables one to analyze the neuronal network both in vivo and in vitro with precise spatio-temporal resolution. Channelrhodopsins (ChRs) are light-sensitive cation channels that depolarize the cell membrane, whereas halorhodopsins and archaerhodopsins are light-sensitive Cl(-) and H(+) transporters, respectively, that hyperpolarize it when exogenously expressed. The cause-effect relationship between a neuron and its function in the brain is thus bi-directionally investigated with evidence of necessity and sufficiency. In this review we discuss the potential of optogenetics with a focus on three major requirements for its application: (i) selection of the light-sensitive proteins optimal for optogenetic investigation, (ii) targeted expression of these selected proteins in a specific group of neurons, and (iii) targeted irradiation with high spatiotemporal resolution. We also discuss recent progress in the application of optogenetics to studies of non-neural cells such as glial cells, cardiac and skeletal myocytes. In combination with stem cell technology, optogenetics may be key to successful research using embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) derived from human patients through optical regulation of differentiation-maturation, through optical manipulation of tissue transplants and, furthermore, through facilitating survival and integration of transplants.
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Affiliation(s)
- Hiromu Yawo
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
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14
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Weick JP, Johnson MA, Skroch SP, Williams JC, Deisseroth K, Zhang SC. Functional control of transplantable human ESC-derived neurons via optogenetic targeting. Stem Cells 2011; 28:2008-16. [PMID: 20827747 DOI: 10.1002/stem.514] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Current methods to examine and regulate the functional integration and plasticity of human ESC (hESC)-derived neurons are cumbersome and technically challenging. Here, we engineered hESCs and their derivatives to express the light-gated channelrhodopsin-2 (ChR2) protein to overcome these deficiencies. Optogenetic targeting of hESC-derived neurons with ChR2 linked to the mCherry fluorophore allowed reliable cell tracking as well as light-induced spiking at physiological frequencies. Optically induced excitatory and inhibitory postsynaptic currents could be elicited in either ChR2(+) or ChR2(-) neurons in vitro and in acute brain slices taken from transplanted severe combined immunodeficient (SCID) mice. Furthermore, we created a clonal hESC line that expresses ChR2-mCherry under the control of the synapsin-1 promoter. On neuronal differentiation, ChR2-mCherry expression was restricted to neurons and was stably expressed for at least 6 months, providing more predictable light-induced currents than transient infections. This pluripotent cell line will allow both in vitro and in vivo analysis of functional development as well as the integration capacity of neuronal populations for cell-replacement strategies.
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Affiliation(s)
- Jason P Weick
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA
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15
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Kleinlogel S, Feldbauer K, Dempski RE, Fotis H, Wood PG, Bamann C, Bamberg E. Ultra light-sensitive and fast neuronal activation with the Ca²+-permeable channelrhodopsin CatCh. Nat Neurosci 2011; 14:513-8. [PMID: 21399632 DOI: 10.1038/nn.2776] [Citation(s) in RCA: 312] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 02/02/2011] [Indexed: 01/19/2023]
Abstract
The light-gated cation channel channelrhodopsin-2 (ChR2) has rapidly become an important tool in neuroscience, and its use is being considered in therapeutic interventions. Although wild-type and known variant ChR2s are able to drive light-activated spike trains, their use in potential clinical applications is limited by either low light sensitivity or slow channel kinetics. We present a new variant, calcium translocating channelrhodopsin (CatCh), which mediates an accelerated response time and a voltage response that is ~70-fold more light sensitive than that of wild-type ChR2. CatCh's superior properties stem from its enhanced Ca²(+) permeability. An increase in [Ca²(+)](i) elevates the internal surface potential, facilitating activation of voltage-gated Na(+) channels and indirectly increasing light sensitivity. Repolarization following light-stimulation is markedly accelerated by Ca²(+)-dependent BK channel activation. Our results demonstrate a previously unknown principle: shifting permeability from monovalent to divalent cations to increase sensitivity without compromising fast kinetics of neuronal activation. This paves the way for clinical use of light-gated channels.
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Affiliation(s)
- Sonja Kleinlogel
- Max Planck Institute of Biophysics, Department of Biophysical Chemistry, Frankfurt am Main, Germany
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Chater TE, Henley JM, Brown JT, Randall AD. Voltage- and temperature-dependent gating of heterologously expressed channelrhodopsin-2. J Neurosci Methods 2010; 193:7-13. [PMID: 20691205 DOI: 10.1016/j.jneumeth.2010.07.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 07/27/2010] [Accepted: 07/27/2010] [Indexed: 10/19/2022]
Abstract
Channelrhodopsins are light-activated channels originally isolated from algae that are being used increasingly as tools to non-invasively stimulate neurones. Despite their widespread use some aspects of their biophysical properties have not been fully characterised. Here we report detailed investigation of the gating kinetics and voltage-dependence of ChR2 transiently expressed in HEK-293 cells. Currents were elicited using light pulses of defined duration and intensity generated by a blue LED. Datasets were gathered both at room temperature (RT, ∼22°C) and 37°C. Current responses to light rose rapidly to a peak and then desensitized to a steady state plateau. When illumination was terminated currents rapidly deactivated. Recovery from desensitization at -85 mV was slow with half-times of 1.4 and 3.1s at 37°C and ∼22°C, respectively. At both temperatures, the reversal potential of ChR2 responses was a few mV positive to 0 mV. Both the peak and plateau phases of ChR2 responses exhibited strong inward rectification with only small outward currents at positive membrane potentials. The rates of ChR2 activation, deactivation and desensitization were ∼2 times faster at 37°C than at ∼22°C. Both the activation and deactivation kinetics of ChR2 were significantly slowed by depolarization at both temperatures. Additionally, the degree of steady state desensitization was greater at more depolarized potentials. The macroscopic desensitization kinetics were not voltage-dependent, but recovery from desensitization was slowed by depolarization. These gating behaviour data provide an important basis for more detailed analysis of the properties and limitations of ChR2 use in more complex systems.
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Affiliation(s)
- T E Chater
- MRC Centre for Synaptic Plasticity, University of Bristol, University Walk, Bristol, UK
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Moritz A, Scheschonka A, Beckhaus T, Karas M, Betz H. Metabotropic glutamate receptor 4 interacts with microtubule-associated protein 1B. Biochem Biophys Res Commun 2009; 390:82-6. [DOI: 10.1016/j.bbrc.2009.09.070] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 09/17/2009] [Indexed: 01/17/2023]
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