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Journal articles on the topic 'Channelrhodopsin'

Author: Grafiati

Published: 4 June 2021

Last updated: 11 March 2023

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1

Idzhilova, Olga S., Gulnur R. Smirnova, Lada E. Petrovskaya, Darya A. Kolotova, Mikhail A. Ostrovsky, and Alexey Y. Malyshev. "Cationic Channelrhodopsin from the Alga Platymonas subcordiformis as a Promising Optogenetic Tool." Biochemistry (Moscow) 87, no. 11 (November 2022): 1327–34. http://dx.doi.org/10.1134/s0006297922110116.

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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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2

Sineshchekov, Oleg A., Hai Li, Elena G. Govorunova, and John L. Spudich. "Photochemical reaction cycle transitions during anion channelrhodopsin gating." Proceedings of the National Academy of Sciences 113, no. 14 (March 21, 2016): E1993—E2000. http://dx.doi.org/10.1073/pnas.1525269113.

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A recently discovered family of natural anion channelrhodopsins (ACRs) have the highest conductance among channelrhodopsins and exhibit exclusive anion selectivity, which make them efficient inhibitory tools for optogenetics. We report analysis of flash-induced absorption changes in purified wild-type and mutant ACRs, and of photocurrents they generate in HEK293 cells. Contrary to cation channelrhodopsins (CCRs), the ion conducting state of ACRs develops in an L-like intermediate that precedes the deprotonation of the retinylidene Schiff base (i.e., formation of an M intermediate). Channel closing involves two mechanisms leading to depletion of the conducting L-like state: (i) Fast closing is caused by a reversible L⇔M conversion. Glu-68 in Guillardia theta ACR1 plays an important role in this transition, likely serving as a counterion and proton acceptor at least at high and neutral pH. Incomplete suppression of M formation in the GtACR1_E68Q mutant indicates the existence of an alternative proton acceptor. (ii) Slow closing of the channel parallels irreversible depletion of the M-like and, hence, L-like state. Mutation of Cys-102 that strongly affected slow channel closing slowed the photocycle to the same extent. The L and M intermediates were in equilibrium in C102A as in the WT. In the position of Glu-123 in channelrhodopsin-2, ACRs contain a noncarboxylate residue, the mutation of which to Glu produced early Schiff base proton transfer and strongly inhibited channel activity. The data reveal fundamental differences between natural ACR and CCR conductance mechanisms and their underlying photochemistry, further confirming that these proteins form distinct families of rhodopsin channels.

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3

Schneider, Franziska, Christiane Grimm, and Peter Hegemann. "Biophysics of Channelrhodopsin." Annual Review of Biophysics 44, no. 1 (June 22, 2015): 167–86. http://dx.doi.org/10.1146/annurev-biophys-060414-034014.

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4

Ernst, Oliver P., Pedro A. Sánchez Murcia, Peter Daldrop, Satoshi P. Tsunoda, Suneel Kateriya, and Peter Hegemann. "Photoactivation of Channelrhodopsin." Journal of Biological Chemistry 283, no. 3 (November 9, 2007): 1637–43. http://dx.doi.org/10.1074/jbc.m708039200.

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Channelrhodopsins (ChRs) are light-gated ion channels that control photomovement of microalgae. In optogenetics, ChRs are widely applied for light-triggering action potentials in cells, tissues, and living animals, yet the spectral properties and photocycle of ChR remain obscure. In this study, we cloned a ChR from the colonial alga Volvox carteri, VChR. After electrophysiological characterization in Xenopus oocytes, VChR was expressed in COS-1 cells and purified. Time-resolved UV-visible spectroscopy revealed a pH-dependent equilibrium of two dark species, D470/D480. Laser flashes converted both with τ ≈ 200 μs into major photointermediates P510/P530, which reverted back to the dark states with τ ≈ 15-100 ms. Both intermediates were assigned to conducting states. Three early intermediates P500/P515 and P390 were detected on a ns to μs time scale. The spectroscopic and electrical data were unified in a photocycle model. The functional expression of VChR we report here paves the way toward a broader structure/function analysis of the recently identified class of light-gated ion channels.

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5

Lórenz-Fonfría, Víctor A., Tom Resler, Nils Krause, Christopher Engelhard, Robert Bittl, Mirka Neumann-Verhoefen, Josef Wachtveitl, et al. "Gating in channelrhodopsin." Biochimica et Biophysica Acta (BBA) - Bioenergetics 1837 (July 2014): e105. http://dx.doi.org/10.1016/j.bbabio.2014.05.251.

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6

Erofeev, Alexander, Evgenii Gerasimov, Anastasia Lavrova, Anastasia Bolshakova, Eugene Postnikov, Ilya Bezprozvanny, and Olga L. Vlasova. "Light Stimulation Parameters Determine Neuron Dynamic Characteristics." Applied Sciences 9, no. 18 (September 5, 2019): 3673. http://dx.doi.org/10.3390/app9183673.

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Optogenetics is a recently developed technique that is widely used to study neuronal function. In optogenetic experiments, neurons encode opsins (channelrhodopsins, halorhodopsins or their derivatives) by means of viruses, plasmids or genetic modification (transgenic lines). Channelrhodopsin are light activated ion channels. Their expression in neurons allows light-dependent control of neuronal activity. The duration and frequency of light stimulation in optogenetic experiments is critical for stable, robust and reproducible experiments. In this study, we performed systematic analyses of these parameters using primary cultures of hippocampal neurons transfected with channelrhodopsin-2 (ChR2). The main goal of this work was to identify the optimal parameters of light stimulation that would result in stable neuronal activity during a repeated light pulse train. We demonstrated that the dependency of the photocurrent on the light pulse duration is described by a right-skewed bell-shaped curve, while the dependence on the stimulus intensity is close to linear. We established that a duration between 10–30 ms of stimulation was the minimal time necessary to achieve a full response. Obtained results will be useful in planning and interpretation of optogenetic experiments.

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7

Berndt, Andre, Soo Yeun Lee, Jonas Wietek, Charu Ramakrishnan, Elizabeth E. Steinberg, Asim J. Rashid, Hoseok Kim, et al. "Structural foundations of optogenetics: Determinants of channelrhodopsin ion selectivity." Proceedings of the National Academy of Sciences 113, no. 4 (December 22, 2015): 822–29. http://dx.doi.org/10.1073/pnas.1523341113.

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The structure-guided design of chloride-conducting channelrhodopsins has illuminated mechanisms underlying ion selectivity of this remarkable family of light-activated ion channels. The first generation of chloride-conducting channelrhodopsins, guided in part by development of a structure-informed electrostatic model for pore selectivity, included both the introduction of amino acids with positively charged side chains into the ion conduction pathway and the removal of residues hypothesized to support negatively charged binding sites for cations. Engineered channels indeed became chloride selective, reversing near −65 mV and enabling a new kind of optogenetic inhibition; however, these first-generation chloride-conducting channels displayed small photocurrents and were not tested for optogenetic inhibition of behavior. Here we report the validation and further development of the channelrhodopsin pore model via crystal structure-guided engineering of next-generation light-activated chloride channels (iC++) and a bistable variant (SwiChR++) with net photocurrents increased more than 15-fold under physiological conditions, reversal potential further decreased by another ∼15 mV, inhibition of spiking faithfully tracking chloride gradients and intrinsic cell properties, strong expression in vivo, and the initial microbial opsin channel-inhibitor–based control of freely moving behavior. We further show that inhibition by light-gated chloride channels is mediated mainly by shunting effects, which exert optogenetic control much more efficiently than the hyperpolarization induced by light-activated chloride pumps. The design and functional features of these next-generation chloride-conducting channelrhodopsins provide both chronic and acute timescale tools for reversible optogenetic inhibition, confirm fundamental predictions of the ion selectivity model, and further elucidate electrostatic and steric structure–function relationships of the light-gated pore.

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8

Hegemann, Peter, Sabine Ehlenbeck, and Dietrich Gradmann. "Multiple Photocycles of Channelrhodopsin." Biophysical Journal 89, no. 6 (December 2005): 3911–18. http://dx.doi.org/10.1529/biophysj.105.069716.

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9

Watanabe, Hiroshi C., Kai Welke, Franziska Schneider, Satoshi Tsunoda, Feng Zhang, Karl Deisseroth, Peter Hegemann, and Marcus Elstner. "Structural Model of Channelrhodopsin." Journal of Biological Chemistry 287, no. 10 (January 11, 2012): 7456–66. http://dx.doi.org/10.1074/jbc.m111.320309.

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10

Nikolic, Konstantin, Nir Grossman, Matthew S. Grubb, Juan Burrone, Chris Toumazou, and Patrick Degenaar. "Photocycles of Channelrhodopsin-2." Photochemistry and Photobiology 85, no. 1 (January 2009): 400–411. http://dx.doi.org/10.1111/j.1751-1097.2008.00460.x.

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11

Heberle, Joachim, Victor Lorenz-Fonfria, Tom Resler, Bernd Schultz, Ramona Schlesinger, Christian Bamann, and Ernst Bamberg. "Molecular mechanism of channelrhodopsin." Biochimica et Biophysica Acta (BBA) - Bioenergetics 1859 (September 2018): e27. http://dx.doi.org/10.1016/j.bbabio.2018.09.084.

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12

Grossman, Nir, Patrick Degenaar, and Konstantin Nikolic. "Spike engineering with Channelrhodopsin-2." Neuroscience Letters 500 (July 2011): e27. http://dx.doi.org/10.1016/j.neulet.2011.05.144.

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13

Radu, Ionela, Christian Bamann, Melanie Nack, Georg Nagel, Ernst Bamberg, and Joachim Heberle. "Conformational Changes of Channelrhodopsin-2." Journal of the American Chemical Society 131, no. 21 (June 3, 2009): 7313–19. http://dx.doi.org/10.1021/ja8084274.

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14

Gerwert, Klaus. "Channelrhodopsin reveals its dark secrets." Science 358, no. 6366 (November 23, 2017): 1000–1001. http://dx.doi.org/10.1126/science.aar2299.

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15

Pescitelli, Gennaro, Hideaki E. Kato, Satomi Oishi, Jumpei Ito, Andrés Daniel Maturana, Osamu Nureki, and Robert W. Woody. "Exciton Circular Dichroism in Channelrhodopsin." Journal of Physical Chemistry B 118, no. 41 (October 7, 2014): 11873–85. http://dx.doi.org/10.1021/jp505917p.

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16

Hontani, Yusaku, Matthias Broser, Arita Silapetere, Benjamin S. Krause, Peter Hegemann, and John T. M. Kennis. "The femtosecond-to-second photochemistry of red-shifted fast-closing anion channelrhodopsin PsACR1." Physical Chemistry Chemical Physics 19, no. 45 (2017): 30402–9. http://dx.doi.org/10.1039/c7cp06414d.

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17

Bamann, Christian, Julia Spitz, Verena Pintschovius, and Ernst Bamberg. "Vectorial Ion Transport by Channelrhodopsin-2." Biophysical Journal 96, no. 3 (February 2009): 662a. http://dx.doi.org/10.1016/j.bpj.2008.12.3500.

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18

Prigge, Matthias, Franziska Schneider, Satoshi S. P. Tsunoda, and Peter Hegemann. "Functional Studies of Volvox Channelrhodopsin Chimeras." Biophysical Journal 98, no. 3 (January 2010): 710a. http://dx.doi.org/10.1016/j.bpj.2009.12.3893.

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19

Gradmann, Dietrich, André Berndt, Franziska Schneider, and Peter Hegemann. "Rectification of the Channelrhodopsin Early Conductance." Biophysical Journal 101, no. 5 (September 2011): 1057–68. http://dx.doi.org/10.1016/j.bpj.2011.07.040.

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20

Deisseroth, Karl, and Peter Hegemann. "The form and function of channelrhodopsin." Science 357, no. 6356 (September 14, 2017): eaan5544. http://dx.doi.org/10.1126/science.aan5544.

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21

Schneider, Franziska, Matthias Prigge, Satoshi P. Tsunoda, Ofer Yizhar, Karl Deisseroth, and Peter Hegemann. "Yellow Optogenetics with Volvox Channelrhodopsin Variants." Biophysical Journal 102, no. 3 (January 2012): 681a—682a. http://dx.doi.org/10.1016/j.bpj.2011.11.3705.

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22

Spakowski, Christian, Joachim Heberle, and Ana-Nicoleta Bondar. "Opening Ion-Transfer Paths of Channelrhodopsin." Biophysical Journal 110, no. 3 (February 2016): 56a. http://dx.doi.org/10.1016/j.bpj.2015.11.369.

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23

Stehfest, Katja, and Peter Hegemann. "Evolution of the Channelrhodopsin Photocycle Model." ChemPhysChem 11, no. 6 (April 21, 2010): 1120–26. http://dx.doi.org/10.1002/cphc.200900980.

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24

Inaguma, Asumi, Hisao Tsukamoto, Hideaki E. Kato, Tetsunari Kimura, Toru Ishizuka, Satomi Oishi, Hiromu Yawo, Osamu Nureki, and Yuji Furutani. "Chimeras of Channelrhodopsin-1 and -2 fromChlamydomonas reinhardtiiExhibit Distinctive Light-induced Structural Changes from Channelrhodopsin-2." Journal of Biological Chemistry 290, no. 18 (March 21, 2015): 11623–34. http://dx.doi.org/10.1074/jbc.m115.642256.

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25

Wang, Hongxia, Richard B. Dewell, Markus U. Ehrengruber, Eran Segev, Jacob Reimer, Michael L. Roukes, and Fabrizio Gabbiani. "Optogenetic manipulation of medullary neurons in the locust optic lobe." Journal of Neurophysiology 120, no. 4 (October 1, 2018): 2049–58. http://dx.doi.org/10.1152/jn.00356.2018.

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The locust is a widely used animal model for studying sensory processing and its relation to behavior. Due to the lack of genomic information, genetic tools to manipulate neural circuits in locusts are not yet available. We examined whether Semliki Forest virus is suitable to mediate exogenous gene expression in neurons of the locust optic lobe. We subcloned a channelrhodopsin variant and the yellow fluorescent protein Venus into a Semliki Forest virus vector and injected the virus into the optic lobe of locusts ( Schistocerca americana). Fluorescence was observed in all injected optic lobes. Most neurons that expressed the recombinant proteins were located in the first two neuropils of the optic lobe, the lamina and medulla. Extracellular recordings demonstrated that laser illumination increased the firing rate of medullary neurons expressing channelrhodopsin. The optogenetic activation of the medullary neurons also triggered excitatory postsynaptic potentials and firing of a postsynaptic, looming-sensitive neuron, the lobula giant movement detector. These results indicate that Semliki Forest virus is efficient at mediating transient exogenous gene expression and provides a tool to manipulate neural circuits in the locust nervous system and likely other insects.NEW & NOTEWORTHY Using Semliki Forest virus, we efficiently delivered channelrhodopsin into neurons of the locust optic lobe. We demonstrate that laser illumination increases the firing of the medullary neurons expressing channelrhodopsin and elicits excitatory postsynaptic potentials and spiking in an identified postsynaptic target neuron, the lobula giant movement detector neuron. This technique allows the manipulation of neuronal activity in locust neural circuits using optogenetics.

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26

Ehrenberg, David, Nils Krause, Mattia Saita, Christian Bamann, Rajiv K. Kar, Kirsten Hoffmann, Dorothea Heinrich, Igor Schapiro, Joachim Heberle, and Ramona Schlesinger. "Atomistic Insight into the Role of Threonine 127 in the Functional Mechanism of Channelrhodopsin-2." Applied Sciences 9, no. 22 (November 15, 2019): 4905. http://dx.doi.org/10.3390/app9224905.

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Channelrhodopsins (ChRs) belong to the unique class of light-gated ion channels. The structure of channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) has been resolved, but the mechanistic link between light-induced isomerization of the chromophore retinal and channel gating remains elusive. Replacements of residues C128 and D156 (DC gate) resulted in drastic effects in channel closure. T127 is localized close to the retinal Schiff base and links the DC gate to the Schiff base. The homologous residue in bacteriorhodopsin (T89) has been shown to be crucial for the visible absorption maximum and dark–light adaptation, suggesting an interaction with the retinylidene chromophore, but the replacement had little effect on photocycle kinetics and proton pumping activity. Here, we show that the T127A and T127S variants of CrChR2 leave the visible absorption maximum unaffected. We inferred from hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and resonance Raman spectroscopy that the hydroxylic side chain of T127 is hydrogen-bonded to E123 and the latter is hydrogen-bonded to the retinal Schiff base. The C=N–H vibration of the Schiff base in the T127A variant was 1674 cm−1, the highest among all rhodopsins reported to date. We also found heterogeneity in the Schiff base ground state vibrational properties due to different rotamer conformations of E123. The photoreaction of T127A is characterized by a long-lived P2380 state during which the Schiff base is deprotonated. The conservative replacement of T127S hardly affected the photocycle kinetics. Thus, we inferred that the hydroxyl group at position 127 is part of the proton transfer pathway from D156 to the Schiff base during rise of the P3530 intermediate. This finding provides molecular reasons for the evolutionary conservation of the chemically homologous residues threonine, serine, and cysteine at this position in all channelrhodopsins known so far.

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27

Doi, Satoko, Arisa Mori, Takashi Tsukamoto, Louisa Reissig, Kunio Ihara, and Yuki Sudo. "Structural and functional roles of the N- and C-terminal extended modules in channelrhodopsin-1." Photochemical & Photobiological Sciences 14, no. 9 (2015): 1628–36. http://dx.doi.org/10.1039/c5pp00213c.

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28

Sineshchekov, Oleg A., Elena G. Govorunova, Hai Li, and John L. Spudich. "Bacteriorhodopsin-like channelrhodopsins: Alternative mechanism for control of cation conductance." Proceedings of the National Academy of Sciences 114, no. 45 (October 25, 2017): E9512—E9519. http://dx.doi.org/10.1073/pnas.1710702114.

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The recently discovered cation-conducting channelrhodopsins in cryptophyte algae are far more homologous to haloarchaeal rhodopsins, in particular the proton pump bacteriorhodopsin (BR), than to earlier known channelrhodopsins. They uniquely retain the two carboxylate residues that define the vectorial proton path in BR in which Asp-85 and Asp-96 serve as acceptor and donor, respectively, of the photoactive site Schiff base (SB) proton. Here we analyze laser flash-induced photocurrents and photochemical conversions in Guillardia theta cation channelrhodopsin 2 (GtCCR2) and its mutants. Our results reveal a model in which the GtCCR2 retinylidene SB chromophore rapidly deprotonates to the Asp-85 homolog, as in BR. Opening of the cytoplasmic channel to cations in GtCCR2 requires the Asp-96 homolog to be unprotonated, as has been proposed for the BR cytoplasmic channel for protons. However, reprotonation of the GtCCR2 SB occurs not from the Asp-96 homolog, but by proton return from the earlier protonated acceptor, preventing vectorial proton translocation across the membrane. In GtCCR2, deprotonation of the Asp-96 homolog is required for cation channel opening and occurs >10-fold faster than reprotonation of the SB, which temporally correlates with channel closing. Hence in GtCCR2, cation channel gating is tightly coupled to intramolecular proton transfers involving the same residues that define the vectorial proton path in BR.

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29

Guo, Yanan, Franziska E. Beyle, Beatrix M. Bold, Hiroshi C. Watanabe, Axel Koslowski, Walter Thiel, Peter Hegemann, Marco Marazzi, and Marcus Elstner. "Active site structure and absorption spectrum of channelrhodopsin-2 wild-type and C128T mutant." Chemical Science 7, no. 6 (2016): 3879–91. http://dx.doi.org/10.1039/c6sc00468g.

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30

Dokukina, I., and O. Weingart. "Spectral properties and isomerisation path of retinal in C1C2 channelrhodopsin." Physical Chemistry Chemical Physics 17, no. 38 (2015): 25142–50. http://dx.doi.org/10.1039/c5cp02650d.

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31

Liang, Ruibin, Jimmy K. Yu, Jan Meisner, Fang Liu, and Todd J. Martinez. "Electrostatic Control of Photoisomerization in Channelrhodopsin 2." Journal of the American Chemical Society 143, no. 14 (April 1, 2021): 5425–37. http://dx.doi.org/10.1021/jacs.1c00058.

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32

Papagiakoumou, Eirini, Francesca Anselmi, Aurélien Bègue, Vincent de Sars, Jesper Glückstad, Ehud Y. Isacoff, and Valentina Emiliani. "Scanless two-photon excitation of channelrhodopsin-2." Nature Methods 7, no. 10 (September 19, 2010): 848–54. http://dx.doi.org/10.1038/nmeth.1505.

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33

Govorunova, Elena G., Oleg A. Sineshchekov, and John L. Spudich. "Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin." Photochemistry and Photobiology 92, no. 2 (February 1, 2016): 257–63. http://dx.doi.org/10.1111/php.12558.

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34

Sineshchekov, Oleg A., Elena G. Govorunova, Hai Li, and John L. Spudich. "Gating mechanisms of a natural anion channelrhodopsin." Proceedings of the National Academy of Sciences 112, no. 46 (November 2, 2015): 14236–41. http://dx.doi.org/10.1073/pnas.1513602112.

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Anion channelrhodopsins (ACRs) are a class of light-gated channels recently identified in cryptophyte algae that provide unprecedented fast and powerful hyperpolarizing tools for optogenetics. Analysis of photocurrents generated byGuillardia thetaACR 1 (GtACR1) and its mutants in response to laser flashes showed thatGtACR1 gating comprises two separate mechanisms with opposite dependencies on the membrane voltage and pH and involving different amino acid residues. The first mechanism, characterized by slow opening and fast closing of the channel, is regulated by Glu-68. Neutralization of this residue (the E68Q mutation) specifically suppressed this first mechanism, but did not eliminate it completely at high pH. Our data indicate the involvement of another, yet-unidentified pH-sensitive group X. Introducing a positive charge at the Glu-68 site (the E68R mutation) inverted the channel gating so that it was open in the dark and closed in the light, without altering its ion selectivity. The second mechanism, characterized by fast opening and slow closing of the channel, was not substantially affected by the E68Q mutation, but was controlled by Cys-102. The C102A mutation reduced the rate of channel closing by the second mechanism by ∼100-fold, whereas it had only a twofold effect on the rate of the first. The results show that anion conductance by ACRs has a fundamentally different structural basis than the relatively well studied conductance by cation channelrhodopsins (CCRs), not attributable to simply a modification of the CCR selectivity filter.

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35

Feldbauer, K., D. Zimmermann, V. Pintschovius, J. Spitz, C. Bamann, and E. Bamberg. "Channelrhodopsin-2 is a leaky proton pump." Proceedings of the National Academy of Sciences 106, no. 30 (July 9, 2009): 12317–22. http://dx.doi.org/10.1073/pnas.0905852106.

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36

Mueller, Maria. "Light-induced Helix Movements in Channelrhodopsin-2." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1067. http://dx.doi.org/10.1107/s2053273314089323.

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Electron crystallography has the unique advantage of visualizing membrane proteins in a native-like lipid environment, which likely favors the native conformation. In addition, it allows for the protein to undergo conformational changes in response to their activating signals. We used 2D crystals of channelrhodopsin-2, a cation-selective light-gated channel from Chlamydomonas reinhardtii (Nagel et al., 2003) to study light-induced conformational changes of this intriguing channel, which is currently a powerful tool in optogenetics. Therefore, 2D crystals of the slow photocycling C128T ChR2 mutant were exposed to 473 nm light and rapidly frozen to trap the open state. Projection difference maps at 6 Å resolution show the location, extent and direction of light-induced conformational changes in ChR2 during the transition from the closed state to the ion-conducting open state. Difference peaks indicate that transmembrane helices (TMHs) 2, 6, and 7 reorient or rearrange during the photocycle. No major differences were found near TMH3 and 4 at the dimer interface. While conformational changes in TMH6 and 7 are known from other microbial-type rhodopsins, our results indicate that TMH2 has a key role in light-induced channel opening and closing in ChR2.

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37

Spitz, Julia, and Ernst Bamberg. "Functional investigation of the light-gated Channelrhodopsin." Biophysical Journal 96, no. 3 (February 2009): 671a. http://dx.doi.org/10.1016/j.bpj.2008.12.3546.

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38

Müller, Maria, Christian Bamann, Ernst Bamberg, and Werner Kühlbrandt. "Light-Induced Helix Movements in Channelrhodopsin-2." Journal of Molecular Biology 427, no. 2 (January 2015): 341–49. http://dx.doi.org/10.1016/j.jmb.2014.11.004.

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39

Hegemann, Peter, Dietrich Gradmann, and Franziska Schneider. "Channelrhodopsin: Ideas about Gating and Ion Transport." Biophysical Journal 102, no. 3 (January 2012): 41a. http://dx.doi.org/10.1016/j.bpj.2011.11.252.

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40

Bamann, Christian, Thomas Sattig, and Ernst Bamberg. "Encoding the Light-Sensitivity of Channelrhodopsin-2." Biophysical Journal 106, no. 2 (January 2014): 381a. http://dx.doi.org/10.1016/j.bpj.2013.11.2156.

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Muders, Vera, Silke Kerruth, Victor Lorenz-Fonfria, Joachim Heberle, and Ramona Schlesinger. "Spectroscopic Analysis of Channelrhodopsin and its Chromophore." Biophysical Journal 106, no. 2 (January 2014): 653a. http://dx.doi.org/10.1016/j.bpj.2013.11.3612.

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Ritter, Eglof, Patrick Piwowarski, Peter Hegemann, and Franz J. Bartl. "Light-dark Adaptation of Channelrhodopsin C128T Mutant." Journal of Biological Chemistry 288, no. 15 (February 25, 2013): 10451–58. http://dx.doi.org/10.1074/jbc.m112.446427.

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Spudich, John L. "Channelrhodopsin Photochromic Reactions Provide Multicolor Optogenetic Control." Biophysical Journal 107, no. 7 (October 2014): 1489–90. http://dx.doi.org/10.1016/j.bpj.2014.08.021.

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Swiersy, A., S. Klapper, and V. Busskamp. "Optogenetik – eine Chance für fortgeschrittene retinale Dystrophien." Klinische Monatsblätter für Augenheilkunde 234, no. 03 (March 2017): 335–42. http://dx.doi.org/10.1055/s-0043-101820.

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ZusammenfassungDie Optogenetik nutzt genetisch modifizierte lichtaktive Proteine, um Zellen durch Licht nicht invasiv zu manipulieren. Der Prototyp dieser Proteine ist Channelrhodopsin2 (ChR2), ein unselektiver Kationenkanal. Dieser kann elektrisch erregbare Zellen durch Lichtimpulse depolarisieren. Die Kombination von Channelrhodopsin und Halorhodopsin (eNpHR), eine hyperpolarisierende lichtgetriebene Cl−-Pumpe, ermöglicht eine komplexe Modulation neuronaler Aktivität sowohl in vitro als auch in vivo. Sehr schnell stellte sich heraus, dass die Optogenetik für die Behandlung von Sehbehinderungen, die mit der Degeneration der Photorezeptoren einhergehen, gute Chancen zur Therapie bietet. Dabei werden funktionslose Photorezeptoren durch die ektopische Expression der hyperpolarisierenden Pumpe eNpHR reaktiviert. Aber auch andere Zellen der Retina können durch die induzierte Expression von ChR2 die Aufgabe des Lichtempfangs übernehmen und damit zu künstlichen Photorezeptoren werden. Mit diesem Übersichtsartikel möchten wir eine kurze Einführung zur Retina und deren Rolle sowohl in der physiologischen als auch in der pathologischen Lichtwahrnehmung geben. Weiterhin werden optogenetische Strategien zur Wiederherstellung der Lichtwahrnehmungen aufgezeigt und strukturelle sowie funktionelle Eigenschaften der auf Rhodopsin basierenden optogenetischen Werkzeuge diskutiert. Letztendlich wird die Anwendbarkeit für die Wiederherstellung des Sehvermögens durch die Optogenetik bewertet.

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Dwenger, Marc, William J. Kowalski, Fei Ye, Fangping Yuan, Joseph P. Tinney, Shuji Setozaki, Takeichiro Nakane, et al. "Chronic optical pacing conditioning of h-iPSC engineered cardiac tissues." Journal of Tissue Engineering 10 (January 2019): 204173141984174. http://dx.doi.org/10.1177/2041731419841748.

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The immaturity of human induced pluripotent stem cell derived engineered cardiac tissues limits their ability to regenerate damaged myocardium and to serve as robust in vitro models for human disease and drug toxicity studies. Several chronic biomimetic conditioning protocols, including mechanical stretch, perfusion, and/or electrical stimulation promote engineered cardiac tissue maturation but have significant technical limitations. Non-contacting chronic optical stimulation using heterologously expressed channelrhodopsin light-gated ion channels, termed optogenetics, may be an advantageous alternative to chronic invasive electrical stimulation for engineered cardiac tissue conditioning. We designed proof-of-principle experiments to successfully transfect human induced pluripotent stem cell derived engineered cardiac tissues with a desensitization resistant, chimeric channelrhodopsin protein, and then optically paced engineered cardiac tissues to accelerate maturation. We transfected human induced pluripotent stem cell engineered cardiac tissues using an adeno-associated virus packaged chimeric channelrhodopsin and then verified optically paced by whole cell patch clamp. Engineered cardiac tissues were then chronically optically paced above their intrinsic beat rates in vitro from day 7 to 14. Chronically optically paced resulted in improved engineered cardiac tissue electrophysiological properties and subtle changes in the expression of some cardiac relevant genes, though active force generation and histology were unchanged. These results validate the feasibility of a novel chronically optically paced paradigm to explore non-invasive and scalable optically paced–induced engineered cardiac tissue maturation strategies.

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Guo, Yanan, Franziska E. Wolff, Igor Schapiro, Marcus Elstner, and Marco Marazzi. "Correction: Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2." Physical Chemistry Chemical Physics 21, no. 18 (2019): 9605. http://dx.doi.org/10.1039/c9cp90114k.

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Correction for ‘Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2’ by Yanan Guo et al., Phys. Chem. Chem. Phys., 2018, 20, 27501–27509.

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Watanabe, Shota, Toru Ishizuka, Shoko Hososhima, Alemeh Zamani, Mohammad Razuanul Hoque, and Hiromu Yawo. "The regulatory mechanism of ion permeation through a channelrhodopsin derived from Mesostigma viride (MvChR1)." Photochemical & Photobiological Sciences 15, no. 3 (2016): 365–74. http://dx.doi.org/10.1039/c5pp00290g.

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Stensitzki, Till, Suliman Adam, Ramona Schlesinger, Igor Schapiro, and Karsten Heyne. "Ultrafast Backbone Protonation in Channelrhodopsin-1 Captured by Polarization Resolved Fs Vis-pump—IR-Probe Spectroscopy and Computational Methods." Molecules 25, no. 4 (February 14, 2020): 848. http://dx.doi.org/10.3390/molecules25040848.

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Channelrhodopsins (ChR) are light-gated ion-channels heavily used in optogenetics. Upon light excitation an ultrafast all-trans to 13-cis isomerization of the retinal chromophore takes place. It is still uncertain by what means this reaction leads to further protein changes and channel conductivity. Channelrhodopsin-1 in Chlamydomonas augustae exhibits a 100 fs photoisomerization and a protonated counterion complex. By polarization resolved ultrafast spectroscopy in the mid-IR we show that the initial reaction of the retinal is accompanied by changes in the protein backbone and ultrafast protonation changes at the counterion complex comprising Asp299 and Glu169. In combination with homology modelling and quantum mechanics/molecular mechanics (QM/MM) geometry optimization we assign the protonation dynamics to ultrafast deprotonation of Glu169, and transient protonation of the Glu169 backbone, followed by a proton transfer from the backbone to the carboxylate group of Asp299 on a timescale of tens of picoseconds. The second proton transfer is not related to retinal dynamics and reflects pure protein changes in the first photoproduct. We assume these protein dynamics to be the first steps in a cascade of protein-wide changes resulting in channel conductivity.

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Guo, Yanan, Franziska E. Wolff, Igor Schapiro, Marcus Elstner, and Marco Marazzi. "Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2." Physical Chemistry Chemical Physics 20, no. 43 (2018): 27501–9. http://dx.doi.org/10.1039/c8cp05210g.

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The first event of the channelrhodopsin-2 (ChR2) photocycle, i.e. trans-to-cis photoisomerization, is studied by means of quantum mechanics/molecular mechanics, taking into account the flexible retinal environment in the ground state.

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Meng, Xiankai, Swetha Murali, Yen-Fu Cheng, Jingrong Lu, Ariel E. Hight, Vivek V. Kanumuri, M. Christian Brown, Jeffrey R. Holt, Daniel J. Lee, and Albert S. B. Edge. "Increasing the expression level of ChR2 enhances the optogenetic excitability of cochlear neurons." Journal of Neurophysiology 122, no. 5 (November 1, 2019): 1962–74. http://dx.doi.org/10.1152/jn.00828.2018.

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Optogenetics comprise a promising alternative to electrical stimulation for characterization of neural circuits and for the next generation of neural prostheses. Optogenetic stimulation relies on expression of photosensitive microbial proteins in animal cells to initiate a flow of ions into the cells in response to visible light. Here, we generated a novel transgenic mouse model in which we studied the optogenetic activation of spiral ganglion neurons, the primary afferent neurons of the auditory system, and showed a strong optogenetic response, with a similar amplitude as the acoustically evoked response. A twofold increase in the level of channelrhodopsin expression significantly increased the photosensitivity at both the single cell and organismal levels but also partially compromised the native electrophysiological properties of the neurons. The importance of channelrhodopsin expression level to optogenetic stimulation, revealed by these quantitative measurements, will be significant for the characterization of neural circuitry and for the use of optogenetics in neural prostheses. NEW & NOTEWORTHY This study reveals a dose-response relationship between channelrhodopsin expression and optogenetic excitation. Both single cell and organismal responses depend on the expression level of the heterologous protein. Expression level of the opsin is thus an important variable in determining the outcome of an optogenetic experiment. These results are key to the implementation of neural prostheses based on optogenetics, such as next generation cochlear implants, which would use light to elicit a neural response to sound.

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