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Kishi KE, Kim YS, Fukuda M, Inoue M, Kusakizako T, Wang PY, Ramakrishnan C, Byrne EFX, Thadhani E, Paggi JM, Matsui TE, Yamashita K, Nagata T, Konno M, Quirin S, Lo M, Benster T, Uemura T, Liu K, Shibata M, Nomura N, Iwata S, Nureki O, Dror RO, Inoue K, Deisseroth K, Kato HE. Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine. Cell 2022; 185:672-689.e23. [PMID: 35114111 PMCID: PMC7612760 DOI: 10.1016/j.cell.2022.01.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 12/13/2021] [Accepted: 01/11/2022] [Indexed: 12/24/2022]
Abstract
ChRmine, a recently discovered pump-like cation-conducting channelrhodopsin, exhibits puzzling properties (large photocurrents, red-shifted spectrum, and extreme light sensitivity) that have created new opportunities in optogenetics. ChRmine and its homologs function as ion channels but, by primary sequence, more closely resemble ion pump rhodopsins; mechanisms for passive channel conduction in this family have remained mysterious. Here, we present the 2.0 Å resolution cryo-EM structure of ChRmine, revealing architectural features atypical for channelrhodopsins: trimeric assembly, a short transmembrane-helix 3, a twisting extracellular-loop 1, large vestibules within the monomer, and an opening at the trimer interface. We applied this structure to design three proteins (rsChRmine and hsChRmine, conferring further red-shifted and high-speed properties, respectively, and frChRmine, combining faster and more red-shifted performance) suitable for fundamental neuroscience opportunities. These results illuminate the conduction and gating of pump-like channelrhodopsins and point the way toward further structure-guided creation of channelrhodopsins for applications across biology.
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Chen K, Ernst P, Liu XM, Zhou L. Optogenetic Studies of Mitochondria. Methods Mol Biol 2022; 2501:311-324. [PMID: 35857235 DOI: 10.1007/978-1-0716-2329-9_15] [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] [Indexed: 05/07/2023]
Abstract
While optogenetic approaches have been widely used for remote control of cell membrane excitability and intracellular signaling pathways, their application in mitochondrial study has been limited, largely due to the challenge of effectively and specifically expressing heterologous light-gated rhodopsin channels in the mitochondria. Here, we describe the methods for expressing functional channelrhodopsin 2 (ChR2) proteins in the mitochondrial inner membrane with an unusually long mitochondrial leading sequence and characterizing optogenetic-mediated mitochondrial membrane potential (ΔΨm) depolarization. We then illustrate how this next-generation optogenetic approach can be used to study the effect of ΔΨm on mitochondrial functions such as mitophagy, programed cell death, and preconditioning-mediated cytoprotection. We anticipate that this innovative technology will enable new insights into the mechanisms by which changes in ΔΨm differentially impacts mitochondrial and cellular functions.
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Ji J, He Q, Luo X, Bang S, Matsuoka Y, McGinnis A, Nackley AG, Ji RR. IL-23 Enhances C-Fiber-Mediated and Blue Light-Induced Spontaneous Pain in Female Mice. Front Immunol 2021; 12:787565. [PMID: 34950149 PMCID: PMC8688771 DOI: 10.3389/fimmu.2021.787565] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/08/2021] [Indexed: 12/30/2022] Open
Abstract
The incidence of chronic pain is especially high in women, but the underlying mechanisms remain poorly understood. Interleukin-23 (IL-23) is a pro-inflammatory cytokine and contributes to inflammatory diseases (e.g., arthritis and psoriasis) through dendritic/T cell signaling. Here we examined the IL-23 involvement in sexual dimorphism of pain, using an optogenetic approach in transgenic mice expressing channelrhodopsin-2 (ChR2) in TRPV1-positive nociceptive neurons. In situ hybridization revealed that compared to males, females had a significantly larger portion of small-sized (100-200 μm2) Trpv1+ neurons in dorsal root ganglion (DRG). Blue light stimulation of a hindpaw of transgenic mice induced intensity-dependent spontaneous pain. At the highest intensity, females showed more intense spontaneous pain than males. Intraplantar injection of IL-23 (100 ng) induced mechanical allodynia in females only but had no effects on paw edema. Furthermore, intraplantar IL-23 only potentiated blue light-induced pain in females, and intrathecal injection of IL-23 also potentiated low-dose capsaicin (500 ng) induced spontaneous pain in females but not males. IL-23 expresses in DRG macrophages of both sexes. Intrathecal injection of IL-23 induced significantly greater p38 phosphorylation (p-p38), a marker of nociceptor activation, in DRGs of female mice than male mice. In THP-1 human macrophages estrogen and chemotherapy co-application increased IL-23 secretion, and furthermore, estrogen and IL-23 co-application, but not estrogen and IL-23 alone, significantly increased IL-17A release. These findings suggest a novel role of IL-23 in macrophage signaling and female-dominant pain, including C-fiber-mediated spontaneous pain. Our study has also provided new insight into cytokine-mediated macrophage-nociceptor interactions, in a sex-dependent manner.
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Wright P, Rodgers J, Wynne J, Bishop PN, Lucas RJ, Milosavljevic N. Viral Transduction of Human Rod Opsin or Channelrhodopsin Variants to Mouse ON Bipolar Cells Does Not Impact Retinal Anatomy or Cause Measurable Death in the Targeted Cells. Int J Mol Sci 2021; 22:ijms222313111. [PMID: 34884916 PMCID: PMC8658283 DOI: 10.3390/ijms222313111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 11/26/2021] [Accepted: 12/01/2021] [Indexed: 11/16/2022] Open
Abstract
The viral gene delivery of optogenetic actuators to the surviving inner retina has been proposed as a strategy for restoring vision in advanced retinal degeneration. We investigated the safety of ectopic expression of human rod opsin (hRHO), and two channelrhodopsins (enhanced sensitivity CoChR-3M and red-shifted ReaChR) by viral gene delivery in ON bipolar cells of the mouse retina. Adult Grm6Cre mice were bred to be retinally degenerate or non-retinally degenerate (homozygous and heterozygous for the rd1Pde6b mutation, respectively) and intravitreally injected with recombinant adeno-associated virus AAV2/2(quad Y-F) serotype containing a double-floxed inverted transgene comprising one of the opsins of interest under a CMV promoter. None of the opsins investigated caused changes in retinal thickness; induced apoptosis in the retina or in transgene expressing cells; or reduced expression of PKCα (a specific bipolar cell marker). No increase in retinal inflammation at the level of gene expression (IBA1/AIF1) was found within the treated mice compared to controls. The expression of hRHO, CoChR or ReaChR under a strong constitutive promoter in retinal ON bipolar cells following intravitreal delivery via AAV2 does not cause either gross changes in retinal health, or have a measurable impact on the survival of targeted cells.
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Unexpected pairings. Cell 2021; 184:5289-5292. [PMID: 34562361 DOI: 10.1016/j.cell.2021.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Being able to precisely turn on or off particular neurons in the brain at will was a major challenge for the neuroscience field, and few could have anticipated that the solution would come from algae. The 2021 Albert Lasker Basic Medical Research Award recognizes the contributions of Peter Hegemann, Dieter Oesterhelt, and Karl Deisseroth for their discovery of light-sensitive microbial proteins that can activate or silence brain cells. Cell editor Nicole Neuman had a conversation with Peter Hegemann about his role in bridging the two fields of microbial phototaxis and neuroscience and his perspective on the nature and future of interdisciplinary science. Excerpts from this conversation are presented below, and the full conversation is available with the article online.
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Kong MS, Kim EJ, Park S, Zweifel LS, Huh Y, Cho J, Kim JJ. 'Fearful-place' coding in the amygdala-hippocampal network. eLife 2021; 10:e72040. [PMID: 34533133 PMCID: PMC8500711 DOI: 10.7554/elife.72040] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/17/2021] [Indexed: 12/03/2022] Open
Abstract
Animals seeking survival needs must be able to assess different locations of threats in their habitat. However, the neural integration of spatial and risk information essential for guiding goal-directed behavior remains poorly understood. Thus, we investigated simultaneous activities of fear-responsive basal amygdala (BA) and place-responsive dorsal hippocampus (dHPC) neurons as rats left the safe nest to search for food in an exposed space and encountered a simulated 'predator.' In this realistic situation, BA cells increased their firing rates and dHPC place cells decreased their spatial stability near the threat. Importantly, only those dHPC cells synchronized with the predator-responsive BA cells remapped significantly as a function of escalating risk location. Moreover, optogenetic stimulation of BA neurons was sufficient to cause spatial avoidance behavior and disrupt place fields. These results suggest a dynamic interaction of BA's fear signalling cells and dHPC's spatial coding cells as animals traverse safe-danger areas of their environment.
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Gerasimov E, Erofeev A, Borodinova A, Bolshakova A, Balaban P, Bezprozvanny I, Vlasova OL. Optogenetic Activation of Astrocytes-Effects on Neuronal Network Function. Int J Mol Sci 2021; 22:9613. [PMID: 34502519 PMCID: PMC8431749 DOI: 10.3390/ijms22179613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 08/24/2021] [Accepted: 09/01/2021] [Indexed: 01/04/2023] Open
Abstract
Optogenetics approach is used widely in neurobiology as it allows control of cellular activity with high spatial and temporal resolution. In most studies, optogenetics is used to control neuronal activity. In the present study optogenetics was used to stimulate astrocytes with the aim to modulate neuronal activity. To achieve this goal, light stimulation was applied to astrocytes expressing a version of ChR2 (ionotropic opsin) or Opto-α1AR (metabotropic opsin). Optimal optogenetic stimulation parameters were determined using patch-clamp recordings of hippocampal pyramidal neurons' spontaneous activity in brain slices as a readout. It was determined that the greatest increase in the number of spontaneous synaptic currents was observed when astrocytes expressing ChR2(H134R) were activated by 5 s of continuous light. For the astrocytes expressing Opto-α1AR, the greatest response was observed in the pulse stimulation mode (T = 1 s, t = 100 ms). It was also observed that activation of the astrocytic Opto-a1AR but not ChR2 results in an increase of the fEPSP slope in hippocampal neurons. Based on these results, we concluded that Opto-a1AR expressed in hippocampal astrocytes provides an opportunity to modulate the long-term synaptic plasticity optogenetically, and may potentially be used to normalize the synaptic transmission and plasticity defects in a variety of neuropathological conditions, including models of Alzheimer's disease and other neurodegenerative disorders.
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Metasuk A, Kitiyanant N, Chetsawang B. An expression system of channelrhodopsin-2 driven by a minimal Arc/Arg3.1 promoter and Tet system was developed in human neuroblastoma cells. Plasmid 2021; 117:102597. [PMID: 34411655 DOI: 10.1016/j.plasmid.2021.102597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/30/2021] [Accepted: 08/12/2021] [Indexed: 11/18/2022]
Abstract
Advances in neuroscience have relied on the development of techniques that examine neuronal cell activities. One major challenge involves the limitations in labeling and controlling neuronal activities relating to the cell's activation state. In this study, the modified human codon-optimized channelrhodopsin-2 photoreceptor hChR2(C128S) was integrated into function with inducible gene expression methods and materials: the Tet system and the highly efficient minimum promoter of Arc/Arg3.1. The system successfully expressed the target fusion gene exclusively in activated SH-SY5Y human neuroblastoma cells while maintaining the essential characteristics of ChR2. The expression of the channelrhodopsin construct was observed, while the expression duration was refined by treatment with doxycycline. The optogenetic construct here tested the application of the minimum Arc/Arg3.1 promoter, an advanced immediate-early gene promoter, for the expression of the channelrhodopsin gene. Along with its noninvasive nature, this expression system promises to serve dual functions as a cell activity indicator and cell actuator, creating the possibility for researchers to precisely label cells according to their activation state and control the activities of specific neuronal cell populations.
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Abe Y, Kwon S, Oishi M, Unekawa M, Takata N, Seki F, Koyama R, Abe M, Sakimura K, Masamoto K, Tomita Y, Okano H, Mushiake H, Tanaka KF. Optical manipulation of local cerebral blood flow in the deep brain of freely moving mice. Cell Rep 2021; 36:109427. [PMID: 34320360 DOI: 10.1016/j.celrep.2021.109427] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/07/2021] [Accepted: 06/29/2021] [Indexed: 11/18/2022] Open
Abstract
An artificial tool for manipulating local cerebral blood flow (CBF) is necessary for understanding how CBF controls brain function. Here, we generate vascular optogenetic tools whereby smooth muscle cells and endothelial cells express optical actuators in the brain. The illumination of channelrhodopsin-2 (ChR2)-expressing mice induces a local reduction in CBF. Photoactivated adenylyl cyclase (PAC) is an optical protein that increases intracellular cyclic adenosine monophosphate (cAMP), and the illumination of PAC-expressing mice induces a local increase in CBF. We target the ventral striatum, determine the temporal kinetics of CBF change, and optimize the illumination intensity to confine the effects to the ventral striatum. We demonstrate the utility of this vascular optogenetic manipulation in freely and adaptively behaving mice and validate the task- and actuator-dependent behavioral readouts. The development of vascular optogenetic animal models will help accelerate research linking vasculature, circuits, and behavior to health and disease.
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Kuruppath P, Belluscio L. The influence of stimulus duration on olfactory perception. PLoS One 2021; 16:e0252931. [PMID: 34111206 PMCID: PMC8191971 DOI: 10.1371/journal.pone.0252931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 05/25/2021] [Indexed: 12/04/2022] Open
Abstract
The duration of a stimulus plays an important role in the coding of sensory information. The role of stimulus duration is extensively studied in the tactile, visual, and auditory system. In the olfactory system, temporal properties of the stimulus are key for obtaining information when an odor is released in the environment. However, how the stimulus duration influences the odor perception is not well understood. To test this, we activated the olfactory bulbs with blue light in mice expressing channelrhodopsin in the olfactory sensory neurons (OSNs) and assessed the relevance of stimulus duration on olfactory perception using foot shock associated active avoidance behavioral task on a "two-arms maze". Our behavior data demonstrate that the stimulus duration plays an important role in olfactory perception and the associated behavioral responses.
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VanGordon MR, Prignano LA, Dempski RE, Rick SW, Rempe SB. Channelrhodopsin C1C2: Photocycle kinetics and interactions near the central gate. Biophys J 2021; 120:1835-1845. [PMID: 33705762 PMCID: PMC8204341 DOI: 10.1016/j.bpj.2021.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/01/2021] [Accepted: 03/03/2021] [Indexed: 12/27/2022] Open
Abstract
Channelrhodopsins (ChR) are light-sensitive cation channels used in optogenetics, a technique that applies light to control cells (e.g., neurons) that have been modified genetically to express those channels. Although mutations are known to affect pore kinetics, little is known about how mutations induce changes at the molecular scale. To address this issue, we first measured channel opening and closing rates of a ChR chimera (C1C2) and selected variants (N297D, N297V, and V125L). Then, we used atomistic simulations to correlate those rates with changes in pore structure, hydration, and chemical interactions among key gating residues of C1C2 in both closed and open states. Overall, the experimental results show that C1C2 and its mutants do not behave like ChR2 or its analogous variants, except V125L, making C1C2 a unique channel. Our atomistic simulations confirmed that opening of the channel and initial hydration of the gating regions between helices I, II, III, and VII of the channel occurs with 1) the presence of 13-cis retinal; 2) deprotonation of a glutamic acid gating residue, E129; and 3) subsequent weakening of the central gate hydrogen bond between the same glutamic acid E129 and asparagine N297 in the central region of the pore. Also, an aspartate (D292) is the unambiguous primary proton acceptor for the retinal Schiff base in the hydrated channel.
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Liang R, Yu JK, Meisner J, Liu F, Martinez TJ. Electrostatic Control of Photoisomerization in Channelrhodopsin 2. J Am Chem Soc 2021; 143:5425-5437. [PMID: 33794085 DOI: 10.1021/jacs.1c00058] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Channelrhodopsin 2 (ChR2) is the most commonly used tool in optogenetics. Because of its faster photocycle compared to wild-type (WT) ChR2, the E123T mutant of ChR2 is a useful optogenetic tool when fast neuronal stimulation is needed. Interestingly, in spite of its faster photocycle, the initial step of the photocycle in E123T (photoisomerization of retinal protonated Schiff base or RPSB) was found experimentally to be much slower than that of WT ChR2. The E123T mutant replaces the negatively charged E123 residue with a neutral T123 residue, perturbing the electric field around the RPSB. Understanding the RPSB photoisomerization mechanism in ChR2 mutants will provide molecular-level insights into how ChR2 photochemical reactivity can be controlled, which will lay the foundation for improving the design of optogenetic tools. In this work, we combine ab initio nonadiabatic dynamics simulation, excited state free energy calculation, and reaction path search to comprehensively characterize the RPSB photoisomerization mechanism in the E123T mutant of ChR2. Our simulation agrees with previous experiments in predicting a red-shifted absorption spectrum and significant slowdown of photoisomerization in the E123T mutant. Interestingly, our simulations predict similar photoisomerization quantum yields for the mutant and WT despite the differences in excited-state lifetime and absorption maximum. Upon mutation, the neutralization of the negative charge on the E123 residue increases the isomerization barrier, alters the reaction pathway, and changes the relative stability of two fluorescent states. Our findings provide new insight into the intricate role of the electrostatic environment on the RPSB photoisomerization mechanism in microbial rhodopsins.
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Guo T, Patel S, Shah D, Chi L, Emadi S, Pierce DM, Han M, Brumovsky PR, Feng B. Optical clearing reveals TNBS-induced morphological changes of VGLUT2-positive nerve fibers in mouse colorectum. Am J Physiol Gastrointest Liver Physiol 2021; 320:G644-G657. [PMID: 33533318 PMCID: PMC8238166 DOI: 10.1152/ajpgi.00363.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/12/2021] [Accepted: 01/27/2021] [Indexed: 01/31/2023]
Abstract
Colorectal hypersensitivity and sensitization of both mechanosensitive and mechanically insensitive afferents develop after intracolonic instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in the mouse, a model of postinfectious irritable bowel syndrome. In mice in which ∼80% of extrinsic colorectal afferents were labeled genetically using the promotor for vesicular glutamate transporter type 2 (VGLUT2), we systematically quantified the morphology of VGLUT2-positive axons in mouse colorectum 7-28 days following intracolonic TNBS treatment. After removal, the colorectum was distended (20 mmHg), fixed with paraformaldehyde, and optically cleared to image VGLUT2-positive axons throughout the colorectal wall thickness. We conducted vector path tracing of individual axons to allow systematic quantification of nerve fiber density and shape. Abundant VGLUT2-positive nerve fibers were present in most layers of the colorectum, except the serosal and longitudinal muscular layers. A small percentage of VGLUT2-positive myenteric plexus neurons was also detected. Intracolonic TNBS treatment significantly reduced the number of VGLUT2-positive nerve fibers in submucosal, myenteric plexus, and mucosal layers at day 7 post-TNBS, which mostly recovered by day 28. We also found that almost all fibers in the submucosa were meandering and curvy, with ∼10% showing pronounced curviness (quantified by the linearity index). TNBS treatment resulted in a significant reduction of the proportions of pronounced curvy fibers in the rectal region at 28 days post-TNBS. Altogether, the present morphological study reveals profound changes in the distribution of VGLUT2-positive fibers in mouse colorectum undergoing TNBS-induced colitis and draws attention to curvy fibers in the submucosa with potential roles in visceral nociception.NEW & NOTEWORTHY We conducted genetic labeling and optical clearing to visualize extrinsic sensory nerve fibers in whole-mount colorectum, which revealed widespread presence of axons in the submucosal layer. Remarkably, axons in the submucosa were meandering and curvy, in contrast to axons in other layers generally aligned with the basal tissues. Intracolonic TNBS treatment led to pronounced changes of nerve fiber density and curviness, suggesting nerve fiber morphologies as potentially contributing factors to sensory sensitization.
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Yi MH, Liu YU, Umpierre AD, Chen T, Ying Y, Zheng J, Dheer A, Bosco DB, Dong H, Wu LJ. Optogenetic activation of spinal microglia triggers chronic pain in mice. PLoS Biol 2021; 19:e3001154. [PMID: 33739978 PMCID: PMC8011727 DOI: 10.1371/journal.pbio.3001154] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 03/31/2021] [Accepted: 02/24/2021] [Indexed: 12/30/2022] Open
Abstract
Spinal microglia are highly responsive to peripheral nerve injury and are known to be a key player in pain. However, there has not been direct evidence showing that selective microglial activation in vivo is sufficient to induce chronic pain. Here, we used optogenetic approaches in microglia to address this question employing CX3CR1creER/+: R26LSL-ReaChR/+ transgenic mice, in which red-activated channelrhodopsin (ReaChR) is inducibly and specifically expressed in microglia. We found that activation of ReaChR by red light in spinal microglia evoked reliable inward currents and membrane depolarization. In vivo optogenetic activation of microglial ReaChR in the spinal cord triggered chronic pain hypersensitivity in both male and female mice. In addition, activation of microglial ReaChR up-regulated neuronal c-Fos expression and enhanced C-fiber responses. Mechanistically, ReaChR activation led to a reactive microglial phenotype with increased interleukin (IL)-1β production, which is likely mediated by inflammasome activation and calcium elevation. IL-1 receptor antagonist (IL-1ra) was able to reverse the pain hypersensitivity and neuronal hyperactivity induced by microglial ReaChR activation. Therefore, our work demonstrates that optogenetic activation of spinal microglia is sufficient to trigger chronic pain phenotypes by increasing neuronal activity via IL-1 signaling.
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Moshkforoush A, Balachandar L, Moncion C, Montejo KA, Riera J. Unraveling ChR2-driven stochastic Ca2+ dynamics in astrocytes: A call for new interventional paradigms. PLoS Comput Biol 2021; 17:e1008648. [PMID: 33566841 PMCID: PMC7875401 DOI: 10.1371/journal.pcbi.1008648] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/20/2020] [Indexed: 01/04/2023] Open
Abstract
Optogenetic targeting of astrocytes provides a robust experimental model to differentially induce Ca2+ signals in astrocytes in vivo. However, a systematic study quantifying the response of optogenetically modified astrocytes to light is yet to be performed. Here, we propose a novel stochastic model of Ca2+ dynamics in astrocytes that incorporates a light sensitive component-channelrhodopsin 2 (ChR2). Utilizing this model, we investigated the effect of different light stimulation paradigms on cells expressing select variants of ChR2 (wild type, ChETA, and ChRET/TC). Results predict that depending on paradigm specification, astrocytes might undergo drastic changes in their basal Ca2+ level and spiking probability. Furthermore, we performed a global sensitivity analysis to assess the effect of variation in parameters pertinent to the shape of the ChR2 photocurrent on astrocytic Ca2+ dynamics. Results suggest that directing variants towards the first open state of the ChR2 photocycle (o1) enhances spiking activity in astrocytes during optical stimulation. Evaluation of the effect of Ca2+ buffering and coupling coefficient in a network of ChR2-expressing astrocytes demonstrated basal level elevations in the stimulated region and propagation of calcium activity to unstimulated cells. Buffering reduced the diffusion range of Ca2+ within the network, thereby limiting propagation and influencing the activity of astrocytes. Collectively, the framework presented in this study provides valuable information for the selection of light stimulation paradigms that elicit desired astrocytic activity using existing ChR2 constructs, as well as aids in the engineering of future application-oriented optogenetic variants.
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Rook N, Tuff JM, Isparta S, Masseck OA, Herlitze S, Güntürkün O, Pusch R. AAV1 is the optimal viral vector for optogenetic experiments in pigeons (Columba livia). Commun Biol 2021; 4:100. [PMID: 33483632 PMCID: PMC7822860 DOI: 10.1038/s42003-020-01595-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 11/13/2020] [Indexed: 01/30/2023] Open
Abstract
Although optogenetics has revolutionized rodent neuroscience, it is still rarely used in other model organisms as the efficiencies of viral gene transfer differ between species and comprehensive viral transduction studies are rare. However, for comparative research, birds offer valuable model organisms as they have excellent visual and cognitive capabilities. Therefore, the following study establishes optogenetics in pigeons on histological, physiological, and behavioral levels. We show that AAV1 is the most efficient viral vector in various brain regions and leads to extensive anterograde and retrograde ChR2 expression when combined with the CAG promoter. Furthermore, transient optical stimulation of ChR2 expressing cells in the entopallium decreases pigeons' contrast sensitivity during a grayscale discrimination task. This finding demonstrates causal evidence for the involvement of the entopallium in contrast perception as well as a proof of principle for optogenetics in pigeons and provides the groundwork for various other methods that rely on viral gene transfer in birds.
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Love AC, Prescher JA. Seeing (and Using) the Light: Recent Developments in Bioluminescence Technology. Cell Chem Biol 2020; 27:904-920. [PMID: 32795417 PMCID: PMC7472846 DOI: 10.1016/j.chembiol.2020.07.022] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/10/2020] [Accepted: 07/24/2020] [Indexed: 02/08/2023]
Abstract
Bioluminescence has long been used to image biological processes in vivo. This technology features luciferase enzymes and luciferin small molecules that produce visible light. Bioluminescent photons can be detected in tissues and live organisms, enabling sensitive and noninvasive readouts on physiological function. Traditional applications have focused on tracking cells and gene expression patterns, but new probes are pushing the frontiers of what can be visualized. The past few years have also seen the merger of bioluminescence with optogenetic platforms. Luciferase-luciferin reactions can drive light-activatable proteins, ultimately triggering signal transduction and other downstream events. This review highlights these and other recent advances in bioluminescence technology, with an emphasis on tool development. We showcase how new luciferins and engineered luciferases are expanding the scope of optical imaging. We also highlight how bioluminescent systems are being leveraged not just for sensing-but also controlling-biological processes.
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Nabel EM, Garkun Y, Koike H, Sadahiro M, Liang A, Norman KJ, Taccheri G, Demars MP, Im S, Caro K, Lopez S, Bateh J, Hof PR, Clem RL, Morishita H. Adolescent frontal top-down neurons receive heightened local drive to establish adult attentional behavior in mice. Nat Commun 2020; 11:3983. [PMID: 32770078 PMCID: PMC7414856 DOI: 10.1038/s41467-020-17787-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 07/17/2020] [Indexed: 01/01/2023] Open
Abstract
Frontal top-down cortical neurons projecting to sensory cortical regions are well-positioned to integrate long-range inputs with local circuitry in frontal cortex to implement top-down attentional control of sensory regions. How adolescence contributes to the maturation of top-down neurons and associated local/long-range input balance, and the establishment of attentional control is poorly understood. Here we combine projection-specific electrophysiological and rabies-mediated input mapping in mice to uncover adolescence as a developmental stage when frontal top-down neurons projecting from the anterior cingulate to visual cortex are highly functionally integrated into local excitatory circuitry and have heightened activity compared to adulthood. Chemogenetic suppression of top-down neuron activity selectively during adolescence, but not later periods, produces long-lasting visual attentional behavior deficits, and results in excessive loss of local excitatory inputs in adulthood. Our study reveals an adolescent sensitive period when top-down neurons integrate local circuits with long-range connectivity to produce attentional behavior.
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Pagan-Diaz GJ, Drnevich J, Ramos-Cruz KP, Sam R, Sengupta P, Bashir R. Modulating electrophysiology of motor neural networks via optogenetic stimulation during neurogenesis and synaptogenesis. Sci Rep 2020; 10:12460. [PMID: 32719407 PMCID: PMC7385114 DOI: 10.1038/s41598-020-68988-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 06/30/2020] [Indexed: 12/12/2022] Open
Abstract
Control of electrical activity in neural circuits through network training is a grand challenge for biomedicine and engineering applications. Past efforts have not considered evoking long-term changes in firing patterns of in-vitro networks by introducing training regimens with respect to stages of neural development. Here, we used Channelrhodopsin-2 (ChR2) transfected mouse embryonic stem cell (mESC) derived motor neurons to explore short and long-term programming of neural networks by using optical stimulation implemented during neurogenesis and synaptogenesis. Not only did we see a subsequent increase of neurite extensions and synaptophysin clustering, but by using electrophysiological recording with micro electrode arrays (MEA) we also observed changes in signal frequency spectra, increase of network synchrony, coordinated firing of actions potentials, and enhanced evoked response to stimulation during network formation. Our results demonstrate that optogenetic stimulation during neural differentiation can result in permanent changes that extended to the genetic expression of neurons as demonstrated by RNA Sequencing. To our knowledge, this is the first time that a correlation between training regimens during neurogenesis and synaptogenesis and the resulting plastic responses has been shown in-vitro and traced back to changes in gene expression. This work demonstrates new approaches for training of neural circuits whose electrical activity can be modulated and enhanced, which could lead to improvements in neurodegenerative disease research and engineering of in-vitro multi-cellular living systems.
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Lemme M, Braren I, Prondzynski M, Aksehirlioglu B, Ulmer BM, Schulze ML, Ismaili D, Meyer C, Hansen A, Christ T, Lemoine MD, Eschenhagen T. Chronic intermittent tachypacing by an optogenetic approach induces arrhythmia vulnerability in human engineered heart tissue. Cardiovasc Res 2020; 116:1487-1499. [PMID: 31598634 PMCID: PMC7314638 DOI: 10.1093/cvr/cvz245] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 07/31/2019] [Accepted: 10/04/2019] [Indexed: 01/01/2023] Open
Abstract
AIMS Chronic tachypacing is commonly used in animals to induce cardiac dysfunction and to study mechanisms of heart failure and arrhythmogenesis. Human induced pluripotent stem cells (hiPSC) may replace animal models to overcome species differences and ethical problems. Here, 3D engineered heart tissue (EHT) was used to investigate the effect of chronic tachypacing on hiPSC-cardiomyocytes (hiPSC-CMs). METHODS AND RESULTS To avoid cell toxicity by electrical pacing, we developed an optogenetic approach. EHTs were transduced with lentivirus expressing channelrhodopsin-2 (H134R) and stimulated by 15 s bursts of blue light pulses (0.3 mW/mm2, 30 ms, 3 Hz) separated by 15 s without pacing for 3 weeks. Chronic optical tachypacing did not affect contractile peak force, but induced faster contraction kinetics, shorter action potentials, and shorter effective refractory periods. This electrical remodelling increased vulnerability to tachycardia episodes upon electrical burst pacing. Lower calsequestrin 2 protein levels, faster diastolic depolarization (DD) and efficacy of JTV-519 (46% at 1 µmol/L) to terminate tachycardia indicate alterations of Ca2+ handling being part of the underlying mechanism. However, other antiarrhythmic compounds like flecainide (69% at 1 µmol/L) and E-4031 (100% at 1 µmol/L) were also effective, but not ivabradine (1 µmol/L) or SEA0400 (10 µmol/L). CONCLUSION We demonstrated a high vulnerability to tachycardia of optically tachypaced hiPSC-CMs in EHT and the effective termination by ryanodine receptor stabilization, sodium or hERG potassium channel inhibition. This new model might serve as a preclinical tool to test antiarrhythmic drugs increasing the insight in treating ventricular tachycardia.
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Peng K, Liu S, Lv F, Fu X, Hussain S, Zhao H, Liu L, Wang S. Wireless Charging Electrochemiluminescence System for Ionic Channel Manipulation in Living Cells. ACS APPLIED MATERIALS & INTERFACES 2020; 12:24655-24661. [PMID: 32391678 DOI: 10.1021/acsami.0c07476] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Optogenetics holds great potential for precisely altering living cell behavior with the aid of light because of its high temporospatial resolution. However, the light-dependent manner severely limits its applications in deep tissues, particularly to those in the visible region. Here, we propose a wireless charging electrochemiluminescence (ECL) system, featured with long-time delayed luminescence, to remotely activate the light-gated ion channel (channelrhodopsin-2, ChR2) on the living cell membrane, followed by the intracellular influx of Ca2+ ions. Upon wireless charging ECL illumination, the influx of Ca2+ into the living cells triggers strong ion indicator fluorescence, suggesting the successful remote control on ChR2. As such, the wireless charging ECL strategy exhibits great potential to wireless control of optogenetics in deep tissues by implanting a device in vivo.
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Warlow SM, Naffziger EE, Berridge KC. The central amygdala recruits mesocorticolimbic circuitry for pursuit of reward or pain. Nat Commun 2020; 11:2716. [PMID: 32483118 PMCID: PMC7264246 DOI: 10.1038/s41467-020-16407-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 05/01/2020] [Indexed: 02/06/2023] Open
Abstract
How do brain mechanisms create maladaptive attractions? Here intense maladaptive attractions are created in laboratory rats by pairing optogenetic channelrhodopsin (ChR2) stimulation of central nucleus of amygdala (CeA) in rats with encountering either sucrose, cocaine, or a painful shock-delivering object. We find that pairings make the respective rats pursue either sucrose exclusively, or cocaine exclusively, or repeatedly self-inflict shocks. CeA-induced maladaptive attractions, even to the painful shock-rod, recruit mesocorticolimbic incentive-related circuitry. Shock-associated cues also gain positive incentive value and are pursued. Yet the motivational effects of paired CeA stimulation can be reversed to negative valence in a Pavlovian fear learning situation, where CeA ChR2 pairing increases defensive reactions. Finally, CeA ChR2 valence can be switched to neutral by pairing with innocuous stimuli. These results reveal valence plasticity and multiple modes for motivation via mesocorticolimbic circuitry under the control of CeA activation.
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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: 18] [Impact Index Per Article: 4.5] [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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Sala-Jarque J, Mesquida-Veny F, Badiola-Mateos M, Samitier J, Hervera A, del Río JA. Neuromuscular Activity Induces Paracrine Signaling and Triggers Axonal Regrowth after Injury in Microfluidic Lab-On-Chip Devices. Cells 2020; 9:cells9020302. [PMID: 32012727 PMCID: PMC7072511 DOI: 10.3390/cells9020302] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/17/2020] [Accepted: 01/23/2020] [Indexed: 12/19/2022] Open
Abstract
Peripheral nerve injuries, including motor neuron axonal injury, often lead to functional impairments. Current therapies are mostly limited to surgical intervention after lesion, yet these interventions have limited success in restoring functionality. Current activity-based therapies after axonal injuries are based on trial-error approaches in which the details of the underlying cellular and molecular processes are largely unknown. Here we show the effects of the modulation of both neuronal and muscular activity with optogenetic approaches to assess the regenerative capacity of cultured motor neuron (MN) after lesion in a compartmentalized microfluidic-assisted axotomy device. With increased neuronal activity, we observed an increase in the ratio of regrowing axons after injury in our peripheral-injury model. Moreover, increasing muscular activity induces the liberation of leukemia inhibitory factor and glial cell line-derived neurotrophic factor in a paracrine fashion that in turn triggers axonal regrowth of lesioned MN in our 3D hydrogel cultures. The relevance of our findings as well as the novel approaches used in this study could be useful not only after axotomy events but also in diseases affecting MN survival.
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Agus V, Janovjak H. All-Optical Miniaturized Co-culture Assay of Voltage-Gated Ca 2+ Channels. Methods Mol Biol 2020; 2173:247-260. [PMID: 32651923 DOI: 10.1007/978-1-0716-0755-8_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Light-activated proteins enable the reversible and spatiotemporal control of cellular events in optogenetics. Optogenetics is also rapidly expanding into the field of drug discovery where it provides cost-effective and noninvasive approaches for cell manipulation in high-throughput screens. Here, we present a prototypical cell-based assay that applies Channelrhodopsin2 (ChR2) to recapitulate physiological membrane potential changes and test for voltage-gated ion channel (VGIC) blockade. ChR2 and the voltage-gated Ca2+ channel 1.2 (CaV1.2) are expressed in individual HEK293 cell lines that are then co-cultured for formation of gap junctions and an electrical syncytium. This co-culture allows identification of blockers using parallel fluorescence plate readers in the 384-well plate format in an all-optical mode of operation. The assay is transferable to other VGICs by modularly combining new and existing cell lines and potentially also to other drug targets.
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