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Mäeots ME, Enchev RI. Structural dynamics: review of time-resolved cryo-EM. Acta Crystallogr D Struct Biol 2022; 78:927-935. [PMID: 35916218 PMCID: PMC9344476 DOI: 10.1107/s2059798322006155] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 06/09/2022] [Indexed: 11/11/2022] Open
Abstract
The structural determination of biological macromolecules has been transformative for understanding biochemical mechanisms and developing therapeutics. However, the ultimate goal of characterizing how structural dynamics underpin biochemical processes has been difficult. This is largely due to significant technical challenges that hinder data collection and analysis on the native timescales of macromolecular dynamics. Single-particle cryo-EM provides a powerful platform to approach this challenge, since samples can be frozen faster than the single-turnover timescales of most biochemical reactions. In order to enable time-resolved analysis, significant innovations in the handling and preparation of cryo-EM samples have been implemented, bringing us closer to the goal of the direct observation of protein dynamics in the milliseconds to seconds range. Here, the current state of time-resolved cryo-EM is reviewed and the most promising future research directions are discussed.
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Affiliation(s)
- Märt-Erik Mäeots
- The Visual Biochemistry Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, United Kingdom
| | - Radoslav I. Enchev
- The Visual Biochemistry Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, United Kingdom
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2
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Kobayashi A, Nobili A, Neier SC, Sadiki A, Distel R, Zhou ZS, Novina CD. Light-Controllable Binary Switch Activation of CAR T Cells. ChemMedChem 2022; 17:e202100722. [PMID: 35146940 PMCID: PMC9304291 DOI: 10.1002/cmdc.202100722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 02/05/2022] [Indexed: 11/29/2022]
Abstract
Major challenges to chimeric antigen receptor (CAR) T cell therapies include uncontrolled immune activity, off-tumor toxicities and tumor heterogeneity. To overcome these challenges, we engineered CARs directed against small molecules. By conjugating the same small molecule to distinct tumor-targeting antibodies, we show that small molecule specific-CAR T cells can be redirected to different tumor antigens. Such binary switches allow control over the degree of CAR T cell activity and enables simultaneous targeting of multiple tumor-associated antigens. We also demonstrate that ultraviolet light-sensitive caging of small molecules blocks CAR T cell activation. Exposure to ultraviolet light, uncaged small molecules and restored CAR T cell-mediated killing. Together, our data demonstrate that a light-sensitive caging system enables an additional level of control over tumor cell killing, which could improve the therapeutic index of CAR T cell therapies.
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Affiliation(s)
- Aya Kobayashi
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
- Broad Institute of Harvard and MITCambridgeMA 02142USA
| | - Alberto Nobili
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
- Broad Institute of Harvard and MITCambridgeMA 02142USA
- Dynamic Cell Therapies, Inc.127 Western Ave.AllstonMA 02134USA
| | - Steven C. Neier
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
- Broad Institute of Harvard and MITCambridgeMA 02142USA
- Binney Street CapitalBostonMA 02215USA
| | - Amissi Sadiki
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
- Department of Chemistry and Chemical BiologyNortheastern UniversityBostonMA 02115USA
- Barnett Institute of Chemical and Biological AnalysisNortheastern UniversityBostonMA 02115USA
| | - Robert Distel
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
| | - Zhaohui Sunny Zhou
- Department of Chemistry and Chemical BiologyNortheastern UniversityBostonMA 02115USA
- Barnett Institute of Chemical and Biological AnalysisNortheastern UniversityBostonMA 02115USA
| | - Carl D. Novina
- Department of Cancer Immunology and VirologyDana-Farber Cancer InstituteBostonMA 02215USA
- Department of MedicineHarvard Medical SchoolBostonMA 02115USA
- Broad Institute of Harvard and MITCambridgeMA 02142USA
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3
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Monteiro DCF, Amoah E, Rogers C, Pearson AR. Using photocaging for fast time-resolved structural biology studies. Acta Crystallogr D Struct Biol 2021; 77:1218-1232. [PMID: 34605426 PMCID: PMC8489231 DOI: 10.1107/s2059798321008809] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 08/23/2021] [Indexed: 12/02/2022] Open
Abstract
Careful selection of photocaging approaches is critical to achieve fast and well synchronized reaction initiation and perform successful time-resolved structural biology experiments. This review summarizes the best characterized and most relevant photocaging groups previously described in the literature. It also provides a walkthrough of the essential factors to consider in designing a suitable photocaged molecule to address specific biological questions, focusing on photocaging groups with well characterized spectroscopic properties. The relationships between decay rates (k in s-1), quantum yields (ϕ) and molar extinction coefficients (ϵmax in M-1 cm-1) are highlighted for different groups. The effects of the nature of the photocaged group on these properties is also discussed. Four main photocaging scaffolds are presented in detail, o-nitrobenzyls, p-hydroxyphenyls, coumarinyls and nitrodibenzofuranyls, along with three examples of the use of this technology. Furthermore, a subset of specialty photocages are highlighted: photoacids, molecular photoswitches and metal-containing photocages. These extend the range of photocaging approaches by, for example, controlling pH or generating conformationally locked molecules.
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Affiliation(s)
- Diana C. F. Monteiro
- Hauptman–Woodward Medical Research Institute, 700 Ellicot Street, Buffalo, NY 14203, USA
| | - Emmanuel Amoah
- Hauptman–Woodward Medical Research Institute, 700 Ellicot Street, Buffalo, NY 14203, USA
| | - Cromarte Rogers
- The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
- Department of Chemistry, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Arwen R. Pearson
- The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
- Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
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4
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Wang T, Ulrich H, Semyanov A, Illes P, Tang Y. Optical control of purinergic signaling. Purinergic Signal 2021; 17:385-392. [PMID: 34156578 PMCID: PMC8410941 DOI: 10.1007/s11302-021-09799-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 06/07/2021] [Indexed: 12/29/2022] Open
Abstract
Purinergic signaling plays a pivotal role in physiological processes and pathological conditions. Over the past decades, conventional pharmacological, biochemical, and molecular biology techniques have been utilized to investigate purinergic signaling cascades. However, none of them is capable of spatially and temporally manipulating purinergic signaling cascades. Currently, optical approaches, including optopharmacology and optogenetic, enable controlling purinergic signaling with low invasiveness and high spatiotemporal precision. In this mini-review, we discuss optical approaches for controlling purinergic signaling and their applications in basic and translational science.
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Affiliation(s)
- Tao Wang
- International Collaborative Centre On Big Science Plan for Purinergic Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China.,Acupuncture and Chronobiology Key Laboratory of Sichuan Province, Chengdu, China
| | - Henning Ulrich
- International Collaborative Centre On Big Science Plan for Purinergic Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China.,Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Alexey Semyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Sechenov First Moscow State Medical University, Moscow, Russia
| | - Peter Illes
- International Collaborative Centre On Big Science Plan for Purinergic Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China. .,Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.
| | - Yong Tang
- International Collaborative Centre On Big Science Plan for Purinergic Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China. .,Acupuncture and Chronobiology Key Laboratory of Sichuan Province, Chengdu, China.
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5
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Hishida R, Horie M, Tsukano H, Tohmi M, Yoshitake K, Meguro R, Takebayashi H, Yanagawa Y, Shibuki K. Feedback inhibition derived from the posterior parietal cortex regulates the neural properties of the mouse visual cortex. Eur J Neurosci 2019; 50:2970-2987. [PMID: 31012509 DOI: 10.1111/ejn.14424] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/22/2019] [Accepted: 04/09/2019] [Indexed: 11/28/2022]
Abstract
Feedback regulation from the higher association areas is thought to control the primary sensory cortex, contribute to the cortical processing of sensory information, and work for higher cognitive functions such as multimodal integration and attentional control. However, little is known about the underlying neural mechanisms. Here, we show that the posterior parietal cortex (PPC) persistently inhibits the activity of the primary visual cortex (V1) in mice. Activation of the PPC causes the suppression of visual responses in V1 and induces the short-term depression, which is specific to visual stimuli. In contrast, pharmacological inactivation of the PPC or disconnection of cortical pathways from the PPC to V1 results in an effect of transient enhancement of visual responses in V1. Two-photon calcium imaging demonstrated that the cortical disconnection caused V1 excitatory neurons an enhancement of visual responses and a reduction of orientation selectivity index (OSI). These results show that the PPC regulates the response properties of V1 excitatory neurons. Our findings reveal one of the functions of the PPC, which may contribute to higher brain functions in mice.
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Affiliation(s)
- Ryuichi Hishida
- Department of Neurophysiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Masao Horie
- Department of Morphological Sciences, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Hiroaki Tsukano
- Department of Neurophysiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Manavu Tohmi
- Department of Neurophysiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Kohei Yoshitake
- Department of Neurophysiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Reiko Meguro
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Katsuei Shibuki
- Department of Neurophysiology, Brain Research Institute, Niigata University, Niigata, Japan
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6
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Light-triggered release of photocaged therapeutics - Where are we now? J Control Release 2019; 298:154-176. [PMID: 30742854 DOI: 10.1016/j.jconrel.2019.02.006] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 02/04/2019] [Accepted: 02/06/2019] [Indexed: 01/02/2023]
Abstract
The current available therapeutics face several challenges such as the development of ideal drug delivery systems towards the goal of personalized treatments for patients benefit. The application of light as an exogenous activation mechanism has shown promising outcomes, owning to the spatiotemporal confinement of the treatment in the vicinity of the diseased tissue, which offers many intriguing possibilities. Engineering therapeutics with light responsive moieties have been explored to enhance the bioavailability, and drug efficacy either in vitro or in vivo. The tailor-made character turns the so-called photocaged compounds highly desirable to reduce the side effects of drugs and, therefore, have received wide research attention. Herein, we seek to highlight the potential of photocaged compounds to obtain a clear understanding of the mechanisms behind its use in therapeutic delivery. A deep overview on the progress achieved in the design, fabrication as well as current and possible future applications in therapeutics of photocaged compounds is provided, so that novel formulations for biomedical field can be designed.
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7
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Direnberger S, Banchi R, Brosel S, Seebacher C, Laimgruber S, Uhl R, Felmy F, Straka H, Kunz L. Analysis of signal processing in vestibular circuits with a novel light-emitting diodes-based fluorescence microscope. Eur J Neurosci 2015; 41:1332-44. [DOI: 10.1111/ejn.12907] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 03/30/2015] [Indexed: 01/01/2023]
Affiliation(s)
- Stephan Direnberger
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
| | - Roberto Banchi
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
- Graduate School of Systemic Neurosciences; Ludwig-Maximilians University Munich; Planegg-Martinsried Germany
| | - Sonja Brosel
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
| | - Christian Seebacher
- Department Biology I; BioImaging Center; Ludwig-Maximilians University Munich; Planegg-Martinsried Germany
| | - Stefan Laimgruber
- Department Biology I; BioImaging Center; Ludwig-Maximilians University Munich; Planegg-Martinsried Germany
| | - Rainer Uhl
- Department Biology I; BioImaging Center; Ludwig-Maximilians University Munich; Planegg-Martinsried Germany
| | - Felix Felmy
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
- Department Biology I; BioImaging Center; Ludwig-Maximilians University Munich; Planegg-Martinsried Germany
| | - Hans Straka
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
| | - Lars Kunz
- Department Biology II; Division of Neurobiology; Ludwig-Maximilians University Munich; Grosshaderner Str. 2 Planegg-Martinsried 82152 Germany
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8
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Hess GP, Lewis RW, Chen Y. Caged neurotransmitters and other caged compounds: design and application. Cold Spring Harb Protoc 2014; 2014:pdb.top084152. [PMID: 25275116 DOI: 10.1101/pdb.top084152] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The approaches using caged neurotransmitters described here enable transient kinetic investigations to be made with membrane-bound proteins (receptors) on a cell surface with the same time resolution as was previously possible only with proteins in solution.
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9
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Armbruster M, Hampton D, Yang Y, Dulla CG. Laser-scanning astrocyte mapping reveals increased glutamate-responsive domain size and disrupted maturation of glutamate uptake following neonatal cortical freeze-lesion. Front Cell Neurosci 2014; 8:277. [PMID: 25249939 PMCID: PMC4158796 DOI: 10.3389/fncel.2014.00277] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 08/22/2014] [Indexed: 12/27/2022] Open
Abstract
Astrocytic uptake of glutamate shapes extracellular neurotransmitter dynamics, receptor activation, and synaptogenesis. During development, glutamate transport becomes more robust. How neonatal brain insult affects the functional maturation of glutamate transport remains unanswered. Neonatal brain insult can lead to developmental delays, cognitive losses, and epilepsy; the disruption of glutamate transport is known to cause changes in synaptogenesis, receptor activation, and seizure. Using the neonatal freeze-lesion (FL) model, we have investigated how insult affects the maturation of astrocytic glutamate transport. As lesioning occurs on the day of birth, a time when astrocytes are still functionally immature, this model is ideal for identifying changes in astrocyte maturation following insult. Reactive astrocytosis, astrocyte proliferation, and in vitro hyperexcitability are known to occur in this model. To probe astrocyte glutamate transport with better spatial precision we have developed a novel technique, Laser Scanning Astrocyte Mapping (LSAM), which combines glutamate transport current (TC) recording from astrocytes with laser scanning glutamate photolysis. LSAM allows us to identify the area from which a single astrocyte can transport glutamate and to quantify spatial heterogeneity in the rate of glutamate clearance kinetics within that domain. Using LSAM, we report that cortical astrocytes have an increased glutamate-responsive area following FL and that TCs have faster decay times in distal, as compared to proximal processes. Furthermore, the developmental shift from GLAST- to GLT-1-dominated clearance is disrupted following FL. These findings introduce a novel method to probe astrocyte glutamate uptake and show that neonatal cortical FL disrupts the functional maturation of cortical astrocytes.
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Affiliation(s)
- Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
| | - David Hampton
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
| | - Yongjie Yang
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
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10
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Activity-dependent structural plasticity of perisynaptic astrocytic domains promotes excitatory synapse stability. Curr Biol 2014; 24:1679-88. [PMID: 25042585 DOI: 10.1016/j.cub.2014.06.025] [Citation(s) in RCA: 248] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 06/05/2014] [Accepted: 06/10/2014] [Indexed: 11/21/2022]
Abstract
BACKGROUND Excitatory synapses in the CNS are highly dynamic structures that can show activity-dependent remodeling and stabilization in response to learning and memory. Synapses are enveloped with intricate processes of astrocytes known as perisynaptic astrocytic processes (PAPs). PAPs are motile structures displaying rapid actin-dependent movements and are characterized by Ca(2+) elevations in response to neuronal activity. Despite a debated implication in synaptic plasticity, the role of both Ca(2+) events in astrocytes and PAP morphological dynamics remain unclear. RESULTS In the hippocampus, we found that PAPs show extensive structural plasticity that is regulated by synaptic activity through astrocytic metabotropic glutamate receptors and intracellular calcium signaling. Synaptic activation that induces long-term potentiation caused a transient PAP motility increase leading to an enhanced astrocytic coverage of the synapse. Selective activation of calcium signals in individual PAPs using exogenous metabotropic receptor expression and two-photon uncaging reproduced these effects and enhanced spine stability. In vivo imaging in the somatosensory cortex of adult mice revealed that increased neuronal activity through whisker stimulation similarly elevates PAP movement. This in vivo PAP motility correlated with spine coverage and was predictive of spine stability. CONCLUSIONS This study identifies a novel bidirectional interaction between synapses and astrocytes, in which synaptic activity and synaptic potentiation regulate PAP structural plasticity, which in turn determines the fate of the synapse. This mechanism may represent an important contribution of astrocytes to learning and memory processes.
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Canepari M, Zecevic D, Vogt KE, Ogden D, De Waard M. Combining calcium imaging with other optical techniques. Cold Spring Harb Protoc 2013; 2013:1125-31. [PMID: 24298025 DOI: 10.1101/pdb.top066167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ca(2+) imaging is a commonly used approach for measuring Ca(2+) signals at high spatial resolution. The method is often combined with electrode recordings to correlate electrical and chemical signals or to investigate Ca(2+) signals following an electrical stimulation. To obtain information on electrical activity at the same spatial resolution, Ca(2+) imaging must be combined with membrane potential imaging. Similarly, stimulation of subcellular compartments requires photostimulation. Thus, combining Ca(2+) imaging with an additional optical technique facilitates the study of a number of physiological questions. The aim of this article is to introduce some basic principles regarding the combination of Ca(2+) imaging with other optical techniques. We discuss the design of the optics, the design of experimental protocols, the optical characteristics of Ca(2+) indicators used in combination with an optical probe, and the affinity of the Ca(2+) indicator in relation to the type of measurement. This information will enable the reader to devise an optimal strategy for combined optical experiments.
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Affiliation(s)
- Marco Canepari
- Inserm U836, Team 3, BP 170, Grenoble cedex 09, F-38042, France
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12
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Abstract
Changes in intracellular free calcium concentration (Δ[Ca(2+)]i) driving physiological events such as neurotransmitter release or Ca(2+)-dependent currents can be monitored using Ca(2+)-sensitive fluorescent dyes. Although these dyes can correlate Δ[Ca(2+)]i with a physiological event, they cannot directly test for causality between changes in [Ca(2+)]i and that event. Photolabile Ca(2+) chelators are Ca(2+)-binding molecules that can alter and, to a certain extent, control [Ca(2+)]i in an inducible manner and with temporal and spatial resolution that surpasses microinjection or ionophore application. Here we discuss the properties of caged Ca(2+) compounds as well as some practical considerations for their use in neuronal cells, where they have proven particularly effective.
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13
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Abstract
Photoactivatable fluorophores switch from a nonemissive to an emissive state upon illumination at an activating wavelength and then emit after irradiation at an exciting wavelength. The interplay of such activation and excitation events can be exploited to switch fluorescence on in a defined region of space at a given interval of time. In turn, the spatiotemporal control of fluorescence translates into the opportunity to implement imaging and spectroscopic schemes that are not possible with conventional fluorophores. Specifically, photoactivatable fluorophores permit the monitoring of dynamic processes in real time as well as the reconstruction of images with subdiffraction resolution. These promising applications can have a significant impact on the characterization of the structures and functions of biomolecular systems. As a result, strategies to implement mechanisms for fluorescence photoactivation with synthetic fluorophores are particularly valuable. In fact, a number of versatile operating principles have already been identified to activate the fluorescence of numerous members of the main families of synthetic dyes. These methods are based on either the irreversible cleavage of covalent bonds or the reversible opening and closing of rings. This paper overviews the fundamental mechanisms that govern the behavior of these photoresponsive systems, illustrates structural designs for fluorescence photoactivation, and provides representative examples of photoactivatable fluorophores in actions.
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Affiliation(s)
- Françisco M. Raymo
- Laboratory for Molecular Photonics, Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33146-0431, USA
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14
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Gallagher ES, Comi TJ, Braun KL, Aspinwall CA. Online photolytic optical gating of caged fluorophores in capillary zone electrophoresis utilizing an ultraviolet light-emitting diode. Electrophoresis 2012; 33:2903-10. [PMID: 22911376 DOI: 10.1002/elps.201200279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 06/23/2012] [Accepted: 06/25/2012] [Indexed: 11/11/2022]
Abstract
Photolytic optical gating (POG) facilitates rapid, on-line and highly sensitive analyses, though POG utilizes UV lasers for sample injection. We present a low-cost, more portable alternative, employing an ultraviolet light-emitting diode (UV-LED) array to inject caged fluorescent dyes via photolysis. Utilizing the UV-LED array, labeled amino acids were injected with nanomolar limits of detection (270 ± 30 nM and 250 ± 30 nM for arginine and citrulline, respectively). When normalized for the difference in light intensity, the UV-LED array provides comparable sensitivity to POG utilizing UV lasers. Additionally, the UV-LED array yielded sufficient beam quality and stability to facilitate coupling with a Hadamard transform, resulting in increased sensitivity. This work shows, for the first time, the use of an UV-LED for online POG with comparable sensitivity to conventional laser sources but at a lower cost.
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Affiliation(s)
- Elyssia S Gallagher
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
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15
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Lee P, Yan P, Ewart P, Kohl P, Loew LM, Bollensdorff C. Simultaneous measurement and modulation of multiple physiological parameters in the isolated heart using optical techniques. Pflugers Arch 2012; 464:403-14. [PMID: 22886365 DOI: 10.1007/s00424-012-1135-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 06/23/2012] [Accepted: 06/26/2012] [Indexed: 10/28/2022]
Abstract
Whole-heart multi-parametric optical mapping has provided valuable insight into the interplay of electrophysiological parameters, and this technology will continue to thrive as dyes are improved and technical solutions for imaging become simpler and cheaper. Here, we show the advantage of using improved 2nd-generation voltage dyes, provide a simple solution to panoramic multi-parametric mapping, and illustrate the application of flash photolysis of caged compounds for studies in the whole heart. For proof of principle, we used the isolated rat whole-heart model. After characterising the blue and green isosbestic points of di-4-ANBDQBS and di-4-ANBDQPQ, respectively, two voltage and calcium mapping systems are described. With two newly custom-made multi-band optical filters, (1) di-4-ANBDQBS and fluo-4 and (2) di-4-ANBDQPQ and rhod-2 mapping are demonstrated. Furthermore, we demonstrate three-parameter mapping using di-4-ANBDQPQ, rhod-2 and NADH. Using off-the-shelf optics and the di-4-ANBDQPQ and rhod-2 combination, we demonstrate panoramic multi-parametric mapping, affording a 360° spatiotemporal record of activity. Finally, local optical perturbation of calcium dynamics in the whole heart is demonstrated using the caged compound, o-nitrophenyl ethylene glycol tetraacetic acid (NP-EGTA), with an ultraviolet light-emitting diode (LED). Calcium maps (heart loaded with di-4-ANBDQPQ and rhod-2) demonstrate successful NP-EGTA loading and local flash photolysis. All imaging systems were built using only a single camera. In conclusion, using novel 2nd-generation voltage dyes, we developed scalable techniques for multi-parametric optical mapping of the whole heart from one point of view and panoramically. In addition to these parameter imaging approaches, we show that it is possible to use caged compounds and ultraviolet LEDs to locally perturb electrophysiological parameters in the whole heart.
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Affiliation(s)
- Peter Lee
- Department of Physics, University of Oxford, Oxford, UK
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16
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Civillico EF, Shoham S, O'Connor DH, Sarkisov DV, Wang SSH. Acousto-optical deflector-based patterned ultraviolet uncaging of neurotransmitter for the study of neuronal integration. Cold Spring Harb Protoc 2012; 2012:2012/8/pdb.top070631. [PMID: 22854573 DOI: 10.1101/pdb.top070631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The method of patterned photoactivation is a natural fit for the study of neuronal dendritic integration. Photoactivatable molecules that influence a wide range of extracellular and intracellular neurophysiological functions are available. The choice of photosensitive molecules depends on the research question and will influence the design of the experimental apparatus. This article describes an acousto-optical deflector (AOD)-based system for rapid ultraviolet (UV) photolysis in arbitrary spatial and temporal patterns. Some basics of caged neurotransmitters and the theory of operation of AODs are covered, as are descriptions for implementing the system.
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17
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Boccaccio A, Sagheddu C, Menini A. Flash photolysis of caged compounds in the cilia of olfactory sensory neurons. J Vis Exp 2011:e3195. [PMID: 22064384 DOI: 10.3791/3195] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Photolysis of caged compounds allows the production of rapid and localized increases in the concentration of various physiologically active compounds. Caged compounds are molecules made physiologically inactive by a chemical cage that can be broken by a flash of ultraviolet light. Here, we show how to obtain patch-clamp recordings combined with photolysis of caged compounds for the study of olfactory transduction in dissociated mouse olfactory sensory neurons. The process of olfactory transduction (Figure 1) takes place in the cilia of olfactory sensory neurons, where odorant binding to receptors leads to the increase of cAMP that opens cyclic nucleotide-gated (CNG) channels. Ca entry through CNG channels activates Ca-activated Cl channels. We show how to dissociate neurons from the mouse olfactory epithelium and how to activate CNG channels or Ca-activated Cl channels by photolysis of caged cAMP or caged Ca. We use a flash lamp to apply ultraviolet flashes to the ciliary region to uncage cAMP or Ca while patch-clamp recordings are taken to measure the current in the whole-cell voltage-clamp configuration.
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Astrocytes display complex and localized calcium responses to single-neuron stimulation in the hippocampus. J Neurosci 2011; 31:8905-19. [PMID: 21677174 DOI: 10.1523/jneurosci.6341-10.2011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Astrocytes show a complex structural and physiological interplay with neurons and respond to neuronal activation in vitro and in vivo with intracellular calcium elevations. These calcium changes enable astrocytes to modulate synaptic transmission and plasticity through various mechanisms. However, the response pattern of astrocytes to single neuronal depolarization events still remains unresolved. This information is critical for fully understanding the coordinated network of neuron-glial signaling in the brain. To address this, we developed a system to map astrocyte calcium responses along apical dendrites of CA1 pyramidal neurons in hippocampal slices using single-neuron stimulation with channelrhodopsin-2. This technique allowed selective neuronal depolarization without invasive manipulations known to alter calcium levels in astrocytes. Light-evoked neuronal depolarization was elicited and calcium events in surrounding astrocytes were monitored using the calcium-sensitive dye Calcium Orange. Stimulation of single neurons caused calcium responses in populations of astrocytes along the apical axis of CA1 cell dendrites. Calcium responses included single events that were synchronized with neuronal stimulation and poststimulus changes in calcium event frequency, both of which were modulated by glutamatergic and purinergic signaling. Individual astrocytes near CA1 cells showed low ability to respond to repeated neuronal depolarization events. However, the response of the surrounding astrocyte population was remarkably accurate. Interestingly, the reliability of responses was graded with respect to astrocyte location along the CA1 cell dendrite, with astrocytes residing in the primary dendrite subregion being most responsive. This study provides a new perspective on the dynamic response property of astrocyte ensembles to neuronal activity.
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Losavio BE, Iyer V, Patel S, Saggau P. Acousto-optic laser scanning for multi-site photo-stimulation of single neuronsin vitro. J Neural Eng 2010; 7:045002. [DOI: 10.1088/1741-2560/7/4/045002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Obi N, Momotake A, Kanemoto Y, Matsuzaki M, Kasai H, Arai T. 1-Acyl-5-methoxy-8-nitro-1,2-dihydroquinoline: a biologically useful photolabile precursor of carboxylic acids. Tetrahedron Lett 2010. [DOI: 10.1016/j.tetlet.2009.12.081] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Li WH. Photo-activatable probes for the analysis of receptor function in living cells. Methods Mol Biol 2010; 591:105-20. [PMID: 19957126 DOI: 10.1007/978-1-60761-404-3_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
Photo-activatable (caged) probes are powerful research tools for biological investigation. The superb maneuverability of a light beam allows researchers to activate caged probes with pinpoint accuracy. Recent developments in caging chemistry and two-photon excitation technique further enhance our capability to perform photo-uncaging with even higher spatial and temporal resolution, offering new photonic approaches to study cell signaling dynamics in greater detail. Here we present a sample method that combines the techniques of photo-activation and digital fluorescence microscopy to assay an important class of intracellular receptors for the second messenger D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P(3), or IP(3)). The imaging assay is performed in fully intact living cells using a caged and cell membrane permeable ester derivative of IP(3), cm-IP(3)/PM.
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Affiliation(s)
- Wen-Hong Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Casey JP, Blidner RA, Monroe WT. Caged siRNAs for Spatiotemporal Control of Gene Silencing. Mol Pharm 2009; 6:669-85. [DOI: 10.1021/mp900082q] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- John P. Casey
- Department of Biological and Agricultural Engineering, Louisiana State University and the LSU Agricultural Center, Baton Rouge, Louisiana 70803
| | - Richard A. Blidner
- Department of Biological and Agricultural Engineering, Louisiana State University and the LSU Agricultural Center, Baton Rouge, Louisiana 70803
| | - W. Todd Monroe
- Department of Biological and Agricultural Engineering, Louisiana State University and the LSU Agricultural Center, Baton Rouge, Louisiana 70803
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Dong CY, Yoon TW, Bates DG, Cho KH. Identification of feedback loops embedded in cellular circuits by investigating non-causal impulse response components. J Math Biol 2009; 60:285-312. [PMID: 19333603 DOI: 10.1007/s00285-009-0263-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 03/03/2009] [Indexed: 12/24/2022]
Abstract
Feedback circuits are crucial dynamic motifs which occur in many biomolecular regulatory networks. They play a pivotal role in the regulation and control of many important cellular processes such as gene transcription, signal transduction, and metabolism. In this study, we develop a novel computationally efficient method to identify feedback loops embedded in intracellular networks, which uses only time-series experimental data and requires no knowledge of the network structure. In the proposed approach, a non-parametric system identification technique, as well as a spectral factor analysis, is applied to derive a graphical criterion based on non-causal components of the system's impulse response. The appearance of non-causal components in the impulse response sequences arising from stochastic output perturbations is shown to imply the presence of underlying feedback connections within a linear network. In order to extend the approach to nonlinear networks, we linearize the intracellular networks about an equilibrium point, and then choose the magnitude of the output perturbations sufficiently small so that the resulting time-series responses remain close to the chosen equilibrium point. In this way, the impulse response sequences of the linearized system can be used to determine the presence or absence of feedback loops in the corresponding nonlinear network. The proposed method utilizes the time profile data from intracellular perturbation experiments and only requires the perturbability of output nodes. Most importantly, the method does not require any a priori knowledge of the system structure. For these reasons, the proposed approach is very well suited to identifying feedback loops in large-scale biomolecular networks. The effectiveness of the proposed method is illustrated via two examples: a synthetic network model with a negative feedback loop and a nonlinear caspase function model of apoptosis with a positive feedback loop.
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Affiliation(s)
- Chao-Yi Dong
- School of Electrical Engineering, Korea University, Seoul 136-713, Korea
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Shaikh TR, Barnard D, Meng X, Wagenknecht T. Implementation of a flash-photolysis system for time-resolved cryo-electron microscopy. J Struct Biol 2008; 165:184-9. [PMID: 19114106 DOI: 10.1016/j.jsb.2008.11.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 11/22/2008] [Accepted: 11/24/2008] [Indexed: 10/21/2022]
Abstract
We describe here the implementation of a flash-photolysis system for time-resolved cryo-electron microscopy. A previously designed computer-controlled cryo-plunging apparatus [White, H.D., Thirumurugan, K., Walker, M.L., Trinick, J., 2003. A second generation apparatus for time-resolved electron cryo-microscopy using stepper motors and electrospray. J. Struct. Biol. 144, 246-252] was used as a hardware platform, onto which a xenon flash lamp and liquid light pipe were mounted. The irradiation initiates a reaction through cleavage of the photolabile blocking group from a biologically active compound. The timespan between flashing and freezing in cryogen is on the order of milliseconds, and defines the fastest observable reaction. Blotting of excess fluid, which takes on the order of 1s, is done before irradiation and thus does not represent a rate-limiting step. A specimen-heating problem, identified by measurements with a thermocouple, was alleviated with the use of thick, aluminum-coated grids.
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Affiliation(s)
- Tanvir R Shaikh
- Resource for the Visualization of Biological Complexity, Wadsworth Center, New York State Department of Health, P.O. Box 509, Empire State Plaza, Albany, NY 12201-0509, USA.
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Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds. SENSORS 2008; 8:6595-6604. [PMID: 27873888 PMCID: PMC3707469 DOI: 10.3390/s8106595] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 10/16/2008] [Accepted: 10/21/2008] [Indexed: 11/16/2022]
Abstract
Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged.
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Shirokova N, Niggli E. Studies of RyR function in situ. Methods 2008; 46:183-93. [PMID: 18848990 DOI: 10.1016/j.ymeth.2008.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 09/12/2008] [Indexed: 10/21/2022] Open
Abstract
The ryanodine receptors (RyRs) are intracellular Ca2+ release channels of the sarcoplasmic reticulum (SR) involved in many cellular responses, including muscle excitation-contraction coupling. Multiple biochemical and biophysical methods are available to study RyR functions. However, most of them are somewhat limited because they can only be used to examine channels which are purified from the SR and no longer in their natural environment. In this review we discuss optical methods for studying RyR functions in situ. We describe several techniques for the investigation of local (microscopic) intracellular Ca2+ signals (a.k.a Ca2+ sparks) by means of confocal microscopy and flash photolysis of caged compounds. We discuss how these studies can and will continue to contribute to our understanding of RyR function in physiological and pathological conditions.
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Affiliation(s)
- Natalia Shirokova
- Department of Pharmacology & Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA.
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Thompson S, Stewart R, Smith JA, Self CH. Light activation of anti-CD3 in vivo reduces the growth of an aggressive ovarian carcinoma. ChemMedChem 2008; 2:1591-3. [PMID: 17979166 DOI: 10.1002/cmdc.200700116] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Stephen Thompson
- Diagnostic and Therapeutic Technologies, School of Clinical and Laboratory Sciences, University of Newcastle upon Tyne, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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Heckel A. Nucleobase-caged phosphoramidites for oligonucleotide synthesis. ACTA ACUST UNITED AC 2008; Chapter 1:Unit 1.17. [PMID: 18428965 DOI: 10.1002/0471142700.nc0117s29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Caged compounds are biologically active agents bearing a photolabile group in a strategic position, which makes them temporarily inactive. These compounds can then be delivered to a biological sample without immediately generating an effect. When the sample is then irradiated, e.g., with a laser in a (confocal) microscope, the activity of the substance is released with exact spatiotemporal and dose control. This unit deals with the synthesis of protected nucleoside phosphoramidites bearing a caging group on the nucleobase, which prevents the nucleobases from forming normal Watson-Crick base pairs. These amidites can be used to generate caged oligodeoxynucleotides with a transitory local perturbation that adds an element of spatiotemporal control to oligonucleotide-based applications.
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Fiber-coupled light-emitting diode for localized photostimulation of neurons expressing channelrhodopsin-2. J Neurosci Methods 2008; 169:27-33. [DOI: 10.1016/j.jneumeth.2007.11.012] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Revised: 10/25/2007] [Accepted: 11/20/2007] [Indexed: 11/17/2022]
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Mikat V, Heckel A. Light-dependent RNA interference with nucleobase-caged siRNAs. RNA (NEW YORK, N.Y.) 2007; 13:2341-2347. [PMID: 17951332 PMCID: PMC2080613 DOI: 10.1261/rna.753407] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 08/29/2007] [Indexed: 05/25/2023]
Abstract
Within the past years RNA interference (RNAi) has become one of the most valuable tools for post-transcriptional gene silencing. Making RNAi temporally and/or spatially controllable would even enlarge its scope of application. Attaching a light-removable protection group to siRNAs is a very promising approach to achieve this control over RNAi. It has been reported that modifying siRNA nucleobases surrounding the mRNA cleavage site between the 10th and 11th nucleotides successfully suppresses RNAi. We investigated the influence of photolabile protection groups at these and the adjacent nucleobases on siRNA activity and chose to incorporate caged deoxynucleotides instead of ribonucleotides. The siRNAs designed by these means were shown to be completely inactive. By irradiation with UV light (366 nm) they could be fully reactivated and showed the same activity as their unmodified siRNA counterparts.
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Affiliation(s)
- Vera Mikat
- University of Bonn, LIMES-Life and Medical Sciences, Kekulé-Institute, 53121 Bonn, Germany
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Optical suppression of seizure-like activity with an LED. Epilepsy Res 2007; 74:201-9. [PMID: 17448638 DOI: 10.1016/j.eplepsyres.2007.03.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Accepted: 03/18/2007] [Indexed: 11/30/2022]
Abstract
The therapy of focal epilepsy remains unsatisfactory for as many as 25% of patients. We tested the hypothesis that an efficient, ultraviolet light emitting diode (UV LED), coupled with a newly developed "caged" gamma-aminobutyric acid (GABA), might be capable of terminating "ictal-like" events in cultured murine neurons. GABA was released from BC204, a recently described caged GABA, using a small, ultraviolet (UV) LED. Ictal-like events were provoked by removal of extracellular magnesium. In preliminary control experiments, the concentration of GABA released from our caged compound was dependent upon the strength and duration of the illumination, and readily achieved micromolar (microM) levels that are known to activate tonic, extrasynaptic GABA(A) receptors. Ultraviolet illumination had no effect when BC204 was not present in the perfusate and the currents produced by BC204 were eliminated by picrotoxin. Within a few seconds of UV illumination, BC204 rapidly terminated ictal-like events at low microM concentration. Uncaging of BC204 also blocked the elevation of intracellular calcium induced by seizure-like discharges in our cultures. While much more technical development is clearly required to extend our observations to a more intact preparation, these results suggest the intriguing possibility of constructing an implantable device to "optically suppress" focal human seizures under closed loop control.
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Sobie EA, Kao JPY, Lederer WJ. Novel approach to real-time flash photolysis and confocal [Ca2+] imaging. Pflugers Arch 2007; 454:663-73. [PMID: 17323075 PMCID: PMC2794040 DOI: 10.1007/s00424-007-0229-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Accepted: 02/03/2007] [Indexed: 10/23/2022]
Abstract
Flash photolysis of "caged" compounds using ultraviolet light is a powerful experimental technique for producing rapid changes in concentrations of bioactive signaling molecules. Studies that employ this technique have used diverse strategies for controlling the spatial and temporal application of light to the specimen. In this paper, we describe a new system for flash photolysis that delivers light from a pulsed, adjustable intensity laser through an optical fiber coupled into the epifluorescence port of a commercial confocal microscope. Photolysis is achieved with extremely brief (5 ns) pulses of ultraviolet light (355 nm) that can be synchronized with respect to confocal laser scanning. The system described also localizes the UV intensity spatially so that uncaging only occurs in defined subcellular regions; moreover, because the microscope optics are used in localization, the photolysis volume can be easily adjusted. Experiments performed on rat ventricular myocytes loaded with the Ca(2+) indicator fluo-3 and the Ca(2+) cage o-nitrophenyl ethylene glycol bis(2-aminoethyl ether)-N,N,N'N'-tetraacetic acid (NP-EGTA) demonstrate the system's capabilities. Localized intracellular increases in [Ca(2+)] can trigger sarcoplasmic reticular Ca(2+) release events such as Ca(2+) sparks and, under certain conditions, regenerative Ca(2+) waves. This relatively simple and inexpensive system is, therefore, a useful tool for examining local signaling in the heart and other tissues.
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Affiliation(s)
- Eric A Sobie
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, One Gustave Levy Place, Box 1215, New York, NY 10029, USA.
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Bernardinelli Y, Azarias G, Chatton JY. In situ fluorescence imaging of glutamate-evoked mitochondrial Na+ responses in astrocytes. Glia 2006; 54:460-70. [PMID: 16886210 DOI: 10.1002/glia.20387] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Astrocytes can experience large intracellular Na+ changes following the activation of the Na+-coupled glutamate transport. The present study investigated whether cytosolic Na+ changes are transmitted to mitochondria, which could therefore influence their function and contribute to the overall intracellular Na+ regulation. Mitochondrial Na+ (Na+(mit)) changes were monitored using the Na+-sensitive fluorescent probe CoroNa Red (CR) in intact primary cortical astrocytes, as opposed to the classical isolated mitochondria preparation. The mitochondrial localization and Na+ sensitivity of the dye were first verified and indicated that it can be safely used as a selective Na+(mit) indicator. We found by simultaneously monitoring cytosolic and mitochondrial Na+ using sodium-binding benzofuran isophthalate and CR, respectively, that glutamate-evoked cytosolic Na+ elevations are transmitted to mitochondria. The resting Na+(mit) concentration was estimated at 19.0 +/- 0.8 mM, reaching 30.1 +/- 1.2 mM during 200 microM glutamate application. Blockers of conductances potentially mediating Na+ entry (calcium uniporter, monovalent cation conductances, K+(ATP) channels) were not able to prevent the Na+(mit) response to glutamate. However, Ca2+ and its exchange with Na+ appear to play an important role in mediating mitochondrial Na+ entry as chelating intracellular Ca2+ with BAPTA or inhibiting Na+/Ca2+ exchanger with CGP-37157 diminished the Na+(mit) response. Moreover, intracellular Ca2+ increase achieved by photoactivation of caged Ca2+ also induced a Na+(mit) elevation. Inhibition of mitochondrial Na/H antiporter using ethylisopropyl-amiloride caused a steady increase in Na+(mit) without increasing cytosolic Na+, indicating that Na+ extrusion from mitochondria is mediated by these exchangers. Thus, mitochondria in intact astrocytes are equipped to efficiently sense cellular Na+ signals and to dynamically regulate their Na+ content.
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Nishigaki T, Wood CD, Shiba K, Baba SA, Darszon A. Stroboscopic illumination using light-emitting diodes reduces phototoxicity in fluorescence cell imaging. Biotechniques 2006; 41:191-7. [PMID: 16925021 DOI: 10.2144/000112220] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Excited fluorophores produce reactive oxygen species that are toxic toward many live cells (phototoxicity) and accelerate bleaching of the fluorophores during the course of extended or repeated measurements (photobleaching). We recently developed an illumination system for fluorescence microscopy using a high power light-emitting diode (LED), which can emit short pulses of light (0.5–2 ms) to excite fluorophores. This system minimizes illumination time, thus reducing phototoxicity and photobleaching artifacts. To demonstrate the usefulness of the new system, we compared images of human sperm loaded with various fluorescent indicators and excited with either a conventional mercury lamp as a continuous excitation light source or the LED as a source of pulsed illumination. We found that sperm motility decreased rapidly and photobleaching was relatively rapid under continuous illumination, whereas under pulsed LED illumination, motility was maintained and photobleaching was much reduced. Therefore, fluorescence microscopy using LED-based pulsed illumination offers significant advantages for long-term live cell imaging, reducing the degree of phototoxicity, and extending the effective lifetime of fluorophores.
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