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GluN3A excitatory glycine receptors control adult cortical and amygdalar circuits. Neuron 2022; 110:2438-2454.e8. [PMID: 35700736 PMCID: PMC9365314 DOI: 10.1016/j.neuron.2022.05.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 04/05/2022] [Accepted: 05/13/2022] [Indexed: 12/20/2022]
Abstract
GluN3A is an atypical glycine-binding subunit of NMDA receptors (NMDARs) whose actions in the brain are mostly unknown. Here, we show that the expression of GluN3A subunits controls the excitability of mouse adult cortical and amygdalar circuits via an unusual signaling mechanism involving the formation of excitatory glycine GluN1/GluN3A receptors (eGlyRs) and their tonic activation by extracellular glycine. eGlyRs are mostly extrasynaptic and reside in specific neuronal populations, including the principal cells of the basolateral amygdala (BLA) and SST-positive interneurons (SST-INs) of the neocortex. In the BLA, tonic eGlyR currents are sensitive to fear-conditioning protocols, are subject to neuromodulation by the dopaminergic system, and control the stability of fear memories. In the neocortex, eGlyRs control the in vivo spiking of SST-INs and the behavior-dependent modulation of cortical activity. GluN3A-containing eGlyRs thus represent a novel and widespread signaling modality in the adult brain, with attributes that strikingly depart from those of conventional NMDARs. In mice, GluN3A is expressed by SST-INs in the cortex and pyramidal neurons in the BLA GluN3A assembles as excitatory glycine GluN1/GluN3A receptors (eGlyRs) eGlyRs detect extracellular glycine levels and generate tonic excitatory currents eGlyRs tune the function of SST-INs in cortex and alter the formation of fear memories in BLA
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2
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Abstract
Glutamate is the major excitatory neurotransmitter in the brain, and photochemical release of glutamate (or uncaging) is a chemical technique widely used by biologists to interrogate its physiology. A basic prerequisite of these optical probes is bio-inertness before photolysis. However, all caged glutamates are known to have strong antagonism toward receptors of γ-aminobutyric acid, the major inhibitory transmitter. We have developed a caged glutamate probe that is inert toward these receptors at concentrations that are effective for photolysis with violet light. Pharmacological tests in vitro revealed that attachment of a fifth-generation (G5) dendrimer (i.e., cloaking) to the widely used 4-methoxy-7-nitro-indolinyl(MNI)-Glu probe prevented such off-target effects while not changing the photochemical properties of MNI-Glu significantly. G5-MNI-Glu was used with optofluidic delivery to stimulate dopamine neurons of the ventral tegmental area of freely moving mice in a conditioned place-preference protocol so as to mediate Pavlovian conditioning.
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Richers MT, Passlick S, Agarwal H, Ellis‐Davies GCR. Dendrimer Conjugation Enables Multiphoton Chemical Neurophysiology Studies with an Extended π‐Electron Caging Chromophore. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201906067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Matthew T. Richers
- Department of NeuroscienceMount Sinai School of Medicine New York NY 10029 USA
| | - Stefan Passlick
- Department of NeuroscienceMount Sinai School of Medicine New York NY 10029 USA
| | - Hitesh Agarwal
- Department of NeuroscienceMount Sinai School of Medicine New York NY 10029 USA
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4
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Richers MT, Passlick S, Agarwal H, Ellis-Davies GCR. Dendrimer Conjugation Enables Multiphoton Chemical Neurophysiology Studies with an Extended π-Electron Caging Chromophore. Angew Chem Int Ed Engl 2019; 58:12086-12090. [PMID: 31216109 PMCID: PMC6707848 DOI: 10.1002/anie.201906067] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Indexed: 12/19/2022]
Abstract
We have developed a caged neurotransmitter using an extended π-electron chromophore for efficient multiphoton uncaging on living neurons. Widely studied in a chemical context, such chromophores are inherently bioincompatible due to their highly lipophilic character. Attachment of two polycarboxylate dendrimers, a method we call "cloaking", to a bisstyrylthiophene (or BIST) core effectively transformed the chromophore into a water-soluble optical probe, whilst maintaining the high two-photon absorption of over 500 GM. Importantly, the cloaked caged compound was biologically inert at the high concentrations required for multiphoton chemical physiology. Thus, in contrast to non-cloaked BIST compounds, the BIST-caged neurotransmitter can be safely delivered onto neurons in acutely isolated brain slices, thereby enabling high-resolution two-photon uncaging without any side effects. We expect that our cloaking method will enable the development of new classes of cell-compatible photolabile probes using a wide variety of extended π-electron caging chromophores.
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Affiliation(s)
- Matthew T Richers
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY, 10029, USA
| | - Stefan Passlick
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY, 10029, USA
| | - Hitesh Agarwal
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY, 10029, USA
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5
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Guruge C, Rfaish SY, Byrd C, Yang S, Starrett AK, Guisbert E, Nesnas N. Caged Proline in Photoinitiated Organocatalysis. J Org Chem 2019; 84:5236-5244. [PMID: 30908906 DOI: 10.1021/acs.joc.9b00220] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Organocatalysis is an emerging field, in which small metal-free organic structures catalyze a diversity of reactions with a remarkable stereoselectivity. The ability to selectively switch on such pathways upon demand has proven to be a valuable tool in biological systems. Light as a trigger provides the ultimate spatial and temporal control of activation. However, there have been limited examples of phototriggered catalytic systems. Herein, we describe the synthesis and application of a caged proline system that can initiate organocatalysis upon irradiation. The caged proline was generated using the highly efficient 4-carboxy-5,7-dinitroindolinyl (CDNI) photocleavable protecting group in a four-step synthesis. Advantages of this system include water solubility, biocompatibility, high quantum yield for catalyst release, and responsiveness to two-photon excitation. We showed the light-triggered catalysis of a crossed aldol reaction, a Mannich reaction, and a self-aldol condensation reaction. We also demonstrated light-initiated catalysis, leading to the formation of a biocide in situ, which resulted in the growth inhibition of E. coli, with as little as 3 min of irradiation. This technique can be broadly applied to other systems, by which the formation of active forms of drugs can be catalytically assembled remotely via two-photon irradiation.
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Affiliation(s)
- Charitha Guruge
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Saad Y Rfaish
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Chanel Byrd
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Shukun Yang
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Anthony K Starrett
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Eric Guisbert
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
| | - Nasri Nesnas
- Department of Biomedical and Chemical Engineering and Sciences , Florida Institute of Technology , Melbourne , Florida 32901 , United States
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Ellis-Davies GCR. Two-Photon Uncaging of Glutamate. Front Synaptic Neurosci 2019; 10:48. [PMID: 30687075 PMCID: PMC6333857 DOI: 10.3389/fnsyn.2018.00048] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 12/11/2018] [Indexed: 01/26/2023] Open
Abstract
Two-photon microscopy produces the excited singlet state of a chromophore with wavelengths approximately double that used for normal excitation. Two photons are absorbed almost simultaneously, via a virtual state, and this makes the excitation technique inherently non-linear. It requires ultra-fast lasers to deliver the high flux density needed to access intrinsically very short lived intermediates, and in combination with lenses of high numerical aperture, this confines axial excitation highly. Since the two-photon excitation volume is similar to a large spine head, the technique has been widely used to study glutamatergic transmission in brain slices. Here I describe the principles of two-photon uncaging of glutamate and provide a practical guide to its application.
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Guruge C, Ouedraogo YP, Comitz RL, Ma J, Losonczy A, Nesnas N. Improved Synthesis of Caged Glutamate and Caging Each Functional Group. ACS Chem Neurosci 2018; 9:2713-2721. [PMID: 29750497 DOI: 10.1021/acschemneuro.8b00152] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Glutamate is an excitatory neurotransmitter that controls numerous pathways in the brain. Neuroscientists make use of photoremovable protecting groups, also known as cages, to release glutamate with precise spatial and temporal control. Various cage designs have been developed and among the most effective has been the nitroindolinyl caging of glutamate. We, hereby, report an improved synthesis of one of the current leading molecules of caged glutamate, 4-carboxymethoxy-5,7-dinitroindolinyl glutamate (CDNI-Glu), which possesses efficiencies with the highest reported quantum yield of at least 0.5. We present the shortest route, to date, for the synthesis of CDNI-Glu in 4 steps, with a total reaction time of 40 h and an overall yield of 20%. We also caged glutamate at the other two functional groups, thereby, introducing two new cage designs: α-CDNI-Glu and N-CDNI-Glu. We included a study of their photocleavage properties using UV-vis, NMR, as well as a physiology experiment of a two-photon uncaging of CDNI-Glu in acute hippocampal brain slices. The newly introduced cage designs may have the potential to minimize the interference that CDNI-Glu has with the GABAA receptor. We are broadly disseminating this to enable neuroscientists to use these photoactivatable tools.
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Affiliation(s)
- Charitha Guruge
- Department of Chemistry, Florida Institute of Technology, Melbourne, Florida 32901, United States
| | - Yannick P. Ouedraogo
- Department of Chemistry, Florida Institute of Technology, Melbourne, Florida 32901, United States
| | - Richard L. Comitz
- Department of Chemistry, Florida Institute of Technology, Melbourne, Florida 32901, United States
| | - Jingxuan Ma
- Department of Chemistry, Florida Institute of Technology, Melbourne, Florida 32901, United States
| | - Attila Losonczy
- Department of Neuroscience, Columbia University, New York, New York 10032, United States
| | - Nasri Nesnas
- Department of Chemistry, Florida Institute of Technology, Melbourne, Florida 32901, United States
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State-dependent diffusion of actin-depolymerizing factor/cofilin underlies the enlargement and shrinkage of dendritic spines. Sci Rep 2016; 6:32897. [PMID: 27595610 PMCID: PMC5011767 DOI: 10.1038/srep32897] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/17/2016] [Indexed: 12/13/2022] Open
Abstract
Dendritic spines are the postsynaptic sites of most excitatory synapses in the brain, and spine enlargement and shrinkage give rise to long-term potentiation and depression of synapses, respectively. Because spine structural plasticity is accompanied by remodeling of actin scaffolds, we hypothesized that the filamentous actin regulatory protein cofilin plays a crucial role in this process. Here we investigated the diffusional properties of cofilin, the actin-severing and depolymerizing actions of which are activated by dephosphorylation. Cofilin diffusion was measured using fluorescently labeled cofilin fusion proteins and two-photon imaging. We show that cofilins are highly diffusible along dendrites in the resting state. However, during spine enlargement, wild-type cofilin and a phosphomimetic cofilin mutant remain confined to the stimulated spine, whereas a nonphosphorylatable mutant does not. Moreover, inhibition of cofilin phosphorylation with a competitive peptide disables spine enlargement, suggesting that phosphorylated-cofilin accumulation is a key regulator of enlargement, which is localized to individual spines. Conversely, spine shrinkage spreads to neighboring spines, even though triggered by weaker stimuli than enlargement. Diffusion of exogenous cofilin injected into a pyramidal neuron soma causes spine shrinkage and reduced PSD95 in spines, suggesting that diffusion of dephosphorylated endogenous cofilin underlies the spreading of spine shrinkage and long-term depression.
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Begemann I, Galic M. Correlative Light Electron Microscopy: Connecting Synaptic Structure and Function. Front Synaptic Neurosci 2016; 8:28. [PMID: 27601992 PMCID: PMC4993758 DOI: 10.3389/fnsyn.2016.00028] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 08/12/2016] [Indexed: 11/20/2022] Open
Abstract
Many core paradigms of contemporary neuroscience are based on information obtained by electron or light microscopy. Intriguingly, these two imaging techniques are often viewed as complementary, yet separate entities. Recent technological advancements in microscopy techniques, labeling tools, and fixation or preparation procedures have fueled the development of a series of hybrid approaches that allow correlating functional fluorescence microscopy data and ultrastructural information from electron micrographs from a singular biological event. As correlative light electron microscopy (CLEM) approaches become increasingly accessible, long-standing neurobiological questions regarding structure-function relation are being revisited. In this review, we will survey what developments in electron and light microscopy have spurred the advent of correlative approaches, highlight the most relevant CLEM techniques that are currently available, and discuss its potential and limitations with respect to neuronal and synapse-specific applications.
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Affiliation(s)
- Isabell Begemann
- DFG Cluster of Excellence 'Cells in Motion', (EXC 1003), University of Muenster, MuensterGermany; Institute of Medical Physics and Biophysics, University Hospital Münster, University of Muenster, MuensterGermany
| | - Milos Galic
- DFG Cluster of Excellence 'Cells in Motion', (EXC 1003), University of Muenster, MuensterGermany; Institute of Medical Physics and Biophysics, University Hospital Münster, University of Muenster, MuensterGermany
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10
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Kantevari S, Passlick S, Kwon HB, Richers MT, Sabatini BL, Ellis-Davies GC. Development of Anionically Decorated Caged Neurotransmitters: In Vitro Comparison of 7-Nitroindolinyl- and 2-(p-Phenyl-o-nitrophenyl)propyl-Based Photochemical Probes. Chembiochem 2016; 17:953-61. [PMID: 26929152 PMCID: PMC4870097 DOI: 10.1002/cbic.201600019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Indexed: 01/26/2023]
Abstract
Neurotransmitter uncaging, especially that of glutamate, has been used to study synaptic function for over 30 years. One limitation of caged glutamate probes is the blockade of γ-aminobutyric acid (GABA)-A receptor function. This problem comes to the fore when the probes are applied at the high concentrations required for effective two-photon photolysis. To mitigate such problems one could improve the photochemical properties of caging chromophores and/or remove receptor blockade. We show that addition of a dicarboxylate unit to the widely used 4-methoxy-7-nitroindolinyl-Glu (MNI-Glu) system reduced the off-target effects by about 50-70 %. When the same strategy was applied to an electron-rich 2-(p-Phenyl-o-nitrophenyl)propyl (PNPP) caging group, the pharmacological improvements were not as significant as in the MNI case. Finally, we used very extensive biological testing of the PNPP-caged Glu (more than 250 uncaging currents at single dendritic spines) to show that nitro-biphenyl caging chromophores have two-photon uncaging efficacies similar to that of MNI-Glu.
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Affiliation(s)
- Srinivas Kantevari
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Stefan Passlick
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Hyung-Bae Kwon
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Cambridge, MA 02115, USA
| | - Matthew T. Richers
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Bernardo L. Sabatini
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Cambridge, MA 02115, USA
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11
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Nadler A, Yushchenko DA, Müller R, Stein F, Feng S, Mulle C, Carta M, Schultz C. Exclusive photorelease of signalling lipids at the plasma membrane. Nat Commun 2015; 6:10056. [PMID: 26686736 PMCID: PMC4703838 DOI: 10.1038/ncomms10056] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 10/28/2015] [Indexed: 12/17/2022] Open
Abstract
Photoactivation of caged biomolecules has become a powerful approach to study cellular signalling events. Here we report a method for anchoring and uncaging biomolecules exclusively at the outer leaflet of the plasma membrane by employing a photocleavable, sulfonated coumarin derivative. The novel caging group allows quantifying the reaction progress and efficiency of uncaging reactions in a live-cell microscopy setup, thereby greatly improving the control of uncaging experiments. We synthesized arachidonic acid derivatives bearing the new negatively charged or a neutral, membrane-permeant coumarin caging group to locally induce signalling either at the plasma membrane or on internal membranes in β-cells and brain slices derived from C57B1/6 mice. Uncaging at the plasma membrane triggers a strong enhancement of calcium oscillations in β-cells and a pronounced potentiation of synaptic transmission while uncaging inside cells blocks calcium oscillations in β-cells and causes a more transient effect on neuronal transmission, respectively. The precise subcellular site of arachidonic acid release is therefore crucial for signalling outcome in two independent systems. Caged signalling intermediates are powerful cell biological tools, however it can be challenging to precisely control where activation occurs. Nadler et al. develop a caging group that specifically targets the plasma membrane, and demonstrate spatially controlled activation of arachidonic acid signalling.
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Affiliation(s)
- André Nadler
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany.,Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Dmytro A Yushchenko
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany.,Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 16610 Prague 6, Czech Republic
| | - Rainer Müller
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Frank Stein
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Suihan Feng
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany
| | - Christophe Mulle
- Institut Interdisciplinaire de Neurosciences, CNRS UMR 5297 Université Bordeaux 2, 146, rue Léo-Saignat, 33077 Bordeaux, France
| | - Mario Carta
- Institut Interdisciplinaire de Neurosciences, CNRS UMR 5297 Université Bordeaux 2, 146, rue Léo-Saignat, 33077 Bordeaux, France
| | - Carsten Schultz
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Meyerhofstraße 1, 69117 Heidelberg, Germany
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12
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Bao C, Zhu L, Lin Q, Tian H. Building biomedical materials using photochemical bond cleavage. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:1647-62. [PMID: 25655424 DOI: 10.1002/adma.201403783] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 12/02/2014] [Indexed: 05/06/2023]
Abstract
Light can be used as an external trigger to precisely determine where and when a process is initiated as well as how much of the process is being consumed. Phototriggers are a type of photoresponsive functional group that undergo an irreversible photolysis reaction by selectively breaking a chemical bond, enabling three fundamental functions: the photoactivation of fluorescent and bioactive molecules; the photocleavable degradation of macromolecular materials; and the photorelease of drugs, active groups, or surface charges from carriers and interfaces. With the expanded applications of light-controlled technology, particularly in living systems, new challenges and improvements of phototriggers are required to fulfill the demands for better sensitivity, faster kinetics, and more-demanding biomedical applications. Here, improvements to several conventional phototriggers are highlighted, and their notable, representative biomedical applications and their challenges are discussed.
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Affiliation(s)
- Chunyan Bao
- Key Laboratory for Advanced Materials, Institute of Fine Chemicals, East China University of Science and Technology, 130# Meilong Road, Shanghai, 200237, China
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Amatrudo JM, Olson JP, Agarwal HK, Ellis-Davies GCR. Caged compounds for multichromic optical interrogation of neural systems. Eur J Neurosci 2014; 41:5-16. [PMID: 25471355 DOI: 10.1111/ejn.12785] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/06/2014] [Accepted: 10/13/2014] [Indexed: 01/16/2023]
Abstract
Caged compounds are widely used by neurophysiologists to study many aspects of cellular signaling in glia and neurons. Biologically inert before irradiation, they can be loaded into cells via patch pipette or topically applied in situ to a defined concentration; photolysis releases the caged compound in a very rapid and spatially defined way. As caged compounds are exogenous optical probes, they include not only natural products such neurotransmitters, calcium and IP3 but non-natural products such as fluorophores, drugs and antibodies. In this Technical Spotlight we provide a short introduction to the uncaging technique by discussing the nitroaromatic caging chromophores most widely used in such experiments [e.g. α-carboxy-ortho-nitrobenyl (CNB), dimethoxynitrobenzyl (DMNB), 4-methoxy-7-nitroindolinyl (MNI) and 4-carboxymethoxy-7-nitroindolinyl (CDNI)]. We show that recently developed caging chromophores [rutheniumbipyridial (RuBi) and 7-diethylaminocoumarin (DEAC)450] that are photolyzed with blue light (~ 430-480 nm range) can be combined with traditional nitroaromatic caged compounds to enable two-color optical probing of neuronal function. For example, one-photon uncaging of either RuBi-GABA or DEAC450-GABA with a 473-nm laser is facile, and can block nonlinear currents (dendritic spikes or action potentials) evoked by two-photon uncaging of CDNI-Glu at 720 nm. We also show that two-photon uncaging of DEAC450-Glu and CDNI-GABA at 900 and 720 nm, respectively, can be used to fire and block action potentials. Our experiments illustrate that recently developed chromophores have taken uncaging out of the 'monochrome era', in which it has existed since 1978, so as to enable multichromic interrogation of neuronal function with single-synapse precision.
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Affiliation(s)
- Joseph M Amatrudo
- Department of Neuroscience, Mount Sinai School of Medicine, New York, NY, 10029, USA
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14
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GABA promotes the competitive selection of dendritic spines by controlling local Ca2+ signaling. Nat Neurosci 2013; 16:1409-16. [PMID: 23974706 DOI: 10.1038/nn.3496] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 07/11/2013] [Indexed: 02/07/2023]
Abstract
Activity-dependent competition of synapses plays a key role in neural organization and is often promoted by GABA; however, its cellular bases are poorly understood. Excitatory synapses of cortical pyramidal neurons are formed on small protrusions known as dendritic spines, which exhibit structural plasticity. We used two-color uncaging of glutamate and GABA in rat hippocampal CA1 pyramidal neurons and found that spine shrinkage and elimination were markedly promoted by the activation of GABAA receptors shortly before action potentials. GABAergic inhibition suppressed bulk increases in cytosolic Ca(2+) concentrations, whereas it preserved the Ca(2+) nanodomains generated by NMDA-type receptors, both of which were necessary for spine shrinkage. Unlike spine enlargement, spine shrinkage spread to neighboring spines (<15 μm) and competed with their enlargement, and this process involved the actin-depolymerizing factor ADF/cofilin. Thus, GABAergic inhibition directly suppresses local dendritic Ca(2+) transients and strongly promotes the competitive selection of dendritic spines.
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Brieke C, Rohrbach F, Gottschalk A, Mayer G, Heckel A. Light-controlled tools. Angew Chem Int Ed Engl 2012; 51:8446-76. [PMID: 22829531 DOI: 10.1002/anie.201202134] [Citation(s) in RCA: 734] [Impact Index Per Article: 61.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Indexed: 12/21/2022]
Abstract
Spatial and temporal control over chemical and biological processes plays a key role in life, where the whole is often much more than the sum of its parts. Quite trivially, the molecules of a cell do not form a living system if they are only arranged in a random fashion. If we want to understand these relationships and especially the problems arising from malfunction, tools are necessary that allow us to design sophisticated experiments that address these questions. Highly valuable in this respect are external triggers that enable us to precisely determine where, when, and to what extent a process is started or stopped. Light is an ideal external trigger: It is highly selective and if applied correctly also harmless. It can be generated and manipulated with well-established techniques, and many ways exist to apply light to living systems--from cells to higher organisms. This Review will focus on developments over the last six years and includes discussions on the underlying technologies as well as their applications.
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Affiliation(s)
- Clara Brieke
- Goethe University Frankfurt, Institute for Organic Chemistry and Chemical Biology Buchmann Institute for Molecular Life Sciences, Max-von-Laue-Strasse 9, 60438 Frankfurt/Main, Germany
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Brieke C, Rohrbach F, Gottschalk A, Mayer G, Heckel A. Lichtgesteuerte Werkzeuge. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201202134] [Citation(s) in RCA: 225] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Clara Brieke
- Goethe‐Universität Frankfurt, Institut für Organische Chemie und Chemische Biologie, Buchmann‐Institut für Molekulare Lebenswissenschaften, Max‐von‐Laue‐Straße 9, 60438 Frankfurt/Main (Deutschland)
| | - Falk Rohrbach
- Universität Bonn, LIMES‐Institut, Gerhard‐Domagk‐Straße 1, 53121 Bonn (Deutschland)
| | - Alexander Gottschalk
- Buchmann‐Institut für Molekulare Lebenswissenschaften, Institut für Biochemie, Max‐von‐Laue‐Straße 15, 60438 Frankfurt/Main (Deutschland)
| | - Günter Mayer
- Universität Bonn, LIMES‐Institut, Gerhard‐Domagk‐Straße 1, 53121 Bonn (Deutschland)
| | - Alexander Heckel
- Goethe‐Universität Frankfurt, Institut für Organische Chemie und Chemische Biologie, Buchmann‐Institut für Molekulare Lebenswissenschaften, Max‐von‐Laue‐Straße 9, 60438 Frankfurt/Main (Deutschland)
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17
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Kantevari S, Gordon GRJ, MacVicar BA, Ellis-Davies GCR. A practical guide to the synthesis and use of membrane-permeant acetoxymethyl esters of caged inositol polyphosphates. Nat Protoc 2011; 6:327-37. [PMID: 21372813 DOI: 10.1038/nprot.2010.194] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This protocol describes a method for efficient chemical synthesis of an analog of inositol-1,4,5-trisphosphate (IP(3)) hexakis acetoxymethyl ester having an ortho-nitroveratryl photochemical caging group on the 6-hydroxyl position. The six esters render the probe membrane permeant, such that it can be loaded into intact living cells in vitro or in vivo. Inside cells, the caged IP(3) is inert until activated by two-photon excitation at 720 nm. The photoliberated signaling molecule can mobilize release of Ca(2+) from intracellular stores on the endoplasmic reticulum. When co-loaded with the fluorescent Ca(2+) indicator rhod-2, one laser can be used for stimulating and monitoring intracellular Ca(2+) signaling with single-cell resolution. This protocol has chemistry and biology sections; the former describes the organic synthesis of the caged IP(3), which requires 12 d, and the latter an application to a day-long study of astrocyte-regulated neuronal function in living brain slices acutely isolated from rats. As Ca(2+) is the single most important intracellular second messenger and the IP(3)-Ca(2+) signaling cascade is used by many cells to produce increases in Ca(2+) concentration, this method should be widely applicable for the study of a variety of physiological processes in intact biological systems.
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Affiliation(s)
- Srinivas Kantevari
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, USA
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