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Lubejko ST, Livrizzi G, Buczynski SA, Patel J, Yung JC, Yaksh TL, Banghart MR. Inputs to the locus coeruleus from the periaqueductal gray and rostroventral medulla shape opioid-mediated descending pain modulation. Sci Adv 2024; 10:eadj9581. [PMID: 38669335 PMCID: PMC11051679 DOI: 10.1126/sciadv.adj9581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 03/26/2024] [Indexed: 04/28/2024]
Abstract
The supraspinal descending pain modulatory system (DPMS) shapes pain perception via monoaminergic modulation of sensory information in the spinal cord. However, the role and synaptic mechanisms of descending noradrenergic signaling remain unclear. Here, we establish that noradrenergic neurons of the locus coeruleus (LC) are essential for supraspinal opioid antinociception. While much previous work has emphasized the role of descending serotonergic pathways, we find that opioid antinociception is primarily driven by excitatory output from the ventrolateral periaqueductal gray (vlPAG) to the LC. Furthermore, we identify a previously unknown opioid-sensitive inhibitory input from the rostroventromedial medulla (RVM), the suppression of which disinhibits LC neurons to drive spinal noradrenergic antinociception. We describe pain-related activity throughout this circuit and report the presence of prominent bifurcating outputs from the vlPAG to the LC and the RVM. Our findings substantially revise current models of the DPMS and establish a supraspinal antinociceptive pathway that may contribute to multiple forms of descending pain modulation.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Biological Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stanley A. Buczynski
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Chemistry and Biochemistry Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Janki Patel
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jean C. Yung
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Tony L. Yaksh
- Departments of Anesthesiology and Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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2
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McClain SP, Ma X, Johnson DA, Johnson CA, Layden AE, Yung JC, Lubejko ST, Livrizzi G, He XJ, Zhou J, Chang-Weinberg J, Ventriglia E, Rizzo A, Levinstein M, Gomez JL, Bonaventura J, Michaelides M, Banghart MR. In vivo photopharmacology with light-activated opioid drugs. Neuron 2023; 111:3926-3940.e10. [PMID: 37848025 DOI: 10.1016/j.neuron.2023.09.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 08/02/2023] [Accepted: 09/14/2023] [Indexed: 10/19/2023]
Abstract
Traditional methods for site-specific drug delivery in the brain are slow, invasive, and difficult to interface with recordings of neural activity. Here, we demonstrate the feasibility and experimental advantages of in vivo photopharmacology using "caged" opioid drugs that are activated in the brain with light after systemic administration in an inactive form. To enable bidirectional manipulations of endogenous opioid receptors in vivo, we developed photoactivatable oxymorphone (PhOX) and photoactivatable naloxone (PhNX), photoactivatable variants of the mu opioid receptor agonist oxymorphone and the antagonist naloxone. Photoactivation of PhOX in multiple brain areas produced local changes in receptor occupancy, brain metabolic activity, neuronal calcium activity, neurochemical signaling, and multiple pain- and reward-related behaviors. Combining PhOX photoactivation with optical recording of extracellular dopamine revealed adaptations in the opioid sensitivity of mesolimbic dopamine circuitry in response to chronic morphine administration. This work establishes a general experimental framework for using in vivo photopharmacology to study the neural basis of drug action.
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Affiliation(s)
- Shannan P McClain
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Xiang Ma
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Desiree A Johnson
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Caroline A Johnson
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Aryanna E Layden
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Jean C Yung
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Susan T Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Biological Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - X Jenny He
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA; Biological Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Jingjing Zhou
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Janie Chang-Weinberg
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Emilya Ventriglia
- Biobehavioral Imaging and Molecular, Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD 21224, USA
| | - Arianna Rizzo
- Departament de Patologia i Terapèutica Experimental, Institut de Neurociències, Universitat de Barcelona, L'Hospitalet de Llobregat 08907, Catalonia, Spain; Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, IDIBELL, L'Hospitalet de Llobregat 08907, Catalonia, Spain
| | - Marjorie Levinstein
- Biobehavioral Imaging and Molecular, Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD 21224, USA
| | - Juan L Gomez
- Biobehavioral Imaging and Molecular, Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD 21224, USA
| | - Jordi Bonaventura
- Departament de Patologia i Terapèutica Experimental, Institut de Neurociències, Universitat de Barcelona, L'Hospitalet de Llobregat 08907, Catalonia, Spain; Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, IDIBELL, L'Hospitalet de Llobregat 08907, Catalonia, Spain
| | - Michael Michaelides
- Biobehavioral Imaging and Molecular, Neuropsychopharmacology Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD 21224, USA
| | - Matthew R Banghart
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA.
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3
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Welsch L, Colantonio E, Frison M, Johnson DA, McClain SP, Mathis V, Banghart MR, Ben Hamida S, Darcq E, Kieffer BL. Mu Opioid Receptor-Expressing Neurons in the Dorsal Raphe Nucleus Are Involved in Reward Processing and Affective Behaviors. Biol Psychiatry 2023; 94:842-851. [PMID: 37285896 PMCID: PMC10850692 DOI: 10.1016/j.biopsych.2023.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 05/12/2023] [Accepted: 05/24/2023] [Indexed: 06/09/2023]
Abstract
BACKGROUND Mu opioid receptors (MORs) are key for reward processing, mostly studied in dopaminergic pathways. MORs are also expressed in the dorsal raphe nucleus (DRN), which is central for the modulation of reward and mood, but MOR function in the DRN remains underexplored. Here, we investigated whether MOR-expressing neurons of the DRN (DRN-MOR neurons) participate in reward and emotional responses. METHODS We characterized DRN-MOR neurons anatomically using immunohistochemistry and functionally using fiber photometry in responses to morphine and rewarding/aversive stimuli. We tested the effect of opioid uncaging on the DRN on place conditioning. We examined the effect of DRN-MOR neuron optostimulation on positive reinforcement and mood-related behaviors. We mapped their projections and selected DRN-MOR neurons projecting to the lateral hypothalamus for a similar optogenetic experimentation. RESULTS DRN-MOR neurons form a heterogeneous neuronal population essentially composed of GABAergic (gamma-aminobutyric acidergic) and glutamatergic neurons. Calcium activity of DRN-MOR neurons was inhibited by rewarding stimuli and morphine. Local photo-uncaging of oxymorphone in the DRN produced conditioned place preference. DRN-MOR neuron optostimulation triggered real-time place preference and was self-administered, promoted social preference, and reduced anxiety and passive coping. Finally, specific optostimulation of DRN-MOR neurons projecting to the lateral hypothalamus recapitulated the reinforcing effects of total DRN-MOR neuron stimulation. CONCLUSIONS Our data show that DRN-MOR neurons respond to rewarding stimuli and that their optoactivation has reinforcing effects and promotes positive emotional responses, an activity which is partially mediated by their projections to the lateral hypothalamus. Our study also suggests a complex regulation of DRN activity by MOR opioids, involving mixed inhibition/activation mechanisms that fine-tune DRN function.
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Affiliation(s)
- Lola Welsch
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Esther Colantonio
- INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Mathilde Frison
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada
| | - Desiree A Johnson
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Shannan P McClain
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Victor Mathis
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, UPR 3212, Strasbourg, France
| | - Matthew R Banghart
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Sami Ben Hamida
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM UMR 1247, Université de Picardie Jules Verne, Amiens, France
| | - Emmanuel Darcq
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Brigitte L Kieffer
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France.
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4
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Lubejko ST, Livrizzi G, Patel J, Yung JC, Yaksh TL, Banghart MR. Inputs to the locus coeruleus from the periaqueductal gray and rostroventral medulla shape opioid-mediated descending pain modulation. bioRxiv 2023:2023.10.10.561768. [PMID: 37873091 PMCID: PMC10592708 DOI: 10.1101/2023.10.10.561768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The supraspinal descending pain modulatory system (DPMS) shapes pain perception via monoaminergic modulation of sensory information in the spinal cord. However, the role and synaptic mechanisms of descending noradrenergic signaling remain unclear. Here, we establish that noradrenergic neurons of the locus coeruleus (LC) are essential for supraspinal opioid antinociception. Unexpectedly, given prior emphasis on descending serotonergic pathways, we find that opioid antinociception is primarily driven by excitatory output from the ventrolateral periaqueductal gray (vlPAG) to the LC. Furthermore, we identify a previously unknown opioid-sensitive inhibitory input from the rostroventromedial medulla (RVM), the suppression of which disinhibits LC neurons to drive spinal noradrenergic antinociception. We also report the presence of prominent bifurcating outputs from the vlPAG to the LC and the RVM. Our findings significantly revise current models of the DPMS and establish a novel supraspinal antinociceptive pathway that may contribute to multiple forms of descending pain modulation.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
- Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
- Biological Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Janki Patel
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Jean C. Yung
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Tony L. Yaksh
- Departments of Anesthesiology and Pharmacology, University of California San Diego, La Jolla, CA, 92093, USA
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
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5
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Layden A, Ma X, Johnson CA, He XJ, Buczynski SA, Banghart MR. A Biomimetic C-Terminal Extension Strategy for Photocaging Amidated Neuropeptides. J Am Chem Soc 2023; 145:19611-19621. [PMID: 37649440 PMCID: PMC10510324 DOI: 10.1021/jacs.3c03913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Indexed: 09/01/2023]
Abstract
Photoactivatable neuropeptides offer a robust stimulus-response relationship that can drive mechanistic studies into the physiological mechanisms of neuropeptidergic transmission. The majority of neuropeptides contain a C-terminal amide, which offers a potentially general site for installation of a C-terminal caging group. Here, we report a biomimetic caging strategy in which the neuropeptide C-terminus is extended via a photocleavable amino acid to mimic the proneuropeptides found in large dense-core vesicles. We explored this approach with four prominent neuropeptides: gastrin-releasing peptide (GRP), oxytocin (OT), substance P (SP), and cholecystokinin (CCK). C-terminus extension greatly reduced the activity of all four peptides at heterologously expressed receptors. In cell type-specific electrophysiological recordings from acute brain slices, subsecond flashes of ultraviolet light produced rapidly activating membrane currents via activation of endogenous G protein-coupled receptors. Subsequent mechanistic studies with caged CCK revealed a role for extracellular proteases in shaping the temporal dynamics of CCK signaling, and a striking switch-like, cell-autonomous anti-opioid effect of transient CCK signaling in hippocampal parvalbumin interneurons. These results suggest that C-terminus extension with a photocleavable linker may be a general strategy for photocaging amidated neuropeptides and demonstrate how photocaged neuropeptides can provide mechanistic insights into neuropeptide signaling that are inaccessible using conventional approaches.
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Affiliation(s)
| | | | - Caroline A. Johnson
- Department of Neurobiology,
School of Biological Sciences, University
of California San Diego, La Jolla, California 92093, United States
| | | | - Stanley A. Buczynski
- Department of Neurobiology,
School of Biological Sciences, University
of California San Diego, La Jolla, California 92093, United States
| | - Matthew R. Banghart
- Department of Neurobiology,
School of Biological Sciences, University
of California San Diego, La Jolla, California 92093, United States
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6
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Ma X, Johnson DA, He XJ, Layden AE, McClain SP, Yung JC, Rizzo A, Bonaventura J, Banghart MR. In vivo photopharmacology with a caged mu opioid receptor agonist drives rapid changes in behavior. Nat Methods 2023; 20:682-685. [PMID: 36973548 PMCID: PMC10569260 DOI: 10.1038/s41592-023-01819-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 02/16/2023] [Indexed: 03/29/2023]
Abstract
Photoactivatable drugs and peptides can drive quantitative studies into receptor signaling with high spatiotemporal precision, yet few are compatible with behavioral studies in mammals. We developed CNV-Y-DAMGO-a caged derivative of the mu opioid receptor-selective peptide agonist DAMGO. Photoactivation in the mouse ventral tegmental area produced an opioid-dependent increase in locomotion within seconds of illumination. These results demonstrate the power of in vivo photopharmacology for dynamic studies into animal behavior.
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Affiliation(s)
- Xiang Ma
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Desiree A Johnson
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Xinyi Jenny He
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Aryanna E Layden
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Shannan P McClain
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Jean C Yung
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Arianna Rizzo
- Departament de Patologia i Terapèutica Experimental, Institut de Neurociències, Universitat de Barcelona, L'Hospitalet de Llobregat, Catalonia, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research (IDIBELL), L'Hospitalet de Llobregat, Catalonia, Spain
| | - Jordi Bonaventura
- Departament de Patologia i Terapèutica Experimental, Institut de Neurociències, Universitat de Barcelona, L'Hospitalet de Llobregat, Catalonia, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research (IDIBELL), L'Hospitalet de Llobregat, Catalonia, Spain
| | - Matthew R Banghart
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
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7
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McClain SP, Ma X, Johnson DA, Johnson CA, Layden AE, Yung JC, Lubejko ST, Livrizzi G, Jenny He X, Zhou J, Ventriglia E, Rizzo A, Levinstein M, Gomez JL, Bonaventura J, Michaelides M, Banghart MR. In vivo photopharmacology with light-activated opioid drugs. bioRxiv 2023:2023.02.02.526901. [PMID: 36778286 PMCID: PMC9915677 DOI: 10.1101/2023.02.02.526901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Traditional methods for site-specific drug delivery in the brain are slow, invasive, and difficult to interface with recordings of neural activity. Here, we demonstrate the feasibility and experimental advantages of in vivo photopharmacology using "caged" opioid drugs that are activated in the brain with light after systemic administration in an inactive form. To enable bidirectional manipulations of endogenous opioid receptors in vivo , we developed PhOX and PhNX, photoactivatable variants of the mu opioid receptor agonist oxymorphone and the antagonist naloxone. Photoactivation of PhOX in multiple brain areas produced local changes in receptor occupancy, brain metabolic activity, neuronal calcium activity, neurochemical signaling, and multiple pain- and reward-related behaviors. Combining PhOX photoactivation with optical recording of extracellular dopamine revealed adaptations in the opioid sensitivity of mesolimbic dopamine circuitry during chronic morphine administration. This work establishes a general experimental framework for using in vivo photopharmacology to study the neural basis of drug action. Highlights A photoactivatable opioid agonist (PhOX) and antagonist (PhNX) for in vivo photopharmacology. Systemic pro-drug delivery followed by local photoactivation in the brain. In vivo photopharmacology produces behavioral changes within seconds of photostimulation. In vivo photopharmacology enables all-optical pharmacology and physiology.
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8
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Lubejko ST, Graham RD, Livrizzi G, Schaefer R, Banghart MR, Creed MC. The role of endogenous opioid neuropeptides in neurostimulation-driven analgesia. Front Syst Neurosci 2022; 16:1044686. [PMID: 36591324 PMCID: PMC9794630 DOI: 10.3389/fnsys.2022.1044686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 11/18/2022] [Indexed: 12/15/2022] Open
Abstract
Due to the prevalence of chronic pain worldwide, there is an urgent need to improve pain management strategies. While opioid drugs have long been used to treat chronic pain, their use is severely limited by adverse effects and abuse liability. Neurostimulation techniques have emerged as a promising option for chronic pain that is refractory to other treatments. While different neurostimulation strategies have been applied to many neural structures implicated in pain processing, there is variability in efficacy between patients, underscoring the need to optimize neurostimulation techniques for use in pain management. This optimization requires a deeper understanding of the mechanisms underlying neurostimulation-induced pain relief. Here, we discuss the most commonly used neurostimulation techniques for treating chronic pain. We present evidence that neurostimulation-induced analgesia is in part driven by the release of endogenous opioids and that this endogenous opioid release is a common endpoint between different methods of neurostimulation. Finally, we introduce technological and clinical innovations that are being explored to optimize neurostimulation techniques for the treatment of pain, including multidisciplinary efforts between neuroscience research and clinical treatment that may refine the efficacy of neurostimulation based on its underlying mechanisms.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Robert D. Graham
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Robert Schaefer
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
- *Correspondence: Matthew R. Banghart,
| | - Meaghan C. Creed
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO, United States
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO, United States
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
- Meaghan C. Creed,
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9
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Liu S, Kim DI, Oh TG, Pao GM, Kim JH, Palmiter RD, Banghart MR, Lee KF, Evans RM, Han S. Neural basis of opioid-induced respiratory depression and its rescue. Proc Natl Acad Sci U S A 2021; 118:e2022134118. [PMID: 34074761 PMCID: PMC8201770 DOI: 10.1073/pnas.2022134118] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Opioid-induced respiratory depression (OIRD) causes death following an opioid overdose, yet the neurobiological mechanisms of this process are not well understood. Here, we show that neurons within the lateral parabrachial nucleus that express the µ-opioid receptor (PBL Oprm1 neurons) are involved in OIRD pathogenesis. PBL Oprm1 neuronal activity is tightly correlated with respiratory rate, and this correlation is abolished following morphine injection. Chemogenetic inactivation of PBL Oprm1 neurons mimics OIRD in mice, whereas their chemogenetic activation following morphine injection rescues respiratory rhythms to baseline levels. We identified several excitatory G protein-coupled receptors expressed by PBL Oprm1 neurons and show that agonists for these receptors restore breathing rates in mice experiencing OIRD. Thus, PBL Oprm1 neurons are critical for OIRD pathogenesis, providing a promising therapeutic target for treating OIRD in patients.
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Affiliation(s)
- Shijia Liu
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Dong-Il Kim
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Tae Gyu Oh
- Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Gerald M Pao
- Molecular and Cellular Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Jong-Hyun Kim
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Richard D Palmiter
- HHMI, University of Washington, Seattle, WA 98195
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, WA 98195
| | - Matthew R Banghart
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Kuo-Fen Lee
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
| | - Ronald M Evans
- Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037
- HHMI, The Salk Institute for Biological Studies, La Jolla, CA 92037
| | - Sung Han
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, CA 92037;
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093
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10
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Abstract
Physiological responses to the opioid neuropeptide enkephalin often involve both mu and delta opioid receptors. To facilitate quantitative studies into opioid signaling, we previously developed a caged [Leu5]-enkephalin that responds to ultraviolet irradiation, but its residual activity at delta receptors confounds experiments that involve both receptors. To reduce residual activity, we evaluated side-chain, N-terminus, and backbone caging sites and further incorporated the dimethoxy-nitrobenzyl moiety to improve sensitivity to ultraviolet light-emitting diodes (LEDs). Residual activity was characterized using an in vitro functional assay, and the power dependence and kinetics of the uncaging response to 355 nm laser irradiation were assayed using electrophysiological recordings of mu opioid receptor-mediated potassium currents in brain slices of rat locus coeruleus. These experiments identified N-MNVOC-LE as an optimal compound. Using ultraviolet LED illumination to photoactivate N-MNVOC-LE in the CA1 region of hippocampus, we found that enkephalin engages both mu and delta opioid receptors to suppress inhibitory synaptic transmission.
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Affiliation(s)
- Matthew R. Banghart
- Division of Biological Sciences, Section on Neurobiology, University of California San Diego, La Jolla, California 92093, United States
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, United States
| | - Xinyi J. He
- Division of Biological Sciences, Section on Neurobiology, University of California San Diego, La Jolla, California 92093, United States
| | - Bernardo L. Sabatini
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, United States
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11
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Olson JP, Banghart MR, Sabatini BL, Ellis-Davies GCR. Spectral evolution of a photochemical protecting group for orthogonal two-color uncaging with visible light. J Am Chem Soc 2013; 135:15948-54. [PMID: 24117060 DOI: 10.1021/ja408225k] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Caged compounds are molecules rendered functionally inert by derivatization with a photochemical protecting group. We describe the design logic behind the development of a diethylaminocoumarin (DEAC) caging chromophore, DEAC450, that absorbs blue light strongly (ε450 = 43,000 M(-1) cm(-1)) and violet light 11-fold more weakly. The absorption minimum is in the wavelength range (340-360 nm) that is traditionally used for photolysis of many widely used nitroaromatic caged compounds (e.g., 4-carboxymethoxy-5,7-dinitroindolinyl(CDNI)-GABA). We used this chromophore to synthesize DEAC450-caged cAMP and found this probe was very stable toward aqueous hydrolysis in the electronic ground state but was photolyzed with a quantum efficiency of 0.78. When DEAC450-cAMP and CDNI-GABA where co-applied to striatal cholinergic interneurons, the caged compounds were photolyzed in an chromatically orthogonal manner using blue and violet light so as to modulate the neuronal firing rate in a bidirectional way.
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Affiliation(s)
- Jeremy P Olson
- Department of Neuroscience, Mount Sinai School of Medicine , New York, New York 10029, United States
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12
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Abstract
The spatiotemporal dynamics of opioid signaling in the brain remain poorly defined. Photoactivatable opioid ligands provide a means to quantitatively measure these dynamics and their underlying mechanisms in brain tissue. Although activation kinetics can be assessed using caged agonists, deactivation kinetics are obscured by slow clearance of agonist in tissue. To reveal deactivation kinetics of opioid signaling we developed a caged competitive antagonist that can be quickly photoreleased in sufficient concentrations to render agonist dissociation effectively irreversible. Carboxynitroveratryl-naloxone (CNV-NLX), a caged analog of the competitive opioid antagonist NLX, was readily synthesized from commercially available NLX in good yield and found to be devoid of antagonist activity at heterologously expressed opioid receptors. Photolysis in slices of rat locus coeruleus produced a rapid inhibition of the ionic currents evoked by multiple agonists of the μ-opioid receptor (MOR), but not of α-adrenergic receptors, which activate the same pool of ion channels. Using the high-affinity peptide agonist dermorphin, we established conditions under which light-driven deactivation rates are independent of agonist concentration and thus intrinsic to the agonist-receptor complex. Under these conditions, some MOR agonists yielded deactivation rates that are limited by G protein signaling, whereas others appeared limited by agonist dissociation. Therefore, the choice of agonist determines which feature of receptor signaling is unmasked by CNV-NLX photolysis.
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Affiliation(s)
- Matthew R Banghart
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (M.R.B., R.C.S., B.L.S.); Vollum Institute, Oregon Health & Science University, Portland, Oregon (J.T.W.); and Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia (L.D.L.)
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13
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Abstract
Incorporation of photoisomerizable chromophores into small molecule ligands represents a general approach for reversibly controlling protein function with light. Illumination at different wavelengths produces photostationary states (PSSs) consisting of different ratios of photoisomers. Thus optimal implementation of photoswitchable ligands requires knowledge of their wavelength sensitivity. Using an azobenzene-based ion channel blocker as an example, this protocol describes a (1)H NMR assay that can be used to precisely determine the isomeric content of photostationary states (PSSs) as a function of illumination wavelength. Samples of the photoswitchable ligand are dissolved in deuterated water and analyzed by UV/VIS spectroscopy to identify the range of illumination wavelengths that produce PSSs. The PSSs produced by these wavelengths are quantified using (1)H NMR spectroscopy under continuous irradiation through a monochromator-coupled fiber-optic cable. Because aromatic protons of azobenzene trans and cis isomers exhibit sufficiently different chemical shifts, their relative abundances at each PSS can be readily determined by peak integration. Constant illumination during spectrum acquisition is essential to accurately determine PSSs from molecules that thermally relax on the timescale of minutes or faster. This general protocol can be readily applied to any photoswitch that exhibits distinct (1)H NMR signals in each photoisomeric state.
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Abstract
Neuropeptides activate G protein-coupled receptors to acutely modulate cellular excitability and synaptic transmission. However, due to the lack of reagents for precise delivery of peptides within dense brain tissue, the spatiotemporal scale over which neuropeptides act is unknown. To achieve rapid and spatially delimited delivery of neuropeptides in mammalian brain tissue, we developed photoactivatable analogs of two opioids: [Leu⁵]-enkephalin (LE) and the 8 amino acid form of Dynorphin A (Dyn-8). These peptides are functionally inactive prior to photolysis, and exposure to ultraviolet (UV) light causes clean release of LE and Dyn-8. Recordings from acute slices of rat locus coeruleus (LC) demonstrated that photorelease of LE activates mu opioid receptor-coupled K+ channels with kinetics that approach the limits imposed by G protein-mediated signaling. Temporally precise and spatially delimited photorelease revealed the kinetics and ionic nature of the mu opioid response and the mechanisms that determine the spatial profile of enkephalinergic volume transmission in LC.
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Affiliation(s)
- Matthew R. Banghart
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Bernardo L. Sabatini
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA
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15
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Tochitsky I, Banghart MR, Mourot A, Yao JZ, Gaub B, Kramer RH, Trauner D. Optochemical control of genetically engineered neuronal nicotinic acetylcholine receptors. Nat Chem 2012; 4:105-11. [PMID: 22270644 DOI: 10.1038/nchem.1234] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 11/21/2011] [Indexed: 12/21/2022]
Abstract
Advances in synthetic chemistry, structural biology, molecular modelling and molecular cloning have enabled the systematic functional manipulation of transmembrane proteins. By combining genetically manipulated proteins with light-sensitive ligands, innately 'blind' neurobiological receptors can be converted into photoreceptors, which allows them to be photoregulated with high spatiotemporal precision. Here, we present the optochemical control of neuronal nicotinic acetylcholine receptors (nAChRs) with photoswitchable tethered agonists and antagonists. Using structure-based design, we produced heteromeric α3β4 and α4β2 nAChRs that can be activated or inhibited with deep-violet light, but respond normally to acetylcholine in the dark. The generation of these engineered receptors should facilitate investigation of the physiological and pathological functions of neuronal nAChRs and open a general pathway to photosensitizing pentameric ligand-gated ion channels.
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Affiliation(s)
- Ivan Tochitsky
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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16
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Mourot A, Kienzler MA, Banghart MR, Fehrentz T, Huber FME, Stein M, Kramer RH, Trauner D. Tuning photochromic ion channel blockers. ACS Chem Neurosci 2011; 2:536-43. [PMID: 22860175 DOI: 10.1021/cn200037p] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 06/09/2011] [Indexed: 12/14/2022] Open
Abstract
Photochromic channel blockers provide a conceptually simple and convenient way to modulate neuronal activity with light. We have recently described a family of azobenzenes that function as tonic blockers of K(v) channels but require UV-A light to unblock and need to be actively switched by toggling between two different wavelengths. We now introduce red-shifted compounds that fully operate in the visible region of the spectrum and quickly turn themselves off in the dark. Furthermore, we have developed a version that does not block effectively in the dark-adapted state, can be switched to a blocking state with blue light, and reverts to the inactive state automatically. Photochromic blockers of this type could be useful for the photopharmacological control of neuronal activity under mild conditions.
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Affiliation(s)
| | - Michael A. Kienzler
- Department of Chemistry and Pharmacology, Ludwig-Maximilians-Universität, München, and Center for Integrated Protein Science, 81377 Munich, Germany
| | | | - Timm Fehrentz
- Department of Chemistry and Pharmacology, Ludwig-Maximilians-Universität, München, and Center for Integrated Protein Science, 81377 Munich, Germany
| | - Florian M. E. Huber
- Department of Chemistry and Pharmacology, Ludwig-Maximilians-Universität, München, and Center for Integrated Protein Science, 81377 Munich, Germany
| | - Marco Stein
- Department of Chemistry and Pharmacology, Ludwig-Maximilians-Universität, München, and Center for Integrated Protein Science, 81377 Munich, Germany
| | | | - Dirk Trauner
- Department of Chemistry and Pharmacology, Ludwig-Maximilians-Universität, München, and Center for Integrated Protein Science, 81377 Munich, Germany
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17
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Fortin DL, Dunn TW, Fedorchak A, Allen D, Montpetit R, Banghart MR, Trauner D, Adelman JP, Kramer RH. Optogenetic photochemical control of designer K+ channels in mammalian neurons. J Neurophysiol 2011; 106:488-96. [PMID: 21525363 DOI: 10.1152/jn.00251.2011] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Currently available optogenetic tools, including microbial light-activated ion channels and transporters, are transforming systems neuroscience by enabling precise remote control of neuronal firing, but they tell us little about the role of indigenous ion channels in controlling neuronal function. Here, we employ a chemical-genetic strategy to engineer light sensitivity into several mammalian K(+) channels that have different gating and modulation properties. These channels provide the means for photoregulating diverse electrophysiological functions. Photosensitivity is conferred on a channel by a tethered ligand photoswitch that contains a cysteine-reactive maleimide (M), a photoisomerizable azobenzene (A), and a quaternary ammonium (Q), a K(+) channel pore blocker. Using mutagenesis, we identify the optimal extracellular cysteine attachment site where MAQ conjugation results in pore blockade when the azobenzene moiety is in the trans but not cis configuration. With this strategy, we have conferred photosensitivity on channels containing Kv1.3 subunits (which control axonal action potential repolarization), Kv3.1 subunits (which contribute to rapid-firing properties of brain neurons), Kv7.2 subunits (which underlie "M-current"), and SK2 subunits (which are Ca(2+)-activated K(+) channels that contribute to synaptic responses). These light-regulated channels may be overexpressed in genetically targeted neurons or substituted for native channels with gene knockin technology to enable precise optopharmacological manipulation of channel function.
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Affiliation(s)
- Doris L Fortin
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA
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18
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Mourot A, Fehrentz T, Kienzler M, Tochitsky I, Banghart MR, Trauner D, Kramer RH. Photopharmacology: Controlling Native Voltage-Gated Ion Channels with Light. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.1143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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19
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Abstract
We report a novel and simple proof-of-concept of a nanoparticulate system that targets any tissue selectively upon illumination. Nanoparticles were covalently functionalized with the amino acid sequence YIGSR, which adheres to the beta1 integrins present on most cell surfaces. This peptide was masked with a caging group, rendering it biologically inert. Illumination with UV light released the caging group from the YIGSR, allowing binding to cells.
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Affiliation(s)
- Tal Dvir
- Department of Chemical Engineering, Massachusetts Institute of Technology, 45 Carleton Street, Cambridge, Massachusetts 02142
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115
| | - Matthew R. Banghart
- Department of Neurobiology, Harvard Medical School, 220 Longwood Ave, Boston, Massachusetts 02115
| | - Brian P. Timko
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge, MA 02139
| | - Robert Langer
- Department of Chemical Engineering, Massachusetts Institute of Technology, 45 Carleton Street, Cambridge, Massachusetts 02142
| | - Daniel S. Kohane
- Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115
- To whom correspondence should be addressed,
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20
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Lester HA, Xiao C, Srinivasan R, Son CD, Miwa J, Pantoja R, Banghart MR, Dougherty DA, Goate AM, Wang JC. Nicotine is a selective pharmacological chaperone of acetylcholine receptor number and stoichiometry. Implications for drug discovery. AAPS J 2009; 11:167-77. [PMID: 19280351 DOI: 10.1208/s12248-009-9090-7] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 02/07/2009] [Indexed: 01/11/2023]
Abstract
The acronym SePhaChARNS, for "selective pharmacological chaperoning of acetylcholine receptor number and stoichiometry," is introduced. We hypothesize that SePhaChARNS underlies classical observations that chronic exposure to nicotine causes "upregulation" of nicotinic receptors (nAChRs). If the hypothesis is proven, (1) SePhaChARNS is the molecular mechanism of the first step in neuroadaptation to chronic nicotine; and (2) nicotine addiction is partially a disease of excessive chaperoning. The chaperone is a pharmacological one, nicotine; and the chaperoned molecules are alpha4beta2* nAChRs. SePhaChARNS may also underlie two inadvertent therapeutic effects of tobacco use: (1) the inverse correlation between tobacco use and Parkinson's disease; and (2) the suppression of seizures by nicotine in autosomal dominant nocturnal frontal lobe epilepsy. SePhaChARNS arises from the thermodynamics of pharmacological chaperoning: ligand binding, especially at subunit interfaces, stabilizes AChRs during assembly and maturation, and this stabilization is most pronounced for the highest-affinity subunit compositions, stoichiometries, and functional states of receptors. Several chemical and pharmacokinetic characteristics render exogenous nicotine a more potent pharmacological chaperone than endogenous acetylcholine. SePhaChARNS is modified by desensitized states of nAChRs, by acid trapping of nicotine in organelles, and by other aspects of proteostasis. SePhaChARNS is selective at the cellular, and possibly subcellular, levels because of variations in the detailed nAChR subunit composition, as well as in expression of auxiliary proteins such as lynx. One important implication of the SePhaChARNS hypothesis is that therapeutically relevant nicotinic receptor drugs could be discovered by studying events in intracellular compartments rather than exclusively at the surface membrane.
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Affiliation(s)
- Henry A Lester
- Division of Biology 156-29, California Institute of Technology, Pasadena, CA 91125, USA.
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21
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Banghart MR, Mourot A, Fortin DL, Kramer RH, Trauner D. Discovery Of Photochromic Ligands That Block Voltage-gated K+ Channels At The Internal TEA Binding Site. Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.1022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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22
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Affiliation(s)
- Matthew R. Banghart
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA)
| | - Alexandre Mourot
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Doris L. Fortin
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Jennifer Z. Yao
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA)
| | - Richard H. Kramer
- Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, California 94720 (USA), Fax: (+1) 510 643-6791
| | - Dirk Trauner
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720 (USA); University of Munich, Butenandtstr. 5-13 (F4.086), D-81377 Munich, Germany, Fax: (+49) (0)89 2180-77972
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23
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Fortin DL, Banghart MR, Dunn TW, Borges K, Wagenaar DA, Gaudry Q, Karakossian MH, Otis TS, Kristan WB, Trauner D, Kramer RH. Photochemical control of endogenous ion channels and cellular excitability. Nat Methods 2008; 5:331-8. [PMID: 18311146 DOI: 10.1038/nmeth.1187] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 01/25/2008] [Indexed: 12/11/2022]
Abstract
Light-activated ion channels provide a precise and noninvasive optical means for controlling action potential firing, but the genes encoding these channels must first be delivered and expressed in target cells. Here we describe a method for bestowing light sensitivity onto endogenous ion channels that does not rely on exogenous gene expression. The method uses a synthetic photoisomerizable small molecule, or photoswitchable affinity label (PAL), that specifically targets K+ channels. PALs contain a reactive electrophile, enabling covalent attachment of the photoswitch to naturally occurring nucleophiles in K+ channels. Ion flow through PAL-modified channels is turned on or off by photoisomerizing PAL with different wavelengths of light. We showed that PAL treatment confers light sensitivity onto endogenous K+ channels in isolated rat neurons and in intact neural structures from rat and leech, allowing rapid optical regulation of excitability without genetic modification.
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Affiliation(s)
- Doris L Fortin
- Department of Molecular and Cell Biology, University of California Berkeley, 121 Life Sciences Addition, Berkeley, California 94720, USA
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Abstract
Ion channels are gated by a variety of stimuli, including ligands, voltage, membrane tension, temperature, and even light. Natural gates can be altered and augmented using synthetic chemistry and molecular biology to develop channels with completely new functional properties. Light-sensitive channels are particularly attractive because optical manipulation offers a high degree of spatial and temporal control. Over the last few decades, several channels have been successfully rendered responsive to light, including the nicotinic acetylcholine receptor, gramicidin A, a voltage-gated potassium channel, an ionotropic glutamate receptor, alpha-hemolysin, and a mechanosensitive channel. Very recently, naturally occurring light-gated cation channels have been discovered. This review covers the molecular principles that guide the engineering of light-gated ion channels for applications in biology and medicine.
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Affiliation(s)
- Matthew R Banghart
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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Chambers JJ, Banghart MR, Trauner D, Kramer RH. Light-induced depolarization of neurons using a modified Shaker K(+) channel and a molecular photoswitch. J Neurophysiol 2006; 96:2792-6. [PMID: 16870840 DOI: 10.1152/jn.00318.2006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To trigger action potentials in neurons, most investigators use electrical or chemical stimulation. Here we describe an optical stimulation method based on semi-synthetic light-activated ion channels. These SPARK (synthetic photoisomerizable azobenzene-regulated K(+)) channels consist of a synthetic azobenzene-containing photoswitch and a genetically modified Shaker K(+) channel protein. SPARK channels with a wild-type selectivity filter elicit hyperpolarization and suppress action potential firing when activated by 390 nm light. A mutation in the pore converts the K(+)-selective Shaker channel into a nonselective cation channel. Activation of this modified channel with the same wavelength of light elicits depolarization of the membrane potential. Expression of these depolarizing SPARK channels in neurons allows light to rapidly and reversibly trigger action potential firing. Hence, hyper- and depolarizing SPARK channels provide a means for eliciting opposite effects on neurons in response to the same light stimulus.
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Affiliation(s)
- James J Chambers
- Department of Molecular and Cell Biology, University of California, Berkley, CA 94720, USA
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