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Ye L, Gao Y, Mok SWF, Liao W, Wang Y, Chen C, Yang L, Zhang J, Shi L. Modulation of alveolar macrophage and mitochondrial fitness by medicinal plant-derived nanovesicles to mitigate acute lung injury and viral pneumonia. J Nanobiotechnology 2024; 22:190. [PMID: 38637808 PMCID: PMC11025283 DOI: 10.1186/s12951-024-02473-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 04/08/2024] [Indexed: 04/20/2024] Open
Abstract
Acute lung injury (ALI) is generally caused by severe respiratory infection and characterized by overexuberant inflammatory responses and inefficient pathogens-containing, the two major processes wherein alveolar macrophages (AMs) play a central role. Dysfunctional mitochondria have been linked with distorted macrophages and hence lung disorders, but few treatments are currently available to correct these defects. Plant-derive nanovesicles have gained significant attention because of their therapeutic potential, but the targeting cells and the underlying mechanism remain elusive. We herein prepared the nanovesicles from Artemisia annua, a well-known medicinal plant with multiple attributes involving anti-inflammatory, anti-infection, and metabolism-regulating properties. By applying three mice models of acute lung injury caused by bacterial endotoxin, influenza A virus (IAV) and SARS-CoV-2 pseudovirus respectively, we showed that Artemisia-derived nanovesicles (ADNVs) substantially alleviated lung immunopathology and raised the survival rate of challenged mice. Macrophage depletion and adoptive transfer studies confirmed the requirement of AMs for ADNVs effects. We identified that gamma-aminobutyric acid (GABA) enclosed in the vesicles is a major molecular effector mediating the regulatory roles of ADNVs. Specifically, GABA acts on macrophages through GABA receptors, promoting mitochondrial gene programming and bioenergy generation, reducing oxidative stress and inflammatory signals, thereby enhancing the adaptability of AMs to inflammation resolution. Collectively, this study identifies a promising nanotherapeutics for alleviating lung pathology, and elucidates a mechanism whereby the canonical neurotransmitter modifies AMs and mitochondria to resume tissue homeostasis, which may have broader implications for treating critical pulmonary diseases such as COVID-19.
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Affiliation(s)
- Lusha Ye
- Institute of Translational Medicine, Zhejiang Shuren University, Hangzhou, 310015, Zhejiang, China
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Yanan Gao
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Simon Wing Fai Mok
- Department of Medicine, Macau University of Science and Technology, Taipa, Macau, China
| | - Wucan Liao
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Yazhou Wang
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Changjiang Chen
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Lijun Yang
- Institute of Translational Medicine, Zhejiang Shuren University, Hangzhou, 310015, Zhejiang, China
| | - Junfeng Zhang
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Liyun Shi
- Institute of Translational Medicine, Zhejiang Shuren University, Hangzhou, 310015, Zhejiang, China.
- Department of Immunology and Medical Microbiology, Nanjing University of Chinese Medicine, Nanjing, 210023, China.
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Pohl F, Germann AL, Mao J, Hou S, Bakare B, Kong Thoo Lin P, Yates K, Nonet ML, Akk G, Kornfeld K, Held JM. UNC-49 is a redox-sensitive GABA A receptor that regulates the mitochondrial unfolded protein response cell nonautonomously. SCIENCE ADVANCES 2023; 9:eadh2584. [PMID: 37910615 PMCID: PMC10619936 DOI: 10.1126/sciadv.adh2584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 09/29/2023] [Indexed: 11/03/2023]
Abstract
The γ-aminobutyric acid-mediated (GABAergic) system participates in many aspects of organismal physiology and disease, including proteostasis, neuronal dysfunction, and life-span extension. Many of these phenotypes are also regulated by reactive oxygen species (ROS), but the redox mechanisms linking the GABAergic system to these phenotypes are not well defined. Here, we report that GABAergic redox signaling cell nonautonomously activates many stress response pathways in Caenorhabditis elegans and enhances vulnerability to proteostasis disease in the absence of oxidative stress. Cell nonautonomous redox activation of the mitochondrial unfolded protein response (mitoUPR) proteostasis network requires UNC-49, a GABAA receptor that we show is activated by hydrogen peroxide. MitoUPR induction by a spinocerebellar ataxia type 3 (SCA3) C. elegans neurodegenerative disease model was similarly dependent on UNC-49 in C. elegans. These results demonstrate a multi-tissue paradigm for redox signaling in the GABAergic system that is transduced via a GABAA receptor to function in cell nonautonomous regulation of health, proteostasis, and disease.
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Affiliation(s)
- Franziska Pohl
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Allison L. Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Jack Mao
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Sydney Hou
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Bayode Bakare
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Paul Kong Thoo Lin
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Kyari Yates
- School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen, UK
| | - Michael L. Nonet
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
- Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Kerry Kornfeld
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Jason M. Held
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, USA
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Arias HR, Pierce SR, Germann AL, Xu SQ, Ortells MO, Sakamoto S, Manetti D, Romanelli MN, Hamachi I, Akk G. Chemical, Pharmacological, and Structural Characterization of Novel Acrylamide-Derived Modulators of the GABA A Receptor. Mol Pharmacol 2023; 104:115-131. [PMID: 37316350 PMCID: PMC10441626 DOI: 10.1124/molpharm.123.000692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 05/22/2023] [Accepted: 06/01/2023] [Indexed: 06/16/2023] Open
Abstract
Acrylamide-derived compounds have been previously shown to act as modulators of members of the Cys-loop transmitter-gated ion channel family, including the mammalian GABAA receptor. Here we have synthesized and functionally characterized the GABAergic effects of a series of novel compounds (termed "DM compounds") derived from the previously characterized GABAA and the nicotinic α7 receptor modulator (E)-3-furan-2-yl-N-p-tolyl-acrylamide (PAM-2). Fluorescence imaging studies indicated that the DM compounds increase apparent affinity to the transmitter by up to 80-fold in the ternary αβγ GABAA receptor. Using electrophysiology, we show that the DM compounds, and the structurally related (E)-3-furan-2-yl-N-phenylacrylamide (PAM-4), have concurrent potentiating and inhibitory effects that can be isolated and observed under appropriate recording conditions. The potentiating efficacies of the DM compounds are similar to those of neurosteroids and benzodiazepines (ΔG ∼ -1.5 kcal/mol). Molecular docking, functionally confirmed by site-directed mutagenesis experiments, indicate that receptor potentiation is mediated by interactions with the classic anesthetic binding sites located in the transmembrane domain of the intersubunit interfaces. Inhibition by the DM compounds and PAM-4 was abolished in the receptor containing the α1(V256S) mutation, suggestive of similarities in the mechanism of action with that of inhibitory neurosteroids. Functional competition and mutagenesis experiments, however, indicate that the sites mediating inhibition by the DM compounds and PAM-4 differ from those mediating the action of the inhibitory steroid pregnenolone sulfate. SIGNIFICANCE STATEMENT: We have synthesized and characterized the actions of novel acrylamide-derived compounds on the mammalian GABAA receptor. We show that the compounds have concurrent potentiating effects mediated by the classic anesthetic binding sites, and inhibitory actions that bear mechanistic resemblance to but do not share binding sites with, the inhibitory steroid pregnenolone sulfate.
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Affiliation(s)
- Hugo R Arias
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Spencer R Pierce
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Allison L Germann
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Sophia Q Xu
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Marcelo O Ortells
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Seiji Sakamoto
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Dina Manetti
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Maria Novella Romanelli
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Itaru Hamachi
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
| | - Gustav Akk
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, Oklahoma (H.R.A.); Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (S.R.P., A.L.G., S.Q.X., G.A.); Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina (M.O.O.); Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan (S.S., I.H.); Department of Neurosciences, Psychology, Drug Research and Child Health Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, Florence, Italy (D.M., M.N.R.); The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri (G.A.)
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Huang D, Alexander PB, Li QJ, Wang XF. GABAergic signaling beyond synapses: an emerging target for cancer therapy. Trends Cell Biol 2023; 33:403-412. [PMID: 36114091 PMCID: PMC10008753 DOI: 10.1016/j.tcb.2022.08.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/16/2022] [Accepted: 08/22/2022] [Indexed: 11/29/2022]
Abstract
Traditionally, γ-aminobutyric acid (GABA) is best known for its role as a primary inhibitory neurotransmitter reducing neuronal excitability in the mammalian central nervous system (CNS), thereby producing calming effects. However, an emerging body of data now supports a function for GABA beyond neurotransmission as a potent factor regulating cancer cell growth and metastasis, as well as the antitumor immune response, by shaping the tumor microenvironment (TME). Here, we review the current knowledge on GABA's effects on the function of tumor cells, tumor-immune interactions, and the underlying molecular mechanisms. Since altered GABAergic signaling is now recognized as a feature of certain types of solid tumors, we also discuss the potential of repurposing existing GABAergic agents as a new class of anticancer therapy.
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Affiliation(s)
- De Huang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Peter B Alexander
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Qi-Jing Li
- Department of Immunology, Duke University Medical Center, Durham, NC, USA
| | - Xiao-Fan Wang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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Arias HR, Germann AL, Pierce SR, Sakamoto S, Ortells MO, Hamachi I, Akk G. Modulation of the mammalian GABA A receptor by type I and type II positive allosteric modulators of the α7 nicotinic acetylcholine receptor. Br J Pharmacol 2022; 179:5323-5337. [PMID: 36082615 PMCID: PMC9669183 DOI: 10.1111/bph.15948] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 08/29/2022] [Accepted: 09/06/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Positive allosteric modulators of the α7 nicotinic acetylcholine (nACh) receptor (α7-PAMs) possess promnesic and procognitive properties and have potential in the treatment of cognitive and psychiatric disorders including Alzheimer's disease and schizophrenia. Behavioural studies in rodents have indicated that α7-PAMs can also produce antinociceptive and anxiolytic effects that may be associated with positive modulation of the GABAA receptor. The overall goal of this study was to investigate the modulatory actions of selected α7-PAMs on the GABAA receptor. EXPERIMENTAL APPROACH We employed a combination of cell fluorescence imaging, electrophysiology, functional competition and site-directed mutagenesis to investigate the functional and structural mechanisms of modulation of the GABAA receptor by three representative α7-PAMs. KEY RESULTS We show that the α7-PAMs at micromolar concentrations enhance the apparent affinity of the GABAA receptor for the transmitter and potentiate current responses from the receptor. The compounds were equi-effective at binary αβ and ternary αβγ GABAA receptors. Functional competition and site-directed mutagenesis indicate that the α7-PAMs bind to the classic anaesthetic binding sites in the transmembrane region in the intersubunit interfaces, which results in stabilization of the active state of the receptor. CONCLUSION AND IMPLICATIONS We conclude that the tested α7-PAMs are micromolar-affinity, intermediate- to low-efficacy allosteric potentiators of the mammalian αβγ GABAA receptor. Given the similarities in the in vitro sensitivities of the α7 nACh and α1β2γ2L GABAA receptors to α7-PAMs, we propose that doses used to produce nACh receptor-mediated behavioural effects in vivo are likely to modulate GABAA receptor function.
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Affiliation(s)
- Hugo R. Arias
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, OK, USA
| | - Allison L. Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Spencer R. Pierce
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Seiji Sakamoto
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Marcelo O. Ortells
- Facultad de Medicina, Universidad de Morón, Morón, and CONICET, Argentina
| | - Itaru Hamachi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
- The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
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Hoyt H, Fantasia RJ, Bhave K, Yang X, Forman SA. Photomotor Responses in Zebrafish and Electrophysiology Reveal Varying Interactions of Anesthetics Targeting Distinct Sites on γ-Aminobutyric Acid Type A Receptors. Anesthesiology 2022; 137:568-585. [PMID: 36018576 PMCID: PMC9588801 DOI: 10.1097/aln.0000000000004361] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Etomidate, barbiturates, alfaxalone, and propofol are anesthetics that allosterically modulate γ-aminobutyric acid type A (GABAA) receptors via distinct sets of molecular binding sites. Two-state concerted coagonist models account for anesthetic effects and predict supra-additive interactions between drug pairs acting at distinct sites. Some behavioral and molecular studies support these predictions, while other findings suggest potentially complex anesthetic interactions. We therefore evaluated interactions among four anesthetics in both animals and GABAA receptors. METHODS The authors used video assessment of photomotor responses in zebrafish larvae and isobolography to evaluate hypnotic drug pair interactions. Voltage clamp electrophysiology and allosteric shift analysis evaluated coagonist interactions in α1β3γ2L receptors activated by γ-aminobutyric acid (GABA) versus anesthetics [log(d, AN):log(d, GABA) ratio]. Anesthetic interactions at concentrations relevant to zebrafish were assessed in receptors activated with low GABA. RESULTS In zebrafish larvae, etomidate interacted additively with both propofol and the barbiturate R-5-allyl-1-methyl m-trifluoromethyl mephobarbital (R-mTFD-MPAB; mean ± SD α = 1.0 ± 0.07 and 0.96 ± 0.11 respectively, where 1.0 indicates additivity), while the four other drug pairs displayed synergy (mean α range 0.76 to 0.89). Electrophysiologic allosteric shifts revealed that both propofol and R-mTFD-MPAB modulated etomidate-activated receptors much less than GABA-activated receptors [log(d, AN):log(d, GABA) ratios = 0.09 ± 0.021 and 0.38 ± 0.024, respectively], while alfaxalone comparably modulated receptors activated by GABA or etomidate [log(d) ratio = 0.87 ± 0.056]. With low GABA activation, etomidate combined with alfaxalone was supra-additive (n = 6; P = 0.023 by paired t test), but etomidate plus R-mTFD-MPAB or propofol was not. CONCLUSIONS In both zebrafish and GABAA receptors, anesthetic drug pairs interacted variably, ranging from additivity to synergy. Pairs including etomidate displayed corresponding interactions in animals and receptors. Some of these results challenge simple two-state coagonist models and support alternatives where different anesthetics may stabilize distinct receptor conformations, altering the effects of other drugs. EDITOR’S PERSPECTIVE
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Affiliation(s)
- Helen Hoyt
- Department of Anesthesia Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Ryan J Fantasia
- School of Biologic Sciences, University of California-San Diego, San Diego, California
| | - Kieran Bhave
- Department of Anesthesia Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Xiaoxuan Yang
- Department of Anesthesiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Stuart A Forman
- Department of Anesthesia Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
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Activation of the Rat α1β2ε GABA A Receptor by Orthosteric and Allosteric Agonists. Biomolecules 2022; 12:biom12070868. [PMID: 35883422 PMCID: PMC9312946 DOI: 10.3390/biom12070868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/10/2022] [Accepted: 06/17/2022] [Indexed: 02/04/2023] Open
Abstract
GABAA receptors are a major contributor to fast inhibitory neurotransmission in the brain. The receptors are activated upon binding the transmitter GABA or allosteric agonists including a number of GABAergic anesthetics and neurosteroids. Functional receptors can be formed by various combinations of the nineteen GABAA subunits cloned to date. GABAA receptors containing the ε subunit exhibit a significant degree of constitutive activity and have been suggested to be unresponsive to allosteric agents. In this study, we have characterized the functional properties of the rat α1β2ε GABAA receptor. We confirm that the α1β2ε receptor exhibits a higher level of constitutive activity than typical of GABAA receptors and show that it is inefficaciously activated by the transmitter and the allosteric agonists propofol, pentobarbital, and allopregnanolone. Manipulations intended to alter ε subunit expression and receptor stoichiometry were largely without effect on receptor properties including sensitivity to GABA and allosteric agonists. Surprisingly, amino acid substitutions at the conserved 9' and 6' positions in the second transmembrane (TM2) domain in the ε subunit did not elicit the expected functional effects of increased constitutive activity and resistance to the channel blocker picrotoxin, respectively. We tested the accessibility of TM2 residues mutated to cysteine using the cysteine-modifying reagent 4-(hydroxymercuri)benzoic acid and found a unique pattern of water-accessible residues in the ε subunit.
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Arias HR, Borghese CM, Germann AL, Pierce SR, Bonardi A, Nocentini A, Gratteri P, Thodati TM, Lim NJ, Adron Harris R, Akk G. (+)-Catharanthine potentiates the GABA A receptor by binding to a transmembrane site at the β(+)/α(-) interface near the TM2-TM3 loop. Biochem Pharmacol 2022; 199:114993. [PMID: 35304861 PMCID: PMC9178925 DOI: 10.1016/j.bcp.2022.114993] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 11/17/2022]
Abstract
(+)-Catharanthine, a coronaridine congener, potentiates the γ-aminobutyric acid type A receptor (GABAAR) and induces sedation through a non-benzodiazepine mechanism, but the specific site of action and intrinsic mechanism have not beendefined. Here, we describe GABAAR subtype selectivity and location of the putative binding site for (+)-catharanthine using electrophysiological, site-directed mutagenesis, functional competition, and molecular docking experiments. Electrophysiological and in silico experiments showed that (+)-catharanthine potentiates the responses to low, subsaturating GABA at β2/3-containing GABAARs 2.4-3.5 times more efficaciously than at β1-containing GABAARs. The activity of (+)-catharanthine is reduced by the β2(N265S) mutation that decreases GABAAR potentiation by loreclezole, but not by the β3(M286C) or α1(Q241L) mutations that reduce receptor potentiation by R(+)-etomidate or neurosteroids, respectively. Competitive functional experiments indicated that the binding site for (+)-catharanthine overlaps that for loreclezole, but not those for R(+)-etomidate or potentiating neurosteroids. Molecular docking experiments suggested that (+)-catharanthine binds at the β(+)/α(-) intersubunit interface near the TM2-TM3 loop, where it forms H-bonds with β2-D282 (TM3), β2-K279 (TM2-TM3 loop), and β2-N265 and β2-R269 (TM2). Site-directed mutagenesis experiments supported the in silico results, demonstrating that the K279A and D282A substitutions, that lead to a loss of H-bonding ability of the mutated residue, and the N265S mutation, impair the gating efficacy of (+)-catharanthine. We infer that (+)-catharanthine potentiates the GABAAR through several H-bond interactions with a binding site located in the β(+)/α(-) interface in the transmembrane domain, near the TM2-TM3 loop, where it overlaps with loreclezole binding site.
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Affiliation(s)
- Hugo R Arias
- Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tahlequah, OK, USA.
| | - Cecilia M Borghese
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA.
| | - Allison L Germann
- Department of Anesthesiology, the Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA.
| | - Spencer R Pierce
- Department of Anesthesiology, the Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA.
| | - Alessandro Bonardi
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmaceutical and Nutraceutical Sciences, Laboratory of Molecular Modeling Cheminformatics & QSAR, University of Florence, Florence, Italy.
| | - Alessio Nocentini
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmaceutical and Nutraceutical Sciences, Laboratory of Molecular Modeling Cheminformatics & QSAR, University of Florence, Florence, Italy.
| | - Paola Gratteri
- Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmaceutical and Nutraceutical Sciences, Laboratory of Molecular Modeling Cheminformatics & QSAR, University of Florence, Florence, Italy.
| | - Thanvi M Thodati
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA.
| | - Natalie J Lim
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA.
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA.
| | - Gustav Akk
- Department of Anesthesiology, the Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA.
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9
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Pierce SR, Germann AL, Steinbach JH, Akk G. The Sulfated Steroids Pregnenolone Sulfate and Dehydroepiandrosterone Sulfate Inhibit the α1 β3 γ2L GABA A Receptor by Stabilizing a Novel Nonconducting State. Mol Pharmacol 2022; 101:68-77. [PMID: 34853153 PMCID: PMC8969134 DOI: 10.1124/molpharm.121.000385] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 11/21/2021] [Indexed: 02/03/2023] Open
Abstract
The GABAA receptor is inhibited by the endogenous sulfated steroids pregnenolone sulfate (PS) and dehydroepiandrosterone sulfate (DHEAS). It has been proposed in previous work that these steroids act by enhancing desensitization of the receptor. Here, we have investigated the modulatory effects of the steroids on the human α1β3γ2L GABAA receptor. Using electrophysiology and quantitative model-based data analysis, we show that exposure to the steroid promotes occupancy of a nonconducting state that retains high affinity to the transmitter but whose properties differ from those of the classic, transmitter-induced desensitized state. From the analysis of the inhibitory actions of two combined steroids, we infer that PS and DHEAS act through shared or overlapping binding sites. SIGNIFICANCE STATEMENT: Previous work has proposed that sulfated neurosteroids inhibit the GABAA receptor by enhancing the rate of entry into the desensitized state. This study shows that the inhibitory steroids pregnenolone sulfate and dehydroepiandrosterone sulfate act through a common interaction site by stabilizing a distinct nonconducting state.
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Affiliation(s)
- Spencer R Pierce
- Department of Anesthesiology (S.R.P., A.L.G., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Department of Anesthesiology (S.R.P., A.L.G., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology (S.R.P., A.L.G., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology (S.R.P., A.L.G., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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10
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Huang D, Wang Y, Thompson JW, Yin T, Alexander PB, Qin D, Mudgal P, Wu H, Liang Y, Tan L, Pan C, Yuan L, Wan Y, Li QJ, Wang XF. Cancer-cell-derived GABA promotes β-catenin-mediated tumour growth and immunosuppression. Nat Cell Biol 2022; 24:230-241. [PMID: 35145222 PMCID: PMC8852304 DOI: 10.1038/s41556-021-00820-9] [Citation(s) in RCA: 94] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 11/23/2021] [Indexed: 12/18/2022]
Abstract
Many cancers have an unusual dependence on glutamine. However, most previous studies have focused on the contribution of glutamine to metabolic building blocks and the energy supply. Here, we report that cancer cells with aberrant expression of glutamate decarboxylase 1 (GAD1) rewire glutamine metabolism for the synthesis of γ-aminobutyric acid (GABA)-a prominent neurotransmitter-in non-nervous tissues. An analysis of clinical samples reveals that increased GABA levels predict poor prognosis. Mechanistically, we identify a cancer-intrinsic pathway through which GABA activates the GABAB receptor to inhibit GSK-3β activity, leading to enhanced β-catenin signalling. This GABA-mediated β-catenin activation both stimulates tumour cell proliferation and suppresses CD8+ T cell intratumoural infiltration, such that targeting GAD1 or GABABR in mouse models overcomes resistance to anti-PD-1 immune checkpoint blockade therapy. Our findings uncover a signalling role for tumour-derived GABA beyond its classic function as a neurotransmitter that can be targeted pharmacologically to reverse immunosuppression.
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Affiliation(s)
- De Huang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Yan Wang
- Institute of Pathology and Southwest Cancer Center, Chongqing, China
- Southwest Hospital, Chongqing, China
| | - J Will Thompson
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
- Proteomics and Metabolomics Shared Resource, Center for Genomic and Computational Biology, Duke University, Durham, NC, USA
| | - Tao Yin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Peter B Alexander
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Diyuan Qin
- Department of Immunology, Duke University Medical Center, Durham, NC, USA
| | | | | | - Yaosi Liang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Lianmei Tan
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Christopher Pan
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Lifeng Yuan
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Ying Wan
- Southwest Hospital, Chongqing, China
| | - Qi-Jing Li
- Department of Immunology, Duke University Medical Center, Durham, NC, USA.
| | - Xiao-Fan Wang
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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11
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Activation of the α1β2γ2L GABA A Receptor by Physiological Agonists. Biomolecules 2021; 11:biom11121864. [PMID: 34944508 PMCID: PMC8699469 DOI: 10.3390/biom11121864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/02/2021] [Accepted: 12/09/2021] [Indexed: 11/21/2022] Open
Abstract
The Cl− permeable GABAA receptor is a major contributor to cellular inhibition in the brain. The receptor is normally activated by synaptically-released or ambient GABA but is sensitive to a number of physiological compounds such as β-alanine, taurine, and neurosteroids that, to various degrees, activate the receptor and modulate responses either to the transmitter or to each other. Here, we describe α1β2γ2L GABAA receptor activation and modulation by combinations of orthosteric and allosteric activators. The overall goal was to gain insight into how changes in the levels of endogenous agonists modulate receptor activity and influence cellular inhibition. Experimental observations and simulations are described in the framework of a cyclic concerted transition model. We also provide general analytical solutions for the analysis of electrophysiological data collected in the presence of combinations of active compounds.
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12
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Sexton CA, Penzinger R, Mortensen M, Bright DP, Smart TG. Structural determinants and regulation of spontaneous activity in GABA A receptors. Nat Commun 2021; 12:5457. [PMID: 34526505 PMCID: PMC8443696 DOI: 10.1038/s41467-021-25633-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/24/2021] [Indexed: 11/25/2022] Open
Abstract
GABAA receptors are vital for controlling neuronal excitability and can display significant levels of constitutive activity that contributes to tonic inhibition. However, the mechanisms underlying spontaneity are poorly understood. Here we demonstrate a strict requirement for β3 subunit incorporation into receptors for spontaneous gating, facilitated by α4, α6 and δ subunits. The crucial molecular determinant involves four amino acids (GKER) in the β3 subunit's extracellular domain, which interacts with adjacent receptor subunits to promote transition to activated, open channel conformations. Spontaneous activity is further regulated by β3 subunit phosphorylation and by allosteric modulators including neurosteroids and benzodiazepines. Promoting spontaneous activity reduced neuronal excitability, indicating that spontaneous currents will alter neural network activity. This study demonstrates how regional diversity in GABAA receptor isoform, protein kinase activity, and neurosteroid levels, can impact on tonic inhibition through the modulation of spontaneous GABAA receptor gating.
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Affiliation(s)
- Craig A Sexton
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Reka Penzinger
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Martin Mortensen
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Damian P Bright
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK.
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13
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Electrophysiology of ionotropic GABA receptors. Cell Mol Life Sci 2021; 78:5341-5370. [PMID: 34061215 PMCID: PMC8257536 DOI: 10.1007/s00018-021-03846-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 04/02/2021] [Accepted: 04/23/2021] [Indexed: 10/30/2022]
Abstract
GABAA receptors are ligand-gated chloride channels and ionotropic receptors of GABA, the main inhibitory neurotransmitter in vertebrates. In this review, we discuss the major and diverse roles GABAA receptors play in the regulation of neuronal communication and the functioning of the brain. GABAA receptors have complex electrophysiological properties that enable them to mediate different types of currents such as phasic and tonic inhibitory currents. Their activity is finely regulated by membrane voltage, phosphorylation and several ions. GABAA receptors are pentameric and are assembled from a diverse set of subunits. They are subdivided into numerous subtypes, which differ widely in expression patterns, distribution and electrical activity. Substantial variations in macroscopic neural behavior can emerge from minor differences in structure and molecular activity between subtypes. Therefore, the diversity of GABAA receptors widens the neuronal repertoire of responses to external signals and contributes to shaping the electrical activity of neurons and other cell types.
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14
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Nors JW, Gupta S, Goldschen-Ohm MP. A critical residue in the α 1M2-M3 linker regulating mammalian GABA A receptor pore gating by diazepam. eLife 2021; 10:64400. [PMID: 33591271 PMCID: PMC7899671 DOI: 10.7554/elife.64400] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/15/2021] [Indexed: 01/29/2023] Open
Abstract
Benzodiazepines (BZDs) are a class of widely prescribed psychotropic drugs that modulate activity of GABAA receptors (GABAARs), neurotransmitter-gated ion channels critical for synaptic transmission. However, the physical basis of this modulation is poorly understood. We explore the role of an important gating domain, the α1M2–M3 linker, in linkage between the BZD site and pore gate. To probe energetics of this coupling without complication from bound agonist, we use a gain of function mutant (α1L9'Tβ2γ2L) directly activated by BZDs. We identify a specific residue whose mutation (α1V279A) more than doubles the energetic contribution of the BZD positive modulator diazepam (DZ) to pore opening and also enhances DZ potentiation of GABA-evoked currents in a wild-type background. In contrast, other linker mutations have little effect on DZ efficiency, but generally impair unliganded pore opening. Our observations reveal an important residue regulating BZD-pore linkage, thereby shedding new light on the molecular mechanism of these drugs.
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Affiliation(s)
- Joseph W Nors
- University of Texas at Austin, Department of Neuroscience, Austin, United States
| | - Shipra Gupta
- University of Texas at Austin, Department of Neuroscience, Austin, United States
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15
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Pierce SR, Germann AL, Evers AS, Steinbach JH, Akk G. Reduced Activation of the Synaptic-Type GABA A Receptor Following Prolonged Exposure to Low Concentrations of Agonists: Relationship between Tonic Activity and Desensitization. Mol Pharmacol 2020; 98:762-769. [PMID: 32978327 DOI: 10.1124/molpharm.120.000088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 09/09/2020] [Indexed: 01/16/2023] Open
Abstract
Synaptic GABAA receptors are alternately exposed to short pulses of a high, millimolar concentration of GABA and prolonged periods of low, micromolar concentration of the transmitter. Prior work has indicated that exposure to micromolar concentrations of GABA can both activate the postsynaptic receptors generating sustained low-amplitude current and desensitize the receptors, thereby reducing the peak amplitude of subsequent synaptic response. However, the precise relationship between tonic activation and reduction of peak response is not known. Here, we have measured the effect of prolonged exposure to GABA or the combination of GABA and the neurosteroid allopregnanolone, which was intended to desensitize a fraction of receptors, on a subsequent response to a high concentration of agonist in human α1β3γ2L receptors expressed in Xenopus oocytes. We show that the reduction in the peak amplitude of the post-exposure test response correlates with the open probability of the preceding desensitizing response. Curve fitting of the inhibitory relationship yielded an IC50 of 12.5 µM and a Hill coefficient of -1.61. The activation and desensitization data were mechanistically analyzed in the framework of a three-state Resting-Active-Desensitized model. Using the estimated affinity, efficacy, and desensitization parameters, we calculated the amount of desensitization that would accumulate during a long (2-minute) application of GABA or GABA plus allopregnanolone. The results indicate that accumulation of desensitization depends on the level of activity rather than agonist or potentiator concentration per se. We estimate that in the presence of 1 µM GABA, approximately 5% of α1β3γ2L receptors are functionally eliminated because of desensitization. SIGNIFICANCE STATEMENT: We present an analytical approach to quantify and predict the loss of activatable GABAA receptors due to desensitization in the presence of transmitter and the steroid allopregnanolone. The findings indicate that the peak amplitude of the synaptic response is influenced by ambient GABA and that changes in ambient concentrations of the transmitter and other GABAergic agents can modify tonically and phasically activated synaptic receptors in opposite directions.
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Affiliation(s)
- Spencer R Pierce
- Department of Anesthesiology (S.R.P., A.L.G., A.S.E., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Department of Anesthesiology (S.R.P., A.L.G., A.S.E., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Alex S Evers
- Department of Anesthesiology (S.R.P., A.L.G., A.S.E., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology (S.R.P., A.L.G., A.S.E., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology (S.R.P., A.L.G., A.S.E., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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16
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Germann AL, Reichert DE, Burbridge AB, Pierce SR, Evers AS, Steinbach JH, Akk G. Analysis of Modulation of the ρ1 GABA A Receptor by Combinations of Inhibitory and Potentiating Neurosteroids Reveals Shared and Distinct Binding Sites. Mol Pharmacol 2020; 98:280-291. [PMID: 32675382 DOI: 10.1124/mol.120.119842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 07/07/2020] [Indexed: 11/22/2022] Open
Abstract
The ρ1 GABAA receptor is prominently expressed in the retina and is present at lower levels in several brain regions and other tissues. Although the ρ1 receptor is insensitive to many anesthetic drugs that modulate the heteromeric GABAA receptor, it maintains a rich and multifaceted steroid pharmacology. The receptor is negatively modulated by 5β-reduced steroids, sulfated or carboxylated steroids, and β-estradiol, whereas many 5α-reduced steroids potentiate the receptor. In this study, we analyzed modulation of the human ρ1 GABAA receptor by several neurosteroids, individually and in combination, in the framework of the coagonist concerted transition model. Experiments involving coapplication of two or more steroids revealed that the receptor contains at least three classes of distinct, nonoverlapping sites for steroids, one each for the inhibitory steroids pregnanolone (3α5βP), 3α5βP sulfate, and β-estradiol. The site for 3α5βP can accommodate the potentiating steroid 5αTHDOC. The findings are discussed with respect to receptor modulation by combinations of endogenous neurosteroids. SIGNIFICANCE STATEMENT: The study describes modulation of the ρ1 GABAA receptor by neurosteroids. The coagonist concerted transition model was used to determine overlap of binding sites for several inhibitory and potentiating steroids.
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Affiliation(s)
- Allison L Germann
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - David E Reichert
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Ariel B Burbridge
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Spencer R Pierce
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Alex S Evers
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Departments of Anesthesiology (A.L.G., A.B.B., S.R.P., A.S.E., J.H.S., G.A.) and Radiology (D.E.R.) and the Taylor Family Institute for Innovative Psychiatric Research (D.E.R., A.S.E., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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17
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Germann AL, Steinbach JH, Akk G. Application of the Co-Agonist Concerted Transition Model to Analysis of GABAA Receptor Properties. Curr Neuropharmacol 2020; 17:843-851. [PMID: 30520374 PMCID: PMC7052843 DOI: 10.2174/1570159x17666181206092418] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 11/16/2018] [Accepted: 11/28/2018] [Indexed: 11/22/2022] Open
Abstract
The co-agonist concerted transition model is a simple and practical solution to analyze various aspects of GABAA receptor function. Several model-based predictions have been verified experimentally in previous reports. We review here the practical implications of the model and demonstrate how it enables simplification of the experimental procedure and data analysis to characterize the effects of mutations or properties of novel ligands. Specifically, we show that the value of EC50 and the magnitude of current response are directly affected by basal activity, and that coapplication of a background agonist acting at a distinct site or use of a gain-of-function mutation can be employed to enable studies of weak activators or mutated receptors with impaired gating. We also show that the ability of one GABAergic agent to potentiate the activity elicited by another is a computable value that depends on the level of constitutive activity of the ion channel and the ability of each agonist to directly activate the receptor. Significantly, the model accurately accounts for situations where the paired agonists interact with the same site compared to distinct sites on the receptor.
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Affiliation(s)
- Allison L Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States.,Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, United States
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States.,Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, United States
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18
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Chuang SH, Reddy DS. Isobolographic Analysis of Antiseizure Activity of the GABA Type A Receptor-Modulating Synthetic Neurosteroids Brexanolone and Ganaxolone with Tiagabine and Midazolam. J Pharmacol Exp Ther 2019; 372:285-298. [PMID: 31843812 DOI: 10.1124/jpet.119.261735] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/13/2019] [Indexed: 12/11/2022] Open
Abstract
Epilepsy is often treated with a combination of antiepileptic drugs. Although neurosteroids are potent anticonvulsants, little is known about their combination potential for the treatment of refractory epilepsy. Here, we investigated the combination efficacy of neurosteroids allopregnanolone (AP, brexanolone) and ganaxolone (GX) with the GABA-reuptake inhibitor tiagabine (TG) or the benzodiazepine midazolam (MDZ) on tonic inhibition in dentate gyrus granule cells and seizure protection in the hippocampus kindling and 6-Hz seizure models. Isobolographic analysis indicated that combinations of GX and TG or AP and TG at three standard ratios (1:1, 3:1, and 1:3) displayed significant synergism in augmenting tonic inhibition. In pharmacological studies, GX, AP, and TG produced dose-dependent antiseizure effects in mice (ED50 = 1.46, 4.20, and 0.20 mg/kg, respectively). The combination of GX and TG at the fixed ratio of 1:1 exerted the greatest combination index (CI = 0.53), indicating strong synergistic interaction in seizure protection. In addition, combination regimens of AP and TG showed robust synergism for seizure protection (CI = 0.4). Finally, combination regimens of GX and MDZ elicited synergistic (CI = 0.6) responses for seizure protection. These results demonstrate striking synergism of neurosteroids and TG combination for seizure protection, likely because of their effects at extrasynaptic GABA type A (GABA-A) receptors from TG-induced elevation in GABA levels. Superadditive antiseizure activity of neurosteroid-MDZ combinations may stem from their actions at both synaptic and extrasynaptic GABA-A receptors. Together, these findings provide a potential mechanistic basis for combination potential of neurosteroids with TG or benzodiazepines for the management of refractory epilepsy, status epilepticus, and seizure disorders. SIGNIFICANCE STATEMENT: This paper investigates for the first time the potential synergistic interactions between two neurosteroids with anticonvulsant properties, allopregnanolone (brexanolone) and the very similar synthetic analog, ganaxolone, and two conventional antiepileptic drugs active at GABA type A receptors: the GABA-reuptake inhibitor tiagabine and a benzodiazepine, midazolam. The results demonstrate a synergistic protective effect of neurosteroid-tiagabine combinations, as well as neurosteroid-midazolam regimens in seizure models.
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Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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19
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Pierce SR, Senneff TC, Germann AL, Akk G. Steady-state activation of the high-affinity isoform of the α4β2δ GABA A receptor. Sci Rep 2019; 9:15997. [PMID: 31690811 PMCID: PMC6831628 DOI: 10.1038/s41598-019-52573-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 10/18/2019] [Indexed: 12/18/2022] Open
Abstract
Activation of GABAA receptors consisting of α4, β2 (or β3), and δ subunits is a major contributor to tonic inhibition in several brain regions. The goal of this study was to analyze the function of the α4β2δ receptor in the presence of GABA and other endogenous and clinical activators and modulators under steady-state conditions. We show that the receptor has a high constitutive open probability (~0.1), but is only weakly activated by GABA that has a maximal peak open probability (POpen,peak) of 0.4, taurine (maximal POpen,peak = 0.4), or the endogenous steroid allopregnanolone (maximal POpen,peak = 0.2). The intravenous anesthetic propofol is a full agonist (maximal POpen,peak = 0.99). Analysis of currents using a cyclic three-state Resting-Active-Desensitized model indicates that the maximal steady-state open probability of the α4β2δ receptor is ~0.45. Steady-state open probability in the presence of combinations of GABA, taurine, propofol, allopregnanolone and/or the inhibitory steroid pregnenolone sulfate closely matched predicted open probability calculated assuming energetic additivity. The results suggest that the receptor is active in the presence of physiological concentrations of GABA and taurine, but, surprisingly, that receptor activity is only weakly potentiated by propofol.
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Affiliation(s)
- Spencer R Pierce
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Thomas C Senneff
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Allison L Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,The Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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Sakamoto S, Yamaura K, Numata T, Harada F, Amaike K, Inoue R, Kiyonaka S, Hamachi I. Construction of a Fluorescent Screening System of Allosteric Modulators for the GABA A Receptor Using a Turn-On Probe. ACS CENTRAL SCIENCE 2019; 5:1541-1553. [PMID: 31572781 PMCID: PMC6764212 DOI: 10.1021/acscentsci.9b00539] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Indexed: 05/23/2023]
Abstract
γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system. The fast inhibitory actions of GABA are mainly mediated by GABAA receptors (GABAARs), which are widely recognized as clinically relevant drug targets. However, it remains difficult to create screening systems for drug candidates that act on GABAARs because of the existence of multiple ligand-binding sites and the delicate pentameric structures of GABAARs. We here developed the first turn-on fluorescent imaging probe for GABAARs, which can be used to quantitatively evaluate ligand-receptor interactions under live cell conditions. Using noncovalent labeling of GABAARs with this turn-on probe, a new imaging-based ligand assay system, which allows discovery of positive allosteric modulators (PAMs) for the GABAAR, was successfully constructed. Our system is applicable to high-throughput ligand screening, and we discovered new small molecules that function as PAMs for GABAARs. These results highlight the power of the use of a turn-on fluorescent probe to screen drugs for complicated membrane proteins that cannot be addressed by conventional methods.
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Affiliation(s)
- Seiji Sakamoto
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kei Yamaura
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Tomohiro Numata
- Department
of Physiology, School of Medicine, Fukuoka
University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Fumio Harada
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kazuma Amaike
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Ryuji Inoue
- Department
of Physiology, School of Medicine, Fukuoka
University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Shigeki Kiyonaka
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Itaru Hamachi
- Department
of Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
- ERATO
Innovative Molecular Technology for Neuroscience Project, Japan Science and Technology Agency (JST), Kyoto 615-8530, Japan
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21
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Germann AL, Pierce SR, Senneff TC, Burbridge AB, Steinbach JH, Akk G. Steady-state activation and modulation of the synaptic-type α1β2γ2L GABA A receptor by combinations of physiological and clinical ligands. Physiol Rep 2019; 7:e14230. [PMID: 31549483 PMCID: PMC6757177 DOI: 10.14814/phy2.14230] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 11/24/2022] Open
Abstract
The synaptic α1β2γ2 GABAA receptor is activated phasically by presynaptically released GABA. The receptor is considered to be inactive between synaptic events when exposed to ambient GABA because of its low resting affinity to the transmitter. We tested the hypothesis that a combination of physiological and/or clinical positive allosteric modulators of the GABAA receptor with ambient GABA generates measurable steady-state activity. Recombinant α1β2γ2L GABAA receptors were expressed in Xenopus oocytes and activated by combinations of low concentrations of orthosteric (GABA, taurine) and allosteric (the steroid allopregnanolone, the anesthetic propofol) agonists, in the absence and presence of the inhibitory steroid pregnenolone sulfate. Steady-state activity was analyzed using the three-state cyclic Resting-Active-Desensitized model. We estimate that the steady-state open probability of the synaptic α1β2γ2L GABAA receptor in the presence of ambient GABA (1 μmol/L), taurine (10 μmol/L), and physiological levels of allopregnanolone (0.01 μmol/L) and pregnenolone sulfate (0.1 μmol/L) is 0.008. Coapplication of a clinical concentration of propofol (1 μmol/L) increases the steady-state open probability to 0.03. Comparison of total charge transfer for phasic and tonic activity indicates that steady-state activity can contribute strongly (~20 to >99%) to integrated activity from the synaptic GABAA receptor.
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Affiliation(s)
- Allison L. Germann
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
| | - Spencer R. Pierce
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
| | - Thomas C. Senneff
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
| | - Ariel B. Burbridge
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
| | - Joe Henry Steinbach
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
- Taylor Family Institute for Innovative Psychiatric ResearchWashington University School of MedicineSt. LouisMissouri
| | - Gustav Akk
- Department of AnesthesiologyWashington University School of MedicineSt. LouisMissouri
- Taylor Family Institute for Innovative Psychiatric ResearchWashington University School of MedicineSt. LouisMissouri
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22
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Germann AL, Pierce SR, Burbridge AB, Steinbach JH, Akk G. Steady-State Activation and Modulation of the Concatemeric α1 β2 γ2L GABA A Receptor. Mol Pharmacol 2019; 96:320-329. [PMID: 31263018 DOI: 10.1124/mol.119.116913] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 06/21/2019] [Indexed: 12/19/2022] Open
Abstract
The two-state coagonist model has been successfully used to analyze and predict peak current responses of the γ-aminobutyric acid type A (GABAA) receptor. The goal of the present study was to provide a model-based description of GABAA receptor activity under steady-state conditions after desensitization has occurred. We describe the derivation and properties of the cyclic three-state resting-active-desensitized (RAD) model. The relationship of the model to receptor behavior was tested using concatemeric α1β2γ2 GABAA receptors expressed in Xenopus oocytes. The receptors were activated by the orthosteric agonists GABA or β-alanine, the allosteric agonist propofol, or combinations of GABA, propofol, pentobarbital, and the steroid allopregnanolone, and the observed steady-state responses were compared with those predicted by the model. A modified RAD model was employed to analyze and describe the actions on steady-state current of the inhibitory steroid pregnenolone sulfate. The findings indicate that the steady-state activity in the presence of multiple active agents that interact with distinct binding sites follows standard energetic additivity. The derived equations enable prediction of peak and steady-state activity in the presence of orthosteric and allosteric agonists, and the inhibitory steroid pregnenolone sulfate. SIGNIFICANCE STATEMENT: The study describes derivation and properties of a three-state resting-active-desensitized model. The model and associated equations can be used to analyze and predict peak and steady-state activity in the presence of one or more active agents.
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Affiliation(s)
- Allison L Germann
- Department of Anesthesiology (A.L.G., S.R.P., A.B.B., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Spencer R Pierce
- Department of Anesthesiology (A.L.G., S.R.P., A.B.B., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Ariel B Burbridge
- Department of Anesthesiology (A.L.G., S.R.P., A.B.B., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology (A.L.G., S.R.P., A.B.B., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology (A.L.G., S.R.P., A.B.B., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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23
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Shin DJ, Germann AL, Covey DF, Steinbach JH, Akk G. Analysis of GABA A Receptor Activation by Combinations of Agonists Acting at the Same or Distinct Binding Sites. Mol Pharmacol 2018; 95:70-81. [PMID: 30337372 DOI: 10.1124/mol.118.113464] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 10/17/2018] [Indexed: 11/22/2022] Open
Abstract
Under both physiologic and clinical conditions GABAA receptors are exposed to multiple agonists, including the transmitter GABA, endogenous or exogenous neuroactive steroids, and various GABAergic anesthetic and sedative drugs. The functional output of the receptor reflects the interplay among all active agents. We have investigated the activation of the concatemeric α1β2γ2L GABAA receptor by combinations of agonists. Simulations of receptor activity using the coagonist concerted transition model demonstrate that the response amplitude in the presence of agonist combinations is highly dependent on whether the paired agonists interact with the same or distinct sites. The experimental data for receptor activation by agonist combinations were in agreement with the established views of the overlap of binding sites for several pairs of orthosteric (GABA, β-alanine, and piperidine-4-sulfonic acid) and/or allosteric agents (propofol, pentobarbital, and several neuroactive steroids). Conversely, the degree of potentiation when two GABAergic agents are coapplied can be used to determine whether the compounds act by binding to the same or distinct sites. We show that common interaction sites mediate the actions of 5α- and 5β-reduced neuroactive steroids, and natural and enantiomeric steroids. Furthermore, the results indicate that the anesthetics propofol and pentobarbital interact with partially shared binding sites. We propose that the findings may be used to predict the efficacy of drug mixtures in combination therapy and thus have potential clinical relevance.
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Affiliation(s)
- Daniel J Shin
- Departments of Anesthesiology (D.J.S., A.L.G., J.H.S., G.A.) and Developmental Biology (D.F.C.), and the Taylor Family Institute for Innovative Psychiatric Research (D.F.C., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Departments of Anesthesiology (D.J.S., A.L.G., J.H.S., G.A.) and Developmental Biology (D.F.C.), and the Taylor Family Institute for Innovative Psychiatric Research (D.F.C., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Douglas F Covey
- Departments of Anesthesiology (D.J.S., A.L.G., J.H.S., G.A.) and Developmental Biology (D.F.C.), and the Taylor Family Institute for Innovative Psychiatric Research (D.F.C., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Departments of Anesthesiology (D.J.S., A.L.G., J.H.S., G.A.) and Developmental Biology (D.F.C.), and the Taylor Family Institute for Innovative Psychiatric Research (D.F.C., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Departments of Anesthesiology (D.J.S., A.L.G., J.H.S., G.A.) and Developmental Biology (D.F.C.), and the Taylor Family Institute for Innovative Psychiatric Research (D.F.C., J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri
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24
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Steinbach JH, Akk G. Applying the Monod-Wyman-Changeux Allosteric Activation Model to Pseudo-Steady-State Responses from GABA A Receptors. Mol Pharmacol 2018; 95:106-119. [PMID: 30333132 DOI: 10.1124/mol.118.113787] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/12/2018] [Indexed: 12/16/2022] Open
Abstract
The Monod-Wyman-Changeux (MWC) cyclic model was described as a kinetic scheme to explain enzyme function and modulation more than 50 years ago and was proposed as a model for understanding the activation of transmitter-gated channels soon afterward. More recently, the MWC model has been used to describe the activation of the GABAA receptor by the transmitter, GABA, and drugs that bind to separate sites on the receptor. It is most interesting that the MWC formalism can also describe the interactions among drugs that activate the receptor. In this review, we describe properties of the MWC model that have been explored experimentally using the GABAA receptor, summarize analytical expressions for activation and interaction for drugs, and briefly review experimental results.
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Affiliation(s)
- Joe Henry Steinbach
- Department of Anesthesiology, and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology, and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri
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25
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Enhanced GABAergic actions resulting from the coapplication of the steroid 3α-hydroxy-5α-pregnane-11,20-dione (alfaxalone) with propofol or diazepam. Sci Rep 2018; 8:10341. [PMID: 29985445 PMCID: PMC6037692 DOI: 10.1038/s41598-018-28754-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 06/29/2018] [Indexed: 11/09/2022] Open
Abstract
Many GABAergic drugs are in clinical use as anesthetics, sedatives, or anxiolytics. We have investigated the actions of the combinations of the neuroactive steroid 3α-hydroxy-5α-pregnane-11,20-dione (alfaxalone) with the intravenous anesthetic propofol or the benzodiazepine diazepam. The goal of the study was to determine whether coapplication of alfaxalone reduces the effective doses and concentrations of propofol and diazepam. Behavioral effects of alfaxalone, propofol, diazepam, and the combinations of the drugs were evaluated during a 30-min activity test in mice. Functional effects of the individual drugs and drug combinations were tested by measuring the decay times of spontaneous inhibitory postsynaptic currents in rat hippocampal neurons, and peak current responses from heterologously expressed concatemeric α1β2γ2L GABAA receptors. Co-administration of alfaxalone increased the sedative actions of propofol and diazepam in mice. The combination of alfaxalone with propofol or diazepam increased the decay times of sIPSCs and shifted the concentration-response relationships for GABA-activated receptors to lower transmitter concentrations. We infer that alfaxalone acts as a co-agonist to enhance the GABAergic effects of propofol and diazepam. We propose that co-administration of alfaxalone, and possibly other neuroactive steroids, can be employed to reduce dosage requirements for propofol and diazepam.
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26
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Olsen RW. GABA A receptor: Positive and negative allosteric modulators. Neuropharmacology 2018; 136:10-22. [PMID: 29407219 PMCID: PMC6027637 DOI: 10.1016/j.neuropharm.2018.01.036] [Citation(s) in RCA: 194] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 01/23/2018] [Accepted: 01/25/2018] [Indexed: 12/11/2022]
Abstract
gamma-Aminobutyric acid (GABA)-mediated inhibitory neurotransmission and the gene products involved were discovered during the mid-twentieth century. Historically, myriad existing nervous system drugs act as positive and negative allosteric modulators of these proteins, making GABA a major component of modern neuropharmacology, and suggesting that many potential drugs will be found that share these targets. Although some of these drugs act on proteins involved in synthesis, degradation, and membrane transport of GABA, the GABA receptors Type A (GABAAR) and Type B (GABABR) are the targets of the great majority of GABAergic drugs. This discovery is due in no small part to Professor Norman Bowery. Whereas the topic of GABABR is appropriately emphasized in this special issue, Norman Bowery also made many insights into GABAAR pharmacology, the topic of this article. GABAAR are members of the ligand-gated ion channel receptor superfamily, a chloride channel family of a dozen or more heteropentameric subtypes containing 19 possible different subunits. These subtypes show different brain regional and subcellular localization, age-dependent expression, and potential for plastic changes with experience including drug exposure. Not only are GABAAR the targets of agonist depressants and antagonist convulsants, but most GABAAR drugs act at other (allosteric) binding sites on the GABAAR proteins. Some anxiolytic and sedative drugs, like benzodiazepine and related drugs, act on GABAAR subtype-dependent extracellular domain sites. General anesthetics including alcohols and neurosteroids act at GABAAR subunit-interface trans-membrane sites. Ethanol at high anesthetic doses acts on GABAAR subtype-dependent trans-membrane domain sites. Ethanol at low intoxicating doses acts at GABAAR subtype-dependent extracellular domain sites. Thus GABAAR subtypes possess pharmacologically specific receptor binding sites for a large group of different chemical classes of clinically important neuropharmacological agents. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- Richard W Olsen
- Department of Molecular & Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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27
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Germann AL, Shin DJ, Kuhrau CR, Johnson AD, Evers AS, Akk G. High Constitutive Activity Accounts for the Combination of Enhanced Direct Activation and Reduced Potentiation in Mutated GABA A Receptors. Mol Pharmacol 2018; 93:468-476. [PMID: 29439087 DOI: 10.1124/mol.117.111435] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 02/07/2018] [Indexed: 11/22/2022] Open
Abstract
GABAA receptors activated by the transmitter GABA are potentiated by several allosterically acting drugs, including the intravenous anesthetic propofol. Propofol can also directly activate the receptor, albeit at higher concentrations. Previous functional studies have identified amino acid residues whose substitution reduces potentiation of GABA-activated receptors by propofol while enhancing the ability of propofol to directly activate the receptor. One interpretation of such observations is that the mutation has specific effects on the sites or processes involved in potentiation or activation. We show here that divergent effects on potentiation and direct activation can be mediated by increased constitutive open probability in the mutant receptor without any specific effect on the interactions between the allosteric drug and the receptor. By simulating GABAA receptor activity using the concerted transition model, we demonstrate that the predicted degree of potentiation is reduced as the level of constitutive activity increases. The model further predicts that a potentiating effect of an allosteric modulator is a computable value that depends on the level of constitutive activity, the amplitude of the response to the agonist, and the amplitude of the direct activating response to the modulator. Specific predictions were confirmed by electrophysiological data from the binary α1β3 and concatemeric ternary β2α1γ2L+β2α1 GABAA receptors. The corollaries of reduced potentiation due to increased constitutive activity are isobolograms that conform to simple additivity and a loss of separation between the concentration-response relationships for direct activation and potentiation.
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Affiliation(s)
- Allison L Germann
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Daniel J Shin
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Christina R Kuhrau
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Alexander D Johnson
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Alex S Evers
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology (A.L.G., D.J.S., C.R.K., A.D.J., A.S.E., G.A.) and Taylor Family Institute for Innovative Psychiatric Research (A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri
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28
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Shin DJ, Germann AL, Johnson AD, Forman SA, Steinbach JH, Akk G. Propofol Is an Allosteric Agonist with Multiple Binding Sites on Concatemeric Ternary GABA A Receptors. Mol Pharmacol 2017; 93:178-189. [PMID: 29192122 DOI: 10.1124/mol.117.110403] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 11/27/2017] [Indexed: 11/22/2022] Open
Abstract
GABAA receptors can be directly activated and potentiated by the intravenous anesthetic propofol. Previous photolabeling, modeling, and functional data have identified two binding domains through which propofol acts on the GABAA receptor. These domains are defined by the β(M286) residue at the β"+"-α"-" interface in the transmembrane region and the β(Y143) residue near the β"-" surface in the junction between the extracellular and transmembrane domains. In the ternary receptor, there are predicted to be two copies of each class of sites, for a total of four sites per receptor. We used β2α1γ2L and β2α1 concatemeric constructs to determine the functional effects of the β(Y143W) and β(M286W) mutations to gain insight into the number of functional binding sites for propofol and the energetic contributions stemming from propofol binding to the individual sites. A mutation of each of the four sites affected the response to propofol, indicating that each of the four sites is functional in the wild-type receptor. The mutations mainly impaired stabilization of the open state by propofol, i.e., reduced gating efficacy. The effects were similar for mutations at either site and were largely additive and independent of the presence of other Y143W or M286W mutations in the receptor. The two classes of sites appeared to differ in affinity for propofol, with the site affected by M286W having about a 2-fold higher affinity. Our analysis indicates there may be one or two additional functionally equivalent binding sites for propofol, other than those modified by substitutions at β(Y143) and β(M286).
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Affiliation(s)
- Daniel J Shin
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
| | - Allison L Germann
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
| | - Alexander D Johnson
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
| | - Stuart A Forman
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
| | - Joe Henry Steinbach
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
| | - Gustav Akk
- Department of Anesthesiology (D.J.S., A.L.G., A.D.J., J.H.S., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (J.H.S., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts (S.A.F.)
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