1
|
Brown E, Swinscoe G, Lefteri DA, Singh R, Moran A, Thompson RF, Maskell D, Beaumont H, Bentham MJ, Donald C, Kohl A, Macdonald A, Ranson N, Foster R, McKimmie CS, Kalli AC, Griffin S. Inhibitors of the small membrane (M) protein viroporin prevent Zika virus infection. eLife 2024; 13:e68404. [PMID: 39177307 PMCID: PMC11449487 DOI: 10.7554/elife.68404] [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: 03/16/2021] [Accepted: 08/22/2024] [Indexed: 08/24/2024] Open
Abstract
Flaviviruses, including Zika virus (ZIKV), are a significant global health concern, yet no licensed antivirals exist to treat disease. The small membrane (M) protein plays well-defined roles during viral egress and remains within virion membranes following release and maturation. However, it is unclear whether M plays a functional role in this setting. Here, we show that M forms oligomeric membrane-permeabilising channels in vitro, with increased activity at acidic pH and sensitivity to the prototypic channel-blocker, rimantadine. Accordingly, rimantadine blocked an early stage of ZIKV cell culture infection. Structure-based channel models, comprising hexameric arrangements of two trans-membrane domain protomers were shown to comprise more stable assemblages than other oligomers using molecular dynamics simulations. Models contained a predicted lumenal rimantadine-binding site, as well as a second druggable target region on the membrane-exposed periphery. In silico screening enriched for repurposed drugs/compounds predicted to bind to either one site or the other. Hits displayed superior potency in vitro and in cell culture compared with rimantadine, with efficacy demonstrably linked to virion-resident channels. Finally, rimantadine effectively blocked ZIKV viraemia in preclinical models, supporting that M constitutes a physiologically relevant target. This could be explored by repurposing rimantadine, or development of new M-targeted therapies.
Collapse
Affiliation(s)
- Emma Brown
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Gemma Swinscoe
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Daniella A Lefteri
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Ravi Singh
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Chemistry, Faculty of Maths and Physical Sciences, University of Leeds, Leeds, United Kingdom
| | - Amy Moran
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Rebecca F Thompson
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Daniel Maskell
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Hannah Beaumont
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Matthew J Bentham
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Claire Donald
- MRC and University of Glasgow Centre for Virus Research, Sir Michael Stoker Building, Glasgow, United Kingdom
| | - Alain Kohl
- MRC and University of Glasgow Centre for Virus Research, Sir Michael Stoker Building, Glasgow, United Kingdom
| | - Andrew Macdonald
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Neil Ranson
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Richard Foster
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Chemistry, Faculty of Maths and Physical Sciences, University of Leeds, Leeds, United Kingdom
| | - Clive S McKimmie
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| | - Antreas C Kalli
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute for Cardiovascular and Metabolic Medicine, Faculty of Medicine and Health, University of Leeds, Leeds, United Kingdom
| | - Stephen Griffin
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom
- Leeds Institute of Medical Research, School of Medicine, Faculty of Medicine and Health, University of Leeds, St James' University Hospital, Leeds, United Kingdom
| |
Collapse
|
2
|
Sikstus S, Benkherouf AY, Soini SL, Uusi-Oukari M. The Influence of AA29504 on GABA A Receptor Ligand Binding Properties and Its Implications on Subtype Selectivity. Neurochem Res 2022; 47:667-678. [PMID: 34727270 PMCID: PMC8847198 DOI: 10.1007/s11064-021-03475-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 09/03/2021] [Accepted: 10/27/2021] [Indexed: 10/26/2022]
Abstract
The unique pharmacological properties of δ-containing γ-aminobutyric acid type A receptors (δ-GABAARs) make them an attractive target for selective and persistent modulation of neuronal excitability. However, the availability of selective modulators targeting δ-GABAARs remains limited. AA29504 ([2-amino-4-(2,4,6-trimethylbenzylamino)-phenyl]-carbamic acid ethyl ester), an analog of K+ channel opener retigabine, acts as an agonist and a positive allosteric modulator (Ago-PAM) of δ-GABAARs. Based on electrophysiological studies using recombinant receptors, AA29504 was found to be a more potent and effective agonist in δ-GABAARs than in γ2-GABAARs. In comparison, AA29504 positively modulated the activity of recombinant δ-GABAARs more effectively than γ2-GABAARs, with no significant differences in potency. The impact of AA29504's efficacy- and potency-associated GABAAR subtype selectivity on radioligand binding properties remain unexplored. Using [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate ([3H]EBOB) binding assay, we found no difference in the modulatory potency of AA29504 on GABA- and THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol)-induced responses between native forebrain GABAARs of wild type and δ knock-out mice. In recombinant receptors expressed in HEK293 cells, AA29504 showed higher efficacy on δ- than γ2-GABAARs in the GABA-independent displacement of [3H]EBOB binding. Interestingly, AA29504 showed a concentration-dependent stimulation of [3H]muscimol binding to γ2-GABAARs, which was absent in δ-GABAARs. This was explained by AA29504 shifting the low-affinity γ2-GABAAR towards a higher affinity desensitized state, thereby rising new sites capable of binding GABAAR agonists with low nanomolar affinity. Hence, the potential of AA29504 to act as a desensitization-modifying allosteric modulator of γ2-GABAARs deserves further investigation for its promising influence on shaping efficacy, duration and plasticity of GABAAR synaptic responses.
Collapse
Affiliation(s)
- Sylvia Sikstus
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Ali Y Benkherouf
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Sanna L Soini
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Mikko Uusi-Oukari
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland.
| |
Collapse
|
3
|
Luo Y, Kusay AS, Jiang T, Chebib M, Balle T. Delta-containing GABA A receptors in pain management: Promising targets for novel analgesics. Neuropharmacology 2021; 195:108675. [PMID: 34153311 DOI: 10.1016/j.neuropharm.2021.108675] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 06/01/2021] [Accepted: 06/11/2021] [Indexed: 12/26/2022]
Abstract
Communication between nerve cells depends on the balance between excitatory and inhibitory circuits. GABA, the major inhibitory neurotransmitter, regulates this balance and insufficient GABAergic activity is associated with numerous neuropathological disorders including pain. Of the various GABAA receptor subtypes, the δ-containing receptors are particularly interesting drug targets in management of chronic pain. These receptors are pentameric ligand-gated ion channels composed of α, β and δ subunits and can be activated by ambient levels of GABA to generate tonic conductance. However, only a few ligands preferentially targeting δ-containing GABAA receptors have so far been identified, limiting both pharmacological understanding and drug-discovery efforts, and more importantly, understanding of how they affect pain pathways. Here, we systemically review and discuss the known drugs and ligands with analgesic potential targeting δ-containing GABAA receptors and further integrate the biochemical nature of the receptors with clinical perspectives in pain that might generate interest among researchers and clinical physicians to encourage analgesic discovery efforts leading to more efficient therapies.
Collapse
Affiliation(s)
- Yujia Luo
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia; Brain and Mind Centre, The University of Sydney, Camperdown, NSW, 2050, Australia
| | - Ali Saad Kusay
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia; Brain and Mind Centre, The University of Sydney, Camperdown, NSW, 2050, Australia
| | - Tian Jiang
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia; Brain and Mind Centre, The University of Sydney, Camperdown, NSW, 2050, Australia
| | - Mary Chebib
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia; Brain and Mind Centre, The University of Sydney, Camperdown, NSW, 2050, Australia
| | - Thomas Balle
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia; Brain and Mind Centre, The University of Sydney, Camperdown, NSW, 2050, Australia.
| |
Collapse
|
4
|
Falk-Petersen CB, Tsonkov TM, Nielsen MS, Harpsøe K, Bundgaard C, Frølund B, Kristiansen U, Gloriam DE, Wellendorph P. Discovery of a new class of orthosteric antagonists with nanomolar potency at extrasynaptic GABA A receptors. Sci Rep 2020; 10:10078. [PMID: 32572053 PMCID: PMC7308271 DOI: 10.1038/s41598-020-66821-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/20/2020] [Indexed: 02/06/2023] Open
Abstract
Brain GABAΑ receptors are ionotropic receptors belonging to the class of Cys-loop receptors and are important drug targets for the treatment of anxiety and sleep disorders. By screening a compound library (2,112 compounds) at recombinant human α4β1δ GABAΑ receptors heterologously expressed in a HEK cell line, we identified a scaffold of spirocyclic compounds with nanomolar antagonist activity at GABAΑ receptors. The initial screening hit 2027 (IC50 of 1.03 μM) was used for analogue search resulting in 018 (IC50 of 0.088 μM). 018 was most potent at α3,4,5-subunit containing receptors, thus showing preference for forebrain-expressed extrasynaptic receptors. Schild analysis of 018 at recombinant human α4β1δ receptors and displacement of [3H]muscimol binding in rat cortical homogenate independently confirmed a competitive profile. The antagonist profile of 018 was further validated by whole-cell patch-clamp electrophysiology, where kinetic studies revealed a slow dissociation rate and a shallow hill slope was observed. Membrane permeability studies showed that 2027 and 018 do not cross membranes, thus making the compounds less attractive for studying central GABAΑ receptors effects, but conversely more attractive as tool compounds in relation to emerging peripheral GABAΑ receptor-mediated effects of GABA e.g. in the immune system.
Collapse
Affiliation(s)
- Christina Birkedahl Falk-Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - Tsonko M Tsonkov
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - Malene Sofie Nielsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - Kasper Harpsøe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | | | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - Uffe Kristiansen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - David E Gloriam
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen Ø, Denmark.
| |
Collapse
|
5
|
Belelli D, Hogenkamp D, Gee KW, Lambert JJ. Realising the therapeutic potential of neuroactive steroid modulators of the GABA A receptor. Neurobiol Stress 2019; 12:100207. [PMID: 32435660 PMCID: PMC7231973 DOI: 10.1016/j.ynstr.2019.100207] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 12/19/2019] [Indexed: 01/27/2023] Open
Abstract
In the 1980s particular endogenous metabolites of progesterone and of deoxycorticosterone were revealed to be potent, efficacious, positive allosteric modulators (PAMs) of the GABAA receptor (GABAAR). These reports were followed by the discovery that such steroids may be synthesised not only in peripheral endocrine glands, but locally in the central nervous system (CNS), to potentially act as paracrine, or autocrine "neurosteroid" messengers, thereby fine tuning neuronal inhibition. These discoveries triggered enthusiasm to elucidate the physiological role of such neurosteroids and explore whether their levels may be perturbed in particular psychiatric and neurological disorders. In preclinical studies the GABAAR-active steroids were shown to exhibit anxiolytic, anticonvulsant, analgesic and sedative properties and at relatively high doses to induce a state of general anaesthesia. Collectively, these findings encouraged efforts to investigate the therapeutic potential of neurosteroids and related synthetic analogues. However, following over 30 years of investigation, realising their possible medical potential has proved challenging. The recent FDA approval for the natural neurosteroid allopregnanolone (brexanolone) to treat postpartum depression (PPD) should trigger renewed enthusiasm for neurosteroid research. Here we focus on the influence of neuroactive steroids on GABA-ergic signalling and on the challenges faced in developing such steroids as anaesthetics, sedatives, analgesics, anticonvulsants, antidepressants and as treatments for neurodegenerative disorders.
Collapse
Affiliation(s)
- Delia Belelli
- Systems Medicine, Neuroscience, Mail Box 6, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, United Kingdom
| | - Derk Hogenkamp
- Department of Pharmacology, 110C Med Surge1, Mail Code 4625, University of California, Irvine, School of Medicine, Irvine, CA, 92697, USA
| | - Kelvin W Gee
- Department of Pharmacology, 110C Med Surge1, Mail Code 4625, University of California, Irvine, School of Medicine, Irvine, CA, 92697, USA
| | - Jeremy J Lambert
- Systems Medicine, Neuroscience, Mail Box 6, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, United Kingdom
| |
Collapse
|
6
|
Neumann S, Boothman-Burrell L, Gowing EK, Jacobsen TA, Ahring PK, Young SL, Sandager-Nielsen K, Clarkson AN. The Delta-Subunit Selective GABA A Receptor Modulator, DS2, Improves Stroke Recovery via an Anti-inflammatory Mechanism. Front Neurosci 2019; 13:1133. [PMID: 31736685 PMCID: PMC6828610 DOI: 10.3389/fnins.2019.01133] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 10/07/2019] [Indexed: 12/22/2022] Open
Abstract
Inflammatory processes are known to contribute to tissue damage in the central nervous system (CNS) across a broad range of neurological conditions, including stroke. Gamma amino butyric acid (GABA), the main inhibitory neurotransmitter in the CNS, has been implicated in modulating peripheral immune responses by acting on GABA A receptors on antigen-presenting cells and lymphocytes. Here, we investigated the effects and mechanism of action of the delta-selective compound, DS2, to improve stroke recovery and modulate inflammation. We report a decrease in nuclear factor (NF)-κB activation in innate immune cells over a concentration range in vitro. Following a photochemically induced motor cortex stroke, treatment with DS2 at 0.1 mg/kg from 1 h post-stroke significantly decreased circulating tumor necrosis factor (TNF)-α, interleukin (IL)-17, and IL-6 levels, reduced infarct size and improved motor function in mice. Free brain concentrations of DS2 were found to be lower than needed for robust modulation of central GABA A receptors and were not affected by the presence and absence of elacridar, an inhibitor of both P-glycoprotein and breast cancer resistance protein (BCRP). Finally, as DS2 appears to dampen peripheral immune activation and only shows limited brain exposure, we assessed the role of DS2 to promote functional recovery after stroke when administered from 3-days after the stroke. Treatment with DS2 from 3-days post-stroke improved motor function on the grid-walking, but not on the cylinder task. These data highlight the need to further develop subunit-selective compounds to better understand change in GABA receptor signaling pathways both centrally and peripherally. Importantly, we show that GABA compounds such as DS2 that only shows limited brain exposure can still afford significant protection and promote functional recovery most likely via modulation of peripheral immune cells and could be given as an adjunct treatment.
Collapse
Affiliation(s)
- Silke Neumann
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.,Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Lily Boothman-Burrell
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Emma K Gowing
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | | | - Philip K Ahring
- School of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Sarah L Young
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | | | - Andrew N Clarkson
- Department of Anatomy, Brain Health Research Centre, Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| |
Collapse
|
7
|
Clarkson AN, Boothman-Burrell L, Dósa Z, Nagaraja RY, Jin L, Parker K, van Nieuwenhuijzen PS, Neumann S, Gowing EK, Gavande N, Ahring PK, Holm MM, Hanrahan JR, Nicolazzo JA, Jensen K, Chebib M. The flavonoid, 2'-methoxy-6-methylflavone, affords neuroprotection following focal cerebral ischaemia. J Cereb Blood Flow Metab 2019; 39:1266-1282. [PMID: 29376464 PMCID: PMC6668512 DOI: 10.1177/0271678x18755628] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tonic inhibitory currents, mediated by extrasynaptic GABAA receptors, are elevated at a delay following stroke. Flavonoids minimise the extent of cellular damage following stroke, but little is known about their mode of action. We demonstrate that the flavonoid, 2'-methoxy-6-methylflavone (0.1-10 µM; 2'MeO6MF), increases GABAA receptor tonic currents presumably via δ-containing GABAA receptors. Treatment with 2'MeO6MF 1-6 h post focal ischaemia dose dependently decreases infarct volume and improves functional recovery. The effect of 2'MeO6MF was attenuated in δ-/- mice, indicating that the effects of the flavonoid were mediated via δ-containing GABAA receptors. Further, as flavonoids have been shown to have multiple modes of action, we investigated the anti-inflammatory effects of 2'MeO6MF. Using a macrophage cell line, we show that 2'MeO6MF can dampen an LPS-induced elevation in NFkB activity. Assessment of vehicle-treated stroke animals revealed a significant increase in circulating IL1β, TNFα and IFγ levels. Treatment with 2'MeO6MF dampened the stroke-induced increase in circulating cytokines, which was blocked in the presence of the pan-AKT inhibitor, GSK690693. These studies support the hypothesis that compounds that potentiate tonic inhibition via δ-containing GABAA receptors soon after stroke can afford neuroprotection.
Collapse
Affiliation(s)
- Andrew N Clarkson
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand.,2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Lily Boothman-Burrell
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Zita Dósa
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Raghavendra Y Nagaraja
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Liang Jin
- 4 Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Kim Parker
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | | | - Silke Neumann
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand.,5 Department of Pathology, University of Otago, Dunedin, New Zealand
| | - Emma K Gowing
- 1 Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin, New Zealand
| | - Navnath Gavande
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Philip K Ahring
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Mai M Holm
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Jane R Hanrahan
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| | - Joseph A Nicolazzo
- 4 Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Kimmo Jensen
- 3 Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Mary Chebib
- 2 Faculty of Pharmacy, The University of Sydney, Sydney, Australia
| |
Collapse
|
8
|
Solomon VR, Tallapragada VJ, Chebib M, Johnston G, Hanrahan JR. GABA allosteric modulators: An overview of recent developments in non-benzodiazepine modulators. Eur J Med Chem 2019; 171:434-461. [DOI: 10.1016/j.ejmech.2019.03.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 02/17/2019] [Accepted: 03/17/2019] [Indexed: 01/13/2023]
|
9
|
Chemogenetic Isolation Reveals Synaptic Contribution of δ GABA A Receptors in Mouse Dentate Granule Neurons. J Neurosci 2018; 38:8128-8145. [PMID: 30076210 DOI: 10.1523/jneurosci.0799-18.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 11/21/2022] Open
Abstract
Two major GABAA receptor classes mediate ionotropic GABA signaling, those containing a δ subunit and those with a γ2 subunit. The classical viewpoint equates γ2-containing receptors with IPSCs and δ-containing receptors with tonic inhibition because of differences in receptor localization, but significant questions remain because the populations cannot be pharmacologically separated. We removed this barrier using gene editing to confer a point mutation on the δ subunit in mice, rendering receptors containing the subunit picrotoxin resistant. By pharmacologically isolating δ-containing receptors, our results demonstrate their contribution to IPSCs in dentate granule neurons and weaker contributions to thalamocortical IPSCs. Despite documented extrasynaptic localization, we found that receptor localization does not preclude participation in isolated IPSCs, including mIPSCs. Further, phasic inhibition from δ subunit-containing receptors strongly inhibited summation of EPSPs, whereas tonic activity had little impact. In addition to any role that δ-containing receptors may play in canonical tonic inhibition, our results highlight a previously underestimated contribution of δ-containing receptors to phasic inhibition.SIGNIFICANCE STATEMENT GABAA receptors play key roles in transient and tonic inhibition. The prevailing view suggests that synaptic γ2-containing GABAA receptors drive phasic inhibition, whereas extrasynaptic δ-containing receptors mediate tonic inhibition. To re-evaluate the impact of δ receptors, we took a chemogenetic approach that offers a sensitive method to probe the synaptic contribution of δ-containing receptors. Our results reveal that localization does not strongly limit the contribution of δ receptors to IPSCs and that δ receptors make an unanticipated robust contribution to phasic inhibition.
Collapse
|
10
|
Delineation of the functional properties and the mechanism of action of AA29504, an allosteric agonist and positive allosteric modulator of GABA A receptors. Biochem Pharmacol 2018; 150:305-319. [DOI: 10.1016/j.bcp.2018.02.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 02/13/2018] [Indexed: 11/22/2022]
|
11
|
Falk-Petersen CB, Søgaard R, Madsen KL, Klein AB, Frølund B, Wellendorph P. Development of a Robust Mammalian Cell-based Assay for Studying Recombinant α 4 β 1/3 δ GABA A Receptor Subtypes. Basic Clin Pharmacol Toxicol 2017; 121:119-129. [PMID: 28299900 DOI: 10.1111/bcpt.12778] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 03/10/2017] [Indexed: 11/29/2022]
Abstract
δ-Containing GABAA receptors are located extrasynaptically and mediate tonic inhibition. Their involvement in brain physiology positions them as interesting drug targets. There is thus a continued interest in establishing reliable recombinant expression systems for δ-containing GABAA receptors. Inconveniently, the recombinant expression of especially α4 β1/3 δ receptors has been found to be notoriously difficult, resulting in mixed receptor populations and/or stoichiometries and differential pharmacology depending on the expression system used. With the aim of developing a facile and robust 96-well format cell-based assay for extrasynaptic α4 β1/3 δ receptors, we have engineered and validated a HEK293 Flp-In™ cell line stably expressing the human GABAA δ-subunit. Upon co-transfection of α4 and β1/3 subunits, at optimized ratios, we have established a well-defined system for expressing α4 β1/3 δ receptors and used the fluorescence-based FLIPR Membrane Potential (FMP) assay to evaluate their pharmacology. Using the known reference compounds GABA and THIP, ternary α4 β1/3 δ and binary α4 β1/3 receptors could be distinguished based on potency and kinetic profiles but not efficacy. As expected, DS2 was able to potentiate only δ-containing receptors, whereas Zn2+ had an inhibitory effect only at binary receptors. By contrast, the hitherto reported δ-selective compounds, AA29504 and 3-OH-2'MeO6MF, were non-selective. The expression system was further validated using patch clamp electrophysiology, in which the superagonism of THIP was confirmed. The established FMP assay set-up, based on transient expression of human α4 and β1/3 subunits into a δ-subunit stable HEK293 Flp-In™ cell line, portrays a simple 96-well format assay as a useful supplement to electrophysiological recordings on δ-containing GABAA receptors.
Collapse
Affiliation(s)
- Christina B Falk-Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Rikke Søgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kenneth L Madsen
- Molecular Neuropharmacology and Genetics Laboratory, Lundbeck Foundation Center for Biomembranes in Nanomedicine, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Anders B Klein
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
12
|
Lau BK, Karim S, Goodchild AK, Vaughan CW, Drew GM. Menthol enhances phasic and tonic GABAA receptor-mediated currents in midbrain periaqueductal grey neurons. Br J Pharmacol 2014; 171:2803-13. [PMID: 24460753 DOI: 10.1111/bph.12602] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 01/05/2014] [Accepted: 01/19/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND AND PURPOSE Menthol, a naturally occurring compound in the essential oil of mint leaves, is used for its medicinal, sensory and fragrant properties. Menthol acts via transient receptor potential (TRPM8 and TRPA1) channels and as a positive allosteric modulator of recombinant GABAA receptors. Here, we examined the actions of menthol on GABAA receptor-mediated currents in intact midbrain slices. EXPERIMENTAL APPROACH Whole-cell voltage-clamp recordings were made from periaqueductal grey (PAG) neurons in midbrain slices from rats to determine the effects of menthol on GABAA receptor-mediated phasic IPSCs and tonic currents. KEY RESULTS Menthol (150-750 μM) produced a concentration-dependent prolongation of spontaneous GABAA receptor-mediated IPSCs, but not non-NMDA receptor-mediated EPSCs throughout the PAG. Menthol actions were unaffected by TRPM8 and TRPA1 antagonists, tetrodotoxin and the benzodiazepine antagonist, flumazenil. Menthol also enhanced a tonic current, which was sensitive to the GABAA receptor antagonists, picrotoxin (100 μM), bicuculline (30 μM) and Zn(2+) (100 μM), but unaffected by gabazine (10 μM) and a GABAC receptor antagonist, 1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid hydrate (TPMPA; 50 μM). In addition, menthol potentiated currents induced by the extrasynaptic GABAA receptor agonist THIP/gaboxadol (10 μM). CONCLUSIONS AND IMPLICATIONS These results suggest that menthol positively modulates both synaptic and extrasynaptic populations of GABAA receptors in native PAG neurons. The development of agents that potentiate GABAA -mediated tonic currents and phasic IPSCs in a manner similar to menthol could provide a basis for novel GABAA -related pharmacotherapies.
Collapse
Affiliation(s)
- Benjamin K Lau
- Pain Management Research Institute, Kolling Institute of Medical Research, Northern Clinical School, The University of Sydney at Royal North Shore Hospital, St Leonards, NSW, Australia
| | | | | | | | | |
Collapse
|
13
|
Altered expression of δGABAA receptors in health and disease. Neuropharmacology 2014; 88:24-35. [PMID: 25128850 DOI: 10.1016/j.neuropharm.2014.08.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 07/28/2014] [Accepted: 08/03/2014] [Indexed: 01/08/2023]
Abstract
γ-Aminobutyric acid type A receptors that contain the δ subunit (δGABAA receptors) are expressed in multiple types of neurons throughout the central nervous system, where they generate a tonic conductance that shapes neuronal excitability and synaptic plasticity. These receptors regulate a variety of important behavioral functions, including memory, nociception and anxiety, and may also modulate neurogenesis. Given their functional significance, δGABAA receptors are considered to be novel therapeutic targets for the treatment of memory dysfunction, pain, insomnia and mood disorders. These receptors are highly responsive to sedative-hypnotic drugs, general anesthetics and neuroactive steroids. A further remarkable feature of δGABAA receptors is that their expression levels are highly dynamic and fluctuate substantially during development and in response to physiological changes including stress and the reproductive cycle. Furthermore, the expression of these receptors varies in pathological conditions such as alcoholism, fragile X syndrome, epilepsy, depression, schizophrenia, mood disorders and traumatic brain injury. Such fluctuations in receptor expression have significant consequences for behavior and may alter responsiveness to therapeutic drugs. This review considers the alterations in the expression of δGABAA receptors associated with various states of health and disease and the implications of these changes.
Collapse
|
14
|
Boddum K, Frølund B, Kristiansen U. The GABAA Antagonist DPP-4-PIOL Selectively Antagonises Tonic over Phasic GABAergic Currents in Dentate Gyrus Granule Cells. Neurochem Res 2014; 39:2078-84. [DOI: 10.1007/s11064-014-1397-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 07/18/2014] [Accepted: 07/18/2014] [Indexed: 11/30/2022]
|
15
|
Ye Z, McGee TP, Houston CM, Brickley SG. The contribution of δ subunit-containing GABAA receptors to phasic and tonic conductance changes in cerebellum, thalamus and neocortex. Front Neural Circuits 2013; 7:203. [PMID: 24391550 PMCID: PMC3870274 DOI: 10.3389/fncir.2013.00203] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/09/2013] [Indexed: 12/13/2022] Open
Abstract
We have made use of the δ subunit-selective allosteric modulator DS2 (4-chloro-N-[2-(2-thienyl)imidazo[1,2-a]pyridine-3-yl benzamide) to assay the contribution of δ-GABAARs to tonic and phasic conductance changes in the cerebellum, thalamus and neocortex. In cerebellar granule cells, an enhancement of the tonic conductance was observed for DS2 and the orthosteric agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol). As expected, DS2 did not alter the properties of GABAA receptor-mediated inhibitory postsynaptic synaptic conductances (IPSCs) supporting a purely extrasynaptic role for δ-GABAARs in cerebellar granule cells. DS2 also enhanced the tonic conductance recorded from thalamic relay neurons of the visual thalamus with no alteration in IPSC properties. However, in addition to enhancing the tonic conductance DS2 also slowed the decay of IPSCs recorded from layer II/III neocortical neurons. A slowing of the IPSC decay also occurred in the presence of the voltage-gated sodium channel blocker TTX. Moreover, under conditions of reduced GABA release the ability of DS2 to enhance the tonic conductance was attenuated. These results indicate that δ-GABAARs can be activated following vesicular GABA release onto neocortical neurons and that the actions of DS2 on the tonic conductance may be influenced by the ambient GABA levels present in particular brain regions.
Collapse
Affiliation(s)
- Zhiwen Ye
- Biophysics Section, Department of Life Sciences, Imperial College London London, UK
| | - Thomas P McGee
- Department of Neuroscience, Physiology and Pharmacology, University College London London, UK
| | - Catriona M Houston
- Biophysics Section, Department of Life Sciences, Imperial College London London, UK
| | - Stephen G Brickley
- Biophysics Section, Department of Life Sciences, Imperial College London London, UK
| |
Collapse
|
16
|
Carver CM, Reddy DS. Neurosteroid interactions with synaptic and extrasynaptic GABA(A) receptors: regulation of subunit plasticity, phasic and tonic inhibition, and neuronal network excitability. Psychopharmacology (Berl) 2013; 230:151-88. [PMID: 24071826 PMCID: PMC3832254 DOI: 10.1007/s00213-013-3276-5] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 08/29/2013] [Indexed: 12/25/2022]
Abstract
RATIONALE Neurosteroids are steroids synthesized within the brain with rapid effects on neuronal excitability. Allopregnanolone, allotetrahydrodeoxycorticosterone, and androstanediol are three widely explored prototype endogenous neurosteroids. They have very different targets and functions compared to conventional steroid hormones. Neuronal γ-aminobutyric acid (GABA) type A (GABA(A)) receptors are one of the prime molecular targets of neurosteroids. OBJECTIVE This review provides a critical appraisal of recent advances in the pharmacology of endogenous neurosteroids that interact with GABA(A) receptors in the brain. Neurosteroids possess distinct, characteristic effects on the membrane potential and current conductance of the neuron, mainly via potentiation of GABA(A) receptors at low concentrations and direct activation of receptor chloride channel at higher concentrations. The GABA(A) receptor mediates two types of inhibition, now characterized as synaptic (phasic) and extrasynaptic (tonic) inhibition. Synaptic release of GABA results in the activation of low-affinity γ2-containing synaptic receptors, while high-affinity δ-containing extrasynaptic receptors are persistently activated by the ambient GABA present in the extracellular fluid. Neurosteroids are potent positive allosteric modulators of synaptic and extrasynaptic GABA(A) receptors and therefore enhance both phasic and tonic inhibition. Tonic inhibition is specifically more sensitive to neurosteroids. The resulting tonic conductance generates a form of shunting inhibition that controls neuronal network excitability, seizure susceptibility, and behavior. CONCLUSION The growing understanding of the mechanisms of neurosteroid regulation of the structure and function of the synaptic and extrasynaptic GABA(A) receptors provides many opportunities to create improved therapies for sleep, anxiety, stress, epilepsy, and other neuropsychiatric conditions.
Collapse
Affiliation(s)
- Chase Matthew Carver
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, 2008 Medical Research and Education Building, 8447 State Highway 47, Bryan, TX, 77807-3260, USA
| | | |
Collapse
|
17
|
Egawa K, Fukuda A. Pathophysiological power of improper tonic GABA(A) conductances in mature and immature models. Front Neural Circuits 2013; 7:170. [PMID: 24167475 PMCID: PMC3807051 DOI: 10.3389/fncir.2013.00170] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/28/2013] [Indexed: 11/25/2022] Open
Abstract
High-affinity extrasynaptic gamma-aminobutyric acid A (GABAA) receptors are tonically activated by low and consistent levels of ambient GABA, mediating chronic inhibition against neuronal excitability (tonic inhibition) and the modulation of neural development. Synaptic (phasic) inhibition is spatially and temporally precise compared with tonic inhibition, which provides blunt yet strong integral inhibitory force by shunting electrical signaling. Although effects of acute modification of tonic inhibition are known, its pathophysiological significance remains unclear because homeostatic regulation of neuronal excitability can compensate for long-term deficit of extrasynaptic GABAA receptor activation. Nevertheless, tonic inhibition is of great interest for its pathophysiological involvement in central nervous system (CNS) diseases and thus as a therapeutic target. Together with the development of experimental models for various pathological states, recent evidence demonstrates such pathological involvements of tonic inhibition in neuronal dysfunction. This review focuses on the recent progress of tonic activation of GABAA conductance on the development and pathology of the CNS. Findings indicate that neuronal function in various brain regions are exacerbated with a gain or loss of function of tonic inhibition by GABA spillover. Disturbance of tonic GABAA conductance mediated by non-synaptic ambient GABA may result in brain mal-development. Therefore, various pathological states (epilepsy, motor dysfunctions, psychiatric disorders, and neurodevelopmental disorders) may be partly attributable to abnormal tonic GABAA conductances. Thus, the tone of tonic conductance and level of ambient GABA may be precisely tuned to maintain the regular function and development of the CNS. Therefore, receptor expression and factors for regulating the ambient GABA concentration are highlighted to gain a deeper understanding of pathology and therapeutic strategy for CNS diseases.
Collapse
Affiliation(s)
- Kiyoshi Egawa
- Department of Neurology, Massachusetts General Hospital Charlestown, MA, USA ; Department of Pediatrics, Hokkaido University Graduate School of Medicine Sapporo, Japan
| | | |
Collapse
|