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Scheper M, Sørensen FNF, Ruffolo G, Gaeta A, Lissner LJ, Anink JJ, Korshunova I, Jansen FE, Riney K, van Hecke W, Mühlebner A, Khodosevich K, Schubert D, Palma E, Mills JD, Aronica E. Impaired GABAergic regulation and developmental immaturity in interneurons derived from the medial ganglionic eminence in the tuberous sclerosis complex. Acta Neuropathol 2024; 147:80. [PMID: 38714540 PMCID: PMC11076412 DOI: 10.1007/s00401-024-02737-7] [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: 03/14/2024] [Revised: 04/25/2024] [Accepted: 04/26/2024] [Indexed: 05/10/2024]
Abstract
GABAergic interneurons play a critical role in maintaining neural circuit balance, excitation-inhibition regulation, and cognitive function modulation. In tuberous sclerosis complex (TSC), GABAergic neuron dysfunction contributes to disrupted network activity and associated neurological symptoms, assumingly in a cell type-specific manner. This GABAergic centric study focuses on identifying specific interneuron subpopulations within TSC, emphasizing the unique characteristics of medial ganglionic eminence (MGE)- and caudal ganglionic eminence (CGE)-derived interneurons. Using single-nuclei RNA sequencing in TSC patient material, we identify somatostatin-expressing (SST+) interneurons as a unique and immature subpopulation in TSC. The disrupted maturation of SST+ interneurons may undergo an incomplete switch from excitatory to inhibitory GABAergic signaling during development, resulting in reduced inhibitory properties. Notably, this study reveals markers of immaturity specifically in SST+ interneurons, including an abnormal NKCC1/KCC2 ratio, indicating an imbalance in chloride homeostasis crucial for the postsynaptic consequences of GABAergic signaling as well as the downregulation of GABAA receptor subunits, GABRA1, and upregulation of GABRA2. Further exploration of SST+ interneurons revealed altered localization patterns of SST+ interneurons in TSC brain tissue, concentrated in deeper cortical layers, possibly linked to cortical dyslamination. In the epilepsy context, our research underscores the diverse cell type-specific roles of GABAergic interneurons in shaping seizures, advocating for precise therapeutic considerations. Moreover, this study illuminates the potential contribution of SST+ interneurons to TSC pathophysiology, offering insights for targeted therapeutic interventions.
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Affiliation(s)
- Mirte Scheper
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.
| | - Frederik N F Sørensen
- Biotech Research and Innovation Centre (BRIC), Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Gabriele Ruffolo
- Department of Physiology and Pharmacology, University of Rome Sapienza, 00185, Rome, Italy
- IRCCS San Raffaele Roma, 00163, Rome, Italy
| | - Alessandro Gaeta
- Department of Physiology and Pharmacology, University of Rome Sapienza, 00185, Rome, Italy
| | - Lilian J Lissner
- Department of Physiology and Pharmacology, University of Rome Sapienza, 00185, Rome, Italy
| | - Jasper J Anink
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Irina Korshunova
- Biotech Research and Innovation Centre (BRIC), Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Floor E Jansen
- Department of Child Neurology, Brain Center University Medical Center, Member of ERN EpiCare, 3584 BA, Utrecht, The Netherlands
| | - Kate Riney
- Faculty of Medicine, The University of Queensland, St Lucia, QLD, 4067, Australia
- Neurosciences Unit, Queensland Children's Hospital, South Brisbane, QLD, 4101, Australia
| | - Wim van Hecke
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Angelika Mühlebner
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Konstantin Khodosevich
- Biotech Research and Innovation Centre (BRIC), Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Dirk Schubert
- Department of Cognitive Neurosciences, Radboudumc, Donders Institute for Brain Cognition and Behaviour, 6525 HR, Nijmegen, The Netherlands
| | - Eleonora Palma
- Department of Physiology and Pharmacology, University of Rome Sapienza, 00185, Rome, Italy
- IRCCS San Raffaele Roma, 00163, Rome, Italy
| | - James D Mills
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Chalfont Centre for Epilepsy, Bucks, SL9 0RJ, UK
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands
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Hardege I, Morud J, Courtney A, Schafer WR. A Novel and Functionally Diverse Class of Acetylcholine-Gated Ion Channels. J Neurosci 2023; 43:1111-1124. [PMID: 36604172 PMCID: PMC9962794 DOI: 10.1523/jneurosci.1516-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 12/02/2022] [Accepted: 12/14/2022] [Indexed: 01/07/2023] Open
Abstract
Fast cholinergic neurotransmission is mediated by acetylcholine-gated ion channels; in particular, excitatory nicotinic acetylcholine receptors play well established roles in virtually all nervous systems. Acetylcholine-gated inhibitory channels have also been identified in some invertebrate phyla, yet their roles in the nervous system are less well understood. We report the existence of multiple new inhibitory ion channels with diverse ligand activation properties in Caenorhabditis elegans We identify three channels, LGC-40, LGC-57, and LGC-58, whose primary ligand is choline rather than acetylcholine, as well as the first evidence of a truly polymodal channel, LGC-39, which is activated by both cholinergic and aminergic ligands. Using our new ligand-receptor pairs we uncover the surprising extent to which single neurons in the hermaphrodite nervous system express both excitatory and inhibitory channels, not only for acetylcholine but also for the other major neurotransmitters. The results presented in this study offer new insight into the potential evolutionary benefit of a vast and diverse repertoire of ligand-gated ion channels to generate complexity in an anatomically compact nervous system.SIGNIFICANCE STATEMENT Here we describe the diversity of cholinergic signaling in the nematode Caenorhabditis elegans We identify and characterize a novel family of ligand-gated ion channels and show that they are preferentially gated by choline rather than acetylcholine and expressed broadly in the nervous system. Interestingly, we also identify one channel gated by chemically diverse ligands including acetylcholine and aminergic ligands. By using our new knowledge of these ligand-gated ion channels, we built a model to predict the synaptic polarity in the C. elegans connectome. This model can be used for generating hypotheses on neural circuit function.
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Affiliation(s)
- Iris Hardege
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Julia Morud
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Amy Courtney
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - William R Schafer
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- Department of Biology, KU Leuven, 3000 Leuven, Belgium
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3
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Sieghart W, Chiou LC, Ernst M, Fabjan J, M Savić M, Lee MT. α6-Containing GABA A Receptors: Functional Roles and Therapeutic Potentials. Pharmacol Rev 2022; 74:238-270. [PMID: 35017178 DOI: 10.1124/pharmrev.121.000293] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 09/08/2021] [Indexed: 12/11/2022] Open
Abstract
GABAA receptors containing the α6 subunit are highly expressed in cerebellar granule cells and less abundantly in many other neuronal and peripheral tissues. Here, we for the first time summarize their importance for the functions of the cerebellum and the nervous system. The cerebellum is not only involved in motor control but also in cognitive, emotional, and social behaviors. α6βγ2 GABAA receptors located at cerebellar Golgi cell/granule cell synapses enhance the precision of inputs required for cerebellar timing of motor activity and are thus involved in cognitive processing and adequate responses to our environment. Extrasynaptic α6βδ GABAA receptors regulate the amount of information entering the cerebellum by their tonic inhibition of granule cells, and their optimal functioning enhances input filtering or contrast. The complex roles of the cerebellum in multiple brain functions can be compromised by genetic or neurodevelopmental causes that lead to a hypofunction of cerebellar α6-containing GABAA receptors. Animal models mimicking neuropsychiatric phenotypes suggest that compounds selectively activating or positively modulating cerebellar α6-containing GABAA receptors can alleviate essential tremor and motor disturbances in Angelman and Down syndrome as well as impaired prepulse inhibition in neuropsychiatric disorders and reduce migraine and trigeminal-related pain via α6-containing GABAA receptors in trigeminal ganglia. Genetic studies in humans suggest an association of the human GABAA receptor α6 subunit gene with stress-associated disorders. Animal studies support this conclusion. Neuroimaging and post-mortem studies in humans further support an involvement of α6-containing GABAA receptors in various neuropsychiatric disorders, pointing to a broad therapeutic potential of drugs modulating α6-containing GABAA receptors. SIGNIFICANCE STATEMENT: α6-Containing GABAA receptors are abundantly expressed in cerebellar granule cells, but their pathophysiological roles are widely unknown, and they are thus out of the mainstream of GABAA receptor research. Anatomical and electrophysiological evidence indicates that these receptors have a crucial function in neuronal circuits of the cerebellum and the nervous system, and experimental, genetic, post-mortem, and pharmacological studies indicate that selective modulation of these receptors offers therapeutic prospects for a variety of neuropsychiatric disorders and for stress and its consequences.
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Affiliation(s)
- Werner Sieghart
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
| | - Lih-Chu Chiou
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
| | - Margot Ernst
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
| | - Jure Fabjan
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
| | - Miroslav M Savić
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
| | - Ming Tatt Lee
- Center for Brain Research, Department of Molecular Neurosciences (W.S.), and Center for Brain Research, Department of Pathobiology of the Nervous System (M.E., J.F.), Medical University Vienna, Vienna, Austria; Graduate Institute of Pharmacology (L.-C.C., M.T.L.), and Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan (L.-C.C., M.T.L.); Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia (M.M.S.); Faculty of Pharmaceutical Sciences, UCSI University, Kuala Lumpur, Malaysia (M.T.L.); and Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan (L.-C.C.)
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4
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Shu HJ, Lu X, Bracamontes J, Steinbach JH, Zorumski CF, Mennerick S. Pharmacological and Biophysical Characteristics of Picrotoxin-Resistant, δSubunit-Containing GABA A Receptors. Front Synaptic Neurosci 2021; 13:763411. [PMID: 34867260 PMCID: PMC8636460 DOI: 10.3389/fnsyn.2021.763411] [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: 08/23/2021] [Accepted: 10/26/2021] [Indexed: 11/21/2022] Open
Abstract
GABAA receptors (GABAARs) play a crucial role in inhibition in the central nervous system. GABAARs containing the δ subunit mediate tonic inhibition, have distinctive pharmacological properties and are associated with disorders of the nervous system. To explore this receptor sub-class, we recently developed mice with δ-containing receptors rendered resistant to the common non-competitive antagonist picrotoxin (PTX). Resistance was achieved with a knock-in point mutation (T269Y; T6’Y) in the mouse genome. Here we characterize pharmacological and biophysical features of GABAARs containing the mutated subunit to contextualize results from the KI mice. Recombinant receptors containing δ T6’Y plus WT α4 and WT β2 subunits exhibited 3-fold lower EC50 values for GABA but not THIP. GABA EC50 values in native receptors containing the mutated subunit were in the low micromolar range, in contrast with some published results that have suggested nM sensitivity of recombinant receptors. Rectification properties of δ-containing GABAARs were similar to γ2-containing receptors. Receptors containing δ T6’Y had marginally weaker sensitivity to positive allosteric modulators, likely a secondary consequence of differing GABA sensitivity. Overexpression of δT6’Y in neurons resulted in robust PTX-insensitive IPSCs, suggesting that δ-containing receptors are readily recruited by synaptically released GABA. Overall, our results give context to the use of δ receptors with the T6’Y mutation to explore the roles of δ-containing receptors in inhibition.
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Affiliation(s)
- Hong-Jin Shu
- Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
| | - Xinguo Lu
- Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
| | - John Bracamontes
- Department of Anesthesiology, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States.,Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
| | - Charles F Zorumski
- Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States.,Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States.,Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
| | - Steven Mennerick
- Department of Psychiatry, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States.,Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States.,Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, MO, United States
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5
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Belelli D, Hales TG, Lambert JJ, Luscher B, Olsen R, Peters JA, Rudolph U, Sieghart W. GABA A receptors in GtoPdb v.2021.3. IUPHAR/BPS GUIDE TO PHARMACOLOGY CITE 2021; 2021. [PMID: 35005623 DOI: 10.2218/gtopdb/f72/2021.3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The GABAA receptor is a ligand-gated ion channel of the Cys-loop family that includes the nicotinic acetylcholine, 5-HT3 and strychnine-sensitive glycine receptors. GABAA receptor-mediated inhibition within the CNS occurs by fast synaptic transmission, sustained tonic inhibition and temporally intermediate events that have been termed 'GABAA, slow' [45]. GABAA receptors exist as pentamers of 4TM subunits that form an intrinsic anion selective channel. Sequences of six α, three β, three γ, one δ, three ρ, one ε, one π and one θ GABAA receptor subunits have been reported in mammals [278, 235, 236, 283]. The π-subunit is restricted to reproductive tissue. Alternatively spliced versions of many subunits exist (e.g. α4- and α6- (both not functional) α5-, β2-, β3- and γ2), along with RNA editing of the α3 subunit [71]. The three ρ-subunits, (ρ1-3) function as either homo- or hetero-oligomeric assemblies [359, 50]. Receptors formed from ρ-subunits, because of their distinctive pharmacology that includes insensitivity to bicuculline, benzodiazepines and barbiturates, have sometimes been termed GABAC receptors [359], but they are classified as GABA A receptors by NC-IUPHAR on the basis of structural and functional criteria [16, 235, 236]. Many GABAA receptor subtypes contain α-, β- and γ-subunits with the likely stoichiometry 2α.2β.1γ [168, 235]. It is thought that the majority of GABAA receptors harbour a single type of α- and β - subunit variant. The α1β2γ2 hetero-oligomer constitutes the largest population of GABAA receptors in the CNS, followed by the α2β3γ2 and α3β3γ2 isoforms. Receptors that incorporate the α4- α5-or α 6-subunit, or the β1-, γ1-, γ3-, δ-, ε- and θ-subunits, are less numerous, but they may nonetheless serve important functions. For example, extrasynaptically located receptors that contain α6- and δ-subunits in cerebellar granule cells, or an α4- and δ-subunit in dentate gyrus granule cells and thalamic neurones, mediate a tonic current that is important for neuronal excitability in response to ambient concentrations of GABA [209, 272, 83, 19, 288]. GABA binding occurs at the β+/α- subunit interface and the homologous γ+/α- subunits interface creates the benzodiazepine site. A second site for benzodiazepine binding has recently been postulated to occur at the α+/β- interface ([254]; reviewed by [282]). The particular α-and γ-subunit isoforms exhibit marked effects on recognition and/or efficacy at the benzodiazepine site. Thus, receptors incorporating either α4- or α6-subunits are not recognised by 'classical' benzodiazepines, such as flunitrazepam (but see [356]). The trafficking, cell surface expression, internalisation and function of GABAA receptors and their subunits are discussed in detail in several recent reviews [52, 140, 188, 316] but one point worthy of note is that receptors incorporating the γ2 subunit (except when associated with α5) cluster at the postsynaptic membrane (but may distribute dynamically between synaptic and extrasynaptic locations), whereas as those incorporating the δ subunit appear to be exclusively extrasynaptic. NC-IUPHAR [16, 235, 3, 2] class the GABAA receptors according to their subunit structure, pharmacology and receptor function. Currently, eleven native GABAA receptors are classed as conclusively identified (i.e., α1β2γ2, α1βγ2, α3βγ2, α4βγ2, α4β2δ, α4β3δ, α5βγ2, α6βγ2, α6β2δ, α6β3δ and ρ) with further receptor isoforms occurring with high probability, or only tentatively [235, 236]. It is beyond the scope of this Guide to discuss the pharmacology of individual GABAA receptor isoforms in detail; such information can be gleaned in the reviews [16, 95, 168, 173, 143, 278, 216, 235, 236] and [9, 10]. Agents that discriminate between α-subunit isoforms are noted in the table and additional agents that demonstrate selectivity between receptor isoforms, for example via β-subunit selectivity, are indicated in the text below. The distinctive agonist and antagonist pharmacology of ρ receptors is summarised in the table and additional aspects are reviewed in [359, 50, 145, 223]. Several high-resolution cryo-electron microscopy structures have been described in which the full-length human α1β3γ2L GABAA receptor in lipid nanodiscs is bound to the channel-blocker picrotoxin, the competitive antagonist bicuculline, the agonist GABA (γ-aminobutyric acid), and the classical benzodiazepines alprazolam and diazepam [198].
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Janzen D, Slavik B, Zehe M, Sotriffer C, Loos HM, Buettner A, Villmann C. Sesquiterpenes and sesquiterpenoids harbor modulatory allosteric potential and affect inhibitory GABA A receptor function in vitro. J Neurochem 2021; 159:101-115. [PMID: 34263932 DOI: 10.1111/jnc.15469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 06/11/2021] [Accepted: 07/07/2021] [Indexed: 11/29/2022]
Abstract
Naturally occurring compounds such as sesquiterpenes and sesquiterpenoids (SQTs) have been shown to modulate GABAA receptors (GABAA Rs). In this study, the modulatory potential of 11 SQTs at GABAA Rs was analyzed to characterize their potential neurotropic activity. Transfected HEK293 cells and primary hippocampal neurons were functionally investigated using electrophysiological whole-cell recordings. Significantly different effects of β-caryophyllene and α-humulene, as well as their respective derivatives β-caryolanol and humulol, were observed in the HEK293 cell system. In neurons, the concomitant presence of phasic and tonic GABAA R configurations accounts for differences in receptor modulation by SQTs. The in vivo presence of the γ2 and δ subunits is important for SQT modulation. While phasic GABAA receptors in hippocampal neurons exhibited significantly altered GABA-evoked current amplitudes in the presence of humulol and guaiol, negative allosteric potential at recombinantly expressed α1 β2 γ2 receptors was only verified for humolol. Modeling and docking studies provided support for the binding of SQTs to the neurosteroid-binding site of the GABAA R localized between transmembrane segments 1 and 3 at the (+ α)-(- α) interface. In sum, differences in the modulation of GABAA R isoforms between SQTs were identified. Another finding is that our results provide an indication that nutritional digestion affects the neurotropic potential of natural compounds.
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Affiliation(s)
- Dieter Janzen
- Institute for Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Benedikt Slavik
- Chair of Aroma and Smell Research, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Markus Zehe
- Institute of Pharmacy and Food Chemistry, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Christoph Sotriffer
- Institute of Pharmacy and Food Chemistry, Julius-Maximilians-University Würzburg, Würzburg, Germany
| | - Helene M Loos
- Chair of Aroma and Smell Research, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Germany.,Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany
| | - Andrea Buettner
- Chair of Aroma and Smell Research, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Erlangen, Germany.,Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany
| | - Carmen Villmann
- Institute for Clinical Neurobiology, University Hospital, Julius-Maximilians-University Würzburg, Würzburg, Germany
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7
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Reyes-Haro D, Cisneros-Mejorado A, Arellano RO. Therapeutic Potential of GABAergic Signaling in Myelin Plasticity and Repair. Front Cell Dev Biol 2021; 9:662191. [PMID: 33889577 PMCID: PMC8056019 DOI: 10.3389/fcell.2021.662191] [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: 01/31/2021] [Accepted: 03/12/2021] [Indexed: 11/17/2022] Open
Abstract
Oligodendrocytes (OLs) produce myelin to insulate axons. This accelerates action potential propagation, allowing nerve impulse information to synchronize within complex neuronal ensembles and promoting brain connectivity. Brain plasticity includes myelination, a process that starts early after birth and continues throughout life. Myelin repair, followed by injury or disease, requires new OLs differentiated from a population derived from oligodendrocyte precursor cells (OPCs) that continue to proliferate, migrate and differentiate to preserve and remodel myelin in the adult central nervous system. OPCs represent the largest proliferative neural cell population outside the adult neurogenic niches in the brain. OPCs receive synaptic inputs from glutamatergic and GABAergic neurons throughout neurodevelopment, a unique feature among glial cells. Neuron-glia communication through GABA signaling in OPCs has been shown to play a role in myelin plasticity and repair. In this review we will focus on the molecular and functional properties of GABAA receptors (GABAARs) expressed by OPCs and their potential role in remyelination.
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Affiliation(s)
- Daniel Reyes-Haro
- Instituto de Neurobiología, Universidad Nacional Autónoma de México Campus Juriquilla, Juriquilla, Mexico
| | - Abraham Cisneros-Mejorado
- Instituto de Neurobiología, Universidad Nacional Autónoma de México Campus Juriquilla, Juriquilla, Mexico
| | - Rogelio O Arellano
- Instituto de Neurobiología, Universidad Nacional Autónoma de México Campus Juriquilla, Juriquilla, Mexico
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8
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Jeong AH, Hwang J, Jo K, Kim S, Ahn Y, Suh HJ, Choi HS. Fermented Gamma Aminobutyric Acid Improves Sleep Behaviors in Fruit Flies and Rodent Models. Int J Mol Sci 2021; 22:3537. [PMID: 33805468 PMCID: PMC8036604 DOI: 10.3390/ijms22073537] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/20/2021] [Accepted: 03/25/2021] [Indexed: 01/05/2023] Open
Abstract
The aim of this study was to investigate the effect of Lactobacillus brevis-fermented γ-aminobutyric acid (LB-GABA) on sleep behaviors in invertebrate and vertebrate models. In Drosophila melanogaster, LB-GABA-treated group showed an 8-9%-longer sleep duration than normal group did. LB-GABA-treated group also showed a 46.7% lower level of nighttime activity with a longer (11%) sleep duration under caffeine-induced arousal conditions. The LB-GABA-mediated inhibition of activity was confirmed as a reduction of total movement of flies using a video tracking system. In the pentobarbital-induced sleep test in mice, LB-GABA (100 mg/kg) shortened the time of onset of sleep by 32.2% and extended sleeping time by 59%. In addition, mRNA and protein level of GABAergic/Serotonergic neurotransmitters were upregulated following treatment with LB-GABA (2.0%). In particular, intestine- and brain-derived GABAA protein levels were increased by sevenfold and fivefold, respectively. The electroencephalography (EEG) analysis in rats showed that LB-GABA significantly increased non-rapid eye movement (NREM) (53%) with the increase in theta (θ, 59%) and delta (δ, 63%) waves, leading to longer sleep time (35%), under caffeine-induced insomnia conditions. LB-GABA showed a dose-dependent agonist activity on human GABAA receptor with a half-maximal effective concentration (EC50) of 3.44 µg/mL in human embryonic kidney 293 (HEK293) cells.
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Affiliation(s)
- A-Hyun Jeong
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
- Interdisciplinary Program in Precision Public Health, Korea University, Seoul 02841, Korea
| | - Jisu Hwang
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
| | - Kyungae Jo
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
| | - Singeun Kim
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
| | - Yejin Ahn
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
| | - Hyung Joo Suh
- Department of Public Health Science, Korea University, Seoul 02841, Korea; (A.-H.J.); (J.H.); (K.J.); (S.K.); (Y.A.); (H.J.S.)
| | - Hyeon-Son Choi
- Department of Food Nutrition, Sangmyung University, Seoul 03016, Korea
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9
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Sadamitsu K, Shigemitsu L, Suzuki M, Ito D, Kashima M, Hirata H. Characterization of zebrafish GABA A receptor subunits. Sci Rep 2021; 11:6242. [PMID: 33737538 PMCID: PMC7973766 DOI: 10.1038/s41598-021-84646-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 02/18/2021] [Indexed: 11/23/2022] Open
Abstract
γ-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system, exerts its effect through the activation of GABA receptors. GABAA receptors are ligand-gated chloride channels composed of five subunit proteins. Mammals have 19 different GABAA receptor subunits (α1–6, β1–3, γ1–3, δ, ε, π, θ, and ρ1–3), the physiological properties of which have been assayed by electrophysiology. However, the evolutionary conservation of the physiological characteristics of diverged GABAA receptor subunits remains unclear. Zebrafish have 23 subunits (α1, α2a, α2b, α3–5, α6a, α6b, β1–4, γ1–3, δ, π, ζ, ρ1, ρ2a, ρ2b, ρ3a, and ρ3b), but the electrophysiological properties of these subunits have not been explored. In this study, we cloned the coding sequences for zebrafish GABAA receptor subunits and investigated their expression patterns in larval zebrafish by whole-mount in situ hybridization. We also performed electrophysiological recordings of GABA-evoked currents from Xenopus oocytes injected with one or multiple zebrafish GABAA receptor subunit cRNAs and calculated the half-maximal effective concentrations (EC50s) for each. Our results revealed the spatial expressions and electrophysiological GABA sensitivities of zebrafish GABAA receptors, suggesting that the properties of GABAA receptor subunits are conserved among vertebrates.
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Affiliation(s)
- Kenichiro Sadamitsu
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan
| | - Leona Shigemitsu
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan
| | - Marina Suzuki
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan
| | - Daishi Ito
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan
| | - Makoto Kashima
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, 252-5258, Japan.
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10
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Ma T, Sato M, Komiya M, Feng X, Tadaki D, Hirano-Iwata A. Advances in Artificial Bilayer Lipid Membranes as a Novel Biosensing Platform: From Drug-screening to Self-assembled Devices. CHEM LETT 2021. [DOI: 10.1246/cl.200764] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Teng Ma
- Advanced Institute for Materials Research (WPI-AIMR), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Madoka Sato
- Research Institute of Electrical Communication (RIEC), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Maki Komiya
- Research Institute of Electrical Communication (RIEC), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Xingyao Feng
- Research Institute of Electrical Communication (RIEC), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Daisuke Tadaki
- Research Institute of Electrical Communication (RIEC), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Ayumi Hirano-Iwata
- Advanced Institute for Materials Research (WPI-AIMR), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
- Research Institute of Electrical Communication (RIEC), 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
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11
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Ordaz RP, Garay E, Limon A, Pérez-Samartín A, Sánchez-Gómez MV, Robles-Martínez L, Cisneros-Mejorado A, Matute C, Arellano RO. GABA A Receptors Expressed in Oligodendrocytes Cultured from the Neonatal Rat Contain α3 and γ1 Subunits and Present Differential Functional and Pharmacological Properties. Mol Pharmacol 2020; 99:133-146. [PMID: 33288547 DOI: 10.1124/molpharm.120.000091] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/05/2020] [Indexed: 12/25/2022] Open
Abstract
Oligodendrocytes (OLs) express functional GABAA receptors (GABAARs) that are activated by GABA released at synaptic contacts with axons or by ambient GABA in extrasynaptic domains. In both instances, the receptors' molecular identity has not been fully defined. Furthermore, data on their structural diversity in different brain regions and information on age-dependent changes in their molecular composition are scant. This lack of knowledge has delayed access to a better understanding of the role of GABAergic signaling between neurons and OLs. Here, we used functional, and pharmacological analyses, as well as gene and protein expression of GABAAR subunits, to explore the subunit combination that could explain the receptor functional profile expressed in OLs from the neonate rat. We found that GABAAR composed of α3β2γ1 subunits mimicked the characteristics of the endogenous receptor when expressed heterologously in Xenopus laevis oocytes. Either α3 or γ1 subunit silencing by small interfering RNA transfection changed the GABA-response characteristics in oligodendrocyte precursor cells, indicating their participation in the endogenous receptor conformation. Thus, α3 subunit silencing shifted the mean EC50 for GABA from 75.1 to 46.6 µM, whereas γ1 silencing reduced the current amplitude response by 55%. We also observed that β-carbolines differentially enhance GABA responses in oligodendroglia as compared with those in neurons. These results contribute to defining the molecular and pharmacological properties of GABAARs in OLs. Additionally, the identification of β-carbolines as selective enhancers of GABAARs in OLs may help to study the role of GABAergic signaling during myelination. SIGNIFICANCE STATEMENT: GABAergic signaling through GABAA receptors (GABAARs) expressed in the oligodendroglial lineage contributes to the myelination control. Determining the molecular identity and the pharmacology of these receptors is essential to define their specific roles in myelination. Using GABAAR subunit expression and silencing, we identified that the GABAAR subunit combination α3β2γ1 conforms the bulk of GABAARs in oligodendrocytes from rat neonates. Furthermore, we found that these receptors have differential pharmacological properties that allow specific positive modulation by β-carbolines.
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Affiliation(s)
- Rainald Pablo Ordaz
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Edith Garay
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Agenor Limon
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Alberto Pérez-Samartín
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - María Victoria Sánchez-Gómez
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Leticia Robles-Martínez
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Abraham Cisneros-Mejorado
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Carlos Matute
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
| | - Rogelio O Arellano
- Instituto de Neurobiología, Laboratorio de Neurofisiología Celular, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, México (R.P.O., E.G., L.R.-M., A.C.-M., R.O.A.); Mitchell Center for Neurodegenerative Diseases, Department of Neurology, School of Medicine, University of Texas Medical Branch at Galveston, Galveston, Texas (A.L.); and Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), Leioa, Spain (A.P.-S., M.V.S.-G., C.M.)
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12
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Serrano-Regal MP, Bayón-Cordero L, Ordaz RP, Garay E, Limon A, Arellano RO, Matute C, Sánchez-Gómez MV. Expression and Function of GABA Receptors in Myelinating Cells. Front Cell Neurosci 2020; 14:256. [PMID: 32973453 PMCID: PMC7472887 DOI: 10.3389/fncel.2020.00256] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/24/2020] [Indexed: 01/14/2023] Open
Abstract
Myelin facilitates the fast transmission of nerve impulses and provides metabolic support to axons. Differentiation of oligodendrocyte progenitor cells (OPCs) and Schwann cell (SC) precursors is critical for myelination during development and myelin repair in demyelinating disorders. Myelination is tightly controlled by neuron-glia communication and requires the participation of a wide repertoire of signals, including neurotransmitters such as glutamate, ATP, adenosine, or γ-aminobutyric acid (GABA). GABA is the main inhibitory neurotransmitter in the central nervous system (CNS) and it is also present in the peripheral nervous system (PNS). The composition and function of GABA receptors (GABARs) are well studied in neurons, while their nature and role in glial cells are still incipient. Recent studies demonstrate that GABA-mediated signaling mechanisms play relevant roles in OPC and SC precursor development and function, and stand out the implication of GABARs in oligodendrocyte (OL) and SC maturation and myelination. In this review, we highlight the evidence supporting the novel role of GABA with an emphasis on the molecular identity of the receptors expressed in these glial cells and the possible signaling pathways involved in their actions. GABAergic signaling in myelinating cells may have potential implications for developing novel reparative therapies in demyelinating diseases.
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Affiliation(s)
- Mari Paz Serrano-Regal
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - Laura Bayón-Cordero
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - Rainald Pablo Ordaz
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Edith Garay
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Agenor Limon
- Department of Neurology, Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, United States
| | - Rogelio O. Arellano
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Carlos Matute
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - María Victoria Sánchez-Gómez
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
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13
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Menzikov SA, Zaichenko DM, Moskovtsev AA, Morozov SG, Kubatiev AA. Ectopic GABA A receptor β3 subunit determines Cl - / HCO 3 - -ATPase and chloride transport in HEK 293FT cells. FEBS J 2020; 288:699-712. [PMID: 32383536 DOI: 10.1111/febs.15359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 04/09/2020] [Accepted: 05/04/2020] [Indexed: 01/20/2023]
Abstract
Neuronal intracellular chloride concentration ([Cl- ]i ) is a crucial determinant of transmission mediated by the γ-aminobutyric acid type A receptor (GABAA R), which subserves synaptic and extrasynaptic inhibition as well as excitation. The Cl- ion is the main carrier of charge through the GABAA R; however, bicarbonate ions ( HCO 3 - ) flowing in the opposite direction can also contribute to the net current. The direction of Cl- and HCO 3 - fluxes is determined by the underlying electrochemical gradient, which is controlled by Cl- transporters and channels. Accumulating evidence suggests that active mechanisms of chloride transport across the GABAA R pore can underlie the regulation of [Cl- ]i . Measurement of Cl- / HCO 3 - -ATPase activity and Cl- transport in HEK 293FT cells expressing homomeric or heteromeric GABAA R ensembles (α2, β3, or γ2) with fluorescent dye for chloride demonstrated that receptor subtypes containing the β3 subunit show enzymatic activity and participate in GABA-mediated or ATP-dependent Cl- transport. GABA-mediated flow of Cl- ions into and out of the cells occurred for a short time period but then rapidly declined. However, Cl- ion flux was stabilized for a long time period in the presence of HCO 3 - ions. The reconstituted β3 subunit isoform, purified as a fusion protein, confirmed that β3 is critical for ATPase; however, only the triplet variant showed the full receptor function. The high sensitivity of the enzyme to γ-phosphate inhibitors led us to postulate that the β3 subunit is catalytic. Our discovery of a GABAA R type that requires ATP consumption for chloride movement provides new insight into the molecular mechanisms of inhibitory signaling.
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Affiliation(s)
| | | | - Aleksey A Moskovtsev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
| | - Sergey G Morozov
- Institute of General Pathology and Pathophysiology, Moscow, Russia
| | - Aslan A Kubatiev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
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14
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Han W, Li J, Pelkey KA, Pandey S, Chen X, Wang YX, Wu K, Ge L, Li T, Castellano D, Liu C, Wu LG, Petralia RS, Lynch JW, McBain CJ, Lu W. Shisa7 is a GABA A receptor auxiliary subunit controlling benzodiazepine actions. Science 2020; 366:246-250. [PMID: 31601770 DOI: 10.1126/science.aax5719] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/27/2019] [Indexed: 12/20/2022]
Abstract
The function and pharmacology of γ-aminobutyric acid type A receptors (GABAARs) are of great physiological and clinical importance and have long been thought to be determined by the channel pore-forming subunits. We discovered that Shisa7, a single-passing transmembrane protein, localizes at GABAergic inhibitory synapses and interacts with GABAARs. Shisa7 controls receptor abundance at synapses and speeds up the channel deactivation kinetics. Shisa7 also potently enhances the action of diazepam, a classic benzodiazepine, on GABAARs. Genetic deletion of Shisa7 selectively impairs GABAergic transmission and diminishes the effects of diazepam in mice. Our data indicate that Shisa7 regulates GABAAR trafficking, function, and pharmacology and reveal a previously unknown molecular interaction that modulates benzodiazepine action in the brain.
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Affiliation(s)
- Wenyan Han
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jun Li
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kenneth A Pelkey
- Cellular and Synaptic Neuroscience Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Saurabh Pandey
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Xiumin Chen
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Ya-Xian Wang
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kunwei Wu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lihao Ge
- Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tianming Li
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - David Castellano
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Chengyu Liu
- Transgenetic Core Facility, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ling-Gang Wu
- Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ronald S Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joseph W Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Chris J McBain
- Cellular and Synaptic Neuroscience Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wei Lu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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15
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Sun MY, Ziolkowski L, Mennerick S. δ subunit-containing GABA A IPSCs are driven by both synaptic and diffusional GABA in mouse dentate granule neurons. J Physiol 2020; 598:1205-1221. [PMID: 31951019 DOI: 10.1113/jp279317] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 01/15/2020] [Indexed: 01/10/2023] Open
Abstract
KEY POINTS Current views suggest γ2 subunit-containing GABAA receptors mediate phasic IPSCs while extrasynaptic δ subunits mediate diffusional IPSCs and tonic current. We have re-examined the roles of the two receptor populations using mice with picrotoxin resistance engineered into receptors containing the δ subunit. Using pharmacological separation, we find that in general δ and γ IPSCs are modulated in parallel by manipulations of transmitter output and diffusion, with evidence favouring modestly more diffusional contribution to δ IPSCs. Our findings also reveal that spontaneous δ IPSCs are mainly driven by channel deactivation, rather than by diffusion of GABA. Understanding the functional contributions of the two receptor classes may help us understand the actions of drug therapies with selective effects on one population over the other. ABSTRACT GABAA receptors mediate transmission throughout the central nervous system and typically contain a δ subunit (δ receptors) or a γ2 subunit (γ2 receptors). δ IPSCs decay slower than γ2 IPSCs, but the reasons are unclear. Transmitter diffusion, rebinding, or slow deactivation kinetics of channels are candidates. We used gene editing to confer picrotoxin resistance on δ receptors in mice, then pharmacologically isolated δ receptors in mouse dentate granule cells to explore IPSCs. γ2 and δ components of IPSCs were modulated similarly by presynaptic manipulations and manipulations of transmitter lifetime, suggesting that GABA release recruits δ receptors proportionally to γ2 receptors. δ IPSCs showed more sensitivity to altered transmitter release and to a rapidly dissociating antagonist, suggesting an additional spillover contribution. Reducing GABA diffusion with 5% dextran increased the peak amplitude and decreased the decay of evoked δ IPSCs but had no effect on δ or dual-component (mainly γ2-driven) spontaneous IPSCs, suggesting that GABA actions can be local for both receptor types. Rapid application of varied [GABA] onto nucleated patches from dentate granule cells demonstrated a deactivation rate of δ receptors similar to that of δ spontaneous IPSCs, consistent with the idea that deactivation and local GABA actions drive δ spontaneous IPSCs. Overall, our results indicate that δ IPSCs are activated by both synaptic and diffusional GABA. Our results are consistent with a functional relationship between δ and γ2 GABAA receptors akin to that of slow NMDA and fast AMPA EPSCs at glutamate synapses.
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Affiliation(s)
- Min-Yu Sun
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave, Box 8134, St Louis, MO, 63110, USA
| | - Luke Ziolkowski
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave, Box 8134, St Louis, MO, 63110, USA
| | - Steven Mennerick
- Department of Psychiatry, Washington University School of Medicine, 660 S. Euclid Ave, Box 8134, St Louis, MO, 63110, USA.,Department of Neuroscience, Washington University School of Medicine, 660 S. Euclid Ave, Box 8134, St Louis, MO, 63110, USA.,Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, 660 S. Euclid Ave, Box 8134, St Louis, MO, 63110, USA
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16
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Komiya M, Kato M, Tadaki D, Ma T, Yamamoto H, Tero R, Tozawa Y, Niwano M, Hirano‐Iwata A. Advances in Artificial Cell Membrane Systems as a Platform for Reconstituting Ion Channels. CHEM REC 2020; 20:730-742. [DOI: 10.1002/tcr.201900094] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/24/2019] [Accepted: 12/27/2019] [Indexed: 01/08/2023]
Affiliation(s)
- Maki Komiya
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical CommunicationTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
| | - Miki Kato
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical CommunicationTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
| | - Daisuke Tadaki
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical CommunicationTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
| | - Teng Ma
- Advanced Institute for Materials ResearchTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
| | - Hideaki Yamamoto
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical CommunicationTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
| | - Ryugo Tero
- Department of Applied Chemistry and Life ScienceToyohashi University of Technology 1-1 Hibarigaoka, Tempaku-cho, Toyohashi Aichi 441-8580 Japan
| | - Yuzuru Tozawa
- Graduate School of Science and EngineeringSaitama University 255 Shimo-Okubo, Sakura-ku, Saitama-shi Saitama 338-8570 Japan
| | - Michio Niwano
- Kansei Fukushi Research InstituteTohoku Fukushi University 6-149-1 Kunimi-ga-oka, Aoba-ku, Sendai-shi Miyagi 989-3201 Japan
| | - Ayumi Hirano‐Iwata
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical CommunicationTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
- Advanced Institute for Materials ResearchTohoku University 2-1-1 Katahira, Aoba-ku, Sendai-shi Miyagi 980-8577 Japan
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17
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Manville RW, Papanikolaou M, Abbott GW. M-Channel Activation Contributes to the Anticonvulsant Action of the Ketone Body β-Hydroxybutyrate. J Pharmacol Exp Ther 2019; 372:148-156. [PMID: 31757819 DOI: 10.1124/jpet.119.263350] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 11/20/2019] [Indexed: 12/26/2022] Open
Abstract
Ketogenic diets are effective therapies for refractory epilepsy, yet the underlying mechanisms are incompletely understood. The anticonvulsant efficacy of ketogenic diets correlates positively to the serum concentration of β-hydroxybutyrate (BHB), the primary ketone body generated by ketosis. Voltage-gated potassium channels generated by KCNQ2-5 subunits, especially KCNQ2/3 heteromers, generate the M-current, a therapeutic target for synthetic anticonvulsants. Here, we report that BHB directly activates KCNQ2/3 channels (EC50 = 0.7 µM), via a highly conserved S5 tryptophan (W265) on KCNQ3. BHB was also acutely effective as an anticonvulsant in the pentylene tetrazole (PTZ) seizure assay in mice. Strikingly, coadministration of γ-amino-β-hydroxybutyric acid, a high-affinity KCNQ2/3 partial agonist that also acts via KCNQ3-W265, similarly reduced the efficacy of BHB in KCNQ2/3 channel activation in vitro and in the PTZ seizure assay in vivo. Our results uncover a novel, unexpected molecular basis for anticonvulsant effects of the major ketone body induced by ketosis. SIGNIFICANCE STATEMENT: Ketogenic diets are used to treat refractory epilepsy but the therapeutic mechanism is not fully understood. Here, we show that clinically relevant concentrations of β-hydroxybutyrate, the primary ketone body generated during ketogenesis, activates KCNQ2/3 potassium channels by binding to a specific site on KCNQ3, an effect known to reduce neuronal excitability. We provide evidence using a mouse chemoconvulsant model that KCNQ2/3 activation contributes to the antiepileptic action of β-hydroxybutyrate.
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Affiliation(s)
- Rían W Manville
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
| | - Maria Papanikolaou
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
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18
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Trent S, Hall J, Connelly WM, Errington AC. Cyfip1 Haploinsufficiency Does Not Alter GABA A Receptor δ-Subunit Expression and Tonic Inhibition in Dentate Gyrus PV + Interneurons and Granule Cells. eNeuro 2019; 6:ENEURO.0364-18.2019. [PMID: 31209152 PMCID: PMC6635810 DOI: 10.1523/eneuro.0364-18.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 05/28/2019] [Accepted: 05/31/2019] [Indexed: 12/01/2022] Open
Abstract
Copy number variation (CNV) at chromosomal region 15q11.2 is linked to increased risk of neurodevelopmental disorders including autism and schizophrenia. A significant gene at this locus is cytoplasmic fragile X mental retardation protein (FMRP) interacting protein 1 (CYFIP1). CYFIP1 protein interacts with FMRP, whose monogenic absence causes fragile X syndrome (FXS). Fmrp knock-out has been shown to reduce tonic GABAergic inhibition by interacting with the δ-subunit of the GABAA receptor (GABAAR). Using in situ hybridization (ISH), qPCR, Western blotting techniques, and patch clamp electrophysiology in brain slices from a Cyfip1 haploinsufficient mouse, we examined δ-subunit mediated tonic inhibition in the dentate gyrus (DG). In wild-type (WT) mice, DG granule cells (DGGCs) responded to the δ-subunit-selective agonist THIP with significantly increased tonic currents. In heterozygous mice, no significant difference was observed in THIP-evoked currents in DGGCs. Phasic GABAergic inhibition in DGGC was also unaltered with no difference in properties of spontaneous IPSCs (sIPSCs). Additionally, we demonstrate that DG granule cell layer (GCL) parvalbumin-positive interneurons (PV+-INs) have functional δ-subunit-mediated tonic GABAergic currents which, unlike DGGC, are also modulated by the α1-selective drug zolpidem. Similar to DGGC, both IPSCs and THIP-evoked currents in PV+-INs were not different between Cyfip1 heterozygous and WT mice. Supporting our electrophysiological data, we found no significant change in hippocampal δ-subunit mRNA expression or protein level and no change in α1/α4-subunit mRNA expression. Thus, Cyfip1 haploinsufficiency, mimicking human 15q11.2 microdeletion syndrome, does not alter hippocampal phasic or tonic GABAergic inhibition, substantially differing from the Fmrp knock-out mouse model.
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Affiliation(s)
- Simon Trent
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
| | - Jeremy Hall
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
| | - William M Connelly
- School of Medicine, University of Tasmania, Hobart, Tasmania 7000, Australia
| | - Adam C Errington
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
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19
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Malomouzh A, Ilyin V, Nikolsky E. Components of the GABAergic signaling in the peripheral cholinergic synapses of vertebrates: a review. Amino Acids 2019; 51:1093-1102. [PMID: 31236726 DOI: 10.1007/s00726-019-02754-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 06/19/2019] [Indexed: 12/23/2022]
Abstract
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system. Since the 1970s, many studies have focused on the role of GABA in the mammalian peripheral nervous system, and particularly in the cholinergic synapses. In this review, we present current findings for the cholinergic neurons of vegetative ganglia as well as for the neurons innervating smooth and striated muscles. Synaptic contacts formed by these neurons contain GABA and the enzyme, glutamic acid decarboxylase, which catalyzes the synthesis of GABA from glutamate. Newly formed GABA is released in the cholinergic synapses and mostly all the peripheral cholinergic synaptic contacts contain iono- and metabotropic GABA receptors. Although the underlying molecular mechanism of the release is not well understood, still, it is speculated that GABA is released by a vesicular and/or non-vesicular way via reversal of the GABA transporter. We also review the signaling role of GABA in the peripheral cholinergic synapses by modulating acetylcholine release, but its exact physiological function remains to be elucidated.
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Affiliation(s)
- Artem Malomouzh
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of Russian Academy of Sciences, P.O. box 30, Kazan, 420111, Russia.
| | - Victor Ilyin
- Neuropharmacology Lab, Kazan Federal University, 18 Kremlyovskaya St, Kazan, 420008, Russia
| | - Evgeny Nikolsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of Russian Academy of Sciences, P.O. box 30, Kazan, 420111, Russia.,Neuropharmacology Lab, Kazan Federal University, 18 Kremlyovskaya St, Kazan, 420008, Russia
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20
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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]
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21
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Vasović D, Divović B, Treven M, Knutson DE, Steudle F, Scholze P, Obradović A, Fabjan J, Brković B, Sieghart W, Ernst M, Cook JM, Savić MM. Trigeminal neuropathic pain development and maintenance in rats are suppressed by a positive modulator of α6 GABA A receptors. Eur J Pain 2019; 23:973-984. [PMID: 30633839 PMCID: PMC6461498 DOI: 10.1002/ejp.1365] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 12/13/2018] [Accepted: 12/19/2018] [Indexed: 01/06/2023]
Abstract
γ-Aminobutyric acid type A (GABAA ) receptors containing the α6 subunit are located in trigeminal ganglia, and their reduction by small interfering RNA increases inflammatory temporomandibular and myofascial pain in rats. We thus hypothesized that enhancing their activity may help in neuropathic syndromes originating from the trigeminal system. Here, we performed a detailed electrophysiological and pharmacokinetic analysis of two recently developed deuterated structurally similar pyrazoloquinolinone compounds. DK-I-56-1 at concentrations below 1 µM enhanced γ-aminobutyric acid (GABA) currents at recombinant rat α6β3γ2, α6β3δ and α6β3 receptors, whereas it was inactive at most GABAA receptor subtypes containing other α subunits. DK-I-87-1 at concentrations below 1 µM was inactive at α6-containing receptors and only weakly modulated other GABAA receptors investigated. Both plasma and brain tissue kinetics of DK-I-56-1 were relatively slow, with half-lives of 6 and 13 hr, respectively, enabling the persistence of estimated free brain concentrations in the range 10-300 nM throughout a 24-hr period. Results obtained in two protocols of chronic constriction injury of the infraorbital nerve in rats dosed intraperitoneally with DK-I-56-1 during 14 days after surgery or with DK-I-56-1 or DK-I-87-1 during 14 days after trigeminal neuropathy were already established, demonstrated that DK-I-56-1 but not DK-I-87-1 significantly reduced the hypersensitivity response to von Frey filaments. SIGNIFICANCE: Neuropathic pain induced by trigeminal nerve damage is poorly controlled by current treatments. DK-I-56-1 that positively modulates α6 GABAA receptors is appropriate for repeated administration and thus may represent a novel treatment option against the development and maintenance of trigeminal neuropathic pain.
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Affiliation(s)
- Dina Vasović
- School of Dental Medicine, University of Belgrade, Belgrade, Serbia
| | - Branka Divović
- Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia
| | - Marco Treven
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Daniel E Knutson
- Department of Chemistry and Biochemistry, Milwaukee Institute of Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Friederike Steudle
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Petra Scholze
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Aleksandar Obradović
- Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia
| | - Jure Fabjan
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Božidar Brković
- School of Dental Medicine, University of Belgrade, Belgrade, Serbia
| | - Werner Sieghart
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Margot Ernst
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - James M Cook
- Department of Chemistry and Biochemistry, Milwaukee Institute of Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin
| | - Miroslav M Savić
- Faculty of Pharmacy, Department of Pharmacology, University of Belgrade, Belgrade, Serbia
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22
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Fischer AU, Müller NIC, Deller T, Del Turco D, Fisch JO, Griesemer D, Kattler K, Maraslioglu A, Roemer V, Xu‐Friedman MA, Walter J, Friauf E. GABA is a modulator, rather than a classical transmitter, in the medial nucleus of the trapezoid body-lateral superior olive sound localization circuit. J Physiol 2019; 597:2269-2295. [PMID: 30776090 PMCID: PMC6462465 DOI: 10.1113/jp277566] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 02/18/2019] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS The lateral superior olive (LSO), a brainstem hub involved in sound localization, integrates excitatory and inhibitory inputs from the ipsilateral and the contralateral ear, respectively. In gerbils and rats, inhibition to the LSO reportedly shifts from GABAergic to glycinergic within the first three postnatal weeks. Surprisingly, we found no evidence for synaptic GABA signalling during this time window in mouse LSO principal neurons. However, we found that presynaptic GABAB Rs modulate Ca2+ influx into medial nucleus of the trapezoid body axon terminals, resulting in reduced synaptic strength. Moreover, GABA elicited strong responses in LSO neurons that were mediated by extrasynaptic GABAA Rs. RNA sequencing revealed highly abundant δ subunits, which are characteristic of extrasynaptic receptors. Whereas GABA increased the excitability of neonatal LSO neurons, it reduced the excitability around hearing onset. Collectively, GABA appears to control the excitability of mouse LSO neurons via extrasynaptic and presynaptic signalling. Thus, GABA acts as a modulator, rather than as a classical transmitter. ABSTRACT GABA and glycine mediate fast inhibitory neurotransmission and are coreleased at several synapse types. Here we assessed the contribution of GABA and glycine in synaptic transmission between the medial nucleus of the trapezoid body (MNTB) and the lateral superior olive (LSO), two nuclei involved in sound localization. Whole-cell patch-clamp experiments in acute mouse brainstem slices at postnatal days (P) 4 and 11 during pharmacological blockade of GABAA receptors (GABAA Rs) and/or glycine receptors demonstrated no GABAergic synaptic component on LSO principal neurons. A GABAergic component was absent in evoked inhibitory postsynaptic currents and miniature events. Coimmunofluorescence experiments revealed no codistribution of the presynaptic GABAergic marker GAD65/67 with gephyrin, a postsynaptic marker for GABAA Rs, corroborating the conclusion that GABA does not act synaptically in the mouse LSO. Imaging experiments revealed reduced Ca2+ influx into MNTB axon terminals following activation of presynaptic GABAB Rs. GABAB R activation reduced the synaptic strength at P4 and P11. GABA appears to act on extrasynaptic GABAA Rs as demonstrated by application of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol, a δ-subunit-specific GABAA R agonist. RNA sequencing showed high mRNA levels for the δ-subunit in the LSO. Moreover, GABA transporters GAT-1 and GAT-3 appear to control extracellular GABA. Finally, we show an age-dependent effect of GABA on the excitability of LSO neurons. Whereas tonic GABA increased the excitability at P4, leading to spike facilitation, it decreased the excitability at P11 via shunting inhibition through extrasynaptic GABAA Rs. Taken together, we demonstrate a modulatory role of GABA in the murine LSO, rather than a function as a classical synaptic transmitter.
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Affiliation(s)
- Alexander U. Fischer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Nicolas I. C. Müller
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe‐University Frankfurt, Theodor‐Stern‐Kai 7D‐60590Frankfurt am MainGermany
| | - Domenico Del Turco
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe‐University Frankfurt, Theodor‐Stern‐Kai 7D‐60590Frankfurt am MainGermany
| | - Jonas O. Fisch
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Désirée Griesemer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Kathrin Kattler
- Genetics/Epigenetic Group, Department of Biological SciencesSaarland UniversityD‐66123Saarbrücken
| | - Ayse Maraslioglu
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Vera Roemer
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
| | - Matthew A. Xu‐Friedman
- Department of Biological SciencesUniversity at BuffaloState University of New YorkBuffaloNY14260USA
| | - Jörn Walter
- Genetics/Epigenetic Group, Department of Biological SciencesSaarland UniversityD‐66123Saarbrücken
| | - Eckhard Friauf
- Animal Physiology Group, Department of BiologyUniversity of KaiserslauternD‐67663KaiserslauternGermany
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23
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Benkherouf AY, Taina KR, Meera P, Aalto AJ, Li XG, Soini SL, Wallner M, Uusi-Oukari M. Extrasynaptic δ-GABA A receptors are high-affinity muscimol receptors. J Neurochem 2019; 149:41-53. [PMID: 30565258 PMCID: PMC6438731 DOI: 10.1111/jnc.14646] [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: 09/27/2018] [Revised: 12/07/2018] [Accepted: 12/13/2018] [Indexed: 12/18/2022]
Abstract
Muscimol, the major psychoactive ingredient in the mushroom Amanita muscaria, has been regarded as a universal non‐selective GABA‐site agonist. Deletion of the GABAA receptor (GABAAR) δ subunit in mice (δKO) leads to a drastic reduction in high‐affinity muscimol binding in brain sections and to a lower behavioral sensitivity to muscimol than their wild type counterparts. Here, we use forebrain and cerebellar brain homogenates from WT and δKO mice to show that deletion of the δ subunit leads to a > 50% loss of high‐affinity 5 nM [3H]muscimol‐binding sites despite the relatively low abundance of δ‐containing GABAARs (δ‐GABAAR) in the brain. By subtracting residual high‐affinity binding in δKO mice and measuring the slow association and dissociation rates we show that native δ‐GABAARs in WT mice exhibit high‐affinity [3H]muscimol‐binding sites (KD ~1.6 nM on α4βδ receptors in the forebrain and ~1 nM on α6βδ receptors in the cerebellum at 22°C). Co‐expression of the δ subunit with α6 and β2 or β3 in recombinant (HEK 293) expression leads to the appearance of a slowly dissociating [3H]muscimol component. In addition, we compared muscimol currents in recombinant α4β3δ and α4β3 receptors and show that δ subunit co‐expression leads to highly muscimol‐sensitive currents with an estimated EC50 of around 1–2 nM and slow deactivation kinetics. These data indicate that δ subunit incorporation leads to a dramatic increase in GABAAR muscimol sensitivity. We conclude that biochemical and behavioral low‐dose muscimol selectivity for δ‐subunit‐containing receptors is a result of low nanomolar‐binding affinity on δ‐GABAARs. ![]()
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Affiliation(s)
- Ali Y Benkherouf
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Kaisa-Riitta Taina
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Pratap Meera
- Department of Neurobiology, University of California, Los Angeles, California, USA
| | - Asko J Aalto
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Xiang-Guo Li
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland.,Turku PET Centre, Abo Akademi University, Turku, Finland.,Turku PET Centre, Turku University Hospital, Turku, Finland
| | - Sanna L Soini
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - Martin Wallner
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California, USA
| | - Mikko Uusi-Oukari
- Centre of Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Turku, Finland
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24
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Indurthi DC, Qudah T, Liao VW, Ahring PK, Lewis TM, Balle T, Chebib M, Absalom NL. Revisiting autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) mutations in the nicotinic acetylcholine receptor reveal an increase in efficacy regardless of stochiometry. Pharmacol Res 2019; 139:215-227. [DOI: 10.1016/j.phrs.2018.11.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 11/21/2018] [Accepted: 11/21/2018] [Indexed: 12/22/2022]
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25
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KOMIYA M, MA T, TADAKI D, HIRANO-IWATA A. Development of an Analytical System for Ion Channel Proteins Based on Artificial Bilayer Lipid Membranes —Screening of Drug Components that Haveing Side Effects on hERG Channels for Personalized Medicine—. BUNSEKI KAGAKU 2018. [DOI: 10.2116/bunsekikagaku.67.749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Maki KOMIYA
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University
| | - Teng MA
- Advanced Institute for Materials Research, Tohoku University
| | - Daisuke TADAKI
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University
| | - Ayumi HIRANO-IWATA
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University
- Advanced Institute for Materials Research, Tohoku University
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26
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Probing the molecular basis for affinity/potency- and efficacy-based subtype-selectivity exhibited by benzodiazepine-site modulators at GABAA receptors. Biochem Pharmacol 2018; 158:339-358. [DOI: 10.1016/j.bcp.2018.08.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 08/14/2018] [Indexed: 12/20/2022]
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27
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Sieghart W, Savić MM. International Union of Basic and Clinical Pharmacology. CVI: GABAA Receptor Subtype- and Function-selective Ligands: Key Issues in Translation to Humans. Pharmacol Rev 2018; 70:836-878. [DOI: 10.1124/pr.117.014449] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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28
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The α6 subunit-containing GABA A receptor: A novel drug target for inhibition of trigeminal activation. Neuropharmacology 2018; 140:1-13. [PMID: 30016665 DOI: 10.1016/j.neuropharm.2018.07.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 06/29/2018] [Accepted: 07/12/2018] [Indexed: 01/21/2023]
Abstract
Novel treatments against migraine are an urgent medical requirement. The α6 subunit-containing GABAA receptors (α6GABAARs) are expressed in trigeminal ganglia (TG), the hub of the trigeminal vascular system (TGVS) that is involved in the pathogenesis of migraine. Here we reveal an unprecedented role of α6GABAARs in ameliorating TGVS activation using several pharmacological approaches in an animal model mimicking pathological changes in migraine. TGVS activation was induced by intra-cisternal (i.c.) instillation of capsaicin in Wistar rats. Centrally, i.c. capsaicin activated the trigeminal cervical complex (TCC) measured by the increased number of c-Fos-immunoreactive (c-Fos-ir) TCC neurons. Peripherally, it elevated calcitonin gene-related peptide immunoreactivity (CGRP-ir) in TG and depleted CGRP-ir in the dura mater. Pharmacological approaches included a recently identified α6GABAAR-selective positive allosteric modulator (PAM), the pyrazoloquinolinone Compound 6, two α6GABAAR-active PAMs (Ro15-4513 and loreclezole), an α6GABAAR-inactive benzodiazepine (diazepam), an α6GABAAR-selective antagonist (furosemide), and a clinically effective antimigraine agent (topiramate). We examined effects of these compounds on both central and peripheral TGVS responses induced by i.c. capsaicin. Compound 6 (3-10 mg/kg, i.p.) significantly attenuated the TCC neuronal activation and TG CGRP-ir elevation, and dural CGRP depletion induced by capsaicin. All these effects of Compound 6 were mimicked by topiramate, Ro15-4513 and loreclezole, but not by diazepam. The brain-impermeable furosemide antagonized the peripheral, but not central, effects of Compound 6. These results suggest that the α6GABAAR in TG is a novel drug target for TGVS activation and that α6GABAAR-selective PAMs have the potential to be developed as a novel pharmacotherapy for migraine.
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29
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Zhu S, Noviello CM, Teng J, Walsh RM, Kim JJ, Hibbs RE. Structure of a human synaptic GABA A receptor. Nature 2018; 559:67-72. [PMID: 29950725 PMCID: PMC6220708 DOI: 10.1038/s41586-018-0255-3] [Citation(s) in RCA: 342] [Impact Index Per Article: 57.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 05/17/2018] [Indexed: 11/08/2022]
Abstract
Fast inhibitory neurotransmission in the brain is principally mediated by the neurotransmitter GABA (γ-aminobutyric acid) and its synaptic target, the type A GABA receptor (GABAA receptor). Dysfunction of this receptor results in neurological disorders and mental illnesses including epilepsy, anxiety and insomnia. The GABAA receptor is also a prolific target for therapeutic, illicit and recreational drugs, including benzodiazepines, barbiturates, anaesthetics and ethanol. Here we present high-resolution cryo-electron microscopy structures of the human α1β2γ2 GABAA receptor, the predominant isoform in the adult brain, in complex with GABA and the benzodiazepine site antagonist flumazenil, the first-line clinical treatment for benzodiazepine overdose. The receptor architecture reveals unique heteromeric interactions for this important class of inhibitory neurotransmitter receptor. This work provides a template for understanding receptor modulation by GABA and benzodiazepines, and will assist rational approaches to therapeutic targeting of this receptor for neurological disorders and mental illness.
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Affiliation(s)
- Shaotong Zhu
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Colleen M Noviello
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jinfeng Teng
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Richard M Walsh
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jeong Joo Kim
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ryan E Hibbs
- Departments of Neuroscience and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Direct neurotransmitter activation of voltage-gated potassium channels. Nat Commun 2018; 9:1847. [PMID: 29748663 PMCID: PMC5945843 DOI: 10.1038/s41467-018-04266-w] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 04/16/2018] [Indexed: 11/25/2022] Open
Abstract
Voltage-gated potassium channels KCNQ2–5 generate the M-current, which controls neuronal excitability. KCNQ2–5 subunits each harbor a high-affinity anticonvulsant drug-binding pocket containing an essential tryptophan (W265 in human KCNQ3) conserved for >500 million years, yet lacking a known physiological function. Here, phylogenetic analysis, electrostatic potential mapping, in silico docking, electrophysiology, and radioligand binding assays reveal that the anticonvulsant binding pocket evolved to accommodate endogenous neurotransmitters including γ-aminobutyric acid (GABA), which directly activates KCNQ5 and KCNQ3 via W265. GABA, and endogenous metabolites β-hydroxybutyric acid (BHB) and γ-amino-β-hydroxybutyric acid (GABOB), competitively and differentially shift the voltage dependence of KCNQ3 activation. Our results uncover a novel paradigm: direct neurotransmitter activation of voltage-gated ion channels, enabling chemosensing of the neurotransmitter/metabolite landscape to regulate channel activity and cellular excitability. M-current is conveyed by voltage-sensitive KCNQ channels, which are enriched in GABAergic neurons and are activated by anticonvulsants such as retigabine. Here the authors show that GABA directly activates KCNQ3, at the residue required for its anticonvulsant activity.
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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]
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Functional properties and mechanism of action of PPTQ, an allosteric agonist and low nanomolar positive allosteric modulator at GABAA receptors. Biochem Pharmacol 2018; 147:153-169. [DOI: 10.1016/j.bcp.2017.11.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/13/2017] [Indexed: 11/23/2022]
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Sahin S, Eulenburg V, Heinlein A, Villmann C, Pischetsrieder M. Identification of eugenol as the major determinant of GABAA-receptor activation by aqueous Syzygium aromaticum L. (clove buds) extract. J Funct Foods 2017. [DOI: 10.1016/j.jff.2017.08.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Amin J, Subbarayan MS. Orthosteric- versus allosteric-dependent activation of the GABA A receptor requires numerically distinct subunit level rearrangements. Sci Rep 2017; 7:7770. [PMID: 28798394 PMCID: PMC5552871 DOI: 10.1038/s41598-017-08031-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 07/07/2017] [Indexed: 12/05/2022] Open
Abstract
Anaesthetic molecules act on synaptic transmission via the allosteric modulation of ligand-gated chloride channels, such as hetero-oligomeric α1β2γ2 GABAA receptors. To elucidate the overall activation paradigm via allosteric versus orthosteric sites, we used highly homologous, but homo-oligomeric, ρ1 receptors that are contrastingly insensitive to anaesthetics and respond partially to several full GABA α1β2γ2 receptor agonists. Here, we coexpressed varying ratios of RNAs encoding the wild-type and the mutated ρ1 subunits, which are anaesthetic-sensitive and respond with full efficacy to partial GABA agonists, to generate distinct ensembles of receptors containing five, four, three, two, one, or zero mutated subunits. Using these experiments, we then demonstrate that, in the pentamer, three anaesthetic-sensitive ρ1 subunits are needed to impart full efficacy to the partial GABA agonists. By contrast, five anaesthetic-sensitive subunits are required for direct activation by anaesthetics alone, and only one anaesthetic-sensitive subunit is sufficient to confer the anaesthetic-dependent potentiation to the GABA current. In conclusion, our data indicate that GABA and anaesthetics holistically activate the GABAA ρ1 receptor through distinct subunit level rearrangements and suggest that in contrast to the global impact of GABA via orthosteric sites, the force of anaesthetics through allosteric sites may not propagate to the neighbouring subunits and, thus, may have only a local and limited effect on the ρ1 GABAA receptor model system.
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Affiliation(s)
- Jahanshah Amin
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA.
| | - Meena S Subbarayan
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
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Chen X, Keramidas A, Lynch JW. Physiological and pharmacological properties of inhibitory postsynaptic currents mediated by α5β1γ2, α5β2γ2 and α5β3γ2 GABA A receptors. Neuropharmacology 2017; 125:243-253. [PMID: 28757051 DOI: 10.1016/j.neuropharm.2017.07.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 07/18/2017] [Accepted: 07/26/2017] [Indexed: 02/07/2023]
Abstract
α5-containing GABAARs are potential therapeutic targets for clinical conditions including age-related dementia, stroke, schizophrenia, Down syndrome, anaesthetic-induced amnesia, anxiety and pain. α5-containing GABAARs are expressed in layer 5 cortical neurons and hippocampal pyramidal neurons where they mediate both tonic currents and slow inhibitory postsynaptic currents (IPSCs). A range of drugs has been developed to specifically modulate these receptors. The main α5-containing GABAARs that are likely to exist in vivo are the α5β1γ2, α5β2γ2 and α5β3γ2 isoforms. We currently have few clues as to how these isoforms are distributed between synaptic and extrasynaptic compartments or their relative roles in controlling neuronal excitability. Accordingly, the aim of this study was to define the basic biophysical and pharmacological properties of IPSCs mediated by the three isoforms in a hippocampal neuron-HEK293 cell co-culture assay. The IPSC decay time constants were slow (α5β1γ2L: 45 ms; α5β1γ2L: 80 ms; α5β3γ2L: 184 ms) and were largely dominated by the intrinsic channel deactivation rates. By comparing IPSC rise times, we inferred that α5β1γ2L GABAARs are located postsynaptically whereas the other two are predominantly perisynaptic. α5β3γ2L GABAARs alone mediated tonic currents. We quantified the effects of four α5-specific inverse agonists (TB-21007, MRK-016, α5IA and L-655708) on IPSCs mediated by the three isoforms. All compounds selectively inhibited IPSC amplitudes and accelerated IPSC decay rates, albeit with distinct isoform specificities. MRK-016 also significantly accelerated IPSC rise times. These results provide a reference for future studies seeking to identify and characterize the properties of IPSCs mediated by α5-containing GABAAR isoforms in neurons.
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Affiliation(s)
- Xiumin Chen
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Angelo Keramidas
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joseph W Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
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36
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Abdul Manan MAF, Cordes DB, Slawin AMZ, Bühl M, Liao VWY, Chua HC, Chebib M, O'Hagan D. The Synthesis and Evaluation of Fluoro-, Trifluoromethyl-, and Iodomuscimols as GABA Agonists. Chemistry 2017; 23:10848-10852. [DOI: 10.1002/chem.201701443] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Indexed: 02/04/2023]
Affiliation(s)
| | - David B. Cordes
- EaStCHEM School of Chemistry; University of St Andrews; North Haugh St Andrews KY16 9ST UK
| | - Alexandra M. Z. Slawin
- EaStCHEM School of Chemistry; University of St Andrews; North Haugh St Andrews KY16 9ST UK
| | - Michael Bühl
- EaStCHEM School of Chemistry; University of St Andrews; North Haugh St Andrews KY16 9ST UK
| | - Vivian W. Y. Liao
- Faculty of Pharmacy; The University of Sydney; Sydney, New South Wales 2006 Australia
| | - Han. C. Chua
- Faculty of Pharmacy; The University of Sydney; Sydney, New South Wales 2006 Australia
| | - Mary Chebib
- Faculty of Pharmacy; The University of Sydney; Sydney, New South Wales 2006 Australia
| | - David O'Hagan
- EaStCHEM School of Chemistry; University of St Andrews; North Haugh St Andrews KY16 9ST UK
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Hirano-Iwata A, Ishinari Y, Yoshida M, Araki S, Tadaki D, Miyata R, Ishibashi K, Yamamoto H, Kimura Y, Niwano M. Reconstitution of Human Ion Channels into Solvent-free Lipid Bilayers Enhanced by Centrifugal Forces. Biophys J 2017; 110:2207-15. [PMID: 27224486 DOI: 10.1016/j.bpj.2016.04.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/11/2016] [Accepted: 04/11/2016] [Indexed: 12/26/2022] Open
Abstract
Artificially formed bilayer lipid membranes (BLMs) provide well-defined systems for functional analyses of various membrane proteins, including ion channels. However, difficulties associated with the integration of membrane proteins into BLMs limit the experimental efficiency and usefulness of such BLM reconstitution systems. Here, we report on the use of centrifugation to more efficiently reconstitute human ion channels in solvent-free BLMs. The method improves the probability of membrane fusion. Membrane vesicles containing the human ether-a-go-go-related gene (hERG) channel, the human cardiac sodium channel (Nav1.5), and the human GABAA receptor (GABAAR) channel were formed, and the functional reconstitution of the channels into BLMs via vesicle fusion was investigated. Ion channel currents were recorded in 67% of the BLMs that were centrifuged with membrane vesicles under appropriate centrifugal conditions (14-55 × g). The characteristic channel properties were retained for hERG, Nav1.5, and GABAAR channels after centrifugal incorporation into the BLMs. A comparison of the centrifugal force with reported values for the fusion force revealed that a centrifugal enhancement in vesicle fusion was attained, not by accelerating the fusion process but by accelerating the delivery of membrane vesicles to the surface of the BLMs, which led to an increase in the number of membrane vesicles that were available for fusion. Our method for enhancing the probability of vesicle fusion promises to dramatically increase the experimental efficiency of BLM reconstitution systems, leading to the realization of a BLM-based, high-throughput platform for functional assays of various membrane proteins.
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Affiliation(s)
- Ayumi Hirano-Iwata
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan.
| | - Yutaka Ishinari
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan
| | - Miyu Yoshida
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan
| | - Shun Araki
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan
| | - Daisuke Tadaki
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan
| | - Ryusuke Miyata
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan
| | | | - Hideaki Yamamoto
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Aoba, Sendai, Japan
| | - Yasuo Kimura
- Department of Electric and Electronic Engineering, School of Engineering, Tokyo University of Technology, Hachioji, Tokyo, Japan
| | - Michio Niwano
- Graduate School of Biomedical Engineering, Tohoku University, Aoba, Sendai, Japan; Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Aoba, Sendai, Japan
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38
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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.
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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
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39
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Bakas T, van Nieuwenhuijzen P, Devenish S, McGregor I, Arnold J, Chebib M. The direct actions of cannabidiol and 2-arachidonoyl glycerol at GABA A receptors. Pharmacol Res 2017; 119:358-370. [DOI: 10.1016/j.phrs.2017.02.022] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 10/20/2022]
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40
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Xu Z, Wu Q, Xu Q, He L. From the Cover: Functional Analysis Reveals Glutamate and Gamma-Aminobutyric Acid-Gated Chloride Channels as Targets of Avermectins in the Carmine Spider Mite. Toxicol Sci 2016; 155:258-269. [DOI: 10.1093/toxsci/kfw210] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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41
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Ahring PK, Bang LH, Jensen ML, Strøbæk D, Hartiadi LY, Chebib M, Absalom N. A pharmacological assessment of agonists and modulators at α4β2γ2 and α4β2δ GABA A receptors: The challenge in comparing apples with oranges. Pharmacol Res 2016; 111:563-576. [DOI: 10.1016/j.phrs.2016.05.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/05/2016] [Accepted: 05/06/2016] [Indexed: 01/24/2023]
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42
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Dauvilliers Y, Evangelista E, Lopez R, Barateau L, Jaussent I, Cens T, Rousset M, Charnet P. Absence of γ-aminobutyric acid-a receptor potentiation in central hypersomnolence disorders. Ann Neurol 2016; 80:259-68. [DOI: 10.1002/ana.24710] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Revised: 06/07/2016] [Accepted: 06/07/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Yves Dauvilliers
- National Reference Network for Narcolepsy, Department of Neurology, Guy de Chauliac Hospital; Montpellier University Hospital Center
- Inserm, U1061, Montpellier; Université Montpellier; France
| | - Elisa Evangelista
- National Reference Network for Narcolepsy, Department of Neurology, Guy de Chauliac Hospital; Montpellier University Hospital Center
| | - Regis Lopez
- National Reference Network for Narcolepsy, Department of Neurology, Guy de Chauliac Hospital; Montpellier University Hospital Center
- Inserm, U1061, Montpellier; Université Montpellier; France
| | - Lucie Barateau
- National Reference Network for Narcolepsy, Department of Neurology, Guy de Chauliac Hospital; Montpellier University Hospital Center
- Inserm, U1061, Montpellier; Université Montpellier; France
| | | | - Thierry Cens
- IBMM CNRS UMR 5247, Université Montpellier; France
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43
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High and low GABA sensitivity α4β2δ GABAA receptors are expressed in Xenopus laevis oocytes with divergent stoichiometries. Biochem Pharmacol 2016; 103:98-108. [DOI: 10.1016/j.bcp.2015.12.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/29/2015] [Indexed: 12/11/2022]
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44
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Klein AB, Nittegaard-Nielsen M, Christensen JT, Al-Khawaja A, Wellendorph P. Demonstration of the dynamic mass redistribution label-free technology as a useful cell-based pharmacological assay for endogenously expressed GABAA receptors. MEDCHEMCOMM 2016. [DOI: 10.1039/c5md00442j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Within the continuous quest for the discovery of pharmacologically interesting compounds, the development of new and superior drug screening assays is desired.
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Affiliation(s)
- Anders B. Klein
- Department of Drug Design and Pharmacology
- Faculty of Health and Medical Sciences
- University of Copenhagen
- DK-2100 Copenhagen
- Denmark
| | - Mia Nittegaard-Nielsen
- Department of Drug Design and Pharmacology
- Faculty of Health and Medical Sciences
- University of Copenhagen
- DK-2100 Copenhagen
- Denmark
| | - Julie T. Christensen
- Department of Drug Design and Pharmacology
- Faculty of Health and Medical Sciences
- University of Copenhagen
- DK-2100 Copenhagen
- Denmark
| | - Anas Al-Khawaja
- Department of Drug Design and Pharmacology
- Faculty of Health and Medical Sciences
- University of Copenhagen
- DK-2100 Copenhagen
- Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology
- Faculty of Health and Medical Sciences
- University of Copenhagen
- DK-2100 Copenhagen
- Denmark
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45
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Stojanovic T, Capo I, Aronica E, Adle-Biassette H, Höger H, Sieghart W, Kovacs GG, Milenkovic I. The α1, α2, α3, and γ2 subunits of GABAA receptors show characteristic spatial and temporal expression patterns in rhombencephalic structures during normal human brain development. J Comp Neurol 2015; 524:1805-24. [PMID: 26518133 DOI: 10.1002/cne.23923] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 10/24/2015] [Accepted: 10/28/2015] [Indexed: 01/13/2023]
Abstract
γ-Aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in adult mammalian brain, mediating its actions chiefly via a pentameric chloride ion channel, the GABAA receptor. Nineteen different subunits (α1-6, β1-3, γ1-3, δ, ε, π, θ, ρ1-3) can give rise to multiple receptor subtypes that are the site of action of many clinically important drugs. In the developing brain, however, GABAA receptors mediate excitatory actions due to an increased chloride concentration within neurons and seem to control cell proliferation, migration, differentiation, synapse maturation, and cell death. Little is known about the distribution of single subunits in the human brain. Here we describe developmental changes in the immunohistochemical distribution of four subunits (α1, α2, α3, and γ2) in the human rhombencephalon. The γ2 was the most abundant subunit in all rhombencephalic structures during development and in adults, whereas α subunits showed a structure- and age-characteristic distribution. The α1 was expressed prenatally in the molecular and Purkinje cell layer, but only postnatally in the granule cell layer and the dentate nucleus. Expression was completely absent in the inferior olivary nucleus. The α2 gradually increased during development, showing some layer specificity in the cerebellar cortex. The α3-immunoreactivity in the cerebellar cortex was relatively weak, but it was abundantly observed in different cell populations in the subcortical cerebellar structures. Structure- and age-characteristic colocalization between subunits during development suggests differences in GABAA receptor composition. Interestingly, subunit expression in several instances differed between human and rodent brain, underlining the importance of immunohistochemical studies in humans.
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Affiliation(s)
- Tamara Stojanovic
- Institute of Neurology, Neurodegeneration Research Group, Medical University of Vienna, Vienna, Austria
| | - Ivan Capo
- Department of Histology and Embryology, Medical Faculty, Vojvodina, Serbia
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, The Netherlands; SEIN - Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands; Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, The Netherlands
| | - Homa Adle-Biassette
- Inserm U1141, Paris, France; Univ. Paris Diderot, Sorbonne Paris Cité, UMRS 676, Paris, France, Department of Pathology, Lariboisière Hospital, APHP, Paris, France
| | - Harald Höger
- Division of Laboratory Animal Science and Genetics, Medical University of Vienna, Vienna, Austria
| | - Werner Sieghart
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Gabor G Kovacs
- Institute of Neurology, Neurodegeneration Research Group, Medical University of Vienna, Vienna, Austria
| | - Ivan Milenkovic
- Institute of Neurology, Neurodegeneration Research Group, Medical University of Vienna, Vienna, Austria.,Department of Neurology, Medical University of Vienna, Vienna, Austria
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Hammer H, Bader BM, Ehnert C, Bundgaard C, Bunch L, Hoestgaard-Jensen K, Schroeder OHU, Bastlund JF, Gramowski-Voß A, Jensen AA. A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Methaqualone (Quaalude). Mol Pharmacol 2015; 88:401-20. [PMID: 26056160 DOI: 10.1124/mol.115.099291] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Accepted: 06/08/2015] [Indexed: 01/09/2023] Open
Abstract
In the present study, we have elucidated the functional characteristics and mechanism of action of methaqualone (2-methyl-3-o-tolyl-4(3H)-quinazolinone, Quaalude), an infamous sedative-hypnotic and recreational drug from the 1960s-1970s. Methaqualone was demonstrated to be a positive allosteric modulator at human α1,2,3,5β2,3γ2S GABAA receptors (GABAARs) expressed in Xenopus oocytes, whereas it displayed highly diverse functionalities at the α4,6β1,2,3δ GABAAR subtypes, ranging from inactivity (α4β1δ), through negative (α6β1δ) or positive allosteric modulation (α4β2δ, α6β2,3δ), to superagonism (α4β3δ). Methaqualone did not interact with the benzodiazepine, barbiturate, or neurosteroid binding sites in the GABAAR. Instead, the compound is proposed to act through the transmembrane β((+))/α((-)) subunit interface of the receptor, possibly targeting a site overlapping with that of the general anesthetic etomidate. The negligible activities displayed by methaqualone at numerous neurotransmitter receptors and transporters in an elaborate screening for additional putative central nervous system (CNS) targets suggest that it is a selective GABAAR modulator. The mode of action of methaqualone was further investigated in multichannel recordings from primary frontal cortex networks, where the overall activity changes induced by the compound at 1-100 μM concentrations were quite similar to those mediated by other CNS depressants. Finally, the free methaqualone concentrations in the mouse brain arising from doses producing significant in vivo effects in assays for locomotion and anticonvulsant activity correlated fairly well with its potencies as a modulator at the recombinant GABAARs. Hence, we propose that the multifaceted functional properties exhibited by methaqualone at GABAARs give rise to its effects as a therapeutic and recreational drug.
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Affiliation(s)
- Harriet Hammer
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Benjamin M Bader
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Corina Ehnert
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Christoffer Bundgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Lennart Bunch
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Kirsten Hoestgaard-Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Olaf H-U Schroeder
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Jesper F Bastlund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Alexandra Gramowski-Voß
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (H.H., L.B., K.H.-J., A.A.J.); NeuroProof, Rostock, Germany (B.M.B., C.E., O.H.-U.S., A.G.-V.); and H. Lundbeck A/S, Valby, Denmark (C.B., J.F.B.)
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Hammer H, Ebert B, Jensen HS, Jensen AA. Functional characterization of the 1,5-benzodiazepine clobazam and its major active metabolite N-desmethylclobazam at human GABA(A) receptors expressed in Xenopus laevis oocytes. PLoS One 2015; 10:e0120239. [PMID: 25798598 PMCID: PMC4370687 DOI: 10.1371/journal.pone.0120239] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Accepted: 02/04/2015] [Indexed: 12/13/2022] Open
Abstract
The 1,5-benzodiazepine clobazam is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in patients 2 years of age or older in the United States, and for treatment of anxiety and various forms of epilepsy elsewhere. Clobazam has been reported to exhibit different in vivo adverse effects and addiction liability profile than the classic 1,4-benzodiazepines. In this study, it was investigated whether the in vitro pharmacological properties of clobazam and its major active metabolite N-desmethylclobazam could explain some of these clinical differences. The functional properties of the two 1,5-benzodiazepines were characterized at the human γ-aminobutyric acid type A receptor (GABAAR) subtypes α1β2γ2S, α2β2γ2S, α3β2γ2S, α5β2γ2S and α6β2δ expressed in Xenopus laevis oocytes by use of two-electrode voltage-clamp electrophysiology and compared to those exhibited by the 1,4-benzodiazepine clonazepam. All three compounds potentiated GABA EC20-evoked responses through the α1,2,3,5β2γ2S GABAARs in a reversible and concentration-dependent manner, with each displaying similar EC50 values at the four subtypes. Furthermore, the degrees of potentiation of the GABA EC20 currents through the four receptors mediated by saturating modulator concentrations did not differ substantially for any of the three benzodiazepines. The three compounds were substantially less potent (200-3900 fold) as positive allosteric modulators at the α6β2δ GABAAR than at the α1,2,3,5β2γ2S receptors. Interestingly, however, clobazam and especially N-desmethylclobazam were highly efficacious potentiators of α6β2δ receptor signaling. Although this activity component is unlikely to contribute to the in vivo effects of clobazam/N-desmethylclobazam, the 1,5-benzodiazepine could constitute an interesting lead for novel modulators targeting this low-affinity binding site in GABAARs. In conclusion, the non-selective modulation exerted by clobazam, N-desmethylclobazam and clonazepam at the α1β2γ2S, α2β2γ2S, α3β2γ2S and α5β2γ2S GABAARs indicate that the observed clinical differences between clobazam and 1,4-benzodiazepines are likely to arise from factors other than their respective pharmacological properties at the GABAARs as investigated here.
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Affiliation(s)
- Harriet Hammer
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Anders A. Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
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48
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Probing α4βδ GABAA receptor heterogeneity: differential regional effects of a functionally selective α4β1δ/α4β3δ receptor agonist on tonic and phasic inhibition in rat brain. J Neurosci 2015; 34:16256-72. [PMID: 25471566 DOI: 10.1523/jneurosci.1495-14.2014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In the present study, the orthosteric GABAA receptor (GABAAR) ligand 4,5,6,7-tetrahydroisothiazolo[5,4-c]pyridin-3-ol (Thio-THIP) was found to possess a highly interesting functional profile at recombinant human GABAARs and native rat GABAARs. Whereas Thio-THIP displayed weak antagonist activity at α1,2,5β2,3γ2S and ρ1 GABAARs and partial agonism at α6β2,3δ GABAARs expressed in Xenopus oocytes, the pronounced agonism exhibited by the compound at α4β1δ and α4β3δ GABAARs was contrasted by its negligible activity at the α4β2δ subtype. To elucidate to which extent this in vitro profile translated into functionality at native GABAARs, we assessed the effects of 100 μm Thio-THIP at synaptic and extrasynaptic receptors in principal cells of four different brain regions by slice electrophysiology. In concordance with its α6β2,3δ agonism, Thio-THIP evoked robust currents through extrasynaptic GABAARs in cerebellar granule cells. In contrast, the compound did not elicit significant currents in dentate gyrus granule cells or in striatal medium spiny neurons (MSNs), indicating predominant expression of extrasynaptic α4β2δ receptors in these cells. Interestingly, Thio-THIP evoked differential degrees of currents in ventrobasal thalamus neurons, a diversity that could arise from differential expression of extrasynaptic α4βδ subtypes in the cells. Finally, whereas 100 μm Thio-THIP did not affect the synaptic currents in ventrobasal thalamus neurons or striatal MSNs, it reduced the current amplitudes recorded from dentate gyrus granule cells, most likely by targeting perisynaptic α4βδ receptors expressed at distal dendrites of these cells. Being the first published ligand capable of discriminating between β2- and β3-containing receptor subtypes, Thio-THIP could be a valuable tool in explorations of native α4βδ GABAARs.
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Abstract
The oocytes of the African clawed frog (Xenopus laevis) comprise one of the most widely used membrane protein expression systems. While frequently used for studies of transporters and ion channels, the application of this system to the study of mechanosensitive ion channels has been overlooked, perhaps due to a relative abundance of native expression systems. Recent advances, however, have illustrated the advantages of the oocyte system for studying plant and bacterial mechanosensitive channels. Here we describe in detail the methods used for heterologous expression and characterization of bacterial and plant mechanosensitive channels in Xenopus oocytes.
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Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mail Code 1137, Saint Louis, MO, 63130, USA
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50
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Sieghart W. Allosteric modulation of GABAA receptors via multiple drug-binding sites. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 72:53-96. [PMID: 25600367 DOI: 10.1016/bs.apha.2014.10.002] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABAA receptors are ligand-gated ion channels composed of five subunits that can be opened by GABA and be modulated by multiple pharmacologically and clinically important drugs. Over the time, hundreds of compounds from different structural classes have been demonstrated to modulate, directly activate, or inhibit GABAA receptors, and most of these compounds interact with more than one binding site at these receptors. Crystal structures of proteins and receptors homologous to GABAA receptors as well as homology modeling studies have provided insights into the possible location of ligand interaction sites. Some of these sites have been identified by mutagenesis, photolabeling, and docking studies. For most of these ligands, however, binding sites are not known. Due to the high flexibility of GABAA receptors and the existence of multiple drug-binding sites, the unequivocal identification of interaction sites for individual drugs is extremely difficult. The existence of multiple GABAA receptor subtypes with distinct subunit composition, the contribution of distinct subunit sequences to binding sites of different receptor subtypes, as well as the observation that even subunits not directly contributing to a binding site are able to influence affinity and efficacy of drugs, contribute to a unique pharmacology of each GABAA receptor subtype. Thus, each receptor subtype has to be investigated to identify a possible subtype selectivity of a compound. Although multiple binding sites make GABAA receptor pharmacology even more complicated, the exploitation of ligand interaction with novel-binding sites also offers additional possibilities for a subtype-selective modulation of GABAA receptors.
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Affiliation(s)
- Werner Sieghart
- Department of Molecular Neurosciences, Center for Brain Research, Medical University Vienna, Vienna, Austria.
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