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Itoh M, Yuzaki M. The hidden face of GluD1 at inhibitory synapses. Cell Res 2024; 34:405-406. [PMID: 38263278 PMCID: PMC11143318 DOI: 10.1038/s41422-024-00931-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024] Open
Affiliation(s)
- Masayuki Itoh
- Department of Neurophysiology, Keio University School of Medicine, Tokyo, Japan
| | - Michisuke Yuzaki
- Department of Neurophysiology, Keio University School of Medicine, Tokyo, Japan.
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Fasham J, Huebner AK, Liebmann L, Khalaf-Nazzal R, Maroofian R, Kryeziu N, Wortmann SB, Leslie JS, Ubeyratna N, Mancini GMS, van Slegtenhorst M, Wilke M, Haack TB, Shamseldin HE, Gleeson JG, Almuhaizea M, Dweikat I, Abu-Libdeh B, Daana M, Zaki MS, Wakeling MN, McGavin L, Turnpenny PD, Alkuraya FS, Houlden H, Schlattmann P, Kaila K, Crosby AH, Baple EL, Hübner CA. SLC4A10 mutation causes a neurological disorder associated with impaired GABAergic transmission. Brain 2023; 146:4547-4561. [PMID: 37459438 PMCID: PMC10629776 DOI: 10.1093/brain/awad235] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/19/2023] [Accepted: 06/06/2023] [Indexed: 11/09/2023] Open
Abstract
SLC4A10 is a plasma-membrane bound transporter that utilizes the Na+ gradient to drive cellular HCO3- uptake, thus mediating acid extrusion. In the mammalian brain, SLC4A10 is expressed in principal neurons and interneurons, as well as in epithelial cells of the choroid plexus, the organ regulating the production of CSF. Using next generation sequencing on samples from five unrelated families encompassing nine affected individuals, we show that biallelic SLC4A10 loss-of-function variants cause a clinically recognizable neurodevelopmental disorder in humans. The cardinal clinical features of the condition include hypotonia in infancy, delayed psychomotor development across all domains and intellectual impairment. Affected individuals commonly display traits associated with autistic spectrum disorder including anxiety, hyperactivity and stereotyped movements. In two cases isolated episodes of seizures were reported in the first few years of life, and a further affected child displayed bitemporal epileptogenic discharges on EEG without overt clinical seizures. While occipitofrontal circumference was reported to be normal at birth, progressive postnatal microcephaly evolved in 7 out of 10 affected individuals. Neuroradiological features included a relative preservation of brain volume compared to occipitofrontal circumference, characteristic narrow sometimes 'slit-like' lateral ventricles and corpus callosum abnormalities. Slc4a10 -/- mice, deficient for SLC4A10, also display small lateral brain ventricles and mild behavioural abnormalities including delayed habituation and alterations in the two-object novel object recognition task. Collapsed brain ventricles in both Slc4a10-/- mice and affected individuals suggest an important role of SLC4A10 in the production of the CSF. However, it is notable that despite diverse roles of the CSF in the developing and adult brain, the cortex of Slc4a10-/- mice appears grossly intact. Co-staining with synaptic markers revealed that in neurons, SLC4A10 localizes to inhibitory, but not excitatory, presynapses. These findings are supported by our functional studies, which show the release of the inhibitory neurotransmitter GABA is compromised in Slc4a10-/- mice, while the release of the excitatory neurotransmitter glutamate is preserved. Manipulation of intracellular pH partially rescues GABA release. Together our studies define a novel neurodevelopmental disorder associated with biallelic pathogenic variants in SLC4A10 and highlight the importance of further analyses of the consequences of SLC4A10 loss-of-function for brain development, synaptic transmission and network properties.
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Affiliation(s)
- James Fasham
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
- Peninsula Clinical Genetics Service, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Antje K Huebner
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany
| | - Lutz Liebmann
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany
| | - Reham Khalaf-Nazzal
- Department of Biomedical Sciences, Faculty of Medicine, Arab American University of Palestine, Jenin, P227, Palestine
| | - Reza Maroofian
- Molecular and Clinical Sciences Institute, St. George’s University of London, London SW17 0RE, UK
| | - Nderim Kryeziu
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany
| | - Saskia B Wortmann
- University Children’s Hospital, Salzburger Landeskliniken (SALK) and Paracelsus Medical University (PMU), 5020 Salzburg, Austria
- Amalia Children’s Hospital, Radboudumc, 6525 GA Nijmegen, The Netherlands
- Institute of Human Genetics, Technische Universität München, 80333 Munich, Germany
| | - Joseph S Leslie
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Nishanka Ubeyratna
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Grazia M S Mancini
- Department of Clinical Genetics, Erasmus Medical Center, 3015 GD Rotterdam, The Netherlands
| | | | - Martina Wilke
- Department of Clinical Genetics, Erasmus Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Tobias B Haack
- Institute of Medical Genetics and Applied Genomics, University of Tuebingen, 72076 Tübingen, Germany
| | - Hanan E Shamseldin
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Joseph G Gleeson
- Rady Children’s Institute for Genomic Medicine, San Diego, CA 92123, USA
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mohamed Almuhaizea
- Department of Neuroscience, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Imad Dweikat
- Department of Biomedical Sciences, Faculty of Medicine, Arab American University of Palestine, Jenin, P227, Palestine
| | - Bassam Abu-Libdeh
- Department of Pediatrics and Genetics, Makassed Hospital and Al-Quds University, East Jerusalem, 95908, Palestine
| | - Muhannad Daana
- Department of Pediatrics, Arab Women’s Union Hospital, Nablus, P400, Palestine
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Dokki, Cairo 12622, Egypt
| | - Matthew N Wakeling
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Lucy McGavin
- Department of Radiology, Derriford Hospital, Plymouth PL6 8DH, UK
| | - Peter D Turnpenny
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
- Peninsula Clinical Genetics Service, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Fowzan S Alkuraya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Henry Houlden
- Molecular and Clinical Sciences Institute, St. George’s University of London, London SW17 0RE, UK
| | - Peter Schlattmann
- Institute for Medical Statistics, Computer Science and Data Science, Jena University Hospital, 07747 Jena, Germany
| | - Kai Kaila
- Molecular and Integrative Biosciences, University of Helsinki, 00014 Helsinki, Finland
- Neuroscience Center, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
| | - Andrew H Crosby
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Emma L Baple
- RILD Wellcome Wolfson Centre, University of Exeter Medical School, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
- Peninsula Clinical Genetics Service, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK
| | - Christian A Hübner
- Institute of Human Genetics, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany
- Center for Rare Diseases, Jena University Hospital, Friedrich Schiller Universität, 07747 Jena, Germany
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3
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Elverson K, Freeman S, Manson F, Warwicker J. Computational Investigation of Mechanisms for pH Modulation of Human Chloride Channels. Molecules 2023; 28:5753. [PMID: 37570721 PMCID: PMC10420675 DOI: 10.3390/molecules28155753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 08/13/2023] Open
Abstract
Many transmembrane proteins are modulated by intracellular or extracellular pH. Investigation of pH dependence generally proceeds by mutagenesis of a wide set of amino acids, guided by properties such as amino-acid conservation and structure. Prediction of pKas can streamline this process, allowing rapid and effective identification of amino acids of interest with respect to pH dependence. Commencing with the calcium-activated chloride channel bestrophin 1, the carboxylate ligand structure around calcium sites relaxes in the absence of calcium, consistent with a measured lack of pH dependence. By contrast, less relaxation in the absence of calcium in TMEM16A, and maintenance of elevated carboxylate sidechain pKas, is suggested to give rise to pH-dependent chloride channel activity. This hypothesis, modulation of calcium/proton coupling and pH-dependent activity through the extent of structural relaxation, is shown to apply to the well-characterised cytosolic proteins calmodulin (pH-independent) and calbindin D9k (pH-dependent). Further application of destabilised, ionisable charge sites, or electrostatic frustration, is made to other human chloride channels (that are not calcium-activated), ClC-2, GABAA, and GlyR. Experimentally determined sites of pH modulation are readily identified. Structure-based tools for pKa prediction are freely available, allowing users to focus on mutagenesis studies, construct hypothetical proton pathways, and derive hypotheses such as the model for control of pH-dependent calcium activation through structural flexibility. Predicting altered pH dependence for mutations in ion channel disorders can support experimentation and, ultimately, clinical intervention.
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Affiliation(s)
- Kathleen Elverson
- Division of Evolution, Infection and Genomics, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Sally Freeman
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Forbes Manson
- Division of Evolution, Infection and Genomics, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK
| | - Jim Warwicker
- Division of Molecular and Cellular Function, Faculty of Biology, Medicine and Health, Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, UK
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4
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Kłopotowski K, Michałowski MA, Gos M, Mosiądz D, Czyżewska MM, Mozrzymas JW. Mutation of valine 53 at the interface between extracellular and transmembrane domains of the β 2 principal subunit affects the GABA A receptor gating. Eur J Pharmacol 2023; 947:175664. [PMID: 36934960 DOI: 10.1016/j.ejphar.2023.175664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 02/09/2023] [Accepted: 03/16/2023] [Indexed: 03/21/2023]
Abstract
GABAA receptors (gamma-aminobutyric acid type A receptors) are pentameric ligand-gated ion channels mediating inhibition in adult mammalian brains. Their static structure has been intensely studied in the past years but the underlying molecular activatory mechanisms remain obscure. The interface between extracellular and transmembrane domains has been recognized as a key player in the receptor gating. However, the role of the valine 53 in the β1-β2 loop of the principal subunit (β2) remains controversial showing differences compared to homologous residues in some cys-loop counterparts such as nAChR. To address the role of the β2V53 residue in the α1β2γ2L receptor gating, we performed high resolution macroscopic and single-channel recordings. To explore underlying molecular mechanisms a variety of substituting amino acids were investigated: Glutamate and Lysine (different electric charge), Alanine (aliphatic, larger than Valine) and Histidine (same residue as in homologous α1H55). We report that mutation of the β2V53 residue results in alterations of nearly all gating transitions including opening/closing, preactivation and desensitization. A dramatic gating impairment was observed for glutamate substitution (β2V53E) but β2V53K mutation had a weak effect. The impact of histidine substitution was also small while β2V53A markedly affected the receptor but to a smaller extent than β2V53E. Considering available structures in desensitized and bicuculline blocked shut states we propose that strongly detrimental effect of β2V53E mutation on receptor activation results from electrostatic interaction between the glutamate and β2K274 on the loop M2-M3 which stabilizes the receptor in the shut state. We conclude that β2V53 is strongly involved in mechanisms underlying the receptor gating.
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Affiliation(s)
- Karol Kłopotowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland.
| | - Michał A Michałowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Michalina Gos
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland
| | - Daniela Mosiądz
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Marta M Czyżewska
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Jerzy W Mozrzymas
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland.
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5
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GABA A receptor proline 273 at the interdomain interface of the β 2 subunit regulates entry into desensitization and opening/closing transitions. Life Sci 2022; 308:120943. [PMID: 36096246 DOI: 10.1016/j.lfs.2022.120943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/29/2022] [Accepted: 09/06/2022] [Indexed: 11/23/2022]
Abstract
AIMS GABAA receptors belong to Cys-loop ion channel family and mediate inhibition in the brain. Despite the abundance of structural data on receptor structure, the molecular scenarios of activation are unknown. In this study we investigated the role of a β2P273 residue in channel gating transitions. This residue is located in a central position of the M2-M3 linker of the interdomain interface, expected to be predisposed to interact with another interfacial element, the β1-β2 loop of the extracellular side. The interactions occurring on this interface have been reported to couple agonist binding to channel gating. MAIN METHODS We recorded micro- and macroscopic current responses of recombinant GABAA receptors mutated at the β2P273 residue (to A, K, E) to saturating GABA. Electrophysiological data served as basis to kinetic modeling, used to decipher which gating transition were affected by mutations. KEY FINDINGS Mutations of this residue impaired macroscopic desensitization and accelerated current deactivation with P273E mutant showing greatest deviation from wild-type. Single-channel analysis revealed alterations mainly in short-lived shut times and shortening of openings, resulting in dramatic changes in intraburst open probability. Kinetic modeling indicated that β2P273 mutants show diminished entry into desensitized and open states as well as faster channel closing transitions. SIGNIFICANCE In conclusion, we demonstrate that β2P273 of the M2-M3 linker is a crucial element of the ECD-TMD interface regulating the receptor's ability to undergo late gating transitions. Henceforth, this region could be an important target for new pharmacological tools affecting GABAAR-mediated inhibition.
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The regulatory role of GABA A receptor in Actinia equina nervous system and the possible effect of global ocean acidification. Pflugers Arch 2021; 473:1851-1858. [PMID: 34633524 PMCID: PMC8599403 DOI: 10.1007/s00424-021-02628-w] [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: 09/14/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 11/25/2022]
Abstract
Global warming and connected acidification of the world ocean attract a substantial amount of research efforts, in particular in a context of their impact on behaviour and metabolism of marine organisms, such as Cnidaria. Nevertheless, mechanisms underlying Cnidarians’ neural signalling and behaviour and their (possible) alterations due to the world ocean acidification remain poorly understood. Here we researched for the first time modulation of GABAA receptors (GABAARs) in Actinia equina (Cnidaria: Anthozoa) by pH fluctuations within a range predicted by the world ocean acidification scenarios for the next 80–100 years and by selective pharmacological activation. We found that in line with earlier studies on vertebrates, both changes of pH and activation of GABAARs with a selective allosteric agonist (diazepam) modulate electrical charge transfer through GABAAR and the whole-cell excitability. On top of that, diazepam modifies the animal behavioural reaction on startle response. However, despite behavioural reactions displayed by living animals are controlled by GABAARs, changes of pH do not alter them significantly. Possible mechanisms underlying the species resistance to acidification impact are discussed.
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Decreased Brain pH and Pathophysiology in Schizophrenia. Int J Mol Sci 2021; 22:ijms22168358. [PMID: 34445065 PMCID: PMC8395078 DOI: 10.3390/ijms22168358] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 07/30/2021] [Accepted: 07/30/2021] [Indexed: 12/26/2022] Open
Abstract
Postmortem studies reveal that the brain pH in schizophrenia patients is lower than normal. The exact cause of this low pH is unclear, but increased lactate levels due to abnormal energy metabolism appear to be involved. Schizophrenia patients display distinct changes in mitochondria number, morphology, and function, and such changes promote anaerobic glycolysis, elevating lactate levels. pH can affect neuronal activity as H+ binds to numerous proteins in the nervous system and alters the structure and function of the bound proteins. There is growing evidence of pH change associated with cognition, emotion, and psychotic behaviors. Brain has delicate pH regulatory mechanisms to maintain normal pH in neurons/glia and extracellular fluid, and a change in these mechanisms can affect, or be affected by, neuronal activities associated with schizophrenia. In this review, we discuss the current understanding of the cause and effect of decreased brain pH in schizophrenia based on postmortem human brains, animal models, and cellular studies. The topic includes the factors causing decreased brain pH in schizophrenia, mitochondria dysfunction leading to altered energy metabolism, and pH effects on the pathophysiology of schizophrenia. We also review the acid/base transporters regulating pH in the nervous system and discuss the potential contribution of the major transporters, sodium hydrogen exchangers (NHEs), and sodium-coupled bicarbonate transporters (NCBTs), to schizophrenia.
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Kłopotowski K, Czyżewska MM, Mozrzymas JW. Glycine substitution of α1F64 residue at the loop D of GABA A receptor impairs gating - Implications for importance of binding site-channel gate linker rigidity. Biochem Pharmacol 2021; 192:114668. [PMID: 34216603 DOI: 10.1016/j.bcp.2021.114668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/27/2021] [Accepted: 06/28/2021] [Indexed: 12/29/2022]
Abstract
GABAA receptors (GABAARs) play a crucial role in mediating inhibition in adult mammalian brains. In the recent years, an impressive progress in revealing the static structure of GABAARs was achieved but the molecular mechanisms underlying their conformational transitions remain elusive. Phenylalanine 64 (α1F64) is located at the loop D of the orthosteric binding site of GABAAR and was found to directly interact with GABA molecule. Mutations of α1F64 were demonstrated to affect not only binding but also some gating properties. Loop D is a rigid β strand which seems to be particularly suitable to convey activatory signaling from the ligand binding site (LBS) to the gate at the channel pore. To test this scenario, we have investigated the substitution of α1F64 with glycine, the smallest amino acid, widely recognized as a rigidity "reducer" of protein structures. To this end, we assessed the impact of the α1F64G mutation in the α1β2γ2L type of GABAARs on gating properties by analyzing both macroscopic responses to rapid agonist applications and single-channel currents. We found that this substitution dramatically altered all gating features of the receptor (opening/closing, preactivation and desensitization) which contrasts with markedly weaker effects of previously considered substitutions (α1F64L and α1F64A). In particular, α1F64G mutation practically abolished the desensitization process. At the same time, the α1F64G mutant maintained gating integrity manifested as single-channel activity in the form of clusters. We conclude that rigidity of the loop D plays a crucial role in conveying the activation signal from the LBS to the channel gate.
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Affiliation(s)
- Karol Kłopotowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland.
| | - Marta M Czyżewska
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland
| | - Jerzy W Mozrzymas
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland.
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The β 2 subunit E155 residue as a proton sensor at the binding site on GABA type A receptors. Eur J Pharmacol 2021; 906:174293. [PMID: 34214584 DOI: 10.1016/j.ejphar.2021.174293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 06/22/2021] [Accepted: 06/28/2021] [Indexed: 11/22/2022]
Abstract
GABA type A receptor plays a key role in inhibitory signaling in the adult central nervous system. This receptor can be modulated by protons but the underlying molecular mechanisms have not been fully explored. To find possible pH-sensor residues, a comparative study for proton-activated GLIC channel and α1β2γ2 GABA receptor was performed and pK 's of respective residues were estimated by numerical algorithms which consider local interactions. β E155, located at the GABA binding site, showed pKa values close to physiological values and dependence on the receptor state and ligation, suggesting a role in modulation by pH. To validate this prediction, pH sensitivity of current responses to GABA was investigated using patch-clamp technique for WT and mutated (β2E155[C, S, Q, L]) GABA receptors. Cysteine mutation preserved pH sensitivity. However, for remaining mutants, the sensitivity to acidification (pH = 6.0) was reduced becoming not statistically significant. The effect of alkaline pH (8.0) was maintained for all mutants with exception for β2E155L for which it was nearly abolished. To further explore the impact of considered mutations, molecular docking was performed which indicated that pH modulation is probably affected by interplay between binding site residues, zwitterion GABA and protons. These data, altogether, indicate that mutation of β2E155 to hydrophobic residue (L) maximally impaired pH modulation while for polar substitutions the effect was smaller. In conclusion, our data provide evidence that a key binding site residue β2E155 plays an important role in proton sensitivity of GABA receptor.
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10
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Hikima T, Lee CR, Witkovsky P, Chesler J, Ichtchenko K, Rice ME. Activity-dependent somatodendritic dopamine release in the substantia nigra autoinhibits the releasing neuron. Cell Rep 2021; 35:108951. [PMID: 33826884 PMCID: PMC8189326 DOI: 10.1016/j.celrep.2021.108951] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/20/2020] [Accepted: 03/15/2021] [Indexed: 12/12/2022] Open
Abstract
Somatodendritic dopamine (DA) release from midbrain DA neurons activates D2 autoreceptors on these cells to regulate their activity. However, the source of autoregulatory DA remains controversial. Here, we test the hypothesis that D2 autoreceptors on a given DA neuron in the substantia nigra pars compacta (SNc) are activated primarily by DA released from that same cell, rather than from its neighbors. Voltage-clamp recording allows monitoring of evoked D2-receptor-mediated inhibitory currents (D2ICs) in SNc DA neurons as an index of DA release. Single-cell application of antibodies to Na+ channels via the recording pipette decreases spontaneous activity of recorded neurons and attenuates evoked D2ICs; antibodies to SNAP-25, a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein, also decrease D2IC amplitude. Evoked D2ICs are nearly abolished by the light chain of botulinum neurotoxin A, which cleaves SNAP-25, whereas synaptically activated GABAB-receptor-mediated currents are unaffected. Thus, somatodendritic DA release in the SNc autoinhibits the neuron that releases it.
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Affiliation(s)
- Takuya Hikima
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Christian R Lee
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Paul Witkovsky
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Julia Chesler
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Konstantin Ichtchenko
- Department of Biochemistry & Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Margaret E Rice
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA; Department of Neuroscience & Physiology, New York University Grossman School of Medicine, New York, NY 10016, USA.
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11
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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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12
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Theparambil SM, Hosford PS, Ruminot I, Kopach O, Reynolds JR, Sandoval PY, Rusakov DA, Barros LF, Gourine AV. Astrocytes regulate brain extracellular pH via a neuronal activity-dependent bicarbonate shuttle. Nat Commun 2020; 11:5073. [PMID: 33033238 PMCID: PMC7545092 DOI: 10.1038/s41467-020-18756-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 09/09/2020] [Indexed: 12/19/2022] Open
Abstract
Brain cells continuously produce and release protons into the extracellular space, with the rate of acid production corresponding to the levels of neuronal activity and metabolism. Efficient buffering and removal of excess H+ is essential for brain function, not least because all the electrogenic and biochemical machinery of synaptic transmission is highly sensitive to changes in pH. Here, we describe an astroglial mechanism that contributes to the protection of the brain milieu from acidification. In vivo and in vitro experiments conducted in rodent models show that at least one third of all astrocytes release bicarbonate to buffer extracellular H+ loads associated with increases in neuronal activity. The underlying signalling mechanism involves activity-dependent release of ATP triggering bicarbonate secretion by astrocytes via activation of metabotropic P2Y1 receptors, recruitment of phospholipase C, release of Ca2+ from the internal stores, and facilitated outward HCO3- transport by the electrogenic sodium bicarbonate cotransporter 1, NBCe1. These results show that astrocytes maintain local brain extracellular pH homeostasis via a neuronal activity-dependent release of bicarbonate. The data provide evidence of another important metabolic housekeeping function of these glial cells.
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Affiliation(s)
- Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Iván Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - Olga Kopach
- Institute of Neurology, University College London, London, UK
| | | | | | | | | | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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13
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Zhang HP, Zhu YX, Zhang ZX, Chai LS, Liu YB, Yu HB, Li Y. New triterpenoids from the roots of Rhododendron molle as positive modulators of GABAA receptors. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.131455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Doughty PT, Hossain I, Gong C, Ponder KA, Pati S, Arumugam PU, Murray TA. Novel microwire-based biosensor probe for simultaneous real-time measurement of glutamate and GABA dynamics in vitro and in vivo. Sci Rep 2020; 10:12777. [PMID: 32728074 PMCID: PMC7392771 DOI: 10.1038/s41598-020-69636-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 07/07/2020] [Indexed: 12/21/2022] Open
Abstract
Glutamate (GLU) and γ-aminobutyric acid (GABA) are the major excitatory (E) and inhibitory (I) neurotransmitters in the brain, respectively. Dysregulation of the E/I ratio is associated with numerous neurological disorders. Enzyme-based microelectrode array biosensors present the potential for improved biocompatibility, localized sample volumes, and much faster sampling rates over existing measurement methods. However, enzymes degrade over time. To overcome the time limitation of permanently implanted microbiosensors, we created a microwire-based biosensor that can be periodically inserted into a permanently implanted cannula. Biosensor coatings were based on our previously developed GLU and reagent-free GABA shank-type biosensor. In addition, the microwire biosensors were in the same geometric plane for the improved acquisition of signals in planar tissue including rodent brain slices, cultured cells, and brain regions with laminar structure. We measured real-time dynamics of GLU and GABA in rat hippocampal slices and observed a significant, nonlinear shift in the E/I ratio from excitatory to inhibitory dominance as electrical stimulation frequency increased from 10 to 140 Hz, suggesting that GABA release is a component of a homeostatic mechanism in the hippocampus to prevent excitotoxic damage. Additionally, we recorded from a freely moving rat over fourteen weeks, inserting fresh biosensors each time, thus demonstrating that the microwire biosensor overcomes the time limitation of permanently implanted biosensors and that the biosensors detect relevant changes in GLU and GABA levels that are consistent with various behaviors.
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Affiliation(s)
- P Timothy Doughty
- Center for Biomedical Engineering and Rehabilitation Sciences, Louisiana Tech University, Ruston, LA, USA
| | - Imran Hossain
- Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA, USA
| | - Chenggong Gong
- Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA, USA
| | - Kayla A Ponder
- Center for Biomedical Engineering and Rehabilitation Sciences, Louisiana Tech University, Ruston, LA, USA
| | - Sandipan Pati
- UAB Epilepsy Center/Department of Neurology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Prabhu U Arumugam
- Center for Biomedical Engineering and Rehabilitation Sciences, Louisiana Tech University, Ruston, LA, USA. .,Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA, USA.
| | - Teresa A Murray
- Center for Biomedical Engineering and Rehabilitation Sciences, Louisiana Tech University, Ruston, LA, USA.
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15
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Crosby KC, Gookin SE, Garcia JD, Hahm KM, Dell'Acqua ML, Smith KR. Nanoscale Subsynaptic Domains Underlie the Organization of the Inhibitory Synapse. Cell Rep 2020; 26:3284-3297.e3. [PMID: 30893601 DOI: 10.1016/j.celrep.2019.02.070] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 01/03/2019] [Accepted: 02/19/2019] [Indexed: 12/15/2022] Open
Abstract
Inhibitory synapses mediate the majority of synaptic inhibition in the brain, thereby controlling neuronal excitability, firing, and plasticity. Although essential for neuronal function, the central question of how these synapses are organized at the subsynaptic level remains unanswered. Here, we use three-dimensional (3D) super-resolution microscopy to image key components of the inhibitory postsynaptic domain and presynaptic terminal, revealing that inhibitory synapses are organized into nanoscale subsynaptic domains (SSDs) of the gephyrin scaffold, GABAARs and the active-zone protein Rab3-interacting molecule (RIM). Gephyrin SSDs cluster GABAAR SSDs, demonstrating nanoscale architectural interdependence between scaffold and receptor. GABAAR SSDs strongly associate with active-zone RIM SSDs, indicating an important role for GABAAR nanoscale organization near sites of GABA release. Finally, we find that in response to elevated activity, synapse growth is mediated by an increase in the number of postsynaptic SSDs, suggesting a modular mechanism for increasing inhibitory synaptic strength.
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Affiliation(s)
- Kevin C Crosby
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Sara E Gookin
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Joshua D Garcia
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Katlin M Hahm
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Katharine R Smith
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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16
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Terejko K, Kaczor PT, Michałowski MA, Dąbrowska A, Mozrzymas JW. The C loop at the orthosteric binding site is critically involved in GABA A receptor gating. Neuropharmacology 2019; 166:107903. [PMID: 31972511 DOI: 10.1016/j.neuropharm.2019.107903] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 11/15/2019] [Accepted: 12/02/2019] [Indexed: 02/02/2023]
Abstract
GABAA receptors (GABAARs) play a crucial role in mammalian adult brain inhibition. The dysfunction of GABAergic drive is related to such disorders as epilepsy, schizophrenia, and depression. Substantial progress has recently been made in describing the static structure of GABAARs, but the molecular mechanisms that underlie the activation process remain elusive. The C loop of the GABAAR structure shows the largest movement upon ligand binding to the orthosteric binding site, a phenomenon that is referred to as "capping." The C loop is known to be involved in agonist binding, but its role in the gating of Cys-loop receptors is still debated. Herein, we investigated this issue by analyzing the impact of a β2F200 residue mutation of the C loop on gating properties of α1β2γ2 GABAARs. Extensive analyses and the modeling of current responses to saturating agonist application demonstrated that this mutation strongly affected preactivation, opening, closing and desensitization, i.e. all considered gating steps. Single-channel analysis revealed that the β2F200 mutation slowed all shut time components, and open times were shortened. Model fitting of these single-channel data further confirmed that the β2F200 mutation strongly affected all of the gating characteristics. We also found that this mutation altered receptor sensitivity to the benzodiazepine flurazepam, which was attributable to a change in preactivation kinetics. In silico analysis indicated that the β2F200 mutation resulted in distortion of the C loop structure, causing the movement of its tip from the binding site. Altogether, we provide the first evidence that C loop critically controls GABAAR gating.
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Affiliation(s)
- Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland.
| | - Przemysław T Kaczor
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland
| | - Agnieszka Dąbrowska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland.
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17
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Γ-Aminobutyric acid in adult brain: an update. Behav Brain Res 2019; 376:112224. [DOI: 10.1016/j.bbr.2019.112224] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 09/09/2019] [Accepted: 09/09/2019] [Indexed: 01/21/2023]
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18
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Kisiel M, Jatczak-Śliwa M, Mozrzymas JW. Protons modulate gating of recombinant α 1β 2γ 2 GABA A receptor by affecting desensitization and opening transitions. Neuropharmacology 2018; 146:300-315. [PMID: 30326242 DOI: 10.1016/j.neuropharm.2018.10.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 09/28/2018] [Accepted: 10/12/2018] [Indexed: 01/27/2023]
Abstract
Protons are potent modulators of GABAA receptors (GABAARs) and α1Phe64 residue was implicated in their pH sensitivity. Recently, we have demonstrated that this residue is involved in flipping transitions which precede channel opening. We thus re-addressed the mechanism of GABAAR modulation by protons by considering the gating scheme extended by flipping. The impact of pH changes was examined on currents mediated by wild-type α1β2γ2 receptors or by their α1Phe64Leu or α1Phe64Cys mutants and elicited by saturating concentrations of full (GABA) or partial (piperidine-4-sulfonic acid) agonists. To describe the impact of extracellular pH on receptor gating, we combined macroscopic analysis of currents elicited by rapid agonist applications with single-channel studies. Acidification (pH 6.0) increased current amplitudes (in the case of leucine mutants effect was stronger when P4S was used) and decreased the rate and the extent of desensitization whereas alkalization (pH 8.0) had the opposite but weaker effect. Deactivation kinetics for wild-type receptors was slowed down by acidification while in the case of mutants this effect was observed upon alkalization. Moreover, α1Phe64 mutations enhanced GABAAR sensitivity to alkaline pH. Single-channel analysis revealed that acidification prolonged burst durations and affected shut but not open time distributions. Model simulations for macroscopic and single-channel activity indicated a novel mechanism in which protons primarily affected opening and desensitization rates but not flipping/unflipping. This evidence for the impact of protons on the receptor gating together with previously demonstrated effect on the agonist binding, point to a complex effect of extracellular pH on GABAAR macromolecule.
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Affiliation(s)
- Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
| | - Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Molecular Physiology and Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
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19
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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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20
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Jang IJ, Davies AJ, Akimoto N, Back SK, Lee PR, Na HS, Furue H, Jung SJ, Kim YH, Oh SB. Acute inflammation reveals GABA A receptor-mediated nociception in mouse dorsal root ganglion neurons via PGE 2 receptor 4 signaling. Physiol Rep 2018; 5:5/8/e13178. [PMID: 28438981 PMCID: PMC5408276 DOI: 10.14814/phy2.13178] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 12/29/2022] Open
Abstract
Gamma‐aminobutyric acid (GABA) depolarizes dorsal root ganglia (DRG) primary afferent neurons through activation of Cl− permeable GABAA receptors but the physiologic role of GABAA receptors in the peripheral terminals of DRG neurons remains unclear. In this study, we investigated the role of peripheral GABAA receptors in nociception using a mouse model of acute inflammation. In vivo, peripheral administration of the selective GABAA receptor agonist muscimol evoked spontaneous licking behavior, as well as spinal wide dynamic range (WDR) neuron firing, after pre‐conditioning with formalin but had no effect in saline‐treated mice. GABAA receptor‐mediated pain behavior after acute formalin treatment was abolished by the GABAA receptor blocker picrotoxin and cyclooxygenase inhibitor indomethacin. In addition, treatment with prostaglandin E2 (PGE2) was sufficient to reveal muscimol‐induced licking behavior. In vitro, GABA induced sub‐threshold depolarization in DRG neurons through GABAA receptor activation. Both formalin and PGE2 potentiated GABA‐induced Ca2+ transients and membrane depolarization in capsaicin‐sensitive nociceptive DRG neurons; these effects were blocked by the prostaglandin E2 receptor 4 (EP4) antagonist AH23848 (10 μmol/L). Furthermore, potentiation of GABA responses by PGE2 was prevented by the selective Nav1.8 antagonist A887826 (100 nmol/L). Although the function of the Na+‐K+‐2Cl‐ co‐transporter NKCC1 was required to maintain the Cl‐ ion gradient in isolated DRG neurons, NKCC1 was not required for GABAA receptor‐mediated nociceptive behavior after acute inflammation. Taken together, these results demonstrate that GABAA receptors may contribute to the excitation of peripheral sensory neurons in inflammation through a combined effect involving PGE2‐EP4 signaling and Na+ channel sensitization.
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Affiliation(s)
- In Jeong Jang
- Pain Laboratory, Dental Research Institute and Department of Neurobiology and Physiology School of Dentistry Seoul National University, Seoul, Korea
| | - Alexander J Davies
- Pain Laboratory, Dental Research Institute and Department of Neurobiology and Physiology School of Dentistry Seoul National University, Seoul, Korea.,Department of Brain and Cognitive Sciences, College of Natural Sciences Seoul National University, Seoul, Korea
| | - Nozomi Akimoto
- Department of Information Physiology, National Institute for Physiological Sciences, Okazaki, Japan
| | - Seung Keun Back
- Department of Physiology, Korea University College of Medicine, Seoul, Korea.,Department of Pharmacology and Biotechnology, College of Medical Engineering Konyang University, Daejeon, Korea
| | - Pa Reum Lee
- Pain Laboratory, Dental Research Institute and Department of Neurobiology and Physiology School of Dentistry Seoul National University, Seoul, Korea.,Department of Brain and Cognitive Sciences, College of Natural Sciences Seoul National University, Seoul, Korea
| | - Heung Sik Na
- Department of Physiology, Korea University College of Medicine, Seoul, Korea
| | - Hidemasa Furue
- Department of Information Physiology, National Institute for Physiological Sciences, Okazaki, Japan
| | - Sung Jun Jung
- Department of Physiology, Hanyang University, Seoul, Korea
| | - Yong Ho Kim
- Pain Laboratory, Dental Research Institute and Department of Neurobiology and Physiology School of Dentistry Seoul National University, Seoul, Korea
| | - Seog Bae Oh
- Pain Laboratory, Dental Research Institute and Department of Neurobiology and Physiology School of Dentistry Seoul National University, Seoul, Korea .,Department of Brain and Cognitive Sciences, College of Natural Sciences Seoul National University, Seoul, Korea
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21
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Kisiel M, Jatczak M, Brodzki M, Mozrzymas JW. Spontaneous activity, singly bound states and the impact of alpha 1Phe64 mutation on GABA AR gating in the novel kinetic model based on the single-channel recordings. Neuropharmacology 2017; 131:453-474. [PMID: 29162430 DOI: 10.1016/j.neuropharm.2017.11.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 10/25/2017] [Accepted: 11/17/2017] [Indexed: 12/31/2022]
Abstract
GABAA receptor is the primary mediator of inhibition in the adult mammalian brain. Our recent studies revealed that a classic gating scheme for GABAAR needed to be updated with an intermediate step (flipping) and that the α1Phe64 mutation at the GABA binding site affects this transition. However, description of flipping at the single-channel level remains incomplete. In particular, its role in singly-bound and spontaneous activity remains unknown. We have performed thus single-channel recordings over wide range of agonist concentration for wild-type α1β2γ2L receptors and α1Phe64 mutants. For WT receptors we observed relatively frequent brief spontaneous openings which were also present at low [GABA]. However, closed times distributions for spontaneous activity and at low [GABA] were clearly different indicating that a proportion of short-lived openings were due to liganded, most likely singly bound receptors. Increasing [GABA] resulted in prolongation of bursts and increased occurrence of bursts with long openings and short closures. Mutations of α1Phe64 residue dramatically affected the open and closed time distributions at high and saturating [GABA], especially in the case of cysteine mutants. However, this mutation weakly affected spontaneous or singly bound activity. Model fitting of our single-channel data led us to propose a novel and, to our knowledge, most complete GABAAR kinetic model in which flipping occurs in singly and doubly bound states. However, spontaneous activity did not reveal involvement of flipping. Moreover, we report that α1Phe64 mutation affects not only the flipping but also the opening/closing transitions indicating its generalized impact on the receptor gating.
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Affiliation(s)
- Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
| | - Magdalena Jatczak
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Physiology and Molecular Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland; Department of Physiology and Molecular Neurobiology, Wrocław University, Wrocław 50-335, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław 50-368, Poland.
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22
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Chen Z, Liu R, Yang SH, Dillon GH, Huang R. Methylene blue inhibits GABA A receptors by interaction with GABA binding site. Neuropharmacology 2017; 119:100-110. [PMID: 28390894 DOI: 10.1016/j.neuropharm.2017.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 03/23/2017] [Accepted: 04/03/2017] [Indexed: 01/11/2023]
Abstract
Methylene blue (MB) is commonly used in diagnostic procedures and is also used to treat various medical conditions. Neurological effects of MB have been reported in clinical observations and experimental studies. Thus the modulation of GABAA receptor function by MB was investigated. Whole-cell GABA-activated currents were recorded from HEK293 cells expressing various GABAA receptor subunit configurations. MB inhibition of GABA currents was apparent at 3 μM, and it had an IC50 of 31 μM in human α1β2γ2 receptors. The MB action was rapid and reversible. MB inhibition was not mediated via the picrotoxin site, as a mutation (T6'F of the β2 subunit) known to confer resistance to picrotoxin had no effect on MB-induced inhibition. Blockade of GABAA receptors by MB was demonstrated across a range of receptors expressing varying subunits, including those expressed at extrasynaptic sites. The sensitivity of α1β2 receptors to MB was similar to that observed in α1β2γ2 receptors, indicating that MB's action via the benzodiazepine or Zn2+ site is unlikely. MB-induced inhibition of GABA response was competitive with respect to GABA. Furthermore, mutation of α1 F64 to A and β2 Y205 to F in the extracellular N-terminus, both residues which are known to comprise GABA binding pocket, remarkably diminished MB inhibition of GABA currents. These data suggest that MB inhibits GABAA receptor function by direct or allosteric interaction with the GABA binding site. Finally, in mouse hippocampal CA1 pyramidal neurons, MB inhibited GABA-activated currents as well as GABAergic IPSCs. We demonstrate that MB directly inhibits GABAA receptor function, which may underlie some of the effects of MB on the CNS.
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Affiliation(s)
- Zhenglan Chen
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Ran Liu
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Shao-Hua Yang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Glenn H Dillon
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - Renqi Huang
- Center for Neuroscience Discovery, Institute of Healthy Aging, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States.
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23
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Albers HE, Walton JC, Gamble KL, McNeill JK, Hummer DL. The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus. Front Neuroendocrinol 2017; 44:35-82. [PMID: 27894927 PMCID: PMC5225159 DOI: 10.1016/j.yfrne.2016.11.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 10/16/2016] [Accepted: 11/22/2016] [Indexed: 12/31/2022]
Abstract
Virtually every neuron within the suprachiasmatic nucleus (SCN) communicates via GABAergic signaling. The extracellular levels of GABA within the SCN are determined by a complex interaction of synthesis and transport, as well as synaptic and non-synaptic release. The response to GABA is mediated by GABAA receptors that respond to both phasic and tonic GABA release and that can produce excitatory as well as inhibitory cellular responses. GABA also influences circadian control through the exclusively inhibitory effects of GABAB receptors. Both GABA and neuropeptide signaling occur within the SCN, although the functional consequences of the interactions of these signals are not well understood. This review considers the role of GABA in the circadian pacemaker, in the mechanisms responsible for the generation of circadian rhythms, in the ability of non-photic stimuli to reset the phase of the pacemaker, and in the ability of the day-night cycle to entrain the pacemaker.
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Affiliation(s)
- H Elliott Albers
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States.
| | - James C Walton
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Karen L Gamble
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - John K McNeill
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Neuroscience Institute, Georgia State University, Atlanta, GA 30302, United States
| | - Daniel L Hummer
- Center for Behavioral Neuroscience, Atlanta, GA 30302, United States; Department of Psychology, Morehouse College, Atlanta, GA 30314, United States
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24
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Chua HC, Chebib M. GABA A Receptors and the Diversity in their Structure and Pharmacology. ADVANCES IN PHARMACOLOGY 2017; 79:1-34. [DOI: 10.1016/bs.apha.2017.03.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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25
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Brodzki M, Rutkowski R, Jatczak M, Kisiel M, Czyzewska MM, Mozrzymas JW. Comparison of kinetic and pharmacological profiles of recombinant α1γ2L and α1β2γ2L GABAA receptors - A clue to the role of intersubunit interactions. Eur J Pharmacol 2016; 784:81-9. [PMID: 27179992 DOI: 10.1016/j.ejphar.2016.05.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 05/10/2016] [Accepted: 05/10/2016] [Indexed: 11/25/2022]
Abstract
The fastest inhibitory mechanism in the CNS is mediated by ionotropic GABAA receptors and it is known that subunit composition critically determines their properties. While a typical GABAA receptor consists of two α, two β and one γ/δ subunit, there are some exceptions, e.g. αβ receptors. Functional α1γ2 GABAA receptors can be expressed in recombinant model (Verdoorn et al., 1990) and although their role remains unknown, it seems appealing to extend their characterization to further explore the structure-function relationship of GABAA receptors. Intriguingly, this receptor is lacking canonical GABA binding sites but it can be activated by GABA and dose-response relationships for α1β2γ2L and α1γ2L receptors overlap. Deactivation kinetics was similar for both receptors but the percentage of the fast component was smaller in the case of α1γ2L receptors and, consequently, the mean deactivation time constant was slower. The rate and extent of macroscopic desensitization were smaller in the case of α1γ2L receptors but they showed slower recovery. Both receptor types had a similar proton sensitivity showing only subtle but significant differences in pH effects on deactivation. Flurazepam exerted a similar effect on both receptors but the rapid deactivation components were differently affected and an opposite effect was observed on desensitization extent. Rebound currents evoked by pentobarbital were undistinguishable for both receptor types. Taking altogether, although some significant differences were found, α1β2γ2L and α1γ2L receptors showed unforeseen similarity. We propose that functioning of GABAA receptors might rely on subunit-subunit cooperative interactions to a larger extent than believed so far.
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Affiliation(s)
- Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland.
| | - Radoslaw Rutkowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Magdalena Jatczak
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland
| | - Magdalena Kisiel
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Marta M Czyzewska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland; Department of Animal Molecular Physiology, Institute of Experimental Biology, University of Wrocław, ul. Cybulskiego 30, 50-205 Wrocław, Poland
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26
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Abstract
Gamma-amino butyric acid (GABA) is the major inhibitory neurotransmitter that is known to be synthesized and released from GABAergic neurons in the brain. However, recent studies have shown that not only neurons but also astrocytes contain a considerable amount of GABA that can be released and activate GABA receptors in neighboring neurons. These exciting new findings for glial GABA raise further interesting questions about the source of GABA, its mechanism of release and regulation and the functional role of glial GABA. In this review, we highlight recent studies that identify the presence and release of GABA in glial cells, we show several proposed potential pathways for accumulation and modulation of glial intracellular and extracellular GABA content, and finally we discuss functional roles for glial GABA in the brain.
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Affiliation(s)
- Bo-Eun Yoon
- Department of Nanobiomedical Science, Dankook University Chungnam, South Korea
| | - C Justin Lee
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST) Seoul, South Korea ; Center for Neural Science and Center for Functional Connectomics, Korea Institute of Science and Technology (KIST) Seoul, South Korea
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27
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Yoon BE, Woo J, Chun YE, Chun H, Jo S, Bae JY, An H, Min JO, Oh SJ, Han KS, Kim HY, Kim T, Kim YS, Bae YC, Lee CJ. Glial GABA, synthesized by monoamine oxidase B, mediates tonic inhibition. J Physiol 2014; 592:4951-68. [PMID: 25239459 DOI: 10.1113/jphysiol.2014.278754] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
GABA is the major inhibitory transmitter in the brain and is released not only from a subset of neurons but also from glia. Although neuronal GABA is well known to be synthesized by glutamic acid decarboxylase (GAD), the source of glial GABA is unknown. After estimating the concentration of GABA in Bergmann glia to be around 5-10 mM by immunogold electron microscopy, we demonstrate that GABA production in glia requires MAOB, a key enzyme in the putrescine degradation pathway. In cultured cerebellar glia, both Ca(2+)-induced and tonic GABA release are significantly reduced by both gene silencing of MAOB and the MAOB inhibitor selegiline. In the cerebellum and striatum of adult mice, general gene silencing, knock out of MAOB or selegiline treatment resulted in elimination of tonic GABA currents recorded from granule neurons and medium spiny neurons. Glial-specific rescue of MAOB resulted in complete rescue of tonic GABA currents. Our results identify MAOB as a key synthesizing enzyme of glial GABA, which is released via bestrophin 1 (Best1) channel to mediate tonic inhibition in the brain.
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Affiliation(s)
- Bo-Eun Yoon
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea Department of Nanobiomedical Science, Dankook University, Chungnam, 330-714, Korea
| | - Junsung Woo
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Ye-Eun Chun
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Heejung Chun
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Seonmi Jo
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, Korea
| | - Jin Young Bae
- Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - Heeyoung An
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea KU-KIST School of Converging Science and Technology, Korea University, Seoul, 136-701, Korea
| | - Joo Ok Min
- Department of Nanobiomedical Science, Dankook University, Chungnam, 330-714, Korea
| | - Soo-Jin Oh
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Kyung-Seok Han
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
| | - Hye Yun Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Taekeun Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Young Soo Kim
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea
| | - Yong Chul Bae
- Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, Daegu, 700-412, Republic of Korea
| | - C Justin Lee
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Center for Neural Science, Korea Institute of Science and Technology (KIST), Seoul, 136-791, Korea Neuroscience Program, University of Science and Technology (UST), Daejeon, 305-350, Korea
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28
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Ding J, Huang C, Peng Z, Xie Y, Deng S, Nie YZ, Xu TL, Ge WH, Li WG, Li F. Electrophysiological characterization of methyleugenol: a novel agonist of GABA(A) receptors. ACS Chem Neurosci 2014; 5:803-11. [PMID: 24980777 DOI: 10.1021/cn500022e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Methyleugenol (ME) is a natural constituent isolated from many plant essential oils having multiple biological effects including anticonvulsant and anesthetic activities, although the underlying mechanisms remain unclear. Here, we identify ME as a novel agonist of ionotropic γ-aminobutyric acid (GABA) receptors. At lower concentrations (∼30 μM), ME significantly sensitized GABA-induced, but not glutamate- or glycine-induced, currents in cultured hippocampal neurons, indicative of a preferentially modulatory role of this compound for A type GABA receptors (GABAARs). In addition, ME at higher concentrations (≥100 μM) induced a concentration-dependent, Cl(-)-permeable current in hippocampal neurons, which was inhibited by a GABAAR channel blocker, picrotoxin, and a competitive GABAAR antagonist, bicuculline, but not a specific glycine receptor inhibitor, strychnine. Moreover, ME activated a similar current mediated by recombinant α1-β2-γ2 or α5-β2-γ2 GABAARs in human embryonic kidney (HEK) cells. Consequently, ME produced a strong inhibition of synaptically driven neuronal excitation in hippocampal neurons. Together, these results suggest that ME represents a novel agonist of GABAARs, shedding additional light on future development of new therapeutics targeting GABAARs. The present study also adds GABAAR activation to the list of molecular targets of ME that probably account for its biological activities.
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Affiliation(s)
- Jing Ding
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
- Department
of Chinese Materia Medica, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou 310053, China
- Neuroscience
Division, Departments of Anatomy, Histology and Embryology, Biochemistry,
and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment
and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Chen Huang
- Neuroscience
Division, Departments of Anatomy, Histology and Embryology, Biochemistry,
and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment
and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Zhong Peng
- Neuroscience
Division, Departments of Anatomy, Histology and Embryology, Biochemistry,
and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment
and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yuxuan Xie
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
| | - Shining Deng
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
| | - Yan-Zhen Nie
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
| | - Tian-Le Xu
- Neuroscience
Division, Departments of Anatomy, Histology and Embryology, Biochemistry,
and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment
and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Wei-Hong Ge
- Department
of Chinese Materia Medica, College of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou 310053, China
| | - Wei-Guang Li
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
- Neuroscience
Division, Departments of Anatomy, Histology and Embryology, Biochemistry,
and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment
and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Fei Li
- Department
of Developmental and Behavioral Pediatrics, Shanghai Institute of
Pediatric Translational Medicine, Shanghai Children’s Medical
Center, Ministry of Education-Shanghai Key Laboratory of Children’s
Environmental Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200129, China
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29
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Stephan J, Friauf E. Functional analysis of the inhibitory neurotransmitter transporters GlyT1, GAT-1, and GAT-3 in astrocytes of the lateral superior olive. Glia 2014; 62:1992-2003. [PMID: 25103283 DOI: 10.1002/glia.22720] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 06/26/2014] [Accepted: 06/27/2014] [Indexed: 01/03/2023]
Abstract
Neurotransmitter clearance from the synaptic cleft is a major function of astrocytes and requires neurotransmitter transporters. In the rodent lateral superior olive (LSO), a conspicuous auditory brainstem center, both glycine and GABA mediate synaptic inhibition. However, the main inhibitory input from the medial nucleus of the trapezoid body (MNTB) appears to be glycinergic by postnatal day (P) 14, when circuit maturation is almost accomplished. Using whole-cell patch-clamp recordings at P3-20, we analyzed glycine transporters (GlyT1) and GABA transporters (GAT-1, GAT-3) in mouse LSO astrocytes, emphasizing on their developmental regulation. Application of glycine or GABA induced a dose- and age-dependent inward current and a respective depolarization. The GlyT1-specific inhibitor sarcosine reduced the maximal glycine-induced current (IGly (max) ) by about 60%. The GAT-1 and GAT-3 antagonists NO711 and SNAP5114, respectively, reduced the maximal GABA-induced current (IGABA (max) ) by about 35%. Furthermore, [Cl(-) ]o reduction decreased IGly (max) and IGABA (max) by about 85 to 95%, showing the Cl(-) dependence of GlyT and GAT. IGABA (max) was stronger than IGly (max) , and the ratio increased developmentally from 1.6-fold to 3.7-fold. Together, our results demonstrate the functional presence of the three inhibitory neurotransmitter transporters GlyT1, GAT-1, and GAT-3 in LSO astrocytes. Furthermore, the uptake capability for GABA was higher than for glycine, pointing toward eminent GABAergic signaling in the LSO. GABA may originate from another source than the MNTB-LSO synapses, namely from another projection or from reversal of astrocytic GATs. Thus, neuronal signaling in the LSO appears to be more versatile than previously thought. GLIA 2014;62:1992-2003.
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Affiliation(s)
- Jonathan Stephan
- Department of Biology, Animal Physiology Group, University of Kaiserslautern, Kaiserslautern, Germany
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30
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Chen ZL, Huang RQ. Extracellular pH modulates GABAergic neurotransmission in rat hypothalamus. Neuroscience 2014; 271:64-76. [PMID: 24780768 DOI: 10.1016/j.neuroscience.2014.04.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 04/14/2014] [Accepted: 04/17/2014] [Indexed: 11/16/2022]
Abstract
Changes in extracellular pH have a modulatory effect on GABAA receptor function. It has been reported that pH sensitivity of the GABA receptor is dependent on subunit composition and GABA concentration. Most of previous investigations focused on GABA-evoked currents, which only reflect the postsynaptic receptors. The physiological relevance of pH modulation of GABAergic neurotransmission is not fully elucidated. In the present studies, we examined the influence of extracellular pH on the GABAA receptor-mediated inhibitory neurotransmission in rat hypothalamic neurons. The inhibitory postsynaptic currents (IPSCs), tonic currents, and the GABA-evoked currents were recorded with whole-cell patch techniques on the hypothalamic slices from Sprague-Dawley rats at 15-26 postnatal days. The amplitude and frequency of spontaneous GABA IPSCs were significantly increased while the external pH was changed from 7.3 to 8.4. In the acidic pH (6.4), the spontaneous GABA IPSCs were reduced in amplitude and frequency. The pH induced changes in miniature GABA IPSCs (mIPSCs) similar to that in spontaneous IPSCs. The pH effect on the postsynaptic GABA receptors was assessed with exogenously applied varying concentrations of GABA. The tonic currents and the currents evoked by sub-saturating concentration of GABA ([GABA]) (10 μM) were inhibited by acidic pH and potentiated by alkaline pH. In contrast, the currents evoked by saturating [GABA] (1mM) were not affected by pH changes. We also investigated the influence of pH buffers and buffering capacity on pH sensitivity of GABAA receptors on human recombinant α1β2γ2 GABAA receptors stably expressed in HEK 293 cells. The pH influence on GABAA receptors was similar in HEPES- and MES-buffered media, and not dependent on protonated buffers, suggesting that the observed pH effect on GABA response is a specific consequence of changes in extracellular protons. Our data suggest that the hydrogen ions suppress the GABAergic neurotransmission, which is mediated by both presynaptic and postsynaptic mechanisms.
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Affiliation(s)
- Z L Chen
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States
| | - R Q Huang
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, United States.
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31
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Abstract
The generation of a synaptic current at the postsynaptic element (PSCs) is the result of a dynamic sequence of events including the release of the neurotransmitter, its diffusion in the synaptic cleft, and the activation of neurotransmitter receptors located at the postsynaptic side. It is widely accepted that the amplitude and the duration of PSCs are largely dictated by the gating properties of postsynaptic receptors. However, the knowledge of the properties of postsynaptic receptors is mostly derived from steady-state analysis, a condition that is substantially different from the non-equilibrium activation of synaptic receptors imposed by submillisecond neurotransmitter exposures. Given the technical limitations to reproduce the brief "synaptic-like" agonist pulse durations, the functioning of postsynaptic receptors during synaptic transmission is not fully elucidated and the "on-demand" postsynaptic activation of synapses cannot be easily achieved. In this chapter, we review the diverse approaches to study receptor gating at times relevant for synaptic transmission and novel optical/optogenetic techniques for controlling synaptic activity at the postsynaptic level. In addition, we emphasize the role of non-equilibrium in unmasking specific features of synaptic receptor gating and the recent advances in photonics for the light-control of neuronal activity at the single-receptor level.
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Affiliation(s)
- Enrica Maria Petrini
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy
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32
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Dagorn A, Chapalain A, Mijouin L, Hillion M, Duclairoir-Poc C, Chevalier S, Taupin L, Orange N, Feuilloley MGJ. Effect of GABA, a bacterial metabolite, on Pseudomonas fluorescens surface properties and cytotoxicity. Int J Mol Sci 2013; 14:12186-204. [PMID: 23743829 PMCID: PMC3709781 DOI: 10.3390/ijms140612186] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 05/23/2013] [Accepted: 05/27/2013] [Indexed: 01/22/2023] Open
Abstract
Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA) and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37) to GABA (10-5 M) increased its necrotic-like activity on eukaryotic (glial) cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABAA receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS) structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied, and only one, MFP05, a strain isolated from human skin, showed structural differences of biofilm maturation after exposure to GABA. These results reveal that GABA can regulate the LPS structure and cytotoxicity of P. fluorescens, but that this property is specific to some strains.
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Affiliation(s)
- Audrey Dagorn
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Annelise Chapalain
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Lily Mijouin
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Mélanie Hillion
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Cécile Duclairoir-Poc
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Sylvie Chevalier
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Laure Taupin
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, Lorient cedex 56321, France; E-Mail:
| | - Nicole Orange
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
| | - Marc G. J. Feuilloley
- Laboratory of Microbiology Signal and Microenvironment LMSM, EA 4312, Normandie University, Rouen University, GRRs SSE, IRIB, VASI, Evreux F-27000, France; E-Mails: (A.D.); (A.C.); (L.M.); (M.H.); (C.D.-P.); (S.C.); (N.O.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +332-32-29-15-42; Fax: +332-32-29-15-50
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Sinning A, Hübner CA. Minireview: pH and synaptic transmission. FEBS Lett 2013; 587:1923-8. [PMID: 23669358 DOI: 10.1016/j.febslet.2013.04.045] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 04/26/2013] [Accepted: 04/26/2013] [Indexed: 11/30/2022]
Abstract
As a general rule a rise in pH increases neuronal activity, whereas it is dampened by a fall of pH. Neuronal activity per se also challenges pH homeostasis by the increase of metabolic acid equivalents. Moreover, the negative membrane potential of neurons promotes the intracellular accumulation of protons. Synaptic key players such as glutamate receptors or voltage-gated calcium channels show strong pH dependence and effects of pH gradients on synaptic processes are well known. However, the processes and mechanisms that allow controlling the pH in synaptic structures and how these mechanisms contribute to normal synaptic function are only beginning to be resolved.
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Affiliation(s)
- Anne Sinning
- Institute of Human Genetics, University Hospital Jena, Friedrich Schiller University Jena, Kollegiengasse 10, D-07743 Jena, Germany
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34
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Huang C, Li WG, Zhang XB, Wang L, Xu TL, Wu D, Li Y. Alpha-asarone from Acorus gramineus alleviates epilepsy by modulating A-Type GABA receptors. Neuropharmacology 2013; 65:1-11. [DOI: 10.1016/j.neuropharm.2012.09.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 08/08/2012] [Accepted: 09/02/2012] [Indexed: 11/25/2022]
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35
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Hugel S, Kadiri N, Rodeau JL, Gaillard S, Schlichter R. pH-dependent inhibition of native GABA(A) receptors by HEPES. Br J Pharmacol 2012; 166:2402-16. [PMID: 22452286 DOI: 10.1111/j.1476-5381.2012.01956.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Artificial buffers such as HEPES are extensively used to control extracellular pH (pH(e) ) to investigate the effect of H(+) ions on GABA(A) receptor function. EXPERIMENTAL APPROACH In neurones cultured from spinal cord dorsal horn (DH), dorsal root ganglia (DRG) and cerebellar granule cells (GC) of neonatal rats, we studied the effect of pH(e) on currents induced by GABA(A) receptor agonists, controlling pH(e) with HCO(3) (-) or different concentrations of HEPES. KEY RESULTS Changing HEPES concentration from 1 to 20 mM at constant pH(e) strongly inhibited the currents induced by submaximal GABA applications, but not those induced by glycine or glutamate, on DH, DRG or GC neurones, increasing twofold the EC(50) for GABA in DH neurones and GC. Submaximal GABA(A) receptor-mediated currents were also inhibited by piperazine-N,N'-bis(2-ethanesulfonic acid) (PIPES), 3-(N-morpholino)propanesulfonic acid, tris(hydroxymethyl)aminomethane or imidazole. PIPES and HEPES, both piperazine derivatives, similarly inhibited GABA(A) receptors, whereas the other buffers had weaker effects and 2-(N-morpholino)ethanesulfonic acid had no effect. HEPES-induced inhibition of submaximal GABA(A) receptor-mediated currents was unaffected by diethylpyrocarbonate, a histidine-modifying reagent. HEPES-induced inhibition of GABA(A) receptors was independent of membrane potential, HCO(3) (-) and intracellular Cl(-) concentration and was not modified by flumazenil, which blocks the benzodiazepine binding site. However, it strongly depended on pH(e) . CONCLUSIONS AND IMPLICATIONS Inhibition of GABA(A) receptors by HEPES depended on pH(e) , leading to an apparent H(+) -induced inhibition of DH GABA(A) receptors, unrelated to the pH sensitivity of these receptors in both low and physiological buffering conditions, suggesting that protonated HEPES caused this inhibition.
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Affiliation(s)
- S Hugel
- Nociception et Douleur, INCI, UPR3212 CNRS, Université de Strasbourg, Strasbourg, France.
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Dagorn A, Hillion M, Chapalain A, Lesouhaitier O, Duclairoir Poc C, Vieillard J, Chevalier S, Taupin L, Le Derf F, Feuilloley MGJ. Gamma-aminobutyric acid acts as a specific virulence regulator in Pseudomonas aeruginosa. MICROBIOLOGY-SGM 2012; 159:339-351. [PMID: 23154974 DOI: 10.1099/mic.0.061267-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Gamma-aminobutyric acid (GABA) is widespread in the environment and can be used by animal and plants as a communication molecule. Pseudomonas species, in particular fluorescent ones, synthesize GABA and express GABA-binding proteins. In this study, we investigated the effects of GABA on the virulence of Pseudomonas aeruginosa. While exposure to GABA (10 µM) did not modify either the growth kinetics or the motility of the bacterium, its cytotoxicity and virulence were strongly increased. The Caenorhabditis elegans 'fast killing test' model revealed that GABA acts essentially through an increase in diffusible toxin(s). GABA also modulates the biofilm formation activity and adhesion properties of PAO1. GABA has no effect on cell surface polarity, biosurfactant secretion or on the lipopolysaccharide structure. The production of several exo-enzymes, pyoverdin and exotoxin A is not modified by GABA but we observed an increase in cyanogenesis which, by itself, could explain the effect of GABA on P. aeruginosa virulence. This mechanism appears to be regulated by quorum sensing. A proteomic analysis revealed that the effect of GABA on cyanogenesis is correlated with a reduction of oxygen accessibility and an over-expression of oxygen-scavenging proteins. GABA also promotes specific changes in the expression of thermostable and unstable elongation factors Tuf/Ts involved in the interaction of the bacterium with the host proteins. Taken together, these results suggest that GABA is a physiological regulator of P. aeruginosa virulence.
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Affiliation(s)
- Audrey Dagorn
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | - Mélanie Hillion
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | - Annelise Chapalain
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | - Olivier Lesouhaitier
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | - Cécile Duclairoir Poc
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | | | - Sylvie Chevalier
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
| | - Laure Taupin
- Laboratoire de Biotechnologie et Chimie Marines, Université de Bretagne-Sud B.P. 92116, 56321 Lorient cedex, France
| | - Franck Le Derf
- SIMA, UMR 6014 COBRA, University of Rouen, 27000 Evreux, France
| | - Marc G J Feuilloley
- Laboratory of Microbiology Signals and Microenvironment (LMSM) EA 4312, University of Rouen, 27000 Evreux, France
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Effects of halothane on GABAergic and glutamatergic transmission in isolated hippocampal nerve-synapse preparations. Brain Res 2012; 1473:9-18. [DOI: 10.1016/j.brainres.2012.07.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Revised: 07/17/2012] [Accepted: 07/18/2012] [Indexed: 01/31/2023]
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The effects of volatile anesthetics on synaptic and extrasynaptic GABA-induced neurotransmission. Brain Res Bull 2012; 93:69-79. [PMID: 22925739 DOI: 10.1016/j.brainresbull.2012.08.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/17/2012] [Accepted: 08/01/2012] [Indexed: 02/02/2023]
Abstract
Examination of volatile anesthetic actions at single synapses provides more direct information by reducing interference by surrounding tissue and extrasynaptic modulation. We examined how volatile anesthetics modulate GABA release by measuring spontaneous or miniature GABA-induced inhibitory postsynaptic currents (mIPSCs, sIPSCs) or by measuring action potential-evoked IPSCs (eIPSCs) at individual synapses. Halothane increased both the amplitude and frequency of sIPSCs. Isoflurane and enflurane increased mIPSC frequency while sevoflurane had no effect. These anesthetics did not alter mIPSC amplitudes. Halothane increased the amplitude of eIPSCs, with a decrease in failure rate (Rf) and paired-pulse ratio. In contrast, isoflurane and enflurane decreased the eIPSC amplitude and increased Rf, while sevoflurane decreased the eIPSC amplitude without affecting Rf. Volatile anesthetics did not change kinetics except for sevoflurane, suggesting that presynaptic mechanisms dominate changes in neurotransmission. Each anesthetic showed somewhat different GABA-induced response and these results suggest that GABA-induced synaptic transmission cannot have a uniformly common site of action as suggested for volatile anesthetics. In contrast, all volatile anesthetics concentration-dependently enhanced the GABA-induced extrasynaptic currents. Extrasynaptic receptors containing α4 and α5 subunits are reported to have high sensitivities to volatile anesthetics. Also, inhibition of GABA uptake by volatile anesthetics results in higher extracellular GABA concentration, which may lead to prolonged activation of extrasynaptic GABAA receptors. The extrasynaptic GABA-induced receptors may be major site of volatile anesthetic-induced neurotransmission. This article is part of a Special Issue entitled 'Extrasynaptic ionotropic receptors'.
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Zeng WZ, Xu TL. Proton production, regulation and pathophysiological roles in the mammalian brain. Neurosci Bull 2012; 28:1-13. [PMID: 22233885 DOI: 10.1007/s12264-012-1068-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The recent demonstration of proton signaling in C. elegans muscle contraction suggests a novel mechanism for proton-based intercellular communication and has stimulated enthusiasm for exploring proton signaling in higher organisms. Emerging evidence indicates that protons are produced and regulated in localized space and time. Furthermore, identification of proton regulators and sensors in the brain leads to the speculation that proton production and regulation may be of major importance for both physiological and pathological functions ranging from nociception to learning and memory. Extracellular protons may play a role in signal transmission by not only acting on adjacent cells but also affecting the cell from which they were released. In this review, we summarize the upstream and downstream pathways of proton production and regulation in the mammalian brain, with special emphasis on the proton extruders and sensors that are critical in the homeostatic regulation of pH, and discuss their potential roles in proton signaling under normal and pathophysiological conditions.
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Affiliation(s)
- Wei-Zheng Zeng
- Neuroscience Division, Department of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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40
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Wyrembek P, Negri R, Kaczor P, Czyżewska M, Appendino G, Mozrzymas JW. Falcarindiol allosterically modulates GABAergic currents in cultured rat hippocampal neurons. JOURNAL OF NATURAL PRODUCTS 2012; 75:610-616. [PMID: 22432736 DOI: 10.1021/np2008522] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Falcarindiol (1), a C-17 polyacetylenic diol, shows a pleiotropic profile of bioactivity, but the mechanism(s) underlying its actions are largely unknown. Large amounts of 1 co-occur in water hemlock (Oenanthe crocata) along with the convulsant polyacetylenic toxin oenanthotoxin (2), a potent GABA(A) receptor (GABA(A)R) inhibitor. Since these compounds are structurally and biogenetically related, it was considered of interest to evaluate whether 1 could affect GABAergic activity, and for this purpose a model of hippocampal cultured neurons was used. Compound 1 significantly increased the amplitude of miniature inhibitory postsynaptic currents, accelerated their onset, and prolonged the decay kinetics. This compound enhanced also the amplitude of currents elicited by 3 μM GABA and accelerated their fading, reducing, however, currents evoked by a saturating (10 mM) GABA concentration. Moreover, kinetic analysis of responses to 10 mM GABA revealed that 1 upregulated the rate and extent of desensitization and slowed the current onset and deactivation. Taken together, these data show that 1 exerts a potent modulatory action on GABA(A)Rs, possibly by modulating agonist binding and desensitization, overall potentially decreasing the toxicity of co-occurring GABA-inhibiting convulsant toxins.
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Affiliation(s)
- Paulina Wyrembek
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
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41
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Wyrembek P, Negri R, Appendino G, Mozrzymas JW. Inhibitory effects of oenanthotoxin analogues on GABAergic currents in cultured rat hippocampal neurons depend on the polyacetylenes' polarity. Eur J Pharmacol 2012; 683:35-42. [PMID: 22445880 DOI: 10.1016/j.ejphar.2012.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 02/21/2012] [Accepted: 03/04/2012] [Indexed: 11/15/2022]
Abstract
Oenanthotoxin (OETX) and dihydro-OETX are polyacetylenic diols occurring in Oenanthe crocata and are known to exert proconvulsant effects. We have recently demonstrated that these compounds downregulated GABAergic currents (Appendino et al., 2009) and that OETX induced open channel block and allosterically modulated GABA(A) receptors (Wyrembek et al., 2010). O. crocata also contains several minor OETX analogues and in the present study we tested whether their effect on GABA(A) receptors depends on the compounds' polarity. We investigated a series of five polyacetylenes characterized by a higher lipophylicity than OETX, (1-acetyl-2,3-dihydrooenanthotoxin - X1, 14-acetyloenanthotoxin-X2, 1-deoxyoenanthotoxin - X3, 14-deoxyoenanthotoxin - X4, 14-dehydro-1-deoxyOETX - X5, polarity sequence: X1>X2>X3>X4>X5). Their effects were tested first on miniature inhibitory postsynaptic currents (mIPSCs). All but X3, significantly decreased the mIPSC amplitudes while X1, X2, X4 decreased, and X3 and X5 increased the mIPSC frequency. The lack of a clear correlation between the compounds' polarity and their effect on mIPSCs might result from their presynaptic effects. We thus considered their impact on current responses to exogenous GABA applications. Amplitude reduction of current responses was most prominent for X1 and virtually absent for X5 indicating a dependence on the compound's polarity. Only X1 and X2 showed open channel block, while the kinetics of currents were affected only by X1 which further supports a dependence of the drug's effects on their polarity. In conclusion, GABA(A) receptors are inhibited and allosterically modulated by naturally occurring OETX analogues (except X5) and these effects are positively correlated with the compounds' polarity.
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Affiliation(s)
- Paulina Wyrembek
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3, 50-358 Wrocław, Poland
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GABA metabolism and transport: effects on synaptic efficacy. Neural Plast 2012; 2012:805830. [PMID: 22530158 PMCID: PMC3316990 DOI: 10.1155/2012/805830] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/19/2011] [Indexed: 11/17/2022] Open
Abstract
GABAergic inhibition is an important regulator of excitability in neuronal networks. In addition, inhibitory synaptic signals contribute crucially to the organization of spatiotemporal patterns of network activity, especially during coherent oscillations. In order to maintain stable network states, the release of GABA by interneurons must be plastic in timing and amount. This homeostatic regulation is achieved by several pre- and postsynaptic mechanisms and is triggered by various activity-dependent local signals such as excitatory input or ambient levels of neurotransmitters. Here, we review findings on the availability of GABA for release at presynaptic terminals of interneurons. Presynaptic GABA content seems to be an important determinant of inhibitory efficacy and can be differentially regulated by changing synthesis, transport, and degradation of GABA or related molecules. We will discuss the functional impact of such regulations on neuronal network patterns and, finally, point towards pharmacological approaches targeting these processes.
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Acidosis, acid-sensing ion channels, and neuronal cell death. Mol Neurobiol 2011; 44:350-8. [PMID: 21932071 DOI: 10.1007/s12035-011-8204-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 09/01/2011] [Indexed: 10/17/2022]
Abstract
Acidosis is a common feature of many neuronal diseases and often accompanied with adverse consequences such as pain and neuronal injury. Before the discovery of acid-sensing ion channels (ASICs), protons were usually considered as a modulator of other ion channels, such as voltage-gated calcium channels, N-methyl-D-aspartate, and γ-amino butyric acid(A) receptor channels. Accordingly, the functional effects of acidosis were considered as consequences of modulations of these channels. Since the first cloning of ASICs in 1997, the conventional view on acidosis-mediated pain and cell injury has been dramatically changed. To date, ASICs, which are directly activated by extracellular protons, are shown to mediate most of the acidosis-associated physiological and pathological functions. For example, ASIC1a channels are reported to mediate acidosis-induced ischemic neuronal death. In this article, we will review the possible mechanisms that underlie ASIC1a channel-mediated neuronal death and discuss ASIC1a channel modulators involved in this process.
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44
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Herbison AE, Moenter SM. Depolarising and hyperpolarising actions of GABA(A) receptor activation on gonadotrophin-releasing hormone neurones: towards an emerging consensus. J Neuroendocrinol 2011; 23:557-69. [PMID: 21518033 PMCID: PMC3518440 DOI: 10.1111/j.1365-2826.2011.02145.x] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The gonadotrophin-releasing hormone (GnRH) neurones represent the final output neurones of a complex neuronal network that controls fertility. It is now appreciated that GABAergic neurones within this network provide an important regulatory influence on GnRH neurones. However, the consequences of direct GABA(A) receptor activation on adult GnRH neurones have been controversial for nearly a decade now, with both hyperpolarising and depolarising effects being reported. This review provides: (i) an overview of GABA(A) receptor function and its investigation using electrophysiological approaches and (ii) re-examines the past and present results relating to GABAergic regulation of the GnRH neurone, with a focus on mouse brain slice data. Although it remains difficult to reconcile the results of the early studies, there is a growing consensus that GABA can act through the GABA(A) receptor to exert both depolarising and hyperpolarising effects on GnRH neurones. The most recent studies examining the effects of endogenous GABA release on GnRH neurones indicate that the predominant action is that of excitation. However, we are still far from a complete understanding of the effects of GABA(A) receptor activation upon GnRH neurones. We argue that this will require not only a better understanding of chloride ion homeostasis in individual GnRH neurones, and within subcellular compartments of the GnRH neurone, but also a more integrative view of how multiple neurotransmitters, neuromodulators and intrinsic conductances act together to regulate the activity of these important cells.
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Affiliation(s)
- A E Herbison
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand.
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Analgesic effect of intrathecally γ-aminobutyric acid transporter-1 inhibitor NO-711 administrating on neuropathic pain in rats. Neurosci Lett 2011; 494:6-9. [DOI: 10.1016/j.neulet.2011.02.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 02/11/2011] [Accepted: 02/11/2011] [Indexed: 10/18/2022]
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46
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Wyrembek P, Lebida K, Mercik K, Szczuraszek K, Szczot M, Pollastro F, Appendino G, Mozrzymas JW. Block and allosteric modulation of GABAergic currents by oenanthotoxin in rat cultured hippocampal neurons. Br J Pharmacol 2010; 160:1302-15. [PMID: 20590622 DOI: 10.1111/j.1476-5381.2010.00644.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Oenanthotoxin (OETX), a polyacetylenic alcohol from plants of the genus Oenanthe, has recently been identified as potent inhibitor of GABA-evoked currents. However, the effects of OETX on the inhibitory postsynaptic currents (IPSCs), as well as the pharmacological mechanism(s) underlying its effects on GABA(A) receptors, remain unknown. The purpose of this study was to elucidate the mechanism underlying the inhibition of GABAergic currents by OETX. EXPERIMENTAL APPROACH Effects of OETX on GABAergic currents were studied using the patch clamp technique on rat cultured hippocampal neurons. Miniature IPSCs (mIPSCs) were recorded in the whole-cell configuration, while the current responses were elicited by ultrafast GABA applications onto the excised patches. KEY RESULTS OETX potently inhibited both mIPSCs and current responses, but its effect was much stronger on synaptic currents. Analysis of the effects of OETX on mIPSCs and evoked currents disclosed a complex mechanism: allosteric modulation of both GABA(A) receptor binding and gating properties and a non-competitive, probably open channel block mechanism. In particular, OETX reduced the binding rate and nearly abolished receptor desensitization. A combination of rapid clearance of synaptic GABA and OETX-induced slowing of binding kinetics is proposed to underlie the potent action of OETX on mIPSCs. CONCLUSIONS AND IMPLICATIONS OETX shows a complex blocking mechanism of GABA(A) receptors, and the impact of this toxin is more potent on mIPSCs than on currents evoked by exogenous GABA. Such effects on GABAergic currents are compatible with the convulsions and epileptic-like activity reported for OETX.
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Affiliation(s)
- Paulina Wyrembek
- Department of Biophysics, Wrocław Medical University, Chałubińskiego, Wrocław, Poland
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Mozrzymas JW. Pharmacological studies reveal novel aspects of the versatility of GABAA receptors. J Physiol 2010; 588:1381-2. [PMID: 20436038 DOI: 10.1113/jphysiol.2010.189910] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics,Wroclaw Medical University, ul. Chałubinskiego 3, 50-368 Wrocław, Poland.
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Jedlicka P, Deller T, Gutkin BS, Backus KH. Activity-dependent intracellular chloride accumulation and diffusion controls GABA(A) receptor-mediated synaptic transmission. Hippocampus 2010; 21:885-98. [PMID: 20575006 DOI: 10.1002/hipo.20804] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2010] [Indexed: 11/06/2022]
Abstract
In the CNS, prolonged activation of GABA(A) receptors (GABA(A)Rs) has been shown to evoke biphasic postsynaptic responses, consisting of an initial hyperpolarization followed by a depolarization. A potential mechanism underlying the depolarization is an acute chloride (Cl(-)) accumulation resulting in a shift of the GABA(A) reversal potential (E(GABA)). The amount of GABA-evoked Cl(-) accumulation and accompanying depolarization depends on presynaptic and postsynaptic properties of GABAergic transmission, as well as on cellular morphology and regulation of Cl(-) intracellular concentration ([Cl(-)](i)). To analyze the influence of these factors on the Cl(-) and voltage behavior, we studied spatiotemporal dynamics of activity-dependent [Cl(-)](i) changes in multicompartmental models of hippocampal cells based on realistic morphological data. Simulated Cl(-) influx through GABA(A) Rs was able to exceed physiological Cl(-) extrusion rates thereby evoking HCO(3)(-) -dependent E(GABA) shift and depolarizing responses. Depolarizations were observed in spite of GABA(A) receptor desensitization. The amplitude of the depolarization was frequency-dependent and determined by intracellular Cl(-) accumulation. Changes in the dendritic diameter and in the speed of GABA clearance in the synaptic cleft were significant sources of depolarization variability. In morphologically reconstructed granule cells subjected to an intense GABAergic background activity, dendritic inhibition was more affected by accumulation of intracellular Cl(-) than somatic inhibition. Interestingly, E(GABA) changes induced by activation of a single dendritic synapse propagated beyond the site of Cl(-) influx and affected neighboring synapses. The simulations suggest that E(GABA) may differ even along a single dendrite supporting the idea that it is necessary to assign E(GABA) to a given GABAergic input and not to a given neuron.
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Affiliation(s)
- Peter Jedlicka
- Institute of Clinical Neuroanatomy, Goethe-University Frankfurt, NeuroScience Center, Frankfurt am Main, Germany.
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Marchionni I, Kasap Z, Mozrzymas JW, Sieghart W, Cherubini E, Zacchi P. New insights on the role of gephyrin in regulating both phasic and tonic GABAergic inhibition in rat hippocampal neurons in culture. Neuroscience 2009; 164:552-62. [PMID: 19660531 DOI: 10.1016/j.neuroscience.2009.07.063] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 07/27/2009] [Accepted: 07/28/2009] [Indexed: 12/21/2022]
Abstract
Gephyrin is a tubulin-binding protein that acts as a scaffold for clustering glycine and GABA(A) receptors at postsynaptic sites. In this study, the role of gephyrin on GABA(A) receptor function was assessed at the post-translational level, using gephyrin-specific single chain antibody fragments (scFv-gephyrin). When expressed in cultured rat hippocampal neurons as a fusion protein containing a nuclear localization signal, scFv-gephyrin were able to remove endogenous gephyrin from GABA(A) receptor clusters. Immunocytochemical experiments revealed a significant reduction in the number of synaptic gamma2-subunit containing GABA(A) receptors and a significant decrease in the density of the GABAergic presynaptic marker vesicular GABA transporter (VGAT). These effects were associated with a slow down of the onset kinetics, a reduction in the amplitude and in the frequency of miniature inhibitory postsynaptic currents (mIPSCs). The quantitative analysis of current responses to ultrafast application of GABA suggested that changes in onset kinetics resulted from modifications in the microscopic gating of GABA(A) receptors and in particular from a reduced entry into the desensitized state. In addition, hampering gephyrin function with scFv-gephyrin induced a significant reduction in GABA(A) receptor-mediated tonic conductance. This effect was probably dependent on the decrease in GABAergic innervation and in GABA release from presynaptic nerve terminals. These results indicate that gephyrin is essential not only for maintaining synaptic GABA(A) receptor clusters in the right position but also for regulating both phasic and tonic inhibition.
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Affiliation(s)
- I Marchionni
- Neuroscience Programme, International School for Advanced Studies, 34014 Trieste, Italy
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Hablitz JJ, Mathew SS, Pozzo-Miller L. GABA vesicles at synapses: are there 2 distinct pools? Neuroscientist 2009; 15:218-24. [PMID: 19436074 DOI: 10.1177/1073858408326431] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fast synaptic inhibition in the neocortex is mediated by the neurotransmitter GABA, acting on GABA( A) receptors. Neurotransmitters, including GABA, are stored in synaptic vesicles at presynaptic nerve terminals. A long-held assumption has been that evoked and spontaneous neurotransmissions draw on the same pools of vesicles. We review the evidence from FM1-43 studies supporting the contention that at least 2 distinct pools of GABA vesicles are present at inhibitory synapses in the rat neocortex. FM1-43 uptake during spontaneous vesicle endocytosis labels a vesicle pool within neocortical inhibitory nerve terminals that is released much more slowly ("reluctant" pool) than those vesicles loaded by electrical stimulation of afferent fibers or hyperkalemic solutions. These multiple pools may play diverse roles in such processes as long-term depression and/or potentiating of inhibitory synaptic transmission, homeostatic plasticity of inhibitory activity, or developmental changes in inhibitory synaptic transmission.
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Affiliation(s)
- John J Hablitz
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama.
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