1
|
Chronister BN, Yang K, Yang AR, Lin T, Tu XM, Lopez-Paredes D, Checkoway H, Suarez-Torres J, Gahagan S, Martinez D, Barr D, Moore RC, Suarez-Lopez JR. Urinary Glyphosate, 2,4-D and DEET Biomarkers in Relation to Neurobehavioral Performance in Ecuadorian Adolescents in the ESPINA Cohort. ENVIRONMENTAL HEALTH PERSPECTIVES 2023; 131:107007. [PMID: 37819080 PMCID: PMC10566341 DOI: 10.1289/ehp11383] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 08/22/2023] [Accepted: 08/30/2023] [Indexed: 10/13/2023]
Abstract
BACKGROUND Herbicides are the most used class of pesticides worldwide, and insect repellents are widely used globally. Yet, there is a dearth of studies characterizing the associations between these chemical groups and human neurobehavior. Experimental studies suggest that glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides can affect neurobehavior and the cholinergic and glutamatergic pathways in the brain. We aim to assess whether herbicides and insect repellents are associated with neurobehavioral performance in adolescents. METHODS We assessed 519 participants (11-17 years of age) living in agricultural communities in Ecuador. We quantified urinary concentrations of glyphosate, 2,4-D, and two N,N-diethyl-meta-toluamide (DEET) insect repellent metabolites [3-(diethylcarbamoyl)benzoic acid (DCBA) and 3-(ethylcarbamoyl)benzoic acid (ECBA)] using isotope-dilution mass spectrometry. We assessed neurobehavioral performance using 9 subtests across 5 domains (attention/inhibitory control, memory/learning, language, visuospatial processing, and social perception). We characterized the associations using generalized estimating equations and multiple imputation for metabolites below detection limits. Models were adjusted for demographic and anthropometric characteristics, urinary creatinine, and sexual maturation. Mediation by salivary cortisol, dehydroepiandrosterone, 17 β -estradiol , and testosterone was assessed using structural equation modeling. RESULTS The mean of each neurobehavioral domain score was between 7.0 and 8.7 [standard deviation (SD) range: 2.0-2.3]. Glyphosate was detected in 98.3% of participants, 2,4-D in 66.2%, DCBA in 63.3%, and ECBA in 33.4%. 2,4-D was negatively associated with all neurobehavioral domains, but statistically significant associations were observed with attention/inhibition [score difference per 50% higher metabolite concentration ( β ) = - 0.19 95% confidence interval (CI): - 0.31 , - 0.07 ], language [β = - 0.12 (95% CI: - 0.23 , - 0.01 )], and memory/learning [β = - 0.11 (95% CI: - 0.22 , 0.01)]. Glyphosate had a statistically significant negative association only with social perception [β = - 0.08 (95% CI: - 0.14 , - 0.01 )]. DEET metabolites were not associated with neurobehavioral performance. Mediation by gender and adrenal hormones was not observed. CONCLUSION This study describes worse neurobehavioral performance associated with herbicide exposures in adolescents, particularly with 2,4-D. Replication of these findings among other pediatric and adult populations is needed. https://doi.org/10.1289/EHP11383.
Collapse
Affiliation(s)
- Briana N.C. Chronister
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
- School of Public Health, San Diego State University, San Diego, California, USA
| | - Kun Yang
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| | - Audrey R. Yang
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| | - Tuo Lin
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| | - Xin M. Tu
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| | | | - Harvey Checkoway
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| | | | - Sheila Gahagan
- Department of Pediatrics, University of California San Diego, San Diego, California, USA
| | | | - Dana Barr
- Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Raeanne C. Moore
- Department of Psychiatry, University of California San Diego, San Diego, California, USA
| | - Jose R. Suarez-Lopez
- The Herbert Wertheim School of Public Health and Human Longevity Science, University of California San Diego, San Diego, California, USA
| |
Collapse
|
2
|
Aubrey KR, Sheipouri D, Balle T, Vandenberg RJ, Otsu Y. Glutamate, d-(-)-2-Amino-5-Phosphonopentanoic Acid, and N-Methyl-d-Aspartate Do Not Directly Modulate Glycine Receptors. Mol Pharmacol 2020; 98:719-729. [PMID: 33051383 DOI: 10.1124/molpharm.120.000127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/03/2020] [Indexed: 11/22/2022] Open
Abstract
Replication studies play an essential role in corroborating research findings and ensuring that subsequent experimental works are interpreted correctly. A previously published paper indicated that the neurotransmitter glutamate, along with the compounds N-methyl-d-aspartate (NMDA) and d-(-)-2-amino-5-phosphonopentanoic acid (AP5), acts as positive allosteric modulators of inhibitory glycine receptors. The paper further suggested that this form of modulation would play a role in setting the spinal inhibitory tone and influencing sensory signaling, as spillover of glutamate onto nearby glycinergic synapses would permit rapid crosstalk between excitatory and inhibitory synapses. Here, we attempted to replicate this finding in primary cultured spinal cord neurons, spinal cord slice, and Xenopus laevis oocytes expressing recombinant human glycine receptors. Despite extensive efforts, we were unable to reproduce the finding that glutamate, AP5, and NMDA positively modulate glycine receptor currents. We paid careful attention to critical aspects of the original study design and took into account receptor saturation and protocol deviations such as animal species. Finally, we explored possible explanations for the experimental discrepancy. We found that solution contamination with a high-affinity modulator such as zinc is most likely to account for the error, and we suggest methods for preventing this kind of misinterpretation in future studies aimed at characterizing high-affinity modulators of the glycine receptor. SIGNIFICANCE STATEMENT: A previous study indicates that glutamate spillover onto inhibitory synapses can directly interact with glycine receptors to enhance inhibitory signalling. This finding has important implications for baseline spinal transmission and may play a role when chronic pain develops. However, we failed to replicate the results and did not observe glutamate, d-(-)-2-amino-5-phosphonopentanoic acid, or N-methyl-d-aspartate modulation of native or recombinant glycine receptors. We ruled out various sources for the discrepancy and found that the most likely cause is solution contamination.
Collapse
Affiliation(s)
- Karin R Aubrey
- Pain Management Research Institute (K.R.A., Y.O.), Kolling Institute of Medical Research, Royal North Shore Hospital and Northern Clinical School, Faculty of Medicine and Health (K.R.A., Y.O.), Pharmacology, Faculty of Medicine and Health (D.S., R.J.V.), Sydney Pharmacy School, Faculty of Medicine and Health (T.B.), and Brain and Mind Centre (T.B.), The University of Sydney, Sydney, Australia
| | - Diba Sheipouri
- Pain Management Research Institute (K.R.A., Y.O.), Kolling Institute of Medical Research, Royal North Shore Hospital and Northern Clinical School, Faculty of Medicine and Health (K.R.A., Y.O.), Pharmacology, Faculty of Medicine and Health (D.S., R.J.V.), Sydney Pharmacy School, Faculty of Medicine and Health (T.B.), and Brain and Mind Centre (T.B.), The University of Sydney, Sydney, Australia
| | - Thomas Balle
- Pain Management Research Institute (K.R.A., Y.O.), Kolling Institute of Medical Research, Royal North Shore Hospital and Northern Clinical School, Faculty of Medicine and Health (K.R.A., Y.O.), Pharmacology, Faculty of Medicine and Health (D.S., R.J.V.), Sydney Pharmacy School, Faculty of Medicine and Health (T.B.), and Brain and Mind Centre (T.B.), The University of Sydney, Sydney, Australia
| | - Robert J Vandenberg
- Pain Management Research Institute (K.R.A., Y.O.), Kolling Institute of Medical Research, Royal North Shore Hospital and Northern Clinical School, Faculty of Medicine and Health (K.R.A., Y.O.), Pharmacology, Faculty of Medicine and Health (D.S., R.J.V.), Sydney Pharmacy School, Faculty of Medicine and Health (T.B.), and Brain and Mind Centre (T.B.), The University of Sydney, Sydney, Australia
| | - Yo Otsu
- Pain Management Research Institute (K.R.A., Y.O.), Kolling Institute of Medical Research, Royal North Shore Hospital and Northern Clinical School, Faculty of Medicine and Health (K.R.A., Y.O.), Pharmacology, Faculty of Medicine and Health (D.S., R.J.V.), Sydney Pharmacy School, Faculty of Medicine and Health (T.B.), and Brain and Mind Centre (T.B.), The University of Sydney, Sydney, Australia
| |
Collapse
|
3
|
Li Q, Jin R, Zhang S, Sun X, Wu J. Transient receptor potential vanilloid four channels modulate inhibitory inputs through differential regulation of GABA and glycine receptors in rat retinal ganglion cells. FASEB J 2020; 34:14521-14538. [PMID: 32892440 DOI: 10.1096/fj.201902937rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 08/07/2020] [Accepted: 08/18/2020] [Indexed: 01/06/2023]
Abstract
The transient receptor potential vanilloid 4 (TRPV4) channel is widely distributed in the retina. Activation of the TRPV4 channel enhances excitatory signaling from bipolar cells to retinal ganglion cells (RGCs), thereby increasing RGC firing rate and membrane excitability. In this study, we investigated the effect of TRPV4 channel activation on the miniature inhibitory postsynaptic current (mIPSC) in rat RGCs. Our results showed that perfusion with HC-067047, a TRPV4-channel antagonist, significantly reduced the amplitude of RGC mIPSCs. Extracellular application of the TRPV4 channel agonist GSK1016790A (GSK101) enhanced the frequency and amplitude of mIPSCs in ON- and OFF-type RGCs; pre-application of HC-067047 blocked the effect of GSK101 on mIPSCs. Furthermore, TRPV4 channels were able to enhance the frequency and amplitude of glycine receptor (GlyR)-mediated mIPSCs and inhibit the frequency of type A γ-aminobutyric acid receptor (GABAA R)-mediated mIPSCs. Upon intracellular administration or intravitreal injection of GSK101, TRPV4 channel activation reduced the release of presynaptic glycine and enhanced the function and expression of postsynaptic GlyRs; however, it inhibited presynaptic release of GABA, but did not affect postsynaptic GABAA Rs. Our study results provide insight regarding the effect of TRPV4 channel activation on RGCs and offer a potential interventional target for retinal diseases involving TRPV4 channels.
Collapse
Affiliation(s)
- Qian Li
- Eye Institute, Eye and ENT Hospital, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Shanghai, China.,Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Ruiri Jin
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Shenghai Zhang
- Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Shanghai, China.,Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Xinghuai Sun
- Eye Institute, Eye and ENT Hospital, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Shanghai, China.,Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| | - Jihong Wu
- Eye Institute, Eye and ENT Hospital, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Shanghai, China.,Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
| |
Collapse
|
4
|
Abstract
The inhibitory glycine receptor is a member of the Cys-loop superfamily of ligand-gated ion channels. It is the principal mediator of rapid synaptic inhibition in the spinal cord and brainstem and plays an important role in the modulation of higher brain functions including vision, hearing, and pain signaling. Glycine receptor function is controlled by only a few agonists, while the number of antagonists and positive or biphasic modulators is steadily increasing. These modulators are important for the study of receptor activation and regulation and have found clinical interest as potential analgesics and anticonvulsants. High-resolution structures of the receptor have become available recently, adding to our understanding of structure-function relationships and revealing agonistic, inhibitory, and modulatory sites on the receptor protein. This Review presents an overview of compounds that activate, inhibit, or modulate glycine receptor function in vitro and in vivo.
Collapse
Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo 11835, Egypt
| | | |
Collapse
|
5
|
Kloc ML, Pradier B, Chirila AM, Kauer JA. NMDA receptor activation induces long-term potentiation of glycine synapses. PLoS One 2019; 14:e0222066. [PMID: 31498817 PMCID: PMC6733442 DOI: 10.1371/journal.pone.0222066] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 08/21/2019] [Indexed: 01/12/2023] Open
Abstract
Of the fast ionotropic synapses, glycinergic synapses are the least well understood, but are vital for the maintenance of inhibitory signaling in the brain and spinal cord. Glycinergic signaling comprises half of the inhibitory signaling in the spinal cord, and glycinergic synapses are likely to regulate local nociceptive processing as well as the transmission to the brain of peripheral nociceptive information. Here we have investigated the rapid and prolonged potentiation of glycinergic synapses in the superficial dorsal horn of young male and female mice after brief activation of NMDA receptors (NMDARs). Glycinergic inhibitory postsynaptic currents (IPSCs) evoked with lamina II-III stimulation in identified GABAergic neurons in lamina II were potentiated by bath-applied Zn2+ and were depressed by the prostaglandin PGE2, consistent with the presence of both GlyRα1- and GlyRα3-containing receptors. NMDA application rapidly potentiated synaptic glycinergic currents. Whole-cell currents evoked by exogenous glycine were also readily potentiated by NMDA, indicating that the potentiation results from altered numbers or conductance of postsynaptic glycine receptors. Repetitive depolarization alone of the postsynaptic GABAergic neuron also potentiated glycinergic synapses, and intracellular EGTA prevented both NMDA-induced and depolarization-induced potentiation of glycinergic IPSCs. Optogenetic activation of trpv1 lineage afferents also triggered NMDAR-dependent potentiation of glycinergic synapses. Our results suggest that during peripheral injury or inflammation, nociceptor firing during injury is likely to potentiate glycinergic synapses on GABAergic neurons. This disinhibition mechanism may be engaged rapidly, altering dorsal horn circuitry to promote the transmission of nociceptive information to the brain.
Collapse
Affiliation(s)
- Michelle L. Kloc
- Dept. of Pharmacology, Physiology and Biotechnology, Brown Institute for Brain Science, Brown University, Providence, RI, United States of America
| | - Bruno Pradier
- Dept. of Pharmacology, Physiology and Biotechnology, Brown Institute for Brain Science, Brown University, Providence, RI, United States of America
| | - Anda M. Chirila
- Dept. of Pharmacology, Physiology and Biotechnology, Brown Institute for Brain Science, Brown University, Providence, RI, United States of America
| | - Julie A. Kauer
- Dept. of Pharmacology, Physiology and Biotechnology, Brown Institute for Brain Science, Brown University, Providence, RI, United States of America
- * E-mail: ,
| |
Collapse
|
6
|
Comhair J, Devoght J, Morelli G, Harvey RJ, Briz V, Borrie SC, Bagni C, Rigo JM, Schiffmann SN, Gall D, Brône B, Molchanova SM. Alpha2-Containing Glycine Receptors Promote Neonatal Spontaneous Activity of Striatal Medium Spiny Neurons and Support Maturation of Glutamatergic Inputs. Front Mol Neurosci 2018; 11:380. [PMID: 30374290 PMCID: PMC6196267 DOI: 10.3389/fnmol.2018.00380] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 09/24/2018] [Indexed: 12/16/2022] Open
Abstract
Glycine receptors (GlyRs) containing the α2 subunit are highly expressed in the developing brain, where they regulate neuronal migration and maturation, promote spontaneous network activity and subsequent development of synaptic connections. Mutations in GLRA2 are associated with autism spectrum disorder, but the underlying pathophysiology is not described yet. Here, using Glra2-knockout mice, we found a GlyR-dependent effect on neonatal spontaneous activity of dorsal striatum medium spiny neurons (MSNs) and maturation of the incoming glutamatergic innervation. Our data demonstrate that functional GlyRs are highly expressed in MSNs of one-week-old mice, but they do not generate endogenous chloride-mediated tonic or phasic current. Despite of that, knocking out the Glra2 severely affects the shape of action potentials and impairs spontaneous activity and the frequency of miniature AMPA receptor-mediated currents in MSNs. This reduction in spontaneous activity and glutamatergic signaling can attribute to the observed changes in neonatal behavioral phenotypes as seen in ultrasonic vocalizations and righting reflex. In adult Glra2-knockout animals, the glutamatergic synapses in MSNs remain functionally underdeveloped. The number of glutamatergic synapses and release probability at presynaptic site remain unaffected, but the amount of postsynaptic AMPA receptors is decreased. This deficit is a consequence of impaired development of the neuronal circuitry since acute inhibition of GlyRs by strychnine in adult MSNs does not affect the properties of glutamatergic synapses. Altogether, these results demonstrate that GlyR-mediated signaling supports neonatal spontaneous MSN activity and, in consequence, promotes the functional maturation of glutamatergic synapses on MSNs. The described mechanism might shed light on the pathophysiological mechanisms in GLRA2-linked autism spectrum disorder cases.
Collapse
Affiliation(s)
- Joris Comhair
- Laboratory of Neurophysiology, ULB-Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium.,BIOMED Research Institute, University of Hasselt, Hasselt, Belgium
| | - Jens Devoght
- BIOMED Research Institute, University of Hasselt, Hasselt, Belgium
| | - Giovanni Morelli
- BIOMED Research Institute, University of Hasselt, Hasselt, Belgium
| | - Robert J Harvey
- School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD, Australia.,Sunshine Coast Health Institute, Birtinya, QLD, Australia
| | - Victor Briz
- Center for Human Genetics and Leuven Research Institute for Neuroscience and Disease, KU Leuven, Leuven, Belgium.,VIB Center for the Biology of Disease, Leuven, Belgium
| | - Sarah C Borrie
- Center for Human Genetics and Leuven Research Institute for Neuroscience and Disease, KU Leuven, Leuven, Belgium.,VIB Center for the Biology of Disease, Leuven, Belgium
| | - Claudia Bagni
- Center for Human Genetics and Leuven Research Institute for Neuroscience and Disease, KU Leuven, Leuven, Belgium.,VIB Center for the Biology of Disease, Leuven, Belgium
| | - Jean-Michel Rigo
- BIOMED Research Institute, University of Hasselt, Hasselt, Belgium
| | - Serge N Schiffmann
- Laboratory of Neurophysiology, ULB-Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium
| | - David Gall
- Laboratory of Neurophysiology, ULB-Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium
| | - Bert Brône
- BIOMED Research Institute, University of Hasselt, Hasselt, Belgium
| | - Svetlana M Molchanova
- Laboratory of Neurophysiology, ULB-Neuroscience Institute, Université Libre de Bruxelles, Brussels, Belgium
| |
Collapse
|
7
|
Winters BD, Golding NL. Glycinergic Inhibitory Plasticity in Binaural Neurons Is Cumulative and Gated by Developmental Changes in Action Potential Backpropagation. Neuron 2018; 98:166-178.e2. [PMID: 29576388 PMCID: PMC5886803 DOI: 10.1016/j.neuron.2018.03.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 01/09/2018] [Accepted: 02/28/2018] [Indexed: 11/20/2022]
Abstract
Utilization of timing-based sound localization cues by neurons in the medial superior olive (MSO) depends critically on glycinergic inhibitory inputs. After hearing onset, the strength and subcellular location of these inhibitory inputs are dramatically altered, but the cellular processes underlying this experience-dependent refinement are unknown. Here we reveal a form of inhibitory long-term potentiation (iLTP) in MSO neurons that is dependent on spiking and synaptic activation but is not affected by their fine-scale relative timing at higher frequencies prevalent in auditory circuits. We find that iLTP reinforces inhibitory inputs coactive with binaural excitation in a cumulative manner, likely well suited for networks featuring persistent high-frequency activity. We also show that a steep drop in action potential size and backpropagation limits induction of iLTP to the first 2 weeks of hearing. These intrinsic changes would deprive more distal inhibitory synapses of reinforcement, conceivably establishing the mature, soma-biased pattern of inhibition.
Collapse
Affiliation(s)
- Bradley D Winters
- The University of Texas at Austin, Department of Neuroscience and Center for Learning and Memory, 1 University Station C7000, Austin TX 78712-0248, USA
| | - Nace L Golding
- The University of Texas at Austin, Department of Neuroscience and Center for Learning and Memory, 1 University Station C7000, Austin TX 78712-0248, USA.
| |
Collapse
|
8
|
Rebas E, Radzik T, Boczek T, Zylinska L. Calcium-engaged Mechanisms of Nongenomic Action of Neurosteroids. Curr Neuropharmacol 2017; 15:1174-1191. [PMID: 28356049 PMCID: PMC5725547 DOI: 10.2174/1570159x15666170329091935] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 01/01/1970] [Accepted: 03/25/2017] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Neurosteroids form the unique group because of their dual mechanism of action. Classically, they bind to specific intracellular and/or nuclear receptors, and next modify genes transcription. Another mode of action is linked with the rapid effects induced at the plasma membrane level within seconds or milliseconds. The key molecules in neurotransmission are calcium ions, thereby we focus on the recent advances in understanding of complex signaling crosstalk between action of neurosteroids and calcium-engaged events. METHODS Short-time effects of neurosteroids action have been reviewed for GABAA receptor complex, glycine receptor, NMDA receptor, AMPA receptor, G protein-coupled receptors and sigma-1 receptor, as well as for several membrane ion channels and plasma membrane enzymes, based on available published research. RESULTS The physiological relevance of neurosteroids results from the fact that they can be synthesized and accumulated in the central nervous system, independently from peripheral sources. Fast action of neurosteroids is a prerequisite for genomic effects and these early events can significantly modify intracellular downstream signaling pathways. Since they may exert either positive or negative effects on calcium homeostasis, their role in monitoring of spatio-temporal Ca2+ dynamics, and subsequently, Ca2+-dependent physiological processes or initiation of pathological events, is evident. CONCLUSION Neurosteroids and calcium appear to be the integrated elements of signaling systems in neuronal cells under physiological and pathological conditions. A better understanding of cellular and molecular mechanisms of nongenomic, calcium-engaged neurosteroids action could open new ways for therapeutic interventions aimed to restore neuronal function in many neurological and psychiatric diseases.
Collapse
Affiliation(s)
- Elzbieta Rebas
- Department of Molecular Neurochemistry, Faculty of Health Sciences, Medical University of Lodz, Poland
| | - Tomasz Radzik
- Department of Molecular Neurochemistry, Faculty of Health Sciences, Medical University of Lodz, Poland
| | - Tomasz Boczek
- Department of Molecular Neurochemistry, Faculty of Health Sciences, Medical University of Lodz, Poland
- Boston Children’s Hospital and Harvard Medical School, Boston, USA
| | - Ludmila Zylinska
- Department of Molecular Neurochemistry, Faculty of Health Sciences, Medical University of Lodz, Poland
| |
Collapse
|
9
|
Sparling BA, DiMauro EF. Progress in the discovery of small molecule modulators of the Cys-loop superfamily receptors. Bioorg Med Chem Lett 2017; 27:3207-3218. [DOI: 10.1016/j.bmcl.2017.04.073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 04/20/2017] [Accepted: 04/24/2017] [Indexed: 12/11/2022]
|
10
|
Plested AJR. Single-Channel Recording of Ligand-Gated Ion Channels. Cold Spring Harb Protoc 2016; 2016:2016/8/pdb.top087239. [PMID: 27480725 DOI: 10.1101/pdb.top087239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Single-channel recordings reveal the microscopic properties of individual ligand-gated ion channels. Such recordings contain much more information than measurements of ensemble behavior and can yield structural and functional information about the receptors that participate in fast synaptic transmission in the brain. With a little care, a standard patch-clamp electrophysiology setup can be adapted for single-channel recording in a matter of hours. Thenceforth, it is a realistic aim to record single-molecule activity with microsecond resolution from arbitrary cell types, including cell lines and neurons.
Collapse
Affiliation(s)
- Andrew J R Plested
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; NeuroCure, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
| |
Collapse
|
11
|
Raltschev C, Hetsch F, Winkelmann A, Meier JC, Semtner M. Electrophysiological Signature of Homomeric and Heteromeric Glycine Receptor Channels. J Biol Chem 2016; 291:18030-40. [PMID: 27382060 DOI: 10.1074/jbc.m116.735084] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Indexed: 11/06/2022] Open
Abstract
Glycine receptors are chloride-permeable, ligand-gated ion channels and contribute to the inhibition of neuronal firing in the central nervous system or to facilitation of neurotransmitter release if expressed at presynaptic sites. Recent structure-function studies have provided detailed insights into the mechanisms of channel gating, desensitization, and ion permeation. However, most of the work has focused only on comparing a few isoforms, and among studies, different cellular expression systems were used. Here, we performed a series of experiments using recombinantly expressed homomeric and heteromeric glycine receptor channels, including their splice variants, in the same cellular expression system to investigate and compare their electrophysiological properties. Our data show that the current-voltage relationships of homomeric channels formed by the α2 or α3 subunits change upon receptor desensitization from a linear to an inwardly rectifying shape, in contrast to their heteromeric counterparts. The results demonstrate that inward rectification depends on a single amino acid (Ala(254)) at the inner pore mouth of the channels and is closely linked to chloride permeation. We also show that the current-voltage relationships of glycine-evoked currents in primary hippocampal neurons are inwardly rectifying upon desensitization. Thus, the alanine residue Ala(254) determines voltage-dependent rectification upon receptor desensitization and reveals a physio-molecular signature of homomeric glycine receptor channels, which provides unprecedented opportunities for the identification of these channels at the single cell level.
Collapse
Affiliation(s)
- Constanze Raltschev
- From the Department of Biomedicine, Cellular Neurophysiology, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Florian Hetsch
- the Division of Cell Physiology, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany, and
| | - Aline Winkelmann
- the Division of Cell Physiology, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany, and
| | - Jochen C Meier
- the Division of Cell Physiology, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany, and
| | - Marcus Semtner
- Cellular Neurosciences, Max-Delbrück-Centrum für Molekulare Medizin (MDC), Robert-Rössle-Strasse 10, 13092 Berlin, Germany
| |
Collapse
|
12
|
Maleeva G, Buldakova S, Bregestovski P. Selective potentiation of alpha 1 glycine receptors by ginkgolic acid. Front Mol Neurosci 2015; 8:64. [PMID: 26578878 PMCID: PMC4624854 DOI: 10.3389/fnmol.2015.00064] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 10/16/2015] [Indexed: 12/18/2022] Open
Abstract
Glycine receptors (GlyRs) belong to the superfamily of pentameric cys-loop receptor-operated channels and are involved in numerous physiological functions, including movement, vision, and pain. In search for compounds performing subunit-specific modulation of GlyRs we studied action of ginkgolic acid, an abundant Ginkgo biloba product. Using patch-clamp recordings, we analyzed the effects of ginkgolic acid in concentrations from 30 nM to 25 μM on α1–α3 and α1/β, α2/β configurations of GlyR and on GABAARs expressed in cultured CHO-K1 cells and mouse neuroblastoma (N2a) cells. Ginkgolic acid caused an increase in the amplitude of currents mediated by homomeric α1 and heteromeric α1/β GlyRs and provoked a left-shift of the concentration-dependent curves for glycine. Even at high concentrations (10–25 μM) ginkgolic acid was not able to augment ionic currents mediated by α2, α2/β, and α3 GlyRs, or by GABAAR consisting of α1/β2/γ2 subunits. Mutation of three residues (T59A/A261G/A303S) in the α2 GlyR subunit to the corresponding ones from the α1 converted the action of ginkgolic acid to potentiation with a distinct decrease in EC50 for glycine, suggesting an important role for these residues in modulation by ginkgolic acid. Our results suggest that ginkgolic acid is a novel selective enhancer of α1 GlyRs.
Collapse
Affiliation(s)
- Galyna Maleeva
- Aix Marseille Université, INS UMR_S 1106 Marseille, France ; INSERM, UMR_S 1106 Marseille, France ; Department of Cytology, Bogomoletz Institute of Physiology Kyiv, Ukraine
| | - Svetlana Buldakova
- Aix Marseille Université, INS UMR_S 1106 Marseille, France ; INSERM, UMR_S 1106 Marseille, France
| | - Piotr Bregestovski
- Aix Marseille Université, INS UMR_S 1106 Marseille, France ; INSERM, UMR_S 1106 Marseille, France
| |
Collapse
|
13
|
Burgos CF, Muñoz B, Guzman L, Aguayo LG. Ethanol effects on glycinergic transmission: From molecular pharmacology to behavior responses. Pharmacol Res 2015; 101:18-29. [PMID: 26158502 DOI: 10.1016/j.phrs.2015.07.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/01/2015] [Accepted: 07/01/2015] [Indexed: 10/23/2022]
Abstract
It is well accepted that ethanol is able to produce major health and economic problems associated to its abuse. Because of its intoxicating and addictive properties, it is necessary to analyze its effect in the central nervous system. However, we are only now learning about the mechanisms controlling the modification of important membrane proteins such as ligand-activated ion channels by ethanol. Furthermore, only recently are these effects being correlated to behavioral changes. Current studies show that the glycine receptor (GlyR) is a susceptible target for low concentrations of ethanol (5-40mM). GlyRs are relevant for the effects of ethanol because they are found in the spinal cord and brain stem where they primarily express the α1 subunit. More recently, the presence of GlyRs was described in higher regions, such as the hippocampus and nucleus accumbens, with a prevalence of α2/α3 subunits. Here, we review data on the following aspects of ethanol effects on GlyRs: (1) direct interaction of ethanol with amino acids in the extracellular or transmembrane domains, and indirect mechanisms through the activation of signal transduction pathways; (2) analysis of α2 and α3 subunits having different sensitivities to ethanol which allows the identification of structural requirements for ethanol modulation present in the intracellular domain and C-terminal region; (3) Genetically modified knock-in mice for α1 GlyRs that have an impaired interaction with G protein and demonstrate reduced ethanol sensitivity without changes in glycinergic transmission; and (4) GlyRs as potential therapeutic targets.
Collapse
Affiliation(s)
- Carlos F Burgos
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Braulio Muñoz
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Leonardo Guzman
- Laboratory of Molecular Neurobiology, Department of Physiology, University of Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile.
| |
Collapse
|
14
|
Badja C, Maleeva G, El-Yazidi C, Barruet E, Lasserre M, Tropel P, Binetruy B, Bregestovski P, Magdinier F. Efficient and cost-effective generation of mature neurons from human induced pluripotent stem cells. Stem Cells Transl Med 2014; 3:1467-72. [PMID: 25355730 DOI: 10.5966/sctm.2014-0024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
For years, our ability to study pathological changes in neurological diseases has been hampered by the lack of relevant models until the recent groundbreaking work from Yamanaka's group showing that it is feasible to generate induced pluripotent stem cells (iPSCs) from human somatic cells and to redirect the fate of these iPSCs into differentiated cells. In particular, much interest has focused on the ability to differentiate human iPSCs into neuronal progenitors and functional neurons for relevance to a large number of pathologies including mental retardation and behavioral or degenerative syndromes. Current differentiation protocols are time-consuming and generate limited amounts of cells, hindering use on a large scale. We describe a feeder-free method relying on the use of a chemically defined medium that overcomes the need for embryoid body formation and neuronal rosette isolation for neuronal precursors and terminally differentiated neuron production. Four days after induction, expression of markers of the neurectoderm lineage is detectable. Between 4 and 7 days, neuronal precursors can be expanded, frozen, and thawed without loss of proliferation and differentiation capacities or further differentiated. Terminal differentiation into the different subtypes of mature neurons found in the human brain were observed. At 6-35 days after induction, cells express typical voltage-gated and ionotrophic receptors for GABA, glycine, and acetylcholine. This specific and efficient single-step strategy in a chemically defined medium allows the production of mature neurons in 20-40 days with multiple applications, especially for modeling human pathologies.
Collapse
Affiliation(s)
- Cherif Badja
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Galyna Maleeva
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Claire El-Yazidi
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Emilie Barruet
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Manon Lasserre
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Philippe Tropel
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Bernard Binetruy
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Piotr Bregestovski
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| | - Frédérique Magdinier
- Medical Genetics and Functional Genomics and Brain Dynamics Institute, Aix-Marseille University, INSERM, Marseille, France; University of California San Francisco, San Francisco, California, USA
| |
Collapse
|
15
|
Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: ligand-gated ion channels. Br J Pharmacol 2014; 170:1582-606. [PMID: 24528238 PMCID: PMC3892288 DOI: 10.1111/bph.12446] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Ligand-gated ion channels are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
Collapse
Affiliation(s)
- Stephen P H Alexander
- School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Sun H, Lu L, Zuo Y, Wang Y, Jiao Y, Zeng WZ, Huang C, Zhu MX, Zamponi GW, Zhou T, Xu TL, Cheng J, Li Y. Kainate receptor activation induces glycine receptor endocytosis through PKC deSUMOylation. Nat Commun 2014; 5:4980. [PMID: 25236484 PMCID: PMC4199113 DOI: 10.1038/ncomms5980] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 08/13/2014] [Indexed: 01/21/2023] Open
Abstract
Surface expression and regulated endocytosis of glycine receptors (GlyRs) play a critical function in balancing neuronal excitability. SUMOylation (SUMO modification) is of critical importance for maintaining neuronal function in the central nervous system. Here we show that activation of kainate receptors (KARs) causes GlyR endocytosis in a calcium- and protein kinase C (PKC)-dependent manner, leading to reduced GlyR-mediated synaptic activity in cultured spinal cord neurons and the superficial dorsal horn of rat spinal cord slices. This effect requires SUMO1/sentrin-specific peptidase 1 (SENP1)-mediated deSUMOylation of PKC, indicating that the crosstalk between KARs and GlyRs relies on the SUMOylation status of PKC. SENP1-mediated deSUMOylation of PKC is involved in the kainate-induced GlyR endocytosis and thus plays an important role in the anti-homeostatic regulation between excitatory and inhibitory ligand-gated ion channels. Altogether, we have identified a SUMOylation-dependent regulatory pathway for GlyR endocytosis, which may have important physiological implications for proper neuronal excitability. Maintenance of proper membrane excitability is vital to neuronal function and in several neuronal types this relies on a balance between receptor-mediated excitation and inhibition. Here the authors report a crosstalk between excitatory kainate receptors and inhibitory glycine receptors that relies on the SUMOylation status of PKC.
Collapse
Affiliation(s)
- Hao Sun
- Department of 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
| | - Li Lu
- Department of 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
| | - Yong Zuo
- Department of 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
| | - Yan Wang
- Department of 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
| | - Yingfu Jiao
- Department of 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-Zheng Zeng
- Department of 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
| | - Chao Huang
- Center for Translational Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary T2N 4 N1, Alberta, Canada
| | - Tong Zhou
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | - Tian-Le Xu
- Department of 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
| | - Jinke Cheng
- Department of 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
| | - Yong Li
- Department of 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
| |
Collapse
|
17
|
Long-term potentiation of glycinergic synapses triggered by interleukin 1β. Proc Natl Acad Sci U S A 2014; 111:8263-8. [PMID: 24830427 DOI: 10.1073/pnas.1401013111] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long-term potentiation (LTP) is a persistent increase in synaptic strength required for many behavioral adaptations, including learning and memory, visual and somatosensory system functional development, and drug addiction. Recent work has suggested a role for LTP-like phenomena in the processing of nociceptive information in the dorsal horn and in the generation of central sensitization during chronic pain states. Whereas LTP of glutamatergic and GABAergic synapses has been characterized throughout the central nervous system, to our knowledge there have been no reports of LTP at mammalian glycinergic synapses. Glycine receptors (GlyRs) are structurally related to GABAA receptors and have a similar inhibitory role. Here we report that in the superficial dorsal horn of the spinal cord, glycinergic synapses on inhibitory GABAergic neurons exhibit LTP, occurring rapidly after exposure to the inflammatory cytokine interleukin-1 beta. This form of LTP (GlyR LTP) results from an increase in the number and/or change in biophysical properties of postsynaptic glycine receptors. Notably, formalin-induced peripheral inflammation in vivo potentiates glycinergic synapses on dorsal horn neurons, suggesting that GlyR LTP is triggered during inflammatory peripheral injury. Our results define a previously unidentified mechanism that could disinhibit neurons transmitting nociceptive information and may represent a useful therapeutic target for the treatment of pain.
Collapse
|
18
|
Bertollini C, Murana E, Mosca L, D'Erme M, Scala F, Francioso A, Catalano M, Limatola C, Bregestovski P, Di Angelantonio S, Ragozzino D. Transient increase in neuronal chloride concentration by neuroactive aminoacids released from glioma cells. Front Mol Neurosci 2012. [PMID: 23189038 PMCID: PMC3505843 DOI: 10.3389/fnmol.2012.00100] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Neuronal chloride concentration ([Cl−]i) is known to be dynamically modulated and alterations in Cl− homeostasis may occur in the brain at physiological and pathological conditions, being also likely involved in glioma-related seizures. However, the mechanism leading to changes in neuronal [Cl−]i during glioma invasion are still unclear. To characterize the potential effect of glioma released soluble factors on neuronal [Cl−]i, we used genetically encoded CFP/YFP-based ratiometric Cl-(apical) Sensor transiently expressed in cultured hippocampal neurons. Exposition of neurons to glioma conditioned medium (GCM) caused rapid and transient elevation of [Cl−]i, resulting in the increase of fluorescence ratio, which was strongly reduced by blockers of ionotropic glutamate receptors APV and NBQX. Furthermore, in HEK cells expressing GluR1-AMPA receptors, GCM activated ionic currents with efficacy similar to those caused by glutamate, supporting the notion that GCM contains glutamate or glutamatergic agonists, which cause neuronal depolarization, activation of NMDA and AMPA/KA receptors leading to elevation of [Cl−]i. Chromatographic analysis of the GCM showed that it contained several aminoacids, including glutamate, whose release from glioma cells did not occur via the most common glial mechanisms of transport, or in response to hypoosmotic stress. GCM also contained glycine, whose action contrasted the glutamate effect. Indeed, strychnine application significantly increased GCM-induced depolarization and [Cl−]i rise. GCM-evoked [Cl−]i elevation was not inhibited by antagonists of Cl− transporters and significantly reduced in the presence of anion channels blocker NPPB, suggesting that Cl− selective channels are a major route for GCM-induced Cl− influx. Altogether, these data show that glioma released aminoacids may dynamically alter Cl− equilibrium in surrounding neurons, deeply interfering with their inhibitory balance, likely leading to physiological and pathological consequences.
Collapse
Affiliation(s)
- Cristina Bertollini
- Department of Physiology and Pharmacology, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome Rome, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Wang L, Li WG, Huang C, Zhu MX, Xu TL, Wu DZ, Li Y. Subunit-specific inhibition of glycine receptors by curcumol. J Pharmacol Exp Ther 2012; 343:371-9. [PMID: 22892339 DOI: 10.1124/jpet.112.195669] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Emerging evidence has suggested that inhibitory glycine receptors (GlyRs) are an important molecular target in the treatment of numerous neurological disorders. Rhizoma curcumae is a medicinal plant with positive neurological effects. In this study, we showed that curcumol, a major bioactive component of R. curcumae, reversibly and concentration-dependently inhibited the glycine-activated current (IGly) in cultured rat hippocampal neurons. The inhibitory effect was neither voltage- nor agonist concentration-dependent. Moreover, curcumol selectively inhibited homomeric α2-containing, but not α1- or α3-containing, GlyRs. The addition of β subunit conferred the curcumol sensitivity of α3-containing, but not α1-containing, GlyRs. Site-directed mutagenesis analysis revealed that a threonine at position 59 of the α2 subunit is critical for the susceptibility of GlyRs to curcumol-mediated inhibition. Furthermore, paralleling a decline of α2 subunit expression during spinal cord development, the degree of IGly inhibition by curcumol decreased with prolonged culture of rat spinal dorsal horn neurons. Taken together, our results suggest that the GlyRs are novel molecular targets of curcumol, which may underlie its pharmaceutical effects in the central nervous system.
Collapse
Affiliation(s)
- Li Wang
- Institute of Chinese Materia Medica, Shanghai Key Laboratory of Complex Prescription, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | | | | | | | | | | | | |
Collapse
|
20
|
Mixed inhibitory synaptic balance correlates with glutamatergic synaptic phenotype in cerebellar unipolar brush cells. J Neurosci 2012; 32:4632-44. [PMID: 22457509 DOI: 10.1523/jneurosci.5122-11.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Inhibitory synapses display a great diversity through varying combinations of presynaptic GABA and glycine release and postsynaptic expression of GABA and glycine receptor subtypes. We hypothesized that increased flexibility offered by this dual transmitter system might serve to tune the inhibitory phenotype to the properties of afferent excitatory synaptic inputs in individual cells. Vestibulocerebellar unipolar brush cells (UBC) receive a single glutamatergic synapse from a mossy fiber (MF), which makes them an ideal model to study excitatory-inhibitory interactions. We examined the functional phenotypes of mixed inhibitory synapses formed by Golgi interneurons onto UBCs in rat slices. We show that glycinergic IPSCs are present in all cells. An additional GABAergic component of large amplitude is only detected in a subpopulation of UBCs. This GABAergic phenotype is strictly anti-correlated with the expression of type II, but not type I, metabotropic glutamate receptors (mGluRs) at the MF synapse. Immunohistochemical stainings and agonist applications show that global UBC expression of glycine and GABA(A) receptors matches the pharmacological profile of IPSCs. Paired recordings of Golgi cells and UBCs confirm the postsynaptic origin of the inhibitory phenotype, including the slow kinetics of glycinergic components. These results strongly suggest the presence of a functional coregulation of excitatory and inhibitory phenotypes at the single-cell level. We propose that slow glycinergic IPSCs may provide an inhibitory tone, setting the gain of the MF to UBC relay, whereas large and fast GABAergic IPSCs may in addition control spike timing in mGluRII-negative UBCs.
Collapse
|
21
|
Teladorsagia circumcincta: Molecular characterisation of the avr-14B subunit and its relatively minor role in ivermectin resistance. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:154-61. [PMID: 24533276 DOI: 10.1016/j.ijpddr.2012.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/27/2012] [Accepted: 03/29/2012] [Indexed: 01/20/2023]
Abstract
Individual mutations (e.g. L256F) and polymorphisms in the avr-14B gene, a glutamate-gated chloride channel subunit, have been associated with ivermectin (IVM) resistance in Caenorhabditis elegans and Cooperia oncophora. The aim of the present study was to determine the full-length coding sequence of the avr-14B subunit homologue in Teladorsagia circumcincta and determine the presence/absence of the putative L256F SNP or any other potential SNPs of interest. Subsequently, we investigated sequence polymorphisms and transcription patterns between four different T. circumcincta isolates: two from Scotland (MTci1 susceptible and MTci5 triple resistant to benzimidazoles, levamisole and IVM) and two from Spain (S-Sp susceptible and R-Sp double resistant to levamisole and IVM). The complete amino acid sequence of the T. circumcincta avr-14B subunit comprises 438 amino acids. Pyrosequencing analysis failed to detect the presence of the L256F mutation in any of the MTci5 or Sp-R samples tested. However, we revealed significant allele frequency changes by means of SSCP analysis of a 106 bp region encompassing the L256F SNP. Allele E showed the greatest change, following IVM exposure in vitro and in vivo, although sequence analysis did not reveal any coding changes. Sequence analysis of the full-length avr-14B coding sequence showed that two SNPs exclusively found in the resistant strain McTi5 (I270F and T305A) are situated in codons involved in the interaction of the receptor with IVM. Moreover, other potentially significant SNPs (K361E and L364M) were identified between transmembrane regions 3 and 4. However, due to the low frequency of all these SNPs, we cannot conclude they confer IVM resistance in T. circumcincta. Moreover, a modest increase in expression of the avr-14B in both resistant isolates has been shown although these differences were not sufficiently great to consider avr-14B to be the sole or even a major determinant of IVM resistance in this species.
Collapse
|
22
|
Different presynaptic nicotinic receptor subtypes modulate in vivo and in vitro the release of glycine in the rat hippocampus. Neurochem Int 2011; 59:729-38. [DOI: 10.1016/j.neuint.2011.06.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 06/27/2011] [Indexed: 01/04/2023]
|
23
|
Specht CG, Grünewald N, Pascual O, Rostgaard N, Schwarz G, Triller A. Regulation of glycine receptor diffusion properties and gephyrin interactions by protein kinase C. EMBO J 2011; 30:3842-53. [PMID: 21829170 DOI: 10.1038/emboj.2011.276] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Accepted: 07/15/2011] [Indexed: 11/09/2022] Open
Abstract
Glycine receptors (GlyRs) can dynamically exchange between synaptic and extrasynaptic locations through lateral diffusion within the plasma membrane. Their accumulation at inhibitory synapses depends on the interaction of the β-subunit of the GlyR with the synaptic scaffold protein gephyrin. An alteration of receptor-gephyrin binding could thus shift the equilibrium between synaptic and extrasynaptic GlyRs and modulate the strength of inhibitory neurotransmission. Using a combination of dynamic imaging and biochemical approaches, we have characterised the molecular mechanism that links the GlyR-gephyrin interaction with GlyR diffusion and synaptic localisation. We have identified a protein kinase C (PKC) phosphorylation site within the cytoplasmic domain of the β-subunit of the GlyR (residue S403) that causes a reduction of the binding affinity between the receptor and gephyrin. In consequence, the receptor's diffusion in the plasma membrane is accelerated and GlyRs accumulate less strongly at synapses. We propose that the regulation of GlyR dynamics by PKC thus contributes to the plasticity of inhibitory synapses and may be involved in maladaptive forms of synaptic plasticity.
Collapse
Affiliation(s)
- Christian G Specht
- Biologie Cellulaire de la Synapse, Institut de Biologie de l'École Normale Supérieure, Inserm U, Paris, France
| | | | | | | | | | | |
Collapse
|
24
|
Lozovaya N, Mukhtarov M, Tsintsadze T, Ledent C, Burnashev N, Bregestovski P. Frequency-Dependent Cannabinoid Receptor-Independent Modulation of Glycine Receptors by Endocannabinoid 2-AG. Front Mol Neurosci 2011; 4:13. [PMID: 21847369 PMCID: PMC3147161 DOI: 10.3389/fnmol.2011.00013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 07/13/2011] [Indexed: 02/02/2023] Open
Abstract
Endocannabinoids are known as retrograde messengers, being released from the postsynaptic neuron and acting on specific presynaptic G-protein-coupled cannabinoid (CB) receptors to decrease neurotransmitter release. Also, at physiologically relevant concentrations cannabinoids can directly modulate the function of voltage-gated and receptor-operated ion channels. Using patch-clamp recording we analyzed the consequences of the direct action of an endocannabinoid, 2-arachidonoylglycerol (2-AG), on the functional properties of glycine receptor channels (GlyRs) and ionic currents in glycinergic synapses. At physiologically relevant concentrations (0.1–1 μM), 2-AG directly affected the functions of recombinant homomeric α1H GlyR: it inhibited peak amplitude and dramatically enhanced desensitization. The action of 2-AG on GlyR-mediated currents developed rapidly, within ∼300 ms. Addition of 1 μM 2-AG strongly facilitated the depression of glycine-induced currents during repetitive (4–10 Hz) application of short (2 ms duration) pulses of glycine to outside-out patches. In brainstem slices from CB1 receptor knockout mice, 2-AG significantly decreased the extent of facilitation of synaptic currents in hypoglossal motoneurons during repetitive (10–20 Hz) stimulation. These observations suggest that endocannabinoids can modulate postsynaptic metaplasticity of glycinergic synaptic currents in a CB1 receptor-independent manner.
Collapse
Affiliation(s)
- Natalia Lozovaya
- INSERM U901, Institut de Neurobiologie de la Méditerranée Marseille, France
| | | | | | | | | | | |
Collapse
|
25
|
Allosteric potentiation of glycine receptor chloride currents by glutamate. Nat Neurosci 2010; 13:1225-32. [PMID: 20835251 DOI: 10.1038/nn.2633] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/13/2010] [Indexed: 11/08/2022]
Abstract
Neuronal excitability in the CNS is primarily controlled by a balance between synaptic excitation and inhibition. In the brainstem and spinal cord, synaptic excitation and inhibition are mediated by the excitatory transmitter glutamate acting on ionotropic glutamate receptor-gated cationic channels and the inhibitory transmitter glycine acting on glycine receptor (GlyR)-gated chloride channels. We found that glutamate and its analog ligands potentiated GlyR-mediated currents in both cultured spinal neurons and spinal cord slices of rats. This potentiation was not dependent on activation of any known glutamate receptor and manifested as an increase in single-channel open probability. Moreover, this glutamate potentiation was seen in HEK293 cells that transiently expressed GlyRs. Our data strongly suggest that glutamate allosterically potentiates GlyR-gated chloride channels, thereby blurring the traditional distinction between excitatory and inhibitory transmitters. Such a rapid homeostatic regulatory mechanism may be important for tuning functional balance between synaptic excitation and inhibition in the CNS.
Collapse
|
26
|
Keramidas A, Harrison NL. The activation mechanism of alpha1beta2gamma2S and alpha3beta3gamma2S GABAA receptors. ACTA ACUST UNITED AC 2010; 135:59-75. [PMID: 20038526 PMCID: PMC2806416 DOI: 10.1085/jgp.200910317] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The α1β2γ2 and α3β3γ2 are two isoforms of γ-aminobutyric acid type A (GABAA) receptor that are widely distributed in the brain. Both are found at synapses, for example in the thalamus, where they mediate distinctly different inhibitory postsynaptic current profiles, particularly with respect to decay time. The two isoforms were expressed in HEK293 cells, and single-channel activity was recorded from outside-out patches. The kinetic characteristics of both isoforms were investigated by analyzing single-channel currents over a wide range of GABA concentrations. α1β2γ2 channels exhibited briefer active periods than α3β3γ2 channels over the entire range of agonist concentrations and had lower intraburst open probabilities at subsaturating concentrations. Activation mechanisms were constructed by fitting postulated schemes to data recorded at saturating and subsaturating GABA concentrations simultaneously. Reaction mechanisms were ranked according to log-likelihood values and how accurately they simulated ensemble currents. The highest ranked mechanism for both channels consisted of two sequential binding steps, followed by three conducting and three nonconducting configurations. The equilibrium dissociation constant for GABA at α3β3γ2 channels was ∼2.6 µM compared with ∼19 µM for α1β2γ2 channels, suggesting that GABA binds to the α3β3γ2 channels with higher affinity. A notable feature of the mechanism was that two consecutive doubly liganded shut states preceded all three open configurations. The lifetime of the third shut state was briefer for the α3β3γ2 channels. The longer active periods, higher affinity, and preference for conducting states are consistent with the slower decay of inhibitory currents at synapses that contain α3β3γ2 channels. The reaction mechanism we describe here may also be appropriate for the analysis of other types of GABAA receptors and provides a framework for rational investigation of the kinetic effects of a variety of therapeutic agents that activate or modulate GABAA receptors and hence influence synaptic and extrasynaptic inhibition in the central nervous system.
Collapse
Affiliation(s)
- Angelo Keramidas
- Department of Anesthesiology, Columbia University, New York, NY 10032, USA.
| | | |
Collapse
|
27
|
LGIC. Br J Pharmacol 2009. [DOI: 10.1111/j.1476-5381.2009.00502.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
28
|
Glycine receptors. Br J Pharmacol 2009. [DOI: 10.1111/j.1476-5381.2009.00502_6.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
29
|
Breitinger HG, Villmann C, Melzer N, Rennert J, Breitinger U, Schwarzinger S, Becker CM. Novel regulatory site within the TM3-4 loop of human recombinant alpha3 glycine receptors determines channel gating and domain structure. J Biol Chem 2009; 284:28624-33. [PMID: 19661067 DOI: 10.1074/jbc.m109.043174] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycine receptors are Cys loop ligand-gated ion channels that mediate fast inhibitory synaptic transmission in the mammalian central nervous system. The functionally distinct splice variants alpha3L and alpha3K of the human glycine receptor differ by a 15-amino acid insert within the long intracellular TM3-4 loop, a region of high intersubunit diversity. In a mutational study, effects of the insert on ion channel function and secondary structure of the TM3-4 loop were investigated. Whole cell current responses and protein surface expression data indicated that the major effect of mutations within the insert was on channel gating. Changes in channel gating correlated with the distribution of charged residues about the splice region. Analysis of complex molecular weight indicated that recombinant TM3-4 loops of alpha3L and alpha3K associated into oligomers of different stoichiometry. Secondary structure analysis suggested that the insert stabilized the overall fold of the large cytoplasmic domain of alpha3L subunits. The absence of the insert resulted in a channel that was still functional, but the TM3-4 cytoplasmic domain appeared not stably folded. Thus, our data identified the spliced insert within the large TM 3-4 loop of alpha3 Gly receptors as a novel regulatory motif that serves a 2-fold role: (i) the presence of the insert stabilizes the overall spatial structure of the domain, and (ii) the insert presents a control unit that regulates gating of the receptor ion channel.
Collapse
Affiliation(s)
- Hans-Georg Breitinger
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91054 Erlangen, Germany
| | | | | | | | | | | | | |
Collapse
|
30
|
Abstract
The time course of currents mediated by native and recombinant glycine receptors was examined with a combination of rapid agonist applications to outside-out patches and single-channel recording. The deactivation time constant of currents evoked by brief, saturating pulses of glycine is profoundly affected by the chloride concentration on the intracellular side of the cell membrane. Deactivation was threefold slower when intracellular chloride was increased from a low level (10 mm), similar to that observed in living mature neurons, to 131 mm ("symmetrical" chloride, often used in pipette internal solutions). Single-channel analysis revealed that high chloride has its greatest effect on the channel closing rate, slowing it by a factor of 2 compared with the value we estimated in the cell-attached mode (in which the channels are at physiological intracellular chloride concentrations). The same effect of chloride was observed when glycinergic evoked synaptic currents were recorded from juvenile rat spinal motoneurons in vitro, because the decay time constant was reduced from approximately 7 ms to approximately 3 ms when cells were dialyzed with 10 mm chloride intracellular recording solution. Our results indicate that the time course of glycinergic synaptic inhibition in intact neurons is much faster than is estimated by measurements in symmetrical chloride and can be modulated by changes in intracellular chloride concentration in the range that can occur in physiological or pathological conditions.
Collapse
|
31
|
Mukhtarov M, Markova O, Real E, Jacob Y, Buldakova S, Bregestovski P. Monitoring of chloride and activity of glycine receptor channels using genetically encoded fluorescent sensors. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:3445-3462. [PMID: 18632458 DOI: 10.1098/rsta.2008.0133] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Genetically encoded probes have become powerful tools for non-invasive monitoring of ions, distributions of proteins and the migration and formation of cellular components. We describe the functional expression of two molecular probes for non-invasive fluorescent monitoring of intracellular Cl ([Cl]i) and the functioning of glycine receptor (GlyR) channels. The first probe is a recently developed cyan fluorescent protein-yellow fluorescent protein-based construct, termed Cl-Sensor, with relatively high sensitivity to Cl (Kapp approximately 30 mM). In this study, we describe its expression in retina cells using in vivo electroporation and analyse changes in [Cl]i at depolarization and during the first three weeks of post-natal development. An application of 40 mM K+ causes an elevation in [Cl]i of approximately 40 mM. In photoreceptors from retina slices of a 6-day-old rat (P6 rat), the mean [Cl]i is approximately 50 mM, and for P16 and P21 rats it is approximately 30-35 mM. The second construct, termed BioSensor-GlyR, is a GlyR channel with Cl-Sensor incorporated into the cytoplasmic domain. This is the first molecular probe for spectroscopic monitoring of the functioning of receptor-operated channels. These types of probes offer a means of screening pharmacological agents and monitoring Cl under different physiological and pathological conditions and permit spectroscopic monitoring of the activity of GlyRs expressed in heterologous systems and neurons.
Collapse
Affiliation(s)
- Marat Mukhtarov
- Institut de Neurobiologie de la Méditerranée (INMED), INSERM U901, Parc Scientifique de Luminy, 13273 Marseille Cedex 09, France
| | | | | | | | | | | |
Collapse
|
32
|
Homeostatic regulation of synaptic GlyR numbers driven by lateral diffusion. Neuron 2008; 59:261-73. [PMID: 18667154 DOI: 10.1016/j.neuron.2008.05.030] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 02/26/2008] [Accepted: 05/29/2008] [Indexed: 11/24/2022]
Abstract
In the spinal cord, most inhibitory synapses have a mixed glycine-GABA phenotype. Using a pharmacological approach, we report an NMDAR activity-dependent regulation of the mobility of GlyRs but not GABA(A)Rs at inhibitory synapses in cultured rat spinal cord neurons. The NMDAR-induced decrease in GlyR lateral diffusion was correlated with an increase in receptor cluster number and glycinergic mIPSC amplitude. Changes in GlyR diffusion properties occurred rapidly and before the changes in the number of synaptic receptors. Regulation of synaptic GlyR content occurred without change in the amount of gephyrin. Moreover, NMDAR-dependent regulation of GlyR lateral diffusion required calcium influx and calcium release from stores. Therefore, excitation may increase GlyR levels at synapses by a calcium-mediated increase in postsynaptic GlyR trapping involving regulation of receptor-scaffold interactions. This provides a mechanism for a rapid homeostatic regulation of the inhibitory glycinergic component at mixed glycine-GABA synapses in response to increased NMDA excitatory transmission.
Collapse
|
33
|
Abstract
The concentration of transmitter in the synaptic cleft and its clearance time are one of the main determinants of synaptic strength. We estimated the time course of glycine at rat lumbar motoneurons synapses in spinal cord slices by recording synaptic currents in the presence of a low-affinity competitive antagonist at glycine receptors [2-(3-carboxypropyl)-3-amino-6-(4-methoxyphenyl)pyridazinium (SR-95531)]. Data were analyzed by using the established activation mechanism for glycine receptors and our measurements of SR-95531 binding rates. We show that this technique alone is not sufficient to determine simultaneously the peak concentration of transmitter and its clearance time. However, we found that block of the glial glycine transporter prolongs the glycine transient. This observation puts additional constraints on the range of possible values of the time course of glycine, indicating that glycine reaches a peak concentration of 2.2-3.5 mM and is cleared from the cleft with a time constant of 0.6-0.9 ms.
Collapse
|
34
|
Liu T, Fujita T, Nakatsuka T, Kumamoto E. Phospholipase A2 Activation Enhances Inhibitory Synaptic Transmission in Rat Substantia Gelatinosa Neurons. J Neurophysiol 2008; 99:1274-84. [DOI: 10.1152/jn.01292.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phospholipase A2 (PLA2) activation enhances glutamatergic excitatory synaptic transmission in substantia gelatinosa (SG) neurons, which play a pivotal role in regulating nociceptive transmission in the spinal cord. By using melittin as a tool to activate PLA2, we examined the effect of PLA2 activation on spontaneous inhibitory postsynaptic currents (sIPSCs) recorded at 0 mV in SG neurons of adult rat spinal cord slices by use of the whole cell patch-clamp technique. Melittin enhanced the frequency and amplitude of GABAergic and glycinergic sIPSCs. The enhancement of GABAergic but not glycinergic transmission was largely depressed by Na+ channel blocker tetrodotoxin or glutamate-receptor antagonists (6-cyano-7-nitroquinoxaline-2,3-dione and/or dl-2-amino-5-phosphonovaleric acid) and also in a Ca2+-free Krebs solution. The effects of melittin on glycinergic sIPSC frequency and amplitude were dose-dependent with an effective concentration of ∼0.7 μM for half-maximal effect and were depressed by PLA2 inhibitor 4-bromophenacyl bromide or aristolochic acid. The melittin-induced enhancement of glycinergic transmission was depressed by lipoxygenase inhibitor nordihydroguaiaretic acid but not cyclooxygenase inhibitor indomethacin. These results indicate that the activation of PLA2 in the SG enhances GABAergic and glycinergic inhibitory transmission in SG neurons. The former action is mediated by glutamate-receptor activation and neuronal activity increase, possibly the facilitatory effect of PLA2 activation on excitatory transmission, whereas the latter action is due to PLA2 and subsequent lipoxygenase activation and is independent of extracellular Ca2+. It is suggested that PLA2 activation in the SG could enhance not only excitatory but also inhibitory transmission, resulting in the modulation of nociception.
Collapse
|
35
|
Markova O, Mukhtarov M, Real E, Jacob Y, Bregestovski P. Genetically encoded chloride indicator with improved sensitivity. J Neurosci Methods 2008; 170:67-76. [PMID: 18279971 DOI: 10.1016/j.jneumeth.2007.12.016] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 12/04/2007] [Accepted: 12/22/2007] [Indexed: 10/22/2022]
Abstract
Chloride (Cl) is the most abundant physiological anion. Abnormalities in Cl regulation are instrumental in the development of several important diseases including motor disorders and epilepsy. Because of difficulties in the spectroscopic measurement of Cl in live tissues there is little knowledge available regarding the mechanisms of regulation of intracellular Cl concentration. Several years ago, a CFP-YFP based ratiometric Cl indicator (Clomeleon) was introduced [Kuner, T., Augustine, G.J. A genetically encoded ratiometric indicator for chloride: capturing chloride transients in cultured hippocampal neurons. Neuron 2000; 27: 447-59]. This construct with relatively low sensitivity to Cl (K(app) approximately 160 mM) allows ratiometric monitoring of Cl using fluorescence emission ratio. Here, we propose a new CFP-YFP-based construct (Cl-sensor) with relatively high sensitivity to Cl (K(app) approximately 30 mM) due to triple YFP mutant. The construct also exhibits good pH sensitivity with pK(alpha) ranging from 7.1 to 8.0 pH units at different Cl concentrations. Using Cl-sensor we determined non-invasively the distribution of [Cl](i) in cultured CHO cells, in neurons of primary hippocampal cultures and in photoreceptors of rat retina. This genetically encoded indicator offers a means for monitoring Cl and pH under different physiological conditions and high-throughput screening of pharmacological agents.
Collapse
Affiliation(s)
- Olga Markova
- Institut de Neurobiologie de la Méditerranée (INMED), INSERM U901, Parc Scientifique de Luminy, Marseille, France.
| | | | | | | | | |
Collapse
|
36
|
Synaptic function and modulation of glycine receptor channels in the hypoglossal nucleus. NEUROPHYSIOLOGY+ 2007. [DOI: 10.1007/s11062-007-0040-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
37
|
Beato M, Sivilotti LG. Single-channel properties of glycine receptors of juvenile rat spinal motoneurones in vitro. J Physiol 2007; 580:497-506. [PMID: 17272347 PMCID: PMC2075563 DOI: 10.1113/jphysiol.2006.125740] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
An essential step in understanding fast synaptic transmission is to establish the activation mechanism of synaptic receptors. The purpose of this work was to extend our detailed single-channel kinetic characterization of α1β glycine channels from rat recombinant receptors to native channels from juvenile (postnatal day 12–16) rat spinal cord slices. In cell-attached patches from ventral horn neurones, 1 mm glycine elicited clusters of channel openings to a single conductance level (41 ± 1 pS, n=12). This is similar to that of recombinant heteromers. However, fewer than 1 in 100 cell-attached patches from spinal neurones contained glycine channels. Outside-out patches gave a much higher success rate, but glycine channels recorded in this configuration appeared different, in that clusters opened to three conductance levels (28 ± 2, 38 ± 1 and 46 ± 1 pS, n=7, one level per cluster, all levels being detected in each patch). Furthermore, open period properties were different for the different conductances. As a consequence of this, the only recordings suitable for kinetic analysis were the cell-attached ones. Low channel density precluded recording at glycine concentrations other than 1 mm, but the 1 mm data allowed us to estimate the fully bound gating constants by global model fitting of the ‘flip’ mechanism of Burzomato and co-workers. Our results suggest that glycine receptors on ventral horn neurones in the juvenile rat are heteromers and have fast gating, similar to that of recombinant α1β receptors.
Collapse
Affiliation(s)
- Marco Beato
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
| | | |
Collapse
|
38
|
Bregestovski P, Spitzer N. Calcium in the function of the nervous system: new implications. Cell Calcium 2005; 37:371-4. [PMID: 15820383 DOI: 10.1016/j.ceca.2005.01.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2004] [Accepted: 01/06/2005] [Indexed: 01/25/2023]
Affiliation(s)
- Piotr Bregestovski
- Institut de Neurobiologie de la Méditerranée (INMED), Parc Scientifique de Luminy, BP13, 13009 Marseille, France.
| | | |
Collapse
|
39
|
Diana MA, Bregestovski P. Calcium and endocannabinoids in the modulation of inhibitory synaptic transmission. Cell Calcium 2005; 37:497-505. [PMID: 15820399 DOI: 10.1016/j.ceca.2005.01.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2004] [Accepted: 01/06/2005] [Indexed: 11/20/2022]
Abstract
Synapses in the central nervous system can be highly plastic devices, being able to modify their efficacy in relaying information in response to several factors. Calcium ions are often fundamental in triggering synaptic plasticity. Here, we will shortly review the effects induced by postsynaptic increases of calcium concentration at GABAergic and glycinergic synapses. Both postsynaptic and presynaptic mechanisms mediating changes in synaptic strength will be examined. Particular attention will be devoted to phenomena of retrograde signaling and, specifically, to the recently discovered role, played by the endocannabinoid system in retrograde synaptic modulation.
Collapse
Affiliation(s)
- Marco A Diana
- Laboratoire de Physiologie Cérébrale, CNRS UMR8118, 45, rue des Saints Pères 75006 Paris, France.
| | | |
Collapse
|
40
|
Shen W. Repetitive light stimulation inducing glycine receptor plasticity in the retinal neurons. J Neurophysiol 2005; 94:2231-8. [PMID: 16105957 DOI: 10.1152/jn.01099.2004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neurotransmitter receptor plasticity is a mechanism that can regulate the temporal and intensity encoding of a synapse. While this has been extensively studied as a mechanism of learning, less is known about such processes in sensory systems. This study examines modulation of glycine receptor function at the first synapse in the retina. It was found that horizontal cells, which are postsynaptic to photoreceptors, have glycine receptor currents that are enhanced when internal calcium is elevated. This can be achieved by glutamatergic synaptic input or by activation of voltage-gated calcium channels. When the retina was maintained in a dark-adapted state, the calcium levels in horizontal cells were relatively low. After a series of brief light stimuli, the internal calcium concentration in horizontal cells was elevated, and the glycine currents were faster and greater in amplitude. The increase of internal calcium levels was caused by increased transmitter release from photoreceptors. Thus glycine receptor function is state dependent and can be rapidly altered by synaptic input from photoreceptors. Light stimulation drives glycine receptor plasticity in the retinal neural network.
Collapse
Affiliation(s)
- Wen Shen
- Department of Biomedical Science, Florida Atlantic Univ., Bldg. BC-71, Rm. 229, 777 Glades Rd., Boca Raton, Florida 33431, USA.
| |
Collapse
|
41
|
Mukhtarov M, Ragozzino D, Bregestovski P. Dual Ca2+ modulation of glycinergic synaptic currents in rodent hypoglossal motoneurones. J Physiol 2005; 569:817-31. [PMID: 16123105 PMCID: PMC1464266 DOI: 10.1113/jphysiol.2005.094862] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Glycinergic synapses are implicated in the coordination of reflex responses, sensory signal processing and pain sensation. Their activity is pre- and postsynaptically regulated, although mechanisms are poorly understood. Using patch-clamp recording and Ca2+ imaging in hypoglossal motoneurones from rat and mouse brainstem slices, we address here the role of cytoplasmic Ca2+ (Ca(i)) in glycinergic synapse modulation. Ca2+ influx through voltage-gated or NMDA receptor channels caused powerful transient inhibition of glycinergic IPSCs. This effect was accompanied by an increase in both the failure rate and paired-pulse ratio, as well as a decrease in the frequency of mIPSCs, suggesting a presynaptic mechanism of depression. Inhibition was reduced by the cannabinoid receptor antagonist SR141716A and occluded by the agonist WIN55,212-2, indicating involvement of endocannabinoid retrograde signalling. Conversely, in the presence of SR141716A, glycinergic IPSCs were potentiated postsynaptically by glutamate or NMDA, displaying a Ca2(+)-dependent increase in amplitude and decay prolongation. Both presynaptic inhibition and postsynaptic potentiation were completely prevented by strong Ca(i) buffering (20 mm BAPTA). Our findings demonstrate two independent mechanisms by which Ca2+ modulates glycinergic synaptic transmission: (i) presynaptic inhibition of glycine release and (ii) postsynaptic potentiation of GlyR-mediated responses. This dual Ca2(+)-induced regulation might be important for feedback control of neurotransmission in a variety of glycinergic networks in mammalian nervous systems.
Collapse
Affiliation(s)
- Marat Mukhtarov
- Institut de Neurobiologie de la Méditerranée, INSERM U29, 163, route de Luminy, 13273 Marseille cedex 09, France
| | | | | |
Collapse
|
42
|
Abstract
The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning GlyR molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.
Collapse
Affiliation(s)
- Joseph W Lynch
- School of Biomedical Sciences, Univ. of Queensland, Brisbane QLD 4072, Australia.
| |
Collapse
|
43
|
Devignot V, Prado de Carvalho L, Bregestovski P, Goblet C. A novel glycine receptor alpha Z1 subunit variant in the zebrafish brain. Neuroscience 2004; 122:449-57. [PMID: 14614909 DOI: 10.1016/s0306-4522(03)00171-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alpha subunits of the inhibitory glycine receptor (GlyR) display genetic heterogeneity in mammals and zebrafish. This diversity is increased in mammals by the alternative splicing mechanism. We report here in zebrafish, the characterization of a new alphaZ1 subunit likely arising from alphaZ1 gene by an alternative splice process (alphaZ1L). This novel cDNA possesses 45 supplementary nucleotides at the putative exon2/exon3 boundary. The corresponding protein contains 15 additional amino acids in the NH2-terminal domain. Heterologous expression of homomeric GlyRalphaZ1L in human embryonic kidney-293 cells generates glycine-gated strychnine-sensitive chloride channels with no obvious discrepancy with pharmacological properties of GlyRalphaZ1. Moreover, zinc modulation of glycine-induced currents is identical in alphaZ1 and alphaZ1L glycine receptors. During ontogenesis, simultaneous alphaZ1 and alphaZ1L mRNA synthesis have been observed. Embryonic and adult alphaZ1 and alphaZ1L mRNA expressions are restricted to the CNS. Embryonic alphaZ1L mRNA anatomical pattern of expression is, however, highly restrained and strictly limited to the rostral part of the brain revealing a highly regionalized function of alphaZ1L in the CNS. This report contributes to the characterization of the diversity of glycine receptor isoforms in zebrafish and emphasizes the common mechanism used among vertebrates for creating GlyR variety and specificity.
Collapse
Affiliation(s)
- V Devignot
- Laboratoire de Biologie Cellulaire et Moléculaire du Neurone, Institut National de la Santé et de la Recherche Médicale U261, Département des Biotechnologies, Institut Pasteur, 25 rue du Dr Roux, F-75724 Paris, France
| | | | | | | |
Collapse
|
44
|
Mangin JM, Baloul M, Prado De Carvalho L, Rogister B, Rigo JM, Legendre P. Kinetic properties of the alpha2 homo-oligomeric glycine receptor impairs a proper synaptic functioning. J Physiol 2003; 553:369-86. [PMID: 12972628 PMCID: PMC2343566 DOI: 10.1113/jphysiol.2003.052142] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Ionotropic glycine receptors (GlyRs) are present in the central nervous system well before the establishment of synaptic contacts. Immature nerve cells are known, at least in the spinal cord, to express alpha2 homomeric GlyRs, the properties of which are relatively unknown compared to those of the adult synaptic form of the GlyR (mainly alpha1/beta heteromeres). Here, the kinetics properties of GlyRs at the single-channel level have been recorded in real-time by means of the patch-clamp technique in the outside-out configuration coupled with an ultra-fast flow application system (< 100 micros). Recordings were performed on chinese hamster ovary (CHO) cells stably transfected with the alpha2 GlyR subunit. We show that the onset, the relaxation and the desensitisation of alpha2 homomeric GlyR-mediated currents are slower by one or two orders of magnitude compared to synaptic mature GlyRs and to other ligand-gated ionotropic channels involved in fast synaptic transmission. First latency analysis performed on single GlyR channels revealed that their slow activation time course was due to delayed openings. When synaptic release of glycine was mimicked (1 mM glycine; 1 ms pulse duration), the opening probability of alpha2 homomeric GlyRs was low (P(o) approximately = 0.1) when compared to mature synaptic GlyRs (Po = 0.9). This low Po is likely to be a direct consequence of the relatively slow activation kinetics of alpha2 homomeric GlyRs when compared to the activation kinetics of mature alpha1/beta GlyRs. Such slow kinetics suggest that embryonic alpha2 homomeric GlyRs cannot be activated by fast neurotransmitter release at mature synapses but rather could be suited for a non-synaptic paracrine-like release of agonist, which is known to occur in the embryo.
Collapse
Affiliation(s)
- J M Mangin
- UMR CNRS 7102 Neurobiologie des Processus Adaptatifs, Université Pierre et Marie Curie, 9 quai St Bernard, 75252 Paris cedex 05, France.
| | | | | | | | | | | |
Collapse
|
45
|
Chesnoy-Marchais D. Potentiation of glycine responses by dideoxyforskolin and tamoxifen in rat spinal neurons. Eur J Neurosci 2003; 17:681-91. [PMID: 12603258 DOI: 10.1046/j.1460-9568.2003.02481.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dideoxyforskolin, a forskolin analogue unable to stimulate adenylate cyclase, and tamoxifen, an antioestrogen widely used against breast cancer, are both known to block some Cl- channels. Their effects on Cl- responses to glycine or GABA have been tested here by using whole-cell recording from cultured spinal neurons. Dideoxyforskolin (4 or 16 microm) and tamoxifen (0.2-5 microm) both potentiate responses to low glycine concentrations. They also induce blocking effects, predominant at high glycine concentrations. At 5 microm, tamoxifen increased responses to 15 microm glycine by a factor >4.5, reaching 20 in some neurons. Potentiation by extracellular dideoxyforskolin or tamoxifen persisted after intracellular application of the modulator and was not due to Zn2+ contamination. Potentiation by tamoxifen also persisted in a Ca2+-free extracellular solution, after intracellular Ca2+ buffering and protein kinase C blockade. Thus, the critical sites of action are not intracellular. The EC50 for glycine was lowered 6.6-fold by 5 microm tamoxifen. The kinetics and voltage-dependence of the effects of tamoxifen on glycine responses support the idea that this hydrophobic drug may act from a site located within the membrane. Tamoxifen (5 micro m) also increased responses to 2 micro m GABA by a factor of 3.5, but barely affected peak responses to 20 microm GABA. The demonstration that tamoxifen affects some of the main inhibitory receptors should be useful for better evaluating its neurological effects. Furthermore, the results identify a new class of molecules that potentiate glycine receptor function.
Collapse
Affiliation(s)
- Dominique Chesnoy-Marchais
- Laboratoire de Neurobiologie Moléculaire et Cellulaire, CNRS UMR-8544, Ecole Normale Supérieure, 46 rue d'Ulm, 75005, Paris, France.
| |
Collapse
|
46
|
Turecek R, Trussell LO. Reciprocal developmental regulation of presynaptic ionotropic receptors. Proc Natl Acad Sci U S A 2002; 99:13884-9. [PMID: 12370408 PMCID: PMC129792 DOI: 10.1073/pnas.212419699] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of ionotropic glycine receptors potentiates glutamate release in mature calyceal nerve terminals of the rat medial nucleus of the trapezoid body, an auditory brainstem nucleus. In young rats, glycine and its receptors are poorly expressed. We therefore asked whether GABA (gamma-aminobutyric acid) might play a larger role than glycine in the regulation of glutamate release in the absence of glycine receptors. Indeed, in rats younger than postnatal day 11 (P11), and before the onset of hearing, calyces expressed high levels of ionotropic GABA(A) receptors but few glycine receptors. Isoguvacine, a selective agonist at GABA(A) receptors, strongly enhanced excitatory postsynaptic currents in young rats but had little effect in rats older than P11. Down-regulation of presynaptic GABA(A) receptors did not reflect global changes in receptor expression, because the magnitude of GABA and glycine responses was similar at P13 in the parent-cell bodies of the calyces, the bushy cells of the cochlear nucleus. In outside-out patches excised from the nonsynaptic face of calyces, GABA and glycine evoked single-channel currents consistent with the properties of postsynaptic GABA(A) and glycine receptors. Inhibitory GABA(B) receptors were present on the calyx at all developmental stages examined. Thus, GABA initially acts on two receptor subtypes, both promoting and inhibiting glutamate release. With age, the former role is transferred to the glycine receptor during the period in which postsynaptic glycinergic transmission is acquired.
Collapse
Affiliation(s)
- Rostislav Turecek
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, L-335A, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | | |
Collapse
|
47
|
Breitinger HG, Villmann C, Rennert J, Ballhausen D, Becker CM. Hydroxylated residues influence desensitization behaviour of recombinant alpha3 glycine receptor channels. J Neurochem 2002; 83:30-6. [PMID: 12358726 DOI: 10.1046/j.1471-4159.2002.01109.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The human glycine receptor subunit alpha3 exists in two splice variants (alpha3K/L), with alpha3L bearing an additional segment of 15 amino acids within the cytoplasmic TM3-4 loop. Homomeric alpha3K glycine receptors show faster desensitization than alpha3L receptors. Ion channel properties were compared of alpha3L, alpha3K, and of the triple mutant alpha3LDeltaOH = alpha3L(T358A/Y367F/S370A), where hydroxyl functions of the spliced insert had been removed by site-directed mutagenesis. Upon recombinant expression in HEK 293 cells, patch-clamp recording experiments revealed that removal of hydroxyl functions primarily affected receptor desensitization. The fraction of non-desensitizing current was 68 +/- 13% for alpha3L, 21 +/- 13% for alpha3K, and 48 +/- 16% for alpha3LDeltaOH. Desensitization time constants at saturating glycine concentration were 8.4 +/- 2.8 s, 1.9 +/- 2.3 s, and 2.8 +/- 0.4 s, for alpha3L, alpha3K, and the triple mutant alpha3LDeltaOH, respectively. In contrast, single-channel and whole-cell properties were similar for all three constructs. Thus, ion channel activation, desensitization, and conductance properties are independently controlled by distinct structural elements. Hydroxyl functions within the M3-4 loop of the glycine receptor alpha3 subunit are crucial, but not exclusive, determinants of receptor desensitization.
Collapse
Affiliation(s)
- Hans-Georg Breitinger
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, D-91054 Erlangen, Germany
| | | | | | | | | |
Collapse
|
48
|
Zhu L, Krnjević K, Jiang Z, McArdle JJ, Ye JH. Ethanol suppresses fast potentiation of glycine currents by glutamate. J Pharmacol Exp Ther 2002; 302:1193-200. [PMID: 12183680 DOI: 10.1124/jpet.102.033894] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Excitatory (glutamate) and inhibitory (GABA(A) and glycine) receptor/channels coexist in many neurons. To assess effects of ethanol on the interaction of glutamate and glycine receptors, glycine-induced current (I(Gly)) was recorded by a whole-cell patch-clamp technique from neurons freshly dissociated from the ventral tegmental area of rats. A conditioning prepulse of glutamate (1-3 s, 1 mM) significantly and reversibly potentiated responses to a pulse of glycine. This potentiation was increased when extracellular calcium was raised to 12 mM and reduced by including 10 mM 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid in the internal recording medium. It was not affected by 5 microM 1-N,O-bis-(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), a selective inhibitor of calcium/calmodulin-dependent protein kinase II. In a concentration-response analysis, a conditioning pulse of glutamate significantly lowered the EC(50) for glycine and increased the maximal I(Gly). Kinetic analysis of the currents indicated that glutamate slowed deactivation of glycine-gated chloride channels; therefore, glutamate may increase the affinity of glycine receptors for glycine. When coapplied with glycine, ethanol (10 mM) potentiated I(Gly) in 35% of neurons from the ventral tegmental area. In contrast, when coapplied with glutamate and glycine, ethanol suppressed the glutamate-induced potentiation of I(Gly) in these neurons. This suppression was also observed when ethanol and glycine were coapplied after a glutamate prepulse. A similar effect was observed when ethanol alone did not potentiate I(Gly). These findings suggest that glutamate-induced calcium influx modulates glycine receptors by a mechanism that can be blocked by ethanol.
Collapse
Affiliation(s)
- Li Zhu
- Department of Anesthesiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103-2714, USA
| | | | | | | | | |
Collapse
|
49
|
Moorhouse AJ, Keramidas A, Zaykin A, Schofield PR, Barry PH. Single channel analysis of conductance and rectification in cation-selective, mutant glycine receptor channels. J Gen Physiol 2002; 119:411-25. [PMID: 11981021 PMCID: PMC2233819 DOI: 10.1085/jgp.20028553] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2001] [Revised: 03/22/2002] [Accepted: 03/22/2002] [Indexed: 11/20/2022] Open
Abstract
Members of the ligand-gated ion channel superfamily mediate fast synaptic transmission in the nervous system. In this study, we investigate the molecular determinants and mechanisms of ion permeation and ion charge selectivity in this family of channels by characterizing the single channel conductance and rectification of alpha1 homomeric human glycine receptor channels (GlyRs) containing pore mutations that impart cation selectivity. The A-1'E mutant GlyR and the selectivity double mutant ([SDM], A-1'E, P-2' Delta) GlyR, had mean inward chord conductances (at -60 mV) of 7 pS and mean outward conductances of 11 and 12 pS (60 mV), respectively. This indicates that the mutations have not simply reduced anion permeability, but have replaced the previous anion conductance with a cation one. An additional mutation to neutralize the ring of positive charge at the extracellular mouth of the channel (SDM+R19'A GlyR) made the conductance-voltage relationship linear (14 pS at both 60 and -60 mV). When this external charged ring was made negative (SDM+R19'E GlyR), the inward conductance was further increased (to 22 pS) and now became sensitive to external divalent cations (being 32 pS in their absence). The effects of the mutations to the external ring of charge on conductance and rectification could be fit to a model where only the main external energy barrier height for permeation was changed. Mean outward conductances in the SDM+R19'A and SDM+R19'E GlyRs were increased when internal divalent cations were absent, consistent with the intracellular end of the pore being flanked by fixed negative charges. This supports our hypothesis that the ion charge selectivity mutations have inverted the electrostatic profile of the pore by introducing a negatively charged ring at the putative selectivity filter. These results also further confirm the role of external pore vestibule electrostatics in determining the conductance and rectification properties of the ligand-gated ion channels.
Collapse
Affiliation(s)
- Andrew J Moorhouse
- Department of Physiology and Pharmacology, University of New South Wales, Sydney 2052, Australia
| | | | | | | | | |
Collapse
|
50
|
Groot-Kormelink PJ, Beato M, Finotti C, Harvey RJ, Sivilotti LG. Achieving optimal expression for single channel recording: a plasmid ratio approach to the expression of alpha 1 glycine receptors in HEK293 cells. J Neurosci Methods 2002; 113:207-14. [PMID: 11772442 DOI: 10.1016/s0165-0270(01)00500-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In single-channel recording, optimal yield of kinetic data is achieved if simultaneous activations of more than one channel are few. When recordings are obtained from recombinant channels, it is therefore important to control the level of expression of the channel at the cell surface, while maintaining a high efficiency of transfection. In the present study, we optimised transfection protocols for single-channel recording from recombinant rat alpha 1 glycine receptors expressed in HEK293 cells. High transfection efficiency was achieved with lipofection (up to 70%). Lipofected cells however did not lend themselves to excised patch recording because of seal instability, especially obvious at hyperpolarised holding potentials. High quality excised patch recordings were reliably achieved with the calcium phosphate-DNA coprecipitation method, with transfection efficiencies around 40%. We achieved good control of the level of receptor expression by a plasmid ratio approach which kept the total amount of plasmid transfected constant while varying the ratio between alpha 1-containing plasmid and empty plasmid vector. The maximum amplitude of glycine-evoked currents was reliably dependent on the percentage of alpha 1-containing plasmid. Optimum results for steady-state single channel experiments at low glycine concentrations were obtained with 5% of alpha 1 plasmid DNA in the transfection mix.
Collapse
Affiliation(s)
- Paul J Groot-Kormelink
- Department of Pharmacology, The School of Pharmacy, 29/39 Brunswick Square, WC1N 1AX London, UK
| | | | | | | | | |
Collapse
|