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Trpevski D, Khodadadi Z, Carannante I, Hellgren Kotaleski J. Glutamate spillover drives robust all-or-none dendritic plateau potentials-an in silico investigation using models of striatal projection neurons. Front Cell Neurosci 2023; 17:1196182. [PMID: 37469606 PMCID: PMC10352111 DOI: 10.3389/fncel.2023.1196182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 05/31/2023] [Indexed: 07/21/2023] Open
Abstract
Plateau potentials are a critical feature of neuronal excitability, but their all-or-none behavior is not easily captured in modeling. In this study, we investigated models of plateau potentials in multi-compartment neuron models and found that including glutamate spillover provides robust all-or-none behavior. This result arises due to the prolonged duration of extrasynaptic glutamate. When glutamate spillover is not included, the all-or-none behavior is very sensitive to the steepness of the Mg2+ block. These results suggest a potentially significant role of glutamate spillover in plateau potential generation, providing a mechanism for robust all-or-none behavior across a wide range of slopes of the Mg2+ block curve. We also illustrate the importance of the all-or-none plateau potential behavior for nonlinear computation with regard to the nonlinear feature binding problem.
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Affiliation(s)
- Daniel Trpevski
- Science for Life Laboratory, Department of Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Zahra Khodadadi
- Science for Life Laboratory, Department of Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Ilaria Carannante
- Science for Life Laboratory, Department of Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Jeanette Hellgren Kotaleski
- Science for Life Laboratory, Department of Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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2
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Doyle MA, Brown JA, Winder DG. GluN2D expression is regulated by restraint stress and supports active stress coping bouts. Neuropharmacology 2023; 225:109377. [PMID: 36528117 PMCID: PMC9839594 DOI: 10.1016/j.neuropharm.2022.109377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 11/22/2022] [Accepted: 12/10/2022] [Indexed: 12/15/2022]
Abstract
Stress coping strategies represent critical responses to environmental challenges, and active coping has been linked to stress resilience in humans. Understanding the neuroadaptations that support these strategies may provide insights into adaptive and maladaptive stress responses. NMDA receptors (NMDARs) play key roles in neuroadaptation, and NMDARs have been specifically implicated in stress responsiveness. Constitutive knockout mice have been used to implicate the GluN2D NMDAR subunit in regulation of stress-sensitive and affective behavior, but the brain regions in which GluN2D expression changes drive these effects remain unknown. Here we report that following an acute restraint stressor, GluN2D subunit expression is specifically decreased in the bed nucleus of the stria terminalis (BNST), a key region involved in stress processing, in male but not female mice, with no differences found in the thalamus or ventral hippocampus in either sex. Rodents engage in active struggling events during restraint stress that may represent active coping strategies to stress. Thus, we assessed active coping bouts during acute and chronic restraint stress sessions in GluN2D knockout mice. During the first restraint session, GluN2D knockout mice exhibited a pronounced decrease in struggling bouts during restraint stress relative to wild-type littermates, consistent with a role of GluN2D in active coping responses to stress. Repeated, daily restraint sessions revealed a sex-specific role of GluN2D expression on certain aspects of active coping behaviors, with male GluN2D KO mice exhibiting a decrease in total coping bouts measured across five sessions. However, BNST-specific knockdown of GluN2D in male mice did not alter active coping bouts, suggesting either a multi-synaptic role of GluN2D and/or a developmental role of GluN2D in this behavior. Altogether, these data are consistent with a growing literature suggesting that exploration of GluN2D control of stress circuit actions may lead to a novel therapeutic target to consider for stress-related mood disorders.
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Affiliation(s)
- Marie A Doyle
- Department of Molecular Physiology and Biophysics, Vanderbilt University, USA; Vanderbilt Center for Addiction Research, Vanderbilt University, USA
| | - Jordan A Brown
- Vanderbilt Center for Addiction Research, Vanderbilt University, USA; Department of Pharmacology, Vanderbilt University, USA
| | - Danny G Winder
- Department of Molecular Physiology and Biophysics, Vanderbilt University, USA; Vanderbilt Center for Addiction Research, Vanderbilt University, USA; Department of Pharmacology, Vanderbilt University, USA; Department of Psychiatry, Vanderbilt University Medical Center, USA.
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Esmethadone (REL-1017) and Other Uncompetitive NMDAR Channel Blockers May Improve Mood Disorders via Modulation of Synaptic Kinase-Mediated Signaling. Int J Mol Sci 2022; 23:ijms232012196. [PMID: 36293063 PMCID: PMC9602945 DOI: 10.3390/ijms232012196] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/04/2022] [Accepted: 10/10/2022] [Indexed: 11/30/2022] Open
Abstract
This article presents a mechanism of action hypothesis to explain the rapid antidepressant effects of esmethadone (REL-1017) and other uncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonists and presents a corresponding mechanism of disease hypothesis for major depressive disorder (MDD). Esmethadone and other uncompetitive NMDAR antagonists may restore physiological neural plasticity in animal models of depressive-like behavior and in patients with MDD via preferential tonic block of pathologically hyperactive GluN2D subtypes. Tonic Ca2+ currents via GluN2D subtypes regulate the homeostatic availability of synaptic proteins. MDD and depressive behaviors may be determined by reduced homeostatic availability of synaptic proteins, due to upregulated tonic Ca2+ currents through GluN2D subtypes. The preferential activity of low-potency NMDAR antagonists for GluN2D subtypes may explain their rapid antidepressant effects in the absence of dissociative side effects.
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Bettini E, Stahl SM, De Martin S, Mattarei A, Sgrignani J, Carignani C, Nola S, Locatelli P, Pappagallo M, Inturrisi CE, Bifari F, Cavalli A, Alimonti A, Pani L, Fava M, Traversa S, Folli F, Manfredi PL. Pharmacological Comparative Characterization of REL-1017 (Esmethadone-HCl) and Other NMDAR Channel Blockers in Human Heterodimeric N-Methyl-D-Aspartate Receptors. Pharmaceuticals (Basel) 2022; 15:ph15080997. [PMID: 36015145 PMCID: PMC9414551 DOI: 10.3390/ph15080997] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 08/05/2022] [Accepted: 08/09/2022] [Indexed: 12/19/2022] Open
Abstract
Excessive Ca2+ currents via N-methyl-D-aspartate receptors (NMDARs) have been implicated in many disorders. Uncompetitive NMDAR channel blockers are an emerging class of drugs in clinical use for major depressive disorder (MDD) and other neuropsychiatric diseases. The pharmacological characterization of uncompetitive NMDAR blockers in clinical use may improve our understanding of NMDAR function in physiology and pathology. REL-1017 (esmethadone-HCl), a novel uncompetitive NMDAR channel blocker in Phase 3 trials for the treatment of MDD, was characterized together with dextromethorphan, memantine, (±)-ketamine, and MK-801 in cell lines over-expressing NMDAR subtypes using fluorometric imaging plate reader (FLIPR), automated patch-clamp, and manual patch-clamp electrophysiology. In the absence of Mg2+, NMDAR subtypes NR1-2D were most sensitive to low, sub-μM glutamate concentrations in FLIPR experiments. FLIPR Ca2+ determination demonstrated low μM affinity of REL-1017 at NMDARs with minimal subtype preference. In automated and manual patch-clamp electrophysiological experiments, REL-1017 exhibited preference for the NR1-2D NMDAR subtype in the presence of 1 mM Mg2+ and 1 μM L-glutamate. Tau off and trapping characteristics were similar for (±)-ketamine and REL-1017. Results of radioligand binding assays in rat cortical neurons correlated with the estimated affinities obtained in FLIPR assays and in automated and manual patch-clamp assays. In silico studies of NMDARs in closed and open conformation indicate that REL-1017 has a higher preference for docking and undocking the open-channel conformation compared to ketamine. In conclusion, the pharmacological characteristics of REL-1017 at NMDARs, including relatively low affinity at the NMDAR, NR1-2D subtype preference in the presence of 1 mM Mg2+, tau off and degree of trapping similar to (±)-ketamine, and preferential docking and undocking of the open NMDAR, could all be important variables for understanding the rapid-onset antidepressant effects of REL-1017 without psychotomimetic side effects.
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Affiliation(s)
- Ezio Bettini
- In Vitro Pharmacology Department, Aptuit, An Evotec Company, 37135 Verona, Italy
| | - Stephen M. Stahl
- Department of Psychiatry, VAMC (SD), University of California, San Diego, CA 92093, USA
- Neuroscience Education Institute, Carlsbad, CA 92008, USA
| | - Sara De Martin
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, 35122 Padua, Italy
| | - Andrea Mattarei
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, 35122 Padua, Italy
| | - Jacopo Sgrignani
- Institute for Research in Biomedicine (IRB), Università della Svizzera Italiana (USI), 6500 Bellinzona, Switzerland
| | - Corrado Carignani
- In Vitro Pharmacology Department, Aptuit, An Evotec Company, 37135 Verona, Italy
| | - Selena Nola
- In Vitro Pharmacology Department, Aptuit, An Evotec Company, 37135 Verona, Italy
| | - Patrizia Locatelli
- Institute for Research in Biomedicine (IRB), Università della Svizzera Italiana (USI), 6500 Bellinzona, Switzerland
| | - Marco Pappagallo
- Department of Anesthesiology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
- Relmada Therapeutics, Coral Gables, FL 33134, USA
| | | | - Francesco Bifari
- Department of Medical Biotechnology and Translational Medicine, University of Milan, 20122 Milan, Italy
| | - Andrea Cavalli
- Institute for Research in Biomedicine (IRB), Università della Svizzera Italiana (USI), 6500 Bellinzona, Switzerland
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Andrea Alimonti
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland
- Institute of Oncology Research, Southern Switzerland, 6500 Bellinzona, Switzerland
- The Institute of Oncology Research, Università della Svizzera Italiana, 6500 Bellinzona, Switzerland
- Veneto Institute of Molecular Medicine, 35129 Padua, Italy
- Department of Medicine, Zurich University, 8006 Zurich, Switzerland
- Department of Medicine—DIMED, University of Padua, 35122 Padua, Italy
| | - Luca Pani
- Relmada Therapeutics, Coral Gables, FL 33134, USA
- Department of Psychiatry and Behavioral Sciences, School of Medicine, University of Miami, Miami, FL 33136, USA
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, 41121 Modena, Italy
| | - Maurizio Fava
- Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114, USA
| | | | - Franco Folli
- Department of Health Sciences, University of Milan, 20122 Milan, Italy
| | - Paolo L. Manfredi
- Relmada Therapeutics, Coral Gables, FL 33134, USA
- Correspondence: ; Tel.: +1-786-629-1376
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Activation of non-classical NMDA receptors by glycine impairs barrier function of brain endothelial cells. Cell Mol Life Sci 2022; 79:479. [PMID: 35951110 PMCID: PMC9372018 DOI: 10.1007/s00018-022-04502-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/04/2022] [Accepted: 07/16/2022] [Indexed: 12/24/2022]
Abstract
Blood–brain barrier (BBB) integrity is necessary to maintain homeostasis of the central nervous system (CNS). NMDA receptor (NMDAR) function and expression have been implicated in BBB integrity. However, as evidenced in neuroinflammatory conditions, BBB disruption contributes to immune cell infiltration and propagation of inflammatory pathways. Currently, our understanding of the pathophysiological role of NMDAR signaling on endothelial cells remains incomplete. Thus, we investigated NMDAR function on primary mouse brain microvascular endothelial cells (MBMECs). We detected glycine-responsive NMDAR channels, composed of functional GluN1, GluN2A and GluN3A subunits. Importantly, application of glycine alone, but not glutamate, was sufficient to induce NMDAR-mediated currents and an increase in intracellular Ca2+ concentrations. Functionally, glycine-mediated NMDAR activation leads to loss of BBB integrity and changes in actin distribution. Treatment of oocytes that express NMDARs composed of different subunits, with GluN1 and GluN3A binding site inhibitors, resulted in abrogation of NMDAR signaling as measured by two-electrode voltage clamp (TEVC). This effect was only detected in the presence of the GluN2A subunits, suggesting the latter as prerequisite for pharmacological modulation of NMDARs on brain endothelial cells. Taken together, our findings argue for a novel role of glycine as NMDAR ligand on endothelial cells shaping BBB integrity.
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Chen S, Xu D, Fan L, Fang Z, Wang X, Li M. Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy. Front Mol Neurosci 2022; 14:797253. [PMID: 35069111 PMCID: PMC8780133 DOI: 10.3389/fnmol.2021.797253] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022] Open
Abstract
Epilepsy is one of the most common neurological disorders characterized by recurrent seizures. The mechanism of epilepsy remains unclear and previous studies suggest that N-methyl-D-aspartate receptors (NMDARs) play an important role in abnormal discharges, nerve conduction, neuron injury and inflammation, thereby they may participate in epileptogenesis. NMDARs belong to a family of ionotropic glutamate receptors that play essential roles in excitatory neurotransmission and synaptic plasticity in the mammalian CNS. Despite numerous studies focusing on the role of NMDAR in epilepsy, the relationship appeared to be elusive. In this article, we reviewed the regulation of NMDAR and possible mechanisms of NMDAR in epilepsy and in respect of onset, development, and treatment, trying to provide more evidence for future studies.
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Affiliation(s)
| | | | | | | | | | - Man Li
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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7
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The glutamatergic synapse: a complex machinery for information processing. Cogn Neurodyn 2021; 15:757-781. [PMID: 34603541 DOI: 10.1007/s11571-021-09679-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/04/2021] [Accepted: 04/16/2021] [Indexed: 10/21/2022] Open
Abstract
Being the most abundant synaptic type, the glutamatergic synapse is responsible for the larger part of the brain's information processing. Despite the conceptual simplicity of the basic mechanism of synaptic transmission, the glutamatergic synapse shows a large variation in the response to the presynaptic release of the neurotransmitter. This variability is observed not only among different synapses but also in the same single synapse. The synaptic response variability is due to several mechanisms of control of the information transferred among the neurons and suggests that the glutamatergic synapse is not a simple bridge for the transfer of information but plays an important role in its elaboration and management. The control of the synaptic information is operated at pre, post, and extrasynaptic sites in a sort of cooperation between the pre and postsynaptic neurons which also involves the activity of other neurons. The interaction between the different mechanisms of control is extremely complicated and its complete functionality is far from being fully understood. The present review, although not exhaustively, is intended to outline the most important of these mechanisms and their complexity, the understanding of which will be among the most intriguing challenges of future neuroscience.
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8
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Watkins JC, Evans RH, Bayés À, Booker SA, Gibb A, Mabb AM, Mayer M, Mellor JR, Molnár E, Niu L, Ortega A, Pankratov Y, Ramos-Vicente D, Rodríguez-Campuzano A, Rodríguez-Moreno A, Wang LY, Wang YT, Wollmuth L, Wyllie DJA, Zhuo M, Frenguelli BG. 21st century excitatory amino acid research: A Q & A with Jeff Watkins and Dick Evans. Neuropharmacology 2021; 198:108743. [PMID: 34363811 DOI: 10.1016/j.neuropharm.2021.108743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In 1981 Jeff Watkins and Dick Evans wrote what was to become a seminal review on excitatory amino acids (EAAs) and their receptors (Watkins and Evans, 1981). Bringing together various lines of evidence dating back over several decades on: the distribution in the nervous system of putative amino acid neurotransmitters; enzymes involved in their production and metabolism; the uptake and release of amino acids; binding of EAAs to membranes; the pharmacological action of endogenous excitatory amino acids and their synthetic analogues, and notably the actions of antagonists for the excitations caused by both nerve stimulation and exogenous agonists, often using pharmacological tools developed by Jeff and his colleagues, they provided a compelling account for EAAs, especially l-glutamate, as a bona fide neurotransmitter in the nervous system. The rest, as they say, is history, but far from being consigned to history, EAA research is in rude health well into the 21st Century as this series of Special Issues of Neuropharmacology exemplifies. With EAAs and their receptors flourishing across a wide range of disciplines and clinical conditions, we enter into a dialogue with two of the most prominent and influential figures in the early days of EAA research: Jeff Watkins and Dick Evans.
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Affiliation(s)
| | | | - Àlex Bayés
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau, Barcelona, Spain and Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Sam A Booker
- Simons Initiative for the Developing Brain, Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Alasdair Gibb
- Research Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Angela M Mabb
- Neuroscience Institute, Georgia State University, Atlanta, GA, United States
| | - Mark Mayer
- Bldg 35A, Room 3D-904, 35A Convent Drive, NINDS, NIH, Bethesda, MD, 20892, USA
| | - Jack R Mellor
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Elek Molnár
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Li Niu
- Chemistry Department, University at Albany, SUNY, 1400 Washington Ave, Albany, NY, 12222, USA
| | - Arturo Ortega
- Department of Toxicology, Cinvestav, Mexico City, Mexico
| | - Yuriy Pankratov
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - David Ramos-Vicente
- Molecular Physiology of the Synapse Laboratory, Biomedical Research Institute Sant Pau, Barcelona, Spain and Universitat Autònoma de Barcelona, Barcelona, Spain
| | | | | | - Lu-Yang Wang
- Program in Neurosciences & Mental Health, SickKids Research Institute and Department of Physiology, University of Toronto, 555 University Ave, Toronto, Ontario, M5G 1X8, Canada
| | - Yu Tian Wang
- Department of Medicine, University of British Columbia, Vancouver, BC, V6T 2B5, Canada
| | - Lonnie Wollmuth
- Depts. of Neurobiology & Behavior and Biochemistry & Cell Biology, Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY, 11794-5230, USA
| | - David J A Wyllie
- Simons Initiative for the Developing Brain, Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Min Zhuo
- Institute of Brain Research, Qingdao International Academician Park, Qingdao, 266000, China
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Booker SA, Wyllie DJA. NMDA receptor function in inhibitory neurons. Neuropharmacology 2021; 196:108609. [PMID: 34000273 DOI: 10.1016/j.neuropharm.2021.108609] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 05/07/2021] [Accepted: 05/08/2021] [Indexed: 12/26/2022]
Abstract
N-methyl-d-aspartate receptors (NMDARs) are present in the majority of brain circuits and play a key role in synaptic information transfer and synaptic plasticity. A key element of many brain circuits are inhibitory GABAergic interneurons that in themselves show diverse and cell-type-specific NMDAR expression and function. Indeed, NMDARs located on interneurons control cellular excitation in a synapse-type specific manner which leads to divergent dendritic integration properties amongst the plethora of interneuron subtypes known to exist. In this review, we explore the documented diversity of NMDAR subunit expression in identified subpopulations of interneurons and assess the NMDAR subtype-specific control of their function. We also highlight where knowledge still needs to be obtained, if a full appreciation is to be gained of roles played by NMDARs in controlling GABAergic modulation of synaptic and circuit function. This article is part of the 'Special Issue on Glutamate Receptors - NMDA receptors'.
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Affiliation(s)
- Sam A Booker
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, UK; Patrick Wild Centre for Research into Autism, Fragile X Syndrome & Intellectual Disabilities, University of Edinburgh, Edinburgh, EH8 9XD, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK.
| | - David J A Wyllie
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, EH8 9XD, UK; Patrick Wild Centre for Research into Autism, Fragile X Syndrome & Intellectual Disabilities, University of Edinburgh, Edinburgh, EH8 9XD, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK; Centre for Brain Development and Repair, InStem, Bangalore, 560065, India.
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GluN2 Subunit-Dependent Redox Modulation of NMDA Receptor Activation by Homocysteine. Biomolecules 2020; 10:biom10101441. [PMID: 33066432 PMCID: PMC7602226 DOI: 10.3390/biom10101441] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/07/2020] [Accepted: 10/12/2020] [Indexed: 12/25/2022] Open
Abstract
Homocysteine (HCY) molecule combines distinct pharmacological properties as an agonist of N-methyl-d-aspartate receptors (NMDARs) and a reducing agent. Whereas NMDAR activation by HCY was elucidated, whether the redox modulation contributes to its action is unclear. Here, using patch-clamp recording and imaging of intracellular Ca2+, we study dithiothreitol (DTT) effects on currents and Ca2+ responses activated by HCY through native NMDARs and recombinant diheteromeric GluN1/2A, GluN1/2B, and GluN1/2C receptors. Within a wide range (1–800 μM) of [HCY]s, the concentration–activation relationships for recombinant NMDARs revealed a biphasicness. The high-affinity component obtained between 1 and 100 µM [HCY]s corresponding to the NMDAR activation was not affected by 1 mM DTT. The low-affinity phase observed at [HCY]s above 200 μM probably originated from thiol-dependent redox modulation of NMDARs. The reduction of NMDAR disulfide bonds by either 1 mM DTT or 1 mM HCY decreased GluN1/2A currents activated by HCY. In contrast, HCY-elicited GluN1/2B currents were enhanced due to the remarkable weakening of GluN1/2B desensitization. In fact, cleaving NMDAR disulfide bonds in neurons reversed the HCY-induced Ca2+ accumulation, making it dependent on GluN2B- rather than GluN2A-containing NMDARs. Thus, estimated concentrations for the HCY redox effects exceed those in the plasma during intermediate hyperhomocysteinemia but may occur during severe hyperhomocysteinemia.
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11
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Salimando GJ, Hyun M, Boyt KM, Winder DG. BNST GluN2D-Containing NMDA Receptors Influence Anxiety- and Depressive-like Behaviors and ModulateCell-Specific Excitatory/Inhibitory Synaptic Balance. J Neurosci 2020; 40:3949-3968. [PMID: 32277042 PMCID: PMC7219300 DOI: 10.1523/jneurosci.0270-20.2020] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 02/26/2020] [Indexed: 12/23/2022] Open
Abstract
Excitatory signaling mediated by NMDARs has been shown to regulate mood disorders. However, current treatments targeting NMDAR subtypes have shown limited success in treating patients, highlighting a need for alternative therapeutic targets. Here, we identify a role for GluN2D-containing NMDARs in modulating emotional behaviors and neural activity in the bed nucleus of the stria terminalis (BNST). Using a GluN2D KO mouse line (GluN2D-/-), we assessed behavioral phenotypes across tasks modeling emotional behavior. We then used a combination of ex vivo electrophysiology and in vivo fiber photometry to assess changes in BNST plasticity, cell-specific physiology, and cellular activity profiles. GluN2D-/- male mice exhibit evidence of exacerbated negative emotional behavior, and a deficit in BNST synaptic potentiation. We also found that GluN2D is functionally expressed on corticotropin-releasing factor (CRF)-positive BNST cells implicated in driving negative emotional states, and recordings in mice of both sexes revealed increased excitatory and reduced inhibitory drive onto GluN2D-/- BNST-CRF cells ex vivo and increased activity in vivo Using a GluN2D conditional KO line (GluN2Dflx/flx) to selectively delete the subunit from the BNST, we find that BNST-GluN2Dflx/flx male mice exhibit increased depressive-like behaviors, as well as altered NMDAR function and increased excitatory drive onto BNST-CRF neurons. Together, this study supports a role for GluN2D-NMDARs in regulating emotional behavior through their influence on excitatory signaling in a region-specific manner, and suggests that these NMDARs may serve as a novel target for selectively modulating glutamate signaling in stress-responsive structures and cell populations.SIGNIFICANCE STATEMENT Excitatory signaling mediated through NMDARs plays an important role in shaping emotional behavior; however, the receptor subtypes/brain regions through which this occurs are poorly understood. Here, we demonstrate that loss of GluN2D-containing NMDARs produces an increase in anxiety- and depressive-like behaviors in mice, deficits in BNST synaptic potentiation, and increased activity in BNST-CRF neurons known to drive negative emotional behavior. Further, we determine that deleting GluN2D in the BNST leads to increased depressive-like behaviors and increased excitatory drive onto BNST-CRF cells. Collectively, these results demonstrate a role for GluN2D-NMDARs in regulating the activity of stress-responsive structures and neuronal populations in the adult brain, suggesting them as a potential target for treating negative emotional states in mood-related disorders.
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Affiliation(s)
- Gregory J Salimando
- Department of Molecular Physics & Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, 37212
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, 37212
- Vanderbilt University Medical Center, Vanderbilt Kennedy Center, Nashville, Tennessee, 37203
- Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, Tennessee, 37232
| | - Minsuk Hyun
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, 02115
| | - Kristen M Boyt
- Bowles Center for Alcohol Studies, Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, 27599
| | - Danny G Winder
- Department of Molecular Physics & Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, 37212
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, 37212
- Vanderbilt University Medical Center, Vanderbilt Kennedy Center, Nashville, Tennessee, 37203
- Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, Tennessee, 37232
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, 37212
- Department of Psychiatry & Behavioral Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, 37212
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12
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Zhu Z, Wang H, Jiang Y, Hua T, Zhang C. Heroin exposure and withdrawal differentially influence expression of NMDA receptor NR2 subunits in the prelimbic region of rat medial prefrontal cortex. Neurosci Lett 2020; 721:134819. [PMID: 32032749 DOI: 10.1016/j.neulet.2020.134819] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/24/2020] [Accepted: 02/03/2020] [Indexed: 11/19/2022]
Abstract
It is widely reported that drug addiction involves the strengthening of specific reward circuits through N-methyl-d-aspartic acid receptor (NMDAR)-dependent synaptic potentiation, and several lines of evidence strongly implicate NMDA receptor 2 (NR2) subunits in drug abuse. To explore the potential mechanism of heroin dependence, this study examined changes in the expression levels of NR2 subunits NR2A-D in the prelimbic (PL) region of the medial prefrontal cortex (mPFC) after repeated heroin administration and subsequent abstinence. The conditioned place preference (CPP) test confirmed successful induction of heroin dependence and withdrawal. Western blotting and qRT-PCR revealed no differences in NR2A subunit expression among heroin-exposure, heroin-withdrawal, and control group rats; in contrast, expression of NR2B was significantly higher in the heroin-exposure group, whereas expression levels of NR2C and NR2D were significantly higher in the heroin-withdrawal group relative to the controls. Further studies are needed to identify the functional significance based on alterations of NR2 subunits.
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Affiliation(s)
- Zaiman Zhu
- College of Life Sciences, Anhui Normal University, Wuhu, 241000, China; Department of Physiology, Wannan Medical College, Wuhu, 241000, China
| | - Hui Wang
- Department of Physiology, Wannan Medical College, Wuhu, 241000, China
| | - Yuxin Jiang
- Department of Physiology, Wannan Medical College, Wuhu, 241000, China
| | - Tianmiao Hua
- College of Life Sciences, Anhui Normal University, Wuhu, 241000, China.
| | - Changzheng Zhang
- Department of Psychology & Guangdong Provincial Key Laboratory of Development and Education for Special Needs Children, Lingnan Normal University, Zhanjiang, 524048, China.
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13
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Houben AM, Keil MS. A calcium-influx-dependent plasticity model exhibiting multiple STDP curves. J Comput Neurosci 2020; 48:65-84. [DOI: 10.1007/s10827-019-00737-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 11/23/2019] [Accepted: 11/28/2019] [Indexed: 11/29/2022]
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14
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Ben Mimouna S, Le Charpentier T, Lebon S, Van Steenwinckel J, Messaoudi I, Gressens P. Involvement of the synapse-specific zinc transporter ZnT3 in cadmium-induced hippocampal neurotoxicity. J Cell Physiol 2019; 234:15872-15884. [PMID: 30714133 DOI: 10.1002/jcp.28245] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/09/2019] [Accepted: 01/16/2019] [Indexed: 01/24/2023]
Abstract
The present study examined the involvement of zinc (Zn)-transporters (ZnT3) in cadmium (Cd)-induced alterations of Zn homeostasis in rat hippocampal neurons. We treated primary rat hippocampal neurons for 24 or 48 hr with various concentrations of CdCl2 (0, 0.5, 5, 10, 25, or 50 μM) and/or ZnCl 2 (0, 10, 30, 50, 70, or 90 μM), using normal neuronal medium as control. By The CellTiter 96 ® Aqueous One Solution Cell Proliferation Assay (MTS; Promega, Madison, WI) assay and immunohistochemistry for cell death markers, 10 and 25 μM of Cd were found to be noncytotoxic doses, and both 30 and 90 μM of Zn as the best concentrations for cell proliferation. We tested these selected doses. Cd, at concentrations of 10 or 25 μM (and depending on the absence or presence of Zn), decreased the percentage of surviving cells. Cd-induced neuronal death was either apoptotic or necrotic depending on dose, as indicated by 7-AAD and/or annexin V labeling. At the molecular level, Cd exposure induced a decrease in hippocampal brain-derived neurotrophic factor-tropomyosin receptor kinase B (BDNF-TrkB) and Erk1/2 signaling, a significant downregulation of the expression of learning- and memory-related receptors and synaptic proteins such as the NMDAR NR2A subunit and PSD-95, as well as the expression of the synapse-specific vesicular Zn transporter ZnT3 in cultured hippocampal neurons. Zn supplementation, especially at the 30 μM concentration, led to partial or total protection against Cd neurotoxicity both with respect to the number of apoptotic cells and the expression of several genes. Interestingly, after knockdown of ZnT3 by small interfering RNA transfection, we did not find the restoration of the expression of this gene following Zn supplementation at 30 μM concentration. These data indicate the involvement of ZnT3 in the mechanism of Cd-induced hippocampal neurotoxicity.
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Affiliation(s)
- Safa Ben Mimouna
- Université de Monastir, Institut Supérieur de Biotechnologie de Monastir, Laboratoire LR11ES41 Génétique Biodiversité et Valorisation des Bio-ressources, Monastir, Tunisie.,PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | | | - Sophie Lebon
- PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | | | - Imed Messaoudi
- Université de Monastir, Institut Supérieur de Biotechnologie de Monastir, Laboratoire LR11ES41 Génétique Biodiversité et Valorisation des Bio-ressources, Monastir, Tunisie
| | - Pierre Gressens
- PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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15
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Hanson E, Armbruster M, Lau LA, Sommer ME, Klaft ZJ, Swanger SA, Traynelis SF, Moss SJ, Noubary F, Chadchankar J, Dulla CG. Tonic Activation of GluN2C/GluN2D-Containing NMDA Receptors by Ambient Glutamate Facilitates Cortical Interneuron Maturation. J Neurosci 2019; 39:3611-3626. [PMID: 30846615 PMCID: PMC6510335 DOI: 10.1523/jneurosci.1392-18.2019] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 01/29/2019] [Accepted: 02/26/2019] [Indexed: 02/03/2023] Open
Abstract
Developing cortical GABAergic interneurons rely on genetic programs, neuronal activity, and environmental cues to construct inhibitory circuits during early postnatal development. Disruption of these events can cause long-term changes in cortical inhibition and may be involved in neurological disorders associated with inhibitory circuit dysfunction. We hypothesized that tonic glutamate signaling in the neonatal cortex contributes to, and is necessary for, the maturation of cortical interneurons. To test this hypothesis, we used mice of both sexes to quantify extracellular glutamate concentrations in the cortex during development, measure ambient glutamate-mediated activation of developing cortical interneurons, and manipulate tonic glutamate signaling using subtype-specific NMDA receptor antagonists in vitro and in vivo We report that ambient glutamate levels are high (≈100 nm) in the neonatal cortex and decrease (to ≈50 nm) during the first weeks of life, coincident with increases in astrocytic glutamate uptake. Consistent with elevated ambient glutamate, putative parvalbumin-positive interneurons in the cortex (identified using G42:GAD1-eGFP reporter mice) exhibit a transient, tonic NMDA current at the end of the first postnatal week. GluN2C/GluN2D-containing NMDA receptors mediate the majority of this current and contribute to the resting membrane potential and intrinsic properties of developing putative parvalbumin interneurons. Pharmacological blockade of GluN2C/GluN2D-containing NMDA receptors in vivo during the period of tonic interneuron activation, but not later, leads to lasting decreases in interneuron morphological complexity and causes deficits in cortical inhibition later in life. These results demonstrate that dynamic ambient glutamate signaling contributes to cortical interneuron maturation via tonic activation of GluN2C/GluN2D-containing NMDA receptors.SIGNIFICANCE STATEMENT Inhibitory GABAergic interneurons make up 20% of cortical neurons and are critical to controlling cortical network activity. Dysfunction of cortical inhibition is associated with multiple neurological disorders, including epilepsy. Establishing inhibitory cortical networks requires in utero proliferation, differentiation, and migration of immature GABAergic interneurons, and subsequent postnatal morphological maturation and circuit integration. Here, we demonstrate that ambient glutamate provides tonic activation of immature, putative parvalbumin-positive GABAergic interneurons in the neonatal cortex via high-affinity NMDA receptors. When this activation is blocked, GABAergic interneuron maturation is disrupted, and cortical networks exhibit lasting abnormal hyperexcitability. We conclude that temporally precise activation of developing cortical interneurons by ambient glutamate is critically important for establishing normal cortical inhibition.
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Affiliation(s)
- Elizabeth Hanson
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience Program, Tufts Sackler School of Biomedical Sciences, Boston, Massachusetts 02111
| | - Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Lauren A Lau
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience Program, Tufts Sackler School of Biomedical Sciences, Boston, Massachusetts 02111
| | - Mary E Sommer
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Zin-Juan Klaft
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Sharon A Swanger
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, and
| | - Farzad Noubary
- Department of Health Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
| | - Jayashree Chadchankar
- AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, and
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111,
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16
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High sensitivity of cerebellar neurons to homocysteine is determined by expression of GluN2C and GluN2D subunits of NMDA receptors. Biochem Biophys Res Commun 2018; 506:648-652. [PMID: 30454701 DOI: 10.1016/j.bbrc.2018.10.140] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 10/23/2018] [Indexed: 10/28/2022]
Abstract
Homocysteine (HCY) induced neurotoxicity largely depends on interaction of this endogenous amino acid with glutamate NMDA receptors (NMDARs). This receptor type is composed by GluN1 and different GluN2 (A, B, C or D) subunits. However, the receptor activity of HCY in brain regions which differ in relative contribution of GluN2 subunits was not tested so far. In the current study, we explored the action of HCY on cerebellar neurons which natively express GluN2C and GluN2D subunits of NMDARs and compared this with the action of HCY on cortical neurons which are mainly composed by GluN2A and GluN2B subunits. To validate obtained results, we also studied the responses to HCY in recombinant GluN1/2C and GluN1/2D NMDARs expressed in HEK293T cells. Responses to HCY were compared to membrane currents evoked by glutamate or by the specific agonist NMDA. First, we found that on HEK cells expressing GluN1/2C or GluN1/2D NMDARs, HCY was full agonist producing membrane currents similar in amplitude to currents induced by glutamate. The EC50 values for these particular receptor subtype activation were 80 μM and 31 μM, respectively. Then, we found that HCY similarly to NMDA, evoked large slightly desensitizing membrane currents in native NMDARs of cerebellar and cortical neurons. In cortical neurons, the ratio of the respective currents (IHCY/INMDA) was 0.16 and did not significantly change during in vitro maturation. In sharp contrast, in cerebellar neurons, the ratio of currents evoked by HCY and NMDA was dramatically increased from 0.31 to 0.72 from 7 to 21 day in culture. We show that least 75% of HCY-induced currents in cerebellum were mediated by GluN2C- or GluN2D-containing NMDARs. Thus, our data revealed a large population of cerebellar NMDA receptors highly sensitive to HCY which suggest potential vulnerability of this brain region to pathological conditions associated with enhanced levels of this neurotoxic amino acid.
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17
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Hansen KB, Yi F, Perszyk RE, Furukawa H, Wollmuth LP, Gibb AJ, Traynelis SF. Structure, function, and allosteric modulation of NMDA receptors. J Gen Physiol 2018; 150:1081-1105. [PMID: 30037851 PMCID: PMC6080888 DOI: 10.1085/jgp.201812032] [Citation(s) in RCA: 337] [Impact Index Per Article: 56.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 07/03/2018] [Indexed: 12/22/2022] Open
Abstract
Hansen et al. review recent structural data that have provided insight into the function and allosteric modulation of NMDA receptors. NMDA-type glutamate receptors are ligand-gated ion channels that mediate a Ca2+-permeable component of excitatory neurotransmission in the central nervous system (CNS). They are expressed throughout the CNS and play key physiological roles in synaptic function, such as synaptic plasticity, learning, and memory. NMDA receptors are also implicated in the pathophysiology of several CNS disorders and more recently have been identified as a locus for disease-associated genomic variation. NMDA receptors exist as a diverse array of subtypes formed by variation in assembly of seven subunits (GluN1, GluN2A-D, and GluN3A-B) into tetrameric receptor complexes. These NMDA receptor subtypes show unique structural features that account for their distinct functional and pharmacological properties allowing precise tuning of their physiological roles. Here, we review the relationship between NMDA receptor structure and function with an emphasis on emerging atomic resolution structures, which begin to explain unique features of this receptor.
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Affiliation(s)
- Kasper B Hansen
- Department of Biomedical and Pharmaceutical Sciences and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT
| | - Feng Yi
- Department of Biomedical and Pharmaceutical Sciences and Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT
| | - Riley E Perszyk
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA
| | - Hiro Furukawa
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY
| | - Lonnie P Wollmuth
- Departments of Neurobiology & Behavior and Biochemistry & Cell Biology, Stony Brook University, Stony Brook, NY
| | - Alasdair J Gibb
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA
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18
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Sibarov DA, Bruneau N, Antonov SM, Szepetowski P, Burnashev N, Giniatullin R. Functional Properties of Human NMDA Receptors Associated with Epilepsy-Related Mutations of GluN2A Subunit. Front Cell Neurosci 2017; 11:155. [PMID: 28611597 PMCID: PMC5447064 DOI: 10.3389/fncel.2017.00155] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 05/15/2017] [Indexed: 12/26/2022] Open
Abstract
Genetic variants of the glutamate activated N-methyl-D-aspartate (NMDA) receptor (NMDAR) subunit GluN2A are associated with the hyperexcitable states manifested by epileptic seizures and interictal discharges in patients with disorders of the epilepsy-aphasia spectrum (EAS). The variants found in sporadic cases and families are of different types and include microdeletions encompassing the corresponding GRIN2A gene as well as nonsense, splice-site and missense GRIN2A defects. They are located at different functional domains of GluN2A and no clear genotype-phenotype correlation has emerged yet. Moreover, GluN2A variants may be associated with phenotypic pleiotropy. Deciphering the consequences of pathogenic GRIN2A variants would surely help in better understanding of the underlying mechanisms. This emphasizes the need for functional studies to unravel the basic functional properties of each specific NMDAR variant. In the present study, we have used patch-clamp recordings to evaluate kinetic changes of mutant NMDARs reconstituted after co-transfection of cultured cells with the appropriate expression vectors. Three previously identified missense variants found in patients or families with disorders of the EAS and situated in the N-terminal domain (p.Ile184Ser) or in the ligand-binding domain (p.Arg518His and p.Ala716Thr) of GluN2A were studied in both the homozygous and heterozygous conditions. Relative surface expression and current amplitude were significantly reduced for NMDARs composed of mutant p.Ile184Ser and p.Arg518His, but not p.Ala716His, as compared with wild-type (WT) NMDARs. Amplitude of whole-cell currents was still drastically decreased when WT and mutant p.Arg518His-GluN2A subunits were co-expressed, suggesting a dominant-negative mechanism. Activation times were significantly decreased in both homozygous and heterozygous conditions for the two p.Ile184Ser and p.Arg518His variants, but not for p.Ala716His. Deactivation also significantly increased for p.Ile184Ser variant in the homozygous but not the heterozygous state while it was increased for p.Arg518His in both states. Our data indicate that p.Ile184Ser and p.Arg518His GluN2A variants both impacted on NMDAR function, albeit differently, whereas p.Ala716His did not significantly influence NMDAR kinetics, hence partly questioning its direct and strong pathogenic role. This study brings new insights into the functional impact that GRIN2A variants might have on NMDAR kinetics, and provides a mechanistic explanation for the neurological manifestations seen in the corresponding human spectrum of disorders.
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Affiliation(s)
- Dmitry A Sibarov
- Laboratory of Comparative Neurophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of SciencesSaint-Petersburg, Russia
| | - Nadine Bruneau
- INMED, Aix-Marseille University, INSERM U901Marseille, France
| | - Sergei M Antonov
- Laboratory of Comparative Neurophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of SciencesSaint-Petersburg, Russia
| | | | - Nail Burnashev
- INMED, Aix-Marseille University, INSERM U901Marseille, France
| | - Rashid Giniatullin
- A. I. Virtanen Institute, University of Eastern FinlandKuopio, Finland.,Laboratory of Neurobiology, Kazan Federal UniversityKazan, Russia
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19
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Iacobucci GJ, Popescu GK. NMDA receptors: linking physiological output to biophysical operation. Nat Rev Neurosci 2017; 18:236-249. [PMID: 28303017 DOI: 10.1038/nrn.2017.24] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
NMDA receptors are preeminent neurotransmitter-gated channels in the CNS, which respond to glutamate in a manner that integrates multiple external and internal cues. They belong to the ionotropic glutamate receptor family and fulfil unique and crucial roles in neuronal development and function. These roles depend on characteristic response kinetics, which reflect the operation of the receptors. Here, we review biologically salient features of the NMDA receptor signal and its mechanistic origins. Knowledge of distinctive NMDA receptor biophysical properties, their structural determinants and physiological roles is necessary to understand the physiological and neurotoxic actions of glutamate and to design effective therapeutics.
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Affiliation(s)
- Gary J Iacobucci
- Department of Biochemistry, University of Buffalo, State University of New York (SUNY), 144 Farber Hall, 3435 Main street, Buffalo, New York 14214, USA
| | - Gabriela K Popescu
- Department of Biochemistry, University of Buffalo, State University of New York (SUNY), 144 Farber Hall, 3435 Main street, Buffalo, New York 14214, USA
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20
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Hansen KB, Yi F, Perszyk RE, Menniti FS, Traynelis SF. NMDA Receptors in the Central Nervous System. Methods Mol Biol 2017; 1677:1-80. [PMID: 28986865 DOI: 10.1007/978-1-4939-7321-7_1] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
NMDA-type glutamate receptors are ligand-gated ion channels that mediate a major component of excitatory neurotransmission in the central nervous system (CNS). They are widely distributed at all stages of development and are critically involved in normal brain functions, including neuronal development and synaptic plasticity. NMDA receptors are also implicated in the pathophysiology of numerous neurological and psychiatric disorders, such as ischemic stroke, traumatic brain injury, Alzheimer's disease, epilepsy, mood disorders, and schizophrenia. For these reasons, NMDA receptors have been intensively studied in the past several decades to elucidate their physiological roles and to advance them as therapeutic targets. Seven NMDA receptor subunits exist that assemble into a diverse array of tetrameric receptor complexes, which are differently regulated, have distinct regional and developmental expression, and possess a wide range of functional and pharmacological properties. The diversity in subunit composition creates NMDA receptor subtypes with distinct physiological roles across neuronal cell types and brain regions, and enables precise tuning of synaptic transmission. Here, we will review the relationship between NMDA receptor structure and function, the diversity and significance of NMDA receptor subtypes in the CNS, as well as principles and rules by which NMDA receptors operate in the CNS under normal and pathological conditions.
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Affiliation(s)
- Kasper B Hansen
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA. .,Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT, USA.
| | - Feng Yi
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA
| | - Riley E Perszyk
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
| | - Frank S Menniti
- MindImmune Therapeutics, Inc., George & Anne Ryan Institute for Neuroscience, Kingston, RI, USA
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
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21
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Sibarov DA, Abushik PA, Giniatullin R, Antonov SM. GluN2A Subunit-Containing NMDA Receptors Are the Preferential Neuronal Targets of Homocysteine. Front Cell Neurosci 2016; 10:246. [PMID: 27847466 PMCID: PMC5088185 DOI: 10.3389/fncel.2016.00246] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/07/2016] [Indexed: 12/30/2022] Open
Abstract
Homocysteine (HCY) is an endogenous redox active amino acid, best known as contributor to various neurodegenerative disorders. Although it is known that HCY can activate NMDA receptors (NMDARs), the mechanisms of its action on receptors composed of different NMDA receptor subunits remains almost unknown. In this study, using imaging and patch clamp technique in cultured cortical neurons and heterologous expression in HEK293T cells we tested the agonist activity of HCY on NMDARs composed of GluN1 and GluN2A subunits (GluN1/2A receptors) and GluN1 and GluN2B subunits (GluN1/2B receptors). We demonstrate that the time courses of Ca2+ transients and membrane currents activated by HCY and NMDA in cortical neurons are drastically different. Application of HCY to cortical neurons induced responses, which in contrast to currents induced by NMDA (both in the presence of glycine) considerably decreased to steady state of small amplitude. In contrast to NMDA, HCY-activated currents at steady state were resistant to the selective GluN2B subunit inhibitor ifenprodil. In calcium-free external solution the decrease of NMDA evoked currents was abolished, suggesting the Ca2+-dependent NMDAR desensitization. Under these conditions HCY evoked currents still declined almost to the baseline suggesting Ca2+-independent desensitization. In HEK293T cells HCY activated NMDARs of GluN1/2A and GluN1/2B subunit compositions with EC50s of 9.7 ± 1.8 and 61.8 ± 8.9 μM, respectively. Recombinant GluN1/2A receptors, however, did not desensitize by HCY, whereas GluN1/2B receptors were almost fully desensitized by HCY. Thus, HCY is a high affinity agonist of NMDARs preferring the GluN1/2A subunit composition. Our data suggest that HCY induced native NMDAR currents in neurons are mainly mediated by the "synaptic type" GluN1/2A NMDARs. This implies that in hyperhomocysteinemia, a disorder with enlarged level of HCY in plasma, HCY may persistently contribute to post-synaptic responses mediated by GluN2A-containing NMDA receptors. On the other hand, HCY toxicity may be limited by desensitization typical for HCY-induced activation of GluN2B-containing extrasynaptic receptors. Our findings, therefore, provide an evidence for the physiological relevance of endogenous HCY, which may represent an effective endogenous modulator of the central excitatory neurotransmission.
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Affiliation(s)
- Dmitry A Sibarov
- Laboratory of Comparative Neurophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint-Petersburg, Russia
| | - Polina A Abushik
- Laboratory of Comparative Neurophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint-Petersburg, Russia
| | - Rashid Giniatullin
- Department of Neurobiology, University of Eastern FinlandKuopio, Finland; Laboratory of Neurobiology, Kazan Federal UniversityKazan, Russia
| | - Sergei M Antonov
- Laboratory of Comparative Neurophysiology, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences Saint-Petersburg, Russia
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22
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Active dendrites regulate the impact of gliotransmission on rat hippocampal pyramidal neurons. Proc Natl Acad Sci U S A 2016; 113:E3280-9. [PMID: 27217559 DOI: 10.1073/pnas.1522180113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
An important consequence of gliotransmission, a signaling mechanism that involves glial release of active transmitter molecules, is its manifestation as N-methyl-d-aspartate receptor (NMDAR)-dependent slow inward currents in neurons. However, the intraneuronal spatial dynamics of these events or the role of active dendrites in regulating their amplitude and spatial spread have remained unexplored. Here, we used somatic and/or dendritic recordings from rat hippocampal pyramidal neurons and demonstrate that a majority of NMDAR-dependent spontaneous slow excitatory potentials (SEP) originate at dendritic locations and are significantly attenuated through their propagation across the neuronal arbor. We substantiated the astrocytic origin of SEPs through paired neuron-astrocyte recordings, where we found that specific infusion of inositol trisphosphate (InsP3) into either distal or proximal astrocytes enhanced the amplitude and frequency of neuronal SEPs. Importantly, SEPs recorded after InsP3 infusion into distal astrocytes exhibited significantly slower kinetics compared with those recorded after proximal infusion. Furthermore, using neuron-specific infusion of pharmacological agents and morphologically realistic conductance-based computational models, we demonstrate that dendritically expressed hyperpolarization-activated cyclic-nucleotide-gated (HCN) and transient potassium channels play critical roles in regulating the strength, kinetics, and compartmentalization of neuronal SEPs. Finally, through the application of subtype-specific receptor blockers during paired neuron-astrocyte recordings, we provide evidence that GluN2B- and GluN2D-containing NMDARs predominantly mediate perisomatic and dendritic SEPs, respectively. Our results unveil an important role for active dendrites in regulating the impact of gliotransmission on neurons and suggest astrocytes as a source of dendritic plateau potentials that have been implicated in localized plasticity and place cell formation.
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23
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Swanger SA, Vance KM, Pare JF, Sotty F, Fog K, Smith Y, Traynelis SF. NMDA Receptors Containing the GluN2D Subunit Control Neuronal Function in the Subthalamic Nucleus. J Neurosci 2015; 35:15971-83. [PMID: 26631477 PMCID: PMC4666920 DOI: 10.1523/jneurosci.1702-15.2015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 10/20/2015] [Accepted: 10/29/2015] [Indexed: 01/25/2023] Open
Abstract
The GluN2D subunit of the NMDA receptor is prominently expressed in the basal ganglia and associated brainstem nuclei, including the subthalamic nucleus (STN), globus pallidus, striatum, and substantia nigra. However, little is known about how GluN2D-containing NMDA receptors contribute to synaptic activity in these regions. Using Western blotting of STN tissue punches, we demonstrated that GluN2D is expressed in the rat STN throughout development [age postnatal day 7 (P7)-P60] and in the adult (age P120). Immunoelectron microscopy of the adult rat brain showed that GluN2D is predominantly expressed in dendrites, unmyelinated axons, and axon terminals within the STN. Using subunit-selective allosteric modulators of NMDA receptors (TCN-201, ifenprodil, CIQ, and DQP-1105), we provide evidence that receptors containing the GluN2B and GluN2D subunits mediate responses to exogenously applied NMDA and glycine, as well as synaptic NMDA receptor activation in the STN of rat brain slices. EPSCs in the STN were mediated primarily by AMPA and NMDA receptors and GluN2D-containing NMDA receptors controlled the slow deactivation time course of EPSCs in the STN. In vivo recordings from the STN of anesthetized adult rats demonstrated that the spike firing rate was increased by the GluN2C/D potentiator CIQ and decreased by the GluN2C/D antagonist DQP-1105, suggesting that NMDA receptor activity can influence STN output. These data indicate that the GluN2B and GluN2D NMDA receptor subunits contribute to synaptic activity in the STN and may represent potential therapeutic targets for modulating subthalamic neuron activity in neurological disorders such as Parkinson's disease.
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Affiliation(s)
| | | | - Jean-François Pare
- Yerkes National Primate Research Center and Morris K. Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, Georgia 30329, and
| | - Florence Sotty
- H. Lundbeck A/S, Division of Neurodegeneration and Biologics, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Karina Fog
- H. Lundbeck A/S, Division of Neurodegeneration and Biologics, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Yoland Smith
- Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322, Yerkes National Primate Research Center and Morris K. Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, Georgia 30329, and
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Sibarov DA, Abushik PA, Poguzhelskaya EE, Bolshakov KV, Antonov SM. Inhibition of Plasma Membrane Na/Ca-Exchanger by KB-R7943 or Lithium Reveals Its Role in Ca-Dependent N-methyl-d-aspartate Receptor Inactivation. J Pharmacol Exp Ther 2015; 355:484-95. [PMID: 26391160 DOI: 10.1124/jpet.115.227173] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 09/18/2015] [Indexed: 01/09/2023] Open
Abstract
To evaluate the possible role of the plasma membrane Na(+)/Ca(2+)-exchanger (NCX) in regulation of N-methyl-d-aspartate (NMDA) receptors (NMDARs), we studied effects of 2-[2-[4-(4-nitrobenzyloxy) phenyl]ethyl]isothiourea methanesulfonate (KB-R7943; KBR) and lithium (inhibitors of NCX) on NMDA-elicited whole-cell currents using the patch-clamp technique on rat cortical neurons and human embryonic kidney 293T cells expressing recombinant NMDARs. KBR inhibited NMDAR currents in a voltage-independent manner with similar potency for receptors of GluN1/2A and GluN1/2B subunit compositions that excludes open-channel block and GluN2B-selective inhibition. The inhibition by KBR depended on glycine (Gly) concentration. At 30 μM NMDA, the KBR IC50 values were 5.3 ± 0.1 and 41.2 ± 8.8 μM for 1 and 300 μM Gly, respectively. Simultaneous application of NMDA + KBR in the absence of Gly induced robust inward NMDAR currents that peaked and then rapidly decreased. KBR, therefore, is an agonist (EC50 is 1.18 ± 0.16 µM) of the GluN1 subunit coagonist binding sites. The decrease of NMDA-elicited currents in the presence of KBR was abolished in Ca(2+)-free solution and was not observed in the presence of extracellular Ca(2+) on 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-loaded neurons, suggesting that Ca(2+) affects NMDARs from the cytosol. In agreement, the substitution of Li(+) for extracellular Na(+) caused a considerable decrease of NMDAR currents, which was not observed in the absence of extracellular Ca(2+). Most likely, the accumulation of intracellular Ca(2+) is caused by the inhibition of Ca(2+) extrusion via NCX. Thus, KBR and Li(+) provoke Ca(2+)-dependent receptor inactivation due to the disruption of Ca(2+) extrusion by the NCX. The data reveal the role of NCX in regulation of Ca(2+)-dependent inactivation of NMDARs.
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Affiliation(s)
- Dmitry A Sibarov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Polina A Abushik
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Ekaterina E Poguzhelskaya
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Konstantin V Bolshakov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
| | - Sergei M Antonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
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25
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Jones KS, Corbin JG, Huntsman MM. Neonatal NMDA receptor blockade disrupts spike timing and glutamatergic synapses in fast spiking interneurons in a NMDA receptor hypofunction model of schizophrenia. PLoS One 2014; 9:e109303. [PMID: 25290690 PMCID: PMC4188593 DOI: 10.1371/journal.pone.0109303] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 09/10/2014] [Indexed: 01/06/2023] Open
Abstract
The dysfunction of parvalbumin-positive, fast-spiking interneurons (FSI) is considered a primary contributor to the pathophysiology of schizophrenia (SZ), but deficits in FSI physiology have not been explicitly characterized. We show for the first time, that a widely-employed model of schizophrenia minimizes first spike latency and increases GluN2B-mediated current in neocortical FSIs. The reduction in FSI first-spike latency coincides with reduced expression of the Kv1.1 potassium channel subunit which provides a biophysical explanation for the abnormal spiking behavior. Similarly, the increase in NMDA current coincides with enhanced expression of the GluN2B NMDA receptor subunit, specifically in FSIs. In this study mice were treated with the NMDA receptor antagonist, MK-801, during the first week of life. During adolescence, we detected reduced spike latency and increased GluN2B-mediated NMDA current in FSIs, which suggests transient disruption of NMDA signaling during neonatal development exerts lasting changes in the cellular and synaptic physiology of neocortical FSIs. Overall, we propose these physiological disturbances represent a general impairment to the physiological maturation of FSIs which may contribute to schizophrenia-like behaviors produced by this model.
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Affiliation(s)
- Kevin S. Jones
- Biology Department, Howard University, Washington, DC, United States of America
- Center for Neuroscience Research, Children’s National Medical Center, Washington, DC, United States of America
| | - Joshua G. Corbin
- Center for Neuroscience Research, Children’s National Medical Center, Washington, DC, United States of America
| | - Molly M. Huntsman
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, and Department of Pediatrics, School of Medicine, University of Colorado, Anschutz Medical Campus, Aurora, CO, United States of America
- * E-mail:
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Khatri A, Burger PB, Swanger SA, Hansen KB, Zimmerman S, Karakas E, Liotta DC, Furukawa H, Snyder JP, Traynelis SF. Structural determinants and mechanism of action of a GluN2C-selective NMDA receptor positive allosteric modulator. Mol Pharmacol 2014; 86:548-60. [PMID: 25205677 DOI: 10.1124/mol.114.094516] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
NMDA receptors are tetrameric complexes of GluN1, GluN2A-D, and GluN3A-B subunits and are involved in normal brain function and neurologic disorders. We identified a novel class of stereoselective pyrrolidinone (PYD) positive allosteric modulators for GluN2C-containing NMDA receptors, exemplified by methyl 4-(3-acetyl-4-hydroxy-1-[2-(2-methyl-1H-indol-3-yl)ethyl]-5-oxo-2,5-dihydro-1H-pyrrol-2-yl)benzoate. Here we explore the site and mechanism of action of a prototypical analog, PYD-106, which at 30 μM does not alter responses of NMDA receptors containing GluN2A, GluN2B, and GluN2D and has no effect on AMPA [α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid] and kainate receptors. Coapplication of 50 μM PYD-106 with a maximally effective concentration of glutamate and glycine increases the response of GluN1/GluN2C NMDA receptors in HEK-293 cells to 221% of that obtained in the absence of PYD (taken as 100%). Evaluation of the concentration dependence of this enhancement revealed an EC50 value for PYD of 13 μM. PYD-106 increased opening frequency and open time of single channel currents activated by maximally effective concentrations of agonist but only had modest effects on glutamate and glycine EC50. PYD-106 selectively enhanced the responses of diheteromeric GluN1/GluN2C receptors but not triheteromeric GluN1/GluN2A/GluN2C receptors. Inclusion of residues encoded by GluN1-exon 5 attenuated the effects of PYD. Three GluN2C residues (Arg194, Ser470, Lys470), at which mutagenesis virtually eliminated PYD function, line a cavity at the interface of the ligand binding and the amino terminal domains in a homology model of GluN1/GluN2C built from crystallographic data on GluN1/GluN2B. We propose that this domain interface constitutes a new allosteric modulatory site on the NMDA receptor.
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Affiliation(s)
- Alpa Khatri
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Pieter B Burger
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Sharon A Swanger
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Kasper B Hansen
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Sommer Zimmerman
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Erkan Karakas
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Dennis C Liotta
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Hiro Furukawa
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - James P Snyder
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
| | - Stephen F Traynelis
- Pharmacology Department (A.K., S.A.S., S.F.T.) and Chemistry Department (S.Z., P.B.B., D.C.L., J.P.S.), Emory University, Atlanta, Georgia; Department of Biomedical and Pharmaceutical Sciences, and Center for Biomolecular Structure and Dynamics (K.B.H.), University of Montana, Missoula, Montana; and Cold Spring Harbor Laboratories (E.K., H.F.), Cold Spring Harbor, New York
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Sühs KW, Fairless R, Williams SK, Heine K, Cavalié A, Diem R. N-Methyl-d-Aspartate Receptor Blockade Is Neuroprotective in Experimental Autoimmune Optic Neuritis. J Neuropathol Exp Neurol 2014; 73:507-18. [DOI: 10.1097/nen.0000000000000073] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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28
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Oda Y, Kodama S, Tsuchiya S, Inoue M, Miyakawa H. Intracellular calcium elevation during plateau potentials mediated by extrasynaptic NMDA receptor activation in rat hippocampal CA1 pyramidal neurons is primarily due to calcium entry through voltage-gated calcium channels. Eur J Neurosci 2014; 39:1613-23. [DOI: 10.1111/ejn.12555] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 02/04/2014] [Accepted: 02/11/2014] [Indexed: 12/21/2022]
Affiliation(s)
- Yoshiaki Oda
- Laboratory of Cellular Neurobiology; School of Life Sciences; Tokyo University of Pharmacy and Life Sciences; Hachioji Tokyo 192-0392 Japan
| | - Satoshi Kodama
- Laboratory of Cellular Neurobiology; School of Life Sciences; Tokyo University of Pharmacy and Life Sciences; Hachioji Tokyo 192-0392 Japan
| | - Sadahiro Tsuchiya
- Laboratory of Cellular Neurobiology; School of Life Sciences; Tokyo University of Pharmacy and Life Sciences; Hachioji Tokyo 192-0392 Japan
| | - Masashi Inoue
- Laboratory of Cellular Neurobiology; School of Life Sciences; Tokyo University of Pharmacy and Life Sciences; Hachioji Tokyo 192-0392 Japan
| | - Hiroyoshi Miyakawa
- Laboratory of Cellular Neurobiology; School of Life Sciences; Tokyo University of Pharmacy and Life Sciences; Hachioji Tokyo 192-0392 Japan
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Huang Z, Gibb AJ. Mg2+ block properties of triheteromeric GluN1-GluN2B-GluN2D NMDA receptors on neonatal rat substantia nigra pars compacta dopaminergic neurones. J Physiol 2014; 592:2059-78. [PMID: 24614743 PMCID: PMC4027860 DOI: 10.1113/jphysiol.2013.267864] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Native NMDA receptors (NMDARs) are tetrameric channels formed by two GluN1 and two GluN2 subunits. So far, seven NMDARs subunits have been identified and they can form diheteromeric or triheteromeric NMDARs (more than one type of GluN2 subunit). Extracellular Mg2+ is an important regulator of NMDARs, and particularly the voltage dependence of Mg2+ block is crucial to the roles of NMDARs in synaptic plasticity and the integration of synaptic activity with neuronal activity. Although the Mg2+ block properties of diheteromeric NMDARs are fully investigated, properties of triheteromeric NMDARs are still not clear. Our previous data suggested that dopaminergic neurones expressed triheteromeric GluN1–GluN2B–GluN2D NMDARs. Here, using NMDARs in dopaminergic neurones from postnatal day 7 (P7) rats as a model system, we characterize the voltage-dependent Mg2+ block properties of triheteromeric NMDARs. In control conditions, external Mg2+ significantly inhibits the whole cell NMDA-evoked current in a voltage-dependent manner with IC50 values of 20.9 μm, 53.3 μm and 173 μm at −90 mV, −70 mV and −50 mV, respectively. When the GluN2B-selective antagonist ifenprodil was applied, the Mg2+ sensitivity of the residual NMDA-mediated currents (which is mainly carried by GluN1–GluN2B–GluN2D NMDARs) is reduced to IC50 values of 45.9 μm (−90 mV), 104 μm (−70 mV) and 276 μm (−50 mV), suggesting that triheteromeric GluN1–GluN2B–GluN2D NMDARs have less affinity for external Mg2+ than GluN1–GluN2B receptors. In addition, fitting INMDA–V curves with a trapping Mg2+ block model shows the triheteromeric GluN1–GluN2B–GluN2D NMDARs have weaker voltage-dependent Mg2+ block (δ = 0.56) than GluN1–GluN2B NMDARs. Finally, our concentration jump and single channel recordings suggest that GluN1–GluN2B–GluN2D rather than GluN1–GluN2D NMDARs are present. These data provide information relevant to Mg2+ block characteristics of triheteromeric NMDARs and may help to better understand synaptic plasticity, which is dependent on these triheteromeric NMDARs.
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Affiliation(s)
- Zhuo Huang
- Department of Molecular and Cellular Pharmacology, State Key Laboratory of Nature and Biomimetic Drugs, Peking University School of Pharmaceutical Sciences, Beijing, 100191, P.R. China
| | - Alasdair J Gibb
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 221] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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31
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Mechanistic and structural determinants of NMDA receptor voltage-dependent gating and slow Mg2+ unblock. J Neurosci 2013; 33:4140-50. [PMID: 23447622 DOI: 10.1523/jneurosci.3712-12.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
NMDA receptor (NMDAR)-mediated currents depend on membrane depolarization to relieve powerful voltage-dependent NMDAR channel block by external magnesium (Mg(o)(2+)). Mg(o)(2+) unblock from native NMDARs exhibits a fast component that is consistent with rapid Mg(o)(2+) -unbinding kinetics and also a slower, millisecond time scale component (slow Mg(o)(2+) unblock). In recombinant NMDARs, slow Mg(o)(2+) unblock is prominent in GluN1/2A (an NMDAR subtype composed of GluN1 and GluN2A subunits) and GluN1/2B receptors, with slower kinetics observed for GluN1/2B receptors, but absent from GluN1/2C and GluN1/2D receptors. Slow Mg(o)(2+) unblock from GluN1/2B receptors results from inherent voltage-dependent gating, which increases channel open probability with depolarization. Here we examine the mechanisms responsible for NMDAR subtype dependence of slow Mg(o)(2+) unblock. We demonstrate that slow Mg(o)(2+) unblock from GluN1/2A receptors, like GluN1/2B receptors, results from inherent voltage-dependent gating. Surprisingly, GluN1/2A and GluN1/2B receptors exhibited equal inherent voltage dependence; faster Mg(o)(2+) unblock from GluN1/2A receptors can be explained by voltage-independent differences in gating kinetics. To investigate the absence of slow Mg(o)(2+) unblock in GluN1/2C and GluN1/2D receptors, we examined the GluN2 S/L site, a site responsible for several NMDAR subtype-dependent channel properties. Mutating the GluN2 S/L site of GluN2A subunits from serine (found in GluN2A and GluN2B subunits) to leucine (found in GluN2C and GluN2D) greatly diminished both voltage-dependent gating and slow Mg(o)(2+) unblock. Therefore, the residue at the GluN2 S/L site governs the expression of both slow Mg(o)(2+) unblock and inherent voltage dependence.
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32
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Modal gating of GluN1/GluN2D NMDA receptors. Neuropharmacology 2013; 71:184-90. [PMID: 23578394 DOI: 10.1016/j.neuropharm.2013.03.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 03/25/2013] [Accepted: 03/26/2013] [Indexed: 11/22/2022]
Abstract
GluN2D-containing NMDA receptors are characterized by an unusually low open probability (0.023), even in the presence of saturating glutamate and glycine. Here, we show that recombinant GluN1/GluN2D NMDA receptors can enter brief periods with exceptionally high open probability (0.65) in excised outside-out and cell-attached single channel recordings. GluN1/GluN2D channels during the enhanced gating mode have similar open durations as occurs outside of the high open probability burst of activity. However, the periods in the high gating mode only exhibit 4 brief closed duration exponential components similar to the briefest observed for openings outside the burst. GluN1/GluN2D receptors also open to a more prominent subconductance level compared to activity outside the high open probability burst. Evaluation of a five-state NMDA receptor gating model suggests that both the opening and closing rate constants differ for the periods of higher open probability compared to the high open probability arm of a gating model previously published for GluN1/GluN2D fit to a representative full length single channel recording. These data demonstrate that GluN2D-containing NMDA receptors can enter a conformation or mode that allows the pore to gate with high probability.
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33
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NMDA receptors with incomplete Mg²⁺ block enable low-frequency transmission through the cerebellar cortex. J Neurosci 2012; 32:6878-93. [PMID: 22593057 DOI: 10.1523/jneurosci.5736-11.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The cerebellar cortex coordinates movements and maintains balance by modifying motor commands as a function of sensory-motor context, which is encoded by mossy fiber (MF) activity. MFs exhibit a wide range of activity, from brief precisely timed high-frequency bursts, which encode discrete variables such as whisker stimulation, to low-frequency sustained rate-coded modulation, which encodes continuous variables such as head velocity. While high-frequency MF inputs have been shown to activate granule cells (GCs) effectively, much less is known about sustained low-frequency signaling through the GC layer, which is impeded by a hyperpolarized resting potential and strong GABA(A)-mediated tonic inhibition of GCs. Here we have exploited the intrinsic MF network of unipolar brush cells to activate GCs with sustained low-frequency asynchronous MF inputs in rat cerebellar slices. We find that low-frequency MF input modulates the intrinsic firing of Purkinje cells, and that this signal transmission through the GC layer requires synaptic activation of Mg²⁺-block-resistant NMDA receptors (NMDARs) that are likely to contain the GluN2C subunit. Slow NMDAR conductances sum temporally to contribute approximately half the MF-GC synaptic charge at hyperpolarized potentials. Simulations of synaptic integration in GCs show that the NMDAR and slow spillover-activated AMPA receptor (AMPAR) components depolarize GCs to a similar extent. Moreover, their combined depolarizing effect enables the fast quantal AMPAR component to trigger action potentials at low MF input frequencies. Our results suggest that the weak Mg²⁺ block of GluN2C-containing NMDARs enables transmission of low-frequency MF signals through the input layer of the cerebellar cortex.
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34
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Vance KM, Hansen KB, Traynelis SF. GluN1 splice variant control of GluN1/GluN2D NMDA receptors. J Physiol 2012; 590:3857-75. [PMID: 22641781 DOI: 10.1113/jphysiol.2012.234062] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
NMDA receptors are ionotropic glutamate receptors that mediate a slow, Ca2+-permeable component of excitatory synaptic transmission in the central nervous system. Recombinant GluN1-1a/GluN2D receptors are characterized by low channel open probability and prolonged deactivation time course following the removal of agonist. Here, we show that the deactivation time course, agonist potency, and single channel properties of GluN2D-containing NMDA receptors are modulated by alternative RNA splicing of GluN1. Our results demonstrate that GluN1 exon 5, which encodes a 21-amino-acid insert in the amino-terminal domain, is a key determinant of GluN1/GluN2D receptor function. GluN1-1b/GluN2D receptors, which contain the residues encoded by exon 5, deactivate with a dual exponential time course described by a τFAST of 410 ms and a τSLOW of 1100 ms. This time course is 3-fold more rapid than that for exon 5-lacking GluN1-1a/GluN2D, which deactivates with a τFAST of 1100 ms and a τSLOW of 3400 ms. Exon 5-containing NMDA receptors also have a two-fold higher open probability (0.037) than exon 5-lacking receptors (0.017). Furthermore, inclusion of exon 5-encoded residues within the GluN1-1b subunit decreases the potency for the endogenous agonist l-glutamate. Evaluation of receptor kinetics for NMDA receptors containing mutated GluN1-1b subunits and wild-type GluN2D identified residue Lys211 in GluN1-1b as a key determinant of exon 5 control of the deactivation time course and glutamate potency. Evaluation of a kinetic model of GluN1/GluN2D gating suggests that residues encoded by exon 5 influence several rate-limiting steps. These data demonstrate that the GluN1 subunit is a key determinant of the kinetic and pharmacological properties of GluN2D-containing NMDA receptors.
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Affiliation(s)
- Katie M Vance
- S. F. Traynelis: Department of Pharmacology, Rollins Research Center, 1510 Clifton Road, Atlanta, GA 30322-3090, USA
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35
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Siegler Retchless B, Gao W, Johnson JW. A single GluN2 subunit residue controls NMDA receptor channel properties via intersubunit interaction. Nat Neurosci 2012; 15:406-13, S1-2. [PMID: 22246434 PMCID: PMC3288527 DOI: 10.1038/nn.3025] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/13/2011] [Indexed: 12/14/2022]
Abstract
NMDA receptors (NMDARs) are glutamate-gated ion channels that are present at most excitatory mammalian synapses. The four GluN2 subunits (GluN2A-D) contribute to four diheteromeric NMDAR subtypes that have divergent physiological and pathological roles. Channel properties that are fundamental to NMDAR function vary among subtypes. We investigated the amino acid residues responsible for variations in channel properties by creating and examining NMDARs containing mutant GluN2 subunits. We found that the NMDAR subtype specificity of three crucial channel properties, Mg(2+) block, selective permeability to Ca(2+) and single-channel conductance, were all controlled primarily by the residue at a single GluN2 site in the M3 transmembrane region. Mutant cycle analysis guided by molecular modeling revealed that a GluN2-GluN1 subunit interaction mediates the site's effects. We conclude that a single GluN2 subunit residue couples with the pore-forming loop of the GluN1 subunit to create naturally occurring variations in NMDAR properties that are critical to synaptic plasticity and learning.
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Affiliation(s)
- Beth Siegler Retchless
- Department of Neuroscience and Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Kalirin binds the NR2B subunit of the NMDA receptor, altering its synaptic localization and function. J Neurosci 2011; 31:12554-65. [PMID: 21880917 DOI: 10.1523/jneurosci.3143-11.2011] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The ability of dendritic spines to change size and shape rapidly is critical in modulating synaptic strength; these morphological changes are dependent upon rearrangements of the actin cytoskeleton. Kalirin-7 (Kal7), a Rho guanine nucleotide exchange factor localized to the postsynaptic density (PSD), modulates dendritic spine morphology in vitro and in vivo. Kal7 activates Rac and interacts with several PSD proteins, including PSD-95, DISC-1, AF-6, and Arf6. Mice genetically lacking Kal7 (Kal7(KO)) exhibit deficient hippocampal long-term potentiation (LTP) as well as behavioral abnormalities in models of addiction and learning. Purified PSDs from Kal7(KO) mice contain diminished levels of NR2B, an NMDA receptor subunit that plays a critical role in LTP induction. Here we demonstrate that Kal7(KO) animals have decreased levels of NR2B-dependent NMDA receptor currents in cortical pyramidal neurons as well as a specific deficit in cell surface expression of NR2B. Additionally, we demonstrate that the genotypic differences in conditioned place preference and passive avoidance learning seen in Kal7(KO) mice are abrogated when animals are treated with an NR2B-specific antagonist during conditioning. Finally, we identify a stable interaction between the pleckstrin homology domain of Kal7 and the juxtamembrane region of NR2B preceding its cytosolic C-terminal domain. Binding of NR2B to a protein that modulates the actin cytoskeleton is important, as NMDA receptors require actin integrity for synaptic localization and function. These studies demonstrate a novel and functionally important interaction between the NR2B subunit of the NMDA receptor and Kalirin, proteins known to be essential for normal synaptic plasticity.
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Marsden W. Stressor-induced NMDAR dysfunction as a unifying hypothesis for the aetiology, pathogenesis and comorbidity of clinical depression. Med Hypotheses 2011; 77:508-28. [DOI: 10.1016/j.mehy.2011.06.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 06/05/2011] [Indexed: 02/07/2023]
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Ruscheweyh R, Wilder-Smith O, Drdla R, Liu XG, Sandkühler J. Long-term potentiation in spinal nociceptive pathways as a novel target for pain therapy. Mol Pain 2011; 7:20. [PMID: 21443797 PMCID: PMC3078873 DOI: 10.1186/1744-8069-7-20] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 03/28/2011] [Indexed: 01/19/2023] Open
Abstract
Long-term potentiation (LTP) in nociceptive spinal pathways shares several features with hyperalgesia and has been proposed to be a cellular mechanism of pain amplification in acute and chronic pain states. Spinal LTP is typically induced by noxious input and has therefore been hypothesized to contribute to acute postoperative pain and to forms of chronic pain that develop from an initial painful event, peripheral inflammation or neuropathy. Under this assumption, preventing LTP induction may help to prevent the development of exaggerated postoperative pain and reversing established LTP may help to treat patients who have an LTP component to their chronic pain. Spinal LTP is also induced by abrupt opioid withdrawal, making it a possible mechanism of some forms of opioid-induced hyperalgesia. Here, we give an overview of targets for preventing LTP induction and modifying established LTP as identified in animal studies. We discuss which of the various symptoms of human experimental and clinical pain may be manifestations of spinal LTP, review the pharmacology of these possible human LTP manifestations and compare it to the pharmacology of spinal LTP in rodents.
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Affiliation(s)
- Ruth Ruscheweyh
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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HSV delivery of a ligand-regulated endogenous ion channel gene to sensory neurons results in pain control following channel activation. Mol Ther 2010; 19:500-6. [PMID: 21081904 DOI: 10.1038/mt.2010.246] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Persistent pain remains a tremendous health problem due to both its prevalence and dearth of effective therapeutic interventions. To maximize pain relief while minimizing side effects, current gene therapy-based approaches have mostly exploited the expression of pain inhibitory products or interfered with pronociceptive ion channels. These methods do not enable control over the timing or duration of analgesia, nor titration to analgesic efficacy. Here, we describe a gene therapy strategy that potentially overcomes these limitations by providing exquisite control over therapy with efficacy in clinically relevant models of inflammatory pain. We utilize a herpes simplex viral (HSV) vector (vHGlyRα1) to express a ligand-regulated chloride ion channel, the glycine receptor (GlyR) in targeted sensory afferents; the subsequent exogenous addition of glycine provides the means for temporal and spatial control of afferent activity, and therefore pain. Use of an endogenous inhibitory receptor not normally present on sensory neurons both minimizes immunogenicity and maximizes therapeutic selectivity.
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Otton HJ, Lawson McLean A, Pannozzo MA, Davies CH, Wyllie DJA. Quantification of the Mg2+-induced potency shift of amantadine and memantine voltage-dependent block in human recombinant GluN1/GluN2A NMDARs. Neuropharmacology 2010; 60:388-96. [PMID: 20955720 DOI: 10.1016/j.neuropharm.2010.10.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 09/30/2010] [Accepted: 10/09/2010] [Indexed: 02/02/2023]
Abstract
Clinically, amantadine and memantine are drugs whose therapeutic utility is linked to their ability to block N-methyl-D-aspartate receptors (NMDARs) in a voltage-dependent manner. Nevertheless many studies that have characterized the pharmacological actions of amantadine and memantine have done so in the absence of physiological levels of Mg(2+) ions. This study quantifies the extent to which Mg(2+) alters the potency of the block produced by both amantadine and memantine at human recombinant GluN1/GluN2A NMDARs. Human recombinant GluN1/GluN2A NMDARs were expressed in Xenopus laevis oocytes and two-electrode voltage-clamp recordings were made at -80, -60 and -40 mV to quantify amantadine and memantine block in the absence and presence of Mg(2+). Amantadine and memantine blocked human GluN1/GluN2A NMDARs in a voltage-dependent manner with IC(50) values (at -80 mV) of 49 ± 6 μM (n = 7) and 1.0 ± 0.3 μM (n = 7), respectively. In the presence of Mg(2+) (1mM) the equivalent IC(50) values were 165 ± 10 μM (n=6) and 6.6 ± 0.3 μM (n = 5). Similarly in the presence of amantadine or memantine the potency of Mg(2+) in blocking GluN1/GluN2A NMDARs was reduced. The decrease in the potencies of both amantadine and memantine in the presence of physiological concentrations of Mg(2+) indicates that other targets (e.g. α7-nicotinic acetylcholine receptors and 5-HT(3) receptors) in addition to NMDARs may well be sites of the therapeutic action of these channel blockers.
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Affiliation(s)
- H J Otton
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
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GABAA receptor inhibition does not affect mGluR-dependent LTD at hippocampal Schaffer collateral-CA1 synapses. Neurosci Lett 2009; 467:20-5. [DOI: 10.1016/j.neulet.2009.09.053] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 09/07/2009] [Accepted: 09/27/2009] [Indexed: 11/23/2022]
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Abstract
N-methyl-D-aspartate receptors (NMDARs) are ligand-gated ion channels belonging to the family of ionotropic glutamate receptors. Functional NMDARs are heterotetrameric assemblies of NR1 subunits with at least one type of NR2 subunits. Various combinations of these subunits form distinct NMDAR subtypes involved in a variety of physiological and pathological processes. Several pharmaceutical companies search subunit-selective drugs for curing various neurological diseases and having favorable side-effect profile. We applied the whole-cell patch-clamp technique for testing NR2B subunit-specific drugs in HEK cells transiently or stably expressing different types of NMDAR subunits. In stable cell lines, we applied an inducible mammalian expression system; cDNAs of NR1 and either NR2A or NR2B subunits were inserted into an ecdyson-inducible mammalian expression vector and were introduced into HEK293 cells. These expression systems proved to be suitable to analyze precisely the subtype selectivity of newly synthesized NR2B-selective NMDAR antagonists by using whole-cell patch-clamp technique.
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Abstract
Ligand-gated ion channels are activated by agonist binding, but may also be modulated by membrane voltage. N-Methyl-d-aspartate receptors (NMDARs) exhibit especially strong voltage dependence due to channel block by external Mg(2+) (Mg(o)(2+)). Here we demonstrate that activity of NMDARs composed of NR1 and NR2B subunits (NR1/2B receptors) is enhanced by depolarization even in 0 Mg(o)(2+), causing slow current relaxations in response to rapid voltage changes. We present a kinetic model of receptor activation that incorporates voltage-dependent gating-associated NR2B subunit conformational changes. The model accurately reproduces current relaxations during depolarizations and subsequent repolarizations in 0 Mg(o)(2+). Model simulations in physiological Mg(o)(2+) concentrations show that voltage-dependent receptor gating also underlies the slow component of Mg(o)(2+) unblock, a phenomenon that previously was shown to influence Mg(o)(2+) unblock kinetics during dendritic spikes. We propose that voltage-dependent gating of NR1/2B receptors confers enhanced voltage and time dependence on NMDAR-mediated signalling.
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Affiliation(s)
- Richard J Clarke
- Department of Neuroscience and Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Chloride-dependent acute excitotoxicity in adult rat retinal ganglion cells. Neuropharmacology 2008; 55:677-86. [PMID: 18586043 DOI: 10.1016/j.neuropharm.2008.06.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Revised: 02/26/2008] [Accepted: 06/02/2008] [Indexed: 11/19/2022]
Abstract
Mechanisms of excitotoxic degeneration of retinal ganglion cells (RGCs) remain controversial, due to the lack of suitable in vitro experimental systems for evaluation of RGC death. In this study, we investigated acute excitotoxicity in RGCs using eyecup preparations obtained from adult rats, with special reference to ionic dependence of N-methyl-D-aspartate (NMDA) and kainate toxicity. Retrograde labeling of RGCs with a fluorescent tracer diamidino yellow, combined with labeling of dead cells by propidium iodide, enabled us to discriminate dead RGCs from other cells in the ganglion cell layer. Exposure of eyecups to NMDA or kainate for 30min followed by 6h post-incubation caused cell death in a subpopulation of RGCs as well as other (presumably displaced amacrine) cells. RGCs in the peripheral area of the retina were less sensitive to NMDA toxicity than those in the central area. Death of RGCs and other retinal cells by NMDA or kainate was largely abolished by substitution of extracellular Cl(-), whereas chelation of extracellular Ca(2+) did not inhibit NMDA or kainate toxicity in RGCs. Strychnine but not bicuculline partially inhibited NMDA-induced RGC death, although these drugs were not effective against kainate-induced RGC death. On the other hand, niflumic acid, a Cl(-) channel blocker, markedly inhibited RGC death induced by kainate as well as by NMDA. These results underscore the important role of Cl(-) in acute excitotoxicity in adult rat RGCs.
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Sharifullina E, Ostroumov K, Grandolfo M, Nistri A. N-methyl-D-aspartate triggers neonatal rat hypoglossal motoneurons in vitro to express rhythmic bursting with unusual Mg2+ sensitivity. Neuroscience 2008; 154:804-20. [PMID: 18468805 DOI: 10.1016/j.neuroscience.2008.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 02/05/2008] [Accepted: 03/04/2008] [Indexed: 10/22/2022]
Abstract
The brainstem nucleus hypoglossus innervates the tongue which must contract rhythmically during respiration, chewing and swallowing. Such rhythmic discharges are due to network bursting mediated by AMPA receptor-dependent glutamatergic transmission. The contribution by hypoglossal motoneurons themselves to rhythmicity remains, however, unclear as they might simply express cyclic patterns produced by premotoneurons or, in analogy to spinal motoneurons, might participate to bursting due to activation of their N-methyl-D-aspartate (NMDA) receptors. Using patch clamp recording from hypoglossal motoneurons in slice preparations of neonatal rat brainstem, we observed that NMDA directly depolarized motoneurons to generate various discharge patterns. Most motoneurons produced transient bursts which were consistently restored by repolarizing membrane potential to rest. Fewer motoneurons generated either sustained bursting or random firing. Rhythmic bursts were recorded from XII nerve rootlets even when single motoneuron bursting required hyperpolarization. NMDA evoked bursts were blocked by the Ca2+ antagonist Cd2+, the gap junction blocker carbenoxolone, or Mg2+ free solution, and partially inhibited by tetrodotoxin or nifedipine. Under voltage clamp, NMDA-induced bursting persisted at negative or positive potentials and was resistant to high extracellular Mg2+ in accordance with the observation of widespread motoneuron expression of NMDA 2D receptor subunits that confer poor Mg2+ sensitivity. It is proposed that NMDA depolarized motoneurons with the contribution of Mg2+ insensitive channels, and triggered bursting via cyclic activation/deactivation of voltage-dependent Na+, Ca2+ and K+ currents spread through gap junctions. The NMDA-evoked bursting pattern was similar to the rhythmic discharges previously recorded from the XII nerve during milk sucking by neonatal rats.
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Affiliation(s)
- E Sharifullina
- Neurobiology Sector, International School for Advanced Studies, Via Beirut 2-4, Trieste, Italy
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Wrighton DC, Baker EJ, Chen PE, Wyllie DJA. Mg2+ and memantine block of rat recombinant NMDA receptors containing chimeric NR2A/2D subunits expressed in Xenopus laevis oocytes. J Physiol 2007; 586:211-25. [PMID: 17962329 DOI: 10.1113/jphysiol.2007.143164] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
N-methyl-d-aspartate receptors (NMDARs) display differences in their sensitivity to the channel blockers Mg(2+) and memantine that are dependent on the identity of the NR2 subunit present in the receptor-channel complex. This study used two-electrode voltage-clamp recordings from Xenopus laevis oocytes expressing recombinant NMDARs to investigate the actions of Mg(2+) and memantine at the two NMDARs displaying the largest differences in sensitivity to these blockers, namely NR1/NR2A and NR1/NR2D NMDARs. In addition, NR2A/2D chimeric subunits have been employed to examine the effects of pore-forming elements and ligand-binding domains (LBD) on the potency of the block produced by each of these inhibitors. Our results show that, as previously documented, NR2D-containing NMDARs are less sensitive to voltage-dependent Mg(2+) block than their NR2A-containing counterparts. The reduced sensitivity is determined by the M1M2M3 membrane-associated regions, as replacing these regions in NR2A subunits with those found in NR2D subunits results in a approximately 10-fold reduction in Mg(2+) potency. Intriguingly, replacing the NR2A LBD with that from NR2D subunits results in a approximately 2-fold increase in Mg(2+) potency. Moreover, when responses mediated by NR1/NR2A NMDARs are evoked by the partial agonist homoquinolinate, rather than glutamate, Mg(2+) also displays an increased potency. Memantine block of glutamate-evoked currents is most potent at NR1/NR2D NMDARs, but no differences are observed in its ability to inhibit NR2A-containing or NR2A/2D chimeric NMDARs. We suggest that the potency of block of NMDARs by Mg(2+) is influenced not only by pore-forming regions but also the LBD and the resulting conformational changes that occur following agonist binding.
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Affiliation(s)
- David C Wrighton
- Centre for Neuroscience Research, Hugh Robson Building, University of Edinburgh, George Square, Edinburgh, UK
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Magnesium ions prevent the development of hyperkinesia evoked by administration of picrotoxin into the rat neostriatum. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2007; 37:821-6. [PMID: 17922247 DOI: 10.1007/s11055-007-0087-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Indexed: 10/22/2022]
Abstract
Chronic experiments on rats were performed to study the effects of daily administration of the GABA(A) receptor antagonist picrotoxin (2 microg) into the rostral neostriatum in rats. Picrotoxin was injected in 1 microl of sterile apyrogenic physiological saline or in 1 microl of 1.0 M or 1.5 M MgCl(2); control animals received physiological saline or 1.0 M MgCl(2). Picrotoxin given in physiological saline induced impairments in conditioned reflex (avoidance) and free motor behavior and produced clear stereotypical imperative movements in the form of choreomyoclonic hyperkinesia of the paws, head, and trunk. These motor impairments resembled the manifestaitons of basal ganglia dysfunction typical of Huntingdon's chorea in humans. Magnesium ions prevented both the development of hyperkinesia and impairments of learned behavior. Given that magnesium is a nonspecific calcium channel antagonist, it can be suggested that one of the leading mechanisms of development of hyperkinesias is impairment of calcium homeostasis in striatal neurons.
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Abstract
Voltage-dependent channel block by external Mg2+ (Mg2+(o)) of NMDA receptors is an essential determinant of synaptic function. The resulting Mg2+(o) inhibition of NMDA responses depends strongly on receptor subunit composition: NR1/2A and NR1/2B receptors are more strongly inhibited by Mg2+(o) than are NR1/2C or NR1/2D receptors. Previous work showed that permeant ions have profound effects on Mg2+(o) block of NMDA receptors composed of NR1, NR2A, and NR2B subunits. Whether permeant ions affect Mg2+(o) inhibition of NR1/2C or NR1/2D receptors is unknown. We investigated the effects of permeant ions on Mg2+(o) block of NR1/2D receptors by integrating results from whole-cell recordings, single-channel recordings, and kinetic modeling. Lowering internal [Cs+] caused a voltage-dependent decrease in the Mg2+(o) IC50 and in the apparent Mg2+(o) unblocking rate, and increase in the apparent Mg2+(o) blocking rate (k(+,app)) of NR1/2D receptors. Lowering external [Na+] caused modest voltage-dependent changes in the Mg2+(o) IC50 and k(+,app). These data can be explained by a kinetic model in which occupation of either of two external permeant ion binding sites prevents Mg2+(o) entry into the channel. Occupation of an internal permeant ion binding site prevents Mg2+(o) permeation and accelerates Mg2+(o) unblock to the external solution. We conclude that variations in permeant ion site properties shape the NR2 subunit dependence of Mg2+(o) block. Furthermore, the external channel entrance varies little among NMDA receptor subtypes. Differences in the Mg2+(o) blocking site, and particularly in the selectivity filter and internal channel entrance, are principally responsible for the subunit dependence of Mg2+(o) block.
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Affiliation(s)
- Anqi Qian
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Jon W. Johnson
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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Clarke RJ, Johnson JW. NMDA receptor NR2 subunit dependence of the slow component of magnesium unblock. J Neurosci 2006; 26:5825-34. [PMID: 16723541 PMCID: PMC6675262 DOI: 10.1523/jneurosci.0577-06.2006] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
NMDA receptor activity is important for many physiological functions, including synapse formation and alterations in synaptic strength. NMDA receptors are composed most commonly of NR1 and NR2 subunits. There are four NR2 subunits (NR2A-NR2D). NR2 subunit expression varies across both brain regions and developmental stages. The identity of the NR2 subunit within a functional NMDA receptor helps to determine many pharmacological and biophysical receptor properties, including strength of block by external Mg2+ (Mg(o)2+). Mg(o)2+ block confers strong voltage dependence to NMDA receptor-mediated responses and is critically important for many of the functions that the NMDA receptor plays within the CNS. Here we describe the NR2 subunit dependence of the kinetics of Mg(o)2+ unblock after rapid depolarizations. We find that Mg(o)2+ unblocks from NR1/2A and NR1/2B receptors with a prominent slow component similar to that previously described in native hippocampal and cortical NMDA receptors. Strikingly, this slow component of Mg(o)2+ unblock is completely absent from NR1/2C and NR1/2D receptors. Thus currents from NR1/2C and NR1/2D receptors respond more rapidly to fast depolarizations than currents from NR1/2A and NR1/2B receptors. In addition, the slow component of Mg(o)2+ unblock from NR1/2B receptors is consistently slower than from NR1/2A receptors. This makes rapid depolarizations, such as action potential waveforms, more efficacious at stimulating Mg(o)2+ unblock from NR1/2A than from NR1/2B receptors. These NR2 subunit differences in the kinetics of Mg(o)2+ unblock are likely to help determine the contribution of each NMDA receptor subtype to current flow during synaptic activity.
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