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Egunlusi AO, Joubert J. NMDA Receptor Antagonists: Emerging Insights into Molecular Mechanisms and Clinical Applications in Neurological Disorders. Pharmaceuticals (Basel) 2024; 17:639. [PMID: 38794209 PMCID: PMC11124131 DOI: 10.3390/ph17050639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 05/04/2024] [Accepted: 05/13/2024] [Indexed: 05/26/2024] Open
Abstract
Neurodegenerative disorders (NDs) include a range of chronic conditions characterized by progressive neuronal loss, leading to cognitive, motor, and behavioral impairments. Common examples include Alzheimer's disease (AD) and Parkinson's disease (PD). The global prevalence of NDs is on the rise, imposing significant economic and social burdens. Despite extensive research, the mechanisms underlying NDs remain incompletely understood, hampering the development of effective treatments. Excitotoxicity, particularly glutamate-mediated excitotoxicity, is a key pathological process implicated in NDs. Targeting the N-methyl-D-aspartate (NMDA) receptor, which plays a central role in excitotoxicity, holds therapeutic promise. However, challenges, such as blood-brain barrier penetration and adverse effects, such as extrapyramidal effects, have hindered the success of many NMDA receptor antagonists in clinical trials. This review explores the molecular mechanisms of NMDA receptor antagonists, emphasizing their structure, function, types, challenges, and future prospects in treating NDs. Despite extensive research on competitive and noncompetitive NMDA receptor antagonists, the quest for effective treatments still faces significant hurdles. This is partly because the same NMDA receptor that necessitates blockage under pathological conditions is also responsible for the normal physiological function of NMDA receptors. Allosteric modulation of NMDA receptors presents a potential alternative, with the GluN2B subunit emerging as a particularly attractive target due to its enrichment in presynaptic and extrasynaptic NMDA receptors, which are major contributors to excitotoxic-induced neuronal cell death. Despite their low side-effect profiles, selective GluN2B antagonists like ifenprodil and radiprodil have encountered obstacles such as poor bioavailability in clinical trials. Moreover, the selectivity of these antagonists is often relative, as they have been shown to bind to other GluN2 subunits, albeit minimally. Recent advancements in developing phenanthroic and naphthoic acid derivatives offer promise for enhanced GluN2B, GluN2A or GluN2C/GluN2D selectivity and improved pharmacodynamic properties. Additional challenges in NMDA receptor antagonist development include conflicting preclinical and clinical results, as well as the complexity of neurodegenerative disorders and poorly defined NMDA receptor subtypes. Although multifunctional agents targeting multiple degenerative processes are also being explored, clinical data are limited. Designing and developing selective GluN2B antagonists/modulators with polycyclic moieties and multitarget properties would be significant in addressing neurodegenerative disorders. However, advancements in understanding NMDA receptor structure and function, coupled with collaborative efforts in drug design, are imperative for realizing the therapeutic potential of these NMDA receptor antagonists/modulators.
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Affiliation(s)
- Ayodeji Olatunde Egunlusi
- Pharmaceutical Chemistry, Faculty of Pharmacy, Rhodes University, P.O. Box 94, Makhanda 6140, South Africa
| | - Jacques Joubert
- Pharmaceutical Chemistry, School of Pharmacy, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa;
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Brunetti V, Soda T, Berra-Romani R, De Sarro G, Guerra G, Scarpellino G, Moccia F. Two Signaling Modes Are Better than One: Flux-Independent Signaling by Ionotropic Glutamate Receptors Is Coming of Age. Biomedicines 2024; 12:880. [PMID: 38672234 PMCID: PMC11048239 DOI: 10.3390/biomedicines12040880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/02/2024] [Accepted: 04/12/2024] [Indexed: 04/28/2024] Open
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamatergic transmission can be mediated by ionotropic glutamate receptors (iGluRs), which mediate rapid synaptic depolarization that can be associated with Ca2+ entry and activity-dependent change in the strength of synaptic transmission, as well as by metabotropic glutamate receptors (mGluRs), which mediate slower postsynaptic responses through the recruitment of second messenger systems. A wealth of evidence reported over the last three decades has shown that this dogmatic subdivision between iGluRs and mGluRs may not reflect the actual physiological signaling mode of the iGluRs, i.e., α-amino-3-hydroxy-5-methyl-4-isoxasolepropionic acid (AMPA) receptors (AMPAR), kainate receptors (KARs), and N-methyl-D-aspartate (NMDA) receptors (NMDARs). Herein, we review the evidence available supporting the notion that the canonical iGluRs can recruit flux-independent signaling pathways not only in neurons, but also in brain astrocytes and cerebrovascular endothelial cells. Understanding the signaling versatility of iGluRs can exert a profound impact on our understanding of glutamatergic synapses. Furthermore, it may shed light on novel neuroprotective strategies against brain disorders.
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Affiliation(s)
- Valentina Brunetti
- Laboratory of General Physiology, Department of Biology and Biotechnology “L. Spallanzani”, 27110 Pavia, Italy; (V.B.); (G.S.)
| | - Teresa Soda
- Department of Health Sciences, School of Medicine and Surgery, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy; (T.S.); (G.D.S.)
| | - Roberto Berra-Romani
- Department of Biomedicine, School of Medicine, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico;
| | - Giovambattista De Sarro
- Department of Health Sciences, School of Medicine and Surgery, Magna Graecia University of Catanzaro, 88100 Catanzaro, Italy; (T.S.); (G.D.S.)
- System and Applied Pharmacology@University Magna Grecia, Science of Health Department, School of Medicine, Magna Graecia University of Catanzaro, 88110 Catanzaro, Italy
| | - Germano Guerra
- Department of Medicine and Health Science “Vincenzo Tiberio”, School of Medicine and Surgery, University of Molise, 86100 Campobasso, Italy;
| | - Giorgia Scarpellino
- Laboratory of General Physiology, Department of Biology and Biotechnology “L. Spallanzani”, 27110 Pavia, Italy; (V.B.); (G.S.)
| | - Francesco Moccia
- Department of Medicine and Health Science “Vincenzo Tiberio”, School of Medicine and Surgery, University of Molise, 86100 Campobasso, Italy;
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Rosano G, Barzasi A, Lynagh T. Loss of activation by GABA in vertebrate delta ionotropic glutamate receptors. Proc Natl Acad Sci U S A 2024; 121:e2313853121. [PMID: 38285949 PMCID: PMC10861852 DOI: 10.1073/pnas.2313853121] [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: 08/23/2023] [Accepted: 12/27/2023] [Indexed: 01/31/2024] Open
Abstract
Ionotropic glutamate receptors (iGluRs) mediate excitatory signals between cells by binding neurotransmitters and conducting cations across the cell membrane. In the mammalian brain, most of these signals are mediated by two types of iGluRs: AMPA and NMDA (i.e. iGluRs sensitive to 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid and N-methyl-D-aspartic acid, respectively). Delta-type iGluRs of mammals also form neurotransmitter-binding channels in the cell membrane, but in contrast, their channel is not activated by neurotransmitter binding, raising biophysical questions about iGluR activation and biological questions about the role of delta iGluRs. We therefore investigated the divergence of delta iGluRs from their iGluR cousins using molecular phylogenetics, electrophysiology, and site-directed mutagenesis. We find that delta iGluRs are found in numerous bilaterian animals (e.g., worms, starfish, and vertebrates) and are closely related to AMPA receptors, both genetically and functionally. Surprisingly, we observe that many iGluRs of the delta family are activated by the classical inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Finally, we identify nine amino acid substitutions that likely gave rise to the inactivity of today's mammalian delta iGluRs, and these mutations abolish activity when engineered into active invertebrate delta iGluRs, partly by inducing receptor desensitization. These results offer biophysical insight into iGluR activity and point to a role for GABA in excitatory signaling in invertebrates.
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Affiliation(s)
- Giulio Rosano
- Michael Sars Centre, University of Bergen, Bergen5008, Norway
| | - Allan Barzasi
- Michael Sars Centre, University of Bergen, Bergen5008, Norway
| | - Timothy Lynagh
- Michael Sars Centre, University of Bergen, Bergen5008, Norway
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4
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Belete TM. Recent Progress in the Development of New Antiepileptic Drugs with Novel Targets. Ann Neurosci 2023; 30:262-276. [PMID: 38020406 PMCID: PMC10662271 DOI: 10.1177/09727531231185991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 05/12/2023] [Indexed: 12/01/2023] Open
Abstract
Background Epilepsy is a chronic neurological disorder that affects approximately 50-70 million people worldwide. Epilepsy has a significant economic and social burden on patients as well as on the country. The recurrent, spontaneous seizure activity caused by abnormal neuronal firing in the brain is a hallmark of epilepsy. The current antiepileptic drugs provide symptomatic relief by restoring the balance of excitatory and inhibitory neurotransmitters. Besides, about 30% of epileptic patients do not achieve seizure control. The prevalence of adverse drug reactions, including aggression, agitation, irritability, and associated comorbidities, is also prevalent. Therefore, researchers should focus on developing more effective, safe, and disease-modifying agents based on new molecular targets and signaling cascades. Summary This review overviews several clinical trials that help identify promising new targets like lactate dehydrogenase inhibitors, c-jun n-terminal kinases, high mobility group box-1 antibodies, astrocyte reactivity inhibitors, cholesterol 24-hydroxylase inhibitors, glycogen synthase kinase-3 beta inhibitors, and glycolytic inhibitors to develop a new antiepileptic drug. Key messages Approximately 30% of epileptic patients do not achieve seizure control. The current anti-seizure drugs are not disease modifying, cure or prevent epilepsy. Lactate dehydrogenase inhibitor, cholesterol 24-hydroxylase inhibitor, glycogen synthase kinase-3 beta inhibitors, and mTOR inhibitors have a promising antiepileptogenic effect.
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Affiliation(s)
- Tafere Mulaw Belete
- Department of Pharmacology, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia, Africa
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5
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Masternak M, Koch A, Laulumaa S, Tapken D, Hollmann M, Jørgensen FS, Kastrup JS. Differences between the GluD1 and GluD2 receptors revealed by GluD1 X-ray crystallography, binding studies and molecular dynamics. FEBS J 2023; 290:3781-3801. [PMID: 36128700 DOI: 10.1111/febs.16631] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 07/29/2022] [Accepted: 09/20/2022] [Indexed: 08/03/2023]
Abstract
Ionotropic glutamate receptors are ligand-gated ion channels essential for fast excitatory neurotransmission in the brain. In contrast to most other members of the iGluR family, the subfamily of delta receptors, GluD1 and GluD2, does not bind glutamate but glycine/D-serine. GluD1 is widely expressed in the brain and the inner ear, where it is required for high-frequency hearing. Furthermore, it has been associated with schizophrenia, autism and depression. X-ray structures of the ligand-binding domain (LBD) of GluD2 have been published; however, no high-resolution structure is available for the ligand-binding domain of GluD1 (GluD1-LBD). Here, we report the X-ray crystal structure of the GluD1-LBD in its apo form at 2.57 Å resolution. Using isothermal titration calorimetry, we show that D-serine binds to the GluD1-LBD in an exothermic manner with a Kd of 160 μm, which is approximately five-fold greater than at GluD2. Furthermore, we identify Glu822 as a critical determinant of receptor activation in GluD1 A654T. In contrast to studies on the GluD2 lurcher mutant A654T, we did not observe any effect of 1 mm D-serine on the spontaneous currents at mouse GluD1 A654T by electrophysiological recordings of Xenopus laevis oocytes as previously also reported by others. These results point towards differences in the structure and dynamics between GluD1 and GluD2. Molecular dynamics simulations were employed to address this observation, suggesting that the apo structure of GluD1 is less flexible than the apo structure of GluD2 and that Pro725 in GluD1 may affect the interlobe closure of the ligand-binding domain of GluD1.
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Affiliation(s)
- Magdalena Masternak
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
| | - Angela Koch
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
- Institute of Neural and Sensory Physiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Saara Laulumaa
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
| | - Daniel Tapken
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
| | - Michael Hollmann
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
| | - Flemming Steen Jørgensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
- Research Cluster on Personalised Medicine, Copenhagen, Denmark
| | - Jette Sandholm Kastrup
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
- Research Cluster on Molecular Neuroprotection, Copenhagen, Denmark
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Li C, Li Z, Xu S, Jiang S, Ye Z, Yu B, Gong S, Li J, Hu Q, Feng B, Wang M, Lu C. Exogenous AMPA downregulates gamma-frequency network oscillation in CA3 of rat hippocampal slices. Sci Rep 2023; 13:10548. [PMID: 37386056 PMCID: PMC10310770 DOI: 10.1038/s41598-023-36876-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 06/12/2023] [Indexed: 07/01/2023] Open
Abstract
Pharmacologically-induced persistent hippocampal γ oscillation in area CA3 requires activation of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs). However, we demonstrated that exogenous AMPA dose-dependently inhibited carbachol (CCH)-induced γ oscillation in the CA3 area of rat hippocampal slices, but the underlying mechanism is not clear. Application of AMPARs antagonist NBQX (1 μM) did not affect γ oscillation power (γ power), nor AMPA-mediated γ power reduction. At 3 μM, NBQX had no effect on γ power but largely blocked AMPA-mediated γ power reduction. Ca2+-permeable AMPA receptor (CP-AMPAR) antagonist IEM1460 or CaMKK inhibitor STO-609 but not CaMKIIα inhibitor KN93 enhanced γ power, indicating that activation of CP-AMPAR or CaMKK negatively modulated CCH-induced γ oscillation. Either CP-AMPAR antagonist or CaMKK inhibitor alone did not affected AMPA-mediated γ power reduction, but co-administration of IEM1460 and NBQX (1 μM) largely prevented AMPA-mediated downregulation of γ suggesting that CP-AMPARs and CI-AMPARs are involved in AMPA downregulation of γ oscillation. The recurrent excitation recorded at CA3 stratum pyramidale was significantly reduced by AMPA application. Our results indicate that AMPA downregulation of γ oscillation may be related to the reduced recurrent excitation within CA3 local neuronal network due to rapid CI-AMPAR and CP-AMPAR activation.
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Affiliation(s)
- Chengzhang Li
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Zhenrong Li
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Sihan Xu
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Sanwei Jiang
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Zhenli Ye
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Bin Yu
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Shixiang Gong
- School of Information Science and Engineering, Yanshan University, Qinhuangdao, China
| | - Junmei Li
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Qilin Hu
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Bingyan Feng
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Mengmeng Wang
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Chengbiao Lu
- Henan International Key Laboratory for Noninvasive Neuromodulation/Key Laboratory of Brain Research of Henan Province, Department of Physiology & Pathophysiology, School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China.
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7
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Kumar J, Popescu GK, Gantz SC. GluD receptors are functional ion channels. Biophys J 2023; 122:2383-2395. [PMID: 37177782 PMCID: PMC10323023 DOI: 10.1016/j.bpj.2023.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/27/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023] Open
Abstract
In this article, we review contemporary evidence that GluD receptors are functional ion channels whose depolarizing currents contribute to their biological functions, akin to all other members of the ionotropic glutamate receptor (iGluR) family.
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Affiliation(s)
- Janesh Kumar
- Laboratory of Membrane Protein Biology, Council of Scientific and Industrial Research (CSIR)-Centre for Cellular and Molecular Biology, Hyderabad, Telangana, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Gabriela K Popescu
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University of Buffalo, SUNY, Buffalo, New York
| | - Stephanie C Gantz
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa; Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa.
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8
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Stephens GJ, Shukla AK. Targeting the cell's gatekeepers for novel drug discovery. Br J Pharmacol 2022; 179:3485-3486. [PMID: 35393664 DOI: 10.1111/bph.15831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
| | - Arun K Shukla
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur, India
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9
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Dutta P, Bharti P, Kumar J, Maiti S. Role of actin cytoskeleton in the organization and function of ionotropic glutamate receptors. Curr Res Struct Biol 2021; 3:277-289. [PMID: 34766008 PMCID: PMC8569634 DOI: 10.1016/j.crstbi.2021.10.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 09/04/2021] [Accepted: 10/09/2021] [Indexed: 12/22/2022] Open
Abstract
Neural networks with precise connection are compulsory for learning and memory. Various cellular events occur during the genesis of dendritic spines to their maturation, synapse formation, stabilization of the synapse, and proper signal transmission. The cortical actin cytoskeleton and its multiple regulatory proteins are crucial for the above cellular events. The different types of ionotropic glutamate receptors (iGluRs) present on the postsynaptic density (PSD) are also essential for learning and memory. Interaction of the iGluRs in association of their auxiliary proteins with actin cytoskeleton regulated by actin-binding proteins (ABPs) are required for precise long-term potentiation (LTP) and long-term depression (LTD). There has been a quest to understand the mechanistic detail of synapse function involving these receptors with dynamic actin cytoskeleton. A major, emerging area of investigation is the relationship between ABPs and iGluRs in synapse development. In this review we have summarized the current understanding of iGluRs functioning with respect to the actin cytoskeleton, scaffolding proteins, and their regulators. The AMPA, NMDA, Delta and Kainate receptors need the stable underlying actin cytoskeleton to anchor through synaptic proteins for precise synapse formation. The different types of ABPs present in neurons play a critical role in dynamizing/stabilizing the actin cytoskeleton needed for iGluRs function.
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Affiliation(s)
- Priyanka Dutta
- National Centre for Cell Science, Pune, Maharashtra, 411007, India
| | - Pratibha Bharti
- National Centre for Cell Science, Pune, Maharashtra, 411007, India
| | - Janesh Kumar
- National Centre for Cell Science, Pune, Maharashtra, 411007, India
| | - Sankar Maiti
- Indian Institute of Science Education and Research, Kolkata, 741246, India
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10
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Burada AP, Vinnakota R, Lambolez B, Tricoire L, Kumar J. Structural biology of ionotropic glutamate delta receptors and their crosstalk with metabotropic glutamate receptors. Neuropharmacology 2021; 196:108683. [PMID: 34181979 DOI: 10.1016/j.neuropharm.2021.108683] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/31/2021] [Accepted: 06/17/2021] [Indexed: 10/21/2022]
Abstract
Enigmatic orphan glutamate delta receptors (GluD) are one of the four classes of the ionotropic glutamate receptors (iGluRs) that play key roles in synaptic transmission and plasticity. While members of other iGluR families viz AMPA, NMDA, and kainate receptors are gated by glutamate, the GluD receptors neither bind glutamate nor evoke ligand-induced currents upon binding of glycine and D-serine. Thus, the GluD receptors were considered to function as structural proteins that facilitate the formation, maturation, and maintenance of synapses in the hippocampus and cerebellum. Recent work has revealed that GluD receptors have extensive crosstalk with metabotropic glutamate receptors (mGlus) and are also gated by their activation. The latest development of a novel optopharamcological tool and the cryoEM structures of GluD receptors would help define the molecular and chemical basis of the GluD receptor's role in synaptic physiology. This article is part of the special Issue on "Glutamate Receptors - Orphan iGluRs".
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Affiliation(s)
- Ananth Prasad Burada
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, 411007, India
| | - Rajesh Vinnakota
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, 411007, India
| | - Bertrand Lambolez
- Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), CNRS, INSERM, Sorbonne Université, Paris, France
| | - Ludovic Tricoire
- Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), CNRS, INSERM, Sorbonne Université, Paris, France.
| | - Janesh Kumar
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, 411007, India.
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11
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Stroebel D, Mony L, Paoletti P. Glycine agonism in ionotropic glutamate receptors. Neuropharmacology 2021; 193:108631. [PMID: 34058193 DOI: 10.1016/j.neuropharm.2021.108631] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 05/21/2021] [Accepted: 05/23/2021] [Indexed: 12/12/2022]
Abstract
Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that mediate the majority of excitatory neurotransmission in the vertebrate CNS. Classified as AMPA, kainate, delta and NMDA receptors, iGluRs are central drivers of synaptic plasticity widely considered as a major cellular substrate of learning and memory. Surprisingly however, five out of the eighteen vertebrate iGluR subunits do not bind glutamate but glycine, a neurotransmitter known to mediate inhibitory neurotransmission through its action on pentameric glycine receptors (GlyRs). This is the case of GluN1, GluN3A, GluN3B, GluD1 and GluD2 subunits, all also binding the D amino acid d-serine endogenously present in many brain regions. Glycine and d-serine action and affinities broadly differ between glycinergic iGluR subtypes. On 'conventional' GluN1/GluN2 NMDA receptors, glycine (or d-serine) acts in concert with glutamate as a mandatory co-agonist to set the level of receptor activity. It also regulates the receptor's trafficking and expression independently of glutamate. On 'unconventional' GluN1/GluN3 NMDARs, glycine acts as the sole agonist directly triggering opening of excitatory glycinergic channels recently shown to be physiologically relevant. On GluD receptors, d-serine on its own mediates non-ionotropic signaling involved in excitatory and inhibitory synaptogenesis, further reinforcing the concept of glutamate-insensitive iGluRs. Here we present an overview of our current knowledge on glycine and d-serine agonism in iGluRs emphasizing aspects related to molecular mechanisms, cellular function and pharmacological profile. The growing appreciation of the critical influence of glycine and d-serine on iGluR biology reshapes our understanding of iGluR signaling diversity and complexity, with important implications in neuropharmacology.
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Affiliation(s)
- David Stroebel
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, Université PSL, CNRS, INSERM, F-75005, Paris, France.
| | - Laetitia Mony
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, Université PSL, CNRS, INSERM, F-75005, Paris, France
| | - Pierre Paoletti
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, Université PSL, CNRS, INSERM, F-75005, Paris, France.
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12
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Frydenvang K, Pickering DS, Kastrup JS. Structural basis for positive allosteric modulation of AMPA and kainate receptors. J Physiol 2021; 600:181-200. [PMID: 33938001 DOI: 10.1113/jp280873] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/26/2021] [Indexed: 11/08/2022] Open
Abstract
This paper summarizes the present knowledge on how positive allosteric modulators (PAMs) interact with the ligand-binding domain (LBD) of AMPA and kainate receptors, based on structure determinations. AMPA and kainate receptors belong to the family of ionotropic glutamate receptors that are responsible for mediating the majority of fast excitatory neurotransmission. These receptors have been related to brain disorders, e.g. Alzheimer's disease and attention deficit hyperactivity disorder. PAMs are small molecules that potentiate AMPA and kainate receptor currents by interfering with receptor desensitization. Therefore, PAMs are considered to be of interest for the development of pharmacological tools. Whereas PAMs for AMPA receptors have been known for several years, only recently have PAMs for kainate receptors been reported. Today, >80 structures are available for AMPA receptors with PAMs. These PAMs bind at the interface between two LBD subunits in the vicinity of residue 775, which is important for functional differences between flip and flop isoforms of AMPA receptors. PAMs can be divided into five classes based on their binding mode. The most potent PAM reported to date belongs to class 3, which comprises dimerized PAMs. Three structures of the kainate receptor GluK1 were determined with PAMs belonging to class 2. One PAM enhances kainate receptor currents 5- to 59-fold but shows 100-fold lower potency compared to AMPA receptors. Selective PAMs for kainate receptors will be of great use as pharmacological tools for functional investigations in vivo and might potentially prove useful as drugs in controlling the activity of neuronal networks.
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Affiliation(s)
- Karla Frydenvang
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, DK- 2100, Denmark
| | - Darryl S Pickering
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, DK- 2100, Denmark
| | - Jette Sandholm Kastrup
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, DK- 2100, Denmark
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