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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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2
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Chen H, Dong Y, Wu Y, Yi F. Targeting NMDA receptor signaling for therapeutic intervention in brain disorders. Rev Neurosci 2023:revneuro-2022-0096. [PMID: 36586105 DOI: 10.1515/revneuro-2022-0096] [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: 07/31/2022] [Accepted: 12/03/2022] [Indexed: 01/01/2023]
Abstract
N-Methyl-d-aspartate (NMDA) receptor hyperfunction plays a key role in the pathological processes of depression and neurodegenerative diseases, whereas NMDA receptor hypofunction is implicated in schizophrenia. Considerable efforts have been made to target NMDA receptor function for the therapeutic intervention in those brain disorders. In this mini-review, we first discuss ion flux-dependent NMDA receptor signaling and ion flux-independent NMDA receptor signaling that result from structural rearrangement upon binding of endogenous agonists. Then, we review current strategies for exploring druggable targets of the NMDA receptor signaling and promising future directions, which are poised to result in new therapeutic agents for several brain disorders.
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Affiliation(s)
- He Chen
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou 510515, P. R. China
| | - Yuanping Dong
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou 510515, P. R. China
| | - Yun Wu
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou 510515, P. R. China
| | - Feng Yi
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou 510515, P. R. China
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3
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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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Park DK, Stein IS, Zito K. Ion flux-independent NMDA receptor signaling. Neuropharmacology 2022; 210:109019. [PMID: 35278420 DOI: 10.1016/j.neuropharm.2022.109019] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 02/23/2022] [Accepted: 02/24/2022] [Indexed: 01/01/2023]
Abstract
NMDA receptors play vital roles in a broad array of essential brain functions, from synaptic transmission and plasticity to learning and memory. Historically, the fundamental roles of NMDARs were attributed to their specialized properties of ion flux. More recently, it has become clear that NMDARs also signal in an ion flux-independent manner. Here, we review these non-ionotropic NMDAR signaling mechanisms that have been reported to contribute to a broad array of neuronal functions and dysfunctions including synaptic transmission and plasticity, cell death and survival, and neurological disorders.
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Affiliation(s)
- Deborah K Park
- Center for Neuroscience, University of California, Davis, CA, 95618, USA
| | - Ivar S Stein
- Center for Neuroscience, University of California, Davis, CA, 95618, USA
| | - Karen Zito
- Center for Neuroscience, University of California, Davis, CA, 95618, USA.
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Cappelli J, Khacho P, Wang B, Sokolovski A, Bakkar W, Raymond S, Ahlskog N, Pitney J, Wu J, Chudalayandi P, Wong AYC, Bergeron R. Glycine-induced NMDA receptor internalization provides neuroprotection and preserves vasculature following ischemic stroke. iScience 2022; 25:103539. [PMID: 34977503 PMCID: PMC8689229 DOI: 10.1016/j.isci.2021.103539] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 10/06/2021] [Accepted: 11/24/2021] [Indexed: 11/26/2022] Open
Abstract
Ischemic stroke is the second leading cause of death worldwide. Following an ischemic event, neuronal death is triggered by uncontrolled glutamate release leading to overactivation of glutamate sensitive N-methyl-d-aspartate receptor (NMDAR). For gating, NMDARs require not only the binding of glutamate, but also of glycine or a glycine-like compound as a co-agonist. Low glycine doses enhance NMDAR function, whereas high doses trigger glycine-induced NMDAR internalization (GINI) in vitro. Here, we report that following an ischemic event, in vivo, GINI also occurs and provides neuroprotection in the presence of a GlyT1 antagonist (GlyT1-A). Mice pretreated with a GlyT1-A, which increases synaptic glycine levels, exhibited smaller stroke volume, reduced cell death, and minimized behavioral deficits following stroke induction by either photothrombosis or endothelin-1. Moreover, we show evidence that in ischemic conditions, GlyT1-As preserve the vasculature in the peri-infarct area. Therefore, GlyT1 could be a new target for the treatment of ischemic stroke. GINI is a dynamic phenomenon which dampens NMDAR-mediated excitotoxicity during stroke GlyT1-antagonists (GlyT1-As) trigger GINI during stroke in vivo GlyT1-As mitigate post-stroke behavioral deficits and preserve peri-infarct vasculature GlyT1 could be a novel and viable therapeutic target for ischemic stroke
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Affiliation(s)
- Julia Cappelli
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Pamela Khacho
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Boyang Wang
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Alexandra Sokolovski
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Wafae Bakkar
- Ottawa Hospital Research Institute, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Sophie Raymond
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Nina Ahlskog
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Julian Pitney
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Junzheng Wu
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Prakash Chudalayandi
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Adrian Y C Wong
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
| | - Richard Bergeron
- Cellular and Molecular Medicine Department, University of Ottawa, 451 Smyth Road, Roger Guindon Building, Room 3501N, Ottawa, ON K1H 8M5, Canada
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6
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Alternative splicing of GluN1 gates glycine site-dependent nonionotropic signaling by NMDAR receptors. Proc Natl Acad Sci U S A 2021; 118:2026411118. [PMID: 34187890 PMCID: PMC8271567 DOI: 10.1073/pnas.2026411118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs), which are critical in the brain, are increasingly being shown to signal without ion flux (i.e., “metabotropically”). What controls the metabotropic function of NMDARs is unknown. We discovered that a form of metabotropic signaling—glycine priming—is controlled by alternative splicing of the mRNA encoding one NMDAR subunit, GluN1. Our discovery was surprising because the spliced exon encodes a peptide cassette in the extracellular region of GluN1 far from the plasma membrane, and yet, metabotropic function requires signaling across the neuronal membrane. Moreover, we found that this metabotropic function of NMDARs is neuron cell–type specific: excitatory neurons show glycine priming, whereas inhibitory neurons do not. These findings have widespread implications for NMDARs in health and disease. N-methyl-D-aspartate (NMDA) receptors (NMDARs), a principal subtype of excitatory neurotransmitter receptor, are composed as tetrameric assemblies of two glycine-binding GluN1 subunits and two glutamate-binding GluN2 subunits. NMDARs can signal nonionotropically through binding of glycine alone to its cognate site on GluN1. A consequence of this signaling by glycine is that NMDARs are primed such that subsequent gating, produced by glycine and glutamate, drives receptor internalization. The GluN1 subunit contains eight alternatively spliced isoforms produced by including or excluding the N1 and the C1, C2, or C2’ polypeptide cassettes. Whether GluN1 alternative splicing affects nonionotropic signaling by NMDARs is a major outstanding question. Here, we discovered that glycine priming of recombinant NMDARs critically depends on GluN1 isoforms lacking the N1 cassette; glycine priming is blocked in splice variants containing N1. On the other hand, the C-terminal cassettes—C1, C2, or C2’—each permit glycine signaling. In wild-type mice, we found glycine-induced nonionotropic signaling at synaptic NMDARs in CA1 hippocampal pyramidal neurons. This nonionotropic signaling by glycine to synaptic NMDARs was prevented in mice we engineered, such that GluN1 obligatorily contained N1. We discovered in wild-type mice that, in contrast to pyramidal neurons, synaptic NMDARs in CA1 inhibitory interneurons were resistant to glycine priming. But we recapitulated glycine priming in inhibitory interneurons in mice engineered such that GluN1 obligatorily lacked the N1 cassette. Our findings reveal a previously unsuspected molecular function for alternative splicing of GluN1 in controlling nonionotropic signaling of NMDARs by activating the glycine site.
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7
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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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8
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Rajani V, Sengar AS, Salter MW. Tripartite signalling by NMDA receptors. Mol Brain 2020; 13:23. [PMID: 32070387 PMCID: PMC7029596 DOI: 10.1186/s13041-020-0563-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 02/03/2020] [Indexed: 12/31/2022] Open
Abstract
N-methyl-d-aspartate receptors (NMDARs) are excitatory glutamatergic receptors that are fundamental for many neuronal processes, including synaptic plasticity. NMDARs are comprised of four subunits derived from heterogeneous subunit families, yielding a complex diversity in NMDAR form and function. The quadruply-liganded state of binding of two glutamate and two glycine molecules to the receptor drives channel gating, allowing for monovalent cation flux, Ca2+ entry and the initiation of Ca2+-dependent signalling. In addition to this ionotropic function, non-ionotropic signalling can be initiated through the exclusive binding of glycine or of glutamate to the NMDAR. This binding may trigger a transmembrane conformational change of the receptor, inducing intracellular protein-protein signalling between the cytoplasmic domain and secondary messengers. In this review, we outline signalling cascades that can be activated by NMDARs and propose that the receptor transduces signalling through three parallel streams: (i) signalling via both glycine and glutamate binding, (ii) signalling via glycine binding, and (iii) signalling via glutamate binding. This variety in signal transduction mechanisms and downstream signalling cascades complements the widespread prevalence and rich diversity of NMDAR activity throughout the central nervous system and in disease pathology.
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Affiliation(s)
- Vishaal Rajani
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada
| | - Ameet S Sengar
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada
| | - Michael W Salter
- Program in Neurosciences & Mental Health, Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada. .,Department of Physiology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.
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9
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Fernández-Cabrera MR, Selvas A, Miguéns M, Higuera-Matas A, Vale-Martínez A, Ambrosio E, Martí-Nicolovius M, Guillazo-Blanch G. Parafascicular thalamic nucleus deep brain stimulation decreases NMDA receptor GluN1 subunit gene expression in the prefrontal cortex. Neuroscience 2017; 348:73-82. [DOI: 10.1016/j.neuroscience.2017.02.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 01/19/2017] [Accepted: 02/07/2017] [Indexed: 01/28/2023]
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10
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Plasma membrane insertion of epithelial sodium channels occurs with dual kinetics. Pflugers Arch 2016; 468:859-70. [DOI: 10.1007/s00424-016-1799-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/04/2016] [Accepted: 02/08/2016] [Indexed: 01/05/2023]
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CPG2 Recruits Endophilin B2 to the Cytoskeleton for Activity-Dependent Endocytosis of Synaptic Glutamate Receptors. Curr Biol 2016; 26:296-308. [PMID: 26776730 DOI: 10.1016/j.cub.2015.11.071] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 09/21/2015] [Accepted: 11/30/2015] [Indexed: 11/23/2022]
Abstract
Internalization of glutamate receptors at the postsynaptic membrane via clathrin-mediated endocytosis (CME) is a key mechanism for regulating synaptic strength. A role for the F-actin cytoskeleton in CME is well established, and recently, PKA-dependent association of candidate plasticity gene 2 (CPG2) with the spine-cytoskeleton has been shown to mediate synaptic glutamate receptor internalization. Yet, how the endocytic machinery is physically coupled to the actin cytoskeleton to facilitate glutamate receptor internalization has not been demonstrated. Moreover, there has been no distinction of endocytic-machinery components that are specific to activity-dependent versus constitutive glutamate receptor internalization. Here, we show that CPG2, through a direct physical interaction, recruits endophilin B2 (EndoB2) to F-actin, thus anchoring the endocytic machinery to the spine cytoskeleton and facilitating glutamate receptor internalization. Regulation of CPG2 binding to the actin cytoskeleton by protein kinase A directly impacts recruitment of EndoB2 and clathrin. Specific disruption of EndoB2 or the CPG2-EndoB2 interaction impairs activity-dependent, but not constitutive, internalization of both NMDA- and AMPA-type glutamate receptors. These results demonstrate that, through direct interactions with F-actin and EndoB2, CPG2 physically bridges the spine cytoskeleton and the endocytic machinery, and this tripartite association is critical specifically for activity-dependent CME of synaptic glutamate receptors.
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McGinnity CJ, Koepp MJ, Hammers A, Riaño Barros DA, Pressler RM, Luthra S, Jones PA, Trigg W, Micallef C, Symms MR, Brooks DJ, Duncan JS. NMDA receptor binding in focal epilepsies. J Neurol Neurosurg Psychiatry 2015; 86:1150-7. [PMID: 25991402 PMCID: PMC4602274 DOI: 10.1136/jnnp-2014-309897] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 04/16/2015] [Indexed: 02/05/2023]
Abstract
OBJECTIVE To demonstrate altered N-methyl-d-aspartate (NMDA) receptor availability in patients with focal epilepsies using positron emission tomography (PET) and [(18)F]GE-179, a ligand that selectively binds to the open NMDA receptor ion channel, which is thought to be overactive in epilepsy. METHODS Eleven patients (median age 33 years, 6 males) with known frequent interictal epileptiform discharges had an [(18)F]GE-179 PET scan, in a cross-sectional study. MRI showed a focal lesion but discordant EEG changes in two, was non-localising with multifocal EEG abnormalities in two, and was normal in the remaining seven patients who all had multifocal EEG changes. Individual patient [(18)F]GE-179 volume-of-distribution (VT) images were compared between individual patients and a group of 10 healthy controls (47 years, 7 males) using Statistical Parametric Mapping. RESULTS Individual analyses revealed a single cluster of focal VT increase in four patients; one with a single and one with multifocal MRI lesions, and two with normal MRIs. Post hoc analysis revealed that, relative to controls, patients not taking antidepressants had globally increased [(18)F]GE-179 VT (+28%; p<0.002), and the three patients taking an antidepressant drug had globally reduced [(18)F]GE-179 VT (-29%; p<0.002). There were no focal abnormalities common to the epilepsy group. CONCLUSIONS In patients with focal epilepsies, we detected primarily global increases of [(18)F]GE-179 VT consistent with increased NMDA channel activation, but reduced availability in those taking antidepressant drugs, consistent with a possible mode of action of this class of drugs. [(18)F]GE-179 PET showed focal accentuations of NMDA binding in 4 out of 11 patients, with difficult to localise and treat focal epilepsy.
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Affiliation(s)
- C J McGinnity
- Division of Neuroscience, Department of Medicine, Imperial College London, London, UK Medical Research Council Clinical Sciences Centre, London, UK Division of Imaging Sciences & Biomedical Engineering, Faculty of Life Sciences & Medicine, King's College London, London, UK
| | - M J Koepp
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK MRI Unit, Epilepsy Society, Chalfont St. Peter, UK
| | - A Hammers
- Division of Neuroscience, Department of Medicine, Imperial College London, London, UK Medical Research Council Clinical Sciences Centre, London, UK Division of Imaging Sciences & Biomedical Engineering, Faculty of Life Sciences & Medicine, King's College London, London, UK Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK MRI Unit, Epilepsy Society, Chalfont St. Peter, UK The Neurodis Foundation, CERMEP Imagerie du Vivant, Lyon, France
| | - D A Riaño Barros
- Division of Neuroscience, Department of Medicine, Imperial College London, London, UK Medical Research Council Clinical Sciences Centre, London, UK
| | - R M Pressler
- Department of Clinical Neurophysiology, Great Ormond Street Hospital for Children NHS Trust, London, UK
| | - S Luthra
- GE Healthcare plc, The Grove Centre, Amersham, UK
| | - P A Jones
- GE Healthcare plc, The Grove Centre, Amersham, UK
| | - W Trigg
- GE Healthcare plc, The Grove Centre, Amersham, UK
| | - C Micallef
- National Hospital for Neurology and Neurosurgery, London, UK
| | - M R Symms
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK MRI Unit, Epilepsy Society, Chalfont St. Peter, UK
| | - D J Brooks
- Division of Neuroscience, Department of Medicine, Imperial College London, London, UK Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - J S Duncan
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK MRI Unit, Epilepsy Society, Chalfont St. Peter, UK
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13
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Zhang XY, Ji F, Wang N, Chen LL, Tian T, Lu W. Glycine induces bidirectional modifications in N-methyl-D-aspartate receptor-mediated synaptic responses in hippocampal CA1 neurons. J Biol Chem 2014; 289:31200-11. [PMID: 25231980 DOI: 10.1074/jbc.m114.570630] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Glycine can persistently potentiate or depress AMPA responses through differential actions on two binding sites: NMDA and glycine receptors. Whether glycine can induce long-lasting modifications in NMDA responses, however, remains unknown. Here, we report that glycine induces long-term potentiation (LTP) or long-term depression (LTD) of NMDA responses (Gly-LTP(NMDA) or Gly-LTD(NMDA)) in a dose-dependent manner in hippocampal CA1 neurons. These modifications of NMDA responses depend on NMDAR activation. In addition, the induction of Gly-LTP(NMDA) requires binding of glycine with NMDARs, whereas Gly-LTD(NMDA) requires that glycine bind with both sites on NMDARs and GlyRs. Moreover, activity-dependent exocytosis and endocytosis of postsynaptic NMDARs underlie glycine-induced bidirectional modification of NMDA excitatory postsynaptic currents. Thus, we conclude that glycine at different levels induces bidirectional plasticity of NMDA responses through differentially regulating NMDA receptor trafficking. Our present findings reveal important functions of the two glycine binding sites in gating the direction of synaptic plasticity in NMDA responses.
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Affiliation(s)
- Xiao-Yan Zhang
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029
| | - Fang Ji
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029
| | - Ning Wang
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029, The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing, Jiangsu Province 210096, China, and
| | - Lin-Lin Chen
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029
| | - Tian Tian
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029
| | - Wei Lu
- From the Department of Neurobiology, Nanjing Medical University, Nanjing, Jiangsu Province 210029, The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing, Jiangsu Province 210096, China, and Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province 226001, China
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