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Kunde SA, Schmerl B, von Sivers J, Ahmadyar E, Gupta T, Rademacher N, Zieger HL, Shoichet SA. JNK activity modulates postsynaptic scaffold protein SAP102 and kainate receptor dynamics in dendritic spines. J Biol Chem 2024; 300:107263. [PMID: 38582451 PMCID: PMC11081805 DOI: 10.1016/j.jbc.2024.107263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 03/22/2024] [Accepted: 03/26/2024] [Indexed: 04/08/2024] Open
Abstract
Synapse formation depends on the coordinated expression and regulation of scaffold proteins. The JNK family kinases play a role in scaffold protein regulation, but the nature of this functional interaction in dendritic spines requires further investigation. Here, using a combination of biochemical methods and live-cell imaging strategies, we show that the dynamics of the synaptic scaffold molecule SAP102 are negatively regulated by JNK inhibition, that SAP102 is a direct phosphorylation target of JNK3, and that SAP102 regulation by JNK is restricted to neurons that harbor mature synapses. We further demonstrate that SAP102 and JNK3 cooperate in the regulated trafficking of kainate receptors to the cell membrane. Specifically, we observe that SAP102, JNK3, and the kainate receptor subunit GluK2 exhibit overlapping expression at synaptic sites and that modulating JNK activity influences the surface expression of the kainate receptor subunit GluK2 in a neuronal context. We also show that SAP102 participates in this process in a JNK-dependent fashion. In summary, our data support a model in which JNK-mediated regulation of SAP102 influences the dynamic trafficking of kainate receptors to postsynaptic sites, and thus shed light on common pathophysiological mechanisms underlying the cognitive developmental defects associated with diverse mutations.
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Affiliation(s)
- Stella-Amrei Kunde
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Bettina Schmerl
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Judith von Sivers
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Elham Ahmadyar
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Taanisha Gupta
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Nils Rademacher
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; German Center for Neurodegenerative Diseases (DZNE) Berlin, Berlin, Germany
| | - Hanna L Zieger
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; CNRS, Interdisciplinary Institute for Neuroscience (IINS), UMR 5297, University of Bordeaux, Bordeaux, France
| | - Sarah A Shoichet
- Neuroscience Research Center NWFZ, Charité - Universitätsmedizin Berlin, Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
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Díaz-Rodríguez SM, Herrero-Turrión MJ, García-Peral C, Gómez-Nieto R. Delving into the significance of the His289Tyr single-nucleotide polymorphism in the glutamate ionotropic receptor kainate-1 ( Grik1) gene of a genetically audiogenic seizure model. Front Mol Neurosci 2024; 16:1322750. [PMID: 38249292 PMCID: PMC10797026 DOI: 10.3389/fnmol.2023.1322750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 12/07/2023] [Indexed: 01/23/2024] Open
Abstract
Genetic abnormalities affecting glutamate receptors are central to excitatory overload-driven neuronal mechanisms that culminate in seizures, making them pivotal targets in epilepsy research. Increasingly used to advance this field, the genetically audiogenic seizure hamster from Salamanca (GASH/Sal) exhibits generalized seizures triggered by high-intensity acoustic stimulation and harbors significant genetic variants recently identified through whole-exome sequencing. Here, we addressed the influence of the missense single-nucleotide polymorphism (C9586732T, p.His289Tyr) in the glutamate receptor ionotropic kainate-1 (Grik1) gene and its implications for the GASH/Sal seizure susceptibility. Using a protein 3D structure prediction, we showed a potential effect of this sequence variation, located in the amino-terminal domain, on the stability and/or conformation of the kainate receptor subunit-1 protein (GluK1). We further employed a multi-technique approach, encompassing gene expression analysis (RT-qPCR), Western blotting, and immunohistochemistry in bright-field and confocal fluorescence microscopy, to investigate critical seizure-associated brain regions in GASH/Sal animals under seizure-free conditions compared to matched wild-type controls. We detected disruptions in the transcriptional profile of the Grik1 gene within the audiogenic seizure-associated neuronal network. Alterations in GluK1 protein levels were also observed in various brain structures, accompanied by an unexpected lower molecular weight band in the inferior and superior colliculi. This correlated with substantial disparities in GluK1-immunolabeling distribution across multiple brain regions, including the cerebellum, hippocampus, subdivisions of the inferior and superior colliculi, and the prefrontal cortex. Notably, the diffuse immunolabeling accumulated within perikarya, axonal fibers and terminals, exhibiting a prominent concentration in proximity to the cell nucleus. This suggests potential disturbances in the GluK1-trafficking mechanism, which could subsequently affect glutamate synaptic transmission. Overall, our study sheds light on the genetic underpinnings of seizures and underscores the importance of investigating the molecular mechanisms behind synaptic dysfunction in epileptic neural networks, laying a crucial foundation for future research and therapeutic strategies targeting GluK1-containing kainate receptors.
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Affiliation(s)
- Sandra M. Díaz-Rodríguez
- Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
- Department of Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, Salamanca, Spain
| | - M. Javier Herrero-Turrión
- Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
- Neurological Tissue Bank INCYL (BTN-INCYL), Salamanca, Spain
| | - Carlos García-Peral
- Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
| | - Ricardo Gómez-Nieto
- Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
- Department of Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, Salamanca, Spain
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Thompson KJ, Watson S, Zanato C, Dall'Angelo S, De Nooij JC, Pace‐Bonello B, Shenton FC, Sanger HE, Heinz BA, Broad LM, Grosjean N, McQuillian JR, Dubini M, Pyner S, Greig I, Zanda M, Bleakman D, Banks RW, Bewick GS. The atypical 'hippocampal' glutamate receptor coupled to phospholipase D that controls stretch-sensitivity in primary mechanosensory nerve endings is homomeric purely metabotropic GluK2. Exp Physiol 2024; 109:81-99. [PMID: 37656490 PMCID: PMC10988755 DOI: 10.1113/ep090761] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 08/08/2023] [Indexed: 09/02/2023]
Abstract
A metabotropic glutamate receptor coupled to phospholipase D (PLD-mGluR) was discovered in the hippocampus over three decades ago. Its pharmacology and direct linkage to PLD activation are well established and indicate it is a highly atypical glutamate receptor. A receptor with the same pharmacology is present in spindle primary sensory terminals where its blockade can totally abolish, and its activation can double, the normal stretch-evoked firing. We report here the first identification of this PLD-mGluR protein, by capitalizing on its expression in primary mechanosensory terminals, developing an enriched source, pharmacological profiling to identify an optimal ligand, and then functionalizing it as a molecular tool. Evidence from immunofluorescence, western and far-western blotting indicates PLD-mGluR is homomeric GluK2, since GluK2 is the only glutamate receptor protein/receptor subunit present in spindle mechanosensory terminals. Its expression was also found in the lanceolate palisade ending of hair follicle, also known to contain the PLD-mGluR. Finally, in a mouse model with ionotropic function ablated in the GluK2 subunit, spindle glutamatergic responses were still present, confirming it acts purely metabotropically. We conclude the PLD-mGluR is a homomeric GluK2 kainate receptor signalling purely metabotropically and it is common to other, perhaps all, primary mechanosensory endings.
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Affiliation(s)
- Karen J. Thompson
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Sonia Watson
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Chiara Zanato
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Sergio Dall'Angelo
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | | | | | | | | | | | | | - Noelle Grosjean
- CNRS UMR 5297, Interdisciplinary Institute of NeuroscienceUniversity of BordeauxBordeauxFrance
| | - Jessica R. McQuillian
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Marina Dubini
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Susan Pyner
- Department of BiosciencesDurham UniversityDurhamUK
| | - Iain Greig
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | - Matteo Zanda
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
| | | | | | - Guy S. Bewick
- Institute of Medical Sciences, School of Medicine, Medical Sciences & NutritionUniversity of AberdeenAberdeenUK
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Nomura T, Taniguchi S, Wang YZ, Yeh NH, Wilen AP, Castillon CCM, Foote KM, Xu J, Armstrong JN, Savas JN, Swanson GT, Contractor A. A Pathogenic Missense Mutation in Kainate Receptors Elevates Dendritic Excitability and Synaptic Integration through Dysregulation of SK Channels. J Neurosci 2023; 43:7913-7928. [PMID: 37802657 PMCID: PMC10669804 DOI: 10.1523/jneurosci.1259-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 09/12/2023] [Accepted: 09/16/2023] [Indexed: 10/08/2023] Open
Abstract
Numerous rare variants that cause neurodevelopmental disorders (NDDs) occur within genes encoding synaptic proteins, including ionotropic glutamate receptors. However, in many cases, it remains unclear how damaging missense variants affect brain function. We determined the physiological consequences of an NDD causing missense mutation in the GRIK2 kainate receptor (KAR) gene, that results in a single amino acid change p.Ala657Thr in the GluK2 receptor subunit. We engineered this mutation in the mouse Grik2 gene, yielding a GluK2(A657T) mouse, and studied mice of both sexes to determine how hippocampal neuronal function is disrupted. Synaptic KAR currents in hippocampal CA3 pyramidal neurons from heterozygous A657T mice exhibited slow decay kinetics, consistent with incorporation of the mutant subunit into functional receptors. Unexpectedly, CA3 neurons demonstrated elevated action potential spiking because of downregulation of the small-conductance Ca2+ activated K+ channel (SK), which mediates the post-spike afterhyperpolarization. The reduction in SK activity resulted in increased CA3 dendritic excitability, increased EPSP-spike coupling, and lowered the threshold for the induction of LTP of the associational-commissural synapses in CA3 neurons. Pharmacological inhibition of SK channels in WT mice increased dendritic excitability and EPSP-spike coupling, mimicking the phenotype in A657T mice and suggesting a causative role for attenuated SK activity in aberrant excitability observed in the mutant mice. These findings demonstrate that a disease-associated missense mutation in GRIK2 leads to altered signaling through neuronal KARs, pleiotropic effects on neuronal and dendritic excitability, and implicate these processes in neuropathology in patients with genetic NDDs.SIGNIFICANCE STATEMENT Damaging mutations in genes encoding synaptic proteins have been identified in various neurodevelopmental disorders, but the functional consequences at the cellular and circuit level remain elusive. By generating a novel knock-in mutant mouse, this study examined the role of a pathogenic mutation in the GluK2 kainate receptor (KAR) subunit, a subclass of ionotropic glutamate receptors. Analyses of hippocampal CA3 pyramidal neurons determined elevated action potential firing because of an increase in dendritic excitability. Increased dendritic excitability was attributable to reduced activity of a Ca2+ activated K+ channel. These results indicate that a pathogenic KAR mutation results in dysregulation of dendritic K+ channels, which leads to an increase in synaptic integration and backpropagation of action potentials into distal dendrites.
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Affiliation(s)
- Toshihiro Nomura
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Sakiko Taniguchi
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Yi-Zhi Wang
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Nai-Hsing Yeh
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Anika P Wilen
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Charlotte C M Castillon
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Kendall M Foote
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Jian Xu
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - John N Armstrong
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Jeffrey N Savas
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Geoffrey T Swanson
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
- Department of Neurobiology, Weinberg College of Arts and Sciences Northwestern University, Chicago, Illinois 60611
| | - Anis Contractor
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
- Department of Psychiatry and Behavioral Sciences Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
- Department of Neurobiology, Weinberg College of Arts and Sciences Northwestern University, Chicago, Illinois 60611
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5
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Gautam D, Naik UP, Naik MU, Yadav SK, Chaurasia RN, Dash D. Glutamate Receptor Dysregulation and Platelet Glutamate Dynamics in Alzheimer's and Parkinson's Diseases: Insights into Current Medications. Biomolecules 2023; 13:1609. [PMID: 38002291 PMCID: PMC10669830 DOI: 10.3390/biom13111609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/31/2023] [Accepted: 11/01/2023] [Indexed: 11/26/2023] Open
Abstract
Two of the most prevalent neurodegenerative disorders (NDDs), Alzheimer's disease (AD) and Parkinson's disease (PD), present significant challenges to healthcare systems worldwide. While the etiologies of AD and PD differ, both diseases share commonalities in synaptic dysfunction, thereby focusing attention on the role of neurotransmitters. The possible functions that platelets may play in neurodegenerative illnesses including PD and AD are becoming more acknowledged. In AD, platelets have been investigated for their ability to generate amyloid-ß (Aß) peptides, contributing to the formation of neurotoxic plaques. Moreover, platelets are considered biomarkers for early AD diagnosis. In PD, platelets have been studied for their involvement in oxidative stress and mitochondrial dysfunction, which are key factors in the disease's pathogenesis. Emerging research shows that platelets, which release glutamate upon activation, also play a role in these disorders. Decreased glutamate uptake in platelets has been observed in Alzheimer's and Parkinson's patients, pointing to a systemic dysfunction in glutamate handling. This paper aims to elucidate the critical role that glutamate receptors play in the pathophysiology of both AD and PD. Utilizing data from clinical trials, animal models, and cellular studies, we reviewed how glutamate receptors dysfunction contributes to neurodegenerative (ND) processes such as excitotoxicity, synaptic loss, and cognitive impairment. The paper also reviews all current medications including glutamate receptor antagonists for AD and PD, highlighting their mode of action and limitations. A deeper understanding of glutamate receptor involvement including its systemic regulation by platelets could open new avenues for more effective treatments, potentially slowing disease progression and improving patient outcomes.
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Affiliation(s)
- Deepa Gautam
- Center for Advanced Research on Platelet Signaling and Thrombosis Biology, Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India
- The Cardeza Foundation for Hematologic Research, Center for Hemostasis, Thrombosis and Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA; (U.P.N.); (M.U.N.); (S.K.Y.)
| | - Ulhas P. Naik
- The Cardeza Foundation for Hematologic Research, Center for Hemostasis, Thrombosis and Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA; (U.P.N.); (M.U.N.); (S.K.Y.)
| | - Meghna U. Naik
- The Cardeza Foundation for Hematologic Research, Center for Hemostasis, Thrombosis and Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA; (U.P.N.); (M.U.N.); (S.K.Y.)
| | - Santosh K. Yadav
- The Cardeza Foundation for Hematologic Research, Center for Hemostasis, Thrombosis and Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA; (U.P.N.); (M.U.N.); (S.K.Y.)
| | - Rameshwar Nath Chaurasia
- The Department of Neurology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India;
| | - Debabrata Dash
- Center for Advanced Research on Platelet Signaling and Thrombosis Biology, Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India
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Gangwar SP, Yen LY, Yelshanskaya MV, Sobolevsky AI. Positive and negative allosteric modulation of GluK2 kainate receptors by BPAM344 and antiepileptic perampanel. Cell Rep 2023; 42:112124. [PMID: 36857176 PMCID: PMC10440371 DOI: 10.1016/j.celrep.2023.112124] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 01/23/2023] [Accepted: 01/31/2023] [Indexed: 02/24/2023] Open
Abstract
Kainate receptors (KARs) are a subtype of ionotropic glutamate receptors that control synaptic transmission in the central nervous system and are implicated in neurological, psychiatric, and neurodevelopmental disorders. Understanding the regulation of KAR function by small molecules is essential for exploring these receptors as drug targets. Here, we present cryoelectron microscopy (cryo-EM) structures of KAR GluK2 in complex with the positive allosteric modulator BPAM344, competitive antagonist DNQX, and negative allosteric modulator, antiepileptic drug perampanel. Our structures show that two BPAM344 molecules bind per ligand-binding domain dimer interface. In the absence of an agonist or in the presence of DNQX, BPAM344 stabilizes GluK2 in the closed state. The closed state is also stabilized by perampanel, which binds to the ion channel extracellular collar sites located in two out of four GluK2 subunits. The molecular mechanisms of positive and negative allosteric modulation of KAR provide a guide for developing new therapeutic strategies.
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Affiliation(s)
- Shanti Pal Gangwar
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168(th) Street, New York, NY 10032, USA
| | - Laura Y Yen
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168(th) Street, New York, NY 10032, USA; Cellular and Molecular Physiology and Biophysics Graduate Program, Columbia University Irving Medical Center, 630 West 168(th) Street, New York, NY 10032, USA
| | - Maria V Yelshanskaya
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168(th) Street, New York, NY 10032, USA
| | - Alexander I Sobolevsky
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168(th) Street, New York, NY 10032, USA.
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Hu TM, Wu CL, Hsu SH, Tsai HY, Cheng FY, Cheng MC. Ultrarare Loss-of-Function Mutations in the Genes Encoding the Ionotropic Glutamate Receptors of Kainate Subtypes Associated with Schizophrenia Disrupt the Interaction with PSD95. J Pers Med 2022; 12:783. [PMID: 35629206 PMCID: PMC9144110 DOI: 10.3390/jpm12050783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 04/28/2022] [Accepted: 05/10/2022] [Indexed: 02/01/2023] Open
Abstract
Schizophrenia is a complex mental disorder with a genetic component. The GRIK gene family encodes ionotropic glutamate receptors of the kainate subtype, which are considered candidate genes for schizophrenia. We screened for rare and pathogenic mutations in the protein-coding sequences of the GRIK gene family in 516 unrelated patients with schizophrenia using the ion semiconductor sequencing method. We identified 44 protein-altered variants, and in silico analysis indicated that 36 of these mutations were rare and damaging or pathological based on putative protein function. Notably, we identified four truncating mutations, including two frameshift deletion mutations (GRIK1p.Phe24fs and GRIK1p.Thr882fs) and two nonsense mutations (GRIK2p.Arg300Ter and GRIK4p.Gln342Ter) in four unrelated patients with schizophrenia. They exhibited minor allele frequencies of less than 0.01% and were absent in 1517 healthy controls from Taiwan Biobank. Functional analysis identified these four truncating mutants as loss-of-function (LoF) mutants in HEK-293 cells. We also showed that three mutations (GRIK1p.Phe24fs, GRIK1p.Thr882fs, and GRIK2p.Arg300Ter) weakened the interaction with the PSD95 protein. The results suggest that the GRIK gene family harbors ultrarare LoF mutations in some patients with schizophrenia. The identification of proteins that interact with the kainate receptors will be essential to determine kainate receptor-mediated signaling in the brain.
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Affiliation(s)
- Tsung-Ming Hu
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
- Department of Future Studies and LOHAS Industry, Fo Guang University, Jiaosi, Yilan County 26247, Taiwan
| | - Chia-Liang Wu
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
| | - Shih-Hsin Hsu
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
| | - Hsin-Yao Tsai
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
| | - Fu-Yu Cheng
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
| | - Min-Chih Cheng
- Department of Psychiatry, Yuli Branch, Taipei Veterans General Hospital, Hualien 98142, Taiwan; (T.-M.H.); (C.-L.W.); (S.-H.H.); (H.-Y.T.); (F.-Y.C.)
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8
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Affiliation(s)
- David J A Wyllie
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Derek Bowie
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
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9
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Zhu Y, Armstrong JN, Contractor A. Kainate receptors regulate the functional properties of young adult-born dentate granule cells. Cell Rep 2021; 36:109751. [PMID: 34551304 PMCID: PMC8525187 DOI: 10.1016/j.celrep.2021.109751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 07/02/2021] [Accepted: 09/01/2021] [Indexed: 11/06/2022] Open
Abstract
Both inhibitory and excitatory neurotransmitter receptors can influence maturation and survival of adult-born neurons in the dentate gyrus; nevertheless, how these two neurotransmitter systems affect integration of new neurons into the existing circuitry is still not fully characterized. Here, we demonstrate that glutamate receptors of the kainate receptor (KAR) subfamily are expressed in adult-born dentate granule cells (abDGCs) and that, through their interaction with GABAergic signaling mechanisms, they alter the functional properties of adult-born cells during a critical period of their development. Both the intrinsic properties and synaptic connectivity of young abDGCs were affected. Timed KAR loss in a cohort of young adult-born neurons in mice disrupted their performance in a spatial discrimination task but not in a hippocampal-dependent fear conditioning task. Together, these results demonstrate the importance of KARs in the proper functional development of young abDGCs.
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Affiliation(s)
- Yiwen Zhu
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - John N Armstrong
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Anis Contractor
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA; Department of Neurobiology, Northwestern University, Chicago, IL 60611, USA.
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10
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Gonzalez CU, Carrillo E, Berka V, Jayaraman V. Structural Arrangement Produced by Concanavalin A Binding to Homomeric GluK2 Receptors. Membranes (Basel) 2021; 11:613. [PMID: 34436376 DOI: 10.3390/membranes11080613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/07/2021] [Accepted: 08/09/2021] [Indexed: 11/17/2022]
Abstract
Kainate receptors are members of the ionotropic glutamate receptor family. They form cation-specific transmembrane channels upon binding glutamate that desensitize in the continued presence of agonists. Concanavalin A (Con-A), a lectin, stabilizes the active open-channel state of the kainate receptor and reduces the extent of desensitization. In this study, we used single-molecule fluorescence resonance energy transfer (smFRET) to investigate the conformational changes underlying kainate receptor modulation by Con-A. These studies showed that Con-A binding to GluK2 homomeric kainate receptors resulted in closer proximity of the subunits at the dimer–dimer interface at the amino-terminal domain as well as between the subunits at the dimer interface at the agonist-binding domain. Additionally, the modulation of receptor functions by monovalent ions, which bind to the dimer interface at the agonist-binding domain, was not observed in the presence of Con-A. Based on these results, we conclude that Con-A modulation of kainate receptor function is mediated by a shift in the conformation of the kainate receptor toward a tightly packed extracellular domain.
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11
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Falcón-Moya R, Martínez-Gallego I, Rodríguez-Moreno A. Kainate receptor modulation of glutamatergic synaptic transmission in the CA2 region of the hippocampus. J Neurochem 2021; 158:1083-1093. [PMID: 34293825 DOI: 10.1111/jnc.15481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 07/16/2021] [Accepted: 07/19/2021] [Indexed: 11/30/2022]
Abstract
Kainate (KA) receptors (KARs) are important modulators of synaptic transmission. We studied here the role of KARs on glutamatergic synaptic transmission in the CA2 region of the hippocampus where the actions of these receptors are unknown. We observed that KA depresses glutamatergic synaptic transmission at Schaffer collateral-CA2 synapses; an effect that was antagonized by NBQX (a KA/AMPA receptors antagonist) under condition where AMPA receptors were previously blocked. The study of paired-pulse facilitation ratio, miniature responses, and fluctuation analysis indicated a presynaptic locus of action for KAR. Additionally, we determined the action mechanism for this depression of glutamate release mediated by the activation of KARs. We found that inhibition of protein kinase A suppressed the effect of KAR activation on evoked excitatory post-synaptic current, an effect that was not suppressed by protein kinase C inhibitors. Furthermore, in the presence of Pertussis toxin, the depression of glutamate release mediated by KAR activation was not present, invoking the participation of a Gi/o protein in this modulation. Finally, the KAR-mediated depression of glutamate release was not suppressed by treatments that affect calcium entry trough voltage-dependent calcium channels or calcium release from intracellular stores. We conclude that KARs present at these synapses mediate a depression of glutamate release through a mechanism that involves the activation of G protein and protein kinase A.
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Affiliation(s)
- Rafael Falcón-Moya
- Laboratorio de Neurociencia Celular y Plasticidad, Departamento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, Sevilla, Spain
| | - Irene Martínez-Gallego
- Laboratorio de Neurociencia Celular y Plasticidad, Departamento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, Sevilla, Spain
| | - Antonio Rodríguez-Moreno
- Laboratorio de Neurociencia Celular y Plasticidad, Departamento de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, Sevilla, Spain
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12
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Affiliation(s)
- Derek Bowie
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, H3G 1Y6, Canada
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13
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Kalev-Zylinska ML, Morel-Kopp MC, Ward CM, Hearn JI, Hamilton JR, Bogdanova AY. Ionotropic glutamate receptors in platelets: opposing effects and a unifying hypothesis. Platelets 2020; 32:998-1008. [PMID: 33284715 DOI: 10.1080/09537104.2020.1852542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Ionotropic glutamate receptors include α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR), kainate receptors (KAR), and N-methyl-D-aspartate receptors (NMDAR). All function as cation channels; AMPAR and KAR are more permeable to sodium and NMDAR to calcium ions. Compared to the brain, receptor assemblies in platelets are unusual, suggesting distinctive functionalities.There is convincing evidence that AMPAR and KAR amplify platelet function and thrombus formation in vitro and in vivo. Transgenic mice lacking GluA1 and GluK2 (AMPAR and KAR subunits, respectively) have longer bleeding times and prolonged time to thrombosis in an arterial model. In humans, rs465566 KAR gene polymorphism associates with altered in vitro platelet responses suggesting enhanced aspirin effect. The NMDAR contribution to platelet function is less well defined. NMDA at low concentrations (≤10 μM) inhibits platelet aggregation and high concentrations (≥100 μM) have no effect. However, open NMDAR channel blockers interfere with platelet activation and aggregation induced by other agonists in vitro; anti-GluN1 antibodies interfere with thrombus formation under high shear rates ex vivo; and rats vaccinated with GluN1 develop iron deficiency anemia suggestive of mild chronic bleeding. In this review, we summarize data on glutamate receptors in platelets and propose a unifying model that reconciles some of the opposing effects observed.
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Affiliation(s)
- Maggie L Kalev-Zylinska
- Blood and Cancer Biology Laboratory, Department of Molecular Medicine & Pathology, University of Auckland, Auckland, New Zealand.,Department of Pathology and Laboratory Medicine, LabPlus Haematology, Auckland City Hospital, Auckland, New Zealand
| | - Marie-Christine Morel-Kopp
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia.,Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, Australia
| | - Christopher M Ward
- Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, Australia.,Northern Blood Research Centre, Kolling Institute, University of Sydney, Sydney, Australia
| | - James I Hearn
- Blood and Cancer Biology Laboratory, Department of Molecular Medicine & Pathology, University of Auckland, Auckland, New Zealand
| | - Justin R Hamilton
- Australian Centre for Blood Diseases, Monash University, Melbourne, Australia
| | - Anna Y Bogdanova
- Red Blood Cell Research Group, Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, Zürich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zürich, Switzerland
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14
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Phillips MB, Nigam A, Johnson JW. Interplay between Gating and Block of Ligand-Gated Ion Channels. Brain Sci 2020; 10:brainsci10120928. [PMID: 33271923 PMCID: PMC7760600 DOI: 10.3390/brainsci10120928] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/21/2020] [Accepted: 11/26/2020] [Indexed: 02/03/2023] Open
Abstract
Drugs that inhibit ion channel function by binding in the channel and preventing current flow, known as channel blockers, can be used as powerful tools for analysis of channel properties. Channel blockers are used to probe both the sophisticated structure and basic biophysical properties of ion channels. Gating, the mechanism that controls the opening and closing of ion channels, can be profoundly influenced by channel blocking drugs. Channel block and gating are reciprocally connected; gating controls access of channel blockers to their binding sites, and channel-blocking drugs can have profound and diverse effects on the rates of gating transitions and on the stability of channel open and closed states. This review synthesizes knowledge of the inherent intertwining of block and gating of excitatory ligand-gated ion channels, with a focus on the utility of channel blockers as analytic probes of ionotropic glutamate receptor channel function.
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Affiliation(s)
- Matthew B. Phillips
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Aparna Nigam
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
| | - Jon W. Johnson
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA; (M.B.P.); (A.N.)
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
- Correspondence: ; Tel.: +1-(412)-624-4295
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15
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Li YJ, Duan GF, Sun JH, Wu D, Ye C, Zang YY, Chen GQ, Shi YY, Wang J, Zhang W, Shi YS. Neto proteins regulate gating of the kainate-type glutamate receptor GluK2 through two binding sites. J Biol Chem 2019; 294:17889-17902. [PMID: 31628192 PMCID: PMC6879349 DOI: 10.1074/jbc.ra119.008631] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 10/15/2019] [Indexed: 12/14/2022] Open
Abstract
The neuropilin and tolloid-like (Neto) proteins Neto1 and Neto2 are auxiliary subunits of kainate-type glutamate receptors (KARs) that regulate KAR trafficking and gating. However, how Netos bind and regulate the biophysical functions of KARs remains unclear. Here, we found that the N-terminal domain (NTD) of glutamate receptor ionotropic kainate 2 (GluK2) binds the first complement C1r/C1s-Uegf-BMP (CUB) domain of Neto proteins (i.e. NTD-CUB1 interaction) and that the core of GluK2 (GluK2ΔNTD) binds Netos through domains other than CUB1s (core-Neto interaction). Using electrophysiological analysis in HEK293T cells, we examined the effects of these interactions on GluK2 gating, including deactivation, desensitization, and recovery from desensitization. We found that NTD deletion does not affect GluK2 fast gating kinetics, the desensitization, and the deactivation. We also observed that Neto1 and Neto2 differentially regulate GluK2 fast gating kinetics, which largely rely on the NTD-CUB1 interactions. NTD removal facilitated GluK2 recovery from desensitization, indicating that the NTD stabilizes the GluK2 desensitization state. Co-expression with Neto1 or Neto2 also accelerated GluK2 recovery from desensitization, which fully relied on the NTD-CUB1 interactions. Moreover, we demonstrate that the NTD-CUB1 interaction involves electric attraction between positively charged residues in the GluK2_NTD and negatively charged ones in the CUB1 domains. Neutralization of these charges eliminated the regulatory effects of the NTD-CUB1 interaction on GluK2 gating. We conclude that KARs bind Netos through at least two sites and that the NTD-CUB1 interaction critically regulates Neto-mediated GluK2 gating.
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Affiliation(s)
- Yan-Jun Li
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Gui-Fang Duan
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Jia-Hui Sun
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Dan Wu
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Chang Ye
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Yan-Yu Zang
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
| | - Gui-Quan Chen
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
- Institute for Brain Sciences, Nanjing University, Nanjing 210032, China
| | - Yong-Yun Shi
- Department of Orthopaedics, Luhe People's Hospital Affiliated to Yangzhou University, Nanjing 211500, China
| | - Jun Wang
- Ministry of Education Key Laboratory of Modern Toxicology, Department of Toxicology, School of Public Health, Nanjing Medical University, Nanjing 211166, China
| | - Wei Zhang
- Institute of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang 050017, China
| | - Yun Stone Shi
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, and Ministry of Education Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210032, China
- Institute for Brain Sciences, Nanjing University, Nanjing 210032, China
- Chemistry and Biomedicine Innovation Center, Nanjing University, Nanjing 210032, China
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16
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Falcón-Moya R, Losada-Ruiz P, Rodríguez-Moreno A. Kainate Receptor-Mediated Depression of Glutamate Release Involves Protein Kinase A in the Cerebellum. Int J Mol Sci 2019; 20:E4124. [PMID: 31450867 DOI: 10.3390/ijms20174124] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 08/20/2019] [Accepted: 08/23/2019] [Indexed: 12/02/2022] Open
Abstract
Kainate (KA) receptors (KAR) have important modulatory roles of synaptic transmission. In the cerebellum, the action mechanisms of KAR-mediated glutamatergic depression are unknown. We studied these mechanisms by recording evoked excitatory postsynaptic currents (eEPSCs) from cerebellar slices using the whole-cell configuration of the patch-clamp technique. We observed that 3 μM KA decreased the amplitude of eEPSCs and increased the number of failures at the synapses established between parallel fibers (PF) and Purkinje neurons, and the effect was antagonized by NBQX under the condition where AMPA receptors were previously blocked. The inhibition of protein kinase A (PKA) suppressed the effect of KAR activation on eEPSC, and effect was not prevented by protein kinase C inhibitors. Furthermore, in the presence of Pertussis toxin, the depression of glutamate release mediated by KAR activation was prevented, invoking the participation of a Gi/o protein in this modulation. Finally, the KAR-mediated depression of glutamate release was not prevented by blocking calcium-permeable KARs or by treatments that affect calcium release from intracellular stores. We conclude that KARs present at these synapses mediate an inhibition of glutamate release through a mechanism that involves the activation of G-protein and protein kinase A.
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17
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Abstract
Quinoxalinediones are an important class of competitive antagonists at ionotropic glutamate receptors (iGluRs), where they are widely used to block α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptor responses. In this study we utilize two prototypic quinoxalinedione antagonists, namely DNQX and CNQX, which quench the intrinsic fluorescence of the ligand binding domain (LBD), to perform in vitro binding assays. We find that binding of DNQX and CNQX at the AMPA receptor GluA2 LBD is strongly pH dependent, whereas glutamate binding is not affected by pH. We also show that the deprotonation of DNQX, CNQX and other quinoxalinediones (NBQX and YM90K) occurs close to physiological pH, which can be explained by the lactam-lactim tautomerization of the quinoxalinedione scaffold. Analysis of our binding data indicates that quinoxalinedione deprotonation is a key requirement for binding, as we find a >100-fold higher affinity for binding of the monoanionic form compared to the neutral form. This suggests a large electrostatic contribution to the interaction with a conserved arginine residue located in the binding pocket of iGluRs. The strong pH dependence of quinoxalinedione binding, which has not previously been reported, is relevant for structure-function studies, but also for the use of quinoxalinediones in physiological experiments and envisioned therapeutic applications.
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Affiliation(s)
- Adela Dudić
- Department of Biology and Biotechnology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
| | - Andreas Reiner
- Department of Biology and Biotechnology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
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18
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Mihály A. The Reactive Plasticity of Hippocampal Ionotropic Glutamate Receptors in Animal Epilepsies. Int J Mol Sci 2019; 20:E1030. [PMID: 30818767 DOI: 10.3390/ijms20051030] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/18/2019] [Accepted: 02/22/2019] [Indexed: 12/21/2022] Open
Abstract
Ionotropic glutamate receptors (iGluRs) mediate the synaptic and metabolic actions of glutamate. These iGluRs are classified within the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type, kainate-type, and N-methyl-d-aspartate (NMDA)-type functional receptor families. The iGluR assemblies are regulated by transcription, alternative splicing, and cytoplasmic post-translational modifications. The iGluR subunit proteins are transported from the endoplasmic reticulum, inserted into the synaptic membranes, and anchored at their action site by different scaffolding and interacting proteins. The functional properties of iGluRs depend on their subunit composition, the amino acid sequence of the protein domains, and the scaffolding proteins in the synaptic membranes. The iGluRs are removed from the membranes by enzymatic action and endocytosis. Hippocampal iGluRs are rearranged through the upregulation and downregulation of the subunits following deafferentation and epileptic seizures. The rearrangement of iGluRs and the alteration of their subunit composition transform neurons into “pathological” cells, determining the further plasticity or pathology of the hippocampal formation. In the present review, we summarize the expression of AMPA, kainate, and NMDA receptor subunits following deafferentation, repeated mild seizures, and status epilepticus. We compare our results to literature descriptions, and draw conclusions as to the reactive plasticity of iGluRs in the hippocampus.
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19
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Abstract
Most excitatory neurotransmission in the mammalian brain is mediated by a family of plasma membrane-bound signaling proteins called ionotropic glutamate receptors (iGluRs). iGluRs assemble at central synapses as tetramers, forming a central ion-channel pore whose primary function is to rapidly transport Na+ and Ca2+ in response to binding the neurotransmitter l-glutamic acid. The pore of iGluRs is also accessible to bulkier cytoplasmic cations, such as the polyamines spermine, spermidine, and putrescine, which are drawn into the permeation pathway, but get stuck and block the movement of other ions. The degree of this polyamine-mediated channel block is highly regulated by processes that control the free cytoplasmic polyamine concentration, the membrane potential, or the iGluR subunit composition. Recently, an additional regulation by auxiliary proteins, most notably transmembrane AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor regulatory proteins (TARPs), cornichons, and neuropilin and tolloid-like proteins (NETOs), has been identified. Here, I review what we have learned of polyamine block of iGluRs and its regulation by auxiliary subunits. TARPs, cornichons, and NETOs attenuate the channel block by enabling polyamines to exit the pore. As a result, polyamine permeation occurs at more negative and physiologically relevant membrane potentials. The structural basis for enhanced polyamine transport remains unresolved, although alterations in both channel architecture and charge-screening mechanisms have been proposed. That auxiliary subunits can attenuate the polyamine block reveals an unappreciated impact of polyamine permeation in shaping the signaling properties of neuronal AMPA- and kainate-type iGluRs. Moreover, enhanced polyamine transport through iGluRs may have a role in regulating cellular polyamine levels.
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Affiliation(s)
- Derek Bowie
- From the Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec H3G 0B1, Canada
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20
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Kiragasi B, Wondolowski J, Li Y, Dickman DK. A Presynaptic Glutamate Receptor Subunit Confers Robustness to Neurotransmission and Homeostatic Potentiation. Cell Rep 2018; 19:2694-2706. [PMID: 28658618 DOI: 10.1016/j.celrep.2017.06.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 04/20/2017] [Accepted: 05/28/2017] [Indexed: 02/05/2023] Open
Abstract
Homeostatic signaling systems are thought to interface with other forms of plasticity to ensure flexible yet stable levels of neurotransmission. The role of neurotransmitter receptors in this process, beyond mediating neurotransmission itself, is not known. Through a forward genetic screen, we have identified the Drosophila kainate-type ionotropic glutamate receptor subunit DKaiR1D to be required for the retrograde, homeostatic potentiation of synaptic strength. DKaiR1D is necessary in presynaptic motor neurons, localized near active zones, and confers robustness to the calcium sensitivity of baseline synaptic transmission. Acute pharmacological blockade of DKaiR1D disrupts homeostatic plasticity, indicating that this receptor is required for the expression of this process, distinct from developmental roles. Finally, we demonstrate that calcium permeability through DKaiR1D is necessary for baseline synaptic transmission, but not for homeostatic signaling. We propose that DKaiR1D is a glutamate autoreceptor that promotes robustness to synaptic strength and plasticity with active zone specificity.
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Affiliation(s)
- Beril Kiragasi
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA; USC Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA
| | - Joyce Wondolowski
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Yan Li
- Section on Neuronal Connectivity, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Dion K Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA.
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21
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Marshall JJ, Xu J, Contractor A. Kainate Receptors Inhibit Glutamate Release Via Mobilization of Endocannabinoids in Striatal Direct Pathway Spiny Projection Neurons. J Neurosci 2018; 38:3901-3910. [PMID: 29540547 PMCID: PMC5907053 DOI: 10.1523/jneurosci.1788-17.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 01/30/2018] [Accepted: 02/10/2018] [Indexed: 01/28/2023] Open
Abstract
Kainate receptors are members of the glutamate receptor family that function by both generating ionotropic currents through an integral ion channel pore and coupling to downstream metabotropic signaling pathways. They are highly expressed in the striatum, yet their roles in regulating striatal synapses are not known. Using mice of both sexes, we demonstrate that GluK2-containing kainate receptors expressed in direct pathway spiny projection neurons (dSPNs) inhibit glutamate release at corticostriatal synapses in the dorsolateral striatum. This inhibition requires postsynaptic kainate-receptor-mediated mobilization of a retrograde endocannabinoid (eCB) signal and activation of presynaptic CB1 receptors. This pathway can be activated during repetitive 25 Hz trains of synaptic stimulation, causing short-term depression of corticostriatal synapses. This is the first study to demonstrate a role for kainate receptors in regulating eCB-mediated plasticity at the corticostriatal synapse and demonstrates an important role for these receptors in regulating basal ganglia circuits.SIGNIFICANCE STATEMENT The GRIK2 gene, encoding the GluK2 subunit of the kainate receptor, has been linked to several neuropsychiatric and neurodevelopmental disorders including obsessive compulsive disorder (OCD). Perseverative behaviors associated with OCD are known to result from pathophysiological changes in the striatum and kainate receptor knock-out mice have striatal-dependent phenotypes. However, the role of kainate receptors in striatal synapses is not known. We demonstrate that GluK2-containing kainate receptors regulate corticostriatal synapses by mobilizing endocannabinoids from direct pathway spiny projection neurons. Synaptic activation of GluK2 receptors during trains of synaptic input causes short-term synaptic depression, demonstrating a novel role for these receptors in regulating striatal circuits.
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Affiliation(s)
- John J Marshall
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611 and
| | - Jian Xu
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611 and
| | - Anis Contractor
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611 and
- Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Evanston, Illinois 60208
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22
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Abstract
Post-translational modification of substrate proteins by SUMO conjugation regulates a diverse array of cellular processes. While predominantly a nuclear protein modification, there is a growing appreciation that SUMOylation of proteins outside the nucleus plays direct roles in controlling synaptic transmission, neuronal excitability, and adaptive responses to cell stress. Furthermore, alterations in protein SUMOylation are observed in a wide range of neurological and neurodegenerative diseases, and several extranuclear disease-associated proteins have been shown to be directly SUMOylated. Here, focusing mainly on SUMOylation of synaptic and mitochondrial proteins, we outline recent developments and discoveries, and present our opinion as to the most exciting avenues for future research to define how SUMOylation of extranuclear proteins regulates neuronal and synaptic function.
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Affiliation(s)
- Jeremy M Henley
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK.
| | - Ruth E Carmichael
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK
| | - Kevin A Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK.
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23
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Xu J, Marshall JJ, Fernandes HB, Nomura T, Copits BA, Procissi D, Mori S, Wang L, Zhu Y, Swanson GT, Contractor A. Complete Disruption of the Kainate Receptor Gene Family Results in Corticostriatal Dysfunction in Mice. Cell Rep 2017; 18:1848-1857. [PMID: 28228252 DOI: 10.1016/j.celrep.2017.01.073] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 09/28/2016] [Accepted: 01/27/2017] [Indexed: 12/22/2022] Open
Abstract
Kainate receptors are members of the glutamate receptor family that regulate synaptic function in the brain. They modulate synaptic transmission and the excitability of neurons; however, their contributions to neural circuits that underlie behavior are unclear. To understand the net impact of kainate receptor signaling, we generated knockout mice in which all five kainate receptor subunits were ablated (5ko). These mice displayed compulsive and perseverative behaviors, including over-grooming, as well as motor problems, indicative of alterations in striatal circuits. There were deficits in corticostriatal input to spiny projection neurons (SPNs) in the dorsal striatum and correlated reductions in spine density. The behavioral alterations were not present in mice only lacking the primary receptor subunit expressed in adult striatum (GluK2 KO), suggesting that signaling through multiple receptor types is required for proper striatal function. This demonstrates that alterations in striatal function dominate the behavioral phenotype in mice without kainate receptors.
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Affiliation(s)
- Jian Xu
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - John J Marshall
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Herman B Fernandes
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Toshihiro Nomura
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Bryan A Copits
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Daniele Procissi
- Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Susumu Mori
- Department of Radiology, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - Lei Wang
- Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Yongling Zhu
- Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Geoffrey T Swanson
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Anis Contractor
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA; Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Evanston, IL 60208, USA.
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24
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Orav E, Atanasova T, Shintyapina A, Kesaf S, Kokko M, Partanen J, Taira T, Lauri SE. NETO1 Guides Development of Glutamatergic Connectivity in the Hippocampus by Regulating Axonal Kainate Receptors. eNeuro 2017; 4:ENEURO. [PMID: 28680963 DOI: 10.1523/ENEURO.0048-17.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 06/01/2017] [Accepted: 06/13/2017] [Indexed: 11/21/2022] Open
Abstract
Kainate-type glutamate receptors (KARs) are highly expressed in the developing brain, where they are tonically activated to modulate synaptic transmission, network excitability and synaptogenesis. NETO proteins are auxiliary subunits that regulate biophysical properties of KARs; however, their functions in the immature brain are not known. Here, we show that NETO1 guides the development of the rodent hippocampal CA3-CA1 circuitry via regulating axonal KARs. NETO deficiency reduced axonal targeting of most KAR subunits in hippocampal neurons in a subtype independent manner. As an interesting exception, axonal delivery of GluK1c was strongly and selectively impaired in the Neto1−/−, but not Neto2−/−, neurons. Correspondingly, the presynaptic GluK1 KAR activity that tonically inhibits glutamate release at immature CA3-CA1 synapses was completely lost in the absence of NETO1 but not NETO2. The deficit in axonal KARs at Neto1−/− neurons resulted in impaired synaptogenesis and perturbed synchronization of CA3 and CA1 neuronal populations during development in vitro. Both these Neto1−/− phenotypes were fully rescued by overexpression of GluK1c, emphasizing the role of NETO1/KAR complex in development of efferent connectivity. Together, our data uncover a novel role for NETO1 in regulation of axonal KARs and identify its physiological significance in development of the CA3-CA1 circuit.
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Evans AJ, Gurung S, Wilkinson KA, Stephens DJ, Henley JM. Assembly, Secretory Pathway Trafficking, and Surface Delivery of Kainate Receptors Is Regulated by Neuronal Activity. Cell Rep 2017; 19:2613-2626. [PMID: 28636947 PMCID: PMC5489663 DOI: 10.1016/j.celrep.2017.06.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Revised: 04/17/2017] [Accepted: 05/25/2017] [Indexed: 01/03/2023] Open
Abstract
Ionotropic glutamate receptor (iGluR) trafficking and function underpin excitatory synaptic transmission and plasticity and shape neuronal networks. It is well established that the transcription, translation, and endocytosis/recycling of iGluRs are all regulated by neuronal activity, but much less is known about the activity dependence of iGluR transport through the secretory pathway. Here, we use the kainate receptor subunit GluK2 as a model iGluR cargo to show that the assembly, early secretory pathway trafficking, and surface delivery of iGluRs are all controlled by neuronal activity. We show that the delivery of de novo kainate receptors is differentially regulated by modulation of GluK2 Q/R editing, PKC phosphorylation, and PDZ ligand interactions. These findings reveal that, in addition to short-term regulation of iGluRs by recycling/endocytosis and long-term modulation by altered transcription/translation, the trafficking of iGluRs through the secretory pathway is under tight activity-dependent control to determine the numbers and properties of surface-expressed iGluRs.
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Affiliation(s)
- Ashley J Evans
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Sonam Gurung
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Kevin A Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - David J Stephens
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Jeremy M Henley
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
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26
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Jaremko WJ, Huang Z, Wen W, Wu A, Karl N, Niu L. Identification and characterization of RNA aptamers: A long aptamer blocks the AMPA receptor and a short aptamer blocks both AMPA and kainate receptors. J Biol Chem 2017; 292:7338-7347. [PMID: 28325839 PMCID: PMC5418036 DOI: 10.1074/jbc.m116.774752] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/17/2017] [Indexed: 11/06/2022] Open
Abstract
AMPA and kainate receptors, along with NMDA receptors, represent different subtypes of glutamate ion channels. AMPA and kainate receptors share a high degree of sequence and structural similarities, and excessive activity of these receptors has been implicated in neurological diseases such as epilepsy. Therefore, blocking detrimental activity of both receptor types could be therapeutically beneficial. Here, we report the use of an in vitro evolution approach involving systematic evolution of ligands by exponential enrichment with a single AMPA receptor target (i.e. GluA1/2R) to isolate RNA aptamers that can potentially inhibit both AMPA and kainate receptors. A full-length or 101-nucleotide (nt) aptamer selectively inhibited GluA1/2R with a KI of ∼5 μm, along with GluA1 and GluA2 AMPA receptor subunits. Of note, its shorter version (55 nt) inhibited both AMPA and kainate receptors. In particular, this shorter aptamer blocked equally potently the activity of both the GluK1 and GluK2 kainate receptors. Using homologous binding and whole-cell recording assays, we found that an RNA aptamer most likely binds to the receptor's regulatory site and inhibits it noncompetitively. Our results suggest the potential of using a single receptor target to develop RNA aptamers with dual activity for effectively blocking both AMPA and kainate receptors.
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Affiliation(s)
- William J Jaremko
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
| | - Zhen Huang
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
| | - Wei Wen
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
| | - Andrew Wu
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
| | - Nicholas Karl
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
| | - Li Niu
- From the Department of Chemistry and Center for Neuroscience Research, University at Albany, SUNY, Albany, New York 12222
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27
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Sheng N, Shi YS, Nicoll RA. Amino-terminal domains of kainate receptors determine the differential dependence on Neto auxiliary subunits for trafficking. Proc Natl Acad Sci U S A 2017; 114:1159-1164. [PMID: 28100490 PMCID: PMC5293104 DOI: 10.1073/pnas.1619253114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The kainate receptor (KAR), a subtype of glutamate receptor, mediates excitatory synaptic responses at a subset of glutamatergic synapses. However, the molecular mechanisms underlying the trafficking of its different subunits are poorly understood. Here we use the CA1 hippocampal pyramidal cell, which lacks KAR-mediated synaptic currents, as a null background to determine the minimal requirements for the extrasynaptic and synaptic expression of the GluK2 subunit. We find that the GluK2 receptor itself, in contrast to GluK1, traffics to the neuronal surface and synapse efficiently and the auxiliary subunits Neto1 and Neto2 caused no further enhancement of these two trafficking processes. However, the regulation of GluK2 biophysical properties by Neto proteins is the same as that of GluK1. We further determine that it is the amino-terminal domains (ATDs) of GluK1 and GluK2 that control the strikingly different trafficking properties between these two receptors. Moreover, the ATDs are critical for synaptic expression of heteromeric receptors at mossy fiber-CA3 synapses and also mediate the differential dependence on Neto proteins for surface and synaptic trafficking of GluK1 and GluK2. These results highlight the fundamental differences between the two major KAR subunits and their interplay with Neto auxiliary proteins.
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Affiliation(s)
- Nengyin Sheng
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143
| | - Yun Stone Shi
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143
- Model Animal Research Center, Key Laboratory of Model Animal for Disease Study of Ministry of Education, Nanjing University, Nanjing 210061, People's Republic of China
| | - Roger A Nicoll
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143;
- Department of Physiology, University of California, San Francisco, CA 94143
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Campana WM, Mantuano E, Azmoon P, Henry K, Banki MA, Kim JH, Pizzo DP, Gonias SL. Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells. FASEB J 2017; 31:1744-1755. [PMID: 28073836 DOI: 10.1096/fj.201601121r] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/03/2017] [Indexed: 12/17/2022]
Abstract
In the peripheral nervous system, Schwann cells (SCs) demonstrate surveillance activity, detecting injury and undergoing trans-differentiation to support repair. SC receptors that detect peripheral nervous system injury remain incompletely understood. We used RT-PCR to profile ionotropic glutamate receptor expression in cultured SCs. We identified subunits required for assembly of N-methyl-d-aspartic acid (NMDA) receptors (NMDA-Rs), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, and kainate receptors. Treatment of SCs with 40-100 µM glutamate or with 0.5-1.0 µM NMDA robustly activated Akt and ERK1/2. The response was transient and bimodal; glutamate concentrations that exceeded 250 µM failed to activate cell signaling. Phosphoprotein profiling identified diverse phosphorylated proteins in glutamate-treated SCs in addition to ERK1/2 and Akt, including p70 S6-kinase, glycogen synthase kinase-3, ribosomal S6 kinase, c-Jun, and cAMP response element binding protein. Activation of SC signaling by glutamate was blocked by EGTA and dizocilpine and by silencing expression of the NMDA-R NR1 subunit. Phosphoinositide 3-kinase/PI3K functioned as an essential upstream activator of Akt and ERK1/2 in glutamate-treated SCs. When glutamate or NMDA was injected directly into crush-injured rat sciatic nerves, ERK1/2 phosphorylation was observed in myelinated and nonmyelinating SCs. Glutamate promoted SC migration by a pathway that required PI3K and ERK1/2. These results identified ionotropic glutamate receptors and NMDA-Rs, specifically, as potentially important cell signaling receptors in SCs.-Campana, W. M., Mantuano, E., Azmoon, P., Henry, K., Banki, M. A., Kim, J. H., Pizzo, D. P., Gonias, S. L. Ionotropic glutamate receptors activate cell signaling in response to glutamate in Schwann cells.
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Affiliation(s)
- Wendy M Campana
- Department of Anesthesiology School of Medicine, University of California, San Diego, La Jolla, California, USA;
| | - Elisabetta Mantuano
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA.,Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Pardis Azmoon
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Kenneth Henry
- Department of Anesthesiology School of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Michael A Banki
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA
| | - John H Kim
- Department of Anesthesiology School of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Donald P Pizzo
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Steven L Gonias
- Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, California, USA;
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Sakha P, Vesikansa A, Orav E, Heikkinen J, Kukko-Lukjanov TK, Shintyapina A, Franssila S, Jokinen V, Huttunen HJ, Lauri SE. Axonal Kainate Receptors Modulate the Strength of Efferent Connectivity by Regulating Presynaptic Differentiation. Front Cell Neurosci 2016; 10:3. [PMID: 26834558 PMCID: PMC4720004 DOI: 10.3389/fncel.2016.00003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 01/04/2016] [Indexed: 11/13/2022] Open
Abstract
Kainate type of glutamate receptors (KARs) are highly expressed during early brain development and may influence refinement of the circuitry, via modulating synaptic transmission and plasticity. KARs are also localized to axons, however, their exact roles in regulating presynaptic processes remain controversial. Here, we have used a microfluidic chamber system allowing specific manipulation of KARs in presynaptic neurons to study their functions in synaptic development and function in vitro. Silencing expression of endogenous KARs resulted in lower density of synaptophysin immunopositive puncta in microfluidically isolated axons. Various recombinant KAR subunits and pharmacological compounds were used to dissect the mechanisms behind this effect. The calcium permeable (Q) variants of the low-affinity (GluK1–3) subunits robustly increased synaptophysin puncta in axons in a manner that was dependent on receptor activity and PKA and PKC dependent signaling. Further, an associated increase in the mean active zone length was observed in electron micrographs. Selective presynaptic expression of these subunits resulted in higher success rate of evoked EPSCs consistent with higher probability of glutamate release. In contrast, the calcium-impermeable (R) variant of GluK1 or the high-affinity subunits (GluK4,5) had no effect on synaptic density or transmission efficacy. These data suggest that calcium permeable axonal KARs promote efferent connectivity by increasing the density of functional presynaptic release sites.
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Affiliation(s)
- Prasanna Sakha
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Biosciences, University of HelsinkiHelsinki, Finland
| | - Aino Vesikansa
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Biosciences, University of HelsinkiHelsinki, Finland
| | - Ester Orav
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Biosciences, University of HelsinkiHelsinki, Finland
| | - Joonas Heikkinen
- Departments of Materials Science and Engineering, Aalto University Espoo, Finland
| | - Tiina-Kaisa Kukko-Lukjanov
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Veterinary Biosciences, University of HelsinkiHelsinki, Finland
| | - Alexandra Shintyapina
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Biosciences, University of HelsinkiHelsinki, Finland
| | - Sami Franssila
- Departments of Materials Science and Engineering, Aalto University Espoo, Finland
| | - Ville Jokinen
- Departments of Materials Science and Engineering, Aalto University Espoo, Finland
| | | | - Sari E Lauri
- Neuroscience Center, University of HelsinkiHelsinki, Finland; Department of Biosciences, University of HelsinkiHelsinki, Finland
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30
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Sheng N, Shi YS, Lomash RM, Roche KW, Nicoll RA. Neto auxiliary proteins control both the trafficking and biophysical properties of the kainate receptor GluK1. eLife 2015; 4. [PMID: 26720915 PMCID: PMC4749551 DOI: 10.7554/elife.11682] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 12/21/2015] [Indexed: 02/02/2023] Open
Abstract
Kainate receptors (KARs) are a subfamily of glutamate receptors mediating excitatory synaptic transmission and Neto proteins are recently identified auxiliary subunits for KARs. However, the roles of Neto proteins in the synaptic trafficking of KAR GluK1 are poorly understood. Here, using the hippocampal CA1 pyramidal neuron as a null background system we find that surface expression of GluK1 receptor itself is very limited and is not targeted to excitatory synapses. Both Neto1 and Neto2 profoundly increase GluK1 surface expression and also drive GluK1 to synapses. However, the regulation GluK1 synaptic targeting by Neto proteins is independent of their role in promoting surface trafficking. Interestingly, GluK1 is excluded from synapses expressing AMPA receptors and is selectively incorporated into silent synapses. Neto2, but not Neto1, slows GluK1 deactivation, whereas Neto1 speeds GluK1 desensitization and Neto2 slows desensitization. These results establish critical roles for Neto auxiliary subunits controlling KARs properties and synaptic incorporation. DOI:http://dx.doi.org/10.7554/eLife.11682.001 Information is transmitted in the brain by cells called neurons. To communicate with neighboring cells, neurons release chemicals called neurotransmitters across a structure called a synapse that forms a junction between the cells. The neurotransmitters bind to receptors on the surface of the receiving neuron, and depending on the type of neurotransmitter released, make that neuron either more or less likely to signal to its neighbors. Excitatory neurotransmitters make neurons more likely to signal, and glutamate is the most common excitatory neurotransmitter in the brain. There are several different types of receptor that can bind to glutamate, one of which – the kainate receptor – is found at relatively few synapses. These synapses include some in the hippocampus, a region of the brain that is important for memory. Researchers have recently identified two auxiliary proteins, called Neto1 and Neto2, that interact with kainate receptors and appear to affect how strongly the kainate receptors respond when glutamate binds to them. However, the effect of the Neto proteins on one particular subunit of the kainate receptors – called GluK1 – had not been investigated in depth. CA1 pyramidal neurons are a group of neurons in the hippocampus that are able to produce kainate receptors, but these receptors are not found in CA1 pyramidal neuron synapses. Sheng et al. have now studied CA1 pyramidal neurons from rats, and found that these cells produce a limited amount of GluK1 on their surfaces. However, when GluK1 is expressed together with Neto1 or Neto2, GluK1 receptors appear on the cell surface. Through an independent mechanism Neto proteins also promote the targeting of surface GluK1 to the synapse. Unexpectedly, GluK1 was excluded from synapses that contain another type of glutamate receptor called AMPA receptors. By measuring the effect of Neto1 and Neto2 on the behavior of GluK1, Sheng et al. found that these proteins modified how the receptor responded to prolonged exposure to glutamate. Specifically, Neto1 increased how quickly GluK1 became desensitized to glutamate, while Neto2 decreased the rate of desensitization. This study demonstrates that Neto proteins play critical roles in controlling the location and biophysical properties of kainate receptors. It will be of interest to see how the present findings apply to other excitatory synapses in the brain. DOI:http://dx.doi.org/10.7554/eLife.11682.002
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Affiliation(s)
- Nengyin Sheng
- Deparment of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
| | - Yun S Shi
- Deparment of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States.,The Model Animal Research Center, Key Laboratory of Model Animal for Disease Study of Ministry of Education, Nanjing University, Nanjing, China
| | - Richa Madan Lomash
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Katherine W Roche
- Receptor Biology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Roger A Nicoll
- Deparment of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
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31
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Xu H, Smith BN. Presynaptic ionotropic glutamate receptors modulate GABA release in the mouse dorsal motor nucleus of the vagus. Neuroscience 2015; 308:95-105. [PMID: 26343294 DOI: 10.1016/j.neuroscience.2015.09.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 08/25/2015] [Accepted: 09/02/2015] [Indexed: 11/21/2022]
Abstract
Regulation of GABA release in the dorsal motor nucleus of the vagus (DMV) potently influences vagal output to the viscera. The presence of functional ionotropic glutamate receptors (iGluRs) on GABAergic terminals that rapidly alter GABA release onto DMV motor neurons has been suggested previously, but the receptor subtypes contributing to the response are unknown. We examined the effect of selective activation and inhibition of iGluRs on tetrodotoxin-insensitive, miniature inhibitory postsynaptic currents (mIPSCs) in DMV neurons using patch-clamp recordings in brainstem slices from mice. Capsaicin, which activates transient receptor potential vanilloid type 1 (TRPV1) receptors and increases mIPSC frequency in the DMV via an iGluR-mediated, heterosynaptic mechanism, was also applied to assess GABA release subsequent to capsaicin-stimulated glutamate release. Application of glutamate, N-methyl-d-aspartate (NMDA), or kainic acid (KA), but not AMPA, resulted in increased mIPSC frequency in most neurons. Inhibition of AMPA/KA receptors reduced mIPSC frequency, but selective antagonism of AMPA receptors did not alter GABA release, implicating the presence of presynaptic KA receptors on GABAergic terminals. Whereas NMDA application increased mIPSC frequency, blocking NMDA receptors was without effect, indicating that presynaptic NMDA receptors were present, but not activated by ambient glutamate levels in the slice. The effect of NMDA was prevented by AMPA/KA receptor blockade, suggesting indirect involvement of NMDA receptors. The stimulatory effect of capsaicin on GABA release was prevented when AMPA/KA or NMDA, but not AMPA receptors were blocked. Results of these studies indicate that presynaptic NMDAR and KA receptors regulate GABA release in the DMV, representing a heterosynaptic arrangement for rapidly modulating parasympathetic output, especially when synaptic excitation is elevated.
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Chida K, Kaneko K, Fujii S, Yamazaki Y. Activity-dependent modulation of the axonal conduction of action potentials along rat hippocampal mossy fibers. Eur J Neurosci 2014; 41:45-54. [PMID: 25345805 DOI: 10.1111/ejn.12762] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/08/2014] [Accepted: 09/25/2014] [Indexed: 01/20/2023]
Abstract
The axonal conduction of action potentials in the nervous system is generally considered to be a stable signal for the relaying of information, and its dysfunction is involved in impairment of cognitive function. Recent evidence suggests that the conduction properties and excitability of axons are more variable than traditionally thought. To investigate possible changes in the conduction of action potentials along axons in the central nervous system, we recorded action potentials from granule cells that were evoked and conducted antidromically along unmyelinated mossy fibers in the rat hippocampus. To evaluate changes in axons by eliminating any involvement of changes in the somata, two latency values were obtained by stimulating at two different positions and the latency difference between the action potentials was measured. A conditioning electrical stimulus of 20 pulses at 1 Hz increased the latency difference and this effect, which lasted for approximately 30 s, was inhibited by the application of an α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor antagonist or a GluK1-containing kainate receptor antagonist, but not by an AMPA receptor-selective antagonist or an N-methyl-d-aspartate receptor antagonist. These results indicated that axonal conduction in mossy fibers is modulated in an activity-dependent manner through the activation of GluK1-containing kainate receptors. These dynamic changes in axonal conduction may contribute to the physiology and pathophysiology of the brain.
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Affiliation(s)
- Kuniaki Chida
- Department of Physiology, Yamagata University School of Medicine, 2-2-2 Iida-Nishi, Yamagata, 990-9585, Japan
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Fujikawa T, Petralia RS, Fitzgerald TS, Wang YX, Millis B, Morgado-Díaz JA, Kitamura K, Kachar B. Localization of kainate receptors in inner and outer hair cell synapses. Hear Res 2014; 314:20-32. [PMID: 24858010 PMCID: PMC4107312 DOI: 10.1016/j.heares.2014.05.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 03/25/2014] [Accepted: 05/07/2014] [Indexed: 11/29/2022]
Abstract
Glutamate plays a role in hair cell afferent transmission, but the receptors that mediate neurotransmission between outer hair cells (OHCs) and type II ganglion neurons are not well defined. A previous study using in situ hybridization showed that several kainate-type glutamate receptor (KAR) subunits are expressed in cochlear ganglion neurons. To determine whether KARs are expressed in hair cell synapses, we performed X-gal staining on mice expressing lacZ driven by the GluK5 promoter, and immunolabeling of glutamate receptors in whole-mount mammalian cochleae. X-gal staining revealed GluK5 expression in both type I and type II ganglion neurons and OHCs in adults. OHCs showed X-gal reactivity throughout maturation from postnatal day 4 (P4) to 1.5 months. Immunoreactivity for GluK5 in IHC afferent synapses appeared to be postsynaptic, similar to GluA2 (GluR2; AMPA-type glutamate receptor (AMPAR) subunit), while GluK2 may be on both sides of the synapses. In OHC afferent synapses, immunoreactivity for GluK2 and GluK5 was found, although GluK2 was only in those synapses bearing ribbons. GluA2 was not detected in adult OHC afferent synapses. Interestingly, GluK1, GluK2 and GluK5 were also detected in OHC efferent synapses, forming several active zones in each synaptic area. At P8, GluA2 and all KAR subunits except GluK4 were detected in OHC afferent synapses in the apical turn, and GluA2, GluK1, GluK3 decreased dramatically in the basal turn. These results indicate that AMPARs and KARs (GluK2/GluK5) are localized to IHC afferent synapses, while only KARs (GluK2/GluK5) are localized to OHC afferent synapses in adults. Glutamate spillover near OHCs may act on KARs in OHC efferent terminals to modulate transmission of acoustic information and OHC electromotility.
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Affiliation(s)
- Taro Fujikawa
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Department of Otolaryngology, Tokyo Medical and Dental University, Bunkyo-ku, 113-8519 Tokyo, Japan
| | - Ronald S Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Tracy S Fitzgerald
- Mouse Auditory Testing Core Facility, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ya-Xian Wang
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Bryan Millis
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Ken Kitamura
- Department of Otolaryngology, Tokyo Medical and Dental University, Bunkyo-ku, 113-8519 Tokyo, Japan
| | - Bechara Kachar
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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Borghuis BG, Looger LL, Tomita S, Demb JB. Kainate receptors mediate signaling in both transient and sustained OFF bipolar cell pathways in mouse retina. J Neurosci 2014; 34:6128-39. [PMID: 24790183 DOI: 10.1523/JNEUROSCI.4941-13.2014] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A fundamental question in sensory neuroscience is how parallel processing is implemented at the level of molecular and circuit mechanisms. In the retina, it has been proposed that distinct OFF cone bipolar cell types generate fast/transient and slow/sustained pathways by the differential expression of AMPA- and kainate-type glutamate receptors, respectively. However, the functional significance of these receptors in the intact circuit during light stimulation remains unclear. Here, we measured glutamate release from mouse bipolar cells by two-photon imaging of a glutamate sensor (iGluSnFR) expressed on postsynaptic amacrine and ganglion cell dendrites. In both transient and sustained OFF layers, cone-driven glutamate release from bipolar cells was blocked by antagonists to kainate receptors but not AMPA receptors. Electrophysiological recordings from bipolar and ganglion cells confirmed the essential role of kainate receptors for signaling in both transient and sustained OFF pathways. Kainate receptors mediated responses to contrast modulation up to 20 Hz. Light-evoked responses in all mouse OFF bipolar pathways depend on kainate, not AMPA, receptors.
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Fritsch B, Reis J, Gasior M, Kaminski RM, Rogawski MA. Role of GluK1 kainate receptors in seizures, epileptic discharges, and epileptogenesis. J Neurosci 2014; 34:5765-75. [PMID: 24760837 PMCID: PMC3996208 DOI: 10.1523/jneurosci.5307-13.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 02/12/2014] [Accepted: 03/07/2014] [Indexed: 11/21/2022] Open
Abstract
Kainate receptors containing the GluK1 subunit have an impact on excitatory and inhibitory neurotransmission in brain regions, such as the amygdala and hippocampus, which are relevant to seizures and epilepsy. Here we used 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), a potent and selective agonist of kainate receptors that include the GluK1 subunit, in conjunction with mice deficient in GluK1 and GluK2 kainate receptor subunits to assess the role of GluK1 kainate receptors in provoking seizures and in kindling epileptogenesis. We found that systemic ATPA, acting specifically via GluK1 kainate receptors, causes locomotor arrest and forelimb extension (a unique behavioral characteristic of GluK1 activation) and induces myoclonic behavioral seizures and electrographic seizure discharges in the BLA and hippocampus. In contrast, the proconvulsant activity of systemic AMPA, kainate, and pentylenetetrazol is not mediated by GluK1 kainate receptors, and deletion of these receptors does not elevate the threshold for seizures in the 6 Hz model. ATPA also specifically activates epileptiform discharges in BLA slices in vitro via GluK1 kainate receptors. Olfactory bulb kindling developed similarly in wild-type, GluK1, and GluK2 knock-out mice, demonstrating that GluK1 kainate receptors are not required for epileptogenesis or seizure expression in this model. We conclude that selective activation of kainate receptors containing the GluK1 subunit can trigger seizures, but these receptors are not necessary for seizure generation in models commonly used to identify therapeutic agents for the treatment of epilepsy.
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Affiliation(s)
- Brita Fritsch
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
- Department of Neurology, University Hospital, 79106 Freiburg, Germany, and
| | - Janine Reis
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
- Department of Neurology, University Hospital, 79106 Freiburg, Germany, and
| | - Maciej Gasior
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Rafal M. Kaminski
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Michael A. Rogawski
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
- Department of Neurology, School of Medicine and Center for Neuroscience, University of California, Davis, Sacramento, California 95817
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36
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Wyeth MS, Pelkey KA, Petralia RS, Salter MW, McInnes RR, McBain CJ. Neto auxiliary protein interactions regulate kainate and NMDA receptor subunit localization at mossy fiber-CA3 pyramidal cell synapses. J Neurosci 2014; 34:622-8. [PMID: 24403160 DOI: 10.1523/JNEUROSCI.3098-13.2014] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Neto1 and Neto2 auxiliary subunits coassemble with NMDA receptors (NMDARs) and kainate receptors (KARs) to modulate their function. In the hippocampus, Neto1 enhances the amplitude and prolongs the kinetics of KAR-mediated currents at mossy fiber (MF)-CA3 pyramidal cell synapses. However, whether Neto1 trafficks KARs to synapses or simply alters channel properties is unresolved. Therefore, postembedding electron microscopy was performed to investigate the localization of GluK2/3 subunits at MF-CA3 synapses in Neto-null mice. Postsynaptic GluK2/3 Immunogold labeling was substantially reduced in Neto-null mice compared with wild types. Moreover, spontaneous KAR-mediated synaptic currents and metabotropic KAR signaling were absent in CA3 pyramidal cells of Neto-null mice. A similar loss of ionotropic and metabotropic KAR function was observed in Neto1, but not Neto2, single knock-out mice, specifically implicating Neto1 in regulating CA3 pyramidal cell KAR localization and function. Additional controversy pertains to the role of Neto proteins in modulating synaptic NMDARs. While Immunogold labeling for GluN2A at MF-CA3 synapses was comparable between wild-type and Neto-null mice, labeling for postsynaptic GluN2B was robustly increased in Neto-null mice. Accordingly, NMDAR-mediated currents at MF-CA3 synapses exhibited increased sensitivity to a GluN2B-selective antagonist in Neto1 knockouts relative to wild types. Thus, despite preservation of the overall MF-CA3 synaptic NMDAR-mediated current, loss of Neto1 alters NMDAR subunit composition. These results confirm that Neto protein interactions regulate synaptic localization of KAR and NMDAR subunits at MF-CA3 synapses, with implications for both ionotropic and metabotropic glutamatergic recruitment of the CA3 network.
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Uzunova G, Hollander E, Shepherd J. The role of ionotropic glutamate receptors in childhood neurodevelopmental disorders: autism spectrum disorders and fragile x syndrome. Curr Neuropharmacol 2014; 12:71-98. [PMID: 24533017 PMCID: PMC3915351 DOI: 10.2174/1570159x113116660046] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 08/20/2013] [Accepted: 09/25/2013] [Indexed: 12/20/2022] Open
Abstract
Autism spectrum disorder (ASD) and Fragile X syndrome (FXS) are relatively common childhood neurodevelopmental disorders with increasing incidence in recent years. They are currently accepted as disorders of the synapse with alterations in different forms of synaptic communication and neuronal network connectivity. The major excitatory neurotransmitter system in brain, the glutamatergic system, is implicated in learning and memory, synaptic plasticity, neuronal development. While much attention is attributed to the role of metabotropic glutamate receptors in ASD and FXS, studies indicate that the ionotropic glutamate receptors (iGluRs) and their regulatory proteins are also altered in several brain regions. Role of iGluRs in the neurobiology of ASD and FXS is supported by a weight of evidence that ranges from human genetics to in vitro cultured neurons. In this review we will discuss clinical, molecular, cellular and functional changes in NMDA, AMPA and kainate receptors and the synaptic proteins that regulate them in the context of ASD and FXS. We will also discuss the significance for the development of translational biomarkers and treatments for the core symptoms of ASD and FXS.
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Affiliation(s)
- Genoveva Uzunova
- Autism and Obsessive Compulsive Spectrum Program, Department of Psychiatry, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210th St, Bronx, New York 10467-2490
| | - Eric Hollander
- Autism and Obsessive Compulsive Spectrum Program, Department of Psychiatry, Montefiore Medical Center, Albert Einstein College of Medicine, 111 East 210th St, Bronx, New York 10467-2490
| | - Jason Shepherd
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, 531A Wintrobe, 20N 1900 E, Salt Lake City, Utah 84132
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38
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Ballaz S, Morales I, Rodríguez M, Obeso JA. Ascorbate prevents cell death from prolonged exposure to glutamate in an in vitro model of human dopaminergic neurons. J Neurosci Res 2013; 91:1609-17. [PMID: 23996657 DOI: 10.1002/jnr.23276] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 06/15/2013] [Accepted: 06/17/2013] [Indexed: 01/31/2023]
Abstract
Ascorbate (vitamin C) is a nonenzymatic antioxidant highly concentrated in the brain. In addition to mediating redox balance, ascorbate is linked to glutamate neurotransmission in the striatum, where it renders neuroprotection against excessive glutamate stimulation. Oxidative stress and glutamatergic overactivity are key biochemical features accompanying the loss of dopaminergic neurons in the substantia nigra that characterizes Parkinson's disease (PD). At present, it is not clear whether antiglutamate agents and ascorbate might be neuroprotective agents for PD. Thus, we tested whether ascorbate can prevent cell death from prolonged exposure to glutamate using dopaminergic neurons of human origin. To this purpose, dopamine-like neurons were obtained by differentiation of SH-SY5Y cells and then cultured for 4 days without antioxidant (antiaging) protection to evaluate glutamate toxicity and ascorbate protection as a model system of potential factors contributing to dopaminergic neuron death in PD. Glutamate dose dependently induced toxicity in dopaminergic cells largely by the stimulation of AMPA and metabotropic receptors and to a lesser extent by N-methyl-D-aspartate and kainate receptors. At relatively physiological levels of extracellular concentration, ascorbate protected cells against glutamate excitotoxicity. This neuroprotection apparently relies on the inhibition of oxidative stress, because ascorbate prevented the pro-oxidant action of the scavenging molecule quercetin, which occurred over the course of prolonged exposure, as is also seen with glutamate. Our findings show the relevance of ascorbate as a neuroprotective agent and emphasize an often underappreciated role of oxidative stress in glutamate excitotoxicity. Occurrence of a glutamate-ascorbate link in dopaminergic neurons may explain previous contradictions regarding their putative role in PD.
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Affiliation(s)
- Santiago Ballaz
- Laboratory of Movement Disorders, Department of Neuroscience, Centre for Applied Medicine Research (CIMA), University of Navarra, Pamplona, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, CIBERNED, Madrid, Spain
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González-González IM, Henley JM. Postsynaptic kainate receptor recycling and surface expression are regulated by metabotropic autoreceptor signalling. Traffic 2013; 14:810-22. [PMID: 23556457 PMCID: PMC3744763 DOI: 10.1111/tra.12071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 04/02/2013] [Accepted: 04/04/2013] [Indexed: 01/01/2023]
Abstract
Kainate receptors (KARs) play fundamentally important roles in controlling synaptic function and regulating neuronal excitability. Postsynaptic KARs contribute to excitatory neurotransmission but the molecular mechanisms underlying their activity-dependent surface expression are not well understood. Strong activation of KARs in cultured hippocampal neurons leads to the downregulation of postsynaptic KARs via endocytosis and degradation. In contrast, low-level activation augments postsynaptic KAR surface expression. Here, we show that this increase in KARs is due to enhanced recycling via the recruitment of Rab11-dependent, transferrin-positive endosomes into spines. Dominant-negative Rab11 or the recycling inhibitor primaquine prevents the kainate-evoked increase in surface KARs. Moreover, we show that the increase in surface expression is mediated via a metabotropic KAR signalling pathway, which is blocked by the protein kinase C inhibitor chelerythrine, the calcium chelator BAPTA and the G-protein inhibitor pertussis toxin. Thus, we report a previously uncharacterized positive feedback system that increases postsynaptic KARs in response to low- or moderate-level agonist activation and can provide additional flexibility to synaptic regulation.
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Affiliation(s)
| | - Jeremy M Henley
- School of Biochemistry, University of Bristol, Medical Sciences Building, University WalkBristol, BS8 1TD, UK
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40
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Abstract
Gating of AMPA- and kainate-selective ionotropic glutamate receptors can be defined in terms of ligand affinity, efficacy and the rate and extent of desensitization. Crucial insights into all three elements have come from structural studies of the ligand-binding domain (LBD). In particular, binding-cleft closure is associated with efficacy, whereas dissociation of the dimer formed by neighbouring LBDs is linked with desensitization. We have explored these relationships in the kainate-selective subunit GluK2 by studying the effects of mutating two residues (K531 and R775) that form key contacts within the LBD dimer interface, but whose truncation unexpectedly attenuates desensitization. One mutation (K531A) also switches the relative efficacies of glutamate and kainate. LBD crystal structures incorporating these mutations revealed several conformational changes that together explain their phenotypes. K531 truncation results in new dimer contacts, consistent with slower desensitization and sideways movement in the ligand-binding cleft correlating with efficacy. The tested mutants also disrupted anion binding; no chloride was detected in the dimer-interface site, including in R775A where absence of chloride was the only structural change evident. From this, we propose that the charge balance in the GluK2 LBD dimer interface maintains a degree of instability, necessary for rapid and complete desensitization.
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Affiliation(s)
- Naushaba Nayeem
- Department of Pharmacology, University of Liverpool, Liverpool L69 3GE, UK
| | - Olga Mayans
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 3GE, UK
| | - Tim Green
- Department of Pharmacology, University of Liverpool, Liverpool L69 3GE, UK
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41
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Copits BA, Swanson GT. Kainate receptor post-translational modifications differentially regulate association with 4.1N to control activity-dependent receptor endocytosis. J Biol Chem 2013; 288:8952-65. [PMID: 23400781 PMCID: PMC3610968 DOI: 10.1074/jbc.m112.440719] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 02/08/2013] [Indexed: 11/06/2022] Open
Abstract
Kainate receptors exhibit a highly compartmentalized distribution within the brain; however, the molecular and cellular mechanisms that coordinate their expression at neuronal sites of action are poorly characterized. Here we report that the GluK1 and GluK2 kainate receptor subunits interact with the spectrin-actin binding scaffolding protein 4.1N through a membrane-proximal domain in the C-terminal tail. We found that this interaction is important for the forward trafficking of GluK2a receptors, their distribution in the neuronal plasma membrane, and regulation of receptor endocytosis. The association between GluK2a receptors and 4.1N was regulated by both palmitoylation and protein kinase C (PKC) phosphorylation of the receptor subunit. Palmitoylation of the GluK2a subunit promoted 4.1N association, and palmitoylation-deficient receptors exhibited reduced neuronal surface expression and compromised endocytosis. Conversely, PKC activation decreased 4.1N interaction with GluK2/3-containing kainate receptors in acute brain slices, an effect that was reversed after inhibition of PKC. Our data and previous studies therefore demonstrate that these two post-translational modifications have opposing effects on 4.1N association with GluK2 kainate and GluA1 AMPA receptors. The convergence of the signaling pathways regulating 4.1N protein association could thus result in the selective removal of AMPA receptors from the plasma membrane while simultaneously promoting the insertion and stabilization of kainate receptors, which may be important for tuning neuronal excitability and synaptic plasticity.
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Affiliation(s)
- Bryan A. Copits
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Geoffrey T. Swanson
- From the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
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42
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Maroto M, Fernández-Morales JC, Padín JF, González JC, Hernández-Guijo JM, Montell E, Vergés J, de Diego AMG, García AG. Chondroitin sulfate, a major component of the perineuronal net, elicits inward currents, cell depolarization, and calcium transients by acting on AMPA and kainate receptors of hippocampal neurons. J Neurochem 2013; 125:205-13. [PMID: 23350646 DOI: 10.1111/jnc.12159] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 10/08/2012] [Accepted: 01/15/2013] [Indexed: 12/19/2022]
Abstract
Chondroitin sulfate (CS) proteoglycans (CSPGs) are the most abundant PGs of the brain extracellular matrix (ECM). Free CS could be released during ECM degradation and exert physiological functions; thus, we aimed to investigate the effects of CS on voltage- and current-clamped rat embryo hippocampal neurons in primary cultures. We found that CS elicited a whole-cell Na(+)-dependent inward current (ICS) that produced drastic cell depolarization, and a cytosolic calcium transient ([Ca(2+)]c). Those effects were similar to those elicited by α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and kainate, were completely blocked by NBQX and CNQX, were partially blocked by GYKI, and were unaffected by MK801 and D-APV. Furthermore, ICS and AMPA currents were similarly potentiated by cyclothiazide, a positive allosteric modulator of AMPA receptors. Because CSPGs have been attributed Ca(2) (+) -dependent roles, such as neural network development, axon pathfinding, plasticity and regeneration after CNS injury, CS action after ECM degradation could be contributing to the mediation of these effects through its interaction with AMPA and kainate receptors.
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Affiliation(s)
- Marcos Maroto
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - José-Carlos Fernández-Morales
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Juan Fernando Padín
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - José C González
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Jesús M Hernández-Guijo
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Eulalia Montell
- Pre-Clinical R&D Area, Pharmascience Division, Bioibérica, Barcelona, Spain
| | - Josep Vergés
- Pre-Clinical R&D Area, Pharmascience Division, Bioibérica, Barcelona, Spain
| | - Antonio M G de Diego
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| | - Antonio G García
- Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.,Instituto de Investigación Sanitaria, Servicio de Farmacología Clínica, Hospital Universitario de la Princesa. Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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Ruiz AJ, Kullmann DM. Ionotropic receptors at hippocampal mossy fibers: roles in axonal excitability, synaptic transmission, and plasticity. Front Neural Circuits 2013; 6:112. [PMID: 23316138 PMCID: PMC3540408 DOI: 10.3389/fncir.2012.00112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/10/2012] [Indexed: 11/30/2022] Open
Abstract
Dentate granule cells process information from the enthorinal cortex en route to the hippocampus proper. These neurons have a very negative resting membrane potential and are relatively silent in the slice preparation. They are also subject to strong feed-forward inhibition. Their unmyelinated axon or mossy fiber ramifies extensively in the hilus and projects to stratum lucidum where it makes giant en-passant boutons with CA3 pyramidal neurons. There is compelling evidence that mossy fiber boutons express presynaptic GABAA receptors, which are commonly found in granule cell dendrites. There is also suggestive evidence for the presence of other ionotropic receptors, including glycine, NMDA, and kainate receptors, in mossy fiber boutons. These presynaptic receptors have been proposed to lead to mossy fiber membrane depolarization. How this phenomenon alters the excitability of synaptic boutons, the shape of presynaptic action potentials, Ca2+ influx and neurotransmitter release has remained elusive, but high-resolution live imaging of individual varicosities and direct patch-clamp recordings have begun to shed light on these phenomena. Presynaptic GABAA and kainate receptors have also been reported to facilitate the induction of long-term potentiation at mossy fiber—CA3 synapses. Although mossy fibers are highly specialized, some of the principles emerging at this connection may apply elsewhere in the CNS.
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Affiliation(s)
- Arnaud J Ruiz
- Department of Pharmacology, UCL School of Pharmacy London, UK
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44
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Wilkinson KA, Konopacki F, Henley JM. Modification and movement: Phosphorylation and SUMOylation regulate endocytosis of GluK2-containing kainate receptors. Commun Integr Biol 2012; 5:223-6. [PMID: 22808340 PMCID: PMC3376071 DOI: 10.4161/cib.19195] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Kainate receptors (KARs) are tetrameric glutamate-gated ion channels composed of combinations of the subunits GluK1-5. Depending on their precise localization and subunit composition, KARs can regulate neurotransmitter release, synaptic function and neuronal excitability. Because of these diverse roles, the regulated and precisely targeted trafficking of KARs is of crucial importance to neuronal function. We previously reported that the KAR subunit GluK2 is post-translationally modified by attachment of Small Ubiquitin-like Modifier 1 (SUMO-1) and that SUMOylation is required for agonist-dependent endocytosis of GluK2. We recently extended these findings to demonstrate that agonist activation leads to PKC-mediated phosphorylation of GluK2 at serine 868, which directly enhances GluK2 SUMOylation and, in turn, leads to endocytosis of the receptor. These new data demonstrate the importance of interplay between two post-translational modifications in orchestrating the temporal and spatial regulation of kainate receptor trafficking.
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Affiliation(s)
- Kevin A Wilkinson
- MRC Centre for Synaptic Plasticity; School of Biochemistry; Medical Sciences Building; University of Bristol; Bristol, UK
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45
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Chamberlain SEL, González-González IM, Wilkinson KA, Konopacki FA, Kantamneni S, Henley JM, Mellor JR. SUMOylation and phosphorylation of GluK2 regulate kainate receptor trafficking and synaptic plasticity. Nat Neurosci 2012; 15:845-52. [PMID: 22522402 PMCID: PMC3435142 DOI: 10.1038/nn.3089] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 03/14/2012] [Indexed: 02/07/2023]
Abstract
Phosphorylation or SUMOylation of the kainate receptor (KAR) subunit GluK2 have both individually been shown to regulate KAR surface expression. However, it is unknown whether phosphorylation and SUMOylation of GluK2 are important for activity-dependent KAR synaptic plasticity. We found that protein kinase C–mediated phosphorylation of GluK2 at serine 868 promotes GluK2 SUMOylation at lysine 886 and that both of these events are necessary for the internalization of GluK2-containing KARs that occurs during long-term depression of KAR-mediated synaptic transmission at rat hippocampal mossy fiber synapses. Conversely, phosphorylation of GluK2 at serine 868 in the absence of SUMOylation led to an increase in KAR surface expression by facilitating receptor recycling between endosomal compartments and the plasma membrane. Our results suggest a role for the dynamic control of synaptic SUMOylation in the regulation of KAR synaptic transmission and plasticity.
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Affiliation(s)
- Sophie E L Chamberlain
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Inmaculada M González-González
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Kevin A Wilkinson
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Filip A Konopacki
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Sriharsha Kantamneni
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jeremy M Henley
- MRC Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Jack R Mellor
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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46
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Gibbons AS, Brooks L, Scarr E, Dean B. AMPA receptor expression is increased post-mortem samples of the anterior cingulate from subjects with major depressive disorder. J Affect Disord 2012; 136:1232-7. [PMID: 22036795 PMCID: PMC3275646 DOI: 10.1016/j.jad.2011.10.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 01/05/2023]
Abstract
BACKGROUND Glutamate is thought to be involved in the pathophysiology of major depressive disorder and bipolar disorder; however, the molecular changes underlying abnormal glutamatergic signalling remain poorly understood. Whilst previous studies have suggested that the NMDA receptor may be involved in the pathophysiology of mood disorders, it is unclear whether the non-NMDA receptors are also involved. Therefore, we sought to examine whether the expression of the non-NMDA, ionotropic glutamate receptors, AMPA receptor and kainate receptor, is altered in mood disorders. METHODS We used [3H]AMPA and [3H]kainate to measure the levels of AMPA and kainate receptor, respectively, in the anterior cingulate (BA 24) and dorsolateral prefrontal cortex (BA 46) from post-mortem CNS in 10 subjects with major depressive disorder, 10 subjects with bipolar disorder and 10 control subjects. RESULTS A 20.7% to 27.7% increase in [3H]AMPA binding density was seen in BA 24 (p<0.05) but not BA 46 (p>0.05) in major depressive disorder compared to control levels. [3H]AMPA binding density was not changed in bipolar disorder in either BA 24 or BA 46 (p>0.05) compared to controls. [3H]Kainate binding was not changed in either BA 24 or BA 46 in either disorder compared to controls (p>0.05). LIMITATIONS Small sample sizes (n=10) were used in this study. The subjects were not drug naïve. CONCLUSIONS Our data suggests increased in AMPA receptor levels in the anterior cingulate are involved in the pathophysiology of major depressive disorder. This data has relevance for the development of new anti-depressant drugs targeted towards the AMPA receptors.
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Affiliation(s)
- Andrew Stuart Gibbons
- Rebecca L Cooper Laboratories, Mental Health Research Institute of Victoria, Parkville, Victoria 3052, Australia.
| | - Lucy Brooks
- Rebecca L Cooper Laboratories, Mental Health Research Institute of Victoria, Parkville, Victoria, Victoria 3052, Australia,Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria 3010, Australia,Department of Neuroscience, The University of Nottingham, Nottingham, UK
| | - Elizabeth Scarr
- Rebecca L Cooper Laboratories, Mental Health Research Institute of Victoria, Parkville, Victoria, Victoria 3052, Australia,Department of Psychiatry, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Brian Dean
- Rebecca L Cooper Laboratories, Mental Health Research Institute of Victoria, Parkville, Victoria, Victoria 3052, Australia,Department of Psychiatry, The University of Melbourne, Parkville, Victoria 3010, Australia,Department of Psychological Medicine, Monash University, Clayton, Victoria 3800, Australia
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Kumar J, Mayer ML. Crystal structures of the glutamate receptor ion channel GluK3 and GluK5 amino-terminal domains. J Mol Biol 2010; 404:680-96. [PMID: 20951142 PMCID: PMC2991425 DOI: 10.1016/j.jmb.2010.10.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 10/05/2010] [Accepted: 10/06/2010] [Indexed: 01/07/2023]
Abstract
Ionotropic glutamate receptors (iGluRs) mediate the majority of fast excitatory synaptic neurotransmission in the central nervous system. The selective assembly of iGluRs into AMPA, kainate, and N-methyl-d-aspartic acid (NMDA) receptor subtypes is regulated by their extracellular amino-terminal domains (ATDs). Kainate receptors are further classified into low-affinity receptor families (GluK1-GluK3) and high-affinity receptor families (GluK4-GluK5) based on their affinity for the neurotoxin kainic acid. These two families share a 42% sequence identity for the intact receptor but only a 27% sequence identity at the level of ATD. We have determined for the first time the high-resolution crystal structures of GluK3 and GluK5 ATDs, both of which crystallize as dimers but with a strikingly different dimer assembly at the R1 interface. By contrast, for both GluK3 and GluK5, the R2 domain dimer assembly is similar to those reported previously for other non-NMDA iGluRs. This observation is consistent with the reports that GluK4-GluK5 cannot form functional homomeric ion channels and require obligate coassembly with GluK1-GluK3. Our analysis also reveals that the relative orientation of domains R1 and R2 in individual non-NMDA receptor ATDs varies by up to 10°, in contrast to the 50° difference reported for the NMDA receptor GluN2B subunit. This restricted domain movement in non-NMDA receptor ATDs seems to result both from extensive intramolecular contacts between domain R1 and domain R2 and from their assembly as dimers, which interact at both R1 and R2 domains. Our results provide the first insights into the structure and function of GluK4-GluK5, the least understood family of iGluRs.
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Affiliation(s)
- Janesh Kumar
- Laboratory of Cellular and Molecular Neurophysiology, Porter Neuroscience Research Center, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Nasu-Nishimura Y, Jaffe H, Isaac JTR, Roche KW. Differential regulation of kainate receptor trafficking by phosphorylation of distinct sites on GluR6. J Biol Chem 2010; 285:2847-56. [PMID: 19920140 PMCID: PMC2807338 DOI: 10.1074/jbc.m109.081141] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Indexed: 11/06/2022] Open
Abstract
Kainate receptors are widely expressed in the brain, and are present at pre- and postsynaptic sites where they play a prominent role in synaptic plasticity and the regulation of network activity. Within individual neurons, kainate receptors of different subunit compositions are targeted to various locations where they serve distinct functional roles. Despite this complex targeting, relatively little is known about the molecular mechanisms regulating kainate receptor subunit trafficking. Here we investigate the role of phosphorylation in the trafficking of the GluR6 kainate receptor subunit. We identify two specific residues on the GluR6 C terminus, Ser(846) and Ser(868), which are phosphorylated by protein kinase C (PKC) and dramatically regulate GluR6 surface expression. By using GluR6 containing phosphomimetic and nonphosphorylatable mutations for these sites expressed in heterologous cells or in neurons lacking endogenous GluR6, we show that phosphorylation of Ser(846) or Ser(868) regulates receptor trafficking through the biosynthetic pathway. Additionally, Ser(846) phosphorylation dynamically regulates endocytosis of GluR6 at the plasma membrane. Our findings thus demonstrate that phosphorylation of PKC sites on GluR6 regulates surface expression of GluR6 at distinct intracellular trafficking pathways, providing potential molecular mechanisms for the PKC-dependent regulation of synaptic kainate receptor function observed during various forms of synaptic plasticity.
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Affiliation(s)
| | - Howard Jaffe
- From NINDS, National Institutes of Health, Bethesda, Maryland 20892
| | - John T. R. Isaac
- From NINDS, National Institutes of Health, Bethesda, Maryland 20892
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Schmid SM, Kott S, Sager C, Huelsken T, Hollmann M. The glutamate receptor subunit delta2 is capable of gating its intrinsic ion channel as revealed by ligand binding domain transplantation. Proc Natl Acad Sci U S A 2009; 106:10320-5. [PMID: 19506248 PMCID: PMC2700928 DOI: 10.1073/pnas.0900329106] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Indexed: 11/18/2022] Open
Abstract
The family of ionotropic glutamate receptors includes 2 subunits, delta1 and delta2, the physiological relevance of which remains poorly understood. Both are nonfunctional in heterologous expression systems, although the isolated, crystallized ligand binding domain (LBD) of delta2 is capable of binding D-serine. To investigate these seemingly contradictory observations we tested whether delta receptors can be ligand gated at all. We used a strategy that replaced the native LBD of delta2 by a proven glutamate-binding LBD. Test transplantations between alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) and kainate receptors (GluR1 and GluR6, respectively) showed that this approach can produce functional chimeras even if only one part of the bipartite LBD is swapped. Upon outfitting delta2 with the LBD of GluR6, the chimera formed glutamate-gated ion channels with low Ca(2+) permeability and unique rectification properties. Ligand-induced conformational changes can thus gate delta2, suggesting that the LBD of this receptor works fundamentally differently from that of other ionotropic glutamate receptors.
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Affiliation(s)
- Sabine M. Schmid
- Department of Biochemistry I–Receptor Biochemistry
- International Graduate School of Neuroscience
| | - Sabine Kott
- Department of Biochemistry I–Receptor Biochemistry
| | - Charlotte Sager
- Department of Biochemistry I–Receptor Biochemistry
- Ruhr University Research School, Ruhr University Bochum, Universitätsstrasse 150, D-44780 Bochum, Germany
| | | | - Michael Hollmann
- Department of Biochemistry I–Receptor Biochemistry
- International Graduate School of Neuroscience
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Barberis A, Sachidhanandam S, Mulle C. GluR6/KA2 kainate receptors mediate slow-deactivating currents. J Neurosci 2008; 28:6402-6. [PMID: 18562611 PMCID: PMC6670893 DOI: 10.1523/jneurosci.1204-08.2008] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Revised: 05/05/2008] [Accepted: 05/05/2008] [Indexed: 11/21/2022] Open
Abstract
Kainate receptors (KARs) are ionotropic glutamate receptors contributing to EPSCs with a slow-decaying component that is likely essential for synaptic integration. The slow kinetics of KAR-EPSCs markedly contrasts with the fast kinetics reported for recombinant KARs expressed in heterologous systems, for reasons that remain unexplained. Here we have studied the properties of recombinant heteromeric GluR6/KA2 receptors, which compose synaptic KARs. We report that, in response to brief glutamate applications, currents mediated by recombinant GluR6/KA2 receptors, but not GluR6 receptors, decay with a time course similar to KAR-EPSCs. Model simulations suggest that, after brief agonist exposures, GluR6/KA2 currents undergo slow deactivation caused by the stabilization of partially bound open states. We propose, therefore, that the GluR6/KA2 gating features could contribute to the slow KAR-EPSC decay kinetics.
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Affiliation(s)
- Andrea Barberis
- Laboratoire Physiologie Cellulaire de la Synapse, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5091, Bordeaux Neuroscience Institute, University of Bordeaux 2, 33077 Bordeaux, France
| | - Shankar Sachidhanandam
- Laboratoire Physiologie Cellulaire de la Synapse, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5091, Bordeaux Neuroscience Institute, University of Bordeaux 2, 33077 Bordeaux, France
| | - Christophe Mulle
- Laboratoire Physiologie Cellulaire de la Synapse, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5091, Bordeaux Neuroscience Institute, University of Bordeaux 2, 33077 Bordeaux, France
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