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Alharbi KS, Almalki WH, Alzarea SI, Kazmi I, Al-Abbasi FA, Afzal O, Altamimi ASA, Albratty M, Najmi A, Gupta G. Anaesthesia-induced Changes in Genomic Expression Leading to Neurodegeneration. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2024; 23:411-419. [PMID: 37157197 DOI: 10.2174/1871527322666230508123558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 02/21/2023] [Accepted: 02/23/2023] [Indexed: 05/10/2023]
Abstract
General anaesthetics (GA) have been in continuous clinical use for more than 170 years, with millions of young and elderly populations exposed to GA to relieve perioperative discomfort and carry out invasive examinations. Preclinical studies have shown that neonatal rodents with acute and chronic exposure to GA suffer from memory and learning deficits, likely due to an imbalance between excitatory and inhibitory neurotransmitters, which has been linked to neurodevelopmental disorders. However, the mechanisms behind anaesthesia-induced alterations in late postnatal mice have yet to be established. In this narrative review, we present the current state of knowledge on early life anaesthesia exposure-mediated alterations of genetic expression, focusing on insights gathered on propofol, ketamine, and isoflurane, as well as the relationship between network effects and subsequent biochemical changes that lead to long-term neurocognitive abnormalities. Our review provides strong evidence and a clear picture of anaesthetic agents' pathological events and associated transcriptional changes, which will provide new insights for researchers to elucidate the core ideas and gain an in-depth understanding of molecular and genetic mechanisms. These findings are also helpful in generating more evidence for understanding the exacerbated neuropathology, impaired cognition, and LTP due to acute and chronic exposure to anaesthetics, which will be beneficial for the prevention and treatment of many diseases, such as Alzheimer's disease. Given the many procedures in medical practice that require continuous or multiple exposures to anaesthetics, our review will provide great insight into the possible adverse impact of these substances on the human brain and cognition.
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Affiliation(s)
- Khalid Saad Alharbi
- Department of Pharmacology, College of Pharmacy, Jouf University, Sakaka, Al-Jouf, Saudi Arabia
| | - Waleed Hassan Almalki
- Department of Pharmacology, College of Pharmacy, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Sami I Alzarea
- Department of Pharmacology, College of Pharmacy, Jouf University, Sakaka, Al-Jouf, Saudi Arabia
| | - Imran Kazmi
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Fahad A Al-Abbasi
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Obaid Afzal
- Department of Pharmaceutical Chemistry, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al Kharj, 11942, Saudi Arabia
| | | | - Mohammed Albratty
- Department of Pharmaceutical Chemistry and Pharmacognosy, College of Pharmacy, Jazan University, P.O. Box. 114, Jazan 45142, Saudi Arabia
| | - Asim Najmi
- Department of Pharmaceutical Chemistry and Pharmacognosy, College of Pharmacy, Jazan University, P.O. Box. 114, Jazan 45142, Saudi Arabia
| | - Gaurav Gupta
- School of Pharmacy, Suresh Gyan Vihar University, Mahal Road, Jagatpura, 302017, Jaipur, India
- Department of Pharmacology, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India
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Masternak M, Koch A, Laulumaa S, Tapken D, Hollmann M, Jørgensen FS, Kastrup JS. Differences between the GluD1 and GluD2 receptors revealed by GluD1 X-ray crystallography, binding studies and molecular dynamics. FEBS J 2023; 290:3781-3801. [PMID: 36128700 DOI: 10.1111/febs.16631] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 07/29/2022] [Accepted: 09/20/2022] [Indexed: 08/03/2023]
Abstract
Ionotropic glutamate receptors are ligand-gated ion channels essential for fast excitatory neurotransmission in the brain. In contrast to most other members of the iGluR family, the subfamily of delta receptors, GluD1 and GluD2, does not bind glutamate but glycine/D-serine. GluD1 is widely expressed in the brain and the inner ear, where it is required for high-frequency hearing. Furthermore, it has been associated with schizophrenia, autism and depression. X-ray structures of the ligand-binding domain (LBD) of GluD2 have been published; however, no high-resolution structure is available for the ligand-binding domain of GluD1 (GluD1-LBD). Here, we report the X-ray crystal structure of the GluD1-LBD in its apo form at 2.57 Å resolution. Using isothermal titration calorimetry, we show that D-serine binds to the GluD1-LBD in an exothermic manner with a Kd of 160 μm, which is approximately five-fold greater than at GluD2. Furthermore, we identify Glu822 as a critical determinant of receptor activation in GluD1 A654T. In contrast to studies on the GluD2 lurcher mutant A654T, we did not observe any effect of 1 mm D-serine on the spontaneous currents at mouse GluD1 A654T by electrophysiological recordings of Xenopus laevis oocytes as previously also reported by others. These results point towards differences in the structure and dynamics between GluD1 and GluD2. Molecular dynamics simulations were employed to address this observation, suggesting that the apo structure of GluD1 is less flexible than the apo structure of GluD2 and that Pro725 in GluD1 may affect the interlobe closure of the ligand-binding domain of GluD1.
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Affiliation(s)
- Magdalena Masternak
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
| | - Angela Koch
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
- Institute of Neural and Sensory Physiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Saara Laulumaa
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
| | - Daniel Tapken
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
| | - Michael Hollmann
- Department of Biochemistry I - Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Germany
| | - Flemming Steen Jørgensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
- Research Cluster on Personalised Medicine, Copenhagen, Denmark
| | - Jette Sandholm Kastrup
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark
- Research Cluster on Molecular Neuroprotection, Copenhagen, Denmark
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3
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Kumar J, Popescu GK, Gantz SC. GluD receptors are functional ion channels. Biophys J 2023; 122:2383-2395. [PMID: 37177782 PMCID: PMC10323023 DOI: 10.1016/j.bpj.2023.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/27/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023] Open
Abstract
In this article, we review contemporary evidence that GluD receptors are functional ion channels whose depolarizing currents contribute to their biological functions, akin to all other members of the ionotropic glutamate receptor (iGluR) family.
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Affiliation(s)
- Janesh Kumar
- Laboratory of Membrane Protein Biology, Council of Scientific and Industrial Research (CSIR)-Centre for Cellular and Molecular Biology, Hyderabad, Telangana, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Gabriela K Popescu
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University of Buffalo, SUNY, Buffalo, New York
| | - Stephanie C Gantz
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, Iowa; Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa.
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4
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Burada AP, Vinnakota R, Kumar J. Cryo-EM structures of the ionotropic glutamate receptor GluD1 reveal a non-swapped architecture. Nat Struct Mol Biol 2020; 27:84-91. [PMID: 31925409 PMCID: PMC7025878 DOI: 10.1038/s41594-019-0359-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 11/27/2019] [Indexed: 01/06/2023]
Abstract
Ionotropic orphan delta receptors (GluD) are not gated by glutamate or
any other endogenous ligand but are grouped with ionotropic glutamate receptors
based on sequence similarity. GluD1 receptors play critical roles in
synaptogenesis, synapse maintenance and have been implicated in neuronal
disorders including schizophrenia, cognitive deficits, and cerebral ataxia. Here
we report cryo-electron microscopy structures of the rat GluD1 receptor
complexed with calcium and the ligand 7-chlorokynurenic acid, elucidating
molecular architecture and principles of receptor assembly. The structures
reveal a non-swapped architecture at the extracellular amino-terminal (ATD) and
ligand-binding domain (LBD) interface. This is in contrast to other families of
ionotropic glutamate receptors (iGluRs) where the dimer partners between the ATD
and LBD layers are swapped. Our results demonstrate that principles of
architecture and symmetry are not conserved between delta receptors and other
iGluRs and provide a molecular blueprint for understanding the functions of the
“orphan” class of iGluRs.
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Affiliation(s)
- Ananth Prasad Burada
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, India
| | - Rajesh Vinnakota
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, India
| | - Janesh Kumar
- Laboratory of Membrane Protein Biology, National Centre for Cell Science, NCCS Complex, S. P. Pune University, Pune, Maharashtra, India.
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Yadav R, Rimerman R, Scofield MA, Dravid SM. Mutations in the transmembrane domain M3 generate spontaneously open orphan glutamate δ1 receptor. Brain Res 2011; 1382:1-8. [PMID: 21215726 DOI: 10.1016/j.brainres.2010.12.086] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 12/28/2010] [Accepted: 12/30/2010] [Indexed: 12/22/2022]
Abstract
Glutamate delta-1 receptors (GluRδ1) are expressed in the adult hippocampus and inner ear and have recently been shown to be important for high-frequency hearing. Similar to the closest homolog glutamate delta-2 receptor (GluRδ2), no agonist-induced currents are observed from GluRδ1 receptors. In an effort to understand the function of the GluRδ1 subunit, we probed the conserved transmembrane 3 (TM3) region of the GluRδ1 subunit, where the GluRδ2 lurcher mutation is localized. Four mutations in the TM3 domain A650C, L652A, A654C, and F655A resulted in spontaneously open GluRδ1 channels suggesting that GluRδ1 receptors can form homomeric receptors. The leak currents were partially blocked by pentamidine but showed negligible inhibition by NASP. It has been demonstrated that extracellular Ca(2+) binds and stabilizes the ligand binding domain (LBD) dimer interface leading to potentiation of currents through GluRδ2(Lc) channels. We found that extracellular Ca(2+) potentiated the spontaneous currents through GluRδ1F655A suggesting that extracellular Ca(2+) may interact with the conserved residues at GluRδ1 LBD dimer interface. A recent study suggested that d-serine and glycine bind to the GluRδ2 LBD and reduce spontaneous currents through the GluRδ2(Lc) channels. d-Serine and glycine produced only a modest reduction of spontaneous currents through GluRδ1F655A and had no effect on the spontaneous current through GluRδ1L652A. However, spontaneous currents in a chimeric GluRδ1-δ2(Lc) were robustly inhibited by d-serine. These results suggest that the activation gate is conserved in GluRδ1 receptors. Moreover, the conformational changes induced by d-serine and extracellular Ca(2+) are conserved among GluRδ1 and GluRδ2 receptors.
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Affiliation(s)
- Roopali Yadav
- Department of Pharmacology, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178, USA
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6
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Sugimoto M, Sasaki S, Watanabe T, Nishimura S, Ideta A, Yamazaki M, Matsuda K, Yuzaki M, Sakimura K, Aoyagi Y, Sugimoto Y. Ionotropic glutamate receptor AMPA 1 is associated with ovulation rate. PLoS One 2010; 5:e13817. [PMID: 21072200 PMCID: PMC2972219 DOI: 10.1371/journal.pone.0013817] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Accepted: 10/14/2010] [Indexed: 11/18/2022] Open
Abstract
Ionotropic glutamate receptors mediate most excitatory neurotransmission in the central nervous system by opening ion channels upon the binding of glutamate. Despite the essential roles of glutamate in the control of reproduction and anterior pituitary hormone secretion, there is a limited understanding of how glutamate receptors control ovulation. Here we reveal the function of the ionotropic glutamate receptor AMPA-1 (GRIA1) in ovulation. Based on a genome-wide association study in Bos taurus, we found that ovulation rate is influenced by a variation in the N-terminal leucine/isoleucine/valine-binding protein (LIVBP) domain of GRIA1, in which serine is replaced by asparagine. GRIA1Asn has a weaker affinity to glutamate than GRIA1Ser, both in Xenopus oocytes and in the membrane fraction of bovine brain. This single amino acid substitution leads to the decreased release of gonadotropin-releasing hormone (GnRH) in immortalized hypothalamic GT1-7 cells. Cows with GRIA1Asn have a slower luteinizing hormone (LH) surge than cows with GRIA1Ser. In addition, cows with GRIA1Asn possess fewer immature ovarian follicles before superovulation and have a lower response to hormone treatment than cows with GRIA1Ser. Our work identified that GRIA1 is a critical mediator of ovulation and that GRIA1 might be a useful target for reproductive therapy.
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Affiliation(s)
| | - Shinji Sasaki
- Shirakawa Institute of Animal Genetics, Nishigo, Japan
| | | | | | | | - Maya Yamazaki
- Brain Research Institute, Niigata University, Niigata, Japan
| | - Keiko Matsuda
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan
| | - Kenji Sakimura
- Brain Research Institute, Niigata University, Niigata, Japan
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Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R. Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev 2010; 62:405-96. [PMID: 20716669 PMCID: PMC2964903 DOI: 10.1124/pr.109.002451] [Citation(s) in RCA: 2552] [Impact Index Per Article: 182.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.
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Affiliation(s)
- Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Rollins Research Center, 1510 Clifton Road, Atlanta, GA 30322-3090, USA.
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8
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To gate or not to gate: are the delta subunits in the glutamate receptor family functional ion channels? Mol Neurobiol 2008; 37:126-41. [PMID: 18521762 DOI: 10.1007/s12035-008-8025-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Accepted: 05/09/2008] [Indexed: 01/01/2023]
Abstract
The two delta receptor subunits remain the most puzzling enigma within the ionotropic glutamate receptor family. Despite the recent elucidation of the ligand-binding domain structure of delta2, many fundamental questions with regard to the subunits' mechanism of function still remain unanswered. Of necessity, the majority of studies on delta receptors focused on the metabotropic function of delta2, since electrophysiological approaches to date are limited to the characterization of spontaneous currents through the delta2-lurcher mutant. Indeed, accumulated evidence primarily from delta2-deficient transgenic mice suggest that major physiological roles of delta2 are mediated via metabotropic signaling by the subunit's C terminus. Why then would the subunits retain a conserved ion channel domain if they do not form functional ion channels? Any progress with regard to ionotropic function of the two delta subunits has been hampered by their largely unknown pharmacology. Even now that a pharmacological profile for delta2 is being established on the basis of the ligand-binding domain structure, wild-type delta2 channels in heterologous expression systems stay closed in the presence of molecules that have been demonstrated to bind to the receptor's ligand-binding domain. In this paper, we review the current knowledge of delta subunits focusing on the disputed ionotropic function.
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9
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Lalonde R, Strazielle C. Spontaneous and induced mouse mutations with cerebellar dysfunctions: behavior and neurochemistry. Brain Res 2006; 1140:51-74. [PMID: 16499884 DOI: 10.1016/j.brainres.2006.01.031] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Accepted: 01/12/2006] [Indexed: 11/20/2022]
Abstract
Grid2(Lc) (Lurcher), Grid2(ho) (hot-foot), Rora(sg) (staggerer), nr (nervous), Agtpbp1(pcd) (Purkinje cell degeneration), Reln(rl) (reeler), and Girk2(Wv) (Weaver) are spontaneous mutations with cerebellar atrophy, ataxia, and deficits in motor coordination tasks requiring balance and equilibrium. In addition to these signs, the Dst(dt) (dystonia musculorum) spinocerebellar mutant displays dystonic postures and crawling. More recently, transgenic models with human spinocerebellar ataxia mutations and alterations in calcium homeostasis have been shown to exhibit cerebellar anomalies and motor coordination deficits. We describe neurochemical characteristics of these mutants with respect to regional brain metabolism as well as amino acid and biogenic amine concentrations, uptake sites, and receptors.
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Affiliation(s)
- R Lalonde
- Université de Rouen, Faculté de Médecine et de Pharmacie, INSERM U614, 76183 Rouen Cedex, France.
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10
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Yamazaki M, Ohno-Shosaku T, Fukaya M, Kano M, Watanabe M, Sakimura K. A novel action of stargazin as an enhancer of AMPA receptor activity. Neurosci Res 2004; 50:369-74. [PMID: 15567474 DOI: 10.1016/j.neures.2004.10.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2004] [Accepted: 10/04/2004] [Indexed: 11/16/2022]
Abstract
Stargazin (gamma-2) is disrupted in the ataxic and epileptic mutant mouse, stargazer (stg). The striking defect in the stg cerebellum is the lack of functional AMPA receptors on granule cells. Recently, it has been reported that gamma-2 and its related molecules are crucial for the surface expression, synaptic targeting and recycling of AMPA receptors, being termed collectively as the transmembrane AMPA receptor regulatory proteins (TARPs). However, it is still unclear whether TARPs directly modulate AMPA receptor activity. Here we report that coexpression of GluRalpha1 (GluR1) with gamma-2 using HEK293 cells and Xenopus oocytes markedly enhanced glutamate-induced currents. This effect was far beyond the increase of AMPA receptor surface expression and accompanied by increased glutamate affinity and subunit cooperativity. Other member of TARPs (gamma-3, gamma-4, and gamma-8) also enhanced the current response through the AMPA receptors. The enhancing effect by gamma-2 coexpression was further observed for homomeric GluRalpha2 (GluR2) channels, which, when expressed alone, are known to produce only a small or negligible current response. These results suggest that gamma-2 not only promotes AMPA receptor surface expression but also directly modulates AMPA receptor activity.
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Affiliation(s)
- Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, 1-757 Asahimachi-dori, Niigata 951-8585, Japan
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Lalonde R, Hayzoun K, Selimi F, Mariani J, Strazielle C. Motor coordination in mice with hotfoot, Lurcher, and double mutations of the Grid2 gene encoding the delta-2 excitatory amino acid receptor. Physiol Behav 2004; 80:333-9. [PMID: 14637233 DOI: 10.1016/j.physbeh.2003.08.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Grid2(ho/ho) is a loss of function gene mutation resulting in abnormal dendritic arborizations of Purkinje cells. These mutants were compared in a series of motor coordination tests requiring balance and equilibrium to nonataxic controls (Grid2(ho/+)) and to a double mutant (Grid2(ho/Lc)) with an inserted Lc mutation. The performance of Grid2(ho/ho) mutant mice was poorer than that of controls on stationary beam, coat hanger, unsteady platform, and rotorod tests. Grid2(ho/Lc) did not differ from Grid2(Lc/+) mice. However, the insertion of the Lc mutation in Grid2(ho/Lc) potentiated the deficits found in Grid2(ho/ho) in stationary beam, unsteady platform, and rotorod tests. These results indicate a deleterious effect of the Lc mutation on Grid2-deficient mice.
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Affiliation(s)
- R Lalonde
- Faculté de Médecine et de Pharmacie, Université de Rouen, 22 bld Gambetta, Bâtiment de Recherche, EMI-INSERM 9906, IFRMP 23, 76183 Rouen, France.
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Abstract
The orphan glutamate receptor delta2 (GluRdelta2) is predominantly expressed in Purkinje cells and plays a crucial role in cerebellar functions: mice that lack the GluRdelta2 gene display ataxia and impaired synaptic plasticity. However, when expressed alone or with other glutamate receptors, GluRdelta2 does not form functional glutamate-gated ion channels nor does it bind to glutamate analogs. Therefore, the mechanisms by which GluRdelta2 participates in cerebellar functions have been elusive. Studies of mutant mice such as lurcher, hotfoot, and GluRdelta2 knockout mice have provided clues to the structure and function of GluRdelta2. GluRdelta2 has a channel pore similar to that of other glutamate receptors; the channel is functional at least when the lurcher mutation is present. GluRdelta2 must be transported to the Purkinje cell surface to function; the absence of surface GluRdelta2 causes the ataxic phenotype of hotfoot mice. In GluRdelta2-null mice, the presence of naked spines not innervated by parallel fibers may influence the sustained innervation of mutant Purkinje cells by multiple climbing fibers. From these results, several hypotheses about mechanisms by which GluRdelta2 functions are proposed in this article. Further characterization of GluRdelta2's functions will provide key insights into normal and abnormal cerebellar functions.
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Affiliation(s)
- Michisuke Yuzaki
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 N. Lauderdale Street, Memphis, TN 38105-2794, USA.
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