1
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Tellios V, Maksoud MJE, Lu WY. The expression and function of glutamate aspartate transporters in Bergmann glia are decreased in neuronal nitric oxide synthase-knockout mice during postnatal development. Glia 2022; 70:858-874. [PMID: 35006609 PMCID: PMC9304205 DOI: 10.1002/glia.24143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 12/28/2021] [Accepted: 12/30/2021] [Indexed: 12/02/2022]
Abstract
Bergmann glia (BG) predominantly use glutamate/aspartate transporters (GLAST) for glutamate uptake in the cerebellum. Recently, nitric oxide (NO) treatment has been shown to upregulate GLAST function and increase glutamate uptake in vitro. We previously discovered that neuronal nitric oxide synthase knockout (nNOS−/−) mice displayed structural and functional neuronal abnormalities in the cerebellum during development, in addition to previously reported motor deficits. Although these developmental deficits have been identified in the nNOS−/− cerebellum, it is unknown whether BG morphology and GLAST expression are also affected in the absence of nNOS in vivo. This study is the first to characterize BG morphology and GLAST expression during development in nNOS−/− mice using immunohistochemistry and western blotting across postnatal development. Results showed that BG in nNOS−/− mice exhibited abnormal morphology and decreased GLAST expression compared with wildtype (WT) mice across postnatal development. Treating ex vivo WT cerebellar slices with the NOS inhibitor L‐NAME decreased GLAST expression while treating nNOS−/− slices with the slow‐release NO‐donor NOC‐18 increased GLAST expression when compared with their respective controls. In addition, treating primary BG isolated from WT mice with the selective nNOS inhibitor 7N decreased the membrane expression of GLAST and influx of Ca2+/Na+, while treating nNOS−/− BG with SNAP increased the membrane expression of GLAST and Ca2+/Na+ influx. Moreover, the effects of SNAP on GLAST expression and Ca2+/Na+ influx in nNOS−/− BG were significantly reduced by a PKG inhibitor. Together, these results reveal a novel role for nNOS/NO signaling in BG development, regulated by a PKG‐mediated mechanism.
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Affiliation(s)
- Vasiliki Tellios
- Graduate Program of Neuroscience, The University of Western Ontario, London, ON, Canada.,Molecular Medicine Group, Robarts Research Institute, London, ON, Canada
| | - Matthew J E Maksoud
- Graduate Program of Neuroscience, The University of Western Ontario, London, ON, Canada.,Molecular Medicine Group, Robarts Research Institute, London, ON, Canada
| | - Wei-Yang Lu
- Graduate Program of Neuroscience, The University of Western Ontario, London, ON, Canada.,Molecular Medicine Group, Robarts Research Institute, London, ON, Canada.,Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada
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2
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Kokubo M, Toya S, Amano I, Takatsuru Y. Early-life stress induces motor coordination dysfunction in adult mice. J Physiol Sci 2018; 68:663-669. [PMID: 29164389 PMCID: PMC10717137 DOI: 10.1007/s12576-017-0580-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/13/2017] [Indexed: 12/26/2022]
Abstract
Although child abuse has become a serious social problem in most countries, the neural mechanisms by which it induces adulthood mental disorders is not yet fully understood. Mice exposed to early-life stresses, such as maternal deprivation (MD) during lactation, are a good model for studying the effects of neglect of humans in early life. Early-life stress induces structural/functional changes of neurons in the hippocampus, prefrontal cortex, and amygdala, and causes mental disorders in adulthood. In this study, we found motor coordination dysfunction in male MD mice. We also found that the expression levels of the aminomethylphosphonic acid receptor subunits GluA1 and GluA3 were high in the cerebellum of male MD mice. The basal activity of the cerebellum detected by field-potential analysis was higher in male MD mice than in male control mice. Caloric stimulation increased the activity of the cerebellum of control mice, but it did not significantly increase the activity of the cerebellum in male MD mice. We concluded that early-life stress induced a functional change in the cerebellum of MD mice and that this change induced motor coordination dysfunctions.
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Affiliation(s)
- Michifumi Kokubo
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Syutaro Toya
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Izuki Amano
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Yusuke Takatsuru
- Department of Medicine, Johmoh Hospital, Maebashi, Gunam, 379-2152, Japan.
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3
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Perkins EM, Clarkson YL, Suminaite D, Lyndon AR, Tanaka K, Rothstein JD, Skehel PA, Wyllie DJA, Jackson M. Loss of cerebellar glutamate transporters EAAT4 and GLAST differentially affects the spontaneous firing pattern and survival of Purkinje cells. Hum Mol Genet 2018; 27:2614-2627. [PMID: 29741614 PMCID: PMC6049029 DOI: 10.1093/hmg/ddy169] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 04/30/2018] [Accepted: 05/01/2018] [Indexed: 12/20/2022] Open
Abstract
Loss of excitatory amino acid transporters (EAATs) has been implicated in a number of human diseases including spinocerebellar ataxias, Alzhiemer's disease and motor neuron disease. EAAT4 and GLAST/EAAT1 are the two predominant EAATs responsible for maintaining low extracellular glutamate levels and preventing neurotoxicity in the cerebellum, the brain region essential for motor control. Here using genetically modified mice we identify new critical roles for EAAT4 and GLAST/EAAT1 as modulators of Purkinje cell (PC) spontaneous firing patterns. We show high EAAT4 levels, by limiting mGluR1 signalling, are essential in constraining inherently heterogeneous firing of zebrin-positive PCs. Moreover mGluR1 antagonists were found to restore regular spontaneous PC activity and motor behaviour in EAAT4 knockout mice. In contrast, GLAST/EAAT1 expression is required to sustain normal spontaneous simple spike activity in low EAAT4 expressing (zebrin-negative) PCs by restricting NMDA receptor activation. Blockade of NMDA receptor activity restores spontaneous activity in zebrin-negative PCs of GLAST knockout mice and furthermore alleviates motor deficits. In addition both transporters have differential effects on PC survival, with zebrin-negative PCs more vulnerable to loss of GLAST/EAAT1 and zebrin-positive PCs more vulnerable to loss of EAAT4. These findings reveal that glutamate transporter dysfunction through elevated extracellular glutamate and the aberrant activation of extrasynaptic receptors can disrupt cerebellar output by altering spontaneous PC firing. This expands our understanding of disease mechanisms in cerebellar ataxias and establishes EAATs as targets for restoring homeostasis in a variety of neurological diseases where altered cerebellar output is now thought to play a key role in pathogenesis.
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Affiliation(s)
- Emma M Perkins
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
| | - Yvonne L Clarkson
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
| | - Daumante Suminaite
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
| | - Alastair R Lyndon
- School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, John Muir Building, Riccarton, Edinburgh, UK
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-Ku, Tokyo, Japan
| | - Jeffrey D Rothstein
- Department of Neurology and Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Paul A Skehel
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
| | - David J A Wyllie
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, India
| | - Mandy Jackson
- The Centre for Discovery Brain Sciences, The University of Edinburgh, Hugh Robson Building, Edinburgh, UK
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4
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Ginsenoside Rb1 confers neuroprotection via promotion of glutamate transporters in a mouse model of Parkinson's disease. Neuropharmacology 2018; 131:223-237. [DOI: 10.1016/j.neuropharm.2017.12.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 11/17/2017] [Accepted: 12/05/2017] [Indexed: 12/18/2022]
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5
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Perkins EM, Suminaite D, Clarkson YL, Lee SK, Lyndon AR, Rothstein JD, Wyllie DJA, Tanaka K, Jackson M. Posterior cerebellar Purkinje cells in an SCA5/SPARCA1 mouse model are especially vulnerable to the synergistic effect of loss of β-III spectrin and GLAST. Hum Mol Genet 2018; 25:4448-4461. [PMID: 28173092 PMCID: PMC5409221 DOI: 10.1093/hmg/ddw274] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/05/2016] [Accepted: 08/11/2016] [Indexed: 12/26/2022] Open
Abstract
Clinical phenotypes of spinocerebellar ataxia type-5 (SCA5) and spectrin-associated autosomal recessive cerebellar ataxia type-1 (SPARCA1) are mirrored in mice lacking β-III spectrin (β-III-/-). One function of β-III spectrin is the stabilization of the Purkinje cell-specific glutamate transporter EAAT4 at the plasma membrane. In β-III-/- mice EAAT4 levels are reduced from an early age. In contrast levels of the predominant cerebellar glutamate transporter GLAST, expressed in Bergmann glia, only fall progressively from 3 months onwards. Here we elucidated the roles of these two glutamate transporters in cerebellar pathogenesis mediated through loss of β-III spectrin function by studying EAAT4 and GLAST knockout mice as well as crosses of both with β-III-/- mice. Our data demonstrate that EAAT4 loss, but not abnormal AMPA receptor composition, in young β-III-/- mice underlies early Purkinje cell hyper-excitability and that subsequent loss of GLAST, superimposed on the earlier deficiency of EAAT4, is responsible for Purkinje cell loss and progression of motor deficits. Yet the loss of GLAST appears to be independent of EAAT4 loss, highlighting that other aspects of Purkinje cell dysfunction underpin the pathogenic loss of GLAST. Finally, our results demonstrate that Purkinje cells in the posterior cerebellum of β-III-/- mice are most susceptible to the combined loss of EAAT4 and GLAST, with degeneration of proximal dendrites, the site of climbing fibre innervation, most pronounced. This highlights the necessity for efficient glutamate clearance from these regions and identifies dysregulation of glutamatergic neurotransmission particularly within the posterior cerebellum as a key mechanism in SCA5 and SPARCA1 pathogenesis.
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Affiliation(s)
- Emma M Perkins
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK
| | - Daumante Suminaite
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK
| | - Yvonne L Clarkson
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK
| | - Sin Kwan Lee
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK
| | - Alastair R Lyndon
- School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, John Muir Building, Riccarton, Edinburgh, UK
| | - Jeffrey D Rothstein
- Department of Neurology and Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - David J A Wyllie
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK.,Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, India
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-Ku, Tokyo, Japan
| | - Mandy Jackson
- The Centre for Integrative Physiology, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, UK
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6
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Sugimoto J, Tanaka M, Sugiyama K, Ito Y, Aizawa H, Soma M, Shimizu T, Mitani A, Tanaka K. Region-specific deletions of the glutamate transporter GLT1 differentially affect seizure activity and neurodegeneration in mice. Glia 2017; 66:777-788. [PMID: 29214672 DOI: 10.1002/glia.23281] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 11/21/2017] [Accepted: 11/24/2017] [Indexed: 11/06/2022]
Abstract
Glial glutamate transporter GLT1 plays a key role in the maintenance of extracellular glutamate homeostasis. Recent human genetic studies have suggested that de novo mutations in GLT1 (EAAT2) cause early-onset epilepsy with multiple seizure types. Consistent with these findings, global GLT1 null mice show lethal spontaneous seizures. The consequences of GLT1 dysfunction vary between different brain regions, suggesting that the role of GLT1 dysfunction in epilepsy may also vary with brain regions. In this study, we generated region-specific GLT1 knockout mice by crossing floxed-GLT1 mice with mice that express the Cre recombinase in a particular domain of the ventricular zone. Selective deletion of GLT1 in the diencephalon, brainstem and spinal cord is sufficient to reproduce the phenotypes (excess mortality, decreased body weight, and lethal spontaneous seizure) of the global GLT1 null mice. By contrast, dorsal forebrain-specific GLT1 knockout mice showed nonlethal complex seizures including myoclonic jerks, hyperkinetic running, spasm and clonic convulsion via the activation of NMDA receptors during a limited period from P12 to P14 and selective neuronal death in cortical layer II/III and the hippocampus. Thus, GLT1 dysfunction in the dorsal forebrain is involved in the pathogenesis of infantile epilepsy and GLT1 in the diencephalon, brainstem and spinal cord may play a critical role in preventing seizure-induced sudden death.
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Affiliation(s)
- Junya Sugimoto
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Moeko Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Kaori Sugiyama
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Yukiko Ito
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Hidenori Aizawa
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Miho Soma
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Tomoko Shimizu
- Laboratory of Physiology, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Akira Mitani
- Laboratory of Physiology, Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.,Center for Brain Integration Research (CBIR), TMDU, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
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7
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Kang S, Li J, Bekker A, Ye JH. Rescue of glutamate transport in the lateral habenula alleviates depression- and anxiety-like behaviors in ethanol-withdrawn rats. Neuropharmacology 2017; 129:47-56. [PMID: 29128307 DOI: 10.1016/j.neuropharm.2017.11.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 11/02/2017] [Accepted: 11/07/2017] [Indexed: 12/21/2022]
Abstract
Alcoholism and psychiatric disorders like depression and anxiety are often comorbid. Although the mechanisms underlying this comorbidity are unclear, emerging evidence suggests that maladaptation of the glial glutamate transporter GLT-1 may play a role. Findings from animal and human studies have linked aversive states, including those related to drugs of abuse and depression, to aberrant activity in the lateral habenula (LHb). The relationship between GLT-1 maladaptation, LHb activity, and abnormal behaviors related to alcohol withdrawal, however, remains unknown. Here we show that dihydrokainic acid (DHK), a GLT-1 blocker, potentiated glutamatergic transmission to LHb neurons in slices from ethanol naïve rats; this potentiation, though, was not observed in slices from rats withdrawn from repeated in vivo ethanol administration, suggesting reduced GLT-1 function. Furthermore, GLT-1 protein expression was reduced in the LHb of withdrawn rats. This reduction was restored by systemic administration of ceftriaxone, a β-lactam antibiotic known to increase GLT-1 expression. Systemic ceftriaxone treatment also normalized the hyperactivity of LHb neurons in slices from withdrawn rats, which was reversed by bath-applied DHK. Finally, systemic administration of ceftriaxone alleviated depression- and anxiety-like behaviors, which was fully blocked by intra-LHb administrations of DHK, suggesting that GLT-1's function in the LHb is critical. These findings highlight the significant role of LHb astrocytic GLT-1 in the hyperactivity of LHb neurons, and in depressive- and anxiety-like behaviors during ethanol withdrawal. Thus, GLT-1 in the LHb could serve as a therapeutic target for psychiatric disorders comorbid with ethanol withdrawal.
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Affiliation(s)
- Seungwoo Kang
- Department of Anesthesiology, Pharmacology, Physiology, and Neuroscience, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, NJ, USA
| | - Jing Li
- Department of Anesthesiology, Pharmacology, Physiology, and Neuroscience, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, NJ, USA
| | - Alex Bekker
- Department of Anesthesiology, Pharmacology, Physiology, and Neuroscience, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, NJ, USA
| | - Jiang-Hong Ye
- Department of Anesthesiology, Pharmacology, Physiology, and Neuroscience, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, NJ, USA.
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8
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Miyazaki T, Yamasaki M, Hashimoto K, Kohda K, Yuzaki M, Shimamoto K, Tanaka K, Kano M, Watanabe M. Glutamate transporter GLAST controls synaptic wrapping by Bergmann glia and ensures proper wiring of Purkinje cells. Proc Natl Acad Sci U S A 2017; 114:7438-7443. [PMID: 28655840 PMCID: PMC5514701 DOI: 10.1073/pnas.1617330114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Astrocytes regulate synaptic transmission through controlling neurotransmitter concentrations around synapses. Little is known, however, about their roles in neural circuit development. Here we report that Bergmann glia (BG), specialized cerebellar astrocytes that thoroughly enwrap Purkinje cells (PCs), are essential for synaptic organization in PCs through the action of the l-glutamate/l-aspartate transporter (GLAST). In GLAST-knockout mice, dendritic innervation by the main ascending climbing fiber (CF) branch was significantly weakened, whereas the transverse branch, which is thin and nonsynaptogenic in control mice, was transformed into thick and synaptogenic branches. Both types of CF branches frequently produced aberrant wiring to proximal and distal dendrites, causing multiple CF-PC innervation. Our electrophysiological analysis revealed that slow and small CF-evoked excitatory postsynaptic currents (EPSCs) were recorded from almost all PCs in GLAST-knockout mice. These atypical CF-EPSCs were far more numerous and had significantly faster 10-90% rise time than those elicited by glutamate spillover under pharmacological blockade of glial glutamate transporters. Innervation by parallel fibers (PFs) was also affected. PF synapses were robustly increased in the entire dendritic trees, leading to impaired segregation of CF and PF territories. Furthermore, lamellate BG processes were retracted from PC dendrites and synapses, leading to the exposure of these neuronal elements to the extracellular milieus. These synaptic and glial phenotypes were reproduced in wild-type mice after functional blockade of glial glutamate transporters. These findings highlight that glutamate transporter function by GLAST on BG plays important roles in development and maintenance of proper synaptic wiring and wrapping in PCs.
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Affiliation(s)
- Taisuke Miyazaki
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Miwako Yamasaki
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Kouichi Hashimoto
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
- Department of Neurophysiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Kazuhisa Kohda
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
- Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Keiko Shimamoto
- Bioorganic Research Institute, Suntory Foundation for Life Sciences, Kyoto, 619-0284, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, School of Biomedical Science and Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan;
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9
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Intracerebral Inoculation of Mouse-Passaged Saffold Virus Type 3 Affects Cerebellar Development in Neonatal Mice. J Virol 2016; 90:10007-10021. [PMID: 27581974 DOI: 10.1128/jvi.00864-16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/22/2016] [Indexed: 01/04/2023] Open
Abstract
Saffold virus (SAFV), a human cardiovirus, is occasionally detected in infants with neurological disorders, including meningitis and cerebellitis. We recently reported that SAFV type 3 isolates infect cerebellar glial cells, but not large neurons, in mice. However, the impact of this infection remained unclear. Here, we determined the neuropathogenesis of SAFV type 3 in the cerebella of neonatal ddY mice by using SAFV passaged in the cerebella of neonatal BALB/c mice. The virus titer in the cerebellum increased following the inoculation of each of five passaged strains. The fifth passaged strain harbored amino acid substitutions in the VP2 (H160R and Q239R) and VP3 (K62M) capsid proteins. Molecular modeling of the capsid proteins suggested that the VP2-H160R and VP3-K62M mutations alter the structural dynamics of the receptor binding surface via the formation of a novel hydrophobic interaction between the VP2 puff B and VP3 knob regions. Compared with the original strain, the passaged strain showed altered growth characteristics in human-derived astroglial cell lines and greater replication in the brains of neonatal mice. In addition, the passaged strain was more neurovirulent than the original strain, while both strains infected astroglial and neural progenitor cells in the mouse brain. Intracerebral inoculation of either the original or the passaged strain affected brain Purkinje cell dendrites, and a high titer of the passaged strain induced cerebellar hypoplasia in neonatal mice. Thus, infection by mouse-passaged SAFV affected cerebellar development in neonatal mice. This animal model contributes to the understanding of the neuropathogenicity of SAFV infections in infants. IMPORTANCE Saffold virus (SAFV) is a candidate neuropathogenic agent in infants and children, but the neuropathogenicity of the virus has not been fully elucidated. Recently, we evaluated the pathogenicity of two clinical SAFV isolates in mice. Similar to other neurotropic picornaviruses, these isolates showed mild infectivity of glial and neural progenitor cells, but not of large neurons, in the cerebellum. However, the outcome of this viral infection in the cerebellum has not been clarified. Here, we examined the tropism of SAFV in the cerebellum. We obtained an in vivo-passaged strain from the cerebella of neonatal mice and examined its genome and its neurovirulence in the neonatal mouse brain. The passaged virus showed high infectivity and neurovirulence in the brain, especially the cerebellum, and affected cerebellar development. This unique neonatal mouse model will be helpful for elucidating the neuropathogenesis of SAFV infections occurring early in life.
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10
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Amano I, Takatsuru Y, Toya S, Haijima A, Iwasaki T, Grasberger H, Refetoff S, Koibuchi N. Aberrant Cerebellar Development in Mice Lacking Dual Oxidase Maturation Factors. Thyroid 2016; 26:741-52. [PMID: 26914863 PMCID: PMC4860669 DOI: 10.1089/thy.2015.0034] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND Thyroid hormone (TH) plays a key role in the developing brain, including the cerebellum. TH deficiency induces organizational changes of the cerebellum, causing cerebellar ataxia. However, the mechanisms causing these abnormalities are poorly understood. Various animal models have been used to study the mechanism. Lacking dual oxidase (DUOX) and its maturation factor (DUOXA) are major inducers of congenital hypothyroidism. Thus, this study examined the organizational changes of the cerebellum using knockout mice of the Duoxa gene (Duoxa-/-). METHODS The morphological, behavioral, and electrophysiological changes were analyzed in wild type (Wt) and Duoxa-deficient (Duoxa-/-) mice from postnatal day (P) 10 to P30. To detect the changes in the expression levels of presynaptic proteins, Western blot analysis was performed. RESULTS The proliferation and migration of granule cells was delayed after P15 in Duoxa-/- mice. However, these changes disappeared by P25. Although the cerebellar structure of Duoxa-/- mice was not significantly different from that of Wt mice at P25, motor coordination was impaired. It was also found that the amplitude of paired-pulse facilitation at parallel fiber-Purkinje cell synapses decreased in Duoxa-/- mice, particularly at P15. There were no differences between expression levels of presynaptic proteins regulating neurotransmitter release at P25. CONCLUSIONS These results indicate that the anatomical catch-up growth of the cerebellum did not normalize its function because of the disturbance of neuronal circuits by the combined effect of hypothyroidism and functional disruption of the DUOX/DUOXA complex.
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Affiliation(s)
- Izuki Amano
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yusuke Takatsuru
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Syutaro Toya
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Asahi Haijima
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Toshiharu Iwasaki
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Helmut Grasberger
- Department of Medicine, The University of Chicago, Chicago, Illinois
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Samuel Refetoff
- Department of Medicine, The University of Chicago, Chicago, Illinois
- Department of Pediatrics, The University of Chicago, Chicago, Illinois
- Department of Genetics, The University of Chicago, Chicago, Illinois
| | - Noriyuki Koibuchi
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
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11
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Chrobak AA, Soltys Z. Bergmann Glia, Long-Term Depression, and Autism Spectrum Disorder. Mol Neurobiol 2016; 54:1156-1166. [PMID: 26809583 PMCID: PMC5310553 DOI: 10.1007/s12035-016-9719-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/12/2016] [Indexed: 12/22/2022]
Abstract
Bergmann glia (BG), a specific type of radial astrocytes in the cerebellum, play a variety of vital functions in the development of this structure. However, the possible role of BG in the development of abnormalities observed in individuals with autism spectrum disorder (ASD) seems to be underestimated. One of the most consistent findings observed in ASD patients is loss of Purkinje cells (PCs). Such a defect may be caused by dysregulation of glutamate homeostasis, which is maintained mainly by BG. Moreover, these glial cells are involved in long-term depression (LTD), a form of plasticity which can additionally subserve neuroprotective functions. The aim of presented review is to summarize the current knowledge about interactions which occur between PC and BG, with special emphasis on those which are relevant to the survival and proper functioning of cerebellar neurons.
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Affiliation(s)
- Adrian Andrzej Chrobak
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Gronostajowa St. 9, Cracow, 30-387, Poland. .,Faculty of Medicine, Jagiellonian University Medical College, Kopernika St. 21A, Cracow, 31-501, Poland.
| | - Zbigniew Soltys
- Department of Neuroanatomy, Institute of Zoology, Jagiellonian University, Gronostajowa St. 9, Cracow, 30-387, Poland
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12
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Ageta-Ishihara N, Yamazaki M, Konno K, Nakayama H, Abe M, Hashimoto K, Nishioka T, Kaibuchi K, Hattori S, Miyakawa T, Tanaka K, Huda F, Hirai H, Hashimoto K, Watanabe M, Sakimura K, Kinoshita M. A CDC42EP4/septin-based perisynaptic glial scaffold facilitates glutamate clearance. Nat Commun 2015; 6:10090. [PMID: 26657011 PMCID: PMC4682051 DOI: 10.1038/ncomms10090] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Accepted: 10/30/2015] [Indexed: 12/31/2022] Open
Abstract
The small GTPase-effector proteins CDC42EP1-5/BORG1–5 interact reciprocally with CDC42 or the septin cytoskeleton. Here we show that, in the cerebellum, CDC42EP4 is exclusively expressed in Bergmann glia and localizes beneath specific membrane domains enwrapping dendritic spines of Purkinje cells. CDC42EP4 forms complexes with septin hetero-oligomers, which interact with a subset of glutamate transporter GLAST/EAAT1. In Cdc42ep4−/− mice, GLAST is dissociated from septins and is delocalized away from the parallel fibre-Purkinje cell synapses. The excitatory postsynaptic current exhibits a protracted decay time constant, reduced sensitivity to a competitive inhibitor of the AMPA-type glutamate receptors (γDGG) and excessive baseline inward current in response to a subthreshold dose of a nonselective inhibitor of the glutamate transporters/EAAT1–5 (DL-TBOA). Insufficient glutamate-buffering/clearance capacity in these mice manifests as motor coordination/learning defects, which are aggravated with subthreshold DL-TBOA. We propose that the CDC42EP4/septin-based glial scaffold facilitates perisynaptic localization of GLAST and optimizes the efficiency of glutamate-buffering and clearance. Glutamate transporters mediate neurotransmitter reuptake at glutamatergic synapses. Here the authors show that CDC42 effector protein CDC42EP4 supports efficient glutamate clearance by promoting the tethering of a glutamate transporter GLAST to perisynaptic clusters of septins in Bergmann glia.
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Affiliation(s)
- Natsumi Ageta-Ishihara
- Division of Biological Sciences, Department of Molecular Biology, Nagoya University Graduate School of Science, Nagoya 464-8602, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Kohtarou Konno
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Hisako Nakayama
- Department of Neurophysiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Manabu Abe
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Kenji Hashimoto
- Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba 260-8670, Japan
| | - Tomoki Nishioka
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Showa, Nagoya 466-8560, Japan
| | - Kozo Kaibuchi
- Department of Cell Pharmacology, Nagoya University Graduate School of Medicine, Showa, Nagoya 466-8560, Japan
| | - Satoko Hattori
- Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Japan
| | - Tsuyoshi Miyakawa
- Division of Systems Medical Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Japan.,Center for Genetic Analysis of Behavior, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Fathul Huda
- Department of Neurophysiology and Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Hirokazu Hirai
- Department of Neurophysiology and Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
| | - Kouichi Hashimoto
- Department of Neurophysiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Makoto Kinoshita
- Division of Biological Sciences, Department of Molecular Biology, Nagoya University Graduate School of Science, Nagoya 464-8602, Japan
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13
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Gubellini P, Melon C, Dale E, Doller D, Kerkerian-Le Goff L. Distinct effects of mGlu4 receptor positive allosteric modulators at corticostriatal vs. striatopallidal synapses may differentially contribute to their antiparkinsonian action. Neuropharmacology 2014; 85:166-77. [PMID: 24866785 DOI: 10.1016/j.neuropharm.2014.05.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/21/2014] [Accepted: 05/15/2014] [Indexed: 12/20/2022]
Abstract
Metabotropic glutamate 4 (mGlu4) receptor is a promising target for the treatment of motor deficits in Parkinson's disease (PD). This is due in part to its localization at key basal ganglia (BG) synapses that become hyperactive in this pathology, particularly striatopallidal synapses. In this context, mGlu4 receptor activation using either orthosteric agonists or positive allosteric modulators (PAMs) improves motor symptoms in rodent PD models in certain conditions. However, literature data show that mGlu4 receptor PAMs have no effect at striatopallidal GABAergic synapses (unless combined with an orthosteric agonist) and on the firing activity of pallidal neurons, and fail to provide significant motor improvement in relevant PD models. This questions the mechanistic hypothesis that mGlu4 receptor PAMs should act at striatopallidal synapses to alleviate PD motor symptoms. To shed light on this issue, we performed brain slice electrophysiology experiments. We show that Lu AF21934, an mGlu4 PAM small-molecule probe-compound, was ineffective at striatopallidal synapses at all concentrations tested, while it significantly inhibited corticostriatal synaptic transmission. Similarly, Lu AF21934 did not affect electrophysiology readouts at striatopallidal synapses in the presence of haloperidol or in 6-hydroxydopamine-lesioned rats. Interestingly, co-application of Lu AF21934 with a glutamate transporter inhibitor revealed a significant inhibitory action at striatopallidal synapses. Possibly, this effect could rely on increased level/permanence of glutamate in the synaptic cleft. Such differential efficacy of mGlu4 receptor PAMs at corticostriatal vs. striatopallidal synapses raises several issues regarding the synaptic target(s) of these drugs in the BG, and challenges the mechanisms by which they alleviate motor deficits in experimental PD models.
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Affiliation(s)
- Paolo Gubellini
- Aix-Marseille Université, CNRS, IBDM UMR7288, 13009 Marseille, France.
| | - Christophe Melon
- Aix-Marseille Université, CNRS, IBDM UMR7288, 13009 Marseille, France
| | - Elena Dale
- Lundbeck Research USA, 215 College Road, Paramus, NJ 07652, USA
| | - Dario Doller
- Lundbeck Research USA, 215 College Road, Paramus, NJ 07652, USA
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14
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Activation of liver X receptor is protective against ethanol-induced developmental impairment of Bergmann glia and Purkinje neurons in the mouse cerebellum. Mol Neurobiol 2013; 49:176-86. [PMID: 23900741 DOI: 10.1007/s12035-013-8510-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 07/08/2013] [Indexed: 10/26/2022]
Abstract
Cerebellar Purkinje cell and granule cell development are coordinated by Bergmann glia, and are particularly sensitive to ethanol (EtOH) exposure. The liver X receptor (LXR) plays important roles in Bergmann glial development. However, the effect of LXR activation on EtOH-mediated impairment of Bergmann glia and subsequently on Purkinje cell dendritogenesis remains undetermined. Therefore, using immunohistochemistry, quantitative real-time PCR and Western blot, we tested the possible protection of LXR agonist T0901317 (T0) on Bergmann glia and Purkinje cell dendritogenesis in mice exposed to ethanol. Results showed that a brief exposure of EtOH on postnatal day (PD 5) significantly decreased the average body weight of mice at PD 6 without alteration in the brain weight. In EtOH-exposed mice, the number of migrating granule cells in the molecular layer was significantly decreased, and this effect was attenuated by pretreatment of T0. EtOH exposure also resulted in the significant reduction of calbindin-labeled Purkinje cells, their maximum dendrite length, and impairment of Purkinje cell dendritogenesis. Furthermore, EtOH induced the activation of microglia in the Purkinje cell layer and impaired the development of Bergmann glia. However, pretreatment of T0 effectively blocked all of these responses. These responses were found to be mediated by the inhibition of upregulated levels of β-catenin and transcription factor LEF1 in the cerebellum. Overall, the results suggest that activating LXRs on postnatal mice exposed to EtOH is protective to Bergmann glia, and thus may play a critical role in preventing EtOH-induced defects during cerebellar development.
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15
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Abstract
Visual information must be relayed through the lateral geniculate nucleus before it reaches the visual cortex. However, not all spikes created in the retina lead to postsynaptic spikes and properties of the retinogeniculate synapse contribute to this filtering. To understand the mechanisms underlying this filtering process, we conducted electrophysiology to assess the properties of signal transmission in the Long-Evans rat. We also performed SDS-digested freeze-fracture replica labeling to quantify the receptor and transporter distribution, as well as EM reconstruction to describe the 3D structure. To analyze the impact of transmitter diffusion on the activity of the receptors, simulations were integrated. We identified that a large contributor to the filtering is the marked paired-pulse depression at this synapse, which was intensified by the morphological characteristics of the contacts. The broad presynaptic and postsynaptic contact area restricts transmitter diffusion two dimensionally. Additionally, the presence of multiple closely arranged release sites invites intersynaptic spillover, which causes desensitization of AMPA receptors. The presence of AMPA receptors that slowly recover from desensitization along with the high presynaptic release probability and multivesicular release at each synapse also contribute to the depression. These features contrast with many other synapses where spatiotemporal spread of transmitter is limited by rapid transmitter clearance allowing synapses to operate more independently. We propose that the micrometer-order structure can ultimately affect the visual information processing.
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16
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Danjo R, Kawasaki F, Ordway RW. A tripartite synapse model in Drosophila. PLoS One 2011; 6:e17131. [PMID: 21359186 PMCID: PMC3040228 DOI: 10.1371/journal.pone.0017131] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 01/21/2011] [Indexed: 11/18/2022] Open
Abstract
Tripartite (three-part) synapses are defined by physical and functional interactions of glia with pre- and post-synaptic elements. Although tripartite synapses are thought to be of widespread importance in neurological health and disease, we are only beginning to develop an understanding of glial contributions to synaptic function. In contrast to studies of neuronal mechanisms, a significant limitation has been the lack of an invertebrate genetic model system in which conserved mechanisms of tripartite synapse function may be examined through large-scale application of forward genetics and genome-wide genetic tools. Here we report a Drosophila tripartite synapse model which exhibits morphological and functional properties similar to those of mammalian synapses, including glial regulation of extracellular glutamate, synaptically-induced glial calcium transients and glial coupling of synapses with tracheal structures mediating gas exchange. In combination with classical and cell-type specific genetic approaches in Drosophila, this model is expected to provide new insights into the molecular and cellular mechanisms of tripartite synapse function.
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Affiliation(s)
- Rie Danjo
- Department of Biology and Center for Molecular and Cellular Neuroscience, Pennsylvania State University, University Park, Pennsylvania
| | - Fumiko Kawasaki
- Department of Biology and Center for Molecular and Cellular Neuroscience, Pennsylvania State University, University Park, Pennsylvania
| | - Richard W. Ordway
- Department of Biology and Center for Molecular and Cellular Neuroscience, Pennsylvania State University, University Park, Pennsylvania
- * E-mail:
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17
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Satake S, Song SY, Konishi S, Imoto K. Glutamate transporter EAAT4 in Purkinje cells controls intersynaptic diffusion of climbing fiber transmitter mediating inhibition of GABA release from interneurons. Eur J Neurosci 2010; 32:1843-53. [PMID: 21070388 DOI: 10.1111/j.1460-9568.2010.07469.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neurotransmitters diffuse out of the synaptic cleft and act on adjacent synapses to exert concerted control of the synaptic strength within neural pathways that converge on single target neurons. The excitatory transmitter released from climbing fibers (CFs), presumably glutamate, is shown to inhibit γ-aminobutyric acid (GABA) release at basket cell (BC)-Purkinje cell (PC) synapses in the rat cerebellar cortex through its extrasynaptic diffusion and activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors on BC axon terminals. This study aimed at examining how the CF transmitter-diffusion-mediated presynaptic inhibition is controlled by glutamate transporters. Pharmacological blockade of the PC-selective neuronal transporter EAAT4 markedly enhanced CF-induced inhibition of GABAergic transmission. Tetanic CF-stimulation elicited long-term potentiation of glutamate transporters in PCs, and thereby attenuated the CF-induced inhibition. Combined use of electrophysiology and immunohistochemistry revealed a significant inverse relationship between the level of EAAT4 expression and the inhibitory action of CF-stimulation on the GABA release at different cerebellar lobules - the CF-induced inhibition was profound in lobule III, where the EAAT4 expression level was low, whereas it was minimal in lobule X, where EAAT4 was abundant. The findings clearly demonstrate that the neuronal glutamate transporter EAAT4 in PCs plays a critical role in the extrasynaptic diffusion of CF transmitter - it appears not only to retrogradely determine the degree of CF-mediated inhibition of GABAergic inputs to the PC by controlling the glutamate concentration for intersynaptic diffusion, but also regulate synaptic information processing in the cerebellar cortex depending on its differential regional distribution as well as use-dependent plasticity of uptake efficacy.
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Affiliation(s)
- Shin'ichiro Satake
- Department of Information Physiology, National Institute for Physiological Sciences (NIPS), Myodaiji-cho, Okazaki, Japan
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18
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Mashimo M, Okubo Y, Yamazawa T, Yamasaki M, Watanabe M, Murayama T, Iino M. Inositol 1,4,5-trisphosphate signaling maintains the activity of glutamate uptake in Bergmann glia. Eur J Neurosci 2010; 32:1668-77. [PMID: 20958799 DOI: 10.1111/j.1460-9568.2010.07452.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The maintenance of synaptic functions is essential for neuronal information processing in the adult brain. Astrocytes express glutamate transporters that rapidly remove glutamate from the extracellular space and they play a critical role in the precise operation of glutamatergic transmission. However, how the glutamate clearance function of astrocytes is maintained remains elusive. Here, we describe a maintenance mechanism for the glutamate uptake capacity of Bergmann glial cells (BGs) in the cerebellum. When inositol 1,4,5-trisphosphate (IP(3) ) signaling was chronically and selectively inhibited in BGs in vivo, the retention time of glutamate around parallel fiber-Purkinje cell synapses was increased. Under these conditions, a decrease in the level of the glutamate/aspartate transporter (GLAST) in BGs was observed. The same effects were observed after chronic in vivo inhibition of purinergic P2 receptors in the cerebellar cortex. These results suggest that the IP(3) signaling cascade is involved in regulating GLAST levels in BGs to maintain glutamate clearance in the mature cerebellum.
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Affiliation(s)
- Masato Mashimo
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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19
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Loss of beta-III spectrin leads to Purkinje cell dysfunction recapitulating the behavior and neuropathology of spinocerebellar ataxia type 5 in humans. J Neurosci 2010; 30:4857-67. [PMID: 20371805 DOI: 10.1523/jneurosci.6065-09.2010] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mutations in SPTBN2, the gene encoding beta-III spectrin, cause spinocerebellar ataxia type 5 in humans (SCA5), a neurodegenerative disorder resulting in loss of motor coordination. How these mutations give rise to progressive ataxia and what the precise role beta-III spectrin plays in normal cerebellar physiology are unknown. We developed a mouse lacking full-length beta-III spectrin and found that homozygous mice reproduced features of SCA5 including gait abnormalities, tremor, deteriorating motor coordination, Purkinje cell loss, and cerebellar atrophy (molecular layer thinning). In vivo analysis reveals an age-related reduction in simple spike firing rate in surviving beta-III(-/-) Purkinje cells, whereas in vitro studies show these neurons to have reduced spontaneous firing, smaller sodium currents, and dysregulation of glutamatergic neurotransmission. Our data suggest an early loss of EAAT4- (protein interactor of beta-III spectrin) and a subsequent loss of GLAST-mediated uptake may play a role in neuronal pathology. These findings implicate a loss of beta-III spectrin function in SCA5 pathogenesis and indicate that there are at least two physiological effects of beta-III spectrin loss that underpin a progressive loss of inhibitory cerebellar output, namely an intrinsic Purkinje cell membrane defect due to reduced sodium currents and alterations in glutamate signaling.
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20
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Takayasu Y, Iino M, Takatsuru Y, Tanaka K, Ozawa S. Functions of glutamate transporters in cerebellar Purkinje cell synapses. Acta Physiol (Oxf) 2009; 197:1-12. [PMID: 19583702 DOI: 10.1111/j.1748-1716.2009.02019.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Glutamate transporters play a critical role in the maintenance of low extracellular concentrations of glutamate, which prevents the overactivation of post-synaptic glutamate receptors. Four distinct glutamate transporters, GLAST/EAAT1, GLT-1/EAAT2, EAAC1/EAAT3 and EAAT4, are distributed in the molecular layer of the cerebellum, especially near glutamatergic synapses in Purkinje cells (PCs). This review summarizes the current knowledge about the differential roles of these transporters at excitatory synapses of PCs. Data come predominantly from electrophysiological experiments in mutant mice that are deficient in each of these transporter genes. GLAST expressed in Bergmann glia contributes to the clearing of the majority of glutamate that floods out of the synaptic cleft immediately after transmitter release from the climbing fibre (CF) and parallel fibre (PF) terminals. It is indispensable to maintain a one-to-one relationship in synaptic transmission at the CF synapses by preventing transcellular glutamate spillover. GLT-1 plays a similar but minor role in the uptake of glutamate as GLAST. Although the loss of neither GLAST nor GLT-1 affects cerebellar morphology, the deletion of both GLAST and GLT-1 genes causes the death of the mutant animal and hinders the folium formation of the cerebellum. EAAT4 removes the low concentrations of glutamate that escape from uptake by glial transporters, preventing the transmitter from spilling over into neighbouring synapses. It also regulates the activation of metabotropic glutamate receptor 1 (mGluR1) in perisynaptic regions at PF synapses, which in turn affects mGluR1-mediated events including slow EPSCs and long-term depression. No change in synaptic function is detected in mice that are deficient in EAAC1.
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Affiliation(s)
- Y Takayasu
- Department of Otolaryngology, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
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21
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Beurrier C, Bonvento G, Kerkerian-Le Goff L, Gubellini P. Role of glutamate transporters in corticostriatal synaptic transmission. Neuroscience 2009; 158:1608-15. [DOI: 10.1016/j.neuroscience.2008.11.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 11/10/2008] [Accepted: 11/11/2008] [Indexed: 10/21/2022]
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22
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Lippman JJ, Lordkipanidze T, Buell ME, Yoon SO, Dunaevsky A. Morphogenesis and regulation of Bergmann glial processes during Purkinje cell dendritic spine ensheathment and synaptogenesis. Glia 2009; 56:1463-77. [PMID: 18615636 DOI: 10.1002/glia.20712] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Astrocytes have an important role in synaptic formation and function but how astrocytic processes become associated with synaptic structures during development is not well understood. Here we analyzed the pattern of growth of the processes extending off the main Bergmann glial (BG) shafts during synaptogenesis in the cerebellum. We found that during this period, BG process outgrowth was correlated with increased ensheathment of dendritic spines. In addition, two-photon time-lapse imaging revealed that BG processes were highly dynamic, and processes became more stable as the period of spine ensheathment progressed. While process motility was dependent on actin polymerization, activity of cytoskeletal regulators Rac1 and RhoG did not play a role in glial process dynamics or density, but was critical for maintaining process length. We extended this finding to probe the relationship between process morphology and ensheathment, finding that shortened processes result in decreased coverage of the spine. Furthermore, we found that areas in which BG expressed dn-Rac1, and therefore had a lower level of synaptic ensheathment, showed an overall increase in synapse number. These analyses reveal how BG processes grow to surround synaptic structures, elucidate the importance of BG process structure for proper development of synaptic ensheathment, and reveal a role for ensheathment in synapse formation.
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Affiliation(s)
- Jocelyn J Lippman
- Department of Neuroscience, Brown University, Box G-LN, Providence, Rhode Island 02912, USA
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23
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Shimamoto K. Glutamate transporter blockers for elucidation of the function of excitatory neurotransmission systems. CHEM REC 2008; 8:182-99. [DOI: 10.1002/tcr.20145] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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24
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Takatsuru Y, Iino M, Tanaka K, Ozawa S. Contribution of glutamate transporter GLT-1 to removal of synaptically released glutamate at climbing fiber-Purkinje cell synapses. Neurosci Lett 2007; 420:85-9. [PMID: 17513050 DOI: 10.1016/j.neulet.2007.04.062] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Revised: 04/20/2007] [Accepted: 04/27/2007] [Indexed: 10/23/2022]
Abstract
Rapid removal of synaptically released glutamate from the extracellular space ensures a high signal-to-noise ratio in excitatory neurotransmission. In the cerebellum, glial glutamate transporters, GLAST and GLT-1, are co-localized in the processes of Bergmann glia wrapping excitatory synapses on Purkinje cells (PCs). Although GLAST is expressed six-fold more abundantly than GLT-1, the decay kinetics of climbing fiber-mediated excitatory postsynaptic currents (CF-EPSCs) in PCs in GLAST(-/-) mice are not different from those in wild-type (WT) mice. This raises a possibility that GLT-1 plays a significant role in clearing glutamate at CF-PC synapses despite its smaller amount of expression. Here, we studied the functions of GLT-1 and GLAST in the clearance of glutamate using GLAST(-/-) mice and GLT-1(-/-) mice. In the presence of cyclothiazide (CTZ) that attenuates the desensitization of AMPA receptors, the decay time constant of CF-EPSCs (tau(w)) in GLT-1(-/-) mice was slower than that in WT mice. However, the degree of this prolongation of tau(w) was less prominent compared to that in GLAST(-/-) mice. The values of tau(w) in GLT-1(-/-) mice and GLAST(-/-) mice were comparable to those estimated in WT mice in the presence of a potent blocker of glial glutamate transporters (2S,3S)-3-[3-(4-methoxybenzoylamino)benzyloxy]aspartate (PMB-TBOA) at 10 and 100 nM, which reduced the amplitudes of glutamate transporter currents elicited by CF stimulation in Bergmann glia to approximately 81 and approximately 28%, respectively. We conclude that GLT-1 plays a minor role compared to GLAST in clearing synaptically released glutamate at CF-PC synapses.
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Affiliation(s)
- Yusuke Takatsuru
- Department of Neurophysiology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan.
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25
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Kleim JA, Markham JA, Vij K, Freese JL, Ballard DH, Greenough WT. Motor learning induces astrocytic hypertrophy in the cerebellar cortex. Behav Brain Res 2007; 178:244-9. [PMID: 17257689 PMCID: PMC2575107 DOI: 10.1016/j.bbr.2006.12.022] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 12/03/2006] [Accepted: 12/28/2006] [Indexed: 01/12/2023]
Abstract
Motor skill learning, but not mere motor activity, is associated with an increase in both synapse number and glial cell volume within the cerebellar cortex. The increase in synapse number has been shown to persist for at least 4 weeks in the absence of continued training. The present experiment similarly examined how a prolonged interruption in training affects the training-induced increase in astrocytic volume. Adult female rats were randomly allocated to either an acrobatic motor learning condition (AC) or a motor control condition (MC). The AC animals were trained to traverse a complex series of obstacles and each AC animal was pair matched with an MC animal that traversed an obstacle-free runway. These groups were further assigned to one of three training conditions. Animals in the early condition were trained for 10 consecutive days, animals in the delay condition received the same 10 days of training followed by a 28-day period without training, and animals in the continuous condition were trained for the entire 38 days. Unbiased stereological techniques were used to determine that AC animals had a significantly greater volume of astrocytes per Purkinje cell in the cerebellar paramedian lobule than the MC animals, a difference which was reduced (and not statistically detectable) among animals in the delay condition. These findings demonstrate that learning triggers the hypertrophy of astrocytic processes and furthermore that, unlike learning-induced synaptogenesis, astrocytic growth is reduced in the absence of continued training.
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Affiliation(s)
- Jeffrey A. Kleim
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL, 32610
| | - Julie A. Markham
- Department of Psychology, University of Illinois, Urbana, Illinois, 61801
- Beckman Institute, University of Illinois, Urbana, Illinois, 61801
| | - Kapil Vij
- Department of Biology, University of Illinois, Urbana, Illinois, 61801
| | - Jennifer L. Freese
- Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois, 61801
| | - David H. Ballard
- Department of Psychology, University of Illinois, Urbana, Illinois, 61801
| | - William T. Greenough
- Department of Psychology, University of Illinois, Urbana, Illinois, 61801
- Department of Biology, University of Illinois, Urbana, Illinois, 61801
- Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois, 61801
- Department of Psychiatry, University of Illinois, Urbana, Illinois, 61801
- Department of Neuroscience Program, University of Illinois, Urbana, Illinois, 61801
- Beckman Institute, University of Illinois, Urbana, Illinois, 61801
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26
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Takayasu Y, Iino M, Shimamoto K, Tanaka K, Ozawa S. Glial glutamate transporters maintain one-to-one relationship at the climbing fiber-Purkinje cell synapse by preventing glutamate spillover. J Neurosci 2006; 26:6563-72. [PMID: 16775144 PMCID: PMC6674041 DOI: 10.1523/jneurosci.5342-05.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A glial glutamate transporter, GLAST, is expressed abundantly in Bergmann glia and plays a major role in glutamate uptake at the excitatory synapses in cerebellar Purkinje cells (PCs). It has been reported that a higher percentage of PCs in GLAST-deficient mice are multiply innervated by climbing fibers (CFs) than in the wild-type (WT) mice, and that CF-mediated EPSCs with small amplitude and slow rise time, designated as atypical slow CF-EPSCs, are observed in these mice. To clarify the mechanism(s) underlying the generation of these atypical CF-EPSCs, we used (2S,3S)-3-[3-(4-methoxybenzoylamino)benzyloxy]aspartate (PMB-TBOA), an inhibitor of glial glutamate transporters. After the application of PMB-TBOA, slow-rising CF-EPSCs were newly detected in WT mice, and their rise and decay kinetics were different from those of conventional fast-rising CF-EPSCs but similar to those of atypical CF-EPSCs in GLAST-deficient mice. Furthermore, both slow-rising CF-EPSCs in the presence of PMB-TBOA in WT mice and atypical CF-EPSCs in GLAST-deficient mice showed much greater paired-pulse depression compared with fast-rising CF-EPSCs. In addition, both of them were more markedly inhibited by gamma-d-glutamyl-glycine, a low-affinity competitive antagonist of AMPA receptors. These results indicated that both of these types of EPSCs were mediated by a low concentration of glutamate released from neighboring CFs. Based on all of these findings, we suggest that glial transporters prevent glutamate released from a single CF from spilling over to neighboring PCs other than the synaptically connected PC, and play an essential role in the maintenance of the functional one-to-one relationship between CFs and PCs.
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Affiliation(s)
- Yukihiro Takayasu
- Department of Neurophysiology, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan.
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