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Sears SM, Hewett SJ. Influence of glutamate and GABA transport on brain excitatory/inhibitory balance. Exp Biol Med (Maywood) 2021; 246:1069-1083. [PMID: 33554649 DOI: 10.1177/1535370221989263] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
An optimally functional brain requires both excitatory and inhibitory inputs that are regulated and balanced. A perturbation in the excitatory/inhibitory balance-as is the case in some neurological disorders/diseases (e.g. traumatic brain injury Alzheimer's disease, stroke, epilepsy and substance abuse) and disorders of development (e.g. schizophrenia, Rhett syndrome and autism spectrum disorder)-leads to dysfunctional signaling, which can result in impaired cognitive and motor function, if not frank neuronal injury. At the cellular level, transmission of glutamate and GABA, the principle excitatory and inhibitory neurotransmitters in the central nervous system control excitatory/inhibitory balance. Herein, we review the synthesis, release, and signaling of GABA and glutamate followed by a focused discussion on the importance of their transport systems to the maintenance of excitatory/inhibitory balance.
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Affiliation(s)
- Sheila Ms Sears
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, 2029Syracuse University, Syracuse, NY 13244, USA
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Malik AR, Willnow TE. Excitatory Amino Acid Transporters in Physiology and Disorders of the Central Nervous System. Int J Mol Sci 2019; 20:ijms20225671. [PMID: 31726793 PMCID: PMC6888459 DOI: 10.3390/ijms20225671] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/07/2019] [Accepted: 11/11/2019] [Indexed: 12/12/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) encompass a class of five transporters with distinct expression in neurons and glia of the central nervous system (CNS). EAATs are mainly recognized for their role in uptake of the amino acid glutamate, the major excitatory neurotransmitter. EAATs-mediated clearance of glutamate released by neurons is vital to maintain proper glutamatergic signalling and to prevent toxic accumulation of this amino acid in the extracellular space. In addition, some EAATs also act as chloride channels or mediate the uptake of cysteine, required to produce the reactive oxygen speciesscavenger glutathione. Given their central role in glutamate homeostasis in the brain, as well as their additional activities, it comes as no surprise that EAAT dysfunctions have been implicated in numerous acute or chronic diseases of the CNS, including ischemic stroke and epilepsy, cerebellar ataxias, amyotrophic lateral sclerosis, Alzheimer’s disease and Huntington’s disease. Here we review the studies in cellular and animal models, as well as in humans that highlight the roles of EAATs in the pathogenesis of these devastating disorders. We also discuss the mechanisms regulating EAATs expression and intracellular trafficking and new exciting possibilities to modulate EAATs and to provide neuroprotection in course of pathologies affecting the CNS.
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Affiliation(s)
- Anna R. Malik
- Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland
- Correspondence:
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Roberts RC, Roche JK, McCullumsmith RE. Localization of excitatory amino acid transporters EAAT1 and EAAT2 in human postmortem cortex: a light and electron microscopic study. Neuroscience 2014; 277:522-40. [PMID: 25064059 PMCID: PMC4164610 DOI: 10.1016/j.neuroscience.2014.07.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 07/14/2014] [Indexed: 01/03/2023]
Abstract
The process of glutamate release, activity, and reuptake involves the astrocyte, the presynaptic and postsynaptic neurons. Glutamate is released into the synapse and may occupy and activate receptors on both neurons and astrocytes. Glutamate is rapidly removed from the synapse by a family of plasma membrane excitatory amino acid transporters (EAATs), also localized to neurons and astrocytes. The purpose of the present study was to examine EAAT labeling in the postmortem human cortex at the light and electron microscopic (EM) levels. The postmortem prefrontal cortex was processed for EAAT1 and EAAT2 immunohistochemistry. At the light microscopic level, EAAT1 and EAAT2 labeling was found in both gray and white matter. Most cellular labeling was in small cells which were morphologically similar to glia. In addition, EAAT1-labeled neurons were scattered throughout, some of which were pyramidal in shape. At the EM level, EAAT1 and EAAT2 labeling was found in astrocytic soma and processes surrounding capillaries. EAAT labeling was also found in small astrocytic processes adjacent to axon terminals forming asymmetric (glutamatergic) synapses. While EAAT2 labeling was most prevalent in astrocytic processes, EAAT1 labeling was also present in neuronal processes including the soma, axons, and dendritic spines. Expression of EAAT1 protein on neurons may be due to the hypoxia associated with the postmortem interval, and requires further confirmation. The localization of EAATs on the astrocytic plasma membrane and adjacent to excitatory synapses is consistent with the function of facilitating glutamate reuptake and limiting glutamate spillover. Establishment that EAAT1 and EAAT2 can be measured at the EM level in human postmortem tissues will permit testing of hypotheses related to these molecules in diseases lacking analogous animal models.
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Affiliation(s)
- R C Roberts
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - J K Roche
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - R E McCullumsmith
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Massie A, Cnops L, Smolders I, McCullumsmith R, Kooijman R, Kwak S, Arckens L, Michotte Y. High-affinity Na+/K+-dependent glutamate transporter EAAT4 is expressed throughout the rat fore- and midbrain. J Comp Neurol 2008; 511:155-72. [DOI: 10.1002/cne.21823] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Billiards SS, Pierson CR, Haynes RL, Folkerth RD, Kinney HC. Is the late preterm infant more vulnerable to gray matter injury than the term infant? Clin Perinatol 2006; 33:915-33; abstract x-xi. [PMID: 17148012 DOI: 10.1016/j.clp.2006.10.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This article addresses the issue of whether the late preterm infant is more susceptible to gray matter injury induced by hypoxia-ischemia than the term infant. Although different gray matter regions display varying patterns of neuronal injury in the face of hypoxia-ischemia during advancing gestational development, little is known about the specific patterns of injury faced by the late preterm infant. This changing pattern of neuronal vulnerability with age likely reflects developmental changes of susceptibility and protective factors essential for responding to energy deprivation at the molecular, cellular, biochemical, and vascular levels. Future research involving closer examination of the late preterm period is essential to provide a greater understanding of the neuronal vulnerability in the face of hypoxic-ischemic injury.
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Affiliation(s)
- Saraid S Billiards
- Department of Pathology, Enders Building, Room 1109, Children's Hospital Boston, Boston, MA 02115, USA.
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Pignataro L, Sitaramayya A, Finnemann SC, Sarthy VP. Nonsynaptic localization of the excitatory amino acid transporter 4 in photoreceptors. Mol Cell Neurosci 2005; 28:440-51. [PMID: 15737735 DOI: 10.1016/j.mcn.2004.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Revised: 10/01/2004] [Accepted: 10/06/2004] [Indexed: 11/27/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) are involved in regulating extracellular glutamate levels at synaptic regions in the CNS. EAAT1, 2, 3, and 5 have been found in the mammalian retina, but the presence of EAAT4 has remained controversial. Recently, we found a high level of EAAT4 mRNA in the human retina, and this observation lead us to examine whether EAAT4 was expressed in the mammalian retina. Immunoblotting studies showed the presence of EAAT4-immunoreactive proteins in human and mouse retinas, corresponding to EAAT4 monomers and dimers. Immunohistochemistry revealed that EAAT4 was localized in rod and cone photoreceptor outer segments in the human retina, and in the outer and inner segments of mouse and ground squirrel retinas. In no case was EAAT4 found in the outer plexiform layer or in any other layer in the retina. EAAT4 expression by photoreceptors was confirmed by immunoblotting a purified rod outer segment preparation, which showed the presence of a 50-kDa EAAT4-immunoreactive protein. In addition, the EAAT4-associated protein, GTRAP41, was found in the human, mouse, and squirrel retinas as well as in the rod outer segment preparation. Further immunocytochemical and co-immunoprecipitation experiments demonstrated that GTRAP41 was colocalized and interacted in vivo with EAAT4. Importantly, glutamate uptake and drug inhibition experiments showed that an EAAT4-like glutamate uptake system is present in the rod outer segments. Finally, we examined whether glutamate signaling mediated by EAAT4 can modulate rod outer segment phagocytosis by the retinal pigment epithelium. Results of the present study show that EAAT4 is present in the outer segments, a nonsynaptic region of photoreceptors, where it might provide a feedback mechanism for sensing extracellular glutamate or serve as an outer barrier to prevent glutamate from escaping from the retina.
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Affiliation(s)
- Leonardo Pignataro
- Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Dunlop J, Zaleska MM, Eliasof S, Moyer JA. Excitatory amino acid transporters as emerging targets for central nervous system therapeutics. ACTA ACUST UNITED AC 2005. [DOI: 10.1517/14728222.3.4.543] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Maragakis NJ, Dietrich J, Wong V, Xue H, Mayer-Proschel M, Rao MS, Rothstein JD. Glutamate transporter expression and function in human glial progenitors. Glia 2004; 45:133-43. [PMID: 14730707 DOI: 10.1002/glia.10310] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Glutamate is the major neurotransmitter of the brain, whose extracellular levels are tightly controlled by glutamate transporters. Five glutamate transporters in the human brain (EAAT1-5) are present on both astroglia and neurons. We characterize the profile of three different human astroglial progenitors in vitro: human glial restricted precursors (HGRP), human astrocyte precursors (HAPC), and early-differentiated astrocytes. EAAT 1, EAAT3, and EAAT4 are all expressed in GRPs with a subsequent upregulation of EAAT1 following differentiation of GRPs into GRP-derived astrocytes in the presence of bone morphogenic protein (BMP-4). This corresponds to a significant increase in the glutamate transport capacity of these cells. EAAT2, the transporter responsible for the bulk of glutamate transport in the adult brain, is not expressed as a full-length protein, nor does it appear to have functional significance (as determined by the EAAT2 inhibitor dihydrokainate) in these precursors. A splice variant of EAAT2, termed EAAT2b, does appear to be present in low levels, however. EAAT3 and EAAT4 expression is reduced as glial maturation progresses both in astrocyte precursors and early-differentiated astrocytes and is consistent with their role in adult tissues as primarily neuronal glutamate transporters. These human glial precursors offer several advantages as tools for understanding glial biology because they can be passaged extensively in the presence of mitogens, afford the potential to study the temporal changes in glutamate transporter expression in a tightly controlled fashion, and are cultured in the absence of neuronal coculture, allowing for the independent study of astroglial biology.
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Affiliation(s)
- Nicholas J Maragakis
- Department of Neurology and Neuroscience, Johns Hopkins University, Meyer 6-109, 600 N. Wolfe Street, Baltimore, MD 21287-5953, USA
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Abstract
The object of this review is to assemble much of the literature concerning Purkinje cell death in cerebellar pathology and to relate this to what is now known about the complex topography of the cerebellar cortex. A brief introduction to Purkinje cells, and their regionalization is provided, and then the data on Purkinje cell death in mouse models and, where appropriate, their human counterparts, have been arranged according to several broad categories--naturally-occurring and targeted mutations leading to Purkinje cell death, Purkinje cell death due to toxins, Purkinje cell death in ischemia, Purkinje cell death in infection and in inherited disorders, etc. The data reveal that cerebellar Purkinje cell death is much more topographically complex than is usually appreciated.
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Affiliation(s)
- Justyna R Sarna
- Genes Development Research Group, Department of Cell Biology & Anatomy, Faculty of Medicine, The University of Calgary, 3330 Hospital Drive NW, Calgary, Alta., Canada T2N 4N1
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Hu WH, Walters WM, Xia XM, Karmally SA, Bethea JR. Neuronal glutamate transporter EAAT4 is expressed in astrocytes. Glia 2003; 44:13-25. [PMID: 12951653 DOI: 10.1002/glia.10268] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
High-affinity excitatory amino acid transporters (EAATs) are essential to terminate glutamatergic neurotransmission and to prevent excitotoxicity. To date, five distinct EAATs have been cloned from animal and human tissues: GLAST (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), EAAT4, and EAAT5. EAAT1 and EAAT2 are commonly known as glial glutamate transporters, whereas EAAT3, EAAT4, and EAAT5 are neuronal. EAAT4 is largely expressed in cerebellar Purkinje cells. In this study, using immunohistochemistry and Western blotting, we found that EAAT4-like immunoreactivity (ir) is enriched in the spinal cord and forebrain. Double-labeled fluorescent immunostaining and confocal image analysis indicated that EAAT4-like ir colocalizes with an astrocytic marker, glial fibrillary acidic protein (GFAP). The astrocytic localization of EAAT4 was further confirmed in astrocyte cultures by double-labeled fluorescent immunocytochemistry and Western blotting. Reverse transcriptase-polymerase chain reaction analysis demonstrated mRNA expression of EAAT4 in astrocyte cultures. Sequencing confirmed the specificity of the amplified fragment. These results demonstrate that EAAT4 is expressed in astrocytes. This astrocytic localization of neuronal EAAT4 may reveal a new function of EAAT4 in the central nervous system.
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Affiliation(s)
- Wen-Hui Hu
- The Miami Project to Cure Paralysis, University of Miami School of Medicine, Miami, Florida 33136, USA
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Piao YS, Mori F, Hayashi S, Tanji K, Yoshimoto M, Kakita A, Wakabayashi K, Takahashi H. Alpha-synuclein pathology affecting Bergmann glia of the cerebellum in patients with alpha-synucleinopathies. Acta Neuropathol 2003; 105:403-9. [PMID: 12624794 DOI: 10.1007/s00401-002-0655-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2002] [Revised: 10/31/2002] [Accepted: 10/31/2002] [Indexed: 11/25/2022]
Abstract
We carried out immunohistochemical examinations of the brains (cerebella) of patients who had suffered from Parkinson's disease (PD), diffuse Lewy body disease (DLBD) or multiple system atrophy (MSA), using antibodies specific for alpha-synuclein. Alpha-synuclein-positive doughnut-shaped structures were found occasionally in the cerebellar molecular layer in some of these patients. Double-labeling immunofluorescence and immunoelectron microscopy studies revealed that these alpha-synuclein-positive doughnut-shaped structures were located in the glial fibrillary acidic protein-positive radial processes of Bergmann glia, corresponding to the outer area of Lewy body-like inclusions, and consisted of granulo-filamentous structures. These findings indicate that, although not frequently, Bergmann glia of the cerebellum are also the targets of alpha-synuclein pathology in alpha-synucleinopathies such as PD, DLBD and MSA.
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Affiliation(s)
- Yue-Shan Piao
- Department of Pathology, Brain Research Institute, Niigata University, 1-757 Asahimachi, 951-8585 Niigata, Japan.
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Suchak SK, Baloyianni NV, Perkinton MS, Williams RJ, Meldrum BS, Rattray M. The 'glial' glutamate transporter, EAAT2 (Glt-1) accounts for high affinity glutamate uptake into adult rodent nerve endings. J Neurochem 2003; 84:522-32. [PMID: 12558972 DOI: 10.1046/j.1471-4159.2003.01553.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The excitatory amino acid transporters (EAAT) removes neurotransmitters glutamate and aspartate from the synaptic cleft. Most CNS glutamate uptake is mediated by EAAT2 into glia, though nerve terminals show evidence for uptake, through an unknown transporter. Reverse-transcriptase PCR identified the expression of EAAT1, EAAT2, EAAT3 and EAAT4 mRNAs in primary cultures of mouse cortical or striatal neurones. We have used synaptosomes and glial plasmalemmal vesicles (GPV) from adult mouse and rat CNS to identify the nerve terminal transporter. Western blotting showed detectable levels of the transporters EAAT1 (GLAST) and EAAT2 (Glt-1) in both synaptosomes and GPVs. Uptake of [3H]D-aspartate or [3H]L-glutamate into these preparations revealed sodium-dependent uptake in GPV and synaptosomes which was inhibited by a range of EAAT blockers: dihydrokainate, serine-o-sulfate, l-trans-2,4-pyrrolidine dicarboxylate (PDC) (+/-)-threo-3-methylglutamate and (2S,4R )-4-methylglutamate. The IC50 values found for these compounds suggested functional expression of the 'glial, transporter, EAAT2 in nerve terminals. Additionally blockade of the majority EAAT2 uptake sites with 100 micro m dihydrokainate, failed to unmask any functional non-EAAT2 uptake sites. The data presented in this study indicate that EAAT2 is the predominant nerve terminal glutamate transporter in the adult rodent CNS.
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Affiliation(s)
- Sachin K Suchak
- Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London, United Kingdom
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Raiteri L, Raiteri M, Bonanno G. Coexistence and function of different neurotransmitter transporters in the plasma membrane of CNS neurons. Prog Neurobiol 2002; 68:287-309. [PMID: 12498989 DOI: 10.1016/s0301-0082(02)00059-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Transporters able to recapture released neurotransmitters into neurons can no longer be considered as cell-specific neuronal markers. In fact, colocalization on one nerve terminal of transporters able to selectively recapture the released endogenously synthesized transmitter (homotransporters) and of transporters that can selectively take up transmitters/modulators originating from neighboring structures (heterotransporters) has been demonstrated to occur on several families of nerve terminals. Activation of heterotransporters often increases the release of the transmitter stored in the terminals on which the heterotransporters are localized. The release caused by heterotransporter activation takes place through multiple mechanisms including exocytosis, either dependent on external Ca(2+) or on Ca(2+) mobilized from intraterminal stores, and homotransporter reversal. Homocarrier-mediated release elicited by heterocarrier activation represents a clear case of transporter-transporter interaction. Although the functional significance of transporter coexpression on one nerve terminal remains to be established, it may in some instances reflect cotransmission. In other cases, heterotransporters may mediate modulation of basal transmitter release in addition to the modulation of the evoked release brought about by presynaptic heteroreceptors. Heterotransporters are also increasingly reported to exist on neuronal soma/dendrites. With the exception of EAAT4, the glutamate transporter/chloride channel situated on GABAergic Purkinje cells in the cerebellum, the functions of somatodendritic heterocarriers is not understood.
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Affiliation(s)
- Luca Raiteri
- Department of Experimental Medicine, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy
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Abstract
Brain tissue has a remarkable ability to accumulate glutamate. This ability is due to glutamate transporter proteins present in the plasma membranes of both glial cells and neurons. The transporter proteins represent the only (significant) mechanism for removal of glutamate from the extracellular fluid and their importance for the long-term maintenance of low and non-toxic concentrations of glutamate is now well documented. In addition to this simple, but essential glutamate removal role, the glutamate transporters appear to have more sophisticated functions in the modulation of neurotransmission. They may modify the time course of synaptic events, the extent and pattern of activation and desensitization of receptors outside the synaptic cleft and at neighboring synapses (intersynaptic cross-talk). Further, the glutamate transporters provide glutamate for synthesis of e.g. GABA, glutathione and protein, and for energy production. They also play roles in peripheral organs and tissues (e.g. bone, heart, intestine, kidneys, pancreas and placenta). Glutamate uptake appears to be modulated on virtually all possible levels, i.e. DNA transcription, mRNA splicing and degradation, protein synthesis and targeting, and actual amino acid transport activity and associated ion channel activities. A variety of soluble compounds (e.g. glutamate, cytokines and growth factors) influence glutamate transporter expression and activities. Neither the normal functioning of glutamatergic synapses nor the pathogenesis of major neurological diseases (e.g. cerebral ischemia, hypoglycemia, amyotrophic lateral sclerosis, Alzheimer's disease, traumatic brain injury, epilepsy and schizophrenia) as well as non-neurological diseases (e.g. osteoporosis) can be properly understood unless more is learned about these transporter proteins. Like glutamate itself, glutamate transporters are somehow involved in almost all aspects of normal and abnormal brain activity.
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Affiliation(s)
- N C Danbolt
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1105, Blindern, N-0317, Oslo, Norway
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Massie A, Vandesande F, Arckens L. Expression of the high-affinity glutamate transporter EAAT4 in mammalian cerebral cortex. Neuroreport 2001; 12:393-7. [PMID: 11209956 DOI: 10.1097/00001756-200102120-00041] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RT-PCR, immunocytochemistry and Western blotting were used to study the expression of the glutamate transporter EAAT4 in the cerebral cortex of cat and mouse. By means of RT-PCR we were able to detect EAAT4 mRNA in the cerebral cortex of both species. Sequencing ensured the specificity of the amplified fragment. Immunocytochemistry and Western blotting enabled us to localize EAAT4 protein in cat and mouse cerebral cortex. Intense EAAT4 immunoreactivity was found in the soma and dendrites of neurons mainly of layers II, III and V. For both species, the signal in the cerebellum was very intense and confined to the molecular and Purkinje cell layer.
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Affiliation(s)
- A Massie
- Laboratory of Neuroendocrinology and Immunological Biotechnology, Katholieke Universiteit Leuven, Belgium
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Inage YW, Itoh M, Wada K, Hoshika A, Takashima S. Glutamate transporters in neonatal cerebellar subarachnoid hemorrhage. Pediatr Neurol 2000; 23:42-8. [PMID: 10963969 DOI: 10.1016/s0887-8994(00)00142-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously described the immunoreactivities of glutamate transporters, EAAT4 and GLAST, in the developing human cerebellum. In the present report, we demonstrate the different expression of EAAT4 and GLAST in the pathologic condition, neonatal subarachnoid hemorrhage. EAAT4 and GLAST were characteristically disturbed in the cerebellar cortices beneath the subarachnoid hemorrhage. In preterm infants with subarachnoid hemorrhage the decrease in EAAT4 immunoreactivity was more prominent than in term infants, and GLAST immunoreactivity in the inner granular cell layer decreased and reappeared later than in term infants with subarachnoid hemorrhage. Although Bergmann's glia removes glutamate from the extracellular space surrounding Purkinje cells in the early stage of hypoxic-ischemic brain damage, the reaction of EAAT4 and GLAST in the cerebellar cortex under the subarachnoid hemorrhage was decreased, and immature glia had a delayed reaction. These characteristics of glutamate transporters in immature cells may lead to cell death and olivocerebellar degeneration.
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Affiliation(s)
- Y W Inage
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Japan
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Chapter VIII Sodium- and potassium-dependent excitatory amino acid transporters in brain plasma membranes. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0924-8196(00)80049-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Itoh M, Suzuki Y, Takashima S. A novel peroxisomal enzyme, D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein: its expression in the developing human brain. Microsc Res Tech 1999; 45:383-8. [PMID: 10402265 DOI: 10.1002/(sici)1097-0029(19990615)45:6<383::aid-jemt5>3.0.co;2-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
D-bifunctional protein, which is a newly recognized peroxisomal enzyme (D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase), demonstrates a characteristic development of pattern in the human brain. At 13 gestational weeks (GW), D-bifunctional protein immunoreactivity first appeared in the brain. Each neuron exhibited increased immunoreactivity along with growth in size as age increased and size with age. Glial cells in the white matter showed immunoreactivity after 30 GW. On the other hand, the L-bifunctional protein immunoreactivity was reported in neurons from 23 or 25 GW and in the white matter from 12 or 14 GW. Because of polymicrogyria in conditions such as infantile Refsum disease and infantile adrenoleukodystrophy, peroxisomal enzymes are thought to play an important role in neuronal migration and possibly myelination. D-bifunctional protein may be relevant to neuronal migration and L-bifunctional protein may be involved in axonal growth and synaptic development. This study is designed to access the ontogeny of D-bifunctional protein in the human brain.
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Affiliation(s)
- M Itoh
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan.
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Lin CL, Tzingounis AV, Jin L, Furuta A, Kavanaugh MP, Rothstein JD. Molecular cloning and expression of the rat EAAT4 glutamate transporter subtype. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 63:174-9. [PMID: 9838098 DOI: 10.1016/s0169-328x(98)00256-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Glutamate transport is a primary mechanism for the synaptic inactivation of glutamate. Excitatory amino acid transporter 4 (EAAT4) is a novel glutamate transporter with properties of a ligand-gated chloride channel that was recently cloned from human brain. Here we report the cloning of rat EAAT4 (rEAAT4) cDNA from rat cerebellum. The nucleotide sequence of rEAAT4 was 88% identical to the human sequence, and the predicted peptide was 89% identical to the human protein. The transport activity encoded by rEAAT4 has high affinity for L-glutamate. In Xenopus laevis oocytes expressing rEAAT4, L-glutamate and other transporter substrates elicited a current predominantly carried by chloride ions. Like human EAAT4, the rEAAT4 mRNA was largely restricted to cerebellar Purkinje cells; the rEAAT4 protein was localized to Purkinje cell somas and dendrites.
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Affiliation(s)
- C L Lin
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
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Abstract
The acidic amino acids, glutamate and aspartate, are the predominant excitatory neurotransmitters in the mammalian CNS. Under many pathologic conditions, these excitatory amino acids (EAAs) accumulate in the extracellular fluid in CNS and the resultant excessive activation of EAA receptors contributes to brain injury through a process known as 'excitotoxicity'. Unlike many other neurotransmitters, there is no evidence for extracellular metabolism of EAAs, rather, they are cleared by Na+-dependent transport mechanisms. Therefore, this transport process is important for ensuring crisp synaptic signaling as well as limiting the excitotoxic potential of EAAs. With the cloning of five distinct EAA transporters, a variety of tools were developed to characterize individual transporter subtypes, including specific antibodies, expression systems, and probes to delete/knock-down expression of each subtype. These tools are beginning to provide fundamental information that has the potential to impact our understanding of EAA physiology and pathophysiology. For example, biophysical studies of the cloned transporters have led to the observation that some subtypes function as ligand-gated ion channels as well as transporters. With these reagents, it has also been possible to explore the relative contributions of each transporter to the clearance of extracellular EAAs and to begin to examine the regulation of specific transporter subtypes. In this review, an overview of the properties of the transporter subtypes will be presented. The evidence which suggests that the transporter, GLT1/EAAT2, may be sufficient to explain a large percentage of forebrain transport will be critically reviewed. Finally, the studies of regulation of GLT-1 in vitro and in vivo will be described.
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Affiliation(s)
- M B Robinson
- Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania 19104-4318, USA.
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