The ‘glial’ glutamate transporter, EAAT2 (Glt-1) accounts for high affinity glutamate uptake into adult rodent nerve endings

Authors

  • Sachin K. Suchak,

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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  • Nicoletta V. Baloyianni,

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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  • Michael S. Perkinton,

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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    • The current address of Michael S. Perkinton is the Department of Neuroscience, Institute of Psychiatry, King's College London.

  • Robert J. Williams,

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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  • Brian S. Meldrum,

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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  • Marcus Rattray

    1. Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London
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Address correspondence and reprint requests to Marcus Rattray, Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London, Hodgkin Building, Guy's Hospital, London SE1 1UL, United Kingdom. E-mail: Marcus.rattray@kcl.ac.uk

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 µm 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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