Excitatory amino acid transporter 5, a retinal glutamate transporter coupled to a chloride conductance

Jeffrey L. Arriza, Scott Eliasof, Michael P. Kavanaugh, Susan G. Amara

Research output: Contribution to journalArticlepeer-review

Abstract

Although a glutamate-gated chloride conductance with the properties of a sodium-dependent glutamate transporter has been described in vertebrate retinal photoreceptors and bipolar cells, the molecular species underlying this conductance has not yet been identified. We now report the cloning and functional characterization of a human excitatory amino acid transporter, EAAT5, expressed primarily in retina. Although EAAT5 shares the structural homologies of the EAAT gene family, one novel feature of the EAAT5 sequence is a carboxy-terminal motif identified previously in N-methyl-D-aspartate receptors and potassium channels and shown to confer interactions with a family of synaptic proteins that promote ion channel clustering. Functional properties of EAAT5 were examined in the Xenopus oocyte expression system by measuring radiolabeled glutamate flux and two-electrode voltage clamp recording. EAAT5-mediated L-glutamate uptake is sodium- and voltage-dependent and chloride-independent. Transporter currents elicited by glutamate are also sodium- and voltage-dependent, but ion substitution experiments suggest that this current is largely curried by chloride ions. These properties of EAAT5 are similar to the glutamate-elicited chloride conductances previously described in retinal neurons, suggesting that the EAAT5-associated chloride conductance may participate in visual processing.

Original languageEnglish
Pages (from-to)4155-4160
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume94
Issue number8
DOIs
StatePublished - Apr 15 1997

Keywords

  • PDZ domain
  • chloride ion
  • uptake

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