RGD Reference Report - Individual subunits of the glutamate transporter EAAC1 homotrimer function independently of each other. - Rat Genome Database

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Individual subunits of the glutamate transporter EAAC1 homotrimer function independently of each other.

Authors: Grewer, C  Balani, P  Weidenfeller, C  Bartusel, T  Tao, Z  Rauen, T 
Citation: Grewer C, etal., Biochemistry. 2005 Sep 6;44(35):11913-23.
RGD ID: 1599319
Pubmed: PMID:16128593   (View Abstract at PubMed)
PMCID: PMC2459315   (View Article at PubMed Central)
DOI: DOI:10.1021/bi050987n   (Journal Full-text)

Glutamate transporters are thought to be assembled as trimers of identical subunits that line a central hole, possibly the permeation pathway for anions. Here, we have tested the effect of multimerization on the transporter function. To do so, we coexpressed EAAC1(WT) with the mutant transporter EAAC1(R446Q), which transports glutamine but not glutamate. Application of 50 microM glutamate or 50 microM glutamine to cells coexpressing similar numbers of both transporters resulted in anion currents of 165 and 130 pA, respectively. Application of both substrates at the same time generated an anion current of 297 pA, demonstrating that the currents catalyzed by the wild-type and mutant transporter subunits are purely additive. This result is unexpected for anion permeation through a central pore but could be explained by anion permeation through independently functioning subunits. To further test the subunit independence, we coexpressed EAAC1(WT) and EAAC1(H295K), a transporter with a 90-fold reduced glutamate affinity as compared to EAAC1(WT), and determined the glutamate concentration dependence of currents of the mixed transporter population. The data were consistent with two independent populations of transporters with apparent glutamate affinities similar to those of EAAC1(H295K) and EAAC1(WT), respectively. Finally, we coexpressed EAAC1(WT) with the pH-independent mutant transporter EAAC1(E373Q), showing two independent populations of transporters, one being pH-dependent and the other being pH-independent. In conclusion, we propose that EAAC1 assembles as trimers of identical subunits but that the individual subunits in the trimer function independently of each other.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
L-glutamate transmembrane transport  IDA 1599319 RGD 

Molecular Function

Objects Annotated

Genes (Rattus norvegicus)
Slc1a1  (solute carrier family 1 member 1)


Additional Information