Function of taurine transporter (Slc6a6/TauT) as a GABA transporting protein and its relevance to GABA transport in rat retinal capillary endothelial cells

Masatoshi Tomi, Ayumi Tajima, Masanori Tachikawa, Ken ichi Hosoya

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54 Citations (Scopus)

Abstract

The purpose of this study was to identify the uptake mechanism of γ-aminobutyric acid (GABA) via taurine transporter (Slc6a6/TauT) and its relationship with GABA transport at the inner BRB. Rat Slc6a6/TauT-transfected HeLa cells exhibited Na+-, Cl--, and concentration-dependent [3H]GABA uptake with a Km of 1.5 mM. Taurine, β-alanine, and GABA markedly inhibited Slc6a6/TauT-mediated uptake of [3H]GABA. The uptake of [3H]GABA by a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2) was Na+-, Cl--, and concentration-dependent with a Km of 2.0 mM. This process was more potently inhibited by substrates of Slc6a6/TauT, taurine and β-alanine, than those of GABA transporters, GABA and betaine. In the presence of taurine, there was competitive inhibition with a Ki of 74 μM. [3H]Taurine also exhibited competitive inhibition with a Ki of 1.8 mM in the presence of GABA. In conclusion, rat Slc6a6/TauT has the ability to use GABA as a substrate and Slc6a6/TauT-mediated GABA transport appears to be present at the inner BRB.

Original languageEnglish
Pages (from-to)2138-2142
Number of pages5
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1778
Issue number10
DOIs
Publication statusPublished - 2008 Oct
Externally publishedYes

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Keywords

  • γ-Aminobutyric acid
  • Blood-retinal barrier
  • Carrier-mediated transport
  • Retinal capillary endothelial cell
  • Taurine transporter

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Biophysics

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