RGD Reference Report - Involvement of γ-aminobutyric acid transporter 2 in the hepatic uptake of taurine in rats. - Rat Genome Database

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Involvement of γ-aminobutyric acid transporter 2 in the hepatic uptake of taurine in rats.

Authors: Ikeda, Saori  Tachikawa, Masanori  Akanuma, Shin-ichi  Fujinawa, Jun  Hosoya, Ken-ichi 
Citation: Ikeda S, etal., Am J Physiol Gastrointest Liver Physiol. 2012 Aug 1;303(3):G291-7. doi: 10.1152/ajpgi.00388.2011. Epub 2012 Jun 7.
RGD ID: 30309926
Pubmed: PMID:22678999   (View Abstract at PubMed)
DOI: DOI:10.1152/ajpgi.00388.2011   (Journal Full-text)

Taurine is essential for the hepatic synthesis of bile salts and, although taurine is synthesized mainly in pericentral hepatocytes, taurine and taurine-conjugated bile acids are abundant in periportal hepatocytes. One possible explanation for this discrepancy is that the active supply of taurine to hepatocytes from the blood stream is a key regulatory factor. The purpose of the present study is to investigate and identify the transporter responsible for taurine uptake by periportal hepatocytes. An in vivo bolus injection of [(3)H]taurine into the rat portal vein demonstrated that 25% of the injected [(3)H]taurine was taken up by the liver on a single pass. The in vivo uptake was significantly inhibited by GABA, taurine, β-alanine, and nipecotic acid, a GABA transporter (GAT) inhibitor, each at a concentration of 10 mM. The characteristics of Na(+)- and Cl(-)-dependent [(3)H]taurine uptake by freshly isolated rat hepatocytes were consistent with those of GAT2 (solute carrier SLC6A13). Indeed, the K(m) value of the saturable uptake (594 μM) was close to that of mouse SLC6A13-mediated taurine transport. Although GABA, taurine, and β-alanine inhibited the [(3)H]taurine uptake by > 50%, each at a concentration of 10 mM, GABA caused a marked inhibition with an IC(50) value of 95 μM. The [(3)H]taurine uptake exhibited a significant reduction when the GAT2 gene was silenced. Immunohistochemical analysis showed that GAT2 was localized on the sinusoidal membrane of the hepatocytes predominantly in the periportal region. These results suggest that GAT2 is responsible for taurine transport from the circulating blood to hepatocytes predominantly in the periportal region.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
gamma-aminobutyric acid import involved_inIMP 30309926PMID:22678999ARUK-UCL 
taurine transmembrane transport involved_inIMP 30309926PMID:22678999ARUK-UCL 

Cellular Component
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
plasma membrane located_inIDA 30309926PMID:22678999ARUK-UCL 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
gamma-aminobutyric acid transmembrane transporter activity enablesIMP 30309926PMID:22678999ARUK-UCL 

Objects Annotated

Genes (Rattus norvegicus)
Slc6a13  (solute carrier family 6 member 13)

Additional Information