Publications

• Hypotaurine Is a Substrate of GABA Transporter Family Members GAT2/Slc6a13 and TAUT/Slc6a6.

  Nishimura T., Higuchi K., Yoshida Y., Sugita-Fujisawa Y., Kojima K., Sugimoto M., Santo M., Tomi M., Nakashima E.

  Hypotaurine is a precursor of taurine and a physiological antioxidant that circulates in adult and fetal plasma. The purpose of the present study was to clarify whether hypotaurine is a substrate of Slc6a/gamma-aminobutyric acid (GABA) transporter family members. Radiolabeled hypotaurine was synth ... >> More

  Hypotaurine is a precursor of taurine and a physiological antioxidant that circulates in adult and fetal plasma. The purpose of the present study was to clarify whether hypotaurine is a substrate of Slc6a/gamma-aminobutyric acid (GABA) transporter family members. Radiolabeled hypotaurine was synthesized from radiolabeled cysteamine and 2-aminoethanethiol dioxygenase. The uptakes of [³H]GABA, [³H]taurine, and [¹⁴C]hypotaurine by HEK293 cells expressing mouse GAT1/Slc6a1, TAUT/Slc6a6, GAT3/Slc6a11, BGT1/Slc6a12, and GAT2/Slc6a13 were measured. TAUT and GAT2 showed strong [¹⁴C]hypotaurine uptake activity, while BGT1 showed moderate activity, and GAT1 and GAT3 showed slight but significant activity. Mouse TAUT and GAT2 both showed Michaelis constants of 11 µM for hypotaurine uptake. GAT2-expressing cells pretreated with hypotaurine showed resistance to H₂O₂-induced oxidative stress. These results suggest that under physiological conditions, TAUT and GAT2 would be major contributors to hypotaurine transfer across the plasma membrane, and that uptake of hypotaurine via GAT2 contributes to the cellular resistance to oxidative stress. << Less

  Biol. Pharm. Bull. 41:1523-1529(2018) [PubMed] [EuropePMC]

• Functional characterization and chromosomal localization of a cloned taurine transporter from human placenta.

  Ramamoorthy S., Leibach F.H., Mahesh V.B., Han H., Yang-Feng T., Blakely R.D., Ganapathy V.

  A cDNA clone highly related to the rat brain taurine transporter has been isolated from a human placental cDNA library. Transfection of this cDNA into HeLa cells results in a marked elevation of taurine transport activity. The activity of the cDNA-induced transporter is dependent on the presence o ... >> More

  A cDNA clone highly related to the rat brain taurine transporter has been isolated from a human placental cDNA library. Transfection of this cDNA into HeLa cells results in a marked elevation of taurine transport activity. The activity of the cDNA-induced transporter is dependent on the presence of Na+ as well as Cl-. The Na+/Cl-/taurine stoichiometry for the cloned transporter is 2:1:1. The transporter is specific for taurine and other beta-amino acids, including beta-alanine, and exhibits high affinity for taurine (Michaelis-Menten constant approximately 6 microM). The clone consists of a coding region 1863 bp long (including the termination codon), flanked by a 376 bp-long 5' non-coding region and a 625 bp-long 3' non-coding region. The nucleotide sequence of the coding region predicts a 620-amino acid protein with a calculated M(r) of 69,853. Northern-blot analysis of poly(A)+ RNA from several human tissues indicates a complex expression pattern differing across tissues. The principal transcript, 6.9 kb in size, is expressed abundantly in placenta and skeletal muscle, at intermediate levels in heart, brain, lung, kidney and pancreas and at low levels in liver. Cultured human cell lines derived from placenta (JAR and BeWo), intestine (HT-29), cervix (HeLa) and retinal pigment epithelium (HRPE), which are known to possess Na(+)- and Cl(-)-coupled taurine transport activity, also contain the 6.9 kb transcript. Somatic cell hybrid and in situ hybridization studies indicate that the cloned taurine transporter is localized to human chromosome 3 p24-->p26. << Less

  Biochem. J. 300:893-900(1994) [PubMed] [EuropePMC]

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