• Biomolecules & Therapeutics
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• v.9 no.1
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• pp.40-45
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• 2001

The activity of taurine transporter is affected by various extracellular stimuli such as ion, hormone and stress. To assess effects of steroid hormones antral cyclosporin A (CsA) on the taurine transporter activity, murine monocytic RAW264.7 cell line was stimulated with dexamethasone (DM), triamcinolone (TA), cortisone (CS), hydrocortisone (HCS), prednisone (PSN), prednisolone (PSL) and methylprednisolone (MPSL) in the presence of 12-0-tetradecanoylphorbol-13-acetate(TPA). Treatment of TPA on the cell line led to significant reduction of taurine transporter activity. However, in case of stimulation of the cells with steroid hormones in the presence of TPA, all of them recovered TPA-induced reduction of the taurine transporter activity. Treatment of the cells with CsA led to significant reduction of the taurine transporter activity. Ionomycin (IM) recovered the reduced taurine transporter activity by CsA, but failed in the presence of EDTA, a calcium chelating agent. These results showed that glucocorticoid hormone recovered TPA-induced reduction of taurine transporter activity and that IM recovered CsA-induced reduction of the transporter activity by increasing intracellular free $Ca^{++}$ concentration.n.

• Journal of Nutrition and Health
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• v.34 no.2
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• pp.150-157
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• 2001

Intestinal absorption of dietary taurine is one of the regulatory component maintaining taurine homeostasis along with renal reabsorption, bile acid conjugation and secretion, and de nobo synthesis of taurine in mammals. Recent observations of decreased enterocytic levels of taurine in response to trauma, infection and surgical insults, postulate the possibility that intestinal taurine absorption might be impaired in such stressed conditions. The aim of the present study was to evaluate changes in enterocytic taurine transporter activity using the human intestinal colon carcinoma cell line, HT-29, in various stress-induced conditions. Pretreatment of the HT-29 cells with dexamethasone, a stress hormone(0.1,1,10 or 100$\mu$M) for 3 hrs, or with E coli heat-stable enterotoxin(10, 100, or 200nM) for 30 minutes in order to induce the condition of enterotoxigenic infection did not influence taurine uptake as compared to the value found in control cells. In contrast, pretreatment of the cells with cholera toxin(10, 100, 500, or 1000ng/ml)for 3hr or 24hr significantly decreased taurine uptake by HT-29 cells to 40~50% of the value found in untreated control cells. Kinetic studies of the taurine transporter activity were conducted in control and cholera toxin treated HT-29 cells with varying taurine concentrations(2~60$\mu$M) in the uptake medium. Pretreatment of the cells with cholera toxin(100ng/ml) for 3hr did not influence the Vmax, but resulted in a 55% increase in the Michaelis-Menten constant(Km) of the taurine transporter compared to those in control cells. These results suggest that cholera toxin-induced reduction in taurine transporter activity in HT-29 cells is associated with decreased affinity of the taurine transporter without altering the amount of transporter protein. Intestinal taurine absorption appears to be reduced in the condition of water-borne diseases caused by bacteria such as V. cholerae. This might influence the taurine status of infants and young children more readily, an age group in which the prevalence of intestinal infection is high and the role of intestinal absorption is crucial for maintaining the body taurine pool. (Korean J Nutrition 34(2) : 150-157, 2001)

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.2
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• pp.314-319
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• 2001

In the present study, effects of $\beta$-alanine, a known taurine antagonist for its structural similarity, on the adaptive regulation and kinetic behavior of the taurine transporter were investigated in the HT-29, human colon carcinoma cell line. Pretreatment of the cell with $\beta$-alanine(10mM) for varying periods from 3 to 30 hrs significantly reduced the taurine uptake compared to the value for control cells. This decrease in the taurine transporter activity was dependent on the incubation time with $\beta$-alanine, and the maximal down-regulation of the transporter activity was observed in cells pretreated with $\beta$-alanine for 24 hrs (25% of the control value, p<0.01). The taurine transporter appears to bind exclusively with $\beta$-alanine in the HT-29 cells since the same concentration of $\alpha$-alanine added in the culture medium for 24 hrs did not influence the taurine uptake. Kinetic analyses of the taurine transporter activity was performed in the HT-29 cell line with varying taurine concentration (5~60$\mu$M) in the uptake medium. Active taurine uptake was significantly lower in $\beta$-alanine pretreated cells compared to the value for control cells in the range of taurine concentration used in the experiment (p<0.001). The cells pretreated with $\beta$-alanine showed a 50% lower maximal velocity (Vmax, 1.7$\pm$2.0 nmole.mg $protein^{-1}$.$30min^{-1}$), and a 99% higher Michaelis constant (Km, 40.3$\pm$7.6$\mu$M) than the control values (3.3$\pm$1.9 nmole.mg $protein^{-1}$.$30min^{-1}$, and 20.3$\pm$2.1$\mu$M, respectively). These results on kinetic data suggest that $\beta$-alanine induced down-regulation of the taurine transporter activity was associated with decreases in both maximal velocity and affinity of the transporter.

• Journal of Nutrition and Health
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• v.33 no.6
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• pp.660-667
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• 2000

Previous studies on the effect of age on intestinal taurine transport in animals have invariably shown a decline in the activity of the transport system with increasing age. In the present study changes in taurine transporter activity were observed during cell differentiation in the human colon carcinoma cell line HT-29 This cell line exhibits various enterocytic characteristics when differentiated and therefore has frequently been used to study the characteristcs and regulation of nutrient and drug absorption in the small intestine at the cellular level. Pre-treatment of the cells with $\beta$-alanine(10mM) reduced the taurine transport activity to 33% of the value for the control cells(p<0.05) which implies that taurine and $\beta$-alanine share a common $\beta$-amino acid transport system for their celluar uptake in the HI-29 was continued until 21 days post seeding. Kinetic studies of the taurine transporter were conducted in the HT-29 cell line with varying taurine concentration(5-60$\mu$M) in the uptake medium Both Vmax and the Michaelis-Menten constant(Km) of taurine transporter were decreased as differentiation of the HT-29 cell line was progressed ; Vmax of the taurine transporter in cells incubated for 4, 14 and 21 days post seeding was 2.79$\pm$3.4m 16.89$\pm$1.74, and 0.85$\pm$0.08 and 0.32$\pm$0.01nmol.mg protein-1 .30min-1 respectively(p<0.001) and Km was 42.3$\pm$3.4, 16.89$\pm$1.74, and 11.2$\pm$3.0$\mu$M respectively (p<0.01) These results indicate that the activity of sodium dependent active taurine transport system in the HT-29 cell line is decreased as confluent cells are differentiated. This phenomenon in cell culture system corresponds well with the earlier observation of lower intestinal taurine transport activity in suckling rats compared to that in adult animals although direct relationship of cell differentiation with in vivo aging process needs further verification.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.156-157
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• 1998

Taurine is synthesized in the body or uptaken from dietary and is distributed in the various organs. It differs from other amino acids by virtue of the fact that a sulfonic acid group replaces the carboxyl group of what would be ${\beta}$-alanine. In order to function within the cell it must be transported into the cells by taurine transporter that is spanned 12 transmembrane domains. The human taurine transporter has long cytoplasmic carboxy and amino termini that may function as regulatory attachment sites for other proteins. Six potential protein kinase C(PKC) phosphorylation sites have been reported in human taurine transporter.

• BMB Reports
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• v.28 no.6
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• pp.527-532
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• 1995

Human taurine transporter has 12 transmembrane domains and its molecular weight is 69.6 kDa. The long cytoplasmic carboxy and amino termini might function as regulatory attachment sites for other proteins. Six potential protein kinase C phosphorylation sites have been reported in human taurine transporter. In this report, we studied the effects of phorbol 12-myristate 13-acetate (PMA) and glucocorticoid hormone on taurine transportation in the RAW 264.7, mouse macrophage cell line. When the cells were incubated with $[^{3}H]taurine$ in the presence or absence of $Na^+$ ion for 40 min at $37^{\circ}C$, the [$[^{3}H]taurine$ uptake rate was 780-times higher in the $Na^{+}-containing$ buffer than in the $Na^{+}-deficient$ buffer, indicating that this cell line expresses taurine transporter protein on the cell surface. THP1, a human promonocyte cell line, also showed a similar property. The $[^{3}H]taurine$ uptake rate was not influenced by the inflammatory inducing cytokines such as interleukin-1, gamma-interferon or interleukin-1+gamma-interferon, but was decreased by the PMA in the RAW 264.7 cell line. This suggests that activation of protein kinase C inhibits taurine transporter activity directly or indirectly. The inhibition of $[^{3}H]taurine$ uptake by PMA was time-dependent. Maximal inhibition occurred in one hr stimulation with PMA Increasing the treatment time beyond one h reduced the $[^{3}H]taurine$ uptake inhibition due to the depletion or inactivation of protein kinase C. The cell line also showed concentration-dependent $[^{3}H]taurine$ uptake under PMA stimulation. The phorbol-ester caused 23% inhibition at the concentration of 1 ${\mu}m$ PMA. The inhibition was significant even at a concentration as low as 10 nM PMA The reduced $[^{3}H]taurine$ uptake could be recovered by treatment with glucocorticosteroid hormone. Dexamethasone led to recover of the reduced taurine uptake induced by phorbol-ester, recovering maximally after one hr. This may suggest that macrophage cells require higher taurine concentration in a stressed state, for the secretion of glucocorticoid hormone is increased by hypothalamo-pituitary-adrenocortical (HPA) axis activation in the blood stream.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.87-87
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• 2003

Taurine (2-aminoethanesulfonic acid, $^{+}NH_3CH_2CH_2{SO_3}^{-}$) is endogenous $\beta$-amino acid which is essential in fetal nutrition and development and is present in abundant quantities in several tissues of fetus. In utero, taurine deficiency causes abnormal development and abnormal function of brain, retina, kidney and myocardium. Thus, transfer of taurine into fetus is important during embryonic development. Taurine transporter (TauT) has 12 hydrophobic membrane -spanning domains, which is typical of the $Na^{+}$- and $Cl^{-}$-dependent transporter gene family. Among the various biosynthetic enzymes of taurine, cysteine sulfinic acid decarboxylase (CSD) is the rate-limiting enzyme for biosynthesis of taurine. However, the enzyme activities of taurine biosynthesis are limited in early stage of embryonic development. To analyze the expression period of TauT and CSD during embryonic development, we have investigated the gene expression of TauT and CSD using reverse transcriptase polymerase chain reaction (RT-PCR) in mouse and chicken embryos. RT-PCR anaylsis revealed that both TauT and CSD mRNAs were already expressed at Day-4.5 in mouse embryo. In chicken whole embryo, TauT and CSD mRNAs began to appear on developing times of 48 hrs and 12 hrs, respectively. TauT mRNA was detected in the organs of heart, brain and eye of the day-3 chicken embryo. Our data show that TauT and CSD mRNAs were expressed in early stage of embryonic development.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.124.2-124.2
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• 2003

Taurine is present in a variety of tissue and exhibits many important physiological functions in the cell. Although it is known that many tissues mediate taurine transport, its functions of taurine transport in bone have not been identified yet. In the present study, we investigated the expression of taurine transporter (TauT) and taurine uptake using mouse stromal ST2 cells and osteoblast-like MC3T3-E1 cells, which is bone related cells. Detection of TauT MRNA expression in these cells were performed by reverse transcription polymerase chain reaction (RT-PCR). (omitted)

• Proceedings of the PSK Conference
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• 2001.10a
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• pp.226.2-226.2
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• 2001

• Biomolecules & Therapeutics
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• v.10 no.2
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• pp.78-84
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• 2002

Taurine (2-ethaneaminosulfonic acid, $^+{NH}_3{CH_2}{CH_2}{SO_3^{-}}$) is endogenous amino acid with functions as modulator of osmoregulation, antioxidation, detoxification, transmembrane calcium transport, and a free radical scavenger in mammalian tissues. Taurine transporter(TAUT) contains 12 transmembrane helices, which are typical of the $Na^+$- and $Cl^-$-dependent transporter gene family, and has been cloned recently from several species and tissues. To analyze the expression of TAUT mRNA, one step RT-PCR was performed from human and mouse cultured cell lines and from various mouse tissues. The primers were designed to encode highly conserved amino acid sequences at the second transmembrane domain and at the fourth and fifth intracellular domains. RT-PCR analysis showed both of the human intestine HT-29 and mouse macrophage RAW264.7 cell lines expressed mRNA of TAUT. To define the expression patterns of the TAUT mRNA in the murine organs, RT-PCR was performed to detect cDNA representing TAUT mRNA from seven different mouse tissues. The TAUT was detected in all of the mouse tissues analyzed such as heart, lung, thymus, kidney, liver, spleen and brain. A large amount of transcript was fecund from heart, liver, spleen, kidney, and brain, while lung contained a very small amount of transcript.