Functional expression of taurine transporter and its up-regulation in developing neurons from mouse cerebral cortex.
OBJECTIVE
In the present study, we investigate the characteristics of taurine transport in primary cultures of neurons from mouse cerebral cortex to understand the possibility that taurine might attenuate the effects of central nervous system drugs.


METHODS
Primary cultured neurons from mouse cerebral cortex were used to determine the transport characteristics of taurine. The expression of taurine transporter (TAUT) in mouse neurons was determined by use of reverse transcriptase-polymerase chain reaction and Western blotting.


RESULTS
In vitro transport of taurine in mouse cerebrocortical neurons at day 9 was Na+-dependent and saturable with a Michaelis-Menten constant (Kt) of 10.6 +/- 4.1 microM and a maximum velocity (Vmax) of 6.68 +/- 0.85 nmol/mg protein/10 min. Na+ and Cl- activation kinetics revealed that the Na+-to-Cl(-)-to-taurine stoichiometry was 2:1:1. Na+-dependent [3H]-taurine transport was competitively inhibited by beta-alanine with an inhibitory constant (Ki) of 47.4 +/- 6.5 microM. Gamma-aminobutyric acid also inhibited Na+-dependent [3H]-taurine transport with relatively low affinity (Ki = 273 +/- 71 microM). TAUT mRNA was detected in mouse primary cultured neurons, and TAUT protein was also expressed at approximately 70 kDa. Na+-dependent taurine transport activity was increased with developing neurons and corresponded with the increasing mRNA and protein level of TAUT.


CONCLUSIONS
The present study revealed that Na+/Cl(-)-coupled taurine transporter TAUT is responsible for taurine uptake in mouse cerebrocortical neurons, and that the expression of TAUT is increased with developing cerebrocortical neurons.
Department of Biochemical Pharmacology, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto, 607-8414, Japan. fujita@mb.kyoto-phu.ac.jp
Takuya
T
Fujita
Ayumi
A
Shimada
Miyuki
M
Wada
Sakiko
S
Miyakawa
Akira
A
Yamamoto
D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D005260:Female; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism; D013379:Substrate Specificity; D013654:Taurine / Q000378:metabolism; D015854:Up-Regulation; D000099247:Taurine Transporters
D026905:Amino Acid Transport Systems; D002712:Chlorides; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D012964:Sodium; D013654:Taurine; D000099247:Taurine Transporters