Molecular characterization of taurine transport in bovine aortic endothelial cells.
Cultured bovine aortic endothelial (BAE) cells expressed a Na(+)/Cl(-)-dependent taurine uptake activity that saturated with an apparent K(0.5) of approximately 4.9 microM for taurine and was inhibited by beta-alanine, guanidinoethane sulfonate, and homotaurine. We isolated a taurine transporter clone from a BAE cell cDNA library that revealed >91% sequence identity at the amino acid level to the previously cloned high-affinity mammalian taurine transporters. The biochemical and pharmacological properties of the bovine taurine transporter cDNA expressed in Xenopus oocyte was similar to those of the high-affinity taurine transporter. Surprisingly, F(-) blocked taurine uptake in BAE cells with an IC(50) of approximately 17.5 mM. The endogenous taurine uptake was also inhibited by the protein kinase C activator phorbol 12-myristate 13-acetate, but not by its inactive analog, 4 alpha-phorbol 12,13-didecanoate. The endogenous uptake was stimulated, however, by hypertonic stress and the increase was due to an increase in the V(max) of taurine uptake. Our results provide the first description of a molecular mechanism that may be responsible for maintaining the intracellular taurine content in the endothelial cells.
Qian
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Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Vinnakota
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Edwards
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Sarkar
H K
HK
D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta; D001692:Biological Transport; D000001:Calcimycin / Q000494:pharmacology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005822:Genetic Vectors; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D012965:Sodium Chloride / Q000494:pharmacology; D013654:Taurine / Q000378:metabolism*; D014316:Tritium; D014981:Xenopus; D000099247:Taurine Transporters
D000001:Calcimycin; D002352:Carrier Proteins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D010703:Phorbol Esters; D012965:Sodium Chloride; D013654:Taurine; D014316:Tritium; D000099247:Taurine Transporters