Human cationic amino acid transporter hCAT-3 is preferentially expressed in peripheral tissues.
At least five distinct carrier proteins form the family of mammalian cationic amino acid transporters (CATs). We have cloned a cDNA containing the complete coding region of human CAT-3. hCAT-3 is glycosylated and localized to the plasma membrane. Transport studies in Xenopus laevis oocytes revealed that hCAT-3 is selective for cationic L-amino acids and exhibits a maximal transport activity similar to other CAT proteins. The apparent substrate affinity and sensitivity to trans-stimulation of hCAT-3 resembles most closely hCAT-2B. This is in contrast to rat and murine CAT-3 proteins that have been reported to display a very low activity and to be inhibited by neutral and anionic L-amino acids as well as D-arginine (Hosokawa, H., et al. (1997) J. Biol. Chem. 272, 8717-8722; Ito, K., and Groudine, M. (1997) J. Biol. Chem. 272, 26780-26786). Also, in adult rat and mouse, CAT-3 has been found exclusively in central neurons. Human CAT-3 expression is not restricted to the brain, in fact, by far the highest expression was found in thymus. Also in other peripheral tissues, hCAT-3 expression was equal to or higher than in most brain regions, suggesting that hCAT-3 is not a neuron-specific transporter.
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Department of Pharmacology, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, 55101 Mainz, Germany.
Wolf
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Boissel
J P
JP
Gnauert
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K
Closs
E I
EI
D000595:Amino Acid Sequence; D026923:Amino Acid Transport Systems, Basic; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D051381:Rats; D013950:Thymus Gland / Q000378:metabolism; D014018:Tissue Distribution; D014982:Xenopus laevis
D026923:Amino Acid Transport Systems, Basic; D002352:Carrier Proteins; D018076:DNA, Complementary; D008565:Membrane Proteins