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Cloning And Expression Of A Novel Na(+)-Dependent Neutral Amino Acid Transporter Structurally Related To Mammalian Na+/Glutamate Cotransporters, Saad Shafqat, Balaji Tamarappoo, Michael S Kilberg, Ram S Puranam, James O. Mcnamara, Ana Guadaño -Ferraz, R.T. Fremeau

Section of Neurology

A cDNA has been isolated from human hippocampus that appears to encode a novel Na(+)-dependent, Cl(-)-independent, neutral amino acid transporter. The putative protein, designated SATT, is 529 amino acids long and exhibits significant amino acid sequence identity (39-44%) with mammalian L-glutamate transporters. Expression of SATT cDNA in HeLa cells induced stereospecific uptake of L-serine, L-alanine, and L-threonine that was not inhibited by excess (3 mM) 2-(methylamino)-isobutyric acid, a specific substrate for the System A amino acid transporter. SATT expression in HeLa cells did not induce the transport of radiolabeled L-cysteine, L-glutamate, or related dicarboxylates. Northern blot hybridization revealed high levels …