Expression of a mouse brain cDNA encoding novel gamma-aminobutyric acid transporter.
A nipecotic acid-resistant gamma-aminobutyric acid (GABA) transporter was cloned from a mouse brain cDNA library. The 2.3-kilobase cDNA clone contains an open reading frame of 1842 nucleotides encoding a protein of 614 amino acids. The predicted amino acid sequence indicates it is a member of the gene family of the sodium-dependent neurotransmitter transporters. The new GABA transporter, named GAT2, is highly homologous to the betaine transporter (BGT1) cloned from canine kidney. However, GAT2 expression in the brain distinguished it from BGT1 which was exclusively expressed in the kidney. The transcripts of GAT2 were found in the cerebral cortex, cerebellum, and brainstem as well as in kidney. Expression of GAT2 in Xenopus oocytes revealed a Km of 79 microM for GABA uptake which is about 10-fold higher than that of the high affinity GABA transporter (GAT1). The pharmacology of GAT2 is different from that of GAT1 because of lack of inhibition by guvacine and nipecotic acid and sensitivity to high concentrations of betaine and beta-alanine. GAT2 transports betaine with a Km of about 200 microM, but no significant transport of beta-alanine could be detected. The presence of mRNA encoding GAT2 in parts of the brain suggests it is a neurotransmitter transporter.
Lopez-Corcuera
B
B
Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110.
Liu
Q R
QR
Mandiyan
S
S
Nelson
H
H
Nelson
N
N
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D001622:Betaine / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics*; D050485:GABA Plasma Membrane Transport Proteins; D015870:Gene Expression; D015723:Gene Library; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D027361:Organic Anion Transporters; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014981:Xenopus; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027361:Organic Anion Transporters; D012333:RNA, Messenger; C493414:Slc6a1 protein, mouse; C490439:Slc6a12 protein, mouse; C072207:betaine plasma membrane transport proteins; D001622:Betaine; D005680:gamma-Aminobutyric Acid; D004247:DNA