Cloning and characterization of excitatory amino acid transporters GLT-1 and EAAC1 in canine brain.

Excitatory amino acid transporters play important roles in termination of glutamatergic neurotransmission and protection of neurons from the excitotoxicity of glutamate in the central nervous system. We herein report isolation of cDNA clones of two distinct excitatory amino acid transporters, GLT-1 and EAAC1, from canine brain cortex by PCR-based cloning, and characterization of these transporter subtypes. Canine GLT-1 and EAAC1 exhibited Na+-dependent glutamate transport with high affinities in a Xenopus oocyte expression system. Despite the similarity in transport kinetics and in the predicted primary structures, GLT-1, EAAC1, and the previously identified GLAST showed different sensitivities to several structural analogues of L-glutamate. In addition, transcripts of these transporter subtypes showed distinct regional distribution in the brain in RT-PCR analysis, suggesting that excitatory amino acid transporters have distinct physiological and pathophysiological roles in the brain.