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 g lutamatergic neurotransmission and protection of neurons from the excitotox icity of glutamate in the central nervous system. We herein report isolatio n of cDNA clones of two distinct excitatory amino acid transporters, GLT-1 and EAAC1, from canine brain cortex by PCR-based cloning, and characterizat ion of these transporter subtypes. Canine GLT-1 and EAAC1 exhibited Na+-dep endent glutamate transport with high affinities in a Xenopus oocyte express ion system. Despite the similarity in transport kinetics and in the predict ed primary structures, GLT-1, EAAC1, and the previously identified GLAST sh owed different sensitivities to several structural analogues of L-glutamate . In addition, transcripts of these transporter subtypes showed distinct re gional distribution in the brain in RT-PCR analysis, suggesting that excita tory amino acid transporters have distinct physiological and pathophysiolog ical roles in the brain.