PT  - JOURNAL ARTICLE
AU  - Keiko Shimamoto
AU  - Ryuichi Sakai
AU  - Kiyo Takaoka
AU  - Noboru Yumoto
AU  - Terumi Nakajima
AU  - Susan G. Amara
AU  - Yasushi Shigeri
TI  - Characterization of Novel L-<em>threo</em>-β-Benzyloxyaspartate Derivatives, Potent Blockers of the Glutamate Transporters
AID  - 10.1124/mol.65.4.1008
DP  - 2004 Apr 01
TA  - Molecular Pharmacology
PG  - 1008--1015
VI  - 65
IP  - 4
4099  - http://molpharm.aspetjournals.org/content/65/4/1008.short
4100  - http://molpharm.aspetjournals.org/content/65/4/1008.full
SO  - Mol Pharmacol2004 Apr 01; 65
AB  - Nontransportable blockers of the glutamate transporters are important tools for investigating mechanisms of synaptic transmission. DL-threo-β-Benzyloxyaspartate (DL-TBOA) is a potent blocker of all subtypes of the excitatory amino acid transporters (EAATs). We characterized novel L-TBOA analogs possessing a substituent on their respective benzene rings. The analogs significantly inhibited labeled glutamate uptake, the most potent of which was (2S,3S)-3-{3-[4-(trifluoromethyl)benzoylamino]benzyloxy}aspartate (TFB-TBOA). In an uptake assay using cells transiently expressing EAATs, the IC50 values of TFB-TBOA for EAAT1, EAAT2, and EAAT3 were 22, 17, and 300 nM, respectively. TFB-TBOA was significantly more potent at inhibiting EAAT1 and EAAT2 compared with L-TBOA (IC50 values for EAAT1-3 were 33, 6.2, and 15 μM, respectively). Electrophysiological analyses revealed that TBOA analogs block the transport-associated currents in all five EAAT subtypes and also block leak currents in EAAT5. The rank order of the analogs for potencies at inhibiting substrate-induced currents was identical to that observed in the uptake assay. However, the kinetics of TFBTBOA differed from the kinetics of L-TBOA, probably because of the strong binding affinity. Notably, TFB-TBOA did not affect other representative neurotransmitter transporters or receptors, including ionotropic and metabotropic glutamate receptors, indicating that it is highly selective for EAATs. Moreover, intracerebroventricular administration of the TBOA analogs induced severe convulsive behaviors in mice, probably because of the accumulation of glutamate. Taken together, these findings indicate that novel TBOA analogs, especially TFB-TBOA, should serve as useful tools for elucidating the physiological roles of the glutamate transporters.