RT Journal Article
SR Electronic
T1 Characterization of Novel L-<em>threo</em>-β-Benzyloxyaspartate Derivatives, Potent Blockers of the Glutamate Transporters
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 1008
OP 1015
DO 10.1124/mol.65.4.1008
VO 65
IS 4
A1 Shimamoto, Keiko
A1 Sakai, Ryuichi
A1 Takaoka, Kiyo
A1 Yumoto, Noboru
A1 Nakajima, Terumi
A1 Amara, Susan G.
A1 Shigeri, Yasushi
YR 2004
UL http://molpharm.aspetjournals.org/content/65/4/1008.abstract
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.