Glutamate transporter blockers for elucidation of the function of excitatory neurotransmission systems.
L-glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Termination of glutamate receptor activation and maintenance of low extracellular glutamate concentrations are mainly achieved by glutamate transporters [excitatory amino acid transporters 1-5 (EAAT1-5)] located in nerve endings and surrounding glial cells. Selective and potent inhibitors have long been required to investigate the physiological significance of transporters in the regulation of synaptic transmission and the pathogenesis of neurological diseases. Non-transportable blockers are desirable because, unlike competitive substrates, they do not cause ion flux and heteroexchange. After a series of possible candidate molecules, we synthesized threo-beta-benzyloxyaspartate (TBOA), the first non-transportable blocker for all subtypes of EAATs. In addition, TBOA analogs with a bulky substituent on their benzene ring showed enhanced inhibition of labeled glutamate uptake. Comparing the effects of substrates and non-transportable blockers revealed the physiological roles of EAATs. We also developed a novel binding assay system using a tritium-labeled TBOA analog. In this review, we describe the design and synthesis of these blockers and the functions of the EAATs elucidated with them.
Shimamoto
Keiko
K
Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan.
D000498:Allyl Compounds / Q000737:chemistry; D027322:Amino Acid Transport System X-AG / Q000037:antagonists & inhibitors*; D000818:Animals; D001224:Aspartic Acid / Q000138:chemical synthesis / Q000494:pharmacology; D001665:Binding Sites; D002227:Carbazoles / Q000737:chemistry; D002384:Catalysis; D002460:Cell Line; D002857:Chromium / Q000737:chemistry; D050491:Glutamate Plasma Membrane Transport Proteins / Q000378:metabolism*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology*; D051381:Rats; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors; D014316:Tritium / Q000737:chemistry
D000498:Allyl Compounds; D027322:Amino Acid Transport System X-AG; D002227:Carbazoles; D050491:Glutamate Plasma Membrane Transport Proteins; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D014179:Neurotransmitter Uptake Inhibitors; D012997:Solvents; C120673:benzyloxyaspartate; D002857:Chromium; D014316:Tritium; D001224:Aspartic Acid