Pharmacological characterization of threo-3-methylglutamic acid with excitatory amino acid transporters in native and recombinant systems

被引:30
作者
Eliasof, S
McIlvain, HB
Petroski, RE
Foster, AC
Dunlop, J
机构
[1] Wyeth Ayerst Res, Wyeth Neurosci, Princeton, NJ 08543 USA
[2] Neurocrine Biosci Inc, San Diego, CA USA
关键词
EAAT; glutamate; methylglutamate; neurotransmitter; transport; uptake;
D O I
10.1046/j.1471-4159.2001.00253.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The glutamate analog (+/-) threo-3-methylglutamate (T3MG) has recently been reported to inhibit the EAAT2 but not EAAT1 subtype of high-affinity, Na+-dependent excitatory amino acid transporter (EAAT). We have examined the effects of T3MG on glutamate-elicited currents mediated by EAATs 1-4 expressed in Xenopus oocytes and on the transport of radiolabeled substrate in mammalian cell lines expressing EAATs 1-3. T3MG was found to be an inhibitor of EAAT2 and EAAT4 but a weak inhibitor of EAAT1 and EAAT3. T3MG competitively inhibited uptake of D-[H-3]-aspartate into both cortical and cerebellar synaptosomes with a similar potency, consistent with its inhibitory activity on the cloned EAAT2 and EAAT4 subtypes. In addition, T3MG produced substrate-like currents in oocytes expressing EAAT4 but not EAAT2. However, T3MG was unable to elicit heteroexchange of preloaded D-[H-3]-aspartate in cerebellar synaptosomes, inconsistent with the behavior of a substrate inhibitor. Finally, T3MG acts as a poor ionotropic glutamate receptor agonist in cultured hippocampal neurons: concentrations greater than 100 muM T3MG were required to elicit significant NMDA receptor-mediated currents. Thus, T3MG represents a pharmacological tool for the study of not only the predominant EAAT2 subtype but also the EAAT4 subtype highly expressed in cerebellum.
引用
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页码:550 / 557
页数:8
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