Journal
NEUROPHARMACOLOGY
Volume 49, Issue 6, Pages 850-861Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.neuropharm.2005.08.009
Keywords
glutamate uptake; transport inhibitors; pharmacophore model; neurotransmitter transporter; molecular modeling
Categories
Funding
- NCRR NIH HHS [RR15583] Funding Source: Medline
- NINDS NIH HHS [R01 NS027600, NS33270, NS1R13536405, NS27600, NS30570] Funding Source: Medline
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The excitatory amino acid transporters (EAATs) play key roles in the regulation of CNS L-glutamate, especially related to synthesis, signal termination, synaptic spillover, and excitotoxic protection. Inhibitors available to delineate EAAT pharmacology and function are essentially limited to those that non-selectively block all EAATs or those that exhibit a substantial preference for EAAT2. Thus, it is difficult to selectively study the other subtypes, particularly EAAT1 and EAAT3. Structure activity studies on a series of beta-substituted aspartate analogues identify L-beta-benzyl-aspartate (L-beta-BA) as among the first blockers that potently and preferentially inhibits the neuronal EAAT3 subtype. Kinetic analysis of D-[H-3]aspartate uptake into C17.2 cells expressing the hEAATs demonstrate that L-beta-threo-BA is the more potent diastereomer, acts competitively, and exhibits a 10-fold preference for EAAT3 compared to EAAT1 and EAAT2. Electrophysiological recordings of EAAT-mediated currents in Xenopus oocytes identify L-beta-BA as a non-substrate inhibitor. Analyzing L-beta-threo-BA within the context of a novel EAAT2 pharmacophore model suggests: (1) a highly conserved positioning of the electrostatic carboxyl and amino groups; (2) nearby regions that accommodate select structural modifications (cyclopropyl rings, methyl groups, oxygen atoms); and (3) a unique region L-beta-threo-BA occupied by the benzyl moieties Of L-TBOA, L-beta-threo-BA and related analogues. It is plausible that the preference Of L-beta-threo-BA and L-TBOA for EAAT3 and EAAT2, respectively, could reside in the latter two pharmacophore regions. (c) 2005 Elsevier Ltd. All rights reserved.
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