Design of an irreversible affinity ligand for the phencyclidine recognition site on N-methyl-D-aspartate-type glutamate receptors.
A series of 1-[1-(2-thienyl)cyclohexyl]piperidine (TCP) analogs were synthesized with the aim of developing a potent ligand for the N-methyl-D-aspartate glutamate receptor subtype. The piperidine moiety of TCP was substituted at the nitrogen position with aliphatic chains of different length or with various polar groups. A correlation between the decrease in the potency of displacement of [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-im ine maleate (MK-801) binding from bovine cortex membranes and the increase of length or polarity of the aliphatic chain was observed. Isonitrile, isothiocyanate and isoselenocyanate groups were substituted at position 4 of the thiophene ring, and the relative binding affinity and alkylating potencies of the derivatized compounds were studied. Among this set of compounds, the one carrying an isothiocyanate group at position 4 of the thiophene ring of the N-ethyl analog of TCP yielded the most efficient alkylating agent, demonstrated by its ability to irreversibly block up to 80% of the [3H]MK-801 binding sites. This affinity ligand did not significantly affect other ligand binding sites of the same N-methyl-D-aspartate receptor complex or of other receptor systems, further demonstrating its functional specificity as a potent alkylating probe for the TCP/MK-801 recognition site. Studies with a radiolabeled adduct of this isothiocyanate N-ethyl derivative, however, indicate that a substantial level of nonspecific covalent incorporation into the membranes occurs at concentrations as low as 10 nM, thereby obscuring any possibility of detecting a specifically labeled protein species.
Casalotti
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SO
Fidia-Georgetown Institute for the Neurosciences, Georgetown University School of Medicine, Washington, DC.
Kozikowski
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AP
Fauq
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A
Tückmantel
W
W
Krueger
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KE
D000345:Affinity Labels / Q000138:chemical synthesis* / Q000378:metabolism; D000478:Alkylation; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D016291:Dizocilpine Maleate / Q000378:metabolism; D005260:Female; D007700:Kinetics; D010622:Phencyclidine / Q000031:analogs & derivatives / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013861:Thiocyanates / Q000378:metabolism / Q000494:pharmacology; D013876:Thiophenes / Q000378:metabolism / Q000494:pharmacology
D000345:Affinity Labels; D016194:Receptors, N-Methyl-D-Aspartate; D013861:Thiocyanates; D013876:Thiophenes; D016291:Dizocilpine Maleate; C012058:tenocyclidine; D010622:Phencyclidine