Allosterically linked noncompetitive antagonist binding sites in the resting nicotinic acetylcholine receptor ion channel

Hugo R. Arias, Elizabeth A. McCardy, Erin Z. Bayer, Martin J. Gallagher, Michael P. Blanton

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Previous studies have established the presence of overlapping binding sites for the noncompetitive antagonists (NCAs) amobarbital, tetracaine, and 3-trifluoromethyl-3-(m-[125I]iodophenyl) diazirine ([125I]TID) within the ion channel of the Torpedo nicotinic acetylcholine receptor (AChR) in the resting state. These well-characterized NCAs and competitive radioligand binding and photolabeling experiments were employed to better characterize the interaction of the dissociative anesthetics ketamine and thienylcycloexylpiperidine (TCP) with the resting AChR. Our experiments yielded what appear to be conflicting results: (i) both ketamine and TCP potentiated [125I]TID photoincorporation into AChR subunits; and (ii) ketamine and TCP had very little effect on [14C]amobarbital binding. Nevertheless, (iii) both ketamine and TCP completely displaced [3H]tetracaine binding (Kis ∼ 20.9 and 2.0 μM, respectively) by a mutually exclusive mechanism. To reconcile these results we propose that, in the resting ion channel, TCP and ketamine bind to a site that is spatially distinct from the TID and barbiturate locus, while tetracaine bridges both binding sites.

Original languageEnglish
Pages (from-to)121-131
Number of pages11
JournalArchives of Biochemistry and Biophysics
Volume403
Issue number1
DOIs
StatePublished - 1 Jul 2002
Externally publishedYes

Fingerprint

Ketamine
Nicotinic Receptors
Ion Channels
Tetracaine
Binding Sites
Amobarbital
Cholinergic Receptors
Dissociative Anesthetics
Diazomethane
Torpedo
Competitive Binding
Experiments

Keywords

  • Conformational states
  • Equilibrium binding
  • Ketamine and phencyclidine binding sites
  • Photoaffinity labeling
  • Torpedo nicotinic acetylcholine receptor

Cite this

Arias, Hugo R. ; McCardy, Elizabeth A. ; Bayer, Erin Z. ; Gallagher, Martin J. ; Blanton, Michael P. / Allosterically linked noncompetitive antagonist binding sites in the resting nicotinic acetylcholine receptor ion channel. In: Archives of Biochemistry and Biophysics. 2002 ; Vol. 403, No. 1. pp. 121-131.
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Allosterically linked noncompetitive antagonist binding sites in the resting nicotinic acetylcholine receptor ion channel. / Arias, Hugo R.; McCardy, Elizabeth A.; Bayer, Erin Z.; Gallagher, Martin J.; Blanton, Michael P.

In: Archives of Biochemistry and Biophysics, Vol. 403, No. 1, 01.07.2002, p. 121-131.

Research output: Contribution to journalArticle

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