Stable expression and functional characterization of a human nicotinic acetylcholine receptor with α6β2 properties: discovery of selective antagonists.
Br J Pharmacol 2011;
163:313-29. [PMID:
21232042 DOI:
10.1111/j.1476-5381.2011.01213.x]
[Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE
Despite growing evidence that inhibition of α6β2-containing (α6β2*) nicotinic acetylcholine receptors (nAChRs) may be beneficial for the therapy of tobacco addiction, the lack of good sources of α6β2*-nAChRs has delayed the discovery of α6β2-selective antagonists. Our aim was to generate a cell line stably expressing functional nAChRs with α6β2 properties, to enable pharmacological characterization and the identification of novel α6β2-selective antagonists.
EXPERIMENTAL APPROACH
Different combinations of the α6, β2, β3, chimeric α6/3 and mutant β3(V273S) subunits were transfected in human embryonic kidney cells and tested for activity in a fluorescent imaging plate reader assay. The pharmacology of rat immune-immobilized α6β2*-nAChRs was determined with ¹²⁵I-epibatidine binding.
KEY RESULTS
Functional channels were detected after co-transfection of α6/3, β2 and β3(V273S) subunits, while all other subunit combinations failed to produce agonist-induced responses. Stably expressed α6/3β2β3(V273S)-nAChR pharmacology was unique, and clearly distinct from α4β2-, α3β4-, α7- and α1β1δε-nAChRs. Antagonist potencies in inhibiting α6/3β2β3(V273S) -nAChRs was similar to their binding affinity for rat native α6β2*-nAChRs. Agonist affinities for α6β2*-nAChRs was higher than their potency in activating α6/3β2β3(V273S)-nAChRs, but their relative activities were equivalent. Focussed set screening at α6/3β2β3(V273S)-nAChRs, followed by cross-screening with the other nAChRs, led to the identification of novel α6β2-selective antagonists.
CONCLUSIONS AND IMPLICATIONS
We generated a mammalian cell line stably expressing nAChRs, with pharmacological properties similar to native α6β2*-nAChRs, and used it to identify novel non-peptide, low molecular weight, α6β2-selective antagonists. We also propose a pharmacophore model of α6β2 antagonists, which offers a starting point for the development of new smoking cessation agents.
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