Functional characterization of mouse α4β2 nicotinic acetylcholine receptors stably expressed in HEK293T cells

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Abstract
Mouse α4β2 nicotinic acetylcholine receptors (nAchRs) were stably expressed in HEK293T cells. The function of this stable cell line, termed mmα4β2, was assessed using an aequorin-based luminescence method that measures agonist-evoked changes in intracellular calcium. Agonist-elicited changes in intracellular calcium were due primarily to direct entry of calcium through the α4β2 channel, although release of calcium from intracellular stores contributed ˜ 28% of the agonist-evoked response. Agonist pharmacologies were very similar between the mmα4β2 cells and most cell lines that stably express human α4β2 nAchRs. Based on agonist profiles and sensitivity to the antagonist dihydro-β-erythroidine (DHβE), the predominant α4β2 nAchR expressed in the mmα4β2 cells exhibits a pharmacology that most resembles the DHβE-sensitive component of 86 Rb + efflux from mouse brain synaptosomes. However, when evaluated with the aequorin assay, the mmα4β2 nAchR was found to be atypically sensitive to blockade by the presumed α7-selective antagonist methyllycaconitine (MLA), exhibiting an IC 50 value of 31 ± 0.1 nm. Similar IC 50 values have been reported for the MLA inhibition of nicotine-stimulated dopamine release, a response that is mediated by β2-subunit-containing nAchRs and not α7-subunit-containing nAchRs. Consequently, at low nanomolar concentrations, MLA may not be as selective for α7-containing nAchRs as previously thought

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