Single‐channel properties of α3β4, α3β4α5 and α3β4β2 nicotinic acetylcholine receptors in mice lacking specific nicotinic acetylcholine receptor subunits

Anna Ciuraszkiewicz,Sigismund Huck,Dieter Platzer,Avi Orr‐Urtreger,Petra Scholze,Wolfgang Schreibmayer

doi:10.1113/jphysiol.2012.246595

Anna Ciuraszkiewicz, Sigismund Huck + Show 4 more

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https://doi.org/10.1113/jphysiol.2012.246595

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Abstract

Previous attempts to measure the functional properties of recombinant nicotinic acetylcholine receptors (nAChRs) composed of known receptor subunits have yielded conflicting results. The use of knockout mice that lack α5, β2, α5β2 or α5β2α7 nAChR subunits enabled us to measure the single-channel properties of distinct α3β4, α3β4α5 and α3β4β2 receptors in superior cervical ganglion (SCG) neurons. Using this approach, we found that α3β4 receptors had a principal conductance level of 32.6 ± 0.8 pS (mean ± SEM) and both higher and lower secondary conductance levels. α3β4α5 receptors had the same conductance as α3β4 receptors, but differed from α3β4 receptors by having an increased channel open time and increased burst duration. By contrast, α3β4β2 receptors differed from α3β4 and α3β4α5 receptors by having a significantly smaller conductance level (13.6 ± 0.5 pS). After dissecting the single-channel properties of these receptors using our knockout models, we then identified these properties – and hence the receptors themselves – in wild-type SCG neurons. This study is the first to identify the single-channel properties of distinct neuronal nicotinic receptors in their native environment.

Highlights

Nicotinic acetylcholine receptors are homopentameric or heteropentameric ligand-gated ion channels containing five identical or different subunits, respectively
superior cervical ganglion (SCG) neurons from α5β2 double-KO mice express a single class of heteropentameric nicotinic acetylcholine receptor (nAChR) containing only α3 and β4 subunits (David et al 2010)
We investigated whether the added presence of the α5 subunit modifies the properties of the α3β4 receptor channel by recording SCG neurons from β2 single-KO mice

Summary

Introduction

Nicotinic acetylcholine receptors (nAChRs) are homopentameric or heteropentameric ligand-gated ion channels containing five identical or different subunits, respectively. The predominant hetero-oligomeric nAChR in the CNS contains α4β2 subunits, whereas α3β4 is the most prevalent channel in the peripheral nervous system (McGehee & Role, 1995). The presence of additional subunits throughout virtually the entire nervous system can potentially give rise to a dazzling variety of receptors that probably differ in their pharmacological and biophysical properties (McGehee & Role, 1995; Gotti et al 2006). In which the receptors contain a defined subunit composition, the properties of nAChRs in individual nerve cells are largely unknown. The properties of these recombinant receptors may not accurately reflect the properties of receptors in their native environment or – even worse – may depend on the host cell type (Papke, 1993; Lewis et al 1997; Sivilotti et al 1997)

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