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

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.

Alterations in the cholinergic system of brain stem neurons in a mouse model of Rett syndrome

“…The ␣ 7 -subunit is usually associated with a large transient peak, whereas the ␣ 3 -and ␣ 4 -subunits are associated with smaller amplitude currents with a longer decay time (24,35,71). In single-channel recordings, the ␣ 5 -subunit increases the mean open time (18), and the insertion of ␤ 3 can shorten the decay time (11). WT LC neurons display a variety of nAChR subunits that contribute to different kinetics of an elicited current (34).…”

Functional nicotinic acetylcholine receptor reconstitution in Au(111)-supported thiolipid monolayers

“…Assuming that the conductance of a single channel is ≈14 -33 pS 42 and that the number of inserted monomers is 10 10 cm -2 as derived from the SPR and AFM data, the current increase in about 0.5 µA cm -2 ( Figure 7a) implies that ≈ 10 5 channels are opened after Carb addition. Assuming that the conductance of a single channel is ≈14 -33 pS 42 and that the number of inserted monomers is 10 10 cm -2 as derived from the SPR and AFM data, the current increase in about 0.5 µA cm -2 ( Figure 7a) implies that ≈ 10 5 channels are opened after Carb addition.…”

Development and characterization of the α3β4α5 nicotinic receptor cellular membrane affinity chromatography column and its application for on line screening of plant extracts

“…Two families of neuronal transmembrane subunits have been identified, the α subunit family composed of 9 members (α2–α10) and the β subunit family composed of 3 members (β2 – β4) [1,2]. Functional nAChRs are constructed from α subunits alone, homomeric nAChRs, or a mixture of α and β subunits, heteromeric nAChRs.…”

“…The homomeric nAChRs are formed using the α7 through α10 subunits, with the α7 nAChR being the most well characterized and abundant subtype. The heteromeric nAChRs were initially believed to be composed of two α2, α3 or α4 subunits and three β subunits, with the α4β2 nAChR being the most abundant subtype in the central nervous system [1,2], and the α3β4 nAChR the most abundant subtype in the peripheral nervous system [2]. However, heteromeric nAChR subtypes containing two α subunits, the α2, α3 or α4 subunit plus the α5 or α6 subunit have also been described [3], with α5 subunits predominantly expressed in combination with α3 and β4 subunits [4,5].…”

“…However, recent data suggest that the presence of the α5 subunit alters the activity of α3β4 nAChRs. Ciuraszkiewicz et al have shown that the addition of α5 subunits to α3β4 nAChRs influences channel open time and burst duration [2]. Increased expression of α3β4α5 nAChR in the habenuolopeduncular pathway results in decreased nicotine aversion usually associated with decreased α3β4 nAChRs expression [4] suggesting that α3β4α5 nAChR inhibition may be a useful target for smoking cessation pharmacotherapies [1].…”