Exploring the functional properties of heteromeric alpha7beta2 nicotinic acetylcholine receptors at the single-channel level

Abstract

The α7 nicotinic acetylcholine receptor (nAChR) is highly expressed in the brain, it is involved in memory and cognition, and it is a promising drug target for neurological disorders. Emerging evidence demonstrates the expression in brain of heteromeric α7β2 receptors whose roles remain unknown. We combine heterologous expression with single-channel recordings to decipher the functional, pharmacological and structural contribution of the β2 subunit to α7-containing receptors. We use a mutant α7 subunit that forms a functional receptor whose single-channel activity cannot be detected due to its low conductance (α7 LC). Co-expression of α7 LC with β2 allows detection of single channels activated by acetylcholine, indicating the presence of α7β2 heteromeric receptors. Analysis of single-channel amplitude populations reveals receptors with three different stoichiometries, containing one, two or three β2 subunits. By introducing mutations in the α7 binding site, we show that activation occurs through the α7-α7 bindingsite interface. To control stoichiometry, α7 and β2 subunits were concatenated by synthetic linkers into pentameric constructs. Several constructs form functional receptors that can be potentiated by α7 positive allosteric modulators. Our results contribute to the understanding of this receptor as a novel drug target of cholinergic signaling