Chapter 10 Structure and function of neuronal nicotinic acetylcholine receptors

Abstract

This chapter discusses some aspects of neuronal acetylcholine receptors (AChRs), reviews some of the recent studies of the mechanism by which chronic exposure to nicotine affects aα4β2 AChRs, and describes some of the pharmacological properties of neuronal AChRs, especially the differences between α7 and α8 AChRs and the usefulness of epibatidine (exo-2-(6-chloro-3-pyridyl)-7-azabicyclo-[2.2.l]-heptane) as a ligand for many types of neuronal AChRs. The basic homologies in structure of receptors in this superfamily have been illustrated in the chapter. Homologies in overall domain relationships are demonstrated by showing that functional mosaics could be made in which the large N-terminal extracellular domain of α7 AChRs could be grafted just before the first transmembrane domain to the C-terminal part of 5HT3 receptors. This resulted in receptors with acetylcholine-gated cation channels having the ion selectivity of 5HT3 receptors. Close similarities in the overall structures of the ion channels are demonstrated by showing that changing only three amino acids in the sequence lining the cation-specific channel of excitatory α7 neuronal AChRs to amino acids typical of the anion-specific channels of inhibitory glycine or GABAA receptors changed the ion selectivity of the mutated a7 AChR channels from cations to anions