Nicotinic acetylcholine receptor chimeras of rat α7 andDrosophilaSAD reveal species-specific agonist binding regions

Abstract

Species-specific agonist binding regions of nicotinic acetylcholine receptors (nAChR) were examined. Imidacloprid and physostigmine (Phy) selectively activated insect nAChR composed of Drosophila second alpha-like subunit (SAD) and chick β2, in contrast to rat α7 nAChR. The Phy-activated currents were α-bungarotoxin (α-BGT) sensitive, suggesting activation at the agonist binding loop C. Several SAD-α7 chimeras were constructed, by switching agonist binding regions, and expressed in oocytes. Though none of the chimeras was activated by a range of nicotinic agonists, [125I]α-BGT binding revealed homomeric assembly of all chimeric cDNAs. Phy differentially displaced [125I]α-BGT from the nAChR chimeras, suggesting that the β subunit is not involved in Phy binding, and that Phy targets the insect agonist binding loop C.