Structure‐activity relationships of acetylcholine derivatives with L ucilia cuprina nicotinic acetylcholine receptor α1 and α2 subunits in chicken β2 subunit hybrid receptors in comparison with chicken nicotinic acetylcholine receptor α4/β2

• Published in: Insect molecular biology 2013-04, Vol.22 (2), p.183-198
• Main Authors: Dederer, H., Berger, M., Meyer, T., Werr, M., Ilg, T.
• Format: Article
• Language: English
• ISSN: 0962-1075; 1365-2583
• DOI: 10.1111/imb.12014

Insect nicotinic acetylcholine ( ACh ) receptors ( nAChRs ) are the targets of several insecticide classes. In the present study, we report the gene identification and cloning of nAChR α1 and α2 subunits ( Lc α1 and Lc α2) from the sheep blowfly L ucilia cuprina . X enopus oocytes voltage clamp experiments as hybrids with the chicken β2 nAChR ( Gg β2) subunit resulted in ACh ‐gated ion channels with distinct dose–response curves for Lc α1/ Gg β2 (effective concentration 50% [ EC 50 ] = 80 n M ; n H  = 1.05), and Lc α2/ Gg β2 ( EC 50  = 5.37 μ M , n H  = 1.46). The neonicotinoid imidacloprid was a potent agonist for the α‐bungarotoxin‐sensitive Lc α1/ Gg β2 ( EC 50 ∼ 20 n M ), while the α‐bungarotoxin‐resistant Lc α2/ Gg β2 showed a 30‐fold lower sensitivity to this insecticide ( EC 50  = 0.62 μ M ). Thirteen close derivatives of ACh were analysed in EC 50 , Hill coefficient and maximum current (relative to ACh ) determinations for Lc α1/ Gg β2 and Lc α2/ Gg β2 and the chicken Gg α4/ Gg β2 nAChRs , and comparisons relative to ACh allowed the definition of novel structure‐activity and structure‐selectivity relationships. In the case of N ‐ethyl‐acetylcholine, the EC 50 of the chicken Gg α4/ Gg β2 rose by a factor of 1000, while for both Lc α1/ Gg β2 and Lc α2/ Gg β2, potency remained unchanged. Further derivatives with insect nAChR selectivity potential were acetyl‐α‐methylcholine and trimethyl‐(3‐methoxy‐3‐oxopropyl)ammonium, followed by acetylhomocholine and trimethyl‐(4‐oxopentyl) ammonium. Our results may provide guidance for the identification or design of insect‐specific nAChR agonists using structure‐based or in silico methods.