Taylor-Wells Jennina, Brooke Basil D, Bermudez Isabel, Jones Andrew K
Faculty of Health and Life Sciences, Department of Biological and Medical Sciences, Oxford Brookes University, Headington, Oxford, UK.
Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
J Neurochem. 2015 Nov;135(4):705-13. doi: 10.1111/jnc.13290. Epub 2015 Sep 17.
A mutation in the second transmembrane domain of the GABA receptor subunit, Rdl, is associated with resistance to insecticides such as dieldrin and fipronil. Molecular cloning of Rdl cDNA from a strain of the malaria mosquito, Anopheles gambiae, which is highly resistant to dieldrin revealed this mutation (A296G) as well as another mutation in the third transmembrane domain (T345M). Wild-type, A296G, T345M and A296G + T345M homomultimeric Rdl were expressed in Xenopus laevis oocytes and their sensitivities to fipronil, deltamethrin, 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT), imidacloprid and spinosad were measured using two-electrode voltage-clamp electrophysiology. Spinosad and DDT had no agonist or antagonist actions on Rdl. However, fipronil, deltamethrin and imidacloprid decreased GABA-evoked currents. These antagonistic actions were either reduced or abolished with the A296G and the A296G + T345M mutations while T345M alone appeared to have no significant effect. In conclusion, this study identifies another mutation in the mosquito Rdl that is associated with insecticide resistance. While T345M itself does not affect insecticide sensitivity, it may serve to offset the structural impact of A296G. The present study also highlights Rdl as a potential secondary target for neonicotinoids and pyrethroids. We show for the first time that deltamethrin (a pyrethroid insecticide) and imidacloprid (a neonicotinoid insecticide) act directly on the insect GABA receptor, Rdl. Our findings highlight Rdl as a potential secondary target of pyrethroids and neonicotinoids mutations in which may contribute to resistance to these widely used insecticides.
γ-氨基丁酸（GABA）受体亚基Rdl的第二个跨膜结构域中的突变与对狄氏剂和氟虫腈等杀虫剂的抗性有关。从对狄氏剂具有高度抗性的疟蚊冈比亚按蚊品系中克隆Rdl cDNA，发现了该突变（A296G）以及第三个跨膜结构域中的另一个突变（T345M）。野生型、A296G、T345M和A296G + T345M同多聚体Rdl在非洲爪蟾卵母细胞中表达，并使用双电极电压钳电生理学测量它们对氟虫腈、溴氰菊酯、1,1,1-三氯-2,2-双（对氯苯基）乙烷（DDT）、吡虫啉和多杀菌素的敏感性。多杀菌素和DDT对Rdl没有激动剂或拮抗剂作用。然而，氟虫腈、溴氰菊酯和吡虫啉降低了GABA诱发的电流。A296G和A296G + T345M突变使这些拮抗作用减弱或消除，而单独的T345M似乎没有显著影响。总之，本研究确定了蚊子Rdl中另一个与杀虫剂抗性相关的突变。虽然T345M本身不影响杀虫剂敏感性，但它可能有助于抵消A296G的结构影响。本研究还强调Rdl是新烟碱类和拟除虫菊酯类的潜在次要靶点。我们首次表明溴氰菊酯（一种拟除虫菊酯类杀虫剂）和吡虫啉（一种新烟碱类杀虫剂）直接作用于昆虫GABA受体Rdl。我们的研究结果强调Rdl是拟除虫菊酯类和新烟碱类的潜在次要靶点，其突变可能导致对这些广泛使用的杀虫剂产生抗性。
