Biological Research Laboratories, Nissan Chemical Corporation, Shiraoka, Saitama, Japan.
Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, Japan.
Pest Manag Sci. 2023 Oct;79(10):4078-4082. doi: 10.1002/ps.7606. Epub 2023 Jun 21.
Fluralaner is the first isoxazoline ectoparasiticide developed to protect companion animals from fleas and ticks. Fluralaner primarily inhibits arthropod γ-aminobutyric acid receptors (GABARs), which are ligand-gated ion channels comprising five subunits arranged around the channel pore. We previously reported that the action site of fluralaner resides at the M1-M3 transmembrane interface between adjacent GABAR subunits. To investigate whether fluralaner interacts with the second transmembrane segment (M2) located deep in the interface, we generated four housefly RDL GABAR mutants with non-conservative amino acid substitutions in the M2 region.
Electrophysiological analysis of GABARs expressed in Xenopus oocytes indicated that S313A and S314A mutants exhibited fluralaner sensitivities similar to that of the wild type. M312S mutant exhibited approximately seven-fold lower sensitivity than that of the wild type. Notably, the N316L mutant was almost insensitive to fluralaner.
The findings of this study indicate that the conserved external amino acid residues of insect GABAR channels play a critical role in the antagonistic effect of fluralaner. © 2023 Society of Chemical Industry.
氟雷拉纳是第一种用于保护伴侣动物免受跳蚤和蜱虫侵害的异噁唑啉类外用寄生虫驱避剂。氟雷拉纳主要抑制节肢动物 γ-氨基丁酸受体（GABARs），GABAR 是由五个亚基围绕通道孔排列组成的配体门控离子通道。我们之前的研究报告表明，氟雷拉纳的作用部位位于相邻 GABAR 亚基之间的 M1-M3 跨膜界面。为了研究氟雷拉纳是否与位于界面深处的第二个跨膜片段（M2）相互作用，我们在果蝇 RDL GABAR 中生成了四个具有 M2 区域非保守氨基酸取代的突变体。
在非洲爪蟾卵母细胞中表达的 GABAR 的电生理分析表明，S313A 和 S314A 突变体对氟雷拉纳的敏感性与野生型相似。M312S 突变体的敏感性比野生型低约七倍。值得注意的是，N316L 突变体对氟雷拉纳几乎不敏感。
本研究的结果表明，昆虫 GABAR 通道的保守外部氨基酸残基在氟雷拉纳的拮抗作用中发挥关键作用。© 2023 化学工业协会。
