GABA receptors (GABA-R) are the target of widely used gabaergic insecticides such as fluralaner, a second generation non-competitive antagonist. Fluralaner blocks GABA-R, binding to a pocket in the transmembrane subunit interface. Because of the location of its binding pocket, it is expected that fluralaner accesses to the receptor by previously partitioning into the bilayer. Therefore, differences in lipid composition of insect and mammal cells become relevant to determine the impact of membrane composition on the nonspecific selectivity of gabaergic insecticides. Insect cells show minimal concentration of cholesterol and they modulate membrane fluidity by regulating PE:PC ratios. On the other hand, vertebrate cholesterol concentration can be as high as 50%, depending on the type of cell. We used experimental Langmuir monolayer and Molecular Dynamics Simulations (MDS) to characterize the effect and interactions of the insecticide fluralaner with model membranes with varying concentrations of POPC:POPE and POPC:CHOL. Monolayer experiments showed that this insecticide reduces film rigidity. MDS showed that fluralaner is located at the interface between the acyl chain and the polar region of the membrane, but this location shifts at high CHOL concentrations towards the phosphate region. This is accompanied by a shift in the orientation of the fluralaner backbone, affecting fluralaner solubility. The presence of CHOL favors fluralaner aggregation, while POPE has the opposite effect, allowing its solubilization and the presence of individual insecticide molecules homogeneously dispersed. Our work suggests that differences in membrane composition could unspecifically influence the selectivity of gabaergic insecticides, modulating fluralaner solubility and fluralaner's access to GABA-R.

中文翻译：

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fluralaner 与二元模型膜的相互作用。对无脊椎动物/脊椎动物选择性的潜在影响


GABA 受体 (GABA-R) 是广泛使用的 gabaergic 杀虫剂的靶标，例如第二代非竞争性拮抗剂 fluralaner。 Fluralaner 阻断 GABA-R，与跨膜亚基界面的口袋结合。由于其结合袋的位置，预计 fluralaner 通过预先分配到双层中来接近受体。因此，昆虫和哺乳动物细胞脂质组成的差异与确定膜组成对伽巴能杀虫剂非特异性选择性的影响相关。昆虫细胞的胆固醇浓度最低，它们通过调节 PE:PC 比率来调节膜流动性。另一方面，脊椎动物的胆固醇浓度可高达 50%，具体取决于细胞类型。我们使用实验性 Langmuir 单层膜和分子动力学模拟 (MDS) 来表征杀虫剂 fluralaner 与不同浓度 POPC:POPE 和 POPC:CHOL 模型膜的效果和相互作用。单层实验表明，这种杀虫剂降低了薄膜的刚性。 MDS 显示 fluralaner 位于酰基链和膜极性区域之间的界面处，但该位置在高 CHOL 浓度下向磷酸盐区域移动。这伴随着 fluralaner 主链方向的变化，影响 fluralaner 的溶解度。 CHOL 的存在有利于 fluralaner 聚集，而 POPE 则具有相反的作用，使其溶解并且单个杀虫剂分子均匀分散。 我们的工作表明，膜组成的差异可能会非特异性地影响加巴能杀虫剂的选择性，调节 fluralaner 的溶解度和 fluralaner 对 GABA-R 的获取。