Selectivity of chirality isoxazoline insecticides upon GABARs among on-target and non-target species via molecular...

The target of the isoxazoline insecticides, including fluralaner, fluxametamide, and isocycloseram, was the γ-aminobutyric acid receptor (GABAR). However, the interaction mechanism between isoxazoline insecticides with different chiral structures and GABAR, as well as the selectivity among on-target and non-target species GABARs remains unclear.

In this study, we integrated homology modeling, molecular dynamics (MD) simulation, molecular docking, and MM-GBSA calculations to explore the inhibition mechanisms of three isoxazoline insecticides. The MM-GBSA calculations indicated that the binding affinity between S-fluralaner with GABAR (-48.43 kcal/mol) was better than that of R-fluralaner (-36.36 kcal/mol). The analysis of sequence alignment revealed that the key residues in the on-target species (Plutella xylostella), namely Ile223, Leu227, Met261, Asn265, Gly282, and Phe285, were allele to Leu223, Met227, Ser261, Arg265, Ala282, and Tyr285 in the non-target species (Danio rerio, Coturnix japonica, and Mus musculus). Consequently, structural analysis reveals that the GABAR site in the on-target species exhibits a more cavity depth, expanded surface area, and increased volume compared to non-target species. These distinctive structural features facilitate enhanced binding affinity with S-fluralaner, thereby contributing to improved species selectivity.

The computational results revealed that the S-conformation of isoxazoline insecticides exhibits higher activity than the R-conformation when binding to GABAR. Notably, S-fluralaner demonstrated effective binding with GABAR in the target species, whereas no binding affinity was observed in non-target species. The findings provide a valuable foundation for the future development of novel, safe, and effective GABAR insecticides. © 2025 Society of Chemical Industry.