Molecular Insights into the Potential Insecticidal Interaction of β-Dihydroagarofuran Derivatives with the H Subunit of V-ATPase

Celangulin V (CV), one of dihydroagarofuran sesquiterpene polyesters isolated from Chinese bittersweet (Celastrus angulatus Maxim), is famous natural botanical insecticide. Decades of research suggests that is displays excellent insecticidal activity against some insects, such as Mythimna separata Walker. Recently, it has been validated that the H subunit of V-ATPase is one of the target proteins of the insecticidal dihydroagarofuran sesquiterpene polyesters. As a continuation of the development of new pesticides from these natural products, a series of β-dihydroagarofuran derivatives have been designed and synthesized. The compound JW-3, an insecticidal derivative of CV with a p-fluorobenzyl group, exhibits higher insecticidal activity than CV. In this study, the potential inhibitory effect aused by the interaction of JW-3 with the H subunit of V-ATPase c was verified by confirmatory experiments at the molecular level. Both spectroscopic techniques and isothermal titration calorimetry measurements showed the binding of JW-3 to the subunit H of V-ATPase was specific and spontaneous. In addition, the possible mechanism of action of the compound was discussed. Docking results indicated compound JW-3 could bind well in ‘the interdomain cleft’ of the V-ATPase subunit H by the hydrogen bonding and make conformation of the ligand–protein complex become more stable. All results are the further validations of the hypothesis, that the target protein of insecticidal dihydroagarofuran sesquiterpene polyesters and their β-dihydroagarofuran derivatives is the subunit H of V-ATPase. The results also provide new ideas for developing pesticides acting on V-ATPase of insects.

Validation of the Target Protein of Insecticidal Dihydroagarofuran Sesquiterpene Polyesters

A series of insecticidal dihydroagarofuran sesquiterpene polyesters were isolated from the root bark of Chinese bittersweet (Celastrus angulatus Max). A previous study indicated that these compounds affect the digestive system of insects, and aminopeptidase N3 and V-ATPase have been identified as the most putative target proteins by affinity chromatography. In this study, the correlation between the affinity of the compounds to subunit H and the insecticidal activity or inhibitory effect on the activity of V-ATPase was analyzed to validate the target protein. Results indicated that the subunit H of V-ATPase was the target protein of the insecticidal compounds. In addition, the possible mechanism of action of the compounds was discussed. The results provide new ideas for developing pesticides acting on V-ATPase of insects.