Characterization of the mechanism of action of a re-engineered spider toxin acting on insect voltage-gated sodium channels

Spider venoms are an exceptionally rich source of insecticidal peptide toxins with significant potential for development into bioinsecticides for agricultural applications and human disease vector control, particularly as resistance to conventional chemical insecticides, such as knockdown resistance (kdr) to pyrethroids, poses a growing challenge to effective pest control. Many venom-derived neurotoxic peptides exhibit high insect selectivity, offering an excellent framework for the development of potent bioinsecticides that are safer and biodegradable. In this study, we evaluated the mechanism of action of a re-engineered peptide toxin, VSE-8419, based on the δ-Amaurobitoxin-Pl1 (Pl1) toxins from the spider Pireneitega luctuosa, targeting insect voltage gated sodium channels. The effects of VSE-8419 and the wild-type peptide Pl1c on a cockroach sodium channel, BgNav1-1a, and a mosquito sodium channel, AaNav1-1 were examined in Xenopus oocytes using the two-electrode voltage clamp technique. Both VSE-8419 and Pl1c shift the voltage dependency of activation in the hyperpolarizing direction, promoting sodium channel activation, a typical action of site 4 sodium channel neurotoxins including scorpion ß-toxins. Interestingly, both VSE-8419 and Pl1c are more potent gating modifiers of sodium channels in the inactivated state than in the resting state. Furthermore, VSE-8419 exhibits similar potency on sodium channels carrying kdr mutations that are resided within or outside of the two predicted pyrethroid receptor sites. Our findings elucidate the mechanism of action of the natural and its engineered peptide toxins on insect sodium channels and highlight the potential of rationally designed peptide toxins as alternative agents to manage pests and human disease vectors.