Purification and characterization of a novel insecticidal Toxin, μ-sparatoxin-Hv2, from the venom of the spider heteropoda venatoria

Abstract

The venom of the spider Heteropoda venatoria produced lethal effect to cockroaches as reported in our previous study, and could be a resource for naturally-occurring insecticides. The present study characterized a novel cockroach voltage-gated sodium channels (NaVs) antagonist, μ-sparatoxin-Hv2 (μ-SPRTX-Hv2 for short), from this venom. μ-SPRTX-Hv2 is composed of 37 amino acids and contains six conserved cysteines. We synthesized the toxin by using the chemical synthesis method. The toxin was lethal to cockroaches when intraperitoneally injected, with a LD 50 value of 2.8 nmol/g of body weight. Electrophysiological data showed that the toxin potently blocked NaVs in cockroach dorsal unpaired median (DUM) neurons, with an IC 50 of 833.7 ± 132.2 nM, but it hardly affected the DUMvoltage-gated potassium channels (KNa V s) and the DUMhigh-voltage-activated calcium channels (HVA CaNa V s). The toxin also did not affect Na V s, HVA CaNa V s, and Kvs in rat dorsal root ganglion (DRG) neurons, as well as NaV subtypes NaNa V 1.3–1.5, NaNa V 1.7, and NaNa V 1.8. No envenomation symptoms were observed when μ-SPRTX-Hv2 was intraperitoneally injected into mouse at the dose of 7.0 μg/g. In summary, μ-SPRTX-Hv2 is a novel insecticidal toxin from H. venatoria venom. It might exhibit its effect by blocking the insect NaNa V s and is a candidate for developing bioinsecticide.