Purification and Characterization of a Novel Insecticidal Toxin, μ-sparatoxin-Hv2, from the Venom of the Spider Heteropoda venatoria

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 (Na(V)s) 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 Na(V)s in cockroach dorsal unpaired median (DUM) neurons, with an IC(50) of 833.7 ± 132.2 nM, but it hardly affected the DUM voltage-gated potassium channels (K(V)s) and the DUM high-voltage-activated calcium channels (HVA Ca(V)s). The toxin also did not affect Na(V)s, HVA Ca(V)s, and Kvs in rat dorsal root ganglion (DRG) neurons, as well as Na(V) subtypes Na(V)1.3–1.5, Na(V)1.7, and Na(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 Na(V)s and is a candidate for developing bioinsecticide.