Neurophysiological action of centrally-acting spider toxin polypeptides derived from Hadronyche versuta and Tegenaria agrestis venom

Authors: BLOOMQUIST, JEFFREY - University Of Florida; COQUEREL, QUENTIN - University Of Florida; HULBERT, D - Vestaron Corporation; Norris, Edmund

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2023
Publication Date: 4/5/2023
Citation: Bloomquist, J.R., Coquerel, Q.R., Hulbert, D., Norris, E.J. 2023. Neurophysiological action of centrally-acting spider toxin polypeptides derived from Hadronyche versuta and Tegenaria agrestis venom. Pesticide Biochemistry and Physiology. 192:105416. https://doi.org/10.1016/j.pestbp.2023.105416.
DOI: https://doi.org/10.1016/j.pestbp.2023.105416

Interpretive Summary: A commercial formulation of Australian blue mountain funnel web spider peptide toxins was introduced for pest control in agriculture. However, little was known about its potential mode of action. We aimed to further understand its mechanism of action by applying it directly to the central nervous system of Drosophila melanogaster, the common vinegar fly. This peptide excited the insect nervous system, followed by a significant decrease in nerve activity at higher doses and exposure times. Its effects were blocked by alpha-bungarotoxin (BGTX), indicating that this spider peptide may act on nicotinic acetylcholine receptors. Co-application of nicotine and this spider toxin caused a synergistic effect on the insect nervous system, and indicates the potential mechanism of this spider peptide. Moreover, these results demonstrate the potential of this molecule in broad pest control applications.

Technical Abstract: Established dogma concerning the action of insecticidal arthropod-derived peptides (e.g., scorpion toxins), was that they acted on the peripheral nervous system and were excluded from the central nervous system (CNS) by barrier systems. Initial evidence for a CNS-directed toxicological effect following parenteral administration was for a novel peptide from the Hobo spider, Tegeneria agrestis. This toxin was inactive on peripheral sensory and motor nerves, but had a potent excitatory effect on the CNS of larval Musca domestica. Recently, a commercialized formulation of GA-omega/kappa-Hxtx-Hv1a, derived from the venom of the Australian blue mountain funnel web spider (Hadronyche versuta) was introduced for use in agriculture by Vestaron Corp (Spear'). Its primary mode of action was found to be central neuroexcitation via positive allosteric modulation of nicotinic acetylcholine receptors (nAchR) of cockroach neurons. In the present study, this peptide showed hyperexcitation followed by a decrease in firing of the Drosophila melanogaster larval CNS that was prevented by co-exposure to 100 nM 'alpha-bungarotoxin ('alpha-BGTX), a classical nAchR noncompetitive antagonist. This effect was mirrored in isobologram analysis, which showed clear antagonism between the two toxins when injected into adult houseflies. Interestingly, U1-agatoxin-Ta1b-QA derived from Tegeneria agrestis (VST-7304) had a similar biphasic action, but showed increased nerve discharge when co-exposed with 100 nM 'alpha-BGTX, and had additive effects when injected together with 'alpha-BGTXin isobologram analyses. Binary mixtures of either Spear or VST-7304 with 30 nM nicotine showed clear evidence of synergized nerve block, which was also observed for mixtures of Spear and VST-7304. Taken together, these data suggest that GA-omega/kappa-Hxtx-Hv1a and U1-agatoxin-Ta1b-QA (VST-7304) have somewhat different and complementary modes of action.