Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators

Herzig, Volker, Sunagar, Kartik, Wilson, David T.R., Pineda, Sandy S., Israel, Mathilde R., Dutertre, Sebastien, McFarland, Brianna Sollod, Undheim, Eivind A.B., Hodgson, Wayne C., Alewood, Paul F., Lewis, Richard J., Bosmans, Frank, Vetter, Irina, King, Glenn F., and Fry, Bryan G. (2020) Australian funnel-web spiders evolved human-lethal δ-hexatoxins for defense against vertebrate predators. Proceedings of the National Academy of Sciences of the United States of America, 117 (40). pp. 24920-24928.

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Abstract

Australian funnel-web spiders are infamous for causing human fatalities, which are induced by venom peptides known as δ-hexatoxins (δ-HXTXs). Humans and other primates did not feature in the prey or predator spectrum during evolution of these spiders, and consequently the primate lethality of δ-HXTXs remains enigmatic. Funnel-web envenomations are mostly inflicted by male spiders that wander from their burrow in search of females during the mating season, which suggests a role for δ-HXTXs in self-defense since male spiders rarely feed during this period. Although 35 species of Australian funnel-web spiders have been described, only nine δ-HXTXs from four species have been characterized, resulting in a lack of understanding of the ecological roles and molecular evolution of δ-HXTXs. Here, by profiling venom-gland transcriptomes of 10 funnel-web species, we report 22 δ-HXTXs. Phylogenetic and evolutionary assessments reveal a remarkable sequence conservation of δ-HXTXs despite their deep evolutionary origin within funnel-web spiders, consistent with a defensive role. We demonstrate that δ-HXTX-Ar1a, the lethal toxin from the Sydney funnel-web spider Atrax robustus, induces pain in mice by inhibiting inactivation of voltage-gated sodium (NaV) channels involved in nociceptive signaling. δ-HXTX-Ar1a also inhibited inactivation of cockroach NaV channels and was insecticidal to sheep blowflies. Considering their algogenic effects in mice, potent insecticidal effects, and high levels of sequence conservation, we propose that the δ-HXTXs were repurposed from an initial insecticidal predatory function to a role in defending against nonhuman vertebrate predators by male spiders, with their lethal effects on humans being an unfortunate evolutionary coincidence.

Item ID: 67583
Item Type: Article (Research - C1)
ISSN: 1091-6490
Copyright Information: (C) National Academy of Sciences
Funders: National Health and Medical Research Council of Australia (NHMRC), Australian Research Council (ARC)
Projects and Grants: NHMRC APP1136889, NHMRC APP1162503, ARC Discovery Grant DP190100304, ARC Future Fellowship FT190100482
Date Deposited: 13 May 2021 02:56
FoR Codes: 34 CHEMICAL SCIENCES > 3404 Medicinal and biomolecular chemistry > 340499 Medicinal and biomolecular chemistry not elsewhere classified @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280103 Expanding knowledge in the biomedical and clinical sciences @ 100%
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