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Made available in DSpace on 2022-04-28T19:44:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-30 Medical Research Council Australian Research Council Endoparasitoid wasps use complex biochemical arsenals to suppress the normal humoral and cellular immune responses of their hosts in order to transform them into a suitable environment for development of their eggs and larvae. Venom injected during oviposition is a key component of this arsenal, but the functions of individual venom toxins are still poorly understood. Furthermore, there has been little investigation of the potential biotechnological use of these venom toxins, for example for control of agricultural pests. The endoparasitoid Cotesia flavipes (Hymenoptera: Braconidae) is a biocontrol agent reared in biofactories and released extensively in Brazil to control the sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae). The objectives of this work were to reveal venom components produced by C. flavipes and explore the function of a major venom peptide, Cf4. Using a combined proteomic/transcriptomic approach, we identified 38 putative venom toxins including both linear and disulfide-rich peptides, hydrolases, protease inhibitors, apolipophorins, lipid-binding proteins, and proteins of the odorant binding families. Because of its high abundance in the venom, we selected Cf4, a 33-residue peptide with three disulfide bonds, for synthesis and further characterization. We found that synthetic Cf4 reduced the capacity of D. saccharalis hemocytes to encapsulate foreign bodies without any effect on phenoloxidase activity, consistent with a role in disruption of the cellular host immune response. Feeding leaves coated with Cf4 to neonate D. saccharalis resulted in increased mortality and significantly reduced feeding compared to caterpillars fed untreated leaves, indicating that Cf4 is a potential candidate for insect pest control through ingestion. This study adds to our knowledge of endoparasitoid wasp venoms composition, host regulation mechanisms and their biotechnological potential for pest management. School of Agricultural and Veterinarian Sciences São Paulo State University (UNESP) Institute for Molecular Bioscience The University of Queensland Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science The University of Queensland School of Agricultural and Veterinarian Sciences São Paulo State University (UNESP) Australian Research Council: CE200100012

Voltage-gated sodium (Na V) channels play a central role in the propagation of action potentials in excitable cells in both humans and insects. Many venomous animals have therefore evolved toxins that modulate the activity of Na V channels in order to subdue their prey and deter predators. Spider venoms in particular are rich in Na V channel modulators, with one-third of all known ion channel toxins from spider venoms acting on Na V channels. Here we review the landscape of spider-venom peptides that have so far been described to target vertebrate or invertebrate Na V channels. These peptides fall into 12 distinct families based on their primary structure and cysteine scaffold. Some of these peptides have become useful pharmacological tools, while others have potential as therapeutic leads because they target specific Na V channel subtypes that are considered to be important analgesic targets. Spider venoms are conservatively predicted to contain more than 10 million bioactive peptides and so far only 0.01% of this diversity been characterised. Thus, it is likely that future research will reveal additional structural classes of spider-venom peptides that target Na V channels. © 2012 Elsevier Ltd.

cDNA libraries are increasingly being used for high-throughput interrogation of animal venomes. Most previous studies have focused on discovery of new venom toxins, whereas the dynamics of toxin transcription and associated cellular processes have received much less attention. Here we provide, for the first time, an analysis of a transcriptome from the venom gland of a scorpion (Hottentotta judaicus) that is not actively engaged in regenerating its venom. We demonstrate a low abundance of toxin-encoding transcripts coupled with a previously unobserved proliferation of protease sequences. Additionally, we identified several low abundance, toxin-like sequences that may represent decommissioned toxins that are unlikely to be translated. These sequences are not evenly distributed across all toxin families, but rather appear more frequently in transcripts related to α-toxins and β-toxins that are known to target voltage-gated sodium channels. The transcriptomic profile of the replete venom gland is very different to that obtained previously from scorpion venom glands actively engaged in venom regeneration, and it highlights our lack of knowledge as to how the dynamics of transcription changes as the gland progresses from venom regeneration to a “resting” state. This study therefore provides an important foundation for future studies into the dynamics of transcription in the venom glands of scorpions and other venomous animals.

Acid sensing ion channels (ASICs) are pH-sensitive channels that are distributed in the central and peripheral nervous system and which are believed to play a key role in pain perception. APETx2, a 42-residue peptide toxin isolated from the sea anemone Anthopleura elegantissima, is the only known selective inhibitor of ASIC3 channels. Here we describe the total chemical synthesis of APETx2 by solid-phase peptide synthesis and native chemical ligation. The folded synthetic toxin had an IC(50) of 57 nM for inhibition of rat ASIC3 channels expressed in Xenopus oocytes, in agreement with the IC(50) reported for the native toxin (63 nM). The native chemical ligation approach should provide an efficient route for synthesis of other pharmacologically useful disulfide-rich toxins from venomous animals.

The complexity of Australian funnel-web spider venoms has been explored via the combined use of MALDI-TOF mass spectrometry coupled with chromatographic separation and the analysis of venom-gland cDNA libraries. The results show that these venoms are far more complex than previously realized. We show that the venoms of Australian funnel-web spiders contain many hundreds of peptides that follow a bimodal distribution, with about 75% of the peptides having a mass of 3000-5000 Da. The mass spectral data were validated by matching the experimentally observed masses with those predicted from peptide sequences derived from analysis of venom-gland cDNA libraries. We show that multiple isoforms of these peptides are found in small chromatographic windows, which suggests that the wide distribution of close molecular weights among the chromatographic fractions probably reflects a diversity of structures and physicochemical properties. The combination of all predicted and measured parameters permits the interpretation of three-dimensional 'venom landscapes' derived from LC-MALDI analysis. We propose that these venom landscapes might have predictive value for the discovery of various groups of pharmacologically distinct toxins in complex venoms.

Numerous species of ticks and mites (collectively known as acarines) are serious pests of animals, humans, and crops. There are few commercially available acaricides and major classes of these chemicals continue to be lost from the marketplace due to resistance development or deregistration by regulatory agencies. There is consequently a pressing need to isolate new and safe acaricidal compounds. In this study, we show that two families of peptide neurotoxins isolated from the venom of the Australian funnel-web spider Hadronyche versuta are lethal to the lone star tick Amblyomma americanum. These toxins, which are specific blockers of arthropod voltage-gated calcium channels, induce a pronounced phenotype characterized by an unusual gait that is rapidly followed by paralysis and death. Remarkably, one of these toxins, the calcium channel blocker omega-atracotoxin-Hv1a, is virtually equipotent whether the toxin is injected or fed to A. americanum.

Spiders are remarkable for their complete reliance on predation as a trophic strategy. Their evolutionary success is due in large part to production of a complex venom that is designed to rapidly subdue or kill their prey. This issue provides an overview of the fascinating complexity of these venoms, a realistic account of the danger they pose to humans, and an examination of their immense but largely untapped potential for drug and insecticide discovery.

Arthropods are the most diverse animal group on the planet. Their ability to inhabit a vast array of ecological niches has inevitably brought them into conflict with humans. Although only a small minority are classified as pest species, they nevertheless destroy about a quarter of the world's annual crop production and transmit an impressive array of pathogens of human and veterinary public health importance. Arthropod pests have been controlled almost exclusively with chemical insecticides since the introduction of DDT in the 1940s. However, the evolution of resistance to many insecticides, coupled with increased awareness of the potential environmental and human and animal health impacts of these chemicals, has stimulated the search for new insecticidal compounds, novel molecular targets, and alternative control methods. Spider venoms are complex chemical cocktails that have evolved to kill or paralyze arthropod prey, and they represent a largely untapped reservoir of insecticidal compounds. This review focuses on several families of invertebrate-specific peptide neurotoxins that were isolated from the venom of Australian funnel-web spiders. These peptides are promising insecticide leads because of their selectivity for invertebrates and activity on previously unvalidated targets. These toxins should facilitate the development of novel target-based screens for new insecticide leads, while their mapped pharmacophores will provide templates for rational design of mimetics that act at these target sites. Furthermore, genes encoding these toxins can be used to improve the efficacy of insect-specific viruses.

We have isolated and determined the amino acid sequence of a novel peptide component from the venom of the Australian funnel-web spider Hadronyche versuta. This 68-residue toxin, ACTX-Hvf17, does not function like classical neurotoxins in modulating ion channel function as evidenced by its lack of insecticidal activity and its inability to affect vertebrate smooth or skeletal muscle contractility. The peptide shows significant sequence homology with mamba intestinal toxin 1 (MIT1) and to a lesser extent with a variety of colipases. The strong structural homology between MIT1 and porcine colipase leads us to propose that ACTX-Hvf17 also adopts the MIT1/colipase three-dimensional fold. However, we show that ACTX-Hvf17 has no colipase activity and does not stimulate muscle contractility like MIT1. We also show that MIT1 and ACTX-Hvf17 display significant sequence homology with the C-terminal cysteine-rich domain of the Dickkopf-1 family of proteins that induce head formation in developing embryos, which leads us to propose that this domain of Dickkopf-1 also adopts the MIT1/colipase fold. (C) 1999 Elsevier Science Ltd. All rights reserved.

pain. Thus, selective blockers of NaV1.7 are likely to be powerful analgesics. However, NaV1.7 is only one of nine human NaV subtypes, and improper function of certain members of this ion channel family can cause debilitating or even lethal channelopathies. Thus, therapeutics designed to target NaV1.7 must have exquisite selectivity. Of particular concern for a NaV1.7-targeted analgesic would be off-target effects on NaV1.5, which is responsible for the rising phase of the cardiac action potential, or the muscle-specific subtype NaV1.4. Modulation of NaV channels is a dominant pharmacology in spider venoms, and hence we decided to screen an extensive panel of >200 spider venoms for blockers of this channel. Using an in-house, high