De Novo Transcriptome Analysis of the Venom of Latrodectus geometricus with the Discovery of an Insect-Selective Na Channel Modulator.

The brown widow spider, Latrodectus geometricus, is a predator of a variety of agricultural insects and is also hazardous for humans. Its venom is a true pharmacopeia representing neurotoxic peptides targeting the ion channels and/or receptors of both vertebrates and invertebrates. The lack of transcriptomic information, however, limits our knowledge of the diversity of components present in its venom. The purpose of this study was two-fold: (1) carry out a transcriptomic analysis of the venom, and (2) investigate the bioactivity of the venom using an electrophysiological bioassay. From 32,505 assembled transcripts, 8 toxin families were classified, and the ankyrin repeats (ANK), agatoxin, centipede toxin, ctenitoxin, lycotoxin, scorpion toxin-like, and SCP families were reported in the L. geometricus venom gland. The diversity of L. geometricus venom was also uncovered by the transcriptomics approach with the presence of defensins, chitinases, translationally controlled tumor proteins (TCTPs), leucine-rich proteins, serine proteases, and other important venom components. The venom was also chromatographically purified, and the activity contained in the fractions was investigated using an electrophysiological bioassay with the use of a voltage clamp on ion channels in order to find if the neurotoxic effects of the spider venom could be linked to a particular molecular target. The findings show that U24-ctenitoxin-Pn1a involves the inhibition of the insect sodium (Nav) channels, BgNav and DmNav. This study provides an overview of the molecular diversity of L. geometricus venom, which can be used as a reference for the venom of other spider species. The venom composition profile also increases our knowledge for the development of novel insecticides targeting voltage-gated sodium channels.

Partial proteomic analysis of brown widow spider (Latrodectus geometricus) venom to determine the biological activities.

Spiders use their venom for defence and to capture prey. These venoms contain a cocktail of biologically active compounds that display several different biological activities, such as large molecules and small molecules including peptides, proteins/enzymes, and other components. Thus, venom constituents have attracted the attention of biochemists and pharmacologists over the years. The brown widow spider (Latrodectus geometricus) is a venomous spider found worldwide, including in Thailand. This spider causes human injuries, and the venom has many potential applications. In this study, we investigated the complexity and pharmacology of brown widow spider venom. Spider crude venom was investigated using partial proteome techniques and enzymatic activity, toxicity, and antibacterial activity assessments. We found that crude venom displayed a wide range of molecular masses from 19 to over 97 kDa, with molecular masses of 66 kDa intensely stained. Peptides and proteins were identified by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), which showed that the crude venom contained a variety of substances, including latrotoxins, apolipophorins, hemocyanins, chitinases, arginine kinase, allergen antigen 5-like protein, astacin-like metalloproteases, and serine proteases. High hyaluronidase activity was observed based on the turbidimetric method. The venom presented toxicity in crickets (PD50 = 0.73 ± 0.10 µg/g body weight), and substantial envenomation symptoms, such as slow-motion movement, paralysis, and even death, were noted. Moreover, this venom exhibited potential antibacterial activity against the gram-positive Bacillus subtilis but not the gram-negative Pseudomonas aeruginosa. Spider venom contains numerous molecules with biological activity, such as latrotoxins, which affect insects, and enzymes. In addition to latrotoxins, certain enzymes in venom are hypothesized to exhibit toxicity and antimicrobial activity. This study provides important information for the further development of natural compounds or insecticidal toxins.