Black widow spider envenomation

Synaptotagmin 1-mediated cell membrane penetration and dopamine release enhancement by latroeggtoxin-VI

Latroeggtoxin-VI (LETX-VI), a proteinaceous neurotoxin mined from the egg transcriptome of spider L. tredecimguttatus, was previously found to promote the release of dopamine from PC12 cells. However, the relevant molecular mechanism has not been fully clear. Here LETX-VI was demonstrated to rapidly penetrate the plasma membrane of PC12 cells via the vesicle exocytosis/endocytosis cycle, during which vesicular transmembrane protein synaptotagmin 1 (Syt1) functions as a receptor, with its vesicle luminal domain interacting with the C-terminal region of LETX-VI. The C-terminal sequence of LETX-VI is the functional region for both entering cells and promoting dopamine release. After gaining entry into the PC12 cells, LETX-VI down-regulated the phosphorylation levels of Syt1 at T201 and T195, thereby facilitating vesicle fusion with plasma membrane and thus promoting dopamine release. The relevant mechanism analysis indicated that LETX-VI has a protein phosphatase 2A (PP2A) activator activity. The present work has not only probed into the Syt1-mediated action mechanism of LETX-VI, but also revealed the structure-function relationship of the toxin, thus suggesting its potential applications in the drug transmembrane delivery and treatment of the diseases related to dopamine release and PP2A activity deficiency.

Comparative proteomic analysis to probe into the differences in protein expression profiles and toxicity bases of Latrodectus tredecimguttatus spiderlings and adult spiders

The early reports and our previous work confirmed the existence of the toxic proteinaceous components in the body of the L. tredecimguttatus newborn and adult spiders. For revealing the differences in the protein expression profiles and toxicity bases of the spiders at different developmental stages, the spiderling and adult spider proteins were comparatively analyzed using a proteomic strategy. Totals of 429 and 958 proteins were identified from the spiderlings and adult spiders, respectively, with 239 proteins being identified from both of them. Although some similarities between the spiderling and adult spider proteomes exist, there are obvious differences between the two proteomes in size, complexity, molecular weight (MW) distribution, acid-base property, and hydropathicity, etc. Gene ontology (GO) analysis demonstrates that, comparing based on the percentages of proteins, the spiderling and adult spider proteins have generally similar distribution profiles with respect to the subcellular localization, molecular function and biological process. However, there are still some differences between these two sets of proteins in some classifications of the three GO categories. For the adult spiders, latrotoxins together with other toxins and toxin-like proteins, etc. constitute their toxicity basis, whereas the toxicity of the spiderlings depends mainly on the synergistic action of atypical latrotoxins and toxin-like proteins, most of which are different from those of the adult spiders, demonstrating that the spiders at different developmental stages have largely different toxicity mechanisms.

Pore-Forming Proteins from Cnidarians and Arachnids as Potential Biotechnological Tools

Animal venoms are complex mixtures of highly specialized toxic molecules. Cnidarians and arachnids produce pore-forming proteins (PFPs) directed against the plasma membrane of their target cells. Among PFPs from cnidarians, actinoporins stand out for their small size and molecular simplicity. While native actinoporins require only sphingomyelin for membrane binding, engineered chimeras containing a recognition antibody-derived domain fused to an actinoporin isoform can nonetheless serve as highly specific immunotoxins. Examples of such constructs targeted against malignant cells have been already reported. However, PFPs from arachnid venoms are less well-studied from a structural and functional point of view. Spiders from the Latrodectus genus are professional insect hunters that, as part of their toxic arsenal, produce large PFPs known as latrotoxins. Interestingly, some latrotoxins have been identified as potent and highly-specific insecticides. Given the proteinaceous nature of these toxins, their promising future use as efficient bioinsecticides is discussed throughout this Perspective. Protein engineering and large-scale recombinant production are critical steps for the use of these PFPs as tools to control agriculturally important insect pests. In summary, both families of PFPs, from Cnidaria and Arachnida, appear to be molecules with promising biotechnological applications.

Anti-Breast Cancer Activity of Latroeggtoxin-V Mined from the Transcriptome of Spider Latrodectus tredecimguttatus Eggs

As a black widow spider, Latrodectus tredecimguttatus has poisonous components not only in venomous glands but also in eggs. Our previous work had carried out a transcriptome analysis of the spider eggs in an attempt to probe into the molecular basis of the egg toxicity. A proteinaceous toxin, named Latroeggtoxin-V, was mined from the identified transcriptome. In this study, the gene of Latroeggtoxin-V was cloned and heterologously expressed, and the anticancer activity of the recombinant Latroeggtoxin-V (rLatroeggtoxin-V) was characterized. Activity assay found that rLatroeggtoxin-V could selectively act on breast cancer line MDA-MB-231 cells, not only arresting their cell cycle, inhibiting their proliferation and migration, but also inducing their apoptosis. Bioinformatics analysis suggested that Latroeggtoxin-V belongs to the ATPase inhibitor protein family and the further activity assay showed that the rLatroeggtoxin-V inhibited the activity of the Na⁺/K⁺-ATPase in MDA-MB-231 cells in a concentration-dependent manner, suggesting that the anticancer activity of Latroeggtoxin-V is based on its affecting the ion transport and receptor functions of Na⁺/K⁺-ATPase. The present work not only laid the foundation for the utilization of Latroeggtoxin-V in the anticancer drug development and the related fields, but also provided a new paradigm for exploration of the proteinaceous toxins under the direction of transcriptomics and bioinformatics.

Transcriptome Analysis to Understand the Toxicity of Latrodectus tredecimguttatus Eggs

Latrodectus tredecimguttatus is a kind of highly venomous black widow spider, with toxicity coming from not only venomous glands but also other parts of its body as well as newborn spiderlings and eggs. Up to date, although L. tredecimguttatus eggs have been demonstrated to be rich in proteinaceous toxins, there is no systematic investigation on such active components at transcriptome level. In this study, we performed a high-throughput transcriptome sequencing of L. tredecimguttatus eggs with Illumina sequencing technology. As a result, 53,284 protein-coding unigenes were identified, of which 14,185 unigenes produced significant hits in the available databases, including 280 unigenes encoding proteins or peptides homologous to known proteinaceous toxins. GO term and KEGG pathway enrichment analyses of the 280 unigenes showed that 375 GO terms and 18 KEGG pathways were significantly enriched. Functional analysis indicated that these unigene-coded toxins have the bioactivities to degrade tissue proteins, inhibit ion channels, block neuromuscular transmission, provoke anaphylaxis, induce apoptosis and hyperalgesia, etc. No known typical proteinaceous toxins in L. tredecimguttatus venomous glands, such as latrotoxins, were identified, suggesting that the eggs have a different toxicity mechanism from that of the venom. Our present transcriptome analysis not only helps to reveal the gene expression profile and toxicity mechanism of the L. tredecimguttatus eggs, but also provides references for the further related researches.

Recent Advances in Research on Widow Spider Venoms and Toxins

Widow spiders have received much attention due to the frequently reported human and animal injures caused by them. Elucidation of the molecular composition and action mechanism of the venoms and toxins has vast implications in the treatment of latrodectism and in the neurobiology and pharmaceutical research. In recent years, the studies of the widow spider venoms and the venom toxins, particularly the α-latrotoxin, have achieved many new advances; however, the mechanism of action of the venom toxins has not been completely clear. The widow spider is different from many other venomous animals in that it has toxic components not only in the venom glands but also in other parts of the adult spider body, newborn spiderlings, and even the eggs. More recently, the molecular basis for the toxicity outside the venom glands has been systematically investigated, with four proteinaceous toxic components being purified and preliminarily characterized, which has expanded our understanding of the widow spider toxins. This review presents a glance at the recent advances in the study on the venoms and toxins from the Latrodectus species.

Arachnids of medical importance in Brazil: main active compounds present in scorpion and spider venoms and tick saliva

Arachnida is the largest class among the arthropods, constituting over 60,000 described species (spiders, mites, ticks, scorpions, palpigrades, pseudoscorpions, solpugids and harvestmen). Many accidents are caused by arachnids, especially spiders and scorpions, while some diseases can be transmitted by mites and ticks. These animals are widely dispersed in urban centers due to the large availability of shelter and food, increasing the incidence of accidents. Several protein and non-protein compounds present in the venom and saliva of these animals are responsible for symptoms observed in envenoming, exhibiting neurotoxic, dermonecrotic and hemorrhagic activities. The phylogenomic analysis from the complementary DNA of single-copy nuclear protein-coding genes shows that these animals share some common protein families known as neurotoxins, defensins, hyaluronidase, antimicrobial peptides, phospholipases and proteinases. This indicates that the venoms from these animals may present components with functional and structural similarities. Therefore, we described in this review the main components present in spider and scorpion venom as well as in tick saliva, since they have similar components. These three arachnids are responsible for many accidents of medical relevance in Brazil. Additionally, this study shows potential biotechnological applications of some components with important biological activities, which may motivate the conducting of further research studies on their action mechanisms.