Combinations of long peptide sequence blocks can be used to describe toxin diversification in venomous animals

Neuropeptide signalling systems - An underexplored target for venom drug discovery

Neuropeptides are signalling molecules mainly secreted from neurons that act as neurotransmitters or peptide hormones to affect physiological processes and modulate behaviours. In humans, neuropeptides are implicated in numerous diseases and understanding their role in physiological processes and pathologies is important for therapeutic development. Teasing apart the (patho)physiology of neuropeptides remains difficult due to ligand and receptor promiscuity and the complexity of the signalling pathways. The current approach relies on a pharmacological toolbox of agonists and antagonists displaying high selectivity for independent receptor subtypes, with the caveat that only few selective ligands have been discovered or developed. Animal venoms represent an underexplored source for novel receptor subtype-selective ligands that could aid in dissecting human neuropeptide signalling systems. Multiple endogenous-like neuropeptides as well as peptides acting on neuropeptide receptors are present in venoms. In this review, we summarise current knowledge on neuropeptides and discuss venoms as a source for ligands targeting neuropeptide signalling systems.

Comparative proteomics reveals recruitment patterns of some protein families in the venoms of Cnidaria

Cnidarians are probably the oldest group of animals to be venomous, yet our current picture of cnidarian venom evolution is highly imbalanced due to limited taxon sampling. High-throughput tandem mass spectrometry was used to determine venom composition of the scyphozoan Chrysaora lactea and two cubozoans Tamoya haplonema and Chiropsalmus quadrumanus. Protein recruitment patterns were then compared against 5 other cnidarian venom proteomes taken from the literature. A total of 28 putative toxin protein families were identified, many for the first time in Cnidaria. Character mapping analysis revealed that 17 toxin protein families with predominantly cytolytic biological activities were likely recruited into the cnidarian venom proteome before the lineage split between Anthozoa and Medusozoa. Thereafter, venoms of Medusozoa and Anthozoa differed during subsequent divergence of cnidarian classes. Recruitment and loss of toxin protein families did not correlate with accepted phylogenetic patterns of Cnidaria. Selective pressures that drive toxin diversification independent of taxonomic positioning have yet to be identified in Cnidaria and now warrant experimental consideration.

Characterising the enzymatic profile of crude tentacle extracts from the South Atlantic jellyfish Olindias sambaquiensis (Cnidaria: Hydrozoa)

Jellyfish venoms are of medical and biotechnological importance, with toxins displaying antimicrobial, analgesic and anti-tumor activities. Although proteolytic enzymes have also been described, detailed characterisation of these proteins is scant in Olindias spp. High throughput mass spectrometry profiling of cnidarian venoms has become increasingly popular since the first description of the proteomic profile of putative toxins isolated from nematocysts of the hydrozoan jellyfish Olindias sambaquiensis describing the presence of orthologous enzymes as presented in venoms of advanced species as snakes. Rigorous bioinformatics analyses can aid functional annotation, but biochemical assays are prerequisite to unambiguously assign toxic function to a peptide or protein. Here we present results that experimentally confirm previously predicted proteomic analysis that crude venom extracts from tentacles of O. sambaquiensis are composed of polypeptides with metalloproteinase, serine proteinase and phospholipases A2 activities. Surprisingly, levels of serine proteinase and phospholipase A2 activities were comparable to those observed in venoms of Bothrops snakes which were used as positive controls in this study. Hence, these data offer new opportunities to explore serine proteinase and phospholipase A2 activities in the clinical sequelae following O. sambaquiensis envenomation, with future possible biopharmaceutical applications.

[Structural Features of Cysteine-Stabilized Polypeptides from Sea Anemones Venoms]

Nowadays, venom-based drug discovery becomes popular again: pharmaceutical companies evaluate animal venom potential as a combinatory library of biologically-active compounds. Collaborations with research groups from academia are intensified, new toxins are being investigated, among which polypeptides are of paramount importance. Sea anemones produce the most diversified, from structural point of view, polypep- tide venom components among other animals. This particular review considers known polypeptide toxins from sea anemones, basically taking into account its classification by primary structural features. The most important functional characteristics are analyzed in each structural class.

Advances in venomics

The term “venomics” was coined to describe the global study of venom and venom glands, targeting comprehensive characterization of the whole toxin profile of a venomous animal by means of proteomics, transcriptomics, genomics and bioinformatics studies.

Bioinformatics-Aided Venomics

Venomics is a modern approach that combines transcriptomics and proteomics to explore the toxin content of venoms. This review will give an overview of computational approaches that have been created to classify and consolidate venomics data, as well as algorithms that have helped discovery and analysis of toxin nucleic acid and protein sequences, toxin three-dimensional structures and toxin functions. Bioinformatics is used to tackle specific challenges associated with the identification and annotations of toxins. Recognizing toxin transcript sequences among second generation sequencing data cannot rely only on basic sequence similarity because toxins are highly divergent. Mass spectrometry sequencing of mature toxins is challenging because toxins can display a large number of post-translational modifications. Identifying the mature toxin region in toxin precursor sequences requires the prediction of the cleavage sites of proprotein convertases, most of which are unknown or not well characterized. Tracing the evolutionary relationships between toxins should consider specific mechanisms of rapid evolution as well as interactions between predatory animals and prey. Rapidly determining the activity of toxins is the main bottleneck in venomics discovery, but some recent bioinformatics and molecular modeling approaches give hope that accurate predictions of toxin specificity could be made in the near future.