The myth of cobra venom cytotoxin: More than just direct cytolytic actions

Cobra venom cytotoxin (CTX) is a non-enzymatic three-finger toxin that constitutes 40-60% of cobra venom. Thus, it plays an important role in the pathophysiology of cobra envenomation, especially in local dermonecrosis. The three-finger hydrophobic loops of CTX determine the cytotoxicity. Nevertheless, the actual mechanisms of cytotoxicity are not fully elucidated as they involve not only cytolytic actions but also intracellular signalling-mediated cell death pathways. Furthermore, the possible transition cell death pattern remains to be explored. The actual molecular mechanisms require further studies to unveil the relationship between different CTXs from different cobra species and cell types which may result in differential cell death patterns. Here, we discuss the biophysical interaction of CTX with the cell membrane involving four binding modes: electrostatic interaction, hydrophobic partitioning, isotropic phase, and oligomerisation. Oligomerisation of CTX causes pore formation in the membrane lipid bilayer. Additionally, the CTX-induced apoptotic pathway can be executed via death receptor-mediated extrinsic pathways and mitochondrial-mediated intrinsic pathways. We also discuss lysosomal-mediated necrosis and the occurrence of necroptosis following CTX action. Collectively, we provided an insight into concentration-dependent transition of cell death pattern which involves different mechanistic actions. This contributes a new direction for further investigation of cytotoxic pathways activated by the CTXs for future development of biotherapeutics targeting pathological effects caused by CTX.

Design of antimicrobial and cytolytic peptides by computational analysis of bacterial, algal, and invertebrate proteomes

The increase of antibiotic resistance in bacterial species has raised the need to search for novel antimicrobial molecules. Antimicrobial peptides are molecules that commonly display an amphipathic character. In this work, we developed a computational strategy to search for new peptide sequences within the proteome of any organism that includes in-house developed software and the use of artificial intelligence tools available online. Eleven peptides were selected after analyzing 63,343 proteins from the proteomes of bacteria, algae and invertebrates. Then, we validated the results by means of several assays which were carried out against five (5) pathogenic bacterial species and two (2) cancer cell lines. As a result, we found that ten of the peptides were antimicrobial, with minimum inhibitory concentration values between 4 and [Formula: see text]. Furthermore, two of the more active peptides were also cytotoxic to human red blood cells and cancer cells. In general, the antimicrobial peptides we discovered produced damage on the bacterial cell membrane that included membrane wrinkling, cell blebbing, and leakage of cytoplasmic material. Based on these results, we concluded that the computational approach proposed for finding sequences encrypted in proteins is appropriate for the discovery of selective and non-selective antimicrobial and anticancer peptides.

The venoms of the lesser (Echiichthys vipera) and greater (Trachinus draco) weever fish- A review

In comparison with other animal venoms, fish venoms remain relatively understudied. This is especially true for that of the lesser Echiichthys vipera and greater weever fish Trachinus draco which, apart from the isolation of their unique venom cytolysins, trachinine and dracotoxin, respectively, remain relatively uncharacterised. Envenomation reports mainly include mild symptoms consisting of nociception and inflammation. However, like most fish venoms, if the venom becomes systemic it causes cardiorespiratory and blood pressure changes. Although T. draco venom has not been studied since the 1990's, recent studies on E. vipera venom have discovered novel cytotoxic components on human cancer cells, but due to the scarcity of research on the molecular make-up of the venom, the molecule(s) causing this cytotoxicity remains unknown. This review analyses past studies on E. vipera and T. draco venom, the methods used in the , the venom constituents characterised, the reported symptoms of envenomation and compares these findings with those from other venomous Scorpaeniformes.

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Research on the weever fish venoms Echiichthys vipera and Trachinus draco has

been scarce.

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E. vipera and T. draco venoms elicit cardiorespiratory symptoms in victims.

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E. vipera and T. draco contain unique cytolysins – Trachinine and Dracotoxin.

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Dracotoxin is haemolytic and contains membrane depolarising activities.

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E. vipera venom triggers apoptosis in human colon carcinoma cells.

Type 1 interferon licenses naïve CD8 T cells to mediate anti-viral cytotoxicity

Naïve T cells, unlike memory T cells, exhibit very limited effector function in response to cognate antigen, but exposure to type 1 interferon (IFN) prior to cognate antigen allows for rapid manifestation of effector functions. A full assessment of the functions of these IFN-sensitized otherwise naïve T cells has not been made, nor has their capacity to be effector cells in vivo. We describe here that IFN-sensitized naïve T cells in the absence of cognate antigen adopt a partial activated phenotype distinguished by the upregulation of the surface activation marker CD69, effector-associated transcription factors Eomes and IRF4, and cytotoxicity effector molecule granzyme B. IFN-sensitized naive T cells lysed target cells in vivo and responded to low concentrations and affinities of cognate ligands. We suggest that this rapid and sensitive effector function of IFN-conditioned naïve CD8 T cells may play a role in pathogen control and help ward off superinfections.

Chironex fleckeri (box jellyfish) venom proteins: expansion of a cnidarian toxin family that elicits variable cytolytic and cardiovascular effects

The box jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterization of two C. fleckeri venom proteins, CfTX-A (∼40 kDa) and CfTX-B (∼42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B, and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/2 (25 μg kg(-1)) caused profound effects on the cardiovascular system of anesthetized rats, whereas CfTX-A/B elicited only minor effects at the same dose. Conversely, the hemolytic activity of CfTX-A/B (HU50 = 5 ng ml(-1)) was at least 30 times greater than that of CfTX-1/2. Structural homology between the cubozoan toxins and insecticidal three-domain Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, whereas structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of box jellyfish toxins from a structural and functional perspective.