Abstract
Animal venoms have evolved over millions of years for prey capture and defense from predators and rivals. Snake venoms, in particular, have evolved a wide diversity of peptides and proteins that induce harmful inflammatory and neurotoxic effects including severe pain and paralysis, hemotoxic effects, such as hemorrhage and coagulopathy, and cytotoxic/myotoxic effects, such as inflammation and necrosis. If untreated, many envenomings result in death or severe morbidity in humans and, despite advances in management, snakebite remains a major public health problem, particularly in developing countries. Consequently, the World Health Organization recently recognized snakebite as a neglected tropical disease that affects ~2.7 million p.a. The major protein classes found in snake venoms are phospholipases, metalloproteases, serine proteases, and three-finger peptides. The mechanisms of action and pharmacological properties of many snake venom toxins have been elucidated, revealing a complex multifunctional cocktail that can act synergistically to rapidly immobilize prey and deter predators. However, despite these advances many snake toxins remain to be structurally and pharmacologically characterized. In this review, the multifunctional features of the peptides and proteins found in snake venoms, as well as their evolutionary histories, are discussed with the view to identifying novel modes of action and improving snakebite treatments.
Highlights
The composition and evolutionary histories of animal venoms have fascinated the scientific community for centuries
Such studies have revealed surprising cross-reactivity of antivenoms against distinct, non-targeted, snake species, such as: (i) the potential utility of Asian antivenoms developed against terrestrial elapid snakes at neutralizing the venom toxicity of potent sea snake venoms (Tan et al, 2015), (ii) the seeming utility of African polyvalent antivenom at neutralizing the venom of a genus of elapid snakes not including in the immunizing mixture (Whiteley et al, 2019), and (iii) the potential for saw-scaled viper antivenom to be used as an alternative treatment for bites by the boomslang (Dispholidus typus) in regions where the appropriate speciesspecific antivenom is unavailable or unaffordable (Ainsworth et al, 2018)
The multifunctional approach adopted by the major components of their venoms, by using multidomain proteins and peptides with promiscuous folds, as well as their diversity of toxic effects, are unique and yet to be identified in other animal venoms at such level of complexity
Summary
The composition and evolutionary histories of animal venoms have fascinated the scientific community for centuries. Certain “colubrid” snakes, whether medically important or not, show evidence of having multiple SVMP toxins in their venom, even if they do not show the sub-class diversity observed in the vipers (Mackessy and Saviola, 2016; Pla et al, 2017; Modahl et al, 2018a; Perry et al, 2018) It is relatively uncommon for elapid snakebites to cause systemic hemotoxicity (Slagboom et al, 2017) and this is likely a consequence of those venoms exhibiting little diversity or abundance of SVMPs, and instead usually being dominated by neurotoxic toxin families such as the 3FTXs and PLA2s (Tasoulis and Isbister, 2017). This occurs through modulation of factors such as fibrinogenase and fibrolase that mediate the coagulation cascade, depletion of pro-coagulation
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