Characterisation of the heterotrimeric presynaptic phospholipase A2 neurotoxin complex from the venom of the common death adder (Acanthophis antarcticus)

Despite the unparalleled diversity of venomous snakes in Australia, research has concentrated on a handful of medically significant species and even of these very few toxins have been fully sequenced. In this study, venom gland transcriptomes were sequenced from eleven species of small Australian elapid snakes, from eleven genera, spanning a broad phylogenetic range. The particularly large number of sequences obtained for three-finger toxin (3FTx) peptides allowed for robust reconstructions of their dynamic molecular evolutionary histories. We demonstrated that each species preferentially favoured different types of α-neurotoxic 3FTx, probably as a result of differing feeding ecologies. The three forms of α-neurotoxin [Type I (also known as (aka): short-chain), Type II (aka: long-chain) and Type III] not only adopted differential rates of evolution, but have also conserved a diversity of residues, presumably to potentiate prey-specific toxicity. Despite these differences, the different α-neurotoxin types were shown to accumulate mutations in similar regions of the protein, largely in the loops and structurally unimportant regions, highlighting the significant role of focal mutagenesis. We theorize that this phenomenon not only affects toxin potency or specificity, but also generates necessary variation for preventing/delaying prey animals from acquiring venom-resistance. This study also recovered the first full-length sequences for multimeric phospholipase A2 (PLA2) ‘taipoxin/paradoxin’ subunits from non-Oxyuranus species, confirming the early recruitment of this extremely potent neurotoxin complex to the venom arsenal of Australian elapid snakes. We also recovered the first natriuretic peptides from an elapid that lack the derived C-terminal tail and resemble the plesiotypic form (ancestral character state) found in viper venoms. This provides supporting evidence for a single early recruitment of natriuretic peptides into snake venoms. Novel forms of kunitz and waprin peptides were recovered, including dual domain kunitz-kunitz precursors and the first kunitz-waprin hybrid precursors from elapid snakes. The novel sequences recovered in this study reveal that the huge diversity of unstudied venomous Australian snakes are of considerable interest not only for the investigation of venom and whole organism evolution but also represent an untapped bioresource in the search for novel compounds for use in drug design and development.

show abstract

“…Such complexes have recently been reported to be present in the venoms of Acanthophis sp . [60,61,62,63]. …”

Section: Resultsmentioning

confidence: 99%

Venom Down Under: Dynamic Evolution of Australian Elapid Snake Toxins

Jackson

Sunagar

Undheim

et al. 2013

Toxins

View full text Add to dashboard Cite

show abstract

“…This is supported by a study demonstrating the ability of antivenoms to reverse the binding of post-synaptic toxins with the nAChR [71,72]. However, neuromuscular blockade mediated by pre-synaptic toxins is not reversed by antivenom, even if the antivenom is able to bind with the toxin because of the irreversibility of pre-synaptic neurotoxicity [70]. The most widely used method for assessing antivenom efficacy is rodent lethality testing.…”

Section: Antivenomsmentioning

confidence: 99%

“…It therefore measures antivenom efficacy only because antivenom is present prior to venom being added. The ability of antivenoms to bind to, and prevent the neurotoxicity of both long- and short-chain post-synaptic neurotoxins as well as pre-synaptic neurotoxins has been extensively investigated in the chick biventer nerve-muscle preparation [67,68,69,70]. Some studies have also demonstrated the ability of antivenom to partially reverse neurotoxicity in the chick biventer nerve-muscle preparation [65].…”

Section: Antivenomsmentioning

confidence: 99%

Antivenom for Neuromuscular Paralysis Resulting From Snake Envenoming

Silva

Hodgson

2017

Toxins

View full text Add to dashboard Cite

Antivenom therapy is currently the standard practice for treating neuromuscular dysfunction in snake envenoming. We reviewed the clinical and experimental evidence-base for the efficacy and effectiveness of antivenom in snakebite neurotoxicity. The main site of snake neurotoxins is the neuromuscular junction, and the majority are either: (1) pre-synaptic neurotoxins irreversibly damaging the presynaptic terminal; or (2) post-synaptic neurotoxins that bind to the nicotinic acetylcholine receptor. Pre-clinical tests of antivenom efficacy for neurotoxicity include rodent lethality tests, which are problematic, and in vitro pharmacological tests such as nerve-muscle preparation studies, that appear to provide more clinically meaningful information. We searched MEDLINE (from 1946) and EMBASE (from 1947) until March 2017 for clinical studies. The search yielded no randomised placebo-controlled trials of antivenom for neuromuscular dysfunction. There were several randomised and non-randomised comparative trials that compared two or more doses of the same or different antivenom, and numerous cohort studies and case reports. The majority of studies available had deficiencies including poor case definition, poor study design, small sample size or no objective measures of paralysis. A number of studies demonstrated the efficacy of antivenom in human envenoming by clearing circulating venom. Studies of snakes with primarily pre-synaptic neurotoxins, such as kraits (Bungarus spp.) and taipans (Oxyuranus spp.) suggest that antivenom does not reverse established neurotoxicity, but early administration may be associated with decreased severity or prevent neurotoxicity. Small studies of snakes with mainly post-synaptic neurotoxins, including some cobra species (Naja spp.), provide preliminary evidence that neurotoxicity may be reversed with antivenom, but placebo controlled studies with objective outcome measures are required to confirm this.

show abstract

“…β 1 ‐P‐EPTX‐Ar1a and β 2 ‐P‐EPTX‐Ar1a share 85% sequence identity with P‐EPTX‐Aa1a beta chain, isolated from A. antarcticus venom , and 70 and 75% sequence identity with the β 1 and β 2 subunits of cannitoxin , respectively. α‐P‐EPTX‐Ar1a shares 94% sequence identity with P‐EPTX‐Aa1a alpha chain, a PLA 2 toxin isolated from A. antarcticus venom , and 84% sequence identity with the α‐subunit of cannitoxin . The γ‐subunit of P‐EPTX‐Ar1a showed 57% sequence identity with the γ‐subunit of cannitoxin and 69% sequence identity with the P‐EPTX‐Aa1a γ‐subunit.…”

Section: Resultsmentioning

confidence: 99%

Differential Myotoxic and Cytotoxic Activities of Pre‐synaptic Neurotoxins from Papuan Taipan (Oxyuranus scutellatus) and Irian Jayan Death Adder (Acanthophis rugosus) Venoms

Chaisakul

Parkington

Konstantakopoulos³

et al. 2013

Basic Clin Pharma Tox

View full text Add to dashboard Cite

Pre-synaptic PLA 2 neurotoxins are important components of many Australasian elapid snake venoms. These toxins disrupt neurotransmitter release. Taipoxin, a pre-synaptic neurotoxin isolated from the venom of the coastal taipan (Oxyuranus scutellatus), causes necrosis and muscle degeneration. The present study examined the myotoxic and cytotoxic activities of venoms from the Papuan taipan (O. scutellatus) and Irian Jayan death adder (Acanthophis rugosus), and also tested their pre-synaptic neurotoxins: cannitoxin and P-EPTX-Ar1a. Based on size-exclusion chromatography analysis, cannitoxin represents 16% of O. scutellatus venom, while P-EPTX-Ar1a represents 6% of A. rugosus venom. In the chick biventer cervicis nerve-muscle preparation, A. rugosus venom displayed significantly higher myotoxic activity than O. scutellatus venom as indicated by inhibition of direct twitches, and an increase in baseline tension. Both cannitoxin and P-EPTX-Ar1a displayed marked myotoxic activity. A. rugosus venom (50-300 lg/ml) produced concentration-dependent inhibition of cell proliferation in a rat skeletal muscle cell line (L6), while 300 lg/ml of O. scutellatus venom was required to inhibit cell proliferation, following 24-hr incubation. P-EPTX-Ar1a had greater cytotoxicity than cannitoxin, inhibiting cell proliferation after 24-hr incubation in L6 cells. Lactate dehydrogenase levels were increased after 1-hr incubation with A. rugosus venom (100-250 lg/ml), O. scutellatus venom (200-250 lg/ml) and P-EPTX-Ar1a (1-2 lM), but not cannitoxin (1-2 lM), suggesting venoms/toxin generated cell necrosis. Thus, A. rugosus and O. scutellatus venoms possess different myotoxic and cytotoxic activities. The proportion of pre-synaptic neurotoxin in the venoms and PLA 2 activity of the whole venoms are unlikely to be responsible for these activities.While snake envenoming is an infrequent occurrence in Australia, it remains an important cause of morbidity and mortality in Papua New Guinea and Irian Jaya [1,2]. Myotoxicity is a critical outcome of systemic toxicity produced by many Australasian elapids, including rarely with death adders (genus Acanthophis) and taipans (genus Oxyuranus). It has been suggested that phospholipase A 2 (PLA 2 ) is the major venom component responsible for myotoxicity [3][4][5]. Indeed, many snake venoms and isolated PLA 2 toxins display myotoxicity and cytotoxicity (e.g. Lys-49 phospholipase A 2 of Bothrops asper snake venom) [6-10] which induce membrane disruption and Ca 2+ influx.Although the Papuan taipan has been regarded as a separate subspecies to the Australian populations, recent taxonomic studies have indicated no significant differentiation between the two populations [11,12]. The clinical features of systemic taipan envenoming include venom-induced consumption coagulopathy, renal toxicity, cardiac disturbances and a descending neuromuscular paralysis [13][14][15]. The venom of the Australian coastal taipan has myotoxic activity causing necrosis and degeneration of mammalian muscle [16]. In contr...

show abstract

Characterisation of the heterotrimeric presynaptic phospholipase A2 neurotoxin complex from the venom of the common death adder (Acanthophis antarcticus)

Cited by 25 publications

References 54 publications

Venom Down Under: Dynamic Evolution of Australian Elapid Snake Toxins

Venom Down Under: Dynamic Evolution of Australian Elapid Snake Toxins

Antivenom for Neuromuscular Paralysis Resulting From Snake Envenoming

Differential Myotoxic and Cytotoxic Activities of Pre‐synaptic Neurotoxins from Papuan Taipan (Oxyuranus scutellatus) and Irian Jayan Death Adder (Acanthophis rugosus) Venoms

Contact Info

Product

Resources

About