Comparative Profiling of Three Atheris Snake Venoms: A. squamigera, A. nitschei and A. chlorechis

Abstract

A proteomic and transcriptomic comparative analysis of the venoms of three Atheris species (A. squamigera, A. nitschei and A. chlorechis) was carried out by size exclusion liquid chromatography, gel electrophoresis, mass spectrometry, and mRNA sequencing. The improved proteomic profiling utilised in this work was combined with transcript studies, advancing our insights into venom composition, protein distribution and inter-species variation among the three bush vipers. Crude venoms of all three samples contained at least 10-20 protein components, ranging in size from ≤ 3 to > 98 kDa. Both approaches yielded converging overall information, pointing to phospholipases, disintegrins, serine proteases and metalloproteases as the major toxin classes, which are likely to explain the local and systemic symptoms observed in envenomation by Atheris genus. Being considered as the main factors involved in the distinct venom-induced pathologies, these identified snake venom proteins are of particular interest in terms of understanding their physiological and biological function as well as for their contribution in potential medical treatments.

Old World Vipers—A Review about Snake Venom Proteomics of Viperinae and Their Variations

“…For example, well-investigated genera include the Oriental vipers Daboia with 24 venom compositions, followed by Palaearctic Vipers Vipera (18 compositions), and saw-scaled vipers Echis (16 compositions). Others like the bush vipers Atheris, with 18 species, only contain three venom proteomes in a single study [ 69 ]. Likewise, five out of 18 Bitis species venom compositions are known ( Table 1 ).…”

“…The African bush vipers, Atheris genus, have a dominating PLA 2 and DI content in their venom with a strong species-specific diversity at high molecular toxins range (30–70 kDa), like svMP and svSP [ 69 ]. Size-exclusion chromatograms reveal a higher correlation between A. squamigera and A. nitschei than to A. chlorechis .…”

Characterising venom variation and antivenom effectiveness within the “True” vipers (Viperinae: Viperidae)

“…All venoms in present study hypothesis, the sister genus Macrovipera has been documented as having Factor X and Factor V activation activity similar to that of Daboia [186]. This is further corroborated by the widespread procoagulant activity within the Viperinae subfamily, including members of Atheris, Bitis, Cerastes, Echis, Eristicophis, Proatheris, and Pseudocerastes, as each genus possesses either majority members or a basal member that clot plasma and/or activate factor X or prothrombin [186][187][188][189]. This indicates that the expression of procoagulant toxins may be the ancestral condition for the true vipers.…”

“…This suggests that the venom may be concurrently cleaving fibrinogen in a degradative manner (see urarachnoides exemplifies this with its ability to cleave both factors X and prothrombin. Factor X activation has been converged upon by numerous snake lineages, vipers in particular [186][187][188][189]. The success of this envenoming strategy is likely underpinned by the high conservation of factor X cleavage sites even between such divergent lineages as amphibians and placental mammals [250].…”

Ruthenium, Not Carbon Monoxide, Inhibits the Procoagulant Activity of Atheris, Echis, and Pseudonaja Venoms

“…To this end, three procoagulant venoms derived from diverse species from Africa and Australia were selected that have already been characterized as inhibited by CORM-2 but not by its iRM by this laboratory [8,10]. The species chosen are displayed in Table 1, and the venom proteomes of these particular and snakes within the same genus are similar in terms of presence of snake venom serine proteases (SVSP), snake venom metalloproteinases (SVMP), and PLA 2 [17][18][19][20][21]. Fortuitously, archived aliquots of these three venoms that were never thawed or used in the original studies [8,10] were maintained at −80 • C and were available for the present investigation to test the hypothesis that inhibition by ruthenium molecular species and not carbon monoxide may be the mechanism by which these procoagulant venoms were inhibited by CORM-2.…”