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Proteomic Comparison and Fibrinogenolytic Activity of Causus Snake Venoms from Short and Long Venom Glands

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Proteomic Comparison and Fibrinogenolytic Activity of Causus Snake Venoms from Short and Long Venom Glands Does size matter? Proteomic comparison and fibrinogenolytic activity of Causus snake venoms from short and long venom glands. F. C. P. COIMBRA1 , B. G. FRY1 1 Venom Evolution Lab, University of Queensland, St. Lucia QLD 4072 Australia. [email protected] INTRODUCTION Causus lichtensteinii (Cl) METHODOLOGY Causus (night adders) Venoms: • Six recognised species • No elongated venom gland • Pooled (multiple adults) lyophilised Causus lichtensteinii • Amphibian specialists system and Causus rhombeatus venom. • One of the smallest of its genus • Active pursuit predator Identification of venom proteins: • Fossorial to semi-fossorial • Feeds on small prey (gracile • 1D & 2D SDS-PAGE and tandem mass spectrometry • Morphologically unique frogs) sequencing. amongst vipers in having Fibrinogenolysis: Stago STA-R Max ® narrow heads • 1D SDS-PAGE of 6 time-point incubation series (0-60 min) of 10 venom concentrations (1.5625-800 μg/mL) • Some have elongated venom with purified human fibrinogen (1 mg/mL). glands • Time until clot measured via a Stago STA-R Max® Causus rhombeatus (Cr) coagulation analyser, incubating 17 venom concentrations (0.00935-2 mg/mL) with human fibrinogen • Elongated venom gland system (1.2 mg/mL), CaCl2, and phospholipid (37 ℃ for 60 min), with thrombin added post-incubation in a Claussian • Largest of its genus method (Clauss, 1957). • Feeds on disproportionaly large • Clot formation & strength measured via prey, up to the same weight as the thromboelastography (TEG®5000) with venom (0.2 snake mg/mL), human fibrinogen (2 mg/mL), CaCl2, and TEG ® 5000 phospholipid incubated at 37 ℃ for 30 min; thrombin added post-30 min and re-run for another 30 min. RESULTS Identification of venom proteins (fig.1) • Predominance of metalloproteases and kallikrein-like serine proteases in both venoms • Similar qualitative toxin composition between species • Typical viperid-venom protein classes Fibrinogenolysis • Fibrinogenolytic activity similar for both venoms • Lysis of Aα and Bβ chains only, with Aα consistently quicker and before that of Bβ chain (fig.2) • Degradation of Bβ by Cr venom quicker than that of Cl venom (fig.3) • At a concentration of ≥ 0.4 mg/mL, Cr venom prevented clotting (fig.4) Figure 1. Proteomic comparison via 1D SDS-PAGE of C. Figure 2. Relative proteolytic action of venoms (1.525-800 μg/mL) upon human fibrinogen (1 • Clot strength (mm) reduced by half for both venoms (fig.5) lichtensteinii (Cl) and C. rhombeatus (Cr) venom. Red mg/mL) (Mean ± SD, N=3). boxes indicate protein bands identified via tandem • SAIMR snake polyvalent antivenom neutralised some of Cr venom mass spectrometry: 1) L-amino acid oxidases. 2-4) fibrinogenolytic activity; however, ineffective against Cl venom (data Snake-venom metalloproteases. 5,6) Kallikrein-like not shown) serine proteases. 7) Cysteine-rich secretory proteins. 8) Phospholipases A2 Figure 4. Anticoagulant effect on 1.2 mg/mL of human fibrinogen incubated with Cr venom for 60 min. (Mean ± Figure 3. Overall view of fibrinogenolytic action after 60 minutes of incubation with venoms SD, N=3. In some cases error bars are smaller than symbol). (Mean ± SD, N=3). REFERENCES Figure 5. Thromboelastography tracings (N=3) of clot formation by post-30 min addition of Coimbra, F.C.P. et al. Does size matter? Venom proteomic and functional comparison between night adder species (Viperidae: Causus) thrombin to à priori venom (0.2 mg/mL) & fibrinogen (2.1 mg/mL) incubation, overlaid with with short and long venom glands. Comparative Biochemistry and Physiology, Part C (2018) 221: 7-14. negative control tracings (N=3). CONCLUSIONS ACKNOWLEDGEMENTS • Both venoms are dominated by snake-venom metalloproteases and kallikrein-like serine proteases, which in viper venoms have convergently evolved fibrinogenolytic activity and are thus likely responsible for the fibrinogenolysis observed in this study. • The cleavage of fibrinogen’s Aα and Bβ chains resulted in an anticoagulant effect and would likely result in hypofibrinogenemia in vivo. • Although toxin classes are conserved between both species, isoformic variability (2D PAGE not shown) may be responsible for differential SAIMR polyvalent antivenom effectiveness. • Given the venoms’ similarities, these results suggest a link between the elongated venom gland system and a predatory niche where venom yield is favoured over venom toxicity and/or diversification for predating upon proportionally larger prey. • However, this study does not represent the full suite of the venoms’ bioactivity, therefore future work on haemotoxic activity should include additional haemostatic components..
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