Purification and functional characterization of AAV1, a novel P-III metalloproteinase, from Formosan Agkistrodon acutus venom

Comparative analysis of Deinagkistrodon acutus venom from Taiwan and China utilizing chromatographic, electrophoretic, and bioinformatic approaches, along with ELISA employing a monospecific antivenom

Deinagkistrodon acutus is a medically important pitviper inhabiting mainly South China and Taiwan. The hemorrhagic effects of its envenoming are compatible to its venom, which is abundant in metalloproteases (svMPs) and C-type lectin-like proteins. In this study, we investigated geographic variations in the venom of D. acutus collected from Taiwan and four Mainland Chinese provinces: Fujian, Jiangxi, Anhui, and Hunan. The variations were assessed through high-performance liquid chromatography, non-metric multidimensional scaling analysis, gel electrophoresis, and enzyme-linked immunosorbent assay (ELISA) with a monospecific antivenom (DaMAV) generated against the Taiwanese D. acutus venom, and discussed based on venom-protein sequences in databases and literature related to D. acutus venom. Additionally, the cross-reactivity of DaMAV against Crotalus horridus and Calloselasma rhodostoma venoms was investigated. We noted differential abundances of D. acutus venom metalloproteases, C-type lectin-like proteins, and phospholipase A2, along with point mutations and selective expression of serine protease isoforms. The ELISA results revealed that the venom from Taiwan was more reactive toward Taiwanese DaMAV than the four Mainland Chinese venoms, consistent with chromatographic profile differences, whereas C. horridus venom presented moderate cross-reactivity with DaMAV. The observed immunoreactivities of these venom with DaMAV can be attributed to the high prevalence of their PIII-svMPs, which are the dominant antigens, and the conservation of PIII-svMP epitopes.

Venomics and antivenomics of Indian spectacled cobra (Naja naja) from the Western Ghats

Venom proteome profiling of Naja naja from the Western Ghats region in Kerala was achieved through SDS-PAGE and RP-HPLC followed by Q-TOF LC-MS/MS analysis, incorporating PEAKS and Novor assisted de novo sequencing methodologies. A total of 115 proteins distributed across 17 different enzymatic and non-enzymatic venom protein families were identified through conventional and 39 peptides through homology-driven proteomics approaches. Fourteen peptides derived through de novo complements the Mascot data indicating the importance of homology-driven approaches in improving protein sequence information. Among the protein families identified, glutathione peroxidase and endonuclease were reported for the first time in the Indian cobra venom. Immunological cross-reactivity assessed using Indian polyvalent antivenoms suggested that VINS showed better EC₅₀ (2.48 µg/mL) value than that of PSAV (6.04 µg/mL) and Virchow (6.03 µg/mL) antivenoms. Western blotting experiments indicated that all the antivenoms elicited poor binding specificities, especially towards low molecular mass proteins. Second-generation antivenomics studies revealed that VINS antivenom was less efficient to detect many low molecular mass proteins such as three-finger toxins and Kunitz-type serine protease Inhibitors. Taken together, the present study enabled a large-scale characterization of the venom proteome of Naja naja from the Western Ghats and emphasized the need for developing more efficient antivenoms.

Exploring the five-paced viper (Deinagkistrodon acutus) venom proteome by integrating a combinatorial peptide ligand library approach with shotgun LC-MS/MS

BACKGROUND

Snake venoms are complex mixtures of toxic proteins or peptides encoded by various gene families that function synergistically to incapacitate prey. In the present study, in order to unravel the proteomic repertoire of Deinagkistrodon acutus venom, some trace abundance components were analyzed.

METHODS

Shotgun proteomic approach combined with shotgun nano-LC-ESI-MS/MS were employed to characterize the medically important D. acutus venom, after collected samples were enriched with the combinatorial peptide ligand library (CPLL).

RESULTS

This avenue helped us find some trace components, undetected before, in D. acutus venom. The results indicated that D. acutus venom comprised 84 distinct proteins from 10 toxin families and 12 other proteins. These results are more than twice the number of venom components obtained from previous studies, which were only 29 distinct proteins obtained through RP-HPLC for the venom of the same species. The present results indicated that in D. acutus venom, the most abundant components (66.9%) included metalloproteinases, serine proteinases, and C-type lectin proteins; the medium abundant components (13%) comprised phospholipases A2 (PLA2) and 5'-nucleotidases and nucleases; whereas least abundant components (6%) were aminopeptidases, L-amino acid oxidases (LAAO), neurotoxins and disintegrins; and the trace components. The last were undetected before the use of conventional shotgun proteomics combined with shotgun nano-LC-ESI-MS/MS, such as cysteine-rich secretory proteins Da-CRPa, phospholipases B-like 1, phospholipases B (PLB), nerve growth factors (NGF), glutaminyl-peptide cyclortransferases (QC), and vascular non-inflammatory molecules 2 (VNN2).

CONCLUSION

These findings demonstrated that the CPLL enrichment method worked well in finding the trace toxin proteins in D. acutus venom, in contrast with the previous venomic characterization of D. acutus by conventional LC-MS/MS. In conclusion, this approach combined with the CPLL enrichment was effective for allowing us to explore the hidden D. acutus venomic profile and extended the list of potential venom toxins.

Atroxlysin-III, A Metalloproteinase from the Venom of the Peruvian Pit Viper Snake Bothrops atrox (Jergón) Induces Glycoprotein VI Shedding and Impairs Platelet Function

Atroxlysin-III (Atr-III) was purified from the venom of Bothrops atrox. This 56-kDa protein bears N-linked glycoconjugates and is a P-III hemorrhagic metalloproteinase. Its cDNA-deduced amino acid sequence reveals a multidomain structure including a proprotein, a metalloproteinase, a disintegrin-like and a cysteine-rich domain. Its identity with bothropasin and jararhagin from Bothrops jararaca is 97% and 95%, respectively. Its enzymatic activity is metal ion-dependent. The divalent cations, Mg²⁺ and Ca²⁺, enhance its activity, whereas excess Zn²⁺ inhibits it. Chemical modification of the Zn²⁺-complexing histidine residues within the active site by using diethylpyrocarbonate (DEPC) inactivates it. Atr-III degrades plasma fibronectin, type I-collagen, and mainly the α-chains of fibrinogen and fibrin. The von Willebrand factor (vWF) A1-domain, which harbors the binding site for GPIb, is not hydrolyzed. Platelets interact with collagen via receptors for collagen, glycoprotein VI (GPVI), and α2β1 integrin. Neither the α2β1 integrin nor its collagen-binding A-domain is fragmented by Atr-III. In contrast, Atr-III cleaves glycoprotein VI (GPVI) into a soluble ~55-kDa fragment (sGPVI). Thereby, it inhibits aggregation of platelets which had been stimulated by convulxin, a GPVI agonist. Selectively, Atr-III targets GPVI antagonistically and thus contributes to the antithrombotic effect of envenomation by Bothrops atrox.

Clinical and laboratory features distinguishing between Deinagkistrodon acutus and Daboia siamensis envenomation

Background

There are 6 species of venomous snakes in Taiwan. Two of them, Deinagkistrodon acutus (D. acutus) and Daboia siamensis (D. siamensis), can cause significant coagulopathy. However, a significant proportion of patients with snakebites cannot identify the correct snake species after envenomation, which hampers the application of antivenom. Hence, the differential diagnosis between the two snakebites by clinical presentations is important. This study aims to compare their clinical and laboratory features for the purpose of differential diagnosis between the two snakebites.

Methods

We retrospectively reviewed the medical records of patients who arrived at the emergency department due to D. acutus or D. siamensis envenomation, between 2003 and 2016, in one medical center in eastern Taiwan. Since these snakebites are rare, we also included 3 cases reported from another hospital in central Taiwan.

Results

In total, 15 patients bitten by D. acutus and 12 patients by D. siamensis were analyzed. Hemorrhagic bulla formation and the need for surgical intervention only presented for D. acutus envenomation cases (Both 53.3% vs. 0.0%, P = 0.003). As to laboratory features, lower platelet counts (20.0 ×  10³/μL [interquartile range, 14–66 × 10³/μL] vs. 149.0 × 10³/μL [102.3–274.3 × 10³/μL], P = 0.001), lower D-dimer level (1423.4 μg/L [713.4–4212.3 μg/L] vs. 12,500.0 μg/L [2351.4–200,000 μg/L], P = 0.008), higher proportion of patients with moderate-to-severe thrombocytopenia (platelet count < 100 × 10³/μL) (80% vs. 16.7%, odds ratio (OR) = 20.0, 95% CI, 2.77–144.31; P = 0.002), and lower proportion of patients with extremely high D-dimer (> 5000 ng/mL) (16.7% vs. 66.7%, adjusted OR = 0.1 (95% CI, 0.01–0.69; P = 0.036) were found among cases of D. acutus envenomation compared to D. siamensis envenomation. The combination of hemorrhagic bulla, thrombocytopenia, and a lack of extremely high D-dimer had good discriminatory power (area under the curve (AUC) = 0.965; 95% CI, 0.904–1.00) for distinguishing D. acutus from D. siamensis envenomation.

Conclusions

The presentation of moderate to severe thrombocytopenia (platelet count < 100 × 10³/μL) and hemorrhagic bulla formation may indicate D. acutus envenomation. However, the envenomed patient with extremely high D-dimer levels may indicate a D. siamensis envenomation. These findings may help diagnose and select the right antivenom in patients with unknown snakebites who present significant coagulopathy.

[Fibrinogen/fibrin-specific enzymes from copperhead (Agkistrodon halys halys) and cobra (Naja oxiana eichwald) snake venoms]

Ability of fractions of cobra's (Naja oxiana Eichwald) and copperhead snake's (Agkistrodon halys halys) venoms to hydrolyze fibrinogen/fibrin was studied. In cobra's snake a component with molecular mass of nearly 60 kDa was found to hydrolyze a-chain of fibrinogen but failed to hydrolyze casein/azocasein and fibrin. A fibrinogen-specific metalloproteinase, the enzyme was inhibited by EDTA. Cobra's venom reduced the mass of donor's fresh blood clots. The copperhead snake's venom and the fractions obtained by gel-filtration (HW-50) and ion exchange chromatography (DEAE-650) were found to hydrolyze casein/azocasein, a- and b-chains of fibrinogen/fibrin and donor's blood clots. The results from the study of the venom and proteolytically active fractions are the evidence for a thrombolytic potential in a copperhead snake's venom.

Structural and biochemical characterisation of VaF1, a P-IIIa fibrinogenolytic metalloproteinase from Vipera ammodytes ammodytes venom

A high molecular mass metalloproteinase with α-fibrinogenolytic activity, termed VaF1, was purified from nose-horned viper (Vipera ammodytes ammodytes) venom. Subcutaneous injection of 9 μg of VaF1 did not induce bleeding in rats. Nevertheless, in vitro it degraded collagen IV, nidogen and fibronectin, components of the extracellular matrix, although with low efficacy and narrow specificity. VaF1 would be expected to exert anti-coagulant action, due to its hydrolysis of fibrinogen, factor X, prothrombin and plasminogen, plasma proteins involved in blood coagulation. The enzyme is a single-chain glycoprotein with a molecular mass of 49.7 kDa, as determined by mass spectrometry, and multiple isoelectric points centred at pH 5.8. The complete amino acid sequence of the precursor of VaF1 was deduced by cloning and sequencing its cDNA. Composed of metalloproteinase, disintegrin-like and cysteine-rich domains, VaF1 is a typical P-IIIa subclass snake venom metalloproteinase. Although it possesses a collagen-binding sequence in its disintegrin-like domain, VaF1 displayed no effect on collagen-induced platelet aggregation in vitro. Two consensus N-glycosylation sites are present in the sequence of VaF1, however, the extent of its glycosylation is low, only 5.2% of the total molecular mass. Interestingly, in standard experimental conditions VaF1 is not recognised by antiserum against the whole venom, so it can contribute to post-serotherapy complications, such as ineffective blood coagulation, in the envenomed patient.

Rapid purification of a new P-I class metalloproteinase from Bothrops moojeni venom with antiplatelet activity

The present study aimed to evaluate the proteolytic and biological activities of a new metalloproteinase from B. moojeni venom. The purification of BmooMPα-II was carried out through two chromatographic steps (ion-exchange and affinity). BmooMPα-II is a monomeric protein with an apparent molecular mass of 22.5 kDa on SDS-PAGE 14% under nonreducing conditions. The N-terminal sequence (FSPRYIELVVVADHGMFTKYKSNLN) revealed homology with other snake venom metalloproteinases, mainly among P-I class. BmooMPα-II cleaves Aα-chain of fibrinogen followed by Bβ-chain, and does not show any effect on the γ-chain. Its optimum temperature and pH for the fibrinogenolytic activity were 30–50°C and pH 8, respectively. The inhibitory effects of EDTA and 1,10-phenantroline on the fibrinogenolytic activity suggest that BmooMPα-II is a metalloproteinase. This proteinase was devoid of haemorrhagic, coagulant, or anticoagulant activities. BmooMPα-II caused morphological alterations in liver, lung, kidney, and muscle of Swiss mice. The enzymatically active protein yet inhibited collagen, ADP, and ristocetin-induced platelet aggregation in a concentration-dependent manner. Our results suggest that BmooMPα-II contributes to the toxic effect of the envenomation and that more investigations to elucidate the mechanisms of inhibition of platelet aggregation may contribute to the studies of snake venom on thrombotic disorders.

Purification and partial characterization of a novel fibrinogenase from the venom of Deinagkistrodon acutus: inhibition of platelet aggregation

A novel fibrinogenase, DAnase, was purified from the venom of Deinagkistrodon acutus by a combination of anion and cation exchange chromatography. Unlike other fibrinogenases which are usually single polypeptide chain proteins, the enzyme was a disulfide-linked dimer with an isoelectric point of 6.03 and an apparent molecular weight of 25kDa on SDS-polyacrylamide gel electrophoresis. DAnase showed α-fibrinogenase activity devoid of fibrinolytic activity. It hydrolyzed rapidly the Aα-chain of fibrinogen and followed by the Bβ-chain and did not cleave the γ-chain. It also exhibited arginine esterase activity. The fibrinogenolytic and arginine esterase activities were completely inhibited by phenylmethanesulfonyl fluoride or tris-(2-carboxyethyl)phosphine hydrochloride, but not by EDTA, indicating that DAnase is a serine protease requiring disulfide bridge(s) for its activity. The protease strongly inhibited ADP-induced platelet aggregation in human platelet-rich plasma but was lack of ADPase activity, indicating that its fibrinogenolytic activity is involved in its inhibition of ADP-induced platelet aggregation. DAnase was devoid of hemorrhagic activity and Factor XIII activation activity. DAnase may have a potential clinical application for the therapy of thrombosis disease.

Albocollagenase, a novel recombinant P-III snake venom metalloproteinase from green pit viper (Cryptelytrops albolabris), digests collagen and inhibits platelet aggregation

Molecular cloning and functional characterization of P-III snake venom metalloproteinases (SVMPs) will give us deeper insights in the pathogenesis of viper bites. This may lead to novel therapy for venom-induced local tissue damages, the complication refractory to current antivenom. The aim of this study was to elucidate the in vitro activities of a new SVMP from the green pit viper (GPV) using recombinant DNA technology. We report, here, a new cDNA clone from GPV (Cryptelytrops albolabris) venom glands encoding 614 amino acid residues P-III SVMP, termed albocollagenase. The conceptually translated protein comprised a signal peptide and prodomain, followed by a metalloproteinase domain containing a zinc-binding motifs, HEXGHXXGXXH-CIM and 9 cysteine residues. The disintegrin-like and cysteine-rich domains possessed 24 cysteines and a DCD (Asp-Cys-Asp) motif. The albocollagenase deduced amino acid sequence alignments showed approximately 70% identity with other P-III SVMPs. Notably, the prodomain was highly conserved, while the metalloproteinase, disintegrin-like and cysteine-rich domains contained several differences. Albocollagenase without the signal peptide and prodomain was expressed in Pichia pastoris with an N-terminal six-histidine tag. After affinity purification from the supernatant of methanol-induced media, SDS-PAGE and Western blot analysis in both reducing and non-reducing conditions showed a protein band of approximately 62 kDa. The recombinant albocollagenase could digest human type IV collagen from human placenta basement membrane within 1 min. After 10-min incubation, it also inhibited collagen-induced platelet aggregation with 50% inhibitory concentration (IC₅₀) of 70 nM. This is the first report of the active recombinant SVMP enzymes expressed in P. pastoris. The results suggest the significant roles of P-III SVMP in local and systemic pathology of envenomated patients. Inhibitors of this SVMP will be investigated in further studies to find a better treatment for viper bites.

Haemostatically active proteins in snake venoms

Snake venom proteins that affect the haemostatic system can cause (a) lowering of blood coagulability, (b) damage to blood vessels, resulting in bleeding, (c) secondary effects of bleeding, e.g. hypovolaemic shock and organ damage, and (d) thrombosis. These proteins may, or may not, be enzymes. We review the data on the most relevant haemostatically active proteinases, phospholipases A₂, L-amino acid oxidases and 5'-nucleotidases from snake venoms. We also survey the non-enzymatic effectors of haemostasis from snake venoms--disintegrins, C-type lectins and three-finger toxins. Medical applications have already been found for some of these snake venom proteins. We describe those that have already been approved as drugs to treat haemostatic disorders or are being used to diagnose such health problems. No clinical applications, however, currently exist for the majority of snake venom proteins acting on haemostasis. We conclude with the most promising potential uses in this respect.

The metalloprotease, NN-PF3 from Naja naja venom inhibits platelet aggregation primarily by affecting α2β1 integrin

NN-PF3 is a non-toxic, anticoagulant, high-molecular-mass (67.81 kDa) metalloprotease from Indian cobra (Naja naja) venom. In the present study, NN-PF3 was investigated for the mechanism of inhibition of collagen-induced aggregation of human platelets. The complete inhibition of collagen-induced aggregation and partial inhibition of ADP- and epinephrine-induced aggregation has the respective IC(50) of 75 ± 5, 185 ± 10, and 232 ± 12 nM, whereas no inhibition of thrombin-, arachidonic acid-, and ristocetin-induced aggregation of platelets was observed in platelet-rich plasma. Further, native NN-PF3 and EDTA-inactivated NN-PF3 inhibited collagen-induced aggregation of washed platelets with respective IC(50) of 75 ± 4 and 180 ± 6 nM. The higher inhibitory effect of native NN-PF3 compared with EDTA-inactivated NN-PF3 suggests the enzymatic and non-enzymatic mechanism of inhibition. NN-PF3 pretreatment affected the collagen binding but not the fibrinogen, and fibronectin binding of washed platelets in adhesion assay suggested that the collagen receptors are affected. Western blot study using anti-integrin α2β1 mAb 6F1 suggested that NN-PF3 binds to integrin α2β1 in a primary structure-dependent manner only and is not cleaved. There was a drastic reduction in the intensity of several intracellular signaling phosphotyrosine protein bands when monoclonal anti-phosphotyrosine antibody was used, suggesting that the major activation pathway of platelets get affected, which occurs through glycoprotein VI. NN-PF3 did not bind to collagen as revealed by Western blot using anti-collagen mAb. Furthermore, neither the proteolytic cleavage of fibrinogen nor its degradation products by NN-PF3 contributed for the collagen-induced platelet aggregation inhibition.

Stejnihagin, a novel snake metalloproteinase from Trimeresurus stejnegeri venom, inhibited L-type Ca2+ channels

Snake venom metalloproteinases (SVMPs) mainly distribute in Crotalid and Viperid snake venom and are classified into the Reprolysin subfamily of the M12 family of metalloproteinases. Previous function investigations have suggested that SVMPs are the key toxins involved in a variety of snake venom-induced pathogenesis including systemic injury, local damage, hemorrhage, edema, hypotension, hypovolemia, inflammation and necrosis. However, up to now, there is no report on ion channels blocking activity about SVMPs. Here, from Trimeresurus stejnegeri venom we purified a component Stejnihagin containing a mixture of Stejnihagin-A and -B, with 86% sequences identity, both as members of SVMPs. In the study, whole-cell patch clamp and vessel tension measurement were employed to identify the effect of Stejnihagin on L-type Ca2+ channels and vessel contraction. The results show that Stejnihagin inhibited L-type Ca2+ channels in A7r5 cells with an IC50 about 37 nM and simultaneously blocked 60 mM K+-induced vessel contraction. Besides, the inhibitory effect of Stejnihagin on L-type Ca2+ channels was also independent of the enzymatic activity. This finding offers new insight into the snake venom metalloproteinase functions and provides a novel pathogenesis of T. stejnegeri venom. Furthermore, it may also provide a clue to study the structure-function relationship of animal toxins and voltage-gated Ca2+ channel.

P-III hemorrhagic metalloproteinases from Russell's viper venom: cloning, characterization, phylogenetic and functional site analyses

Two homologous P-III hemorrhagic metalloproteinases were purified from Russell's viper venoms from Myanmar and Kolkata (eastern India), and designated as daborhagin-M and daborhagin-K, respectively. They induced severe dermal hemorrhage in mice at a minimum hemorrhagic dose of 0.8-0.9 microg. Daborhagin-M specifically hydrolyzed an Aalpha-chain of fibrinogen, fibronectin, and type IV collagen in vitro. Analyses of its cleavage sites on insulin chain B and kinetic specificities toward oligopeptides suggested that daborhagin-M prefers hydrophobic residues at the P(1), P(1)', and P(2)' positions on the substrates. Of the eight Daboia geographic venom samples analyzed by Western blotting, only those from Myanmar and eastern India showed a strong positive band at 65kDa, which correlated with the high risk of systemic hemorrhagic symptoms elicited by Daboia envenoming in both regions. The full sequence of daborhagin-K was determined by cDNA cloning and sequencing, and then confirmed by peptide mass fingerprinting. Furthermore, molecular phylogenetic analyses based on 27 P-IIIs revealed the co-evolution of two major P-III classes with distinct hemorrhagic potencies, and daborhagin-K belongs to the most hemorrhagic subclass. By comparing the absolute complexity profiles between these two classes, we identified four structural motifs probably responsible for the phylogenetic subtyping and hemorrhagic potencies of P-III SVMPs.

Structural and functional characterization of a P-III metalloproteinase, leucurolysin-B, from Bothrops leucurus venom

Leucurolysin-B (leuc-B) is an hemorrhagic metalloproteinase found in the venom of Bothrops leucurus (white-tailed-jararaca) snake. By means of liquid chromatography consisting of gel filtration on Sephracryl S-200, S-300 and ion-exchange on DEAE Sepharose, leuc-B was purified to homogeneity. The proteinase has an apparent molecular mass of 55kDa as revealed by the reduced SDS-PAGE, and represents approximately 1.2% of the total protein in B. leucurus venom. The partial amino acid sequence of leuc-B was determined by automated Edman sequencing of peptides derived from digests of the S-reduced and alkylated protein with trypsin. Leuc-B exhibits the characteristic motif of metalloproteinases, HEXXHXXGXXH and a methionine-containing turn of similar conformation ("Met-turn"), which forms a hydrophobic basis for the zinc ions and the three histidine residues involved as ligands. Leuc-B has been characterized as a P-III metalloproteinase and possesses a multidomain structure including a metalloproteinase, a disintegrin-like (ECD sequence instead of the typical RGD motif) and a cysteine-rich C-terminal domain. Leuc-B contains three potential sites of N-glycosylation. The enzyme only cleaves the Ala14-Leu15 peptide bond of the oxidized insulin B-chain and preferentially hydrolyzes the Aalpha-chain of fibrinogen and the alpha-chain of fibrin. Its proteolytic activity was completely inhibited by metal chelating agents but not by other typical proteinase inhibitors. In addition, its enzymatic activity was stimulated by the divalent cations Ca2+ and Mg2+ but inhibited by Zn2+ and Cu2+. The catalytic activity of leuc-B on extracellular matrix proteins could readily lead to loss of capillary integrity resulting in hemorrhage occurring at those sites (MHD=30ng in rabbit), with alterations in platelet function. In summary, here we report the isolation and the structure-function relationship of a P-III snake venom metalloproteinase.