Comparative gender peptidomics of Bothrops atrox venoms: are there differences between them?

Bothrops atrox is known to be the pit viper responsible for most snakebites and human fatalities in the Amazon region. It can be found in a wide geographical area including northern South America, the east of Andes and the Amazon basin. Possibly, due to its wide distribution and generalist feeding, intraspecific venom variation was reported by previous proteomics studies. Sex-based and ontogenetic variations on venom compositions of Bothrops snakes were also subject of proteomic and peptidomic analysis. However, the venom peptidome of B. atrox remains unknown. Methods: We conducted a mass spectrometry-based analysis of the venom peptides of individual male and female specimens combining bottom-up and top-down approaches. Results: We identified in B. atrox a total of 105 native peptides in the mass range of 0.4 to 13.9 kDa. Quantitative analysis showed that phospholipase A2 and bradykinin potentiating peptides were the most abundant peptide families in both genders, whereas disintegrin levels were significantly increased in the venoms of females. Known peptides processed at non-canonical sites and new peptides as the Ba1a, which contains the SVMP BATXSVMPII1 catalytic site, were also revealed in this work. Conclusion: The venom peptidomes of male and female specimens of B. atrox were analyzed by mass spectrometry-based approaches in this work. The study points to differences in disintegrin levels in the venoms of females that may result in distinct pathophysiology of envenomation. Further research is required to explore the potential biological implications of this finding.(AU)

cDNA cloning, heterologous expression, protein folding and immunogenic properties of a phospholipase A2 from Bothrops ammodytoides venom.

A mRNA transcript that codes for a phospholipase (PLA2) was isolated from a single venom gland of the Bothrops ammodytoides viper. The PLA2 transcript was cloned onto a pCR®2.1-TOPO vector and subsequently expressed heterologously in the E. coli strain M15, using the pQE30 vector. The recombinant phospholipase was named rBamPLA2_1, and is composed of an N-terminal fusion protein of 16 residues, along with 122 residues from the mature protein that includes 14 cysteines that form 7 disulfide bonds. Following bacterial expression, rBamPLA2_1 was obtained from inclusion bodies and extracted using a chaotropic agent. rBamPLA2_1 had an experimental molecular mass of 15,692.5 Da that concurred with its theoretical molecular mass. rBamPLA2_1 was refolded in in vitro conditions and after refolding, three main protein fractions with similar molecular masses, were identified. Although, the three fractions were considered to represent different oxidized cystine isoforms, their secondary structures were comparable. All three recombinant isoforms were active on egg-yolk phospholipid and recognized similar cell membrane phospholipids to be native PLA2s, isolated from B. ammodytoides venom. A mixture of the three rBamPLA2_1 cystine isoforms was used to immunize a horse in order to produce serum antibodies (anti-rBamPLA2_1), which partially inhibited the indirect hemolytic activity of B. ammodytoides venom. Although, anti-rBamPLA2_1 antibodies were not able to recognize crotoxin, a PLA2 from the venom of a related but different viper genus, Crotalus durissus terrificus, they recognized PLA2s in other venoms from regional species of Bothrops.

Bothrops jararaca accessory venom gland is an ancillary source of toxins to the snake.

In Viperidae snakes, it has been attributed to the main venom gland, a component of the venom gland apparatus, the function of synthesizing all venom toxins and storing them inside a basal-central lumen. However, the role of the accessory gland is still unknown. Here, we analyzed the proteome and the transcriptome of the accessory gland during venom production and secretion cycle. We showed that the accessory gland expresses and synthesizes toxins that are similar to those produced by the main venom gland such as C-type lectin/C-type lectin-like proteins, metalloproteinase, phospholipase A2, cysteine rich secretory protein, nerve growth factor, vascular endothelial growth factor, serine proteinase, and l-amino acid oxidase. Our data have shown that toxin synthesis in the accessory gland is asynchronous when compared to the same process in the venom gland. Moreover, this gland also expresses inhibitors of venom phospholipases A2 and metalloproteinases. Transcriptome analysis showed that the transcripts that correspond to toxins in the accessory gland have a good correlation to the main venom gland transcripts. Therefore, it is proposed that the accessory gland is an ancillary source of toxins to the snake, and provides inhibitors that could control venom toxicity (and integrity) during storage. SIGNIFICANCE: In this study, we propose that the accessory venom gland acts as an important ancillary source of toxins to the snake, in lieu of a depleted main venom gland, and provides inhibiting agents that control venom toxicity (and integrity) during its storage.

Expression, purification and characterization of a novel recombinant SVTLE, r-agkihpin-2, from Gloydius halys Pallas venom gland in Escherichia coli.

In our previous work, a thrombin-like enzyme (TLE), agkihpin, was successfully isolated, purified, cloned and named from the venom of Gloydius halys Pallas, having fibrinolytic, fibrinogenolytic and thrombosis-reduced activities, attenuating migration of liver cancer cell, and without bleeding risk. To explore the possibility of agkihpin as a thrombolytic and/or anti-metastasis agent in the future, in this study recombinant agkihpin was expressed and purified in Escherichia coli, and its biological activities investigated. Thus, r-agkihpin-2 was successfully expressed and purified and confirmed by Western blot and peptide mass fingerprinting. After purification and renaturation, 46 mg (399 U) of active r-agkihpin-2 was obtained from 1 L bacterial culture. The results of the arginine esterase activity assay, fibrin plate test fibrinogenolytic activity assay, thrombin-induced venous thrombosis assay, Scratch-Wound assay and bleeding assay showed that active r-agkihpin-2 had slightly lower TAME hydrolytic, fibrinolytic, fibrinogenolytic, thrombus-reduced and migration-attenuated activities than those of native agkihpin, and had no bleeding risk. These findings confirmed that, active r-agkihpin-2 could be further investigated for thrombolytic and/or anti-metastasis drug discovery in the future.

Recombinant expression of the precursor of the hemorrhagic metalloproteinase HF3 and its non-catalytic domains using a cell-free synthesis system.

Snake venom metalloproteinases (SVMPs) participate in snakebite pathology such as hemorrhage, inflammation, and necrosis. They are synthesized as latent multi-domain precursors whose processing generates either catalytically active enzymes or free non-enzymatic domains. Recombinant expression of the precursor of P-III class SVMPs has failed due to the instability of the multi-domain polypeptide structure. Conversely, functional recombinant non-catalytic domains were obtained by prokaryotic expression systems. Here, we show for the first time the recombinant expression of the precursor of HF3, a highly hemorrhagic SVMP from Bothrops jararaca, and its non-catalytic domains, using an E. coli-based cell-free synthesis system. The precursor of HF3, composed of pro-, metalloproteinase-, disintegrin-like-, and cysteine-rich domains, and containing 38 Cys residues, was successfully expressed and purified. A protein composed of the disintegrin-like and cysteine-rich domains (DC protein) and the cysteine-rich domain alone (C protein) were expressed in vitro individually and purified. Both proteins were shown to be functional in assays monitoring the interaction with matrix proteins and in modulating the cleavage of fibrinogen by HF3. These data indicate that recombinant expression using prokaryotic-based cell-free synthesis emerges as an attractive alternative for the study of the structure and function of multi-domain proteins with a high content of Cys residues.

Expression and functional characterization of a recombinant targeted toxin with an uPA cleavable linker in Pichia pastoris.

A recombinant targeted toxin (Disintegrin-Conj-Mel) was developed that contained a disintegrin connected to cytotoxic melittin by a urokinase plasminogen activator (uPA)-cleavable linker. This recombinant targeted toxin was designed to target tumor cells expressing integrin αvß3. The fusion gene was expressed under the control of the promoter AOX1 in Pichia pastoris. Electrophoresis by SDS-PAGE and Western blotting assays of culture broth from a methanol-induced expression strain, demonstrated that an approximately 13 kDa fusion protein was secreted into the culture medium. The molecular weight was that calculated from the predicted amino acid sequence. After optimizing the growth and expression conditions of the transformant strain, about 160 mg/L of the recombinant protein was achieved. The recombinant protein was purified to more than 95% purity by SP Sepharose ion exchange chromatography and Sephadex G-75 gel filtration chromatography. The hemolysis bioactivity test revealed that the fusion had no hemolytic activity or cytotoxicity against uPA non-expressing 293 cells, but exerted dose-dependent inhibition on uPA-expressing A549 cell proliferation.

"Insularin, a disintegrin from Bothrops insularis venom: inhibition of platelet aggregation and endothelial cell adhesion by the native and recombinant GST-insularin proteins".

Insularin (INS) was obtained from Bothrops insularis venom by reversed-phase high-performance liquid chromatography using a C(18) column and characterized as a disintegrin by peptide mass fingerprint and inhibition of ADP-induced platelet aggregation. A cDNA coding for P-II a metalloproteinase/disintegrin was cloned from a cDNA library from B. insularis venom glands. The deduced protein sequence possesses 73 amino acid residues, including the N-terminal, internal peptides of native insularin, the ARGDNP-sequence and 12 cysteines in a conserved alignment. This cDNA fragment was subcloned in the pGEX-4T-1 vector and expressed in a prokaryotic expression system as a fusion protein with glutathione S-transferase (GST-INS). Both native and recombinant insularin inhibited ADP-induced platelet aggregation and endothelial cells (HUVEC) adhesion with similar activities indicating that GST-INS folded correctly and preserved the integrin-binding loop. Insularin may be a tool in studies that involve platelets and endothelial cell adhesion dependent on alphaIIbeta3 and alphavbeta3 integrins.

Snake venomics of Central American pitvipers: clues for rationalizing the distinct envenomation profiles of Atropoides nummifer and Atropoides picadoi.

We report the proteomic characterization of the Central American pitvipers Atropoides nummifer and Atropoides picadoi. The crude venoms were fractionated by reverse-phase high-performance liquid chromatography (HPLC), followed by analysis of each chromatographic fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), N-terminal sequencing, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass fingerprinting, and collision-induced dissociation-tandem mass spectrometry (CID-MS/MS) of tryptic peptides. Each venom contained a number of bradykinin-potentiating peptides and around 25-27 proteins of molecular masses in the range of 7-112 kDa, belonging to only nine different toxin families (disintegrin, DC fragment, snake venom vascular endothelial growth factor, phospholipases A2, serine protease, cysteine-rich secretory proteins, C-type lectins, L-amino acid oxidase, and Zn2+-dependent metalloproteases), albeit distinctly distributed among the two Atropoides species. In addition, A. nummifer expresses low amounts of a three-finger toxin not detected in the venom of A. picadoi. The major toxins of A. nummifer belong to the PLA2 (relative abundance, 36.5%) and the serine proteinase (22%) families, whereas the most abundant A. picadoi toxins are Zn2+-dependent metalloproteinases (66.4%). We estimate that the similarity of venom proteins between the two Atropoides taxa may be around 14-16%. The high degree of differentiation in the venom proteome among congeneric taxa emphasizes unique aspects of venom composition of related species of Atropoides snakes and points to a strong role for adaptive diversification via natural selection as a cause of this distinctiveness. On the other hand, their distinct venom toxin compositions provide clues for rationalizing the low hemorrhagic, coagulant, and defibrinating activities and the high myotoxic and proteolytic effects evoked by A. nummifer snakebite in comparison to other crotaline snake venoms and the high hemorrhagic activity of A. picadoi.

Inhibitory effect of the salmosin gene transferred by cationic liposomes on the progression of B16BL6 tumors.

Salmosin is a novel disintegrin containing the Arg-Gly-Asp sequence that significantly inhibits platelet aggregation, basic fibroblast growth factor-induced endothelial cell proliferation, and tumor progression by antagonizing integrin-mediated cell interactions. Previously, it was shown that daily administration of salmosin was able to inhibit tumor-derived angiogenesis and adherence and proliferation of tumor cells, resulting in suppression of tumor progression. However, it is very difficult to maintain a therapeutic level of salmosin in the blood by systemic administration of the protein. Hence, an alternative strategy for antiangiogenic cancer therapy, based on the in vivo expression of the salmosin gene administered with cationic liposomes, was investigated. The salmosin peptides expressed in vitro inhibited the proliferation of bovine capillary endothelial cells in a dose-dependent manner, presumably as a result of inhibition of cell adhesion mediated via alpha(v)beta(3) integrin. Subcutaneous administration of the salmosin gene resulted in systemic expression of the gene product and concomitant inhibition of the growth of B16BL6 melanoma cells. Suppression of pulmonary metastases, verified by experimental and spontaneous metastasis models in mice, also resulted from salmosin gene treatment. These results suggest that administration of the salmosin gene complexed to cationic liposomes is effective in maintaining antiangiogenic salmosin at an effective therapeutic level and may be clinically applicable to anticancer gene therapy.

Molecular cloning and expression of a functional snake venom vascular endothelium growth factor (VEGF) from the Bothrops insularis pit viper. A new member of the VEGF family of proteins.

During the generation of abundant expressed sequence tags from the Viperidae snake Bothrops insularis venom glands, we identified for the first time a cDNA coding for a putative vascular endothelial growth factor-like (VEGF-like) protein. The deduced primary sequence, after complete sequencing of the longest snake venom VEGF (svVEGF) cDNA, displayed similarity with vertebrate VEGFs and with the hypotensive factor from Vipera aspis venom. Its cDNA was subcloned, expressed in Escherichia coli with a His(6) tag as an insoluble monomer, and purified by Ni(2+)-affinity chromatography after 8 m urea extraction. Antiserum against svVEGF was generated and tested in Western blot against proteins from snake venoms and cellular extracts. The mature svVEGF appears to be ubiquitously distributed throughout snake venoms and was also confirmed by Northern blot studies of other related Viperidae species and by cDNA cloning of svVEGF from Bothrops jararaca pit viper. The produced recombinant protein dimerizes after refolding processes and was biologically characterized, showing ability to increase vascular permeability. These results established that svVEGF is a novel and important active toxin during the early stages of bothropic snake bite envenoming and represents a new member of the VEGF family of proteins.

Characterization of beta-adrenoceptors responsible for venom production in the venom gland of the snake Bothrops jararaca.

We have shown that the stimulation of beta-adrenoceptors is an important step in venom production in the Bothrops jararaca venom gland. In the present study, the pharmacological profile of the beta-adrenoceptor present in Bothrops jararaca venom gland was characterized by radioligand binding assay and by the ability of isoprenaline to promote accumulation of cyclic AMP in dispersed secretory cells. In both cases, the venom glands were obtained from non-extracted snakes (quiescent stage) or from snakes which venom was extracted 4 days before sacrifice (venom production stimulated stage). [125I]-iodocyanopindolol ([125I]-ICYP) bound to extracted gland membranes in a concentration-dependent and saturable manner, but with low affinity. Propranolol, beta1- or beta2-selective adrenoceptors ligands displaced the [125I]-ICYP binding with low affinity, while selective beta3-adrenoceptor ligands did not displace the [125I]-ICYP binding. The displacement of [125I]-ICYP by propranolol was similar in non-extracted and extracted glands, showing the presence of beta-adrenoceptors in both stages. In dispersed secretory cells of non-extracted glands, isoprenaline (1 microM) increased the cyclic AMP production and propranolol (10 microM) was able to block this effect. On the other hand, in extracted glands, isoprenaline had no effect. The results suggest that the beta-adrenoceptors present in the Bothrops jararaca venom glands are different from those (beta1, beta2 or beta3) described in mammals, but are coupled to the Gs protein, like the known beta-adrenoceptor subtypes. Moreover, previous in vivo stimulation of venom production desensitizes the beta-adrenoceptors system and, although the receptors could be detected by binding studies, they are not coupled to the Gs protein, indicating that beta-adrenoceptors stimulation contributes to the initial steps of venom synthesis.

Jararhagin ECD-containing disintegrin domain: expression in escherichia coli and inhibition of the platelet-collagen interaction.

Jararhagin, a hemorrhagin from Bothrops jararaca venom, is a soluble snake venom component comprising metalloproteinase and disintegrin cysteine-rich domains and, therefore, is structurally closely related to the membrane-bound A Disintegrin And Metalloproteinase (ADAMs) protein family. Its hemorrhagic activity is associated with the effects of both metalloproteinase and disintegrin domains; the metalloproteinase enzymatically damages the endothelium and the disintegrin domain inhibits platelet-collagen interactions. The expression of whole jararhagin or its disintegrin domain has never been attempted before. The aim of this study was to investigate whether we could express the disintegrin domain of jararhagin and to verify whether this domain displays an inhibitory effect on the platelet-collagen interaction. Therefore, the cDNA fragment coding for the disintegrin plus cysteine-rich domains of jararhagin was cloned into the pET32a vector, used to transform the Escherichia coli AD494(DE3)pLysS strain. The thioredoxin-disintegrin fusion protein was recovered from the soluble extract of the cells, yielding up to 50 mg/liter culture. The fusion protein was isolated using polyhistidine binding resin which resulted in a main band of 45 kDa recognized by anti-native jararhagin antibodies. Antibodies raised in rabbits against the fusion protein had high enzyme-linked immunosorbent assay titers against native jararhagin and detected a band of 52 kDa on Western blots of whole B. jararaca venom demonstrating that these antibodies recognize the parent jararhagin molecule. Treatment of the fusion protein with enterokinase, followed by further capture of the enzyme, resulted in a band of 30 kDa, the expected size for jararhagin-C. Further purification of the cleaved disintegrin using FPLC Mono-Q columns resulted in one fraction capable of efficiently inhibiting collagen-induced platelet aggregation in a dose-dependent manner (IC(50) of 8.5 microg/ml).

cDNA sequences for four snake venom metalloproteinases: structure, classification, and their relationship to mammalian reproductive proteins.

Presented here are four new cDNA sequences for hemorrhagic metalloproteinases from Crotalus atrox venom, hemorrhagic toxins a, b, c, and d. Comparison of the translated open reading frames to the mature protein sequences gives evidence for post-translational processing at both the amino and carboxyl termini. This comparison is also the basis for a new classification system for these precursors, based on their different sizes. Protein sequences in the zymogen region support the hypothesis of a cysteine-switch type mechanism of maintaining latency. The coordination geometry around the active site zinc ion is discussed. The relationship between these venom metalloproteinases and a family of mammalian reproductive proteins is also supported by these sequences. The cysteine pattern of the carboxyl-terminal domain of the largest proteinase, hemorrhagic toxin a, is compared to other venom proteinases and to the mammalian proteins, showing both striking similarities and subtle differences. It would appear that these hemorrhagic toxins have resulted from deletions and subsequent divergence from a larger ancestor, one they may have shared with the aforementioned mammalian reproductive proteins.