Gallic acid anti-myotoxic activity and mechanism of action, a snake venom phospholipase A2 toxin inhibitor, isolated from the medicinal plant Anacardium humile

Snakebite envenoming is the cause of an ongoing health crisis in several regions of the world, particularly in tropical and neotropical countries. This scenario creates an urgent necessity for new practical solutions to address the limitations of current therapies. The current study investigated the isolation, phytochemical characterization, and myotoxicity inhibition mechanism of gallic acid (GA), a myotoxin inhibitor obtained from Anacardium humile. The identification and isolation of GA was achieved by employing analytical chromatographic separation, which exhibited a compound with retention time and nuclear magnetic resonance spectra compatible with GA's commercial standard and data from the literature. GA alone was able to inhibit the myotoxic activity induced by the crude venom of Bothrops jararacussu and its two main myotoxins, BthTX-I and BthTX-II. Circular dichroism (CD), fluorescence spectroscopy (FS), dynamic light scattering (DLS), and interaction studies by molecular docking suggested that GA forms a complex with BthTX-I and II. Surface plasmon resonance (SPR) kinetics assays showed that GA has a high affinity for BthTX-I with a K_D of 9.146 × 10^-7 M. Taken together, the two-state reaction mode of GA binding to BthTX-I, and CD, FS and DLS assays, suggest that GA is able to induce oligomerization and secondary structure changes for BthTX-I and -II. GA and other tannins have been shown to be effective inhibitors of snake venoms' toxic effects, and herein we demonstrated GA's ability to bind to and inhibit a snake venom PLA₂, thus proposing a new mechanism of PLA₂ inhibition, and presenting more evidence of GA's potential as an antivenom compound.

Small Angle X-ray Scattering, Molecular Modeling, and Chemometric Studies from a Thrombin-Like (Lmr-47) Enzyme of Lachesis m. rhombeata Venom

INTRODUCTION

Snakebite envenomation is considered a neglected tropical disease, and SVTLEs critical elements are involved in serious coagulopathies that occur on envenoming. Although some enzymes of this group have been structurally investigated, it is essential to characterize other proteins to better understand their unique properties such as the Lachesis muta rhombeata 47 kDa (Lmr-47) venom serine protease.

METHODS

The structure of Lmr-47 was studied in solution, using SAXS, DLS, CD, and in silico by homology modeling. Molecular docking experiments simulated 21 competitive inhibitors.

RESULTS

At pH 8.0, Lmr-47 has an Rg of 34.5 ± 0.6 Å, Dmax of 130 Å, and SR of 50 Å, according to DLS data. Kratky plot analysis indicates a rigid shape at pH 8.0. Conversely, the pH variation does not change the center of mass's intrinsic fluorescence, possibly indicating the absence of fluorescent amino acids in the regions affected by pH variation. CD experiments show a substantially random coiled secondary structure not affected by pH. The low-resolution model of Lmr-47 presented a prolate elongated shape at pH 8.0. Using the 3D structure obtained by molecular modeling, docking experiments identified five good and three suitable competitive inhibitors.

CONCLUSION

Together, our work provided insights into the structure of the Lmr-47 and identified inhibitors that may enhance our understanding of thrombin-like family proteins.

BoaγPLI from Boa constrictor Blood is a Broad-Spectrum Inhibitor of Venom PLA2 Pathophysiological Actions

The use of venom in predation exerts a corresponding selection pressure for the evolution of venom resistance. One of the mechanisms related to venom resistance in animals (predators or prey of snakes) is the presence of molecules in the blood that can bind venom toxins, and inhibit their pharmacological effects. One such toxin type are venom phospholipase A₂s (PLA₂s), which have diverse effects including anticoagulant, myotoxic, and neurotoxic activities. BoaγPLI isolated from the blood of Boa constrictor has been previously shown to inhibit venom PLA₂s that induced myotoxic and edematogenic activities. Recently, in addition to its previously described and very potent neurotoxic effect, the venoms of American coral snakes (Micrurus species) have been shown to have anticoagulant activity via PLA₂ toxins. As coral snakes eat other snakes as a major part of their diet, neonate Boas could be susceptible to predation by this sympatric species. Thus, this work aimed to ascertain if BoaγPLI provided a protective effect against the anticoagulant toxicity of venom from the model species Micrurus laticollaris in addition to its ability shown previously against other toxin types. Using a STA R Max coagulation analyser robot to measure the effect upon clotting time, and TEG5000 thromboelastographers to measure the effect upon clot strength, we evaluated the ability of BoaγPLI to inhibit M. laticollaris venom. Our results indicate that BoaγPLI is efficient at inhibiting the M. laticollaris anticoagulant effect, reducing the time of coagulation (restoring them closer to non-venom control values) and increasing the clot strength (restoring them closer to non-venom control values). These findings demonstrate that endogenous PLA₂ inhibitors in the blood of non-venomous snakes are multi-functional and provide broad resistance against a myriad of venom PLA₂-driven toxic effects including coagulotoxicity, myotoxicity, and neurotoxicity. This novel form of resistance could be evidence of selective pressures caused by predation from venomous snakes and stresses the need for field-based research aimed to expand our understanding of the evolutionary dynamics of such chemical arms race.

"Computational and Functional Characterization of a Hemorrhagic Metalloproteinase Purified from Cerastes cerastes Venom"

Structural and functional aspects of snake venoms metalloproteinases (SVMPs) have been extensively studied due to their role in envenomation. However, in the detection of certain coagulation disorders these biomolecules have been used and applied for the production of new thrombolytic drugs. CcMP-II, a SVMP-II metalloproteinase with a hemorrhagic activity, isolated from the venom of Cerastes cerastes, its sequence of 472 amino acids was identified. Predicted 3D structure showed an arrangement of CcMP-II into two distinct domains: i) a metalloproteinase domain where the zinc-binding motif is found (HXXGHNLGIDH) in addition to the sequence Cys-Ile-Met (CIM) at the Met-turn and ii) disintegrin-like domain containing RGD motif. CcMP-II inhibits platelet aggregation induced by collagen in a dose-dependent manner with an IC₅₀ value estimated of 0.11 nM. This proteinase inhibits also aggregation of platelet stimulated by collagen even if the metal chelating agents (EDTA and 1, 10-phenontroline) are present suggesting that anti-aggregating effect is not due to its metalloproteinase domain, but to its disintegrin-like domain. Capillary pathological modifications caused by CcMP-II following intramuscular injection have as well been examined in mice. The key morphological alterations of the capillary vessels were clearly apparent from the ultrastructural study. The CcMP-II can play a key function in the pathogenesis of disorders that occurs following envenomation of Cerastes cerastes. The three-dimensional model of CcMP-II was built to explain structure-function relationships in ADAM/ADAMTs, a family of proteins having significant therapeutic potential. In order to explain structure-function relationships in ADAM / ADAMT, a family of proteins with considerable therapeutic potential, the three-dimensional model of CcMP-II was constructed.

Biogeographic venom variation in Russell's viper (Daboia russelii) and the preclinical inefficacy of antivenom therapy in snakebite hotspots

BACKGROUND

Snakebite in India results in over 58,000 fatalities and a vast number of morbidities annually. The majority of these clinically severe envenomings are attributed to Russell's viper (Daboia russelii), which has a near pan-India distribution. Unfortunately, despite its medical significance, the influence of biogeography on the composition and potency of venom from disparate D. russelii populations, and the repercussions of venom variation on the neutralisation efficacy of marketed Indian antivenoms, remain elusive.

METHODS

Here, we employ an integrative approach comprising proteomic characterisation, biochemical analyses, pharmacological assessment, and venom toxicity profiling to elucidate the influence of varying ecology and environment on the pan-Indian populations of D. russelii. We then conducted in vitro venom recognition experiments and in vivo neutralisation assays to evaluate the efficacy of the commercial Indian antivenoms against the geographically disparate D. russelii populations.

FINDINGS

We reveal significant intraspecific variation in the composition, biochemical and pharmacological activities and potencies of D. russelii venoms sourced from five distinct biogeographic zones across India. Contrary to our understanding of the consequences of venom variation on the effectiveness of snakebite therapy, commercial antivenom exhibited surprisingly similar neutralisation potencies against the majority of the investigated populations, with the exception of low preclinical efficacy against the semi-arid population from northern India. However, the ability of Indian antivenoms to counter the severe morbid effects of Daboia envenoming remains to be evaluated.

CONCLUSION

The concerning lack of antivenom efficacy against the north Indian population of D. russelii, as well as against two other 'big four' snake species in nearby locations, underscores the pressing need to develop pan-India effective antivenoms with improved efficacy in high snakebite burden locales.

Sulfur Compounds as Inhibitors of Enzymatic Activity of a Snake Venom Phospholipase A2: Benzyl 4-nitrobenzenecarbodithioate as a Case of Study

Snakebite is a neglected disease with a high impact in tropical and subtropical countries. Therapy based on antivenom has limited efficacy in local tissue damage caused by venoms. Phospholipases A₂ (PLA₂) are enzymes that abundantly occur in snake venoms and induce several systemic and local effects. Furthermore, sulfur compounds such as thioesters have an inhibitory capacity against a snake venom PLA₂. Hence, the objective of this work was to obtain a carbodithioate from a thioester with known activity against PLA₂ and test its ability to inhibit the same enzyme. Benzyl 4-nitrobenzenecarbodithioate (I) was synthesized, purified, and characterized using as precursor 4-nitrothiobenzoic acid S-benzyl ester (II). Compound I showed inhibition of the enzymatic activity a PLA₂ isolated from the venom of the Colombian rattlesnake Crotalus durissus cumanensis with an IC₅₀ of 55.58 μM. This result is comparable with the reported inhibition obtained for II. Computational calculations were performed to support the study, and molecular docking results suggested that compounds I and II interact with the active site residues of the enzyme, impeding the normal catalysis cycle and attachment of the substrate to the active site of the PLA₂.

Cysteine-Rich Secretory Proteins (CRISPs) From Venomous Snakes: An Overview of the Functional Diversity in A Large and Underappreciated Superfamily

The CAP protein superfamily (Cysteine-rich secretory proteins (CRISPs), Antigen 5 (Ag5), and Pathogenesis-related 1 (PR-1) proteins) is widely distributed, but for toxinologists, snake venom CRISPs are the most familiar members. Although CRISPs are found in the majority of venoms, very few of these proteins have been functionally characterized, but those that have been exhibit diverse activities. Snake venom CRISPs (svCRISPs) inhibit ion channels and the growth of new blood vessels (angiogenesis). They also increase vascular permeability and promote inflammatory responses (leukocyte and neutrophil infiltration). Interestingly, CRISPs in lamprey buccal gland secretions also manifest some of these activities, suggesting an evolutionarily conserved function. As we strive to better understand the functions that CRISPs serve in venoms, it is worth considering the broad range of CRISP physiological activities throughout the animal kingdom. In this review, we summarize those activities, known crystal structures and sequence alignments, and we discuss predicted functional sites. CRISPs may not be lethal or major components of venoms, but given their almost ubiquitous occurrence in venoms and the accelerated evolution of svCRISP genes, these venom proteins are likely to have functions worth investigating.

The distinct evolutionary properties of the tripartite motif-containing protein 39 in the Chinese softshell turtle based on its structural and functional characterization

The tripartite motif (TRIM)-containing proteins are a diverse family of proteins that are involved in the regulation of innate immune responses. TRIM39 is a member of the TRIM family and contains E3 ubiquitin ligase activity. In this study, a TRIM39 homolog from the Chinese softshell turtle (Pelodiscus sinensis), PsTRIM39, was identified, and its functional characterization was investigated. PsTRIM39 is a protein of 470 amino acids containing a conserved RING-finger domain, B-BOX domain, PRY domain and SPRY domain in the TRIM family. Sequence structure and phylogenetic analysis indicated PsTRIM39 has the closest relationship with that of birds. Transcriptional profiling analysis revealed that PsTRIM39 mRNA was upregulated after challenge with Aeromonas hydrophila or the soft-shelled turtle virus, iridovirus. The subcellular localization of PsTRIM39 was in the cytoplasm, which is similar to that of fish. Furthermore, PsTRIM39 colocalized with lysosomes in Fathead minnow (FHM) cells, indicating that it may play a role in immune-related function. An NFκB functional assay showed that overexpression of PsTRIM39 enhanced NFκB activity in FHM cells, which is different from that of mammalian TRIM39. Taken together, these results provide, for the first time, the structural and functional characterization of a TRIM family member in the innate immune responses of reptiles and suggest that PsTRIM39 has distinct evolutionary properties representing the transitional stage from lower vertebrates to higher vertebrates in evolution.

Intervention on immunodeficiency mice and structural identification of enzymatic peptides from Mauremys mutica and Cuora trifasciata

ETHNOPHARMACOLOGY RELEVANCY

Mauremys mutica (Asian yellow pond turtle, YPT) and Cuora trifasciata (Chinese three-striped box turtle, TBT) are traditional Chinese medicine. They possess many biological characteristics, such as immune-enhancement, anti-inflammatory, anti-cancer effects. They have been used as folk anti-cancer drugs in central and southern China for a long time. However, there was no reports of comparing the immune-enhancement effect of YPT and TBT, nor of identifying the structures of YPT peptides and TBT peptides.

AIMS OF THE STUDY

The aim of this study was to evaluate the protective efficacy of YPT and TBT on immunodeficient mice and to compare the primary structures of YPT peptides and TBT peptides.

MATERIALS AND METHODS

The protein extracts were extracted using 100 °C water, and peptides were obtained by hydrolyzing protein extracts using alkaline protease. Cyclophosphamide (CTX) was used to induce immunodeficiency in mice. The immune enhancement effect was evaluated by measuring body weight gain curve, thymus index, spleen index, serum SOD activity and GSH-Px activity. Primary structure of peptides was identified by HPLC-ESI-MS/MS.

RESULTS

The protein extracts and peptides of the YPT and TBT had certain recovery effects on immunodeficient mice. YPT peptide has the best effect on the recovery of damaged immune organs and the improvement of SOD and GSH-Px activities in mice. In the identification of the primary structure of the polypeptide, we find that YPT and TBT contain some similar peptides as well as different peptides, and the concentration of the peptide segments in HPLC data is very different. The difference of biological activity may be determined by both the difference of specific peptide structure and concentration.

CONCLUSIONS

Two kinds of healthy turtle protein extracts and peptides could have immune-enhancement function, and peptides obtained by enzymatic hydrolysis of YPT protein extracts have the best immune-enhancement effect. The identification of the primary structure of the peptide segment preliminarily showed that its biological activity was affected by the amino acid sequence and the concentration of part of the peptide segment. It laid a foundation for the follow-up search of immune-enhancement peptides and the development of high-value YPT products.

The isolation and characterization of a new snake venom cysteine-rich secretory protein (svCRiSP) from the venom of the Southern Pacific rattlesnake and its effect on vascular permeability

A novel snake venom cysteine-rich secretory protein (svCRiSP), Hellerin, was purified from C. o. helleri venom using sequential reverse phase and cation-exchange chromatography. Gel electrophoresis, N-terminal sequencing, and LC-MS/MS sequencing identified a single protein with a molecular mass of approximately 24.8 kDa and confirmed its identity as a svCRiSP. Hellerin had cytotoxic effects on human umbilical vein endothelial cells (HUVECs) in a dose-dependent manner but not in human dermal lymphatic endothelial cells (HDLECs) and human dermal blood endothelial cells (HDBECs). Hellerin produced a dramatic increase in both blood vascular permeability in vivo, and in the trans-epithelial permeability of cultured HDLEC and HDBEC cells. This is the first study that describes the effect of a svCRiSP on vascular, blood and lymphatic permeability.

Protease Activity Profiling of Snake Venoms Using High-Throughput Peptide Screening

Snake venom metalloproteinases (SVMPs) and snake venom serine proteinases (SVSPs) are among the most abundant enzymes in many snake venoms, particularly among viperids. These proteinases are responsible for some of the clinical manifestations classically seen in viperid envenomings, including hemorrhage, necrosis, and coagulopathies. The objective of this study was to investigate the enzymatic activities of these proteins using a high-throughput peptide library to screen for the proteinase targets of the venoms of five viperid (Echis carinatus, Bothrops asper, Daboia russelii, Bitis arietans, Bitis gabonica) and one elapid (Naja nigricollis) species of high medical importance. The proteinase activities of these venoms were each tested against 360 peptide substrates, yielding 2160 activity profiles. A nonlinear regression model that accurately described the observed enzymatic activities was fitted to the experimental data, allowing for the comparison of cleavage rates across species. In this study, previously unknown protein targets of snake venom proteinases were identified, potentially implicating novel human and animal proteins that may be involved in the pathophysiology of viper envenomings. The functional relevance of these targets was further evaluated and discussed. These new findings may contribute to our understanding of the clinical manifestations and underlying biochemical mechanisms of snakebite envenoming by viperid species.

New Insights on Moojase, a Thrombin-Like Serine Protease from Bothrops moojeni Snake Venom

Snake venom serine proteases (SVSPs) are enzymes that are capable of interfering in various parts of the blood coagulation cascade, which makes them interesting candidates for the development of new therapeutic drugs. Herein, we isolated and characterized Moojase, a potent coagulant enzyme from Bothrops moojeni snake venom. The toxin was isolated from the crude venom using a two-step chromatographic procedure. Moojase is a glycoprotein with N-linked glycans, molecular mass of 30.3 kDa and acidic character (pI 5.80⁻6.88). Sequencing of Moojase indicated that it is an isoform of Batroxobin. Moojase was able to clot platelet-poor plasma and fibrinogen solutions in a dose-dependent manner, indicating thrombin-like properties. Moojase also rapidly induced the proteolysis of the Aα chains of human fibrinogen, followed by the degradation of the Bβ chains after extended periods of incubation, and these effects were inhibited by PMSF, SDS and DTT, but not by benzamidine or EDTA. RP-HPLC analysis of its fibrinogenolysis confirmed the main generation of fibrinopeptide A. Moojase also induced the fibrinolysis of fibrin clots formed in vitro, and the aggregation of washed platelets, as well as significant amidolytic activity on substrates for thrombin, plasma kallikrein, factor Xia, and factor XIIa. Furthermore, thermofluor analyses and the esterase activity of Moojase demonstrated its very high stability at different pH buffers and temperatures. Thus, studies such as this for Moojase should increase knowledge on SVSPs, allowing their bioprospection as valuable prototypes in the development of new drugs, or as biotechnological tools.

Biochemical characterization of venom from Pseudoboa neuwiedii (Neuwied's false boa; Xenodontinae; Pseudoboini)

In this work, we examined the proteolytic and phospholipase A₂ (PLA₂) activities of venom from the opisthoglyphous colubrid Pseudoboa neuwiedii. Proteolytic activity (3 and 10 μg of venom) was comparable to that of Bothrops neuwiedii venom but less than Bothrops atrox. This activity was inhibited by EDTA and 1,10-phenanthroline but only slightly affected (≤30% inhibition) by PMSF and AEBSF, indicating it was mediated by snake venom metalloproteinases (SVMPs). The pH and temperature optima for proteolytic activity were 8.0 and 37 °C, respectively. The venom had no esterase activity, whereas PLA₂ activity was similar to B. atrox, greater than B. neuwiedii but less than B. jararacussu. SDS-PAGE revealed venom proteins >100 kDa, 45-70 kDa, 21-24 kDa and ~15 kDa, and mass spectrometry of protein bands revealed SVMPs, cysteine-rich secretory proteins (CRISPs) and PLA₂, but no serine proteinases. In gelatin zymography, the most active bands occurred at 65-68 kDa (seen with 0.05-0.25 μg of venom). Caseinolytic activity occurred at 50-66 kDa and was generally weaker than gelatinolytic activity. RP-HPLC of venom yielded 15 peaks, five of which showed gelatinolytic activity; peak 7 was the most active and apparently contained a P-III class SVMP. The venom showed α-fibrinogenase activity, without affecting the β and γ chains; this activity was inhibited by EDTA and 1,10-phenanthroline. The venom did not clot rat citrated plasma but reduced the rate and extent of coagulation after plasma recalcification. In conclusion, P. neuwiedii venom is highly proteolytic and could potentially affect coagulation in vivo by degrading fibrinogen via SVMPs.

Edema Induced by a Crotalus durissus terrificus Venom Serine Protease (Cdtsp 2) Involves the PAR Pathway and PKC and PLC Activation

Snake venom serine proteases (SVSPs) represent an essential group of enzymatic toxins involved in several pathophysiological effects on blood homeostasis. Some findings suggest the involvement of this class of enzymatic toxins in inflammation. In this paper, we purified and isolated a new gyroxin isoform from the Crotalus durissus terrificus (Cdt) venom, designated as Cdtsp 2, which showed significant proinflammatory effects in a murine model. In addition, we performed several studies to elucidate the main pathway underlying the edematogenic effect induced by Cdtsp 2. Enzymatic assays and structural analysis (primary structure analysis and three-dimensional modeling) were closely performed with pharmacological assays. The determination of edematogenic activity was performed using Cdtsp 2 isolated from snake venom, and was applied to mice treated with protein kinase C (PKC) inhibitor, phospholipase C (PLC) inhibitor, dexamethasone (Dexa), antagonists for protease-activated receptors (PARs), or saline (negative control). Additionally, we measured the levels of cyclooxygenase 2 (COX-2), malondialdehyde (MDA), and prostaglandin E2 (PGE2). Cdtsp 2 is characterized by an approximate molecular mass of 27 kDa, an isoelectric point (pI) of 4.5, and significant fibrinolytic activity, as well as the ability to hydrolyze Nα-benzoyl-l-arginine 4-nitroanilide (BAPNA). Its primary and three-dimensional structures revealed Cdtsp 2 as a typical snake venom serine protease that induces significant edema via the metabolism of arachidonic acid (AA), involving PARs, PKC, PLC, and COX-2 receptors, as well as inducing a significant increase in MDA levels. Our results showed that Cdtsp 2 is a serine protease with significant enzymatic activity, and it may be involved in the degradation of PAR1 and PAR2, which activate PLC and PKC to mobilize AA, while increasing oxidative stress. In this article, we provide a new perspective for the role of SVSPs beyond their effects on blood homeostasis.

Identification, characterization and expression analysis of MAVS in Pelodiscus sinensis after challenge with Poly I:C

Pelodiscus sinensis, which is one of the important reptile species in the aquaculture industry in China, frequently suffers from serious infectious diseases caused by viruses. However, there is a lack of biological knowledge about its antiviral innate immunity. In this study, we identified and characterized the open reading frame (ORF) of PsMAVS cDNA in P. sinensis. It consisted of 2691 nucleotides encoding a protein of 896 amino acid residues, which were composed of an N-terminal CARD, a central proline-rich domain and a C-terminal TM domain. Based on the amino acid sequence, phylogenetic analyses revealed a closer relationship of PsMAVS with those of Chelonia. qRT-PCR analysis indicated that PsMAVS was ubiquitously expressed in all of the examined healthy tissues with different expression levels; it was expressed at high levels in spleen, muscle and heart and at moderate levels in kidney, liver, intestine, intestinum crissum and oesophagus. PsMAVS was detected in embryos at 10 days post hatching, and it gradually upregulated with the embryonic development stage. Its expression levels in the examined tissues were all upregulated significantly after challenge with Poly I:C. The PsMAVS protein was detected in the intestinal tissues from both the challenge and the control groups, and it was distributed widely in the cytoplasm of the intestinal cells, suggesting PsMAVS plays multiple roles in the complicated mechanisms of immune defence against virus invasion in P. sinensis.

Proteomic and functional variation within black snake venoms (Elapidae: Pseudechis)

Pseudechis (black snakes) is an Australasian elapid snake genus that inhabits much of mainland Australia, with two representatives confined to Papua New Guinea. The present study is the first to analyse the venom of all 9 described Pseudechis species (plus one undescribed species) to investigate the evolution of venom composition and functional activity. Proteomic results demonstrated that the typical Pseudechis venom profile is dominated by phospholipase A₂ toxins. Strong cytotoxicity was the dominant function for most species. P. porphyriacus, the most basal member of the genus, also exhibited the most divergent venom composition, being the only species with appreciable amounts of procoagulant toxins. The relatively high presence of factor Xa recovered in P. porphyriacus venom may be related to a predominantly amphibian diet. Results of this study provide important insights to guide future ecological and toxinological investigations.

Rattling the border wall: Pathophysiological implications of functional and proteomic venom variation between Mexican and US subspecies of the desert rattlesnake Crotalus scutulatus

While some US populations of the Mohave rattlesnake (Crotalus scutulatus scutulatus) are infamous for being potently neurotoxic, the Mexican subspecies C. s. salvini (Huamantlan rattlesnake) has been largely unstudied beyond crude lethality testing upon mice. In this study we show that at least some populations of this snake are as potently neurotoxic as its northern cousin. Testing of the Mexican antivenom Antivipmyn showed a complete lack of neutralisation for the neurotoxic effects of C. s. salvini venom, while the neurotoxic effects of the US subspecies C. s. scutulatus were time-delayed but ultimately not eliminated. These results document unrecognised potent neurological effects of a Mexican snake and highlight the medical importance of this subspecies, a finding augmented by the ineffectiveness of the Antivipmyn antivenom. These results also influence our understanding of the venom evolution of Crotalus scutulatus, suggesting that neurotoxicity is the ancestral feature of this species, with the US populations which lack neurotoxicity being derived states.

Heterologous expression of the antimyotoxic protein DM64 in Pichia pastoris

Snakebite envenomation is a neglected condition that constitutes a public health problem in tropical and subtropical countries, including Brazil. Interestingly, some animals are resistant to snake envenomation due to the presence of inhibitory glycoproteins in their serum that target toxic venom components. DM64 is an acidic glycoprotein isolated from Didelphis aurita (opossum) serum that has been characterized as an inhibitor of the myotoxicity induced by bothropic toxins bearing phospholipase A₂ (PLA₂) structures. This antitoxic protein can serve as an excellent starting template for the design of novel therapeutics against snakebite envenomation, particularly venom-induced local tissue damage. Therefore, the aim of this work was to produce a recombinant DM64 (rDM64) in the methylotrophic yeast Pichia pastoris and to compare its biological properties with those of native DM64. Yeast fermentation in the presence of Pefabloc, a serine protease inhibitor, stimulated cell growth (~1.5-fold), increased the rDM64 production yield approximately 10-fold and significantly reduced the susceptibility of rDM64 to proteolytic degradation. P. pastoris fermentation products were identified by mass spectrometry and Western blotting. The heterologous protein was efficiently purified from the culture medium by affinity chromatography (with immobilized PLA₂ myotoxin) and/or an ion exchange column. Although both native and recombinant DM64 exhibit different glycosylation patterns, they show very similar electrophoretic mobilities after PNGase F treatment. rDM64 formed a noncovalent complex with myotoxin II (Lys49-PLA₂) from Bothrops asper and displayed biological activity that was similar to that of native DM64, inhibiting the cytotoxicity of myotoxin II by 92% at a 1:1 molar ratio.

Snakebite envenomation causes medical emergencies that, depending on the species responsible for the bite, involve different organs and tissues. Envenomation by snakebite is a worldwide problem, and Brazil presents a high incidence of Bothrops bites. Bothrops venoms cause pathological alterations with prominent local effects, such as edema, blistering, hemorrhage, dermonecrosis and myonecrosis, usually followed by poor tissue regeneration and permanent sequelae. Bleeding, coagulopathy, cardiovascular shock and renal failure are typical systemic effects of these venoms. The clinical treatment for snakebite envenoming is intravenous administration of the specific antivenom. However, serotherapy does not efficiently protect against local tissue damage. Additional challenges faced by classical antivenom therapy include the wide antigenic variation of venoms across species and even within the same snake species and the frequent occurrence of adverse reactions that are associated with the administration of immunobiologicals. The development of new effective toxin inhibitors based on the structure of natural antiophidic proteins is an attractive therapeutic alternative. DM64 is a myotoxin inhibitor that was isolated from opossum serum, and its expression as a recombinant protein is paramount to the characterization of its structure-function relationship, an essential step toward the development of alternative strategies to better manage bothropic snakebite envenomations.

Strong and widespread action of site-specific positive selection in the snake venom Kunitz/BPTI protein family

S1 family of serine peptidases is the largest family of peptidases. They are specifically inhibited by the Kunitz/BPTI inhibitors. Kunitz domain is characterized by the compact 3D structure with the most important inhibitory loops for the inhibition of S1 peptidases. In the present study we analysed the action of site-specific positive selection and its impact on the structurally and functionally important parts of the snake venom Kunitz/BPTI family of proteins. By using numerous models we demonstrated the presence of large numbers of site-specific positively selected sites that can reach between 30-50% of the Kunitz domain. The mapping of the positively selected sites on the 3D model of Kunitz/BPTI inhibitors has shown that these sites are located in the inhibitory loops 1 and 2, but also in the Kunitz scaffold. Amino acid replacements have been found exclusively on the surface, and the vast majority of replacements are causing the change of the charge. The consequence of these replacements is the change in the electrostatic potential on the surface of the Kunitz/BPTI proteins that may play an important role in the precise targeting of these inhibitors into the active site of S1 family of serine peptidases.

Natural Inhibitors of Snake Venom Metalloendopeptidases: History and Current Challenges

The research on natural snake venom metalloendopeptidase inhibitors (SVMPIs) began in the 18th century with the pioneering work of Fontana on the resistance that vipers exhibited to their own venom. During the past 40 years, SVMPIs have been isolated mainly from the sera of resistant animals, and characterized to different extents. They are acidic oligomeric glycoproteins that remain biologically active over a wide range of pH and temperature values. Based on primary structure determination, mammalian plasmatic SVMPIs are classified as members of the immunoglobulin (Ig) supergene protein family, while the one isolated from muscle belongs to the ficolin/opsonin P35 family. On the other hand, SVMPIs from snake plasma have been placed in the cystatin superfamily. These natural antitoxins constitute the first line of defense against snake venoms, inhibiting the catalytic activities of snake venom metalloendopeptidases through the establishment of high-affinity, non-covalent interactions. This review presents a historical account of the field of natural resistance, summarizing its main discoveries and current challenges, which are mostly related to the limitations that preclude three-dimensional structural determinations of these inhibitors using “gold-standard” methods; perspectives on how to circumvent such limitations are presented. Potential applications of these SVMPIs in medicine are also highlighted.

Colubrid Venom Composition: An -Omics Perspective

Snake venoms have been subjected to increasingly sensitive analyses for well over 100 years, but most research has been restricted to front-fanged snakes, which actually represent a relatively small proportion of extant species of advanced snakes. Because rear-fanged snakes are a diverse and distinct radiation of the advanced snakes, understanding venom composition among "colubrids" is critical to understanding the evolution of venom among snakes. Here we review the state of knowledge concerning rear-fanged snake venom composition, emphasizing those toxins for which protein or transcript sequences are available. We have also added new transcriptome-based data on venoms of three species of rear-fanged snakes. Based on this compilation, it is apparent that several components, including cysteine-rich secretory proteins (CRiSPs), C-type lectins (CTLs), CTLs-like proteins and snake venom metalloproteinases (SVMPs), are broadly distributed among "colubrid" venoms, while others, notably three-finger toxins (3FTxs), appear nearly restricted to the Colubridae (sensu stricto). Some putative new toxins, such as snake venom matrix metalloproteinases, are in fact present in several colubrid venoms, while others are only transcribed, at lower levels. This work provides insights into the evolution of these toxin classes, but because only a small number of species have been explored, generalizations are still rather limited. It is likely that new venom protein families await discovery, particularly among those species with highly specialized diets.

Anti-osteoarthritic activity of Bungarus fasciatus venom fraction BF-F47 involving molecular markers in the rats

A heat stable protein BF-F47 was purified from the crude venom of Bungarus fasciatus by CM cellulose ion exchange chromatography and HPLC. Osteoarthritis (OA) was developed in male albino Wistar rats by collagenase injection. BF-F47 treatment significantly restored urinary hydroxyproline and glucosamine in OA rats. Serum acid phosphatase, alkaline phosphatase, creatinine and serum molecular markers TNF-α, IL-1β, IL-17, cytokine induced neutrophil chemoattractant-1, matrix metalloproteinase-1, cathepsin-K, osteocalcin and PGE2 were also significantly altered. BF-F47 showed partial restoration of osteoarthritis joints. Thus, BF-F47 induced anti-osteoarthritic activity in Wistar rats acted through molecular markers of arthritis and inflammation.

Discovery and characterisation of a novel toxin from Dendroaspis angusticeps, named Tx7335, that activates the potassium channel KcsA

Due to their central role in essential physiological processes, potassium channels are common targets for animal toxins. These toxins in turn are of great value as tools for studying channel function and as lead compounds for drug development. Here, we used a direct toxin pull-down assay with immobilised KcsA potassium channel to isolate a novel KcsA-binding toxin (called Tx7335) from eastern green mamba snake (Dendroaspis angusticeps) venom. Sequencing of the toxin by Edman degradation and mass spectrometry revealed a 63 amino acid residue peptide with 4 disulphide bonds that belongs to the three-finger toxin family, but with a unique modification of its disulphide-bridge scaffold. The toxin induces a dose-dependent increase in both open probabilities and mean open times on KcsA in artificial bilayers. Thus, it unexpectedly behaves as a channel activator rather than an inhibitor. A charybdotoxin-sensitive mutant of KcsA exhibits similar susceptibility to Tx7335 as wild-type, indicating that the binding site for Tx7335 is distinct from that of canonical pore-blocker toxins. Based on the extracellular location of the toxin binding site (far away from the intracellular pH gate), we propose that Tx7335 increases potassium flow through KcsA by allosterically reducing inactivation of the channel.

Mass spectrometry guided venom profiling and bioactivity screening of the Anatolian Meadow Viper, Vipera anatolica

This contribution reports on the first characterization of the venom proteome and the bioactivity screening of Vipera anatolica, the Anatolian Meadow Viper. The crude venom as well as an isolated dimeric disintegrin showed remarkable cytotoxic activity against glioblastoma cells. Due to the rare occurrence and the small size of this species only little amount of venom was available, which was profiled by means of a combination of bottom-up and top-down mass spectrometry. From this analysis we identified snake venom metalloproteases, cysteine-rich secretory protein isoforms, a metalloprotease inhibitor, several type A2 phospholipases, disintegrins, a snake venom serine protease, a C-type lectin and a Kunitz-type protease inhibitor. Furthermore, we detected several isoforms of above mentioned proteins as well as previously unknown proteins, indicating an extensive complexity of the venom which would have remained undetected with conventional venomic approaches.

Structural Basis for the Inhibition of a Phospholipase A2-Like Toxin by Caffeic and Aristolochic Acids

One of the main challenges in toxicology today is to develop therapeutic alternatives for the treatment of snake venom injuries that are not efficiently neutralized by conventional serum therapy. Venom phospholipases A2 (PLA2s) and PLA2-like proteins play a fundamental role in skeletal muscle necrosis, which can result in permanent sequelae and disability. This leads to economic and social problems, especially in developing countries. In this work, we performed structural and functional studies with Piratoxin-I, a Lys49-PLA2 from Bothropspirajai venom, complexed with two compounds present in several plants used in folk medicine against snakebites. These ligands partially neutralized the myotoxic activity of PrTX-I towards binding on the two independent sites of interaction between Lys49-PLA2 and muscle membrane. Our results corroborate the previously proposed mechanism of action of PLA2s-like and provide insights for the design of structure-based inhibitors that could prevent the permanent injuries caused by these proteins in snakebite victims.

Development of Plate Reader and On-Line Microfluidic Screening to Identify Ligands of the 5-Hydroxytryptamine Binding Protein in Venoms

The 5-HT3 receptor is a ligand-gated ion channel, which is expressed in the nervous system. Its antagonists are used clinically for treatment of postoperative- and radiotherapy-induced emesis and irritable bowel syndrome. In order to better understand the structure and function of the 5-HT3 receptor, and to allow for compound screening at this receptor, recently a serotonin binding protein (5HTBP) was engineered with the Acetylcholine Binding Protein as template. In this study, a fluorescence enhancement assay for 5HTBP ligands was developed in plate-reader format and subsequently used in an on-line microfluidic format. Both assay types were validated using an existing radioligand binding assay. The on-line microfluidic assay was coupled to HPLC via a post-column split which allowed parallel coupling to a mass spectrometer to collect MS data. This high-resolution screening (HRS) system is well suitable for compound mixture analysis. As a proof of principle, the venoms of Dendroapsis polylepis, Pseudonaja affinis and Pseudonaja inframacula snakes were screened and the accurate masses of the found bioactives were established. To demonstrate the subsequent workflow towards structural identification of bioactive proteins and peptides, the partial amino acid sequence of one of the bioactives from the Pseudonaja affinis venom was determined using a bottom-up proteomics approach.

[Characterization of retrotransposon Bov-B LINE reverse transcriptase gene sequences in parthenogenetic lizards Darevskia unisexualis and bisexual species D. nairensis and D. valentini]

Cloning and sequencing of the partial reverse transcriptase gene (750 bp) of the Bov-B LINE retrotransposon have been held in parthenogenetic lizards Darevskia unisexualis and its assumed parental bisexual species D. nairensis and D.valentini. It was shown that the percentage of transcriptionally active copies of this gene, which does not contain a stop codon, is almost the same in the three species and is about 75%. The intragenomic divergence level of these sequences is low and was found to be 2.6% in D. unisexualis, 1.9% in D. nairensis, and 1.6% in D. valentini. The phylogenetic analysis shows the distribution of copies of D. unisexualis in each of the two clusters of RT sequences characteristic of D. nairensis and D. valentini. This result supports the view of the hybrid origin of D. unisexualis and does not exclude intraspecific hybridization between D. nairensis and D. valentini.

Functional variability of snake venom metalloproteinases: adaptive advantages in targeting different prey and implications for human envenomation

Snake venom metalloproteinases (SVMPs) are major components in most viperid venoms that induce disturbances in the hemostatic system and tissues of animals envenomated by snakes. These disturbances are involved in human pathology of snake bites and appear to be essential for the capture and digestion of snake's prey and avoidance of predators. SVMPs are a versatile family of venom toxins acting on different hemostatic targets which are present in venoms in distinct structural forms. However, the reason why a large number of different SVMPs are expressed in some venoms is still unclear. In this study, we evaluated the interference of five isolated SVMPs in blood coagulation of humans, birds and small rodents. P-III class SVMPs (fractions Ic, IIb and IIc) possess gelatinolytic and hemorrhagic activities, and, of these, two also show fibrinolytic activity. P-I class SVMPs (fractions IVa and IVb) are only fibrinolytic. P-III class SVMPs reduced clotting time of human plasma. Fraction IIc was characterized as prothrombin activator and fraction Ic as factor X activator. In the absence of Ca²⁺, a firm clot was observed in chicken blood samples with fractions Ic, IIb and partially with fraction IIc. In contrast, without Ca²⁺, only fraction IIc was able to induce a firm clot in rat blood. In conclusion, functionally distinct forms of SVMPs were found in B. neuwiedi venom that affect distinct mechanisms in the coagulation system of humans, birds and small rodents. Distinct SVMPs appear to be more specialized to rat or chicken blood, strengthening the current hypothesis that toxin diversity enhances the possibilities of the snakes for hunting different prey or evading different predators. This functional diversity also impacts the complexity of human envenoming since different hemostatic mechanisms will be targeted by SVMPs accounting for the complexity of the response of humans to venoms.

Synergism between basic Asp49 and Lys49 phospholipase A2 myotoxins of viperid snake venom in vitro and in vivo

Two subtypes of phospholipases A₂ (PLA₂s) with the ability to induce myonecrosis, ‘Asp49’ and ‘Lys49’ myotoxins, often coexist in viperid snake venoms. Since the latter lack catalytic activity, two different mechanisms are involved in their myotoxicity. A synergism between Asp49 and Lys49 myotoxins from Bothrops asper was previously observed in vitro, enhancing Ca²⁺ entry and cell death when acting together upon C2C12 myotubes. These observations are extended for the first time in vivo, by demonstrating a clear enhancement of myonecrosis by the combined action of these two toxins in mice. In addition, novel aspects of their synergism were revealed using myotubes. Proportions of Asp49 myotoxin as low as 0.1% of the Lys49 myotoxin are sufficient to enhance cytotoxicity of the latter, but not the opposite. Sublytic amounts of Asp49 myotoxin also enhanced cytotoxicity of a synthetic peptide encompassing the toxic region of Lys49 myotoxin. Asp49 myotoxin rendered myotubes more susceptible to osmotic lysis, whereas Lys49 myotoxin did not. In contrast to myotoxic Asp49 PLA₂, an acidic non-toxic PLA₂ from the same venom did not markedly synergize with Lys49 myotoxin, revealing a functional difference between basic and acidic PLA₂ enzymes. It is suggested that Asp49 myotoxins synergize with Lys49 myotoxins by virtue of their PLA₂ activity. In addition to the membrane-destabilizing effect of this activity, Asp49 myotoxins may generate anionic patches of hydrolytic reaction products, facilitating electrostatic interactions with Lys49 myotoxins. These data provide new evidence for the evolutionary adaptive value of the two subtypes of PLA₂ myotoxins acting synergistically in viperid venoms.

Immunolocalization of specific beta-proteins in pad lamellae of the digits in the lizard Anolis carolinensis suggests that cysteine-rich beta-proteins provides flexibility

Knowledge of beta-protein (beta-keratin) sequences in Anolis carolinensis facilitates the localization of specific sites in the skin of this lizard. The epidermal distribution of two new beta-proteins (betakeratins), HgGC8 and HgG13, has been analyzed by Western blotting, light and ultrastructural immunocytochemistry. HgGC8 includes 16 kDa members of the glycine-cysteine medium-rich subfamily and is mainly expressed in the beta-layer of adhesive setae but not in the setae. HgGC8 is absent in other epidermal layers of the setae and is weakly expressed in the beta-layer of other scales. HgG13 comprises members of 17-kDa glycine-rich proteins and is absent in the setae, diffusely distributed in the beta layer of digital scales and barely present in the beta-layer of other scales. It appears that the specialized glycine-cysteine medium rich beta-proteins such as HgGC8 in the beta-layer, and of HgGC10 and HgGC3 in both alpha- and betalayers, are key proteins in the formation of the flexible epidermal layers involved in the function of these modified scales in adaptation to contact and adhesion on surfaces.

A major phospholipase A2 from Daboia russelii russelii venom shows potent anticoagulant action via thrombin inhibition and binding with plasma phospholipids

This is the first report on antithrombin effects of a phospholipase A2 (RVAPLA2) purified from venom of Daboia russelii russelii. The N-terminal sequence as well as in-gel tryptic digested peptides of RVAPLA2 showed significant homology with PLA2s from Russell's viper venom. RVAPLA2 demonstrated highest specific activity in hydrolyzing phosphatidylcholine (1.8 × 10(6) U/mg) with Km and Vmax values of 0.61 mM and 132.3 μmol/min, respectively. RVAPLA2 exerted dose-dependent catalytic and strong anticoagulant activities; however, studies indicated dissociation of its catalytic and anticoagulant sites. The anticoagulant action of RVAPLA2 was partially contributed by catalytic hydrolysis of plasma phospholipids. RVAPLA2 showed strong anticoagulant effect via thrombin inhibition with a Ki value of 380 nM as well as by binding to pro-coagulant phospholipids of plasma. In ex-vivo conditions, RVAPLA2 (1.0 μM) was non-hemolytic and non-cytotoxic to mammalian cells. It did not inhibit the collagen-induced aggregation of platelets. RVAPLA2 at a dose of 5 mg/kg was not lethal to mice after 48 h of injection. It demonstrated in vivo anticoagulant activity possibly due to targeting thrombin and binding with plasma phospholipids.

Immunohistochemical detection of a unique protein within cells of snakes having inclusion body disease, a world-wide disease seen in members of the families Boidae and Pythonidae

Inclusion body disease (IBD) is a worldwide disease in captive boa constrictors (boa constrictor) and occasionally in other snakes of the families Boidae and Pythonidae. The exact causative agent(s) and pathogenesis are not yet fully understood. Currently, diagnosis of IBD is based on the light microscopic identification of eosinophilic intracytoplasmic inclusion bodies in hematoxylin and eosin stained tissues or blood smears. An antigenically unique 68 KDa protein was identified within the IBD inclusion bodies, called IBD protein. A validated immuno-based ante-mortem diagnostic test is needed for screening snakes that are at risk of having IBD. In this study, despite difficulties in solubilizing semi-purified inclusion bodies, utilizing hybridoma technology a mouse anti-IBD protein monoclonal antibody (MAB) was produced. The antigenic specificity of the antibody was confirmed and validated by western blots, enzyme-linked immunosorbent assay, immuno-transmission electron microscopy, and immunohistochemical staining. Paraffin embedded tissues of IBD positive and negative boa constrictors (n=94) collected from 1990 to 2011 were tested with immunohistochemical staining. In boa constrictors, the anti-IBDP MAB had a sensitivity of 83% and specificity of 100% in detecting IBD. The antibody also cross-reacted with IBD inclusion bodies in carpet pythons (Morelia spilota) and a ball python (python regius). This validated antibody can serve as a tool for the development of ante-mortem immunodiagnostic tests for IBD.

[Extraction, purification and identification of type II collagen from Agkistrodon acutus]

The object of the research was to extract, purify and identify the type II collagen of Agkistrodon acutus. Type II collagen of A. acutus was extracted by enzyme decomposition method, and purified by ion exchange column chromatography. It was characterized by SDS-PAGE gel electrophoresis, ultraviolet spectrophotometry, infrared absorption spectroscopy and mass spectroscopy. The results showed that the size of C II was about 130 kDa. It absorbed at 223 nm. IR spectrum obtained showed that the triple helical domains of amino-acid sequences were characterized by the repetition of triplets Gly-X-Y. The MS spectrum graphically stated that C II extracted from cow and A. acutus have the similar peptides. The C II of A. acutus was obtained by extraction and purification. Appraisal analysis by SDS-PAGE, UV, IR and MS, C II of A. acutus was consistent with the standard C II of cow. It was proved that the extracted protein was C II.

Structure of the polypeptide crotamine from the Brazilian rattlesnake Crotalus durissus terrificus

The crystal structure of the myotoxic, cell-penetrating, basic polypeptide crotamine isolated from the venom of Crotalus durissus terrificus has been determined by single-wavelength anomalous dispersion techniques and refined at 1.7 Å resolution. The structure reveals distinct cationic and hydrophobic surface regions that are located on opposite sides of the molecule. This surface-charge distribution indicates its possible mode of interaction with negatively charged phospholipids and other molecular targets to account for its diverse pharmacological activities. Although the sequence identity between crotamine and human β-defensins is low, the three-dimensional structures of these functionally related peptides are similar. Since crotamine is a leading member of a large family of myotoxic peptides, its structure will provide a basis for the design of novel cell-penetrating molecules.

Molecular cloning and expression of α-globin and β-globin genes from crocodile (Crocodylus siamensis)

The first report of complete nucleotide sequences for α- and β-globin chains from the Siamese hemoglobin (Crocodylus siamensis) is given in this study. The cDNAs encoding α- and β-globins were cloned by RT-PCR using the degenerate primers and by the rapid amplification of cDNA ends method. The full-length α-globin cDNA contains an open reading frame of 423 nucleotides encoding 141 amino acid residues, whereas the β-globin cDNA contains an open reading frame of 438 nucleotides encoding 146 amino acid residues. The authenticity of both α- and β-globin cDNA clones were also confirmed by the heterologous expression in Escherichia coli (E. coli). This is the first time that the recombinant C. siamensis globins were produced in prokaryotic system. Additionally, the heme group was inserted into the recombinant proteins and purified heme-bound proteins were performed by affinity chromatography using Co(2+)-charged Talon resins. The heme-bound proteins appeared to have a maximum absorbance at 415 nm, indicated that the recombinant proteins bound to oxygen and formed active oxyhemoglobin (HbO2). The results indicated that recombinant C. siamensis globins were successfully expressed in prokaryotic system and possessed an activity as ligand binding protein.

Antinociceptive activity and pathway of the pallanalgesin isolated from venom of Agkistrodon halys (Pallas)

CONTEXT

Venom of Agkstrodon halys (Pallas) is a traditional Chinese medicine for the control of severe pain, but its analgesic mechanism is not clear.

OBJECTIVE

To isolate the analgesic fraction from the venom, evaluate the profile of its action on pain using preclinical nociceptive tests and determine the involvement of neurotransmitters in its action.

MATERIALS AND METHODS

Venom was separated with SPXL resin, and further purified by Superdex 75 and Superdex 30 resin. Its biochemical characteristics were analyzed including molecular weight (MW), isoelectric point (pI) and amino acid sequence. Animal pain models were applied including the hot plate test, acetic acid-induced writhing test, formalin test, Randall-Selitto pressure test, antagonistic test, spinalized rats test and intracerebral injection test. The endogenous neuropeptides leucine-enkephalin, β-endorphin and P substance were determined by HPLC in the tissues of brain and spinal cord.

RESULTS

An analgesic protein named pallanalgesin (MW 16.6 kDa, pI 8.8) was obtained from the venom of A. halys. It had significant antinociceptive activity in different animal pain models of thermal, chemical and mechanical stimulation. It effects both central and peripheral nerve systems, and it is related to opiate receptors and monoamines rather than acetylcholine receptors. Pallanalgesin could modulate the levels of neuropeptides in the brain and spinal cord, which contributes to the recovery of nerve injury and pain control.

CONCLUSION

As a novel analgesic, pallanalgesin has been found to explain the function of the venom of A. halys on severe pain control in traditional uses, and can be used as a new analgesic in the future.

Identification of a functionally distinct truncated BDNF mRNA splice variant and protein in Trachemys scripta elegans

Brain-derived neurotrophic factor (BDNF) has a diverse functional role and complex pattern of gene expression. Alternative splicing of mRNA transcripts leads to further diversity of mRNAs and protein isoforms. Here, we describe the regulation of BDNF mRNA transcripts in an in vitro model of eyeblink classical conditioning and a unique transcript that forms a functionally distinct truncated BDNF protein isoform. Nine different mRNA transcripts from the BDNF gene of the pond turtle Trachemys scripta elegans (tBDNF) are selectively regulated during classical conditioning: exon I mRNA transcripts show no change, exon II transcripts are downregulated, while exon III transcripts are upregulated. One unique transcript that codes from exon II, tBDNF2a, contains a 40 base pair deletion in the protein coding exon that generates a truncated tBDNF protein. The truncated transcript and protein are expressed in the naïve untrained state and are fully repressed during conditioning when full-length mature tBDNF is expressed, thereby having an alternate pattern of expression in conditioning. Truncated BDNF is not restricted to turtles as a truncated mRNA splice variant has been described for the human BDNF gene. Further studies are required to determine the ubiquity of truncated BDNF alternative splice variants across species and the mechanisms of regulation and function of this newly recognized BDNF protein.

Structural and phylogenetic studies with MjTX-I reveal a multi-oligomeric toxin--a novel feature in Lys49-PLA2s protein class

The mortality caused by snakebites is more damaging than many tropical diseases, such as dengue haemorrhagic fever, cholera, leishmaniasis, schistosomiasis and Chagas disease. For this reason, snakebite envenoming adversely affects health services of tropical and subtropical countries and is recognized as a neglected disease by the World Health Organization. One of the main components of snake venoms is the Lys49-phospholipases A₂, which is catalytically inactive but possesses other toxic and pharmacological activities. Preliminary studies with MjTX-I from Bothrops moojeni snake venom revealed intriguing new structural and functional characteristics compared to other bothropic Lys49-PLA₂s. We present in this article a comprehensive study with MjTX-I using several techniques, including crystallography, small angle X-ray scattering, analytical size-exclusion chromatography, dynamic light scattering, myographic studies, bioinformatics and molecular phylogenetic analyses.Based in all these experiments we demonstrated that MjTX-I is probably a unique Lys49-PLA₂, which may adopt different oligomeric forms depending on the physical-chemical environment. Furthermore, we showed that its myotoxic activity is dramatically low compared to other Lys49-PLA₂s, probably due to the novel oligomeric conformations and important mutations in the C-terminal region of the protein. The phylogenetic analysis also showed that this toxin is clearly distinct from other bothropic Lys49-PLA₂s, in conformity with the peculiar oligomeric characteristics of MjTX-I and possible emergence of new functionalities inresponse to environmental changes and adaptation to new preys.

DNA-interactive properties of crotamine, a cell-penetrating polypeptide and a potential drug carrier

Crotamine, a 42-residue polypeptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, has been shown to be a cell-penetrating protein that targets chromosomes, carries plasmid DNA into cells, and shows specificity for actively proliferating cells. Given this potential role as a nucleic acid-delivery vector, we have studied in detail the binding of crotamine to single- and double-stranded DNAs of different lengths and base compositions over a range of ionic conditions. Agarose gel electrophoresis and ultraviolet spectrophotometry analysis indicate that complexes of crotamine with long-chain DNAs readily aggregate and precipitate at low ionic strength. This aggregation, which may be important for cellular uptake of DNA, becomes less likely with shorter chain length. 25-mer oligonucleotides do not show any evidence of such aggregation, permitting the determination of affinities and size via fluorescence quenching experiments. The polypeptide binds non-cooperatively to DNA, covering about 5 nucleotide residues when it binds to single (ss) or (ds) double stranded molecules. The affinities of the protein for ss- vs. ds-DNA are comparable, and inversely proportional to salt levels. Analysis of the dependence of affinity on [NaCl] indicates that there are a maximum of ∼3 ionic interactions between the protein and DNA, with some of the binding affinity attributable to non-ionic interactions. Inspection of the three-dimensional structure of the protein suggests that residues 31 to 35, Arg-Trp-Arg-Trp-Lys, could serve as a potential DNA-binding site. A hexapeptide containing this sequence displayed a lower DNA binding affinity and salt dependence as compared to the full-length protein, likely indicative of a more suitable 3D structure and the presence of accessory binding sites in the native crotamine. Taken together, the data presented here describing crotamine-DNA interactions may lend support to the design of more effective nucleic acid drug delivery vehicles which take advantage of crotamine as a carrier with specificity for actively proliferating cells.

Myelin basic protein undergoes a broader range of modifications in mammals than in lower vertebrates

Myelin basic protein (MBP) is an important component of the myelin sheath surrounding neurons, and it is directly affected in demyelinating diseases. MBP contains a relatively large number of post-translational modifications (PTMs), which have been reported to play a role in multiple sclerosis, while MBPs from lower vertebrates have been reported to be incapable of inducing multiple sclerosis or allergic encephalitis. This study reveals the extent of differences in PTM patterns for mammalian and nonmammalian MBPs. This included intact mass and de novo sequence analysis of approximately 85% of rattlesnake MBP, the first reptile MBP to be characterized, and of bovine MBP. We identified 12 PTMs at 11 sites in the five bovine MBP charge components, which include both previously reported and novel modifications. The most notable modification is an acetylation of lysine 121. Other modifications found in bovine MBP include N-terminal acetylation in components C1, C2, and C3; oxidation of methionine 19 in all five components; all charge isomers having both a mono- and dimethylated (symmetric) arginine at position 106; deimination in arginines 23 and 47 found only in component C8b; deimination of arginine 96 and deamidation in glutamine 102 found in components C2, C3, C8a, and C8b; phosphorylation in threonine 97 restricted to charge components C2 and C3; deimination in arginine 161 only found in component C3; deamidation of glutamine 120 was only observed in C3. All four deiminated arginines and one acetylated lysine were first experimentally revealed in this study for bovine MBP. Mascot database searching combined with de novo sequence analysis of rattlesnake MBP provided more than 85% sequence coverage. A few PTMs were also revealed in rattlesnake MBP: mono- and dimethylated Arg, protein N-terminal acetylation, and deiminated Arg. Overall, snake MBP was found to undergo less modification than bovine MBP on the basis of the mass heterogeneity of the intact protein, the bottom-up structure analysis, and the limited complexity of rattlesnake MBP chromatography. The combined data from this study and information from previous studies extend the known MBP PTMs, and PTMs unique to higher vertebrates are proposed.

Jararhagin, a hemorrhagic snake venom metalloproteinase from Bothrops jararaca

Jararhagin is a metalloproteinase isolated from Bothrops jararaca snake venom, which has been extensively studied. These studies showed its involvement on most of the systemic and local damaging effects of snakebite envenomings. In this review we comment on the major targets of jararhagin as the vascular endothelium, platelets and coagulation factors and also its action on other cell systems as inflammatory cells and their mediators, cancer and cell signaling. The mechanisms of jararhagin action are discussed together with structural features essential for the expression of its biological activities. The studies reviewed here denote jararhagin as a prototype for studies of snake venom metalloproteinases, bringing new insights into cellular-matrix interactions and adding for the improvement of snakebite treatment.

Phylogenetic analysis of serine proteases from Russell's viper (Daboia russelli siamensis) and Agkistrodon piscivorus leucostoma venom

Serine proteases are widely found in snake venoms. They have variety of functions including contributions to hemostasis. In this study, five serine proteases were cloned and characterized from two different cDNA libraries: factor V activator (RVV-V), alpha fibrinogenase (RVAF) and beta fibrinogenase (RVBF) from Russell's viper (Daboia russelli siamensis), and plasminogen activator (APL-PA) and protein C activator (APL-C) from Agkistrodon piscivorus leucostoma. The snake venom serine proteases were clustered in phylogenetic tree according to their functions. K(A)/K(S) values suggested that accelerated evolution has occurred in the mature protein coding regions in cDNAs of snake venom serine proteases.

Functional expression of spider neurotoxic peptide huwentoxin-I in E. coli

The coding sequence of huwentoxin-I, a neurotoxic peptide isolated from the venom of the Chinese spider Ornithoctonus huwena, was amplified by PCR using the cDNA library constructed from the spider venom glands. The cloned fragment was inserted into the expression vector pET-40b and transformed into the E. coli strain BL21 (DE3). The expression of a soluble fusion protein, disulfide interchange protein (DsbC)-huwentoxin-I, was auto-induced in the periplasm of E. coli in the absence of IPTG. After partial purification using a Ni-NTA column, the expressed fusion protein was digested using enterokinase to release heteroexpressed huwentoxin-I and was further purified using RP-HPLC. The resulting peptide was subjected to gel electrophoresis and mass spectrometry analysis. The molecular weight of the heteroexpressed huwentoxin-I was 3750.69, which is identical to that of the natural form of the peptide isolated from spider venom. The physiological properties of the heteroexpressed huwentoxin-I were further analyzed using a whole-cell patch clamp assay. The heteroexpressed huwentoxin-I was able to block currents generated by human Na(v1.7) at an IC₅₀ of 640 nmole/L, similar to that of the natural huwentoxin-I, which is 630 nmole/L.

Structure-function relationship of king cobra cathelicidin

King cobra cathelicidin (OH-CATH) is composed of 34 amino acid residues having strong antibacterial and very weak hemolytic activities as reported by us recently. OH-CATH can be served as a valuable template to develop novel therapeutic drugs. In this study, OH-CATH and six of its analogs were synthesized to explore their structure-function relationships based on their bactericidal and hemolytic activities. Experimental results of OH-CATH(3-34) and OH-CATH(5-34) indicated that the N-terminal 4 amino acid residues of OH-CATH played an important role on its hemolytic activity but had weak effects on its bactericidal activity. Among OH-CATH and its analogs, OH-CATH(5-34) had the lowest hemolytic activity while maintained strong antimicrobial activity. To evaluate its potential usage, the biological activities of OH-CATH(5-34) were compared with those of pexiganan. The bactericidal activity of OH-CATH(5-34) against 5 different species (11 laboratory strains) was 2-4 times stronger than that of pexiganan (4-16 microg/ml vs 8-32 microg/ml). Hemolytic activity of OH-CATH(5-34) against human erythrocytes was 0.69% while that of pexiganan was 16.5% at the dosage of 200 microg/ml. OH-CATH(5-34) showed very weak cytotoxic activities against primary rabbit ventricular endothelial cells and four human cancer cell lines whereas pexiganan showed strong cytotoxic activity against these five cell lines (IC(50)=20-90 microg/ml). The intravenous LD(50) value of OH-CATH(5-34) on mice was 7-fold higher than that of pexiganan (175 mg/kg vs 25mg/kg). Taken together, our results suggested that OH-CATH(5-34) should be considered as an excellent candidate for developing therapeutic drugs.

Snake venoms as a source of compounds modulating sperm physiology: Secreted phospholipases A2 from Oxyuranus scutellatus scutellatus impact sperm motility, acrosome reaction and in vitro fertilization in mice

The goal of this study was to identify new compounds from venoms able to modulate sperm physiology and more particularly sperm motility. For this purpose, we screened the effects of 16 snake venoms cleared of molecules higher than 15 kDa on sperm motility. Venoms rich in neurotoxins like those from Oxyuranus scutellatus scutellatus or Daboia russelii, were highly potent inhibitors of sperm motility. In contrast, venoms rich in myotoxins like those from Echis carinatus, Bothrops alternatus and Macrovipera lebetina, were inactive. From the main pharmacologically-active fraction of the Taipan snake O. scutellatus s., a proteomic approach allowed us to identify 16 different proteins, among which OS1 and OS2, two secreted phospholipases A2 (sPLA(2)). Purified OS1 and OS2 mimicked the inhibitory effect on sperm motility and were likely responsible for the inhibitory effect of the active fraction. OS1 and OS2 triggered sperm acrosome reaction and induced lipid rearrangements of the plasma membrane. The catalytic activity of OS2 was required to modulate sperm physiology since catalytically inactive mutants had no effect. Finally, sperm treated with OS2 were less competent than control sperm to initiate in vitro normal embryo development. This is the first report characterizing sPLA(2) toxins that modulate in vitro sperm physiology.

Cloning and expression of the estrogen receptor-alpha (Esr1) from the Harderian gland of the sea turtle (Lepidochelys olivacea)

The effects of estradiol on the Harderian gland (HG) are believed to be partially regulated by the transcriptional regulation of the estrogen-related genes via estrogen receptor (ER). In reptiles, however, it has not been well established whether the HG contains or expresses steroid nuclear receptors. As a first step toward investigating the molecular mechanisms of estrogen signalling in the HG, we isolated the cDNA for ERalpha in the sea turtle Lepidochelys olivacea. ERalpha was cloned using RT-PCR coupled with 5' and 3' RACE procedures. The cDNA contains a complete open reading frame encoding 588 amino acid residues. Comparative analysis of this amino acid sequence showed moderate to strong conservation of the ERalpha (Esr1) gene within divergent vertebrate groups. In transfection studies, the cloned ER displayed high affinity K(d)=0.25nM and high specificity for 17beta-estradiol. Binding assays using sucrose density gradients demonstrated a specific 7-7.5 S binding component in the HG cytosolic fractions. RT-qPCR analysis showed significant ERalpha mRNA expression in the liver, HG, lung and brain. Altogether, these results provide evidence for the expression of intracellular ERs in the HG of the sea turtle and suggest that ERalpha may be an important modulator of the estrogen-mediated response in the HG of reptiles.

Binding of a venom Lys-49 phospholipase A2 to LPS and suppression of its effects on mouse macrophages

The Lys49-phospholipases A(2) (K49-PLAs) are abundant in many pit vipers' venom. They are highly basic myotoxins and capable of binding membranes but lack hydrolytic activity. Considerable attention has been directed to its antibacterial activity but the exact mechanisms remain unclear. We now evaluate the roles of a K49-PLA from Trimeresurus stejnegeri venom in antagonizing the effects of lipopolysaccharide (LPS) on mouse macrophages (RAW264.7 cells). The K49-PLA markedly reduced LPS-stimulated production of NO, MCP-1, RANTES, and iNOS. RT-PCR analysis also confirmed its suppression of LPS-induced transcription of these cellular proteins. Moreover, LPS-induced activation of NFkappaB was dramatically abolished, while phosphorylation and degradation of IkappaB were also inhibited. Other types of venom phospholipases tested did not show the same effects as K49-PLA. Finally, strong binding between K49-PLA and LPS with a dissociation constant at the order of 10nM was shown by microcalorimetry titration. These findings provide unprecedented evidence that a low dose of K49-PLA possesses potent anti-inflammatory and antibacterial properties, which raises the prospect of a new therapeutic approach against sepsis.

Cytotoxicity induced in myotubes by a Lys49 phospholipase A2 homologue from the venom of the snake Bothrops asper: Evidence of rapid plasma membrane damage and a dual role for extracellular calcium

Acute muscle tissue damage, myonecrosis, is a typical consequence of envenomations by snakes of the family Viperidae. Catalytically-inactive Lys49 phospholipase A(2) homologues are abundant myotoxic components in viperid venoms, causing plasma membrane damage by a mechanism independent of phospholipid hydrolysis. However, the precise mode of action of these myotoxins remains unsolved. In this work, a cell culture model of C2C12 myotubes was used to assess the action of Bothrops asper myotoxin II (Mt-II), a Lys49 phospholipase A(2) homologue. Mt-II induced a dose- and time-dependent cytotoxic effect associated with plasma membrane disruption, evidenced by the release of the cytosolic enzyme lactate dehydrogenase and the penetration of propidium iodide. A rapid increment in cytosolic Ca(2+) occurred after addition of Mt-II. Such elevation was associated with hypercontraction of myotubes and blebbing of plasma membrane. An increment in the Ca(2+) signal was observed in myotube nuclei. Elimination of extracellular Ca(2+) resulted in increased cytotoxicity upon incubation with Mt-II, suggesting a membrane-protective role for extracellular Ca(2+). Chelation of cytosolic Ca(2+) with BAPTA-AM did not modify the cytotoxic effect, probably due to the large increment induced by Mt-II in cytosolic Ca(2+) which overrides the chelating capacity of BAPTA-AM. It is concluded that Mt-II induces rapid and drastic plasma membrane lesion and a prominent Ca(2+) influx in myotubes. Extracellular Ca(2+) plays a dual role in this model: it protects the membrane from the cytolytic action of the toxin; at the same time, the Ca(2+) influx that occurs after membrane disruption is likely to play a key role in the intracellular degenerative events associated with Mt-II-induced myotube damage.

Fungicidal activity of a phospholipase-A2-derived synthetic peptide variant against Candida albicans

pEM-2, a 13-mer synthetic peptide variant derived from myotoxin II, a phospholipase A(2) homologue present in Bothrops asper snake venom, has shown potent bactericidal activity in previous studies due to the combination of cationic and hydrophobic amino acids, including three tryptophan-substituted residues in its sequence. This study reports that pEM-2 also exerts potent fungicidal activity against a variety of clinically relevant Candida species, killing 100% of yeasts at concentrations near 10 mg/l (5 microM), as indicated by plate counting assays. Thus, this peptide displays a broad-spectrum antimicrobial activity, in the absence of hemolytic activity. The fungicidal action of pEM-2 against Candida can be partially inhibited by increasing concentrations of extracellular divalent cations (Ca(+2) or Mg(+2)), in agreement with its proposed membrane-permeabilizing mechanism of action.

New method for characterizing highly disulfide-bridged peptides in complex mixtures: application to toxin identification from crude venoms

Animal venoms are highly complex mixtures that can contain many disulfide-bridged toxins. This work presents an LC-MALDI approach allowing (1) a rapid classification of toxins according to their number of disulfide bonds and (2) a rapid top-down sequencing of the toxins using a new MALDI matrix enhancing in-source decay (ISD). The crude venom is separated twice by LC: the fractions of the first separation are spotted on the MALDI matrix alpha-cyano-4-hydroxycinnamic acid (CHCA) and the others using 1,5-diaminonaphthalene (1,5-DAN). CHCA spots are more convenient for obtaining a precise mass fingerprint of a large number of peptides; however, the analysis of 1,5-DAN spots allows the number of disulfide bridges to be counted owing to their partial in-plume reduction by this particular matrix. Subsequently, the disulfide bonds of all peptides present in the crude venom were reduced by an excess of tris(carboxyethyl)phosphine before the LC separation and were subjected to the same analysis in CHCA and 1,5-DAN. Toxins were sequenced using a TOF/TOF analysis of metastable fragments from CHCA spots and ISD fragmentation from 1,5-DAN spots. Novel conotoxin sequences were found using this approach. The use of 1,5-DAN for ISD top-down sequencing is also illustrated for higher molecular weight toxins such as snake cardiotoxins and neurotoxins (>6500 Da), where sequence coverage >70% is obtained from the c-ion series.