Purification, molecular cloning and mechanism of action of graminelysin I, a snake-venom-derived metalloproteinase that induces apoptosis of human endothelial cells

Comparison of Protein Variation in Protobothrops mucrosquamatus Venom between Northern and Southeast Taiwan and Association with Human Envenoming Effects

Reports of bite from Protobothrops mucrosquamatus (Pmu) are frequent in Taiwan, and its wide-spread distribution and diverse habitats drove us to investigate its envenoming effects and relevant venom variations. We used reversed-phase high-performance liquid chromatography and mass spectrometry to analyze 163 Pmu venom samples collected from northern and southeastern Taiwan. Twenty-two major protein fractions were separated and analyzed, and their contents were determined semi-quantitatively. The results showed that despite the trivial differences in the protein family, there is an existing variation in acidic phospholipases A₂s, serine proteinases, metalloproteinases, C-type lectin-like proteins, and other less abundant components in the Pmu venoms. Moreover, clinical manifestations of 209 Pmu envenomed patients hospitalized in northern or southeastern Taiwan revealed significant differences in local symptoms, such as ecchymosis and blistering. The mechanism of these local effects and possibly relevant venom components were examined. Further analysis showed that certain venom components with inter-population variation might work alone or synergistically with others to aggravate the local effects. Therefore, our findings of the venom variation may help one to improve antivenom production and better understand and manage Pmu bites.

Structure-Function Relationship of the Disintegrin Family: Sequence Signature and Integrin Interaction

Disintegrins are small cysteine-rich proteins found in a variety of snake venom. These proteins selectively modulate integrin function, heterodimeric receptors involved in cell-cell and cell-matrix interaction that are widely studied as therapeutic targets. Snake venom disintegrins emerged from the snake venom metalloproteinase and are classified according to the sequence size and number of disulfide bonds. Evolutive structure and function diversification of disintegrin family involves a stepwise decrease in the polypeptide chain, loss of cysteine residues, and selectivity. Since the structure elucidation of echistatin, the description of the structural properties of disintegrins has allowed the investigation of the mechanisms involved in integrin-cell-extracellular matrix interaction. This review provides an analysis of the structures of all family groups enabling the description of an expanded classification of the disintegrin family in seven groups. Each group presents a particular disulfide pattern and sequence signatures, facilitating the identification of new disintegrins. The classification was based on the disintegrin-like domain of the human metalloproteinase (ADAM-10). We also present the sequence and structural signatures important for disintegrin-integrin interaction, unveiling the relationship between the structure and function of these proteins.

P-I metalloproteinases and L-amino acid oxidases from Bothrops species inhibit angiogenesis

BACKGROUND

Snake venoms are composed of pharmacologically active proteins that are evolutionarily diverse, stable and specific to targets. Hence, venoms have been explored as a source of bioactive molecules in treating numerous diseases. Recent evidences suggest that snake venom proteins may affect the formation of new blood vessels. Excessive angiogenesis has been implicated in several pathologies including tumours, diabetic retinopathy, arthritis, inter alia. In the present study, we have examined the effects of P-I metalloproteinases isolated from Bothrops moojeni (BmMP-1) and Bothrops atrox (BaMP-1) and L-amino acid oxidases (LAAO) isolated from B. moojeni (BmLAAO) and B. atrox (BaLAAO) on biochemical and functional aspects of angiogenesis.

METHODS

P-I metalloproteinases and LAAO were purified from venom by molecular size exclusion and ion-exchange chromatography and subsequently confirmed using mass spectrometry. The P-I metalloproteinases were characterized by azocaseinolytic, fibrinogenolytic and gelatinase activity and LAAO activity was assessed by enzyme activity on L-amino acids. Influence of these proteins on apoptosis and cell cycle in endothelial cells was analysed by flow cytometry. The angiogenic activity was determined by in vitro 3D spheroid assay, Matrigel tube forming assay, and in vivo agarose plug transformation in mice.

RESULTS

P-I metalloproteinases exhibited azocaseinolytic activity, cleaved α and partially β chain of fibrinogen, and displayed catalytic activity on gelatin. LAAO showed differential activity on L-amino acids. Flow cytometry analysis indicated that both P-I metalloproteinases and LAAO arrested the cells in G0/G1 phase and further induced both necrosis and apoptosis in endothelial cells. In vitro, P-I metalloproteinases and LAAO exhibited significant anti-angiogenic properties in 3D spheroid and Matrigel models by reducing sprout outgrowth and tube formation. Using agarose plug transplants in mice harbouring P-I metalloproteinases and LAAO we demonstrated a marked disruption of vasculature at the periphery.

CONCLUSION

Our research suggests that P-I metalloproteinases and LAAO exhibit anti-angiogenic properties in vitro and in vivo.

Snake Venom Metalloproteinases (SVMPs): A structure-function update

Snake venom metalloproteinases (SVMPs) represent a diverse group of multi-domain proteins with several biological activities such as the ability to induce hemorrhage, proteolytic degradation of fibrinogen and fibrin, induction of apoptosis and inhibition of platelet aggregation. Due to these activities, SVMPs are responsible for many of the well-known pathological phenotypes in snake envenomations caused particularly by species from the Viperidae family and the Crotalinae subfamily. These proteins have been classified based on their size and domain structure into P–I, P-II and P-III classes. Comparatively, members of the P–I SVMPs possess the simplest structures, formed by the catalytic metalloproteinase domain only; the P-II SVMPs are moderately more complex, having the canonical disintegrin domain in addition to the metalloproteinase domain; members of the P-III class are more structurally varied, comprising the metalloproteinase, disintegrin-like, and cysteine-rich domains. Proteolytic cleavage, repeated domain loss and presence of other ancillary domains are responsible for structural diversities in the P-III class. However, studies continue to unveil the relationship between the structure and function of these proteins. In this review, we recovered evidences from literature on the structural peculiarities and functional classification of Snake Venom Metalloproteinases. In addition, we reflect on diversities that exist among each class while taking into account specific and up-to-date class-based activities.

Cytotoxic effects of Pseudocerastes persicus venom and its HPLC fractions on lung cancer cells

BACKGROUND

Several studies have pointed out that certain snake venoms contain compounds presenting cytotoxic activities that selectively interfere with cancer cell metabolism. In this study, Pseudocerastes persicus venom and its fractions were investigated for their anticancer potential on lung cancer cells.

METHODS

Lung cancer cells (A549) and normal fibroblast cells (Hu02) were treated with the P. persicus venom and its HPLC fractions and the cell cytotoxic effects were analyzed using MTT and lactate dehydrogenase release assays. Apoptosis was determined in venom-treated cell cultures using caspase-3 and caspase-9 assay kits.

RESULTS

The treatment of cells with HPLC fraction 21 (25-35 kDa) of P. persicus venom resulted in high LDH release in normal fibroblast cells and high caspase-3 and caspase-9 activities in lung cancer cells. These results indicate that fraction 21 induces apoptosis in cancer cells, whereas necrosis is predominantly caused by cell death in the normal cells. Fraction 21 at the final concentration of 10 μg/mL killed approximately 60% of lung cancer cells, while in normal fibroblast cells very low cell cytotoxic effect was observed.

CONCLUSION

HPLC fraction 21 at low concentrations displayed promising anticancer properties with apoptosis induction in the lung cancer cells. This fraction may, therefore, be considered a promising candidate for further studies.

A Deep Insight into the Sialome of Rhodnius neglectus, a Vector of Chagas Disease

BACKGROUND

Triatomines are hematophagous insects that act as vectors of Chagas disease. Rhodnius neglectus is one of these kissing bugs found, contributing to the transmission of this American trypanosomiasis. The saliva of hematophagous arthropods contains bioactive molecules responsible for counteracting host haemostatic, inflammatory, and immune responses.

METHODS/PRINCIPAL FINDINGS

Next generation sequencing and mass spectrometry-based protein identification were performed to investigate the content of triatomine R. neglectus saliva. We deposited 4,230 coding DNA sequences (CDS) in GenBank. A set of 636 CDS of proteins of putative secretory nature was extracted from the assembled reads, 73 of them confirmed by proteomic analysis. The sialome of R. neglectus was characterized and serine protease transcripts detected. The presence of ubiquitous protein families was revealed, including lipocalins, serine protease inhibitors, and antigen-5. Metalloproteases, disintegrins, and odorant binding protein families were less abundant.

CONCLUSIONS/SIGNIFICANCE

The data presented improve our understanding of hematophagous arthropod sialomes, and aid in understanding hematophagy and the complex interplay among vectors and their vertebrate hosts.

Hemorrhage Caused by Snake Venom Metalloproteinases: A Journey of Discovery and Understanding

The historical development of discoveries and conceptual frames for understanding the hemorrhagic activity induced by viperid snake venoms and by hemorrhagic metalloproteinases (SVMPs) present in these venoms is reviewed. Histological and ultrastructural tools allowed the identification of the capillary network as the main site of action of SVMPs. After years of debate, biochemical developments demonstrated that all hemorrhagic toxins in viperid venoms are zinc-dependent metalloproteinases. Hemorrhagic SVMPs act by initially hydrolyzing key substrates at the basement membrane (BM) of capillaries. This degradation results in the weakening of the mechanical stability of the capillary wall, which becomes distended owing of the action of the hemodynamic biophysical forces operating in the circulation. As a consequence, the capillary wall is disrupted and extravasation occurs. SVMPs do not induce rapid toxicity to endothelial cells, and the pathological effects described in these cells in vivo result from the mechanical action of these hemodynamic forces. Experimental evidence suggests that degradation of type IV collagen, and perhaps also perlecan, is the key event in the onset of microvessel damage. It is necessary to study this phenomenon from a holistic, systemic perspective in which the action of other venom components is also taken into consideration.

Snake venoms are integrated systems, but abundant venom proteins evolve more rapidly

Background

While many studies have shown that extracellular proteins evolve rapidly, how selection acts on them remains poorly understood. We used snake venoms to understand the interaction between ecology, expression level, and evolutionary rate in secreted protein systems. Venomous snakes employ well-integrated systems of proteins and organic constituents to immobilize prey. Venoms are generally optimized to subdue preferred prey more effectively than non-prey, and many venom protein families manifest positive selection and rapid gene family diversification. Although previous studies have illuminated how individual venom protein families evolve, how selection acts on venoms as integrated systems, is unknown.

Results

Using next-generation transcriptome sequencing and mass spectrometry, we examined microevolution in two pitvipers, allopatrically separated for at least 1.6 million years, and their hybrids. Transcriptomes of parental species had generally similar compositions in regard to protein families, but for a given protein family, the homologs present and concentrations thereof sometimes differed dramatically. For instance, a phospholipase A₂ transcript comprising 73.4 % of the Protobothrops elegans transcriptome, was barely present in the P. flavoviridis transcriptome (<0.05 %). Hybrids produced most proteins found in both parental venoms. Protein evolutionary rates were positively correlated with transcriptomic and proteomic abundances, and the most abundant proteins showed positive selection. This pattern holds with the addition of four other published crotaline transcriptomes, from two more genera, and also for the recently published king cobra genome, suggesting that rapid evolution of abundant proteins may be generally true for snake venoms. Looking more broadly at Protobothrops, we show that rapid evolution of the most abundant components is due to positive selection, suggesting an interplay between abundance and adaptation.

Conclusions

Given log-scale differences in toxin abundance, which are likely correlated with biosynthetic costs, we hypothesize that as a result of natural selection, snakes optimize return on energetic investment by producing more of venom proteins that increase their fitness. Natural selection then acts on the additive genetic variance of these components, in proportion to their contributions to overall fitness. Adaptive evolution of venoms may occur most rapidly through changes in expression levels that alter fitness contributions, and thus the strength of selection acting on specific secretome components.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1832-6) contains supplementary material, which is available to authorized users.

Snake venom metalloproteinases: structure, function and relevance to the mammalian ADAM/ADAMTS family proteins

Metalloproteinases are among the most abundant toxins in many Viperidae venoms. Snake venom metalloproteinases (SVMPs) are the primary factors responsible for hemorrhage and may also interfere with the hemostatic system, thus facilitating loss of blood from the vasculature of the prey. SVMPs are phylogenetically most closely related to mammalian ADAM (a disintegrin and metalloproteinase) and ADAMTS (ADAM with thrombospondin type-1 motif) family of proteins and, together with them, constitute the M12B clan of metalloendopeptidases. Large SVMPs, referred to as the P-III class of SVMPs, have a modular architecture with multiple non-catalytic domains. The P-III SVMPs are characterized by higher hemorrhagic and more diverse biological activities than the P-I class of SVMPs, which only have a catalytic domain. Recent crystallographic studies of P-III SVMPs and their mammalian counterparts shed new light on structure-function properties of this class of enzymes. The present review will highlight these structures, particularly the non-catalytic ancillary domains of P-III SVMPs and ADAMs that may target the enzymes to specific substrates. This article is part of a Special Issue entitled: Proteolysis 50years after the discovery of lysosome.

Effects of snake venom proteases on human fibrinogen chains

BACKGROUND

Proteomic approach is an effective method to study changes in human plasma proteome. Coagulopathies are commonly encountered in victims of viper envenomation which were treated with an administration of immunoglobulin. Unfortunately, this treatment shows significant risk to the patient due to an anaphylactic reaction. Since Echis carinatus Venom (EV) toxins mainly acts both directly and indirectly on fibrinogen, we planned to establish a suitable analysis of its beta (FIBB) e gamma (FIBG) chains. This study will help us to understand the mechanism of envenomation and to find alternative treatments other than the common treatment with the administration of IgG.

STUDY DESIGN AND METHODS

We evaluated the EV proteolytic activity on whole human plasma proteome from the blood of an healthy volunteer. Two-dimensional electrophoresis (2-DE) using mini-gel was performed to analyse EV effects on the differents fibrinogen chains.

RESULTS

Changes in whole plasma proteome were focused on fibrinogen beta and gamma chains after EV incubation. Protein spots were detected and analyzed using ImageMaster 2D Platinum software. Results were represented as mean +/- standard deviation (mean+/-SD) with p<0.05 as a statistically significant value. 2-DE gel analysis showed that some spots of FIBB disappeared and some spots of FIBG decreased.

CONCLUSION

We found that the proteomic approach is a valid method in studying in-depth causes of different diseases, in particular those are involved in coagulopathies linked with proteins like fibrinogen from victims of viper envenomation.

Activation of c-Jun N-terminal kinase is essential for mitochondrial membrane potential change and apoptosis induced by doxycycline in melanoma cells

BACKGROUND AND PURPOSE

Tetracyclines were recently found to induce tumour cell death, but the early processes involved in this cytotoxic effect remain unclear.

EXPERIMENTAL APPROACH

Viability of human and mouse melanoma cells was determined by MTT assay and flow cytometry. Kinase/protein/caspase activation was measured by Western blotting and mitochondrial membrane potential (DeltaPsi(m)) was analyzed by fluorescence microscopy and flow cytometry.

KEY RESULTS

Human and mouse melanoma cells were treated with doxycycline or minocycline but only doxycycline was cytotoxic. This cell death (apoptosis) in A2058 cells involved activation of caspase-3, -7 and -9 and contributed to inhibition, by doxycycline, of matrix metalloproteinase (MMP) activity and migration of these cells. Doxycycline induced intra-cellular reactive oxygen species (ROS) production, apoptosis signal-regulated kinase 1 (ASK1), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) activation at an early stage of treatment and induced mitochondrial cytochrome c release into cytosol and DeltaPsi(m) change during apoptosis. The JNK inhibitor/small interference RNA inhibited doxycycline-induced JNK activation, DeltaPsi(m) change and apoptosis, but did not affect ASK1 activation, suggesting a role of ASK1 for JNK activation in melanoma cell apoptosis. Two ROS scavengers reduced doxycycline-induced JNK and caspase activation, and apoptosis. Taken together, the results suggest the involvement of a ROS-ASK1-JNK pathway in doxycycline-induced melanoma cell apoptosis.

CONCLUSIONS AND IMPLICATIONS

We have shown a promising cytotoxic effect of doxycycline on melanoma cells, have identified ROS and ASK1 as the possible initiators and have demonstrated that JNK activation is necessary for doxycycline-induced melanoma cell apoptosis.

Cell death induced by Bothrops asper snake venom metalloproteinase on endothelial and other cell lines

Two adherent cell lines, BAEC and HeLa, and non-adherent Jurkat, were treated with snake venom metalloproteinase BaP1 to determine whether cytotoxicity, previously reported for this toxin, could be mediated by the process of anoikis. It was observed that there was no correlation between the ability of this toxin to induce loss of adherence, and the cytotoxic effect, since concentrations that do not induce loss of adherence (3-6 microg/mL), were able to trigger 50% of cytotoxicity in BAEC. In the case of HeLa, where toxicity was very low (less than 20% at maximun concentrations and times of exposure), significant detachment and no toxicity was observed at concentrations of 1.5 microg/mL, showing also no correlation between both events. We also observed differences between BAEC toxicity measured by XTT reduction and DNA fragmentation determined by flow cytometry (as an indicator of apoptosis), since concentrations that induce 100% of cytotoxicity barely showed any DNA fragmentation (12% at 24h), suggesting that if apoptosis was involved, DNA damage is still not present, although chromatin condensation, another indicator of apoptosis, is observed in 40% of the cells. Inhibition of BAEC cytotoxicity by caspase inhibitors indicate that apoptosis is playing a role in this process, but other mechanisms of cell death could be participating also. Another way to determine whether the mechanism of cell death was related to anoikis was using a non-adherent cell line, which should show substrate independence. We determined by TUNEL that at 50 microg/ml BaP1 triggered 50% of apoptosis at 96 h, an effect that was seen earlier, suggesting also that if this toxin was inducing apoptosis in a non-adherent cell line, the mechanism could not be related to loss of attachment. Cell cycle arrest in S phase was also observed in Jurkat cells, an effect that could be leading to apoptosis. In conclusion, since there was no correlation between cell detachment and cytotoxicity (and apoptosis) in adherent cell lines and due to the ability of BaP1 to induce apoptosis in a non-adherent cell line, we suggest that this enzyme is toxic by a mechanism not related to anoikis, and that in the case of Jurkat cells, it is likely to be related to its ability to induce cell cycle arrest. Processes other than apoptosis could be also involved in the cell death mechanism mediated by BaP1 on BAEC.

Cytoskeletal rearrangement and cell death induced by Bothrops alternatus snake venom in cultured Madin–Darby canine kidney cells

Bothrops snake venoms cause renal damage, with renal failure being the main cause of death in humans bitten by these snakes. In this work, we investigated the cytoskeletal rearrangement and cytotoxicity caused by Bothrops alternatus venom in cultured Madin–Darby canine kidney (MDCK) cells. Incubation with venom (10 and 100 µg/mL) significantly (p <0.05) decreased the cellular uptake of neutral red dye after 1 and 3 h. Venom (100 µg/mL) also markedly decreased the transepithelial electrical resistance (RT) across MDCK monolayers. Staining with rhodamine-conjugated phalloidin revealed disarray of the cytoskeleton that involved the stress fibers at the basal cell surface and focal adhesion-associated F-actin in the cell–matrix contact region. Feulgen staining showed a significant decrease in the number of cells undergoing mitosis and an increase in the frequency of altered nuclei. Scanning electron microscopy revealed a decrease in the number of microvilli and the presence of cells with a fusiform format. Flow cytometry with annexin V and propidium iodide showed that cell death occurred by necrosis, with little apoptosis, a conclusion supported by the lack of DNA fragmentation characteristic of apoptosis. Pretreating the cells with catalase significantly attenuated the venom-induced loss of viability, indicating a possible involvement of H2O2 in the cellular damage; less protection was observed with superoxide dismutase or Nω-nitro-l-arginine methyl ester. These results indicate that Bothrops alternatus venom is cytotoxic to cultured MDCK cells, possibly via the action of reactive oxygen species. This cytotoxicity could contribute to nephrotoxicity after envenoming by this species.

Identification, cloning, expression and functional characterization of an astacin-like metalloprotease toxin from Loxosceles intermedia (brown spider) venom

Injuries caused by brown spiders (Loxosceles genus) are associated with dermonecrotic lesions with gravitational spreading and systemic manifestations. The venom has a complex composition containing many different toxins, of which metalloproteases have been described in many different species of this genus. These toxins may degrade extracellular matrix constituents acting as a spreading factor. By using a cDNA library from an Loxosceles intermedia venom gland, we cloned and expressed a 900 bp cDNA, which encoded a signal peptide and a propeptide, which corresponded to a 30 kDa metalloprotease, now named LALP (Loxosceles astacin-like protease). Recombinant LALP was refolded and used to produce a polyclonal antiserum, which showed cross-reactivity with a 29 kDa native venom protein. CD analysis provided evidence that the recombinant LALP toxin was folded correctly, was still in a native conformation and had not aggregated. LALP addition to endothelial cell cultures resulted in de-adhesion of the cells, and also in the degradation of fibronectin and fibrinogen (this could be inhibited by the presence of the bivalent chelator 1,10-phenanthroline) and of gelatin in vitro. Sequence comparison (nucleotide and deduced amino acid), phylogenetic analysis and analysis of the functional recombinant toxin revealed that LALP is related in both structure and function to the astacin family of metalloproteases. This suggests that an astacin-like toxin is present in a animal venom secretion and indicates that recombinant LALP will be a useful tool for future structural and functional studies on venom and the astacin family.

Antithrombotic effect of a protein-type I class snake venom metalloproteinase, kistomin, is mediated by affecting glycoprotein Ib-von Willebrand factor interaction

Binding of von Willebrand factor (vWF) to platelet glycoprotein (GP) Ib-IX-V mediates platelet activation in the early stage of thrombus formation. Kistomin, a snake venom metalloproteinase (SVMP) purified from venom of Calloselasma rhodostoma, has been shown to inhibit vWF-induced platelet aggregation. However, its action mechanism, structure-function relationship, and in vivo antithrombotic effects are still largely unknown. In the present study, cDNA encoding kistomin precursor was cloned and revealed that kistomin is a P-I class SVMP with only a proteinase domain. Further analysis indicated that kistomin specifically inhibited vWF-induced platelet aggregation through binding and cleavage of platelet GPIbalpha and vWF. Cleavage of platelet GPIbalpha by kistomin resulted in release of 45- and 130-kDa soluble fragments, indicating that kistomin cleaves GPIbalpha at two distinct sites. In parallel, cleavage of vWF by kistomin also resulted in the formation of low-molecular-mass multimers of vWF. In ex vivo and in vivo studies, kistomin cleaved platelet GPIbalpha in whole blood. Moreover, GPIbalpha agonist-induced platelet aggregation ex vivo was inhibited, and tail-bleeding time was prolonged in mice administered kistomin intravenously. Kistomin's in vivo antithrombotic effect was also evidenced by prolonging the occlusion time in mesenteric microvessels of mice. In conclusion, kistomin, a P-I class metalloproteinase, has a relative specificity for GPIbalpha and vWF and its proteolytic activity on GPIbalpha-vWF is responsible for its antithrombotic activity both in vitro and in vivo. Kistomin can be useful as a tool for studying metalloproteinase-substrate interactions and has a potential being developed as an antithrombotic agent.

Cytotoxic, thrombolytic and edematogenic activities of leucurolysin-a, a metalloproteinase from Bothrops leucurus snake venom

Leucurolysin-a (leuc-a), a 23 kDa non-hemorrhagic metalloproteinase, is found in venom of the viper Bothrops leucurus. Here, we examine the biological consequences of leuc-a, including thrombolytic activity, direct effects on endothelial cells in culture and edematogenic activity in vivo. We demonstrate fibrinolytic activity of leuc-a, in which the protease specifically degrades alpha, beta, and gamma-gamma chains. While not causing hemorrhaging, leuc-a does cause thrombolytic activities in whole blood clots. Endothelial cells are highly resistant to leuc-a in culture. Cell viability suffered only when cells were exposed to large quantities of the protease. Nevertheless, leuc-a induces changes in cell morphology. The impact of leuc-a on cell adhesion was confirmed by an adhesion assay, in which cell adhesion to fibronectin decreased due to leuc-a. This mild cellular impact is unlike that of crude venom, where lower concentrations triggered cell death and a greater reduction in cell adhesion. Also, leuc-a increased microvessel permeability with marked edema in mice peritoneum and foot pads. These effects are similar to those of other P-I class SVPMs. These in vivo effects were weaker when crude venom was tested. In conclusion, albeit not showing significant hemorrhagic activity, leuc-a can induce a prominent edema which appears to be significant in the local effects observed after B. leucurus venom accidents.

Isolation and characterization of a novel P-II class snake venom metalloproteinase from Trimeresurus stejnegeri

Stejnitin, a novel class P-II snake venom metalloproteinase (SVMP) with a molecular weight of about 35kDa, was purified from Trimeresurus stejnegeri venom. The cDNA of stejnitin encoded a polypeptide of 295 amino acid residues which comprises a signal peptide, proprotein, metalloproteinase domain, spacer and disintegrin domain. The protein sequence deduced from cDNA was confirmed by peptide mass fingerprinting analysis. It is highly homologous to the members of subclass P-IIa SVMPs which comprises metalloproteinase and disintegrin together. Results from DNA fragmentation and flow cytometry analysis also indicated that stejnitin is able to induce apoptosis of ECV304 cells (R=0.908, P=0.012).

Loss of introns along the evolutionary diversification pathway of snake venom disintegrins evidenced by sequence analysis of genomic DNA from Macrovipera lebetina transmediterranea and Echis ocellatus

Analysis of cDNAs from Macrovipera lebetina transmediterranea (Mlt) and Echis ocellatus (Eo) venom gland libraries encoding disintegrins argued strongly for a common ancestry of the messengers of short disintegrins and those for precursors of dimeric disintegrin chains. We now report the sequence analysis of disintegrin-coding genes from these two vipers. Genomic DNAs for dimeric disintegrin subunits Ml_G1 and Ml_G2 (Mlt) and Eo_D3 (Eo) contain single 1-kb introns exhibiting the 5'-GTAAG (donor)/3'-AG (acceptor) consensus intron splicing signature. On the other hand, the short RTS-disintegrins Ml_G3 (Mlt) and Eo_RTS (Eo) and the short RGD-disintegrin ocellatusin (Eo) are transcribed from intronless genomic DNA sequences, indicating that the evolutionary pathway leading to the emergence of short disintegrins involved the removal of all intronic sequences. The insertion position of the intron within Ml_G1, Ml_G2, and Eo_D3 is conserved in the genes for vertebrate ADAM (A disintegrin and metalloproteinase) protein disintegrin-like domains and within the gene for the medium-size snake disintegrins halystatins 2 and 3. However, a comparative analysis of currently available disintegrin(-like) genes outlines the view that a minimization of both the gene organization and the protein structure underlies the evolution of the snake venom disintegrin family.

Molecular diversity of disintegrin-like domains within metalloproteinase precursors of Bothrops jararaca

Disintegrins are small peptides isolated from the venom of several snake families which act as integrin-antagonists or agonists, interacting with a variety of biological processes mediated by integrins. In this work we describe five new disintegrin-like domains within metalloproteinase precursor sequences, obtained from a Bothrops jararaca venom gland cDNA library. Among the new disintegrin-like domains, four were contained in PIII metalloproteinase precursors, with three of them presenting ECD-motifs and one presenting a new KCD-motif. Moreover, we found three disintegrin-like domains within PII metalloproteinase precursors. Two of them are similar to the already described disintegrins jarastatin and jararacin. The third molecule is unusual, presenting some typical PIII metalloproteinase characteristics but lacking the cysteine-rich domain being, thus, classified as a PII metalloproteinase. Only few reports presented molecules with these characteristics. Sequence analysis suggests that these molecules are intermediate steps between the more ancient PIII and the more recent PII metalloproteinases. We also investigated disintegrin N-terminus diversity in B. jararaca crude venom by purifying jarastatin and jararacin and analyzing them by mass spectrometry.

Blood cells as targets of snake toxins

Snake venoms are mixtures of enzymes and peptides which exert toxicological effects by targeting their substrates or receptors upon envenomation. Snake venom proteins widely affect vascular system including circulating blood cells, coagulation factors, and vascular wall components. Many of the toxic proteins have multiple targets. For example, some metalloproteinase domain-containing snake venom protein cleaves not only fibrinogen but also receptors on platelets. Also, it is frequent that toxins from different snake venom protein families are capable of binding to a common target on cells. Most of the cytotoxic effects in the venom are usually results of the activities of metalloproteinase, C-type lectin, disintegrin, cysteine-rich protein, as well as phospholipase A(2). There has been a growing interest in studying the structure and function of these snake venom proteins because many of them have high structural homologies to proteins found in human. Therefore, the understanding of how these toxins interact with their targets may contribute to the discovery of novel physiological processes and the development of therapeutic agents for cardiovascular diseases. In this review, we summarize how snake toxins target blood cells with an emphasis on their effects on platelet function.

A snake venom metalloproteinase that inhibited cell proliferation and induced morphological changes of ECV304 cells

TSV-DM, a basic metalloproteinase with a molecular weight of 110kDa, was purified from Trimeresurus stejnegeri venom. TSV-DM degraded the Aalpha chain of fibrinogen more rapidly than the Bbeta chain in a dose dependent manner. The cDNA of TSV-DM encoded a polypeptide of 622 amino acid residues, which comprises a signal peptide, proprotein, metalloproteinase domain, spacer, disintegrin-like domain and cysteine-rich domain. The protein sequence deduced from cDNA was confirmed by peptide mass fingerprinting analysis. It is highly homologous to the members of subclass P-IIIb snake venom metalloproteinase, which comprises vascular apoptosis-inducing proteins. TSV-DM inhibited cell proliferation and induced cell morphologic changes transiently of ECV304 cells. However, DNA fragmentation and DNA content analysis demonstrated that this metalloproteinase could not induce ECV304 cells apoptosis.

Membrane type 1-matrix metalloproteinase induces endothelial cell morphogenic differentiation by a caspase-dependent mechanism

Membrane-type 1 matrix metalloproteinase (MT1-MMP) has been suggested to play an essential role in angiogenesis. Based on recent evidence suggesting that the sprouting and branching of capillaries during angiogenesis involves apoptosis, we investigated the involvement of this process in MT1-MMP-dependent morphogenic differentiation of EC into capillary-like structures. We found that MT1-MMP sensitizes EC to apoptosis, since reduction of MT1-MMP expression abolished vimentin fragmentation in apoptotic HUVECs while overexpression of the enzyme induced caspase-3 activity in BAECs subjected to pro-apoptotic treatments. MT1-MMP-mediated caspase-3 activation likely occurs through the mitochondrial pathway since it was abrogated by Bcl-2, but not by CrmA overexpression. Reduction of MT1-MMP expression in HUVECs reduced morphogenic differentiation that was correlated with diminished vimentin fragmentation, whereas its overexpression in BAECs stimulated both processes. Inactivation of the catalytic activity or removal of the cytoplasmic domain of MT1-MMP markedly reduced its ability to induce both morphogenic differentiation and caspase-3 activation. The inhibitory effects of the anti-apoptotic protein Bcl-2 and the caspase inhibitor zVAD-fmk further suggested the involvement of apoptosis during MT1-MMP-mediated morphogenic differentiation. Our results show that the ability of MT1-MMP to induce EC morphogenic differentiation involves its activation of a caspase-dependent mechanism.

A novel metalloprotease from Vipera lebetina venom induces human endothelial cell apoptosis

A novel endothelial cell apoptosis inducing metalloprotease (VLAIP) was found in the snake venom of Vipera lebetina. This metalloprotease is a heterodimeric glycoprotein with molecular mass of about 106 kDa. The protease hydrolyzes azocasein, fibrinogen and oxidized insulin B-chain. The enzyme readily hydrolyzes the Aalpha-chain and more slowly Bbeta-chain of fibrinogen. VLAIP does not cleave fibrin. The complete amino acid sequences of the two different monomers of VLAIP are deduced from the nucleotide sequences of cDNAs encoding these proteins. The full-length cDNA sequences of the VLAIP-A and VLAIP-B encode open reading frames of 616 and 614 amino acids that include signal peptide, propeptide and mature metalloproteinase with disintegrin-like and cysteine-rich domains. VLAIP belongs to the metalloprotease/disintegrin family of reprolysins and has high identity with the proteins that induce apoptosis of endothelial cells. Treatment of HUVEC cells with VLAIP induces changes in the attachment of cells to the substrate and causes cell death. We demonstrated that VLAIP inhibits endothelial cell adhesion to extracellular matrix proteins: fibrinogen, fibronectin, vitronectin, collagen I, and collagen IV. The induction of apoptosis by VLAIP was shown by means of a typical DNA fragmentation pattern of apoptotic cells as well as by monitoring phosphatidylserine externalization using annexin V-FITC staining and flow cytometric analysis.

Structural considerations of the snake venom metalloproteinases, key members of the M12 reprolysin family of metalloproteinases

The importance of proteinases in the pathologies associated with Viperid envenoming has long been appreciated. Over the past 40 years substantial research has clearly implicated metalloproteinases in the venom (snake venom metalloproteinases; SVMPs) as playing key roles in the development of such symptoms as hemorrhage, edema, hypotension, hypovolemia, inflammation and necrosis. In spite of this wealth of information there are still many unresolved questions pertaining to the structural basis for the various SVMPS giving rise to the diversity of activities. In this short review we will not attempt to provide an exhaustive collation of structural studies on the SVMPs; however, we will give a brief outline of the structural classification of the SVMPs; as well as relate them to the other members of the reprolysin family of metalloproteinases, the ADAMs. The information put forth in the text does not allow specific conclusions to be drawn on the structural basis for SVMP functional diversity, but it is our goal that it will allow for the development of testable hypotheses that can be experimentally pursued. What the reader will observe is that there are very interesting structural features displayed by the various SVMP classes and subclasses that provide insight into their functional characteristics.

Hemorrhage induced by snake venom metalloproteinases: biochemical and biophysical mechanisms involved in microvessel damage

Zinc-dependent metalloproteinases are responsible for the hemorrhagic activity characteristic of viperid snake venoms. Snake venom metalloproteinases (SVMPs) are classified in various groups (P-I-IV), according to their domain composition. P-III SVMPs, comprising metalloproteinase, disintegrin-like and cysteine-rich domains, exert more potent hemorrhagic activity than P-I SVMPs, which present only the metalloproteinase domain. SVMPs degrade various components of the basement membrane and are also able to hydrolyze endothelial cell membrane proteins, such as integrins and cadherins, involved in cell-matrix and cell-cell adhesion. In addition, disintegrin-like and cysteine-rich domains interact with endothelial cell integrins, interfering with their adhesion to extracellular matrix. Hemorrhage induced by SVMPs is an extremely rapid event in vivo, with capillary endothelial cells showing drastic structural alterations within few minutes. In contrast, observations in cell culture conditions do not evidence such rapid endothelial cell damage. Instead, the main effect is detachment and rounding of these cells; it is only after several hours of incubation that cells show evidence of apoptotic damage. This apparent discrepancy between in vivo and in vitro observations can be explained if biophysical forces operating on microvessels in vivo are taken into consideration. It is proposed that SVMP-induced hemorrhage occurs in vivo by a 'two-step' mechanism. Initially, SVMPs degrade basement membrane and adhesion proteins, thus weakening the capillary wall and perturbing the interactions between endothelial cells and the basement membrane. Then, transmural pressure acting on the weakened capillary wall causes distention. As a consequence, endothelial cells become very thin, until the integrity of the capillary wall is lost at some points, where extravasation occurs. In addition, endothelial cells become more susceptible to blood flow-dependent shear stress, which further contributes to capillary wall disruption.

Snake venom disintegrins: evolution of structure and function

Disintegrins represent a family of polypeptides present in the venoms of various vipers that selectively block the function of integrin receptors. Here, we review our current view and hypothesis on the emergence and the structural and functional diversification of disintegrins by accelerated evolution and the selective loss of disulfide bonds of duplicated genes. Research on disintegrins is relevant for understanding the biology of viper venom toxins, but also provides information on new structural determinants involved in integrin recognition that may be useful in basic and clinical research. The role of the composition, conformation, and dynamics of the integrin inhibitory loop acting in concert with the C-terminal tail in determining the selective inhibition of integrin receptors is discussed.

The snake venom metalloproteases berythractivase and jararhagin activate endothelial cells

PIII snake venom metalloproteases (SVMPs) are metalloproteases structurally related to ADAMs (a disintegrin and metalloprotease human family of proteins). Berythractivase and jararhagin are PIII SVMPs with 69% homology that have different hemostatic properties. In order to clarify these differences and further characterize the biological effects of these proteins, we have analyzed the effect of both proteases on human umbilical-vein endothelial cell functions. We found that both proteins enhanced nitric oxide generation, prostacyclin production and interleukin-8 release. Berythractivase but not jararhagin increased the expression of decay accelerating factor. Jararhagin decreased cell viability in a concentration-dependent manner and induced cellular apoptosis, while berythractivase did not modulate cell survival. Our results show for the first time that, besides the known anti-aggregating or procoagulant effects of PIII SVMPs, these proteins trigger endothelial cell effector responses. Although structurally related, berythractivase and jararhagin induce a dissimilar generation and release of endothelial molecules that may account for their different hemorrhagic activity.

The purification and partial characterisation of two novel metalloproteinases from the venom of the West African carpet viper, Echis ocellatus

Separation of previously uncharacterised Echis ocellatus venom by phenyl-Superose FPLC (Fast Liquid Protein Chromatography) yielded eight protein fractions. Three of these displayed high proteolytic activity when assayed by in vivo and in vitro assays (including enzyme linked immunosorbant assay), and were further separated using Superdex 75 and Mono-Q FPLC. This resulted in the purification of a non-haemorrhagic 24 kDa metalloproteinase (EoVMP1, pI 7.0), and a haemorrhagic 56 kDa metalloproteinase (EoVMP2, pI 5.5). Following tryptic digest, short amino acid sequences of EoVMP1 and EoVMP2 were obtained using Edman degradation. Both sequences displayed homology when aligned with existing snake venom metalloproteinases (SVMPs). The strong homology observed among previously well-characterised SVMPs suggests that principles governing the interaction of substrates and inhibitors are likely to be similar for EoVMP1, EoVMP2 and all members of the reprolysin family.

Snake venom disintegrins: novel dimeric disintegrins and structural diversification by disulphide bond engineering

We report the isolation and amino acid sequences of six novel dimeric disintegrins from the venoms of Vipera lebetina obtusa (VLO), V. berus (VB), V. ammodytes (VA), Echis ocellatus (EO) and Echis multisquamatus (EMS). Disintegrins VLO4, VB7, VA6 and EO4 displayed the RGD motif and inhibited the adhesion of K562 cells, expressing the integrin alpha5beta1 to immobilized fibronectin. A second group of dimeric disintegrins (VLO5 and EO5) had MLD and VGD motifs in their subunits and blocked the adhesion of the alpha4beta1 integrin to vascular cell adhesion molecule 1 with high selectivity. On the other hand, disintegrin EMS11 inhibited both alpha5beta1 and alpha4beta1 integrins with almost the same degree of specificity. Comparison of the amino acid sequences of the dimeric disintegrins with those of other disintegrins by multiple-sequence alignment and phylogenetic analysis, in conjunction with current biochemical and genetic data, supports the view that the different disintegrin subfamilies evolved from a common ADAM (a disintegrin and metalloproteinase-like) scaffold and that structural diversification occurred through disulphide bond engineering.