Analysis of a cDNA sequence encoding a novel member of the snake venom metalloproteinase, disintegrin-like, cysteine-rich (MDC) protein family from Agkistrodon contortrix laticinctus

Gene expression profiling of the venom gland from the Venezuelan mapanare (Bothrops colombiensis) using expressed sequence tags (ESTs)

BACKGROUND

Bothrops colombiensis is a highly dangerous pit viper and responsible for over 70% of snakebites in Venezuela. Although the composition in B. colombiensis venom has been identified using a proteome analysis, the venom gland transcriptome is currently lacking.

RESULTS

We constructed a cDNA library from the venom gland of B. colombiensis, and a set of 729 high quality expressed sequence tags (ESTs) was identified. A total number of 344 ESTs (47.2% of total ESTs) was related to toxins. The most abundant toxin transcripts were metalloproteinases (37.5%), phospholipases A2s (PLA2, 29.7%), and serine proteinases (11.9%). Minor toxin transcripts were linked to waprins (5.5%), C-type lectins (4.1%), ATPases (2.9%), cysteine-rich secretory proteins (CRISP, 2.3%), snake venom vascular endothelium growth factors (svVEGF, 2.3%), L-amino acid oxidases (2%), and other putative toxins (1.7%). While 160 ESTs (22% of total ESTs) coded for translation proteins, regulatory proteins, ribosomal proteins, elongation factors, release factors, metabolic proteins, and immune response proteins. Other proteins detected in the transcriptome (87 ESTs, 11.9% of total ESTs) were undescribed proteins with unknown functions. The remaining 138 (18.9%) cDNAs had no match with known GenBank accessions.

CONCLUSION

This study represents the analysis of transcript expressions and provides a physical resource of unique genes for further study of gene function and the development of novel molecules for medical applications.

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

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

ADAM-15 disintegrin-like domain structure and function

The ADAM (a disintegrin-like and metalloproteinase) proteins are a family of transmembrane cell-surface proteins with important functions in adhesion and proteolytic processing in all animals. Human ADAM-15 is the only member of the ADAM family with the integrin binding motif Arg-Gly-Asp (RGD) in its disintegrin-like domain. This motif is also found in most snake venom disintegrins and other disintegrin-like proteins. This unique RGD motif within ADAM-15 serves as an integrin ligand binding site, through which it plays a pivotal role in interacting with integrin receptors, a large family of heterodimeric transmembrane glycoproteins. This manuscript will present a review of the RGD-containing disintegrin-like domain structures and the structural features responsible for their activity as antagonists of integrin function in relation to the canonical RGD template.

Leberagin-C, A disintegrin-like/cysteine-rich protein from Macrovipera lebetina transmediterranea venom, inhibits alphavbeta3 integrin-mediated cell adhesion

Leberagin-C, a new member of the disintegrin-like/cysteine-rich (D/C) family, was purified to homogeneity from the venom of Tunisian snake Macrovipera lebetina transmediterranea. It is a monomeric protein with a molecular mass of 25,787 Da. Its complete sequence of 205 amino acid residues was established by cDNA cloning. The leberagin-C shows many conserved sequences with other known D/C proteins, like the SECD binding sites and a pattern of 28 cysteines. It is the first purified protein from M. lebetina transmediterranea with only two disintegrin-like/cysteine-rich domains. Leberagin-C is able to inhibit platelet aggregation induced by thrombin and arachidonic acid with IC(50) of 40 and 50 nM respectively. It was also able to inhibit the adhesion of melanoma tumour cells on fibrinogen and fibronectin, by interfering with the function of alphavbeta3 and, to a lesser extent, with alphavbeta6 and alpha5beta1 integrins. To our knowledge, leberagin-C is the sole described D/C protein that does not specifically interact with the alpha2beta1 integrin. Structure-activity relationship study of leberagin-C suggested that there are some important amino acid differences with jararhagin, the most studied PIII metalloprotease from Bothrops jararaca, notably around the SECD motif in its disintegrin-like domain. Other regions implicated in leberagin-C specificities could not be excluded.

Molecular cloning and characterization of cDNAs encoding metalloproteinases from snake venom glands

Snake venom metalloproteinases (SVMPs) are a superfamily of zinc-dependent proteases and participate in a number of important biological, physiological and pathophysiological processes. In this work, we simultaneously amplified nine cDNAs encoding different classes of metalloproteinases from glands of four different snake species (Agkistrodon contortrix laticinctus, Crotalus atrox, Crotalus viridis viridis and Agkistrodon piscivorus leucostoma) by RT-PCR with a pair of primers. Among the encoded metalloproteinases, two enzymes (AclVMP-I and AplVMP-I), three enzymes (CaVMP-II, CvvVMP-II and AplVMP-II) and four enzymes (AclVMP-III, CaVMP-III, CvvVMP-III and AplVMP-III) with the characteristic motif (HEXXHXXGXXH) of metalloproteinase belong to type P-I, P-II and P-III enzymes, respectively. Disintegrin domains of CaVMP-II and CvvVMP-II from two Crotatus snakes contain RGD-motif whereas AplVMP-II from Agkistrodon snake has KGD-motif. Instead of R/KGD-motif within disintegrin domain of SVMP-II enzyme, CaVMP-III, CvvVMP-III and AplVMP-III enzymes contain SECD-motif, while AclVMP-III has DDCD-motif in their corresponding position of disintegrin-like domains. There are 12 Cys amino acids in cysterin-rich domains of each P-III enzyme. Moreover, a disintegrin precursor (AplDis) with RGD-motif also simultaneously amplified from the glands of A.p. leucostoma while amplifying AplVMP-II and AplVMP-III, which indicated that different types of SVMPs and related genes are present in a single species of snake and share a consensus sequence at the 3' and 5' untranslated regions. RT-PCR result also showed that P-III is highly expressed in Crotalus snakes than in Agkistrodon snakes. Aligning the deduced amino acid sequence of these enzymes with other SVMPs from GenBank database indicated that this is the first report on the isolation of cDNAs encoding P-II and P-III enzymes from C.v. viridis and A.p. leucostoma snakes. The availability of these SVMP sequences directly facilitated further studies of structure characterization and diversified function analysis.

cDNA cloning, expression and fibrin(ogen)olytic activity of two low-molecular weight snake venom metalloproteinases

Two cDNA clones, AplVMP1 and AplVMP2, were isolated from a snake (Agkistrodon piscivorus leucostoma) venom gland cDNA library. The full-length cDNA sequence of AplVMP1 with a calculated molecular mass of 46.61 kDa is 1233 bp in length. AplVMP1 encodes PI class metalloproteinase with an open reading frame of 411 amino acid residues that includes signal peptide, pro-domain and metalloproteinase domains. The full-length cDNA of the AplVMP2 (1371 bp) has a calculated molecular mass of 51.16 kDa and encodes PII class metalloproteinase. The open reading frame of AplVMP2 with a 457 amino acid residues is composed of signal peptide, pro-domain, metalloproteinase and disintegrin domains. AplVMP1 and AplVMP2 showed 85% and 93% amino acid identical to PI class enzyme Agkistrodon contortrix laticinctus ACLPREF and PII class enzyme Agkistrodon piscivorus piscivorus piscivostatin, respectively. When expressed in Escherichia coli, most of recombinant proteins of AplVMP1 and AplVMP2 were in insoluble inclusion bodies, with soluble yields of 0.7 mg/l and 0.4 mg/l bacterial culture, respectively. Both affinity purified recombinant proteins show proteolytic activity on fibrinogen, although having an activity lower than that of crude A. p. leucostoma venom. Proteolytic activities of AplVMP1 and AplVMP2 were completely abolished after incubation with a final concentration of 100 microM of EDTA or 1,10-phenanthroline. Both AplVMP1 and AplVMP2 were active in a fibrin-agarose plate but devoid of hemorrhagic activity when injected (up to 50 microg) subcutaneously into mice, and had no capacity to inhibit platelet aggregation.

Snake venom metalloproteases--structure and function of catalytic and disintegrin domains

Snake venoms are relevant sources of toxins that have evolved towards the engineering of highly active compounds. In the last years, research efforts have produced great advance in their understanding and uses. Metalloproteases with disintegrin domains are among the most abundant toxins in many Viperidae snake venoms. This review will focus on the structure, function and possible applications of the metalloprotease and disintegrin domains.

Alternagin-C, a disintegrin-like protein from the venom of Bothrops alternatus, modulates alpha2beta1 integrin-mediated cell adhesion, migration and proliferation

The alpha2beta1 integrin is a major collagen receptor that plays an essential role in the adhesion of normal and tumor cells to the extracellular matrix. Alternagin-C (ALT-C), a disintegrin-like protein purified from the venom of the Brazilian snake Bothrops alternatus, competitively interacts with the alpha2beta1 integrin, thereby inhibiting collagen binding. When immobilized in plate wells, ALT-C supports the adhesion of fibroblasts as well as of human vein endothelial cells (HUVEC) and does not detach cells previously bound to collagen I. ALT-C is a strong inducer of HUVEC proliferation in vitro. Gene expression analysis was done using an Affimetrix HU-95A probe array with probe sets of approximately 10,000 human genes. In human fibroblasts growing on collagen-coated plates, ALT-C up-regulates the expression of several growth factors including vascular endothelial growth factor, as well as some cell cycle control genes. Up-regulation of the vascular endothelial growth factor gene and other growth factors could explain the positive effect on HUVEC proliferation. ALT-C also strongly activates protein kinase B phosphorylation, a signaling event involved in endothelial cell survival and angiogenesis. In human neutrophils, ALT-C has a potent chemotactic effect modulated by the intracellular signaling cascade characteristic of integrin-activated pathways. Thus, ALT-C acts as a survival factor, promoting adhesion, migration and endothelial cell proliferation after binding to alpha2beta1 integrin on the cell surface. The biological activities of ALT-C may be helpful as a therapeutic strategy in tissue regeneration as well as in the design of new therapeutic agents targeting alpha2beta1 integrin.

Insularinase A, a prothrombin activator from Bothrops insularis venom, is a metalloprotease derived from a gene encoding protease and disintegrin domains

The first low-molecular-mass metalloprotease presenting prothrombin activating activity was purified from Bothrops insularis venom and named insularinase A. It is a single-chain protease with a molecular mass of 22 639 Da. cDNA sequence analysis revealed that the disintegrin domain of the precursor protein is post-translationally processed, producing the mature insularinase A. Analysis of its deduced amino acid sequence showed a high similarity with several fibrin(ogen)olytic metalloproteases and only a moderate similarity with prothrombin activators. However, SDS-PAGE of prothrombin after activation by insularinase A showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin independently of the prothrombinase complex. In addition, insularinase A activates factor X and hydrolyses fibrinogen and fibrin. Chelating agents fully inhibit all insularinase A activities. Insularinase A induced neither detachment nor apoptosis of human endothelial cells and was also not able to trigger an endothelial proinflammatory cell response. Nitric oxide and prostacyclin levels released by endothelial cells were significantly increased after treatment with insularinase A. Our results show that, although its primary structure is related to class P-I fibrin(ogen)olytic metalloproteases, insularinase A is functionally similar to group A prothrombin activators.

BaG, a new dimeric metalloproteinase/disintegrin from the Bothrops alternatus snake venom that interacts with alpha5beta1 integrin

The alpha(5)beta(1) integrin is one of the major fibronectin receptors which plays an essential role in the adhesion of normal and tumor cells to extracellular matrix. Here, we describe the isolation and characterization of a novel dimeric metalloproteinase/disintegrin, which is an inhibitor of fibronectin binding to the alpha(5)beta(1) integrin. This protein (BaG) was isolated from the venom of the South American snake Bothrops alternatus by gelatin-Sepharose affinity and anion exchange chromatography. The molecular mass of BaG was approximately 130 kDa under non-reducing conditions and 55 kDa under reducing conditions by SDS-PAGE. BaG shows proteolytic activity on casein that was inhibited by EDTA. 1,10-phenanthroline-treated BaG (BaG-I) inhibits ADP-induced platelet aggregation with an IC(50) of 190 nM. BaG-I inhibits fibronectin-mediated K562 cell adhesion with an IC(50) of 3.75 microM. K562 cells bind to BaG-I probably through interaction with alpha(5)beta(1) integrin, since anti-alpha(5)beta(1) antibodies inhibited K562 cell adhesion to BaG-I. In addition, BaG-I induces the detachment of K562 cells that were bound to fibronectin. In summary, we have purified a novel, dimeric snake venom metalloproteinase/disintegrin that binds to the alpha(5)beta(1) integrin.

A prothrombin activator from Bothrops erythromelas (jararaca-da-seca) snake venom: characterization and molecular cloning

A novel prothrombin activator enzyme, which we have named 'berythractivase', was isolated from Bothrops erythromelas (jararaca-da-seca) snake venom. Berythractivase was purified by a single cation-exchange-chromatography step on a Resource S (Amersham Biosciences) column. The overall purification (31-fold) indicates that berythractivase comprises about 5% of the crude venom. It is a single-chain protein with a molecular mass of 78 kDa. SDS/PAGE of prothrombin after activation by berythractivase showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin, independent of the prothrombinase complex. Chelating agents, such as EDTA and o -phenanthroline, rapidly inhibited the enzymic activity of berythractivase, like a typical metalloproteinase. Human fibrinogen A alpha-chain was slowly digested only after longer incubation with berythractivase, and no effect on the beta- or gamma-chains was observed. Berythractivase was also capable of triggering endothelial proinflammatory and procoagulant cell responses. von Willebrand factor was released, and the surface expression of both intracellular adhesion molecule-1 and E-selectin was up-regulated by berythractivase in cultured human umbilical-vein endothelial cells. The complete berythractivase cDNA was cloned from a B. erythromelas venom-gland cDNA library. The cDNA sequence possesses 2330 bp and encodes a preproprotein with significant sequence similarity to many other mature metalloproteinases reported from snake venoms. Berythractivase contains metalloproteinase, desintegrin-like and cysteine-rich domains. However, berythractivase did not elicit any haemorrhagic response. These results show that, although the primary structure of berythractivase is related to that of snake-venom haemorrhagic metalloproteinases and functionally similar to group A prothrombin activators, it is a prothrombin activator devoid of haemorrhagic activity. This is a feature not observed for most of the snake venom metalloproteinases, including the group A prothrombin activators.

Molecular cloning of HR1a and HR1b, high molecular hemorrhagic factors, from Trimeresurus flavoviridis venom

HR1a and HR1b are two high molecular weight (P-III class) hemorrhagic factors in the venom of Trimeresurus flavoviridis. In this study, we cloned cDNAs of the HR1a and HR1b precursors and analyzed their nucleotide sequences. The cDNA for HR1a was 2368 nucleotides in length and encoded an open reading frame (ORF) of 609 amino acids; that for HR1b was 2237 nucleotides and encoded an ORF of 614 amino acids. Both cDNAs belonged to the N-III class consisting of signal, pro, metalloproteinase, disintegrin-like and cysteine-rich regions, and shared strong amino acid sequence similarity (74.4%). The HR1b precursor was found to have an additional seven amino acid sequence at the carboxyl terminus compared with a mature form of HR1b.

Molecular cloning and sequence analysis of cDNA encoding flavoridin, a disintegrin from the venom of Trimeresurus flavoviridis

We isolated a cDNA of 2001bp encoding the full-length precursor of flavoridin, which is one of the four disintegrins in the venom of Trimeresurus flavoviridis, and analyzed the cDNA nucleotide sequence. The deduced amino acid sequence of the open reading frame consisted of a pro-domain (190 residues), a metalloproteinase domain (205 residues), a spacer domain (18 residues) and a disintegrin (flavoridin) domain (70 residues), thus indicating that the flavoridin precursor belongs to the P-II class of snake venom metalloproteinases. The unknown metalloproteinase domain shared strong sequence similarity with HR2a (71.2% identity) and H(2)-proteinase (74.1% identity), a low molecular mass hemorrhagic metalloproteinase and a non-hemorrhagic metalloproteinase in the same snake venom, respectively.

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

Apoptosis, a programmed, physiological mode of cell death, is important in tissue homoeostasis. Here we report that a new metalloproteinase, graminelysin I, purified from Trimeresurus gramineus venom, induced apoptosis of human endothelial cells as examined by electrophoresis and flow cytometry. Graminelysin I contains only a metalloproteinase domain. It is a single-chain proteinase with a molecular mass of 27020 Da. cDNA sequence analysis revealed that the disintegrin-like and cysteine-rich domains of the putative precursor protein of graminelysin I are likely to be processed post-translationally, producing the proteinase domain (graminelysin I). Graminelysin I cleaved the alpha chain of fibrinogen preferentially and cleaved the beta chain either on longer incubation or at higher concentration. Graminelysin I inhibited the adhesion of human umbilical-vein endothelial cells (HUVECs) to immobilized fibrinogen and induced HUVECs detachment in a dose-dependent manner. These effects on HUVECs were abolished when graminelysin I was pretreated with EDTA. However, graminelysin I did not inhibit the adhesion of HUVECs to immobilized collagen. HUVECs were susceptible to death after treatment with graminelysin I when they were cultured on immobilized fibrinogen. In contrast, HUVECs were rather resistant to treatment with graminelysin I if they were cultured on immobilized collagen. Furthermore, graminelysin I induced apoptosis of HUVECs in a dose-dependent manner. Similarly, its apoptosis-inducing activity was blocked if it was treated with EDTA. These results suggest that the catalytic activity of graminelysin I on matrix proteins contributes to its apoptosis-inducing activity.

The disintegrin-like domain of the snake venom metalloprotease alternagin inhibits alpha2beta1 integrin-mediated cell adhesion

The alpha2beta1 integrin is a major collagen receptor that plays an essential role in the adhesion of normal and tumor cells to the extracellular matrix. Here we describe the isolation of a novel metalloproteinase/disintegrin, which is a potent inhibitor of the collagen binding to alpha2beta1 integrin. This 55-kDa protein (alternagin) and its disintegrin domain (alternagin-C) were isolated from Bothrops alternatus snake venom. Amino acid sequencing of alternagin-C revealed the disintegrin structure. Alternagin and alternagin-C inhibit collagen I-mediated adhesion of K562-alpha2beta1-transfected cells. The IC50 was 134 and 100 nM for alternagin and alternagin-C, respectively. Neither protein interfered with the adhesion of cells expressing alphaIIbeta3, alpha1beta1, alpha5beta1, alpha4beta1 alphavbeta3, and alpha9beta1 integrins to other ligands such as fibrinogen, fibronectin, and collagen IV. Alternagin and alternagin-C also mediated the adhesion of the K562-alpha2beta1-transfected cells. Our results show that the disintegrin-like domain of alternagin is responsible for its ability to inhibit collagen binding to alpha2beta1 integrin.

Molecular cloning and functional characterization of a snake venom metalloprotease

A cDNA clone, MT-d, encoding metalloprotease precursor was isolated from snake (Agkistrodon halys brevicaudus) venom gland cDNA library. MT-d-I protein containing both metalloprotease and disintegrin domains, and MT-d-II protein containing the metalloprotease domain only were expressed in Escherichia coli and refolded successfully into their functional forms. Each of the refolded enzyme species exhibited distinct substrate specificity. Proteolytic activity of the MT-d-1 was able to hydrolyse type I gelatin, type-III and V collagens in contrast with the catalytic function of MT-d-II. MT-d-I protein having metalloprotease activity was also able to inhibit platelet aggregation. Functionally active MT-d-I protein underwent autoproteolytic processing in vitro to produce metalloprotease and disintegrin; this processing was accompanied by significant changes in the substrate specificity of the enzyme activity. Experimental evidence strongly suggests that the disintegrin domain in the metalloprotease precursor modulates the catalytic function of the enzyme in hydrolysing extracellular matrix proteins.