Characterization of a cDNA encoding the precursor of platelet aggregation inhibition and metalloproteinase from Trimeresurus mucrosquamatus venom

Clinical manifestations and treatments of Protobothrops mucrosquamatus bite and associated factors for wound necrosis and subsequent debridement and finger or toe amputation surgery

INTRODUCTION

Protobothrops mucrosquamatus bite induces wound necrosis, coagulopathy, thrombocytopenia, rhabdomyolysis, and acute renal failure. The severity of the hematological derangements and associated factors for wound necrosis and subsequent surgery and the appropriate management of these conditions have not been well characterized. Although severe renal failure requiring hemodialysis has been reported following P. mucrosquamatus bite, the culprit snake may be erroneously classified.

MATERIALS AND METHODS

A total of 186 patients with P. mucrosquamatus bites were retrospectively evaluated. They were categorized into group 1 (patients receiving debridement or finger/toe amputation) and group 2 (all other patients) to identify the associated factors for surgery. Characteristic data were compared between groups 1 and 2 and between definite and suspected cases.

RESULTS

No differences were observed between definite and suspected cases in terms of symptomatology and management. Of the 186 patients, 7 (3.8%) were asymptomatic, 179 (96.2%) experienced tissue swelling and pain, and 107 (57.5%) had local ecchymosis. Coagulopathy, thrombocytopenia, and renal impairment were found in 13 (7%), 19 (10.2%), and 7 (3.8%) patients, respectively. None of the patients required transfusion therapy or hemodialysis. Furthermore, no systemic bleeding or death occurred. Antivenom was administered to all 179 envenomed patients at a median of 1.5 h post-bite. The median total dose of the specific antivenom was 5.5 vials. In multivariate logistic regression analysis, finger as the bite site, bullae and blister formation, and wound infection were significantly associated with wound necrosis; whereas finger as the bite site and bullae and blister formation were related to debridement or finger/toe amputation.

DISCUSSION AND CONCLUSIONS

Protobothrops mucrosquamatus envenomation mainly exerts effects on local tissue. Systemic effects are uncommon and generally nonsevere and transient after the treatment with the specific antivenom. We speculated that severe renal failure requiring hemodialysis is not a typical finding of P. mucrosquamatus envenomation. Patients with finger as the bite site and bullae or blister formation should be carefully examined for wound necrosis, secondary infection, and subsequent surgery. Further evaluations of the efficacy of antivenom against local tissue effects and the effect of selective antibiotics in the management of bite wound infection are urgently required. Although the antivenom manufacturer suggested a skin test prior to use, we believed that it could be omitted because it does not accurately predict the allergic responses.

An αIIb β3 antagonist prevents thrombosis without causing Fc receptor γ-chain IIa-mediated thrombocytopenia

Essentials FcγRIIa-mediated thrombocytopenia is associated with drug-dependent antibodies (DDAbs). We investigated the correlation between αIIb β3 binding epitopes and induction of DDAbs. An FcγRIIa-transgenic mouse model was used to evaluate thrombocytopenia among anti-thrombotics. An antithrombotic with binding motif toward αIIb β-propeller domain has less bleeding tendency.

SUMMARY

Background Thrombocytopenia, a common side effect of Arg-Gly-Asp-mimetic antiplatelet drugs, is associated with drug-dependent antibodies (DDAbs) that recognize conformation-altered integrin αIIb β3 . Objective To explore the correlation between αIIb β3 binding epitopes and induction of DDAb binding to conformation-altered αIIb β3 , we examined whether two purified disintegrins, TMV-2 and TMV-7, with distinct binding motifs have different effects on induction of αIIb β3 conformational change and platelet aggregation in the presence of AP2, an IgG1 inhibitory mAb raised against αIIb β3 . Methods We investigated the possible mechanisms of intrinsic platelet activation of TMV-2 and TMV-7 in the presence of AP2 by examining the signal cascade, tail bleeding time and immune thrombocytopenia in Fc receptor γ-chain IIa (FcγRIIa) transgenic mice. Results TMV-7 has a binding motif that recognizes the αIIb β-propeller domain of αIIb β3 , unlike that of TMV-2. TMV-7 neither primed the platelets to bind ligand, nor caused a conformational change of αIIb β3 as identified with the ligand-induced binding site mAb AP5. In contrast to eptifibatide and TMV-2, cotreatment of TMV-7 with AP2 did not induce FcγRIIa-mediated platelet aggregation and the downstream activation cascade. Both TMV-2 and TMV-7 efficaciously prevented occlusive thrombosis in vivo. Notably, both eptifibatide and TMV-2 caused severe thrombocytopenia mediated by FcγRIIa, prolonged tail bleeding time in vivo, and repressed human whole blood coagulation indexes, whereas TMV-7 did not impair hemostatic capacity. Conclusions TMV-7 shows antiplatelet and antithrombotic activities resulting from a mechanism different from that of all other tested αIIb β3 antagonists, and may offer advantages as a therapeutic agent with a better safety profile.

The disintegrin, trimucrin, suppresses LPS-induced activation of phagocytes primarily through blockade of NF-κB and MAPK activation

In addition to antiplatelet activity, disintegrin, a small-mass RGD-containing polypeptide, has been shown to exert anti-inflammatory effects but the mechanism involved remains unclear. In this study, we report that trimucrin, a disintegrin from the venom of Trimeresurus mucrosquamatus, inhibits lipopolysaccharide (LPS)-induced stimulation of THP-1 and RAW 264.7 cells. We also investigate the underlying mechanism. Trimucrin decreased the release of proinflammatory cytokines including tumor necrosis factor α (TNFα), interleukin-6 (IL-6), nitric oxide, and reactive oxygen species (ROS), and inhibited the adhesion and migration of LPS-activated phagocytes. Trimucrin significantly blocked the expression of nuclear factor kappaB (NF-κB)-related downstream inducible enzymes such as inducible nitric oxide synthase (iNOS) and COX-2. In addition, its anti-inflammatory effect was associated with the decreased mitogen-activated protein kinase (MAPK) phosphorylation. Furthermore, trimucrin concentration dependently inhibited LPS-induced phosphorylation of focal adhesion kinase (FAK), PI3K, and Akt. Trimucrin also reversed the DNA-binding activity of NF-κB by suppressing the LPS-induced nuclear translocation of p65 and the cytosolic IκB release. Flow cytometric analyses showed that trimucrin bound to cells in a concentration-dependent manner. The anti-αVβ3 mAb also specifically decreased the binding of fluorescein isothiocyanate (FITC)-conjugated trimucrin. Binding assays demonstrated that integrin αVβ3 was the binding site for trimucrin on THP-1 and RAW 264.7 cells. In conclusion, we showed that trimucrin decreases the inflammatory reaction through the attenuation of iNOS expression and nitric oxide (NO) production by blocking MAP kinase and the NF-κB activation in LPS-stimulated THP-1 and RAW 264.7 cells.

Cloning and identification of a novel P-II class snake venom metalloproteinase from Gloydius halys

Ahpfibrase was a new snake venom metalloproteinase (SVMP) which was cloned from Gloydius halys. The cDNA sequence with 1,891 base pairs encodes an open reading frame of 477 amino acids which includes a 17 amino acid signal peptide, plus a 171 amino acid segment of zymogen-like propeptide, a metalloproteinase domain of 200 amino acids, a spacer of 16 amino acids, and a disintegrin-like peptide of 73 amino acids. The metalloproteinase domain contained a conserved signature zinc-binding motif HEXXHXXGXXH in the catalytic region and a methionine-turn CIM. To determine the activity of ahpfibrase, the coding region including both the metalloproteinase domain and disintegrin region was amplified by PCR, inserted into the pET25b(+) vector, and expressed in Escherichia coli. The recombinant protein was recovered from inclusion bodies with 8 M urea and refolding was performed by fed-batch dilution method, and purified recombinant ahpfibrase showed the fibrinolytic activity and platelet aggregation-inhibition ability.

Neutralization of venom-induced hemorrhage by equine antibodies raised by immunization with a plasmid encoding a novel P-II metalloproteinase from the lancehead pitviper Bothrops asper

In this work, the cDNA encoding a novel P-II type metalloproteinase from Bothrops asper venom glands was cloned, sequenced and used for DNA immunization of animals with accelerated DNA-coated tungsten microparticles and the helius Gene Gun system. Specific antibodies against B. asper venom antigens were induced in mice co-immunized with the plasmid encoding the P-II metalloproteinase together with an expression plasmid encoding the murine IL-2. Similarly, specific antibodies against B. asper venom antigens were also induced in a horse co-immunized with the plasmid encoding the P-II metalloproteinase, together with a plasmid encoding the equine IL-6. The equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid cross react with several proteins of B. asper, Crotalus durissus durissus, and Lachesis stenophrys venoms in western blot, demonstrating antigenic similarity between the cloned metalloproteinase and other metalloproteinases present in these venoms. Furthermore, the equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid completely neutralized the hemorrhagic activity of the whole B. asper venom and partially the hemorrhagic activity of C. durissus durissus venom. The neutralizing ability of the produced antibodies raises, for the first time, the possibility of developing therapeutic antivenoms in horses by DNA immunization using tungsten microparticles.

Comparative proteomics and subtyping of venom phospholipases A2 and disintegrins of Protobothrops pit vipers

To explore the venom diversity and systematics of pit vipers under the genus Protobothrops, the venom phospholipases A2 (PLA2s) of P. mangshanensis, P. elegans and P. tokarensis were purified and characterized for the first time. The results were compared with the corresponding venom data of other co-generic species including P. mucrosquamatus, P. flavoviridis and P. jerdonii. Based on sequence features at the N-terminal regions, we identified five PLA2 subtypes, i.e., the Asp49-PLA2s with N6, E6 or R6 substitution and the Lys49-PLA2. However, not all subtypes were expressed in each of the species. Venom N6-PLA2s from P. mangshanensis and P. tokarensis venom were weakly neurotoxic toward chick biventer cervicis tissue preparations. The venoms of P. tokarensis and P. flavoviridis contained identical PLA2 isoforms. In most Protobothrop disintegrins, sequences flanking the RGD-motif are conserved. Phylogenetic analyses based on amino acid sequences of both families of the acidic PLA2s and the disintegrins clarify that these species could belong to a monophyletic group.

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.

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.

The disulfide bond pattern of catrocollastatin C, a disintegrin-like/cysteine-rich protein isolated from Crotalus atrox venom

The disulfide bond pattern of catrocollastatin-C was determined by N-terminal sequencing and mass spectrometry. The N-terminal disintegrin-like domain is a compact structure including eight disulfide bonds, seven of them in the same pattern as the disintegrin bitistatin. The protein has two extra cysteine residues (XIII and XVI) that form an additional disulfide bond that is characteristically found in the disintegrin-like domains of cellular metalloproteinases (ADAMs) and PIII snake venom Zn-metalloproteinases (SVMPs). The C-terminal cysteine-rich domain of catrocollastatin-C contains five disulfide bonds between nearest-neighbor cysteines and a long range disulfide bridge between CysV and CysX. These results provide structural evidence for a redefinition of the disintegrin-like and cysteine-rich domain boundaries. An evolutionary pathway for ADAMs, PIII, and PII SVMPs based on disulfide bond engineering is also proposed.

Purification, cloning and sequence analyses for pro-metalloprotease-disintegrin variants from Deinagkistrodon acutus venom and subclassification of the small venom metalloproteases

Acidic and basic hemorrhagic metalloproteases were purified from the venom of Deinagkistrodon acutus (from Fujian Province, China) using gel filtration and anion exchange on FPLC and reversed-phase HPLC. Their hemorrhagic activities and N-terminal sequences were characterized. Extensive screening of the venom gland cDNA after PCR amplification resulted in the identification and sequencing of a total of seven cDNA clones encoding the multidomain precursors of six acidic and one alkaline low molecular mass metalloproteases. Two of the precursors contain a processable disintegrin domain. Disintegrins of 5 kDa were also purified from the venom. The partial amino-acid sequences and molecular masses determined by electrospray ionization mass spectrometry of the purified proteins specifically match those deduced from two of the cDNA sequences. Moreover, phylogenetic analyses based on 30 complete sequences of low molecular mass venom metalloproteases revealed that they may be classified into three functional subtypes: acidic hemorrhagins, basic and moderate hemorrhagins, and nonhemorrhagic enzymes. Subtype-specific amino-acid substitutions in the C-terminal regions of the enzymes were highlighted to explore the structure-activity relationships of the enzymes.

Nucleotide sequence of a cDNA encoding a common precursor of disintegrin flavostatin and hemorrhagic factor HR2a from the venom of Trimeresurus flavoviridis

The venom of Trimeresurus flavoviridis has three disintegrins that act as platelet aggregation inhibitors by binding to integrin alphaIIb beta3 on platelets through its Arg-Gly-Asp sequence. We isolated the cDNA encoding the flavostatin precursor that is one of the disintegrins in T. flavoviridis venom. The open reading frame consisted of four regions, a pre-peptide region, a metalloprotease region, a spacer region and a disintegrin region, indicating that the flavostatin precursor belongs to the metalloprotease/disintegrin family. Surprisingly, the deduced amino acid sequence of the metalloprotease region was completely consistent with that of hemorrhagic metalloprotease HR2a, which indicated that this metalloprotease released from the flavostatin precursor functions as a hemorrhagic factor. These observations indicated that a disintegrin and a hemorrhagic metalloprotease were synthesized as a common precursor. Thus, our results support the hypothesis that a disintegrin is synthesized as a metalloprotease/disintegrin precursor and matures by cleavage from the precursor molecule.

Isolation, sequence analysis, and biological activity of atrolysin E/D, the non-RGD disintegrin domain from Crotalus atrox venom

Crotalid snake venom metalloproteinases often have associated with them nonproteinase domains that may be processed from the mature proteinases. Nascent atrolysin E, from the western diamondback rattlesnake, Crotalus atrox, has a metalloproteinasedomain and a non-RGD disintegrin domain that is lacking in the mature metalloproteinase. In this studywe report on the isolation, sequence analysis, andbiological activity of the 7.4-kDa atrolysin E disintegrin domain (atrolysin E/D). Atrolysin E/D represents approximately 0.2% of the total protein fromthe crude venom. The protein begins with a glycinyl residue found in the latter part of the spacer region. The sequence of atrolysin E/D is identical to thatof the non-RGD disintegrin domain of atrolysin E. The structure is termed a non-RGD disintegrin sincein lieu of the characteristic RGD sequence, a Met-Val-Asp (MVD) is found instead. Nevertheless, the protein is a potent inhibitor of both collagen- and ADP-stimulated platelet aggregation with IC50 values of 4 and 8 nM, respectively. A cyclized synthetic peptide, Ac-CRVSMVDRNDDTC-NH2, which represents the sequence of the atrolysin E/D non-RGD loop, was demonstrated to be an effective inhibitor of platelet aggregation. Therefore, this region of atrolysin E/D's structure, as in the disintegrins proper, is important for the biological activity of the protein. Thus, like the non-RGD disintegrin barbourin from Sistrurus miliarius barbouri, a RGD sequence in the context of the disintegrin protein backbone is not an absolute requirement for platelet aggregation inhibitory activity. These data underscore the biochemical and functional complexity of crotalid snake venoms due to differential proteolytic processing of the precursor metalloproteinases and exemplify how the processed fragments may contribute to the observed pathological effects of the venom.

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

In this paper, we present a cDNA sequence encoding a full-length precursor form of a new member (ACLD) of the metalloproteinase-disintegrin-like protein family from the venom glands of Agkistrodon contortrix laticinctus (broad-banded copperhead) snake. Comparison of the deduced amino acid sequence of ACLD with those of other members of the metalloproteinase-disintegrin protein family from both mammalian and snake venom origin suggests that some conserved residues may be involved in processing of the disintegrin domain.

Cloning and expression of a cysteine-rich venom protein from Trimeresurus mucrosquamatus (Taiwan habu)

A full-length cDNA for cysteine-rich venom protein (CRVP) was constructed by immunoscreening and 5'-rapid amplification of cDNA ends from a cDNA library of venom gland of Trimeresurus mucrosquamatus. The predicted CRVP consisted of 183 amino acid residues including a putative signal peptide of 21 residues. Northern blot hybridization suggested the tissue-specific expression in venom gland and its corresponding length of cDNA. The predicted amino acid sequence of CRVP was homologous to a rat epididymal metalloprotein and a lizard helothermine. Amino acid sequence analysis suggested that CRVP may be a venom metalloprotein targeted against ryanodine receptors and Ca2+ release. Moreover, CRVP expressed in Escherichia coli exhibited the same antigenicity as their native venom forms of T. mucrosquamatus. This is the first report in the cloning and expression of a CRVP from the venom gland of T. mucrosquamatus.

Pharmacological activity of the interdomain segment between metalloproteinase and disintegrin domains

Metalloproteinases (haemorrhagic or non-haemorrhagic), disintegrins and most probably C-type lectin-related proteins are derived by the proteolysis of a common precursor protein. There is a short interdomain segment between the metalloproteinase and disintegrin domains which will be released into the venom. To determine whether this region of the molecule contributes to the biological role of the precursors or the products derived by the proteolysis of the precursors, we synthesized a peptide based on this short segment and examined its toxicity and biological activity. The synthetic peptide did not show any lethal toxicity, anticoagulant and antiplatelet effects. However, the peptide appeared to lower the blood pressure or normotensive rats upon infusion, but did not affect the blood levels of triglyceride, total cholesterol, high-density lipoproteins or low-density lipoproteins. The peptide, however, failed to exhibit any effect on spontaneously hypertensive rats and hence may not have a potential as an antihypertensive agent. Based on these results, we conclude that this interdomain segment may not contribute significantly to the biological activity of precursor proteins.

Isolation and amino acid sequence of flavostatin, a novel disintegrin from the venom of Trimeresurus flavoviridis

Flavostatin, a novel disintegrin purified from the venom of Trimeresurus flavoviridis, consists of 68 amino acids, including an Arg-Gly-Asp sequence and 12 Cys residues at positions highly conserved among disintegrins. The N-terminal sequence of flavostatin was identical to those of triflavin and flavoridin, previously reported disintegrins from the Trimeresurus flavoviridis venom. Differences among the C-terminal sequences of these disintegrins are considered to affect their biological potencies. Isolated flavostatin inhibited ADP collage, and thrombin receptor agonist peptide-induced platelet aggregation in human platelet-rich plasma with an IC50 range of 59 to 98 nM. Contrary to expectations, these values were similar to those for triflavin.

Are C-type lectin-related proteins derived by proteolysis of metalloproteinase/disintegrin precursor proteins?

Metalloproteinases and disintegrins, non-enzymatic inhibitors of platelet aggregation, are derived by proteolysis from common precursors. A closer examination of the cDNA and amino acid sequences of these precursors indicated that the putative signal peptide may be an internal hydrophobic segment and that the sequences are incomplete at the 5'-region. The studies indicated that C-type lectin-related proteins are also derived from the amino terminal region of these precursors. Based on these findings, a five-domain structure is proposed for the precursors.

Do we know the complete sequence of metalloproteinase and nonenzymatic platelet aggregation inhibitor (disintegrin) precursor proteins?

Recent evidence indicates that metalloproteinases and disintegrins, nonenzymatic inhibitors of platelet aggregation, are derived by proteolysis from common precursors. Although proteins and polypeptides with various domain structures have been identified, proteins containing proprotein domains or the complete mature precursors have not yet been isolated. This prompted a closer examination of the putative start codon, signal peptide and the segment upstream of these regions. A critical evaluation of sequence information of these precursors indicates that the putative signal peptide identified in these precursors may be an internal hydrophobic segment within the precursor. There is also evidence to indicate that C-type lectin-related proteins are also derived from these precursors. Thus the available sequence data of the precursors appear to be incomplete.