The interaction of the antitoxin DM43 with a snake venom metalloproteinase analyzed by mass spectrometry and surface plasmon resonance.

DM43 is a circulating dimeric antitoxin isolated from Didelphis aurita, a South American marsupial naturally immune to snake envenomation. This endogenous inhibitor binds non-covalently to jararhagin, the main hemorrhagic metalloproteinase from Bothrops jararaca snake venom, and efficiently neutralizes its toxicity. The aim of this study was to apply mass spectrometry (MS) and surface plasmon resonance (SPR) to improve the molecular characterization of this heterocomplex. The stoichiometry of the interaction was confirmed by nanoelectrospray ionization-quadrupole-time-of-flight MS; from native solution conditions, the complex showed a molecular mass of ~94 kDa, indicating that one molecule of jararhagin (50 kDa) interacts with one monomer of DM43 (43 kDa). Although readily observed in solution, the dimeric structure of the inhibitor was barely preserved in the gas phase. This result suggests that, in contrast to the toxin-antitoxin complex, hydrophobic interactions are the primary driving force for the inhibitor dimerization. For the real-time interaction analysis, the toxin was captured on a sensor chip derivatized with the anti-jararhagin monoclonal antibody MAJar 2. The sensorgrams obtained after successive injections of DM43 in a concentration series were globally fitted to a simple bimolecular interaction, yielding the following kinetic rates for the DM43/jararhagin interaction: k(a) = 3.54 ± 0.03 × 10(4) M(-1) s(-1) and k(d) = 1.16 ± 0.07 × 10(-5) s(-1), resulting in an equilibrium dissociation constant (K(D) ) of 0.33 ± 0.06 nM. Taken together, MS and SPR results show that DM43 binds to its target toxin with high affinity and constitute the first accurate quantitative study on the extent of the interaction between a natural inhibitor and a metalloproteinase toxin, with unequivocal implications for the use of this kind of molecule as template for the rational development of novel antivenom therapies.

Different regions of the class P-III snake venom metalloproteinase jararhagin are involved in binding to alpha2beta1 integrin and collagen.

SVMPs are multi-domain proteolytic enzymes in which disintegrin-like and cysteine-rich domains bind to cell receptors, plasma or ECM proteins. We have recently reported that jararhagin, a P-III class SVMP, binds to collagen with high affinity through an epitope located within the Da-disintegrin sub-domain. In this study, we evaluated the binding of jararhagin to alpha(2)beta(1) integrin (collagen receptor) using monoclonal antibodies and recombinant jararhagin fragments. In solid phase assays, binding of jararhagin to alpha(2)beta(1) integrin was detectable from concentrations of 20 nM. Using recombinant fragments of jararhagin, only fragment JC76 (residues 344-421), showed a significant binding to recombinant alpha(2)beta(1) integrin. The anti-jararhagin monoclonal antibody MAJar 3 efficiently neutralised binding of jararhagin to collagen, but not to recombinant alpha(2)beta(1) integrin nor to cell-surface-exposed alpha(2)beta(1) integrin (alpha(2)-K562 transfected cells and platelets). The same antibody neutralised collagen-induced platelet aggregation. Our data suggest that jararhagin binding to collagen and alpha(2)beta(1) integrin occurs by two independent motifs, which are located on disintegrin-like and cysteine-rich domains, respectively. Moreover, toxin binding to collagen appears to be sufficient to inhibit collagen-induced platelet aggregation.

Characterisation of local inflammatory response induced by Thalassophryne nattereri fish venom in a mouse model of tissue injury.

The Thalassophryne nattereri fish venom induces a severe burning pain, oedema, and necrosis observed both clinically and experimentally. The present study was carried out in order to describe the pattern of local acute inflammatory response after T. nattereri venom injection. Our findings show that the edematogenic response induced by T. nattereri venom in footpad of mice was dose- and time dependent, and remained significantly elevated over 48 h after injection. Analysis of footpad homogenates were tested for the presence of TNF-alpha, IL-1beta and IL-6, and demonstrated augmented levels of these cytokines. Our results showed that the injection of venom developed an inadequate cellular inflammatory response evidenced by poor infiltration of mononuclear cells, preceded by decreased number of these cells in peripheral blood. In contrast, we observed an early intense recruitment of neutrophil to peritoneal cavity, accompanied by a significant decrease in the number of mononuclear cells. A drastic increase in the total amount of cells, mainly in neutrophils, followed by mononuclear cell recruitment was observed 24 h. In addition, we also demonstrated that T. nattereri venom affects the viability of mononuclear cells (J774A1) in culture. We conclude that the scarcity of inflammatory cellular influx into local lesions (intraplantar) induced by T. nattereri venom could be a consequence of an impaired blood flow in venules at injured tissue and cytotoxic effect of the venom on inflammatory cells can contribute to this impairment.

Phylogenetic conservation of a snake venom metalloproteinase epitope recognized by a monoclonal antibody that neutralizes hemorrhagic activity.

Snake venom metalloproteinases (SVMPs) are present in large quantities in venoms of viper snakes and also in some elapids. Jararhagin is a representative of a P-III multidomain hemorrhagic SVMP present in Bothrops jararaca venom. It is comprised of a catalytic, a disintegrin-like and a cysteine-rich domain. Seven anti-jararhagin monoclonal antibodies (MAJar 1-7) were produced, of which six reacted with the disintegrin domain. MAJar 3 recognized an epitope present at the C-terminal part of the disintegrin-like domain, and neutralized jararhagin-induced hemorrhage. In this study, we evaluated the reactivity of these monoclonal antibodies with venoms from 27 species of snakes belonging to different families. MAJar 3 recognized most of the hemorrhagic venoms. By ELISA, MAJar 3 reacted strongly with venoms from Viperidae family and weakly with Colubridae and Elapidae venoms. This recognition pattern was due to bands between 50 and 80 kDa, corresponding to P-III SVMPs. This antibody preferentially neutralized the hemorrhage induced by venoms of Bothrops snakes. This fact suggests that the epitope recognized by MAJar 3 is present in other metalloproteinases throughout snake phylogeny. However, slight structural differences in the epitope may result in insufficient affinity for neutralization of biological activities.

Snake venom metalloproteinases: structure/function relationships studies using monoclonal antibodies.

Snake Venom Metalloproteinases (SVMPs) are synthesized as zymogens and undergo proteolytic processing resulting in a variety of multifunctional proteins. Jararhagin is a P-III SVMP, isolated from the venom of Bothrops jararaca, comprising metalloproteinase, disintegrin-like and cysteine-rich domains. The catalytic domain is responsible for the hemorrhagic activity. The disintegrin-like/cysteine-rich domains block alpha2beta1 integrin binding to collagen and apparently enhance the hemorrhagic activity of SVMPs. The relevance of disintegrin-like domain is described in this paper using a series of mouse anti-jararhagin monoclonal antibodies (MAJar 1-7). MAJar 3 was the only antibody able to completely neutralize jararhagin hemorrhagic activity. Neutralization of catalytic activity was partial by incubation with MAJar 1. MAJars 1 and 3 efficiently neutralized jararhagin binding to collagen with IC50 of 330 and 8.4 nM, respectively. MAJars 1 and 3 recognized the C-terminal portion of the disintegrin domain, which is apparently in conformational proximity with the catalytic domain according to additivity tests. These data suggest that disintegrin-like domain epitopes are in close contact with catalytic site or functionally modulate the expression of hemorrhagic activity in SVMPs.