STUDY OF INTERACTION SNAKE VENOM METALLOPROTEINASES WITH PLATELETS RECEPTORS

VENTURA, JS¹; MODESTO, JCA¹; SCHATTNER, M²; CHUDZINSKI-TAVASSI, AM¹. 

1 Laboratório de Bioquímica e Biofísica, Instituto Butantan, São Paulo, Brasil; 2 Academia Nacional de Medicina, Buenos Aires, Argentina.

Snake venoms are rich source of different classes of metalloproteases (SVMPs) that interferes in the hemostatic system of their victims. In this study we have evaluated the effect of two PI and two PIII-highly homologous SVMPs purified from Bothrops snake venoms on hemostatic parameters such as platelet function, surface glycoprotein interference, FX and prothrombin activation, fibrinogen and plasminogen degradation. The PI named P141 from B. insularis and B151 from B. brazili are characterised as a fibrino(geno)lytic proteins able to activate prothrombin. Berythractivase (Be) is a non haemorrhagic PIII purified from B. erythromelas its main activity is to induce prothrombin activation and Jarharagin (Ja), a haemorrhagic and highly fibrino(geno)lytic PIII was obtained from snake venom B. jararaca. All proteins caused a slight inhibition on the platelet aggregation induced by thrombin in diferents concentrations. We observed that while Be, Ja (2mM) and B151 (9mM) inhibited all the platelet aggregation function induced by collagen, the same effect was not observed to P141. Flow citometry analysis showed that, all proteins promoted a reduction of surface GPIb. This effect was abolished when the proteins were treated with EDTA. Already for a2b1 receptor of collagen, the protein B151 promoted an increase of subunit b1 of a2b1 integrin and this effect was abolished when the protein were treated with EDTA. Be and Ja (2mM) promoted a reduction of subunit a2, and this effect does not abolished when the proteins were treated with EDTA, suggesting that the catalytic domain is not responsable for this activity. Neither protein promoted detectable changes in GPIIb and P-selectin (basal or induced by thrombin). The proteins Be and P141 were able to generate active thrombin in presence or absence of prothrombinase components. All proteins degraded a and b chains fibrinogen  and  plasminogen generation a fragment similar to angiostatin.  In conclusion the results strongly suggests the role of the domain HEXXHXXGXXH on the GPIb actions induced by the SVMPs here studied. The specificity by collagen receptors on platelet surface could be related not only with disintegrin–like sequences because ithis structure is present only in Ja and Be. All studied proteins exert basically the same functions depending of substrate x enzyme ratio.

Supported by FAPESP

Correspondence to: jsventura@ig.com.br