Neuwlectin, a novel C-type lectin from Bothrops neuwiedi venom, inhibits platelet aggregation induced by cancer cells and angiogenesis

Abstract

C-type lectins are the major non-enzymatic protein constituents in Viperidae venoms. Neuwlectin, a novel member of the C-type lectin family, was purified to homogeneity from Bothrops neuwiedi venom and characterized as a 32.2 kDa homodimer of 16.2 kDa subunits by MALDI-TOF. In this study, we investigated its effect on platelet aggregation triggered by cancer cells and on angiogenesis. Each subunit contains 135 amino acids with eight cysteine residues and shares high sequence similarity to homologous snake venom Ca²-dependent C-type lectins. Neuwlectin induced agglutination of rabbit and human erythrocytes, which was largely inhibited by EDTA, d-galactose, and d-lactose. Adhesion assays using plasma and extracellular matrix proteins evidenced preferential binding to fibrinogen in a concentration-dependent manner. Furthermore, neuwlectin binds to major platelet collagen receptor glycoprotein (GP) VI, and alphaV integrin, suggesting a role in thrombosis and metastasis. Notably, neuwlectin inhibited approximately 40% of washed platelet aggregation mediated by convulxin, and ∼50% aggregation promoted by MDA-MB-231 breast tumor cells. Although the lectin did not inhibit the platelet adhesion to different substrates, neuwlectin inhibits the adhesion of tumor cells to vitronectin. Its antiangiogenic effect was analyzed in the chick chorioallantoic membrane assay, where neuwlectin reduced vessel formation comparable to the VEGF-targeting monoclonal antibody bevacizumab. In conclusion, neuwlectin represents a promising model for the development of antimetastatic agents, acting through GPVI and alphaV integrin binding to inhibit platelet aggregation and angiogenesis.

Keywords: Angiogenesis; C-type lectin; Platelet; Snake venom; Tumor cells.