Identification of inhibitors of α2β1 integrin, members of C-lectin type proteins, in Echis sochureki venom

Snake venom antagonists of α2β1 Integrin have been identified as members of a C-lectin type family of proteins (CLP). In the present study, we characterized three new CLPs isolated from Echis sochureki venom, which interact with this Integrin. These proteins were purified using a combination of gel filtration, ion exchange chromatography and reverse phase HPLC. Sochicetin-A and sochicetin-B potently inhibited adhesion of cells expressing α2β1 Integrin and binding of isolated α2β1 ectodomain to Collagen I, as well as bound to recombinant GST-α2A domain in ELISA, whereas activity of sochicetin-C in these assays was approximately two orders of magnitude lower. Structurally, sochicetin-B and sochicetin-C are typical heterodimeric αβ CLPs, whereas sochicetin-A exhibits a trimer of its subunits (αβ)₃ in the quaternary structure. Immobilized sochicetins supported adhesion of glioma cell lines, LN18 and LBC3, whereas in a soluble form they partially inhibited adhesion of these cells to Collagen I. Glioma cells spread very poorly on sochicetin-A, showing no Cytoskeleton rearrangement typical for adhesion to Collagen I or fibronectin. Adhesion on CLP does not involve focal adhesion elements, such as vinculin. Sochicetin-A also inhibited collagen-induced platelet aggregation, similar to Other CLPs' action on the blood coagulation system.