, 1993) the next

step was to investigate selleck kinase inhibitor whether toxins induce death following cell detachment. As shown in Fig. 4A, treatment of adherent HeLa cells with venom or natterins, and not nattectin, resulted in a dramatic loss of adherent cells, which is consistent with the increased LDH leakage observed (data not shown). In addition, venom or natterins greatly affected total viability of cells at suspension, inducing cell death; and nattectin rescues cells from death by apoptosis (Fig. 4B). These results demonstrate that natterins act on the matrix to induce cell detachment and on cells to induce death; and nattectin is an important factor for survival of cells. The integrin α5β1 is the major integrin expressed by HeLa cells (at 2700–3200 receptors/cell), which bind to the 70 kDa amino terminal region of fibronectin, which contains the RGD sequence (Pankov and Yamada, 2002). Because cell surface levels of β1 integrins are linked to the ability of HeLa cells to adhere to the ECM, we determined the effects of nattectin on cell adhesion using neutralizing antibodies GSK269962 in vivo to subunits β1 and also to α5. In Fig. 5A, we observed a slight increase (13%) in adherent cells to dishes coated with nattectin (column 2) compared to plastic (column 1). Then, the blocking of α5/β1 subunits results in the 39% of inhibition of the cell adhesion to nattectin-adsorbed dishes (column 4). In addition, HeLa cells loss the viability

after blocking of α5/β1 subunits when plated on nattectin-coated dishes (Fig. 5B). Adhesion molecules play a pivotal role in cell adhesion and resistance to death. In order to clarify whether nattectin binds to α5 or β1 subunits on cell surface, HeLa cells were exposed to nattectin for 4 h at 4 °C and PLEK2 then stained with antibodies to integrin subunits. We found a significant decrease of CD29 expression in HeLa cells treated with nattectin, showing that this lectin significantly binds the β1 integrin subunit, and no binding was observed to α5 subunit (CD49e, Fig. 5C).

These results mean that the adherence and viability of HeLa cells to nattectin are mostly because of the binding the β1 integrin subunit. Combined proteomic and transcriptomic approaches to study the composition of the venom of T. nattereri venomous fish ( Magalhães et al., 2006) revealed the primary structures of the major toxins as a family of proteases natterins, never described in venoms and a C-type lectin nattectin. Natterins presents nociceptive, edema-inducing and kininogenase activity similar to that presented by the whole venom ( Lopes-Ferreira et al., 2004 and Magalhães et al., 2005) and nattectin, which contains the QPD (Gln-Pro-Asp) sequence in the carbohydrate recognition domain recognizes Gal-β(1–3)-N-acetylgalactosamine. Here we now report that extracellular matrix components as well as the integrin β1 subunit are targets for the natterins and nattectin.