T-2 Toxin Exposure Induces Apoptosis in TM3 Cells by Inhibiting Mammalian Target of Rapamycin/Serine/Threonine Protein Kinase(mTORC2/AKT) to Promote Ca(2+)Production

Although mTOR (the mammalian target of rapamycin) can regulate intracellular free Ca(2+)concentration in normal cultured podocytes, it remains elusive as to how mTORC2/AKT-mediated Ca(2+)participates in the process of T-2 toxin-induced apoptosis. The potential signaling responsible for intracellular Ca(2+) concentration changes was investigated using immunoblot assays in an in vitro model of TM3 cell injury induced by T-2 toxin. Changes in Ca(2+) were assessed using the Ca(2+)-sensitive fluorescent indictor dye Fura 2-AM. The cytotoxicity of TM3 cells was assessed with an MTT bioassay, and apoptosis was measured using Annexin V-FITC staining. Following T-2 toxin treatment, the growth of cells, phospho-mTORSer2481, phospho-mTORSer2448, and phospho-AktSer473 were significantly decreased in a time-dependent manner, whereas Ca(2+) and apoptosis were increased. T-2 toxin-induced apoptosis was prevented by BAPTA-AM (a Ca(2+)chelator) and MHY1485 (an mTOR activator), and the application of mTOR activator MHY1485 also prevented the increase of intracellular free Ca(2+)concentration in TM3 cells. Our results strongly suggest that T-2 toxin exposure induces apoptosis in TM3 cells by inhibiting mTORC2/AKT to promote Ca(2+) production.