Ota-güdümlü global translasyon baskılanmasının incelenmesi

Ochratoxin A (OTA) is a widespread nephrotoxic mycotoxin produced by Aspergillus and Penicillium species, known to exert cytotoxic effects through disruption of cellular homeostasis. One of its widely recognized effects is the suppression of global protein synthesis, which was linked to phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α), though the underlying mechanism remained unresolved. In this MSc thesis, I investigated the role of eIF2α kinases GCN2, PKR, and PERK in OTA-induced stress response across human (HK-2), rat (WB-F344), and mouse (MEF) cell lines using selective chemical inhibitors. Time-course experiments confirmed that OTA induces a robust, time-dependent phosphorylation of eIF2α alongside significant global translation repression in all models. GCN2 inhibition resulted in pronounced reduction in p-eIF2α levels and partial recovery in translation, while effects of PKR and PERK exhibited more cell-type-specific outcomes. Notably, inhibition of ISR kinases exacerbated OTA-induced cytotoxicity with prolonged exposure, underscoring a protective role. I further explored the interplay between eIF2α signaling and the PI3K/Akt/mTOR pathway, a known survival axis also activated by OTA. Results revealed bidirectional crosstalk: eIF2α kinases, especially GCN2, promoted Akt/mTORC1 activation, while PI3K/Akt activity sustained eIF2α phosphorylation. Inhibition of either pathway disrupted this balance and enhanced cytotoxicity. These findings suggest that eIF2α phosphorylation not only inhibits global translation but also drives pro-survival adaptation through interconnected cytoprotective signaling. This study reveals a coordinated OTA stress response dependent on eIF2α phosphorylation and PI3K/Akt/mTOR signaling, offering new insights into adaptation mechanisms and potential therapeutic strategies in toxin-related pathologies.