B04: Pichlmair

Various stressors, including viral infections, induce the accumulation of various reactive oxygen species (ROS). The exact molecular details as how and which ROS species is sensed in a concentration dependent manner and how such sensing mechanisms contribute to activation of distinct cellular pathways is only partially understood. Different ROS species contribute to various cell death modalities including apoptosis, necroptosis and ferroptosis. We identified a previously undescribed caspase independent ROS-induced cell-death program that we named oxeiptosis. Upon reaching a toxic level of intracellular ROS, the cellular ROS sensor and antioxidant factor KEAP1 releases the mitochondria-tethered phosphatase PGAM5, which then dephosphorylates the mitochondrial protein AIFM1 at Serine116 (S116). Unlike apoptosis, this pathway is caspase independent (i.e. independent of classical apoptosis, pyroptosis) and operates in absence of RIPK3 (essential for necroptosis) and in presence of ferroptosis inhibitors. Here, we want to evaluate the molecular basis as to how KEAP1 integrates the strength or nature of the ROS signal to induce cell death (Aim A), how oxeiptosis signalling contributes to other forms of cell death in order to relate the functional consequences of oxeiptosis (Aim B) and which forms of cell death are induced by viral pathogens (Aim C). To these aims we will employ a combination of proteomics and mutational analysis, in particular of the c-terminal cysteine rich region of KEAP1 and determine the effect of these mutations in terms of experimental oxeiptosis induction. We hypothesize that ROS concentration dependent oxidation of these cysteine residues may allow to measure ROS concentration to modulate the decision between cell protection or cell death. Moreover, we will test which biological insults lead to oxeiptosis and which subcellular ROS localization leads to oxeiptosis induction. To evaluate the potential relation of oxeiptosis to other forms of cell death, we will study cellular proteome and phophoproteome expression after stimulation of oxeiptosis and other forms of cell death. These data will be used for advanced network analyses to understand how oxeiptosis may be similar or distinct to other cell death pathways and to identify communication shortcuts between different types of cell death.