ERXCUE

How cells adapt to an increase in their secretory load sets a delicate balance between health and disease and pave the way for pathologies ranging from cancer to diabetes. The Endoplasmic Reticulum (ER) directs this adaptation through a dedicated signaling: the Unfolded Protein Response (UPR). Adaptive UPR safeguards ER functions but also preemptively eliminate cells considered in ER failure (terminal UPR). We obtained the first evidence that disabling of the thiol-reductase system, namely the glutathione (GSH) and Thioredoxin (TXN) pathways, may be required to engage terminal UPR and we observed that modulating GSH levels influence the pro-death switch. Our goal is thus to thoroughly describe i) how thiol-redox metabolism is rewired during adaptive or maladaptive ER stress responses ii) to challenge these regulations as a game-changer of cell fate and iii) to disclose redox mechanisms at play and thus identify possible metabolic crosstalk. To do so, we will combine the expertise of three teams, integrating cell biology, proteomics and metabolomics approaches. Initial investigations will take advantage of a genetically engineered HeLa cell model for ER overload, to benefit from clear-cut and reproducible settings of adaptive and maladaptive UPR. Comparing these conditions, omics will identify "signature" modifications affecting i) the levels/redox states of thiol-redox proteins and ii) that of metabolites relevant to GSH and TXN systems. Previously and newly identified GSH/TXN related activities will be tested for their ability to inflect cell trajectory and for their impact on ‘state of the art’ GSH/TXN functions (redox and ER homeostasis, UPR signaling) but also on new processes highlitghted by the redoxome analysis. As an initial validation, we will finally confront the occurence of the depicted redox agenda in a model of myeloma cells. We think this will help reveal vulnerabilities or by-passing metabolic crosstalk to better tackle secretion-related pathologies.