IRE1? deficiency promotes tumor cell death and eIF2? degradation through PERK dipendent autophagy.

ABSTRACT: Sensors of endoplasmic reticulum (ER) stress function in a co-ordinated manner. In the present study we investigated the relationship between IRE1? and PERK pathways and survival of ER stressed U937 cells and BC3 cells. To this end, we investigated the effects of a subcytotoxic concentration of Tunicamycin in IRE1?-proficient and in IRE1?-deficient cells, by pharmacological inhibition with 4?8?C or down-regulation by specific siRNA. We show that either type of IRE1? deficiency affects eIF2? expression and causes cell death increase. GSK2606414, a PERK inhibitor, and PERK specific siRNA prevent eIF2? down-regulation and restore cell survival. Degradation of this protein is due to autophagy, as it is prevented by bafilomycin and not by proteasome inhibition. Furthermore, activation of the autophagy flux is PERK dependent. Also the Cathepsin B inhibitor CA074 prevents eIF2? from degradation and reduces cell death. Altogether, these results show that IRE1? deficiency in ER stressed cells leads to an unexpected decrease of eIF2?, an important molecule for protein translation, through PERK dependent autophagy. Thus, IRE1/XBP1 inhibitors may represent a feasible strategy for tumor therapy, while PERK inhibitors may vanish the goal.

SUBMITTER: Storniolo A 

PROVIDER: S-EPMC5841272 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature