ER-stress-induced transcriptional regulation increases protein synthesis leading to cell death

Abstract

Protein misfolding in the endoplasmic reticulum (ER) leads to cell death through PERK-mediated phosphorylation of eIF2α, although the mechanism is not understood. ChIP-seq and mRNA-seq of activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP), key transcription factors downstream of p-eIF2α, demonstrated that they interact to directly induce genes encoding protein synthesis and the unfolded protein response, but not apoptosis. Forced expression of ATF4 and CHOP increased protein synthesis and caused ATP depletion, oxidative stress and cell death. The increased protein synthesis and oxidative stress were necessary signals for cell death. We show that eIF2α-phosphorylation-attenuated protein synthesis, and not Atf4 mRNA translation, promotes cell survival. These results show that transcriptional induction through ATF4 and CHOP increases protein synthesis leading to oxidative stress and cell death. The findings suggest that limiting protein synthesis will be therapeutic for diseases caused by protein misfolding in the ER.

Upregulation of tryptophanyl-tRNA synthethase adapts human cancer cells to nutritional stress caused by tryptophan degradation

“…eIF2α phosphorylation enhances translation 28 and transcription of ATF4 29 . In line, ATF4 protein (Figure 4L) and ATF4 mRNA (Fig.…”

Imaging of single cell responses to ER stress indicates that the relative dynamics of IRE1/XBP1 and PERK/ATF4 signalling rather than a switch between signalling branches determine cell survival

“…20 Additionally, a recent study proposed that increased protein synthesis driven by ATF4/CHOP after re-initiation of general translation increases the amount of reactive oxygen species, thus leading to apoptosis. 13 Therefore, a slower increase in ATF4 levels could be protective. Indeed, in our experiments, we found that the rate of ATF4 translation was slower in surviving cells compared with cells that succumbed to ER stress.…”

“…12 ATF4 and CHOP can interact in the induction of their targets, which include genes involved in protein synthesis and amino acid synthesis and transport. 13 Furthermore, GADD34, a regulatory subunit of the protein phosphatase 1 complex, which dephosphorylates eIF2α, is induced by ATF4. 14 Dephosphorylation of eIF2α allows re-initiation of general translation, Real-time qPCR analysis of levels of spliced Xbp1 mRNA in IRE1-reporter and parental cells in response to ER stress (g) and Chop mRNA in PERK-reporter and parental cells (h).…”

“…Post hoc Tukey pairwise comparison found no significant differences between parental and reporter cells at the different time points which has been proposed to lead to cell death through increase in protein synthesis and load in the ER leading to an increase in ROS. 13 To address the dual roles of IRE1 and PERK signalling in triggering ER stress-dependent cell death, we chose a single cell time lapse imaging approach. This technique allowed monitoring the activation patterns of the IRE1 and PERK signalling pathways in real time on a single cell level.…”

Endoplasmic reticulium protein profiling of heat-stressed Jurkat cells by one dimensional electrophoresis and liquid chromatography tandem mass spectrometry

“…The ER uses its protein folding status as a signal to orchestrate downstream adaptive or apoptotic responses. The unfolded protein response (UPR) is a cellular adaptive response that evolved to restore protein-folding homeostasis by reducing protein synthesis through phosphorylation of eIF2a (Han et al 2013). The UPR pathway, which is conserved from yeast to humans, is triggered by activation of three sensors that are localized in the ER membrane.…”