The regulation of ferroptosis by MESH1 through the activation of the integrative stress response

AbstractAll organisms exposed to metabolic and environmental stresses have developed various stress adaptive strategies to maintain homeostasis. The main bacterial stress survival mechanism is the stringent response triggered by the accumulation “alarmone” (p)ppGpp, whose level is regulated by RelA and SpoT. While metazoan genomes encode MESH1 (Metazoan SpoT Homolog 1) with ppGpp hydrolase activity, neither ppGpp nor the stringent response is found in metazoa. The deletion of Mesh1 in Drosophila triggers a transcriptional response reminiscent of the bacterial stringent response. However, the function of MESH1 remains unknown until our recent discovery of MESH1 as the first cytosolic NADPH phosphatase that regulates ferroptosis. To further understand whether MESH1 knockdown triggers a similar transcriptional response in mammalian cells, here, we employed RNA-Seq to analyze the transcriptome response to MESH1 knockdown in human cancer cells. We find that MESH1 knockdown induced different genes involving endoplasmic reticulum (ER) stress, especially ATF3, one of the ATF4-regulated genes in the integrative stress responses (ISR). Furthermore, MESH1 knockdown increased ATF4 protein, eIF2a phosphorylation, and induction of ATF3, XBPs, and CHOP mRNA. ATF4 induction contributes to ~30% of the transcriptome induced by MESH1 knockdown. Concurrent ATF4 knockdown re-sensitizes MESH1-depleted RCC4 cells to ferroptosis, suggesting its role in the ferroptosis protection mediated by MESH1 knockdown. ATF3 induction is abolished by the concurrent knockdown of NADK, implicating a role of NADPH accumulation in the integrative stress response. Collectively, these results suggest that MESH1 depletion triggers ER stress and ISR as a part of its overall transcriptome changes to enable stress survival of cancer cells. Therefore, the phenotypic similarity of stress tolerance caused by MESH1 removal and NADPH accumulation is in part achieved by ISR to regulate ferroptosis.

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Secretion of Novel SEL1L Endogenous Variants Is Promoted by ER Stress/UPR via Endosomes and Shed Vesicles in Human Cancer Cells

PLoS ONE ◽

10.1371/journal.pone.0017206 ◽

2011 ◽

Vol 6 (2) ◽

pp. e17206 ◽

Cited By ~ 9

Author(s):

Monica Cattaneo ◽

Lavinia Vittoria Lotti ◽

Simone Martino ◽

Massimo Alessio ◽

Antonio Conti ◽

...

Keyword(s):

Er Stress ◽

Cancer Cells ◽

Human Cancer ◽

Human Cancer Cells ◽

Shed Vesicles

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Conserved Roles of C. elegans and Human MANFs in Sulfatide Binding and Cytoprotection

10.1101/263731 ◽

2018 ◽

Author(s):

Meirong Bai ◽

Roman Vozdek ◽

Aleš Hnízda ◽

Chenxiao Jiang ◽

Bingying Wang ◽

...

Keyword(s):

Stress Response ◽

Er Stress ◽

Stress Responses ◽

Mammalian Cells ◽

Dopamine Neurons ◽

Lipid Mediator ◽

Outer Cell ◽

Dependent Manner ◽

C Elegans ◽

Er Stress Response

AbstractMesencephalic Astrocyte-Derived Neurotrophic Factor (MANF) is an endoplasmic reticulum (ER) protein that can be secreted and protect dopamine neurons and cardiomyocytes from ER stress and apoptosis. The mechanism of action of extracellular MANF has long been elusive. From a genetic screen for mutants with abnormal ER stress response, we identified the gene Y54G2A.23 as the evolutionarily conserved C. elegans MANF orthologue. We find that MANF binds to the lipid sulfatide, also known as 3-O-sulfogalactosylceramide present in serum and outer-cell membrane leaflets, directly in isolated forms and in reconstituted lipid micelles. Sulfatide binding promotes cellular MANF uptake and cytoprotection from hypoxia-induced cell death. Heightened ER stress responses of MANF-null C. elegans mutants and mammalian cells are alleviated by human MANF in a sulfatide-dependent manner. Our results demonstrate conserved roles of MANF in sulfatide binding and ER stress response, supporting sulfatide as a long-sought lipid mediator of MANF’s cytoprotection.

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Mammalian stringent-like response mediated by the cytosolic NADPH phosphatase MESH1

10.1101/325266 ◽

2018 ◽

Cited By ~ 10

Author(s):

Chien-Kuang Cornelia Ding ◽

Joshua Rose ◽

Jianli Wu ◽

Tianai Sun ◽

Kai-Yuan Chen ◽

...

Keyword(s):

Crystal Structure ◽

Stress Response ◽

Enzymatic Activity ◽

Mammalian Cells ◽

Stringent Response ◽

Nutrient Deprivation ◽

Stress Survival ◽

Transcriptional Changes ◽

Mammalian Genomes ◽

Reallocation Of Resources

Nutrient deprivation triggers stringent response in bacteria, allowing rapid reallocation of resources from proliferation toward stress survival. Critical to this process is the accumulation/degradation of (p)ppGpp regulated by the RelA/SpoT homologues. While mammalian genomes encode MESH1, a homologue of the bacterial (p)ppGpp hydrolase SpoT, neither (p)ppGpp nor its synthetase has been identified in mammalian cells. Therefore, the function of MESH1 remains a mystery. Here, we report that human MESH1 is an efficient cytosolic NADPH phosphatase, an unexpected enzymatic activity that is captured by the crystal structure of the MESH1-NADPH complex. MESH1 depletion promotes cell survival under ferroptosis-inducing conditions by sustaining the level of NADPH, an effect that is reversed by the simultaneous depletion of the cytosolic NAD(H) kinase, NADK, but not its mitochondrial counterpart NADK2. Importantly, MESH1 depletion also triggers extensive transcriptional changes that are distinct from the canonical integrated stress response but resemble the bacterial stringent response, implicating MESH1 in a previously uncharacterized stress response in mammalian cells.

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Widespread PERK-dependent repression of ER targets in response to ER stress

10.1101/487934 ◽

2018 ◽

Author(s):

Nir Gonen ◽

Niv Sabath ◽

Christopher B. Burge ◽

Reut Shalgi

Keyword(s):

Gene Expression ◽

Stress Response ◽

Er Stress ◽

Stress Responses ◽

Disulfide Bonds ◽

Mammalian Cells ◽

Early Gene ◽

Short Exposure ◽

Er Stress Response ◽

Specific Subset

AbstractThe UPR (Unfolded Protein Response) is a well-orchestrated response to ER protein folding and processing overload, integrating both transcriptional and translational outputs. Its three arms in mammalian cells, the PERK translational response arm, together with the ATF6 and IRE1-XBP1-mediated transcriptional arms, have been thoroughly investigated.Using ribosome footprint profiling, we performed a deep characterization of gene expression programs involved in the early and late ER stress responses, within WT or PERK -/- Mouse Embryonic Fibroblasts (MEFs). We found that both repression and activation gene expression programs, affecting hundreds of genes, are significantly hampered in the absence of PERK. Specifically, PERK -/- cells do not show global translational inhibition, nor do they specifically activate early gene expression programs upon short exposure to ER stress. Furthermore, while PERK -/- cells do activate/repress late ER-stress response genes, the response is substantially weaker. Importantly, we highlight a widespread PERK-dependent repression gene expression program, consisting of ER targeted proteins, including transmembrane proteins, glycoproteins, and proteins with disulfide bonds. This phenomenon occurs in various different cell types, and has a major translational regulatory component. Moreover, we revealed a novel interplay between PERK and the XBP1-ATF6 arms of the UPR, whereby PERK attenuates the expression of a specific subset of XBP1-ATF6 targets, further illuminating the complexity of the integrated ER stress response.

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CHOP Is Involved in Endoplasmic Reticulum Stress-induced Apoptosis by Enhancing DR5 Expression in Human Carcinoma Cells

Journal of Biological Chemistry ◽

10.1074/jbc.m406933200 ◽

2004 ◽

Vol 279 (44) ◽

pp. 45495-45502 ◽

Cited By ~ 522

Author(s):

Hirohito Yamaguchi ◽

Hong-Gang Wang

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Er Stress ◽

Cancer Cells ◽

Human Cancer ◽

Carcinoma Cells ◽

Human Carcinoma ◽

Human Cancer Cells ◽

Induced Apoptosis ◽

Hct116 Cells

It has been shown that excess stress to the endoplasmic reticulum (ER) triggers apoptosis, but the mechanisms underlying these processes remain unclear. We and others have reported previously that DR5 expression is up-regulated in thapsigargin (THG)-treated human cancer cells. Here, we provide evidence that CHOP is involved in THG up-regulation of DR5, which is a critical step for ER stress-induced apoptosis in human cancer cells. In human colon cancer HCT116 cells, knockdown of DR5 by siRNA blocked THG-induced Bax conformational change along with caspase-3 activation and cell death. Moreover, inhibition of CHOP expression attenuated DR5 up-regulation and apoptosis induced by THG, whereas ectopic expression of DR5 restored the sensitivity of CHOP siRNA-transfected cells to THG-induced apoptosis. In addition to HCT116 cells, inhibition of CHOP or DR5 induction also attenuated THG-induced cell death in other cancer cell lines including LNCaP, A2780S, and DU145, indicating that CHOP and DR5 are critical for ER stress-mediated apoptosis in human carcinoma cells. Furthermore, we identified a potential CHOP-binding site in the 5′-flanking region of the DR5 gene. Mutation of this site abrogated the enhanced reporter activity in response to THG treatment. Together, our findings suggest that CHOP regulates ER stress-induced apoptosis, at least in part, through enhancing DR5 expression in some types of human cancer cells.

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