bims-unfpre 2020-11-01 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2020–11–01
eightteen papers selected by
Susan Logue, University of Manitoba

ATF4 links ER stress with reticulophagy in glioblastoma cells.
Mastering organismal aging through the endoplasmic reticulum proteostasis network.
Inhibiting IRE1α-endonuclease activity decreases tumor burden in a mouse model for hepatocellular carcinoma.
Transmissible Endoplasmic Reticulum Stress: A Novel Perspective on Tumor Immunity.
A human tissue screen identifies a regulator of ER secretion as a brain size determinant.
IRE1α-JNK pathway-mediated autophagy promotes cell survival in response to endoplasmic reticulum stress during the initial phase of hepatic steatosis.
NR4A1 counteracts JNK activation incurred by ER stress or ROS in pancreatic β-cells for protection.
Stress relief for cancer immunotherapy: implications for the ER stress response in tumor immunity.
Depletion of eukaryotic initiation factor 5B (eIF5B) reprograms the cellular transcriptome and leads to activation of endoplasmic reticulum (ER) stress and c-Jun N-terminal kinase (JNK).
Simvastatin Induces Unfolded Protein Response and Enhances Temozolomide-Induced Cell Death in Glioblastoma Cells.
Targeted inhibition of GRP78 by HA15 promotes apoptosis of lung cancer cells accompanied by ER stress and autophagy.
The effects of aging on host resistance and disease tolerance to SARS-CoV-2 infection.
Palmitate-induced IRE1-XBP1-ZEB signaling represses desmoplakin expression and promotes cancer cell migration.
A novel reticulophagy receptor, Epr1: a bridge between the phagophore protein Atg8 and ER transmembrane VAP proteins.
JDP2 is directly regulated by ATF4 and modulates TRAIL sensitivity by suppressing the ATF4-DR5 axis.
A small protein encoded by a putative lncRNA regulates apoptosis and tumorigenicity in human colorectal cancer cells.
Interaction between goniothalamin and peroxisomal multifunctional enzyme type 2 triggering endoplasmic reticulum stress.
Targeting the ubiquitin-proteasome system in a pancreatic cancer subtype with hyperactive MYC.

Autophagy. 2020 Oct 28. 1-17

ATF4 links ER stress with reticulophagy in glioblastoma cells.

Svenja Zielke, Simon Kardo, Laura Zein, Muriel Mari, Adriana Covarrubias-Pinto, Maximilian N Kinzler, Nina Meyer, Alexandra Stolz, Simone Fulda, Fulvio Reggiori, Donat Kögel, Sjoerd J L van Wijk.

  Selective degradation of the endoplasmic reticulum (ER; reticulophagy) is a type of autophagy involved in the removal of ER fragments. So far, amino acid starvation as well as ER stress have been described as inducers of reticulophagy, which in turn restores cellular energy levels and ER homeostasis. Here, we explored the autophagy-inducing mechanisms that underlie the autophagic cell death (ACD)-triggering compound loperamide (LOP) in glioblastoma cells. Interestingly, LOP triggers upregulation of the transcription factor ATF4, which is accompanied by the induction of additional ER stress markers. Notably, knockout of ATF4 significantly attenuated LOP-induced autophagy and ACD. Functionally, LOP also specifically induces the engulfment of large ER fragments within autophagosomes and lysosomes as determined by electron and fluorescence microscopy. LOP-induced reticulophagy and cell death are predominantly mediated through the reticulophagy receptor RETREG1/FAM134B and, to a lesser extent, TEX264, confirming that reticulophagy receptors can promote ACD. Strikingly, apart from triggering LOP-induced autophagy and ACD, ATF4 is also required for LOP-induced reticulophagy. These observations highlight a key role for ATF4, RETREG1 and TEX264 in response to LOP-induced ER stress, reticulophagy and ACD, and establish a novel mechanistic link between ER stress and reticulophagy, with possible implications for additional models of drug-induced ER stress. Abbreviations: ACD: autophagic cell death; ATF6: activating transcription factor 6; ATL3: atlastin 3; BafA1: bafilomycin A1; CCPG1: cell cycle progression gene 1; co-IP: co-immunoprecipitation; DDIT3/CHOP: DNA damage inducible transcript 3; ER: endoplasmic reticulum; EIF2A/eIF2α: eukaryotic translation initiation factor 2A; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ERN1/IRE1α: endoplasmic reticulum to nucleus signaling 1; GABARAP: GABA type A receptor-associated protein; GBM: glioblastoma multiforme; HSPA5/BiP: heat shock protein family (Hsp70) member 5; LOP: loperamide; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; RETREG1/FAM134B: reticulophagy regulator 1; RTN3L: reticulon 3 long; SEC62: SEC62 homolog, protein translocation factor; TEX264: testis-expressed 264, reticulophagy receptor; UPR: unfolded protein response.

Keywords:  HSPA5/BiP; MEFs; MZ-54; RETREG1/FAM134B; TEX264; autophagic cell death; loperamide; p-eIF2α; selective autophagy

DOI:  https://doi.org/10.1080/15548627.2020.1827780
Aging Cell. 2020 Oct 31. e13265

Mastering organismal aging through the endoplasmic reticulum proteostasis network.

Rebecca C Taylor, Claudio Hetz.

  The aging process is characterized by a progressive decline in the function of most tissues, representing the main risk factor in the development of a variety of human diseases. Studies in multiple animal models have demonstrated that interventions that improve the capacity to maintain endoplasmic reticulum (ER) proteostasis prolong life and healthspan. ER stress is monitored by the unfolded protein response (UPR), a signaling pathway that mediates adaptive processes to restore proteostasis or the elimination of damaged cells by apoptosis. Here, we discuss recent advances in understanding the significance of the UPR to aging and its implications for the maintenance of cell physiology of various cell types and organs. The possible benefits of targeting the UPR to extend healthspan and reduce the risk of developing age-related diseases are also discussed.

Keywords:  ER stress; aging; autophagy; cell-nonautonomous; protein misfolding; proteostasis

DOI:  https://doi.org/10.1111/acel.13265
Elife. 2020 Oct 26. pii: e55865. [Epub ahead of print]9

Inhibiting IRE1α-endonuclease activity decreases tumor burden in a mouse model for hepatocellular carcinoma.

Nataša Pavlović, Carlemi Calitz, Kess Thanapirom, Guiseppe Mazza, Krista Rombouts, Pär Gerwins, Femke Heindryckx.

  Hepatocellular carcinoma (HCC) is a liver tumor that usually arises in patients with cirrhosis. Hepatic stellate cells are key players in the progression of HCC, as they create a fibrotic micro-environment and produce growth factors and cytokines that enhance tumor cell proliferation and migration. We assessed the role of endoplasmic reticulum (ER) stress in the cross-talk between stellate cells and HCC-cells. Mice with a fibrotic HCC were treated with the IRE1α-inhibitor 4μ8C, which reduced tumor burden and collagen deposition. By co-culturing HCC-cells with stellate cells, we found that HCC-cells activate IREα in stellate cells, thereby contributing to their activation. Inhibiting IRE1α blocked stellate cell activation, which then decreased proliferation and migration of tumor cells in different in vitro 2D and 3D co-cultures. In addition, we also observed cell-line specific direct effects of inhibiting IRE1α in tumor cells.

Keywords:  cancer biology; mouse

DOI:  https://doi.org/10.7554/eLife.55865
Front Cell Dev Biol. 2020 ;8 846

Transmissible Endoplasmic Reticulum Stress: A Novel Perspective on Tumor Immunity.

Zhou Jiang, Geru Zhang, Liwei Huang, Yihang Yuan, Chenzhou Wu, Yi Li.

  As the first compartment of the protein secretory pathway, the endoplasmic reticulum (ER) acts as a protein synthesis factory, maintaining proteostasis and ER homeostasis. However, a variety of intrinsic and extrinsic perturbations, such as cancer, can disrupt the homeostasis and result in a large accumulation of misfolded/unfolded proteins in the ER lumen, thereby provoking a specific cellular state addressed as "ER stress". Then the unfolded protein response (UPR), an adaptive signaling pathway, is triggered to address the stress and restore the homeostasis. A novel aspect of ER stress is that it can be transmitted from cancer cells to tumor-infiltrating myeloid cells through certain cancer cell-released soluble factors, which is termed as transmissible ER stress (TERS) or ER stress resonance (ERSR). In this review, we provide a comprehensive overview of the link between cancer and ER stress as well as the possible soluble factors mediating TERS. We further elaborate the cell-extrinsic effects of TERS on tumor immunity, and how it indirectly modulates cancer development and progression, which is expected to add a new dimension to anticancer therapy.

Keywords:  cancer; transmissible ER stress; tumor immunity; tumor-derived extracellular vesicles; unfolded protein response

DOI:  https://doi.org/10.3389/fcell.2020.00846
Science. 2020 Oct 29. pii: eabb5390. [Epub ahead of print]

A human tissue screen identifies a regulator of ER secretion as a brain size determinant.

Christopher Esk, Dominik Lindenhofer, Simon Haendeler, Roelof A Wester, Florian Pflug, Benoit Schroeder, Joshua A Bagley, Ulrich Elling, Johannes Zuber, Arndt von Haeseler, Jürgen A Knoblich.

Loss-of-function (LOF) screens provide a powerful approach to identify regulators in biological processes. Pioneered in laboratory animals, LOF screens of human genes are currently restricted to two-dimensional (2D) cell culture hindering testing of gene functions requiring tissue context. Here we present CRISPR-LIneage tracing at Cellular resolution in Heterogenous Tissue (CRISPR-LICHT), enabling parallel LOF studies in human cerebral organoid tissue. We used CRISPR-LICHT to test 173 microcephaly candidate genes revealing 25 to be involved in known and uncharacterized microcephaly-associated pathways. We characterized Immediate Early Response 3 Interacting Protein 1 (IER3IP1) regulating the unfolded protein response (UPR) and extracellular matrix (ECM) protein secretion crucial for tissue integrity, with dysregulation resulting in microcephaly. Our human tissue screening technology identifies microcephaly genes and mechanisms involved in brain size control.

DOI: https://doi.org/10.1126/science.abb5390
Life Sci. 2020 Oct 26. pii: S0024-3205(20)31421-1. [Epub ahead of print] 118668

IRE1α-JNK pathway-mediated autophagy promotes cell survival in response to endoplasmic reticulum stress during the initial phase of hepatic steatosis.

Pengbo Wu, Tian Tian, Jinbo Zhao, Qi Song, Xiaoman Wu, Yitian Guo, Yuanjie Yu, Shiyun Tan, Xia Hongmiao.

   AIMS: It has been widely reported that autophagy and inositol-requiring enzyme-1α (IRE1α)-c-Jun N-terminal kinase (JNK) pathway was involved in cell survival under endoplasmic reticulum (ER) stress, but their specific roles in hepatic steatosis remain unclear. This study aimed to determine the interaction between autophagy and IRE1α-JNK pathway on cell survival in response to ER stress during the initial phase of hepatic steatosis.
METHODS: Hepatic steatosis was induced in HepG2 cells by supplementing oleic acid (OA). Lipid accumulation was evaluated by BODIPY493/503 staining. ER stress and IRE1α-JNK signaling were investigated by western blot. Autophagy was monitored by western blot, GFP-LC3 plasmid and immunofluorescence staining, while apoptosis was determined by western blotting, Annexin-V-FITC/PI staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.
KEY FINDINGS: Aggravated lipid accumulation was found under increased ER stress during the initial phase of hepatic steatosis. Meanwhile, an increase of autophagy and no alteration of apoptosis were observed under increased ER stress. Interestingly, autophagy was induced by ER stress, while autophagy suppression led to an increase of apoptosis in response to ER stress Moreover, further study showed that IRE1α-JNK pathway was activated after ER stress and consequently induced autophagy, which promoted cell survival in the initial phase of hepatic steatosis.
SIGNIFICANCE: We conclude that IRE1α-JNK pathway was activated during ER stress in the initial phase of hepatic steatosis and promoted cell survival by enhancing autophagy. Targeting IRE1α-JNK-autophagy signaling may provide new insight into preventive strategies for hepatic steatosis.

Keywords:  Apoptosis; Autophagy; Hepatic steatosis; IRE1α; JNK

DOI:  https://doi.org/10.1016/j.lfs.2020.118668
J Cell Mol Med. 2020 Oct 30.

NR4A1 counteracts JNK activation incurred by ER stress or ROS in pancreatic β-cells for protection.

Ze-Qing Pu, Dong Liu, Hanse Pablick Patherny Lobo Mouguegue, Cheng-Wen Jin, Esha Sadiq, Dan-Dan Qin, Tian-Fu Yu, Chen Zong, Ji-Cui Chen, Ru-Xing Zhao, Jing-Yu Lin, Jie Cheng, Xiao Yu, Xia Li, Yu-Chao Zhang, Yuan-Tao Liu, Qing-Bo Guan, Xiang-Dong Wang.

  Sustained hyperglycaemia and hyperlipidaemia incur endoplasmic reticulum stress (ER stress) and reactive oxygen species (ROS) overproduction in pancreatic β-cells. ER stress or ROS causes c-Jun N-terminal kinase (JNK) activation, and the activated JNK triggers apoptosis in different cells. Nuclear receptor subfamily 4 group A member 1 (NR4A1) is an inducible multi-stress response factor. The aim of this study was to explore the role of NR4A1 in counteracting JNK activation induced by ER stress or ROS and the related mechanism. qPCR, Western blotting, dual-luciferase reporter and ChIP assays were applied to detect gene expression or regulation by NR4A1. Immunofluorescence was used to detect a specific protein expression in β-cells. Our data showed that NR4A1 reduced the phosphorylated JNK (p-JNK) in MIN6 cells encountering ER stress or ROS and reduced MKK4 protein in a proteasome-dependent manner. We found that NR4A1 increased the expression of cbl-b (an E3 ligase); knocking down cbl-b expression increased MKK4 and p-JNK levels under ER stress or ROS conditions. We elucidated that NR4A1 enhanced the transactivation of cbl-b promoter by physical association. We further confirmed that cbl-b expression in β-cells was reduced in NR4A1-knockout mice compared with WT mice. NR4A1 down-regulates JNK activation by ER stress or ROS in β-cells via enhancing cbl-b expression.

Keywords:  ER stress; NR4A1 (Nur77); ROS; cbl-b; p-JNK; pancreatic β-cells

DOI:  https://doi.org/10.1111/jcmm.16028
Cancer Immunol Immunother. 2020 Oct 26.

Stress relief for cancer immunotherapy: implications for the ER stress response in tumor immunity.

Alex M Andrews, Megan D Tennant, Jessica E Thaxton.

  The solid tumor microenvironment is replete with factors that present a stress to infiltrating immune cells. Endoplasmic reticulum (ER) stress sensor PKR-like ER kinase (PERK) is primed to sense and respond to the burden of misfolded proteins in the ER lumen induced by cell stressors. PERK has documented roles as a master regulator of acute and chronic responses to cell stress as well as in the regulation of cell metabolism. Here, we provide an overview of the roles of PERK based on what is known and remains to be tested in immune cells in tumors and impacts on tumor control. PERK is one of several ER kinases able to preferentially induce activating transcription factor 4 (ATF4) as a response to cell stress. ATF4 orchestrates the oxidative stress response and governs amino acid metabolism. We discuss the tested role of ATF4 in tumor immunity and provide insight on the dueling protective and deleterious roles that ATF4 may play in the stress of solid tumors.

Keywords:  ATF4; Cancer immunotherapy; ER stress; Metabolism; PERK; T cell; Translation

DOI:  https://doi.org/10.1007/s00262-020-02740-3
Cell Stress Chaperones. 2020 Oct 29.

Depletion of eukaryotic initiation factor 5B (eIF5B) reprograms the cellular transcriptome and leads to activation of endoplasmic reticulum (ER) stress and c-Jun N-terminal kinase (JNK).

Kamiko R Bressler, Joseph A Ross, Slava Ilnytskyy, Keiran Vanden Dungen, Katrina Taylor, Kush Patel, Athanasios Zovoilis, Igor Kovalchuk, Nehal Thakor.

  During the integrated stress response (ISR), global translation initiation is attenuated; however, noncanonical mechanisms allow for the continued translation of specific transcripts. Eukaryotic initiation factor 5B (eIF5B) has been shown to play a critical role in canonical translation as well as in noncanonical mechanisms involving internal ribosome entry site (IRES) and upstream open reading frame (uORF) elements. The uORF-mediated translation regulation of activating transcription factor 4 (ATF4) mRNA plays a pivotal role in the cellular ISR. Our recent study confirmed that eIF5B depletion removes uORF2-mediated repression of ATF4 translation, which results in the upregulation of growth arrest and DNA damage-inducible protein 34 (GADD34) transcription. Accordingly, we hypothesized that eIF5B depletion may reprogram the transcriptome profile of the cell. Here, we employed genome-wide transcriptional analysis on eIF5B-depleted cells. Further, we validate the up- and downregulation of several transcripts from our RNA-seq data using RT-qPCR. We identified upregulated pathways including cellular response to endoplasmic reticulum (ER) stress, and mucin-type O-glycan biosynthesis, as well as downregulated pathways of transcriptional misregulation in cancer and T cell receptor signaling. We also confirm that depletion of eIF5B leads to activation of the c-Jun N-terminal kinase (JNK) arm of the mitogen-activated protein kinase (MAPK) pathway. This data suggests that depletion of eIF5B reprograms the cellular transcriptome and influences critical cellular processes such as ER stress and ISR.

Keywords:  ATF4; ER stress; Eukaryotic initiation factor 5B (eIF5B); ISR; JNK; Transcriptome

DOI:  https://doi.org/10.1007/s12192-020-01174-1
Cells. 2020 Oct 22. pii: E2339. [Epub ahead of print]9(11):

Simvastatin Induces Unfolded Protein Response and Enhances Temozolomide-Induced Cell Death in Glioblastoma Cells.

Sanaz Dastghaib, Shahla Shojaei, Zohreh Mostafavi-Pour, Pawan Sharma, John B Patterson, Afshin Samali, Pooneh Mokarram, Saeid Ghavami.

  Glioblastoma (GBM) is the most prevalent malignant primary brain tumor with a very poor survival rate. Temozolomide (TMZ) is the common chemotherapeutic agent used for GBM treatment. We recently demonstrated that simvastatin (Simva) increases TMZ-induced apoptosis via the inhibition of autophagic flux in GBM cells. Considering the role of the unfolded protein response (UPR) pathway in the regulation of autophagy, we investigated the involvement of UPR in Simva-TMZ-induced cell death by utilizing highly selective IRE1 RNase activity inhibitor MKC8866, PERK inhibitor GSK-2606414 (PERKi), and eIF2α inhibitor salubrinal. Simva-TMZ treatment decreased the viability of GBM cells and significantly increased apoptotic cell death when compared to TMZ or Simva alone. Simva-TMZ induced both UPR, as determined by an increase in GRP78, XBP splicing, eukaryote initiation factor 2α (eIF2α) phosphorylation, and inhibited autophagic flux (accumulation of LC3β-II and inhibition of p62 degradation). IRE1 RNase inhibition did not affect Simva-TMZ-induced cell death, but it significantly induced p62 degradation and increased the microtubule-associated proteins light chain 3 (LC3)β-II/LC3β-I ratio in U87 cells, while salubrinal did not affect the Simva-TMZ induced cytotoxicity of GBM cells. In contrast, protein kinase RNA-like endoplasmic reticulum kinase (PERK) inhibition significantly increased Simva-TMZ-induced cell death in U87 cells. Interestingly, whereas PERK inhibition induced p62 accumulation in both GBM cell lines, it differentially affected the LC3β-II/LC3β-I ratio in U87 (decrease) and U251 (increase) cells. Simvastatin sensitizes GBM cells to TMZ-induced cell death via a mechanism that involves autophagy and UPR pathways. More specifically, our results imply that the IRE1 and PERK signaling arms of the UPR regulate Simva-TMZ-mediated autophagy flux inhibition in U251 and U87 GBM cells.

Keywords:  ER stress; autophagy; autophagy flux; glioblastoma; mevalonate cascade; statin

DOI:  https://doi.org/10.3390/cells9112339
Biol Open. 2020 Oct 28. pii: bio.053298. [Epub ahead of print]

Targeted inhibition of GRP78 by HA15 promotes apoptosis of lung cancer cells accompanied by ER stress and autophagy.

Jingjing Wu, Youqile Wu, Xuemei Lian.

  This study aimed to investigate the pathophysiological role of GRP78 in the survival of lung cancer cells. Lung cancer patient data from public databases were used to analyze the expression of GRP78 and its influence on prognoses. In vivo, GRP78 protein expression was analyzed in an established urethane-induced lung tumor mouse model. In vitro, the effects of targeted inhibition of GRP78 by HA15 in lung cancer cells were assessed, with cell viability analyzed using a CCK-8 assay, cell proliferation using an EdU assay, apoptosis and cell cycle using flow cytometry, subcellular structure using electron microscopy, and relative mRNA and protein expression using RT-PCR, western blotting or immunofluorescence assay. The results showed that GRP78 was highly expressed in the lung tissue of lung cancer mice model or patients, and was associated with a poor prognosis. After inhibition of GRP78 in lung cancer cells by HA15, cell viability was decreased in a dose- and time-dependent manner, proliferation was suppressed and apoptosis promoted. Unfolded protein response signaling pathway proteins were activated, and the autophagy-related proteins and mRNAs were upregulated. Therefore, targeted inhibition of GRP78 by HA15 promotes apoptosis of lung cancer cells accompanied by ER stress and autophagy.

Keywords:  Autophagy; ER stress; GRP78; Lung cancer

DOI:  https://doi.org/10.1242/bio.053298
FEBS J. 2020 Oct 30.

The effects of aging on host resistance and disease tolerance to SARS-CoV-2 infection.

Darren Z L Mok, Candice Yuen Yue Chan, Eng Eong Ooi, Chan Kuan Rong.

  The ongoing coronavirus disease 2019 (COVID-19) crisis caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered a large-scale pandemic that is afflicting millions of individuals in over 200 countries. The clinical spectrum caused by SARS-CoV-2 infections can range from asymptomatic infection to mild undifferentiated febrile illness to severe respiratory disease with multiple complications. Elderly patients (aged 60 and above) with co-morbidities such as cardiovascular diseases and diabetes mellitus appear to be at highest risk for a severe disease outcome. To protect against pulmonary immunopathology caused by SARS-CoV-2 infection, the host primarily depends on two distinct defence strategies: resistance and disease tolerance. Resistance is the ability of the host to suppress and eliminate incoming viruses. By contrast, disease tolerance refers to host responses that promote host health regardless of their impact on viral replication. Disruption of either resistance or disease tolerance mechanisms or both could underpin predisposition to elevated risk of severe disease during viral infection. Aging can disrupt host resistance and disease tolerance by compromising immune functions, weakening of the unfolded protein response, progressive mitochondrial dysfunction, and altering metabolic processes. A comprehensive understanding of the molecular mechanisms underlying declining host defence in elderly individuals could thus pave the way to provide new opportunities and approaches for the treatment of severe COVID-19.

Keywords:  COVID-19; ER stress; SARS-CoV-2; aging; immunometabolism; immunosenescence; resistance; tolerance

DOI:  https://doi.org/10.1111/febs.15613
Mol Cancer Res. 2020 Oct 26. pii: molcanres.0480.2019. [Epub ahead of print]

Palmitate-induced IRE1-XBP1-ZEB signaling represses desmoplakin expression and promotes cancer cell migration.

Aritro Nath, Amrita Oak, Kevin Y Chen, Irene Li, R Chauncey Splichal, Jason Portis, Sean Foster, S P Walton, Christina Chan.

Elevated uptake of saturated fatty acid palmitate is associated with metastatic progression of cancer cells; however, the precise signaling mechanism behind the phenomenon is unclear. The loss of cell adhesion proteins, such as desmoplakin (DSP), is a key driving event in the transformation of cancer cells to more aggressive phenotypes. Here we investigated the mechanism by which palmitate induces the loss of DSP in liver and breast cancer cells. We propose that palmitate activates the IRE1-XBP1 branch of the endoplasmic reticulum (ER) stress pathway to upregulate the ZEB transcription factor, leading to transcriptional repression of DSP. Using liver and breast cancer cells treated with palmitate, we found loss of DSP leads to increased cell migration independent of E-cadherin. We report that the ZEB family of transcription factors function as direct transcriptional repressors of DSP. CRISPR-mediated knockdown of IRE1 confirmed that the transcription of ZEB, loss of DSP, and enhanced migration in the presence of palmitate is dependent on the IRE1-XBP1 pathway. Additionally, by analyzing the somatic expression and copy number variation profiles of over 11,000 tumor samples, we corroborate our hypothesis and establish the clinical relevance of DSP loss via ZEB in human cancers. Implications: Provides mechanistic link on palmitate-induced activation of IRE1α to cancer cell migration.

DOI: https://doi.org/10.1158/1541-7786.MCR-19-0480
Autophagy. 2020 Oct 29. 1-2

A novel reticulophagy receptor, Epr1: a bridge between the phagophore protein Atg8 and ER transmembrane VAP proteins.

Ying Yang, Daniel J Klionsky.

  Reticulophagy, a type of selective autophagy that specifically targets and degrades parts of the endoplasmic reticulum (ER) network (sheets or tubules), plays a crucial role in the responses to ER stress. The selectivity of the ER cargo recognition relies on the unique reticulophagy receptors, which tether and deliver cargos to phagophores, the precursors to autophagosomes. Various integral membrane proteins have been well characterized as reticulophagy receptors, including Atg39, Atg40, RETREG1/FAM134B, SEC62, RTN3L, CCPG1, TEX264, and ATL3, in both yeast and mammals in the past five years. In a recent paper, Zhao et al. discovered in fission yeast a novel reticulophagy receptor, Epr1, which bridges the ER and phagophore by binding to Atg8 and VAPs, a mechanism different from the aforementioned reticulophagy receptors.

Keywords:  Autophagy; endoplasmic reticulum; stress; vacuole; yeast

DOI:  https://doi.org/10.1080/15548627.2020.1837457
FEBS Open Bio. 2020 Oct 27.

JDP2 is directly regulated by ATF4 and modulates TRAIL sensitivity by suppressing the ATF4-DR5 axis.

Máté János Engler, Junsei Mimura, Shun Yamazaki, Ken Itoh.

  Jun dimerization protein 2 (JDP2) is a bZip type transcription factor, which acts as a repressor or activator of several cellular processes, including cell differentiation and chromatin remodeling. Previously, we found that a stress-responsive transcription factor, known as activating transcription factor 4 (ATF4) enhances JDP2 gene expression in human astrocytoma U373MG and cervical cancer HeLa cells; however, the role of JDP2 in the ATF4-mediated stress response remained unclear. Here, we reported that siRNA-mediated JDP2 knockdown enhances the expression of several ATF4 target genes, including ASNS, and death receptors 4 and 5 (DR4 and DR5) in HeLa cells. In addition, the results of a transient reporter assay indicate that JDP2 overexpression represses ER stress-mediated DR5 promoter activation suggesting that JDP2 negatively regulates ATF4-mediated gene expression. Curiously, knockdown of JDP2 increases the sensitivity of cells to TNF-related apoptosis-inducing ligand (TRAIL), which induces apoptosis in cancer cells through DR4 and DR5. These results indicate that JDP2 functions as a negative feedback regulator of the ATF4 pathway and contributes to TRAIL resistance in cancer cells.

Keywords:  ATF4; DR5; JDP2; TRAIL; cancer

DOI:  https://doi.org/10.1002/2211-5463.13017
Elife. 2020 Oct 28. pii: e53734. [Epub ahead of print]9

A small protein encoded by a putative lncRNA regulates apoptosis and tumorigenicity in human colorectal cancer cells.

Xiao Ling Li, Lőrinc Pongor, Wei Tang, Sudipto Das, Bruna R Muys, Matthew F Jones, Sarah B Lazar, Emily A Dangelmaier, Corrine Cr Hartford, Ioannis Grammatikakis, Qinyu Hao, Qinyu Sun, Aaron Schetter, Jennifer L Martindale, BinWu Tang, Lisa M Jenkins, Ana I Robles, Robert L Walker, Stefan Ambs, Raj Chari, Svetlana A Shabalina, Myriam Gorospe, Perwez S Hussain, Curtis C Harris, Paul S Meltzer, Kannanganattu V Prasanth, Mirit I Aladjem, Thorkell Andresson, Ashish Lal.

  Long noncoding RNAs (lncRNAs) are often associated with polysomes, indicating coding potential. However, only a handful of endogenous proteins encoded by putative lncRNAs have been identified and assigned a function. Here, we report the discovery of a putative gastrointestinal tract-specific lncRNA (LINC00675) that is regulated by the pioneer transcription factor FOXA1 and encodes a conserved small protein of 79 amino acids which we termed FORCP (FOXA1-Regulated Conserved Small Protein). FORCP transcript is undetectable in most cell types but is abundant in well-differentiated colorectal cancer (CRC) cells where it functions to inhibit proliferation, clonogenicity and tumorigenesis. The epitope-tagged and endogenous FORCP protein predominantly localizes to the endoplasmic reticulum (ER). In response to ER stress, FORCP depletion results in decreased apoptosis. Our findings on the initial characterization of FORCP demonstrate that FORCP is a novel, conserved small protein encoded by a mis-annotated lncRNA that regulates apoptosis and tumorigenicity in well-differentiated CRC cells.

Keywords:  cancer biology; chromosomes; gene expression; human

DOI:  https://doi.org/10.7554/eLife.53734
Heliyon. 2020 Oct;6(10): e05200

Interaction between goniothalamin and peroxisomal multifunctional enzyme type 2 triggering endoplasmic reticulum stress.

Thanet Sophonnithiprasert, Ornjira Aruksakunwong, Etsu Tashiro, Yasumitsu Kondoh, Makoto Muroi, Hiroyuki Osada, Masaya Imoto, Ramida Watanapokasin.

  Endoplasmic reticulum stress is one of the pathways involved in cell cytotoxicity. In this study, goniothalamin, one of styryllactone compounds found in plant Goniothalamus spp., was observed to trigger ER stress in HeLa cell line. In addition, we demonstrated that peroxisomal multifunctional enzyme type2 (MFE2) was a specific goniothalamin-binding protein using an in vitro goniothalamin-linked bead pull-down assay. Since MFE2 has been reported to be an important mediator enzyme for peroxisomal β-oxidation of a very long chain fatty acid metabolism, therefore computational molecular docking analysis was performed to confirm the binding of goniothalamin and MFE2. The results indicated that goniothalamin structure binds to scp-2 domain, enoyl-CoA hydratase 2 domain and (3R)-hydroxyacyl-CoA dehydrogenase domain of MFE2. To further determine the effect of MFE2 on ER stress induction, MFE2 knockdown by siRNA in HeLa cell was conducted. The results implied that MFE2 triggered CHOP, a key mediator of ER stress-induced apoptosis, expression. Therefore, these data inferred that goniothalamin may interrupt the MFE2 function resulting in lipid metabolism perturbation associated with ER stress-independent activation of unfolded protein response. This is the first report to show that goniothalamin binds directly to MFE2 triggering ER stress activation probably through the lipid metabolism perturbation.

Keywords:  Biochemistry; Bioinformatics; Cell biology; Computational molecular docking; Endoplasmic reticulum stress; Goniothalamin; Molecular biology; Peroxisomal multifunctional enzyme type 2 (MFE2)

DOI:  https://doi.org/10.1016/j.heliyon.2020.e05200
Mol Oncol. 2020 Oct 25.

Targeting the ubiquitin-proteasome system in a pancreatic cancer subtype with hyperactive MYC.

Katharina Lankes, Z Zonera Hassan, María Josefina Doffo, Christian Schneeweis, Svenja Lier, Rupert Öllinger, Roland Rad, Oliver H Krämer, Ulrich Keller, Dieter Saur, Maximilian Reichert, Günter Schneider, Matthias Wirth.

  The myelocytomatosis oncogene (MYC) is an important driver in a subtype of pancreatic ductal adenocarcinoma (PDAC). However, MYC remains a challenging therapeutic target, therefore identifying druggable synthetic lethal interactions in MYC-active PDAC may lead to novel precise therapies. First, to identify networks with hyperactive MYC, we profiled transcriptomes of established human cell lines, murine primary PDAC cell lines and accessed publicly available repositories to analyze transcriptomes of primary human PDAC. Networks active in MYC hyperactive subtypes were analyzed by gene set enrichment analysis. Next, we performed an unbiased pharmacological screen to define MYC-associated vulnerabilities. Hits were validated by analysis of drug-response repositories and genetic gain- and loss-of-function experiments. In these experiments, we discovered that the proteasome inhibitor Bortezomib triggers a MYC-associated vulnerability. In addition, by integrating publicly available data, we found the unfolded protein response as a signature connected to MYC. Furthermore, increased sensitivity of MYC-hyperactive PDACs to Bortezomib was validated in genetically modified PDAC cells. In sum, we provide evidence that perturbing the ubiquitin proteasome system might be an option to target MYC hyperactive PDAC cells. Our data provide the rationale to further develop precise targeting of the ubiquitin-proteasome system as a subtype-specific therapeutic approach.

Keywords:  MYC; UPR; UPS; apoptosis; pancreatic cancer; proteasome inhibitor

DOI:  https://doi.org/10.1002/1878-0261.12835