bims-unfpre 2022-01-16 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2022–01–16
eight papers selected by
Susan Logue, University of Manitoba

EI24 promotes cell adaption to ER stress by coordinating IRE1 signaling and calcium homeostasis.
A small molecule UPR modulator for diabetes identified by high throughput screening.
Regulation of the unfolded protein response transducer IRE1α by SERPINH1 aggravates periodontitis with diabetes mellitus via prolonged ER stress.
Endoplasmic reticulum stress inhibits AR expression via the PERK/eIF2α/ATF4 pathway in luminal androgen receptor triple-negative breast cancer and prostate cancer.
Endoplasmic reticulum stress and the unfolded protein response in skeletal muscle of subjects suffering from peritoneal sepsis.
KEPI Plays a Negative Role in the Repression that Accompanies Translational Inhibition Guided by the uORF Element of Human chop Transcript during Stress Response.
Mechanisms of liver injury in high fat sugar diet fed mice that lack hepatocyte X-box binding protein 1.
THEM6-mediated reprogramming of lipid metabolism supports treatment resistance in prostate cancer.

EMBO Rep. 2022 Jan 10. e51679

EI24 promotes cell adaption to ER stress by coordinating IRE1 signaling and calcium homeostasis.

Yiwei Xu, Jie Chen, Jianguo Chen, Junlin Teng.

  The endoplasmic reticulum (ER) is a subcellular organelle crucial for protein folding and calcium storage. Accumulation of unfolded proteins or calcium depletion causes ER stress. Deficiency of ER stress adaptation leads to apoptosis, which is associated with several human disorders. Here, we reveal that ER transmembrane protein EI24 promotes cell adaptation to ER stress by coordinating the IRE1 branch of the unfolded protein response (UPR) and calcium signaling. Under nonstressed conditions, EI24 binds to the kinase domain of IRE1 to inhibit its activation. Upon ER stress, EI24 disassociates from IRE1 to permit UPR activation, and meanwhile targets IP3R1 to prevent ER calcium depletion, which together promote cell adaptation to ER stress. EI24 knockout causes failure of ER stress adaptation and apoptosis. Thus, EI24 is a novel anti-apoptotic factor implicated in ER stress signaling.

Keywords:  EI24; ER stress; apoptosis; calcium; unfolded protein response

DOI:  https://doi.org/10.15252/embr.202051679
Acta Pharm Sin B. 2021 Dec;11(12): 3983-3993

A small molecule UPR modulator for diabetes identified by high throughput screening.

Valeria Marrocco, Tuan Tran, Siying Zhu, Seung Hyuk Choi, Ana M Gamo, Sijia Li, Qiangwei Fu, Marta Diez Cunado, Jason Roland, Mitch Hull, Van Nguyen-Tran, Sean Joseph, Arnab K Chatterjee, Nikki Rogers, Matthew S Tremblay, Weijun Shen.

  Unfolded protein response (UPR) is a stress response that is specific to the endoplasmic reticulum (ER). UPR is activated upon accumulation of unfolded (or misfolded) proteins in the ER's lumen to restore protein folding capacity by increasing the synthesis of chaperones. In addition, UPR also enhances degradation of unfolded proteins and reduces global protein synthesis to alleviate additional accumulation of unfolded proteins in the ER. Herein, we describe a cell-based ultra-high throughput screening (uHTS) campaign that identifies a small molecule that can modulate UPR and ER stress in cellular and in vivo disease models. Using asialoglycoprotein receptor 1 (ASGR) fused with Cypridina luciferase (CLuc) as reporter assay for folding capacity, we have screened a million small molecule library and identified APC655 as a potent activator of protein folding, that appears to act by promoting chaperone expression. Furthermore, APC655 improved pancreatic β cell viability and insulin secretion under ER stress conditions induced by thapsigargin or cytokines. APC655 was also effective in preserving β cell function and decreasing lipid accumulation in the liver of the leptin-deficient (ob/ob) mouse model. These results demonstrate a successful uHTS campaign that identified a modulator of UPR, which can provide a novel candidate for potential therapeutic development for a host of metabolic diseases.

Keywords:  ASGR, asialoglycoprotein receptor 1; ATF4, activating transcription factor 4; ATF6, activating transcription factor 6α/β; BID, twice a day; CLuc, Cypridina luciferase; Cell signaling; Chaperones; Diabetes; EGFP-VSVG, enhanced green fluorescence protein-vesicular stomatitis virus ts045 G protein; ER stress; ER, endoplasmic reticulum; ERP72, endoplasmic reticulum proteins 72; Endoplasmic reticulum; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GLuc, Gaussia luciferase; GRP78, 78-kDa glucose-regulated protein; GRPRP94, glucose-regulated protein 94; GSIS, glucose stimulated insulin secretion; IKKβ, inhibitor of nuclear factor kappa-B kinase subunit beta; IL1β, interleukin 1β; INFγ, interferon gamma; IRE1, inositol requiring enzyme 1α/β; Liver; Metabolic diseases; NASH, nonalcoholic steatohepatitis; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; Nod, non-obese diabetic; OGTT, oral glucose tolerance test; PERK, PKR-like ER kinase; Pancreas; Protein folding; SP1/2, serine protease1/2; Small molecules; T1/2D, type1/2 diabetes; TG, thapsigargin; TNFα, tumor necrosis factor alpha; Tm, tunicamycin; UPR, unfolded protein response; Unfolded protein response; XBP1, X-box-binding protein 1; i.p., intraperitoneal; uHTS, ultra-high throughput screening; β cells

DOI:  https://doi.org/10.1016/j.apsb.2021.05.018
Cell Signal. 2022 Jan 05. pii: S0898-6568(22)00001-8. [Epub ahead of print] 110241

Regulation of the unfolded protein response transducer IRE1α by SERPINH1 aggravates periodontitis with diabetes mellitus via prolonged ER stress.

Mengdi Li, Shuheng Huang, Yong Zhang, Zhi Song, Haijun Fu, Zhengmei Lin, Xin Huang.

  The hyperglycemic microenvironment induced by diabetes mellitus aggravates the inflammatory response, in which the IRE1α signal transduction pathway of the unfolded protein response (UPR) participates. However, the mechanism by which hyperglycemia regulates the IRE1α signaling pathway and affects endoplasmic reticulum (ER) homeostasis in human gingival epithelium in periodontitis with diabetes mellitus remains unknown. Our current data provide evidence that diabetes mellitus causes a hyperinflammatory response in the gingival epithelium, which accelerates periodontal inflammation. Next, we assessed UPR-IRE1α signaling in periodontitis with diabetes mellitus by examining human clinical gingival epithelium samples from healthy subjects, subjects with periodontitis and subjects with periodontitis with diabetes mellitus and by in vitro challenge of human epithelial cells with a hyperglycemic microenvironment. The results showed that a hyperglycemic microenvironment inhibited the IRE1α/XBP1 axis, decreased the expression of a UPR target gene (GRP78), and ultimately impaired the UPR, causing ER stress to be prolonged or more severe in human gingival epithelium. Subsequently, RNA sequencing (RNA-seq) data was analyzed to investigate the expression of ER-related genes in human gingival epithelium. Experiments verified that the mechanism by which periodontitis is aggravated in individuals with diabetes mellitus may involve decreased SERPINH1 expression. Furthermore, experiments in SERPINH1-knockdown and SERPINH1-overexpression models established in vitro indicated that SERPINH1 might act as an activator of IRE1α, maintaining human gingival epithelium homeostasis and reducing proinflammatory cytokine expression by preventing prolonged ER stress induced by high-glucose conditions. In conclusion, regulation of the UPR transducer IRE1α by SERPINH1 alleviates periodontitis with diabetes mellitus by mitigating prolonged ER stress. This finding provides evidence for the further study of periodontitis with diabetes mellitus.

Keywords:  ER stress; Gingival epithelial barrier immunity; Periodontitis with diabetes mellitus; SERPINH1; UPR-IRE1α

DOI:  https://doi.org/10.1016/j.cellsig.2022.110241
NPJ Breast Cancer. 2022 Jan 10. 8(1): 2

Endoplasmic reticulum stress inhibits AR expression via the PERK/eIF2α/ATF4 pathway in luminal androgen receptor triple-negative breast cancer and prostate cancer.

Xiaoli Li, Duanfang Zhou, Yongqing Cai, Xiaoping Yu, Xiangru Zheng, Bo Chen, Wenjun Li, Hongfang Zeng, Moustapha Hassan, Ying Zhao, Weiying Zhou.

Androgen receptor (AR) is an important prognostic marker and therapeutic target in luminal androgen receptor triple-negative breast cancer (LAR TNBC) and prostate cancer (PCa). Endoplasmic reticulum (ER) stress may activate the unfolded protein response (UPR) to regulate associated protein expression and is closely related to tumor growth and drug resistance. The effect of ER stress on AR expression and signaling remains unclear. Here, we focused on the regulation and underlying mechanism of AR expression induced by ER stress in LAR TNBC and PCa. Western blotting and quantitative RT-PCR results showed that AR expression was markedly decreased under ER stress induced by thapsigargin and brefeldin A, and this effect was dependent on PERK/eIF2α/ATF4 signaling activation. Chromatin immunoprecipitation-PCR and luciferase reporter gene analysis results showed that ATF4 bound to the AR promoter regions to inhibit its activity. Moreover, ATF4 overexpression inhibited tumor proliferation and AR expression both in vitro and in vivo. Collectively, these results demonstrated that ER stress could decrease AR mRNA and protein levels via PERK/eIF2α/ATF4 signaling in LAR TNBC and PCa. Targeting the UPR may be a treatment strategy for AR-dependent TNBC and PCa.

DOI: https://doi.org/10.1038/s41523-021-00370-1
Sci Rep. 2022 Jan 11. 12(1): 504

Endoplasmic reticulum stress and the unfolded protein response in skeletal muscle of subjects suffering from peritoneal sepsis.

Uta Barbara Metzing, Christian von Loeffelholz, Ricardo Steidl, Bernd Romeike, René Winkler, Falk Rauchfuß, Utz Settmacher, Christian Stoppe, Sina M Coldewey, Claudia Weinmann, Martin O Weickert, Ralf A Claus, Andreas L Birkenfeld, Christian Kosan, Paul Horn.

We provide a descriptive characterization of the unfolded protein response (UPR) in skeletal muscle of human patients with peritoneal sepsis and a sepsis model of C57BL/6J mice. Patients undergoing open surgery were included in a cross-sectional study and blood and skeletal muscle samples were taken. Key markers of the UPR and cluster of differentiation 68 (CD68) as surrogate of inflammatory injury were evaluated by real-time PCR and histochemical staining. CD68 mRNA increased with sepsis in skeletal muscle of patients and animals (p < 0.05). Mainly the inositol-requiring enzyme 1α branch of the UPR was upregulated as shown by elevated X-box binding-protein 1 (XBP1u) and its spliced isoform (XBP1s) mRNA (p < 0.05, respectively). Increased expression of Gadd34 indicated activation of PRKR-Like Endoplasmic Reticulum Kinase (PERK) branch of the UPR, and was only observed in mice (p < 0.001) but not human study subjects. Selected cell death signals were upregulated in human and murine muscle, demonstrated by increased bcl-2 associated X protein mRNA and TUNEL staining (p < 0.05). In conclusion we provide a first characterization of the UPR in skeletal muscle in human sepsis.

DOI: https://doi.org/10.1038/s41598-021-04517-9
Gene. 2022 Jan 11. pii: S0378-1119(21)00755-1. [Epub ahead of print] 146160

KEPI Plays a Negative Role in the Repression that Accompanies Translational Inhibition Guided by the uORF Element of Human chop Transcript during Stress Response.

Hung-Chieh Lee, Chi-Cheng Hsieh, Huai-Jen Tsai.

  Translation of the downstream coding sequence of some mRNAs may be repressed by the upstream open reading frame (uORF) at their 5'-end. The mechanism underlying this uORF-mediated translational inhibition (uORF-MTI) is not fully understood in vivo. Recently, it was found that zebrafish Endouc or its human orthologue ENDOU (Endouc/ENDOU) plays a positive role in repressing the uORF-MTI of human chop (uORFchop-MTI) during stress by blocking its activity However, the repression of uORFchop-MTI assisted by an as-yet unidentified negative effector remains to be elucidated. Compared to the upregulated chop transcript, we herein report that the KEPI (kinase-enhancedPP1 inhibitor) transcript was downregulated in the zebrafish embryos treated with both heat shock and hypoxia. Quantitative RT-PCR also revealed that the level of kepi mRNA was noticeably decreased in both heat-shock-treated and hypoxia-exposed embryos. When kepi mRNA was microinjected into the one-celled embryos from transgenic line huORFZ, the translation of downstream GFP reporter controlled by the uORFchop-MTI was reduced in the hypoxia-exposed embryos. In contrast, when KEPI was knocked down by injection of antisense Morpholino oligonucleotide, the translation of downstream GFP reporter was induced and expressed in the brain and spinal cord of injected embryos in the absence of stress. During normal condition, overexpression of KEPI increased eIF2α phosphorylation, resulting in inducing the translation of uORF-tag mRNA, such as atf4 and chop mRNAs. However, during stress condition, overexpression of KEPI decreased eIF2α phosphorylation, resulting in reducing the GFP reporter and CHOP proteins. This is the first report to demonstrate that KEPI plays a negative role in uORFchop -mediated translation during ER stress.

Keywords:  CHOP; ER stress; KEPI; Zebrafish; translational control; uORF

DOI:  https://doi.org/10.1016/j.gene.2021.146160
PLoS One. 2022 ;17(1): e0261789

Mechanisms of liver injury in high fat sugar diet fed mice that lack hepatocyte X-box binding protein 1.

Xiaoying Liu, Sarah A Taylor, Kyle D Gromer, Danny Zhang, Susan C Hubchak, Brian E LeCuyer, Takao Iwawaki, Zengdun Shi, Don C Rockey, Richard M Green.

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of liver diseases in the United States and can progress to cirrhosis, end-stage liver disease and need for liver transplantation. There are limited therapies for NAFLD, in part, due to incomplete understanding of the disease pathogenesis, which involves different cell populations in the liver. Endoplasmic reticulum stress and its adaptative unfolded protein response (UPR) signaling pathway have been implicated in the progression from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH). We have previously shown that mice lacking the UPR protein X-box binding protein 1 (XBP1) in the liver demonstrated enhanced liver injury and fibrosis in a high fat sugar (HFS) dietary model of NAFLD. In this study, to better understand the role of liver XBP1 in the pathobiology of NAFLD, we fed hepatocyte XBP1 deficient mice a HFS diet or chow and investigated UPR and other cell signaling pathways in hepatocytes, hepatic stellate cells and immune cells. We demonstrate that loss of XBP1 in hepatocytes increased inflammatory pathway expression and altered expression of the UPR signaling in hepatocytes and was associated with enhanced hepatic stellate cell activation after HFS feeding. We believe that a better understanding of liver cell-specific signaling in the pathogenesis of NASH may allow us to identify new therapeutic targets.

DOI: https://doi.org/10.1371/journal.pone.0261789
EMBO Mol Med. 2022 Jan 11. e14764

THEM6-mediated reprogramming of lipid metabolism supports treatment resistance in prostate cancer.

Arnaud Blomme, Coralie Peter, Ernest Mui, Giovanny Rodriguez Blanco, Ning An, Louise M Mason, Lauren E Jamieson, Grace H McGregor, Sergio Lilla, Chara Ntala, Rachana Patel, Marc Thiry, Sonia H Y Kung, Marine Leclercq, Catriona A Ford, Linda K Rushworth, David J McGarry, Susan Mason, Peter Repiscak, Colin Nixon, Mark J Salji, Elke Markert, Gillian M MacKay, Jurre J Kamphorst, Duncan Graham, Karen Faulds, Ladan Fazli, Martin E Gleave, Edward Avezov, Joanne Edwards, Huabing Yin, David Sumpton, Karen Blyth, Pierre Close, Daniel J Murphy, Sara Zanivan, Hing Y Leung.

  Despite the clinical benefit of androgen-deprivation therapy (ADT), the majority of patients with advanced prostate cancer (PCa) ultimately develop lethal castration-resistant prostate cancer (CRPC). In this study, we identified thioesterase superfamily member 6 (THEM6) as a marker of ADT resistance in PCa. THEM6 deletion reduces in vivo tumour growth and restores castration sensitivity in orthograft models of CRPC. Mechanistically, we show that the ER membrane-associated protein THEM6 regulates intracellular levels of ether lipids and is essential to trigger the induction of the ER stress response (UPR). Consequently, THEM6 loss in CRPC cells significantly alters ER function, reducing de novo sterol biosynthesis and preventing lipid-mediated activation of ATF4. Finally, we demonstrate that high THEM6 expression is associated with poor survival and correlates with high levels of UPR activation in PCa patients. Altogether, our results highlight THEM6 as a novel driver of therapy resistance in PCa as well as a promising target for the treatment of CRPC.

Keywords:  ATF4; ER stress; lipid metabolism; prostate cancer; therapy resistance

DOI:  https://doi.org/10.15252/emmm.202114764