bims-unfpre Biomed News
on Unfolded protein response
Issue of 2021–10–17
eleven papers selected by
Susan Logue, University of Manitoba
  1. A high-throughput genetic screening protocol to measure lipid bilayer stress-induced unfolded protein response in Saccharomyces cerevisiae.
  2. Genome-wide mRNA profiling identifies X-box-binding protein 1 (XBP1) as an IRE1 and PUMA repressor.
  3. Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis.
  4. Gut bacterial metabolites modulate endoplasmic reticulum stress.
  5. The interaction of S100A16 and GRP78 actives endoplasmic reticulum stress-mediated through the IRE1α/XBP1 pathway in renal tubulointerstitial fibrosis.
  6. Folding Mitochondrial-Mediated Cytosolic Proteostasis Into the Mitochondrial Unfolded Protein Response.
  7. Activation of the XBP1s/O-GlcNAcylation Pathway Improves Functional Outcome After Cardiac Arrest and Resuscitation in Young and Aged Mice.
  8. The Role of BiP and the IRE1α-XBP1 Axis in Rhabdomyosarcoma Pathology.
  9. ERAP2 is a novel target involved in autophagy and activation of pancreatic stellate cells via UPR signaling pathway.
  10. Sestrin2-Mediated Autophagy Contributes to Drug Resistance via Endoplasmic Reticulum Stress in Human Osteosarcoma.
  11. Targeting the Integrated Stress Response in Cancer Therapy.
  1. STAR Protoc. 2021 Dec 17. 2(4): 100868
    A high-throughput genetic screening protocol to measure lipid bilayer stress-induced unfolded protein response in Saccharomyces cerevisiae.
    Nurulain Ho, Wei Sheng Yap, Guillaume Thibault.
      The endoplasmic reticulum (ER) stress is defined by the accumulation of unfolded proteins at the ER and perturbation at the ER membrane, known as lipid bilayer stress (LBS). In turn, ER stress triggers the unfolded protein response (UPR) to restore ER homeostasis. Here, we provide a modified protocol based on the synthetic genetic array analysis in Saccharomyces cerevisiae to identify genetic perturbations that induce the UPR by LBS. This method is adaptable to other canonical stress pathways. For complete details on the use and execution of this protocol, please refer to Ho et al. (2020), Jonikas et al. (2009) and Baryshnikova et al. (2010).
    Keywords:  Cell Membrane; Cell-based Assays; Flow Cytometry/Mass Cytometry; Gene Expression; Genetics; High Throughput Screening; Model Organisms; Signal Transduction
    DOI:  https://doi.org/10.1016/j.xpro.2021.100868
  2. Cell Mol Life Sci. 2021 Oct 12.
    Genome-wide mRNA profiling identifies X-box-binding protein 1 (XBP1) as an IRE1 and PUMA repressor.
    Magdalena Gebert, Aleksandra Sobolewska, Sylwia Bartoszewska, Aleksandra Cabaj, David K Crossman, Jarosław Króliczewski, Piotr Madanecki, Michał Dąbrowski, James F Collawn, Rafal Bartoszewski.
      Accumulation of misfolded proteins in ER activates the unfolded protein response (UPR), a multifunctional signaling pathway that is important for cell survival. The UPR is regulated by three ER transmembrane sensors, one of which is inositol-requiring protein 1 (IRE1). IRE1 activates a transcription factor, X-box-binding protein 1 (XBP1), by removing a 26-base intron from XBP1 mRNA that generates spliced XBP1 mRNA (XBP1s). To search for XBP1 transcriptional targets, we utilized an XBP1s-inducible human cell line to limit XBP1 expression in a controlled manner. We also verified the identified XBP1-dependent genes with specific silencing of this transcription factor during pharmacological ER stress induction with both an N-linked glycosylation inhibitor (tunicamycin) and a non-competitive inhibitor of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) (thapsigargin). We then compared those results to the XBP1s-induced cell line without pharmacological ER stress induction. Using next-generation sequencing followed by bioinformatic analysis of XBP1-binding motifs, we defined an XBP1 regulatory network and identified XBP1 as a repressor of PUMA (a proapoptotic gene) and IRE1 mRNA expression during the UPR. Our results indicate impairing IRE1 activity during ER stress conditions accelerates cell death in ER-stressed cells, whereas elevating XBP1 expression during ER stress using an inducible cell line correlated with a clear prosurvival effect and reduced PUMA protein expression. Although further studies will be required to test the underlying molecular mechanisms involved in the relationship between these genes with XBP1, these studies identify a novel repressive role of XBP1 during the UPR.
    Keywords:  BBC3; ER stress; ERN1; UPR; XBP1s; XBP1u
    DOI:  https://doi.org/10.1007/s00018-021-03952-1
  3. Int J Mol Sci. 2021 Oct 05. pii: 10772. [Epub ahead of print]22(19):
    Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis.
    Chang Ho Kang, Eun Seon Lee, Ganesh M Nawkar, Joung Hun Park, Seong Dong Wi, Su Bin Bae, Ho Byoung Chae, Seol Ki Paeng, Jong Chan Hong, Sang Yeol Lee.
      Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.
    Keywords:  endoplasmic reticulum (ER) stress; light signaling; unfolded protein response (UPR)
    DOI:  https://doi.org/10.3390/ijms221910772
  4. Genome Biol. 2021 Oct 15. 22(1): 292
    Gut bacterial metabolites modulate endoplasmic reticulum stress.
    Xiaobo Ke, Kwontae You, Matthieu Pichaud, Henry J Haiser, Daniel B Graham, Hera Vlamakis, Jeffrey A Porter, Ramnik J Xavier.
       BACKGROUND: The endoplasmic reticulum (ER) is a membranous organelle that maintains proteostasis and cellular homeostasis, controlling the fine balance between health and disease. Dysregulation of the ER stress response has been implicated in intestinal inflammation associated with inflammatory bowel disease (IBD), a chronic condition characterized by changes to the mucosa and alteration of the gut microbiota. While the microbiota and microbially derived metabolites have also been implicated in ER stress, examples of this connection remain limited to a few observations from pathogenic bacteria. Furthermore, the mechanisms underlying the effects of bacterial metabolites on ER stress signaling have not been well established.
    RESULTS: Utilizing an XBP1s-GFP knock-in reporter colorectal epithelial cell line, we screened 399 microbiome-related metabolites for ER stress pathway modulation. We find both ER stress response inducers (acylated dipeptide aldehydes and bisindole methane derivatives) and suppressors (soraphen A) and characterize their activities on ER stress gene transcription and translation. We further demonstrate that these molecules modulate the ER stress pathway through protease inhibition or lipid metabolism interference.
    CONCLUSIONS: Our study identified novel links between classes of gut microbe-derived metabolites and the ER stress response, suggesting the potential for these metabolites to contribute to gut ER homeostasis and providing insight into the molecular mechanisms by which gut microbes impact intestinal epithelial cell homeostasis.
    Keywords:  ER stress; Intestinal epithelial homeostasis; Microbial metabolites; Unfolded protein response
    DOI:  https://doi.org/10.1186/s13059-021-02496-8
  5. Cell Death Dis. 2021 Oct 13. 12(10): 942
    The interaction of S100A16 and GRP78 actives endoplasmic reticulum stress-mediated through the IRE1α/XBP1 pathway in renal tubulointerstitial fibrosis.
    Runbing Jin, Anran Zhao, Shuying Han, Dan Zhang, Hui Sun, Min Li, Dongming Su, Xiubin Liang.
      Recent studies have indicated that the development of acute and chronic kidney disease including renal fibrosis is associated with endoplasmic reticulum (ER) stress. S100 calcium-binding protein 16 (S100A16) as a novel member of the S100 family is involved in kidney disease; however, few studies have examined fibrotic kidneys for a relationship between S100A16 and ER stress. In our previous study, we identified GRP78 as a protein partner of S100A16 in HK-2 cells. Here, we confirmed a physical interaction between GRP78 and S100A16 in HK-2 cells and a markedly increased expression of GRP78 in the kidneys of unilateral ureteral occlusion mice. S100A16 overexpression in HK-2 cells by infection with Lenti-S100A16 also induced upregulation of ER stress markers, including GRP78, p-IRE1α, and XBP1s. Immunofluorescence staining demonstrated that the interaction between S100A16 and GRP78 predominantly occurred in the ER of control HK-2 cells. By contrast, HK-2 cells overexpressing S100A16 showed colocalization of S100A16 and GRP78 mainly in the cytoplasm. Pretreatment with BAPTA-AM, a calcium chelator, blunted the upregulation of renal fibrosis genes and ER stress markers induced by S100A16 overexpression in HK-2 cells and suppressed the cytoplasmic colocalization of GRP78 and S100A16. Co-immunoprecipitation studies suggested a competitive binding between S100A16 and IRE1α with GRP78 in HK-2 cells. Taken together, our findings demonstrate a significant increase in S100A16 expression in the cytoplasm following renal injury. GRP78 then moves into the cytoplasm and binds with S100A16 to promote the release of IRE1α. The subsequent phosphorylation of IRE1α then leads to XBP1 splicing that activates ER stress.
    DOI:  https://doi.org/10.1038/s41419-021-04249-8
  6. Front Cell Dev Biol. 2021 ;9 715923
    Folding Mitochondrial-Mediated Cytosolic Proteostasis Into the Mitochondrial Unfolded Protein Response.
    Edmund Charles Jenkins, Mrittika Chattopadhyay, Doris Germain.
      Several studies reported that mitochondrial stress induces cytosolic proteostasis. How mitochondrial stress activates proteostasis in the cytosol remains unclear. However, the cross-talk between the mitochondria and cytosolic proteostasis has far reaching implications for treatment of proteopathies including neurodegenerative diseases. This possibility appears within reach since selected drugs have begun to emerge as being able to stimulate mitochondrial-mediated cytosolic proteostasis. In this review, we focus on studies describing how mitochondrial stress activates proteostasis in the cytosol across multiple model organisms. A model is proposed linking mitochondrial-mediated regulation of cytosolic translation, folding capacity, ubiquitination, and proteasome degradation and autophagy as a multi layered control of cytosolic proteostasis that overlaps with the integrated stress response (ISR) and the mitochondrial unfolded protein response (UPRmt). By analogy to the conductor in an orchestra managing multiple instrumental sections into a dynamically integrated musical piece, the cross-talk between these signaling cascades places the mitochondria as a major conductor of cellular integrity.
    Keywords:  estrogen receptor alpha; heat shock; mitochondria; mitochondrial UPR; mitochondrial integrated stress response; proteasome; translation
    DOI:  https://doi.org/10.3389/fcell.2021.715923
  7. Shock. 2021 Nov 01. 56(5): 755-761
    Activation of the XBP1s/O-GlcNAcylation Pathway Improves Functional Outcome After Cardiac Arrest and Resuscitation in Young and Aged Mice.
    Ran Li, Yuntian Shen, Xuan Li, Liping Lu, Zhuoran Wang, Huaxin Sheng, Ulrike Hoffmann, Wei Yang.
       ABSTRACT: After cardiac arrest (CA) and resuscitation, the unfolded protein response (UPR) is activated in various organs including the brain. However, the role of the UPR in CA outcome remains largely unknown. One UPR branch involves spliced X-box-binding protein-1 (XBP1s). Notably, XBP1s, a transcriptional factor, can upregulate expression of specific enzymes related to glucose metabolism, and subsequently boost O-linked β-N-acetylglucosamine modification (O-GlcNAcylation). The current study is focused on effects of the XBP1 UPR branch and its downstream O-GlcNAcylation on CA outcome. Using both loss-of-function and gain-of-function mouse genetic tools, we provide the first evidence that activation of the XBP1 UPR branch in the post-CA brain is neuroprotective. Specifically, neuron-specific Xbp1 knockout mice had worse CA outcome, while mice with neuron-specific expression of Xbp1s in the brain had better CA outcome. Since it has been shown that the protective role of the XBP1s signaling pathway under ischemic conditions is mediated by increasing O-GlcNAcylation, we then treated young mice with glucosamine, and found that functional deficits were mitigated on day 3 post CA. Finally, after confirming that glucosamine can boost O-GlcNAcylation in the aged brain, we subjected aged mice to 8 min CA, and then treated them with glucosamine. We found that glucosamine-treated aged mice performed significantly better in behavioral tests. Together, our data indicate that the XBP1s/O-GlcNAc pathway is a promising target for CA therapy.
    DOI:  https://doi.org/10.1097/SHK.0000000000001732
  8. Cancers (Basel). 2021 Sep 30. pii: 4927. [Epub ahead of print]13(19):
    The Role of BiP and the IRE1α-XBP1 Axis in Rhabdomyosarcoma Pathology.
    Mahmoud Aghaei, Ahmad Nasimian, Marveh Rahmati, Philip Kawalec, Filip Machaj, Jakub Rosik, Bhavya Bhushan, S Zahra Bathaie, Negar Azarpira, Marek J Los, Afshin Samali, David Perrin, Joseph W Gordon, Saeid Ghavami.
       BACKGROUND: Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma in children, and is associated with a poor prognosis in patients presenting with recurrent or metastatic disease. The unfolded protein response (UPR) plays pivotal roles in tumor development and resistance to therapy, including RMS.
    METHODS: In this study, we used immunohistochemistry and a tissue microarray (TMA) on human RMS and normal skeletal muscle to evaluate the expression of key UPR proteins (GRP78/BiP, IRE1α and cytosolic/nuclear XBP1 (spliced XBP1-sXBP1)) in the four main RMS subtypes: alveolar (ARMS), embryonal (ERMS), pleomorphic (PRMS) and sclerosing/spindle cell (SRMS) RMS. We also investigated the correlation of these proteins with the risk of RMS and several clinicopathological indices, such as lymph node involvement, distant metastasis, tumor stage and tumor scores.
    RESULTS: Our results revealed that the expression of BiP, sXBP1, and IRE1α, but not cytosolic XBP1, are significantly associated with RMS (BiP and sXBP1 p-value = 0.0001, IRE1 p-value = 0.001) in all of the studied types of RMS tumors (n = 192) compared to normal skeletal muscle tissues (n = 16). In addition, significant correlations of BiP with the lymph node score (p = 0.05), and of IRE1α (p value = 0.004), cytosolic XBP1 (p = 0.001) and sXBP1 (p value = 0.001) with the stage score were observed. At the subtype level, BiP and sXBP1 expression were significantly associated with all subtypes of RMS, whereas IRE1α was associated with ARMS, PRMS and ERMS, and cytosolic XBP1 expression was associated with ARMS and SRMS. Importantly, the expression levels of IRE1α and sXBP1 were more pronounced in ARMS than in any of the other subtypes. The results also showed correlations of BiP with the lymph node score in ARMS (p value = 0.05), and of sXBP1 with the tumor score in PRMS (p value = 0.002).
    CONCLUSIONS: In summary, this study demonstrates that the overall UPR is upregulated and, more specifically, that the IRE1/sXBP1 axis is active in RMS. The subtype and stage-specific dependency on the UPR machinery in RMS may open new avenues for the development of novel targeted therapeutic strategies and the identification of specific tumor markers in this rare but deadly childhood and young-adult disease.
    Keywords:  GRP78; IRE1; rhabdomyosarcoma; spliced XBP1; unfolded protein response
    DOI:  https://doi.org/10.3390/cancers13194927
  9. Pancreatology. 2021 Oct 05. pii: S1424-3903(21)00576-7. [Epub ahead of print]
    ERAP2 is a novel target involved in autophagy and activation of pancreatic stellate cells via UPR signaling pathway.
    Weiyu Guan, Kohei Nakata, Akiko Sagara, Chika Iwamoto, Sho Endo, Ryota Matsuda, Sokichi Matsumoto, Naoki Ikenaga, Koji Shindo, Taiki Moriyama, Hideya Onishi, Kenoki Ohuchida, Yoshinao Oda, Masafumi Nakamura.
       BACKGROUND/OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is characterized by excessive desmoplasia and autophagy-dependent tumorigenic growth. Pancreatic stellate cells (PSCs) as a predominant stromal cell type play a critical role in PDAC biology. We have previously reported that autophagy facilitates PSC activation, however, the mechanism remains unknown. We investigated the mechanism of autophagy in PSC activation.
    METHODS: We compared gene expression profiles between patient-derived PSCs from pancreatic cancer and chronic pancreatitis using a microarray. The stromal expression of target gene in specimen of PDAC patients (n = 63) was analyzed. The effect of target gene on autophagy and activation of PSCs was investigated by small interfering RNAs transfection, and the relationship between autophagy and ER stress was investigated. We analyzed the growth and fibrosis of xenografted tumor by orthotopic models.
    RESULTS: In analysis of gene expression microarray, endoplasmic reticulum aminopeptidase 2 (ERAP2) upregulated in cancer-associated PSCs was identified as the target gene. High stromal ERAP2 expression is associated with a poor prognosis of PDAC patients. Knockdown of ERAP2 inhibited unfolded protein response mediated autophagy, and led to inactivation of PSCs, thereby attenuating tumor-stromal interactions by inhibiting production of IL-6 and fibronectin. In vivo, the promoting effect of PSCs on xenografted tumor growth and fibrosis was inhibited by ERAP2 knockdown.
    CONCLUSIONS: Our findings demonstrate a novel mechanism of PSCs activation regulated by autophagy. ERAP2 as a promising therapeutic target may provide a novel strategy for the treatment of PDAC.
    Keywords:  Endoplasmic reticulum stress; Stromal remodeling; Tumor-stromal interaction; Tunicamycin
    DOI:  https://doi.org/10.1016/j.pan.2021.09.012
  10. Front Cell Dev Biol. 2021 ;9 722960
    Sestrin2-Mediated Autophagy Contributes to Drug Resistance via Endoplasmic Reticulum Stress in Human Osteosarcoma.
    Zhen Tang, Xinghui Wei, Tian Li, Wei Wang, Hao Wu, Hui Dong, Yichao Liu, Feilong Wei, Lei Shi, Xiaokang Li, Zheng Guo, Xin Xiao.
      One contributor to the high mortality of osteosarcoma is its reduced sensitivity to chemotherapy, but the mechanism involved is unclear. Improving the sensitivity of osteosarcoma to chemotherapy is urgently needed to improve patient survival. We found that chemotherapy triggered apoptosis of human osteosarcoma cells in vitro and in vivo; this was accompanied by increased Sestrin2 expression. Importantly, autophagy was also enhanced with increased Sestrin2 expression. Based on this observation, we explored the potential role of Sestrin2 in autophagy of osteosarcoma. We found that Sestrin2 inhibited osteosarcoma cell apoptosis by promoting autophagy via inhibition of endoplasmic reticulum stress, and this process is closely related to the PERK-eIF2α-CHOP pathway. In addition, our study showed that low Sestrin2 expression can effectively reduce autophagy of human osteosarcoma cells after chemotherapy, increase p-mTOR expression, decrease Bcl-2 expression, promote osteosarcoma cell apoptosis, and slow down tumour progression in NU/NU mice. Sestrin2 activates autophagy by inhibiting mTOR via the PERK-eIF2α-CHOP pathway and inhibits apoptosis via Bcl-2. Therefore, our results explain one underlying mechanism of increasing the sensitivity of osteosarcoma to chemotherapy and suggest that Sestrin2 is a promising gene target.
    Keywords:  Sestrin2; apoptosis; autophagy; drug resistance; endoplasmic reticulum stress
    DOI:  https://doi.org/10.3389/fcell.2021.722960
  11. Front Pharmacol. 2021 ;12 747837
    Targeting the Integrated Stress Response in Cancer Therapy.
    Xiaobing Tian, Shengliang Zhang, Lanlan Zhou, Attila A Seyhan, Liz Hernandez Borrero, Yiqun Zhang, Wafik S El-Deiry.
      The integrated stress response (ISR) is an evolutionarily conserved intra-cellular signaling network which is activated in response to intrinsic and extrinsic stresses. Various stresses are sensed by four specialized kinases, PKR-like ER kinase (PERK), general control non-derepressible 2 (GCN2), double-stranded RNA-dependent protein kinase (PKR) and heme-regulated eIF2α kinase (HRI) that converge on phosphorylation of serine 51 of eIF2α. eIF2α phosphorylation causes a global reduction of protein synthesis and triggers the translation of specific mRNAs, including activating transcription factor 4 (ATF4). Although the ISR promotes cell survival and homeostasis, when stress is severe or prolonged the ISR signaling will shift to regulate cellular apoptosis. We review the ISR signaling pathway, regulation and importance in cancer therapy.
    Keywords:  ATF4; CHOP; apoptosis; cancer treatment; integrated stress responses
    DOI:  https://doi.org/10.3389/fphar.2021.747837
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