bims-unfpre Biomed News
on Unfolded protein response
Issue of 2024‒04‒14
eleven papers selected by
Susan Logue, University of Manitoba
  1. XBP1s activates METTL3/METTL14 for ER-phagy and paclitaxel sensitivity regulation in breast cancer.
  2. Endoplasmic Reticulum Stress Induces Vasodilation in Liver Vessels That Is Not Mediated by Unfolded Protein Response.
  3. Endoplasmic Reticulum Stress and Unfolded Protein Response in Vernal Keratoconjunctivitis.
  4. ARV1 deficiency induces lipid bilayer stress and enhances rDNA stability by activating the unfolded protein response in Saccharomyces cerevisiae.
  5. Cell migration: Collective cell migration is intrinsically stressful.
  6. The inositol-requiring enzyme 1 (IRE1) endoplasmic reticulum stress pathway promotes MDA-MB-231 cell survival and renewal in response to the aryl-ureido fatty acid CTU.
  7. Discovery and Validation of a Novel Inhibitor of HYPE-mediated AMPylation.
  8. Endogenous fluorescent reporters for heat shock proteins are not detectable after stress induction.
  9. Massive ER protein disposal by reticulophagy receptors and selective disposal by TOLLIP.
  10. Endoplasmic reticulum stress and death receptor-mediated apoptosis in the neuronal differentiation of adult adipose-derived stromal cells.
  11. Role of Sphingosine Kinase 1 in Glucolipotoxicity-Induced Early Activation of Autophagy in INS-1 Pancreatic β Cells.
  1. Cancer Lett. 2024 Apr 04. pii: S0304-3835(24)00239-8. [Epub ahead of print] 216846
    XBP1s activates METTL3/METTL14 for ER-phagy and paclitaxel sensitivity regulation in breast cancer.
    Jiajia Wang, Pengyu Fan, Peng Shen, Cong Fan, Pan Zhao, Yao Shen, Kewei Dong, Rui Ling, Suning Chen, Jian Zhang.
      Cancer cells employ the unfolded protein response (UPR) or induce autophagy, especially selective removal of certain ER domains via reticulophagy (termed ER-phagy), to mitigate endoplasmic reticulum (ER) stress for ER homeostasis when encountering microenvironmental stress. N6-methyladenosine (m6A) is one of the most abundant epitranscriptional modifications and plays important roles in various biological processes. However, the molecular mechanism of m6A modification in the ER stress response is poorly understood. In this study, we first found that ER stress could dramatically elevate m6A methylation levels through XBP1s-dependent transcriptional upregulation of METTL3/METTL14 in breast cancer (BC) cells. Further MeRIP sequencing and relevant validation results confirmed that ER stress caused m6A methylation enrichment on target genes for ER-phagy. Mechanistically, METTL3/METTL14 increased ER-phagy machinery formation by promoting m6A modification of the ER-phagy regulators CALCOCO1 and p62, thus enhancing their mRNA stability. Of note, we further confirmed that the chemotherapeutic drug paclitaxel (PTX) could induce ER stress and increase m6A methylation for ER-phagy. Furthermore, the combination of METTL3/METTL14 inhibitors with PTX demonstrated a significant synergistic therapeutic effect in both BC cells and xenograft mice. Thus, our data built a novel bridge on the crosstalk between ER stress, m6A methylation and ER-phagy. Most importantly, our work provides novel evidence of METTL3 and METTL14 as potential therapeutic targets for PTX sensitization in breast cancer.
    Keywords:  CALCOCO1; ER stress; ER-Phagy; Paclitaxel; XBP1; m6A; p62
    DOI:  https://doi.org/10.1016/j.canlet.2024.216846
  2. Int J Mol Sci. 2024 Mar 30. pii: 3865. [Epub ahead of print]25(7):
    Endoplasmic Reticulum Stress Induces Vasodilation in Liver Vessels That Is Not Mediated by Unfolded Protein Response.
    Sergejs Zavadskis, Anna Shiganyan, Andrea Müllebner, Johannes Oesterreicher, Wolfgang Holnthoner, Johanna Catharina Duvigneau, Andrey V Kozlov.
      There is a growing body of evidence that ER stress and the unfolded protein response (UPR) play a key role in numerous diseases. Impaired liver perfusion and ER stress often accompany each other in liver diseases. However, the exact impact of ER stress and UPR on the hepatic perfusion is not fully understood. The aim of this study was to disclose the effect of ER stress and UPR on the size of liver vessels and on the levels of Ca2+ and nitric oxide (NO), critical regulators of vascular tonus. This study was carried out in precisely cut liver tissue slices. Confocal microscopy was used to create 3D images of vessels. NO levels were determined either using either laser scan microscopy (LSM) in cells or by NO-analyser in medium. Ca2+ levels were analysed by LSM. We show that tunicamycin, an inducer of ER stress, acts similarly with vasodilator acetylcholine. Both exert a similar effect on the NO and Ca2+ levels; both induce significant vasodilation. Notably, this vasodilative effect persisted despite individual inhibition of UPR pathways-ATF-6, PERK, and IRE1-despite confirming the activation of UPR. Experiments with HUVEC cells showed that elevated NO levels did not result from endothelial NO synthase (eNOS) activation. Our study suggests that tunicamycin-mediated ER stress induces liver vessel vasodilation in an NO-dependent manner, which is mediated by intracellular nitrodilator-activatable NO store (NANOS) in smooth muscle cells rather than by eNOS.
    Keywords:  Ca2+; NO; endoplasmic reticulum stress; ex-vivo model; nitrodilators; unfolded protein response; vascular tonus
    DOI:  https://doi.org/10.3390/ijms25073865
  3. Invest Ophthalmol Vis Sci. 2024 Apr 01. 65(4): 23
    Endoplasmic Reticulum Stress and Unfolded Protein Response in Vernal Keratoconjunctivitis.
    Andrea Leonardi, Alice Donato, Umberto Rosani, Antonino Di Stefano, Fabiano Cavarzeran, Paola Brun.
      Purpose: Vernal keratoconjunctivitis (VKC) is an ocular allergic disease characterized by a type 2 inflammation, tissue remodeling, and low quality of life for the affected patients. We investigated the involvement of endoplasmic reticulum (ER) stress and unfolded protein response in VKC.Methods: Conjunctival imprints from VKC patients and normal subjects (CTs) were collected, and RNA was isolated, reverse transcribed, and analyzed with the Affymetrix microarray. Differentially expressed genes between VKC patients and CTs were evaluated. Genes related to ER stress, apoptosis, and autophagy were further considered. VKC and CT conjunctival biopsies were analyzed by immunohistochemistry (IHC) with specific antibodies against unfolded protein response (UPR), apoptosis, and inflammation. Conjunctival fibroblast and epithelial cell cultures were exposed to the conditioned medium of activated U937 monocytes and analyzed by quantitative PCR for the expression of UPR, apoptosis, autophagy, and inflammatory markers.
    Results: ER chaperones HSPA5 (GRP78/BiP) and HYOU1 (GRP170) were upregulated in VKC patients compared to CTs. Genes encoding for ER transmembrane proteins, PKR-like ER kinase (PERK), activating transcription factor 6 (ATF6), ER-associated degradation (ERAD), and autophagy were upregulated, but not those related to apoptosis. Increased positive reactivity of BiP and ATF6 and unchanged expression of apoptosis markers were confirmed by IHC. Cell cultures in stress conditions showed an overexpression of UPR, proinflammatory, apoptosis, and autophagy markers.
    Conclusions: A significant overexpression of genes encoding for ER stress, UPR, and pro-inflammatory pathway components was reported for VKC. Even though these pathways may lead to ER homeostasis, apoptosis, or inflammation, ER stress in VKC may predominantly contribute to promote inflammation.
    DOI:  https://doi.org/10.1167/iovs.65.4.23
  4. J Biol Chem. 2024 Apr 06. pii: S0021-9258(24)01774-5. [Epub ahead of print] 107273
    ARV1 deficiency induces lipid bilayer stress and enhances rDNA stability by activating the unfolded protein response in Saccharomyces cerevisiae.
    Sujin Hong, Hyeon-Geun Lee, Won-Ki Huh.
      The stability of ribosomal DNA (rDNA) is maintained through transcriptional silencing by the NAD+-dependent histone deacetylase Sir2 in Saccharomyces cerevisiae. Alongside proteostasis, rDNA stability is a crucial factor regulating the replicative lifespan (RLS) of S. cerevisiae. The unfolded protein response (UPR) is induced by misfolding of proteins or an imbalance of membrane lipid composition and is responsible for degrading misfolded proteins and restoring endoplasmic reticulum (ER) membrane homeostasis. Recent investigations have suggested that the UPR can extend the RLS of yeast by enhancing protein quality control mechanisms, but the relationship between the UPR and rDNA stability remains unknown. In this study, we found that the deletion of ARV1, which encodes an ER protein of unknown molecular function, activates the UPR by inducing lipid bilayer stress. In arv1Δ cells, the UPR and the cell wall integrity pathway are activated independently of each other, and the high osmolarity glycerol (HOG) pathway is activated in a manner dependent on Ire1, which mediates the UPR. Activated Hog1 translocates the stress response transcription factor Msn2 to the nucleus, where it promotes the expression of nicotinamidase Pnc1, a well-known Sir2 activator. Following Sir2 activation, rDNA silencing and rDNA stability are promoted. Furthermore, the loss of other ER proteins, such as Pmt1 or Bst1, and ER stress induced by tunicamycin or inositol depletion also enhance rDNA stability in a Hog1-dependent manner. Collectively, these findings suggest that the induction of the UPR enhances rDNA stability in S. cerevisiae by promoting the Msn2-Pnc1-Sir2 pathway in a Hog1-dependent manner.
    Keywords:  Arv1; Saccharomyces cerevisiae; Sir2; high osmolarity glycerol (HOG); rDNA silencing; unfolded protein response (UPR)
    DOI:  https://doi.org/10.1016/j.jbc.2024.107273
  5. Curr Biol. 2024 Apr 08. pii: S0960-9822(24)00243-4. [Epub ahead of print]34(7): R275-R278
    Cell migration: Collective cell migration is intrinsically stressful.
    Heng Wang, Jiong Chen.
      Collective cell migration is a key cellular process in development and disease. A new study reports that ER stress is induced during collective cell migration and an intrinsic mechanism prevents migratory cells from over-reacting to ER stress.
    DOI:  https://doi.org/10.1016/j.cub.2024.02.061
  6. Int J Biochem Cell Biol. 2024 Apr 10. pii: S1357-2725(24)00062-1. [Epub ahead of print] 106571
    The inositol-requiring enzyme 1 (IRE1) endoplasmic reticulum stress pathway promotes MDA-MB-231 cell survival and renewal in response to the aryl-ureido fatty acid CTU.
    Md Khalilur Rahman, Balasubrahmanyam Umashankar, Hassan Choucair, Kirsi Bourget, Tristan Rawling, Michael Murray.
      Current treatment options for triple-negative breast cancer (TNBC) are limited to toxic drug combinations of low efficacy. We recently identified an aryl-substituted fatty acid analogue, termed CTU, that effectively killed TNBC cells in vitro and in mouse xenograft models in vivo without producing toxicity. However, there was a residual cell population that survived treatment. The present study evaluated the mechanisms that underlie survival and renewal in CTU-treated MDA-MB-231 TNBC cells. RNA-seq profiling identified several pro-inflammatory signaling pathways that were activated in treated cells. Increased expression of cyclooxygenase-2 and the cytokines IL-6, IL-8 and GM-CSF was confirmed by real-time RT-PCR, ELISA and Western blot analysis. Increased self-renewal was confirmed using the non-adherent, in vitro colony-forming mammosphere assay. Neutralizing antibodies to IL-6, IL-8 and GM-CSF, as well as cyclooxygenase-2 inhibition suppressed the self-renewal of MDA-MB-231 cells post-CTU treatment. IPA network analysis identified major NF-κB and XBP1 gene networks that were activated by CTU; chemical inhibitors of these pathways and esiRNA knock-down decreased the production of pro-inflammatory mediators. NF-κB and XBP1 signaling was in turn activated by the endoplasmic reticulum (ER)-stress sensor inositol-requiring enzyme 1 (IRE1), which mediates the unfolded protein response. Co-treatment with an inhibitor of IRE1 kinase and RNase activities, decreased phospho-NF-κB and XBP1s expression and the production of pro-inflammatory mediators. Further, IRE1 inhibition also enhanced apoptotic cell death and prevented the activation of self-renewal by CTU. Taken together, the present findings indicate that the IRE1 ER-stress pathway is activated by the anti-cancer lipid analogue CTU, which then activates secondary self-renewal in TNBC cells.
    Keywords:  IRE1; NF-κB; XBP-1s; mammosphere assay; pro-inflammatory mediators; self-renewal
    DOI:  https://doi.org/10.1016/j.biocel.2024.106571
  7. Cell Stress Chaperones. 2024 Apr 08. pii: S1355-8145(24)00063-4. [Epub ahead of print]
    Discovery and Validation of a Novel Inhibitor of HYPE-mediated AMPylation.
    Ali Camara, Heerak Chugh, Alyssa George, Lukas Dolidze, Kevin Ryu, Katrina J Holly, Daniel P Flaherty, Seema Mattoo.
      AMPylation-the covalent transfer of an AMP from ATP onto a target protein-is catalyzed by the human enzyme HYPE/FicD to regulate its substrate, the heat shock chaperone BiP. HYPE-mediated AMPylation of BiP is critical for maintaining proteostasis in the ER (endoplasmic reticulum) and mounting an UPR (unfolded protein response) in times of proteostatic imbalance. Thus, manipulating HYPE's enzymatic activity is a key therapeutic strategy towards the treatment of various protein misfolding diseases, including neuropathy and early onset diabetes associated with two recently identified clinical mutations of HYPE. Herein, we present an optimized, fluorescence polarization-based, high-throughput screening (HTS) assay to discover activators and inhibitors of HYPE-mediated AMPylation. After challenging our HTS assay with over 30,000 compounds, we discovered a novel AMPylase inhibitor, I2.10. We also determined a low micromolar IC50 for I2.10 and employed biorthogonal counter-screens to validate its efficacy against HYPE's AMPylation of BiP. Further, we report low cytotoxicity of I2.10 on human cell lines. We thus established an optimized, high-quality HTS assay amenable to tracking HYPE's enzymatic activity at scale, and provide the first novel small-molecule inhibitor capable of perturbing HYPE-directed AMPylation of BiP in vitro. Our HTS assay and I2.10 compound serve as a platform for further development of HYPE-specific small-molecule therapeutics.
    Keywords:  AMPylation/adenylylation; BiP/GRP78/HSPA5; ER stress; HYPE/FICD; UPR; diabetes; drug discovery; fluorescence polarization; high-throughput screen; neurodegeneration; posttranslational modification
    DOI:  https://doi.org/10.1016/j.cstres.2024.04.001
  8. MicroPubl Biol. 2024 ;2024
    Endogenous fluorescent reporters for heat shock proteins are not detectable after stress induction.
    Priya Thirumaran, Rebecca Cornell, Roger Pocock.
      Mitochondria and the endoplasmic reticulum (ER) utilise unique unfolded protein response (UPR) mechanisms to maintain cellular proteostasis. Heat shock proteins (HSPs) are UPR chaperones induced by specific stressors to promote protein folding. Previous research has successfully employed transgenic reporters in Caenorhabditis elegans to report HSP induction. However, transgenic reporters are overexpressed and only show promoter regulation and not post-transcriptional regulation. To examine endogenous HSP regulation, we attempted to generate and validate endogenous reporters for mitochondrial ( HSP-60 ) and ER ( HSP-4 ) chaperones. Using CRISPR/Cas9 technology, F2A-GFP-H2B coding DNA was inserted downstream of each HSP gene and stress induction assays conducted to validate these tools. Endogenous reporters were successfully generated for hsp-4 and hsp-60 . However, GFP induction could not be detected with these endogenous reporters upon stress induction, likely due to low level expression.
    DOI:  https://doi.org/10.17912/micropub.biology.001049
  9. Autophagy. 2024 Apr 11. 1-2
    Massive ER protein disposal by reticulophagy receptors and selective disposal by TOLLIP.
    Yuki Hayashi, Hidenori Ichijo.
      Proteostasis of the endoplasmic reticulum (ER) is maintained by coordinated action of two major catabolic pathways: proteasome-dependent ER-associated degradation (ERAD) and less characterized lysosomal pathways. Recent studies on ER-specific autophagy (termed "reticulophagy") have highlighted the importance of lysosomes for ER proteostasis. Key to this process are proteins termed reticulophagy receptors that connect ER fragments and Atg8-family proteins, facilitating the lysosomal degradation of both native and aberrant ER proteins in a relatively nonselective manner. In contrast, our recent work identified TOLLIP as a novel type of cargo receptor specifically dedicated to the lysosomal degradation of aberrant ER membrane proteins. The clients of TOLLIP include an engineered model substrate, which mimics an ER-retained aberrant membrane protein, and motor neuron disease-linked misfolded mutants of VAPB and BSCL2/Seipin. TOLLIP acts as a receptor to connect these aberrant ER membrane proteins and phosphatidylinositol-3-phosphate (PtdIns3P) by recognizing the former through its misfolding-sensing intrinsically disordered region (IDR) and ubiquitin-binding CUE domain, and the latter through its C2 domain. These interactions enable PtdIns3P-dependent vesicular trafficking of aberrant membrane proteins to lysosomes without promoting reticulophagic turnover of bulk ER.
    Keywords:  ER stress; ER-phagy; ERAD; TOLLIP; motor neuron disease; reticulophagy
    DOI:  https://doi.org/10.1080/15548627.2024.2340417
  10. Heliyon. 2024 Apr 15. 10(7): e28608
    Endoplasmic reticulum stress and death receptor-mediated apoptosis in the neuronal differentiation of adult adipose-derived stromal cells.
    Pingshu Zhang, Wen Li, Xinyue Zheng, Hongjie Luo, Qing Liu, Qingxi Long, Qi Yan, Xiaodong Yuan.
      Apoptosis is the primary cause of cell death in the differentiation of Adipose-derived stromal cells (ADSCs) into neurons. However, the relationship between endoplasmic reticulum stress (ERS) and death receptor-mediated apoptosis in ADSC-induced neuronal differentiation is not clear. ADSCs were isolated and induced to differentiate into neurons using β-mercaptoethanol. The expression of neuron-specific enolase (NSE), GRP94, CHOP, Fas/FasL, TNFR1/TNF-α, DR5/TRAIL, Caspase8, and Caspase3 in ADSCs was examined using immunocytochemistry and Western blotting before induction, during pre-induction, and after induction. Transmission electron microscopy (TEM) was used to observe changes in the morphology of the endoplasmic reticulum (ER), and the MTT assay was employed to measure cell viability in the uninduced and induced groups. Additionally, the number of apoptotic cells during the induction process was measured using flow cytometry with Annexin V/PI. With increasing induction time, the positive expression rates of CHOP, Fas/FasL, Caspase8, Caspase-3, and NSE gradually increased, while the positive expression rate of GRP94 decreased. TNFR1/TNF-α and DR5/TRAIL peaked at 5 h post-induction and then decreased at 8 h. TEM revealed swelling and expansion of the ER, vacuolar changes, and degranulation in cells. The MTT assay showed a gradual decrease in the absorbance of surviving cells in all groups. Flow cytometry indicated an increasing rate of apoptosis in cells. Therefore, ERS in the normal culture and growth of ADSCs, manifesting as enhanced unfolded protein response (UPR), maintains the normal survival of ADSCs. However, in the process of ADSC-induced differentiation into neurons, ERS and death receptor-mediated apoptosis are significant causes of cell death.
    Keywords:  Adipose-derived stromal cells; Apoptosis; Death receptors; Endoplasmic reticulum stress; Induction; Neurons
    DOI:  https://doi.org/10.1016/j.heliyon.2024.e28608
  11. Cells. 2024 Apr 05. pii: 636. [Epub ahead of print]13(7):
    Role of Sphingosine Kinase 1 in Glucolipotoxicity-Induced Early Activation of Autophagy in INS-1 Pancreatic β Cells.
    Nicolas Coant, Karima Rendja, Lara Bellini, Mélissa Flamment, Jeannine Lherminier, Bernard Portha, Patrice Codogno, Hervé Le Stunff.
      Insulin-producing pancreatic β cells play a crucial role in the regulation of glucose homeostasis, and their failure is a key event for diabetes development. Prolonged exposure to palmitate in the presence of elevated glucose levels, termed gluco-lipotoxicity, is known to induce β cell apoptosis. Autophagy has been proposed to be regulated by gluco-lipotoxicity in order to favor β cell survival. However, the role of palmitate metabolism in gluco-lipotoxcity-induced autophagy is presently unknown. We therefore treated INS-1 cells for 6 and 24 h with palmitate in the presence of low and high glucose concentrations and then monitored autophagy. Gluco-lipotoxicity induces accumulation of LC3-II levels in INS-1 at 6 h which returns to basal levels at 24 h. Using the RFP-GFP-LC3 probe, gluco-lipotoxicity increased both autophagosomes and autolysosmes structures, reflecting early stimulation of an autophagy flux. Triacsin C, a potent inhibitor of the long fatty acid acetyl-coA synthase, completely prevents LC3-II formation and recruitment to autophagosomes, suggesting that autophagic response requires palmitate metabolism. In contrast, etomoxir and bromo-palmitate, inhibitors of fatty acid mitochondrial β-oxidation, are unable to prevent gluco-lipotoxicity-induced LC3-II accumulation and recruitment to autophagosomes. Moreover, bromo-palmitate and etomoxir potentiate palmitate autophagic response. Even if gluco-lipotoxicity raised ceramide levels in INS-1 cells, ceramide synthase 4 overexpression does not potentiate LC3-II accumulation. Gluco-lipotoxicity also still stimulates an autophagic flux in the presence of an ER stress repressor. Finally, selective inhibition of sphingosine kinase 1 (SphK1) activity precludes gluco-lipotoxicity to induce LC3-II accumulation. Moreover, SphK1 overexpression potentiates autophagic flux induced by gluco-lipotxicity. Altogether, our results indicate that early activation of autophagy by gluco-lipotoxicity is mediated by SphK1, which plays a protective role in β cells.
    Keywords:  autophagy; cell death; ceramides; gluco-lipotoxicity; pancreatic β cells; sphingosine kinase 1; sphingosine-1-phosphate; type 2 diabetes
    DOI:  https://doi.org/10.3390/cells13070636
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