bims-unfpre Biomed News
on Unfolded protein response
Issue of 2020‒10‒25
seven papers selected by
Susan Logue
University of Manitoba

  1. Front Med (Lausanne). 2020 ;7 568096
    Luís A, Hackl M, Jafarmadar M, Keibl C, Jilge JM, Grillari J, Bahrami S, Kozlov AV.
      Circulating microRNAs (miRNA) alterations have been reported in severe trauma patients but the pathophysiological relevance of these changes is still unclear. miRNAs are critical biologic regulators of pathological events such as hypoxia and inflammation, which are known to induce endoplasmic reticulum (ER) stress. ER stress is emerging as an important process contributing to the development of single and/or multiple organ dysfunction after trauma hemorrhagic shock (THS) accompanied by impaired tissue microcirculation and inflammation. Here, we aim to bring new insights into the involvement of miRNAs associated with ER stress in THS. THS was induced in rats by a median laparotomy and blood withdrawal until mean arterial pressure (MAP) dropped to 30-35 mmHg followed by a restrictive (40 min) and full reperfusion (60 min) with Ringer's solution. Tunicamycin was used to induce ER stress. Blood samples were collected 24 h after THS for the determination of pathological changes in the blood (PCB) and circulating miRNAs. Plasma levels of circulating miRNAs were compared between THS, tunicamycin, and sham groups and correlated to biomarkers of PCB. MiRNA profile of THS animals showed that 40 out of 91 (44%) miRNAs were significantly upregulated compared to sham (p < 0.01). The data showed a very strong correlation between liver injury and miR-122-5p (r = 0.91, p < 0.00001). MiR-638, miR-135a-5p, miR-135b-5p, miR-668-3p, miR-204-5p, miR-146a-5p, miR-200a-3p, miR-17-5p, miR-30a-5p, and miR-214-3p were found positively correlated with lactate (r > 0.7, p < 0.05), and negatively with base excess (r ≤ 0.8, p < 0.05) and bicarbonate (r ≤ 0.8, p < 0.05), which are clinical parameters that reflected the shock severity. Tunicamycin significantly modified the microRNA profile of the animals, 33 out of 91 miRNAs were found differentially expressed. In addition, principal component analysis revealed that THS and tunicamycin induced similar changes in plasma miRNA patterns. Strikingly, the data showed that 15 (25.9%) miRNAs were regulated by both THS and tunicamycin (p < 0.01). This included miR-122-5p, a liver-specific microRNA, but also miR-17-5p and miR-125b-5p which are miRNAs remarkably involved in unfolded protein response (UPR)-mediating pro-survival signaling (IRE1α). Since miRNAs associated with ER stress are clearly correlated with THS, our data strongly suggest that interaction between miRNAs and ER stress is an important pathologic event occurring during THS. Overall, we consider that the miRNA profile developed in this study can provide a rationale for the development of bench-to-bedside strategies that target miRNAs in critical care diseases or be used as biomarkers in the prognosis of trauma patients.
    Keywords:  ER stress; circulating miRNAs; multiple organ dysfunction; organ damage; trauma hemorrhagic shock
  2. Thorax. 2020 Oct 19. pii: thoraxjnl-2019-213738. [Epub ahead of print]
    Bradley KL, Stokes CA, Marciniak SJ, Parker LC, Condliffe AM.
      The lungs are exposed to a range of environmental toxins (including cigarette smoke, air pollution, asbestos) and pathogens (bacterial, viral and fungal), and most respiratory diseases are associated with local or systemic hypoxia. All of these adverse factors can trigger endoplasmic reticulum (ER) stress. The ER is a key intracellular site for synthesis of secretory and membrane proteins, regulating their folding, assembly into complexes, transport and degradation. Accumulation of misfolded proteins within the lumen results in ER stress, which activates the unfolded protein response (UPR). Effectors of the UPR temporarily reduce protein synthesis, while enhancing degradation of misfolded proteins and increasing the folding capacity of the ER. If successful, homeostasis is restored and protein synthesis resumes, but if ER stress persists, cell death pathways are activated. ER stress and the resulting UPR occur in a range of pulmonary insults and the outcome plays an important role in many respiratory diseases. The UPR is triggered in the airway of patients with several respiratory diseases and in corresponding experimental models. ER stress has been implicated in the initiation and progression of pulmonary fibrosis, and evidence is accumulating suggesting that ER stress occurs in obstructive lung diseases (particularly in asthma), in pulmonary infections (some viral infections and in the setting of the cystic fibrosis airway) and in lung cancer. While a number of small molecule inhibitors have been used to interrogate the role of the UPR in disease models, many of these tools have complex and off-target effects, hence additional evidence (eg, from genetic manipulation) may be required to support conclusions based on the impact of such pharmacological agents. Aberrant activation of the UPR may be linked to disease pathogenesis and progression, but at present, our understanding of the context-specific and disease-specific mechanisms linking these processes is incomplete. Despite this, the ability of the UPR to defend against ER stress and influence a range of respiratory diseases is becoming increasingly evident, and the UPR is therefore attracting attention as a prospective target for therapeutic intervention strategies.
    Keywords:  airway epithelium; asthma; innate immunity; respiratory infection; viral infection
  3. mSphere. 2020 Oct 21. pii: e00879-20. [Epub ahead of print]5(5):
    Guirao-Abad JP, Weichert M, Albee A, Deck K, Askew DS.
      The unfolded protein response (UPR) is a signaling network that maintains homeostasis of the endoplasmic reticulum (ER). In the human-pathogenic fungus Aspergillus fumigatus, the UPR is initiated by activation of an endoribonuclease (RNase) domain in the ER transmembrane stress sensor IreA, which splices the downstream mRNA hacAu into its active form, hacAi, encoding the master transcriptional regulator of the pathway. Small-molecule inhibitors against IRE1, the human ortholog of IreA, have been developed for anticancer therapy, but their effects on the fungal UPR are unexplored. Here, we demonstrate that the IRE1 RNase inhibitor 4μ8C prevented A. fumigatus from increasing the levels of hacAi mRNA, thereby blocking induction of downstream UPR target gene expression. Treatment with 4μ8C had minimal effects on growth in minimal medium but severely impaired growth on a collagen substrate that requires high levels of hydrolytic enzyme secretion, mirroring the phenotype of other fungal UPR mutants. 4μ8C also increased sensitivity to carvacrol, a natural compound that disrupts ER integrity in fungi, and hygromycin B, which correlated with reduced expression of glycosylation-related genes. Interestingly, treatment with 4μ8C was unable to induce all of the phenotypes attributed to the loss of the canonical UPR in a ΔhacA mutant but showed remarkable similarity to the phenotype of an RNase-deficient IreA mutant that is also unable to generate the hacAi mRNA. These results establish proof of principle that pharmacological inhibition of the canonical UPR pathway is feasible in A. fumigatus and support a noncanonical role for the hacAu mRNA in ER stress response.IMPORTANCE The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response.
    Keywords:  4μ8C; A. fumigatus ; ER stress; Hac1; HacA; IRE1; Ire1; IreA; RNase; STF-083010; UPR; XBP1; Xbp1; secretion
  4. Oncogenesis. 2020 Oct 18. 9(10): 93
    Giuli MV, Diluvio G, Giuliani E, Franciosa G, Di Magno L, Pignataro MG, Tottone L, Nicoletti C, Besharat ZM, Peruzzi G, Pelullo M, Palermo R, Canettieri G, Talora C, d'Amati G, Bellavia D, Screpanti I, Checquolo S.
      Unfolded protein response (UPR) is a conserved adaptive response that tries to restore protein homeostasis after endoplasmic reticulum (ER) stress. Recent studies highlighted the role of UPR in acute leukemias and UPR targeting has been suggested as a therapeutic approach. Aberrant Notch signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL), as downregulation of Notch activity negatively affects T-ALL cell survival, leading to the employment of Notch inhibitors in T-ALL therapy. Here we demonstrate that Notch3 is able to sustain UPR in T-ALL cells, as Notch3 silencing favored a Bip-dependent IRE1α inactivation under ER stress conditions, leading to increased apoptosis via upregulation of the ER stress cell death mediator CHOP. By using Juglone, a naturally occurring naphthoquinone acting as an anticancer agent, to decrease Notch3 expression and induce ER stress, we observed an increased ER stress-associated apoptosis. Altogether our results suggest that Notch3 inhibition may prevent leukemia cells from engaging a functional UPR needed to compensate the Juglone-mediated ER proteotoxic stress. Notably, in vivo administration of Juglone to human T-ALL xenotransplant models significantly reduced tumor growth, finally fostering the exploitation of Juglone-dependent Notch3 inhibition to perturb the ER stress/UPR signaling in Notch3-dependent T-ALL subsets.
  5. Cells. 2020 Oct 18. pii: E2314. [Epub ahead of print]9(10):
    Roscoe JM, Sevier CS.
      The endoplasmic reticulum (ER) has emerged as a source of hydrogen peroxide (H2O2) and a hub for peroxide-based signaling events. Here we outline cellular sources of ER-localized peroxide, including sources within and near the ER. Focusing on three ER-localized proteins-the molecular chaperone BiP, the transmembrane stress-sensor IRE1, and the calcium pump SERCA2-we discuss how post-translational modification of protein cysteines by H2O2 can alter ER activities. We review how changed activities for these three proteins upon oxidation can modulate signaling events, and also how cysteine oxidation can serve to limit the cellular damage that is most often associated with elevated peroxide levels.
    Keywords:  BiP; IRE1; SERCA2; cysteine oxidation; endoplasmic reticulum (ER); hydrogen peroxide; reactive oxygen species (ROS); redox signaling; unfolded protein response (UPR)
  6. Heliyon. 2020 Oct;6(10): e05217
    Barua D, Abbasi B, Gupta A, Gupta S.
      Somatic mutations of the estrogen receptor 1 gene (ESR1) is an emerging mechanism of acquired resistance to endocrine therapy in hormonal breast cancers. Hotspot point mutations in the ligand- binding domain of estrogen receptor α (ER) and genomic rearrangements producing ESR1 fusion genes are the two major types of mutations that are associated with endocrine resistance. The crosstalk between X-box binding protein 1 (XBP1), a key transcription factor of the unfolded protein response (UPR) and ER signalling creates a positive feedback loop that results in increased expression of XBP1 in ER-positive breast cancer. Here we report that XBP1 co-operated with point mutants (Y537S, D538G) and fusion mutants (ESR1-YAP1, ESR1-DAB2) of ESR1 to increase their transcriptional activity. XBP1 was required for optimal expression of estrogen-regulated genes, and up to 40% of XBP1-dependent genes were estrogen-responsive genes. Knockdown of XBP1 in genome-edited MCF7 cells expressing Y537S mutant reduced their growth, re-sensitized them to anti-estrogens and attenuated the constitutive and estrogen-stimulated expression of estrogen-regulated genes. Our study provides a rationale for overcoming endocrine resistance in breast cancers expressing ESR1 mutation by combining the XBP1 targeting agents with anti-estrogen agents.
    Keywords:  Biochemistry; Cancer research; Cell biology; ER-Positive breast cancer; ESR1 mutations; Endocrine resistance; Molecular biology; Transcriptomics; XBP1
  7. J Clin Invest. 2020 Oct 19. pii: 143197. [Epub ahead of print]
    Grant S, Lester HA.
      Useful animal models of disease in neuroscience can make accurate predictions about a therapeutic outcome, a feature known as predictive validity. In this issue of the JCI, Knowland et al. provide an improved model to assess nicotinic acetylcholine receptor (nAChR) ligands for treating chronic pain. The authors identify two proteins, the voltage-dependent calcium channel auxiliary subunit BARP and the unfolded protein response sensor IRE1α, that are required for robust heterologous expression of α6β4, an nAChR subtype in dorsal root ganglia (DRG). This nAChR is a candidate for the analgesic effects of nicotine as well as the frog toxin epibatidine. Now researchers can efficiently screen for α6β4 nAChR-selective agonists using heterologous expression systems. Candidates that emerge will enable researchers to test the predictive validity of mouse models for chronic pain in the nAChR context. If all these steps work, one can envision a class of non-opioid nAChR-targeted analgesics for chronic pain.