bims-ershed Biomed News
on ER Stress in Health and Diseases
Issue of 2022‒01‒30
seven papers selected by
Matías Eduardo González Quiroz
Worker’s Hospital

  1. J Alzheimers Dis Rep. 2021 ;5(1): 855-869
      Background: Tauopathies are a group of neurodegenerative diseases associated with the accumulation of misfolded tau protein. The mechanisms underpinning tau-dependent proteinopathy remain to be elucidated. A protein quality control pathway within the endoplasmic reticulum, the unfolded protein response (UPR), has been suggested as a possible pathway modulating cellular responses in a range of neurodegenerative diseases, including those associated with misfolded cytosolic tau.Objective: In this study we investigated three different clinically defined tauopathies to establish whether these diseases are accompanied by the activation of UPR.
    Methods: We used PCR and western blotting to probe for the modulation of several reliable UPR markers in mRNA and proteins extracted from three distinct tauopathies: 20 brain samples from Alzheimer's disease patients, 11 from Pick's disease, and 10 from progressive supranuclear palsy. In each disease samples from these patients were compared with equal numbers of age-matched non-demented controls.
    Results: Our investigation showed that different markers of UPR are not changed at the late stage of any of the human tauopathies investigated. Interestingly, UPR signatures were often observed in non-demented controls.
    Conclusion: These data from late-stage human cortical tissue report an activation of UPR markers within the aged brain across all cohorts investigated and further support the emerging evidence that the accumulation of misfolded cytosolic tau does not drive a disease-associated activation of UPR.
    Keywords:  Alzheimer’s disease; BiP; Pick’s disease; XBP-1; endoplasmic reticulum; progressive supranuclear palsy; tau
  2. Front Immunol. 2021 ;12 764861
      Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) infections are life-long and highly prevalent in the human population. These viruses persist in the host, eliciting either symptomatic or asymptomatic infections that may occur sporadically or in a recurrent manner through viral reactivations. Clinical manifestations due to symptomatic infection may be mild such as orofacial lesions, but may also translate into more severe diseases, such as ocular infections that may lead to blindness and life-threatening encephalitis. A key feature of herpes simplex viruses (HSVs) is that they have evolved molecular determinants that hamper numerous components of the host's antiviral innate and adaptive immune system. Importantly, HSVs infect and negatively modulate the function of dendritic cells (DCs), by inhibiting their T cell-activating capacity and eliciting their apoptosis after infection. Previously, we reported that HSV-2 activates the splicing of the mRNA of XBP1, which is related to the activity of the unfolded protein response (UPR) factor Inositol-Requiring Enzyme 1 alpha (IRE-1α). Here, we sought to evaluate if the activation of the IRE-1α pathway in DCs upon HSV infection may be related to impaired DC function after infection with HSV-1 or HSV-2. Interestingly, the pharmacological inhibition of the endonuclease activity of IRE-1α in HSV-1- and HSV-2-infected DCs significantly reduced apoptosis in these cells and enhanced their capacity to migrate to lymph nodes and activate virus-specific CD4+ and CD8+ T cells. These findings suggest that the activation of the IRE-1α-dependent UPR pathway in HSV-infected DCs may play a significant role in the negative effects that these viruses exert over these cells and that the modulation of this signaling pathway may be relevant for enhancing the function of DCs upon infection with HSVs.
    Keywords:  HSV-1; HSV-2; IRE-1α; T-cell activation; adaptive immunity; apoptosis; dendritic cells; unfolded protein response (UPR)
  3. Biochem Pharmacol. 2022 Jan 24. pii: S0006-2952(22)00026-0. [Epub ahead of print] 114932
      Neck pain and low back pain are two of the major diseases, which causes patients a low quantify of life and a heavy economic burden, intervertebral disc degeneration (IDD) contributes to them, and the mechanism is not totally clear. The increased inflammatory cytokines including interleukin (IL)-1β and tumor necrosis factor (TNF)α and downstream signaling pathways are involved. Inositol requiring enzyme 1 (IRE1) is a crucial enzyme that regulates endoplasmic reticulum (ER) stress. It is reported that IRE1 plays an important role in the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. Considering this, we performed a series of experiments in vitro and in vivo to evaluate the role of IRE1 in the progress of IDD. We demonstrated that IRE1 pathway was induced by IL-1β, inhibition of IRE1 suppressed the matrix degeneration of NP cells and ameliorated IDD grade in the punctured rat model. Further results indicated that inhibition of IRE1 suppressed H2O2 induced cell senescence, IL-1β-induced cellular reactive oxygen species (ROS) level and the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. It also played a crucial role in the apoptosis of NP cells and the progress of macrophage polarization. Our findings demonstrated that inhibition of IRE1 could suppress the degeneration of NP cells and prevent IDD in vivo. IRE1 may be a potential target for IDD treatment.
    Keywords:  IL-1β; IRE1; intervertebral disc degeneration; nucleus pulposus cells; senescence
  4. Prostate. 2022 Jan 28.
      BACKGROUND: Despite the clinical success of androgen receptor (AR)-targeted therapies, prostate cancer (PCa) inevitably progresses to castration-resistant prostate cancer (CRPC). Transcription factor 6 α (ATF6α), an effector of the unfolded protein response (UPR) that modulates the cellular response to endoplasmic reticulum (ER) stress, has been linked to tumor development, metastasis, and relapse. However, the role of ATF6α in CRPC remains unclear.METHODS: The effect of ATF6α on the CRPC-like phenotype in PCa cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carb-Oxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS), 5-Bromo-2-deoxyUridine (BrdU) incorporation analysis, and cell death assay. Mechanistically, bioinformatic analysis was utilized to evaluate the potential of PLA2G4A as the target of ATF6α. Moreover, Western blot analysis, real-time polymerase chain reaction, chromatin immunoprecipitation, arachidonic acid (AA), and prostaglandin E2 (PGE2) assays were performed to identify the regulatory effect of ATF6α on PLA2G4A.
    RESULTS: In this study, we found that the increase of ATF6α expression in response to androgen deprivation generates PCa cells with a CRPC-like phenotype. PCa cells with high levels of ATF6α expression are resistant to ferroptosis, and genetic and pharmacological inhibition of ATF6α could, therefore, promote the ferroptotic death of tumor cells and delay PCa progression. Molecular analyses linked ATF6α regulation of ferroptosis to the PLA2G4A-mediated release of AA and the resulting increase in PGE2 production, the latter of which acts as an antiferroptotic factor.
    CONCLUSIONS: This study defines ATF6α as a novel antiferroptotic regulator that exacerbates PCa progression. In addition, our data establish ATF6α-PLA2G4A signaling as an important pathological pathway in PCa, and targeting this pathway may be a novel treatment strategy.
    Keywords:  AA; ATF6α; CRPC; PGE2; PLA2G4A; ferroptosis
  5. Biochem Biophys Res Commun. 2022 Jan 15. pii: S0006-291X(22)00055-9. [Epub ahead of print]594 57-62
      DNA-damaging agents, such as radiation and chemotherapy, are common in cancer treatment, but the dosing has proven to be challenging, leading to severe side effects in some patients. Hence, to be able to personalize DNA-damaging chemotherapy, it is important to develop fast and reliable methods to measure the resulting DNA damage in patient cells. Here, we demonstrate how single DNA molecule imaging using fluorescence microscopy can quantify DNA-damage caused by the topoisomerase II (TopoII) poison etoposide. The assay uses an enzyme cocktail consisting of base excision repair (BER) enzymes to repair the DNA damage caused by etoposide and label the sites using a DNA polymerase and fluorescently labeled nucleotides. Using this DNA-damage detection assay we find a large variation in etoposide induced DNA-damage after in vitro treatment of blood cells from healthy individuals. We furthermore used the TopoII inhibitor ICRF-193 to show that the etoposide-induced damage in DNA was TopoII dependent. We discuss how our results support a potential future use of the assay for personalized dosing of chemotherapy.
    Keywords:  Base excision repair; Chemotherapy; DNA damage; Nick translation; Single molecule imaging; Single-strand breaks
  6. Cancer Lett. 2022 Jan 19. pii: S0304-3835(22)00026-X. [Epub ahead of print]
      Contrary to high doses irradiation (HDR), the biological consequences of dose irradiation (LDR) in breast cancer remain unclear due to the complexity of human epidemiological studies. LDR induces DNA damage that activates p53-mediated tumor-suppressing pathways promoting DNA repair, cell death, and growth arrest. Monoallelic p53 mutations are one of the earliest and the most frequent genetic events in many subtypes of cancer including ErbB2 breast cancer. Using MMTV/ErbB2 mutant p53 (R172H) heterozygous mouse model we found differential p53 genotype-specific effect of LDR vs. HDR on mammary tumorigenesis. Following LDR, mutant p53 heterozygous tumor cells exhibit aberrant ATM/DNA-PK signaling with defects in sensing of double-strand DNA brakes and deficient DNA repair. In contrast, HDR-induced genotoxic stress is sufficient to reach the threshold of DNA damage that is necessary for wtp53 induced DNA repair and cell cycle arrest. As a result, mutant p53 endows dominant-negative effect promoting mammary tumorigenesis after low-impact DNA damage leading to the selection of a genetically unstable proliferative population, with negligible mutagenic effect on tumors carrying wtp53 allele.
    Keywords:  53BP1; ATM; DNA damage; DNA-PK; Low-dose γ-radiation; Mutant p53
  7. J Biol Chem. 2022 Jan 20. pii: S0021-9258(22)00047-3. [Epub ahead of print] 101607
      The stromal interaction molecule 1 (STIM1) is an endoplasmic reticulum (ER) Ca2+ sensor that regulates the activity of Orai plasma membrane Ca2+ channels to mediate the store-operated Ca2+ entry (SOCE) pathway essential for immunity. Unc-93 homologue B1 (UNC93B1) is a multiple membrane-spanning ER protein that acts as a trafficking chaperone by guiding nucleic-acid sensing toll-like receptors (TLRs) to their respective endosomal signaling compartments. We previously showed that UNC93B1 interacts with STIM1 to promote antigen cross-presentation in dendritic cells, but the STIM1 binding site(s) and activation step(s) impacted by this interaction remained unknown. In this study, we show that UNC93B1 interacts with STIM1 in the ER lumen by binding to residues in close proximity to the transmembrane domain. Cysteine cross-linking in-vivo showed that UNC93B1 binding promotes the zipping of transmembrane and proximal cytosolic helices within resting STIM1 dimers, priming STIM1 for translocation. In addition, we show that UNC93B1 deficiency reduces SOCE and STIM1/Orai1 interactions and targets STIM1 to lighter ER domains, while UNC93B1 expression accelerates the recruitment of STIM1 to cortical ER domains. We conclude that UNC93B1 therefore acts as a trafficking chaperone by maintaining the pool of resting STIM1 proteins in a state primed for activation, enabling their rapid translocation in an extended conformation to cortical ER signaling compartments.
    Keywords:  calcium signaling; innate immunity; ion channels; membrane contact sites; protein trafficking