bims-unfpre Biomed News
on Unfolded protein response
Issue of 2020‒05‒17
nine papers selected by
Susan Logue
University of Manitoba


  1. Nat Commun. 2020 May 14. 11(1): 2401
    Dufey E, Bravo-San Pedro JM, Eggers C, González-Quiroz M, Urra H, Sagredo AI, Sepulveda D, Pihán P, Carreras-Sureda A, Hazari Y, Sagredo EA, Gutierrez D, Valls C, Papaioannou A, Acosta-Alvear D, Campos G, Domingos PM, Pedeux R, Chevet E, Alvarez A, Godoy P, Walter P, Glavic A, Kroemer G, Hetz C.
      The molecular connections between homeostatic systems that maintain both genome integrity and proteostasis are poorly understood. Here we identify the selective activation of the unfolded protein response transducer IRE1α under genotoxic stress to modulate repair programs and sustain cell survival. DNA damage engages IRE1α signaling in the absence of an endoplasmic reticulum (ER) stress signature, leading to the exclusive activation of regulated IRE1α-dependent decay (RIDD) without activating its canonical output mediated by the transcription factor XBP1. IRE1α endoribonuclease activity controls the stability of mRNAs involved in the DNA damage response, impacting DNA repair, cell cycle arrest and apoptosis. The activation of the c-Abl kinase by DNA damage triggers the oligomerization of IRE1α to catalyze RIDD. The protective role of IRE1α under genotoxic stress is conserved in fly and mouse. Altogether, our results uncover an important intersection between the molecular pathways that sustain genome stability and proteostasis.
    DOI:  https://doi.org/10.1038/s41467-020-15694-y
  2. Cells. 2020 May 08. pii: E1160. [Epub ahead of print]9(5):
    Riaz TA, Junjappa RP, Handigund M, Ferdous J, Kim HR, Chae HJ.
      Inositol-requiring transmembrane kinase endoribonuclease-1α (IRE1α) is the most prominent and evolutionarily conserved unfolded protein response (UPR) signal transducer during endoplasmic reticulum functional upset (ER stress). A IRE1α signal pathway arbitrates yin and yang of cellular fate in objectionable conditions. It plays several roles in fundamental cellular physiology as well as in several pathological conditions such as diabetes, obesity, inflammation, cancer, neurodegeneration, and in many other diseases. Thus, further understanding of its molecular structure and mechanism of action during different cell insults helps in designing and developing better therapeutic strategies for the above-mentioned chronic diseases. In this review, recent insights into structure and mechanism of activation of IRE1α along with its complex regulating network were discussed in relation to their basic cellular physiological function. Addressing different binding partners that can modulate IRE1α function, UPRosome triggers different downstream pathways depending on the cellular backdrop. Furthermore, IRE1α are in normal cell activities outside the dominion of ER stress and activities under the weather of inflammation, diabetes, and obesity-related metaflammation. Thus, IRE1 as an ER stress sensor needs to be understood from a wider perspective for comprehensive functional meaning, which facilitates us with assembling future needs and therapeutic benefits.
    Keywords:  IRE1α; ROS; calcium; endoplasmic reticulum stress; insulin resistance; metaflammation; obesity; type 2 diabetes
    DOI:  https://doi.org/10.3390/cells9051160
  3. Trends Cell Biol. 2020 Jun;pii: S0962-8924(20)30055-6. [Epub ahead of print]30(6): 428-439
    Anderson NS, Haynes CM.
      Eukaryotic cells must accurately monitor the integrity of the mitochondrial network to overcome environmental insults and respond to physiological cues. The mitochondrial unfolded protein response (UPRmt) is a mitochondrial-to-nuclear signaling pathway that maintains mitochondrial proteostasis, mediates signaling between tissues, and regulates organismal aging. Aberrant UPRmt signaling is associated with a wide spectrum of disorders, including congenital diseases as well as cancers and neurodegenerative diseases. Here, we review recent research into the mechanisms underlying UPRmt signaling in Caenorhabditis elegans and discuss emerging connections between the UPRmt signaling and a translational regulation program called the 'integrated stress response'. Further study of the UPRmt will potentially enable development of new therapeutic strategies for inherited metabolic disorders and diseases of aging.
    Keywords:  integrated stress response; mitochondria; mitochondrial unfolded protein response; stress signaling
    DOI:  https://doi.org/10.1016/j.tcb.2020.03.001
  4. Cell Stem Cell. 2020 May 05. pii: S1934-5909(20)30155-7. [Epub ahead of print]
    Guallar D, Fuentes-Iglesias A, Souto Y, Ameneiro C, Freire-Agulleiro O, Pardavila JA, Escudero A, Garcia-Outeiral V, Moreira T, Saenz C, Xiong H, Liu D, Xiao S, Hou Y, Wu K, Torrecilla D, Hartner JC, Blanco MG, Lee LJ, López M, Walkley CR, Wang J, Fidalgo M.
      RNA editing of adenosine to inosine (A to I) is catalyzed by ADAR1 and dramatically alters the cellular transcriptome, although its functional roles in somatic cell reprogramming are largely unexplored. Here, we show that loss of ADAR1-mediated A-to-I editing disrupts mesenchymal-to-epithelial transition (MET) during induced pluripotent stem cell (iPSC) reprogramming and impedes acquisition of induced pluripotency. Using chemical and genetic approaches, we show that absence of ADAR1-dependent RNA editing induces aberrant innate immune responses through the double-stranded RNA (dsRNA) sensor MDA5, unleashing endoplasmic reticulum (ER) stress and hindering epithelial fate acquisition. We found that A-to-I editing impedes MDA5 sensing and sequestration of dsRNAs encoding membrane proteins, which promote ER homeostasis by activating the PERK-dependent unfolded protein response pathway to consequently facilitate MET. This study therefore establishes a critical role for ADAR1 and its A-to-I editing activity during cell fate transitions and delineates a key regulatory layer underlying MET to control efficient reprogramming.
    Keywords:  ADAR1; ER stress; MET; RNA A-to-I editing; UPR; iPSC; innate immune response; pluripotency; somatic cell reprogramming; subcellular localization
    DOI:  https://doi.org/10.1016/j.stem.2020.04.016
  5. Semin Cell Dev Biol. 2020 May 08. pii: S1084-9521(18)30313-6. [Epub ahead of print]
    Shrestha N, Reinert RB, Qi L.
      Type 1 and type 2 diabetes are associated with loss of β cell function. Optimal β cell function is linked to protein homeostasis in the endoplasmic reticulum (ER). Here, we review the roles of ER protein quality-control mechanisms, including the unfolded protein response (UPR), autophagy (specifically ER-phagy) and ER-associated degradation (ERAD), in β cells. We propose that different quality control mechanisms may control different aspects of β cell biology (i.e. function, survival, and identity), thereby contributing to disease pathogenesis.
    Keywords:  ER; ER-phagy; ERAD; UPR; diabetes; β cells
    DOI:  https://doi.org/10.1016/j.semcdb.2020.04.006
  6. Cell Death Differ. 2020 May 15.
    Gandelman M, Dansithong W, Figueroa KP, Paul S, Scoles DR, Pulst SM.
      Staufen-1 (STAU1) is an RNA-binding protein that becomes highly overabundant in numerous neurodegenerative disease models, including those carrying mutations in presenilin1 (PSEN1), microtubule-associated protein tau (MAPT), huntingtin (HTT), TAR DNA-binding protein-43 gene (TARDBP), or C9orf72. We previously reported that elevations in STAU1 determine autophagy defects and its knockdown is protective in models of several neurodegenerative diseases. Additional functional consequences of STAU1 overabundance, however, have not been investigated. We studied the role of STAU1 in the chronic activation of the unfolded protein response (UPR), a common feature among neurodegenerative diseases and often directly associated with neuronal death. Here we report that STAU1 is a novel modulator of the UPR, and is required for apoptosis induced by activation of the PERK-CHOP pathway. STAU1 levels increased in response to multiple endoplasmic reticulum (ER) stressors, and exogenous expression of STAU1 was sufficient to cause apoptosis through the PERK-CHOP pathway of the UPR. Cortical neurons and skin fibroblasts derived from Stau1-/- mice showed reduced UPR and apoptosis when challenged with thapsigargin. In fibroblasts from individuals with SCA2 or with ALS-causing TDP-43 and C9ORF72 mutations, we found highly increased STAU1 and CHOP levels in basal conditions, and STAU1 knockdown restored CHOP levels to normal. Taken together, these results show that STAU1 overabundance reduces cellular resistance to ER stress and precipitates apoptosis.
    DOI:  https://doi.org/10.1038/s41418-020-0553-9
  7. Cell Death Dis. 2020 May 12. 11(5): 360
    Coppin L, Jannin A, Ait Yahya E, Thuillier C, Villenet C, Tardivel M, Bongiovanni A, Gaston C, de Beco S, Barois N, van Seuningen I, Durand E, Bonnefond A, Vienne JC, Vamecq J, Figeac M, Vincent A, Delacour D, Porchet N, Pigny P.
      Cellular stress response contributes to epithelial defense in adaptation to environment changes. Galectins play a pivotal role in the regulation of this response in malignant cells. However, precise underlying mechanisms are largely unknown. Here we demonstrate that Galectin-3, a pro and anti-apoptotic lectin, is required for setting up a correct cellular response to stress by orchestrating several effects. First, Galectin-3 constitutes a key post-transcriptional regulator of stress-related mRNA regulons coordinating the cell metabolism, the mTORC1 complex or the unfolded protein response (UPR). Moreover, we demonstrated the presence of Galectin-3 with mitochondria-associated membranes (MAM), and its interaction with proteins located at the ER or mitochondrial membranes. There Galectin-3 prevents the activation and recruitment at the mitochondria of the regulator of mitochondria fission DRP-1. Accordingly, loss of Galectin-3 impairs mitochondrial morphology, with more fragmented and round mitochondria, and dynamics both in normal and cancer epithelial cells in basal conditions. Importantly, Galectin-3 deficient cells also display changes of the activity of the mitochondrial respiratory chain complexes, of the mTORC1/S6RP/4EBP1 translation pathway and reactive oxygen species levels. Regarding the ER, Galectin-3 did not modify the activities of the 3 branches of the UPR in basal conditions. However, Galectin-3 favours an adaptative UPR following ER stress induction by Thapsigargin treatment. Altogether, at the ER-mitochondria interface, Galectin-3 coordinates the functioning of the ER and mitochondria, preserves the integrity of mitochondrial network and modulates the ER stress response.
    DOI:  https://doi.org/10.1038/s41419-020-2556-3
  8. Autophagy. 2020 May 13.
    Muñoz-Guardiola P, Casas J, Megías-Roda E, Solé S, Perez-Montoyo H, Yeste-Velasco M, Erazo T, Diéguez-Martínez N, Espinosa-Gil S, Muñoz-Pinedo C, Yoldi G, Abad JL, Segura MF, Moran T, Romeo M, Bosch-Barrera J, Oaknin A, Alfón J, Domènech C, Fabriàs G, Velasco G, Lizcano JM.
      ABTL0812 is a first-in-class small molecule with anti-cancer activity, which is currently in clinical evaluation in a phase 2 trial in patients with advanced endometrial and squamous non-small cell lung carcinoma (NCT03366480). Previously, we showed that ABTL0812 induces TRIB3 pseudokinase expression, resulting in the inhibition of the AKT-MTORC1 axis and macroautophagy/autophagy-mediated cancer cell death. However, the precise molecular determinants involved in the cytotoxic autophagy caused by ABTL0812 remained unclear. Using a wide range of biochemical and lipidomic analyses, we demonstrated that ABTL0812 increases cellular long-chain dihydroceramides by impairing DEGS1 (delta 4-desaturase, sphingolipid 1) activity, which resulted in sustained ER stress and activated unfolded protein response (UPR) via ATF4-DDIT3-TRIB3 that ultimately promotes cytotoxic autophagy in cancer cells. Accordingly, pharmacological manipulation to increase cellular dihydroceramides or incubation with exogenous dihydroceramides resulted in ER stress, UPR and autophagy-mediated cancer cell death. Importantly, we have optimized a method to quantify mRNAs in blood samples from patients enrolled in the ongoing clinical trial, who showed significant increased DDIT3 and TRIB3 mRNAs. This is the first time that UPR markers are reported to change in human blood in response to any drug treatment, supporting their use as pharmacodynamic biomarkers for compounds that activate ER stress in humans. Finally, we found that MTORC1 inhibition and dihydroceramide accumulation synergized to induce autophagy and cytotoxicity, phenocopying the effect of ABTL0812. Given the fact that ABTL0812 is under clinical development, our findings support the hypothesis that manipulation of dihydroceramide levels might represents a new therapeutic strategy to target cancer.
    Keywords:  ER stress; UPR; autophagy; cancer; clinical trial; dihydroceramide
    DOI:  https://doi.org/10.1080/15548627.2020.1761651
  9. F1000Res. 2020 ;pii: F1000 Faculty Rev-290. [Epub ahead of print]9
    Briggs MD, Dennis EP, Dietmar HF, Pirog KA.
      Cartilage comprises a single cell type, the chondrocyte, embedded in a highly complex extracellular matrix. Disruption to the cartilage growth plate leads to reduced bone growth and results in a clinically diverse group of conditions known as genetic skeletal diseases (GSDs). Similarly, long-term degradation of articular cartilage can lead to osteoarthritis (OA), a disease characterised by joint pain and stiffness. As professionally secreting cells, chondrocytes are particularly susceptible to endoplasmic reticulum (ER) stress and this has been identified as a core disease mechanism in a group of clinically and pathologically related GSDs. If unresolved, ER stress can lead to chondrocyte cell death. Recent interest has focused on ER stress as a druggable target for GSDs and this has led to the first clinical trial for a GSD by repurposing an antiepileptic drug. Interestingly, ER stress markers have also been associated with OA in multiple cell and animal models and there is increasing interest in it as a possible therapeutic target for treatment. In summary, chondrocyte ER stress has been identified as a core disease mechanism in GSDs and as a contributory factor in OA. Thus, chondrocyte ER stress is a unifying factor for both common and rare cartilage-related diseases and holds promise as a novel therapeutic target.
    Keywords:  cartilage; chondrocyte; drug repurposing; endoplasmic reticulum; osteoarthritis; skeletal dysplasia
    DOI:  https://doi.org/10.12688/f1000research.22275.1