bims-unfpre Biomed News
on Unfolded protein response
Issue of 2020‒09‒13
fourteen papers selected by
Susan Logue
University of Manitoba


  1. Carcinogenesis. 2020 Sep 11. pii: bgaa095. [Epub ahead of print]
    Vieri M, Preisinger C, Schemionek M, Salimi A, Patterson JB, Samali A, H Brümmendorf T, Appelmann I, Kharabi Masouleh B.
      BCR-ABL1-positive acute lymphoblastic leukemia (ALL) cell survival is dependent on the inositol requiring enzyme 1 alpha (IRE1α) branch of the unfolded protein response. In the current study, we have focused on exploring the efficacy of a simultaneous pharmacological inhibition of BCR-ABL1 and IRE1α in Philadelphia positive (Ph +) ALL, using tyrosine kinase inhibitor (TKI) nilotinib and the IRE1α inhibitor MKC-8866.The combination of 0.5 µM nilotinib and 30 µM MKC-8866 in Ph + ALL cell lines led to a synergistic effect on cell viability. To mimic this dual inhibition on a genetic level, pre-B cells from conditional Xbp1+/fl mice were transduced with a BCR-ABL1 construct and with either tamoxifen-inducible cre or empty vector. Cells showed a significant sensitization to the effect of TKIs after induction of the heterozygous deletion. Finally, we performed a phosphoproteomic analysis on Ph + ALL cell lines treated with the combination of nilotinib and MKC-8866 to identify potential targets involved in their synergistic effect. An enhanced activation of p38 mitogen-activated protein kinase α (p38α MAPK) was identified. In line with this findings, p38 MAPK, as well as another important ER-stress related kinase, c-Jun N terminal kinase (JNK) were found to mediate the potentiated cytotoxic effect induced by the combination of MKC-8866 and nilotinib, since the targeting of p38 MAPK with its specific inhibitor BIRB-796 or JNK with JNK-in-8 hindered the synergistic effect observed upon treatment with nilotinib and MKC-8866. In conclusion, the identified combined action of nilotinib and MKC-8866 might represent a successful therapeutic strategy in high-risk Ph + ALL.
    DOI:  https://doi.org/10.1093/carcin/bgaa095
  2. iScience. 2020 Aug 25. pii: S2589-0042(20)30695-7. [Epub ahead of print]23(9): 101503
    Zhang K, Liu H, Song Z, Jiang Y, Kim H, Samavati L, Nguyen HM, Yang ZQ.
      Dysregulation of inositol-requiring enzyme 1 (IRE1), the primary transducer of Unfolded Protein Response (UPR), has been observed in tumor initiation and progression, but the underlying mechanism remains to be further elucidated. In this study, we identified that the IRE1 gene is frequently amplified and over-expressed in aggressive luminal B breast cancer cells and that IRE1 upregulation is significantly associated with worse overall survival of patients with breast cancer. IRE1 processes and mediates degradation of a subset of tumor suppressor microRNAs (miRNAs), including miR-3607, miR-374a, and miR-96, via a mechanism called Regulated IRE1-Dependent Decay (RIDD). IRE1-dependent degradation of tumor suppressor miR-3607 leads to elevation of RAS oncogene GTPase RAB3B in breast cancer cells. Inhibition of IRE1 endoribonuclease activity with the pharmacological compound 4μ8C or genetic approaches effectively suppresses luminal breast cancer cell proliferation and aggressive cancer phenotypes. Our work revealed the IRE1-RIDD-miRNAs pathway that promotes malignancy of luminal breast cancer.
    Keywords:  Bioinformatics; Cancer; Molecular Mechanism of Gene Regulation
    DOI:  https://doi.org/10.1016/j.isci.2020.101503
  3. Cell Rep. 2020 Sep 08. pii: S2211-1247(20)31114-1. [Epub ahead of print]32(10): 108125
    Burkewitz K, Feng G, Dutta S, Kelley CA, Steinbaugh M, Cram EJ, Mair WB.
      Individually, dysfunction of both the endoplasmic reticulum (ER) and mitochondria has been linked to aging, but how communication between these organelles might be targeted to promote longevity is unclear. Here, we provide evidence that, in Caenorhabditis elegans, inhibition of the conserved unfolded protein response (UPRER) mediator, activating transcription factor (atf)-6, increases lifespan by modulating calcium homeostasis and signaling to mitochondria. Atf-6 loss confers longevity via downregulation of the ER calcium buffer, calreticulin. ER calcium release via the inositol triphosphate receptor (IP3R/itr-1) is required for longevity, while IP3R/itr-1 gain of function is sufficient to extend lifespan. Highlighting coordination between organelles, the mitochondrial calcium import channel mcu-1 is also required for atf-6 longevity. IP3R inhibition leads to impaired mitochondrial bioenergetics and hyperfusion, which is sufficient to suppress long life in atf-6 mutants. This study reveals the importance of organellar calcium handling as a critical output for the UPRER in determining the quality of aging.
    Keywords:  InsP3R; UPR; aging; calreticulin; interorganelle communication; longevity
    DOI:  https://doi.org/10.1016/j.celrep.2020.108125
  4. Am J Respir Cell Mol Biol. 2020 Sep 11.
    Dastghaib S, Kumar PS, Aftabi S, Damera G, Dalvand A, Sepanjnia A, Kiumarsi M, Aghanoori MR, Sohal SS, Ande SR, Alizadeh J, Mokarram P, Ghavami S, Sharma P, Zeki AA.
      Lung cells are constantly exposed to various internal and external stressors that disrupt protein homeostasis. To cope with these stimuli, cells evoke a highly conserved adaptive mechanism called the unfolded protein response (UPR). UPR stressors can impose greater protein secretory demands on the endoplasmic reticulum (ER) resulting in the development, differentiation, and survival of these cell types to meet these increasing functional needs. Dysregulation of the UPR leads to the development of the disease. The UPR and ER stress are involved in several human conditions such as chronic inflammation, neurodegeneration, metabolic syndrome, and cancer. Further, potent and specific compounds that target the UPR pathway are under development as future therapies. The focus of this review is to thoroughly describe the effects of both internal and external stressors on the ER in asthma. Further, we discuss how the UPR signaling pathway is activated in the lungs to overcome cellular damage. We also present an overview of the pathogenic mechanisms with a brief focus on potential strategies for pharmacological interventions.
    Keywords:  Asthma; ER stress; Endoplasmic Reticulum (ER); Unfolded Protein Response
    DOI:  https://doi.org/10.1165/rcmb.2019-0235TR
  5. Front Mol Neurosci. 2020 ;13 138
    Govindarajulu M, Pinky PD, Steinke I, Bloemer J, Ramesh S, Kariharan T, Rella RT, Bhattacharya S, Dhanasekaran M, Suppiramaniam V, Amin RH.
      Dysbiosis of gut microbiota is strongly associated with metabolic diseases including diabetes mellitus, obesity, and cardiovascular disease. Recent studies indicate that Trimethylamine N-oxide (TMAO), a gut microbe-dependent metabolite is implicated in the development of age-related cognitive decline. However, the mechanisms of the impact of TMAO on neuronal function has not been elucidated. In the current study, we investigated the relationship between TMAO and deficits in synaptic plasticity in an Alzheimer's model (3×Tg-AD) and insulin resistance (Leptin deficient db/db) mouse by measuring plasma and brain levels of TMAO. We observed increased TMAO levels in the plasma and brain of both db/db and 3×Tg-AD mice in comparison to wild-type mice. Besides, TMAO levels further increased as mice progressed in age. Deficits in synaptic plasticity, in the form of reduced long-term potentiation (LTP), were noted in both groups of mice in comparison to wild-type mice. To further explore the impact of TMAO on neuronal function, we utilized an ex-vivo model by incubating wild-type hippocampal brain slices with TMAO and found impaired synaptic transmission. We observed that TMAO induced the PERK-EIF2α-ER stress signaling axis in TMAO treated ex-vivo slices as well as in both db/db and 3×Tg-AD mice. Lastly, we also observed altered presynaptic and reduced postsynaptic receptor expression. Our findings suggest that TMAO may induce deficits in synaptic plasticity through the ER stress-mediated PERK signaling pathway. Our results offer novel insight into the mechanism by which TMAO may induce cognitive deficits by promoting ER stress and identifies potential targets for therapeutic intervention.
    Keywords:  Alzheimer’s disease; dysbiosis; endoplasmic reticulum stress (ER stress); insulin resistance; long-term potentiation (LTP); synaptic plasticity; trimethylamine N-oxide (TMAO)
    DOI:  https://doi.org/10.3389/fnmol.2020.00138
  6. FEBS J. 2020 Sep 07.
    Doerflinger M, Reljic B, Menassa J, Nedeva C, Jose I, Faou P, Mackiewicz L, Mansell A, Pellegrini M, Hotchkiss R, Puthalakath H.
      Sepsis remains to be a major contributor to mortality in ICUs and immune suppression caused by immune cell apoptosis determines the overall patient survival. However, diagnosis of sepsis-induced lymphopenia remains problematic with no accurate prognostic techniques or biomarkers for cell death available. Developing reliable prognostic tools for sepsis-mediated cell death is not only important for identifying patients at increased risk of immune suppression but also to monitor treatment progress of currently trialed immunotherapy strategies. We have previously shown an important role for endoplasmic reticulum stress (ER stress) in inducing sepsis-mediated cell death and here report on the identification of a secreted form of the ER chaperone BiP (Immunoglobulin Binding Protein) as a novel circulating prognostic biomarker for immune cell death and ER stress during sepsis. Using biochemical purification and mass spectrometry coupled with an established in vitro sepsis cell death assay, we identified BiP/Grp78 as a factor secreted by LPS-activated macrophages that is capable of inducing cell death in target cells. Quantitative ELISA analysis showed significantly elevated levels of circulating BiP in mice undergoing polymicrobial sepsis, which was absent in Bim-/- mice that are protected from sepsis-induced lymphopenia. Using blood serum from human sepsis patients, we could detect a significant difference in levels of secreted BiP in sepsis patients compared to non-septic controls, suggesting that secreted circulating BiP could indeed be used as a prognostic marker that is directly correlative to immune cell death during sepsis.
    Keywords:  BiP; ER stress; Sepsis; biomarker; cell death; immunosuppression
    DOI:  https://doi.org/10.1111/febs.15552
  7. FEBS J. 2020 Sep 05.
    Girardin SE, Cuziol C, Philpott DJ, Arnoult D.
      The integrated stress response (ISR) is an evolutionary conserved stress response pathway that leads to a global arrest in translation as well as to the expression of specific genes, such as the transcription factor ATF4, to promote cellular recovery. The central nexus of this pathway is the phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2α) by one of the four eIF2α kinases that sense specific cellular stressors. The heme-regulated inhibitor (HRI) is one of these kinases and it was initially reported to be activated in response to heme deprivation. Nevertheless, further studies have established that cytosolic proteotoxicity, resulting from oxidative or osmotic stress, heat shock and proteasome inhibition, is the predominant trigger for HRI to induce the ISR. In this review, we present newly identified functions of HRI in innate immunity, proteostasis and mitochondrial stress. Indeed, HRI-mediated signaling defines a novel cytosolic unfolded protein response (cUPR) required for the proper formation of some innate immune signalosomes and the control of toxic protein aggregates, and this eIF2α kinase also serves as a relay for mitonuclear communication after a mitochondrial stress.
    Keywords:  HRI; ISR; innate immunity; mitochondrial stress; proteostasis
    DOI:  https://doi.org/10.1111/febs.15553
  8. FASEB J. 2020 Sep 12.
    Lu J, Shen H, Li Q, Xiong F, Xie R, Yuan M, Yang JK.
      Adult patients with dysfunction in human ether-a-go-go 2 (hERG2) protein, encoded by KCNH6, present with hypoinsulinemia and hyperglycemia. However, the mechanism of KCNH6 action in glucose disorders has not been clearly defined. Previous studies identified that sustained endoplasmic reticulum (ER) stress-mediated apoptosis of pancreatic β-cells and directly contributed to diabetes. In the present study, we showed that Kcnh6 knockout (KO) mice had impaired glucose tolerance mediated by high ER stress levels, and showed increased apoptosis and elevated intracellular calcium levels in pancreatic β-cells. In contrast, KCNH6 overexpression in islets isolated from C57BL/6J mice attenuated ER stress induced by thapsigargin or palmitic acid. This effect contributed to better preservation of β-cells, as reflected in increased β cell survival and enhanced glucose-stimulated insulin secretion. These results were further corroborated by studies evaluating KCNH6 overexpression in KO islets. Similarly, induction of Kcnh6 in KO mice by lentivirus injection improved glucose tolerance by reducing pancreatic ER stress and apoptosis. Our data provide new insights into how Kcnh6 deficiency causes ER calcium depletion and β cell dysfunction.
    Keywords:  KCNH6; apoptosis; endoplasmic reticulum stress; insulin; pancreatic β-cells
    DOI:  https://doi.org/10.1096/fj.202001218R
  9. J Cell Biol. 2020 Oct 05. pii: e202006111. [Epub ahead of print]219(10):
    Becuwe M, Bond LM, Pinto AFM, Boland S, Mejhert N, Elliott SD, Cicconet M, Graham MM, Liu XN, Ilkayeva O, Saghatelian A, Walther TC, Farese RV.
      The endoplasmic reticulum is a cellular hub of lipid metabolism, coordinating lipid synthesis with continuous changes in metabolic flux. Maintaining ER lipid homeostasis despite these fluctuations is crucial to cell function and viability. Here, we identify a novel mechanism that is crucial for normal ER lipid metabolism and protects the ER from dysfunction. We identify the molecular function of the evolutionarily conserved ER protein FIT2 as a fatty acyl-coenzyme A (CoA) diphosphatase that hydrolyzes fatty acyl-CoA to yield acyl 4'-phosphopantetheine. This activity of FIT2, which is predicted to be active in the ER lumen, is required in yeast and mammalian cells for maintaining ER structure, protecting against ER stress, and enabling normal lipid storage in lipid droplets. Our findings thus solve the long-standing mystery of the molecular function of FIT2 and highlight the maintenance of optimal fatty acyl-CoA levels as key to ER homeostasis.
    DOI:  https://doi.org/10.1083/jcb.202006111
  10. Am J Cancer Res. 2020 ;10(8): 2621-2634
    Chou CW, Yang RY, Chan LC, Li CF, Sun L, Lee HH, Lee PC, Sher YP, Ying H, Hung MC.
      The immune checkpoint blockade therapy has emerged as encouraging treatment strategies in various cancer types. Anti-PD-L1 (programmed death-ligand 1) antibodies have been approved for triple-negative breast cancer, however the response rate yet to be optimized. It would be imperative to further understand and investigate the molecular mechanisms of PD-L1 regulation. Here, we identified glucose regulatory protein 78 (GRP78), a major endoplasmic reticulum (ER) stress responding protein, as a novel binding partner of PD-L1. GRP78 interacts with PD-L1 at the ER region and increases PD-L1 levels via regulating its stability. ER stress, triggered by different stimuli such as conventional chemotherapy, leads to the induction of PD-L1 in a GRP78-dependent manner. We showed that GRP78 modulates the response to chemotherapy, and dual-high levels of GRP78 and PD-L1 correlates with poor relapse-free survival in triple-negative breast cancer. Altogether, our study provides novel molecular insights into the regulatory mechanism of PD-L1 by revealing its interaction with GRP78, and offers a rationale to target GRP78 as a potential therapeutic strategy to enhance anti-tumor immunity.
    Keywords:  ER stress; GRP78; PD-L1; Triple-negative breast cancer
  11. iScience. 2020 Aug 21. pii: S2589-0042(20)30685-4. [Epub ahead of print]23(9): 101493
    Neal S, Syau D, Nejatfard A, Nadeau S, Hampton RY.
      ER-associated degradation (ERAD) targets misfolded ER proteins for degradation. Retrotranslocation, a key feature of ERAD, entails removal of ubiquitinated substrates into the cytosol for proteasomal destruction. Recently, it has been shown that the Hrd1 E3 ligase forms a retrotranslocation channel for luminal (ERAD-L) substrates. Conversely, our studies found that integral membrane (ERAD-M) substrates exit the ER through a distinct pathway mediated by the Dfm1 rhomboid protein. Those studies also revealed a second, Hrd1-dependent pathway of ERAD-M retrotranslocation can arise in dfm1Δ null. Here we show that, in the dfm1Δ null, the HRD complex undergoes remodeling to a form that mediates ERAD-M retrotranslocation. Specifically, Hrd1's normally present stochiometric partner Hrd3 is efficiently removed during suppressive remodeling, allowing Hrd1 to function in this novel capacity. Neither Hrd1 autoubiquitination nor its cytosolic domain is required for suppressive ERAD-M retrotranslocation. Thus, the HRD complex displays remarkable functional flexibility in response to ER stress.
    Keywords:  Biological Sciences; Cell Biology; Molecular Biology
    DOI:  https://doi.org/10.1016/j.isci.2020.101493
  12. FASEB J. 2020 Sep 06.
    He P, Mann-Collura O, Fling J, Edara N, Hetz R, Razzaque MS.
      Inorganic phosphate (Pi) is an essential nutrient for human health. Due to the changes in our dietary pattern, dietary Pi overload engenders systemic phosphotoxicity, including excessive Pi-related vascular calcification and chronic tissue injury. The molecular mechanisms of the seemingly distinct phenotypes remain elusive. In this study, we investigated Pi-mediated cellular response in HEK293 and HeLa cells. We found that abnormally high Pi directly mediates diverse cellular toxicity in a dose-dependent manner. Up to 10 mM extracellular Pi promotes cell proliferation by activating AKT signaling cascades and augmenting cell cycle progression. By introducing additional Pi, higher than the concentration of 40 mM, we observed significant cell damage caused by the interwoven Pi-related biological processes. Elevated Pi activates mitogen-activated protein kinase (MAPK) signaling, encompassing extracellular signal-regulated kinase 1/2 (ERK1/2), p38 and Jun amino-terminal kinase (JNK), which consequently potentiates Pi triggered lethal epithelial-mesenchymal transition (EMT). Synergistically, high Pi-caused endoplasmic reticulum (ER) stress also contributes to apparent apoptosis. To counteract, Pi-activated AKT signaling promotes cell survival by activating the mammalian target of rapamycin (mTOR) signaling and blocking ER stress. Pharmacologically or genetically abrogating Pi transport, the impact of high Pi-induced cytotoxicity could be reduced. Taken together, abnormally high extracellular Pi results in a broad spectrum of toxicity by rewiring complicated signaling networks that control cell growth, cell death, and homeostasis.
    Keywords:  EMT; ER stress; MAPK; apoptosis; cytotoxicity; phosphate
    DOI:  https://doi.org/10.1096/fj.202000799RR
  13. Cells. 2020 Sep 08. pii: E2052. [Epub ahead of print]9(9):
    Lin WL, Hung JH, Huang W.
      Hepatitis B is the most prevalent viral hepatitis worldwide, affecting approximately one-third of the world's population. Among HBV factors, the surface protein is the most sensitive biomarker for viral infection, given that it is expressed at high levels in all viral infection phases. The large HBV surface protein (LHBs) contains the integral pre-S1 domain, which binds to the HBV receptor sodium taurocholate co transporting polypeptide on the hepatocyte to facilitate viral entry. The accumulation of viral LHBs and its prevalent pre-S mutants in chronic HBV carriers triggers a sustained endoplasmic reticulum (ER) overload response, leading to ER stress-mediated cell proliferation, metabolic switching and genomic instability, which are associated with pro-oncogenic effects. Ground glass hepatocytes identified in HBV-related hepatocellular carcinoma (HCC) patients harbor pre-S deletion variants that largely accumulate in the ER lumen due to mutation-induced protein misfolding and are associated with increased risks of cancer recurrence and metastasis. Moreover, in contrast to the major HBs, which is decreased in tumors to a greater extent than it is in peritumorous regions, LHBs is continuously expressed during tumorigenesis, indicating that LHBs serves as a promising biomarker for HCC in people with CHB. Continuing efforts to delineate the molecular mechanisms by which LHBs regulates pathological changes in CHB patients are important for establishing a correlation between LHBs biomarkers and HCC development.
    Keywords:  endoplasmic reticulum; ground glass hepatocyte; hepatitis B virus; hepatocellular carcinoma; large surface protein; pre-S deletion; sodium taurocholate cotransporting polypeptide; viral entry
    DOI:  https://doi.org/10.3390/cells9092052
  14. Neurochem Int. 2020 Sep 05. pii: S0197-0186(20)30216-3. [Epub ahead of print] 104825
    Cui Y, Wen X, Nan Y, Xiang G, Wei Z, Wei L, Xia Y, Li Q.
      PTEN-induced putative kinase 1 (PINK1) mutation induces autosomal recessive Parkinson's Disease (PD), mitochondrial dysfunction is the central pathogenic process. However, more and more studies presented the bulk of the damage to neurons with mitochondrial dysfunction stems from the endoplasmic reticulum (ER) stress. In mitochondria damaged PINK1B9 fly model how protein kinase RNA-like ER kinase (PERK) arm of ER stress functions remains a mystery. Thus, we generated both PERK overexpressed (PEK OE) and down expressed (PEK RNAi) PINK1B9 flies and monitored their motor activity. We found PEK OE decreased the abnormal wing posture rate and rescued PINK1B9 flies' motor activity. Furthermore, we observed the increased number of dopaminergic neurons of protocerebral posterior lateral 1 (PPL1) and the tyrosine hydroxylase (TH) protein levels in PINK1B9 flies. When testing the mitochondrial morphology in flight muscle with TEM, we found that the shape of the mitochondria became normal. The ATP levels of flight muscle tissues were significantly elevated in PEK OE PINK1B9 flies with the increased function of mitochondrial Electron Transport Chain (ETC) Complex I (CI) but not Complex Ⅱ (CⅡ) which is further confirmed by oxygen consumption experiments, Western Blot, and RT-PCR to examine the corresponding subunits. We suggest that overexpression of PERK can rescue PINK1B9 PD flies' pathogenic phenotypes and it is linked with the improved mitochondrial function especially CI of ETC but not CⅡ. Our findings may pave a way for the target of the drug for alleviating the suffering of PINK1 mutant autosomal recessive PD patients.
    Keywords:  Drosophila; PERK; PINK1; Parkinson’s disease; mitochondria
    DOI:  https://doi.org/10.1016/j.neuint.2020.104825