bims-unfpre Biomed news
on Unfolded protein response
Issue of 2019‒01‒06
twelve papers selected by
Susan Logue
Apoptosis Research Centre

  1. J Biol Chem. 2019 Jan 04. pii: jbc.RA118.005761. [Epub ahead of print]
    Liu Z, Li C, Kang N, Malhi H, Shah VH, Maiers JL.
      Transforming growth factor β (TGFβ) potently activates hepatic stellate cells (HSCs), which promotes production and secretion of extracellular matrix (ECM) proteins and hepatic fibrogenesis. Increased ECM synthesis and secretion in response to TGFβ is associated with endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). TGFβ and UPR signaling pathways are tightly intertwined during HSC activation, but the regulatory mechanism that connects these two pathways is poorly understood. Here, we found that TGFβ treatment of immortalized HSCs (i.e. LX-2 cells) induces phosphorylation of the UPR sensor inositol-requiring enzyme 1α (IRE1α) in a SMAD2/3-procollagen I-dependent manner. We further show that IRE1α mediates HSC activation downstream of TGFβ and that its role depends on activation of a signaling cascade involving apoptosis signaling kinase 1 (ASK1) and c-Jun N-terminal Kinase (JNK). ASK1-JNK signaling promoted phosphorylation of the UPR-associated transcription factor CCAAT/enhancer binding protein β (c/EBPβ), which is crucial for TGFβ- or IRE1α-mediated LX-2 activation. Pharmacological inhibition of c/EBPβ expression with the antiviral drug adefovir dipivoxil attenuated TGFβ-mediated activation of LX-2 or primary rat HSCs in vitro and hepatic fibrogenesis in vivo. Finally, we identified a critical relationship between c/EBPβ and the transcriptional regulator p300 during HSC activation. p300 knockdown disrupted TGFβ- or UPR-induced HSC activation, and pharmacological inhibition of the c/EBPβ-p300 complex decreased TGFβ-induced HSC activation. These results indicate that TGFβ-induced IRE1α signaling is critical for HSC activation through a c/EBPβ-p300-dependent mechanism and suggest c/EBPβ as a druggable target for managing fibrosis.
    Keywords:  IRE1α; adefovir divipoxil; apoptosis signal-regulating kinase 1 (ASK1); c-Jun N-terminal kinase (JNK); c/EBPβ; cell signaling; collagen; endoplasmic reticulum stress (ER stress); fibronectin; fibrosis; p300
  2. Toxicology. 2018 Dec 31. pii: S0300-483X(18)30320-2. [Epub ahead of print]
    Yuan Y, Yang J, Chen J, Zhao S, Wang T, Zou H, Wang Y, Gu J, Liu X, Bian J, Liu Z.
      The heavy metal cadmium (Cd) is well known to be neurotoxic. Studies have shown that apoptosis plays an essential role in Cd-induced brain injury; however, the mechanisms underlying this injury accompanied by apoptosis have yet to be elucidated. The endoplasmic reticulum (ER) stress plays a key part in the regulation of apoptosis. ER stress is defined as accumulation of unfolded or misfolded proteins in the ER. Here, we demonstrated the role of ER stress on Cd-evoked apoptosis in neuronal cells, as well as the neuroprotective effects of the antioxidant alpha-lipoic acid (α-LA) on Cd-induced ER stress and neuronal injury. In vitro, we observed that Cd activated ER associated proteins via the eIF2α-ATF4 pathway in primary rat cerebral cortical neurons. Furthermore, the ER-stress inhibitor salubrinal blocked the dephosphorylation of eukaryotic translation initiation factor 2α (eIF2α) and significantly reduced the induction of ER stress marker CHOP, the increase of the B-cell lymphoma-2 associate X protein (Bax)/B-cell lymphoma-2 (Bcl-2) ratio, and apoptosis induced by Cd. In addition, Z-ATAD-FMK (a caspase-12 inhibitor) counteracted the Cd-induced activation of caspase-12 and -3, and apoptosis. These in vitro results collectively suggested that ER stress was required for Cd-induced neuronal apoptosis. Importantly, α-LA inhibited the activation of the ER stress eIF2α-ATF4 pathway, the increase of the Bax/Bcl-2 ratio, the activation of caspase-12 and -3, and the apoptosis induced by Cd. In vivo, we also found that the administration of α-LA alleviated Cd-induced neuronal injury, inhibited the activation of the ER stress eIF2α-ATF4 pathway, restored the Bax/Bcl-2 ratio, and prevented the activation of caspase-12 and -3. Taken together, our results demonstrated that Cd triggered protein changes in the ER accompanied by apoptosis via the eIF2α-ATF4 signaling pathway in the neuronal cells of rats, both in vitro and in vivo. Furthermore, we demonstrated for the first time that α-LA protected neurons from Cd-induced injury partly by inhibiting ER stress in rat cerebral cortical neurons.
    Keywords:  Cadmium; alpha-lipoic acid; apoptosis; eIF2α-ATF4 pathway; endoplasmic reticulum stress; rat cerebral cortical neurons
  3. Am J Hum Genet. 2019 Jan 03. pii: S0002-9297(18)30451-8. [Epub ahead of print]104(1): 179-185
    Edvardson S, Nicolae CM, Noh GJ, Burton JE, Punzi G, Shaag A, Bischetsrieder J, De Grassi A, Pierri CL, Elpeleg O, Moldovan GL.
      Accumulation of unfolded proteins in the endoplasmic reticulum (ER) initiates a stress response mechanism to clear out the unfolded proteins by either facilitating their re-folding or inducing their degradation. When this fails, an apoptotic cascade is initiated so that the affected cell is eliminated. IRE1α is a critical sensor of the unfolded-protein response, essential for initiating the apoptotic signaling. Here, we report an infantile neurodegenerative disorder associated with enhanced activation of IRE1α and increased apoptosis. Three unrelated affected individuals with congenital microcephaly, infantile epileptic encephalopathy, and profound developmental delay were found to carry heterozygous variants (c.932T>C [p.Leu311Ser] or c.935T>C [p.Leu312Pro]) in RNF13, which codes for an IRE1α-interacting protein. Structural modeling predicted that the variants, located on the surface of the protein, would not alter overall protein folding. Accordingly, the abundance of RNF13 and IRE1α was not altered in affected individuals' cells. However, both IRE1α-mediated stress signaling and stress-induced apoptosis were increased in affected individuals' cells. These results indicate that the RNF13 variants confer gain of function to the encoded protein and thereby lead to altered signaling of the ER stress response associated with severe neurodegeneration in infancy.
    Keywords:  ER stress; RNF13; XBP1 splicing; epilepsy; microcephaly
  4. Cell Stress Chaperones. 2019 Jan 02.
    Martínez-Puente DH, Pérez-Trujillo JJ, Gutiérrez-Puente Y, Rodríguez-Rocha H, García-García A, Saucedo-Cárdenas O, Montes-de-Oca-Luna R, Loera-Arias MJ.
      Very promising results have been observed with a deoxyribonucleic acid (DNA) vaccine based on human papillomavirus type-16 (HPV-16) antigen retention and delivery system in the endoplasmic reticulum (ER). However, the mechanism by which these antigens are processed once they reach this organelle is still unknown. Therefore, we evaluated whether this system awakens a stress response in the ER. Different DNA constructs based on E6 and E7 mutant antigens fused to an ER signal peptide (SP), a signal for retention in the ER (KDEL), or both signals (SPK), were transfected into HEK-293 cells. Overexpression of E6 and E7 antigens targeted to the ER (SP, and SPK constructs) induced ER stress, which was indicated by an increase of the ER-stress markers GRP78/BiP and CHOP. Additionally, the ER stress response was mediated by the ATF4 transcription factor, which was translocated into the nucleus. Besides, the overexpressed antigens were degraded by the proteasome. Through a cycloheximide-chase assay, we demonstrated that when both protein synthesis and proteasome were inhibited, the overexpressed antigens were degraded. Interestingly, when proteasome was blocked autophagy was increased and the ER stress response decreased. Taken together, these results indicate that the antigens are initially degraded by the ERAD pathway, and autophagy degradation pathway can be induced to compensate the proteasome inhibition. Therefore, we provided a new insight into the mechanism by which E6 and E7 mutant antigens are processed once they reach the ER, which will help to improve the development of more effective vaccines against cancer.
    Keywords:  E7; ER targeting; GRP78/BiP; KDEL signal; Signal peptide; Stress response
  5. Biol Pharm Bull. 2019 ;42(1): 94-102
    Park E, Gim J, Kim DK, Kim CS, Chun HS.
      Glutamate-mediated cytotoxicity has been implicated in the pathogenesis of neurological diseases, including Parkinson's disease, Alzheimer's disease, and stroke. In this study, we investigated the protective effects of alpha-lipoic acid (ALA), a naturally occurring thiol antioxidant, on glutamate-induced cytotoxicity in cultured C6 astroglial cells. Exposure to high-dose glutamate (10 mM) caused oxidative stress and mitochondrial dysfunction through the elevation of reactive oxygen species, depletion of glutathione, and loss of the mitochondrial membrane potential (ΔΨm). Pretreatment with ALA (200 µM), however, significantly inhibited the glutamate-induced oxidative stress and mitochondrial dysfunction. ALA pretreatment dose-dependently suppressed glutamate-induced apoptotic events including altered nuclear morphology and activation of caspase-3. In addition, ALA significantly attenuated glutamate-induced endoplasmic reticulum (ER) stress markers; namely, glucose-regulated protein 78 (GRP78), activating transcription factor 6 (ATF6), protein kinase regulated by RNA (PKR)-like ER-associated kinase (PERK), eukaryotic translation initiation factor 2 alpha (eIF2α), inositol-requiring enzyme 1 (IRE1), CCAAT/enhancer binding protein homologous protein (CHOP), and caspase-12. We confirmed that CHOP and caspase-12 are key mediators of glutamate-induced ER stress. Furthermore, exposure of the cells to a caspase-12-specific inhibitor and CHOP small interfering RNAs (siRNAs) led to restoration of the ΔΨm that was damaged by glutamate treatment. These results suggest that ALA can effectively suppress oxidative stress, mitochondrial dysfunction, and ER stress in astroglial cells.
    Keywords:  alpha-lipoic acid; apoptosis; glutamate; mitochondrial dysfunction
  6. J Breast Cancer. 2018 Dec;21(4): 354-362
    Han CC, Wan FS.
      Cellular stress severely disrupts endoplasmic reticulum (ER) function, leading to the abnormal accumulation of unfolded or misfolded proteins in the ER and subsequent development of endoplasmic reticulum stress (ERS). To accommodate the occurrence of ERS, cells have evolved a highly conserved, self-protecting signal transduction pathway called the unfolded protein response. Notably, ERS signaling is involved in the development of a variety of diseases and is closely related to tumor development, particularly in breast cancer. This review discusses recent research regarding associations between ERS and tumor metastasis. The information presented here will help researchers elucidate the precise mechanisms underlying ERS-mediated tumor metastasis and provide new directions for tumor therapies.
    Keywords:  Breast neoplasms; Endoplasmic reticulum stress; Neoplasm metastasis; Unfolded protein response
  7. Biochem Biophys Res Commun. 2018 Dec 26. pii: S0006-291X(18)32757-8. [Epub ahead of print]
    Xia S, Wang J, Kalionis B, Zhang W, Zhao Y.
      Acute pancreatitis (AP) is a severe and frequently lethal disorder, but the precise mechanisms are not well understood and there is lack of effective drugs. Therefore, our study examined the in vivo intervention effects of genistein and elucidated its mechanism in acute experimental pancreatitis models. We used cerulein or taurocholate to induce acute pancreatitis (AP) in Sprague-Dawley rats with prior genistein treatment. Histological examination of the pancreas was performed and the expression of unfolded protein response (UPR) components and apoptotic mediators like caspase 12 and c-Jun N-terminal protein kinase (JNK) were measured. The amount of apoptosis in pancreatic acinar cells was also determined. Our studies found that the severity of cerulein- or taurocholate-induced AP was rescued by prior genistein treatment. Genistein stimulated the activation of multiple endoplasmic reticulum (ER) stress-related regulators like GRP78, PERK, eIF2α, and upregulated the expression of the apoptotic genes, caspase 12 and CHOP. Moreover, TUNEL assays showed that genistein treatment promoted acinar cell apoptosis. Taken together, we speculated that ER stress-associated apoptotic pathways in AP are induced by genistein, which showed cytoprotective capacity in the exocrine pancreas. These data suggest novel therapeutic strategies that employ genistein in the prevention of AP.
    Keywords:  Acute pancreatitis; Apoptosis; Endoplasmic reticulum; Genistein
  8. Mol Cell. 2018 Dec 04. pii: S1097-2765(18)30983-3. [Epub ahead of print]
    Cagnetta R, Wong HH, Frese CK, Mallucci GR, Krijgsveld J, Holt CE.
      Local translation is rapidly regulated by extrinsic signals during neural wiring, but its control mechanisms remain elusive. Here we show that the extracellular cue Sema3A induces an initial burst in local translation that precisely controls phosphorylation of the translation initiation factor eIF2α via the unfolded protein response (UPR) kinase PERK. Strikingly, in contrast to canonical UPR signaling, Sema3A-induced eIF2α phosphorylation bypasses global translational repression and underlies an increase in local translation through differential activity of eIF2B mediated by protein phosphatase 1. Ultrasensitive proteomics analysis of axons reveals 75 proteins translationally controlled via the Sema3A-p-eIF2α pathway. These include proteostasis- and actin cytoskeleton-related proteins but not canonical stress markers. Finally, we show that PERK signaling is needed for directional axon migration and visual pathway development in vivo. Thus, our findings reveal a noncanonical eIF2 signaling pathway that controls selective changes in axon translation and is required for neural wiring.
    Keywords:  PERK; Sema3A; axon; axon branching; axon guidance; eIF2B; eIF2α; local translation; retinal ganglion cell; unfolded protein response
  9. J Cell Mol Med. 2019 Jan 04.
    Yin C, Dai X, Huang X, Zhu W, Chen X, Zhou Q, Wang C, Zhao C, Zou P, Liang G, Rajamanickam V, Wang O, Zhang X, Cui R.
      Triple-negative breast cancer (TNBC) is a subtype of breast cancer with poor clinical outcome and currently no effective targeted therapies are available. Alantolactone (ATL), a sesquiterpene lactone, has been shown to have potential anti-tumour activity against various cancer cells. However, the underlying mechanism and therapeutic effect of ATL in the TNBC are largely unknown. In the present study, we found that ATL suppresses TNBC cell viability by reactive oxygen species (ROS) accumulation and subsequent ROS-dependent endoplasmic reticulum (ER) stress both in vitro and in vivo. Thioredoxin reductase 1 (TrxR1) expression and activity of were significantly up-regulated in the TNBC tissue specimens compare to the normal adjacent tissues. Further analyses showed that ATL inhibits the activity of TrxR1 both in vitro and in vivo in TNBC and knockdown of TrxR1 in TNBC cells sensitized ATL-induced cell apoptosis and ROS increase. These results will provide pre-clinical evidences that ATL could be a potential therapeutic agent against TNBC by promoting ROS-ER stress-mediated apoptosis through partly targeting TrxR1.
    Keywords:  ER-stress; ROS; Triple-negative breast cancer; TrxR1; alantolactone
  10. Carcinogenesis. 2018 Dec 28.
    Direito I, Fardilha M, Helguero LA.
      Resistant Breast and Prostate cancer remain a major clinical problem and new therapeutic approaches and better predictors of therapeutic response are clearly needed. Due to the involvement of the Unfolded Protein Response (UPR) in cell proliferation and apoptosis evasion, an increasing number of publications support the hypothesis that impairments in this network trigger and/or exacerbate cancer. Moreover, UPR activation could contribute to the development of drug-resistance phenotypes in both breast and prostate cancers. Therefore, targeting this pathway has recently emerged as a promising strategy in anti-cancer therapy. This review addresses the contribution of UPR to breast and prostate tissues homeostasis and its significance to cancer endocrine response with focus on the current progress on UPR research related to cancer biology, detection, prognosis and treatment are also discussed.
  11. Cell Immunol. 2018 Dec 21. pii: S0008-8749(18)30389-7. [Epub ahead of print]
    Yang F, Liu Y, Ren H, Zhou G, Yuan X, Shi X.
      During the process of NAFLD progression, ER-stress is activated in macrophages and induces the pro-inflammatory polarization of macrophage. As one of the three ER membrane resident proteins, pancreatic eIF-2alpha kinase (PERK) plays an important role in ER stress, but its participation in macrophage polarization is largely unknown. In this study, we found that the PA mediated ER-stress activation could induce M1-type polarization in macrophages, and this phenotype polarization could be inhibited by ER-stress inhibitor 4-PBA as well as GSK2656157, an inhibitor of PERK. Moreover, the knockdown of PERK altered the STAT1 and STAT6 pathways in macrophages, which then led to the M1-to-M2 phenotypic shift. In summary, we found that PERK could regulate the phenotypic polarization of macrophages. This finding may provide new insight into the suppression of pathological progression of fatty liver or liver ischemia reperfusion injury induced by M1-type macrophages.
    Keywords:  ER-stress; Macrophage; PERK; Phenotypes polarization
  12. Biochem Biophys Res Commun. 2018 Dec 26. pii: S0006-291X(18)32759-1. [Epub ahead of print]
    Yi E, Oh J, Kang HR, Song MJ, Park SH.
      BST2 is an antiviral factor that inhibits the release of enveloped virus at the plasma membrane via an unusual topology in which its N-terminal is in the cytosol while its C-terminal is anchored by glycophosphatidylinositol (GPI). BST2-deficient cells showed substantially higher release of virions than wild type cells. Influenza-infected BST2-deficient cells showed greatly reduced cytopathic effect (CPE) than wild type cells despite their generally robust virus production. This finding prompted us to determine whether BST2 was involved in the apoptotic process of virus-infected host cells. Our results revealed that BST2 might be involved in IRE1α-mediated ER stress pathway by increasing spliced form XBP-1. Consequently, levels of cytochrome C, caspase-3, caspase-9, and PARP as representative molecules of apoptosis were significantly increased in wild type cells than those in BST2-deficient cells. These results suggest that BST2 might participate in innate host defense by augmenting ER-stress-induced apoptotic signaling to inhibit the replication and spread of virus.
    Keywords:  Apoptosis; BST2; ER stress; Influenza virus; Tetherin