bims-unfpre Biomed news
on Unfolded protein response
Issue of 2018‒12‒23
fourteen papers selected by
Susan Logue
Apoptosis Research Centre

  1. J Biol Chem. 2018 Dec 18. pii: jbc.REV118.002804. [Epub ahead of print]
    Pobre KFR, Poet GJ, Hendershot LM.
      The endoplasmic reticulum (ER) represents the entry point into the secretory pathway where nascent proteins encounter a specialized environment for their folding and maturation. Inherent to these processes is a dedicated quality-control system that detects proteins that fail to mature properly and targets them for cytosolic degradation. An imbalance in protein folding and degradation can result in the accumulation of unfolded proteins in the ER, resulting in the activation of a signaling cascade that restores proper homeostasis in this organelle. The ER heat shock protein 70 (Hsp70) family member ER chaperone BiP (BiP) is an ATP-dependent chaperone that plays a critical role in these processes. BiP interacts with specific ER-localized DnaJ family members (ERdjs), which stimulate BiP's ATP-dependent substrate interactions, with several ERdjs also binding directly to unfolded protein clients. Recent structural and biochemical studies have provided detailed insights into the allosteric regulation of client binding by BiP and have enhanced our understanding of how specific ERdjs enable BiP to perform its many functions in the ER. In this review, we discuss how BiP's functional cycle and interactions with ERdjs enables it to regulate protein homeostasis in the ER and ensures protein quality control.
    Keywords:  ATPase; BiP; ER-localized DnaJ proteins; GRP78; endoplasmic reticulum (ER); endoplasmic-reticulum-associated protein degradation (ERAD); heat shock protein (HSP); molecular chaperone; protein folding; protein misfolding; stress response; unfolded protein response (UPR)
  2. Sci Rep. 2018 Dec 18. 8(1): 17939
    Delbrel E, Soumare A, Naguez A, Label R, Bernard O, Bruhat A, Fafournoux P, Tremblais G, Marchant D, Gille T, Bernaudin JF, Callard P, Kambouchner M, Martinod E, Valeyre D, Uzunhan Y, Planès C, Boncoeur E.
      Endoplasmic Reticulum (ER) stress of alveolar epithelial cells (AECs) is recognized as a key event of cell dysfunction in pulmonary fibrosis (PF). However, the mechanisms leading to AECs ER stress and ensuing unfolded protein response (UPR) pathways in idiopathic PF (IPF) remain unclear. We hypothesized that alveolar hypoxic microenvironment would generate ER stress and AECs apoptosis through the hypoxia-inducible factor-1α (HIF-1α). Combining ex vivo, in vivo and in vitro experiments, we investigated the effects of hypoxia on the UPR pathways and ER stress-mediated apoptosis, and consecutively the mechanisms linking hypoxia, HIF-1α, UPR and apoptosis. HIF-1α and the pro-apoptotic ER stress marker C/EBP homologous protein (CHOP) were co-expressed in hyperplastic AECs from bleomycin-treated mice and IPF lungs, not in controls. Hypoxic exposure of rat lungs or primary rat AECs induced HIF-1α, CHOP and apoptosis markers expression. In primary AECs, hypoxia activated UPR pathways. Pharmacological ER stress inhibitors and pharmacological inhibition or silencing of HIF-1α both prevented hypoxia-induced upregulation of CHOP and apoptosis. Interestingly, overexpression of HIF-1α in normoxic AECs increased UPR pathways transcription factors activities, and CHOP expression. These results indicate that hypoxia and HIF-1α can trigger ER stress and CHOP-mediated apoptosis in AECs, suggesting their potential contribution to the development of IPF.
  3. Cell Physiol Biochem. 2018 Dec 14. 51(6): 2955-2971
    Song S, Tan J, Miao Y, Sun Z, Zhang Q.
      BACKGROUND/AIMS: Intermittent hypoxia (IH) causes apoptosis in pancreatic β-cells, but the potential mechanisms remain unclear. Endoplasmic reticulum (ER) stress, autophagy, and apoptosis are interlocked in an extensive crosstalk. Thus, this study aimed to investigate the contributions of ER stress and autophagy to IH-induced pancreatic β-cell apoptosis.METHODS: We established animal and cell models of IH, and then inhibited autophagy and ER stress by pharmacology and small interfering RNA (siRNA) in INS-1 cells and rats. The levels of biomarkers for autophagy, ER stress, and apoptosis were evaluated by immunoblotting and immunofluorescence. The number of autophagic vacuoles was observed by transmission electron microscopy.
    RESULTS: IH induced autophagy activation both in vivo and in vitro, as evidenced by increased autophagic vacuole formation and LC3 turnover, and decreased SQSTM1 level. The levels of ER-stress-related proteins, including GRP78, CHOP, caspase 12, phosphorylated (p)-protein kinase RNA-like ER kinase (PERK), p-eIF2α, and activating transcription factor 4 (ATF4) were increased under IH conditions. Inhibition of ER stress with tauroursodeoxycholic acid or 4-phenylbutyrate partially blocked IH-induced autophagy in INS-1 cells. Furthermore, inhibition of PERK with GSK2606414 or siRNA blocked the ERstress-related PERK/eIF2α/ATF4 signaling pathway and inhibited autophagy induced by IH, which indicates that IH-induced autophagy activation is dependent on this signaling pathway. Promoting autophagy with rapamycin alleviated IH-induced apoptosis, whereas inhibition of autophagy with chloroquine or autophagy-related gene (Atg5 and Atg7) siRNA aggravated pancreatic β-cell apoptosis caused by IH.
    CONCLUSION: IH induces autophagy activation through the ER-stress-related PERK/eIF2α/ATF4 signaling pathway, which is a protective response to pancreatic β-cell apoptosis caused by IH.
    Keywords:  Apoptosis; Autophagy; ER stress; Intermittent hypoxia; Pancreatic β-cells
  4. Nat Commun. 2018 12 17. 9(1): 5340
    Govindarajan S, Gaublomme D, Van der Cruyssen R, Verheugen E, Van Gassen S, Saeys Y, Tavernier S, Iwawaki T, Bloch Y, Savvides SN, Lambrecht BN, Janssens S, Elewaut D, Drennan MB.
      Activated invariant natural killer T (iNKT) cells rapidly produce large amounts of cytokines, but how cytokine mRNAs are induced, stabilized and mobilized following iNKT activation is still unclear. Here we show that an endoplasmic reticulum stress sensor, inositol-requiring enzyme 1α (IRE1α), links key cellular processes required for iNKT cell effector functions in specific iNKT subsets, in which TCR-dependent activation of IRE1α is associated with downstream activation of p38 MAPK and the stabilization of preformed cytokine mRNAs. Importantly, genetic deletion of IRE1α in iNKT cells reduces cytokine production and protects mice from oxazolone colitis. We therefore propose that an IRE1α-dependent signaling cascade couples constitutive cytokine mRNA expression to the rapid induction of cytokine secretion and effector functions in activated iNKT cells.
  5. Cells. 2018 Dec 20. pii: E4. [Epub ahead of print]8(1):
    Dong Z, Cui H.
      In normal physiological condition, the maintenance of cellular proteostasis is a prerequisite for cell growth, functioning, adapting to changing micro-environments, and responding to extracellular stress. Cellular proteostasis is maintained by specific proteostasis networks (PNs) to prevent protein misfolding, aggregating, and accumulating in subcellular compartments. Commonly, the PNs are composed of protein synthesis, molecular chaperones, endoplasmic reticulum (ER), unfolded protein response (UPR), stress response pathways (SRPs), secretions, ubiquitin proteasome system (UPS), and autophagy-lysosomal pathways (ALPs). Although great efforts have been made to explore the underlying detailed mechanisms of proteostasis, there are many questions remain to explore, especially in proteostasis regulated by the ALPs. Proteostasis out-off-balance is correlated with various human diseases such as diabetes, stroke, inflammation, hypertension, pulmonary fibrosis, and Alzheimer's disease. , enhanced regulation of PNs is observed in tumors, thereby indicating that proteostasis may play a pivotal role in tumorigenesis and cancer development. Recently, inhibitors targeting the UPS have shown to be failed in solid tumor treatment. However, there is growing evidence showing that the ALPs play important roles in regulation of proteostasis alone or with a crosstalk with other PNs in tumors. In this review, we provide insights into the proteostatic process and how it is regulated by the ALPs, such as macroautophagy, aggrephagy, chaperone-mediated autophagy, microautophagy, as well as mitophagy during tumor development.
    Keywords:  aggregates; aggrephagy; autophagy-lysosomal pathways; chaperones; protein misfolding; proteostasis; proteostasis networks; tumors
  6. Front Pharmacol. 2018 ;9 1423
    Huang Q, Lan T, Lu J, Zhang H, Zhang D, Lou T, Xu P, Ren J, Zhao D, Sun L, Li X, Wang J.
      DiDang Tang (DDT), a Chinese traditional medicine formula, contains 4 Chinese traditional medicine substances, has been widely used to treat intracerebral hemorrhage (ICH) patients. However, the molecular mechanisms of DDT for protecting neurons from oxygen and glucose deprivation (OGD)-induced endoplasmic reticulum (ER) stress and apoptosis after ICH still remains elusive. In this study, high-performance liquid chromatography fingerprint analysis was performed to learn the features of the chemical compositions of DDT. OGD-induced ER stress, Ca2+ overload, and mitochondrial apoptosis were investigated in nerve growth factor -induced PC12, primary neuronal cells, and ICH rats to evaluate the protective effect of DDT. We found that DDT treatment protected neurons against OGD-induced damage and apoptosis by increasing cell viability and reducing the release of lactate dehydrogenase. DDT decreased OGD-induced Ca2+ overload and ER stress through the blockade of the glucose-regulated protein 78 (GRP78)- inositol-requiring protein 1α (IRE1)/ protein kinase RNA-like ER kinase (PERK) pathways and also inhibited apoptosis by decreasing mitochondrial damage. Moreover, we observed similar findings when we studied DDT for inhibition of ER stress in a rat model of ICH. In addition, our experiments further confirmed the neuroprotective potential of DDT against tunicamycin (TM)-induced neural damage. Our in vitro and in vivo results indicated that the neuroprotective effect of DDT against ER stress damage and apoptosis occurred mainly by blocking the GPR78-IRE1/PERK pathways. Taken together, it provides reliable experimental evidence and explains the molecular mechanism of DDT for the treatment of patients with ICH.
    Keywords:  DiDang Tang; GRP78-IRE1/PERK pathways; apoptosis; endoplasmic reticulum stress (ER stress); mitochondrial dysfunction; oxygen and glucose deprivation
  7. J Cell Biochem. 2018 Dec 16.
    Zhang Y, Wu J, Jing H, Huang G, Sun Z, Xu S.
      Long noncoding RNA (lncRNA) maternally expressed 3 (MEG3) has been implicated as a tumor suppressor gene in several human cancer types. However, little is known regarding its involvement and potential mechanism in human breast cancer. In this study, we explored the effect of MEG3 on the growth of human breast cancer cell line MDA-MB-231 in vitro and in vivo, and sought to elucidate the potential signaling mechanisms. Ectopic overexpression of MEG3 using a lentiviral vector Lv-MEG3 significantly inhibited breast cancer cell growth in vitro and a cancer xenograft growth in vivo. MEG3 overexpression led to marked increase of apoptosis in breast cancer cells as determined using flow cytometry and fragmented DNA labeling. Moreover, ectopic expression of MEG3 increased the expression of endoplasmic reticulum (ER) stress-related proteins required for unfolded protein response, including glucose-regulated protein 78 (GRP78), inositol-requiring enzyme 1 (IRE1), protein kinase RNA (PKR)-like ER kinase (PERK), and activated transcription factor 6 (ATF6), as well as proapoptotic proteins CCAAT/enhancer binding protein homologous protein (CHOP) and caspase-3. Finally, MEG3 overexpression markedly increased nuclear factor κB (NF-κB) expression, NF-κB translocation to the nucleus, and p53 expression, whereas pharmacological inhibition of NF-κB completely abolished MEG3-induced activation of p53. Together, these results suggest that MEG3 inhibits breast cancer growth and induces breast cancer apoptosis, partially via the activation of the ER stress, NF-κB and p53 pathways, and that NF-κB signaling is required for MEG3-induced p53 activation in breast cancer cells. Our results indicate targeting lncRNA MEG3 may represent a novel strategy for breast cancer therapy.
    Keywords:  apoptosis; breast cancer; endoplasmic reticulum stress; maternally expressed 3; nuclear factor κB; p53
  8. Life Sci. 2018 Dec 13. pii: S0024-3205(18)30805-1. [Epub ahead of print]
    Wang L, Yun L, Wang X, Sha L, Wang L, Sui Y, Zhang H.
      AIM: Colorectal cancer (CRC) is a common human malignancy which accounts for 600,000 deaths annually at the global level. Soyasapogenol B (Soy B), an ingredient of soybean, has been found to exert anti-proliferative activities in vitro in human breast cancer cells. The current study aimed to evaluate the efficacy of Soy B in suppressing CRC.METHODS AND MATERIALS: The effect of Soy B on cell viability was assessed using the Cell Counting Kit-8 (CCK-8) assay. The effect of Soy B on cell proliferation was determined using colony formation assay. The percentage of apoptotic cells was determined by the TUNEL assay and flow cytometry following Annexin V-FITC/Propidium Iodide (PI) double staining. JC-1 staining was performed to examine the change in mitochondrial membrane potential. Autophagy was examined by acridine orange staining and mRFP-GFP-LC3 adenovirus transfection. Caspase-12 activities were determined by ELISA kit. Western blotting was used to determine the expression of relevant proteins. To investigate the role of autophagy in the pro-death and pro-apoptotic activities of Soy B, autophagy inhibitors Bafilomycin A1 (Baf-A1) and Atg5 siRNA were utilized. TUDCA and CHOP shRNA were utilized to block ER stress. Moreover, a CRC xenograft murine model was used to analyze the therapeutic efficacy of Soy B in vivo.
    KEY FINDINGS: Soy B treatment decreased the number of viable cells and colonies formed in CRC cell lines. Moreover, Soy B treatment promoted the apoptotic cell death via the intrinsic pathway and autophagy which positively contributed to cell death and apoptosis. In addition, our results showed that ER stress, triggered by Soy B, mediated apoptosis and autophagy. In vivo results revealed that Soy B could suppress tumor growth, which was associated with increased ER stress, accompanied with apoptosis and autophagy induction.
    SIGNIFICANCE: Soy B was able to promote cell death in vitro and in vivo. Our findings highlight the possibility of utilizing Soy B as a chemotherapeutic agent to prevent and treat CRC.
    Keywords:  Apoptosis; Autophagy; Colorectal cancer; Endoplasmic reticulum stress; Soy B
  9. Cancer Discov. 2018 Dec 18. pii: CD-18-0348. [Epub ahead of print]
    Ojha R, Leli NM, Onorati A, Piao S, Verginadis II, Tameire F, Rebecca VW, Chude CI, Murugan S, Fennelly C, Noguera-Ortega E, Liu S, Xu X, Krepler C, Xiao M, Xu W, Wei Z, Frederick DT, Boland G, Mitchell TC, Karakousis GC, Schuchter LM, Flaherty KT, Zhang G, Herlyn M, Koumenis C, Amaravadi RK.
      Resistance to BRAF and MEK inhibitor (BRAFi+MEKi) in BRAF mutant tumors occurs through heterogeneous mechanisms, including ERK reactivation and autophagy. Little is known about the mechanisms by which ERK reactivation, or autophagy are induced by BRAFi+MEKi. Here we report that in BRAF mutant melanoma cells, BRAFi+MEKi induced SEC61-dependent ER translocation of the MAPK pathway via GRP78 and KSR2. Inhibition of ER translocation prevented ERK reactivation and autophagy. Following ER translocation, ERK exited the ER and was rephosphorylated by PERK. Reactivated ERK phosphorylated ATF4, which activated cytoprotective autophagy. Upregulation of GRP78 and phosphorylation of ATF4 was detected in tumors of patients resistant to BRAFi+MEKi. ER translocation of the MAPK pathway was demonstrated in therapy-resistant patient-derived xenografts. Expression of a dominant negative ATF4 mutant conferred sensitivity to BRAFi+MEKi in vivo. This mechanism reconciles two major targeted therapy resistance pathways and identifies druggable targets, whose inhibition would likely enhance the response to BRAFi+MEKi.
  10. Front Immunol. 2018 ;9 2887
    Betts BC, Locke FL, Sagatys EM, Pidala J, Walton K, Menges M, Reff J, Saha A, Djeu JY, Kiluk JV, Lee MC, Kim J, Kang CW, Tang CA, Frieling J, Lynch CC, List A, Rodriguez PC, Blazar BR, Conejo-Garcia JR, Del Valle JR, Hu CA, Anasetti C.
      Acute graft- vs. -host disease (GVHD) is an important cause of morbidity and death after allogeneic hematopoietic cell transplantation (HCT). We identify a new approach to prevent GVHD that impairs monocyte-derived dendritic cell (moDC) alloactivation of T cells, yet preserves graft- vs.-leukemia (GVL). Exceeding endoplasmic reticulum (ER) capacity results in a spliced form of X-box binding protein-1 (XBP-1s). XBP-1s mediates ER stress and inflammatory responses. We demonstrate that siRNA targeting XBP-1 in moDCs abrogates their stimulation of allogeneic T cells. B-I09, an inositol-requiring enzyme-1α (IRE1α) inhibitor that prevents XBP-1 splicing, reduces human moDC migration, allo-stimulatory potency, and curtails moDC IL-1β, TGFβ, and p40 cytokines, suppressing Th1 and Th17 cell priming. B-I09-treated moDCs reduce responder T cell activation via calcium flux without interfering with regulatory T cell (Treg) function or GVL effects by cytotoxic T lymphocytes (CTL) and NK cells. In a human T cell mediated xenogeneic GVHD model, B-I09 inhibition of XBP-1s reduced target-organ damage and pathogenic Th1 and Th17 cells without impacting donor Tregs or anti-tumor CTL. DC XBP-1s inhibition provides an innovative strategy to prevent GVHD and retain GVL.
    Keywords:  GvHD; GvL; XBP-1S; dendritic cell (DC); er stress
  11. J Cell Physiol. 2018 Dec 21.
    Mosca L, Pagano M, Ilisso CP, Cave DD, Desiderio V, Mele L, Caraglia M, Cacciapuoti G, Porcelli M.
      S-Adenosyl-l-methionine (AdoMet) is a naturally and widely occurring sulfonium compound that plays a primary role in cell metabolism and acts as the principal methyl donor in many methylation reactions. AdoMet also exhibits antiproliferative and proapoptotic activities in different cancer cells. However, the molecular mechanisms underlying the effects exerted by AdoMet have only been partially studied. In the current study, we evaluated the antiproliferative effect of AdoMet on Cal-33 oral and JHU-SCC-011 laryngeal squamous cancer cells to define the underlying mechanisms. We demonstrated that AdoMet induced apoptosis in Cal-33 and JHU-SCC-011 cells, involving a caspase-dependent mechanism paralleled by an increased Bax/Bcl-2 ratio. Moreover, we showed, for the first time, that AdoMet induced ER-stress in Cal-33 cells and activated the unfolded protein response, which can be responsible for apoptosis induction through the activation of CHOP and JNK. In addition, AdoMet-induced ER-stress was followed by autophagy with a consistent increase in the levels of the autophagic marker LC3B-II, which was indeed potentiated by the autophago-lysosome inhibitor chloroquine. As both escape from apoptosis and decreased activation of JNK are mechanisms of resistance to cisplatin (cDPP), an agent usually used in cancer therapy, we have evaluated the effects of AdoMet in combination with cDPP on Cal-33 cells. Our data showed that the combined treatment resulted in a strong synergism in inhibiting cell proliferation and in enhancing apoptosis via intrinsic mechanism. These results demonstrate that AdoMet has ER-stress-mediated antiproliferative activity and synergizes with cDDP on cell growth inhibition, thus providing the basis for its use in new anticancer strategies.
    Keywords:  ER-stress; S-Adenosylmethionine; apoptosis; autophagy; cisplatin; drug combination; human head and neck cancer cells
  12. Oncol Rep. 2018 Dec 19.
    Guo L, Ma L, Liu C, Lei Y, Tang N, Huang Y, Huang G, Li D, Wang Q, Liu G, Tang M, Jing Z, Deng Y.
      Endoplasmic reticulum protein 29 (ERp29), an endoplasmic reticulum (ER) protein, participates in ER stress (ERS), but little is known about the association of ERp29 with ERS in the metastasis and prognosis of cancerous diseases. The present study revealed that ERp29 was important to ERS and interfered with the malignant behaviors of colorectal cancer (CRC). Experiments in in vitro and in animal models revealed that ERS inhibited the cell growth and suppressed the metastatic capacity of CRC cells, but ERp29 counteracted these effects. Furthermore, it was demonstrated that ERp29 recovered the migration and metastatic behaviors of CRC cells suppressed by ERS, mediated only when it combined with cullin5 (CUL5). ERp29 also relied on CUL5 to promote epithelial‑mesenchymal transition. From the immunohistochemical examination of CRC tissues, the high expression of ERp29 was revealed to predict the poor prognosis of 457 CRC cases. The retrospective analysis of the clinicopathological data of patients with CRC was consistent with the results of the in vitro and in vivo experiments. Thus, ERp29 protected CRC cells from ERS‑mediated reduction of malignancy to promote metastasis and may be a potential target of medical intervention for CRC therapy.
  13. Oncogene. 2018 Dec 21.
    Tiemann K, Garri C, Lee SB, Malihi PD, Park M, Alvarez RM, Yap LP, Mallick P, Katz JE, Gross ME, Kani K.
      Anterior gradient 2 (AGR2) is a member of the protein disulfide isomerase (PDI) family, which plays a role in the regulation of protein homeostasis and the unfolded protein response pathway (UPR). AGR2 has also been characterized as a proto-oncogene and a potential cancer biomarker. Cellular localization of AGR2 is emerging as a key component for understanding the role of AGR2 as a proto-oncogene. Here, we provide evidence that extracellular AGR2 (eAGR2) promotes tumor metastasis in various in vivo models. To further characterize the role of the intracellular-resident versus extracellular protein, we performed a comprehensive protein-protein interaction screen. Based on these results, we identify AGR2 as an interacting partner of the mTORC2 pathway. Importantly, our data indicates that eAGR2 promotes increased phosphorylation of RICTOR (T1135), while intracellular AGR2 (iAGR2) antagonizes its levels and phosphorylation. Localization of AGR2 also has opposing effects on the Hippo pathway, spheroid formation, and response to chemotherapy in vitro. Collectively, our results identify disparate phenotypes predicated on AGR2 localization. Our findings also provide credence for screening of eAGR2 to guide therapeutic decisions.
  14. Oncol Rep. 2018 Dec 19.
    Kim JL, Lee DH, Jeong S, Kim BR, Na YJ, Park SH, Jo MJ, Jeong YA, Oh SC.
      Imatinib is a powerful tyrosine kinase inhibitor that specifically targets BCR‑ABL, c‑KIT, and PDGFR kinases, and is used in the treatment of chronic myelogenous leukemia, gastrointestinal stromal tumors, and other types of cancers. However, the possible anticancer effects of imatinib in gastric cancer have not yet been explored. The present study evaluated the in vitro effects of imatinib on gastric cancer cells and determined the molecular mechanism underlying these effects. We determined that imatinib induced mitochondria‑mediated apoptosis of gastric cancer cells by involving endoplasmic reticulum (ER) stress‑associated activation of c‑Jun NH2‑terminal kinase (JNK). We also found that imatinib suppressed cell proliferation in a time‑ and dose‑dependent manner. Cell cycle analysis revealed that imatinib‑treated AGS cells were arrested in the G2/M phase of the cell cycle. Moreover, imatinib‑treated cells exhibited increased levels of phosphorylated JNK, and of the transcription factor C/EBP homologous protein, an ER stress‑associated apoptotic molecule. Results of cell viability assays revealed that treatment with a combination of imatinib and chemotherapy agents irinotecan or 5‑Fu synergistically inhibited cell growth, compared with treatment with any of these drugs alone. These data indicated that imatinib exerted cytotoxic effects on gastric cancer cells by inducing apoptosis mediated by reactive oxygen species generation and ER stress‑associated JNK activation. Furthermore, we revealed that imatinib induced the apoptosis of gastric cancer cells by inhibiting platelet‑derived growth factor receptor signaling. Collectively, our results strongly support the use of imatinib in the treatment of treating gastric cancer.