bims-unfpre Biomed News
on Unfolded protein response
Issue of 2020‒07‒12
twelve papers selected by
Susan Logue
University of Manitoba

  1. Int J Mol Sci. 2020 Jul 04. pii: E4757. [Epub ahead of print]21(13):
    Pellegrini P, Selvaraju K, Faustini E, Mofers A, Zhang X, Ternerot J, Schubert A, Linder S, D Arcy P.
      The proteasome is a validated target of cancer therapeutics. Inhibition of proteasome activity results in the activation of the unfolded protein response (UPR) characterized by phosphorylation of eukaryotic initiation factor 2α (eIF2α), global translational arrest, and increased expression of the proapoptotic CHOP (C/EBP homologous protein) protein. Defects in the UPR response has been reported to result in altered sensitivity of tumor cells to proteasome inhibitors. Here, we characterized the effects of the deubiquitinase (DUB) inhibitor VLX1570 on protein homeostasis, both at the level of the UPR and on protein translation, in acute lymphoblastic leukemia (ALL). Similar to the 20S inhibitor bortezomib, VLX1570 induced accumulation of polyubiquitinated proteins and increased expression of the chaperone Grp78/Bip in ALL cells. Both compounds induced cleavage of PARP (Poly (ADP-ribose) polymerase) in ALL cells, consistent with induction of apoptosis. However, and in contrast to bortezomib, VLX1570 treatment resulted in limited induction of the proapoptotic CHOP protein. Translational inhibition was observed by both bortezomib and VLX1570. We report that in distinction to bortezomib, suppression of translation by VXL1570 occurred at the level of elongation. Increased levels of Hsc70/Hsp70 proteins were observed on polysomes following exposure to VLX1570, possibly suggesting defects in nascent protein folding. Our findings demonstrate apoptosis induction in ALL cells that appears to be uncoupled from CHOP induction, and show that VLX1570 suppresses protein translation by a mechanism distinct from that of bortezomib.
    Keywords:  acute lymphocytic leukemia; bortezomib; proteasome; translation
  2. J Dairy Sci. 2020 Jul 01. pii: S0022-0302(20)30500-2. [Epub ahead of print]
    Sharmin MM, Mizusawa M, Hayashi S, Arai W, Sakata S, Yonekura S.
      Fatty acids play important roles in the regulation of endoplasmic reticulum (ER) stress-induced apoptosis in different cells. Currently, the effects of fatty acids on bovine mammary epithelial cells (MEC) remain unknown. Our study examined bovine MEC viability and measured unfolded protein response (UPR)-related gene and protein expressions following fatty acid treatments. To evaluate the role of fatty acids, we treated MAC-T cells (a line of MEC) with 100 to 400 μM of saturated (palmitic and stearic acid) and unsaturated (palmitoleic, oleic, linoleic, and linolenic acid) fatty acids and 1 to 5 mM of short- and medium-chain fatty acids (acetic, propionic, butyric, and octanoic acid). Thereafter, we determined UPR-related gene expression using quantitative real-time PCR. Palmitic acid stimulated expression of XBP1s, ATF4, ATF6α, and C/EBP homologous protein (CHOP). Stearic acid increased expression of XBP1s and CHOP and decreased expression of ATF4 and ATF6α. Results of Western blot analysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that palmitic and stearic acid reduced MAC-T cell viability and induced extreme ER stress by increasing the protein expression of ER stress markers, such as phospho-PKR-like endoplasmic reticulum kinase, phospho-eIF2α, cleaved CASP-3, and CHOP. Among unsaturated long-chain fatty acids, palmitoleic acid increased expression of ATF4 and ATF6α. Oleic acid increased expression of XBP1s, ATF4, and ATF6α. Linoleic and linolenic acids increased expression of XBP1s, ATF4, and ATF6α but decreased expression of XBP1s and ATF6α at the highest dose. Although palmitoleic, oleic, and linoleic acid decreased CHOP expression, only palmitoleic acid increased MAC-T cell viability. Therefore, unsaturated long-chain fatty acids did not induce severe ER stress. Acetic, propionic, and butyric acids decreased expression of ATF4, ATF6α, and CHOP and increased XBP1s expression. Although only octanoic acid increased ATF4 and ATF6α expressions, it lowered expression of XBP1s and CHOP. Although fatty acid treatment did not increase the levels of ER stress proteins, butyric and octanoic acids reduced cell viability, possibly because of early differentiation. These results suggest that saturated fatty acids play important roles in MEC viability by inducing severe ER stress compared with unsaturated fatty acids. In addition, acetic and propionic acids (short- and medium-chain fatty acids) reduced ER stress. Therefore, the present study reflects the new insight that serum fatty acid concentration plays an important role in maintaining the lactation physiology of dairy cows.
    Keywords:  apoptosis; endoplasmic reticulum stress; mammary epithelial cells; unfolded protein response
  3. Biomolecules. 2020 Jul 06. pii: E1005. [Epub ahead of print]10(7):
    Ortiz E, Sanchis P, Bizzotto J, Lage-Vickers S, Labanca E, Navone N, Cotignola J, Vazquez E, Gueron G.
      The inflammatory tumor microenvironment is a fertile niche accelerating prostate cancer (PCa). We have reported that heme-oxygenase (HO-1) had a strong anti-tumoral effect in PCa. We previously undertook an in-depth proteomics study to build the HO-1 interactome in PCa. In this work, we used a bioinformatics approach to address the biological significance of HO-1 interactors. Open-access PCa datasets were mined to address the clinical significance of the HO-1 interactome in human samples. HO-1 interactors were clustered into groups according to their expression profile in PCa patients. We focused on the myxovirus resistance gene (MX1) as: (1) it was significantly upregulated under HO-1 induction; (2) it was the most consistently downregulated gene in PCa vs. normal prostate; (3) its loss was associated with decreased relapse-free survival in PCa; and (4) there was a significant positive correlation between MX1 and HMOX1 in PCa patients. Further, MX1 was upregulated in response to endoplasmic reticulum stress (ERS), and this stress triggered apoptosis and autophagy in PCa cells. Strikingly, MX1 silencing reversed ERS. Altogether, we showcase MX1 as a novel HO-1 interactor and downstream target, associated with ERS in PCa and having a high impact in the clinical setting.
    Keywords:  endoplasmic reticulum stress; heme-oxygenase 1 (HO-1); myxovirus resistance protein (MX1); prostate cancer; unfolded protein response
  4. Acta Pharmacol Sin. 2020 Jul 09.
    Tian JH, Wu Q, He YX, Shen QY, Rekep M, Zhang GP, Luo JD, Xue Q, Liu YH.
      Endoplasmic reticulum stress (ER stress) plays a key role in the development of cardiac hypertrophy and diabetic cardiomyopathy (DCM). Zonisamide (ZNS) was originally developed as an antiepileptic drug. Studies have shown that ZNS suppresses ER stress-induced neuronal cell damage in the experimental models of Parkinson's disease. Herein, we investigated whether ZNS improved DCM by attenuating ER stress-induced apoptosis. C57BL/6J mice were fed with high-fat diet (HFD) and intraperitoneally injected with low-dose streptozotocin (STZ) to induce type 2 diabetes mellitus (T2DM), and then treated with ZNS (40 mg·kg-1·d-1, i.g.) for 16 weeks. We showed that ZNS administration slightly ameliorated the blood glucose levels, but significantly alleviated diabetes-induced cardiac dysfunction and hypertrophy. Furthermore, ZNS administration significantly inhibited the Bax and caspase-3 activity, upregulated Bcl-2 activity, and decreased the proportion of TUNEL-positive cells in heart tissues. We analyzed the hallmarks of ER stress in heart tissues, and revealed that ZNS administration significantly decreased the protein levels of GRP78, XBP-1s, ATF6, PERK, ATF4, and CHOP, and elevated Hrd1 protein. In high glucose (HG)-treated primary cardiomyocytes, application of ZNS (3 μM) significantly alleviated HG-induced cardiomyocyte hypertrophy and apoptosis. ZNS application also suppressed activated ER stress in HG-treated cardiomyocytes. Moreover, preapplication of the specific ER stress inducer tunicamycin (10 ng/mL) eliminated the protective effects of ZNS against HG-induced cardiac hypertrophy and ER stress-mediated apoptosis. Our findings suggest that ZNS improves the cardiac diastolic function in diabetic mice and prevents T2DM-induced cardiac hypertrophy by attenuating ER stress-mediated apoptosis.
    Keywords:  apoptosis; diabetic cardiomyopathy; endoplasmic reticulum stress; zonisamide
  5. Sci Adv. 2020 Jun;6(26): eaaz9805
    Higuchi-Sanabria R, Shen K, Kelet N, Frankino PA, Durieux J, Bar-Ziv R, Sing CN, Garcia EJ, Homentcovschi S, Sanchez M, Wu R, Tronnes SU, Joe L, Webster B, Ahilon-Jeronimo A, Monshietehadi S, Dallarda S, Pender C, Pon LA, Zoncu R, Dillin A.
      Recent work has highlighted the fact that lysosomes are a critical signaling hub of metabolic processes, providing fundamental building blocks crucial for anabolic functions. How lysosomal functions affect other cellular compartments is not fully understood. Here, we find that lysosomal recycling of the amino acids lysine and arginine is essential for proper ER quality control through the UPRER. Specifically, loss of the lysine and arginine amino acid transporter LAAT-1 results in increased sensitivity to proteotoxic stress in the ER and decreased animal physiology. We find that these LAAT-1-dependent effects are linked to glycine metabolism and transport and that the loss of function of the glycine transporter SKAT-1 also increases sensitivity to ER stress. Direct lysine and arginine supplementation, or glycine supplementation alone, can ameliorate increased ER stress sensitivity found in laat-1 mutants. These data implicate a crucial role in recycling lysine, arginine, and glycine in communication between the lysosome and ER.
  6. Cell Stress Chaperones. 2020 Jul 06.
    Moghadami AA, Aboutalebi Vand Beilankouhi E, Kalantary-Charvadeh A, Hamzavi M, Mosayyebi B, Sedghi H, Ghorbani Haghjo A, Nazari Soltan Ahmad S.
      Non-small cell lung cancer is the most common type of lung cancer, accounting for more than 80% of this tumor. Ubiquitin-specific protease (USP) 14 is one of the 100 deubiquitinating enzymes that is overexpressed in lung cancer and has been validated as a therapeutic target. The aim of this study is to determine whether the accumulation of ubiquitinated proteins results in endoplasmic reticulum (ER) stress-mediated autophagy. To inhibit USP-14, A549 lung cancer cells were treated with USP-14 siRNA and IU1-47 (20 μM). The protein level, mRNA expression, and cell cycle analysis were evaluated using Western blot, real-time PCR, and flow cytometry, respectively. We found that treating A549 cells with USP14 inhibitors significantly reduced the proliferation rate and induced cell cycle arrest at G2/M phase. We also found that USP14 inhibitors did not induce apoptosis but actually induced autophagy through accumulation of ubiquitinated proteins/ER stress/unfolded protein response (UPR) axis. Moreover, we have for the first time demonstrated that the USP14 inhibition induces ER stress-mediated autophagy in A549 cells by activation of c-Jun N-terminal kinase 1 (JNK1). In conclusion, the current investigation represents a new mechanism by which inhibition of USP14 triggers autophagy via ER stress-mediated UPR in A549 cells.
    Keywords:  Autophagy; Endoplasmic reticulum stress; JNK; NSCLC; Ubiquitin-proteasome
  7. J Cell Mol Med. 2020 Jul 06.
    Zhang D, Fan R, Lei L, Lei L, Wang Y, Lv N, Chen P, Williamson RA, Wang B, Hu J.
      Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into a variety of cell types. Bortezomib, the first approved proteasome inhibitor used for the treatment of multiple myeloma (MM), has been shown to induce osteoblast differentiation, making it beneficial for myeloma bone disease. In the present study, we aimed to investigate the effects and underlying mechanisms of bortezomib on the cell cycle during osteogenic differentiation. We confirmed that low doses of bortezomib can induce MSCs towards osteogenic differentiation, but high doses are toxic. In the course of bortezomib-induced osteogenic differentiation, we observed cell cycle exit characterized by G0 /G1 phase cell cycle arrest with a significant reduction in cell proliferation. Additionally, we found that the cell cycle exit was tightly related to the induction of the cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1 . Notably, we further demonstrated that the up-regulation of p21Cip1 and p27Kip1 is transcriptionally dependent on the bortezomib-activated ER stress signalling branch Ire1α/Xbp1s. Taken together, these findings reveal an intracellular pathway that integrates proteasome inhibition, osteogenic differentiation and the cell cycle through activation of the ER stress signalling branch Ire1α/Xbp1s.
    Keywords:  Xbp1s; bortezomib; cell cycle; mesenchymal stem cells; p21Cip1; p27Kip1
  8. Cell Rep. 2020 Jul 07. pii: S2211-1247(20)30827-5. [Epub ahead of print]32(1): 107846
    Kobiita A, Godbersen S, Araldi E, Ghoshdastider U, Schmid MW, Spinas G, Moch H, Stoffel M.
      The ability of pancreatic β-cells to respond to increased demands for insulin during metabolic stress critically depends on proper ribosome homeostasis and function. Excessive and long-lasting stimulation of insulin secretion can elicit endoplasmic reticulum (ER) stress, unfolded protein response, and β-cell apoptosis. Here we show that the diabetes susceptibility gene JAZF1 is a key transcriptional regulator of ribosome biogenesis, global protein, and insulin translation. JAZF1 is excluded from the nucleus, and its expression levels are reduced upon metabolic stress and in diabetes. Genetic deletion of Jazf1 results in global impairment of protein synthesis that is mediated by defects in ribosomal protein synthesis, ribosomal RNA processing, and aminoacyl-synthetase expression, thereby inducing ER stress and increasing β-cell susceptibility to apoptosis. Importantly, JAZF1 function and its pleiotropic actions are impaired in islets of murine T2D and in human islets exposed to metabolic stress. Our study identifies JAZF1 as a central mediator of metabolic stress in β-cells.
    Keywords:  ER stress; Jazf1; aminoacyl-tRNA synthetase; apoptosis; diabetes; insulin; rRNA processing; ribosomal proteins; ribosome biogenesis; transcription
  9. Neuron. 2020 Jun 26. pii: S0896-6273(20)30469-4. [Epub ahead of print]
    Liu X, Beaudoin JD, Davison CA, Kosmaczewski SG, Meyer BI, Giraldez AJ, Hammarlund M.
      The xbp-1 mRNA encodes the XBP-1 transcription factor, a critical part of the unfolded protein response. Here we report that an RNA fragment produced from xbp-1 mRNA cleavage is a biologically active non-coding RNA (ncRNA) essential for axon regeneration in Caenorhabditis elegans. We show that the xbp-1 ncRNA acts independently of the protein-coding function of the xbp-1 transcript as part of a dual output xbp-1 mRNA stress response axis. Structural analysis indicates that the function of the xbp-1 ncRNA depends on a single RNA stem; this stem forms only in the cleaved xbp-1 ncRNA fragment. Disruption of this stem abolishes the non-coding, but not the coding, function of the endogenous xbp-1 transcript. Thus, cleavage of the xbp-1 mRNA bifurcates it into a coding and a non-coding pathway; modulation of the two pathways may allow neurons to fine-tune their response to injury and other stresses.
    Keywords:  C. elegans; RNA processing; XBP1; axon regeneration; ncRNA; neuronal injury response; non-coding RNA; xbp-1
  10. Am J Pathol. 2020 Jul 07. pii: S0002-9440(20)30332-1. [Epub ahead of print]
    Hammock BD, Wang W, Gilligan MM, Panigrahy D.
      Severe coronavirus-19 (COVID-19) symptoms, including systemic inflammatory response and multi-system organ failure, are now affecting thousands of infected patients and causing widespread mortality. Coronavirus infection causes tissue damage, which triggers the endoplasmic reticulum (ER) stress response and subsequent eicosanoid and cytokine storms. While pro-inflammatory eicosanoids including prostaglandins, thromboxanes, and leukotrienes are critical mediators of physiological processes such as inflammation, fever, allergy, and pain, their role in COVID-19 are poorly characterized. Arachidonic acid derived epoxyeicosatrienoic acids (EETs) could alleviate the systemic hyper-inflammatory response in COVID-19 infection by modulating ER stress and stimulating the resolution of inflammation. Soluble epoxide hydrolase (sEH) inhibitors, which increase endogenous EET levels, exhibit potent anti-inflammatory activity and inhibit various pathologic processes in preclinical disease models including pulmonary fibrosis, thrombosis, and acute respiratory distress syndrome. Therefore, targeting eicosanoids and sEH could be a novel therapeutic approach in combating COVID-19. In this review, we discuss the predominant role of eicosanoids in regulating the inflammatory cascade and propose the potential application of sEH inhibitors in alleviating COVID-19 symptoms. We also discuss the host-protective action of omega-3 fatty acid-derived epoxyeicosanoids and specialized pro-resolving mediators (SPMs) in regulating anti-inflammation and anti-viral response. Future studies determining the eicosanoid profile in COVID-19 patient or preclinical model are pivotal in providing the novel insight of coronavirus-host interaction and inflammation modulation.
  11. Sci Rep. 2020 Jul 09. 10(1): 11327
    Herath V, Gayral M, Adhikari N, Miller R, Verchot J.
      The endoplasmic reticulum (ER) immunoglobulin binding proteins (BiPs) are molecular chaperones involved in normal protein maturation and refolding malformed proteins through the unfolded protein response (UPR). Plant BiPs belong to a multi-gene family contributing to development, immunity, and responses to environmental stresses. This study identified three BiP homologs in the Solanum tuberosum (potato) genome using phylogenetic, amino acid sequence, 3-D protein modeling, and gene structure analysis. These analyses revealed that StBiP1 and StBiP2 grouped with AtBiP2, whereas StBiP3 grouped with AtBiP3. While the protein sequences and folding structures are highly similar, these StBiPs are distinguishable by their expression patterns in different tissues and in response to environmental stressors such as treatment with heat, chemicals, or virus elicitors of UPR. Ab initio promoter analysis revealed that potato and Arabidopsis BiP1 and BiP2 promoters were highly enriched with cis-regulatory elements (CREs) linked to developmental processes, whereas BiP3 promoters were enriched with stress related CREs. The frequency and linear distribution of these CREs produced two phylogenetic branches that further resolve the groups identified through gene phylogeny and exon/intron phase analysis. These data reveal that the CRE architecture of BiP promoters potentially define their spatio-temporal expression patterns under developmental and stress related cues.
  12. Int J Mol Sci. 2020 Jul 06. pii: E4777. [Epub ahead of print]21(13):
    He F, Ru X, Wen T.
      Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that regulates the cellular defense against toxic and oxidative insults through the expression of genes involved in oxidative stress response and drug detoxification. NRF2 activation renders cells resistant to chemical carcinogens and inflammatory challenges. In addition to antioxidant responses, NRF2 is involved in many other cellular processes, including metabolism and inflammation, and its functions are beyond the originally envisioned. NRF2 activity is tightly regulated through a complex transcriptional and post-translational network that enables it to orchestrate the cell's response and adaptation to various pathological stressors for the homeostasis maintenance. Elevated or decreased NRF2 activity by pharmacological and genetic manipulations of NRF2 activation is associated with many metabolism- or inflammation-related diseases. Emerging evidence shows that NRF2 lies at the center of a complex regulatory network and establishes NRF2 as a truly pleiotropic transcription factor. Here we summarize the complex regulatory network of NRF2 activity and its roles in metabolic reprogramming, unfolded protein response, proteostasis, autophagy, mitochondrial biogenesis, inflammation, and immunity.
    Keywords:  NRF2; UPR; autophagy; inflammation; metabolism; oxidative stress; proteostasis; transcription factor