bims-unfpre Biomed News
on Unfolded protein response
Issue of 2022–09–11
six papers selected by
Susan Logue, University of Manitoba
  1. An endoplasmic reticulum targeting green fluorescent protein chromophore-based probe for the detection of viscosity.
  2. Assessment of eIF2α phosphorylation during immunogenic cell death.
  3. BOK controls ER proteostasis and physiological ER stress responses in neurons.
  4. Cell Cycle Analysis of ER Stress and Autophagy.
  5. ER Stress Response and Induction of Apoptosis in Malignant Pleural Mesothelioma: The Achilles Heel Targeted by the Anticancer Ruthenium Drug BOLD-100.
  6. HCA (2-Hydroxy-Docosahexaenoic Acid) Induces Apoptosis and Endoplasmic Reticulum Stress in Pancreatic Cancer Cells.
  1. Chem Commun (Camb). 2022 Sep 07.
    An endoplasmic reticulum targeting green fluorescent protein chromophore-based probe for the detection of viscosity.
    Xiaoqin Wei, Yiming Zhu, Xiang Yu, Lei Cai, Nanan Ruan, Luling Wu, Nengqin Jia, Tony D James, Chusen Huang.
      The occurrence of endoplasmic reticulum (ER) stress is the main cause of a variety of biological processes that are closely related to numerous diseases. The homeostasis of the ER microenvironment can be disrupted under ER stress. In this research, by linking a pentafluorophenyl to the green fluorescent protein chromophore, we have developed a new ER-targeting fluorescent probe (GE-Y) for measuring changes of intracellular ER viscosity caused by ER stress. Importantly, an increase in ER viscosity was observed using GE-Y in cells undergoing autophagy. As such, our research provides an ideal tool for studying ER stress and autophagy.
    DOI:  https://doi.org/10.1039/d2cc00118g
  2. Methods Cell Biol. 2022 ;pii: S0091-679X(22)00003-6. [Epub ahead of print]172 83-98
    Assessment of eIF2α phosphorylation during immunogenic cell death.
    Lucillia Bezu, Juliette Humeau, Marion Leduc, Hui Pan, Guido Kroemer, Oliver Kepp.
      Immunogenic cell death (ICD) is a modality of cellular demise that when it is induced by certain anticancer treatments can ignite an adaptive anticancer immune response. ICD is characterized by the emission of a specific set of danger-associated molecular patterns (DAMPs) including calreticulin exposure at the plasma membrane, ATP liberation, HMGB1 exodus and type-I IFN release. The apical signaling triggering the appearance of these hallmarks involves the phosphorylation on serine 51 of the α-subunit of eukaryotic initiation factor 2 (EIF2), a key protein in the orchestration of endoplasmic reticulum (ER) stress responses. EIF2α can be phosphorylated by a family of four EIF2A kinases: EIF2AK1-4 (best known as heme regulated inhibitor, HRI, protein kinase R, PKR, protein kinase R-like endoplasmic reticulum kinase, PERK, and general control non-derepressible 2, GCN2), that each respond to a specific type of cellular stress. Here, we describe different techniques to investigate the biochemical pathways leading to eIF2α phosphorylation in the context of ICD.
    Keywords:  Endoplasmic reticulum stress; Gene editing; Image analysis; Immunogenic cell death; eIF2α
    DOI:  https://doi.org/10.1016/bs.mcb.2022.01.003
  3. Front Cell Dev Biol. 2022 ;10 915065
    BOK controls ER proteostasis and physiological ER stress responses in neurons.
    Franziska Walter, Beatrice D'Orsi, Anagha Jagannathan, Heiko Dussmann, Jochen H M Prehn.
      The Bcl-2 family proteins BAK and BAX control the crucial step of pore formation in the mitochondrial outer membrane during intrinsic apoptosis. Bcl-2-related ovarian killer (BOK) is a Bcl-2 family protein with a high sequence similarity to BAK and BAX. However, intrinsic apoptosis can proceed in the absence of BOK. Unlike BAK and BAX, BOK is primarily located on the endoplasmic reticulum (ER) and Golgi membranes, suggesting a role for BOK in regulating ER homeostasis. In this study, we report that BOK is required for a full ER stress response. Employing previously characterized fluorescent protein-based ER stress reporter cell systems, we show that BOK-deficient cells have an attenuated response to ER stress in all three signaling branches of the unfolded protein response. Fluo-4-based confocal Ca2+ imaging revealed that disruption of ER proteostasis in BOK-deficient cells was not linked to altered ER Ca2+ levels. Fluorescence recovery after photobleaching (FRAP) experiments using GRP78/BiP-eGFP demonstrated that GRP78 motility was significantly lower in BOK-deficient cells. This implied that less intraluminal GRP78 was freely available and more of the ER chaperone bound to unfolded proteins. Collectively, these experiments suggest a new role for BOK in the protection of ER proteostasis and cellular responses to ER stress.
    Keywords:  Bcl-2 family; ER stress; ER stress reporters; calcium signaling; live-cell imaging; proteostasis; unfolded protein response
    DOI:  https://doi.org/10.3389/fcell.2022.915065
  4. Methods Mol Biol. 2022 ;2543 155-166
    Cell Cycle Analysis of ER Stress and Autophagy.
    A Popat, A A Patel, Gary Warnes.
      Autophagy and ER stress are most often studied employing a Western blotting approach to the measurement of autophagy by LC3B upregulation and the ER stress sensor signaling proteins PERK (protein kinase R-like endoplasmic reticulum kinase), IRE1, and ATF6 which initiate protein refolding and elongation of the ER until ER homeostasis is returned. If the misfolding of proteins is increased, then ER stress is maintained, and microautophagy of the ER or specifically reticulophagy occurs. However, LC3B, PERK, protein misfolding, and changes in ER mass (reticulophagy) can also be measured in a cell cycle-dependent manner by flow cytometry and the use of antibodies, protein misfolding, and ER tracking fluorescent probes.
    Keywords:  Autophagy; ER stress; Misfolded proteins; PERK; Reticulophagy
    DOI:  https://doi.org/10.1007/978-1-0716-2553-8_13
  5. Cancers (Basel). 2022 Aug 26. pii: 4126. [Epub ahead of print]14(17):
    ER Stress Response and Induction of Apoptosis in Malignant Pleural Mesothelioma: The Achilles Heel Targeted by the Anticancer Ruthenium Drug BOLD-100.
    Elia Ranzato, Gregorio Bonsignore, Simona Martinotti.
      Malignant mesothelioma is a rare cancer arising from the serosal surfaces of the body, mainly from the pleural layer. This cancer is strongly related to asbestos exposure and shows a very inauspicious prognosis, because there are scarce therapeutic options for this rare disease. Thus, there is an urgent need to develop novel therapeutic approaches to treat this form of cancer. To explore the biology of malignant pleural mesothelioma (MPM), we previously observed that MPM cell lines show high expression of the GRP78 protein, which is a chaperone protein and the master regulator of the unfolded protein response (UPR) that resides in the endoplasmic reticulum (ER). Based on our previous studies showing the importance of GRP78 in MPM, we observed that BOLD-100, a specific modulator of GRP78 and the UPR, shows cytotoxicity against MPM cells. Our studies demonstrated that BOLD-100 increases ROS production and Ca2+ release from the ER, leading to ER stress activation and, ultimately, to cell death. Our in vitro data strongly suggest that BOLD-100 inhibits the growth of MPM cell lines, proposing the application as a single agent, or in combination with other standard-of-care drugs, to treat MPM.
    Keywords:  GRP78; ROS; apoptosis; calcium; endoplasmic reticulum; malignant pleural mesothelioma; mitochondria; unfolded protein response (UPR)
    DOI:  https://doi.org/10.3390/cancers14174126
  6. Int J Mol Sci. 2022 Aug 31. pii: 9902. [Epub ahead of print]23(17):
    HCA (2-Hydroxy-Docosahexaenoic Acid) Induces Apoptosis and Endoplasmic Reticulum Stress in Pancreatic Cancer Cells.
    Roberto Beteta-Göbel, Marc Miralles, Javier Fernández-Díaz, Raquel Rodríguez-Lorca, Manuel Torres, Paula Fernández-García, Pablo V Escribá, Victoria Lladó.
      Pancreatic cancer has a high mortality rate due to its aggressive nature and high metastatic rate. When coupled to the difficulties in detecting this type of tumor early and the lack of effective treatments, this cancer is currently one of the most important clinical challenges in the field of oncology. Melitherapy is an innovative therapeutic approach that is based on modifying the composition and structure of cell membranes to treat different diseases, including cancers. In this context, 2-hydroxycervonic acid (HCA) is a melitherapeutic agent developed to combat pancreatic cancer cells, provoking the programmed cell death by apoptosis of these cells by inducing ER stress and triggering the production of ROS species. The efficacy of HCA was demonstrated in vivo, alone and in combination with gemcitabine, using a MIA PaCa-2 cell xenograft model of pancreatic cancer in which no apparent toxicity was evident. HCA is metabolized by α-oxidation to C21:5n-3 (heneicosapentaenoic acid), which in turn also showed anti-proliferative effect in these cells. Given the unmet clinical needs associated with pancreatic cancer, the data presented here suggest that the use of HCA merits further study as a potential therapy for this condition.
    Keywords:  ER stress; HCA; apoptosis; membrane lipid therapy; pancreatic cancer
    DOI:  https://doi.org/10.3390/ijms23179902
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