bims-unfpre 2023-11-05 papers

Issue of 2023–11–05
six papers selected by
Susan Logue, University of Manitoba

bioRxiv. 2023 Oct 20. pii: 2023.10.19.563191. [Epub ahead of print]

Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum functions.

Melissa J Mann, Chris Melendez-Suchi, Maria Sukhoplyasova, Ashley R Flory, Mary Carson Irvine, Anuradha R Iyer, Hannah Vorndran, Christopher J Guerriero, Jeffrey L Brodsky, Linda M Hendershot, Teresa M Buck.

GRP170, a product of the Hyou1 gene, is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds non-native proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of embryonic fibroblasts from mice in which LoxP sites were engineered in the Hyou1 loci ( Hyou1 LoxP/LoxP ). A doxycycline-regulated Cre recombinase was also stably introduced into these cells. Induction of Cre resulted in excision of Hyou1 and depletion of Grp170 protein, culminating in apoptotic cell death. As Grp170 levels fell we observed increased steady-state binding of BiP to a client, slowed degradation of a misfolded BiP substrate, and BiP accumulation in NP40-insoluble fractions. Consistent with disrupted BiP functions, we observed reactivation of BiP storage pools and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and insights into mutations in the Hyou1 locus and human disease.

DOI: https://doi.org/10.1101/2023.10.19.563191

bioRxiv. 2023 Oct 17. pii: 2023.10.17.562797. [Epub ahead of print]

Modulating the Unfolded Protein Response with ISRIB Mitigates Cisplatin Ototoxicity.

Jiang Li, Stephanie L Rouse, Ian R Matthews, Elliott H Sherr, Dylan K Chan.

Cisplatin is a common chemotherapy drug with a nearly universal side effect of ototoxicity. The cellular mechanisms underlying cisplatin ototoxicity are poorly understood. Efforts in drug development to prevent or reverse cisplatin ototoxicity have largely focused on pathways of oxidative stress and apoptosis. An effective treatment for cisplatin ototoxicity, sodium thiosulfate, is associated with reduced survival in disseminated hepatoblastoma, highlighting the need for more specific drugs. The unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways have been shown to be involved in the pathogenesis of noise-induced hearing loss and cochlear synaptopathy in vivo , and these pathways have been implicated broadly in cisplatin cytotoxicity. This study sought to determine whether the UPR can be targeted to prevent cisplatin ototoxicity. Neonatal cochlear cultures and HEK cells were exposed to cisplatin and UPR-modulating drugs, and UPR marker gene expression and cell death measured. Treatment with ISRIB, a drug that activates eif2B and downregulates the pro-apoptotic PERK/CHOP pathway of the UPR, was tested in an in vivo mouse model of cisplatin ototoxicity and well as a head and neck squamous cell carcinoma (HNSCC) cell-based assay of cisplatin cytotoxicity. Cisplatin exhibited a biphasic, non-linear dose-response of cell death and apoptosis that correlated with different patterns of UPR marker gene expression in HEK cells and cochlear cultures. ISRIB treatment protected against cisplatin-induced hearing loss and hair-cell death, but did not impact cisplatin's cytotoxic effects on HNSCC cell viability. These findings demonstrate that targeting the pro-apoptotic PERK/CHOP pathway with ISRIB can mitigate cisplatin ototoxicity without reducing anti-cancer cell effects, suggesting that this may be a viable strategy for drug development.

DOI: https://doi.org/10.1101/2023.10.17.562797

Biochim Biophys Acta Mol Cell Res. 2023 Oct 29. pii: S0167-4889(23)00191-X. [Epub ahead of print] 119618

The ubiquitin-proteasome pathway inhibitor TAK-243 has major effects on calcium handling in mammalian cells.

Xiaokong Gao, Katherine R Keller, Caden G Bonzerato, Peng Li, Michael Laemmerhofer, Richard J H Wojcikiewicz.

The ubiquitin-proteasome pathway (UPP) is a major route for protein degradation and a key regulatory mechanism in mammalian cells. UPP inhibitors, including TAK-243, a first-in-class inhibitor of the E1 ubiquitin-activating enzyme, are currently being used and tested for treatment of a range of diseases, particularly cancer. Here, we reveal that TAK-243 has major effects on Ca2+ handling in a range of cultured mammalian cells (αT3, HeLa and SH-SY5Y). Effects were seen on agonist-induced Ca2+ mobilization, basal cytosolic Ca2+ levels, Ca2+ leak from the endoplasmic reticulum (ER), store-operated Ca2+ entry and mitochondrial Ca2+ uptake. These effects correlated with induction of ER stress, and most seemed to be underpinned by enhanced Ca2+ leak from the ER. Overall, these data indicate that TAK-243 reprograms the Ca2+-handling properties of mammalian cells and that these effects should be considered when UPP inhibitors are employed as therapeutic agents.

Keywords: Calcium; Endoplasmic reticulum; Inositol 1,4,5-trisphosphate receptor; Intracellular signaling; TAK-243; cancer

DOI: https://doi.org/10.1016/j.bbamcr.2023.119618

Nat Commun. 2023 Nov 01. 14(1): 6982

Hepatocyte FBXW7-dependent activity of nutrient-sensing nuclear receptors controls systemic energy homeostasis and NASH progression in male mice.

Hui Xia, Catherine R Dufour, Younes Medkour, Charlotte Scholtes, Yonghong Chen, Christina Guluzian, Wafa B'chir, Vincent Giguère.

Nonalcoholic steatohepatitis (NASH) is epidemiologically associated with obesity and diabetes and can lead to liver cirrhosis and hepatocellular carcinoma if left untreated. The intricate signaling pathways that orchestrate hepatocyte energy metabolism and cellular stress, intrahepatic cell crosstalk, as well as interplay between peripheral tissues remain elusive and are crucial for the development of anti-NASH therapies. Herein, we reveal E3 ligase FBXW7 as a key factor regulating hepatic catabolism, stress responses, systemic energy homeostasis, and NASH pathogenesis with attenuated FBXW7 expression as a feature of advanced NASH. Multiomics and pharmacological intervention showed that FBXW7 loss-of-function in hepatocytes disrupts a metabolic transcriptional axis conjointly controlled by the nutrient-sensing nuclear receptors ERRα and PPARα, resulting in suppression of fatty acid oxidation, elevated ER stress, apoptosis, immune infiltration, fibrogenesis, and ultimately NASH progression in male mice. These results provide the foundation for developing alternative strategies co-targeting ERRα and PPARα for the treatment of NASH.

DOI: https://doi.org/10.1038/s41467-023-42785-3

Biochim Biophys Acta Rev Cancer. 2023 Oct 30. pii: S0304-419X(23)00155-5. [Epub ahead of print] 189006

Role of stress granules in tumorigenesis and cancer therapy.

Tiansheng Li, Zhaoyang Zeng, Chunmei Fan, Wei Xiong.

Stress granules (SGs) are membrane-less organelles that cell forms via liquid-liquid phase separation (LLPS) under stress conditions such as oxidative stress, ER stress, heat shock and hypoxia. SG assembly is a stress-responsive mechanism by regulating gene expression and cellular signaling pathways. Cancer cells face various stress conditions in tumor microenvironment during tumorigenesis, while SGs contribute to hallmarks of cancer including proliferation, invasion, migration, avoiding apoptosis, metabolism reprogramming and immune escape. Here, we review the connection between SGs and cancer development, the limitation of SGs on current cancer therapy and promising cancer therapeutic strategies targeting SGs in the future.

Keywords: Cancer; Cancer therapy; Liquid-liquid phase separation; Stress granule

DOI: https://doi.org/10.1016/j.bbcan.2023.189006

Sci Adv. 2023 11 03. 9(44): eadh2584

UNC-49 is a redox-sensitive GABAA receptor that regulates the mitochondrial unfolded protein response cell nonautonomously.

Franziska Pohl, Allison L Germann, Jack Mao, Sydney Hou, Bayode Bakare, Paul Kong Thoo Lin, Kyari Yates, Michael L Nonet, Gustav Akk, Kerry Kornfeld, Jason M Held.

The γ-aminobutyric acid-mediated (GABAergic) system participates in many aspects of organismal physiology and disease, including proteostasis, neuronal dysfunction, and life-span extension. Many of these phenotypes are also regulated by reactive oxygen species (ROS), but the redox mechanisms linking the GABAergic system to these phenotypes are not well defined. Here, we report that GABAergic redox signaling cell nonautonomously activates many stress response pathways in Caenorhabditis elegans and enhances vulnerability to proteostasis disease in the absence of oxidative stress. Cell nonautonomous redox activation of the mitochondrial unfolded protein response (mitoUPR) proteostasis network requires UNC-49, a GABAA receptor that we show is activated by hydrogen peroxide. MitoUPR induction by a spinocerebellar ataxia type 3 (SCA3) C. elegans neurodegenerative disease model was similarly dependent on UNC-49 in C. elegans. These results demonstrate a multi-tissue paradigm for redox signaling in the GABAergic system that is transduced via a GABAA receptor to function in cell nonautonomous regulation of health, proteostasis, and disease.

DOI: https://doi.org/10.1126/sciadv.adh2584