bims-unfpre 2023-05-28 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2023–05–28
twelve papers selected by
Susan Logue, University of Manitoba

A novel IRE1 kinase inhibitor for adjuvant glioblastoma treatment.
Interplay between calcium and endoplasmic reticulum stress.
Unfolding the Interactions between Endoplasmic Reticulum Stress and Oxidative Stress.
Targeting unfolded protein response reverts ER stress and ER Ca2+ homeostasis in cardiomyocytes expressing the pathogenic variant of Lamin A/C R321X.
An ER-accumulated mutant of yeast Pma1 causes membrane-related stress to induce the unfolded protein response.
Activation of endoplasmic reticulum stress in premature aging via the inner nuclear membrane protein SUN2.
Unfolded Protein Response Factor ATF6 Augments T Helper Cell Responses and Promotes Mixed Granulocytic Airway Inflammation.
Physapruin A Exerts Endoplasmic Reticulum Stress to Trigger Breast Cancer Cell Apoptosis via Oxidative Stress.
Myogenesis in C2C12 Cells Requires Phosphorylation of ATF6α by p38 MAPK.
Protective Effect and Mechanism of Xbp1s Regulating HBP/O-GlcNAcylation through GFAT1 on Brain Injury after SAH.
A comprehensive signature based on endoplasmic reticulum stress-related genes in predicting prognosis and immunotherapy response in melanoma.
Cell surface GRP78: a potential mechanism of therapeutic resistant tumors.

iScience. 2023 May 19. 26(5): 106687

A novel IRE1 kinase inhibitor for adjuvant glioblastoma treatment.

Diana Pelizzari-Raymundo, Dimitrios Doultsinos, Raphael Pineau, Chloé Sauzay, Thodoris Koutsandreas, Timothy Langlais, Antonio Carlesso, Elena Gkotsi, Luc Negroni, Tony Avril, Aristotelis Chatziioannou, Eric Chevet, Leif A Eriksson, Xavier Guillory.

  Inositol-requiring enzyme 1 (IRE1) is a major mediator of the unfolded protein response (UPR), which is activated upon endoplasmic reticulum (ER) stress. Tumor cells experience ER stress due to adverse microenvironmental cues, a stress overcome by relying on IRE1 signaling as an adaptive mechanism. Herein, we report the discovery of structurally new IRE1 inhibitors identified through the structural exploration of its kinase domain. Characterization in in vitro and in cellular models showed that they inhibit IRE1 signaling and sensitize glioblastoma (GB) cells to the standard chemotherapeutic, temozolomide (TMZ). Finally, we demonstrate that one of these inhibitors, Z4P, permeates the blood-brain barrier (BBB), inhibits GB growth, and prevents relapse in vivo when administered together with TMZ. The hit compound disclosed herein satisfies an unmet need for targeted, non-toxic IRE1 inhibitors and our results support the attractiveness of IRE1 as an adjuvant therapeutic target in GB.

Keywords:  Biological sciences; Medicine; Molecular neuroscience; Neuroscience

DOI:  https://doi.org/10.1016/j.isci.2023.106687
Cell Calcium. 2023 May 12. pii: S0143-4160(23)00065-9. [Epub ahead of print]113 102753

Interplay between calcium and endoplasmic reticulum stress.

Jody Groenendyk, Marek Michalak.

  Cellular homeostasis is crucial for the healthy functioning of the organism. Disruption of cellular homeostasis activates endoplasmic reticulum (ER) stress coping responses including the unfolded protein response (UPR). There are three ER resident stress sensors responsible for UPR activation - IRE1α, PERK and ATF6. Ca2+ signaling plays an important role in stress responses including the UPR and the ER is the main Ca2+ storage organelle and a source of Ca2+ for cell signaling. The ER contains many proteins involved in Ca2+ import/export/ storage, Ca2+ movement between different cellular organelles and ER Ca2+ stores refilling. Here we focus on selected aspects of ER Ca2+ homeostasis and its role in activation of the ER stress coping responses.

Keywords:  Calcium homeostasis; Endoplasmic reticulum; Membrane contact sites; Sarcoplasmic reticulum; Unfolded protein response

DOI:  https://doi.org/10.1016/j.ceca.2023.102753
Antioxidants (Basel). 2023 Apr 22. pii: 981. [Epub ahead of print]12(5):

Unfolding the Interactions between Endoplasmic Reticulum Stress and Oxidative Stress.

Gideon Ong, Susan E Logue.

  Oxidative stress is caused by an imbalance in cellular redox state due to the accumulation of reactive oxygen species (ROS). While homeostatic levels of ROS are important for cell physiology and signaling, excess ROS can induce a variety of negative effects ranging from damage to biological macromolecules to cell death. Additionally, oxidative stress can disrupt the function of redox-sensitive organelles including the mitochondria and endoplasmic reticulum (ER). In the case of the ER, the accumulation of misfolded proteins can arise due to oxidative stress, leading to the onset of ER stress. To combat ER stress, cells initiate a highly conserved stress response called the unfolded protein response (UPR). While UPR signaling, within the context of resolving ER stress, is well characterised, how UPR mediators respond to and influence oxidative stress is less defined. In this review, we evaluate the interplay between oxidative stress, ER stress and UPR signaling networks. Specifically, we assess how UPR signaling mediators can influence antioxidant responses.

Keywords:  antioxidants; endoplasmic reticulum; reactive oxygen species; unfolded protein response

DOI:  https://doi.org/10.3390/antiox12050981
J Transl Med. 2023 05 22. 21(1): 340

Targeting unfolded protein response reverts ER stress and ER Ca2+ homeostasis in cardiomyocytes expressing the pathogenic variant of Lamin A/C R321X.

Giusy Pietrafesa, Roberta De Zio, Simona Ida Scorza, Maria Francesca Armentano, Martino Pepe, Cinzia Forleo, Giuseppe Procino, Andrea Gerbino, Maria Svelto, Monica Carmosino.

   BACKGROUND: We previously demonstrated that an Italian family affected by a severe dilated cardiomyopathy (DCM) with history of sudden deaths at young age, carried a mutation in the Lmna gene encoding for a truncated variant of the Lamin A/C protein (LMNA), R321X. When expressed in heterologous systems, such variant accumulates into the endoplasmic reticulum (ER), inducing the activation of the PERK-CHOP pathway of the unfolded protein response (UPR), ER dysfunction and increased rate of apoptosis. The aim of this work was to analyze whether targeting the UPR can be used to revert the ER dysfunction associated with LMNA R321X expression in HL-1 cardiac cells.
METHODS: HL-1 cardiomyocytes stably expressing LMNA R321X were used to assess the ability of 3 different drugs targeting the UPR, salubrinal, guanabenz and empagliflozin to rescue ER stress and dysfunction. In these cells, the state of activation of both the UPR and the pro-apoptotic pathway were analyzed monitoring the expression levels of phospho-PERK, phospho-eIF2α, ATF4, CHOP and PARP-CL. In addition, we measured ER-dependent intracellular Ca2+ dynamics as indicator of proper ER functionality.
RESULTS: We found that salubrinal and guanabenz increased the expression levels of phospho-eIF2α and downregulated the apoptosis markers CHOP and PARP-CL in LMNA R321X-cardiomyocytes, maintaining the so-called adaptive UPR. These drugs also restored ER ability to handle Ca2+ in these cardiomyocytes. Interestingly, we found that empagliflozin downregulated the apoptosis markers CHOP and PARP-CL shutting down the UPR itself through the inhibition of PERK phosphorylation in LMNA R321X-cardiomyocytes. Furthermore, upon empagliflozin treatment, ER homeostasis, in terms of ER ability to store and release intracellular Ca2+ was also restored in these cardiomyocytes.
CONCLUSIONS: We provided evidence that the different drugs, although interfering with different steps of the UPR, were able to counteract pro-apoptotic processes and to preserve the ER homeostasis in R321X LMNA-cardiomyocytes. Of note, two of the tested drugs, guanabenz and empagliflozin, are already used in the clinical practice, thus providing preclinical evidence for ready-to-use therapies in patients affected by the LMNA R321X associated cardiomyocytes.

Keywords:  Cardiomyocytes; Cardiomyopathy; ER stress; Empagliflozin; Guanabenz; Lamin A/C

DOI:  https://doi.org/10.1186/s12967-023-04170-y
Biochem Biophys Res Commun. 2023 May 15. pii: S0006-291X(23)00607-1. [Epub ahead of print]667 58-63

An ER-accumulated mutant of yeast Pma1 causes membrane-related stress to induce the unfolded protein response.

Huong Thi Phuong, Yuki Ishiwata-Kimata, Yukio Kimata.

  Upon dysfunction of the endoplasmic reticulum (ER), namely ER stress, eukaryotic cells provoke the unfolded protein response (UPR), which is triggered by ER stress sensors including Ire1. While the ER luminal domain of Ire1 is known to directly recognize misfolded soluble proteins accumulated in the ER, the transmembrane domain of Ire1 is involved in its self-association and activation upon membrane lipid-related abnormalities, which are so-called lipid bilayer stress (LBS). Here we inquired how the ER accumulation of misfolded transmembrane proteins induces the UPR. In yeast Saccharomyces cerevisiae cells, a multi-transmembrane protein, Pma1, is not transported to the cell surface but aggregates on the ER membrane when carrying a point mutation (Pma1-2308). Here, we show that GFP-tagged Ire1 co-localized with the Pma1-2308-mCherry puncta. This co-localization and the UPR induced by Pma1-2308-mCherry were compromised by a point mutation in Ire1 that specifically impairs its activation upon LBS. We presume that Pma1-2308-mCherry locally affects the properties (probably the thickness) of the ER membrane at its aggregation sites, where Ire1 is then recruited, self-associated, and then activated.

Keywords:  Endoplasmic reticulum; Lipid bilayer stress; Saccharomyces cerevisiae; Unfolded protein response; Yeast

DOI:  https://doi.org/10.1016/j.bbrc.2023.05.044
Cell Rep. 2023 May 19. pii: S2211-1247(23)00545-4. [Epub ahead of print]42(5): 112534

Activation of endoplasmic reticulum stress in premature aging via the inner nuclear membrane protein SUN2.

Sandra Vidak, Leonid A Serebryannyy, Gianluca Pegoraro, Tom Misteli.

  One of the major cellular mechanisms to ensure cellular protein homeostasis is the endoplasmic reticulum (ER) stress response. This pathway is triggered by accumulation of misfolded proteins in the ER lumen. The ER stress response is also activated in the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). Here, we explore the mechanism of activation of the ER stress response in HGPS. We find that aggregation of the diseases-causing progerin protein at the nuclear envelope triggers ER stress. Induction of ER stress is dependent on the inner nuclear membrane protein SUN2 and its ability to cluster in the nuclear membrane. Our observations suggest that the presence of nucleoplasmic protein aggregates can be sensed, and signaled to the ER lumen, via clustering of SUN2. These results identify a mechanism of communication between the nucleus and the ER and provide insight into the molecular disease mechanisms of HGPS.

Keywords:  CP: Cell biology; ER stress; Hutchinson-Gilford progeria syndrome; chaperones; transmembrane proteins; unfolded protein response

DOI:  https://doi.org/10.1016/j.celrep.2023.112534
Mucosal Immunol. 2023 May 18. pii: S1933-0219(23)00038-7. [Epub ahead of print]

Unfolded Protein Response Factor ATF6 Augments T Helper Cell Responses and Promotes Mixed Granulocytic Airway Inflammation.

Dandan Wu, Xing Zhang, Kourtney M Zimmerly, Ruoning Wang, Chunqing Wang, Russell Hunter, Xiang Wu, Matthew Campen, Meilian Liu, Xuexian O Yang.

  The unfolded protein response (UPR) is associated with the risk of asthma, including treatment-refractory severe asthma. Several recent studies demonstrated a pathogenic role of activating transcription factor 6α (ATF6α or ATF6), one of the essential arms of UPR, in airway structural cells. However, its role in T helper (TH) cells has not been well examined. In this study, we found that ATF6 was selectively induced by STAT6 and STAT3 in TH2 and TH17 cells, respectively. ATF6 upregulated UPR genes and promoted the differentiation and cytokine secretion of TH2 and TH17 cells. T cell-specificAtf6-deficiency impaired TH2 and TH17 responses in vitro and in vivo and attenuated mixed granulocytic experimental asthma. ATF6 inhibitor Ceapin A7 suppressed ATF6 downstream gene expression and TH cell cytokine expression in both murine and human memory CD4+ T cells. At the chronic stage of asthma, administration of Ceapin A7 lessened TH2 and TH17 responses in vivo, leading to alleviation of both airway neutrophilia and eosinophilia. Thus, our results demonstrate a critical role of ATF6 in TH2 and TH17 cell-driven mixed granulocytic airway disease, suggesting a novel option to combat steroid-resistant mixed and even T2-low endotypes of asthma by targeting ATF6.

Keywords:  ATF6; ER stress; TH17; TH2; mixed granulocytic asthma

DOI:  https://doi.org/10.1016/j.mucimm.2023.05.007
Int J Mol Sci. 2023 May 16. pii: 8853. [Epub ahead of print]24(10):

Physapruin A Exerts Endoplasmic Reticulum Stress to Trigger Breast Cancer Cell Apoptosis via Oxidative Stress.

Tzu-Jung Yu, Jun-Ping Shiau, Jen-Yang Tang, Ammad Ahmad Farooqi, Yuan-Bin Cheng, Ming-Feng Hou, Chia-Hung Yen, Hsueh-Wei Chang.

  Physalis plants are commonly used traditional medicinal herbs, and most of their extracts containing withanolides show anticancer effects. Physapruin A (PHA), a withanolide isolated from P. peruviana, shows antiproliferative effects on breast cancer cells involving oxidative stress, apoptosis, and autophagy. However, the other oxidative stress-associated response, such as endoplasmic reticulum (ER) stress, and its participation in regulating apoptosis in PHA-treated breast cancer cells remain unclear. This study aims to explore the function of oxidative stress and ER stress in modulating the proliferation and apoptosis of breast cancer cells treated with PHA. PHA induced a more significant ER expansion and aggresome formation of breast cancer cells (MCF7 and MDA-MB-231). The mRNA and protein levels of ER stress-responsive genes (IRE1α and BIP) were upregulated by PHA in breast cancer cells. The co-treatment of PHA with the ER stress-inducer (thapsigargin, TG), i.e., TG/PHA, demonstrated synergistic antiproliferation, reactive oxygen species generation, subG1 accumulation, and apoptosis (annexin V and caspases 3/8 activation) as examined by ATP assay, flow cytometry, and western blotting. These ER stress responses, their associated antiproliferation, and apoptosis changes were partly alleviated by the N-acetylcysteine, an oxidative stress inhibitor. Taken together, PHA exhibits ER stress-inducing function to promote antiproliferation and apoptosis of breast cancer cells involving oxidative stress.

Keywords:  ER expansion; N-acetylcysteine; ROS; aggresome; caspase activation; withanolide

DOI:  https://doi.org/10.3390/ijms24108853
Biomedicines. 2023 May 16. pii: 1457. [Epub ahead of print]11(5):

Myogenesis in C2C12 Cells Requires Phosphorylation of ATF6α by p38 MAPK.

Valentina Pagliara, Giuseppina Amodio, Vincenzo Vestuto, Silvia Franceschelli, Nicola Antonino Russo, Vittorio Cirillo, Giovanna Mottola, Paolo Remondelli, Ornella Moltedo.

  Activating transcription factor 6α (ATF6α) is an endoplasmic reticulum protein known to participate in unfolded protein response (UPR) during ER stress in mammals. Herein, we show that in mouse C2C12 myoblasts induced to differentiate, ATF6α is the only pathway of the UPR activated. ATF6α stimulation is p38 MAPK-dependent, as revealed by the use of the inhibitor SB203580, which halts myotube formation and, at the same time, impairs trafficking of ATF6α, which accumulates at the cis-Golgi without being processed in the p50 transcriptional active form. To further evaluate the role of ATF6α, we knocked out the ATF6α gene, thus inhibiting the C2C12 myoblast from undergoing myogenesis, and this occurred independently from p38 MAPK activity. The expression of exogenous ATF6α in knocked-out ATF6α cells recover myogenesis, whereas the expression of an ATF6α mutant in the p38 MAPK phosphorylation site (T166) was not able to regain myogenesis. Genetic ablation of ATF6α also prevents the exit from the cell cycle, which is essential for muscle differentiation. Furthermore, when we inhibited differentiation by the use of dexamethasone in C2C12 cells, we found inactivation of p38 MAPK and, consequently, loss of ATF6α activity. All these findings suggest that the p-p38 MAPK/ATF6α axis, in pathophysiological conditions, regulates myogenesis by promoting the exit from the cell cycle, an essential step to start myoblasts differentiation.

Keywords:  C2C12; activating transcription factor 6 α (ATF6α); myogenesis; p38 Mitogen-Activated Protein Kinase (MAPK); unfolded protein response

DOI:  https://doi.org/10.3390/biomedicines11051457
Biomedicines. 2023 Apr 24. pii: 1259. [Epub ahead of print]11(5):

Protective Effect and Mechanism of Xbp1s Regulating HBP/O-GlcNAcylation through GFAT1 on Brain Injury after SAH.

Kefan Wu, Lili Chen, Zhen Qiu, Bo Zhao, Jiabao Hou, Shaoqin Lei, Meng Jiang, Zhongyuan Xia.

  (1) SAH induces cellular stress and endoplasmic reticulum stress, activating the unfolded protein response (UPR) in nerve cells. IRE1 (inositol-requiring enzyme 1) is a protein that plays a critical role in cellular stress response. Its final product, Xbp1s, is essential for adapting to changes in the external environment. This process helps maintain proper cellular function in response to various stressors. O-GlcNAcylation, a means of protein modification, has been found to be involved in SAH pathophysiology. SAH can increase the acute O-GlcNAcylation level of nerve cells, which enhances the stress capacity of nerve cells. The GFAT1 enzyme regulates the level of O-GlcNAc modification in cells, which could be a potential target for neuroprotection in SAH. Investigating the IRE1/XBP1s/GFAT1 axis could offer a promising avenue for future research. (2) Methods: SAH was induced using a suture to perforate an artery in mice. HT22 cells with Xbp1 loss- and gain-of-function in neurons were generated. Thiamet-G was used to increase O-GlcNAcylation; (3) Results: Severe neuroinflammation caused by subarachnoid hemorrhage leads to extensive endoplasmic reticulum stress of nerve cells. Xbp1s, the final product of unfolded proteins induced by endoplasmic reticulum stress, can induce the expression of the hexosamine pathway rate limiting enzyme GFAT1, increase the level of O-GlcNAc modification of cells, and have a protective effect on neural cells; (4) Conclusions: The correlation between Xbp1s displayed by immunohistochemistry and O-GlcNAc modification suggests that the IRE1/XBP1 branch of unfolded protein reaction plays a key role in subarachnoid hemorrhage. IRE1/XBP1 branch is a new idea to regulate protein glycosylation modification, and provides a promising strategy for clinical perioperative prevention and treatment of subarachnoid hemorrhage.

Keywords:  HBP; O-GlcNAc; Xbp1s; subarachnoid hemorrhage

DOI:  https://doi.org/10.3390/biomedicines11051259
Sci Rep. 2023 May 22. 13(1): 8232

A comprehensive signature based on endoplasmic reticulum stress-related genes in predicting prognosis and immunotherapy response in melanoma.

Longqing Liu, Dilang Yao, Zhiwei Chen, Shidong Duan.

Melanoma is considered as one of the most invasion types of skin cancer with high mortality rates. Although combination of immune checkpoint therapy with local surgical excision provide a novel promising therapeutic strategies, the overall prognosis of melanoma patients remains unsatisfactory. Endoplasmic reticulum (ER) stress, a process of protein misfolding and undue accumulation, has been proven to play an indispensable regulatory role in tumor progression and tumor immunity. However, whether the signature based ER genes has predictive value for the prognosis and immunotherapy of melanoma has not been systematically manifested. In this study, the LASSO regression and multivariate Cox regression were applied to construct a novel signature for predicting melanoma prognosis both in the training and testing set. Intriguingly, we found that patients endowed with high- and low-risk scores displayed differences in clinicopathologic classification, immune cell infiltration level, tumor microenvironment, and immune checkpoint treatment response. Subsequently, based on molecular biology experiments, we validated that silencing the expression of RAC1, an ERG composed of the risk signature, could restrain the proliferation and migration, promote apoptosis, as well as increase the expression of PD-1/PD-L1 and CTLA4 in melanoma cells. Taken together, the risk signature was regarded as promising predictors for melanoma prognosis and might provide prospective strategies to ameliorate patients' response to immunotherapy.

DOI: https://doi.org/10.1038/s41598-023-35031-9
Cancer Cell Int. 2023 May 23. 23(1): 100

Cell surface GRP78: a potential mechanism of therapeutic resistant tumors.

Rajalakshmi Amaresan, Udhayakumar Gopal.

  GRP78 is a protein that acts as a chaperone within the endoplasmic reticulum (ER) and has multiple functions. It is induced by stress and abets cells from survival. Despite, multiple Stress conditions like ER, chronic psychological and nutritional stress, hypoxia, chemotherapy, radiation therapy, and drug resistance induce cell surface GRP78 (CS-GRP78) expression in cancer cells. Further, CS-GRP78 is associated with increased malignancy and resistance to anti-cancer therapies and is considered a high-value druggable target. Recent preclinical research suggests that targeting CS-GRP78 with anti-GRP78 monoclonal antibodies (Mab) in combination with other agents may be effective in reversing the failure of chemotherapy, radiotherapy, or targeted therapies and increasing the efficacy of solid tumors treatment. This article will review recent evidence on the role of CS-GRP78 in developing resistance to anti-cancer treatments and the potential benefits of combining anti-GRP78 Mab with other cancer therapies for specific patient populations. Furthermore, our limited understanding of how CS-GRP78 regulated in human studies is a major drawback for designing effective CS-GRP78-targeted therapies. Hence, more research is still warranted to translate these potential therapies into clinical applications.

Keywords:  C38 monoclonal antibody; CS-GRP78; Chemoresitance; Drug resistance; ER-stress; Radioresistance; anti-GRP78 autoantibody

DOI:  https://doi.org/10.1186/s12935-023-02931-9