bims-unfpre 2024-01-28 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2024–01–28
nine papers selected by
Susan Logue, University of Manitoba

Platelets induce endoplasmic reticulum stress in macrophages in vitro.
Excess dietary sodium partially restores salt and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron.
A new role for IFRD1 in regulation of ER stress in bladder epithelial homeostasis.
SIRT7 sustains tumor development and radioresistance by repressing endoplasmic reticulum stress-induced apoptosis in cutaneous melanoma.
Endoplasmic reticulum stress interferes with the development of type 1 regulating T cells.
Endoplasmic Reticulum Membrane Homeostasis and the Unfolded Protein Response.
CHIP suppresses the proliferation and migration of A549 cells by mediating the ubiquitination of eIF2α and upregulation of tumor suppressor RBM5.
Heat shock response during the resolution of inflammation and its progressive suppression in chronic-degenerative inflammatory diseases.
The unfolded protein response of the endoplasmic reticulum protects Caenorhabditis elegans against DNA damage caused by stalled replication forks.

J Thromb Haemost. 2024 Jan 24. pii: S1538-7836(24)00046-1. [Epub ahead of print]

Platelets induce endoplasmic reticulum stress in macrophages in vitro.

Martina Derler, Theresa Teubenbacher, Anna Carapuig, Bernhard Nieswandt, Johannes Fessler, Dagmar Kolb, Marion Mussbacher.

   BACKGROUND: Endoplasmic reticulum (ER) stress is a key feature of lipid-laden macrophages and contributes to the development of atherosclerotic plaques. Blood platelets are known to interact with macrophages and finetune effector functions such as inflammasome activation and phagocytosis. However, the effect of platelets on ER stress induction is unknown. The objective of this study is to elucidate the potential of platelets to regulate ER stress in macrophages in vitro.
METHODS: Bone marrow-derived macrophages (BMDM) and RAW 264.7 cells were incubated with isolated murine platelets, and ER stress and inflammation markers were determined by RT-qPCR, western blotting, and ELISA. ER morphology was investigated by electron microscopy. Cell viability, lipid accumulation, and activation were measured by flow cytometry. To gain mechanistic insights, co-incubation experiments were performed with platelet decoys/releasates, as well as lipopolysaccharide, blocking antibodies, and TLR4 inhibitors.
RESULTS: Co-incubation of platelets and macrophages led to elevated levels of ER stress markers (BIP, IRE1α, CHOP, XBP1 splicing) in murine and human macrophages, which led to a pronounced enlargement of the ER. Macrophage ER stress was accompanied by increased release of pro-inflammatory cytokines and intracellular lipid accumulation, but not cell death. Platelet decoys, but not platelet releasates or lysate from other cells, phenocopied the effect of platelets. Blocking TLR4 inhibited inflammatory activation of macrophages but did not affect ER stress induction by platelet co-incubation.
CONCLUSION: This study is the first to demonstrate that platelets induce ER stress and UPR in macrophages by heat-sensitive membrane proteins independent of inflammatory activation of macrophages.

Keywords:  ER stress; atherosclerosis; blood platelets; macrophages; unfolded protein response

DOI:  https://doi.org/10.1016/j.jtha.2024.01.009
bioRxiv. 2024 Jan 14. pii: 2024.01.13.575426. [Epub ahead of print]

Excess dietary sodium partially restores salt and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron.

Aidan Porter, Hannah E Vorndran, Allison L Marciszyn, Stephanie M Mutchler, Arohan R Subramanya, Thomas R Kleyman, Linda M Hendershot, Jeffrey L Brodsky, Teresa M Buck.

The maintenance of fluid and electrolyte homeostasis by the kidney requires proper folding and trafficking of ion channels and transporters in kidney epithelia. Each of these processes requires a specific subset of a diverse class of proteins termed molecular chaperones. One such chaperone is GRP170, which is an Hsp70-like, endoplasmic reticulum (ER)-localized chaperone that plays roles in protein quality control and protein folding in the ER. We previously determined that loss of GRP170 in the mouse nephron leads to hypovolemia, electrolyte imbalance, and rapid weight loss. In addition, GRP170-deficient mice develop an AKI-like phenotype, typified by tubular injury, elevation of clinical kidney injury markers, and induction of the unfolded protein response (UPR). By using an inducible GRP170 knockout cellular model, we confirmed that GRP170 depletion induces the UPR, triggers an apoptotic response, and disrupts protein homeostasis. Based on these data, we hypothesized that UPR induction underlies hyponatremia and volume depletion in rodents, but that these and other phenotypes might be rectified by supplementation with high salt. To test this hypothesis, control and GRP170 tubule-specific knockout mice were provided with a diet containing 8% sodium chloride. We discovered that sodium supplementation improved electrolyte imbalance and reduced clinical kidney injury markers, but was unable to restore weight or tubule integrity. These results are consistent with UPR induction contributing to the kidney injury phenotype in the nephron-specific GR170 knockout model, and that the role of GRP170 in kidney epithelia is essential to both maintain electrolyte balance and cellular protein homeostasis.

DOI: https://doi.org/10.1101/2024.01.13.575426
bioRxiv. 2024 Jan 10. pii: 2024.01.09.574887. [Epub ahead of print]

A new role for IFRD1 in regulation of ER stress in bladder epithelial homeostasis.

Bisiayo E Fashemi, Amala K Rougeau, Arnold M Salazar, Steven J Bark, Rayvanth Chappidi, Jeffrey W Brown, Charles J Cho, Jason C Mills, Indira U Mysorekar.

A healthy bladder requires the homeostatic maintenance of and rapid regeneration of urothelium upon stress/injury/infection. Several factors have been identified to play important roles in urothelial development, injury and disease response, however, little is known about urothelial regulation at homeostasis. Here, we identify a new role for IFRD1, a stress-induced gene that has recently been demonstrated to play a critical role in adult tissue proliferation and regeneration, in maintenance of urothelial function/ homeostasis in a mouse model. We show that the mouse bladder expresses IFRD1 at homeostasis and its loss alters the global transcriptome of the bladder with significant accumulation of cellular organelles including multivesicular bodies with undigested cargo, lysosomes and mitochondria. We demonstrate that IFRD1 interacts with several mRNA-translation-regulating factors in human urothelial cells and that the urothelium of Ifrd1 -/- mice reveal decreased global translation and enhanced endoplasmic reticulum (ER) stress response. Ifrd1 -/- bladders have activation of the unfolded protein response (UPR) pathway, specifically the PERK arm, with a concomitant increase in oxidative stress and spontaneous exfoliation of urothelial cells. Further, we show that such increase in cell shedding is associated with a compensatory proliferation of the basal cells but impaired regeneration of superficial cells. Finally, we show that upon loss of IFRD1, mice display aberrant voiding behavior. Thus, we propose that IFRD1 is at the center of many crucial cellular pathways that work together to maintain urothelial homeostasis, highlighting its importance as a target for diagnosis and/or therapy in bladder conditions.

DOI: https://doi.org/10.1101/2024.01.09.574887
Cell Signal. 2024 Jan 18. pii: S0898-6568(24)00026-3. [Epub ahead of print]116 111058

SIRT7 sustains tumor development and radioresistance by repressing endoplasmic reticulum stress-induced apoptosis in cutaneous melanoma.

Bingyao Meng, Minna Xu, Zihan Chen, Jia You, Rui Zhou, Jian Guan, Liang Zhou.

  Cutaneous melanoma is one of the most malignant human tumors and possesses strong resistance to radiotherapy. However, the mechanisms contribute to such radioresistance of melanoma is unclear. In this study, SIRT7 is identified to be higher-expressed in melanoma and positively correlated with melanoma staging. Under ionizing radiation (IR)-treatment condition, loss of SIRT7 compromised the survivability of melanoma cells showed by decreased proliferation, colony formation, migration, but enhancing apoptosis. Transcriptomic sequencing analysis indicated the apoptosis induced after SIRT7 knockdown is tightly related with the induction of endoplasmic reticulum stress (ER stress) by IR treatment. Loss of SIRT7 enhanced EIF2α acetylation and activated its phosphorylation to induce the expression of ER stress proteins including DDIT3, XBP1 and GRP78, among which DDIT3 is responsible for apoptosis induction. SIRT7 depletion enriched ER stress-activated transcription factor ATF4 at the promoter region of DDIT3 gene to transactivate its expression and induces apoptotic cascade in both mock- and IR-treatment conditions. Consistently, SIRT7 is highly upregulated in radioresistant melanoma cell strain and still modulates the ER-stress responsive genes to maintain the homeostasis of melanoma. Collectively, SIRT7 negatively regulates ER stress-activated apoptosis to enhance the survivability of melanoma cells in both non-IR- and IR-treatment conditions. Our study highlights the role of SIRT7 in repressing ER stress and the following apoptosis to sustain tumor development and mediate radioresistance in melanoma, which may suggest a novel intervention target for melanoma therapy.

Keywords:  Apoptosis; Cutaneous melanoma; DDIT3; Endoplasmic reticulum stress; SIRT7

DOI:  https://doi.org/10.1016/j.cellsig.2024.111058
Inflamm Res. 2024 Jan 24.

Endoplasmic reticulum stress interferes with the development of type 1 regulating T cells.

Baisui Feng, Huazhen Liu, Wenkai Yao, Yan Li, Gaohui Wu, Liteng Yang, Pingchang Yang.

   BACKGROUND: A variety of stimuli can cause endoplasmic reticulum (ER) stress, which is a common cellular reaction. It is not yet clear how ER stress contributes to the pathogenesis of ulcerative colitis (UC). The deregulation of regulatory T cell (Treg) is associated with UC. The goal of this study is to shed light on how ER stress affects Treg's development.
METHODS: CD4+ CD25- T cells were isolated from blood samples collected from UC patients and healthy control (HC) subjects. ER stress-associated molecule expression in CD4+ CD25- T cell was assessed by RNA sequencing and RT-qPCR.
RESULTS: The presence of ER stress in peripheral CD4+ CD25- T cells was observed in patients with UC compared to HC subjects. The induction of ER stress in HC CD4+ CD25- T cells by polyclonal activation was made worse by the presence of 3-methyl-4-nitrophenol (MNP; a common environmental pollutant). Exposure to MNP in culture resulted in an increase in the expression of ring finger protein 20 (Rnf20) in CD4+ CD25- T cells. The synergistic effects of MNP and ER stress on the reduction of IL-10 levels in CD4+ CD25- T cells are mediated by Rnf20, which prevents the development of Tr1 cells. Inhibition of Rnf20 resulted in the development of Tr1 cells from CD4+ CD25- T cells in UC patients.
CONCLUSIONS: The synergistic effects of ER stress and MNP interfere with the development of Tr1 cells. The development of Tr1 from CD4+ CD25- T cells in patients with UC is re-established by Rnf20 inhibition.

Keywords:  CD4 T cell; Colitis; Endoplasmic reticulum stress; Immune regulation; Immunity

DOI:  https://doi.org/10.1007/s00011-023-01841-w
Cold Spring Harb Perspect Biol. 2024 Jan 22. pii: a041400. [Epub ahead of print]

Endoplasmic Reticulum Membrane Homeostasis and the Unfolded Protein Response.

Robert Ernst, Mike F Renne, Aamna Jain, Alexander von der Malsburg.

The endoplasmic reticulum (ER) is the key organelle for membrane biogenesis. Most lipids are synthesized in the ER, and most membrane proteins are first inserted into the ER membrane before they are transported to their target organelle. The composition and properties of the ER membrane must be carefully controlled to provide a suitable environment for the insertion and folding of membrane proteins. The unfolded protein response (UPR) is a powerful signaling pathway that balances protein and lipid production in the ER. Here, we summarize our current knowledge of how aberrant compositions of the ER membrane, referred to as lipid bilayer stress, trigger the UPR.

DOI: https://doi.org/10.1101/cshperspect.a041400
J Biol Chem. 2024 Jan 23. pii: S0021-9258(24)00049-8. [Epub ahead of print] 105673

CHIP suppresses the proliferation and migration of A549 cells by mediating the ubiquitination of eIF2α and upregulation of tumor suppressor RBM5.

Bo Jin, Mengran Wang, Yiheng Sun, Priscilla Ann Hweek Lee, Xiangqi Zhang, Yao Lu, Bo Zhao.

  The PERK-eIF2α pathway plays an essential role in endoplasmic reticulum (ER) stress. When the PERK-eIF2α pathway is activated, PERK phosphorylates eIF2α (p-eIF2α) at Ser51 and quenches global protein synthesis. In this study, we verified eIF2α as a bona fide substrate of the E3 ubiquitin ligase CHIP both in vitro and in cells. CHIP mediated the ubiquitination and degradation of nonphosphorylated eIF2α in a chaperone-independent manner and promoted the upregulation of the transcription factor ATF4 under ER stress conditions. ATF4 induced the transcriptional enhancement of the tumor suppressor genes PTEN and RBM5. Although transcription was enhanced, the PTEN protein was subsequently degraded by CHIP, but the expression of the RBM5 protein was upregulated, thereby suppressing the proliferation and migration of A549 cells. Overall, our study established a new mechanism that deepened the understanding of the PERK-eIF2α pathway through the ubiquitination and degradation of eIF2α. The crosstalk between the phosphorylation and ubiquitination of eIF2α shed light on a new perspective for tumor progression.

Keywords:  CHIP; ER stress; PERK; RBM5; eIF2; phosphorylation; protein degradation; ubiquitination

DOI:  https://doi.org/10.1016/j.jbc.2024.105673
Cell Stress Chaperones. 2024 Jan 18. pii: S1355-8145(24)00042-7. [Epub ahead of print]

Heat shock response during the resolution of inflammation and its progressive suppression in chronic-degenerative inflammatory diseases.

Helena Trevisan Schroeder, Carlos Henrique de Lemos Muller, Thiago Gomes Heck, Mauricio Krause, Paulo Ivo Homem de Bittencourt.

  The heat shock response (HSR) is a crucial biochemical pathway that orchestrates the resolution of inflammation, primarily under proteotoxic stress conditions. This process hinges on the upregulation of heat shock proteins (HSPs) and other chaperones, notably the 70kDa family of HSPs (HSP70s), under the command of the heat shock transcription factor-1 (HSF1). However, in the context of chronic degenerative disorders characterized by persistent low-grade inflammation - such as insulin resistance, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases - a gradual suppression of the HSR does occur. This work delves into the mechanisms behind this phenomenon. It explores how the Western diet and sedentary lifestyle, culminating in the endoplasmic reticulum (ER) stress within adipose tissue cells, trigger a cascade of events. This cascade includes the unfolded protein response (UPR) and activation of the NLRP3 inflammasome, leading to the emergence of the senescence-associated secretory phenotype (SASP) and the propagation of inflammation throughout the body. Notably, the activation of the NLRP3 inflammasome not only fuels inflammation but also sabotages the HSR by degrading HuR, a crucial mRNA-binding protein responsible for maintaining HSF1 mRNA expression and stability on heat shock gene promoters. This paper underscores the imperative need to comprehend how chronic inflammation stifles the HSR and the clinical significance of evaluating the HSR using cost-effective and accessible tools. Such understanding is pivotal in the development of innovative strategies aimed at the prevention and treatment of these chronic inflammatory ailments, which continue to exact a heavy toll on global health and well-being.

Keywords:  HSP70; chronic inflammatory diseases; exercise; heat shock response; insulin resistance; obesity

DOI:  https://doi.org/10.1016/j.cstres.2024.01.002
G3 (Bethesda). 2024 Jan 24. pii: jkae017. [Epub ahead of print]

The unfolded protein response of the endoplasmic reticulum protects Caenorhabditis elegans against DNA damage caused by stalled replication forks.

Jiaming Xu, Brendil Sabatino, Junran Yan, Glafira Ermakova, Kelsie R S Doering, Stefan Taubert.

  All animals must maintain genome and proteome integrity, especially when experiencing endogenous or exogenous stress. To cope, organisms have evolved sophisticated and conserved response systems: unfolded protein responses (UPRs) ensure proteostasis while DNA damage responses (DDRs) maintains genome integrity. Emerging evidence suggests that UPRs and DDRs crosstalk, but this remains poorly understood. Here, we demonstrate that depletion of the DNA primases pri-1 or pri-2, which synthesize RNA primers at replication forks and whose inactivation causes DNA damage, activates the UPR of the endoplasmic reticulum (UPR-ER) in Caenorhabditis elegans, with especially strong activation in the germline. We observed activation of both the inositol-requiring-enzyme 1 (ire-1) and the protein kinase RNA-like ER kinase (pek-1) branches of the UPR-ER. Interestingly, activation of the UPR-ER output gene heat shock protein 4 (hsp-4) was partially independent of its canonical activators, ire-1 and X-box binding protein (xbp-1), and instead required the third branch of the UPR-ER, activating transcription factor 6 (atf-6), suggesting functional redundancy. We further found that primase depletion specifically induces the UPR-ER, but not the distinct cytosolic or mitochondrial UPRs, suggesting that primase inactivation causes compartment-specific rather than global stress. Functionally, loss of ire-1 or pek-1 sensitized animals to replication stress caused by hydroxyurea. Finally, transcriptome analysis of pri-1 embryos revealed several deregulated processes that could cause UPR-ER activation, including protein glycosylation, calcium signaling, and fatty acid desaturation. Together, our data show that the UPR-ER, but not other UPRs, responds to replication fork stress and that the UPR-ER is required to alleviate this stress.

Keywords:  BiP; DNA damage; DNA replication; UPR; primase

DOI:  https://doi.org/10.1093/g3journal/jkae017