bims-unfpre 2021-10-10 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2021–10–10
nine papers selected by
Susan Logue, University of Manitoba

Ubiquitination of ATF6 by disease-associated RNF186 promotes the innate receptor-induced unfolded protein response.
The transcription factor Xrp1 is required for PERK-mediated antioxidant gene induction in Drosophila.
Site-1 and site-2 proteases: A team of two in regulated proteolysis.
Stress response proteins NRP1 and NRP2 are pro-survival factors that inhibit cell death during ER stress.
ORMDL3 regulates cigarette smoke-induced endoplasmic reticulum stress in airway smooth muscle cells.
TXNIP links anticipatory unfolded protein response to estrogen reprogramming glucose metabolism in breast cancer cells.
GPX7 Facilitates BMSCs Osteoblastogenesis via ER Stress and mTOR Pathway.
Sirt1 promotes tissue regeneration in zebrafish through regulating the mitochondrial unfolded protein response.
Epithelial XBP1 coordinates TP53-driven DNA damage responses and suppression of intestinal carcinogenesis.

J Clin Invest. 2021 Sep 01. pii: e145472. [Epub ahead of print]131(17):

Ubiquitination of ATF6 by disease-associated RNF186 promotes the innate receptor-induced unfolded protein response.

Kishu Ranjan, Matija Hedl, Saloni Sinha, Xuchen Zhang, Clara Abraham.

  Properly balancing microbial responses by the innate immune system through pattern recognition receptors (PRRs) is critical for intestinal immune homeostasis. Ring finger protein 186 (RNF186) genetic variants are associated with inflammatory bowel disease (IBD). However, functions for the E3 ubiquitin ligase RNF186 are incompletely defined. We found that upon stimulation of the PRR nucleotide-binding oligomerization domain containing 2 (NOD2) in human macrophages, RNF186 localized to the ER, formed a complex with ER stress sensors, ubiquitinated the ER stress sensor activating transcription factor 6 (ATF6), and promoted the unfolded protein response (UPR). These events, in turn, led to downstream signaling, cytokine secretion, and antimicrobial pathway induction. Importantly, RNF186-mediated ubiquitination of K152 on ATF6 was required for these outcomes, highlighting a key role for ATF6 ubiquitination in PRR-initiated functions. Human macrophages transfected with the rare RNF186-A64T IBD risk variant and macrophages from common rs6426833 RNF186 IBD risk carriers demonstrated reduced NOD2-induced outcomes, which were restored by rescuing UPR signaling. Mice deficient in RNF186 or ATF6 demonstrated a reduced UPR in colonic tissues, increased weight loss, and less effective clearance of bacteria with dextran sodium sulfate-induced injury and upon oral challenge with Salmonella Typhimurium. Therefore, we identified that RNF186 was required for PRR-induced, UPR-associated signaling leading to key macrophage functions; defined that RNF186-mediated ubiquitination of ATF6 was essential for these functions; and elucidated how RNF186 IBD risk variants modulated these outcomes.

Keywords:  Immunology; Innate immunity; Macrophages

DOI:  https://doi.org/10.1172/JCI145472
Elife. 2021 Oct 04. pii: e74047. [Epub ahead of print]10

The transcription factor Xrp1 is required for PERK-mediated antioxidant gene induction in Drosophila.

Brian Brown, Sahana Mitra, Finnegan D Roach, Deepika Vasudevan, Hyung Don Ryoo.

  PERK is an endoplasmic reticulum (ER) transmembrane sensor that phosphorylates eIF2a to initiate the Unfolded Protein Response (UPR). eIF2a phosphorylation promotes stress-responsive gene expression most notably through the transcription factor ATF4 that contains a regulatory 5' leader. Possible PERK effectors other than ATF4 remain poorly understood. Here, we report that the bZIP transcription factor Xrp1 is required for ATF4-independent PERK signaling. Cell type-specific gene expression profiling in Drosophila indicated that delta-family glutathione-S-transferases (gstD) are prominently induced by the UPR-activating transgene Rh1G69D. Perk was necessary and sufficient for such gstD induction, but ATF4 was not required. Instead, Perk and other regulators of eIF2a phosphorylation regulated Xrp1 protein levels to induce gstDs. The Xrp1 5' leader has a conserved upstream Open Reading Frame (uORF) analogous to those that regulate ATF4 translation. The gstD-GFP reporter induction required putative Xrp1 binding sites. These results indicate that antioxidant genes are highly induced by a previously unrecognized UPR signaling axis consisting of PERK and Xrp1.

Keywords:  D. melanogaster; genetics; genomics

DOI:  https://doi.org/10.7554/eLife.74047
Biochim Biophys Acta Mol Cell Res. 2021 Oct 04. pii: S0167-4889(21)00192-0. [Epub ahead of print] 119138

Site-1 and site-2 proteases: A team of two in regulated proteolysis.

Tatyana Danyukova, Kenneth Schöneck, Sandra Pohl.

  The site-1 and site-2 proteases (S1P and S2P) were identified over 20 years ago, and the functions of both have been addressed in numerous studies ever since. Whereas S1P processes a set of substrates independently of S2P, the latter acts in concert with S1P in a mechanism, called regulated intramembrane proteolysis, that controls lipid metabolism and response to unfolded proteins. This review summarizes the molecular roles that S1P and S2P jointly play in these processes. As S1P and S2P deficiencies mainly affect connective tissues, yet with varying phenotypes, we discuss the segregated functions of S1P and S2P in terms of cell homeostasis and maintenance of the connective tissues. In addition, we provide experimental data that point at S2P, but not S1P, as a critical regulator of cell adaptation to proteotoxicity or lipid imbalance. Therefore, we hypothesize that S2P can also function independently of S1P activity.

Keywords:  ER stress; Site-1 protease; lipid homeostasis; site-2 protease; unfolded protein response

DOI:  https://doi.org/10.1016/j.bbamcr.2021.119138
Plant Physiol. 2021 Jul 20. pii: kiab335. [Epub ahead of print]

Stress response proteins NRP1 and NRP2 are pro-survival factors that inhibit cell death during ER stress.

Yuhua Yang, Xu Liu, Wenbin Zhang, Qian Qian, Limeng Zhou, Shu Liu, Yuge Li, Xingliang Hou.

Environmental stresses cause an increased number of unfolded or misfolded proteins to accumulate in the endoplasmic reticulum (ER), resulting in ER stress. To restore ER homeostasis and survive, plants initiate an orchestrated signaling pathway known as the unfolded protein response (UPR). Asparagine-rich protein (NRP) 1 and NRP2, two homologous proteins harboring a Development and Cell Death domain, are associated with various stress responses in Arabidopsis (Arabidopsis thaliana), but the relevant molecular mechanism remains obscure. Here, we show that NRP1 and NRP2 act as key pro-survival factors during the ER stress response and that they inhibit cell death. Loss-of-function of NRP1 and NRP2 results in decreased tolerance to the ER stress inducer tunicamycin (TM), accelerating cell death. NRP2 is constitutively expressed while NRP1 is induced in plants under ER stress. In Arabidopsis, basic leucine zipper protein (bZIP) 28 and bZIP60 are important transcription factors in the UPR that activates the expression of many ER stress-related genes. Notably, under ER stress, bZIP60 activates NRP1 by directly binding to the UPRE-I element in the NRP1 promoter. These findings reveal a pro-survival strategy in plants wherein the bZIP60-NRPs cascade suppresses cell death signal transmission, improving survival under adverse conditions.

DOI: https://doi.org/10.1093/plphys/kiab335
J Allergy Clin Immunol. 2021 Oct 05. pii: S0091-6749(21)01514-1. [Epub ahead of print]

ORMDL3 regulates cigarette smoke-induced endoplasmic reticulum stress in airway smooth muscle cells.

Rui Chen, Charalambos Michaeloudes, Yingmin Liang, Pankaj K Bhavsar, Kian Fan Chung, Mary Sm Ip, Judith Cw Mak.

   BACKGROUND: Orosomucoid 1-Like Protein 3 (ORMDL3), a transmembrane protein localized in the endoplasmic reticulum (ER), has been genetically associated with chronic obstructive pulmonary disease (COPD), in addition to childhood-onset asthma. However, the functional role of ORMDL3 in the pathogenesis of COPD is still unknown.
OBJECTIVE: As cigarette smoke is the major risk factor for COPD, we aimed to investigate the role of ORMDL3 on cigarette smoke-induced in human airway smooth muscle cells (HASMCs) injury.
METHODS: The mRNA and protein expression of ORMDL3 was examined in HASMCs from nonsmokers and smokers without or with COPD. Knockdown of ORMDL3 in primary healthy HASMCs was performed using siRNA prior to exposure to cigarette smoke medium (CSM) for 24 hours. Inflammatory, proliferative/apoptotic, ER stress and mitochondrial markers were evaluated.
RESULTS: Elevation of ORMDL3 mRNA and protein expression was observed in HASMCs of smokers without or with COPD. CSM caused significant upregulation of ORMDL3 expression in healthy nonsmokers. ORMDL3 knockdown regulated CSM-induced inflammation, cell proliferation and apoptosis. Silencing ORMDL3 led to reduction of CSM-induced ER stress via inhibition of unfolded protein response (UPR) pathways such as activating transcription factor (ATF)6 and protein kinase RNA-like ER kinase (PERK). ORMDL3 was also involved in CSM-induced mitochondrial dysfunction via the mitochondrial fission process.
CONCLUSION: We report the induction of ORMDL3 in human airway smooth muscle cells after cigarette smoke exposure. ORMDL3 may mediate cigarette smoke-induced activation of unfolded protein response pathways during airway smooth muscle cell injury.

Keywords:  ORMDL3; chronic obstructive pulmonary disease; cigarette smoke; unfolded protein response

DOI:  https://doi.org/10.1016/j.jaci.2021.09.028
Endocrinology. 2021 Oct 06. pii: bqab212. [Epub ahead of print]

TXNIP links anticipatory unfolded protein response to estrogen reprogramming glucose metabolism in breast cancer cells.

Yuanzhong Wang, Shiuan Chen.

  Estrogen and estrogen receptor (ER) play a fundamental role in breast cancer. To adapt the rapid proliferation of ER+ breast cancer cells, estrogen increases glucose uptake and reprograms glucose metabolism. Meanwhile, estrogen/ER activates the anticipatory unfolded protein response (UPR) preparing cancer cells for the increased protein production required for subsequent cell proliferation. Here, we report that thioredoxin-interacting protein (TXNIP) is an important regulator of glucose metabolism in ER+ breast cancer cells, and estrogen/ER increases glucose uptake and reprograms glucose metabolism via activating anticipatory unfolded protein response (UPR) and subsequently repressing TXNIP expression. By using two widely used ER+ breast cancer cell lines MCF7 and T47D, we showed that MCF7 cells express high TXNIP levels and exhibit mitochondrial oxidative phosphorylation (OXPHOS) phenotype, while T47D cells express low TXNIP levels and display aerobic glycolysis (Warburg effect) phenotype. Knockdown of TXNIP promoted glucose uptake and Warburg effect, while forced overexpression of TXNIP inhibited glucose uptake and Warburg effect. We further showed that estrogen represses TXNIP expression and activates UPR sensor inositol-requiring enzyme 1 (IRE1) via ER in the breast cancer cells, and IRE1 activity is required for estrogen suppression of TXNIP expression and estrogen-induced cell proliferation. Together, our study suggests that TXNIP is involved in estrogen-induced glucose uptake and metabolic reprogramming in ER+ breast cancer cells, and links anticipatory UPR to estrogen reprogramming glucose metabolism.

Keywords:  TXNIP; breast cancer; estrogen; glucose metabolism; unfolded protein response

DOI:  https://doi.org/10.1210/endocr/bqab212
J Cell Mol Med. 2021 Oct 09.

GPX7 Facilitates BMSCs Osteoblastogenesis via ER Stress and mTOR Pathway.

Xuchen Hu, Boer Li, Fanzi Wu, Xiaoyu Liu, Mengyu Liu, Chenglin Wang, Yu Shi, Ling Ye.

  Emerging evidence indicates extensive oxidative stress is a consequence of obesity which impairs bone formation. Glutathione peroxidase 7 (GPX7) is a conserved endoplasmic reticulum (ER) retention protein, lacking of which causes accumulation of reactive oxygen species (ROS) and promotes adipogenesis. Since the imbalance between osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cell (BMSC) leads to severe bone diseases such as osteoporosis, it is critical to investigate the potential protective role of Gpx7 in osteogenesis. Here, we provide evidence that deficiency of Gpx7 reduces osteogenesis, but increases adipogenesis in both human BMSCs (hBMSCs) and mouse mesenchymal stem cell line. Interestingly, further studies indicate this defect can be alleviated by the ER stress antagonist, but not the ROS inhibitor, unveiling an unexpected finding that, unlike adipogenesis, lacking of Gpx7 inhibits osteogenesis mediating by induced ER stress instead of enhanced ROS. Furthermore, the mTOR signalling pathway is found down-regulation during osteogenic differentiation in Gpx7-deficient condition, which can be rescued by relief of ER stress. Taken together, for the first time we identify a novel function of Gpx7 in BMSCs' osteogenic differentiation and indicate that Gpx7 may protect against osteoporotic deficits in humans through ER stress and mTOR pathway interplay.

Keywords:  BMSCs; ER stress; GPX7; osteogenic differentiation

DOI:  https://doi.org/10.1111/jcmm.16974
iScience. 2021 Oct 22. 24(10): 103118

Sirt1 promotes tissue regeneration in zebrafish through regulating the mitochondrial unfolded protein response.

Yi-Fan Lin, Jessica Sam, Todd Evans.

  The mitochondrial unfolded protein response (UPRmt) is an organellar stress signaling pathway that functions to detect and restore disruption of mitochondrial proteostasis. The UPRmt is involved in a wide range of physiological and disease conditions, including aging, stem cell maintenance, innate immunity, neurodegeneration, and cancer. Here we report that the UPRmt is integral to zebrafish fin regeneration. Taking advantage of a novel zebrafish UPRmt reporter, we observed that UPRmt activation occurs in regenerating fin tissue shortly after injury. Through chemical and genetic approaches, we discovered that the Sirt1-UPRmt pathway, best known for its role in promoting lifespan extension, is crucial for fin regeneration. The metabolism of NAD+ is an important contributor to Sirt1 activity in this context. We propose that Sirt1 activation induces mitochondrial biogenesis in injured fin tissue, which leads to UPRmt activation and promotes tissue regeneration.

Keywords:  Cell biology; Developmental biology; Molecular biology

DOI:  https://doi.org/10.1016/j.isci.2021.103118
Gastroenterology. 2021 Sep 29. pii: S0016-5085(21)03606-4. [Epub ahead of print]

Epithelial XBP1 coordinates TP53-driven DNA damage responses and suppression of intestinal carcinogenesis.

Lina Welz, Nassim Kakavand, Xiang Hang, Georg Laue, Go Ito, Miguel Gomes Silva, Christina Plattner, Neha Mishra, Felicitas Tengen, Christoph Ogris, Moritz Jesinghaus, Felix Wottawa, Philipp Arnold, Leena Kaikkonen, Stefanie Stengel, Florian Tran, Saumya Das, Arthur Kaser, Zlatko Trajanoski, Richard Blumberg, Christoph Roecken, Dieter Saur, Markus Tschurtschenthaler, Stefan Schreiber, Philip Rosenstiel, Konrad Aden.

   BACKGROUND AIMS: Throughout life, the intestinal epithelium undergoes constant self-renewal from intestinal stem cells. Together with genotoxic stressors and failing DNA repair, this self-renewal causes susceptibility towards malignant transformation. X-box binding protein 1 (XBP1) is a stress sensor involved in the unfolded protein response (UPR). We hypothesized that XBP1 acts as a signaling hub to regulate epithelial DNA damage responses.
METHODS: Data from the TCGA were analyzed for association of XBP1 with CRC survival and molecular interactions between XBP1 andp53 pathway activity. The role of XBP1 in orchestrating p53-driven DNA damage response was tested in-vitro, in mouse models of chronic intestinal epithelial DNA damage (Xbp1/H2bfl/fl, Xbp1ΔIEC, H2bΔIEC, H2b/Xbp1ΔIEC) and via orthotopic tumor organoid transplantation. Transcriptome analysis of intestinal organoids was performed to identify molecular targets of Xbp1-mediated DNA damage response.
RESULTS: In the TCGA dataset of CRC, low XBP1 expression was significantly associated with poor overall survival (OS) and reduced p53 pathway activity. In-vivo, H2b/Xbp1ΔIEC mice developed spontaneous intestinal carcinomas. Orthotopic tumor organoid transplantation revealed a metastatic potential of H2b/Xbp1ΔIEC-derived tumors. RNA sequencing of intestinal organoids (H2b/Xbp1fl/fl, H2bΔIEC, H2b/Xbp1ΔIEC, H2b/p53ΔIEC) identified a transcriptional program downstream of p53, in which XBP1 directs DNA damage-induced Ddit4l expression. DDIT4L inhibits mTOR-mediated phosphorylation of 4E-BP1. Pharmacological mTOR inhibition suppressed epithelial hyperproliferation via 4E-BP1.
CONCLUSIONS: Our data suggest a crucial role for XBP1 in coordinating epithelial DNA damage responses and stem cell function via a p53-DDIT4L-dependent feedback mechanism.

Keywords:  CRC; DNA damage; XBP1; intestinal epithelial cell; p53

DOI:  https://doi.org/10.1053/j.gastro.2021.09.057