bims-unfpre 2022-07-24 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2022–07–24
eight papers selected by
Susan Logue, University of Manitoba

Human PERK rescues unfolded protein response-deficient yeast cells.
TMBIM6 promotes diabetic tubular epithelial cell survival and albumin endocytosis by inhibiting the endoplasmic reticulum stress sensor, IRE1α.
Inhibitors of eIF4G1-eIF1 uncover its regulatory role of ER/UPR stress-response genes independent of eIF2α-phosphorylation.
ERO1-alpha deficiency and activation of protein translation synergistically impair breast tumor resilience.
Activation of the canonical ER Stress IRE1-XBP1 Pathway by Insulin Regulates Glucose and Lipid Metabolism.
Unfolded Protein Response Differentially Modulates the Platelet Phenotype.
PRMT1 suppresses doxorubicin-induced cardiotoxicity by inhibiting endoplasmic reticulum stress.
A Novel Defined Endoplasmic Reticulum Stress-Related lncRNA Signature for Prognosis Prediction and Immune Therapy in Glioma.

MicroPubl Biol. 2022 ;2022

Human PERK rescues unfolded protein response-deficient yeast cells.

Wei Sheng Yap, Guillaume Thibault.

Protein folding and quality control is tightly regulated at the endoplasmic reticulum (ER), and its disruption is associated with many diseases. In eukaryotes, the accumulation of unfolded protein in the ER is sensed by the three sensors, IRE1, PERK, and ATF6 to activate the unfolded protein response (UPR) to restore ER homeostasis. However, uncoupling the sensing of each sensor and their respective downstream pathways has been challenging as the absence of one is compensated by the remaining two sensors. Here, we report a fully functional human PERK (hPERK) chimeric protein expressed in Saccharomyces cerevisiae that could be used for high throughput screen to identify new PERK inhibitory or activating compounds as well as to characterize the PERK stress sensing mechanisms.

DOI: https://doi.org/10.17912/micropub.biology.000592
Mol Biol Rep. 2022 Jul 20.

TMBIM6 promotes diabetic tubular epithelial cell survival and albumin endocytosis by inhibiting the endoplasmic reticulum stress sensor, IRE1α.

Huidi Xie, Yang Shi, Ying Zhou, Hongfang Liu.

   AIM: Reduced albumin reabsorption in proximal tubular epithelial cells (PTECs), resulting from decreased megalin plasma membrane (PM) localization due to prolonged endoplasmic reticulum (ER) stress, potentially contributes to albuminuria in early diabetic kidney disease (DKD). To examine this possibility, we investigated the cytoprotective effect of TMBIM6 in promoting diabetic PTEC survival and albumin endocytosis by attenuating ER stress with an IRE1α inhibitor, KIRA6.
METHODS AND RESULTS: Renal TMBIM6 distribution and expression were determined by immunohistochemistry, western blotting, and qPCR, whereas tubular injury was evaluated in db/db mice. High-glucose (HG)-treated HK-2 cells were either treated with KIRA6 or transduced with a lentiviral vector for TMBIM6 overexpression. ER stress was measured by western blotting and ER-Tracker Red staining, whereas apoptosis was determined by performing TUNEL assays. Megalin expression was measured by immunofluorescence, and albumin endocytosis was evaluated after incubating cells with FITC-labeled albumin. Tubular injury and TMBIM6 downregulation occurred in db/db mouse renal cortical tissues. Both KIRA6 treatment and TMBIM6 overexpression inhibited ER stress by decreasing the levels of phosphorylated IRE1α, XBP1s, GRP78, and CHOP, and stabilizing ER expansion in HG-treated HK-2 cells. TUNEL assays performed with KIRA6-treated or TMBIM6-overexpressing cells showed a significant decrease in apoptosis, consistent with the significant downregulation of BAX and upregulation of BCL-2, as measured by immunoblotting. Both KIRA6 and TMBIM6 overexpression promoted megalin PM localization and restored albumin endocytosis in HG-treated HK-2 cells.
CONCLUSION: TMBIM6 promoted diabetic PTEC survival and albumin endocytosis by negatively regulating the IRE1α branch of ER stress.

Keywords:  Albumin endocytosis; Diabetic kidney disease; Diabetic renal tubular injury; Endoplasmic reticulum stress

DOI:  https://doi.org/10.1007/s11033-022-07744-z
Proc Natl Acad Sci U S A. 2022 Jul 26. 119(30): e2120339119

Inhibitors of eIF4G1-eIF1 uncover its regulatory role of ER/UPR stress-response genes independent of eIF2α-phosphorylation.

Urmila Sehrawat, Ora Haimov, Benjamin Weiss, Ana Tamarkin-Ben Harush, Shaked Ashkenazi, Alexander Plotnikov, Tzahi Noiman, Dena Leshkowitz, Gil Stelzer, Rivka Dikstein.

  During translation initiation, eIF4G1 dynamically interacts with eIF4E and eIF1. While the role of eIF4E-eIF4G1 is well established, the regulatory functions of eIF4G1-eIF1 are poorly understood. Here, we report the identification of the eIF4G1-eIF1 inhibitors i14G1-10 and i14G1-12. i14G1s directly bind eIF4G1 and inhibit translation in vitro and in the cell, and their effects on translation are dependent on eIF4G1 levels. Translatome analyses revealed that i14G1s mimic eIF1 and eIF4G1 perturbations on the stringency of start codon selection and the opposing roles of eIF1-eIF4G1 in scanning-dependent and scanning-independent short 5' untranslated region (UTR) translation. Remarkably, i14G1s activate ER/unfolded protein response (UPR) stress-response genes via enhanced ribosome loading, elevated 5'UTR translation at near-cognate AUGs, and unexpected concomitant up-regulation of coding-region translation. These effects are, at least in part, independent of eIF2α-phosphorylation. Interestingly, eIF4G1-eIF1 interaction itself is negatively regulated by ER stress and mTOR inhibition. Thus, i14G1s uncover an unknown mechanism of ER/UPR translational stress response and are valuable research tools and potential drugs against diseases exhibiting dysregulated translation.

Keywords:  eIF1; eIF4G1; i14G1-10; i14G1-12; translation

DOI:  https://doi.org/10.1073/pnas.2120339119
Br J Pharmacol. 2022 Jul 19.

ERO1-alpha deficiency and activation of protein translation synergistically impair breast tumor resilience.

Ersilia Varone, Alessandra Decio, Maria Chiara Barbera, Marco Bolis, Laura Di Rito, Federica Pisati, Raffaella Giavazzi, Ester Zito.

   BACKGROUND AND PURPOSE: Endoplasmic reticulum (ER) stress triggers an adaptive response in tumors which fosters their cell survival and resilience to stress. Activation of the ER stress response, through its PERK branch, promotes phosphorylation of the α-subunit of the translation initiation factor eIF2alpha, repressing general protein translation and selectively augmenting the translation of ATF4 with the downstream CHOP transcription factor and the protein disulfide oxidase ERO1.
EXPERIMENTAL APPROACH: Here we show that ISRIB, a small molecule that inhibits the action of the phosphorylated α-subunit of eIF2, activating protein translation, synergistically interacts with the genetic deficiency of protein disulfide oxidase ERO1, enfeebling breast tumor growth and spread.
KEY RESULTS: ISRIB represses the CHOP signal but, surprisingly, it does not inhibit ERO1. Mechanistically ISRIB increases the ER protein load with a marked perturbing effect on ERO1-deficient triple-negative breast cancer cells, which display impaired proteostasis and have adapted to living with a low client protein load in hypoxia, while ERO1 deficiency also impairs VEGF-dependent angiogenesis. ERO1-deficient triple-negative breast cancer xenografts have an augmented ER stress response and its PERK branch. ISRIB acts synergistically with ERO1 deficiency, inhibiting the growth of triple-negative breast cancer xenografts by impairing proliferation and angiogenesis, while it is not so effective on the xenograft counterparts with ERO1.
CONCLUSIONS AND IMPLICATIONS: These results demonstrate that ISRIB together with ERO1 deficiency synergistically shatter the PERK-dependent adaptive ER stress response by restarting protein synthesis in the setting of impaired proteostasis, finally promoting tumor cytotoxicity. Therefore, our findings suggest two surprising features in breast tumors: ERO1 is not regulated via CHOP under hypoxic conditions, and ISRIB offers a therapeutic option to efficiently inhibit tumor progression in those tumors with limited ERO1 and high PERK, and thus impaired proteostasis.

Keywords:  ERO1 alpha; Endoplasmic reticulum Stress; ISRIB (Integrated Stress Response Inhibitor); PERK pathway; UPR (unfolded protein response); breast cancer

DOI:  https://doi.org/10.1111/bph.15927
J Biol Chem. 2022 Jul 18. pii: S0021-9258(22)00725-6. [Epub ahead of print] 102283

Activation of the canonical ER Stress IRE1-XBP1 Pathway by Insulin Regulates Glucose and Lipid Metabolism.

Jinghua Peng, Caolitao Qin, Balamurugan Ramatchandirin, Alexia Pearah, Shaodong Guo, Mehboob Hussain, Liqing Yu, Fredric E Wondisford, Ling He.

  Knockout of the transcription factor X-box binding protein (XBP1) is known to decrease liver glucose production and lipogenesis. However, whether insulin can regulate gluconeogenesis and lipogenesis through XBP1 and how insulin activates the inositol-requiring enzyme (IRE1)-XBP1 ER stress pathway remain unexplored. Here we report that in the fed state, insulin-activated kinase AKT directly phosphorylates IRE1 at S724, which in turn mediates the splicing of XBP1u mRNA, thus favoring the generation of the spliced form, XBP1s, in the liver of mice. Subsequently, XBP1s stimulates the expression of lipogenic genes and upregulates liver lipogenesis as previously reported. Intriguingly, we find that fasting leads to an increase in XBP1u along with a drastic decrease in XBP1s in the liver of mice, and XBP1u, not XBP1s, significantly increases PKA-stimulated CRE reporter activity in cultured hepatocytes. Furthermore, we demonstrate overexpression of XBP1u significantly increases cAMP-stimulated expression of rate-limiting gluconeogenic genes, G6pc and Pck1, and glucose production in primary hepatocytes. Re-expression of XBP1u in the liver of mice with XBP1 depletion significantly increases fasted blood glucose levels and gluconeogenic gene expression. These data support an important role of XBP1u in upregulating gluconeogenesis in the fasted state. Taken together, we reveal that insulin signaling via AKT controls the expression of XBP1 isoforms, and that XBP1u and XBP1s function in different nutritional states to regulate liver gluconeogenesis and lipogenesis, respectively.

Keywords:  AKT; IRE1; XBP1; insulin; liver glucose production; triglyceride

DOI:  https://doi.org/10.1016/j.jbc.2022.102283
Circ Res. 2022 Jul 18. 101161CIRCRESAHA121320530

Unfolded Protein Response Differentially Modulates the Platelet Phenotype.

Kanika Jain, Tarun Tyagi, Jing Du, Xiaoyue Hu, Kanchi Patell, Kathleen A Martin, John Hwa.

   BACKGROUND: Unfolded protein response (UPR) is a multifaceted signaling cascade that alleviates protein misfolding. Although well studied in nucleated cells, UPR in absence of transcriptional regulation has not been described. Intricately associated with cardiovascular diseases, platelets, despite being anucleate, respond rapidly to stressors in blood. We investigate the UPR in anucleate platelets and explore its role, if any, on platelet physiology and function.
METHODS: Human and mouse platelets were studied using a combination of ex vivo and in vivo experiments. Platelet lineage-specific knockout mice were generated independently for each of the 3 UPR pathways, PERK (protein kinase RNA [PKR]-like endoplasmic reticulum kinase), XBP1 (X-binding protein), and ATF6 (activating transcription factor 6). Diabetes patients were prospectively recruited, and platelets were evaluated for activation of UPR under chronic pathophysiological disease conditions.
RESULTS: Tunicamycin induced the IRE1α (inositol-requiring enzyme-1alpha)-XBP1 pathway in human and mouse platelets, while oxidative stress predominantly activated the PERK pathway. PERK deletion significantly increased platelet aggregation and apoptosis and phosphorylation of PLCγ2, PLCβ3, and p38 MAPK. Deficiency of XBP1 increased platelet aggregation, with higher PLCβ3 and PKCδ activation. ATF6 deletion mediated a relatively modest effect on platelet phenotype with increased PKA (protein kinase A). Platelets from diabetes patients exhibited a positive correlation between disease severity, platelet activation, and protein aggregation, with only IREα-XBP1 activation. Moreover, IRE1α inhibition increased platelet aggregation, while clinically approved chemical chaperone, 4-sodium 4-phenylbutyrate reduced the platelet hyperactivation.
CONCLUSIONS: We show for the first time, that UPR activation occurs in platelets and can be independent of genomic regulation, with selective induction being specific to the source and severity of stress. Each UPR pathway plays a key role and can differentially modulate the platelet activation pathways and phenotype. Targeting the specific arms of UPR may provide a new antiplatelet strategy to mitigate thrombotic risk in diabetes and other cardiovascular diseases.

Keywords:  anucleate; diabetes; platelets; protein misfolding; unfolded protein response

DOI:  https://doi.org/10.1161/CIRCRESAHA.121.320530
Cell Signal. 2022 Jul 18. pii: S0898-6568(22)00174-7. [Epub ahead of print] 110412

PRMT1 suppresses doxorubicin-induced cardiotoxicity by inhibiting endoplasmic reticulum stress.

Su Woo Kim, Byeong-Yun Ahn, Thi Thuy Vy Tran, Jung-Hoon Pyun, Jong-Sun Kang, Young-Eun Leem.

  Doxorubicin (Dox) is a widely used anti-cancer drug that has a significant limitation, which is cardiotoxicity. Its cardiotoxic side effect is dose dependent and occurs through any age. Dox has been known to exert its toxic effect through oxidative stress, but an emerging mechanism is endoplasmic reticulum (ER) stress that activates proapoptotic pathway involving PERK/ATF4/CHOP axis. These stresses lead to dysfunction of myocardium associated with cell death. Although accumulating evidence support their involvement to Dox-induced cardiotoxicity, the mechanism is not well elucidated. Protein arginine methyltransferases 1 (PRMT1) has been known to play a role in cardiomyocyte cell survival through modulation of ER response. In this study, we demonstrate an important role of PRMT1 in Dox-induced cardiotoxicity via ER stress. Depletion of PRMT1 in H9c2 cardiomyocytes enhanced Dox-stimulated cell death, and increased reactive oxygen species (ROS) production and DNA damage by enhancing the levels of proapoptotic cleaved Caspase-3 and γH2AX in response to Dox. Consistently, overexpression of PRMT1 attenuated the apoptotic effect of Dox. In addition, the acute treatment of Dox induced a substantial increase in PRMT1 activity and the translocation of PRMT1 to ER. Overexpression of PRMT1 in cardiomyocyte diminished Dox-induced ER stress, and ATF4 methylation by PRMT1 was involved in the suppression of ER stress. Taken together, our data suggest that PRMT1 is a novel target molecule for protection from Dox-induced cardiotoxicity.

Keywords:  Cardiotoxicity; Doxorubicin; ER stress; PRMT1

DOI:  https://doi.org/10.1016/j.cellsig.2022.110412
Front Oncol. 2022 ;12 930923

A Novel Defined Endoplasmic Reticulum Stress-Related lncRNA Signature for Prognosis Prediction and Immune Therapy in Glioma.

Yinfei Zheng, Xiaoyu Yue, Cheng Fang, Zhuang Jia, Yuxiang Chen, Han Xie, Jiajia Zhao, Zhihao Yang, Lianxin Li, Zhigang Chen, Erbao Bian, Bing Zhao.

  Gliomas are a group of the most aggressive primary central nervous system tumors with limited treatment options. The abnormal expression of long non-coding RNA (lncRNA) is related to the prognosis of glioma. However, the role of endoplasmic reticulum (ER) stress-associated lncRNAs in glioma prognosis has not been reported. In this paper, we obtained ER stress-related lncRNAs by co-expression analysis, and then a risk signature composed of 6 ER stress-related lncRNAs was constructed using Cox regression analysis. Glioma samples in The Cancer Genome Atlas (TCGA) were separated into high- and low-risk groups based on the median risk score. Compared with the low-risk group, patients in the high-risk group had shorter survival times. Additionally, we verified the predictive ability of these candidate lncRNAs in the testing set. Three glioma patient subgroups (cluster 1/2/3) were identified by consensus clustering. We further analysed the abundance of immune-infiltrating cells and the expression levels of immune checkpoint molecules in both three subgroups and two risk groups, respectively. Immunotherapy and anticancer drug response prediction showed that ER stress-related lncRNA risk signature positively correlates with responding to immune checkpoints and chemosensitivity. Functional analysis showed that these gene sets are enriched in the malignant process of tumors. Finally, LINC00519 was chosen for functional experiments. The silence of LINC00519 restrained the migration and invasion of glioma cells. Hence, those results indicated that ER stress-related lncRNA risk signature could be a potential treatment target and a prognosis biomarker for glioma patients.

Keywords:  endoplasmic reticulum stress; glioma; immune; lncRNA; prognosis; risk signature

DOI:  https://doi.org/10.3389/fonc.2022.930923