bims-unfpre 2022-08-21 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2022‒08‒21
eight papers selected by
Susan Logue
University of Manitoba

TGFβ1 regulates HRas-mediated activation of IRE1α through the PERK-RPAP2 axis in keratinocytes.
ER stress and inflammation crosstalk in obesity.
A Novel ER Stress Mediator TMTC3 Promotes Squamous Cell Carcinoma Progression by Activating GRP78/PERK Signaling Pathway.
ER stress and UPR in Alzheimer's disease: mechanisms, pathogenesis, treatments.
Sorafenib combined with STAT3 knockdown triggers ER stress-induced HCC apoptosis and cGAS-STING-mediated anti-tumor immunity.
PERK promotes immunosuppressive M2 macrophage phenotype by metabolic reprogramming and epigenetic modifications through the PERK-ATF4-PSAT1 axis.
Loss of FOXA2 induces ER stress and hepatic steatosis and alters developmental gene expression in human iPSC-derived hepatocytes.
Bortezomib- and carfilzomib-resistant myeloma cells show increased activity of all three arms of the unfolded protein response.

Mol Carcinog. 2022 Aug 17.

TGFβ1 regulates HRas-mediated activation of IRE1α through the PERK-RPAP2 axis in keratinocytes.

Saie Mogre, Nicholas Blazanin, Hailey Walsh, Jack Ibinson, Chase Minnich, Chih-Chi Andrew Hu, Adam B Glick.

  Transforming Growth Factor β1 (TGFβ1) is a critical regulator of tumor progression in response to HRas. Recently, TGFβ1 has been shown to trigger ER stress in many disease models; however, its role in oncogene-induced ER stress is unclear. Oncogenic HRas induces the unfolded protein response (UPR) predominantly via the Inositol-requiring enzyme 1α (IRE1α) pathway to initiate the adaptative responses to ER stress, with importance for both proliferation and senescence. Here, we show a role of the UPR sensor proteins IRE1α and (PKR)-like endoplasmic reticulum kinase (PERK) to mediate the tumor-suppressive roles of TGFβ1 in mouse keratinocytes expressing mutant forms of HRas. TGFβ1 suppressed IRE1α phosphorylation and activation by HRas both in in vitro and in vivo models while simultaneously activating the PERK pathway. However, the increase in ER stress indicated an uncoupling of ER stress and IRE1α activation by TGFβ1. Pharmacological and genetic approaches demonstrated that TGFβ1-dependent dephosphorylation of IRE1α was mediated by PERK through RNA Polymerase II Associated Protein 2 (RPAP2), a PERK-dependent IRE1α phosphatase. In addition, TGFβ1-mediated growth arrest in oncogenic HRas keratinocytes was partially dependent on PERK-induced IRE1α dephosphorylation and inactivation. Together, these results demonstrate a critical cross-talk between UPR proteins that is important for TGFβ1-mediated tumor suppressive responses.

Keywords:  ER stress; HRas; IRE1α; PERK; TGFβ1; proliferation; unfolded protein response

DOI:  https://doi.org/10.1002/mc.23453
Med Res Rev. 2022 Aug 17.

ER stress and inflammation crosstalk in obesity.

Amir Ajoolabady, Cynthia Lebeaupin, Ne N Wu, Randal J Kaufman, Jun Ren.

  The endoplasmic reticulum (ER) governs the proper folding of polypeptides and proteins through various chaperones and enzymes residing within the ER organelle. Perturbation in the ER folding process ensues when overwhelmed protein folding exceeds the ER handling capacity, leading to the accumulation of misfolded/unfolded proteins in the ER lumen-a state being referred to as ER stress. In turn, ER stress induces a gamut of signaling cascades, termed as the "unfolded protein response" (UPR) that reinstates the ER homeostasis through a panel of gene expression modulation. This type of UPR is usually deemed "adaptive UPR." However, persistent or unresolved ER stress hyperactivates UPR response, which ultimately, triggers cell death and inflammatory pathways, termed as "maladaptive/terminal UPR." A plethora of evidence indicates that crosstalks between ER stress (maladaptive UPR) and inflammation precipitate obesity pathogenesis. In this regard, the acquisition of the mechanisms linking ER stress to inflammation in obesity might unveil potential remedies to tackle this pathological condition. Herein, we aim to elucidate key mechanisms of ER stress-induced inflammation in the context of obesity and summarize potential therapeutic strategies in the management of obesity through maneuvering ER stress and ER stress-associated inflammation.

Keywords:  ER stress; adipocytes; inflammation; insulin resistance; obesity

DOI:  https://doi.org/10.1002/med.21921
Int J Biol Sci. 2022 ;18(13): 4853-4868

A Novel ER Stress Mediator TMTC3 Promotes Squamous Cell Carcinoma Progression by Activating GRP78/PERK Signaling Pathway.

Hongyu Yuan, Zitong Zhao, Zichan Guo, Liying Ma, Jing Han, Yongmei Song.

  During tumor progression, tumor cells are exposed to various stress conditions, which result in endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) to restore ER homeostasis. Accumulating evidence reported the orchestrating role of ER stress in epithelial-mesenchymal transition (EMT) progress, but the detailed mechanism was unclear. Here, we identified ectopic expression of TMTC3 in cells undergoing ER stress and verified the association with EMT markers through the cellular model of ER stress and database analysis. TMTC3 was abnormally highly expressed in squamous cell carcinomas (SCCs), and regulated by TP63, an SCCs-specific transcription factor. Biological function experiments indicated that TMTC3 promoted a malignant phenotype in vitro, and accelerated tumor growth and metastasis in vivo. RNA-seq analyses and further experiments revealed that TMTC3 promoted the expression of EMT markers via interleukin-like EMT inducer (ILEI, FAM3C). Further studies on the mechanism showed that TMTC3 disrupted the interaction between PERK and GRP78 to activate the PERK pathway and promote the nuclear translocation of ATF4, which increased the transcriptional activity of ILEI. These findings indicated that TMTC3 activates GRP78/PERK signaling pathway during ER stress-induced EMT, which might serve as a potential therapeutic target in SCCs.

Keywords:  EMT; ER stress; TMTC3; squamous cell carcinoma

DOI:  https://doi.org/10.7150/ijbs.72838
Cell Death Dis. 2022 Aug 15. 13(8): 706

ER stress and UPR in Alzheimer's disease: mechanisms, pathogenesis, treatments.

Amir Ajoolabady, Dan Lindholm, Jun Ren, Domenico Pratico.

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by gradual loss of memory and cognitive function, which constitutes a heavy burden on the healthcare system globally. Current therapeutics to interfere with the underlying disease process in AD is still under development. Although many efforts have centered on the toxic forms of Aβ to effectively tackle AD, considering the unsatisfactory results so far it is vital to examine other targets and therapeutic approaches as well. The endoplasmic reticulum (ER) stress refers to the build-up of unfolded or misfolded proteins within the ER, thus, perturbing the ER and cellular homeostasis. Emerging evidence indicates that ER stress contributes to the onset and development of AD. A thorough elucidation of ER stress machinery in AD pathology may help to open up new therapeutic avenues in the management of this devastating condition to relieve the cognitive dementia symptoms. Herein, we aim at deciphering the unique role of ER stress in AD pathogenesis, reviewing key findings, and existing controversy in an attempt to summarize plausible therapeutic interventions in the management of AD pathophysiology.

DOI: https://doi.org/10.1038/s41419-022-05153-5
Cancer Lett. 2022 Aug 15. pii: S0304-3835(22)00364-0. [Epub ahead of print] 215880

Sorafenib combined with STAT3 knockdown triggers ER stress-induced HCC apoptosis and cGAS-STING-mediated anti-tumor immunity.

Xueyao Wang, Rui Hu, Zhenwei Song, Huajun Zhao, Zhaoyi Pan, Yujie Feng, Yating Yu, Qiuju Han, Jian Zhang.

  Sorafenib is the first-line treatment for advanced hepatocellular carcinoma (HCC). However, it is difficult to alleviate this disease process using single-agent chemotherapy. Using combination therapies for advanced HCC has become a major trend. Given that STAT3 overexpression is involved in chemotherapy resistance and the immune escape of HCC cells, it has become a potential therapeutic target for HCC in recent years. GEO database analysis showed that STAT3 levels in tumor tissues from non-responders were significantly higher than those in responders to sorafenib. Our studies demonstrated that STAT3 knockdown promoted sorafenib-induced ER stress-induced apoptosis. Importantly, the DNA released by dead HCC cells stimulated the cGAS-STING signaling pathway in CD103+ DCs and promoted type I interferon production, thus, enhancing the anti-tumor function of CD8+ T and NK cells. In conclusion, our results revealed that the combination strategy of sorafenib and STAT3 knockdown might be a potential treatment strategy for HCC, directly and efficiently disturbing the tumor features of HCC cells while improving the tumor microenvironment via the cGAS-STING-Type I IFNs axis of DCs, inducing anti-HCC immune responses.

Keywords:  CD103(+) DCs; ER stress; PKR; STING; cGAS; p-eIF2α

DOI:  https://doi.org/10.1016/j.canlet.2022.215880
Immunometabolism (Cobham). 2022 Jul;4(3): e00007

PERK promotes immunosuppressive M2 macrophage phenotype by metabolic reprogramming and epigenetic modifications through the PERK-ATF4-PSAT1 axis.

Uday P Pratap, Ratna K Vadlamudi.

  The endoplasmic reticulum (ER) is a specialized organelle that participates in multiple cellular functions including protein folding, maturation, trafficking, and degradation to maintain homeostasis. However, hostile conditions in the tumor microenvironment (TME) disturb ER homeostasis. To overcome these conditions, cells activate ER stress response pathways, which are shown to augment the suppressive phenotypes of immune cells; however, the molecular mechanisms underpinning this process remain elusive. Here, we discuss a recent study by Raines et al, that suggests the role of the helper T-cell 2 (TH2) cytokine interleukin-4 (IL-4), and the TME in facilitating a protein kinase RNA-like ER kinase (PERK)-signaling cascade in macrophages, which promotes immunosuppressive M2 macrophage activation and proliferation. Further, the authors showed that PERK signaling promotes both mitochondrial respirations to fulfill cellular energy requirements and signaling through ATF4, which regulate phosphoserine aminotransferase 1 (PSAT1) activity to mediate the serine biosynthesis pathway. These results highlight a previously uncharacterized role for PERK in cellular metabolism and epigenetic modification in M2 macrophages, and thus offers a new therapeutic strategy for overcoming the immunosuppressive effects in the TME.

Keywords:  ER stress; M2 macrophage; endoplasmic reticulum; myeloid cell-derived suppressor cells; protein kinase RNA-like ER kinase; tumor-associated macrophages

DOI:  https://doi.org/10.1097/IN9.0000000000000007
Cell Death Dis. 2022 Aug 16. 13(8): 713

Loss of FOXA2 induces ER stress and hepatic steatosis and alters developmental gene expression in human iPSC-derived hepatocytes.

Maryam Aghadi, Ramy Elgendy, Essam M Abdelalim.

FOXA2 has been known to play important roles in liver functions in rodents. However, its role in human hepatocytes is not fully understood. Recently, we generated FOXA2 mutant induced pluripotent stem cell (FOXA2-/-iPSC) lines and illustrated that loss of FOXA2 results in developmental defects in pancreatic islet cells. Here, we used FOXA2-/-iPSC lines to understand the role of FOXA2 on the development and function of human hepatocytes. Lack of FOXA2 resulted in significant alterations in the expression of key developmental and functional genes in hepatic progenitors (HP) and mature hepatocytes (MH) as well as an increase in the expression of ER stress markers. Functional assays demonstrated an increase in lipid accumulation, bile acid synthesis and glycerol production, while a decrease in glucose uptake, glycogen storage, and Albumin secretion. RNA-sequencing analysis further validated the findings by showing a significant increase in genes associated with lipid metabolism, bile acid secretion, and suggested the activation of hepatic stellate cells and hepatic fibrosis in MH lacking FOXA2. Overexpression of FOXA2 reversed the defective phenotypes and improved hepatocyte functionality in iPSC-derived hepatic cells lacking FOXA2. These results highlight a potential role of FOXA2 in regulating human hepatic development and function and provide a human hepatocyte model, which can be used to identify novel therapeutic targets for FOXA2-associated liver disorders.

DOI: https://doi.org/10.1038/s41419-022-05158-0
Am J Cancer Res. 2022 ;12(7): 3280-3293

Bortezomib- and carfilzomib-resistant myeloma cells show increased activity of all three arms of the unfolded protein response.

Tadeusz Kubicki, Kinga Bednarek, Magdalena Kostrzewska-Poczekaj, Magdalena Luczak, Krzysztof Lewandowski, Lidia Gil, Malgorzata Jarmuz-Szymczak, Dominik Dytfeld.

Proteasome inhibitors are among the most potent classes of drugs in multiple myeloma treatment. One of the main challenges in myeloma therapy is acquired resistance to drugs. Several theories have been proposed to describe the mechanisms responsible for resistance to the most commonly used proteasome inhibitors bortezomib and carfilzomib. This study aimed to describe functional differences between sensitive myeloma cells (MM1S WT) and their daughter cell lines resistant to either bortezomib (MM1S/R BTZ) or carfilzomib (MM1S/R CFZ), as well as between both resistant cell lines. Bortezomib- and carfilzomib-resistant cell lines were successfully generated by continuous exposure to the drugs. When exposed to different drugs than during the resistance generation period, MM1S/R BTZ cells showed cross-resistance to carfilzomib, whereas MM1S/R CFZ cells were similarly sensitive to bortezomib as MM1S WT cells. Following proteomic profiling, unsupervised principal component analysis revealed that the MM1S/R BTZ and MM1S/R CFZ cell lines differed significantly from the MM1S WT cell line and from each other. Canonical pathway analysis showed similar pathways enriched in both comparisons - MM1S WT vs. MM1S/R CFZ and MM1S WT vs. MM1S/R BTZ. However, important differences were present in the statistical significance of particular pathways. Key alterations included the ubiquitin-proteasome system, metabolic pathways responsible for redox homeostasis and the unfolded protein response. In functional studies, both drugs continued to reduce chymotrypsin-like proteasome activity in resistant cells. However, the baseline activity of all three catalytic domains of the proteasome was higher in the resistant cells. Differences in generation of reactive oxygen species were identified in MM1S/R BTZ (decreased) and MM1S/CFZ cells (increased) in comparison to MM1S WT cells. Both baseline and drug-induced activity of the unfolded protein response were higher in resistant cells than in MM1S WT cells and included all three arms of this pathway: IRE1α/XBP1s, ATF6 and EIF2α/ATF4 (downstream effectors of PERK). In conclusion, contrary to some previous reports, resistant MM1S cells show upregulation of unfolded protein response activity, reflecting the heterogeneity of multiple myeloma and prompting further studies on the role of this pathway in resistance to proteasome inhibitors.

Keywords: Multiple myeloma; bortezomib; carfilzomib; proteasome; proteomics; resistance; unfolded protein response