bims-unfpre 2023-08-06 papers

Issue of 2023–08–06
six papers selected by
Susan Logue, University of Manitoba

ACS Chem Biol. 2023 Jul 31.

Divergent Proteome Reactivity Influences Arm-Selective Activation of the Unfolded Protein Response by Pharmacological Endoplasmic Reticulum Proteostasis Regulators.

Gabriel M Kline, Ryan J Paxman, Chung-Yon Lin, Nicole Madrazo, Leonard Yoon, Julia M D Grandjean, Kyunga Lee, Karina Nugroho, Evan T Powers, R Luke Wiseman, Jeffery W Kelly.

Pharmacological activation of the activating transcription factor 6 (ATF6) arm of the unfolded protein response (UPR) has proven useful for ameliorating proteostasis deficiencies in cellular and mouse models of numerous etiologically diverse diseases. Previous high-throughput screening efforts identified the small molecule AA147 as a potent and selective ATF6 activating compound that operates through a mechanism involving metabolic activation of its 2-amino-p-cresol substructure affording a quinone methide, which then covalently modifies a subset of endoplasmic reticulum (ER) protein disulfide isomerases (PDIs). Another compound identified in this screen, AA132, also contains a 2-amino-p-cresol moiety; however, this compound showed less transcriptional selectivity, instead globally activating all three arms of the UPR. Here, we show that AA132 activates global UPR signaling through a mechanism analogous to that of AA147, involving metabolic activation and covalent modification of proteins including multiple PDIs. Chemoproteomic-enabled analyses show that AA132 covalently modifies PDIs to a greater extent than AA147. However, the extent of PDI labeling by AA147 approaches a plateau more rapidly than PDI labeling by AA132. These observations together suggest that AA132 can access a larger pool of proteins for covalent modification, possibly because its activated form is less susceptible to quenching than activated AA147. In other words, the lower reactivity of activated AA132 allows it to persist longer and modify more PDIs in the cellular environment. Collectively, these results suggest that AA132 globally activates the UPR through increased engagement of ER PDIs. Consistent with this, reducing the cellular concentration of AA132 decreases PDI modifications and enables selective ATF6 activation. Our results highlight the relationship between metabolically activatable-electrophile stability, ER proteome reactivity, and the transcriptional response observed with the enaminone chemotype of ER proteostasis regulators, enabling continued development of next-generation ATF6 activating compounds.

DOI: https://doi.org/10.1021/acschembio.3c00042

J Biol Chem. 2023 Jul 29. pii: S0021-9258(23)02142-7. [Epub ahead of print] 105114

ER stress decreases exosome production through adiponectin/T-cadherin-dependent and -independent pathways.

Keita Fukuoka, Ryohei Mineo, Shunbun Kita, Shiro Fukuda, Tomonori Okita, Emi Kawada-Horitani, Masahito Iioka, Kohei Fujii, Keitaro Kawada, Yuya Fujishima, Hitoshi Nishizawa, Maeda Norikazu, Iichiro Shimomura.

Exosomes, extracellular vesicles (EVs) produced within cells, mediate both the disposal of intracellular waste and communication with distant cells, and they are involved in a variety of disease processes. Although disease modifications of exosome cargos have been well studied, it has been poorly investigated how disease processes, such as endoplasmic reticulum (ER) stress, affect EV production. We previously reported that adiponectin, an adipocyte-secreted salutary factor, increases systemic exosome levels through T-cadherin-mediated enhancement of exosome biogenesis. In the present study, we demonstrated that adiponectin/T-cadherin-dependent EV production was susceptible to ER stress and that low-dose tunicamycin significantly reduced EV production in the presence, but not in the absence, of adiponectin. Moreover, pharmacological or genetic activation of IRE1α, a central regulator of ER stress, downregulated T-cadherin at the mRNA and protein levels as well as attenuated EV production. In addition, adiponectin/T-cadherin-independent EV production was attenuated under ER stress conditions. Repeated administration of tunicamycin to mice decreased circulating small EVs without decreasing tissue T-cadherin expression. Mechanistically, IRE1α activation by silencing of the XBP1 transcription factor upregulated the canonical IFN pathway and decreased EV production. The IFN pathway, when it was activated by polyinosinic-polycytidylic acid [poly(I:C)], also significantly attenuated EV production. Thus, we concluded that ER stress decreases exosome production through adiponectin/T-cadherin-dependent and -independent pathways.

Keywords: Adiponectin; ER stress; Exosome; Extracellular vesicle; T-cadherin

DOI: https://doi.org/10.1016/j.jbc.2023.105114

Front Oncol. 2023 ;13 1196546

CCDC85A is regulated by miR-224-3p and augments cancer cell resistance to endoplasmic reticulum stress.

So Takahashi, Kurara Takagane, Go Itoh, Sei Kuriyama, Michinobu Umakoshi, Akiteru Goto, Kazuyoshi Yanagihara, Masakazu Yashiro, Katsunori Iijima, Masamitsu Tanaka.

MicroRNAs (miRNAs) play pivotal roles in the tumor microenvironment. Here, we analyzed miRNAs in tumor stromal fibroblasts. Expression of miR-224-3p in cancer-associated fibroblasts (CAF) from scirrhous gastric cancer patients was lower than in normal fibroblasts (NF). Introduction of a miR-224-3p mimic attenuated migration and invasion of CAF. Coiled-coil domain containing 85A (CCDC85A), whose function in tumors is not understood, was the target gene of miR-224-3p. Immunohistological analysis revealed that CCDC85A is expressed to varying degrees by cancer cells and CAFs in gastric and pancreatic carcinomas. Downregulation of CCDC85A in cancer cells revealed that these cells are vulnerable to endoplasmic reticulum (ER) stress induced by thapsigargin or tunicamycin, which were ameliorated after addback of CCDC85A. Injection of NF-derived exosomes containing miR-224-3p into the xenograft tumor increased tumor shrinkage by cisplatin treatment. Mechanistically, CCDC85A associated with the molecular chaperone GRP78 and GRP94, thereby inhibiting association of these negative regulators of the unfolded protein response (UPR), leading to sustained activation of PERK and downstream eIF2〈 and ATF4 upon ER stress. These data suggest a novel miR-224-3p-mediated function for CCDC85A: protection from ER stress and cisplatin resistance.

Keywords: CCDC85A; ER stress; cisplatin resistance; exosomes; miR224-3p

DOI: https://doi.org/10.3389/fonc.2023.1196546

iScience. 2023 Aug 18. 26(8): 107312

Advanced oxidation protein products induce Paneth cells defects by endoplasmic reticulum stress in Crohn's disease.

Jie Shi, Weidong Wang, Shibo Sun, Xiaoping Xu, Jieying Fei, Qian Zhou, Caolitao Qin, Shiyu Ou, Fengfei Wu, Fang Ting Wu, Tianyan Xu, Lan Bai, Fang Xie.

Paneth cells (PC) play a key role in the innate immune response of intestine epithelium, and PC defects contribute to the pathogenesis of Crohn's disease (CD). In this study, we utilized active CD tissues and advanced oxidation protein products (AOPP)-challenged C57BL/6 mouse model to investigate the effect of AOPP on PC defects in CD. We found that AOPP accumulated in active CD tissues and was negatively associated with lysozyme expression, while positively correlated with the presence of ER stress markers. Furthermore, AOPP treatment induced PC defects mainly through excessive ER stress in vivo, and AOPP also caused mitochondria-associated ER membranes formation and mitochondrial dysfunction. In addition, the effects of AOPP could be attenuated by the administration of ER stress inhibitor, TUDCA. These findings suggest a pathogenic role of AOPP contributing to PC defects and may provide the basis for developing new strategies to managing CD.

Keywords: Cell biology

DOI: https://doi.org/10.1016/j.isci.2023.107312

EMBO J. 2023 Jul 31. e111252

RNF26 binds perinuclear vimentin filaments to integrate ER and endolysosomal responses to proteotoxic stress.

Tom Cremer, Lenard M Voortman, Erik Bos, Marlieke Lm Jongsma, Laurens R Ter Haar, Jimmy Jll Akkermans, Cami Mp Talavera Ormeño, Ruud Hm Wijdeven, Jelle de Vries, Robbert Q Kim, George Mc Janssen, Peter A van Veelen, Roman I Koning, Jacques Neefjes, Ilana Berlin.

Proteotoxic stress causes profound endoplasmic reticulum (ER) membrane remodeling into a perinuclear quality control compartment (ERQC) for the degradation of misfolded proteins. Subsequent return to homeostasis involves clearance of the ERQC by endolysosomes. However, the factors that control perinuclear ER integrity and dynamics remain unclear. Here, we identify vimentin intermediate filaments as perinuclear anchors for the ER and endolysosomes. We show that perinuclear vimentin filaments engage the ER-embedded RING finger protein 26 (RNF26) at the C-terminus of its RING domain. This restricts RNF26 to perinuclear ER subdomains and enables the corresponding spatial retention of endolysosomes through RNF26-mediated membrane contact sites (MCS). We find that both RNF26 and vimentin are required for the perinuclear coalescence of the ERQC and its juxtaposition with proteolytic compartments, which facilitates efficient recovery from ER stress via the Sec62-mediated ER-phagy pathway. Collectively, our findings reveal a scaffolding mechanism that underpins the spatiotemporal integration of organelles during cellular proteostasis.

Keywords: ER stress; ERphagy; RNF26; endolysosomes; intermediate filaments

DOI: https://doi.org/10.15252/embj.2022111252

Cell Death Dis. 2023 Aug 04. 14(8): 497

SQLE promotes pancreatic cancer growth by attenuating ER stress and activating lipid rafts-regulated Src/PI3K/Akt signaling pathway.

Ruiyuan Xu, Jianlu Song, Rexiati Ruze, Yuan Chen, Xinpeng Yin, Chengcheng Wang, Yupei Zhao.

Pancreatic cancer (PC), a highly lethal malignancy, commonly exhibits metabolic reprogramming that results in therapeutic vulnerabilities. Nevertheless, the mechanisms underlying the impacts of aberrant cholesterol metabolism on PC development and progression remain elusive. In this study, we found that squalene epoxidase (SQLE) is a crucial mediator of cholesterol metabolism in PC growth. We observed a profound upregulation of SQLE in PC tissues, and its high expression was correlated with poor patient outcomes. Our functional experiments demonstrated that SQLE facilitated cell proliferation, induced cell cycle progression, and inhibited apoptosis in vitro, while promoting tumor growth in vivo. Mechanistically, SQLE was found to have a dual role. First, its inhibition led to squalene accumulation-induced endoplasmic reticulum (ER) stress and subsequent apoptosis. Second, it enhanced de novo cholesterol biosynthesis and maintained lipid raft stability, thereby activating the Src/PI3K/Akt signaling pathway. Significantly, employing SQLE inhibitors effectively suppressed PC cell proliferation and xenograft tumor growth. In summary, this study reveals SQLE as a novel oncogene that promotes PC growth by mitigating ER stress and activating lipid raft-regulated Src/PI3K/Akt signaling pathway, highlighting the potential of SQLE as a therapeutic target for PC.

DOI: https://doi.org/10.1038/s41419-023-05987-7