bims-unfpre 2025-05-25 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2025–05–25
eight papers selected by
Susan Logue, University of Manitoba

PERK Regulates Epithelial-Mesenchymal Transition Through Autophagy and Lipid Metabolism in Lens Epithelial Cells.
JAK1/2 Inhibitors Alleviate the Damage of Intercellular Adhesion by Reducing Endoplasmic Reticulum Stress-Induced Apoptosis in Pemphigus Vulgaris.
Endoplasmic Reticulum Stress Induces Liquid-Liquid Phase Separation of GRP78 and Modulates Protein Aggregation Dynamics.
The Arf pathway is required for resolving ER stress during T cell activation.
Neutrophil extracellular traps induce fibroblast ferroptosis via IRE1α/XBP1-mediated ER stress to impair diabetic wound healing.
ER tubular body: an ER-derived compartment for redirecting autophagy to secretory functions.
The role of LECT2 in kidney fibrosis progression and endoplasmic reticulum stress.
Stepwise ATP translocation into the endoplasmic reticulum by human SLC35B1.

Invest Ophthalmol Vis Sci. 2025 May 01. 66(5): 35

PERK Regulates Epithelial-Mesenchymal Transition Through Autophagy and Lipid Metabolism in Lens Epithelial Cells.

Xiaoran Wang, Baoxin Chen, Jieping Chen, Mi Huang, Shan Huang.

Purpose: Pathological epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) plays a crucial role in the formation of lens fibrosis, particularly in fibrotic posterior capsular opacification and anterior subcapsular cataract (ASC). Here we investigated the potential roles of endoplasmic reticulum (ER) stress in the development of lens fibrosis.
Methods: RNA sequencing was performed to examine global gene expression changes in patients with ASC, as well as in TGFβ2-induced human lens explants and rabbit primary LECs. Rabbit LECs were treated with TGFβ2 in the presence or absence of the ER stress modulator, PERK inhibitor ISRIB, and autophagy inducer for in vitro studies. In vivo investigations were carried out using a mouse model of injury-induced capsular fibrosis, with ISRIB administration. To uncover the underlying mechanisms, we conducted lipidomics analysis, transmission electron microscopy, immunostaining, quantitative PCR, Western blot, and capillary Western immunoassay.
Results: ER stress genes were upregulated in patients with ASC, TGFβ2-stimulated human explants and primary LECs. Pharmacologic ER stress induction promoted EMT, while its inhibition reduced TGFβ2-induced mesenchymal gene levels. Blocking the PERK axis of ER stress with ISRIB or targeting downstream factor ATF4 suppressed EMT, whereas the IRE1 axis showed no effect. Consistent with these in vitro observations, anterior chamber injection of ISRIB also reduced subcapsular plaque formation in a mouse model of lens fibrosis by suppressing SMAD2/3 activation. Mechanistically, ISRIB suppressed LC3-II conversion and P62 degradation, indicating autophagy suppression. Lipidomics revealed phosphatidylethanolamine (PE), essential for autophagosome formation, was downregulated in TGFβ2-treated LECs and upregulated with ISRIB cotreatment. Inducing autophagy with rapamycin significantly rescued the mesenchymal gene suppression by ISRIB, whereas autophagy inhibitor CQ produced opposite effects.
Conclusions: ER stress, particularly the PERK axis, promotes LECs' EMT through autophagy and PE metabolism, offering potential therapeutic targets for the treatment of lens fibrosis.

DOI: https://doi.org/10.1167/iovs.66.5.35
Exp Dermatol. 2025 May;34(5): e70121

JAK1/2 Inhibitors Alleviate the Damage of Intercellular Adhesion by Reducing Endoplasmic Reticulum Stress-Induced Apoptosis in Pemphigus Vulgaris.

Xi Chen, Mei-Nian Xu, Zheng-Quan Wu, Rong Huang, Hong-Yan Lu, Xiaoming Peng, Kang Zeng, Chang-Xing Li.

  Pemphigus vulgaris (PV), a severe autoimmune disease with high morbidity and mortality, necessitates innovative therapies to improve outcomes while minimising the adverse effects of conventional immunosuppressants. Immunohistochemical analysis revealed elevated phosphorylated Janus kinase (p-JAK)1 and p-JAK2 expression in PV lesions, complemented by transcriptome data showing JAK/STAT pathway dysregulation. Using a PV acantholysis model, we demonstrated that Ruxolitinib, a JAK1/2 inhibitor, significantly reduced keratinocyte apoptosis, enhanced cell adhesion, and alleviated endoplasmic reticulum (ER) stress. Additionally, Ruxolitinib mitigated tunicamycin-induced ER stress and apoptosis in HaCaT cells. These findings establish a crucial role for JAK1/2 in PV pathogenesis, demonstrating that their inhibition alleviates ER stress, reduces apoptosis, and improves cell adhesion. Our results provide a theoretical foundation for the clinical application of JAK inhibitors in PV treatment.

Keywords:  JAK inhibitors; endoplasmic reticulum stress; keratinocyte adhesion; keratinocyte apoptosis; pemphigus vulgaris

DOI:  https://doi.org/10.1111/exd.70121
ACS Sens. 2025 May 23.

Endoplasmic Reticulum Stress Induces Liquid-Liquid Phase Separation of GRP78 and Modulates Protein Aggregation Dynamics.

Jiaqi Li, Xiangyu Zi, Jiabao Fang, Min Liang, Minzi Ju, Zhenglong Sun, Baoxing Shen, Xin Zhang.

  Abnormal protein aggregation is a hallmark of neurodegenerative diseases, disrupting cellular homeostasis. Glucose-regulated protein 78 (GRP78), a key endoplasmic reticulum (ER) chaperone, plays a crucial role in protein folding and the ER stress response. Recent studies suggest that GRP78 undergoes liquid-liquid phase separation (LLPS) to form dynamic condensates; however, its functional implications under pathological conditions remain unclear. In this study, we designed and synthesized two fluorescent probes (ER-Pro and Agg-Pro) for specifically labeling GRP78 and monitoring microenvironmental polarity changes during protein phase transition. By integrating fluorescence lifetime imaging microscopy and confocal microscopy, we demonstrated that GRP78 undergoes LLPS under ER stress and recruits the amyotrophic lateral sclerosis-associated mutant protein SOD1(A4V), influencing its aggregation dynamics. Further investigations revealed that SOD1(A4V) aggregation is accompanied by local polarity changes, highlighting a potential role for GRP78 LLPS in protein quality control. Our findings provide new insights into ER homeostasis regulation and the pathogenesis of neurodegenerative diseases, offering potential strategies for early diagnosis and therapeutic intervention.

Keywords:  endoplasmic reticulum stress; fluorescence lifetime imaging; liquid−liquid phase separation; polarity sensitivity; protein aggregation

DOI:  https://doi.org/10.1021/acssensors.5c00807
Int Immunol. 2025 May 23. pii: dxaf028. [Epub ahead of print]

The Arf pathway is required for resolving ER stress during T cell activation.

Mami Sumiyoshi, Yui Kotani, Chikako Shimokawa, Sukhonthip Khueangchiangkhwang, Yoichi Maekawa, Yoshiyuki Matsuo, Yoshiki Yasukochi, Koichiro Higasa, Yasunori Kanaho, Toshio Watanabe, Satoshi Matsuda.

  Upon antigen recognition, T cells undergo rapid cell proliferation and differentiation, which is accompanied by a drastic change in cellular metabolism. The ADP-ribosylation factor (Arf) pathway contributes to cellular homeostasis by orchestrating vesicle trafficking, and our previous study using mice lacking both Arf1 and Arf6 (Arf-KO) revealed that Th17-mediated autoimmune diseases were markedly suppressed in Arf-KO mice though its precise mechanism remained elusive. Here, we show that Arf pathway modulates cellular metabolism in T cell activation and survival. We found that the lack of Arf1 and Arf6 resulted in hyper-activation of mTORC1, a master regulator of cellular metabolism, as well as unresolved endoplasmic reticulum (ER) stress, leading to exaggerated apoptosis during T cell activation. We further demonstrated that treatment with IL-21, a potent inducer of Tfh differentiation, rescued Arf-KO T cells from apoptosis by attenuating ER stress in vitro. Accordingly, antigen-specific antibody production and host defenses against infections such as Leishmania major or Heligmosomoides polygyrus infections were significantly preserved in Arf-KO mice. Taken together, these findings provide mechanistic insights linking the Arf pathway with T cells homeostasis during activation and identify the Arf pathway as an ideal therapeutic target for autoimmune diseases with a low risk of opportunistic infections.

Keywords:  IL-21; Tfh; mTORC1; metabolic reprogramming

DOI:  https://doi.org/10.1093/intimm/dxaf028
Free Radic Biol Med. 2025 May 14. pii: S0891-5849(25)00674-4. [Epub ahead of print]236 17-27

Neutrophil extracellular traps induce fibroblast ferroptosis via IRE1α/XBP1-mediated ER stress to impair diabetic wound healing.

Hongbo Zhao, Yanhong Liu.

  Delayed wound healing in diabetes markedly increases the risk of amputation and systemic infection. However, the underlying molecular mechanisms are unclear. Fibroblasts are essential in wound repair through collagen secretion, and their dysfunction severely impairs wound healing and tissue regeneration. Increasing evidence indicates that excessive production of neutrophil extracellular traps (NETs) exacerbates local inflammation and induces cell death, thereby delaying wound healing. Despite these findings, the precise mechanisms underlying NETs-induced impairment of wound healing remain poorly understood. This study utilized in vitro and in vivo models to examine the molecular mechanisms by which NETs facilitate fibroblast ferroptosis through endoplasmic reticulum (ER) stress and contribute to impaired diabetic wound healing. Our findings demonstrate that NETs induce ferroptosis in fibroblasts, thus impairing their collagen secretion capacity. We further demonstrate that IRE1α/XBP1, a key ER stress pathway, participates in NETs-induced ferroptosis in fibroblasts. Furthermore, targeting this pathway markedly improved diabetic wound healing. These findings highlight a novel molecular target and potential therapeutic strategy for the treatment of treating refractory diabetic wounds.

Keywords:  Diabetic wound; Endoplasmic reticulum stress; Ferroptosis; Fibroblast; Neutrophil extracellular traps

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.05.391
Autophagy. 2025 May 19.

ER tubular body: an ER-derived compartment for redirecting autophagy to secretory functions.

Min Seok Song, Hun Ju Sim, Shin Hye Noh, Vivek Malhotra, Min Goo Lee.

  The secretion of proteins that do not follow the well-characterized endoplasmic reticulum (ER)-Golgi apparatus pathway, known as unconventional protein secretion (UCPS), is gradually revealing its complexities. Our study has identified an ER-based tubulovesicular network, termed ER tubular body (ER-TB), as a central compartment in this process. We demonstrate that ER-TBs are formed by two reticulophagy receptors, ATL3 and RTN3L, under conditions of cellular stress. In addition to their role in stress-induced secretion, the activation of UCPS via ER-TBs facilitates cell surface trafficking of trafficking-deficient transmembrane proteins such as ΔF508-CFTR. Furthermore, their involvement in ER remodeling and vesicle trafficking suggests a potential role in viral replication, particularly in the formation of membrane compartments utilized by positive-strand RNA viruses. By uncovering ER-TBs as key cellular structures in stress-induced UCPS and demonstrating their regulation by autophagy-related factors, our findings offer valuable insights into protein homeostasis, viral pathogenesis, and potential therapeutic strategies for diseases linked to trafficking defects.

Keywords:  ATL3; ER stress; ER tubular body; RTN3L; compartment for unconventional protein secretion; unconventional protein secretion

DOI:  https://doi.org/10.1080/15548627.2025.2508935
Life Sci. 2025 May 19. pii: S0024-3205(25)00349-2. [Epub ahead of print]375 123714

The role of LECT2 in kidney fibrosis progression and endoplasmic reticulum stress.

Yang Hu, Hai-Jun Ou, Hong-Lei Wang, Wei-Jie Zhou.

   AIMS: Our previous studies showed that Leukocyte Cell-Derived Chemotaxin 2 (LECT2), as a ligand for Tie1, modulates vascular endothelial cell function, promoting hepatic fibrosis. These findings prompted an investigation into whether LECT2 effects kidney fibrosis. This study aimed to elucidate the role of LECT2 in kidney fibrosis and its regulation of C/EBP homologous protein (CHOP) expression.
MATERIALS AND METHODS: We utilized Lect2-KO mice, Lect2-2 A-Cre-Rosa26-LSL-tdTomato reporter mice, and EA.hy926 cells overexpressing LECT2 to establish models of kidney fibrosis and endoplasmic reticulum stress (ERS). The expression characteristics of LECT2 in fibrotic kidneys, its effects on CHOP expression, and the mechanisms by which LECT2 modulates kidney fibrosis were systematically investigated.
KEY FINDINGS: Lect2 expression was upregulated in clinical fibrotic kidney samples and mouse models of fibrotic kidneys. Lect2-KO mice demonstrated reduced fibrosis and less impairment of kidney function in a kidney fibrosis model. In Lect2-KO mice, expression of the ERS marker CHOP was increased, and vascular endothelial cells were activated to express CHOP earlier, reducing kidney function damage. Overexpression of LECT2 decreased apoptosis, promoted cell survival, and upregulated the expression of profibrotic factors through activation of the EGFR/AKT/PI3K pathway. Lect2 deficiency in fibrotic kidneys led to attenuated myofibroblast activation and reduced collagen deposition.
SIGNIFICANCE: The absence of LECT2 alleviates kidney fibrosis by inhibiting the EGFR/PI3K/AKT pathway, activating ERS, promoting partial endothelial cell apoptosis, and reducing the secretion of profibrotic factors. LECT2 emerges as a promising therapeutic target for kidney fibrosis, and its inhibition offers a potential strategy for CKD treatment.

Keywords:  CHOP; Endoplasmic reticulum stress; Kidney fibrosis; LECT2

DOI:  https://doi.org/10.1016/j.lfs.2025.123714
Nature. 2025 May 21.

Stepwise ATP translocation into the endoplasmic reticulum by human SLC35B1.

Ashutosh Gulati, Do-Hwan Ahn, Albert Suades, Yurie Hult, Gernot Wolf, So Iwata, Giulio Superti-Furga, Norimichi Nomura, David Drew.

ATP generated in the mitochondria is exported by an ADP/ATP carrier of the SLC25 family1. The endoplasmic reticulum (ER) cannot synthesize ATP but must import cytoplasmic ATP to energize protein folding, quality control and trafficking2,3. It was recently proposed that a member of the nucleotide sugar transporter family, termed SLC35B1 (also known as AXER), is not a nucleotide sugar transporter but a long-sought-after ER importer of ATP4. Here we report that human SLC35B1 does not bind nucleotide sugars but indeed executes strict ATP/ADP exchange with uptake kinetics consistent with the import of ATP into crude ER microsomes. A CRISPR-Cas9 cell-line knockout demonstrated that SLC35B1 clusters with the most essential SLC transporters for cell growth, consistent with its proposed physiological function. We have further determined seven cryogenic electron microscopy structures of human SLC35B1 in complex with an Fv fragment and either bound to an ATP analogue or ADP in all major conformations of the transport cycle. We observed that nucleotides were vertically repositioned up to approximately 6.5 Å during translocation while retaining key interactions with a flexible substrate-binding site. We conclude that SLC35B1 operates by a stepwise ATP translocation mechanism, which is a previously undescribed model for substrate translocation by an SLC transporter.

DOI: https://doi.org/10.1038/s41586-025-09069-w