bims-cemest 2025-03-09 papers

bims-cemest

Biomed News

on Cell metabolism and stress

Issue of 2025–03–09
28 papers selected by
Jessica Rosarda, Uniformed Services University

Polysome profiling is an extensible tool for the analysis of bulk protein synthesis, ribosome biogenesis, and the specific steps in translation.
A BiP-centric view of endoplasmic reticulum functions and of my career.
Disease-Associated Factors at the Endoplasmic Reticulum-Golgi Interface.
When Proteins Go Berserk: The Unfolded Protein Response and ER stress.
Mitochondria-associated endoplasmic reticulum membranes and myocardial ischemia: from molecular mechanisms to therapeutic strategies.
Mitochondrial proteostasis and cellular health: insights from chaperones and autophagy.
Molecular docking- and reporter-based screening identify dicoumarol against ER stress-induced liver injury in mice through inhibiting IRE1α activity.
Cytoplasmic ribosomes on mitochondria alter the local membrane environment for protein import.
An ISR-independent role of GCN2 prevents excessive ribosome biogenesis and mRNA translation.
Alterations in ether phospholipids metabolism activate the conserved UPR-Xbp1- PDIA3/ERp60 signaling to maintain intestinal homeostasis.
A subcellular map of translational machinery composition and regulation at the single-molecule level.
CHOP aggravates hepatocyte apoptosis upon endoplasmic reticulum stress by down-regulating autophagy.
The pathways of secretory cargo export at the endoplasmic reticulum.
Tools to Dissect Lipid Droplet Regulation, Players, and Mechanisms.
Dynamic Lipidome Reorganization in Response to Heat Shock Stress.
Crosstalk between O-GlcNAcylation and phosphorylation in metabolism: regulation and mechanism.
Mechanistic insights into protein biogenesis and maturation on the ribosome.
Palmitic acid-induced insulin resistance triggers granulosa cell senescence by disruption of the UPRmt/mitophagy/lysosome axis.
Two sides of the same coin: heat shock proteins as biomarkers and therapeutic targets for some complex diseases.
Heat Shock-Induced PI(4)P Increase Drives HSPA1A Translocation to the Plasma Membrane in Cancer and Stressed Cells through PI4KIII Alpha Activation.
Heat shock protein 70 in Alzheimer's disease and other dementias: A possible alternative therapeutic.
Functional Specialization of S-Adenosylmethionine Synthases Links Phosphatidylcholine to Mitochondrial Function and Stress Survival.
Impact of tyrosine amination on the aggregation and neurotoxicity of amyloid-β.
The contribution of the Golgi and the endoplasmic reticulum to calcium and pH homeostasis in Toxoplasma gondii.
High-throughput screening identifies a novel small-molecule modulator of Hsp70 that selectively enhances ubiquitination and degradation of misfolded neuronal NO synthase.
Astrocyte-secreted factors modulate synaptic protein synthesis as revealed by puromycin labeling of isolated synaptosomes.
Repurposing peripheral immunocytes of Bacillus Calmette Guerin-vaccinated melanoma patients to reveal preventive Alzheimer's disease mechanisms, possibly via the unfolded protein response.
Crucial roles of Grr1 in splicing and translation of HAC1 mRNA upon unfolded stress response.

Mol Biol Cell. 2025 Mar 05. mbcE24080341

Polysome profiling is an extensible tool for the analysis of bulk protein synthesis, ribosome biogenesis, and the specific steps in translation.

Ambar Rodriguez-Martinez, Sara K Young-Baird.

Protein synthesis is an essential and highly regulated cellular process. Here, we demonstrate the versatility of polysome profiling - a methodology traditionally used to assess levels of protein synthesis - to monitor ribosomal integrity and modulation of specific steps in mRNA translation. Using expanded polysome profiling methodologies, we systematically illustrate defects in ribosome biogenesis, translation initiation, and translational elongation in different cellular conditions. We additionally provide instruction for how a modified polysome profiling protocol can be leveraged to identify and characterize the function of factors that regulate protein synthesis. These methodologies are broadly applicable to a range of physiological conditions and human diseases in which ribosome biogenesis or the phases of protein synthesis are distinctly regulated or dysregulated.

DOI: https://doi.org/10.1091/mbc.E24-08-0341
J Mol Biol. 2025 Feb 28. pii: S0022-2836(25)00118-4. [Epub ahead of print] 169052

A BiP-centric view of endoplasmic reticulum functions and of my career.

Linda M Hendershot.

  After completing my post-doctoral training at the University of Alabama, Birmingham and a brief period on the faculty there, I joined the Department of Tumor Cell Biology at St. Jude Children's Research Hospital in 1987 as an Assistant Member and started my independent research program. For the following 37 years, I led a relatively small basic research group comprised at various times of post-doctoral fellows, graduate students, undergraduate students, and research technicians; many of whom I am still in contact. Last year I closed the lab and transitioned to an emeritus position at St. Jude. I continue to maintain several research collaborations covering areas of research that have long been dear to my heart. My post-doctoral studies on BiP revealed that it controlled immunoglobulin assembly and transport, and as such, played a critical role in fidelity of the immune response. My lab continued to define BiP's functions in protein folding and subunit assembly, as well as, in degradation using biochemical, cell-based, and biophysical analyses. Several ER localized co-factors that regulate the activity of BiP and allow it to contribute to its multiple ER functions were identified by our group. These include DnaJ family members and nucleotide change factors. Through a variety of collaborative studies, we pursued BiP's functions in maintaining the permeability barrier of the translocon, contributing to ER calcium stores, and regulating the up-stream transducers of the UPR, a stress response that is activated by the accumulation of unfolded proteins in the ER.

Keywords:  ER stress; Endoplasmic Reticulum; Immunoglobulins; Molecular chaperones; Quality Control of Protein Maturation; Secretory pathway protein biosynthesis; UPR

DOI:  https://doi.org/10.1016/j.jmb.2025.169052
Traffic. 2025 Jan-Mar;26(1-3):26(1-3): e70001

Disease-Associated Factors at the Endoplasmic Reticulum-Golgi Interface.

Miharu Maeda, Masashi Arakawa, Kota Saito.

  The endoplasmic reticulum (ER)-Golgi interface is essential for directing the transport of proteins synthesized in the ER to the Golgi apparatus via the ER-Golgi intermediate compartment, as well as for recycling proteins back to the ER. This transport is facilitated by various components, including COPI and COPII coat protein complexes and the transport protein particle complex. Recently, the ER-Golgi transport pathway has gained attention due to emerging evidence of nonvesicular transport mechanisms and the regulation of trafficking through liquid-liquid phase separation. Numerous diseases have been linked to mutations in proteins localized at the ER-Golgi interface, highlighting the need for comprehensive analysis of these conditions. This review examines the disease phenotypes associated with dysfunctional ER-Golgi transport factors and explores their cellular effects, providing insights into potential therapeutic strategies.

Keywords:  COPI; COPII; ER exit site; ERGIC; Golgi; TRAPP complex; disease‐associated factor; endoplasmic reticulum; liquid‐phase separation; nonvesicular transport

DOI:  https://doi.org/10.1111/tra.70001
Nephron. 2025 Mar 04. 1-14

When Proteins Go Berserk: The Unfolded Protein Response and ER stress.

Doria Meiseles, Narkis Arbeli, Moran Dvela-Levitt.

Background The cellular proteostasis machinery is essential for maintaining protein homeostasis by employing quality control systems that identify, sequester, and eliminate damaged or misfolded proteins. However, the accumulation of misfolded proteins can overwhelm these protective mechanisms, disrupting proteostasis. This phenomenon is a hallmark of numerous pathologies, including a variety of genetic disorders. In the secretory pathway, the buildup of misfolded proteins triggers endoplasmic reticulum (ER) stress, which activates the unfolded protein response (UPR). The UPR serves as an adaptive mechanism, aiming to alleviate stress and restore cellular homeostasis. However, if ER stress is prolonged or severe, the UPR may fail to restore balance and apoptosis is induced. Summary This review introduces the intricate signaling pathways activated by the three UPR transmembrane sensors: protein-kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring enzyme 1 (IRE1), and activating transcription factor 6 (ATF6). We briefly present the roles of the distinct transcriptional programs activated by each sensor in modulating the cellular response to protein stress and in determining cell fate. We discuss how genetic variants and environmental factors contribute to the heterogeneity observed in protein misfolding diseases. Finally, we critically evaluate select therapeutic strategies, specifically protein stabilization, trafficking modulation, and UPR sensor targeting approaches. Key message This review introduces the potential consequences of protein misfolding, which may not only impair protein function, but can also lead to toxic protein accumulation and stress induction. Using Fabry disease as a compelling example, we suggest that future therapeutic intervention may require nuanced, combination approaches that address both loss and gain of protein function.

DOI: https://doi.org/10.1159/000544971
J Transl Med. 2025 Mar 06. 23(1): 277

Mitochondria-associated endoplasmic reticulum membranes and myocardial ischemia: from molecular mechanisms to therapeutic strategies.

Chen Chen, Guohua Dai, Maoxia Fan, Xingmeng Wang, Kaibin Niu, Wulin Gao.

  Myocardial ischemia has the highest disease burden among all cardiovascular diseases making it a significant challenge to the global public health. It can result in myocardial cell damage and death due to impaired mitochondrial and endoplasmic reticulum (ER) functions. These two organelles are important regulators of cell death. In recent years, research has shifted from isolated studies of individual organelles to a more integrative approach, with a particular focus on their membrane contact sites-Mitochondria-Associated Endoplasmic Reticulum Membranes (MAMs). These dynamic microdomains play a crucial role in regulating material exchange and signal transduction between the endoplasmic reticulum and mitochondria. This review comprehensively describes the intricate structure of MAMs and their multifaceted roles in cellular pathophysiological processes. Particular focus was directed at the far-reaching effects of MAMs in regulating key pathological events including calcium homeostasis, mitochondrial dysfunction, ER stress, oxidative stress, and autophagy in ischemic heart disease (IHD). The potential treatment targets and regulatory mechanisms of MAMs were discussed and summarized, providing novel research directions and treatment approaches for improving myocardial ischemia-related diseases.

Keywords:  Calcium homeostasis; Cellular stress; Mitochondria-associated endoplasmic reticulum membranes; Myocardial ischemia

DOI:  https://doi.org/10.1186/s12967-025-06262-3
J Physiol. 2025 Mar 06.

Mitochondrial proteostasis and cellular health: insights from chaperones and autophagy.

Yuvraj Anandrao Jagtap, Akash Choudhary, Sumit Kinger, Prashant Kumar, Sudipta Bhattacharyya, Hem Chandra Jha, Rohan Dhiman, Vivek Sharma, Anil K Suresh, Krishna Mohan Poluri, Amit Mishra.

  Mitochondria are a cell's powerhouse and also have a vital part in cellular processes. The emerging role of mitochondria in several crucial processes highlights their cellular and physiological importance. Mitochondrial homeostasis mechanisms, including proteostasis pathways, are vital for mitochondrial health. Failure of these processes has an important role in establishment of numerous complex disease conditions, such as neurodegeneration and imperfect ageing. However, details of mitochondrial impairments and their contribution to the pathology of neurodegeneration are poorly understood. This review systematically discusses the involvement of mitochondrial homeostasis mechanisms and their role in rejuvenating cellular health and fitness. We also focus on various cellular protein quality control mechanisms essential for mitochondrial proteostasis and how their failure leads to mitochondrial functional disturbances observed in disease conditions. We discuss recent findings based on mitostasis-associated chaperones, mitoproteases, and autophagy responses, which can lead to emergence of new possible therapeutic interventions against complex diseases.

Keywords:  chaperones; mitochondrial dynamics; mitochondrial homeostasis; mitophagy; mitoproteases; neurodegeneration; proteostasis

DOI:  https://doi.org/10.1113/JP287635
Life Sci. 2025 Mar 04. pii: S0024-3205(25)00160-2. [Epub ahead of print] 123526

Molecular docking- and reporter-based screening identify dicoumarol against ER stress-induced liver injury in mice through inhibiting IRE1α activity.

Jifeng Yang, Wei Luo, Yanyu Chen, Yimin Zhou, Jiahai Wang, Lin Mi, Guojun Shi.

   AIMS: Drug-induced liver injury is among the most challenging liver disorders. Endoplasmic reticulum (ER) is responsible for the correct protein folding and secretion, which are highly active in hepatocytes. Failure in maintaining the proper protein folding under pathological condition or external stimuli leads to the unfolded protein response (UPR) to restore ER homeostasis or induce cell death. IRE1α pathway is the most conserved UPR branch with diverse physiological and pathological functions. This study aimed to screen for natural compounds to alleviate hepatic ER stress and liver injury by modulating IRE1α activity.
MATERIALS AND METHODS: ATP-competitive molecules from chemical libraries were recognized by virtual screening for targeting the IRE1α kinase domain. IRE1α activity-based XBP1s-reporter cell lines with flow cytometric analysis were employed to validate candidates from chemical libraries. Then the functions of the top candidate compound on IRE1α signaling were analyzed followed by the treatment with ER stress agonists in vitro. Finally, the candidate compound was used to treat ER stress-induced acute liver injury to evaluate its protective effect in vivo.
KEY FINDINGS: Dicoumarol (DIC) was discovered as a potential inhibitor of IRE1α activation in HEK293T cells, HepG2 cells and primary hepatocytes. Particularly, DIC ameliorates tunicamycin (Tm)- and carbon tetrachloride (CCl4)-induced acute hepatic ER stress to protect against liver injury.
SIGNIFICANCE: This study established a drug screening strategy against IRE1α activation and identified potential new therapeutic effects of DIC in treating liver injury-related diseases.

Keywords:  Dicoumarol; Drug screening; Endoplasmic reticulum stress; IRE1α; Liver injury; XBP1s-reporter

DOI:  https://doi.org/10.1016/j.lfs.2025.123526
J Cell Biol. 2025 Apr 07. pii: e202407110. [Epub ahead of print]224(4):

Cytoplasmic ribosomes on mitochondria alter the local membrane environment for protein import.

Ya-Ting Chang, Benjamin A Barad, Juliette Hamid, Hamidreza Rahmani, Brian M Zid, Danielle A Grotjahn.

Most of the mitochondria proteome is nuclear-encoded, synthesized by cytoplasmic ribosomes, and targeted to the mitochondria posttranslationally. However, a subset of mitochondrial-targeted proteins is imported co-translationally, although the molecular mechanisms governing this process remain unclear. We employ cellular cryo-electron tomography to visualize interactions between cytoplasmic ribosomes and mitochondria in Saccharomyces cerevisiae. We use surface morphometrics tools to identify a subset of ribosomes optimally oriented on mitochondrial membranes for protein import. This allows us to establish the first subtomogram average structure of a cytoplasmic ribosome at the mitochondrial surface in the native cellular context, which showed three distinct connections with the outer mitochondrial membrane surrounding the peptide exit tunnel. Further, this analysis demonstrated that cytoplasmic ribosomes primed for mitochondrial protein import cluster on the outer mitochondrial membrane at sites of local constrictions of the outer and inner mitochondrial membranes. Overall, our study reveals the architecture and the spatial organization of cytoplasmic ribosomes at the mitochondrial surface, providing a native cellular context to define the mechanisms that mediate efficient mitochondrial co-translational protein import.

DOI: https://doi.org/10.1083/jcb.202407110
Life Sci Alliance. 2025 May;pii: e202403014. [Epub ahead of print]8(5):

An ISR-independent role of GCN2 prevents excessive ribosome biogenesis and mRNA translation.

Mónica Román-Trufero, Istvan T Kleijn, Kevin Blighe, Jinglin Zhou, Paula Saavedra-García, Abigail Gaffar, Marilena Christoforou, Axel Bellotti, Joel Abrahams, Abdelmadjid Atrih, Douglas Lamont, Marek Gierlinski, Pooja Jayaprakash, Audrey M Michel, Eric O Aboagye, Mariia Yuneva, Glenn R Masson, Vahid Shahrezaei, Holger W Auner.

The integrated stress response (ISR) is a corrective physiological programme to restore cellular homeostasis that is based on the attenuation of global protein synthesis and a resource-enhancing transcriptional programme. GCN2 is the oldest of four kinases that are activated by diverse cellular stresses to trigger the ISR and acts as the primary responder to amino acid shortage and ribosome collisions. Here, using a broad multi-omics approach, we uncover an ISR-independent role of GCN2. GCN2 inhibition or depletion in the absence of discernible stress causes excessive protein synthesis and ribosome biogenesis, perturbs the cellular translatome, and results in a dynamic and broad loss of metabolic homeostasis. Cancer cells that rely on GCN2 to keep protein synthesis in check under conditions of full nutrient availability depend on GCN2 for survival and unrestricted tumour growth. Our observations describe an ISR-independent role of GCN2 in regulating the cellular proteome and translatome and suggest new avenues for cancer therapies based on unleashing excessive mRNA translation.

DOI: https://doi.org/10.26508/lsa.202403014
iScience. 2025 Mar 21. 28(3): 111946

Alterations in ether phospholipids metabolism activate the conserved UPR-Xbp1- PDIA3/ERp60 signaling to maintain intestinal homeostasis.

Stephanie Makdissi, Rihab Loudhaief, Smitha George, Tabatha Weller, Minna Salim, Ahsan Malick, Yizhu Mu, Brendon D Parsons, Francesca Di Cara.

  Intestinal epithelium regeneration and homeostasis must be tightly regulated. Alteration of epithelial homeostasis is a major contributing factor to diseases such as colorectal cancer and inflammatory bowel diseases. Many pathways involved in epithelial regeneration have been identified, but more regulators remain undiscovered. Metabolism has emerged as an overlooked regulator of intestinal epithelium homeostasis. Using the model organism Drosophila melanogaster, we found that ether lipids metabolism is required to maintain intestinal epithelial homeostasis. Its dysregulation in intestinal progenitors causes the activation of the unfolded protein response of the endoplasmic reticulum (UPR) that triggers Xbp1 and upregulates the conserved disulfide isomerase PDIA3/ERp60. Activation of the Xbp1-ERp60 signaling causes Jak/Stat-mediated increase in progenitor cells, compromising epithelial barrier function and survival in males but not females. This study identified ether lipids-PDIA3/ERp60 as a key regulator of intestinal progenitor homeostasis in health that, if altered, causes pathological conditions in the intestinal epithelium.

Keywords:  Cell biology; Lipidomics; Molecular biology

DOI:  https://doi.org/10.1016/j.isci.2025.111946
Science. 2025 Mar 07. 387(6738): eadn2623

A subcellular map of translational machinery composition and regulation at the single-molecule level.

Zijian Zhang, Adele Xu, Yunhao Bai, Yuxiang Chen, Kitra Cates, Craig Kerr, Abel Bermudez, Teodorus Theo Susanto, Kelsie Wysong, Fernando J García Marqués, Garry P Nolan, Sharon Pitteri, Maria Barna.

Millions of ribosomes are packed within mammalian cells, yet we lack tools to visualize them in toto and characterize their subcellular composition. In this study, we present ribosome expansion microscopy (RiboExM) to visualize individual ribosomes and an optogenetic proximity-labeling technique (ALIBi) to probe their composition. We generated a super-resolution ribosomal map, revealing subcellular translational hotspots and enrichment of 60S subunits near polysomes at the endoplasmic reticulum (ER). We found that Lsg1 tethers 60S to the ER and regulates translation of select proteins. Additionally, we discovered ribosome heterogeneity at mitochondria guiding translation of metabolism-related transcripts. Lastly, we visualized ribosomes in neurons, revealing a dynamic switch between monosomes and polysomes in neuronal translation. Together, these approaches enable exploration of ribosomal localization and composition at unprecedented resolution.

DOI: https://doi.org/10.1126/science.adn2623
Cell Stress Chaperones. 2025 Feb 27. pii: S1355-8145(25)00011-2. [Epub ahead of print]

CHOP aggravates hepatocyte apoptosis upon endoplasmic reticulum stress by down-regulating autophagy.

Jia-Yu Wu, Bing Han, Ting Yang, Lu Zheng, Yi-Xin Guo, Jia-Yao Li, Xiao-Yu Guo, Huan-Huan Yin, Ru-Jia Xie.

   BACKGROUND: Endoplasmic reticulum (ER) stress-associated apoptosis is involved in various liver diseases, including liver fibrosis, nonalcoholic fatty liver disease, and cirrhosis. Hepatocytes respond to ER stress by eliciting unfolded protein response (UPR) and enhancing autophagy. Autophagy is a pivotal mechanism for sustaining normal ER function, through degradation of damaged ER fragments and removal of abnormal protein aggregates in the ER lumen. Failure to restore ER homeostasis via autophagy is harmful to hepatocytes and contributes to ER stress-associated apoptosis. Recent findings indicated that C/EBP homologous protein (CHOP) could exacerbate ER stress-related apoptosis by down-regulating autophagy, but the underlying mechanism remains elusive.
AIM: To investigate the impact of CHOP on ER stress-induced apoptosis in rat hepatocytes, and the potential molecular mechanisms.
METHODS: BRL-3A cells were pre-treated with rapamycin (RAP) and 3-methyladenine, then treated with dithiothreitol (DTT). Growth and apoptotic rates were detected using real-time cellular analysis (RTCA) and flow cytometry, respectively. ER stress-associated molecule levels were determined via western blotting. CHOP, small interfering RNA, and the lentivirus vector system were used to transfect BRL-3A cells and observe the impact of CHOP gene silencing or overexpression on autophagy and apoptosis. Chromatin immunoprecipitation (ChIP) was used to confirm whether CHOP binds directly to ATG12, ATG5, and LC3 promotor regions undergoing ER stress.
RESULTS: ER stress-associated molecules were dramatically upregulated in BRL-3A hepatocytes and hepatocyte apoptosis was augmented. RAP pre-treatment significantly reduced DTT-induced expression of ER stress-associated molecules; conversely, 3-MA pre-treatment promoted DTT-induced levels of ER stress-associated apoptotic molecules. Following the decreased CHOP expression in hepatocytes, the level of autophagy-associated molecules dramatically increased, and DTT-induced hepatocyte apoptosis decreased. However, opposite trends were observed in CHOP overexpression cells. A negative regulation of CHOP on autophagy-associated molecules including ATG12, ATG5, and LC3 in BRL-3A cells upon DTT treatment was detected via ChIP.
CONCLUSION: CHOP enhancement during ER stress inhibits autophagy and promotes hepatocyte apoptosis; however, the decreased CHOP gene expression could attenuate DTT-induced hepatocyte apoptosis. Overexpression of CHOP could aggravate DTT-induced hepatocyte apoptosis.

Keywords:  Apoptosis; Autophagy; C/EBP homologous protein; Endoplasmic reticulum stress; Hepatocyte

DOI:  https://doi.org/10.1016/j.cstres.2025.02.005
Nat Commun. 2025 Mar 03. 16(1): 2138

The pathways of secretory cargo export at the endoplasmic reticulum.

Vivek Malhotra.

Palade's original model proposed that secretory cargo is transported between stable compartments via vesicles. However, recent findings challenge this view, suggesting that secretory pathway compartments are dynamic, with cargo itself dictating whether transfer occurs via vesicles or through the continuity and maturation of compartmental structures. At the heart of this process is TANGO1, a key component of a molecular machine that works in concert with COPII proteins to construct export routes tailored to the size and quantity of secretory cargo.

DOI: https://doi.org/10.1038/s41467-025-57408-2
ACS Chem Biol. 2025 Mar 04.

Tools to Dissect Lipid Droplet Regulation, Players, and Mechanisms.

Jinmin Liu, Yimon Aye.

Spurred by the authors' own recent discovery of reactive metabolite-regulated nexuses involving lipid droplets (LDs), this perspective discusses the latest knowledge and multifaceted approaches toward deconstructing the function of these dynamic organelles, LD-associated localized signaling networks, and protein players. Despite accumulating knowledge surrounding protein families and pathways of conserved importance for LD homeostasis surveillance and maintenance across taxa, much remains to be understood at the molecular level. In particular, metabolic stress-triggered contextual changes in LD-proteins' localized functions, crosstalk with other organelles, and feedback signaling loops and how these are specifically rewired in disease states remain to be illuminated with spatiotemporal precision. We hope this perspective promotes an increased interest in these essential organelles and innovations of new tools and strategies to better understand context-specific LD regulation critical for organismal health.

DOI: https://doi.org/10.1021/acschembio.4c00835
bioRxiv. 2025 Feb 23. pii: 2025.02.18.638884. [Epub ahead of print]

Dynamic Lipidome Reorganization in Response to Heat Shock Stress.

Luis Solano, Uri Keshet, Andrew Reinschmidt, Yonny Chavez, William Drew Hulsy, Oliver Fiehn, Nikolas Nikolaidis.

  The heat shock response (HSR) is a conserved cellular mechanism critical for adaptation to environmental and physiological stressors, with broad implications for cell survival, immune responses, and cancer biology. While the HSR has been extensively studied at the proteomic and transcriptomic levels, the role of lipid metabolism and membrane reorganization remains underexplored. Here, we integrate mass spectrometry-based lipidomics with RNA sequencing to characterize global lipidomic and transcriptomic changes in HeLa cells exposed to three conditions: control, heat shock (HS), and HS with eight hours of recovery. Heat shock-induced extensive lipid remodeling, including significant increases in fatty acids, glycerophospholipids, and sphingolipids, with partial normalization during recovery. Transcriptomic analysis identified over 2,700 upregulated and 2,300 downregulated genes under heat shock, with GO enrichment suggesting potential transcriptional contributions to lipid metabolism. However, transcriptional changes alone did not fully explain the observed lipidomic shifts, suggesting additional layers of regulation. Joint pathway analysis revealed enrichment in glycerophospholipid and sphingolipid metabolism, while network analysis identified lipid transport regulators (STAB2, APOB), stress-linked metabolic nodes (KNG1), and persistent sphingolipid enrichment during recovery. These findings provide a comprehensive framework for understanding lipid-mediated mechanisms of the HSR and highlight the importance of multi-omics integration in stress adaptation and disease biology.

Keywords:  Cellular Stress Adaptation; Heat Shock Response; Lipidomics

DOI:  https://doi.org/10.1101/2025.02.18.638884
Cell Death Differ. 2025 Mar 05.

Crosstalk between O-GlcNAcylation and phosphorylation in metabolism: regulation and mechanism.

Qijie Zhao, Shisheng Zhou, Wenhui Lou, Hui Qian, Zhiwei Xu.

Cells produce metabolic intermediates through catalytic reactions, mainly via post-translational modifications. The modification of proteins by O-linked N-acetylglucosamine, known as O-GlcNAcylation, is one of the most common post-translational modifications. As O-GlcNAcylation and phosphorylation can occur at serine or threonine residues, it is crucial that the interplay between these two modifications is vital to bioenergetic and biosynthetic demand. Although emerging recognition linking O-GlcNAc modification and phosphorylation to protein functions has been obtained, the issue of how altered O-GlcNAcylation or phosphorylation regulates each other in the metabolic system remains uncertain. The combination of cell biological and proteomic approaches over the recent few years has not only highlighted the interactions between O-GlcNAcylation and phosphorylation in protein function but also prompted us to elucidate the underlying mechanisms behind this crosstalk controlling metabolic homeostasis. The purpose of this review is to summarize recent advances in the O-GlcNAcylation/phosphorylation regulation of the metabolic process. An extensive exploration of this interplay has significant implications for metabolic control systems, including glucose, lipid, and nucleotide metabolism, where dysregulation in O-GlcNAcylation and phosphorylation of metabolic syndrome is essential.

DOI: https://doi.org/10.1038/s41418-025-01473-z
J Mol Biol. 2025 Feb 28. pii: S0022-2836(25)00122-6. [Epub ahead of print] 169056

Mechanistic insights into protein biogenesis and maturation on the ribosome.

Alfred Lentzsch, Jae Ho Lee, Shu-Ou Shan.

  The ribosome is a major cellular machine that converts genetic information into biological function. Emerging data show that the ribosome is not only a protein synthesis machine, but also participates in the maturation of the nascent protein into properly folded and active molecules. The ribosome surface near the opening of the polypeptide exit tunnel can interact directly with the newly synthesized protein and, more importantly, provides a platform where numerous protein biogenesis factors assemble, gain access to the nascent chain, and direct them into diverse biogenesis pathways. In this article, we review the current understanding of cotranslational protein maturation pathways, with an emphasis on systems in which biochemical studies provided a high-resolution molecular understanding and yielded generalizable mechanistic principles.

Keywords:  membrane protein folding; molecular chaperone; protein folding; protein modification and processing; protein targeting; ribosome

DOI:  https://doi.org/10.1016/j.jmb.2025.169056
Chem Biol Interact. 2025 Feb 27. pii: S0009-2797(25)00080-8. [Epub ahead of print]411 111450

Palmitic acid-induced insulin resistance triggers granulosa cell senescence by disruption of the UPRmt/mitophagy/lysosome axis.

Yuan Tian, Pengge Pan, Xiaoqiang Luo, Yaqi Sun, Xintong Yang, Hui Gao, Yanzhou Yang.

  Insulin resistance (IR) is the main pathological feature of polycystic ovary syndrome (PCOS), but the adverse impacts of IR on ovary and granulosa cells (GCs) are unknown. Therefore, the role of palmitic acid (PA) induced IR in GCs, and a mitochondrial proteostasis and mitochondrial homeostasis control system, the mitochondrial unfolded protein response (UPRmt)/mitophagy/lysosome axis were investigated to uncover the side effect and the mechanism of IR on GCs. Our results revealed that IR in GC was successfully constructed by 100 μM PA treatment accompanied with cell senescence. In addition, mitochondrial function was impaired by IR-induced GC senescence accompanied by significantly increased reactive oxygen species (ROS) and decreased mitochondrial membrane potential, and mitochondrial proteostasis was impaired by a dysfunctional UPRmt and increased protein aggregation, leading to more unfolded and misfolded proteins accumulating in mitochondria. Mitochondrial homeostasis was maintained by the mitophagy/lysosome degradation system, although mitophagy was significantly increased, lysosomes were damaged; hence, malfunctional mitochondria were not cleared by the mitophagy/lysosome degradation system, more ROS were produced by malfunctional mitochondria. Therefore, accelerated GC senescence was triggered by excessive ROS, and reversed by the mitophagy inhibitor cyclosporin A (CsA) accompanied with reduced IR. Additionally, the mice were administered with PA, and results revealed that the accelerated ovarian aging was caused by PA, which might be attributed to GC senescence. In conclusion, GC senescence was triggered in PA-induced IR by disruption of the UPRmt/mitophagy/lysosome axis, and IR induced GC senescence was reversed by the CsA.

Keywords:  Cell senescence; Granulosa cells; Mitophagy; Ovarian aging; Palmitic acid; UPR(mt)

DOI:  https://doi.org/10.1016/j.cbi.2025.111450
Front Mol Biosci. 2025 ;12 1491227

Two sides of the same coin: heat shock proteins as biomarkers and therapeutic targets for some complex diseases.

Xolani Henry Makhoba.

  Heat shock proteins are molecular chaperones that play crucial roles in the folding and unfolding of complex polypeptides within the cellular system. These molecules are involved in various processes, including vesicular transport, prevention of protein aggregation in the cytosol, and cell signaling. They are also linked to autoimmunity, infection immunity, and tumor immunology. Stressors like heat shock, exposure to heavy metals, cytokines, reactive oxygen species, inflammation, and viruses can influence the production of these molecules. In complex diseases such as cancer, malaria, and COVID-19, heat shock proteins are considered both biomarkers and drug targets. The upregulation of small heat shock proteins like hsp27 and major heat shock proteins 70/90 has been recognized as crucial biomarkers and therapeutic targets for cancer. Additionally, it has been reported that the invasion of Plasmodium falciparum, the causative agent of malaria, leads to the upregulation of heat shock proteins such as hsp40, hsp70, and hsp90. This sudden increase is a protective mechanism from the human host and enhances the parasite's growth, making these proteins significant as biomarkers and malarial drug targets. The presence of the SARS-CoV-2 virus in the human cellular system correlates with a substantial increase in heat shock protein 70 production from host cells. Furthermore, our research group has demonstrated that SARS-CoV-2 hijacks the host's heat shock proteins, and we are currently developing tools to prevent the virus from utilizing the host's protein folding system. This review aims to highlight the role of heat shock proteins as biomarkers and therapeutic targets for selected refractory diseases, focusing on cancer, malaria, and COVID-19. A fundamental molecular docking study was performed to investigate the interaction between a non-structural complex from SARS-CoV-2 and chosen small molecules, which is emphasized in this review.

Keywords:  biomarkers; critical diseases; drug targets; heat shock proteins; therapeutic targets

DOI:  https://doi.org/10.3389/fmolb.2025.1491227
bioRxiv. 2025 Feb 20. pii: 2025.02.16.638537. [Epub ahead of print]

Heat Shock-Induced PI(4)P Increase Drives HSPA1A Translocation to the Plasma Membrane in Cancer and Stressed Cells through PI4KIII Alpha Activation.

Alberto Arce, Rachel Altman, Allen Badolian, Jensen Low, Azalea Blythe Cuaresma, Uri Keshet, Oliver Fiehn, Robert V Stahelin, Nikolas Nikolaidis.

HSPA1A, a major heat shock protein, is known to translocate to the plasma membrane (PM) in response to cellular stress and cancer, where it plays protective roles in membrane integrity and stress resistance. Although phosphatidylinositol 4-phosphate [PI(4)P] is essential in this translocation, the signals that trigger and facilitate HSPA1A's movement remain undefined.Given that membrane lipid composition dynamically shifts during stress, we hypothesized that heat shock-induced PI(4)P changes are crucial for HSPA1A's PM localization. To test this hypothesis, we investigated the mechanisms driving PI(4)P changes and HSPA1A PM localization under heat shock. Lipidomic analysis, enzyme-linked immunosorbent assay (ELISA), and confocal imaging revealed a rapid PI(4)P increase at the PM post-heat shock, with levels peaking at 0 hours and declining by 8 hours. RNA sequencing and protein quantification indicated no transcriptional increase in PI4KIII alpha, the kinase responsible for PI(4)P synthesis, suggesting an alternative regulatory mechanism. Hypothesizing that heat shock enhances PI4KIII alpha activity, we performed ELISA coupled with immunoprecipitation, confirming a significant rise in PI4KIII alpha activity following heat shock. Functional analyses further demonstrated that RNAi-mediated PI4KIII alpha depletion or pharmacological PI(4)P reduction, using GSK-A1, impairs HSPA1A's localization to the PM, confirming that HSPA1A translocation is PI(4)P-dependent. Our findings identify PI4KIII alpha activity as a key regulator of PI(4)P accumulation and subsequent HSPA1A recruitment to the PM in stressed and cancer cells. This lipid-mediated response offers new insights into stress adaptation and potentially modifiable pathways for therapeutic interventions to control HSPA1A function in cancer.

DOI: https://doi.org/10.1101/2025.02.16.638537
J Alzheimers Dis Rep. 2025 Jan-Dec;9:9 25424823241307021

Heat shock protein 70 in Alzheimer's disease and other dementias: A possible alternative therapeutic.

Antonio Valle-Medina, Claudia Camelia Calzada-Mendoza, María Esther Ocharan-Hernández, Carlos Alberto Jiménez-Zamarripa, Teresa Juárez-Cedillo.

  Alzheimer's disease (AD) is considered a global health issue with a high social burden due to the level of disability it causes in those who suffer from it. In the absence of a therapeutic alternative for this disease, we will follow one of the biochemical pathways involved in the development of AD, which is related to molecular chaperones. The molecules are responsible for eliminating toxins and misfolded proteins at the cerebral level. These chaperones are a set of proteins from the heat shock proteins (HSPs) family, which, among their functions, help maintain homeostasis and protect cells against stress. Various authors have described the activity of HSPs in different neurodegenerative diseases, highlighting the activity of heat shock protein 70 (HSP70) in the presence of aberrant proteins characteristic of neurodegeneration, such as amyloid-β (Aβ) and tau. The role of HSP70 in AD and other dementias lies in its mechanism, which, along with other proteins from the HSP family, has the capacity to eliminate Aβ aggregates by promoting catalytic pathways. In this review, we explore the biological role of the HSP70 protein in AD and other dementias and its potential therapeutic use.

Keywords:  Alzheimer's disease; amyloid-β; amyloid-β protein precursor; heat shock protein 70; heat shock proteins; hyperphosphorylated tau protein

DOI:  https://doi.org/10.1177/25424823241307021
bioRxiv. 2025 Feb 22. pii: 2025.02.20.639242. [Epub ahead of print]

Functional Specialization of S-Adenosylmethionine Synthases Links Phosphatidylcholine to Mitochondrial Function and Stress Survival.

Athena L Munden, Dominique S Lui, Daniel P Higgins, Matthew J Fanelli, Thien-Kim Ngyuen, Katherine M Edwards, Maria Ericsson, Adwait A Godbole, John A Haley, Caroline Lewis, Jessica B Spinelli, Benjamin Harrison, Daniel Raftery, Danijel Djukovic, Daniel E L Promislow, Dana L Miller, Amy K Walker.

S-adenosylmethionine (SAM), produced by SAM synthases, is critical for various cellular regulatory pathways and the synthesis of diverse metabolites. Studies have often equated the effects of knocking down one synthase with broader SAM-dependent outcomes such as histone methylation or phosphatidylcholine (PC) production. Humans and many other organisms express multiple SAM synthases. Evidence in Caenorhabditis elegans , which possesses four SAM synthase genes, suggest that the enzymatic source of SAM impacts its function. For instance, loss of sams-1 leads to enhanced heat shock survival and increased lifespan, whereas reducing sams-4 adversely affects heat stress survival. Here, we show that SAMS-1 contributes to a variety of intermediary metabolic pathways, whereas SAMS-4 is more important to generate SAM for methylation reactions. We demonstrate that loss of sams-1 exerts age-dependent effects on nuclear-encoded mitochondrial gene expression, mitochondrial metabolites, and may induce mitophagy. We propose a mechanistic model where reduced SAM from SAMS-1 acts through PC to impact mitochondria, thereby enhancing survival during heat stress.

DOI: https://doi.org/10.1101/2025.02.20.639242
Int J Biol Macromol. 2025 Mar 03. pii: S0141-8130(25)02251-2. [Epub ahead of print]306(Pt 3): 141700

Impact of tyrosine amination on the aggregation and neurotoxicity of amyloid-β.

Ting Hu, Jinming Wu, Shitao Fu, Hailing Li, Zhonghong Gao.

  The tyrosine residue in amyloid-β (Aβ) is susceptible to attack by various reactive nitrogen intermediates, leading to the formation of 3-nitrotyrosine (3-NT), a post-translational modification associated with the pathophysiology of Alzheimer's disease (AD). Although considered a "dead-end" product, emerging evidence suggests that 3-NT can be reduced to 3-aminotyrosine (3-AT) in vivo. This study aims to validate the amination of Aβ tyrosine under physiological conditions and systematically investigate its impact on the aggregation and neurotoxicity of Aβ42. Our investigations reveal that tyrosine amination mitigates the highly ordered β-structure content of Aβ42, thereby modulating its aggregation pathway, which is primarily dominated by the multi-step secondary nucleation. Aminotyrosine fibrils exhibit enhanced fragmentation, increasing fibril elongation rate, and insoluble aggregate production. Concurrently, tyrosine amination attenuates the neurotoxicity of Aβ42 by reducing intracellular reactive oxygen species (ROS) production and mitigating cell membrane disruption. Tyrosine amination substantially alters the aggregation and physiological properties of Aβ42. Nitration of Aβ42 and subsequent conversion to tyrosine-aminated Aβ42 may represent an intrinsic defensive response against AD under nitrative stress.

Keywords:  Alzheimer's disease; Amyloid-β (Aβ); Kinetics; Neurodegenerative disease; Protein aggregation; Protein modifications; Tyrosine amination

DOI:  https://doi.org/10.1016/j.ijbiomac.2025.141700
J Biol Chem. 2025 Mar 03. pii: S0021-9258(25)00221-2. [Epub ahead of print] 108372

The contribution of the Golgi and the endoplasmic reticulum to calcium and pH homeostasis in Toxoplasma gondii.

Abigail Calixto, Katherine Moen, Silvia Nj Moreno.

  The cytosolic Ca2+ concentration of all cells is highly regulated demanding the coordinated operation of Ca2+ pumps, channels, exchangers and binding proteins. In the protozoan parasite Toxoplasma gondii calcium homeostasis, essential for signaling, governs critical virulence traits. However, the identity of most molecular players involved in signaling and homeostasis in T. gondii are unknown or poorly characterized. In this work we studied a putative calcium proton exchanger, TgGT1_319550 (TgCAXL1), which belongs to a family of Ca2+/proton exchangers that localize to the Golgi apparatus. We localized TgCAXL1 to the Golgi and the endoplasmic reticulum (ER) of T. gondii and validated its role as a Ca2+/proton exchanger by yeast complementation. Characterization of a knock-out mutant for TgCAXL1 (Δcaxl) underscored the role of TgCAXL1 in Ca2+ storage by the ER and acidic stores, most likely the Golgi. Most interestingly, TgCAXL1 function is linked to the Ca2+ pumping activity of the Sarcoplasmic Reticulum Ca2+-ATPase (TgSERCA). TgCAXL1 functions in cytosolic pH regulation and recovery from acidic stress. Our data showed for the first time the role of the Golgi in storing and modulating Ca2+ signaling in T. gondii and the potential link between pH regulation and TgSERCA activity, which is essential for filling intracellular stores with Ca2+.

Keywords:  Calcium signaling; SERCA; Toxoplasma gondii; calcium proton exchanger; pH homeostasis

DOI:  https://doi.org/10.1016/j.jbc.2025.108372
Mol Pharmacol. 2025 Feb;pii: S0026-895X(24)23014-5. [Epub ahead of print]107(2): 100008

High-throughput screening identifies a novel small-molecule modulator of Hsp70 that selectively enhances ubiquitination and degradation of misfolded neuronal NO synthase.

Anthony M Garcia, Amanda K Davis, Cristian Martinez-Ramos, Yoshihiro Morishima, Miranda Lau, Emily Xu, Arya Sunil, Haoming Zhang, Andrew Alt, Andrew P Lieberman, Yoichi Osawa.

  The Hsp90 and Hsp70 chaperones act as a protein quality control system for several hundred client proteins, including many implicated in neurodegenerative disorders. Hsp90 and Hsp70 are widely thought to be important drug targets. Although many structurally distinct compounds have been developed to target Hsp90, relatively few are known to target Hsp70 and even fewer have been tested in protein quality control systems. To address this, we describe a high-throughput thermal shift-based screen to find compounds that bind and stabilize Hsp70 and then employ assays with misfolded forms of a well-established client protein, neuronal NO synthase (nNOS), to identify compounds that enhance ubiquitination of client proteins. The ubiquitination assay employed a quantitative ELISA method to measure Hsp70:CHIP-dependent ubiquitination of heme-deficient nNOS, which is a model of a misfolded client, in reaction mixtures containing purified E1, E2, Hsp70, CHIP, and ubiquitin. We screened 44,447 molecules from the Maybridge and ChemDiv libraries and found one compound, protein folding disease compound 15 (PFD-15), that enhanced in vitro nNOS ubiquitination with an EC50 of approximately 8 μM. PFD-15 was tested in human embryonic kidney 293 cells stably transfected with a C331A nNOS, a mutation that makes nNOS a preferred client protein for ubiquitination. In this model, PFD-15 decreased steady-state levels of C331A nNOS, but not the wild-type nNOS, in a time- and concentration-dependent manner by a process attenuated by lactacystin, an inhibitor to the proteasome. PFD-15 appears to enhance binding of Hsp70 and CHIP to client proteins without interference of protein quality control mechanisms, enabling the selective clearance of misfolded proteins. SIGNIFICANCE STATEMENT: There are few treatment options for neurodegenerative diseases, which are widely thought to be caused by formation of toxic misfolded proteins. One novel approach is to enhance the Hsp90/Hsp70 protein quality control machinery to remove these misfolded proteins. Targeting Hsp70 may have advantages over targeting Hsp90, but fewer compounds targeting Hsp70 have been developed relative to those for Hsp90. The current study provides a novel approach to enhance the number of compounds targeting the Hsp70's role in protein quality control.

Keywords:  Chaperone; Degradation; Hsp70; Protein quality control; Ubiquitination

DOI:  https://doi.org/10.1016/j.molpha.2024.100008
Front Mol Neurosci. 2025 ;18 1427036

Astrocyte-secreted factors modulate synaptic protein synthesis as revealed by puromycin labeling of isolated synaptosomes.

Aida de la Cruz-Gambra, Jimena Baleriola.

  The synaptic proteome can be shaped by proteins transported from the neuronal soma and/or by mRNAs that are delivered to synapses where proteins are locally synthesized. This last mechanism is known as local translation. Local translation has been extensively studied in neurons in physiological conditions and, more recently, in neurological disorders, in which local transcriptomes and translatomes become dysregulated. It is widely believed that in neurons, the main source of localized transcripts is the neuronal soma and that localized translation is primarily regulated by the neuron itself. However, we wondered whether glial cells, especially astrocytes, could contribute to the modulation of synaptic local protein synthesis. To address this question, we compared levels of proteins produced in synaptic compartments in neuronal and neuron-astrocyte co-cultures using modified Boyden chambers or astrocyte-conditioned medium. We developed a methodology to measure local protein synthesis by puromycin labeling of isolated synaptosomes devoid of somatic input. Our results show that synaptic local translation is enhanced or retained when neurons are cultured in the presence of astrocytes and in response to astrocyte-conditioned medium. Puromycin labeling coupled with proximity ligation identified Rpl26 as one of the proteins whose local synthesis is regulated by astrocyte-secreted factors. Our results thus unravel the contribution of glia to synaptic protein synthesis and point to a previously unexplored extra layer of complexity in the regulation of local translation in neurons.

Keywords:  astrocyte-secreted factors; local translation; proteins; puromycilation assays and astrocyte-neuron communication; synaptosomes

DOI:  https://doi.org/10.3389/fnmol.2025.1427036
J Alzheimers Dis Rep. 2025 Jan-Dec;9:9 25424823241309664

Repurposing peripheral immunocytes of Bacillus Calmette Guerin-vaccinated melanoma patients to reveal preventive Alzheimer's disease mechanisms, possibly via the unfolded protein response.

Benjamin Y Klein, Inna Ben-David, Ofer N Gofrit, Charles L Greenblatt.

   Background: Alzheimer's disease (AD) dysfunctional unfolded protein response (UPR) is revealed by amyloid-β aggregates. Normally, UPR reacts to endoplasmic reticulum stress by resolving misfolded/aggregated proteins, and UPR failure induces brain-cell apoptosis consistent with AD pathology. Peripheral blood mononuclear cells (PBMC) and immunocyte brain infiltrates are involved in AD pathogenesis, whose risk is lowered by the Bacillus Calmette Guerin (BCG) vaccine. Hypothetically, BCG prevents AD caused by UPR-driven apoptosis in PBMC brain infiltrates, corrected by BCG-vaccinated PBMC brain infiltrates.
Objective: To reveal whether BCG shifts the UPR towards cell survival. Method: PBMC proteins from 6 individuals were compared by immuno-electrophoresis before and after BCG hypervaccination. Cryopreserved PBMC provided an opportunity to analyze the BCG impact on the UPR, although their donor destiny to develop AD was unknown. UPR signaling responsive to BCG was recorded to examine if BCG can influence UPR signaling and thereby explain the previously demonstrated AD prevention by BCG.
Results: UPR signal levels were scored according to positive versus negative cell survival odds by the BCG impact on a dozen UPR signals. The balance between positive and negative scores of individuals emphasizes the impact of the BCG vaccine on the UPR. The antiapoptotic UPR signals under BCG show opposite trends to UPR signals in AD brains, reported by the literature. In conclusion, 3/6 individuals had superior PBMC survival chances under BCG.
Conclusions: These results suggest that the UPR is part of the mechanism responsible for reducing the risk of AD, as previously shown among BCG-treated bladder cancer patients.

Keywords:  Alzheimer's disease; Bacillus Calmette Guerin vaccine; capillary-Immunoelectrophoresis; endoplasmic reticulum stress response; peripheral blood mononuclear cells

DOI:  https://doi.org/10.1177/25424823241309664
Nat Commun. 2025 Mar 04. 16(1): 2172

Crucial roles of Grr1 in splicing and translation of HAC1 mRNA upon unfolded stress response.

Nichika Sato, Yu Nakano, Yasuko Matsuki, Shota Tomomatsu, Sihan Li, Yoshitaka Matsuo, Toshifumi Inada.

In the process of the unfolded protein response (UPR), the Hac1p protein is induced through a complex regulation of the HAC1 mRNA. This includes the mRNA localization on the endoplasmic reticulum (ER) membrane and stress-triggered splicing. In yeast, a specific ribosome ubiquitination process, the monoubiquitination of eS7A by the E3 ligase Not4, facilitates the translation of HAC1i, a spliced form of the HAC1 mRNA. Upon UPR, the mono-ubiquitination of eS7A increases due to the downregulation of Ubp3, a deubiquitinating enzyme of eS7A. However, the exact mechanisms behind these regulations have remained unknown. In this study, an E3 ligase, Grr1, an F-box protein component of the SCF ubiquitin ligase complex, which is responsible for Ubp3 degradation, has been identified. Grr1-mediated Ubp3 degradation is required to maintain the level of eS7A monoubiquitination that facilitates Hac1p translation depending on the ORF of HAC1i. Grr1 also facilitates the splicing of HAC1u mRNA independently of Ubp3 and eS7A ubiquitination. Finally, we propose distinct roles of Grr1 upon UPR, HAC1u splicing, and HAC1i mRNA translation. Grr1-mediated Ubp3 degradation is crucial for HAC1i mRNA translation, highlighting the crucial role of ribosome ubiquitination in translational during UPR.

DOI: https://doi.org/10.1038/s41467-025-57360-1