Dietary phospholipids alleviate high fat diet-induced intestinal lipid deposition through ATF4-PPARα-MTTP/SAR1B pathway in yellow catfish.

The PERK-eIF2α branch activates the NLRP3 inflammasome through the NF-κB signaling pathway to suppress NDV replication.

Capsaicin attenuates methylglyoxal-induced neurotoxicity via the ATF4-Sestrin2 signaling and direct scavenging of methylglyoxal.

Targeting gut-microbiota-dependent choline metabolite trimethylamine N-oxide ameliorates bone health in ovariectomized mice.

The unfolded protein response (UPR) is a central adaptive mechanism that safeguards protein homeostasis in the endoplasmic reticulum (ER). In the heart, UPR signaling contributes to cellular remodeling and survival across a range of pathological contexts, including ischemia, pressure overload, and cardiometabolic stress. Among the three canonical UPR branches, the PKR-like ER kinase (PERK) pathway plays a critical role in modulating translational control and redox balance during stress adaptation. Despite its functional importance, the molecular dynamics of PERK activation and assembly remain incompletely understood. Here, we investigate the oligomerization behavior of PERK in living cells using advanced fluorescence microscopy. We identify a concentration-dependent mechanism of PERK self-association, as well as a distinct population of oligomeric PERK whose assembly state remains stable upon ER stress induction. These findings challenge the traditional view of stress-induced oligomerization as a prerequisite for PERK activation and suggest the existence of non-canonical modes of PERK assembly with potential regulatory significance.

Cancer cells face continual stressors, which they must overcome to proliferate and survive in the body. Under these conditions, essential biochemical pathways are disrupted, contributing to various stress responses that either promote adaptation and survival or eventual cell death. The evolutionarily conserved integrated stress response (ISR) is a key adaptive mechanism that transiently rewires the transcriptome and translatome in response to various stressors. While the ISR is activated in healthy cells under moderate stress, cancers especially rely on this pathway to overcome harsh conditions experienced during tumor growth and metastasis. We explore the pro-tumorigenic role of the ISR, along with the upstream stress-sensing kinases that activate it. These include protein kinase R-like endoplasmic reticulum kinase, general control non-derepressible 2, double-stranded RNA-dependent protein kinase, and heme-regulated eukaryotic translation initiation factor 2α kinase (HRI), which initiate an ISR in response to diverse stressors by phosphorylating their shared substrate, eukaryotic initiation factor-2α. An in-depth understanding of the pro-survival functions of the ISR and the contexts in which it is pro-tumorigenic is necessary to leverage the ISR as a therapeutic strategy.

ABSTRACT Background Tauroursodeoxycholic acid (TUDCA) has been shown to improve endothelial dysfunction in type 2 diabetes mellitus (T2DM). However, its role in attenuating endothelial insulin resistance in diabetes is not well understood. Objectives This study aimed to investigate TUDCA’s potential therapeutic effect on endothelial insulin resistance and its underlying mechanisms. Methods Twenty-seven male Sprague Dawley rats were categorized into control (CON, n = 9), diabetes (DM, n = 9), and diabetes treated with TUDCA (DMT, n = 9). Diabetes was induced using a high-fat diet and low-dose streptozotocin. TUDCA (150 mg/kg) was administered to the DMT group during the last two weeks of a 15-week study. Aortic tissues were analyzed for insulin-mediated relaxation, endoplasmic reticulum (ER) stress markers [inositol-requiring kinase 1 (IRE-1), protein kinase-like ER kinase (PERK), and binding immunoglobulin protein (BIP)], end othelial function markers [endothelial nitric oxide synthase (eNOS), protein kinase B (Akt), and insulinreceptor substrate-1 (IRS-1)], oxidative stress [superoxide dismutase activity (SOD) and malondialdehyde level (MDA)] and inflammation [tumor necrosis factor-alpha (TNF-a)] markers. Results Insulin-mediated relaxation was impaired in diabetic rats (−56.7%) compared to controls (0%), accompanied by elevated ER stress markers and reduced eNOS, Akt, and IRS-1 expression. TUDCA treatment improved relaxation responses (−6.2%) significantly reduced ER stress markers and restored the expression of endothelial markers.

Coronaviruses pose a serious threat to public health, driving the need for antiviral therapeutics and vaccines. Therefore, it is paramount to understand how this family of viruses evades cellular antiviral responses and establishes productive infection. The conserved coronavirus nonstructural protein 1 (nsp1) has been shown to inhibit host protein synthesis and, in some coronaviruses, promote host messenger RNA (mRNA) degradation while viral mRNAs are protected. We showed previously that severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) induces activation of host integrated stress response (ISR) kinases protein kinase R (PKR) and PKR-like endoplasmic reticulum kinase (PERK), which promote phosphorylation of eukaryotic initiation factor 2 (eIF2α) and consequent inhibition of host protein synthesis. In contrast, eIF2α remains unphosphorylated during Middle East respiratory syndrome coronavirus (MERS-CoV) infection. To investigate the interactions of nsp1 and the ISR kinases, we utilized recombinant SARS-CoV-2 and MERS-CoV expressing nsp1 with mutations in each of two conserved domains. Upon infection with SARS-CoV-2 nsp1 mutants, translation was shut down in wildtype (WT) and PKR knockout (KO) cells but rescued in PERK KO cells, likely due to reduced p-eIF2α. In contrast, translation was rescued during infection with the analogous MERS-CoV nsp1 mutants even in WT cells. Moreover, SARS-CoV-2 WT suppressed expression of GADD34, a negative regulator of eIF2α phosphorylation, while SARS-CoV-2 nsp1 mutants induced GADD34. In contrast, MERS-CoV WT induced GADD34. Utilizing single-molecule fluorescence in situ hybridization, we found that SARS-CoV-2 and MERS-CoV nsp1 promote host mRNA degradation during WT, but not nsp1 mutant, infection. Thus, SARS-CoV-2 and MERS-CoV differ in interactions with the ISR and nsp1 control of host protein synthesis.

UFL1 deficiency impairs skeletal muscle development by activating PERK/eIF2α/ATF4/CHOP pathway-dependent apoptosis.

Group A Streptococcus host-pathogen dual crosstalk.

Sanguinarine triggers apoptosis and ferroptosis synchronously by directly binding BiP in lung squamous cell carcinoma.

Dairy cows with ketosis display immune dysfunction and a high incidence of infectious diseases, which may partly be attributed to excessive endoplasmic reticulum stress (ERS) and apoptosis in macrophages. The objective of the present study was to assess the role of ERS in macrophage apoptosis of ketotic dairy cows. Compared with healthy cows, the apoptosis number of macrophages and the protein abundance of glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), and activating transcription factor 6 (ATF6); the ratio of phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK)/PERK, phosphorylated inositol-requiring enzyme 1 (p-IRE1)/IRE1 and phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α)/eIF2α; and mean fluorescence intensity of C/EBP homology protein (CHOP) were greater in cows with clinically ketosis (CK). Treatment with FFA increased protein abundance of GRP78, CHOP, ATF6 and p-IRE1/IRE1, and mean fluorescence intensity of CHOP. Furthermore, FFA increased the protein abundance of cysteinyl aspartate-specific proteinase-3 (Caspase-3) and mean fluorescence intensity of Caspase-3 but decreased the Bcl-2/Bax protein abundance ratio, which was accompanied by an increase in the number macrophage apoptosis. Inhibition of ERS via TUDCA attenuated the increased macrophage apoptosis and the activated apoptotic pathways induced by Tn or FFA. Thus, hyperphysiological concentrations of FFA induce apoptosis in macrophages by triggering ERS in ketotic dairy cows.

Brucellosis is a widespread zoonotic disease caused by Brucella, a genus of facultative intracellular bacteria that infects livestock and humans. Brucella primarily replicates within the endoplasmic reticulum (ER) of host cells, where it establishes a specialized replicative niche. This ER localization disrupts ER structure and induces ER stress. The unfolded protein response (UPR) is a critical cellular pathway that maintains ER homeostasis by restoring protein-folding capacity and regulating stress responses. However, how Brucella manipulates host UPR pathways to promote its intracellular survival and pathogenesis remains poorly understood. Here, we identify the Brucella outer membrane protein Omp25 as a key factor in promoting its intracellular survival and proliferation by activating the host UPR. Omp25 directly binds to the ER chaperone binding-immunoglobulin protein, inducing the release and activation of the UPR sensors, PKR-like ER kinase, inositol-requiring enzyme 1 alpha, and activating transcription factor 6, thereby modulating ER homeostasis to favor bacterial replication. In addition, Omp25 enhances inflammatory cytokine expression via the binding-immunoglobulin protein-inositol-requiring enzyme 1 alpha-NF-κB signaling axis. The omp25-deleted strains (Δomp25) show impaired intracellular replication and reduced UPR activation and result in attenuated induction of inflammatory genes in infected cells compared with WT strains. In vivo, mice infected with an omp25 mutant strain exhibit lower bacterial burdens and milder tissue pathology compared with mice infected with the WT strain. These findings uncover a mechanism by which Omp25 facilitates Brucella intracellular proliferation through UPR modulation and highlight Omp25 as a potential target for therapeutic interventions and next-generation attenuated vaccines.

With aging, the morphology and function of the parotid glands are impaired, and the current mechanism is unknown. The integrity of mitochondria-associated membranes (MAMs), the structure connecting mitochondria and the endoplasmic reticulum (ER), is compromised during aging. This study investigated the effects of aging on MAMs and ER stress in the parotid glands of mice. Here, aged mice presented abnormalities in gland morphology and mitochondrial morphology and reduced MAMs integrity. Protein kinase R-like endoplasmic reticulum kinase (PERK) signaling is the primary mediator of ER stress, which is activated in the parotid glands of aged mice. Furthermore, aging-induced MFN2 downregulation disrupts mitochondrial dynamics. In addition, aging reduces MAMs function by blocking the MFN2-PERK interaction. Treatment with 4-phenylbutyric acid (4-PBA) improved MAMs integrity, inhibited the PERK pathway, and reduced apoptosis. Like 4-PBA, GSK2606414, a pharmacological antagonist of PERK, regulates ER stress and MAMs. Collectively, our data highlight disruption of the MFN2-PERK axis-mediated ER-mitochondrion connection as a cause of aging-induced parotid gland dysfunction.

PERK (Protein kinase R-like endoplasmic reticulum kinase), encoded by EIF2AK3, is a key ER stress sensor that regulates protein synthesis and the unfolded protein response (UPR). Its dysregulation is linked to cancer development and progression. This study investigated EIF2AK3/PERK expression across 28 tumour types (n = 7,251) and their matched normal adjacent tissues (NATs; n = 667) from the Cancer Genome Atlas (TCGA) database, along with additional normal tissue samples from the Genotype-Tissue Expression (GTEx) project (n = 1,736), and 1,179 tumour cell lines, examining correlations with patient demographics, tumour stage, survival and genetic alterations. Transcriptomic analysis revealed EIF2AK3 upregulation in multiple cancers, with proteomic data supporting increased PERK protein levels in specific tumour types. EIF2AK3 expression was correlated with age, gender, tumour stage and survival endpoints in a context-dependent manner. Mutational analysis identified frequent EIF2AK3 alterations, including missense, gain and amplification events. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the cell cycle, proteoglycans in cancer and focal adhesion pathways were among the most consistently enriched across tumour types, particularly in tumours with high EIF2AK3 expression. These tumours also showed enrichment in Rap1 signalling, PI3K-Akt signalling, cytoskeletal regulation, ubiquitin-mediated proteolysis and nucleocytoplasmic transport, indicating a stress-adaptive invasive phenotype. In contrast, tumours with low EIF2AK3 expression demonstrated enrichment in focal adhesion, AGE-RAGE signalling and cytoskeletal organisation, suggesting a tumour state dependent on adhesion integrity and extracellular matrix (ECM) interaction rather than stress-induced plasticity. Gene Ontology (GO) enrichment analysis supported these observations, with high EIF2AK3 tumours displaying strong associations with cell adhesion, ECM structural remodelling and actin binding, while low EIF2AK3 tumours showed enrichment in cytoskeletal stability and axonogenesis. Hierarchical clustering revealed a distinct gene cluster associated with EIF2AK3 across several tumour types. Protein-protein interaction (PPI) and enrichment analyses linked this cluster to tumour progression and cell adhesion. These findings underscore the central role of EIF2AK3/PERK in regulating cancer-associated pathways. Its expression stratifies tumours into biologically distinct phenotypes, with one favouring ER stress adaptation and invasiveness, and the other reliant on ECM organisation and adhesion homeostasis. EIF2AK3 may thus serve as a potential therapeutic target in multiple cancers.

Long-term nutritional excess causes hepatic steatosis, endoplasmic reticulum (ER) stress, hyperglycemia, and hyperlipidemia. Mitogen-activated protein kinase phosphatase-3 (MKP-3) is a well-established stress-regulated protein and a regulator of gluconeogenesis. Our previous study revealed that acute ER stress reduced gluconeogenesis and MKP-3 protein stability. However, the expression of MKP-3 and its regulatory mechanisms in chronic ER stress remain unclear. The aim of this study was to investigate the effects of chronic ER stress on hepatic MKP-3 expression and its role in the regulation of gluconeogenesis. The results show that long-term administration of thapsigargin (Tg) or palmitic acid promoted gene expression of Mkp-3 and gluconeogenic genes Pepck, G6pc, and Pgc1α in primary mouse hepatocytes. In addition, a long-term high-fat diet (HFD) or Tg administration significantly increased hepatic ER stress and blood glucose level in mice, while inducing the expression of Mkp-3 and hepatic gluconeogenic genes Pepck, G6pc and Pgc1α. Further study revealed that liver-specific Mkp-3 knockout (Mkp-3 LKO) reversed the blood glucose level and expression levels of gluconeogenic genes those were induced by long-term HFD in mice. Moreover, activation of the PKR-like ER kinase (PERK) by its agonist increased hepatic Mkp-3 expression, whereas inhibitor of PERK suppressed the expression of Mkp-3 under Tg administration. These results suggest that chronic high-fat diet might promote hepatic gluconeogenesis via the PERK/MKP-3 pathway. Consequently, this study identified a potential therapeutic target for treating obesity-related hyperglycemia.

Sphingosine-1-phosphate receptor 1 (S1PR1) signaling has been linked to the regulation of immunosuppressive cell populations within the tumor microenvironment (TME); however, its role in shaping anti-tumor CD8⁺ T cell responses remains poorly defined. Herein, we demonstrate that intratumoral CD8⁺ T cells express S1PR1, with expression predominantly enriched in the terminally exhausted subset. Transcriptomic profiling, combined with pharmacological inhibition and genetic knockdown, reveals that S1PR1-S1P signaling activates the PERK (protein kinase R (PKR)-like endoplasmic reticulum kinase)-CHOP (C/EBP homologous protein) axis of the endoplasmic reticulum stress response. CHOP, in turn, upregulates transcription of Map3k13 and Map3k15, triggering downstream MAPK signaling and culminating in activation of p38MAPK. Activation of this pathway impairs CD8⁺ T cell metabolism and effector function while increasing apoptotic susceptibility. This ultimately limits the persistence and accumulation of functional CD8⁺ T cells within the TME, thereby compromising their responsiveness to anti-PD-1 therapy. Targeting the S1PR1-S1P axis or its downstream effectors offers a promising strategy to improve cancer immunotherapy outcomes.

Cadmium chloride administered through drinking water disrupts the gut-liver axis through intestinal barrier failure, endoplasmic reticulum stress, and PIEZO1 signaling in broiler chickens

Repetitive mild traumatic brain injury (rmTBI) produces cumulative cellular stress that can lead to progressive brain dysfunction, yet the mechanisms governing vulnerability to repeated injury remain unclear. Protein kinase RNA-like endoplasmic reticulum kinase (PERK) regulates cellular proteostasis through the unfolded protein response and is implicated in neurodegeneration and acute brain injury. Here, we directly tested the role of PERK deficiency in shaping the brain’s response to rmTBI. Using a mouse model of neuronal PERK deficiency, we combined spatial proteomics and tissue analyses with resting-state functional MRI and diffusion tensor imaging to assess molecular, functional, and structural outcomes after rmTBI. PERK deficiency increased susceptibility to rmTBI-induced disruption of protein homeostasis, altered large-scale functional connectivity, and exacerbated white matter microstructural changes consistent with axonal and myelin damage. Molecular alterations were spatially aligned with imaging-defined network and white matter abnormalities. These findings identify PERK signaling as a key determinant of brain resilience to repetitive mild injury and link ER stress dysregulation to network-level dysfunction following rmTBI.

This study aimed to compare in vivo cerebral gadolinium (Gd3+) accumulation, associated unfolded protein response (UPR), and oxidative stress parameters in rats after exposure to gadolinium-based contrast agents (GBCAs). This study was designed as a controlled, experimental animal study to evaluate the accumulation of Gd3+ in the basal ganglia of rats following the administration of 0.6 mmol/kg gadopentetate dimeglumine (linear) and gadoterate meglumine (macrocyclic). Male Sprague-Dawley rats were exposed to the contrast agents for 24 and 72 h, and then the basal ganglia tissues were collected postmortem. The tissue levels of Gd3+ accumulation, activating transcription factor-6 (ATF6), inositol-requiring enzyme-1 (IRE-1), protein kinase RNA-like endoplasmic reticulum kinase (PERK), damage-inducible transcript-3 (DDIT3), total antioxidant status (TAS), and total oxidant status (TOS) were determined. Linear GBCA-treated rats had persistent Gd3+ levels over time, whereas a significant reduction from 24 to 72 h was observed in macrocyclic GBCA-treated rats (p < 0.001). PERK, DDIT3, and ATF6 expressions were significantly elevated after linear GBCA exposure (p < 0.05), while no significant increase was observed in the macrocyclic GBCA-treated group. However, IRE-1, TAS, and TOS levels were not significantly different in either group. Linear and macrocyclic GBCAs demonstrated distinct patterns of cerebral Gd3+ accumulation and UPR levels in rats. Accordingly, GBCA administration should be reserved for instances where it is necessary, such as when contrast enhancement is clinically required.