Human dental pulp stem cells (hDPSCs) play pivotal roles in the regeneration of pulp-dentin complex, yet their odontogenic differentiation is critically modulated by the inflammatory microenvironment. Protein kinase R-like endoplasmic reticulum kinase (PERK), a key regulator of endoplasmic reticulum stress, is highly enriched in mitochondria-associated endoplasmic reticulum membranes (MAMs) and exerts critical functions. However, its precise mechanisms in inflammatory regulation and cellular differentiation remain elusive. This study elucidates the PERK-centred regulatory mechanism in MAMs that governs inflammation-impaired odontogenic differentiation of hDPSCs, potentially involving IP3R-dependent calcium flux and dynamic protein interactions in MAMs. Rat pulpitis models and in vitro lipopolysaccharide (LPS)-induced inflammatory models of hDPSCs were established to investigate the effects of PERK signalling in odontogenesis under inflammatory conditions. Lentivirus-mediated silencing of PERK was performed to evaluate its role in LPS-induced inflammation. Molecular mechanisms were analysed using RNA sequencing, immunofluorescence, and transmission electron microscopy analyses. LPS stimulation activated the PERK signalling pathway, significantly upregulating MAM-related molecules (IP3R, VDAC1, GRP75) and enhancing PERK/VDAC1 colocalization and the formation of endoplasmic reticulum-mitochondria coupling structures. PERK silencing effectively mitigated LPS-induced mitochondrial swelling, ER dilatation, and calcium influx dysregulation, while restoring alkaline phosphatase activity and odontogenic differentiation potential. Mechanistically, PERK suppressed hDPSC mineralization by modulating IP3R-mediated calcium signalling pathway in MAMs. This study demonstrates that LPS-induced inflammatory stress reprograms hDPSCs bioactivity via PERK-centric control of MAMs likely through quantitative enhancement, structure specialization, and functional potentiation. The underlying mechanisms may involve IP3R-mediated regulation of calcium ion influx and protein interactions within MAMs.

Lipopolysaccharide (LPS)-mediated systemic inflammatory response accounts for the LPS pathogenicity in multi organs as lung and testis. LPS could cause a dysregulation of host response to infection, which may lead to life-threatening organ dysfunction. Accordingly, in our study, the probable protective impact of capmatinib against the LPS-induced acute inflammatory response was explored and the possible causal mechanisms were examined. Male Albino mice were pretreated with capmatinib (5 or 10 mg/kg, daily, orally) for 3 days then received single intraperitoneal injection of LPS (10 mg/kg) at day three. Capmatinib administration amended lung and testicular dysfunction as manifested by improved histopathological results and restored oxidant/antioxidant balance. Capmatinib effectively down-regulated protein kinase R-like endoplasmic reticulum kinase/phosphatidylinositol 3-kinase (PERK/PI3K) signaling pathway concomitant with toll-like receptor 4/nuclear factor kappa B (TLR4/NF-κB) inflammatory pathway mitigation besides caspase-1/gasdermin D (GSDMD)-N-terminal pathway inhibition. Collectively, the current study emphasized that capmatinib had potential protective effect against LPS-induced pulmonary and testicular injury.

Low-intensity extracorporeal shock wave therapy (LiESWT) is a promising noninvasive therapy for stress urinary incontinence (SUI). We assessed whether LiESWT restores urethral function in a vaginal distension (VD)-induced rat model of SUI, focusing on pelvic floor tissue remodeling and endoplasmic reticulum stress pathway as potential mechanisms. Eighty-one female Sprague-Dawley rats underwent functional and tissue analyses. Sneezing was induced to assess urethral pressure responses. Leak point pressure (LPP) was measured with or without hypogastric and pudendal nerve transections. Tissue remodeling and molecular pathways were assessed using histological and molecular expression analyses. In VD rats, baseline urethral pressure (9.9 ± 4.3 vs 17.6 ± 3.1 cmH2O) and LPP (27.4 ± 4.7 vs 37.0 ± 7.0 cmH2O) were lower than in normal rats (both p < 0.05). LiESWT restored the baseline urethral pressure (16.3 ± 4.7 cmH2O) and LPP (37.5 ± 4.9 cmH2O) in VD rats (p < 0.05). Notably, LPP enhancement persisted after bilateral hypogastric and pudendal nerve transections. Additionally, LiESWT tended to reduce VD-induced vaginal smooth muscle fibrosis histologically, whereas collagen type I alpha and elastin mRNA expression remained elevated in both groups. Western blotting revealed no sustained activation of protein kinase R-like endoplasmic reticulum kinase (PERK) at 96h after the final LiESWT. LiESWT enhanced urethral function in the VD-induced SUI model by potentially facilitating pelvic floor tissue remodeling, thereby restoring passive urethral closure. The absence of sustained PERK activation in the late phase indicates the safety of LiESWT for SUI.

Coronaviruses (CoVs) encode a variety of transmembrane proteins that are translated and processed at the endoplasmic reticulum (ER). Three host ER resident transmembrane proteins, activating transcription factor 6 (ATF6), inositol-requiring enzyme 1 (IRE1), and PKR-like endoplasmic reticulum kinase (PERK), sense the accumulation of unfolded proteins in the ER and initiate the unfolded protein response (UPR) to maintain ER proteostasis. We observed that SARS-CoV-2 Spike broadly activated all three arms of the UPR, whereas the Membrane (M) protein selectively inhibited ATF6. ATF6 has a unique activation mechanism whereby ER stress triggers translocation to the Golgi where ATF6 is processed by resident proteases to release the ATF6-N transcription factor. We observed that M inhibited the stress-induced production of ATF6-N, suggesting that ATF6 failed to engage with Golgi proteases for processing. M also inhibited sterol regulatory element binding protein-2 (SREBP2)-mediated activation of sterol responses and stimulator of interferon response cGAMP interactor 1 (STING)-mediated activation of interferon responses, both of which are activated in the ER and require translocation to the Golgi for interactions that yield transcriptional responses. We observed that M accumulated in the cis-Golgi, and triggered dispersal of the trans-Golgi network (TGN). Using a cargo sorting assay, we determined that ER-to-Golgi cargo trafficking was intact in the presence of M, but cargo accumulated with M in the cis-Golgi and did not proceed further in the secretory pathway. We also observed aberrant cholesterol accumulation at the cis-Golgi with M, consistent with our observation of M association with detergent resistant membranes. Together, these data suggest that CoV M proteins interfere with Golgi architecture and trafficking. Because CoV egress does not require the canonical secretory pathway, this mechanism could allow the virus to selectively interfere with host responses to infection without impeding egress of nascent virions.

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.

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

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

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

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

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.

Polydopamine nanoparticles reprogram macrophage polarization via SERCA2-associated calcium remodeling to support osteogenic differentiation under inflammatory conditions.

The unfolded protein response (UPR) plays an important role in tumor progression and cellular stress adaptation. In hepatocellular carcinoma (HCC), pharmacological inhibition of the protein kinase R-like endoplasmic reticulum kinase (PERK) is a potential therapeutic strategy, yet its effects on tumor growth and the microenvironment remain unclear. We investigated the selective PERK inhibitor AMG PERK 44 in a diethylnitrosamine (DEN)-induced mouse model of advanced HCC. Tumor burden, proliferation, fibrosis, immune-related gene expression, and ER stress signaling were assessed alongside analyses of single-cell RNA-sequencing data from HCC mouse models and liver-specific PERK knockout mice. Our results show that AMG PERK 44 did not alter tumor number nor cause a decrease in tumor area and proliferation. Furthermore, fibrotic burden was unchanged, although fibrosis architecture and stromal gene expression (TGF-β, CTGF, F4/80) were modified. Despite PERK inhibition, the expression of ER stress associated genes (CHOP, EIF2AK3, ERdj4) increased. Single-cell analysis revealed context-dependent PERK activity, highest in dendritic cells and macrophages under inflammatory and tumor conditions, while PERK knockout livers showed impaired UPR responses after tunicamycin treatment. Finally, AMG PERK 44 did not enhance idarubicin efficacy and caused no major off-target effects. These findings highlight the context-dependent role of PERK in the HCC microenvironment and its implications for targeting UPR pathways in liver cancer. Impact statement This study provides an evaluation of PERK as a therapeutic target in hepatocellular carcinoma by demonstrating that its inhibition does not produce the anticipated anti-tumor effects in advanced disease, but instead exerts nuanced, context-dependent influences on the tumor microenvironment.

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.

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.

The unfolded protein response (UPR) serves as a pivotal regulatory mechanism that enables cells to mitigate endoplasmic reticulum proteostasis disturbance. The evolutionarily conserved pathway encompasses three core signalings, namely the inositol-requiring enzyme 1α-X-Box-protein-1s (IRE1α-XBP1s), protein kinase RNA-like endoplasmic reticulum kinase-eukaryotic initiation factor-2α-activating transcription factor 4 (PERK-eIF2α-ATF4), and activating transcription factor 6 (ATF6) pathways. Notably, the activation of UPR pathway modulates the phenotype and functional properties of immune cells, and is intricately involved in the pathogenesis and progression of diverse immune-related disorders. In this review, we provide a systematic overview of the molecular mechanisms underlying UPR activation in different immune cell subsets, and further delve into the regulatory roles of UPR signaling in the survival, development, differentiation, and effector functions of immune cells. Collectively, this review aims to provide a theoretical framework for comprehensively elucidating the pivotal roles of UPR in immune responses and the pathogenesis of immune-related diseases.

SELENOS Is Associated with Endoplasmic Reticulum Stress Activation in Selenium Deficiency-Induced Nutritional Muscular Dystrophy in Chicks Exposed to Heat Stress.

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

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

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.