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Proviral functions of HMGB1 in HAdV-C5 replication compartments.

UNLABELLED: Human adenoviruses (HAdVs) induce significant reorganization of the nuclear environment, leading to the formation of virus-induced subnuclear structures known as replication compartments (RCs). Within these RCs, viral genome replication, gene expression, and modulation of cellular antiviral responses are tightly coordinated, making them valuable models for studying virus-host interactions. In a recent study, we analyzed the protein composition of HAdV type 5 (HAdV-C5) RCs isolated from infected primary cells at different time points during infection using quantitative proteomics. We identified several chromatin modifiers, including the high-mobility group box 1 protein (HMGB1) as components associated with RCs and demonstrated that HMGB1 can be relocalized to RCs from different HAdV species, thereby modulating viral replication in a species-specific manner. In the present work, using click-chemistry and proximity ligation assays, we discovered that HMGB1 localizes to sites of DNA replication within RCs and that its interaction with DBP in RCs is dependent on both DNA replication and RC assembly. HMGB1-knockdown experiments demonstrated that HMGB1 is required for efficient viral gene expression. However, despite its proviral role in viral replication, we found that HMGB1 levels decreased in late stages of infection due to transcriptional downregulation. Furthermore, by overexpressing HMGB1, we showed that this regulation of HMGB1 levels during infection is critical for optimal HAdV-C5 replication. These results highlight the complex regulatory relationship between HMGB1 and HAdV-C5 infection. IMPORTANCE: In an extensive proteomics analysis, we found that HMGB1, an important cellular chromatin protein, was enriched in adenovirus replication compartments. In this study, we aimed to better understand the role of HMGB1 in the infection process of a human DNA virus, HAdV-C5. We tested different virus types, including some with specific gene deletions and mutations. Our results showed that during infection, HMGB1 levels decreased because the virus suppressed its production. Despite this, even at lower levels, HMGB1 still helped the virus replicate by interacting with key viral proteins and DNA at sites where the virus is actively replicating. Overall, our findings highlight how HMGB1 plays a crucial role in facilitating efficient virus replication, making it an important factor in the infection process.

HMGB1 Protein

HMGB1 as a convergent host factor in virus-induced carcinogenesis.

High-mobility group box 1 (HMGB1) is a chromatin-associated protein and a prototypical damage-associated molecular pattern whose dual intracellular and extracellular functions are increasingly implicated in cancer progression. Because viral proteins can harness HMGB1 to facilitate their own replication and remodel the microenvironment of transformed cells, human oncogenic viruses provide an instructive model for examining this duality. In this conceptual review, we organized the available evidence around two functional nodes. At the first node, intracellular HMGB1 supports viral replication, acting on viral chromatin in Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus, and on structured viral RNA in hepatitis C virus. At the second node, viral infection or specific viral oncoproteins induce HMGB1 secretion, which promotes infected-cell survival and remodels the tumor microenvironment, as reported for KSHV, hepatitis B virus, and human T-cell leukemia virus type 1. Human papillomavirus engage a receptor-level variant of this node through the HMGB1-TLR4 axis. Only KSHV currently supports both nodes in matched experimental systems. Therefore, we present a sequential two-node arrangement as a hypothesis, instead of an established property of oncogenic viruses. We further considered how viruses reverse the tumor-suppressive, genome-stabilizing functions of nuclear HMGB1, with conserved and divergent strategies apparent across viral families; why the absence of HMGB1 data for Merkel cell polyomavirus is a tractable and informative gap; and which HMGB1- and RAGE-directed agents are realistically positioned for evaluation in virus-associated cancers.

Damage-associated molecular pattern

Parkin Induces Ubiquitination and Large Extracellular Vesicle Release of HMGB1 to Activate Antitumor Immunity.

UNLABELLED: Parkin (PRKN) is a mitochondria-associated E3 ubiquitin ligase that mediates mitophagy and organelle quality control. More recently, PRKN has been implicated in stimulating antitumor immunity and reprogramming the tumor immune microenvironment. In this study, we showed that PRKN ubiquitinates the alarmin molecule, high-mobility group box-1 (HMGB1) on Lys146 (K146) using predominantly K48 linkages. By molecular modeling, the in-between-ring domain of PRKN (Gln326-Leu358) made extensive contacts with the amino-terminus A-box of HMGB1 (Met1-Ser42), forming a mitochondria-associated PRKN-HMGB1 complex that juxtaposes K146 to ubiquitin active site residues Gly76 and Arg74. Instead of proteasomal degradation, PRKN ubiquitination of K146 enabled the loading of HMGB1 but not HMGB1 K146A mutant, onto autophagy- and mitochondria-derived large extracellular vesicles (LEV). In turn, released PRKN-HMGB1-LEV stimulated a potent IFN and cytokine response in recipient cells, expanding CD8+ T-cell subsets with effector (CD69+/KLRG1+), self-renewal (TCF1+/PD-1+), and cytotoxic (KLRG1+/GrzB+) properties. Conditional expression of PRKN induced HMGB1 release, activated intratumoral CD8+ T cells, and suppressed syngeneic tumor growth in vivo in a response that was abolished by HMGB1 silencing. These data identify that PRKN-LEV-regulated release of HMGB1 reprograms antitumor immunity via stimulation of IFN signaling and expansion of specialized CD8+ T-cell subsets. SIGNIFICANCE: Parkin ubiquitinates the alarmin molecule HMGB1 to enable its regulated release in large extracellular vesicles that activate interferon signaling, expand specialized CD8+ T-cell subsets, and promote antitumor immunity.

HMGB1 Protein

Network Interactions of Circulating FGF23, HRG-HMGB1, and Cardiac Disease in CKD.

KEY POINTS: Multitrait analysis of genome-wide association study boosts the statistical power to identify novel genetic traits for fibroblast growth factor 23. A functional genomics approach aided network discovery to identify histidine-rich glycoprotein (HRG) and high-mobility group protein box 1 (HMGB1) as key regulators of cardiac disease in CKD. Integration of clinical and genetic data enhances the discovery power and is crucial for understanding the genetic underpinnings of mineral bone disorder related to CKD. BACKGROUND: Genome-wide association studies (GWAS) have identified numerous genetic loci associated with mineral metabolism markers but have exclusively focused on single-trait analysis. In this study, we performed a multitrait analysis of GWAS (MTAG) of mineral metabolism, exploring overlapping genetic architecture between traits to identify novel genetic associations for fibroblast growth factor 23 (FGF23). METHODS: We applied MTAG to variants common to GWAS of five genetically correlated mineral metabolism markers in participants of European ancestry. We integrated UK Biobank GWAS for blood levels for phosphate, 25-hydroxyvitamin D, and calcium (n=366,484) and Cohorts for Heart and Aging Research in Genetic Epidemiology GWAS for parathyroid hormone (n=29,155) and FGF23 (n=13,716). We then used supervised and unsupervised deep machine learning to identify novel associations between genetic traits and FGF23. RESULTS: MTAG increased the effective sample size for mineral metabolism markers to n=50,325 for FGF23. After clumping, MTAG identified independent genome-wide significant single-nucleotide polymorphisms for all traits, including 62 loci for FGF23. Many of these loci have not been previously reported in single-trait analyses. Through a functional genomics approach, we identified histidine-rich glycoprotein (HRG) and high-mobility group box 1 (HMGB1) as master regulators of downstream canonical pathways associated with circulating FGF23, and both genes were highly enriched in hypertrophied cardiac tissue of deceased hemodialysis patients. In addition, we found that DNMT3A was associated with uremic toxin, 8-hydroxy-2-deoxyguanosine, a biomarker of DNA damage. In silico gene perturbation analysis revealed that DNMT3A is protective in patients with heart failure caused by hypertrophied or dilated cardiomyopathy. CONCLUSIONS: Our findings highlight the importance of MTAG analysis of mineral metabolism markers to boost the number of genome-wide significant loci for FGF23 to identify novel genetic traits. Functional genomics revealed novel networks that inform unique cellular functions and identified HRG and HMGB1 as key master regulators of FGF23 and cardiovascular disease in CKD.

bones, stones, and mineral metabolism

Proteomic insights into platelet dysregulation and pathogenic mechanisms of chronic thromboembolic pulmonary hypertension.

BACKGROUND: Undissolved thrombus blocks the pulmonary arteries in chronic thromboembolic pulmonary hypertension (CTEPH), a potentially fatal illness that raises pulmonary resistance, causes right heart failure, and even results in death. Although platelets are linked to vascular dysfunction and thrombus formation, it is yet unknown what precise proteome alterations and mechanistic roles they play in CTEPH. METHODS: We extracted platelet-rich plasma from peripheral blood and separated the plasma to obtain enriched platelet pellet (EPP). Quantitative proteomics was used to examine EPP from CTEPH patients and healthy controls using mass spectrometry. The relationship between protein levels and clinical markers of right heart function was examined. Platelet activity, morphology, and interactions with other blood components were evaluated using transmission electron microscopy, immunofluorescence, and flow cytometry. RESULTS: The proteomic investigation found that 179 proteins were differentially expressed in CTEPH patients. The analysis revealed that these proteins were involved in crucial processes such as complement and coagulation cascades, phagosome, and neutrophil extracellular trap (NET) formation. Elevated proteins, specifically NOX2, PAD4, ITGB2, and HMGB1, have been associated to platelet-neutrophil aggregates and NET formation. In addition, enhanced P-selectin expression in platelets and plasma confirmed greater platelet activation in CTEPH patients. Notably, PAD4 and NOX2 levels showed a substantial correlation with hemodynamic parameters and right heart dysfunction. MPO-DNA, a NET marker associated with P-selectin and ITGB2 expression, was discovered in higher concentrations in CTEPH patients' plasmas. CONCLUSION: Platelet aggregation and activation in CTEPH encourage the formation of NETs, which advances the disease and prolongs thrombus. Right heart insufficiency and hemodynamic markers had a strong correlation with PAD4 and NOX2 levels, indicating that these biomarkers may be employed to assess the severity and prognosis of CTEPH disease and offer a fresh approach to targeted treatment. The results highlight the need for additional study to elucidate platelet-mediated pathways and create therapies for CTEPH that target platelets.

Humans

Chemoselective Tagging of Protein Methacrylation.

Protein lysine methacrylation (Kmea) is a recently identified post-translational modification whose biofunction remains poorly understood. Until now, there has been no chemical labeling method for Kmea modification, which has severely hindered the discovery and functional studies of methacrylated proteins. Here, we developed a photocatalytic thia-Michael reaction system for the chemoselective labeling of protein methacrylation. By exploiting the dual effect of steric hindrance and the stability of the generated C-center radical, the reaction interference of the structural isomer crotonylation can be efficiently avoided. Based on this reaction, a multifunctional water-soluble benzenethiol-azide probe azDSH was designed and synthesized, and a workflow for the specific labeling, enrichment, and identification of Kmea proteins was developed. Proteomic identification of histone and nuclear protein extracts and whole-cell lysate revealed a number of novel Kmea proteins and modification sites besides histones, such as HMGB1, TdIF2, UHRF1, HNRPD, BRWD1, TAF1, TACC1, and SETD3, providing new targets for the study of epigenetic regulation. This study provides an effective method for the analysis of protein methacrylation modifications in biological systems.

Humans

Nuclear Proteome Map of Mouse Heart Chambers.

Heart specialization involves nuclear programs; however, chamber-specific regulation of the nuclear proteome landscape remains unknown. In this study, we isolated the nucleus from four major anatomical regions of healthy mouse heart (fresh) and employed quantitative mass spectrometry-based proteomics to construct a comprehensive nuclear proteome landscape of left ventricle (LV, 2403 proteins), right ventricle (RV, 2242 proteins), left atrium (LA, 2368 proteins), and right atrium (RA, 1816 proteins). This led to the discovery of nuclear regional proteome signatures (ventricular signature, 297 proteins; atrial signature, 183 proteins) associated with oxidative metabolism and redox regulation, ferroptosis, extracellular-matrix remodeling, SUMO- and stress-responsive control and transcriptional regulation. Chamber-level analyses further identify distinct nuclear features in LV (120 proteins), LA (188 proteins), and RA (72 proteins). In addition, we defined conserved core nuclear proteome (230 proteins) shared across all anatomical regions, enriched for transcription-regulator complexes, nucleolar/ribosome-associated, RNA-processing, and chromatin-organization components. Within this core network, we report 78 transcription factors/co-factors and select nuclear, chromatin and RNA export-associated proteins, including 29 specific factors (e.g., Alpk3, Rbm14, Arglu1, Hmgb1, Myef2, Sf1) associated with the heart. Regionally, we verified spatial localization in heart of H2ac21 and Sun2 in LA and Ptbp2 in LV by immunofluorescence. This study provides insights into the chamber-resolved view of the nuclear proteome in the heart, establishes a framework for linking nuclear proteomic signatures to atrial and ventricular biology, unique features of the heart nuclear proteome landscape relative to other organs, and a baseline for studying nuclear remodeling in cardiac pathophysiology.

Animals

Effect of Chang'an decoction on ulcerative colitis by regulating T helper 17 cells and regulatory T cellsRab27 in the p53/high mobility group box 1 pathway.

OBJECTIVE: To explore the effect of Chang'an decoction (, CAD) of ameliorating the immune imbalances in ulcerative colitis (UC) by regulating Rab27 in the P53/high mobility group box 1 pathway. METHODS: The functions and important signaling pathways of the Rab27- and UC-related genes were analyzed viathe use of microarray data from the gene expression omnibus database, gene ontology database, Kyoto encyclopedia of genes and genomes database and gene set enrichment analysis. Dextran sulfate sodium salt-induced colitis mouse model was used to verify the bioinformatics results. Colon length, body weight, and disease activity index were measured. Hematoxylin and eosin staining was applied to validate the histopathology. Tight junction proteins were detected by immunohistochemistry. The proportions of T helper 17 cells (Th17) and regulatory T cells (Treg) in mesenteric lymph nodes were measured viaflow cytometry. Proinflammatory cytokines like interleukin (IL) 17 (IL-17), IL-21 and IL-22 and anti-inflammatory cytokines like transforming growth factor β and IL-10 in the serum and colon of mice were detected by enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively. The expression levels of high mobility group box 1 (HMGB1), P53 and phospho- P53 (P-P53) in colonic tissues were detected by immunofluorescence and Western blotting. RESULTS: Bioinformatics analysis revealed that compared with normal tissues, the expression of Rab27 was significantly increased in UC tissues. Receiver operating characteristic curve showed that Rab27 has the potential to be used as a biomarker for the diagnosis of disease activity. Enrichment analysis showed that UC and Rab27 were mainly associated with small molecule transport, nutrient metabolism, transmembrane transport and the downstream pathway of P53. According to animal experiments, the expression of Rab27 was increased in UC tissues, which aggravated the colonic pathological damage, activated the expression of HMGB1, and also leaded to the imbalance of Th17 and Treg cells. After CAD intervention, Rab27 overexpression, weight loss, colon shortening, and pathological damage were substantial reduced, the expression of tight junction proteins, zona occludens 1 and Occludin were increased. The effect of CAD at high-dose was more obvious. In addition, CAD upgraded the number of Treg cells and the production of TGF-β and IL-10, while decreasing the number of Th17 cells and the expression of inflammatory cytokines (IL-17, IL-21, and IL-22). Moreover, colon inflammation was alleviated by CAD, as indicated by the regulation of HMGB1 and P-P53 expression. CONCLUSION: The expression of Rab27, HMGB1 and P-P53 could be decreased by CAD, and the balance of Th17 and Treg cells as well as their related cytokines could be regulated by CAD.

Animals

KEAP1 loss-of-function suppresses immunogenic ferroptosis and limits PD-1 blockade efficacy through an NRF2-FSP1 pathway.

Loss-of-function mutations in Kelch-like ECH-associated protein 1 (KEAP1) frequently occur in lung adenocarcinoma and are associated with poor prognosis and limited benefit from immunotherapy. However, the mechanisms linking KEAP1 deficiency to immune evasion remain elusive. We combined clinical data analysis, in vivo tumor models, and in vitro co-culture systems to investigate how KEAP1 deficiency shapes dendritic cell (DC) biology and response to PD-1 blockade. Ferroptosis induction assays, damage-associated molecular patterns (DAMPs) quantification, cytokine profiling, and mechanistic interrogation of the FSP1-CoQ10 axis were performed to delineate pathways.KEAP1 mutations correlated with poor response to PD-1 blockade and reduced DC infiltration. In mice, KEAP1-deficient tumors exhibited accelerated growth and reduced DC and CD8+ T-cell infiltration, consistent with an immune-cold phenotype. Mechanistically, KEAP1 loss impaired DC function in vitro, as evidenced by reduced maturation, phagocytosis, and naïve CD8+ T-cell priming capacity. This defect was linked to two mechanisms. First, KEAP1-deficient tumor cells resisted ferroptosis and failed to release immunogenic DAMPs, including extracellular ATP, HMGB1, and calreticulin. Second, KEAP1 deficiency reprogrammed the cytokine secretion profile, with downregulation of CCL2, IL-6, CXCL1, and CXCL2, thereby diminishing DC recruitment and inflammatory signaling. Notably, inhibition of the FSP1-CoQ10 antioxidant axis restored ferroptosis-associated immunogenic cell death. Our study identifies KEAP1 deficiency as a driver of immune-cold tumor microenvironments and resistance to PD-1 blockade, acting through impaired ferroptosis-induced immunogenic cell death and disrupted DC function. Genetic FSP1 deletion restored ferroptosis-associated immunogenicity and DC activation in KEAP1-deficient cells, supporting FSP1 as a potential therapeutic target for further in vivo evaluation.

DAMPs

Glutathione reductase deficiency potentiates the immunogenicity of ferroptosis and cuproptosis via amplified reactive oxygen species accumulation and cGAS-STING pathway activation.

BACKGROUND: Cancer remains a major therapeutic challenge due to drug resistance and metastasis, processes driven by oxidative stress and redox imbalance. Targeting this vulnerability through ferroptosis (iron-dependent lipid peroxidation) and cuproptosis (copper-driven mitochondrial dysfunction), two ROS-mediated cell death pathways, offers a promising therapeutic strategy. However, clinical translation is hindered by incomplete understanding of their redox regulation and limited immunogenicity. METHODS: A genome-wide CRISPR knockout screen was performed to identify key regulators of ferroptosis. Genetic depletion or pharmacological inhibition of candidate genes was evaluated across multiple cancer cell lines for sensitivity to ferroptosis inducer RSL3 and the cuproptosis inducer elesclomol (Es). Antitumor efficacy was assessed in xenograft, orthotopic, metastatic, and syngeneic mouse models, alone or combined with immune checkpoint inhibitors. Mechanistic studies also examined ROS production, mitochondrial stress, mitochondrial DNA release, cGAS-STING activation, and immune responses within the tumor microenvironment. RESULTS: Glutathione reductase (GSR), a central enzyme maintaining reduced glutathione (GSH) homeostasis, was identified as the top suppressor of ferroptosis. GSR knockout or pharmacological inhibition markedly sensitized diverse cancer cell lines to RSL3-induced ferroptosis, while GSR overexpression conferred resistance. Strikingly, GSR depletion also enhanced sensitivity to cuproptosis triggered by the copper ionophore Es. In multiple in vivo tumor models, GSR inhibition synergizes with RSL3 or Es to suppress tumor growth, inhibit lung metastasis, and prolong survival. Mechanistically, GSR deficiency amplified ROS production, induced mitochondrial stress, and triggered the cytosolic mitochondrial DNA release under ferroptotic or cuproptotic stress, activating the cGAS-STING pathway in vitro and in vivo. This increased inflammatory cytokine production, promoted immunogenic cell death, and enhanced the release of damage-associated molecular patterns (DAMPs), including HMGB1. Together, GSR inhibition combined with a ferroptosis or cuproptosis inducer transformed the tumor microenvironment into a highly immune stimulatory state, thereby enhancing the efficacy of immune checkpoint blockade through increased dendritic cell activation and T-cell infiltration and activation. CONCLUSIONS: GSR represents a key molecular node connecting and modulating ferroptosis and cuproptosis through redox regulation. Targeting GSR amplifies ROS-mediated immunogenic cell death, triggers cGAS-STING activation in cancer cells, and enhances the efficacy of cancer immunotherapy, providing a promising redox-based therapeutic strategy.

Ferroptosis

Oncolytic HSV-1-Mediated JAG1 Blockade Induces Glioma Senescence-Associated Secretory Phenotype to Increase Macrophage Activation and Cetuximab-Mediated Senolysis.

UNLABELLED: Oncolytic HSV-1 (oHSV) treatment induces Notch signaling and myelosuppression in the tumor microenvironment (TME) of preclinical cancer models. Clinically, the Notch ligand JAG1 was upregulated in patients with recurrent high-grade glioma treated with the oHSV CAN-3110 and correlated with poor prognosis. To better understand endogenous JAG1-mediated signaling in glioma cells and tumor-associated macrophages (TAM), we engineered a JAG1-antagonizing oHSV (OD-0J1) and interrogated its impact on cancer and myeloid cells in the TME. OD-0J1 antagonized JAG1-mediated Notch signaling and suppressed tumor growth in athymic nude and humanized mice, an effect reliant on Notch signaling in tumor cells. Kinome profiling revealed that OD-0J1 treatment suppressed CDK1, resulting in activation of the G2-M cell cycle checkpoint. Cell cycle arrest led to senescence and correlated with increased reactive oxygen species, p62, and autophagosome accumulation and senescence-associated β-galactosidase activity. OD-0J1-induced senescence resulted in increased production of inflammatory chemokines and damage-associated molecular patterns (DAMP), such as IL1β, HMGB1, and extracellular ATP. Coculturing macrophages with OD-0J1-infected tumor cells led to stimulation of chemotactic and proinflammatory pathways, as well as increased Fc receptor activation. Single-cell RNA sequencing and flow cytometric analysis of F4/80+ cells isolated from tumors showed a shift from tumor-supporting TAMs to inflammatory macrophages upon OD-0J1 treatment. Heightened EGFR activation in senescent cells was a mechanism to escape cell death, which created a unique opportunity for cetuximab as a senolytic agent. Combination therapy reduced EGFR signaling and induced macrophage-mediated antibody-dependent cellular cytotoxicity, thereby increasing the antitumor therapeutic efficacy of OD-0J1. SIGNIFICANCE: Leveraging JAG1 antagonism in the context of oncolytic virotherapy rewires macrophage polarization within the tumor microenvironment, which has wide implications for sensitizing tumors to antibodies, senolytic agents, and BiTE therapies.

Humans