RESUMEN
The HMGB1 protein typically serves as a DNA chaperone that assists DNA-repair enzymes and transcription factors but can translocate from the nucleus to the cytoplasm or even to extracellular space upon some cellular stimuli. One of the factors that triggers the translocation of HMGB1 is its phosphorylation near a nuclear localization sequence by protein kinase C (PKC), although the exact modification sites on HMGB1 remain ambiguous. In this study, using spectroscopic methods, we investigated the HMGB1 phosphorylation and its impact on the molecular properties of the HMGB1 protein. Our nuclear magnetic resonance (NMR) data on the full-length HMGB1 protein showed that PKC specifically phosphorylates the A-box domain, one of the DNA binding domains of HMGB1. Phosphorylation of S46 and S53 was particularly efficient. Over a longer reaction time, PKC phosphorylated some additional residues within the HMGB1 A-box domain. Our fluorescence-based binding assays showed that the phosphorylation significantly reduces the binding affinity of HMGB1 for DNA. Based on the crystal structures of HMGB1-DNA complexes, this effect can be ascribed to electrostatic repulsion between the negatively charged phosphate groups at the S46 side chain and DNA backbone. Our data also showed that the phosphorylation destabilizes the folding of the A-box domain. Thus, phosphorylation by PKC weakens the DNA-binding affinity and folding stability of HMGB1.
Asunto(s)
ADN , Proteína HMGB1 , Pliegue de Proteína , Proteína Quinasa C , Proteína HMGB1/metabolismo , Proteína HMGB1/química , Fosforilación , ADN/metabolismo , ADN/química , Proteína Quinasa C/metabolismo , Proteína Quinasa C/química , Estabilidad Proteica , Humanos , Unión Proteica , Animales , Resonancia Magnética Nuclear Biomolecular , Modelos Moleculares , Dominios ProteicosRESUMEN
The receptor for advanced glycation end products (RAGE) plays a crucial role in inflammation-related pathways and various chronic diseases. Despite the recognized significance of N-glycosylation in the ligand-binding V domain (VD) of RAGE, a comprehensive understanding of the site-activity and structure-activity relationships is lacking due to the challenges in obtaining homogeneous glycoprotein samples through biological expression. Here, we combined chemical and chemoenzymatic approaches to synthesize RAGE-VD and its congeners with Asn3-glycosylation by incorporating precise N-glycan structures. Evaluation of these samples revealed that, in comparison to other RAGE-VD forms, α2,6-sialylated N-glycosylation at the Asn3 site results in more potent inhibition of HMGB1-induced nuclear factor-κB (NF-κB) expression in RAGE-overexpressing cells. Hydrogen/deuterium exchange-mass spectrum analysis revealed a sialylated RAGE-VD-induced interaction region within HMGB1. Conversely, Asn3 N-glycosylation in VD has negligible effects on RAGE-VD/S100B interactions. This study established an approach for accessing homogeneously glycosylated RAGE-VD and explored the modulatory effects of N-glycosylation on the interactions between RAGE-VD and its ligand proteins.
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Polisacáridos , Receptor para Productos Finales de Glicación Avanzada , Receptor para Productos Finales de Glicación Avanzada/metabolismo , Receptor para Productos Finales de Glicación Avanzada/química , Humanos , Polisacáridos/química , Polisacáridos/metabolismo , Glicosilación , Glicoproteínas/metabolismo , Glicoproteínas/química , Dominios Proteicos , FN-kappa B/metabolismo , Proteína HMGB1/metabolismo , Proteína HMGB1/químicaRESUMEN
Cisplatin, a cornerstone in cancer chemotherapy, is known for its DNA-binding capacity and forms lesions that lead to cancer cell death. However, the repair of these lesions compromises cisplatin's effectiveness. This study investigates how phosphorylation of HMGB1, a nuclear protein, modifies its binding to cisplatin-modified DNA (CP-DNA) and thus protects it from repair. Despite numerous methods for detecting protein-DNA interactions, quantitative approaches for understanding their molecular mechanism remain limited. Here, we applied click chemistry-based single-molecule force spectroscopy, achieving high-precision quantification of the interaction between phosphorylated HMGB1 and CP-DNA. This method utilizes a synergy of click chemistry and enzymatic ligation for precise DNA-protein immobilization and interaction in the system. Our results revealed that HMGB1 binds to CP-DNA with a significantly high rupture force of â¼130 pN, stronger than most natural DNA-protein interactions and varying across different DNA sequences. Moreover, Ser14 is identified as the key phosphorylation site, enhancing the interaction's kinetic stability by 35-fold. This increase in stability is attributed to additional hydrogen bonding suggested by molecular dynamics (MD) simulations. Our findings not only reveal the important role of phosphorylated HMGB1 in potentially improving cisplatin's therapeutic efficacy but also provide a precise method for quantifying protein-DNA interactions.
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Cisplatino , Química Clic , ADN , Proteína HMGB1 , Simulación de Dinámica Molecular , Proteína HMGB1/metabolismo , Proteína HMGB1/química , Cisplatino/química , Cisplatino/farmacología , Cisplatino/metabolismo , Fosforilación , ADN/química , ADN/metabolismo , Humanos , Unión Proteica , Antineoplásicos/química , Antineoplásicos/farmacologíaRESUMEN
Many human proteins possess intrinsically disordered regions containing consecutive aspartate or glutamate residues ("D/E repeats"). Approximately half of them are DNA/RNA-binding proteins. In this study, using nuclear magnetic resonance (NMR) spectroscopy, we investigated the electrostatic properties of D/E repeats and their influence on folded domains within the same protein. Local electrostatic potentials were directly measured for the HMGB1 protein, its isolated D/E repeats, and DNA-binding domains by NMR. The data provide quantitative information about the electrostatic interactions between distinct segments of HMGB1. Due to the interactions between the D/E repeats and the DNA-binding domains, local electrostatic potentials of the DNA-binding domains within the full-length HMGB1 protein were largely negative despite the presence of many positively charged residues. Our NMR data on counterions and electrostatic potentials show that the D/E repeats and DNA have similar electrostatic properties and compete for the DNA-binding domains. The competition promotes dissociation of the protein-DNA complex and influences the molecular behavior of the HMGB1 protein. These effects may be general among the DNA/RNA-binding proteins with D/E repeats.
Asunto(s)
Proteína HMGB1 , Resonancia Magnética Nuclear Biomolecular , Dominios Proteicos , Electricidad Estática , Humanos , Proteína HMGB1/química , Proteína HMGB1/metabolismo , ADN/química , Proteínas Intrínsecamente Desordenadas/química , Modelos MolecularesRESUMEN
Liquid-liquid phase separation (LLPS) of G-quadruplex (GQ) is involved in many crucial cellular processes, while the quadruplex-folding and their functions are typically modulated by specific DNA-binding proteins. However, the regulatory mechanism of binding proteins, particularly the well-folded proteins, on the LLPS of GQs is largely unknown. Here, we investigated the effect of HMGB1 on the condensation of a G-quadruplex of KRAS promoter (GQKRAS). The results show that these two rigid macro-biomolecules undergo co-condensation through a mutual promotion manner, while neither of them can form LLPS alone. Fluidity measurements confirm that the liquid-like droplets are highly dynamic. HMGB1 facilitates and stabilizes the quadruplex folding of GQKRAS, and this process enhances their co-condensation. The KRAS promoter DNA retains quadruplex folding in the droplets; interference with the GQ-folding disrupts the co-condensation of GQKRAS/HMGB1. Mechanistic studies reveal that electrostatic interaction is a key driving force of the interaction and co-condensation of GQKRAS/HMGB1; meanwhile, the recognition of two macro-biomolecules plays a crucial role in this process. This result indicates that the phase separation of GQs can be modulated by DNA binding proteins, and this process could also be an efficient way to recruit specific DNA binding proteins.
Asunto(s)
G-Cuádruplex , Proteína HMGB1 , Regiones Promotoras Genéticas , Proteínas Proto-Oncogénicas p21(ras) , ADN/genética , ADN/química , Proteína HMGB1/química , Proteína HMGB1/metabolismo , Proteínas Proto-Oncogénicas p21(ras)/genética , Humanos , Separación de FasesRESUMEN
Fifty years since the initial discovery of HMGB1 in 1973 as a structural protein of chromatin, HMGB1 is now known to regulate diverse biological processes depending on its subcellular or extracellular localization. These functions include promoting DNA damage repair in the nucleus, sensing nucleic acids and inducing innate immune responses and autophagy in the cytosol and binding protein partners in the extracellular environment and stimulating immunoreceptors. In addition, HMGB1 is a broad sensor of cellular stress that balances cell death and survival responses essential for cellular homeostasis and tissue maintenance. HMGB1 is also an important mediator secreted by immune cells that is involved in a range of pathological conditions, including infectious diseases, ischaemia-reperfusion injury, autoimmunity, cardiovascular and neurodegenerative diseases, metabolic disorders and cancer. In this Review, we discuss the signalling mechanisms, cellular functions and clinical relevance of HMGB1 and describe strategies to modify its release and biological activities in the setting of various diseases.
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Proteína HMGB1 , Neoplasias , Humanos , Proteína HMGB1/química , Proteína HMGB1/metabolismo , Muerte Celular , Inmunidad Innata , Transducción de SeñalRESUMEN
High mobility group B1 (HMGB1) is an architectural protein that recognizes the DNA damage sites formed by the platinum anticancer drugs. However, the impact of HMGB1 binding on the structural alterations of the platinum drug-treated single dsDNA molecules has remained largely unknown. Herein, the structural alterations induced by the platinum drugs, the mononuclear cisplatin and it's analog the trinuclear BBR3464, have been probed in presence of HMGB1, by atomic force microscopy (AFM) and AFM-based force spectroscopy. It is observed that the drug-induced DNA loop formation enhanced upon HMGB1 binding, most likely as a result of HMGB1-induced increase in DNA conformational flexibility that allowed the drug-binding sites to come close and form double adducts, thereby resulting in enhanced loop formation via inter-helix cross-linking. Since HMGB1 enhances DNA flexibility, the near-reversible structural transitions as observed in the force-extension curves (for 1 h drug treatment), generally occurred at lower forces in presence of HMGB1. The DNA structural integrity was largely lost after 24 h drug treatment as no reversible transition could be observed. The Young's modulus of the dsDNA molecules, as estimated from the force-extension analysis, increased upon drug treatment, due to formation of the drug-induced covalent cross-links and consequent reduction in DNA flexibility. The Young's modulus increased further in presence of HMGB1 due to HMGB1-induced enhancement in DNA flexibility that could ease formation of the drug-induced covalent cross-links. To our knowledge, this is the first report that shows an increase in the stiffness of the platinum drug-treated DNA molecules in presence of HMGB1.
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Antineoplásicos , Proteína HMGB1 , Platino (Metal)/farmacología , Proteína HMGB1/química , Proteína HMGB1/metabolismo , ADN/química , Cisplatino/farmacología , Antineoplásicos/farmacología , Antineoplásicos/química , Conformación de Ácido NucleicoRESUMEN
Non-histone nuclear proteins HMGB1 and HMGB2 (High Mobility Group) are involved in many biological processes, such as replication, transcription, and repair. The HMGB1 and HMGB2 proteins consist of a short N-terminal region, two DNA-binding domains, A and B, and a C-terminal sequence of glutamic and aspartic acids. In this work, the structural organization of calf thymus HMGB1 and HMGB2 proteins and their complexes with DNA were studied using UV circular dichroism (CD) spectroscopy. Post-translational modifications (PTM) of HMGB1 and HMGB2 proteins were determined with MALDI mass spectrometry. We have shown that despite the similar primary structures of the HMGB1 and HMGB2 proteins, their post-translational modifications (PTMs) demonstrate quite different patterns. The HMGB1 PTMs are located predominantly in the DNA-binding A-domain and linker region connecting the A and B domains. On the contrary, HMGB2 PTMs are found mostly in the B-domain and within the linker region. It was also shown that, despite the high degree of homology between HMGB1 and HMGB2, the secondary structure of these proteins is also slightly different. We believe that the revealed structural properties might determine the difference in the functioning of the HMGB1 and HMGB2 as well as their protein partners.
Asunto(s)
Proteína HMGB1 , Proteína HMGB2 , ADN/química , ADN/metabolismo , Proteínas del Grupo de Alta Movilidad , Proteína HMGB1/química , Proteína HMGB1/metabolismo , Proteína HMGB2/química , Proteína HMGB2/metabolismo , Factores de Transcripción , Unión Proteica , Animales , BovinosRESUMEN
Thousands of genetic variants in protein-coding genes have been linked to disease. However, the functional impact of most variants is unknown as they occur within intrinsically disordered protein regions that have poorly defined functions1-3. Intrinsically disordered regions can mediate phase separation and the formation of biomolecular condensates, such as the nucleolus4,5. This suggests that mutations in disordered proteins may alter condensate properties and function6-8. Here we show that a subset of disease-associated variants in disordered regions alter phase separation, cause mispartitioning into the nucleolus and disrupt nucleolar function. We discover de novo frameshift variants in HMGB1 that cause brachyphalangy, polydactyly and tibial aplasia syndrome, a rare complex malformation syndrome. The frameshifts replace the intrinsically disordered acidic tail of HMGB1 with an arginine-rich basic tail. The mutant tail alters HMGB1 phase separation, enhances its partitioning into the nucleolus and causes nucleolar dysfunction. We built a catalogue of more than 200,000 variants in disordered carboxy-terminal tails and identified more than 600 frameshifts that create arginine-rich basic tails in transcription factors and other proteins. For 12 out of the 13 disease-associated variants tested, the mutation enhanced partitioning into the nucleolus, and several variants altered rRNA biogenesis. These data identify the cause of a rare complex syndrome and suggest that a large number of genetic variants may dysregulate nucleoli and other biomolecular condensates in humans.
Asunto(s)
Nucléolo Celular , Proteína HMGB1 , Humanos , Arginina/genética , Arginina/metabolismo , Nucléolo Celular/genética , Nucléolo Celular/metabolismo , Nucléolo Celular/patología , Proteína HMGB1/química , Proteína HMGB1/genética , Proteína HMGB1/metabolismo , Proteínas Intrínsecamente Desordenadas/química , Proteínas Intrínsecamente Desordenadas/genética , Proteínas Intrínsecamente Desordenadas/metabolismo , Síndrome , Mutación del Sistema de Lectura , Transición de FaseRESUMEN
Chronic and persistent inflammation associated with excessive high mobility group protein 1 (HMGB1) is a risk factor for various diseases. Dietary intake of kaempferol has been proven to be effective in reducing HMGB1 levels and the degree of inflammation, but the structural mechanism remains unclear. In this context, we first investigated the interaction between bioactive kaempferol and HMGB1 using multi-spectroscopic and molecular simulation techniques. The surface plasmon resonance (SPR) data indicated that kaempferol binds directly to HMGB1 with a Kd value of 2.89 × 10-5 M. Binding of kaempferol with HMGB1 led to the intrinsic fluorescence quenching and modest secondary structure change of HMGB1 supported by fluorescence spectrometry and circular dichroism (CD). Using dynamic light scattering (DLS), it was found that kaempferol induced the aggregation of HMGB1 protein complex to form larger particles. On HMGB1-activated RAW264.7 cells, kaempferol co-incubation exhibited a remarkable inhibitory effect on nitric oxide (NO) release with an IC50 value of 5.02 µM, which was lower than that of quercetin. In silico, kaempferol binds to HMGB1 mainly through hydrogen bonds and hydrophobic forces. Collectively, our study showed kaempferol as a potential HMGB1 inhibitor, mainly acting by direct binding to HMGB1 and inducing its conformational changes, which provides clues for the treatment of chronic inflammation by kaempferol.
Asunto(s)
Proteína HMGB1 , Humanos , Proteína HMGB1/química , Proteína HMGB1/metabolismo , Quempferoles , Dicroismo Circular , Espectrometría de Fluorescencia , Inflamación , Simulación del Acoplamiento Molecular , Unión ProteicaRESUMEN
Metabolites are important for cell fate determination. Fructose-1,6-bisphosphate (F1,6P) is the rate-limiting product in glycolysis and the rate-limiting substrate in gluconeogenesis. Here, it is discovered that the nuclear-accumulated F1,6P impairs cancer cell viability by directly binding to high mobility group box 1 (HMGB1), the most abundant non-histone chromosome structural protein with paradoxical roles in tumor development. F1,6P disrupts the association between the HMGB1 A-box and C-tail by targeting K43/K44 residues, inhibits HMGB1 oligomerization, and stabilizes P53 protein by increasing P53-HMGB1 interaction. Moreover, F1,6P lowers the affinity of HMGB1 for DNA and DNA adducts, which sensitizes cancer cells to chemotherapeutic drug(s)-induced DNA replication stress and DNA damage. Concordantly, F1,6P resensitizes cancer cells with chemotherapy resistance, impairs tumor growth and enhances chemosensitivity in mice, and impedes the growth of human tumor organoids. These findings reveal a novel role for nuclear-accumulated F1,6P and underscore the potential utility of F1,6P as a drug for cancer therapy.
Asunto(s)
Fructosadifosfatos , Proteína HMGB1 , Neoplasias , Animales , Humanos , Ratones , Daño del ADN , Glucólisis , Proteína HMGB1/química , Proteína HMGB1/genética , Proteína HMGB1/metabolismo , Neoplasias/metabolismo , Proteína p53 Supresora de Tumor/genética , Fructosadifosfatos/metabolismoRESUMEN
OBJECTIVE: To explore the clinical value of high mobility group box-1 (HMGB-1), C-reactive protein (CRP), procalcitonin (PCT), and CRP to albumin (Alb) ratio in the diagnosis and evaluation of the severity of sepsis in children. PATIENTS AND METHODS: A total of 90 children, 50 with sepsis and 40 with general infection, whose symptoms did not meet the criteria for diagnosis of sepsis, were admitted to the Pediatrics Department of Jingzhou Central Hospital in Hubei Province between November 2021 and December 2022, were enrolled and selected as experimental and control group, respectively. The serum of two groups was collected within 24 hours after admission, the levels of HMGB-1 were detected by enzyme-linked immunosorbent assay (ELISA), and CRP, PCT, Alb, and hospitalization days were recorded. The differences in indicators between the two groups were compared, and correlation analysis was performed between hospitalization days and various indicators. The receiver operating characteristic (ROC) curve was drawn to evaluate the independent or combined value of CRP, PCT, HMGB-1, and CRP/Alb ratio in the early diagnosis of sepsis in children. RESULTS: These four indicators of children with sepsis were significantly higher than those in the general infection group (all p=0.000). The levels of CRP, PCT and CRP/Alb ratio were significantly positively correlated with the hospitalization days (r=0.329, 0.333, 0.329; p=0.02, 0.01, 0.002). The area under curve (AUC) of CRP, PCT, HMGB-1, and CRP/Alb ratio for the diagnosis of sepsis in children was 0.798, 0.817, 0.838, 0.809, respectively, and that of the combination of four indicators was 0.952. CONCLUSIONS: CRP, PCT, HMGB-1, and CRP/Alb ratio resulted as effective indicators for early diagnosis and evaluation of childhood sepsis, having a higher value in combined diagnosis.
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Proteína C-Reactiva , Proteína HMGB1 , Sepsis , Albúmina Sérica , Proteína C-Reactiva/química , Niño , Proteína HMGB1/química , Humanos , Polipéptido alfa Relacionado con Calcitonina/química , Pronóstico , Curva ROC , Sepsis/diagnóstico , Albúmina Sérica/químicaRESUMEN
BACKGROUND: This paper aims to investigate the correlation between high mobility group protein-1 (HMG-b1), antioxidant enzyme-1 (paraoxon-1, PON-1), monocyte chemoattractant protein-1 (monocyte chemoattractant protein-1, MCP-1), P. gingivalis, and MSAF. MATERIALS AND METHODS: The total sample size comprised of 73 cases in both groups. These patients were further subdivided into 2 groups: the MSAF group and the control group. 38 women were in the MSAF group and 35 women with term amniotic fluid serum were in the control group. The MSAF group was selected as a full-term singleton amniotic fluid fecal infection group. Clinical data were collected, and specimens were collected. Fecal staining of amniotic fluid and full-term amniotic fluid removes the placenta and umbilical cord blood. The expression of HMGB1 in the placenta was observed by immune-histochemical staining of MSAF and control groups. The content of PON-1 in cord blood was determined by ELISA. RESULTS: Correlation between maternal and neonatal clinical data and MSAF was done; MSAF group mean gestational age was 41.38 ± 1.40 weeks; control group mean gestational age was 39.20 ± 1.24 weeks. This study found no correlation between the birth weight, maternal age, sex, first/transmaternal, hyperthyroidism, hypothyroidism, and anemia between the MSAF and control group with nonsignificant P value (P > 0.05). However, the fatal age, gestational diabetes, gestational hypertension, umbilical cord abnormalities, placental abnormalities, and neonatal asphyxia factors were statistically different with a significant P value of <0.05 between both groups. HMGB1 and Periodontal P. gingivalis are mostly expressed in placental trophoblast, vascular endothelial cells, and amniotic epithelial and interstitial cells. After HE staining of 72 placentas by HE in MSAF and control, 6 had acute chorioamnionitis (5.1 control), 32 had chronic (23.9), 35 had abnormal placentas, and three in MSAF had chorionic columnar metaplasia. In immune-histochemistry experiments, the HMGB1 expression intensity of placental tissue was higher in the MSAF group (P < 0.05); however, the level of PON-1 was lower in the MSAF group as compared to the controls (P < 0.05). CONCLUSIONS: Gestational age and placental abnormalities are clinical high-risk factors for MSAF. HMGB1, PON-1, MCP-1, and Periodontal P. gingivalis may be involved in the development of MSAF, suggesting an oxidative/antioxidant imbalance with inflammation, and may be one of the mechanisms for MSAF development.
Asunto(s)
Líquido Amniótico , Arildialquilfosfatasa , Quimiocina CCL2 , Proteína HMGB1 , Porphyromonas gingivalis , Líquido Amniótico/química , Antioxidantes , Arildialquilfosfatasa/química , Infecciones por Bacteroidaceae , Quimiocina CCL2/química , Células Endoteliales , Femenino , Proteína HMGB1/química , Humanos , Lactante , Recién Nacido , Masculino , Meconio , Periodoncio/microbiología , Placenta , EmbarazoRESUMEN
Carriers of heterozygous germline BAP1 mutations (BAP1+/-) are affected by the "BAP1 cancer syndrome." Although they can develop almost any cancer type, they are unusually susceptible to asbestos carcinogenesis and mesothelioma. Here we investigate why among all carcinogens, BAP1 mutations cooperate with asbestos. Asbestos carcinogenesis and mesothelioma have been linked to a chronic inflammatory process promoted by the extracellular release of the high-mobility group box 1 protein (HMGB1). We report that BAP1+/- cells secrete increased amounts of HMGB1, and that BAP1+/- carriers have detectable serum levels of acetylated HMGB1 that further increase when they develop mesothelioma. We linked these findings to our discovery that BAP1 forms a trimeric protein complex with HMGB1 and with histone deacetylase 1 (HDAC1) that modulates HMGB1 acetylation and its release. Reduced BAP1 levels caused increased ubiquitylation and degradation of HDAC1, leading to increased acetylation of HMGB1 and its active secretion that in turn promoted mesothelial cell transformation.
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Amianto , Proteína HMGB1/química , Histona Desacetilasa 1/química , Proteínas Supresoras de Tumor/química , Ubiquitina Tiolesterasa/química , Animales , Biomarcadores de Tumor/metabolismo , Carcinogénesis , Núcleo Celular/metabolismo , Femenino , Interacción Gen-Ambiente , Mutación de Línea Germinal , Proteína HMGB1/genética , Heterocigoto , Histona Desacetilasa 1/genética , Incidencia , Inflamación , Masculino , Mesotelioma/metabolismo , Ratones , Mutación , Pronóstico , Unión Proteica , Proteínas Supresoras de Tumor/metabolismo , Ubiquitina/química , Ubiquitina Tiolesterasa/metabolismoRESUMEN
The human natural killer (HNK-1) carbohydrate plays important roles during nervous system development, regeneration after trauma and synaptic plasticity. Four proteins have been identified as receptors for HNK-1: the laminin adhesion molecule, high-mobility group box 1 and 2 (also called amphoterin) and cadherin 2 (also called N-cadherin). Because of HNK-1's importance, we asked whether additional receptors for HNK-1 exist and whether the four identified proteins share any similarity in their primary structures. A set of 40,000 sequences homologous to the known HNK-1 receptors was selected and used for large-scale sequence alignments and motif searches. Although there are conserved regions and highly conserved sites within each of these protein families, there was no sequence similarity or conserved sequence motifs found to be shared by all families. Since HNK-1 receptors have not been compared regarding binding constants and since it is not known whether the sulfated or non-sulfated part of HKN-1 represents the structurally crucial ligand, the receptors are more heterogeneous in primary structure than anticipated, possibly involving different receptor or ligand regions. We thus conclude that the primary protein structure may not be the sole determinant for a bona fide HNK-1 receptor, rendering receptor structure more complex than originally assumed.
Asunto(s)
Antígenos CD57/metabolismo , Cadherinas/metabolismo , Proteína HMGB1/metabolismo , Proteína HMGB2/metabolismo , Laminina/metabolismo , Oligosacáridos/metabolismo , Secuencia de Aminoácidos , Animales , Sitios de Unión , Antígenos CD57/química , Cadherinas/química , Proteína HMGB1/química , Proteína HMGB2/química , Humanos , Laminina/química , Ligandos , Regeneración Nerviosa/fisiología , Plasticidad Neuronal/fisiología , Oligosacáridos/química , Unión Proteica , Dominios ProteicosRESUMEN
BACKGROUND: High mobility group box 1 protein (HMGB1) is an alarmin following its release by immune cells upon cellular activation or stress. High levels of extracellular HMGB1 play a critical role in impairing the clearance of invading pulmonary pathogens and dying neutrophils in the injured lungs of cystic fibrosis (CF) and acute respiratory distress syndrome (ARDS). A heparin derivative, 2-O, 3-O desulfated heparin (ODSH), has been shown to inhibit HMGB1 release from a macrophage cell line and is efficacious in increasing bacterial clearance in a mouse model of pneumonia. Thus, we hypothesized that ODSH can attenuate the bacterial burden and inflammatory lung injury in CF and we conducted experiments to determine the underlying mechanisms. METHODS: We determined the effects of ODSH on lung injury produced by Pseudomonas aeruginosa (PA) infection in CF mice with the transmembrane conductance regulator gene knockout (CFTR-/-). Mice were given ODSH or normal saline intraperitoneally, followed by the determination of the bacterial load and lung injury in the airways and lung tissues. ODSH binding to HMGB1 was determined using surface plasmon resonance and in silico docking analysis of the interaction of the pentasaccharide form of ODSH with HMGB1. RESULTS: CF mice given 25 mg/kg i.p. of ODSH had significantly lower PA-induced lung injury compared to mice given vehicle alone. The CF mice infected with PA had decreased levels of nitric oxide (NO), increased levels of airway HMGB1 and HMGB1-impaired macrophage phagocytic function. ODSH partially attenuated the PA-induced alteration in the levels of NO and airway HMGB1 in CF mice. In addition, ODSH reversed HMGB1-impaired macrophage phagocytic function. These effects of ODSH subsequently decreased the bacterial burden in the CF lungs. In a surface plasmon resonance assay, ODSH interacted with HMGB1 with high affinity (KD = 3.89 × 10-8 M) and induced conformational changes that may decrease HMGB1's binding to its membrane receptors, thus attenuating HMGB1-induced macrophage dysfunction. CONCLUSIONS: The results suggest that ODSH can significantly decrease bacterial infection-induced lung injury in CF mice by decreasing both HMGB1-mediated impairment of macrophage function and the interaction of HMGB1 with membrane receptors. Thus, ODSH could represent a novel approach for treating CF and ARDS patients that have HMGB1-mediated lung injury.
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Fibrosis Quística/complicaciones , Fibrosis Quística/metabolismo , Proteína HMGB1/genética , Heparina/análogos & derivados , Macrófagos/inmunología , Macrófagos/metabolismo , Neumonía Bacteriana/etiología , Neumonía Bacteriana/metabolismo , Animales , Carga Bacteriana , Biomarcadores , Regulador de Conductancia de Transmembrana de Fibrosis Quística/genética , Regulador de Conductancia de Transmembrana de Fibrosis Quística/metabolismo , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Proteína HMGB1/química , Proteína HMGB1/metabolismo , Heparina/química , Heparina/metabolismo , Interacciones Huésped-Patógeno/genética , Interacciones Huésped-Patógeno/inmunología , Inmunohistoquímica , Masculino , Ratones , Ratones Noqueados , Modelos Moleculares , Óxido Nítrico/metabolismo , Fagocitosis/inmunología , Neumonía Bacteriana/patología , Unión Proteica , Células RAW 264.7 , Relación Estructura-ActividadRESUMEN
Highly negatively charged segments containing only aspartate or glutamate residues ("D/E repeats") are found in many eukaryotic proteins. For example, the C-terminal 30 residues of the HMGB1 protein are entirely D/E repeats. Using nuclear magnetic resonance (NMR), fluorescence, and computational approaches, we investigated how the D/E repeats causes the autoinhibition of HMGB1 against its specific binding to cisplatin-modified DNA. By varying ionic strength in a wide range (40-900 mM), we were able to shift the conformational equilibrium between the autoinhibited and uninhibited states toward either of them to the full extent. This allowed us to determine the macroscopic and microscopic equilibrium constants for the HMGB1 autoinhibition at various ionic strengths. At a macroscopic level, a model involving the autoinhibited and uninhibited states can explain the salt concentration-dependent binding affinity data. Our data at a microscopic level show that the D/E repeats and other parts of HMGB1 undergo electrostatic fuzzy interactions, each of which is weaker than expected from the macroscopic autoinhibitory effect. This discrepancy suggests that the multivalent nature of the fuzzy interactions enables strong autoinhibition at a macroscopic level despite the relatively weak intramolecular interaction at each site. Both experimental and computational data suggest that the D/E repeats interact preferentially with other intrinsically disordered regions (IDRs) of HMGB1. We also found that mutations mimicking post-translational modifications relevant to nuclear export of HMGB1 can moderately modulate DNA-binding affinity, possibly by impacting the autoinhibition. This study illuminates a functional role of the fuzzy interactions of D/E repeats.
Asunto(s)
Proteína HMGB1/antagonistas & inhibidores , Proteína HMGB1/metabolismo , Proteínas Intrínsecamente Desordenadas/antagonistas & inhibidores , Proteínas Intrínsecamente Desordenadas/metabolismo , Electricidad Estática , Sitios de Unión , ADN/química , ADN/metabolismo , Proteína HMGB1/química , Humanos , Proteínas Intrínsecamente Desordenadas/química , Modelos Moleculares , Simulación de Dinámica Molecular , Resonancia Magnética Nuclear Biomolecular , Unión Proteica , Conformación ProteicaRESUMEN
BACKGROUND: During sepsis or sterile tissue injury, the nuclear protein high mobility group box 1 (HMGB1) can be released to the extracellular space and ultimately into systemic circulation, where it mediates systemic inflammation and remote organ failure. The proinflammatory effects of HMGB1 can be suppressed by recombinant thrombomodulin (rTM), in part through a mechanism involving thrombin-rTM-mediated degradation of HMGB1. Given that HMGB1 is proinflammatory but the HMGB1 degradation product (desHMGB1) is not, an analytical method that discriminates between these two molecules may provide a more in-depth understanding of HMGB1-induced pathogenicity as well as rTM-mediated therapeutic efficiency. METHODS: A peptide that has a shared amino-terminal structure with desHMGB1 was synthesized. C3H/lpr mice were immunized with the desHMGB1 peptide conjugate, and antibody-secreting hybridoma cells were developed using conventional methods. The reactivity and specificity of the antibodies were then analyzed using antigen-coated enzyme-linked immunosorbent assay (ELISA) as well as antibody-coated ELISA. Next, plasma desHMGB1 levels were examined in a cecal ligation and puncture (CLP)-induced septic mouse model treated with rTM. RESULTS: Through a series of screening steps, we obtained a monoclonal antibody that recognized desHMGB1 but did not recognize intact HMGB1. ELISA using this antibody specifically detected desHMGB1, which was significantly increased in CLP-induced septic mice treated with rTM compared with those treated with saline. CONCLUSIONS: In this study, we obtained a desHMGB1-specific monoclonal antibody. ELISA using the novel monoclonal antibody may be an option for the in-depth analysis of HMGB1-induced pathogenicity as well as rTM-mediated therapeutic efficiency.
Asunto(s)
Biomarcadores , Ensayo de Inmunoadsorción Enzimática , Proteína HMGB1/metabolismo , Animales , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática/métodos , Ensayo de Inmunoadsorción Enzimática/normas , Proteína HMGB1/sangre , Proteína HMGB1/química , Ratones , Ratones Endogámicos C3H , Péptidos/metabolismo , Proteolisis , Sepsis/sangre , Sepsis/etiología , Sepsis/metabolismo , PorcinosRESUMEN
Macrophage plasticity enables cells to obtain different functions over a broad proinflammatory and repairing spectrum. In different conditions, macrophages can be induced by high-mobility group box 1 (HMGB1), a nuclear DNA-binding protein that activates innate immunity, to polarize towards a pro- (M1) or anti-inflammatory (M2) phenotype. In this study, we investigated the phenotypes of murine bone-marrow-derived macrophages (BMDMs) induced by different HMGB1 redox isoforms in depth. Our results demonstrate that disulfide HMGB1 (dsHMGB1) induces a unique macrophage phenotype that secretes pro-inflammatory cytokines, rather than inducing metabolic changes leading to nitric oxide production. Fully reduced HMGB1 (frHMGB1) did not induce macrophage polarization. The migrating function of BMDMs was measured by scratch assay after the stimulation with dsHMGB1 and frHMGB1. Both dsHMGB1 and frHMGB1 induced cell migration. We found that dsHMGB1 mediates cytokine secretion and cellular motility, mainly through toll-like receptor 4 (TLR4). Importantly, our data shows that dsHMGB1 and frHMGB1 induce distinct BMDM polarization phenotypes, and that dsHMGB1 induces a unique phenotype differing from the classical proinflammatory macrophage phenotype.
Asunto(s)
Movimiento Celular/efectos de los fármacos , Disulfuros/química , Proteína HMGB1 , Macrófagos/metabolismo , Animales , Femenino , Proteína HMGB1/química , Proteína HMGB1/farmacología , Ratones , Oxidación-Reducción , Receptor Toll-Like 4/metabolismoRESUMEN
Inflammation is a biological process that exists in a large number of diseases. If the magnitude or duration of inflammation becomes uncontrolled, inflammation may cause pathological damage to the host. HMGB1 and NF-κB have been shown to play pivotal roles in inflammation-related diseases. New drugs aimed at inhibiting HMGB1 expression have become a key research focus. In the present study, we showed that paeonol (Pae), the main active component of Paeonia suffruticosa, decreases the expression of inflammatory cytokines and inhibits the translocation of HMGB1 induced by lipopolysaccharide (LPS). By constructing HMGB1-overexpressing (HMGB1+ ) and HMGB1-mutant (HMGB1m ) RAW264.7 cells, we found that the nuclear HMGB1 could induce an LPS-tolerant state in RAW264.7 cells and that paeonol had no influence on the expression of inflammatory cytokines in HMGB1m RAW264.7 cells. In addition, the anti-inflammatory property of paeonol was lost in HMGB1 conditional knockout mice, indicating that HMGB1 is a target of paeonol and a mediator through which paeonol exerts its anti-inflammatory function. Additionally, we also found that HMGB1 and P50 competitively bound with P65, thus inactivating the NF-κB pathway. Our research confirmed the anti-inflammation property of paeonol and suggests that inhibiting the translocation of HMGB1 could be a new strategy for treating inflammation.