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1.
Nat Commun ; 12(1): 5068, 2021 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-34417460

RESUMO

p53 regulates several signaling pathways to maintain the metabolic homeostasis of cells and modulates the cellular response to stress. Deficiency or excess of nutrients causes cellular metabolic stress, and we hypothesized that p53 could be linked to glucose maintenance. We show here that upon starvation hepatic p53 is stabilized by O-GlcNAcylation and plays an essential role in the physiological regulation of glucose homeostasis. More specifically, p53 binds to PCK1 promoter and regulates its transcriptional activation, thereby controlling hepatic glucose production. Mice lacking p53 in the liver show a reduced gluconeogenic response during calorie restriction. Glucagon, adrenaline and glucocorticoids augment protein levels of p53, and administration of these hormones to p53 deficient human hepatocytes and to liver-specific p53 deficient mice fails to increase glucose levels. Moreover, insulin decreases p53 levels, and over-expression of p53 impairs insulin sensitivity. Finally, protein levels of p53, as well as genes responsible of O-GlcNAcylation are elevated in the liver of type 2 diabetic patients and positively correlate with glucose and HOMA-IR. Overall these results indicate that the O-GlcNAcylation of p53 plays an unsuspected key role regulating in vivo glucose homeostasis.


Assuntos
Acetilglucosamina/metabolismo , Glucose/metabolismo , Fígado/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Sequência de Bases , Restrição Calórica , Linhagem Celular , Colforsina/farmacologia , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/metabolismo , Epinefrina/metabolismo , Glucagon/metabolismo , Glucocorticoides/metabolismo , Gluconeogênese/efeitos dos fármacos , Glicosilação , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Hidrocortisona/metabolismo , Hiperglicemia/complicações , Hiperglicemia/metabolismo , Resistência à Insulina , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Fígado/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/complicações , Obesidade/metabolismo , Fosfoenolpiruvato Carboxiquinase (GTP)/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Estabilidade Proteica/efeitos dos fármacos , Ácido Pirúvico/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transcrição Genética/efeitos dos fármacos , Proteína Supressora de Tumor p53/genética
2.
Proc Natl Acad Sci U S A ; 118(29)2021 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-34266954

RESUMO

Intestinal inflammation is the underlying basis of colitis and the inflammatory bowel diseases. These syndromes originate from genetic and environmental factors that remain to be fully identified. Infections are possible disease triggers, including recurrent human food-poisoning by the common foodborne pathogen Salmonella enterica Typhimurium (ST), which in laboratory mice causes progressive intestinal inflammation leading to an enduring colitis. In this colitis model, disease onset has been linked to Toll-like receptor-4-dependent induction of intestinal neuraminidase activity, leading to the desialylation, reduced half-life, and acquired deficiency of anti-inflammatory intestinal alkaline phosphatase (IAP). Neuraminidase (Neu) inhibition protected against disease onset; however, the source and identity of the Neu enzyme(s) responsible remained unknown. Herein, we report that the mammalian Neu3 neuraminidase is responsible for intestinal IAP desialylation and deficiency. Absence of Neu3 thereby prevented the accumulation of lipopolysaccharide-phosphate and inflammatory cytokine expression in providing protection against the development of severe colitis.

3.
Sci Rep ; 10(1): 19908, 2020 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-33199824

RESUMO

O-linked ß-N-acetylglucosamine (O-GlcNAc) is a post-translational modification which occurs on the hydroxyl group of serine or threonine residues of nucleocytoplasmic proteins. It has been reported that the presence of this single sugar motif regulates various biological events by altering the fate of target proteins, such as their function, localization, and degradation. This study identified SMAD4 as a novel O-GlcNAc-modified protein. SMAD4 is a component of the SMAD transcriptional complex, a major regulator of the signaling pathway for the transforming growth factor-ß (TGF-ß). TGF-ß is a powerful promoter of cancer EMT and metastasis. This study showed that the amount of SMAD4 proteins changes according to cellular O-GlcNAc levels in human lung cancer cells. This observation was made based on the prolonged half-life of SMAD4 proteins. The mechanism behind this interaction was that O-GlcNAc impeded interactions between SMAD4 and GSK-3ß which promote proteasomal degradation of SMAD4. In addition, O-GlcNAc modification on SMAD4 Thr63 was responsible for stabilization. As a result, defects in O-GlcNAcylation on SMAD4 Thr63 attenuated the reporter activity of luciferase, the TGF-ß-responsive SMAD binding element (SBE). This study's findings imply that cellular O-GlcNAc may regulate the TGF-ß/SMAD signaling pathway by stabilizing SMAD4.


Assuntos
Acetilglucosamina/química , Neoplasias da Mama/patologia , Glicogênio Sintase Quinase 3 beta/metabolismo , Neoplasias Pulmonares/patologia , Processamento de Proteína Pós-Traducional , Proteólise , Proteína Smad4/química , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Feminino , Glicogênio Sintase Quinase 3 beta/genética , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Serina , Transdução de Sinais , Proteína Smad4/genética , Proteína Smad4/metabolismo , Treonina , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta/metabolismo , Células Tumorais Cultivadas , Ubiquitina/metabolismo
4.
Cell Death Dis ; 11(9): 815, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994395

RESUMO

O-GlcNAc transferase (OGT) is an enzyme that catalyzes the O-GlcNAc modification of nucleocytoplasmic proteins and is highly expressed in many types of cancer. However, the mechanism regulating its expression in cancer cells is not well understood. This study shows that OGT is a substrate of the E3 ubiquitin ligase X-linked inhibitor of apoptosis (XIAP) which plays an important role in cancer pathogenesis. Although LSD2 histone demethylase has already been reported as an E3 ubiquitin ligase in lung cancer cells, we identified XIAP as the main E3 ubiquitin ligase in colon cancer cells. Interestingly, OGT catalyzes the O-GlcNAc modification of XIAP at serine 406 and this modification is required for the E3 ubiquitin ligase activity of XIAP toward specifically OGT. Moreover, O-GlcNAcylation of XIAP suppresses colon cancer cell growth and invasion by promoting the proteasomal degradation of OGT. Therefore, our findings regarding the reciprocal regulation of OGT and XIAP provide a novel molecular mechanism for controlling cancer growth and invasion regulated by OGT and O-GlcNAc modification.


Assuntos
Neoplasias do Colo/metabolismo , N-Acetilglucosaminiltransferases/metabolismo , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/fisiologia , Neoplasias do Colo/patologia , Glicosilação , Células HCT116 , Células HEK293 , Humanos , Invasividade Neoplásica , Transfecção , Ubiquitinação
5.
Biochem Biophys Res Commun ; 529(3): 692-698, 2020 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-32736694

RESUMO

Unlike other types of glycosylation, O-GlcNAcylation is a single glycosylation which occurs exclusively in the nucleus and cytosol. O-GlcNAcylation underlie metabolic diseases, including diabetes and obesity. Furthermore, O-GlcNAcylation affects different oncogenic processes such as osteoblast differentiation, adipogenesis and hematopoiesis. Emerging evidence suggests that skeletal muscle differentiation is also regulated by O-GlcNAcylation, but the detailed molecular mechanism has not been fully elucidated. In this study, we showed that hyper-O-GlcNAcylation reduced the expression of myogenin, a transcription factor critical for terminal muscle development, in C2C12 myoblasts differentiation by O-GlcNAcylation on Thr9 of myocyte-specific enhancer factor 2c. Furthermore, we showed that O-GlcNAcylation on Mef2c inhibited its DNA binding affinity to myogenin promoter. Taken together, we demonstrated that hyper-O-GlcNAcylation attenuates skeletal muscle differentiation by increased O-GlcNAcylation on Mef2c, which downregulates its DNA binding affinity.


Assuntos
Acetilglucosamina/metabolismo , Diferenciação Celular , Desenvolvimento Muscular , Mioblastos/citologia , Acilação , Animais , Linhagem Celular , Glicosilação , Células HEK293 , Humanos , Fatores de Transcrição MEF2/metabolismo , Camundongos , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , Mioblastos/metabolismo
6.
Proc Natl Acad Sci U S A ; 117(25): 14259-14269, 2020 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-32513743

RESUMO

The Hippo pathway controls organ size and tissue homeostasis by regulating cell proliferation and apoptosis. The LATS-mediated negative feedback loop prevents excessive activation of the effectors YAP/TAZ, maintaining homeostasis of the Hippo pathway. YAP and TAZ are hyperactivated in various cancer cells which lead to tumor growth. Aberrantly increased O-GlcNAcylation has recently emerged as a cause of hyperactivation of YAP in cancer cells. However, the mechanism, which induces hyperactivation of TAZ and blocks LATS-mediated negative feedback, remains to be elucidated in cancer cells. This study found that in breast cancer cells, abnormally increased O-GlcNAcylation hyperactivates YAP/TAZ and inhibits LATS2, a direct negative regulator of YAP/TAZ. LATS2 is one of the newly identified O-GlcNAcylated components in the MST-LATS kinase cascade. Here, we found that O-GlcNAcylation at LATS2 Thr436 interrupted its interaction with the MOB1 adaptor protein, which connects MST to LATS2, leading to activation of YAP/TAZ by suppressing LATS2 kinase activity. LATS2 is a core component in the LATS-mediated negative feedback loop. Thus, this study suggests that LATS2 O-GlcNAcylation is deeply involved in tumor growth by playing a critical role in dysregulation of the Hippo pathway in cancer cells.


Assuntos
Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Proteínas Supressoras de Tumor/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Apoptose , Proliferação de Células , Células HEK293 , Homeostase , Humanos , Fosforilação
7.
Front Immunol ; 11: 589259, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33603735

RESUMO

Post-translational modifications, including O-GlcNAcylation, play fundamental roles in modulating cellular events, including transcription, signal transduction, and immune signaling. Several molecular targets of O-GlcNAcylation associated with pathogen-induced innate immune responses have been identified; however, the direct regulatory mechanisms linking O-GlcNAcylation with antiviral RIG-I-like receptor signaling are not fully understood. In this study, we found that cellular levels of O-GlcNAcylation decline in response to infection with Sendai virus. We identified a heavily O-GlcNAcylated serine-rich region between amino acids 249-257 of the mitochondrial antiviral signaling protein (MAVS); modification at this site disrupts MAVS aggregation and prevents MAVS-mediated activation and signaling. O-GlcNAcylation of the serine-rich region of MAVS also suppresses its interaction with TRAF3; this prevents IRF3 activation and production of interferon-ß. Taken together, these results suggest that O-GlcNAcylation of MAVS may be a master regulatory event that promotes host defense against RNA viruses.


Assuntos
Acetilglucosamina/imunologia , Proteínas Adaptadoras de Transdução de Sinal/imunologia , Infecções por Respirovirus/imunologia , Vírus Sendai , Acilação , Linhagem Celular , Interações Hospedeiro-Patógeno/imunologia , Humanos , Imunidade Inata , Mitocôndrias/imunologia , Transdução de Sinais
8.
Cell Host Microbe ; 24(4): 500-513.e5, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30308156

RESUMO

Sepsis is a life-threatening inflammatory syndrome accompanying a bloodstream infection. Frequently secondary to pathogenic bacterial infections, sepsis remains difficult to treat as a singular disease mechanism. We compared the pathogenesis of murine sepsis experimentally elicited by five bacterial pathogens and report similarities among host responses to Gram-negative Salmonella and E. coli. We observed that a host protective mechanism involving de-toxification of lipopolysaccharide by circulating alkaline phosphatase (AP) isozymes was incapacitated during sepsis caused by Salmonella or E. coli through activation of host Toll-like receptor 4, which triggered Neu1 and Neu3 neuraminidase induction. Elevated neuraminidase activity accelerated the molecular aging and clearance of AP isozymes, thereby intensifying disease. Mice deficient in the sialyltransferase ST3Gal6 displayed increased disease severity, while deficiency of the endocytic lectin hepatic Ashwell-Morell receptor was protective. AP augmentation or neuraminidase inhibition diminished inflammation and promoted host survival. This study illuminates distinct routes of sepsis pathogenesis, which may inform therapeutic development.


Assuntos
Fosfatase Alcalina/metabolismo , Infecções por Escherichia coli/microbiologia , Interações Hospedeiro-Patógeno , Lipopolissacarídeos/metabolismo , Neuraminidase/metabolismo , Infecções por Salmonella/microbiologia , Sepse/microbiologia , Fosfatase Alcalina/genética , Animais , Modelos Animais de Doenças , Escherichia coli/patogenicidade , Infecções por Escherichia coli/sangue , Infecções por Escherichia coli/enzimologia , Infecções por Escherichia coli/patologia , Humanos , Inflamação/sangue , Inflamação/enzimologia , Inflamação/microbiologia , Inflamação/patologia , Camundongos , Camundongos Knockout , Neuraminidase/genética , Infecções por Salmonella/sangue , Infecções por Salmonella/enzimologia , Infecções por Salmonella/patologia , Salmonella typhimurium/patogenicidade , Sepse/sangue , Sepse/enzimologia , Sepse/patologia , Receptor 4 Toll-Like/efeitos dos fármacos
9.
Science ; 358(6370)2017 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-29269445

RESUMO

Intestinal inflammation is the central pathological feature of colitis and the inflammatory bowel diseases. These syndromes arise from unidentified environmental factors. We found that recurrent nonlethal gastric infections of Gram-negative Salmonella enterica Typhimurium (ST), a major source of human food poisoning, caused inflammation of murine intestinal tissue, predominantly the colon, which persisted after pathogen clearance and irreversibly escalated in severity with repeated infections. ST progressively disabled a host mechanism of protection by inducing endogenous neuraminidase activity, which accelerated the molecular aging and clearance of intestinal alkaline phosphatase (IAP). Disease was linked to a Toll-like receptor 4 (TLR4)-dependent mechanism of IAP desialylation with accumulation of the IAP substrate and TLR4 ligand, lipopolysaccharide-phosphate. The administration of IAP or the antiviral neuraminidase inhibitor zanamivir was therapeutic by maintaining IAP abundance and function.


Assuntos
Fosfatase Alcalina/deficiência , Colo/microbiologia , Doenças Inflamatórias Intestinais/microbiologia , Intoxicação Alimentar por Salmonella/complicações , Salmonella typhimurium , Receptor 4 Toll-Like/metabolismo , Fosfatase Alcalina/administração & dosagem , Animais , Colo/imunologia , Colo/patologia , Inibidores Enzimáticos/administração & dosagem , Doenças Inflamatórias Intestinais/tratamento farmacológico , Doenças Inflamatórias Intestinais/enzimologia , Doenças Inflamatórias Intestinais/patologia , Lipopolissacarídeos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Neuraminidase/antagonistas & inibidores , Recidiva , Sialiltransferases/genética , Sialiltransferases/metabolismo , Receptor 4 Toll-Like/genética , Zanamivir/administração & dosagem
10.
Ann Occup Environ Med ; 29: 40, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28912953

RESUMO

BACKGROUND: On September 27, 2012, at 3:43 pm, a hydrogen fluoride spill occurred in a manufacturing plant located at the 4th complex of the Gumi National Industrial Complex in Gumi City, South Korea. The present study aimed to evaluate the psychological effects of the hydrogen fluoride spill on the members of the community and to investigate their relationships with physical symptoms and changes in psychological effects occurring as time passed after the accident. METHODS: The 1st phase involved a survey of 1359 individuals that was conducted 1 month after the spill, and the 2nd phase involved a survey of 711 individuals that was conducted 7 months after the accident. The questionnaires included items for assessing demographic characteristics, hydrogen fluoride exposure level, physical symptoms, and psychological status. Physical symptoms were assessed to determine the persistence of irritations. Psychological status was assessed to investigate the impact of event level using the Impact of Event Scale - Revised Korean version (IES-R-K), and the anxiety level was assessed using the Beck Anxiety Inventory (BAI). RESULTS: As the hydrogen fluoride exposure level increased, the impact of event and anxiety levels increased significantly both 1 and 7 months after the accident (p < 0.05). The mean score of the impact of event levels decreased significantly from 33.33 ± 14.64 at 1 month after the accident to 28.68 ± 11.80 at 7 months after the accident (p < 0.05). The mean score of the anxiety levels increased significantly from 5.16 ± 6.59 at 1 month after the accident to 6.79 ± 8.41 at 7 months after the accident (p < 0.05). The risk of persistent physical symptoms at 7 months after the accident was significantly higher in females. The risk of persistent physical symptoms also increased significantly, with increasing age, hydrogen fluoride exposure, and impact of event levels (p < 0.05). CONCLUSIONS: The present study found that the impact of event level and anxiety level increased with increasing hydrogen fluoride exposure. Anxiety levels persisted even after time passed. The risk of persistent physical symptoms at 7 months after the accident was higher in females, and it increased with increasing age, hydrogen fluoride exposure level, and impact of event levels.

11.
Mar Pollut Bull ; 111(1-2): 463-467, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27381986

RESUMO

On January 31, 2014, an oil spill accident occurred in Yeosu, South Korea. A total 800-899kl of oil from the pipeline was spilled into the sea. After the oil spill, the KIOST (Korea Institute of Ocean Science & Technology) researched PAHs (polycyclic aromatic hydrocarbons) in various media, but sedimentary PAHs were not analyzed despite their longer persistency than in other media. Therefore, this study examined PAH levels in intertidal sediments around Gwangyang Bay and identified PAH sources using oil fingerprinting. PAH residual levels showed a dramatic decrease during the four months after the accident and then remained at a relatively constant level. Analysis through regression equations indicate that this study area is likely to be restored to the PAH levels prior to the accident. Furthermore, the source analysis and oil fingerprinting analysis showed that PAH contamination in this study was unlikely to have originated from the spilled oil.


Assuntos
Sedimentos Geológicos/análise , Poluição por Petróleo , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes Químicos da Água/análise , Baías/análise , Monitoramento Ambiental , Recuperação e Remediação Ambiental/métodos , Sedimentos Geológicos/química , Poluição por Petróleo/análise , Análise de Regressão , República da Coreia
12.
Nat Immunol ; 17(6): 613-4, 2016 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-27196512
13.
Proc Natl Acad Sci U S A ; 112(44): 13657-62, 2015 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-26489654

RESUMO

The composition and functions of the secreted proteome are controlled by the life spans of different proteins. However, unlike intracellular protein fate, intrinsic factors determining secreted protein aging and turnover have not been identified and characterized. Almost all secreted proteins are posttranslationally modified with the covalent attachment of N-glycans. We have discovered an intrinsic mechanism of secreted protein aging and turnover linked to the stepwise elimination of saccharides attached to the termini of N-glycans. Endogenous glycosidases, including neuraminidase 1 (Neu1), neuraminidase 3 (Neu3), beta-galactosidase 1 (Glb1), and hexosaminidase B (HexB), possess hydrolytic activities that temporally remodel N-glycan structures, progressively exposing different saccharides with increased protein age. Subsequently, endocytic lectins with distinct binding specificities, including the Ashwell-Morell receptor, integrin αM, and macrophage mannose receptor, are engaged in N-glycan ligand recognition and the turnover of secreted proteins. Glycosidase inhibition and lectin deficiencies increased protein life spans and abundance, and the basal rate of N-glycan remodeling varied among distinct proteins, accounting for differences in their life spans. This intrinsic multifactorial mechanism of secreted protein aging and turnover contributes to health and the outcomes of disease.


Assuntos
Proteínas/metabolismo , Glicosilação , Polissacarídeos/metabolismo , Processamento de Proteína Pós-Traducional
14.
Environ Monit Assess ; 186(8): 5209-20, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24744211

RESUMO

We analyzed national data on blood lead levels (BLL) and blood cadmium levels (BCL) in residents living near 38 abandoned metal mining areas (n = 5,682, 18-96 years old) in Korea that were collected by the first Health Effect Surveillance for Residents in Abandoned Metal mines (HESRAM) from 2008 to 2011. The geometric mean BCL and BLL were 1.60 µg/L (95 % CI = 1.57-1.62 µg/L) and 2.87 µg/dL (95 % CI = 2.84-2.90 µg/dL), respectively, notably higher than levels in the general population in Korea and other countries. We found significantly higher BLL and BCL levels in people living within 2 km of an abandoned metal mine (n = 3,165, BCL = 1.87 µg/L, BLL = 2.91 µg/dL) compared to people living more than 2 km away (n = 2,517, BCL = 1.31 µg/L, BLL = 2.82 µg/dL; P < 0.0001) and to the general population values reported in the literature.


Assuntos
Cádmio/sangue , Exposição Ambiental/estatística & dados numéricos , Poluentes Ambientais/sangue , Chumbo/sangue , Mineração , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Monitoramento Ambiental , Feminino , Humanos , Masculino , Metais/sangue , Pessoa de Meia-Idade , República da Coreia , Adulto Jovem
15.
Environ Pollut ; 178: 322-8, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23603469

RESUMO

Metal contamination from mining activity is of great concern because of potential health risks to the local inhabitants. In the present study, we investigated the levels of Cd, Cu, As, Pb, and Zn in environmental samples and foodstuffs grown in the vicinity of the mines in Goseong, Korea, and evaluated potential health risks among local residents. Soils near the mines exceeded the soil quality standard values of Cu, As, and Zn contamination. The concentrations of Cd, Cu, Pb, and Zn in crop samples collected from the study area were significantly higher than those of the reference area. Some rice samples collected from the study area exceeded the maximum permissible level of 0.2 mg Cd/kg. The intake of rice was identified as a major contributor (≥75%) to the estimated daily intake among the residents. The average estimated daily intakes of metals were, however, below the provisional tolerable daily intake.


Assuntos
Exposição Ambiental/estatística & dados numéricos , Metais Pesados/análise , Mineração , Poluentes do Solo/análise , Contaminação de Alimentos/estatística & dados numéricos , Nível de Saúde , Indicadores Básicos de Saúde , República da Coreia , Medição de Risco
16.
Blood ; 120(5): 1015-26, 2012 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-22700726

RESUMO

Binding of selectins to their glycan ligands is a prerequisite for successful leukocyte trafficking. During synthesis and transport through the secretory pathway, selectin ligands are constructed with the participation of one or more sialyltransferases of the ST3Gal subfamily. Previous studies established that ST3Gal-IV only partially contributes to selectin ligand formation, indicating that other ST3Gal-sialyltransferases are involved. By generating and analyzing St3gal6-null mice and St3gal4/St3gal6 double-deficient mice, in the present study, we found that binding of E- and P-selectin to neutrophils and L-selectin binding to lymph node high endothelial venules is reduced in the absence of ST3Gal-VI and to a greater extent in double-deficient mice. In an ex vivo flow chamber assay, P- and E-selectin-dependent leukocyte rolling was mildly reduced in St3gal6-null mice and more severely in double-deficient mice. In inflamed cremaster muscle venules of St3gal6-null mice, we found impaired P-selectin-dependent, but not E-selectin-dependent leukocyte rolling, whereas in double-deficient mice, E-selectin-dependent rolling was almost completely absent. Furthermore, neutrophil recruitment into the inflamed peritoneal cavity and lymphocyte homing to secondary lymphoid organs were impaired in St3gal6-null mice and more severely in double-deficient mice. The results of the present study demonstrate the coordinated participation of both ST3Gal-VI and ST3Gal-IV in the synthesis of functional selectin ligands.


Assuntos
Selectinas/biossíntese , Sialiltransferases/fisiologia , Animais , Capilares/metabolismo , Capilares/fisiologia , Selectina E/metabolismo , Regulação Enzimológica da Expressão Gênica/fisiologia , Hemostasia/genética , Migração e Rolagem de Leucócitos/genética , Ligantes , Camundongos , Camundongos Knockout , Mutagênese Sítio-Dirigida , Selectina-P/metabolismo , Ligação Proteica , Fluxo Sanguíneo Regional/genética , Fluxo Sanguíneo Regional/fisiologia , Selectinas/metabolismo , Sialiltransferases/genética , Sialiltransferases/metabolismo , Distribuição Tecidual
17.
Glycobiology ; 22(10): 1289-301, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22735313

RESUMO

Gangliosides-sialylated glycosphingolipids-are the major glycoconjugates of nerve cells. The same four structures-GM1, GD1a, GD1b and GT1b-comprise the great majority of gangliosides in mammalian brains. They share a common tetrasaccharide core (Galß1-3GalNAcß1-4Galß1-4Glcß1-1'Cer) with one or two sialic acids on the internal galactose and zero (GM1 and GD1b) or one (GD1a and GT1b) α2-3-linked sialic acid on the terminal galactose. Whereas the genes responsible for the sialylation of the internal galactose are known, those responsible for terminal sialylation have not been established in vivo. We report that St3gal2 and St3gal3 are responsible for nearly all the terminal sialylation of brain gangliosides in the mouse. When brain ganglioside expression was analyzed in adult St3gal1-, St3gal2-, St3gal3- and St3gal4-null mice, only St3gal2-null mice differed significantly from wild type, expressing half the normal amount of GD1a and GT1b. St3gal1/2-double-null mice were no different than St3gal2-single-null mice; however, St3gal2/3-double-null mice were >95% depleted in gangliosides GD1a and GT1b. Total ganglioside expression (lipid-bound sialic acid) in the brains of St3gal2/3-double-null mice was equivalent to that in wild-type mice, whereas total protein sialylation was reduced by half. St3gal2/3-double-null mice were small, weak and short lived. They were half the weight of wild-type mice at weaning and displayed early hindlimb dysreflexia. We conclude that the St3gal2 and St3gal3 gene products (ST3Gal-II and ST3Gal-III sialyltransferases) are largely responsible for ganglioside terminal α2-3 sialylation in the brain, synthesizing the major brain gangliosides GD1a and GT1b.


Assuntos
Encéfalo/metabolismo , Gangliosídeos/biossíntese , Animais , Camundongos , Camundongos Knockout , Sialiltransferases/deficiência , Sialiltransferases/metabolismo
18.
EMBO J ; 29(22): 3787-96, 2010 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-20959806

RESUMO

Protein O-phosphorylation often occurs reciprocally with O-GlcNAc modification and represents a regulatory principle for proteins. O-phosphorylation of serine by glycogen synthase kinase-3ß on Snail1, a transcriptional repressor of E-cadherin and a key regulator of the epithelial-mesenchymal transition (EMT) programme, results in its proteasomal degradation. We show that by suppressing O-phosphorylation-mediated degradation, O-GlcNAc at serine112 stabilizes Snail1 and thus increases its repressor function, which in turn attenuates E-cadherin mRNA expression. Hyperglycaemic condition enhances O-GlcNAc modification and initiates EMT by transcriptional suppression of E-cadherin through Snail1. Thus, dynamic reciprocal O-phosphorylation and O-GlcNAc modification of Snail1 constitute a molecular link between cellular glucose metabolism and the control of EMT.


Assuntos
Acetilglucosamina/metabolismo , Hiperglicemia/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Caderinas/genética , Caderinas/metabolismo , Linhagem Celular Tumoral , Movimento Celular , Transição Epitelial-Mesenquimal , Regulação da Expressão Gênica , Glucose/metabolismo , Células HEK293 , Células HeLa , Humanos , Dados de Sequência Molecular , Fosforilação , Estabilidade Proteica , RNA Mensageiro/genética , Serina/metabolismo , Fatores de Transcrição da Família Snail , Fatores de Transcrição/genética
19.
Biochem Biophys Res Commun ; 391(1): 756-61, 2010 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-19944066

RESUMO

Hyperglycemia induces activation of glutathione peroxidase 1 (GPX1), an anti-oxidant enzyme essential for cell survival during oxidative stress. However, the mechanism of GPX1 activation is unclear. Here, we report that hyperglycemia-induced protein glycosylation by O-linked N-acetylglucosamine (O-GlcNAc) is crucial for activation of GPX1 and for its binding to c-Abl and Arg kinases. GPX1 itself is modified with O-GlcNAc on its C-terminus. We also demonstrate that pharmacological injection of the O-GlcNAcase inhibitor NTZ induces GPX1 activation in the mouse liver. Our findings suggest a crucial role for GPX1 and its O-GlcNAc modification in hyperglycemia and diabetes mellitus.


Assuntos
Acetilglucosamina/metabolismo , Diabetes Mellitus/enzimologia , Glutationa Peroxidase/metabolismo , Hiperglicemia/enzimologia , Acilação , Animais , Linhagem Celular , Ativação Enzimática , Feminino , Glutationa Peroxidase/genética , Humanos , Camundongos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Ratos
20.
Proc Natl Acad Sci U S A ; 105(45): 17345-50, 2008 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-18988733

RESUMO

The transcription factor NFkappaB is activated by phosphorylation and acetylation and plays important roles in inflammatory and immune responses in the cell. Additionally, posttranslational modification of the NFkappaB p65 subunit by O-linked N-acetylglucosamine (O-GlcNAc) has been reported, but the modification site of O-GlcNAc on NFkappaB p65 and its exact function have not been elucidated. In this work, we show that O-GlcNAcylation of NFkappaB p65 decreases binding to IkappaB alpha and increases transcriptional activity under hyperglycemic conditions. Also, we demonstrate that both Thr-322 and Thr-352 of NFkappaB p65 can be modified with O-GlcNAc, but modification on Thr-352, not Thr-322, is important for transcriptional activation. Our findings suggest that site-specific O-GlcNAcylation may be a reason why NFkappaB activity increases continuously under hyperglycemic conditions.


Assuntos
Hiperglicemia/metabolismo , N-Acetilglucosaminiltransferases/metabolismo , NF-kappa B/metabolismo , Processamento de Proteína Pós-Traducional/fisiologia , beta-N-Acetil-Hexosaminidases/metabolismo , Acetilação , Animais , Ensaio de Desvio de Mobilidade Eletroforética , Immunoblotting , Imunoprecipitação , Luciferases , Camundongos , Camundongos Knockout , Modelos Biológicos , NF-kappa B/genética , Fosforilação
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