REFERENCES


Choose an author or browse all
Choose the species or browse all
Choose a criteria for sorting
 Reverse sorting
Search for a protein
Search for a single PMID
Select O-GlcNAc references filter

Click to expand (8 results)


Macauley MS, Shan X, Yuzwa SA, Gloster TM, Vocadlo DJ. Elevation of Global O-GlcNAc in rodents using a selective O-GlcNAcase inhibitor does not cause insulin resistance or perturb glucohomeostasis. Chemistry & biology 2010 17(9) 20851344
Abstract:
The O-GlcNAc modification is proposed to be a nutrient sensor with studies suggesting that global increases in O-GlcNAc levels cause insulin resistance and impaired glucohomeostasis. We address this hypothesis by using a potent and selective inhibitor of O-GlcNAcase, known as NButGT, in a series of in vivo studies. Treatment of rats and mice with NButGT, for various time regimens and doses, dramatically increases O-GlcNAc levels throughout all tissues but does not perturb insulin sensitivity or alter glucohomeostasis. NButGT also does not affect the severity or onset of insulin resistance induced by a high-fat diet. These results suggest that pharmacological increases in global O-GlcNAc levels do not cause insulin resistance nor do they appear to disrupt glucohomeostasis. Therefore, the protective benefits of elevated O-GlcNAc levels may be achieved without deleteriously affecting glucohomeostasis.
O-GlcNAc proteins:
SP1
Species: Rattus norvegicus
Download
Majumdar G, Harrington A, Hungerford J, Martinez-Hernandez A, Gerling IC, Raghow R, Solomon S. Insulin dynamically regulates calmodulin gene expression by sequential o-glycosylation and phosphorylation of sp1 and its subcellular compartmentalization in liver cells. The Journal of biological chemistry 2006 281(6) 16332679
Abstract:
O-glycosylation and phosphorylation of Sp1 are thought to modulate the expression of a number of genes in normal and diabetic state. Sp1 is an obligatory transcription factor for constitutive and insulin-responsive expression of the calmodulin gene (Majumdar, G., Harmon, A., Candelaria, R., Martinez-Hernandez, A., Raghow, R., and Solomon, S. S. (2003) Am. J. Physiol. 285, E584-E591). Here we report the temporal dynamics of accumulation of total, O-GlcNAc-modified, and phosphorylated Sp1 in H-411E hepatoma cells by immunohistochemistry with monospecific antibodies, confocal microscopy, and matrix-assisted laser desorption and ionization-time of flight mass spectrometry. Insulin elicited sequential and reciprocal post-translational modifications of Sp1. The O-glycosylation of Sp1 and its nuclear accumulation induced by insulin peaked early (approximately 30 min), followed by a steady decline of O-GlcNAc-modified Sp1 to negligible levels by 240 min. The accumulation of phosphorylated Sp1 in the nuclei of insulin-treated cells showed an opposite pattern, increasing steadily until reaching a maximum around 240 min after treatment. Analyses of the total, O-GlcNAc-modified, or phosphorylated Sp1 by Western blot and mass spectrometry corroborated the sequential and reciprocal control of post-translational modifications of Sp1 in response to insulin. Treatment of cells with streptozotocin (a potent inhibitor of O-GlcNAcase) led to hyperglycosylation of Sp1 that failed to be significantly phosphorylated. The mass spectrometry data indicated that a number of common serine residues of Sp1 undergo time-dependent, reciprocal O-glycosylation and phosphorylation, paralleling its rapid translocation from cytoplasm to the nucleus. Later, changes in the steady state levels of phosphorylated Sp1 mimicked the enhanced steady state levels of calmodulin mRNA seen after insulin treatment. Thus, O-glycosylation of Sp1 appears to be critical for its localization into the nucleus, where it undergoes obligatory phosphorylation that is needed for Sp1 to activate calmodulin gene expression.
O-GlcNAc proteins:
SP1, SP1
Species: Rattus norvegicus, Homo sapiens
Download
Goldberg HJ, Whiteside CI, Hart GW, Fantus IG. Posttranslational, reversible O-glycosylation is stimulated by high glucose and mediates plasminogen activator inhibitor-1 gene expression and Sp1 transcriptional activity in glomerular mesangial cells. Endocrinology 2006 147(1) 16365142
Abstract:
Metabolic flux through the hexosamine biosynthetic pathway (HBP) is increased in the presence of high glucose (HG) and potentially stimulates the expression of genes associated with the development of diabetic nephropathy. A number of synthetic processes are coupled to the HBP, including enzymatic intracellular O-glycosylation (O-GlcNAcylation), the addition of single O-linked N-acetylglucosamine monosaccharides to serine or threonine residues. Despite much data linking flow through the HBP and gene expression, the exact contribution of O-GlcNAcylation to HG-stimulated gene expression remains unclear. In glomerular mesangial cells, HG-stimulated plasminogen activator inhibitor-1 (PAI-1) gene expression requires the HBP and the transcription factor, Sp1. In this study, the specific role of O-GlcNAcylation in HG-induced PAI-1 expression was tested by limiting this modification with a dominant-negative O-linked N-acetylglucosamine transferase, by overexpression of neutral beta-N-acetylglucosaminidase, and by knockdown of O-linked beta-N-acetylglucosamine transferase expression by RNA interference. Decreasing O-GlcNAcylation by these means inhibited the ability of HG to increase endogenous PAI-1 mRNA and protein levels, the activity of a PAI-1 promoter-luciferase reporter gene, and Sp1 transcriptional activation. Conversely, treatment with the beta-N-acetylglucosaminidase inhibitor, O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate, in the presence of normal glucose increased Sp1 O-GlcNAcylation and PAI-1 mRNA and protein levels. These findings demonstrate for the first time that among the pathways served by the HBP, O-GlcNAcylation, is obligatory for HG-induced PAI-1 gene expression and Sp1 transcriptional activation in mesangial cells.
O-GlcNAc proteins:
SP1
Species: Rattus norvegicus
Download
Dauphinee SM, Ma M, Too CK. Role of O-linked beta-N-acetylglucosamine modification in the subcellular distribution of alpha4 phosphoprotein and Sp1 in rat lymphoma cells. Journal of cellular biochemistry 2005 96(3) 16052526
Abstract:
The mTOR alpha4 phosphoprotein is a prolactin (PRL)-downregulated gene product that is found in the nucleus of PRL-dependent rat Nb2 lymphoma cells. Alpha4 lacks a nuclear localization signal (NLS) and the mechanism of its nuclear targeting is unknown. Post-translational modification by O-linked beta-N-acetylglucosamine (O-GlcNAc) moieties has been implicated in the nuclear transport of some proteins, including transcription factor Sp1. The nucleocytoplasmic enzymes O-beta-N-acetylglucosaminyltransferase (OGT) and O-beta-N-acetylglucosaminidase (O-GlcNAcase) adds or remove O-GlcNAc moieties, respectively. If O-GlcNac moieties contribute to the nuclear targeting of alpha4, a decrease in O-GlcNAcylation (e.g., by inhibition of OGT) may redistribute alpha4 to the cytosol. The present study showed that alpha4 and Sp1 were both O-GlcNAcylated in quiescent and PRL-treated Nb2 cells. PRL alone or PRL + streptozotocin (STZ; an O-GlcNAcase inhibitor) significantly (P O-GlcNAc/alpha4 ratio above that in control quiescent cells. However, PRL + alloxan (ALX; an OGT inhibitor) or ALX alone did not decrease O-GlcNAcylation of alpha4 below that of controls and alpha4 remained nuclear. In comparison, PRL (+/-ALX/STZ) greatly increased Sp1 protein levels, caused a significant decrease in the GlcNAc/Sp1 ratio (P O-GlcNAc moieties and its nuclear distribution was not affected by siOGT. In summary, alpha4 and Sp1 contained O-GlcNAc moieties, which contributed to their nuclear targeting in Nb2 cells.
O-GlcNAc proteins:
IGBP1, SP1
Species: Rattus norvegicus
Download
Walgren JL, Vincent TS, Schey KL, Buse MG. High glucose and insulin promote O-GlcNAc modification of proteins, including alpha-tubulin. American journal of physiology. Endocrinology and metabolism 2003 284(2) 12397027
Abstract:
Increased flux through the hexosamine biosynthesis pathway has been implicated in the development of glucose-induced insulin resistance and may promote the modification of certain proteins with O-linked N-acetylglucosamine (O-GlcNAc). L6 myotubes (a model of skeletal muscle) were incubated for 18 h in 5 or 25 mM glucose with or without 10 nM insulin. As assessed by immunoblotting with an O-GlcNAc-specific antibody, high glucose and/or insulin enhanced O-GlcNAcylation of numerous proteins, including the transcription factor Sp1, a known substrate for this modification. To identify novel proteins that may be O-GlcNAc modified in a glucose concentration/insulin-responsive manner, total cell membranes were separated by one- or two-dimensional gel electrophoresis. Selected O-GlcNAcylated proteins were identified by mass spectrometry (MS) analysis. MS sequencing of tryptic peptides identified member(s) of the heat shock protein 70 (HSP70) family and rat alpha-tubulin. Immunoprecipitation/immunoblot studies demonstrated several HSP70 isoforms and/or posttranslational modifications, some with selectively enhanced O-GlcNAcylation following exposure to high glucose plus insulin. In conclusion, in L6 myotubes, Sp1, membrane-associated HSP70, and alpha-tubulin are O-GlcNAcylated; the modification is markedly enhanced by sustained increased glucose flux.
O-GlcNAc proteins:
HS71A, TBA1A, SP1
Species: Rattus norvegicus
Download
Clark RJ, McDonough PM, Swanson E, Trost SU, Suzuki M, Fukuda M, Dillmann WH. Diabetes and the accompanying hyperglycemia impairs cardiomyocyte calcium cycling through increased nuclear O-GlcNAcylation. The Journal of biological chemistry 2003 278(45) 12941958
Abstract:
Diabetic cardiomyopathy is characterized by impaired cardiac contractility leading to poor myocardial performance. We investigated the role that the hexosamine pathway, and especially altered nuclear O-Glc-NAcylation, plays in the development of diabetic cardiomyopathy. Incubating neonatal rat cardiomyocytes in high glucose (25 mM) resulted in prolonged calcium transients when compared with myocytes incubated in normal glucose (5.5 mM), which is consistent with delayed myocardial relaxation. High glucose-treated myocytes also exhibited reduced sarcoendoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) mRNA and protein expression, decreased SERCA2a promoter activity, and increased O-GlcNAcylation of nuclear proteins compared with myocytes treated with normal glucose. Exposure of myocytes to 8 mM glucosamine or an adenovirus expressing O-GlcNAc-transferase (OGT) resulted in prolonged calcium transient decays and significantly reduced SERCA2a protein levels, whereas treatment with an adenovirus encoding O-GlcNAcase (GCA) resulted in improved calcium transients and SERCA2a protein levels in myocytes exposed to high glucose. Effects of elevated glucose or altered O-GlcNAcylation were also observed on essential transcription factors involved in cardiomyocyte function. High glucose-treated myocytes (with or without OGT adenovirus) exhibited increased levels of O-GlcNAcylated specificity protein 1 compared with control myocytes, whereas infecting high glucose-treated myocytes with GCA adenovirus reduced the degree of specificity protein 1 Glc-NAcylation. Treatment of myocytes with 25 mM glucose, 8 mM glucosamine, or OGT adenovirus also significantly reduced levels of myocytes enhancer factor-2A protein compared with control myocytes, whereas infection with GCA adenovirus resulted in improved myocytes enhancer factor-2 expression. Our results suggest that the hexosamine pathway, and O-GlcNAcylation in particular, is important in impaired cardiac myocyte function and the development of diabetic cardiomyopathy.
O-GlcNAc proteins:
SP1
Species: Rattus norvegicus
Download
Zhang F, Su K, Yang X, Bowe DB, Paterson AJ, Kudlow JE. O-GlcNAc modification is an endogenous inhibitor of the proteasome. Cell 2003 115(6) 14675536
Abstract:
The ubiquitin proteasome system classically selects its substrates for degradation by tagging them with ubiquitin. Here, we describe another means of controlling proteasome function in a global manner. The 26S proteasome can be inhibited by modification with the enzyme, O-GlcNAc transferase (OGT). This reversible modification of the proteasome inhibits the proteolysis of the transcription factor Sp1 and a hydrophobic peptide through inhibition of the ATPase activity of 26S proteasomes. The Rpt2 ATPase in the mammalian proteasome 19S cap is modified by O-GlcNAc in vitro and in vivo and as its modification increases, proteasome function decreases. This mechanism may couple proteasomes to the general metabolic state of the cell. The O-GlcNAc modification of proteasomes may allow the organism to respond to its metabolic needs by controlling the availability of amino acids and regulatory proteins.
O-GlcNAc proteins:
SP1
Species: Rattus norvegicus
Download
Han I, Kudlow JE. Reduced O glycosylation of Sp1 is associated with increased proteasome susceptibility. Molecular and cellular biology 1997 17(5) 9111324
Abstract:
Sp1 is a ubiquitously expressed transcription factor that is particularly important for the regulation of TATA-less genes that encode housekeeping proteins. Most growth factors and receptors are also encoded by such genes. Sp1 is multiply O glycosylated by covalent linkage of the monosaccharide N-acetylglucosamine (O-GlcNAc) to serine and threonine residues. Based on an earlier observation that growth factor gene transcription can be regulated by glucose and glucosamine in vascular smooth muscle cells, we determined whether Sp1 glycosylation could be regulated and if this modification altered Sp1 function. We found that Sp1 becomes hyperglycosylated when cells are exposed to 5 mM glucosamine, whereas under glucose starvation, stimulation with cyclic AMP (cAMP) results in nearly complete deglycosylation of this protein. Correlating with this hypoglycosylated state, Sp1 is rapidly proteolytically degraded by an enzyme(s) that can be inhibited by specific proteasome inhibitors, lactacystin and LLnL. Treatment of cells with glucose or glucosamine protects Sp1 from cAMP-mediated degradation, whereas blockade of glucosamine synthesis abrogates glucose but not glucosamine protection. This effect on Sp1 is specific, in that the Stat-3 and E2F transcription factors did not undergo degradation under these conditions. The O-GlcNAc modification of Sp1 may play a role as a nutritional checkpoint. In the absence of adequate nutrition, Sp1 becomes hypoglycosylated and thereby subject to proteasome degradation. This process could potentially result in reduced general transcription, thereby conserving nutrients.
O-GlcNAc proteins:
SP1, SP1
Species: Rattus norvegicus, Homo sapiens
Download
Page 1 of 1