Vang S, Helton ES, Guo Y, Burpee B, Rose E, Easter M, Bollenbecker S, Hirsch MJ, Matthews EL, Jones LI, Howze PH 4th, Rajasekaran V, Denson R, Cochran P, Attah IK, Olson H, Clair G, Melkani G, Krick S, Barnes JW.
O-GlcNAc transferase regulates collagen deposition and fibrosis resolution in idiopathic pulmonary fibrosis.
Frontiers in immunology2024
15
38665916
Abstract: Idiopathic pulmonary fibrosis (IPF) is a chronic pulmonary disease that is characterized by an excessive accumulation of extracellular matrix (ECM) proteins (e.g. collagens) in the parenchyma, which ultimately leads to respiratory failure and death. While current therapies exist to slow the progression, no therapies are available to resolve fibrosis.
Qiu Y, Su Y, Xie E, Cheng H, Du J, Xu Y, Pan X, Wang Z, Chen DG, Zhu H, Greenberg PD, Li G.
Mannose metabolism reshapes T cell differentiation to enhance anti-tumor immunity.
Cancer cell202439642888
Abstract: Cellular metabolic status profoundly influences T cell differentiation, persistence, and anti-tumor efficacy. Our single-cell metabolic analyses of T cells reveal that diminished mannose metabolism is a prominent feature of T cell dysfunction. Conversely, experimental augmentation/restoration of mannose metabolism in adoptively transferred T cells via D-mannose supplementation enhances anti-tumor activity and restricts exhaustion differentiation both in vitro and in vivo. Mechanistically, D-mannose treatment induces intracellular metabolic programming and increases the O-GlcNAc transferase (OGT)-mediated O-GlcNAcylation of β-catenin, which preserves Tcf7 expression and epigenetic stemness, thereby promoting stem-like programs in T cells. Furthermore, in vitro expansion with D-mannose supplementation yields T cell products for adoptive therapy with stemness characteristics, even after extensive long-term expansion, that exhibits enhanced anti-tumor efficacy. These findings reveal cell-intrinsic mannose metabolism as a physiological regulator of CD8+ T cell fate, decoupling proliferation/expansion from differentiation, and underscoring the therapeutic potential of mannose modulation in cancer immunotherapy.
Liu J, Hao Y, Wang C, Jin Y, Yang Y, Gu J, Chen X.
An Optimized Isotopic Photocleavable Tagging Strategy for Site-Specific and Quantitative Profiling of Protein O-GlcNAcylation in Colorectal Cancer Metastasis.
ACS chemical biology2022
17(3)
35254053
Abstract: O-linked-β-N-acetylglucosamine (O-GlcNAc) glycosylation is a ubiquitous protein post-translational modification of the emerging importance in metazoans. Of the thousands of O-GlcNAcylated proteins identified, many carry multiple modification sites with varied stoichiometry. To better match the scale of O-GlcNAc sites and their dynamic nature, we herein report an optimized strategy, termed isotopic photocleavable tagging for O-GlcNAc profiling (isoPTOP), which enables quantitative and site-specific profiling of O-GlcNAcylation with excellent specificity and sensitivity. In HeLa cells, ∼1500 O-GlcNAcylation sites were identified with the optimized procedures, which led to quantification of ∼1000 O-GlcNAcylation sites with isoPTOP. Furthermore, we apply isoPTOP to probe the O-GlcNAcylation dynamics in a pair of colorectal cancer (CRC) cell lines, SW480 and SW620 cells, which represent primary carcinoma and metastatic cells, representatively. The stoichiometric differences of 625 O-GlcNAcylation sites are quantified. Of these quantified sites, many occur on important regulators involved in tumor progression and metastasis. Our results provide a valuable database for understanding the functional role of O-GlcNAc in CRC. IsoPTOP should be applicable for investigating O-GlcNAcylation dynamics in various pathophysiological processes.
Xie X, Wu Q, Zhang K, Liu Y, Zhang N, Chen Q, Wang L, Li W, Zhang J, Liu Y.
O-GlcNAc modification regulates MTA1 transcriptional activity during breast cancer cell genotoxic adaptation.
Biochimica et biophysica acta. General subjects2021
1865(8)
34019948
Abstract: Chromatin modifier metastasis-associated protein 1 (MTA1), closely associated with tumor angiogenesis in breast cancer, plays an important role in gene expression and cancer cell behavior. Recently, an association between O-GlcNAc transferase (OGT) and MTA1 was identified by mass spectroscopy. However, the potential relationship between MTA1 and O-GlcNAc modification has not yet explored.
Hua Q, Zhang B, Xu G, Wang L, Wang H, Lin Z, Yu D, Ren J, Zhang D, Zhao L, Zhang T.
CEMIP, a novel adaptor protein of OGT, promotes colorectal cancer metastasis through glutamine metabolic reprogramming via reciprocal regulation of β-catenin.
Oncogene2021
40(46)
34608265
Abstract: Metastasis is the leading cause of colorectal cancer (CRC)-induced death. However, the underlying molecular mechanisms of CRC metastasis are poorly understood. Metabolic reprogramming is an intrinsic feature of cancer, which have complicated effects on cancer metastasis. Here, we find that a novel metastasis-related protein, cell migration-inducing and hyaluronan-binding protein (CEMIP), can act as a novel adaptor protein of O-GlcNAc transferase (OGT) to promote CRC metastasis through glutamine metabolic reprogramming. Mechanistically, CEMIP interacts with OGT and β-catenin, which leads to elevated O-GlcNAcylation of β-catenin and enhanced β-catenin nuclear translocation from cytomembrane. Furthermore, accumulated β-catenin in nucleus enhances the transcription of CEMIP to reciprocally regulate β-catenin and contributes to over-expression of glutaminase 1 and glutamine transporters (SLC1A5 and SLC38A2). Combinational inhibition of CEMIP and glutamine metabolism could dramatically attenuate the metastasis of CRC in vivo. Collectively, this study reveals the importance of glutamine metabolic reprogramming in CEMIP-induced CRC metastasis, indicating the great potential of CEMIP and glutamine metabolism for CRC metastasis prevention.
Ramirez DH, Yang B, D'Souza AK, Shen D, Woo CM.
Truncation of the TPR domain of OGT alters substrate and glycosite selection.
Analytical and bioanalytical chemistry2021
413(30)
34725712
Abstract: O-GlcNAc transferase (OGT) is an essential enzyme that installs O-linked N-acetylglucosamine (O-GlcNAc) to thousands of protein substrates. OGT and its isoforms select from these substrates through the tetratricopeptide repeat (TPR) domain, yet the impact of truncations to the TPR domain on substrate and glycosite selection is unresolved. Here, we report the effects of iterative truncations to the TPR domain of OGT on substrate and glycosite selection with the model protein GFP-JunB and the surrounding O-GlcNAc proteome in U2OS cells. Iterative truncation of the TPR domain of OGT maintains glycosyltransferase activity but alters subcellular localization of OGT in cells. The glycoproteome and glycosites modified by four OGT TPR isoforms were examined on the whole proteome and a single target protein, GFP-JunB. We found the greatest changes in O-GlcNAc on proteins associated with mRNA splicing processes and that the first four TPRs of the canonical nucleocytoplasmic OGT had the broadest substrate scope. Subsequent glycosite analysis revealed that alteration to the last four TPRs corresponded to the greatest shift in the resulting O-GlcNAc consensus sequence. This dataset provides a foundation to analyze how perturbations to the TPR domain and expression of OGT isoforms affect the glycosylation of substrates, which will be critical for future efforts in protein engineering of OGT, the biology of OGT isoforms, and diseases associated with the TPR domain of OGT.
Jia C, Li H, Fu D, Lan Y.
GFAT1/HBP/O-GlcNAcylation Axis Regulates β-Catenin Activity to Promote Pancreatic Cancer Aggressiveness.
BioMed research international2020
2020
32149084
Abstract: Reprogrammed glucose and glutamine metabolism are essential for tumor initiation and development. As a branch of glucose and metabolism, the hexosamine biosynthesis pathway (HBP) generates uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) and contributes to the O-GlcNAcylation process. However, the spectrum of HBP-dependent tumors and the mechanisms by which the HBP promotes tumor aggressiveness remain areas of active investigation. In this study, we analyzed the activity of the HBP and its prognostic value across 33 types of human cancers. Increased HBP activity was observed in pancreatic ductal adenocarcinoma (PDAC), and higher HBP activity predicted a poor prognosis in PDAC patients. Genetic silencing or pharmacological inhibition of the first and rate-limiting enzyme of the HBP, glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), inhibited PDAC cell proliferation, invasive capacity, and triggered cell apoptosis. Notably, these effects can be restored by addition of UDP-GlcNAc. Moreover, similar antitumor effects were noticed by pharmacological inhibition of GFAT1 with 6-diazo-5-oxo-l-norleucine (DON) or Azaserine. PDAC is maintained by oncogenic Wnt/β-catenin transcriptional activity. Our data showed that GFAT1 can regulate β-catenin expression via modulation of the O-GlcNAcylation process. TOP/FOP-Flash and real-time qPCR analysis showed that GFAT1 knockdown inhibited β-catenin activity and the transcription of its downstream target genes CCND1 and MYC. Ectopic expression of a stabilized form of β-catenin restored the suppressive roles of GFAT1 knockdown on PDAC cell proliferation and invasion. Collectively, our findings indicate that higher GFAT1/HBP/O-GlcNAcylation exhibits tumor-promoting roles by maintaining β-catenin activity in PDAC.
Kasprowicz A, Spriet C, Terryn C, Rigolot V, Hardiville S, Alteen MG, Lefebvre T, Biot C.
Exploring the Potential of β-Catenin O-GlcNAcylation by Using Fluorescence-Based Engineering and Imaging.
Molecules (Basel, Switzerland)2020
25(19)
33019562
Abstract: Monitoring glycosylation changes within cells upon response to stimuli remains challenging because of the complexity of this large family of post-translational modifications (PTMs). We developed an original tool, enabling labeling and visualization of the cell cycle key-regulator β-catenin in its O-GlcNAcylated form, based on intramolecular Förster resonance energy transfer (FRET) technology in cells. We opted for a bioorthogonal chemical reporter strategy based on the dual-labeling of β-catenin with a green fluorescent protein (GFP) for protein sequence combined with a chemically-clicked imaging probe for PTM, resulting in a fast and easy to monitor qualitative FRET assay. We validated this technology by imaging the O-GlcNAcylation status of β-catenin in HeLa cells. The changes in O-GlcNAcylation of β-catenin were varied by perturbing global cellular O-GlcNAc levels with the inhibitors of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Finally, we provided a flowchart demonstrating how this technology is transposable to any kind of glycosylation.
Gao S, Miao Y, Liu Y, Liu X, Fan X, Lin Y, Qian P, Zhou J, Dai Y, Xia L, Zhu P, Zhu J.
Reciprocal Regulation Between O-GlcNAcylation and β-Catenin Facilitates Cell Viability and Inhibits Apoptosis in Liver Cancer.
DNA and cell biology2019
38(4)
30762425
Abstract: Abnormal expression of O-Linked β-N-acetylglucosamine (O-GlcNAc) and β-catenin is a general feature of cancer and contributes to transformed phenotypes. In this study, we identified the interaction between O-GlcNAc and β-catenin, and explored their effects on the progression of liver cancer. Our results demonstrated that upregulation of O-GlcNAc was induced by high glucose, whereas the application of PuGNAc and GlcNAc increased β-catenin protein expression levels, as well as the protein's stability and nuclear accumulation in the liver cancer cell lines HEP-G2 and HuH-7. In addition, overexpression of β-catenin could increase O-GlcNAc expression levels through upregulation of uridine 5'-diphosphate (UDP)-N-acetylglucosamine pyrophosphorylase 1 (UAP1) protein expression, protein stability, and inhibition of its ubiquitination. Moreover, the O-GlcNAcylation of β-catenin promoted the proliferation, colony formation, and repressed the induction of apoptosis in HEP-G2 and HuH-7 cells. Knockdown of β-catenin reduced cell proliferation, colony formation, and tumorigenesis, and promoted cell apoptosis through the downregulation of UAP1 expression. In conclusion, this study revealed that the reciprocal regulation between O-GlcNAcylation and β-catenin facilitated the proliferation of liver cancer.
Lenin R, Nagy PG, Jha KA, Gangaraju R.
GRP78 translocation to the cell surface and O-GlcNAcylation of VE-Cadherin contribute to ER stress-mediated endothelial permeability.
Scientific reports2019
9(1)
31346222
Abstract: Increased O-GlcNAcylation, a well-known post-translational modification of proteins causally linked to various detrimental cellular functions in pathological conditions including diabetic retinopathy (DR). Previously we have shown that endothelial activation induced by inflammation and hyperglycemia results in the endoplasmic reticulum (ER) stress-mediated intercellular junction alterations accompanied by visual deficits in a tie2-TNF-α transgenic mouse model. In this study, we tested the hypothesis that increased ER stress via O-GlcNAcylation of VE-Cadherin likely contribute to endothelial permeability. We show that ER stress leads to GRP78 translocation to the plasma membrane, increased O-GlcNAcylation of proteins, particularly VE-Cadherin resulting in a defective complex partnering leading to the loss of retinal endothelial barrier integrity and increased transendothelial migration of monocytes. We further show an association of GRP78 with the VE-Cadherin under these conditions. Interestingly, cells exposed to ER stress inhibitor, tauroursodeoxycholic acid partially mitigated all these effects. Our findings suggest an essential role for ER stress and O-GlcNAcylation in altering the endothelial barrier function and reveal a potential therapeutic target in the treatment of DR.
Berthier A, Vinod M, Porez G, Steenackers A, Alexandre J, Yamakawa N, Gheeraert C, Ploton M, Maréchal X, Dubois-Chevalier J, Hovasse A, Schaeffer-Reiss C, Cianférani S, Rolando C, Bray F, Duez H, Eeckhoute J, Lefebvre T, Staels B, Lefebvre P.
Combinatorial regulation of hepatic cytoplasmic signaling and nuclear transcriptional events by the OGT/REV-ERBα complex.
Proceedings of the National Academy of Sciences of the United States of America2018
115(47)
30397120
Abstract: The nuclear receptor REV-ERBα integrates the circadian clock with hepatic glucose and lipid metabolism by nucleating transcriptional comodulators at genomic regulatory regions. An interactomic approach identified O-GlcNAc transferase (OGT) as a REV-ERBα-interacting protein. By shielding cytoplasmic OGT from proteasomal degradation and favoring OGT activity in the nucleus, REV-ERBα cyclically increased O-GlcNAcylation of multiple cytoplasmic and nuclear proteins as a function of its rhythmically regulated expression, while REV-ERBα ligands mostly affected cytoplasmic OGT activity. We illustrate this finding by showing that REV-ERBα controls OGT-dependent activities of the cytoplasmic protein kinase AKT, an essential relay in insulin signaling, and of ten-of-eleven translocation (TET) enzymes in the nucleus. AKT phosphorylation was inversely correlated to REV-ERBα expression. REV-ERBα enhanced TET activity and DNA hydroxymethylated cytosine (5hmC) levels in the vicinity of REV-ERBα genomic binding sites. As an example, we show that the REV-ERBα/OGT complex modulates SREBP-1c gene expression throughout the fasting/feeding periods by first repressing AKT phosphorylation and by epigenomically priming the Srebf1 promoter for a further rapid response to insulin. Conclusion: REV-ERBα regulates cytoplasmic and nuclear OGT-controlled processes that integrate at the hepatic SREBF1 locus to control basal and insulin-induced expression of the temporally and nutritionally regulated lipogenic SREBP-1c transcript.
Chen Y, Jin L, Xue B, Jin D, Sun F, Wen C.
NRAGE induces β-catenin/Arm O-GlcNAcylation and negatively regulates Wnt signaling.
Biochemical and biophysical research communications2017
487(2)
28427939
Abstract: The Wnt pathway is crucial for animal development, as well as tumor formation. Understanding the regulation of Wnt signaling will help to elucidate the mechanism of the cell cycle, cell differentiation and tumorigenesis. It is generally accepted that in response to Wnt signals, β-catenin accumulates in the cytoplasm and is imported into the nucleus where it recruits LEF/TCF transcription factors to activate the expression of target genes. In this study, we report that human NRAGE, a neurotrophin receptor p75 (p75NTR) binding protein, markedly suppresses the expression of genes activated by the Wnt pathway. Consistent with this finding, loss of function of NRAGE by RNA interference (RNAi) activates the Wnt pathway. Moreover, NRAGE suppresses the induction of axis duplication by microinjected β-catenin in Xenopus embryos. To our surprise, NRAGE induces nuclear localization of β-catenin and increases its DNA binding ability. Further studies reveal that NRAGE leads to the modification of β-catenin/Arm with O-linked beta-N-acetylglucosamine (O-GlcNAc), and failure of the association between β-catenin/Arm and pygopus(pygo) protein, which is required for transcriptional activation of Wnt target genes. Therefore, our findings suggest a novel mechanism for regulating Wnt signaling.
Wang S, Yang F, Petyuk VA, Shukla AK, Monroe ME, Gritsenko MA, Rodland KD, Smith RD, Qian WJ, Gong CX, Liu T.
Quantitative proteomics identifies altered O-GlcNAcylation of structural, synaptic and memory-associated proteins in Alzheimer's disease.
The Journal of pathology2017
243(1)
28657654
Zhou F, Huo J, Liu Y, Liu H, Liu G, Chen Y, Chen B.
Elevated glucose levels impair the WNT/β-catenin pathway via the activation of the hexosamine biosynthesis pathway in endometrial cancer.
The Journal of steroid biochemistry and molecular biology2016
159
26923859
Abstract: Endometrial cancer (EC) is one of the most common gynecological malignancies in the world. Associations between fasting glucose levels (greater than 5.6mmol/L) and the risk of cancer fatality have been reported. However, the underlying link between glucose metabolic disease and EC remains unclear. In the present study, we explored the influence of elevated glucose levels on the WNT/β-catenin pathway in EC. Previous studies have suggested that elevated concentrations of glucose can drive the hexosamine biosynthesis pathway (HBP) flux, thereby enhancing the O-GlcNAc modification of proteins. Here, we cultured EC cell lines, AN3CA and HEC-1-B, with various concentrations of glucose. Results showed that when treated with high levels of glucose, both lines showed increased expression of β-catenin and O-GlcNAcylation levels; however, these effects could be abolished by the HBP inhibitors, Azaserine and 6-Diazo-5-oxo-l-norleucine, and be restored by glucosamine. Moreover the AN3CA and HEC-1-B cells that were cultured with or without PUGNAc, an inhibitor of the O-GlcNAcase, showed that PUGNAc increased β-catenin levels. The results suggest that elevated glucose levels increase β-catenin expression via the activation of the HBP in EC cells. Subcellular fractionation experiments showed that AN3CA cells had a higher expression of intranuclear β-catenin in high glucose medium. Furthermore, TOP/FOP-Flash and RT-PCR results showed that glucose-induced increased expression of β-catenin triggered the transcription of target genes. In conclusion, elevated glucose levels, via HBP, increase the O-GlcNAcylation level, thereby inducing the over expression of β-catenin and subsequent transcription of the target genes in EC cells.
Lin W, Gao L, Chen X.
Protein-Specific Imaging of O-GlcNAcylation in Single Cells.
Chembiochem : a European journal of chemical biology2015
16(18)
26488919
Abstract: Thousands of intracellular proteins are post-translationally modified with O-GlcNAc, and O-GlcNAcylation impacts the function of modified proteins and mediates diverse biological processes. However, the ubiquity of this important glycosylation makes it highly challenging to probe the O-GlcNAcylation state of a specific protein at the cellular level. Herein, we report the development of a FLIM-FRET-based strategy, which exploits the spatial proximity of the O-GlcNAc moiety and the attaching protein, for protein-specific imaging of O-GlcNAcylation in single cells. We demonstrated this strategy by imaging the O-GlcNAcylation state of tau and β-catenin inside the cells. Furthermore, the changes in tau O-GlcNAcylation were monitored when the overall cellular O-GlcNAc was pharmacologically altered by using the OGT and OGA inhibitors. We envision that the FLIM-FRET strategy will be broadly applicable to probe the O-GlcNAcylation state of various proteins in the cells.
Ha JR, Hao L, Venkateswaran G, Huang YH, Garcia E, Persad S.
β-catenin is O-GlcNAc glycosylated at Serine 23: implications for β-catenin's subcellular localization and transactivator function.
Experimental cell research2014
321(2)
24342833
Abstract: We have previously reported that β-catenin is post-translationally modified with a single O-linked attachment of β-N-acetyl-glucosamine (O-GlcNAc). We showed that O-GlcNAc regulated β-catenin's subcellular localization and transcriptional activity.
Olivier-Van Stichelen S, Dehennaut V, Buzy A, Zachayus JL, Guinez C, Mir AM, El Yazidi-Belkoura I, Copin MC, Boureme D, Loyaux D, Ferrara P, Lefebvre T.
O-GlcNAcylation stabilizes β-catenin through direct competition with phosphorylation at threonine 41.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology2014
28(8)
24744147
Abstract: Dysfunctions in Wnt signaling increase β-catenin stability and are associated with cancers, including colorectal cancer. In addition, β-catenin degradation is decreased by nutrient-dependent O-GlcNAcylation. Human colon tumors and colons from mice fed high-carbohydrate diets exhibited higher amounts of β-catenin and O-GlcNAc relative to healthy tissues and mice fed a standard diet, respectively. Administration of the O-GlcNAcase inhibitor thiamet G to mice also increased colonic expression of β-catenin. By ETD-MS/MS, we identified 4 O-GlcNAcylation sites at the N terminus of β-catenin (S23/T40/T41/T112). Furthermore, mutation of serine and threonine residues within the D box of β-catenin reduced O-GlcNAcylation by 75%. Interestingly, elevating O-GlcNAcylation in human colon cell lines drastically reduced phosphorylation at T41, a key residue of the D box responsible for β-catenin stability. Analyses of β-catenin O-GlcNAcylation mutants reinforced T41 as the most crucial residue that controls the β-catenin degradation rate. Finally, inhibiting O-GlcNAcylation decreased the β-catenin/α-catenin interaction necessary for mucosa integrity, whereas O-GlcNAcase silencing improved this interaction. These results suggest that O-GlcNAcylation regulates not only the stability of β-catenin, but also affects its localization at the level of adherens junctions. Accordingly, we propose that O-GlcNAcylation of β-catenin is a missing link between the glucose metabolism deregulation observed in metabolic disorders and the development of cancer.
Jin FZ, Yu C, Zhao DZ, Wu MJ, Yang Z.
A correlation between altered O-GlcNAcylation, migration and with changes in E-cadherin levels in ovarian cancer cells.
Experimental cell research2013
319(10)
23524144
Abstract: O-GlcNAcylation is a dynamic and reversible posttranslational modification of nuclear and cytoplasmic proteins. In recent years, the roles of O-GlcNAcylation in several human malignant tumors have been investigated, and O-GlcNAcylation was found to be linked to cellular features relevant to metastasis. In this study, we modeled four diverse ovarian cancer cells and investigated the effects of O-GlcNAcylation on ovarian cancer cell migration. We found that total O-GlcNAcylation level was elevated in HO-8910PM cells compared to OVCAR3 cells. Additionally, through altering the total O-GlcNAcylation level by OGT silencing or OGA inhibition, we found that the migration of OVCAR3 cells was dramatically enhanced by PUGNAc and Thiamet G treatment, and the migration ability of HO-8910PM cells was significantly inhibited by OGT silencing. Furthermore, we also found that the expression of E-cadherin, an O-GlcNAcylated protein in ovarian cancer cells, was reduced by OGA inhibition in OVCAR3 cells and elevated by OGT silencing in HO-8910PM cells. These results indicate that O-GlcNAcylation could enhance ovarian cancer cell migration and decrease the expression of E-cadherin. Our studies also suggest that O-GlcNAcylation might become another potential target for the therapy of ovarian cancer.
Olivier-Van Stichelen S, Drougat L, Dehennaut V, El Yazidi-Belkoura I, Guinez C, Mir AM, Michalski JC, Vercoutter-Edouart AS, Lefebvre T.
Serum-stimulated cell cycle entry promotes ncOGT synthesis required for cyclin D expression.
Oncogenesis2012
1(12)
23552487
Abstract: Nuclear and cytoplasmic O-GlcNAc transferase (OGT) is a unique and universally expressed enzyme catalyzing O-GlcNAcylation of thousands of proteins. Although OGT interferes with many crucial intracellular processes, including cell cycle, only few studies have focused on elucidating the precise role of the glycosyltransferase during cell cycle entry. We first demonstrated that starved MCF7 cells reincubated with serum quickly induced a significant OGT increase concomitantly to activation of PI3K and MAPK pathways. Co-immunoprecipitation experiments performed upon serum stimulation showed a progressive interaction between OGT and β-catenin, a major factor in the regulation of cell cycle. OGT expression was also observed in starved HeLa cells reincubated with serum. In these cells, the O-GlcNAcylation status of the β-catenin-2XFLAG was increased following stimulation. Moreover, β-catenin-2XFLAG was heavily O-GlcNAcylated in exponentially proliferating HeLa cells when compared to confluent cells. Furthermore, blocking OGT activity using the potent inhibitor Ac-5SGlcNAc prevented serum-stimulated cyclin D1 synthesis and slightly delayed cell proliferation. At last, interfering with OGT expression (siOGT) blocked cyclin D1 expression and decreased PI3K and MAPK activation. Together, our data indicate that expression and catalytic activity of OGT are necessary and essential for G0/G1 transition.
Donadio AC, Lobo C, Tosina M, de la Rosa V, Martín-Rufián M, Campos-Sandoval JA, Matés JM, Márquez J, Alonso FJ, Segura JA.
Antisense glutaminase inhibition modifies the O-GlcNAc pattern and flux through the hexosamine pathway in breast cancer cells.
Journal of cellular biochemistry2008
103(3)
17614351
Abstract: Glutamine behaves as a key nutrient for tumors and rapidly dividing cells. Glutaminase is the main glutamine-utilizing enzyme in these cells, and its activity correlates with glutamine consumption and growth rate. We have carried out the antisense L-type glutaminase inhibition in human MCF7 breast cancer cells, in order to study its effect on the hexosamine pathway and the pattern of protein O-glycosylation. The antisense mRNA glutaminase expressing cells, named ORF19, presented a 50% lower proliferation rate than parental cells, showing a more differentiated phenotype. ORF19 cells had an 80% reduction in glutamine:fructose-6-P amidotransferase activity, which is the rate-limiting step of the hexosamine pathway. Although the overall cellular protein O-glycosylation did not change, the O-glycosylation status of several key proteins was altered. O-glycosylation of O-GlcNAc transferase (OGT), the enzyme that links N-acetylglucosamine to proteins, was fivefold lower in ORF19 than in wild type cells. Inhibition of glutaminase also provoked a 10-fold increase in Sp1 expression, and a significant decrease in the ratio of O-glycosylated to total protein for both Sp1 and the Rpt2 proteasome component. These changes were accompanied by a higher Sp1 transcriptional activity. Proteome analysis of O-glycosylated proteins permitted the detection of two new OGT target proteins: the chaperonin TCP-1 theta and the oncogene Ets-related protein isoform 7. Taken together, our results support the hexosamine pathway and the O-glycosylation of proteins being a sensor mechanism of the nutritional and energetic states of the cell.
Sayat R, Leber B, Grubac V, Wiltshire L, Persad S.
O-GlcNAc-glycosylation of beta-catenin regulates its nuclear localization and transcriptional activity.
Experimental cell research2008
314(15)
18586027
Abstract: Beta-catenin plays a role in intracellular adhesion and regulating gene expression. The latter role is associated with its oncogenic properties. Phosphorylation of beta-catenin controls its intracellular expression but mechanism/s that regulates the nuclear localization of beta-catenin is unknown. We demonstrate that O-GlcNAc glycosylation (O-GlcNAcylation) of beta-catenin negatively regulates its levels in the nucleus. We show that normal prostate cells (PNT1A) have significantly higher amounts of O-GlcNAcylated beta-catenin compared to prostate cancer (CaP) cells. The total nuclear levels of beta-catenin are higher in the CaP cells than PNT1A but only a minimal fraction of the nuclear beta-catenin in the CaP cells are O-GlcNAcylated. Increasing the levels of O-GlcNAcylated beta-catenin in the CaP cells with PUGNAc (O- (2-acetamido-2-deoxy-d-gluco-pyranosylidene) amino-N-phenylcarbamate) treatment is associated with a progressive decrease in the levels of beta-catenin in the nucleus. TOPFlash reporter assay and mRNA expressions of beta-catenin's target genes indicate that O-GlcNAcylation of beta-catenin results in a decrease in its transcriptional activity. We define a novel modification of beta-catenin that regulates its nuclear localization and transcriptional function.
Hatsell S, Medina L, Merola J, Haltiwanger R, Cowin P.
Plakoglobin is O-glycosylated close to the N-terminal destruction box.
The Journal of biological chemistry2003
278(39)
12847106
Abstract: Plakoglobin provides a key linkage in protein chains that connect desmosomal and classical cadherins to the cytoskeleton. It is also present in a significant cytosolic pool that has the capacity to impact on canonical Wnt signaling by competing for interaction with partner proteins of beta-catenin. The closely related protein, beta-catenin, is rapidly targeted for proteasomal degradation by phosphorylation of a "destruction box" within the N-terminal domain. Inhibition of this process forms the basis of Wnt signaling. This destruction box is also found in the N-terminal domain of plakoglobin. We report that plakoglobin is modified by the addition of O-GlcNAc at a single site in close proximity to the destruction box. O-GlcNAc modification has been proposed to counteract phosphorylation, provide protection from proteasomal degradation, mediate signal transduction, silence transcription, and regulate multimolecular protein assembly. This finding has potential implications for understanding the roles of plakoglobin.