O-linked N-acetylglucosamine (O-GlcNAc) is a post-translational modification involving an attachment of a single β-N-acetylglucosamine moiety to serine or threonine residues in nuclear and cytoplasmic proteins. Cellular O-GlcNAc levels are regulated by two enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which add and remove the modification, respectively. The levels of O-GlcNAc can rapidly change in response to fluctuations in the extracellular environment; however, O-GlcNAcylation returns to a baseline level quickly after stimulus removal. This process termed O-GlcNAc homeostasis appears to be critical to the regulation of many cellular functions including cell cycle progress, stress response, and gene transcription. Disruptions in O-GlcNAc homeostasis are proposed to lead to the development of diseases, such as cancer, diabetes, and Alzheimer’s disease. O-GlcNAc homeostasis is correlated with the expression of OGT and OGA. We reason that alterations in O-GlcNAc levels affect OGA and OGT transcription. We treated several human cell lines with Thiamet-G (TMG, an OGA inhibitor) to increase overall O-GlcNAc levels resulting in decreased OGT protein expression and increased OGA protein expression. OGT transcript levels slightly declined with TMG treatment, but OGA transcript levels were significantly increased. Pretreating cells with protein translation inhibitor cycloheximide did not stabilize OGT or OGA protein expression in the presence of TMG; nor did TMG stabilize OGT and OGA mRNA levels when cells were treated with RNA transcription inhibitor actinomycin D. Finally, we performed RNA Polymerase II chromatin immunoprecipitation at the OGA promoter and found that RNA Pol II occupancy at the transcription start site was lower after prolonged TMG treatment. Together, these data suggest that OGA transcription was sensitive to changes in O-GlcNAc homeostasis and was potentially regulated by O-GlcNAc.

Autophagy can degrade cargos with the help of selective autophagy receptors such as p62/SQSTM1, which facilitates the degradation of ubiquitinated cargo. While the process of autophagy has been linked to aging, the impact of selective autophagy in lifespan regulation remains unclear. We have recently shown in Caenorhabditis elegans that transcript levels of sqst-1/p62 increase upon a hormetic heat shock, suggesting a role of SQST-1/p62 in stress response and aging. Here, we find that sqst-1/p62 is required for hormetic benefits of heat shock, including longevity, improved neuronal proteostasis, and autophagy induction. Furthermore, overexpression of SQST-1/p62 is sufficient to induce autophagy in distinct tissues, extend lifespan, and improve the fitness of mutants with defects in proteostasis in an autophagy-dependent manner. Collectively, these findings illustrate that increased expression of a selective autophagy receptor is sufficient to induce autophagy, enhance proteostasis and extend longevity, and demonstrate an important role for sqst-1/p62 in proteotoxic stress responses.

Dysfunctional mitochondria and generation of reactive oxygen species (ROS) promote chronic diseases, which have spurred interest in the molecular mechanisms underlying these conditions. Previously, we have demonstrated that disruption of post-translational modification of proteins with β-linked -acetylglucosamine (-GlcNAcylation) via overexpression of the GlcNAc-regulating enzymesGlcNAc transferase (OGT) or GlcNAcase (OGA) impairs mitochondrial function. Here, we report that sustained alterations inGlcNAcylation either by pharmacological or genetic manipulation also alter metabolic function. Sustained GlcNAc elevation in SH-SY5Y neuroblastoma cells increased OGA expression and reduced cellular respiration and ROS generation. Cells with elevatedGlcNAc levels had elongated mitochondria and increased mitochondrial membrane potential, and RNA-sequencing analysis indicated transcriptome reprogramming and down-regulation of the NRF2-mediated antioxidant response. Sustained GlcNAcylation in mouse brain and liver validated the metabolic phenotypes observed in the cells, and OGT knockdown in the liver elevated ROS levels, impaired respiration, and increased the NRF2 antioxidant response. Moreover, elevatedGlcNAc levels promoted weight loss and lowered respiration in mice and skewed the mice toward carbohydrate-dependent metabolism as determined by indirect calorimetry. In summary, sustained elevation in GlcNAcylation coupled with increased OGA expression reprograms energy metabolism, a finding that has potential implications for the etiology, development, and management of metabolic diseases.

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Background: The addition or removal of the O-GlcNAc post-translational modification (O-GlcNAc cycling) regulates mitotic progression.Results: Increased O-GlcNAc cycling disrupted spindle size and shape partially through the loss of Aurora kinase B phosphorylation of histones. Inhibition of O-GlcNAc removal rescued the spindle phenotype.Conclusion: These data suggest that O-GlcNAc cycling is a requirement for spindle function.Significance: Proper spindle development requires O-GlcNAc cycling.

One mode of ␥-globin gene silencing involves a GATA-1⅐FOG-1⅐Mi2␤ repressor complex that binds to the ؊566 GATA site relative to the A ␥-globin gene cap site. However, the mechanism of how this repressor complex is assembled at the ؊566 GATA site is unknown. In this study, we demonstrate that the O-linked N-acetylglucosamine (O-GlcNAc) processing enzymes, O-GlcNAc-transferase (OGT) and O-GlcNAcase (OGA), interact with the A ␥-globin promoter at the ؊566 GATA repressor site; however, mutation of the GATA site to GAGA significantly reduces OGT and OGA promoter interactions in ␤-globin locus yeast artificial chromosome (␤-YAC) bone marrow cells. When WT ␤-YAC bone marrow cells are treated with the OGA inhibitor Thiamet-G, the occupancy of OGT, OGA, and Mi2␤ at the A ␥-globin promoter is increased. In addition, OGT and Mi2␤ recruitment is increased at the A ␥-globin promoter when ␥-globin becomes repressed in postconception day E18 human ␤-YAC transgenic mouse fetal liver. Furthermore, we show that Mi2␤ is modified with O-GlcNAc, and both OGT and OGA interact with Mi2␤, GATA-1, and FOG-1. Taken together, our data suggest that O-GlcNAcylation is a novel mechanism of ␥-globin gene regulation mediated by modulating the assembly of the GATA-1⅐FOG-1⅐Mi2␤ repressor complex at the ؊566 GATA motif within the promoter.

Alterations in O-GlcNAc cycling, the addition and removal of O-GlcNAc, lead to mitotic defects and increased aneuploidy. Herein, we generated stable O-GlcNAcase (OGA, the enzyme that removes OGlcNAc) knockdown HeLa cell lines and characterized the effect of the reduction in OGA activity on cell cycle progression. After release from G 1 /S, the OGA knockdown cells progressed normally through S phase but demonstrated mitotic exit defects. Cyclin A was increased in the knockdown cells while Cyclin B and D expression was reduced. Retinoblastoma protein (RB) phosphorylation was also increased in the knockdown compared to control. At M phase, the knockdown cells showed more compact spindle chromatids than control cells and had a greater percentage of cells with multipolar spindles. Furthermore, the timing of the inhibitory tyrosine phosphorylation of Cyclin Dependent Kinase 1 (CDK1) was altered in the OGA knockdown cells. Although expression and localization of the chromosomal passenger protein complex (CPC) was unchanged, histone H3 threonine 3 phosphorylation was decreased in one of the OGA knockdown cell lines. The Ewing Sarcoma Breakpoint Region 1 Protein (EWS) participates in organizing the CPC at the spindle and is a known substrate for O-GlcNAc transferase (OGT, the enzyme that adds OGlcNAc). EWS O-GlcNAcylation was significantly increased in the OGA knockdown cells promoting uneven localization of the mitotic midzone. Our data suggests that O-GlcNAc cycling is an essential mechanism for proper mitotic signaling and spindle formation, and alterations in the rate of O-GlcNAc cycling produces aberrant spindles and promotes aneuploidy.

Edited by Gerald W. Hart Chronic, low-grade inflammation increases the risk for atherosclerosis, cancer, and autoimmunity in diseases such as obesity and diabetes. Levels of CD4 ؉ T helper 17 (Th17) cells, which secrete interleukin 17A (IL-17A), are increased in obesity and contribute to the inflammatory milieu; however, the relationship between signaling events triggered by excess nutrient levels and IL-17A-mediated inflammation is unclear. Here, using cytokine, quantitative real-time PCR, immunoprecipitation, and ChIP assays, along with lipidomics and MS-based approaches, we show that increased levels of the nutrient-responsive, post-translational protein modification, O-GlcNAc, are present in naive CD4 ؉ T cells from a diet-induced obesity murine model and that elevated O-GlcNAc levels increase IL-17A production. We also found that increased binding of the Th17 master transcription factor RAR-related orphan receptor ␥ t variant (ROR␥t) at the IL-17 gene promoter and enhancer, as well as significant alterations in the intracellular lipid microenvironment, elevates the production of ligands capable of increasing ROR␥t transcriptional activity. Importantly, the rate-limiting enzyme of fatty acid biosynthesis, acetyl-CoA carboxylase 1 (ACC1), is O-GlcNAcylated and necessary for production of these ROR␥t-activating ligands. Our results suggest that increased O-GlcNAcylation of cellular proteins may be a potential link between excess nutrient levels and pathological inflammation. CD4 ϩ T cells orchestrate the adaptive immune response. Activation of naive CD4 ϩ T cells in response to a pathogen prompts their differentiation into various effectors (e.g. T This work was supported in part by the Molecular Regulation of Cell Development and Differentiation COBRE P30GM122731 (to P. E. F. and C. S.) and a University of Kansas Medical Center Biomedical Research Training Program grant (to M. M.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This article contains Figs. S1-S3 and Tables S1-S4.