Project description:Exogenous glucocorticoids are widely used in the clinic for the treatment of inflammatory disorders and auto-immune diseases. Unfortunately, their use is hampered by many side effects and therapy resistance. Efforts to find more selective glucocorticoid receptor (GR) agonists and modulators (called SEGRAMs), able to separate anti-inflammatory effects via gene suppression from metabolic effects via gene activation, have been unsuccessful so far. In this study, we characterized a set of functionally diverse GR ligands in A549 cells, first using a panel of luciferase-based reporter gene assays evaluating GR-driven gene activation and gene suppression. We expanded this minimal assay set with novel luciferase-based read-outs monitoring GR protein levels, GR dimerization and GR Serine 211 (Ser211) phosphorylation status and compared their outcomes with compound effects on the mRNA levels of known GR target genes in A549 cells and primary hepatocytes. We found that luciferase reporters evaluating GR-driven gene activation and gene repression were not always reliable predictors for effects on endogenous target genes. Remarkably, our novel assay monitoring GR Ser211 phosphorylation levels proved to be the most reliable predictor for compound effects on almost all tested endogenous GR targets, both driven by gene activation and repression. The integration of this novel assay in existing screening platforms may therefore increase chances to find novel GR ligands with an improved therapeutic benefit.
Project description:ra15-05_tt1 - tt1-gr - Discover TT1 donwstream targets - An inducible line carrying TT1, an early marker of endothelium development, fused to the rat glucocorticoid receptor (GR), that allows a dexamethasone (DEX)-mediated posttranslational induction of the proteins, has been created. Siliques have been first treated with cycloheximide, an inhibitor of protein synthesis, to prevent indirect transcriptional effects of the inducible TT1 transcription factor. RNA profiling experiments (CATMA microarrays) will be then conducted before and after DEX induction of TT1. These experiments will unveil direct downstream target genes of the TT1 transcription factor.
Project description:The Glucocorticoid Receptor (GR) is both one of the most widely used clinical drug targets and a very potent metabolic regulator. GR belongs to the nuclear hormone receptor family of ligand-gated transcription factors that govern mammalian physiology. Upon ligand binding, GR enters the nucleus to regulate gene expression both positively and negatively. It is known to bind to consensus DNA sequences termed glucocorticoid response elements (GREs), but the mechanisms determining transcriptional activation versus repression remain an unresolved molecular paradox. Prevailing models suggest that tethering of GR to AP-1 or NF-κB via protein-protein interactions, rather than direct DNA binding, specifies negative regulation. However, here we show that the repression of inflammatory genes as well as all other glucocorticoid responses, require direct DNA binding of GR. Generating GR point mutant mice that retain the ability to tether via protein-protein interactions while unable to recognize DNA sequences, we demonstrate that response element recognition via the Zinc finger is absolutely required for both transcriptional activation and repression. We have used ChIP-Seq and RNA-Seq in inflammatory and metabolic cells and tissues together with proteomics to reveal that DNA binding of GR is necessary for the assembly of a functional SWI/SNF coregulator complex. Generally, the desired anti-inflammatory actions of GR are attributed to the silencing of inflammatory genes, while its adverse effects are believed to result from the transcriptional upregulation of metabolic targets. Our findings not only challenge classical models and dogmas of GR mediated gene regulation, but will provide an important basis for the development of novel immunosuppressants with reduced side effect profiles.
Project description:Glucocorticoid receptor (GR) is a ligand dependent transcription factor that plays a central role in inflammation. Part of a complex cellular network, GR activity is further modulated via protein–protein interactions . The regulation of GR by 14-3-3 proteins has been previously reported, though with differing sites of phosphorylation identified and variable consequences assigned. Hence, we sought to examine this protein–protein interaction and, using phosphorylated GR peptides, biophysical studies and X-ray crystallography, we identified key residues within the ligand binding domain of GR, T524 and S617, whose phosphorylation results in recognition by 14-3-3. Investigation of the kinases responsible for phosphorylation of these sites assigned a key role for MINK1 and cell-based approaches confirmed the importance of these two GR phosphosites and MINK1 in GR–14-3-3 binding. Together our results provide a molecular-level insight into 14-3-3 regulation of GR and highlight both MINK1 and the GR–14-3-3 axis as potential targets for future therapeutic intervention.
Project description:The glucocorticoid receptor (GR) regulates adaptive transcriptional programs that alter metabolism in response to stress. Network properties that allow GR to tune gene expression to match specific physiologic demands are poorly understood. We analyzed the transcriptional consequences of GR activation in murine lungs deficient for Klf15, a transcriptional regulator of amino acid metabolism that is induced by glucocorticoids and fasting
Project description:The glucocorticoid receptor (GR) regulates adaptive transcriptional programs that alter metabolism in response to stress. Network properties that allow GR to tune gene expression to match specific physiologic demands are poorly understood. We analyzed the transcriptional consequences of GR activation in murine lungs deficient for Klf15, a transcriptional regulator of amino acid metabolism that is induced by glucocorticoids and fasting Wild type and Klf15 KO mice were treated with dexamethsone or saline control for 4 and 8 hours.
Project description:The Glucocorticoid Receptor (GR) is a potent metabolic regulator and a major drug target. While GR was shown to play various important roles in circadian biology, its rhythmic genomic actions have never been studied. Here we mapped GR’s genome-wide chromatin occupancy in mouse livers throughout the day/night cycle. We show how GR partitions metabolic processes during fasting (cellular maintenance, gluconeogenesis) and feeding (lipid and amino acid metabolism) by time-dependent binding and target gene regulation. Highlighting the dominant role GR plays in synchronizing circadian pathways, we find that the majority of oscillating genes harbor GR binding sites and depend on GR for amplitude stability . Surprisingly, this rhythmic pattern is altered by exposure to high fat diet in a ligand-independent manner. We show how the remodeling of oscillatory gene expression and GR binding result from a concomitant increase with Stat5 co-occupancy in obese mice, and that loss of GR reduces circulating glucose and triglycerides differentially during feeding and fasting. Altogether, our findings highlight GR’s fundamental role in the rhythmic orchestration of hepatic metabolism.
Project description:Glucocorticoid receptor (GR) is an essential transcription factor (TF), controlling metabolism, development and immune responses. SUMOylation regulates chromatin occupancy and target gene expression of GR in a locus-selective manner, but the mechanism of regulation has remained elusive. Here, we show using selective isolation of chromatin-associated proteins that the protein network around chromatin-bound GR is affected by SUMOylation, with several nuclear receptor coregulators and chromatin modifiers being more avidly associated with SUMOylation-deficient than SUMOylation competent GR. This difference is reflected in our chromatin accessibility and gene expression data, showing that the SUMOylation-deficient GR is more potent in opening chromatin at glucocorticoid-regulated enhancers and inducing expression of their target loci. Our results thus show that SUMOylation determines GR specificity by regulating the chromatin protein network and accessibility at GR-driven enhancers. We speculate that a similar mechanism is utilized by many other SUMOylated TFs.
Project description:lec1::gr induction - Identification of LEC1 target genes - Induction of 14 days old LEC1::GR seedlings , different treatments (EtOH, DEX, DEX+ABA, induction) for 8 hours
Project description:Glucocorticoid receptor (GR) is an essential transcription factor (TF), controlling metabolism, development and immune responses. SUMOylation regulates chromatin occupancy and target gene expression of GR in a locus-selective manner, but the mechanism of regulation has remained elusive. Here, we identify the protein network around chromatin-bound GR by using selective isolation of chromatin-associated proteins and show that the network is affected by receptor SUMOylation, with several nuclear receptor coregulators and chromatin modifiers preferring interaction with SUMOylation-deficient GR and proteins implicated in transcriptional repression preferring interaction with SUMOylation-competent GR. This difference is reflected in our chromatin binding, chromatin accessibility and gene expression data, showing that the SUMOylation-deficient GR is more potent in binding and opening chromatin at glucocorticoid-regulated enhancers and inducing expression of target loci. Blockage of SUMOylation by a SUMO-activating enzyme inhibitor (ML-792) phenocopied to a large extent the consequences of GR SUMOylation deficiency on chromatin binding and target gene expression. Our results thus show that SUMOylation modulates the specificity of GR by regulating its chromatin protein network and accessibility at GR-bound enhancers. We speculate that many other SUMOylated TFs utilize a similar regulatory mechanism.