Glucocorticoid Regulated Transcriptome in Wild-type and GR-C3 Knockin Mouse Embryonic Fibroblasts
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ABSTRACT: Glucocorticoids are primary stress hormones and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by severe side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced by alternative translation initiation; however, the role individual isoforms play in controlling tissue-specific responses to glucocorticoids in vivo is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. The GR-C3 knockin mice die at birth due to respiratory distress but can be completely rescued by antenatal glucocorticoid administration. To evaluate the GR-C3 transcriptome, we prepared mouse embryonic fibroblasts (MEFs) from E12.5 wild-type (WT) and GR-C3 knockin embryos and treated the cells with vehicle or the synthetic glucocorticoid Dexamethasone (Dex) for 6 hours. The GR-C3 isoform was found to have a markedly different gene-regulatory profile than GR in WT MEFs.
Project description:Glucocorticoids are primary stress hormones and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by severe side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced by alternative translation initiation; however, the role individual isoforms play in controlling tissue-specific responses to glucocorticoids in vivo is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. The GR-C3 knockin mice die at birth due to respiratory distress but can be completely rescued by antenatal glucocorticoid administration. Rescued GR-C3 mice exhibited alterations in circadian rhythm in a sexually dimorphic manner and in sensitivity to lipopolysaccharide (LPS)-induced endotoxemia. To evaluate the ability of glucocorticoids to protect against LPS-induced inflammation, we measured gene expression in spleens from WT and rescued GR-C3 knockin mice that had been treated with vehicle or LPS for 3 and 24 hours. The GR-C3 isoform was found to be deficient in its ability to repress a large cohort of immune and inflammatory genes.
Project description:Glucocorticoids regulate diverse physiologic processes and synthetic derivatives of these natural hormones are widely used in the treatment of inflammatory diseases. However, chronic administration often triggers insensitivity and serious side effects including osteoporosis. The underlying mechanisms regulating these side effects are not completely understood. We report here that human osteosarcoma U-2 OS bone cells lacking the glucocorticoid receptor (GR) are resistant to glucocorticoid killing whereas the expression of wild-type GR activates an apoptotic program. Furthermore, we show that the translationally generated GR isoforms from a single GR gene have distinct abilities to induce apoptosis in these cells. Only cells expressing selective GR isoforms underwent apoptosis upon dexamethasone treatment and microarray analysis demonstrated that GR isoforms selectively stimulated the expression of pro-apoptotic enzymes such as caspase 6 and granzyme A. Chromatin immunoprecipitation assays further revealed that GR isoform-dependent induction of pro-apoptotic genes is likely due to selective coregulator recruitment and chromatin modification. Together, these findings provide evidence for a direct apoptotic effect of glucocorticoids on bone cells via selective GR isoforms and delineate multiple molecular components involved in tissue-specific glucocorticoid-induced bone cell apoptosis. Keywords: time course, isoform comparison
Project description:Synthetic glucocorticoids are widely prescribed in the treatment of ocular infections and disorders. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR); however, the molecular and physiological functions of GR signaling in the cornea are poorly understood. In this study, we show that treatment of mice with glucocorticoid eye drops led to a profound regulation of the corneal transcriptome. To determine the global transcriptional profile of GR activity in the cornea, we treated adult wild-type male mice with dexamethasone (a synthetic glucocorticoid) eye drops or vehicle eye drops for 6 hours and then performed RNA sequencing on RNA extracted from whole corneas. All the animals used for this study were adrenalectomized to remove endogenous glucocorticoids. These data demonstrate that a short exposure of glucocorticoids to the cornea results in major changes in the gene expression landscape.
Project description:Glucocorticoids are primary stress hormones that regulate many physiological processes, and synthetic derivatives of these molecules and are widely used in the clinic. The cellular response to glucocorticoids is remarkably diverse; however, the molecular factors that govern tissue specificity are poorly understood. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR). To discover new proteins that interact with GR and modulate its function, we performed a yeast 2 hybrid assay using as bait the hinge region of GR. The MyoD family inhibitor domain-containing (MDFIC) protein was identified as a binding partner for GR. Knockdown of MDFIC in A549 cells alters the GR transcriptome. To further investigate the functional effect of MDFIC on the GR transcriptome, we performed a genome-wide microarray in COS-1 cells that were transfected with GR alone or GR and MDFIC. The transfected cells were treated with vehicle or the synthetic glucocorticoid Dexamethasone (Dex) for 6 hours. Overexpression of MDFIC was found to expand the GR transcriptome.
Project description:Glucocorticoids are primary stress hormones that regulate many physiological processes, and synthetic derivatives of these molecules and are widely used in the clinic. The cellular response to glucocorticoids is remarkably diverse; however, the molecular factors that govern tissue specificity are poorly understood. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR). To discover new proteins that interact with GR and modulate its function, we performed a yeast 2 hybrid assay using as bait the hinge region of GR. The MyoD family inhibitor domain-containing (MDFIC) protein was identified as a binding partner for GR. To investigate the function of the GR-MDFIC interaction, we performed a genome-wide microarray in intact and MDFIC deficient A549 cells that were treated with the synthetic glucocorticoid Dexamethasone (Dex). A large cohort of genes was differentially regulated by GR depending on the presence or absence of MDFIC. These findings identify a new binding partner for cytoplasmic GR that modulates the receptor transcriptome and contributes to the tissue specific actions of glucocorticoids.
Project description:Synthetic glucocorticoids are widely prescribed in the treatment of ocular infections and disorders. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR); however, the molecular and physiological functions of GR signaling in the cornea are poorly understood. To understand the direct role of GR signaling in the cornea, we developed mice with conditional knockout of GR in the corneal epithelium. Global transcriptomic approaches revealed that loss of GR signaling in the cornea resulted in the dysregulation of a large cohort of genes strongly associated with an enhanced immune response.
Project description:Glucocorticoids are primary stress hormones that regulate many physiological processes, and synthetic derivatives of these molecules and are widely used in the clinic. The cellular response to glucocorticoids is remarkably diverse; however, the molecular factors that govern tissue specificity are poorly understood. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR). To discover new proteins that interact with GR and modulate its function, we performed a yeast 2 hybrid assay using as bait the hinge region of GR. The MyoD family inhibitor domain-containing (MDFIC) protein was identified as a binding partner for GR. Knockdown of MDFIC in A549 cells alters the GR transcriptome. Overexpression of MDFIC with GR in COS-1 cells also modulates the GR transcriptome by expanding the number of genes regulated in response to glucocorticoid treatment. Our findings in A549 cells suggest that MDFIC alters the gene regulatory profile of GR by modulating receptor phosphorylation at several residues, including S211. To further investigate the molecular link between MDFIC-mediated effects on GR phosphorylation at S211 and alterations in the GR transcriptome, we performed a genome-wide microarray in COS-1 cells that were transfected with the GR phosphorylation mutant S211A or S211A and MDFIC. The transfected cells were treated with vehicle or the synthetic glucocorticoid Dexamethasone (Dex) for 6 hours. The ability of MDFIC to expand the GR transcriptome was attenuated in cells expressing S211A mutant.
Project description:The glucocorticoid receptor (GR) regulates gene expression upon activation by glucocorticoid (GC) hormones. In zebrafish, two GR splice variants exist: the canonical GR α-isoform (GRα), and the GR β-isoform (GRβ). The exact function of GRb remains elusive. We have investigated the transcriptional role of GRa and GRb in the zebrafish embryo model by injecting mebryos with two splice-blocking morpholinos (one leading to knockdown of both GR α- and β-isoforms, and another targeting the alternative splicing of the GR pre-mRNA in favor of the GR β-isoform) and with GRβ mRNA (resulting in specific GRβ overexpression). Transcriptome profiling was performed on total RNA isolated from 30 hpf embryos. Our results show that GRb does not act as a dominant-negative inhibitor of GRa, and that GRa regulates two distinct gene clusters, which are mainly involved in the metabolism of the embryo.
Project description:Glucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies. We tested the hypothesis by treateing rats with the synthetic glucocorticoid dexamethasone and the AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR).
Project description:Glucocorticoids regulate diverse physiologic processes and synthetic derivatives of these natural hormones are widely used in the treatment of inflammatory diseases. However, chronic administration often triggers insensitivity and serious side effects including osteoporosis. The underlying mechanisms regulating these side effects are not completely understood. We report here that human osteosarcoma U-2 OS bone cells lacking the glucocorticoid receptor (GR) are resistant to glucocorticoid killing whereas the expression of wild-type GR activates an apoptotic program. Furthermore, we show that the translationally generated GR isoforms from a single GR gene have distinct abilities to induce apoptosis in these cells. Only cells expressing selective GR isoforms underwent apoptosis upon dexamethasone treatment and microarray analysis demonstrated that GR isoforms selectively stimulated the expression of pro-apoptotic enzymes such as caspase 6 and granzyme A. Chromatin immunoprecipitation assays further revealed that GR isoform-dependent induction of pro-apoptotic genes is likely due to selective coregulator recruitment and chromatin modification. Together, these findings provide evidence for a direct apoptotic effect of glucocorticoids on bone cells via selective GR isoforms and delineate multiple molecular components involved in tissue-specific glucocorticoid-induced bone cell apoptosis. Experiment Overall Design: U-2 OS cells were transfected with the BD Clontech pTET-OFF regulatory plasmid to establish the U-OFF parental cell line. MluI and EcoRV ends were generated onto the coding region of hGR-alpha, -A, -B, -C, or -D using PCR amplification of the pCMVhGR-alpha or -A plasmid. The pTRE2hyg vector was digested with MluI and EcoRV and the two DNAs were ligated to form the pTRE2hGR-alpha,-A, -B, -C, or -D plasmid. Each DNA construct was individually transfected into the U-OFF cells and clones were selected which stably expressed either hGR-alpha, -A, -B, -C, or -D using 200 microg/ml of geneticin and 500 mircorg/ml of hygromycin. Several clones were obtained for each receptor, and the receptor levels were compared using western blot analyses. In these cell lines, the expression of hGR can be repressed by the addition of tetracycline or the derivative doxycycline to the media. U-2 OS (human osteosarcoma) cells were maintained in DMEM/F-12 supplemented with 10% FCS:CS, 2 mM glutamine and pen-strep and selected clones were maintained in the same media with the addition of 200 microg/ml Geneticin and 200 mircrog/ml hygromycin. All cells were maintained in a humidified, 5% CO2 atmosphere. Cells were either not treated (0 hours) or were treated with 100 nM dexamethasone for 6, 12, or 24 hours. Experiment Overall Design: Total RNA was amplified using the Agilent Low RNA Input Fluorescent Linear Amplification Kit protocol. Starting with 500ng of total RNA, Cy3 labeled cRNA was produced according to manufacturer's protocol. For each sample, 1.5ug of Cy3 labeled cRNAs were fragmented using the Agilent In Situ Hybridization Kit protocol. Hybridizations were performed for 17 hours in a rotating hybridization oven at 65 degrees at 4 RPM. Slides were washed with 6X SSPE + 0.005% N-lauroyl sarcosine for 1 minute then 0.06X SSPE + 0.005% N-lauroyl sracosine for 1 minute at 37 degrees. The slides were dried by slowly removing from second wash solution and then scanned with an Agilent G2565 Scanner (10micron and with XDR) and processed with Agilent Feature Extraction v9.1. The resulting files were imported into the Rosetta Resolver system (Version 6.0). This system performs data pre-processing and error modeling.