Dataset Information

The role of glucocorticoid receptor phosphorylation in Mcl-1 and NOXA gene expression.

ABSTRACT:

Background

The cyclin-dependent kinase (CDK) and mitogen-activated protein kinase (MAPK) mediated phosphorylation of glucocorticoid receptor (GR) exerts opposite effects on GR transcriptional activity and affects other posttranslational modifications within this protein. The major phosphorylation site of human GR targeted by MAPK family is the serine 226 and multiple kinase complexes phosphorylate receptor at the serine 211 residue. We hypothesize that GR posttranslational modifications are involved in the determination of the cellular fate in human lymphoblastic leukemia cells. We investigated whether UV signalling through alternative GR phosphorylation determined the cell type specificity of glucocorticoids (GCs) mediated apoptosis.

Results

We have identified putative Glucocorticoid Response Elements (GREs) within the promoter regulatory regions of the Bcl-2 family members NOXA and Mcl-1 indicating that they are direct GR transcriptional targets. These genes were differentially regulated in CEM-C7-14, CEM-C1-15 and A549 cells by glucocorticoids and JNK pathway. In addition, our results revealed that the S211 phosphorylation was dominant in CEM-C7-14, whereas the opposite was the case in CEM-C1-15 where prevalence of S226 GR phosphorylation was observed. Furthermore, multiple GR isoforms with cell line specific patterns were identified in CEM-C7-14 cells compared to CEM-C1-15 and A549 cell lines with the same antibodies.

Conclusions

GR phosphorylation status kinetics, and site specificity as well as isoform variability differ in CEM-C7-14, CEM-C1-15, and A549 cells. The positive or negative response to GCs induced apoptosis in these cell lines is a consequence of the variable equilibrium of NOXA and Mcl-1 gene expression potentially mediated by alternatively phosphorylated GR, as well as the balance of MAPK/CDK pathways controlling GR phosphorylation pattern. Our results provide molecular base and valuable knowledge for improving the GC based therapies of leukaemia.

SUBMITTER: Lynch JT

PROVIDER: S-EPMC2834612 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Publications

The role of glucocorticoid receptor phosphorylation in Mcl-1 and NOXA gene expression.

Lynch James T JT Rajendran Ramkumar R Xenaki Georgia G Berrou Ilhem I Demonacos Constantinos C Krstic-Demonacos Marija M

Molecular cancer 20100215

<h4>Background</h4>The cyclin-dependent kinase (CDK) and mitogen-activated protein kinase (MAPK) mediated phosphorylation of glucocorticoid receptor (GR) exerts opposite effects on GR transcriptional activity and affects other posttranslational modifications within this protein. The major phosphorylation site of human GR targeted by MAPK family is the serine 226 and multiple kinase complexes phosphorylate receptor at the serine 211 residue. We hypothesize that GR posttranslational modifications ...[more]

PMID: 20156337

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Project description:In response to environmental stressors and a variety of inflammatory cytokines, p38 MAPKs become directly activated. Here we report the human glucocorticoid receptor (GR) Serine 134 as a novel target for p38 MAPK. Unlike most other phosphorylation events that occur on the GR, phosphorylation of Ser134 was found to be hormone-independent in several human and rat cell types. Instead we found phosphorylation of Ser134 was induced by a variety of stress-activating stimuli, including: glucose starvation, ultraviolet irradiation, osmotic shock, and oxidative stress. Pharmacological inhibitors and shRNA-mediated knockdown experiments correlate this phosphorylation with the activation of p38 MAPK. Compared to wild-type GR, cells expressing a mutant receptor incapable of phosphorylation at Ser134 (S134A GR) had a significantly altered hormone-dependent genome-wide transcriptional response to glucocorticoids. Moreover, we show that although WT GR regulated roughly half as many genes as S134A GR, WT receptor selectively activated significantly more genes associated with endocrine and inflammatory disease than the mutant receptor, suggesting that the phosphorylation status of Ser134 is critical for modulating GR function. Phosphorylation of Ser134 did not alter either nuclear translocation or the stability of the GR protein in the absence or presence of ligand. However, phosphorylation of Ser134 significantly increased the association of the GR with the zeta isoform the 14-3-3 class of signaling proteins, resulting in a blunted hormone-dependent transcriptional response of LAD1 and IGFBP1 but not GILZ. Together these data suggest that the phosphorylation of Ser134 acts as a molecular sensor on the GR, monitoring the level of cellular stress to allow for altered 14-3-3zeta cofactor association, ultimately modifying glucocorticoid signaling in a gene-dependent manner. Our results reveal one mechanism that may allow cellular stress to dictate the transcriptional response of cells to hormone. U2OS cells, a human osteosarcoma cell line, were transfected with either WT GR or S134A GR and put under antibiotic selection to produce a stable mixed population of cells expressing comparable levels of GR. 10^6 cells were treated with 100nM Dexamethasone (DEX) or vehicle control for 6 hours. Three biological and one hybridization replicate are included for each sample.

Dataset Information

The role of glucocorticoid receptor phosphorylation in Mcl-1 and NOXA gene expression.

Background

Results

Conclusions

Publications

The role of glucocorticoid receptor phosphorylation in Mcl-1 and NOXA gene expression.

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