Glycogen Synthase Kinase-3β Is Involved in Ligand-Dependent Activation of Transcription and Cellular Localization of the Glucocorticoid Receptor

• Published in: Molecular endocrinology (Baltimore, Md.) Md.), 2012-09, Vol.26 (9), p.1508-1520
• Main Authors: Rubio-Patiño, Camila, Palmeri, Claudia M, Pérez-Perarnau, Alba, Cosialls, Ana M, Moncunill-Massaguer, Cristina, González-Gironès, Diana M, Pons-Hernández, Lluís, López, José M, Ventura, Francesc, Gil, Joan, Pons, Gabriel, Iglesias-Serret, Daniel
• Format: Article
• Language: English
• Subjects: Apoptosis - genetics; Apoptosis - physiology; Blotting, Western; Cell Survival - genetics; Cell Survival - physiology; Chromatin Immunoprecipitation; Enzyme Inhibitors - pharmacology; Flow Cytometry; Glycogen Synthase Kinase 3 - antagonists & inhibitors; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Humans; Indoles - pharmacology; Maleimides - pharmacology; Microscopy, Confocal; Original Research; Protein Binding; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Transcription, Genetic - genetics; Tumor Cells, Cultured
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/me.2011-1366

Glucocorticoids (GC) induce cell cycle arrest and apoptosis in different cell types and therefore are widely used to treat a variety of diseases including autoimmune disorders and cancer. This effect is mediated by the GC receptor (GR), a ligand-activated transcription factor that translocates into the nucleus where it modulates transcription of target genes in a promoter-specific manner. Glycogen synthase kinase-3 (GSK3) regulates GR response by genomic and nongenomic mechanisms, although the specific role of each isoform is not well defined. We used GSK3 pharmacological inhibitors and isoform-specific small interfering RNA to evaluate the role of GSK3 in the genomic regulation induced by GC. GSK3 inhibition resulted in the reduction of GC-induced mRNA expression of GC-induced genes such as BIM, HIAP1, and GILZ. Knockdown of GSK3β but not GSK3α reduced endogenous GILZ induction in response to dexamethasone and GR-dependent reporter gene activity. Chromatin immunoprecipitation experiments revealed that GSK3 inhibition impaired the dexamethasone-mediated binding of GR and RNA polymerase II to endogenous GILZ promoter. These results indicate that GSK3β is important for GR transactivation activity and that GSK3β inhibition suppresses GC-stimulated gene expression. Furthermore, we show that genomic regulation by the GR is independent of known GSK3β phosphorylation sites. We propose that GC-dependent transcriptional activation requires functional GSK3β signaling and that altered GSK3β activity influences cell response to GC.