Glucocorticoid Receptor Regulates Transcription by Binding to Glucocorticoid Responsive Element in Proximal Promoter Region.

Glucocorticoid osteoporosis is a serious side effect of long term glucocorticoid uptake and it is caused by osteoblast apoptosis and imbalance in the major bone remodeling pathway RANK/RANKL/OPG. The impact of glucocorticoid on the maintenance of RANK/RANKL/OPG is well explored; dexamethasone was shown to disturb the ratio between and level by decreasing the expression level of and increasing level of . Here, were aimed to decipher whether glucocorticoid receptor directly influences promoter activity and its transcriptional regulation. We demonstrate that overexpression of glucocorticoid receptor (GR) NR3C1 increased promoter activity in human osteosarcoma, cervical cancer (2-fold) and adenocarcinoma cells (4.5-fold). Mutational analysis revealed that +352 site in the promoter is functional glucocorticoid responsive element (GRE) since the effect of GR on promoter activity was diminished by mutation at this site. Overexpression of upregulated mRNA expression 1.5-fold in human A549 and HOS cells. On the other hand silencing of caused slight decrease in mRNA level, suggesting that NR3C1 directly accounts for transcriptional regulation. Using electrophoretic mobility shift assay we demonstrate that NR3C1 binds to the proximal promoter region. Our study provides evidences that NR3C1 directly upregulates transcription in human cell lines and connects the missing link in the mechanism of RANK/RANKL/OPG imbalance of glucocorticoid induced osteoporosis.