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Dexamethasone‐induced up‐regulation of the human norepinephrine transporter involves the glucocorticoid receptor and increased binding of C/EBP‐β to the proximal promoter of norepinephrine transporter
Author(s) -
Zha Qinqin,
Wang Yan,
Fan Yan,
Zhu MengYang
Publication year - 2011
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2011.07448.x
Subject(s) - chromatin immunoprecipitation , glucocorticoid receptor , glucocorticoid , hormone response element , antiglucocorticoid , transactivation , norepinephrine transporter , medicine , endocrinology , ccaat enhancer binding proteins , mifepristone , dexamethasone , response element , biology , chemistry , microbiology and biotechnology , norepinephrine , gene expression , promoter , transcription factor , nuclear protein , gene , biochemistry , dopamine , cancer , genetics , breast cancer , pregnancy , estrogen receptor
J. Neurochem. (2011) 119 , 654–663. Abstract Previously, we have found glucocorticoids up‐regulate norepinephrine (NE) transporter (NET) expression in vitro . However, the underlying transcriptional mechanism is poorly understood. In this study, the role of glucocorticoids on the transcriptional regulation of NET was investigated. Exposure of neuroblastoma SK‐N‐BE(2)M17 cells to dexamethasone (Dex) significantly increased NET mRNA and protein levels in a time‐ and dose‐dependent manner. This effect was attenuated by glucocorticoid receptor (GR) antagonist mifepristone, suggesting that up‐regulation of NET by Dex was mediated by the GR. In reporter gene assays, exposure of cells to Dex resulted in dose‐dependent increases of luciferase activity that were also prevented by mifepristone. Serial deletions of the NET promoter delineated Dex‐responsiveness to a −301 to −148 bp region containing a CCAAT/enhancer binding protein‐β (C/EBP‐β) response element. Co‐immunoprecipitation experiments demonstrated that Dex treatment caused the interaction of the GR with C/EBP‐β. Chromatin immunoprecipitation (ChIP) assay revealed that Dex exposure resulted in binding of both GR and C/EBP‐β to the NET promoter. Further experiments showed that mutation of the C/EBP‐β response element abrogated C/EBP‐β‐ and GR‐mediated transactivation of NET. These findings demonstrate that Dex‐induced increase in NET expression is mediated by the GR via a non‐conventional transcriptional mechanism involving interaction of C/EBP‐β with a C/EBP‐β response element.