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Am J Physiol Endocrinol Metab (February 20, 2007). doi:10.1152/ajpendo.00708.2006
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Submitted on December 22, 2006
Accepted on February 15, 2007

Aldosterone-induced Epidermal Growth Factor Receptor (EGFR) expression: Interaction Between the Human Mineralocorticoid Receptor and the Human EGFR Promoter

Claudia Grossmann1, Alexander W Krug2, Ruth Freudinger1, Sigrid Mildenberger1, Katharina Völker3, and Michael Gekle1*

1 Physiologisches Institut, Universitaet Wuerzburg, Wuerzburg, Germany
2 Medizinische Klinik III, Universitaet Dresden, Dresden, Germany
3 Physiologisches Institut, Universitaet Wuerzburg, Würzburg, Germany

* To whom correspondence should be addressed. E-mail: michael.gekle{at}mail.uni-wuerzburg.de.

Aldosterone plays a key role in cardiovascular and renal injury. The underlying mechanisms are not completely understood. Because the epidermal growth factor receptor (EGFR) is involved in the development of fibrosis and vascular dysfunction, upregulation of EGFR expression by aldosterone-bound mineralocorticoid receptor (MR) is an attractive hypothesis. We investigated the effect of aldosterone on EGFR expression in the aorta of adrenalectomized rats and in human aorta smooth muscle cells (HAoSMC) in primary culture. Aldosterone, but not dexamethasone, stimulated EGFR expression in vivo in the aorta as well as in HAoSMC. EGFR degradation was not affected. Aldosterone-induced EGFR expression in HAoSMC was dose-dependent and prevented by spironolactone. Furthermore, incubation of HAoSMC with aldosterone led to enhanced EGF-induced ERK1/2-phosphorylation and an EGFR-dependent increase in media fibronectin. EGFR promoter reporter gene assay as well as chromatin immunoprecipitation data indicate that MR interacts with the EGFR promoter. With deletion constructs we gained evidence that this interaction takes place between the hMR and the EGFR promoter regions 316-163 (stronger activation site, EC50~1.0 nM) and 163-1 (weaker activation site, EC50~0.7 nM), which do not comprise canonical GRE elements and are not activated by the human glucocorticoid receptor. The interactions require in part the N-terminal domains of MR. ELISA-based transcription factor DNA binding assay with in vitro synthesized hMR suggest direct binding to region 163-1. Our results indicate that aldosterone leads to enhanced EGFR expression via an interaction with the EGFR promoter which is MR-specific and could contribute to the aldosterone-induced increase in fibronectin abundance.




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N. J. Brown
Aldosterone and Vascular Inflammation
Hypertension, February 1, 2008; 51(2): 161 - 167.
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