Glucocorticoid receptor plays an indispensable role in mineralocorticoid receptor-dependent transcription in GR-deficient BE(2)C and T84 cells in vitro.
The mineralocorticoid receptor (MR) plays an important functional role in the central nervous system; however, the molecular mechanism of MR-dependent gene expression is not entirely clear. In this study, we examined the MR-dependent transcriptional regulation using a human neuronal cell line BE(2)C and an MR/GR-dependent reporter gene (HRE-luciferase) in vitro. Western blot analysis revealed that the cell line expresses MR but not glucocorticoid receptor (GR). In this experimental condition, unexpectedly, the MR-specific ligand aldosterone did not induce HRE-dependent transcription in a native or MR-overexpressed condition, whereas significant transcriptional induction by aldosterone was observed when the GR was co-expressed. The effect of aldosterone was completely inhibited by the MR antagonist spironolactone, indicating an MR-dependent effect. We found similar results in T84 colonic cells expressing neither MR nor GR, such that the aldosterone effect was obtained only when both receptors were co-expressed. The co-operative effect of GR was not obvious with the dimer-deficient mutant GR. Finally, the above findings were reproducible with different promoters containing HRE such as ENaC and MMTV. These results suggest that GR plays an indispensable role in MR-dependent transcription, possibly by forming a MR/GR heterodimer or by acting as a co-activator of MR/MR homodimer.
Tsugita
Makoto
M
Department of Endocrinology, Metabolism, and Nephrology, Kochi Medical School, Kochi University, Kohasu, Oko-cho, Nankoku 783-8505, Japan.
Iwasaki
Yasumasa
Y
Nishiyama
Mitsuru
M
Taguchi
Takafumi
T
Shinahara
Masayuki
M
Taniguchi
Yoshinori
Y
Kambayashi
Machiko
M
Nishiyama
Akira
A
Gomez-Sanchez
Celso E
CE
Terada
Yoshio
Y
Hashimoto
Kozo
K
D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003907:Dexamethasone / Q000494:pharmacology; D019281:Dimerization; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D011965:Receptors, Glucocorticoid / Q000172:deficiency / Q000378:metabolism*; D018161:Receptors, Mineralocorticoid / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D000450:Aldosterone; D003907:Dexamethasone