The last decade has witnessed tremendous progress in the understanding of the mineralocorticoid receptor (MR), its molecular mechanism of action, and its implications for physiology and pathophysiology. After the initial cloning of MR, and identification of its gene structure and promoters, it now appears as a major actor in protein-protein interaction networks. The role of transcriptional coregulators and the determinants of mineralocorticoid selectivity have been elucidated.Targeted oncogenesis and transgenic mouse models have identified unexpected sites of MR expression and novel roles for MR in non-epithelial tissues. These experimental approaches have contributed to the generation of new cell lines for the characterization of aldosterone signaling pathways, and have also facilitated a better understanding of MR physiology in the heart, vasculature, brain and adipose tissues. This review describes the structure, molecular mechanism of action and transcriptional regulation mediated by MR, emphasizing the most recent developments at the cellular and molecular level. Finally, through insights obtained from mouse models and human disease, its role in physiology and pathophysiology will be reviewed. Future investigations of MR biology should lead to new therapeutic strategies, modulating cell-specific actions in the management of cardiovascular disease, neuroprotection, mineralocorticoid resistance, and metabolic disorders. Received July 20th, 2007; Accepted Novemeber 2nd, 2007; Published Novemeber 30th, 2007 | Abbreviations: 11β-HSD2: 11β-hydroxysteroid dehydrogenase 2; ACE: angiotensin converting enzyme; ACTH: adrenocorticotrophic hormone; ADAMTS1: a disintegrin and metalloproteinase with thrombospondin-like motifs 1; adPHA1: autosomal dominant pseudohypoaldosteronism type 1; AF1: activation function 1; AF2: activation function 2; ANF: atrial natriuretic factor; AR: androgen receptor; ASC2: activating signal cointegrator 2; BMP2: bone morphogenetic protein 2; CBP: CREB binding protein; CHIF: channel-inducing factor; CNS: central nervous system; DAXX: death-associated protein 6; DBD: DNA binding domain; EGF-R: epidermal growth factor receptor; Egr-1: early growth response gene-1; ELL: eleven-nineteen lysine-rich leukemia; ENaC: epithelial sodium channel; ERK: extracellular signal-regulated kinase; ET-1: endothelin-1; FAF1: Fas associated factor 1; FLASH: FLICE associated huge; G6PD: glucose-6-phosphate dehydrogenase; GILZ: glucocorticoid-induced leucine zipper protein; GR: glucocorticoid receptor; GRE: glucocorticoid responsive element; HAS2: hyaluronic acid synthase 2; HDAC: histone deacetylase; hMR: human mineralocorticoid receptor; HRE: hormone responsive element; hsp: heat shock protein; KS-WNK1: kidney specific with no lysine [K] kinase 1; LBD: ligand binding domain; LXRβ: liver X receptor β; MAPK: mitogen-activated protein kinase; MDM2: murine double minute gene 2; MR: mineralocorticoid receptor; MRE: mineralocorticoid responsive element; NAD: nicotinamide adenine dinucleotide; NCoR: nuclear receptor core...

Aldosterone is a major regulator of salt balance and blood pressure, exerting its effects via the mineralocorticoid receptor (MR). To analyze the regulatory mechanisms controlling tissue-specific expression of the human MR (hMR) in vivo, we have developed transgenic mouse models expressing the SV40 large T antigen (TAg) under the control of each of the two promoters of the hMR gene (P1 or P2). Unexpectedly, all five P1-TAg founder animals died prematurely from voluminous malignant liposarcomas originating from brown adipose tissue, as evidenced by the expression of the mitochondrial uncoupling protein ucp1, indicating that the proximal P1 promoter was transcriptionally active in brown adipocytes. No such hibernoma occurred in P2-TAg transgenic mice. Appropriate tissue-specific usage of P1 promoter sequences was confirmed by demonstrating the presence of endogenous MR in both neoplastic and normal brown adipose tissue. Several cell lines were derived from hibernomas; among them, the T37i cells can undergo terminal differentiation into brown adipocytes, which remain capable of expressing ucp1 upon adrenergic or retinoic acid stimulation. These cells possess endogenous functional MR, thus providing a new model to explore molecular mechanisms of mineralocorticoid action. Our data broaden the known functions of aldosterone and suggest a potential role for MR in adipocyte differentiation and regulation of thermogenesis.

The mineralocorticoid receptor (MR), a ligand-dependent transcription factor, mediates aldosterone actions in a large variety of tissues. To explore the functional implication of MR in pathophysiology, transgenic mouse models were generated using the proximal human MR (hMR) promoter to drive expression of hMR in aldosterone target tissues. Tissue-specific analysis of transgene expression in two independent transgenic animal (TG) lines by ribonuclease protection assays revealed that hMR is expressed in all mineralocorticoid-sensitive tissues, most notably in the kidney and the heart. TG exhibit both renal and cardiac abnormalities. Enlarged kidneys were histologically associated with renal tubular dilation and cellular vacuolization whose prevalence increased with aging. Renal clearance studies also disclosed a significant decrease in urinary potassium excretion rate in TG. hMRexpressing animals had normal blood pressure but developed mild dilated cardiomyopathy (increased left ventricle diameters and decreased shortening fraction), which was accompanied by a significant increase in heart rate. Differential gene expression analysis revealed a 2-to 5-fold increase in cardiac expression of atrial natriuretic peptide, serum-and glucocorticoid-induced kinase, and early growth response gene 1 as detected by microarrays; renal serum-and glucocorticoid-induced kinase was also induced significantly. Altogether, TG exhibited specific alteration of renal and cardiac functions, thus providing useful pathophysiological models to gain new insights into the tissue-specific mineralocorticoid signaling pathways.

Brain-derived neurotrophic factor (BDNF) is involved in many functions such as neuronal growth, survival, synaptic plasticity and memorization. Altered expression levels are associated with many pathological situations such as depression, epilepsy, Alzheimer’s, Huntington’s and Parkinson’s diseases. Glucocorticoid receptor (GR) is also crucial for neuron functions, via binding of glucocorticoid hormones (GCs). GR actions largely overlap those of BDNF. It has been proposed that GR could be a regulator of BDNF expression, however the molecular mechanisms involved have not been clearly defined yet. Herein, we analyzed the effect of a GC agonist dexamethasone (DEX) on BDNF expression in mouse neuronal primary cultures and in the newly characterized, mouse hippocampal BZ cell line established by targeted oncogenesis. Mouse Bdnf gene exhibits a complex genomic structure with 8 untranslated exons (I to VIII) splicing onto one common and unique coding exon IX. We found that DEX significantly downregulated total BDNF mRNA expression by around 30%. Expression of the highly expressed exon IV and VI containing transcripts was also reduced by DEX. The GR antagonist RU486 abolished this effect, which is consistent with specific GR-mediated action. Transient transfection assays allowed us to define a short 275 bp region within exon IV promoter responsible for GR-mediated Bdnf repression. Chromatin immunoprecipitation experiments demonstrated GR recruitment onto this fragment, through unidentified transcription factor tethering. Altogether, GR downregulates Bdnf expression through direct binding to Bdnf regulatory sequences. These findings bring new insights into the crosstalk between GR and BDNF signaling pathways both playing a major role in physiology and pathology of the central nervous system.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-017-0295-x) contains supplementary material, which is available to authorized users.