Specific hydroxylations determine selective corticosteroid recognition by human glucocorticoid and mineralocorticoid receptors

AbstractThe ligand binding domains of the human mineralocorticoid receptor (hMR) and glucocorticoid receptor (hGR) display a high sequence homology. Aldosterone and cortisol, the major mineralocorticoid and glucocorticoid hormones, are very closely related, leading to the cross-binding of these hormones to both receptors. The present study reports on the mechanism by which hMR and hGR are activated preferentially by their cognate hormones. We found that the ability of corticosteroids to stimulate the receptor’s transactivation function is depending on the stability of the steroid-receptor complexes. In the light of a hMR structural model we propose that contacts through the corticosteroid C21 hydroxyl group are sufficient to stabilize hMR but not hGR and that additional contacts through the C11- and C17-hydroxyl groups are required for hGR

Aldosterone receptor assay in rat kidney cytosol

A method has been developed to measure aldosterone receptors using rat kidney cytosol preparations. Addition of 0.1 M Na molybdate to homogenization buffer markedly diminished receptor inactivation, allowing for more accurate assessment of affinity and total number of receptors. Statistical analysis of Scatchard plots was used to resolve curvilinear plots into high affinity (type I) and a low affinity (type II) components. Aldosterone and deoxycorticosterone compete most effectively for binding to type I sites, whereas dexamethasone competes most effectively for binding to type II sites. Molybdate does not alter the location of the 8.0S peak on density gradient analysis. Assay of type I sites revealed 47.7 +/- 1.7fmol/ml cytosol protein in male adrenalectomized rats. Constant of dissociation (KD) was measured at 5.08 x 10-10 M. Non-adrenalectomized male rats had 24.4 +/- 3.0 fmol/mg protein type I sites. Addition of molybdate to homogenization buffer combined with statistical analysis of curvilinear Scatchard plots allows for accurate and reproducible measurement of high affinity aldosterone receptors in rat kidney cytosol.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23214/1/0000143.pd

The mineralocorticoid receptor: insights into its molecular and (patho)physiological biology

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

Nestorone® as a Novel Progestin for Nonoral Contraception:Structure-Activity Relationships and Brain Metabolism Studies

Nestorone® (NES) is a highly potent non-androgenic progestin being developed for contraception. NES is a synthetic progestin that may possess neuroprotective and myelin regenerative potential as an added health benefits. In receptor transactivation experiments, NES displayed greater potency than progesterone to transactivate the human progesterone receptor (hPR). This was confirmed by docking experiments which revealed that NES adopts the same docking position within the PR ligand-binding domain (LBD) as progesterone and forms additional stabilizing contacts between 17α-acetoxy and 16-methylene groups and PR LBD supporting its higher potency than progesterone. The analogue 13-ethyl NES also establishes similar contacts as NES with Met909, leading to comparable potency as NES. In contrast, NES is not stabilized within the human androgen receptor (hAR)-LBD leading to negligible AR transactivation. Since progesterone acts in the brain by both PR-binding and indirectly via the metabolite allopregnanolone binding to GABA_A receptor (GABA_A_R), we investigated if NES is metabolized to 3α, 5α-tetrahydronestorone (3α, 5α-THNES) in the brain and if this metabolite could interact with GABA_A_R. In female mice, low concentrations of reduced NES metabolites were identified by Gas Chromatography-Mass Spectrometry in both plasma and brain. However, electrophysiological studies showed that 3α, 5α-THNES exhibited only limited activity to enhance GABAAR-evoked responses with WSS-1 cells and did not modulate synaptic GABA_A_Rs of mouse cortical neurons. Thus the inability of reduced metabolite of NES (3α, 5α-THNES) to activate GABA_A_R suggests that the neuroprotective and myelin regenerative effects of NES are mediated via PR binding and not via its interaction with the GABA_A_R

Mécanismes d'activation et d'inactivation du récepteur minéralocorticoïde (approches structurale et fonctionnelle)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF