PT  - JOURNAL ARTICLE
AU  - Marie-Edith Rafestin-Oblin
AU  - Jerome Fagart
AU  - Anny Souque
AU  - Cendrine Seguin
AU  - Marcelle Bens
AU  - Alain Vandewalle
TI  - 11β-Hydroxyprogesterone Acts as a Mineralocorticoid Agonist in Stimulating Na<sup>+</sup> Absorption in Mammalian Principal Cortical Collecting Duct Cells
AID  - 10.1124/mol.62.6.1306
DP  - 2002 Dec 01
TA  - Molecular Pharmacology
PG  - 1306--1313
VI  - 62
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/62/6/1306.short
4100  - http://molpharm.aspetjournals.org/content/62/6/1306.full
SO  - Mol Pharmacol2002 Dec 01; 62
AB  - The binding of mineralocorticoid hormones to the mineralocorticoid receptor is the first step in a cascade of events leading to the stimulation of Na+ reabsorption by renal cortical collecting duct (CCD) principal cells. The agonist properties of mineralocorticoid hormones are linked to contacts between their 21-hydroxyl group and Asn770, a residue of the ligand-binding domain of the human mineralocorticoid receptor (hMR). Here, we investigate whether the presence of a hydroxyl group at position 11, 17, or 20 could also alter the activity of progesterone (P), a mineralocorticoid antagonist without the 21-hydroxyl group. Both 17α-hydroxyprogesterone (17OHP) and 20α-hydroxyprogesterone (20OHP) antagonized the aldosterone-induced trans-activation activity (IC50: 17OHP, 10−7 M; 20OHP, 10−8 M) of the hMR transiently expressed in COS-7 cells lacking steroid receptors. In cultured mouse mpkCCDcl4principal cells, 17OHP and 20OHP also prevented the aldosterone-stimulated amiloride-sensitive component of the short-circuit current (Ams I sc), reflecting Na+ absorption mediated by the epithelial Na+channel (ENaC). In contrast, 11β-hydroxyprogesterone (11OHP) activated the transiently expressed hMR in COS-7 cells in a dose-dependent manner (ED50: 10−8 M) and, like aldosterone, stimulated Ams I sc in mpkCCDcl4 cells. Docking 11OHP within the hMR-ligand-binding domain homology model revealed that the agonist activity of 11OHP is caused by contacts between its 11β-hydroxyl group and Asn770. Furthermore, 11OHP was unable to activate the mutant hMR/N770A, in which Ala is substituted for Asn at position 770. These findings demonstrate that in the absence of the 21-hydroxyl group, the 11β-hydroxyl group can produce the contact with the hMR-Asn770 required for the hMR activation leading to stimulated Na+absorption.