Identification and characterization of a ligand-selective mineralocorticoid receptor coactivator.
The mineralocorticoid receptor (MR) is unique in responding to 2 physiological ligands: aldosterone and cortisol. In epithelial tissues, aldosterone selectivity is determined by the activity of 11β-hydroxysteroid dehydrogenase type 2. In other tissues, cortisol is the primary ligand. To understand the structural determinants of ligand-specific MR activation, we sought to identify coregulatory molecules that interact with the ligand-binding domain (LBD) of the MR. A yeast-2-hybrid (Y2H) kidney cDNA library was screened with the human MR-LBD in the presence of aldosterone and cortisol. One clone, identified as aldosterone-specific in the Y2H assay, exhibited a 7-fold greater response, aldosterone vs. cortisol, in a mammalian-2-hybrid (M2H) assay. This clone encodes the region of the tesmin gene that has 2 leucine-x-x-leucine-leucine (LxxLL) motifs. Full-length tesmin coactivates (>2-fold) MR-mediated transactivation in the presence of aldosterone, but not of cortisol; this specificity is observed with a range of promoters. GST pulldown and coimmunoprecipitation of the MR by tesmin supports a direct interaction, mediated by the 2 LxxLL motifs. Tesmin thus represents a novel MR coregulator that exhibits a differential interaction, providing further evidence of the adoption of ligand-dependent conformations by the MR-LBD.
['Rogerson|Fraser M|FM|', 'Yao|Yi-Zhou|YZ|', 'Young|Morag J|MJ|', 'Fuller|Peter J|PJ|']
D000450:Aldosterone D000818:Animals D001665:Binding Sites D019556:COS Cells D002522:Chlorocebus aethiops D006801:Humans D006854:Hydrocortisone D008668:Metallothionein D056918:Nuclear Receptor Coactivators D011401:Promoter Regions, Genetic D011485:Protein Binding D018161:Receptors, Mineralocorticoid D013379:Substrate Specificity D020798:Two-Hybrid System Techniques
aldosterone cortisol nuclear receptors