Identification and Characterization of a Ligand-Selective Mineralocorticoid Receptor Coactivator

FASEB J. 2014 Oct;28(10):4200-10. doi: 10.1096/fj.13-242479. Epub 2014 Jun 6.

Abstract

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.

Keywords: aldosterone; cortisol; nuclear receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldosterone / metabolism
  • Animals
  • Binding Sites
  • COS Cells
  • Chlorocebus aethiops
  • Humans
  • Hydrocortisone / metabolism
  • Metallothionein / chemistry
  • Metallothionein / genetics
  • Metallothionein / metabolism*
  • Nuclear Receptor Coactivators / chemistry
  • Nuclear Receptor Coactivators / genetics
  • Nuclear Receptor Coactivators / metabolism*
  • Promoter Regions, Genetic
  • Protein Binding
  • Receptors, Mineralocorticoid / genetics
  • Receptors, Mineralocorticoid / metabolism*
  • Substrate Specificity
  • Two-Hybrid System Techniques

Substances

  • Nuclear Receptor Coactivators
  • Receptors, Mineralocorticoid
  • tesmin
  • Aldosterone
  • Metallothionein
  • Hydrocortisone