Structural and Biochemical Mechanisms for the Specificity of Hormone Binding and Coactivator Assembly by Mineralocorticoid Receptor

Abstract

Mineralocorticoid receptor (MR) controls sodium homeostasis and blood pressure through hormone binding and coactivator recruitment. Here, we report a 1.95 A crystal structure of the MR ligand binding domain containing a single C808S mutation bound to corticosterone and the fourth LXXLL motif of steroid receptor coactivator-1 (SRC1-4). Through a combination of biochemical and structural analyses, we demonstrate that SRC1-4 is the most potent MR binding motif and mutations that disrupt the MR/SRC1-4 interactions abolish the ability of the full-length SRC1 to coactivate MR. The structure also reveals a compact steroid binding pocket with a unique topology that is primarily defined by key residues of helices 6 and 7. Mutations swapping a single residue at position 848 from helix H7 between MR and glucocorticoid receptor (GR) switch their hormone specificity. Together, these findings provide critical insights into the molecular basis of hormone binding and coactivator recognition by MR and related steroid receptors.

Aldosterone Modulates Steroid Receptor Binding to the Endothelin-1 Gene (edn1)

“…However, these antagonists are known to inhibit hormone receptors by altering receptor conformation and disrupting coactivator recruitment (70). Indeed, proper transcriptional coactivation by MR and GR requires the recruitment of SRC-1 (6,71). ChIP analysis revealed that SRC-1 was recruited to the edn1 promoter in the presence of aldosterone.…”

3D model of amphioxus steroid receptor complexed with estradiol

“…Moreover, His-506 has a stabilizing contact with the 17β-hydroxyl on E2. This interaction between histidine and E2 is unique to vertebrate ERs and is not found in other adrenal and sex steroid receptors [27][28][29][30][31] including the lamprey PR and CR [9]. Also stabilizing E2 in amphioxus SR are contacts between the 17β-hydroxyl on E2 and…”

“…Moreover, the SR does not bind 3-ketosteroids. This may be due to the presence of Glu-346 instead of a Gln, which acts as a hydrogen bond donor to the C3-ketone in the PR [31], GR [27], AR [30] and MR [28,29]. Indeed, Ekena et al [32] showed that in human ERα, conversion of Glu-353 to Gln increases the affinity of mutant human ERα for testosterone by 140-fold, providing a parsimonious mechanism for the evolution of receptors that respond to 3-ketosteroids from an ER.…”

NF-YC Functions as a Corepressor of Agonist-bound Mineralocorticoid Receptor

“…Nuclear receptor coregulators are composed of both coactivators and corepressors and are defined as cellular factors, which interact with nuclear receptors to potentiate or attenuate transactivation (5)(6)(7)(8)(9)(10)(11)(12). A subset of coregulators may contribute to tissue and ligand specificity to MR-mediated responses due to their structural and functional diversity.…”

“…Unexpectedly, among over 300 coregulators, the number of MR-interacting coregulators identified to date is very limited (9,13). MR ligand-binding domain interacts strongly with only a few specific coactivator peptides, such as p160 family coacti-* This work was supported by an investigator-initiated research grant from vators, steroid receptor coactivator-1 (SRC-1), SRC-2, and SRC-3, activating signal cointegrator 2, and peroxisome proliferator-activated receptor ␥ coactivator-1␣ in the presence of aldosterone (9,(13)(14)(15). In addition, several coactivators, such as RHA (16), ELL (12), and Ubc9 (17), interact with the MR N-terminal AF-1 domain.…”