Structural and Biochemical Mechanisms for the Specificity of Hormone Binding and Coactivator Assembly by Mineralocorticoid Receptor
[MCR_HUMAN] Defects in NR3C2 are a cause of pseudohypoaldosteronism 1, autosomal dominant (PHA1A) [MIM:177735]. A salt wasting disease resulting from target organ unresponsiveness to mineralocorticoids. PHA1A is a mild form characterized by target organ defects confined to kidney. Patients may present with neonatal renal salt wasting with hyperkalaemic acidosis despite high aldosterone levels. These patients improve with age and usually become asymptomatic without treatment.     Defects in NR3C2 are a cause of early-onset hypertension with severe exacerbation in pregnancy (EOHSEP) [MIM:605115]. Inheritance is autosomal dominant. The disease is characterized by the onset of severe hypertension before the age of 20, and by suppression of aldosterone secretion.    [NCOA1_HUMAN] Note=A chromosomal aberration involving NCOA1 is a cause of rhabdomyosarcoma. Translocation t(2;2)(q35;p23) with PAX3 generates the NCOA1-PAX3 oncogene consisting of the N-terminus part of PAX3 and the C-terminus part of NCOA1. The fusion protein acts as a transcriptional activator. Rhabdomyosarcoma is the most common soft tissue carcinoma in childhood, representing 5-8% of all malignancies in children.
[MCR_HUMAN] Receptor for both mineralocorticoids (MC) such as aldosterone and glucocorticoids (GC) such as corticosterone or cortisol. Binds to mineralocorticoid response elements (MRE) and transactivates target genes. The effect of MC is to increase ion and water transport and thus raise extracellular fluid volume and blood pressure and lower potassium levels. [NCOA1_HUMAN] Nuclear receptor coactivator that directly binds nuclear receptors and stimulates the transcriptional activities in a hormone-dependent fashion. Involved in the coactivation of different nuclear receptors, such as for steroids (PGR, GR and ER), retinoids (RXRs), thyroid hormone (TRs) and prostanoids (PPARs). Also involved in coactivation mediated by STAT3, STAT5A, STAT5B and STAT6 transcription factors. Displays histone acetyltransferase activity toward H3 and H4; the relevance of such activity remains however unclear. Plays a central role in creating multisubunit coactivator complexes that act via remodeling of chromatin, and possibly acts by participating in both chromatin remodeling and recruitment of general transcription factors. Required with NCOA2 to control energy balance between white and brown adipose tissues. Required for mediating steroid hormone response. Isoform 2 has a higher thyroid hormone-dependent transactivation activity than isoform 1 and isoform 3.      
Publication Abstract from PubMed
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.
Structural and biochemical mechanisms for the specificity of hormone binding and coactivator assembly by mineralocorticoid receptor.,Li Y, Suino K, Daugherty J, Xu HE Mol Cell. 2005 Aug 5;19(3):367-80. PMID:16061183
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