A single amino acid mutation of ala-773 in the mineralocorticoid receptor confers agonist properties to 11beta-substituted spirolactones.
Sequence analysis revealed a strong homology between the ligand-binding domain (LBD) of the human mineralocorticoid receptor (hMR) and glucocorticoid receptor (hGR). Nevertheless, steroids with bulky C11-substituents bind to hGR, unlike hMR. In this report, a mutant hMR, in which the residue Ala-773 facing the C11 steroid position was replaced by a glycine (A773G), was assayed for its capacity to bind steroids, to interact with receptor coactivators, and to stimulate transcription. The capacity of A773G to bind aldosterone and C11-substituted spirolactones was the same as that of the wild-type receptor. The agonist properties of aldosterone, as well as the antagonist feature of compounds bearing a 11beta-allenyl group and a C17-ketone function, remain unchanged. In contrast, C11-substituted steroids with a 17gamma-lactonic ring displayed antagonist properties with hMR and acted as potent agonists with A773G. An agonist-dependent hMR interaction with SRC-1 was observed for both the wild-type and the mutant receptors. The hMR activation process is discussed in the light of the hMR-LBD homology model based on the structural data of the human progesterone receptor LBD.
Auzou
G
G
Institut National de la Santé et de la Recherche Médicale U439, Montpellier, France.
Fagart
J
J
Souque
A
A
Hellal-Lévy
C
C
Wurtz
J M
JM
Moras
D
D
Rafestin-Oblin
M E
ME
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D051548:Histone Acetyltransferases; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D056920:Nuclear Receptor Coactivator 1; D018161:Receptors, Mineralocorticoid / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013148:Spironolactone / Q000031:analogs & derivatives / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
D018161:Receptors, Mineralocorticoid; D014157:Transcription Factors; D013148:Spironolactone; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1; D000409:Alanine