The amino terminus of the human AR is target for corepressor action and antihormone agonism.
Antiandrogens inhibit the ligand-induced transactivation by the androgen receptor (AR) and have a widespread use in the treatment of prostate cancer but their mode of action is not fully understood. Here we show that the ability of the antiandrogen cyproterone acetate (CPA) to inhibit transactivation by the human AR (hAR) involves the corepressor SMRT (silencing mediator for retinoic acid and thyroid hormone receptor). We detect binding of SMRT to hAR when treating with the antiandrogen CPA, but not with the antihormones casodex or hydroxyflutamide. Interestingly, we find that SMRT binds to the N terminus of the hAR. Thereby, SMRT modulates the activity of hAR in receptor-negative CV1 cells. In addition, we have used receptor point mutants that exhibit normal transactivation potential and unchanged partial agonistic activity when treated with CPA, but lack both SMRT binding and SMRT-mediated inhibition of CPA-bound AR. This indicates that mechanisms involved in hAR-mediated transactivation are distinct from antihormone-induced receptor inactivation. Furthermore, we show that treatment of transfected cells with a cAMP analog or coexpression of the catalytic subunit of PKA, known to activate hAR, inhibits the binding of SMRT to the AR. This suggests that the association of SMRT with hAR is regulated at the level of cross-talk mechanisms and that ligand-independent receptor activation is due to corepressor dissociation. Taken together, we provide novel insights in AR regulation, antihormone action, and functional nuclear receptor-corepressor interaction.
Dotzlaw
Helmut
H
Genetisches Institut, Justus-Liebig-University, D-35392 Giessen, Germany.
Moehren
Udo
U
Mink
Sigrun
S
Cato
Andrew C B
AC
Iñiguez Lluhí
Jorge A
JA
Baniahmad
Aria
A
D000726:Androgen Antagonists / Q000494:pharmacology*; D000813:Anilides / Q000494:pharmacology; D000818:Animals; D020134:Catalytic Domain; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017373:Cyproterone Acetate / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D005485:Flutamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000882:Haplorhini; D006801:Humans; D008024:Ligands; D008297:Male; D009570:Nitriles; D056985:Nuclear Receptor Co-Repressor 2; D017354:Point Mutation; D011487:Protein Conformation / Q000187:drug effects; D011944:Receptors, Androgen / Q000187:drug effects* / Q000378:metabolism; D012097:Repressor Proteins / Q000494:pharmacology*; D014105:Tosyl Compounds; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection
D000726:Androgen Antagonists; D000813:Anilides; D004268:DNA-Binding Proteins; D008024:Ligands; C539130:NCOR2 protein, human; D009570:Nitriles; D056985:Nuclear Receptor Co-Repressor 2; D011944:Receptors, Androgen; D012097:Repressor Proteins; D014105:Tosyl Compounds; C014290:hydroxyflutamide; D017373:Cyproterone Acetate; D005485:Flutamide; C053541:bicalutamide; D017868:Cyclic AMP-Dependent Protein Kinases