Mutation of histidine 874 in the androgen receptor ligand-binding domain leads to promiscuous ligand activation and altered p160 coactivator interactions.
The androgen receptor (AR) signaling pathway is a major therapeutic target in the treatment of prostate cancer. The AR functions as a ligand-activated transcription factor in the presence of the cognate hormone ligands testosterone and dihydrotestosterone (DHT). We have characterized a highly conserved sequence at the C-terminal end of helix 10/11 in the ligand-binding domain (LBD), which is prone to receptor point mutations in prostate cancer. This sequence includes threonine 877 that is involved in hydrogen bonding to the D ring of the steroid molecule and leads to promiscuous ligand activation of the AR when mutated to alanine or serine. A second mutation in this region, H874Y, also results in a receptor protein that has broadened ligand-binding specificity, but retains an affinity for DHT (K(d) = 0.77 nm) similar to that of the wild-type receptor. The structure of the mutant LBD, expressed in Escherichia coli, is not dramatically altered compared with the wild-type AR-LBD in the presence of DHT, but shows a modestly increased sensitivity to protease digestion in the absence of hormone. This mutant AR showed wild-type AR-LBD/N-terminal domain interactions, but significantly enhanced binding and transactivation activity with all three members of the p160 family of coactivator proteins. Together, these phenotypic changes are likely to confer a selective advantage for tumor cells in a low androgen environment resulting from hormone therapy.
Duff
Jennifer
J
School of Medical Sciences, Institute of Medical Sciences Building, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, United Kingdom.
McEwan
Iain J
IJ
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D006639:Histidine / Q000235:genetics*; D006801:Humans; D008024:Ligands; D008297:Male; D008969:Molecular Sequence Data; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism; D017354:Point Mutation; D011471:Prostatic Neoplasms / Q000235:genetics*; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011944:Receptors, Androgen / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
D008024:Ligands; D051958:Nuclear Receptor Coactivator 2; D011944:Receptors, Androgen; D015534:Trans-Activators; D006639:Histidine