Specificity of ligand-dependent androgen receptor stabilization: receptor domain interactions influence ligand dissociation and receptor stability.

Abstract

The molecular basis for the different physiological effects of testosterone (T) and dihydrotestosterone (DHT) was investigated using recombinantly expressed wild-type and mutant androgen receptor (AR). Rates of androgen dissociation from nuclear and cytoplasmic AR were compared with hormone- and concentration-dependent receptor degradation rates. T dissociates from AR 3 times faster than DHT or methyltrienolone (R1881) and is less effective in stabilizing the receptor. Analysis of AR deletion mutants and AR/glucocorticoid receptor chimeras indicates that the AR NH2-terminal domain has a specific role in stabilizing the receptor by slowing the rate of ligand dissociation and AR degradation. Amino acid mutations that abolish receptor dimerization, nuclear localization, or DNA-binding activity have no significant effect on androgen dissociation or AR degradation. A naturally occurring steroid-binding domain mutation (Val889 to Met) that causes androgen insensitivity, but does not alter equilibrium androgen binding affinity, lowered the androgen-binding capacity as a result of increased rates of androgen dissociation and AR degradation. Thus, AR stabilization and function require prolonged receptor occupancy with androgen, with a similar extent of stabilization observed at higher concentrations of faster dissociating androgens and lower concentrations of slower dissociating androgens. Retention of receptor-bound androgen is enhanced by an interaction between the AR NH2-terminal and steroid-binding domains. The ligand specificity and concentration dependence of receptor stabilization provide an explanation for physiological differences in the actions of T and DHT.

Identification of genes targeted by the androgen and PKA signaling pathways in prostate cancer cells

“…In the control transfection with scramble siRNA (ARc), R1881 increased levels of AR protein ( Figure 4a). This was consistent with ligand stabilizing the AR protein to increase levels as previously reported (Kemppainen et al, 1992;Zhou et al, 1995). FSK did not significantly alter the levels of AR protein (P ¼ 0.091).…”

Androgen receptor phosphorylation and stabilization in prostate cancer by cyclin-dependent kinase 1

“…Although Cdk1 inhibitors could suppress both Ser-81 phosphorylation and AR transcriptional activity, previous transfection studies in AR-negative cell lines have shown that Ser-81 is not required for AR transcriptional activity (13,35). We similarly found that transfected ARs and an S81A mutant had comparable levels of androgen-stimulated transcriptional activity in HeLa cells, as assessed on an ARE 4 -luciferase reporter gene (Fig.…”

Tea polyphenols down-regulate the expression of the androgen receptor in LNCaP prostate cancer cells

“…It is well recognized that androgens can enhance AR protein levels by increasing the half-life, as well as by stimulating the phosphorylation Zhou et al, 1995;Kemppainen et al, 1992;Krongrad et al, 1991) of the AR. It has been shown that agonistbound AR is more resistant to in vitro proteolytic digestion than an unbound AR, indicating a conformational change of the AR induced by androgens.…”