Isolation and characterization of androgen receptor mutant, AR(M749L), with hypersensitivity to 17-β estradiol treatment

Abstract

Estrogens, primarily 17β-estradiol (E2), may play important roles in male physiology via the androgen receptor (AR). It has already been shown that E2 modulates AR function in LNCaP prostate cancer cells and xenograft CWR22 prostate cancer tissues. Using a molecular model of E2 bound-AR-ligand binding domain (LBD) and employing site-directed mutagenesis strategies, we screened several AR mutants that were mutated at E2-AR contact sites. We found a mutation at amino acid 749, AR(M749L), which confers AR hypersensitivity to E2. The reporter assays demonstrate that E2 can function, like androgen, to induce AR(M749L) transactivation. This E2-induced AR mutant transactivation is a direct effect of the AR(M749L), because the transactivation was blocked by antiandrogens. The hypersensitivity of AR(M749L) to E2 is not due to increased affinity of AR(M749L) for E2, rather it may be due to the existence of the proper conformation necessary to maintain E2 binding to the AR-LBD long enough to result in E2-induced transactivation. AR(M749L) transactivation can be further enhanced in the presence of AR coregulators, such as ARA70 and SRC-1. Therefore, amino acid 749 may represent an important site within the AR-LBD that is involved in interaction with E2 that, when mutated, allows E2 induction of AR transactivation.