Abstract
We demonstrate that endogenous phosphatases are active in cytosolic and nuclear androgen receptor fractions from the rat ventral prostate. Under our androgen binding assay conditions, the effect of acid phosphatase inhibitors (sodium fluoride, tartaric acid, sodium orthovanadate) on the endogenous phosphatases could be correlated with an increase in dihydrotestosterone (DHT) binding to fractions of partially purified cytosolic androgen receptor. In contrast, tetramisole, an alkaline phosphatase inhibitor, did not alter the binding of DHT to the same receptor fraction. Immunoprecipitation of androgen receptor fractions with polyclonal anti-phosphotyrosine antibody resulted in the recovery of [3H]-DHT binding activity from nuclear receptor fractions and partially purified cytosolic receptor fractions prepared from 20- to 24-hr castrated rats. In control fractions depleted of androgen receptor, negligible levels of binding activity were recovered following immunoprecipitation with the antibody. Therefore, acid phosphatases may be acting on phosphotyrosyl residues of the androgen receptor, thus playing a role in the dephosphorylation and inactivation of the androgen receptor.
Published Version
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