AMINO-ACID SUBSTITUTIONS IN THE HORMONE-BINDING DOMAIN OF THE HUMAN ANDROGEN RECEPTOR ALTER THE STABILITY OF THE HORMONE-RECEPTOR COMPLEX

We have investigated the basis of androgen resistance in seven unrelat ed individuals with complete testicular feminization or Reifenstein sy ndrome caused by single amino acid substitutions in the hormone-bindin g domain of the androgen receptor. Monolayer-binding assays of culture d genital skin fibroblasts demonstrated absent ligand binding, qualita tive abnormalities of androgen binding, or a decreased amount of quali tatively normal receptor. The consequences of these mutations were exa mined by introducing the mutations by site-directed mutagenesis into t he androgen receptor cDNA sequence and expressing the mutant cDNAs in mammalian cells. The effects of the amino acid substitutions on the bi nding of different androgens and on the capacity of the ligand-bound r eceptors to activate a reporter gene were investigated. Substantial di fferences were found in the responses of the mutant androgen receptors to incubation with testosterone, 5 alpha-dihydrotestosterone, and mib olerone. In several instances, increased doses of hormone or increased frequency of hormone addition to the incubation medium resulted in no rmal or near normal activation of a reporter gene by cells expressing the mutant androgen receptors. These studies suggest that the stabilit y of the hormone receptor complex is a major determinant of receptor f unction in vivo.