Structure-function analysis of three widely dispersed point mutations in the hormone-binding domain of the human androgen receptor

Three point mutations have been found in the hormone-binding domain (HBD) of the human androgen receptor (hAR): one in the N-terminal end (Ile663Asn in a family with partial androgen insensitivity syndrome (PAIS)); one in the middle, (Leu820Val in a family with PAIS); and one in the C-terminal end (Pro903Ser, in a family with complete AIS). The positions 663 and 903 were the most terminal mutation sites in the HBD found to date. The three mutant hARs have been previously characterized biochemically in genital skin fibroblasts. In the family with the Leu820Val substitution, the mother and the grandmother were found to be carriers for the same mutation. To prove their pathogenicity, each of the three mutations has been reproduced in an hAR expression vector that was transfected into COS-1 cells. In COS-1 cells, the complexes from Pro903Ser and Leu820Val had: increased thermolability; increased dissociation rates; decreased affinity; and abnormal transactivation. There was a hierarchy in the severity of the mutations expressed in kinetic and transactivation assays that correlated with the severity of the clinical phenotype. The pathogenicity of the Pro903Ser and the Leu820Val mutations was thereby confirmed. In COS-1 cells, the AR with Ile663Asn had normal thermolability, normal dissociation rates, and normal transactivation, but a decreased affinity. Although this sequence alteration has only been found in a PAIS patient, its pathogenicity is not considered to be proven. More sensitive assays are needed for this purpose