A and B forms of the androgen receptor are present in human genital skin fibroblasts.

Two forms of the androgen receptor (AR) protein (apparent molecular masses, approximately 110 kDa and approximately 87 kDa) are present in human genital skin fibroblasts. The 87-kDa isoform (AR-A) contains an intact C terminus but lacks the normal N terminus found in the 110-kDa isoform (AR-B). AR-A is the same size as the mutant form of AR produced in fibroblasts from an androgen-resistant individual (R776) by initiation of AR synthesis at the internal Met-188 residue of AR-B. The ratio of AR-B to AR-A in fibroblasts derived from normal individuals is approximately 10:1. The AR isoforms detected in these experiments resemble the A and B forms of the human progesterone receptor, which also are encoded by a single gene and differ by the absence or presence of an N-terminal segment. The A and B forms of the human progesterone receptor differ in their ability to activate target genes and are regulated differently in various types of cells. The identification of similar forms of human AR raises the possibility that AR-A and AR-B also subserve different functions.