Purification of androgen receptors in human sebocytes and hair

Human sebaceous glands (SG) and hair follicles (HF) are target structures in the skin for androgen action. They contain steroid enzymes, capable of transforming weak androgens into the target-tissue-active androgens testosterone (T) and dihydrotestosterone (DHT), which bind to the androgen receptor (AR) to regulate cellular transcription. The AR from HF and SG from human scalp tissue has been purified greater than 86,000 times by phenyl-sepharose, DEAE-sephacel, gel filtration chromatography, and ultrafiltration. Sucrose density gradient analysis and non-denaturing gradient polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE revealed two molecular species of AR, an active form called monomer, capable of binding DHT with great specificity (4S, m = 62,000 Da, Kd = 0.6 nM, Bmax 8260 fmol/micrograms protein), and the other, an inactive form of the monomer called tetramer (10.8S, m = 252,000 Da, Kd = 2.9 nM). The two species are interconvertible, and after purification each appeared as a single band on SDS-PAGE. The conversion of the monomer to the tetramer AR form is influenced by reduced and oxidized glutathione, and possibly by an endogenous disulfide converting factor (DCF). Furthermore, biochemical events in the androgenic signal transduction sequence were shown to be stimulated by androgens via the AR. These include the total nuclear AR content, chromatin binding of AR complexes, and stimulation of RNA polymerase II, thus influencing gene expression, which is important in understanding regulation of HF growth and SG proliferation.