Androgen Receptor Bioassay for Environmental Monitoring

Target Background

The androgen receptor is activated by binding of either of the androgenic hormones testosterone or dihydrotestosterone. The androgen receptor is most closely related to the progesterone receptor, and progestins in higher dosages can block the androgen receptor. The main function of the androgen receptor is as a DNA binding transcription factor which regulates gene expression; however, the androgen receptor has other functions as well.

Androgen regulated genes are critical for the development and maintenance of the male sexual phenotype. In some cell types testosterone interacts directly with androgen receptors while in others testosterone is converted by 5-alpha-reductase to dihydrotestosterone, an even more potent agonist for androgen receptor activation. Testosterone appears to be the primary androgen receptor activating hormone in the Wolffian duct while dihydrotestosterone is the main androgenic hormone in the urogenital sinus, urogenital tubercle, and hair follicles. Hence testosterone is primarily responsible for the development of male primary sexual characteristics while dihydrotestosterone is responsible for secondary male characteristics.

INDIGO’s Androgen Receptor assay system utilizes proprietary mammalian cells engineered to provide constitutive, high-level expression of full length, unmodified Human Androgen Receptor (NR3C4), a ligand-dependent transcription factor commonly referred to as AR.

INDIGO’s Reporter Cells include the luciferase reporter gene functionally linked to a bona fide AR-responsive promoter. Therefore, quantifying changes in luciferase expression in the treated reporter cells provides a sensitive surrogate measure of the changes in AR activity. Luciferase gene expression occurs after ligand-bound AR undergoes nuclear translocation, DNA binding, recruitment, and assembly of the co-activators and accessory factors required to form a functional transcription complex, culminating in expression of the target gene. Unlike some other cell-based assay strategies, the readout from INDIGO’s reporter cells demands the same orchestration of all intracellular molecular interactions and events that can be expected to occur in vivo.

The principle application of this assay product is in the screening of test samples to quantify functional activities, either agonist or antagonist, that they may exert against the human androgen receptor.