Regulation of Steroid Hormone Receptor Function By the 52-kDa FK506-Binding Protein (FKBP52)

The large FK506-binding protein FKBP52 has been characterized as an important positive regulator of androgen, glucocorticoid and progesterone receptor signaling pathways. FKBP52 associates with receptor–Hsp90 complexes and is proposed to have roles in both receptor hormone binding and receptor subcellular localization. Data from biochemical and cellular studies have been corroborated in whole animal models as  fkbp52 -deficient male and female mice display characteristics of androgen, glucocorticoid and/or progesterone insensitivity. FKBP52 receptor specificity and the specific phenotypes displayed by the  fkbp52 -deficient mice have firmly established FKBP52 as a promising target for the treatment of a variety of hormone-dependent diseases. Recent studies demonstrated that the FKBP52 FK1 domain and the proline-rich loop within this domain are functionally important for FKBP52 regulation of receptor function. Based on these data, efforts are currently underway to target the FKBP52 FK1 domain and the proline-rich loop with small molecule inhibitors.