FKBP4 Antibody #11826

FKBP4 (also known as FKBP52) is a member of the immunophilin protein family. FKBP4 does not demonstrate appreciable immunosuppressant activity typical of this family, despite its ability to bind the immunosuppressants FK506 and rapamycin (1,2). While FKBP4 plays an important role in immunoregulatory gene expression in B and T lymphocytes, its role in regulating steroid hormone receptor signaling and cytoskeletal dynamics is garnering significant interest. FKBP4 contains two peptidyl-prolyl cis-trans isomerase (PPIase) domains, the first of which is implicated in steroid receptor signaling while the second interacts with tubulin and other cytoskeletal components. The maturation of cytoplasmic steroid hormone receptors into a functional conformation requires multiple chaperone and co-chaperone components, including HSP90, p23, and FKBP4 (3,4). FKBP4 interacts with HSP90 to facilitate the folding of androgen, glucocorticoid, and progesterone steroid hormone receptors. Indeed, the functionality of these receptors is impaired in the absence of FKBP4, and research studies have found that null mice demonstrate signs of androgen insensitivity syndrome (5). In addition, FKBP4, which is expressed at high levels in the brain, interacts with hyperphosphorylated Tau and antagonizes Tau's ability to promote microtubule polymerization (6). FKBP4 can also suppress amyloid β toxicity in Drosophila by processing APP (Alzheimer's Amyloid Precursor Protein) to unfold aggregates (7).