FKBP4, also known as FK506-binding protein 4 or FKBP52, is a member of the FK506-binding protein (FKBP) family, which are peptidyl-prolyl cis-trans isomerases (PPIases) that function as molecular chaperones. FKBP4 is primarily found in the cytoplasm and nucleus of cells and is involved in regulating protein folding, trafficking, and signal transduction. One of the primary functions of FKBP4 is its role as a co-chaperone for steroid hormone receptors, including the glucocorticoid receptor (GR) and androgen receptor (AR). FKBP4 interacts with these receptors in the cytoplasm, facilitating their proper folding and assembly into functional complexes with heat shock proteins (HSPs). Upon ligand...