FKBP51

FKBP51, encoded by FKBP5, is an Hsp90-associated immunophilin co-chaperone that regulates glucocorticoid receptor sensitivity and steroid receptor signaling^[1]. Mechanistically, FKBP51 integrates into GR:Hsp90 complexes and antagonizes FKBP52-dependent potentiation of glucocorticoid receptor activity^[2]. In cancer signaling models, FKBP51 acts as an Akt-PHLPP scaffold and promotes Akt dephosphorylation, linking FKBP51 biology to chemotherapy response research^[3]. In stress-related disease studies, FKBP5 polymorphisms associate with antidepressant response, depressive episode recurrence, and childhood-abuse-dependent PTSD symptom risk^[4][5]. Compared with FKBP52, FKBP51 remains a key isoform because selective ligand design must overcome their conserved FK1 binding domains and opposing GR functions^[2][6]. For experimental applications, SAFit1 and SAFit2 provide selective FKBP51 inhibition through induced fit, supporting isoform-focused studies of stress behavior, neuroendocrine feedback, and target engagement^[6][7].- FKBP51 research should prioritize GR:Hsp90 regulation, FKBP52 contrast, and stress-related experimental models. - SAFit-class inhibitors enable isoform-selective FKBP51 perturbation but require careful probe validation.