FKBP5 Gene

FK506-binding protein 5 (FKBP5) is an immunophilin protein, which means it plays a role in regulating the immune system. FKBP5 is not preferentially expressed in the brain but has been identified as a candidate gene for major depressive disorder because it seems to interact with the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is a complex biological mechanism that controls the body’s reaction to stress. It is strongly linked to the neurophysiology of depression. Binder and colleagues (2004) found that a functional polymorphism of FKBP5 correlated significantly with the response of depressed patients to antidepressants. Individuals with this polymorphism showed less HPA axis hyperactivity (a hallmark of major depression) during the depressive episode.