FKBP5 encodes FK506-binding protein 51, an immunophilin with peptidyl-prolyl isomerase activity that serves as a critical regulator of stress responses and cellular signaling pathways. The protein functions as a co-chaperone modulating glucocorticoid receptor activity and acts as a key component in hypothalamic-pituitary-adrenal (HPA) axis regulation 1. FKBP5 mediates stress hormone system function through complex gene-environment interactions involving genetic variants and epigenetic modifications at glucocorticoid response elements, with childhood trauma-dependent DNA demethylation leading to long-term dysregulation 2. The protein regulates cellular processes through multiple pathways, including inhibition of PI3K/AKT signaling and promotion of NF-κB activation 3. FKBP5 also modulates autophagy and protein clearance mechanisms, with reduced levels leading to enhanced autophagic flux and decreased mutant huntingtin levels 4. Dysregulation of FKBP5 is implicated in stress-related psychiatric disorders including depression and PTSD, with epigenetic changes showing intergenerational transmission effects 56. The protein represents a promising therapeutic target, with FKBP5 antagonists showing potential for treating stress-related disorders and neurodegenerative diseases 74.