FKBP5 and post-traumatic stress disorder: For example, SNPs in the FKBP5 gene that encodes the co-chaperone heat shock protein 90 (HSP90), which regulates cortisol binding to glucocorticoid receptors, have been linked to a heightened risk for developing psychopathologies such as PTSD, as they alter glucocorticoid sensitivity and stress hormone regulation [111].