Peptidyl-prolyl cis-trans isomerase FKBP4

FKBP4 is a peptidyl-prolyl cis-trans isomerase and immunophilin protein with dual enzymatic and co-chaperone functions (UniProt: Q02790). It acts as a component of steroid receptor complexes by interacting with heat-shock protein 90, facilitating intracellular trafficking between cytoplasm and nucleus. The protein also regulates neuronal growth cones through TRPC1 channel modulation and controls microtubule dynamics by inhibiting tau-mediated microtubule assembly. Additionally, it may protect mitochondria against oxidative stress.

FKBP4 is broadly expressed across tissues and participates in steroid hormone signaling and cytoskeletal regulation pathways. No baseline disease associations are noted in UniProt.

In Alzheimer's disease, FKBP4 shows ambiguous regulation (Chaparral AD proteomics). Analysis of post-mortem AD brain versus age-matched controls across four subcellular fractions yielded a mean log2 fold-change of 0.39, indicating subtle variability in abundance across fractions. The ambiguous direction suggests differential regulation depending on subcellular compartment, warranting further investigation into its role in AD pathology.