Immunophilin protein with PPIase and co-chaperone activities (By similarity). Component of unliganded steroid receptors heterocomplexes through interaction with heat-shock protein 90 (HSP90). May play a role in the intracellular trafficking of heterooligomeric forms of steroid hormone receptors between cytoplasm and nuclear compartments (By similarity). The isomerase activity controls neuronal growth cones via regulation of TRPC1 channel opening. Acts also as a regulator of microtubule dynamics by inhibiting MAPT/TAU ability to promote microtubule assembly.
Specificity
Natural and recombinant Human Peptidyl-prolyl cis-trans isomerase FKBP4
Homodimer. Associates with HSP90 and HSP70 in unactivated steroid hormone receptor complexes. Also interacts with peroxisomal phytanoyl-CoA alpha-hydroxylase (PHYH). Interacts with HSF1 in the HSP90 complex. Associates with tubulin (By similarity). Interacts with MAPT/TAU (By similarity). Interacts with NR3C1 and dynein (By similarity). Interacts (via TPR domain) with S100A1, S100A2 and S100A6; the interaction is Ca(2+) dependent. Interaction with S100A1 and S100A2 (but not with S100A6) leads to inhibition of FKBP4-HSP90 interaction.