A Glucocorticoid-regulating Molecule, Fkbp5, May Interact with Mitogen-activated Protein Kinase Signaling in the Organ of Corti of Mice Cochleae

FKBP5 is a 51-Da FK506-binding protein and member of the immunophilin family involved in controlling the signaling of glucocorticoid receptor from the cytosol to nucleus. Fkbp5 has previously been shown to be expressed in murine cochlear tissue, including the organ of Corti (i.e., the sensory epithelium of the cochlea). Fkbp5 mice as used in this study show hearing loss in the low-frequency (8-kHz) range and click-evoked auditory brainstem response (ABR) threshold compared to wild-type mice. Both Fkbp5 and wild-type mice showed hearing loss at all frequencies and click-ABR thresholds at 24 h and 14 days following acoustic overexposure (AO). Tissues of the organ of Corti were subjected to RNA sequencing and KEGG pathway analysis. In Fkbp5 mice before AO, the mitogen-activated protein kinase (MAPK) signaling pathway was dysregulated compared to wild-type mice. In wild-type mice at 12 h following AO, the most significantly modulated KEGG pathway was the TNF signaling pathway and major MAPK molecules p38 and Jun were involved in the TNF signaling pathway. In Fkbp5 mice at 12 h following AO, the MAPK signaling pathway was dysregulated compared to wild-type mice following AO. In conclusion, Fkbp5 interacts with MAPK signaling in the organ of Corti in mice cochleae.