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Published on: June 16, 2022
Role of FK506 binding protein 5 (FKBP5) in osteoclast differentiation
Miho Kimura1, Tatsuo Nagai, Reiko Matsushita
1Department of Rheumatology and Infectious Diseases, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa, 228-8555, Japan.
Objectives:
We previously disclosed the enhanced expression of FK506 binding protein 5 (FKBP5) messenger RNA (mRNA) in bone marrow (BM) CD34(+) cells in rheumatoid arthritis (RA), in which systemic osteoporosis takes place. Since BM CD34(+) cells are precursors of osteoclasts, it is possible that FKBP5 overexpression might lead to osteoporosis by affecting osteoclastogenesis. We therefore explore the influences of FKBP5 in osteoclast differentiation.
Methods:
Stable transfectants of RAW264.7 overexpressing murine FKBP5 gene were established. Osteoclast differentiation was induced by receptor activator of nuclear factor kappa B (NF-κB) ligand and was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and pit formation assay.
Results:
FKBP5 transfectants of RAW264.7 generated higher numbers of TRAP-positive multinucleated cells with increased activity of pit formation on calcium phosphate-coated culture slides than mock transfectants. The enhancement of osteoclast differentiation of FKBP5 transfectants was only partially inhibited by N-acetyl L-cysteine. Finally, glucocorticoid enhanced FKBP5 mRNA expression as well as osteoclast differentiation of RAW264.7 cells in a dose-dependent manner.
Conclusions:
These results indicate that FKBP5 promotes osteoclast differentiation by a mechanism distinct from NF-κB activation. Moreover, the data suggest that FKBP5 might play a role in bone destruction and development of osteoporosis in RA as well as in glucocorticoid-induced osteoporosis.
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