Vol.23 No.6

Original Article

Role of FK506 binding protein 5 (FKBP5) in osteoclast differentiation

Authors

Miho Kimura1 , Tatsuo Nagai1 , Reiko Matsushita1 , Atsushi Hashimoto1 , Toshiyuki Miyashita2 , Shunsei Hirohata1

  • Department of Rheumatology and Infectious Diseases, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara Kanagawa, 228-8555, Japan
  • Department of Molecular Genetics, Graduate School of Medical Science, Kitasato University School of Medicine, Sagamihara Kanagawa, 252-0374, Japan
Received:

24 October 2012

Accepted:

29 November 2012

Published online:

21 December 2012

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Abstract

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-jB) 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-jB 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.

Key words

Rheumatoid arthritis, Osteoporosis, Glucocorticoid, RANKL, NF-κB