Eun-Ju Chang
1, Jeongim Ha
1, Frank Oerlemans
2, You Jin Lee
3, Soo Woong Lee
4, Jiyoon Ryu
1, Hyung Joon Kim
1, Youngkyun Lee
1, Hyun-Man Kim
1, Je-Yong Choi
5, Jin Young Kim
6, Chan Soo Shin
7, Youngmi Kim Pak
8, Sakae Tanaka
9, Bé Wieringa
2, Zang Hee Lee
1 & Hong-Hee Kim
1
Osteoclasts differentiate from precursor cells of the monocyte-macrophage lineage and subsequently become activated to be competent for bone resorption through programs primarily governed by receptor activator of nuclear factor-
B ligand in cooperation with macrophage colony-stimulating factor
1, 2, 3. Proteins prominently expressed at late phases of osteoclastogenesis and with a supportive role in osteoclast function are potential therapeutic targets for bone-remodeling disorders. In this study, we used a proteomics approach to show that abundance of the brain-type cytoplasmic creatine kinase (Ckb) is greatly increased during osteoclastogenesis. Decreasing Ckb abundance by RNA interference or blocking its enzymatic activity with a pharmacological inhibitor, cyclocreatine, suppressed the bone-resorbing activity of osteoclasts grown
in vitro via combined effects on actin ring formation, RhoA GTPase activity and vacuolar ATPase function. Activities of osteoclasts derived from
Ckb-/- mice were similarly affected.
In vivo studies showed that
Ckb-/- mice were better protected against bone loss induced by ovariectomy, lipopolysaccharide challenge or interleukin-1 treatment than wild-type controls. Furthermore, administration of cyclocreatine or adenoviruses harboring
Ckb small hairpin RNA attenuated bone loss in rat and mouse models. Our findings establish an important role for Ckb in the bone-resorbing function of osteoclasts and underscore its potential as a new molecular target for antiresorptive drug development.
1. Department of Cell and Developmental Biology, Brain Korea 21, School of Dentistry, Seoul National University, 28 Yeongon-Dong, Jongno-gu, Seoul 110-749, Korea.
2. Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
3. Research Division, Jeonnam Biotechnology Research Center, 121 Naepyeongri, Hwasun-gun, Jeollanamdo 519-801, Korea.
4. Department of Microbiology, Center for Viral Disease Research, College of Medicine, Inje University, 633-165 Gaegeum-Dong, Busanjin-gu, Busan 614-735, Korea.
5. Department of Biochemistry and Cell Biology, School of Medicine and Skeletal Diseases Genome Research Center, Kyungpook National University, 101 Dong-in Dong, Jung-gu, Daegu 700-422, Korea.
6. Korea Basic Science Institute, 52 Eoeun-Dong, Yusung-gu, Daejeon 305-333, Korea.
7. Department of Internal Medicine, Seoul National University College of Medicine, 28 Yeongon-Dong, Jongno-gu, Seoul 110-744, Korea.
8. Age-related and Brain Disease Research Center, Department of Nanopharmaceutical and Life Sciences, Kyung Hee University, 1 Hoegi-Dong, Dongdaemun-gu, Seoul 130-701, Korea.
9. Department of Orthopaedic Surgery, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-gu, Tokyo 113-0033, Japan.
Correspondence to: Hong-Hee Kim1
Correspondence to: Bé Wieringa2