Brain-type creatine kinase has a crucial role in osteoclast-mediated bone resorption.
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-kappaB ligand in cooperation with macrophage colony-stimulating factor. 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.
Chang
Eun-Ju
EJ
Department of Cell and Developmental Biology, Brain Korea 21, School of Dentistry, Seoul National University, 28 Yeongon-Dong, Jongno-gu, Seoul 110-749, Korea.
Ha
Jeongim
J
Oerlemans
Frank
F
Lee
You Jin
YJ
Lee
Soo Woong
SW
Ryu
Jiyoon
J
Kim
Hyung Joon
HJ
Lee
Youngkyun
Y
Kim
Hyun-Man
HM
Choi
Je-Yong
JY
Kim
Jin Young
JY
Shin
Chan Soo
CS
Pak
Youngmi Kim
YK
Tanaka
Sakae
S
Wieringa
Bé
B
Lee
Zang Hee
ZH
Kim
Hong-Hee
HH
D000818:Animals; D015153:Blotting, Western; D001862:Bone Resorption / Q000201:enzymology*; D052276:Creatine Kinase, BB Form / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D051379:Mice; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D010010:Osteoclasts / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D052276:Creatine Kinase, BB Form