title: CCN2 enhances RANKL-induced osteoclast differentiation via direct binding to RANK and OPG.
abstract: CCN family protein 2/connective tissue growth factor (CCN2/CTGF) is a multi-potent factor for mesenchymal cells such as chondrocytes, osteoblasts, osteoclasts, and endothelial cells. CCN2 is also known as a modulator of other cytokines and receptors via direct molecular interactions with them. We screened additional factors binding to CCN2 and found receptor activator of NF-kappa B (RANK) as one of them. RANK is also known as TNF-related activation-induced cytokine (TRANCE) receptor, and its signaling plays a critical role in osteoclastogenesis. Notable affinity between CCN2 and RANK was confirmed by using surface plasmon resonance (SPR) analysis. In fact, CCN2 enhanced the RANK-mediated signaling, such as occurs in NF-kappa B, p38 and JNK pathways, in pre-osteoclastic RAW264.7 cells; whereas CCN2 had no influence on RANK-RANK ligand (RANKL) binding. Moreover, CCN2 also significantly bound to osteoprotegerin (OPG), which is a decoy receptor of RANKL. Of note, OPG markedly inhibited the binding between CCN2 and RANK; and CCN2 canceled the inhibitory effect of OPG on osteoclast differentiation. These findings suggest CCN2 as a candidate of the fourth factor in the RANK/RANKL/OPG system for osteoclastogenesis, which regulates OPG and RANK via direct interaction.
authors.affiliation: Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School, Okayama, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Aoyama
authors.affiliation: Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School, Okayama, Japan; Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Science, Okayama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kubota
authors.affiliation: Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School, Okayama, Japan.
authors.forename: Hany Mohamed
authors.initials: HM
authors.lastname: Khattab
authors.affiliation: Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Science, Okayama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishida
authors.affiliation: Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School, Okayama, Japan; Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Science, Okayama, Japan. Electronic address: takigawa@md.okayama-u.ac.jp.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Takigawa
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D055513:Connective Tissue Growth Factor / Q000502:physiology*; D051379:Mice; D010010:Osteoclasts / Q000166:cytology*; D053244:Osteoprotegerin / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism / Q000502:physiology*; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism*; D015398:Signal Transduction; D020349:Surface Plasmon Resonance
chemical_list: C526318:CCN2 protein, mouse; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D055513:Connective Tissue Growth Factor
keywords: CCN2 family protein 2 (CCN2); Osteoclast; Osteoprotegerin (OPG); RANK ligand (RANKL); Receptor activator of nuclear factor-κB ligand (RANK)