• Molecules and Cells
• /
• v.39 no.4
• /
• pp.316-321
• /
• 2016

The receptor activator of nuclear factor ${\kappa}B$ (RANK) and its ligand RANKL are key regulators of osteoclastogenesis and well-recognized targets in developing treatments for bone disorders associated with excessive bone resorption, such as osteoporosis. Our previous work on the structure of the RANK-RANKL complex revealed that Loop3 of RANK, specifically the non-canonical disulfide bond at the tip, performs a crucial role in specific recognition of RANKL. It also demonstrated that peptide mimics of Loop3 were capable of interfering with the function of RANKL in osteoclastogenesis. Here, we reported the structure-based design of a smaller peptide with enhanced inhibitory efficiency. The kinetic analysis and osteoclast differentiation assay showed that in addition to the sharp turn induced by the disulfide bond, two consecutive arginine residues were also important for binding to RANKL and inhibiting osteoclastogenesis. Docking and molecular dynamics simulations proposed the binding mode of the peptide to the RANKL trimer, showing that the arginine residues provide electrostatic interactions with RANKL and contribute to stabilizing the complex. These findings provided useful information for the rational design of therapeutics for bone diseases associated with RANK/RANKL function.

• BMB Reports
• /
• v.45 no.3
• /
• pp.171-176
• /
• 2012

Receptor activator of NF-${\kappa}B$ ligand (RANKL) triggers the differentiation of bone marrow-derived monocyte/macrophage precursor cells (BMMs) of hematopoietic origin into osteoclasts through the activation of mitogen-activated protein (MAP) kinases and transcription factors. Recently, reactive oxygen species (ROS) and antioxidant enzymes were shown to be closely associated with RANKL-mediated osteoclast differentiation. Although glutaredoxin2 (Glrx2) plays a role in cellular redox homeostasis, its role in RANKL-mediated osteoclastogenesis is unclear. We found that Glrx2 isoform b (Glrx2b) expression is induced during RANKLmediated osteoclastogenesis. Over-expression of Glrx2b strongly enhanced RANKL- mediated osteoclastogenesis. In addition, Glrx2b-transduced BMMs enhanced the expression of key transcription factors c-Fos and NFATc1, but pre-treatment with SB203580, a p38-specific inhibitor, completely blocked this enhancement. Conversely, down-regulation of Glrx2b decreased RANKL- mediated osteoclastogenesis and the expression of c-Fos and NFATc1 proteins. Also, Glrx2b down-regulation attenuated the RANKL-induced activation of p38. Taken together, these results suggest that Glrx2b enhances RANKL-induced osteoclastogenesis via p38 activation.

• The korean journal of orthodontics
• /
• v.35 no.4 s.111
• /
• pp.262-274
• /
• 2005

Tooth movement is a result of mutual physiologic responses between the periodontal ligament and alveolar bone stimulated by mechanical strain. The PDL cell and osteoblast are known to have an influence on bone formation by controlling collagen synthesis and alkaline phosphatase activation. Moreover. recent studies have shown that the PDL cell and osteoblast release osteoprotegerin (OPG) and the receptor activator of nuclear factor ぉ ligand (RANKL) to control the level of osteoclast differentiation and activation which in turn influences bone resorption. In this study. progressively increased, continuous tensional force was applied to PDL cells. The objective was to find out which kind of biochemical reactions occur after tensional force application and to illuminate the alveolar bone resorption and apposition mechanism. Continuous and progressively increased tensile force was applied to PDL cells cultured on a petriperm dish with a flexible membrane The amount of $PGE_2$ and ALP synthesis were measured after 1, 3, 0 and 12 hours of force application. Secondly RT-PCR analysis was carried out for OPG and RANKL which control osteoclast differentiation and MMP-1 -8, -9, -13 aud TIMP-1 which regulate the resolution of collagen and resorption of the osteoid layer According to the results. we concluded that progressively increased, concluded force application to human PDL cells reduces $PGE_2$ synthesis, and increases OPG mRNA expression.

• International Journal of Oral Biology
• /
• v.38 no.1
• /
• pp.37-42
• /
• 2013

Receptor activator of NF-${\kappa}B$ ligand (RANKL) is an essential cytokine for osteoclast differentiation, activation and survival. T lymphocytes such as $T_{17}$ cells, a subset of T helper cells that produce IL-17, play an important role in rheumatoid arthritic bone resorption by producing inflammatory cytokines and RANKL. It has not yet been clearly elucidated how T cell activation induces RANKL expression. T cell receptor activation induces the activation of nuclear factor of activated T cell (NFAT) and expression of its target genes. In this study, we examined the role of NFAT in T cell activation-induced RANKL expression. EL-4, a murine T lymphocytic cell line, was used. When T cell activation was induced by phorbol 12-myristate 13-acetate (PMA) and ionomycin, RANKL expression increased in a time-dependent manner. In the presence of cyclosporin, an inhibitor of NFAT activation, this PMA/ionomycin-induced RANKL expression was blocked. Overexpression of either NFATc1 or NFATc3 induced RANKL expression. Chromatin immunoprecipitation results demonstrated that PMA/ionomycin treatment induced the binding of NFATc1 and NFATc3 to the mouse RANKL gene promoter. These results suggest that NFATc1 and NFATc3 mediates T cell receptor activation-induced RANKL expression in T lymphocytes.