title: Identification and characterization of anti-osteoclastogenic peptides derived from the cytoplasmic tail of receptor activator of nuclear factor kappa B.
abstract: Pathological bone resorption by osteoclasts is primarily treated with bisphosphonates. Because the administration of bisphosphonates is associated with a risk for multiple adverse symptoms, a precise understanding of the mechanisms underlying osteoclastogenesis is required to develop drugs with minimal side-effects. Osteoclastogenesis depends on receptor activator of nuclear factor kappa B (RANK) signaling mediated by TRAF6. We previously identified a highly conserved domain in the cytoplasmic tail of RANK (HCR), which did not share any significant homology with other proteins and was essential for osteoclastogenesis. HCR acts as a platform for the formation of Gab2- and Vav3-containing signal complexes, and ectopic expression of the HCR peptide inhibits osteoclastogenesis. Here, we uncover the mechanisms of HCR peptide-mediated inhibition of osteoclastogenesis. Expression of either the amino- or carboxyl-terminal half of the HCR peptide (N- or C-peptide) independently inhibited RANK signaling prior to cell-cell fusion. In contrast, expression of the GY-peptide, which is a part of the C-peptide, did not significantly affect prefusion RANK signaling, but did inhibit cell-cell fusion to prevent formation of multinucleated mature osteoclasts. Moreover, Gab2, which is involved in RANK signaling by binding TRAF6, bound the C-peptide but not the N-peptide, suggesting that the C- and the N-peptides sequester TRAF6 in a Gab2-dependent and Gab2-independent manner, respectively. In contrast, the GY-peptide did not bind Gab2 but could bind Vav3, which mediates signaling for cell-cell fusion. Collectively, we propose that the HCR peptide inhibits osteoclastogenesis through two modes of action-inhibition of (1) prefusion RANK signaling and (2) cell-cell fusion by blocking TRAF6- and Vav3-mediated signaling, respectively.
authors.affiliation: Division of Cellular and Molecular Biology, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Shirokane-dai, Minato-ku, Tokyo, 108-8639, Japan.
authors.forename: Yuu
authors.initials: Y
authors.lastname: Taguchi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kiga
authors.forename: Jin
authors.initials: J
authors.lastname: Gohda
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Inoue
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D002096:C-Peptide / Q000235:genetics / Q000378:metabolism; D002459:Cell Fusion; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010010:Osteoclasts / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002096:C-Peptide; C490894:Gab2 protein, mouse; D010455:Peptides; D010750:Phosphoproteins; D051567:Proto-Oncogene Proteins c-vav; D053246:Receptor Activator of Nuclear Factor-kappa B; D048029:TNF Receptor-Associated Factor 6; C505687:Tnfrsf11a protein, mouse; C496622:Vav3 protein, mouse