title: Bone morphogenetic protein-2 enhances Wnt/beta-catenin signaling-induced osteoprotegerin expression.
abstract: Wnt/beta-catenin signaling plays an important role in the developing skeletal system. Our previous studies demonstrated that Wnt/beta-catenin signaling inhibits the ability of bone morphogenetic protein (BMP)-2 to suppress myotube formation in the multipotent mesenchymal cell line C2C12 and that this inhibition is mediated by Id1. In this study, we examined the role of intracellular signaling by Wnt/beta-catenin and BMP-2 in regulating the expression of osteoprotegerin (OPG) and of the receptor activator of NFkappaB ligand (RANKL). OPG expression was induced by Wnt/beta-catenin signaling in C2C12 cells and osteoblastic MC3T3-E1 cells. Silencing of glycogen synthase kinase-3beta also increased OPG expression. In contrast, R expression was suppressed by Wnt/beta-catenin signaling. In a transfection assay, beta-catenin induced the activity of a reporter gene, a 1.5 kb fragment of the 5'-flanking region of the OPG gene. Deletion and mutation analysis revealed that Wnt/beta-catenin signaling regulates transcription of OPG via a promoter region containing two Wnt/beta-catenin responsive sites. BMP-2 enhanced Wnt/beta-catenin-dependent transcriptional activation of the OPG promoter. In response to BMP-2 stimulation, Smad 1 and 4 interacted with Wnt/beta-catenin responsive sites. These results show that the regulation of OPG expression is mediated through two transcription pathways that involve the OPG promoter.
authors.affiliation: Department of Biochemistry and Molecular Biology, Hokkaido University, Sapporo, Japan.
authors.forename: Mari M
authors.initials: MM
authors.lastname: Sato
authors.forename: Aiko
authors.initials: A
authors.lastname: Nakashima
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nashimoto
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Yawaka
authors.forename: Masato
authors.initials: M
authors.lastname: Tamura
mesh_terms: D000818:Animals; D001665:Binding Sites; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology / Q000502:physiology*; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000378:metabolism; D051379:Mice; D053244:Osteoprotegerin / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D051785:Smad Proteins / Q000378:metabolism; D051822:T Cell Transcription Factor 1 / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D051153:Wnt Proteins / Q000378:metabolism / Q000502:physiology*; D051176:beta Catenin / Q000378:metabolism / Q000502:physiology*
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D051821:Lymphoid Enhancer-Binding Factor 1; D053244:Osteoprotegerin; D012333:RNA, Messenger; D051785:Smad Proteins; D051822:T Cell Transcription Factor 1; C506031:Tnfrsf11b protein, mouse; D051153:Wnt Proteins; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3