title: EGF Inhibits Wnt/β-Catenin-Induced Osteoblast Differentiation by Promoting β-Catenin Degradation.
abstract: Bone morphogenetic protein (BMP) and canonical Wnts are representative developmental signals that enhance osteoblast differentiation and bone formation. Previously, we demonstrated that epidermal growth factor (EGF) inhibits BMP2-induced osteoblast differentiation by inducing Smurf1 expression. However, the regulatory role of EGF in Wnt/β-catenin-induced osteoblast differentiation has not been elucidated. In this study, we investigated the effect of EGF on Wnt/β-catenin signaling-induced osteoblast differentiation using the C2C12 cell line. EGF significantly suppressed the expression of osteoblast marker genes, which were induced by Wnt3a and a GSK-3β inhibitor. EGF increased the expression levels of Smurf1 mRNA and protein. Smurf1 knockdown rescued Wnt/β-catenin-induced osteogenic marker gene expression in the presence of EGF. EGF treatment or Smurf1 overexpression did not affect β-catenin mRNA expression levels, but reduced β-catenin protein levels and TOP-Flash activity. EGF and Smurf1 promoted β-catenin ubiquitination. Co-immunoprecipitation and GST pull-down assays showed that Smurf1 associates with β-catenin. These results suggest that EGF/Smurf1 inhibits Wnt/β-catenin-induced osteogenic differentiation and that Smurf1 downregulates Wnt/β-catenin signaling by enhancing proteasomal degradation of β-catenin.
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.|Departments of Anatomy, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Kanitsak
authors.initials: K
authors.lastname: Boonanantanasarn
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.|Laboratory of Molecular Signaling, Division of Oral Biology and Medicine, School of Dentistry and Broad Stem Cell Research Center, University of California, Los Angeles, USA.
authors.forename: Hye-Lim
authors.initials: HL
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, College of Dentistry, Gangneung-Wonju National University, Gangwondo, Korea.
authors.forename: Kyunghwa
authors.initials: K
authors.lastname: Baek
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Kyung Mi
authors.initials: KM
authors.lastname: Woo
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Hyun-Mo
authors.initials: HM
authors.lastname: Ryoo
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Jeong-Hwa
authors.initials: JH
authors.lastname: Baek
authors.affiliation: Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Gwan-Shik
authors.initials: GS
authors.lastname: Kim
mesh_terms: D002454:Cell Differentiation / Q000235:genetics*; D004815:Epidermal Growth Factor / Q000096:biosynthesis* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D057809:HEK293 Cells; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics; D059748:Proteolysis; D012333:RNA, Messenger / Q000096:biosynthesis; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000235:genetics; D060509:Wnt3A Protein / Q000037:antagonists & inhibitors; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; C555510:WNT3A protein, human; D060509:Wnt3A Protein; D051176:beta Catenin; D004815:Epidermal Growth Factor; C498342:SMURF1 protein, human; D044767:Ubiquitin-Protein Ligases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3
keywords: EPIDERMAL GROWTH FACTOR; OSTEOBLAST; SMURF1; WNT; β-CATENIN