title: Beta ig-h3 mediates osteoblast adhesion and inhibits differentiation.
abstract: betaig-h3 is an extracellular matrix (ECM) protein induced by TGF-beta, and it has motifs interacting with the alpha3beta1, alphavbeta5, and alphavbeta3 integrins. Our previous study shows the role of betaig-h3 in osteoblast differentiation and its involvement in melorheostosis, a rare bone disease. Here we demonstrate that betaig-h3 expression is down-regulated during the early stage of differentiation of the murine preosteoblastic cell line, KS483. The recombinant betaig-h3 and its FAS1 domain significantly inhibited in vitro osteoblast differentiation as evaluated by matrix mineralization/bone nodule formation. Furthermore, inhibition of expression of osteoblast differentiation marker genes [such as type I collagen, alkaline phosphatase, and osteocalcin (OC)] was accompanied by suppression of osteoblast-specific transcription factors, Cbfa1/Runx2 and osterix. Flow cytometric analyses, cell adhesion, and inhibition assays disclosed alphavbeta3 and alphavbeta5 as the principal integrins mediating the adhesion of osteoblastic cells to betaig-h3. The disruption of interactions between betaig-h3 and osteoblasts by a function-blocking antibody specific for alphavbeta3 but not for alphavbeta5 abolished the inhibitory effect of betaig-h3 on osteoblast differentiation. We suggest that these interacting integrins may play an important role in betaig-h3-mediated inhibition of osteoblast differentiation.
authors.affiliation: Institute of Cell and Matrix Biology Research, Department of Biochemistry, School of Medicine, Kyungpook National University, Daegu 700-422, South Korea.
authors.forename: Narendra
authors.initials: N
authors.lastname: Thapa
authors.forename: Kae-Bok
authors.initials: KB
authors.lastname: Kang
authors.forename: In-San
authors.initials: IS
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001857:Bone Matrix / Q000378:metabolism / Q000502:physiology; D002113:Calcification, Physiologic / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D006131:Growth Inhibitors / Q000502:physiology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000099222:betaIG-H3 Protein
chemical_list: D016326:Extracellular Matrix Proteins; D006131:Growth Inhibitors; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein