title: Osteoactivin promotes osteoblast adhesion through HSPG and αvβ1 integrin.
abstract: Osteoactivin (OA), also known as glycoprotein nmb (gpnmb) plays an important role in the regulation of osteoblast differentiation and function. OA induced osteoblast differentiation and function in vitro by stimulating alkaline phosphatase (ALP) activity, osteocalcin production, nodule formation, and matrix mineralization. Recent studies reported a role for OA in cell adhesion and integrin binding. In this study, we demonstrate that recombinant osteoactivin (rOA) as a matricellular protein stimulated adhesion, spreading and differentiation of MC3T3-E1 osteoblast-like cells through binding to αv β1 integrin and heparan sulfated proteoglycans (HSPGs). MC3T3-E1 cell adhesion to rOA was blocked by neutralizing anti-OA or anti-αv and β1 integrin antibodies. rOA stimulated-osteoblast adhesion was also inhibited by soluble heparin and sodium chlorate. Interestingly, rOA stimulated-osteoblast adhesion promoted an increase in FAK and ERK activation, resulting in the formation of focal adhesions, cell spreading and enhanced actin cytoskeleton organization. In addition, differentiation of primary osteoblasts was augmented on rOA coated-wells marked by increased alkaline phosphatase staining and activity. Taken together, these data implicate OA as a matricellular protein that stimulates osteoblast adhesion through binding to αv β1 integrin and cell surface HSPGs, resulting in increased cell spreading, actin reorganization, and osteoblast differentiation with emphasis on the positive role of OA in osteogenesis.
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University (NEOMED), Rootstown, Ohio; School of Biomedical Sciences, Kent State University, Kent, Ohio.
authors.forename: Fouad M
authors.initials: FM
authors.lastname: Moussa
authors.forename: Israel Arango
authors.initials: IA
authors.lastname: Hisijara
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Sondag
authors.forename: Ethan M
authors.initials: EM
authors.lastname: Scott
authors.forename: Nagat
authors.initials: N
authors.lastname: Frara
authors.forename: Samir M
authors.initials: SM
authors.lastname: Abdelmagid
authors.forename: Fayez F
authors.initials: FF
authors.lastname: Safadi
mesh_terms: D016475:3T3 Cells; D008841:Actin Cytoskeleton / Q000502:physiology; D000469:Alkaline Phosphatase / Q000096:biosynthesis; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D002704:Chlorates / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000096:biosynthesis; D005136:Eye Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000096:biosynthesis; D022001:Focal Adhesions; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology; D011485:Protein Binding; D051381:Rats; D019030:Receptors, Vitronectin / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins
chemical_list: D000906:Antibodies; D002704:Chlorates; D005136:Eye Proteins; C445671:Gpnmb protein, mouse; D019812:Heparan Sulfate Proteoglycans; D008562:Membrane Glycoproteins; D019030:Receptors, Vitronectin; D011994:Recombinant Proteins; C094340:integrin alphavbeta1; D006493:Heparin; D051417:Focal Adhesion Kinase 1; C496051:Ptk2 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D000469:Alkaline Phosphatase; C032706:sodium chlorate
keywords: ADHESION; INTEGRIN; OSTEOACTIVIN; OSTEOBLAST; OSTEOBLAST DIFFERENTIATION