Evidence that human bone cells in culture contain binding sites for osteogenic protein-1.
Recent studies have shown that osteogenic protein (OP)-1 or bone morphogenetic protein (BMP)-7 increases proliferation and differentiation of human bone cells (HBCs) in culture and modulates production of IGF system components. In order to study the mechanism by which OP-1 causes these effects, we sought to test the hypothesis that the effects of OP-1 are mediated at least in part by specific receptors (for OP-1) in HBCs. Binding studies with serum-free cultures of normal HBCs and human osteosarcoma cells showed a maximum binding of 15-25% for [125I]OP-1; the binding was time- and temperature-dependent in different experiments. Scatchard analysis of [125]OP-1 binding to TE85 human osteosarcoma cells showed at least two binding sites, about 30,000 and 60,000 per cell with apparent Kd of 2.5 x 10(-10)M and 1 x 10(-9)M, respectively. [125]OP-1 binding to TE85 cells was displaced by unlabeled OP-1 (16-1000 ng/ml), with a 50% displacement at 250 ng/ml. BMP-2 effectively displaced [125]OP-1 binding to HBCs while TGF-beta 1 did not. Affinity cross-linking studies showed that [125]OP-1 interacted specifically with three binding sites with apparent M(r) of 34, 65 and > 205kDa. The findings of this study demonstrate that the effects of OP-1 on HBCs may be mediated in part via BMP-specific receptors.
Malpe
R
R
Department of Biochemistry, Loma Linda University, CA.
Baylink
D J
DJ
Sampath
T K
TK
Mohan
S
S
D001665:Binding Sites; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism*; D003432:Cross-Linking Reagents; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D012516:Osteosarcoma / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D016212:Transforming Growth Factor beta; D014407:Tumor Cells, Cultured
C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D003432:Cross-Linking Reagents; D011506:Proteins; D011956:Receptors, Cell Surface; D016212:Transforming Growth Factor beta