Malpe R, Baylink D J, Sampath T K, Mohan S
Department of Biochemistry, Loma Linda University, CA.
Biochem Biophys Res Commun. 1994 Jun 30;201(3):1140-7. doi: 10.1006/bbrc.1994.1824.
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.
近期研究表明，成骨蛋白（OP）-1或骨形态发生蛋白（BMP）-7可促进培养的人骨细胞（HBCs）增殖与分化，并调节胰岛素样生长因子（IGF）系统成分的产生。为研究OP-1产生这些效应的机制，我们试图验证如下假说：OP-1的效应至少部分是由HBCs中的特异性受体（针对OP-1）介导的。对正常HBCs和人骨肉瘤细胞的无血清培养物进行的结合研究显示，[125I]OP-1的最大结合率为15%-25%；在不同实验中，结合具有时间和温度依赖性。对[125]OP-1与TE85人骨肉瘤细胞结合情况的Scatchard分析显示至少有两个结合位点，每个细胞约30,000和60,000个，表观解离常数（Kd）分别为2.5×10^(-10)M和1×10^(-9)M。未标记的OP-1（16-1000 ng/ml）可取代[125]OP-1与TE85细胞的结合，250 ng/ml时50%的结合被取代。BMP-2可有效取代[125]OP-1与HBCs的结合，而转化生长因子（TGF）-β1则不能。亲和交联研究表明，[125]OP-1与三个表观相对分子质量（M(r)）分别为34、65和>205 kDa的结合位点特异性相互作用。本研究结果表明，OP-1对HBCs的效应可能部分通过BMP特异性受体介导。
