Matrix GLA protein, a regulatory protein for bone morphogenetic protein-2
Matrix GLA protein, a regulatory protein for bone morphogenetic protein-2
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DOI：
10.1074/jbc.m109683200
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发表时间：
2002-02-08
影响因子：
4.8
通讯作者：
Boström, K
中科院分区：
文献类型：
--
作者：
Zebboudj, AF;Imura, M;Boström, K
基质 GLA 蛋白 (MGP) 已被确定为软骨和脉管系统中的钙化抑制剂。这种效应的部分原因可能是其对骨形态发生蛋白 2 (BMP-2) 的骨诱导活性的影响。为了检测 MGP 和 BMP-2 之间的结合，我们使用标记有 FLAG 和 c-Myc 的 MGP 和 BMP-2 进行免疫沉淀。结果显示BMP-2与MGP共沉淀。为了量化 MGP 对 BMP-2 活性的影响，我们测定了碱性磷酸酶活性并显示了剂量依赖性效应。然而，相对于 BMP-2 而言，MGP 水平较低（过量 15 倍），导致 BMP-2 的骨诱导作用显着增强。交联研究表明，MGP 的抑制水平会消除 BMP-2 受体结合。免疫印迹显示 Smad1（BMP 信号系统的一部分）的激活相应减少。提高 MGP 水平会导致 Smad1 激活增加。为了确定 MGP 存在下 BMP-2 的细胞定位，对全细胞和细胞合成基质进行了结合测定。 MGP 的抑制水平导致 BMP-2 的基质结合增加，表明 MGP 部分通过基质缔合抑制 BMP-2。这些结果表明 MGP 是一种 BMP-2 调节蛋白。
Matrix GLA protein (MGP) has been identified as a calcification inhibitor in cartilage and vasculature. Part of this effect may be attributed to its influence on osteoinductive activity of bone morphogenetic protein-2 (BMP-2). To detect binding between MGP and BMP-2, we performed immunoprecipitation using MGP and BMP-2 tagged with FLAG and c-Myc. The results showed co-precipitation of BMP-2 with MGP. To quantify the effect of MGP on BMP-2 activity, we assayed for alkaline phosphatase activity and showed a dose-dependent effect. Low levels of MGP relative to BMP-2 (15-fold excess), however, resulted in pronounced enhancement of the osteoinductive effect of BMP-2. Cross-linking studies showed that inhibitory levels of MGP abolished BMP-2 receptor binding. Immunoblotting showed a corresponding decrease in activation of Smad1, part of the BMP signaling system. Enhancing levels of MGP resulted in increased Smad1 activation. To determine the cellular localization of BMP-2 in the presence of MGP, binding assays were performed on whole cells and cell-synthesized matrix. Inhibitory levels of MGP yielded increased matrix binding of BMP-2, suggesting that MGP inhibits BMP-2 in part via matrix association. These results suggest that MGP is a BMP-2 regulatory protein.