Molecular Mechanism of Matrix GLA Protein (MGP)

钙化在血管疾病中是普遍存在的，并且显著地导致发病率和死亡率。矩阵 GLA蛋白（MGP）是一种所谓的钙化抑制剂，在动脉粥样硬化病变中上调。删除 MGP基因的突变导致小鼠和人类的动脉钙化和形态异常。 MGP是通过维生素K依赖性g-羧化修饰的分泌蛋白。当隔离于 骨，它是加工和缺乏七个C-末端氨基酸。 MGP的机制知之甚少。然而，我们的实验数据表明， 转化生长因子-β 1（TGF-β 1）和骨形态发生蛋白（BMP）信号传导。数据显示， BMP-2和BMP-4诱导TGF-β 1受体表达中BMP和TGF-β 1之间的潜在联系 激活素样激酶受体1（ALK 1）。通过ALK 1的信号传导诱导MGP，MGP提供阴性 BMP的反馈调节。还观察到MGP与特异性受体之间的相互作用。 三个假设将在这次赠款测试。第一个假设是MGP调节TGF-β 1和BMP 在受体水平上的信号传导，导致改变SMAD信号传导和基因表达。我们将描述 TGF-β 1、BMP-2和BMP-4诱导的SMAD信号转导和相关报告基因的激活， MGP的存在，并鉴定受MGP调节的TGF-1/ BMP受体。第二 假设MGP参与特定的蛋白质-蛋白质相互作用，其可能被C-末端改变， 处理.我们将使用特定的方法来表征包括TGF-β受体在内的相互作用， 免疫沉淀结合一般蛋白质组学方法。第三个假设是MGP 在发育中的动脉和动脉粥样硬化病变中作为BMP抑制剂发挥作用。我们将生成一个 转基因小鼠用于BMP抑制剂头蛋白的靶向条件表达。Noggin的表达将是 在MGP缺失小鼠中诱导，试图替代MGP并消除钙化。诺金的效果也会 在LDL受体缺失小鼠的动脉粥样硬化病变中测定。 我们的研究结果将增加对血管和心脏瓣膜钙化的了解，这是心脏病的常见问题。 此外，它还可以提供有关如何为不必要的钙化设计新治疗方法的信息。

Calcification is ubiquitous in vascular disease, and contributes significantly to morbidity and mortality. Matrix GLA protein (MGP) is an alleged calcification inhibitor that is up-regulated in atherosclerotic lesions. Deletion of the MGP gene results in arterial calcification and in morphological abnormalities in mice and humans. MGP is a secreted protein that is modified by vitamin K-dependent g-carboxylation. When isolated from bone, it is processed and lacks seven C-terminal amino acids. The mechanism of MGP is poorly understood. However, our experimental data points to a role in transforming growth factor-fi (TGF-fi) and bone morphogenetic protein (BMP) signaling. The data suggest a potential link between BMP and TGF-li in that BMP2 and BMP-4 induce expression of the TGF-R, receptor Activin-like Kinase receptor 1 (ALK1). Signaling through ALK1 induces MGP, which provides negative feedback regulation for BMP. Interactions between MGP and specific receptors were also observed. Three hypotheses will be tested in this grant. The first hypothesis is that MGP regulates TGF-fi and BMP signaling at the receptor level, resulting in altered SMAD signaling and gene expression. We will characterize activation of SMAD signaling and relevant reporter genes induced by TGF-li1, BMP-2 and BMP-4 in presence of MGP, and identify the TGF-li / BMP receptors that are regulated by MGP. The second hypothesis is that MGP participates in specific protein-protein interactions that may be altered by C-terminal processing. We will characterize the interactions, which include the TGF-ft receptors, using specific immunoprecipitations in combination with a general proteomic approach. The third hypothesis is that MGP functions as a BMP inhibitor in developing arteries and in atherosclerotic lesions. We will generate a transgenic mouse for targeted, conditional expression of the BMP-inhibitor Noggin. Noggin expression will be induced in MGP null mice in attempt to replace MGP and abolish calcification. The effect of Noggin will also be determined in atherosclerotic lesions in LDL-receptor null mice. Our results will add insight to calcification of vessels and heart valves, a common problem in heart disease. In addition, it may provide information on how to design new treatments for unwanted calcification.