REGULATION OF MINERALIZATION IN SKELETAL TISSUES

描述(申请人提供)：这项研究的长期目标是确定骨骼组织中矿化的调节机制。生理性矿化发生在生长板软骨、骨和牙齿中，并局限于特定部位。不受控制的(病理性)矿化具有严重后果，并导致发病率和死亡率。因此，了解成矿作用的调控机制至关重要。在我们上一次资助期间，我们在理解钙稳态在矿化调节中的作用方面取得了重大进展。通过膜联蛋白通道介导的钙内流调节矿化相关基因的表达，以及矿化相关基质小泡的释放。有趣的是，Annexin V的过表达不仅导致矿化增加，而且上调了ank基因的表达。ANK是新近发现的一种将细胞内焦磷酸(PPI)转运到细胞外基质的蛋白质。人类Ank基因突变与关节软骨和骨骼的广泛矿化有关。我们的初步研究结果表明，矿化生长板软骨中Ank的高表达导致细胞外PPI增加。胞外PPI的增加导致APase的表达和活性上调，进而导致矿化。这些发现导致了一种假说，即Ank通过调节PPI动态平衡和APase的表达和活性，是矿化的积极生理调节因子。在目标1和目标2中，我们建议确定Ank如何调节矿化过程以及APase的表达和活性。在目标3中，我们建议确定在矿化过程开始之前或在矿化过程启动期间调控ank基因表达的机制。这项研究直接涉及调控骨骼组织矿化过程的机制，并研究了一种蛋白质的作用，这种蛋白质如果发生突变，就会导致软骨和骨骼的病理性或广泛矿化。因此，这一建议可能为预防病理性矿化提供一个新的治疗靶点。

DESCRIPTION (provided by applicant): The long term goal of this study is to determine mechanisms regulating mineralization in skeletal tissues. Physiological mineralization occurs in growth plate cartilage, bone and teeth, and is restricted to specific sites. Uncontrolled (pathological) mineralization has severe consequences and leads to morbidity and mortality. Therefore, an understanding of the regulatory mechanisms of mineralization is of crucial importance. During our last funding period we made major progress in understanding the role of calcium homeostasis in the regulation of mineralization. Calcium influx mediated through annexin channels regulates the expression of mineralization-related genes, and the release of mineralization-competent matrix vesicles. Interestingly, overexpression of annexin V resulted not only in increased mineralization but also upregulation of ank gene expression. Ank is a newly discovered protein which transports intracellular pyrophosphate (PPi) to the extracellular millieu. Human mutations in Ank are associated with extensive mineralization in articular cartilage and bone. Our preliminary findings reveal that high expression of Ank in mineralizing growth plate cartilage results in increased extracellular PPi. Increased extracellular PPi lead to upregulation of APase expression and activity, and subsequent mineralization. These findings lead to one hypothesis that Ank is a positive physiological regulator of mineralization by regulating PPi homeostasis and APase expression and activities. In Aims 1 and 2 we propose to determine how Ank regulates the mineralization process and the expression and activities of APase. In Aim 3 we propose to determine the mechanisms regulating ank gene expression during or just before the initiation of the mineralization process. This study relates directly to mechanisms regulating the mineralization process of skeletal tissues and investigates the role of a protein which has been shown if mutated to lead to pathological or extensive mineralization in cartilage and bone. Therefore, this proposal might provide a novel therapeutic target to prevent pathological mineralization.