REGULATION OF MINERALIZATION IN SKELETAL TISSUES

描述（由申请人提供）：本研究的长期目标是确定骨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，并且局限于特定部位。不受控制的（病理性）矿化具有严重的后果，可导致发病率和死亡率。因此，了解矿化的调控机制至关重要。在我们最后的资助期间，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和矿化基质囊泡的释放。有趣的是，膜联蛋白V的过表达不仅导致矿化增加，还导致ank基因表达上调。Ank是一种新发现的将细胞内焦磷酸盐（PPi）转运到细胞外的蛋白。人类Ank突变与关节软骨和骨的广泛矿化有关。我们的初步研究结果显示，Ank在矿化生长板软骨中的高表达导致细胞外PPi增加。细胞外PPi升高导致APase表达和活性上调，并随之矿化。这些发现提出了一种假设，即Ank通过调节PPi稳态和APase的表达和活性，是矿化的积极生理调节剂。在Aims 1和2中，我们提出确定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期间或之前调节库基因表达的机制。本研究直接涉及调节骨组织矿化过程的机制，并研究了一种蛋白质的作用，该蛋白质已被证明如果突变会导致软骨和骨的病理或广泛矿化。因此，该建议可能为防止病理性矿化提供新的治疗靶点。

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.