The Role and Mechanism of RGS12 in Bone Resorption

描述(申请人提供)：破骨细胞是主要的骨吸收细胞，它们的活动对骨骼健康有深远的影响。骨骼功能不全的疾病，如骨质疏松症，典型的特征是相对于骨形成，破骨细胞性骨吸收增强。因此，更全面地了解破骨细胞区别于其前体细胞并使骨骼退化的机制，对于开发这些经常使人虚弱的疾病的治疗方法至关重要。最近的研究表明，G蛋白信号转导调节蛋白(RGS)在钙振荡的调节中起着重要的作用。RGS12基因是G蛋白的大调节子，具有PDZ、PTB、Rap结合域和GoLoco结构域等多种功能模块。在原代培养的背根神经节神经元中，RGS12通过其PTB结构域与酪氨酸磷酸化钙通道直接相互作用。我们发现，小鼠RGS12基因主要在RANKL诱导的破骨细胞样细胞(OCs)中表达。RNA干扰(RNAi)抑制RGS12的表达可抑制RANKL诱导的细胞外钙振荡和破骨细胞终末分化。然而，没有体内证据表明RGS12信号在破骨细胞分化和骨吸收中具有普遍的必要性。根据我们的初步数据和RGS12的性质，我们推测RGS12通过调节钙振荡和与钙通道的相互作用，在破骨细胞基因表达、破骨细胞分化和激活中发挥重要作用。为了检验这一假设，我们提出了两个具体目标。目的1，利用基因敲除技术产生RGS12缺失等位基因，研究RGS12在骨吸收中的作用。目的2利用RGS12基因敲除模型，研究RGS12基因在破骨细胞内钙信号调控、破骨细胞基因表达调控以及破骨细胞分化和活化中的作用，从而为人类骨病尤其是骨质疏松症的诊断和治疗提供新的思路。

DESCRIPTION (provided by applicant): Osteoclasts are the principal bone-resorbing cells, and their activity has a profound impact on skeletal health. Disorders of skeletal insufficiency, such as osteoporosis, are typically characterized by enhanced osteoclastic bone resorption relative to bone formation. A more complete understanding of the mechanisms by which osteoclasts differentiate from their precursors and degrade the skeleton is therefore critical to developing therapies for these often-debilitating diseases. Recent evidence showed that Regulator of G-protein signaling (RGS) proteins, play an important part in the regulation of Ca 2+ oscillations. RGS12 gene is a large regulator of G protein, having multiple functional modules, such as PDZ, PTB (phosphor-tyrosine binding), Rap binding domains and GoLoCo domain. RGS12 is capable of direct interactions through its PTB domain with the tyrosine-phosphorylated calcium channel in culture of primary dorsal root ganglion neurons. We have found that mouse RGS12 gene was predominately expressed in RANKL-induced osteoclast like cells (OLCs). Knockdown of RGS12 expression using RNA interference (RNAi) inhibited Ca 2+ oscillations and osteoclast terminal differentiation induced by RANKL in vitro. Nevertheless, there is no in vivo evidence for a general requirement for RGS12 signaling in osteoclast differentiation and bone resorption. Based on our preliminary data and the nature of RGS12, we hypothesized that RGS12 plays an essential role in osteoclast gene expression, osteoclast differentiation and activation through the regulation of Ca2+ oscillations and interaction with calcium channel. To test this hypothesis, we propose two specific aims. In aim 1, to generate RGS12 null allele to study the role of RGS12 in bone resorption using knockout technology. In aim 2, using RGS12 knockout model to define the function of RGS12 in regulating Ca2+ signal in osteoclast, in osteoclast gene expression regulation, and in osteoclast differentiation and activation so as to apply this knowledge to develop new diagnostics and therapeutics for human diseases of bone, especially for osteoporosis