Molecular Mechanisms in Bone Resorption

描述（由申请人提供）：骨质疏松症是一种公共卫生问题，影响美国约2500万人。无论病因如何，骨质疏松症的特征在于骨重建的不平衡，使得成骨细胞骨吸收超过成骨细胞骨形成，这导致低骨量。巨颌症的特异性时间和局部表达表明它是一种独特的、新的人类破骨细胞生成、骨吸收和骨质减少的模型。这也是诱人的推测，独特的物理特性的嘴和牙槽骨可以提供一个链接之间的骨坏死的颌骨和巨像症。例如，在这两种情况下，尽管整个骨骼暴露于氨基二膦酸盐或表达SH3BP2突变，但骨病变仅限于颌骨。我们已经评估了17个先天巨像症先证者，发现所有的SH3BP2突变都激活了活化T细胞的核因子（活化T细胞的核因子c1或NFATc1是破骨细胞生成的主开关），并诱导RAW 264.7前骨细胞系中抗酒石酸酸性磷酸酶（TRAP）的表达。我们最近的研究表明，SH3BP2刺激磷脂酰肌醇特异性磷脂酶C（PI-PLC），磷酸肌醇3（IP3）的产生导致钙从内质网释放。细胞内钙的增加可以激活钙调神经磷酸酶，其使NFATc1去磷酸化并促进其易位到细胞核，从而导致破骨细胞生成。假设：巨像症患者中的SH3BP2突变改变了SH3BP2与其他调节或信号蛋白的结合，至少有一个结果是NFATc1活性增强和随后的破骨细胞生成。该项目的总体目标是确定SH3BP2在调节破骨细胞生成中的作用。我们建议通过观察突变型和野生型SH3BP2磷酸化（特异性目的1），结合（特异性目的2）和功能（特异性目的3）来检查这一点。候选人将利用K02计划提供的资源和时间访问实验室，学习病毒感染和破骨细胞生成，小鼠表型分析以及人类疾病遗传分析方法的新技术。此外，他将扩大与克利夫兰诊所和附近附属凯斯西储的高级基础研究人员的合作。这些研究人员将提供如何运行一个成功的实验室的例子，并提供有关候选人的研究进展的定期反馈，以及作为基础和技术科学问题和故障排除的优秀资源。 公共卫生相关性：关于骨吸收机制的新信息可能有助于开发新的策略来减少骨吸收，并可能导致骨质疏松症的新治疗方法。我们建议使用模型的cherubism，一种罕见的疾病，其特点是巨细胞骨吸收肿瘤的骨骼的颌骨，探索新的途径，调节骨吸收。K02对该项目的资助将通过保护他在实验室的时间来帮助候选人作为一名独立的科学家显着发展。

DESCRIPTION (provided by applicant): Osteoporosis is a public health problem that affects approximately 25 million people in the United States. Regardless of the etiology, osteoporosis is characterized by an imbalance in bone remodeling, such that osteoclastic bone resorption exceeds osteoblastic bone formation, which leads to low bone mass. The specific timing and localized expression of cherubism indicates that it is a unique and novel model of human osteoclastogenesis, bone resorption and osteopenia. It is also tempting to speculate that the unique physical characteristics of the mouth and alveolar bone can provide a link between osteonecrosis of the jaw and cherubism. For example, in both conditions bone lesions are limited to the jaw despite the entire skeleton being exposed to aminobisphosphonates or expressing the SH3BP2 mutation. We have assessed 17 cherubism probands and have found that all of the SH3BP2 mutations activate nuclear factor of activated T cells (nuclear factor of activated T cells c1 or NFATc1 is the master switch of osteoclastogenesis) and induce expression of tartrate resistant acid phosphatase (TRAP) in the RAW 264.7 pre-osteoclastic cell line. Our recent studies suggest that SH3BP2 stimulates a phosphatidylinositol-specific phospholipase C (PI-PLC), and the production of inositol phosphate 3 (IP3) leads to release of calcium from the endoplasmic reticulum. The increase in intracellular calcium can activate calcineurin, which dephosphorylates NFATc1 and promotes its translocation to the nucleus leading to osteoclastogenesis. Hypothesis: SH3BP2 mutations in cherubism patients alter binding of SH3BP2 to other regulatory or signaling proteins, with at least one result being enhanced NFATc1 activity and consequent osteoclastogenesis. The overall goal of this project is to determine the role of SH3BP2 in regulating osteoclastogenesis. We propose to examine this by looking at mutant and wild-type SH3BP2 phosphorylation (specific aim 1), binding (specific aim 2), and function (specific aim 3). The candidate will use the resources and time made available through the K02 program to visit the laboratories to learn novel techniques in viral infection and osteoclastogenesis, mouse phenotyping, and approaches to genetic analysis of human disease. Moreover he will expand his collaborative efforts with senior basic investigators at Cleveland Clinic and nearby affiliated Case Western Reserve. These investigators will provide examples of how to run a successful lab and provide periodic feedback on the progress of the candidate's research as well as being excellent resources for basic and technical scientific problems and troubleshooting. PUBLIC HEALTH RELEVANCE: New information about mechanisms of bone resorption may facilitate the development of novel strategies to decrease bone resorption and may lead to new treatments for osteoporosis. We propose to use the model of cherubism, a rare disorder characterized by giant cell bone resorptive tumors of the bones of the jaw, to explore novel pathways that regulate bone resorption. K02 funding for this project will help the candidate develop significantly as an independent scientist by protecting his time in the lab.