Molecular Mechanisms in Bone Resorption

描述(由申请人提供)：骨质疏松症是一个公共健康问题，在美国大约有2500万人受到影响。无论病因如何，骨质疏松症都以骨重建失衡为特征，破骨细胞性骨吸收超过成骨细胞性骨形成，从而导致骨量减少。这种特殊的时机和局部表达表明，它是人类破骨细胞发生、骨吸收和骨量减少的一种独特而新颖的模型。人们也很容易推测，口腔和牙槽骨的独特物理特征可能在颌骨坏死和小天使症之间提供了联系。例如，在这两种情况下，尽管整个骨骼暴露在氨基二磷酸或表达SH3BP2突变，但骨骼损伤仅限于颌骨。我们对17个大骨节症先证者进行了研究，发现所有SH3BP2突变都激活了活化的T细胞的核因子(活化的T细胞的核因子c1或nFATc1是破骨细胞形成的主开关)，并诱导了RAW 264.7破骨前细胞株的酒石酸抗性酸性磷酸酶(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)，而肌醇磷酸3(IP3)的产生导致内质网钙的释放。细胞内钙的增加可以激活钙调神经磷酸酶，使NFATc1去磷酸化，促进其移位到细胞核，从而导致破骨细胞的形成。假设：大猩猩患者的SH3BP2突变改变了SH3BP2与其他调节或信号蛋白的结合，至少一个结果是NFATc1活性增强，并随后发生破骨细胞形成。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的磷酸化(特异性目标1)、结合(特异性目标2)和功能(特异性目标3)来检验这一点。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形成、小鼠表型鉴定以及人类疾病基因分析方法方面的新技术。此外，他将扩大与克利夫兰诊所和附近附属凯斯西储医院的高级基础调查人员的合作努力。这些研究人员将提供如何运行一个成功的实验室的例子，并就候选人的研究进展提供定期反馈，以及成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：有关骨吸收机制的新信息可能有助于开发减少骨吸收的新策略，并可能导致骨质疏松症的新治疗方法。我们建议使用颌骨巨细胞骨吸收瘤为特征的一种罕见疾病--大骨节症的模型，来探索调节骨吸收的新途径。K02为这个项目提供的资金将通过保护他在实验室的时间来帮助候选人显著发展为一名独立的科学家。

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.