Calcium Regulation in Osteoclasts

描述(申请人提供)：健康的骨维持由成骨细胞介导的骨形成和由破骨细胞介导的骨吸收的平衡。当破骨细胞被过度招募或不适当地激活时，许多疾病状态，包括慢性牙周炎、骨质疏松症、类风湿性关节炎、Paget病和癌症转移。破骨细胞通过一系列涉及细胞因子、信号转导和微环境的复杂事件，在整个生命过程中不断地由驻留在骨髓中的造血干细胞产生。CA2信号在破骨细胞生成的调控中起着重要作用。在破骨细胞形成的早期阶段，细胞内钙库耗尽而激活的钙通道被认为参与了钙信号的传递。然而，这些通道在破骨细胞形成中控制钙信号的确切分子和机制在很大程度上是未知的。利用分子、细胞生物学和整体动物研究相结合的方法，我们发现瞬时受体电位通道TRPC1在早期促进破骨细胞的形成，而其抑制物小细胞浆蛋白I-MFA则具有相反的作用。缺乏这两个基因的小鼠可以纠正I-MFA缺失小鼠增强的破骨细胞生成，这表明TRPC1介导的钙信号在破骨细胞形成中比I-MFA具有显性作用。因此，我们认为TRPC1和I-MFA通过调节钙信号对破骨细胞的形成起重要作用。这一假说将通过分子、生物物理、细胞和组织水平的综合方法进行验证，方法是询问TRPC1和I-MFA是否以及如何影响早期破骨细胞前体细胞的增殖和“启动”(特定目标1)，TRPC1和I-MFA如何调节破骨细胞中的钙信号(特定目标2和3)，以及TRPC1和I-MFA是否以细胞自主的方式影响体内和体外的破骨细胞生成，以及进一步它们是否影响实验诱导的破骨细胞生成动物模型中的破骨细胞招募(特定目标4)。我们的研究将进一步了解破骨细胞发育和功能调节中的关键途径，这是识别和开发新的治疗干预措施以控制破骨细胞生成和防止骨丢失所必需的。

DESCRIPTION (provided by applicant): Healthy bone maintains a balance of bone formation mediated by osteoblasts and bone resorption mediated by osteoclasts. Many disease states, including chronic periodontitis, osteoporosis, rheumatoid arthritis, Paget's disease, and cancer metastases develop when osteoclasts are excessively recruited or inappropriately activated. Osteoclasts are constantly made throughout life from hematopoietic stem cells residing in the bone marrow through a series of complex events involving cytokine signaling and the microenvironment. Ca2+ signaling has an essential role in the regulation of osteoclastogenesis. Ca2+ channels activated in response to the depletion of intracellular Ca2+ stores have been suggested to mediate Ca2+ signaling in early stages of osteoclast formation. However, the exact molecules and the mechanism by which these channels control Ca2+ signaling in osteoclastogenesis are largely unknown. Using a combination of molecular, cell biological and whole animal studies, we show that the Transient Receptor Potential channel, TRPC1, enhances osteoclastogenesis at an early stage, whereas its inhibitor, the small cytosolic protein, I-mfa has an opposite effect. Enhanced osteoclastogenesis in I-mfa-null mice is corrected in mice lacking both genes indicating that TRPC1-mediated Ca2+ signaling has a dominant effect over I-mfa in osteoclast formation. Therefore, we propose that TRPC1 and I-mfa are essential for osteoclastogenesis by regulating Ca2+ signaling. This hypothesis will be tested by an integrated approach at the molecular, biophysical, cellular, and organismal levels by asking whether and how TRPC1 and I-mfa affect proliferation and "priming" of early osteoclast progenitors (Specific Aim 1), how TRPC1 and I-mfa modulate Ca2+ signaling in osteoclasts (Specific Aims 2 and 3), and whether TRPC1 and I-mfa affect osteoclastogenesis in a cell-autonomous fashion in vivo and in vitro and further, whether they affect osteoclast recruitment in experimentally induced animal models of osteoclastogenesis (Specific Aim 4). Our studies will lead to further understanding of critical pathways in the regulation of osteoclast development and function, which is needed to identify and develop new therapeutic interventions to control osteoclastogenesis and prevent bone loss.