Calcium Regulation in Osteoclasts

描述（由申请人提供）：健康骨维持成骨细胞介导的骨形成和破骨细胞介导的骨吸收的平衡。当破骨细胞被过度募集或不适当地激活时，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、佩吉特病和癌症转移发展。破骨细胞在整个生命过程中不断地由骨髓中的造血干细胞通过一系列涉及细胞因子信号传导和微环境的复杂事件产生。Ca 2+信号在破骨细胞生成的调节中发挥着重要作用。在破骨细胞形成的早期阶段，响应于细胞内Ca 2+储存的耗尽而激活的Ca 2+通道已经被认为介导Ca 2+信号传导。然而，这些通道控制破骨细胞生成中的Ca 2+信号传导的确切分子和机制在很大程度上是未知的。使用分子，细胞生物学和整个动物的研究相结合，我们表明，瞬时受体电位通道，TRPC 1，在早期阶段，增强破骨细胞生成，而其抑制剂，小胞质蛋白，I-mfa具有相反的效果。在I-mfa-null小鼠中增强的破骨细胞生成在缺乏这两种基因的小鼠中得到纠正，表明TRPC 1介导的Ca 2+信号传导在破骨细胞形成中对I-mfa具有显性作用。因此，我们认为TRPC 1和I-mfa通过调节Ca 2+信号对破骨细胞的生成是必不可少的。这一假设将通过在分子、生物物理、细胞和生物体水平上的综合方法进行检验，通过询问TRPC 1和I-mfa是否以及如何影响早期破骨细胞祖细胞的增殖和“启动”。（具体目标1），TRPC 1和I-mfa如何调节破骨细胞中的Ca 2+信号传导（具体目的2和3），以及TRPC 1和I-mfa是否在体内和体外以细胞自主方式影响破骨细胞生成，以及进一步，它们是否影响破骨细胞生成的实验诱导动物模型中的破骨细胞募集（具体目标4）。我们的研究将进一步了解破骨细胞发育和功能调节的关键途径，这是确定和开发新的治疗干预措施以控制破骨细胞生成和预防骨丢失所必需的。

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.