Calcium Regulation in Osteoclasts

描述（申请人提供）：健康的骨骼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。许多疾病状态，包括慢性牙周炎、骨质疏松、类风湿关节炎、佩吉特病和癌症转移，都是在破骨细胞过度募集或不适当激活时发生的。在整个生命过程中，骨髓中的造血干细胞通过一系列涉及细胞因子信号和微环境的复杂事件不断产生破骨细胞。Ca2+信号在破骨细胞发生的调控中起重要作用。响应细胞内Ca2+储存的消耗而激活的Ca2+通道已被认为在破骨细胞形成的早期阶段介导Ca2+信号。然而，这些通道在破骨细胞发生中控制Ca2+信号的确切分子和机制在很大程度上是未知的。通过结合分子、细胞生物学和全动物研究，我们发现瞬时受体电位通道TRPC1在早期阶段促进破骨细胞的发生，而它的抑制剂小细胞质蛋白I-mfa具有相反的作用。I-mfa缺失小鼠的破骨细胞生成增强在缺乏这两个基因的小鼠中得到纠正，这表明trpc1介导的Ca2+信号在破骨细胞形成中比I-mfa具有主导作用。因此，我们提出TRPC1和I-mfa通过调节Ca2+信号对破骨细胞的形成至关重要。这一假设将通过分子、生物物理、细胞和组织水平的综合方法进行验证，通过询问TRPC1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”（Specific Aim 1）， TRPC1和I-mfa如何调节破骨细胞中的Ca2+信号（Specific Aims 2和3），以及TRPC1和I-mfa是否在体内和体外以细胞自主的方式影响破骨细胞的形成。在实验诱导的破骨细胞发生动物模型中，它们是否影响破骨细胞募集（Specific Aim 4）。我们的研究将进一步了解破骨细胞发育和功能调控的关键途径，这是识别和开发新的治疗干预措施来控制破骨细胞发生和预防骨质流失所必需的。

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.