The Mechanisms of Bone Mass Regulation by FIP200

描述（由申请人提供）：拟定研究的长期目标是了解骨骼肌中关键细胞功能调节的细胞信号传导机制。 发展/疾病在这个建议中，我们专注于FIP200（FAK-family Interacting Protein of 200 kDa）在成骨细胞分化调控中的作用。FIP200最初被鉴定为新型FAK和Pyk 2抑制剂。最近，FIP200被确定为哺乳动物自噬的重要组成部分。尽管我们知道FIP200是胚胎发生和癌症发展中的关键信号节点，但FIP200在多大程度上调节骨代谢尚不清楚。在我们的初步研究中，我们发现：1。成骨细胞中的FIP 200条件性敲除导致严重的骨质疏松表型; 2.成骨细胞分化在FIP200无效的原代成骨细胞培养物中大大受损; 3.原代颅骨成骨细胞具有活跃的基础和高诱导性自噬活性。然而，表达GFP-LC3的FIP200无效原代颅骨成骨细胞在饥饿和雷帕霉素处理后未能形成点状膜结构，表明FIP200无效成骨细胞具有自噬缺陷; 4. FIP200缺失的成骨细胞具有大的泛素阳性聚集体，这是这些细胞中有缺陷的自噬的另一个指示;和5.早期新生的FIP200 Osx-CKO小鼠有显着的生长迟缓，自然发生的饥饿作为一个结果，突然失去母体血液供应。因此，我们推测FIP200通过调节成骨细胞自噬来调节骨量。该项目的总体目标是确定FIP 200调节成骨细胞功能和骨量的分子机制和信号通路，使用分子，细胞生物学和小鼠遗传学方法的组合。本提案的具体目标是：目标1。确定FIP200通过其自噬作用调节成骨细胞功能的程度。目标二。阐明FIP200调控出生后早期骨发育的机制。目标3：确定FIP200在成年小鼠骨稳态中的作用。卫生保健：作为一个主要的公共健康威胁，骨质疏松症存在于估计4400万50岁及以上的男性和女性中，占美国该年龄组人口的55%。本研究以独特的小鼠疾病模型为基础，对探讨骨质疏松症发病机制的分子和细胞机制具有重要价值。这将使我们能够通过自噬来定义一种新的骨量调节机制，这对于开发治疗骨质疏松症等骨骼疾病的新疗法至关重要。1

DESCRIPTION (provided by applicant): The long term goal of the proposed studies is to understand the mechanisms of cell signaling in the regulation of key cellular functions in skeletal development/disease. In this proposal, we focus on the role of FIP200 (FAK-family Interacting Protein of 200 kDa) in the regulation of osteoblast differentiation. FIP200 was initially identifie as a novel FAK and Pyk2 inhibitor. Recently, FIP200 was identified as an essential component of mammalian autophagy. Despite our knowledge about FIP200 as a key signaling node in both embryogenesis and cancer development, it is unknown to what extent FIP200 regulates bone metabolism. In our preliminary studies, we found: 1. FIP200 conditional knockout in osteoblasts led to a severe osteopenic phenotype; 2. Osteoblast differentiation was greatly impaired in FIP200-null primary osteoblast cultures; 3. Primary calvarial osteoblasts have active basal and high inductive autophagy activity. However, FIP200 null primary calvarial osteoblasts expressing GFP-LC3 failed to form punctuate membrane structures in response to starvation and rapamycin treatment, indicating that FIP200 null osteoblasts had autophagy deficiency; 4. FIP200-null osteoblasts had large ubiquitin-positive aggregates, another indication of defective autophagy in these cells; and 5. Early neonatal FIP200 Osx-CKO mice had significant growth retardation in response to naturally occurring starvation as a result of sudden loss of maternal blood supply. Therefore, we hypothesize that FIP200 regulates bone mass through its regulation on osteoblast autophagy. The overall objective of the proposed project is to determine the molecular mechanisms and signaling pathways by which FIP200 regulates osteoblast function and bone mass using a combination of molecular, cell biological and mouse genetic approaches. The specific aims of this proposal are: Aim 1. To determine to what extent FIP200 regulates osteoblast function through its autophagic role. Aim 2. To elucidate the mechanism by which FIP200 regulates early postnatal bone development. Aim 3. To determine the role of FIP200 in bone homeostasis in adult mice. Health relevence: As a major public health threat, osteoporosis is present in an estimated 44 million men and women aged 50 and older, which represents 55 percent of the population in that age group in the USA. The proposed study with unique mouse disease model is highly valuable for determining the molecular and cellular mechanisms of pathogenesis of osteoporosis. It will allow us to define a novel bone mass regulation mechanism by autophagy, which is fundamentally important for the development of new therapeutics to treat bone diseases including osteoporosis. 1