mTOR SIGNALING: A NOVEL MECHANISM OF WNT'S ANABOLIC EFFECTS ON BONE

骨质疏松症是一种主要的公共健康问题，其特征是骨量和骨骼减少。 矿物质密度。WNT信号促进出生后骨量增加。我们的长期目标是澄清 Wnt信号通路对骨的合成代谢作用的分子机制。我们 假设，在成骨细胞中，1)Wnt信号调节mTOR(哺乳动物同源的靶 雷帕霉素)活性，一种在调节蛋白质中起中心作用的必需的丝氨酸/苏氨酸激酶 2)mTOR在介导Wnt对骨的合成代谢作用中起关键作用。 这些假设是基于：1)我们的生化分析表明，Wnt信号 途径在体内和体外调节非成骨细胞的mTOR活性；2)常染色体 显性高骨量疾病(HBM)和结节硬化性骨发育不良(TSC)的特点是 骨骼和颅面骨中的成骨细胞和骨硬化性改变，因此都被归类 与硬化性骨发育不良有关；在这两种疾病中，Wnt和mTOR信号的过度活跃有关， 分别进行了分析。这两种疾病相似的临床和病理组织学特征提示有可能 Wnt和mTOR信号之间的功能连锁。具体的目标是： 目的1：确定Wnt信号在体内和体外是否促进骨组织中mTOR活性。 目的2：阐明Wnt信号调节mTOR活性的潜在机制。 目的3.确定WNT对骨的合成代谢效应是否需要mTOR。 ； 这些特定目标的成功完成将1)为WNT的分子机制提供关键的见解 信号对骨骼的合成代谢影响，2)为相似的临床和 硬化性骨发育不良的两种亚型，即HBM和TSC的共同病理组织学特征 损害，以及3)涉及雷帕霉素，一种特定的mTOR抑制剂，及其衍生物在治疗硬化中的作用 由过度活跃的Wnt信号引起的骨骼疾病。

Osteoporosis is a leading public health problem that is characterized by reduced bone mass and bone mineral density. Wnt signaling promotes postnatal bone mass accrual. Our long-term goal is to elucidate the molecular mechanisms underlying the anabolic effects of Wnt signaling pathway on bone. We hypothesize that, in osteoblasts, 1) Wnt signaling regulates mTOR (mammalian homolog of target of rapamycin) activity, an essential serine/threonine kinase that plays a central role in regulating protein synthesis and cell growth; and 2) mTOR plays a critical role in mediating Wnt's anabolic effects on bone. These hypotheses are based on: 1) our biochemical analyses have demonstrated that the Wnt signaling pathway regulates mTOR activity in non-osteoblasts both in vivo and in vitro; and 2) both autosomal dominant high bone mass disease (HBM) and tuberous sclerosing bone dysplasia (TSC) are featured by osteoblastic and osteosclerotic changes in skeletal and craniofacial bones, thus both having being classified to sclerosing bone dysplasia; in these two diseases, hyperactivity of Wnt and mTOR signaling are implicated, respectively. The similar clinical and pathohistological features of these two diseases suggest a possible functional linkage between Wnt and mTOR signaling. The Specific Aimsare: Aim 1: Determine whether Wnt signaling promotes mTOR activity in bone, both in vivo and in vitro. Aim 2: Elucidate the underlying mechanisms by which Wnt signaling regulates mTOR activity. Aim 3. Determine whether mTOR is required for Wnt anabolic effects on bone. ; Successful completion of these specific aims will 1) shed critical insight into the molecular mechanism of Wnt signaling' anabolic effects on bone, 2) provide a logical explanation for the similar clinical and pathohistological features shared by two subtypes of sclerosing bone dysplasias, i.e. HBM and TSC bone lesions, and 3) implicates rapamycin, a specific mTOR inhibitor, and the derivatives in treating sclerosing bone diseases caused by hyperactive Wnt signaling.