G PROTEIN SIGNALING IN OSTEOBLASTS

成骨细胞中的 G 蛋白信号传导

• 批准号: 7049877
• 负责人: Robert Nissenson
• 金额: $ 33.83万
• 依托单位: NORTHERN CALIFORNIA INSTITUTE/RES/EDU
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-02-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7049877
• 关键词: G protein; biological signal transduction; bone density; bone metabolism; cell differentiation; genetically modified animals; hormone regulation /control mechanism; laboratory mouse; osteoblasts; parathyroid hormones

DESCRIPTION (provided by applicant): Extrinsic factors such as hormones, growth factors, and mechanical strain produce their effects on skeletal growth and remodeling via actions on osteoblasts. Accordingly, there is great interest in defining how specific intracellular signaling pathways mediate the effects of these factors in controlling osteoblast function. G protein signaling occurs in response to many skeletal stimuli, and the consequence of this signaling depends on the nature of the G protein; the temporal delivery of the signal; and the phenotypic state of the osteoblast. A clearer understanding of how calciotropic agents such as PTH elicit their complex effects in bone requires studies that address these issues directly in an in vivo context. In the present proposal, we will assess the role of Gs and Gi signaling in osteoblasts in mediating anabolic skeletal responses. In one approach, novel G protein-coupled receptors termed RASSLs will be targeted to osteoblasts in transgenic mice. RASSLs activate specific G protein pathways in response to administration of synthetic agonists. Activation of Gs- and Gi RASSLs will allow us to dissect the role of these pathways in skeletal responses. In a second approach, Gs and Gi function will be ablated in osteoblasts in vivo by cre-mediated excision of functional Gs-alpha alleles and by targeted expression of the catalytic subunit of pertussis toxin, respectively. We will determine the effects of ablating these signaling pathways on normal skeletal homeostasis and on the anabolic response to PTH. Mechanistic studies will be carried out to assess the effects of G protein signals on osteoblast proliferation and apoptosis in vivo and in bone marrow stromal cells (BMSCs) isolated from the transgenic mice. Convergence of G protein signals with two pathways recently shown to be essential for bone formation - the LRP/canonical Wnt pathway and the recently identified RSK2/ATF4 pathway- will be explored in BMSCs. We propose to: 1) assess the role of osteoblast Gs and Gi signaling in the regulation of skeletal homeostasis in mature mice. We will determine the effects of regulated, intermittent Gs and Gi signaling in osteoblasts at different stages of differentiation; determine the skeletal effect of conditional knockout of Gs and Gi signaling; and assess the mechanisms by which manipulation of Gs and Gi signaling elicits these effects; and 2) determine the contribution of Gs and Gi signaling to the anabolic response to PTH and the mechanisms of these effects. These studies will shed new light on the control of bone formation and bone resorption by G protein signaling in osteoblasts at different stages of differentiation. They may also provide new links between G protein signals and anabolic effects in bone, thereby identifying new therapeutic targets for the treatment of osteoporosis. LAY DESCRIPTION: We will explore how activation of specific signals in bone-forming cells can lead to increases in bone mass. The results may lead to new approaches to the treatment of osteoporosis.

描述（由申请人提供）：诸如激素，生长因子和机械菌株之类的外部因素会对骨骼生长产生影响，并通过对成骨细胞的作用进行重塑。因此，定义特定的细胞内信号通路如何介导这些因素控制成骨细胞功能的影响非常感兴趣。 G蛋白信号传导是对许多骨骼刺激的响应而发生的，该信号的后果取决于G蛋白的性质。信号的时间传递；以及成骨细胞的表型状态。对诸如PTH之类的钙化剂如何在骨骼中引起其复杂作用的更清晰的了解需要在体内直接解决这些问题的研究。在本提案中，我们将评估GS和GI信号在成骨细胞中介导合代代谢骨骼反应中的作用。在一种方法中，称为RASSL的新型G蛋白偶联受体将针对转基因小鼠的成骨细胞。 RASSL响应合成激动剂的给药而激活特定的G蛋白途径。 GS和GI RASSL的激活将使我们能够剖析这些途径在骨骼反应中的作用。在第二种方法中，通过CRE介导的功能性GS-Alpha等位基因的切除以及分别通过靶向百叶窗毒素的催化亚基的靶向表达，将GS和GI功能在体内覆盖在成骨细胞中。我们将确定烧毁这些信号通路对正常骨骼稳态的影响以及对PTH的合成代谢反应。将进行机械研究，以评估G蛋白信号对体内成骨细胞增殖和凋亡的影响，以及从转基因小鼠中分离出的骨髓基质细胞（BMSC）。 G蛋白信号与最近证明是骨形成必不可少的两个途径的收敛性-LRP/canonical Wnt途径和最近确定的RSK2/ATF4途径 - 将在BMSC中探索。我们建议：1）评估成骨细胞GS和GI信号在成熟小鼠骨骼稳态调节中的作用。我们将在分化的不同阶段确定在成骨细胞中受调节的，间歇性GS和GI信号的影响；确定GS和GI信号的条件敲除的骨骼效应；并评估操纵GS和GI信号引起这些影响的机制； 2）确定GS和GI信号传导对合成代谢响应对PTH的贡献以及这些作用的机制。这些研究将为分化的不同阶段的成骨细胞中G蛋白信号传导控制骨形成和骨吸收的新启示。它们还可以在骨骼中提供G蛋白信号与合成代谢作用之间的新联系，从而确定治疗骨质疏松症的新治疗靶标。 外表描述：我们将探讨骨形成细胞中特定信号的激活如何导致骨骼量的增加。结果可能会导致治疗骨质疏松症的新方法。