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.

性状（申请人提供）：激素、生长因子、机械应变等外在因素通过作用于成骨细胞，对骨骼生长和重塑产生影响。因此，有很大的兴趣，在确定如何特定的细胞内信号通路介导的影响，这些因素在控制成骨细胞的功能。G蛋白信号传导响应于许多骨骼刺激而发生，并且这种信号传导的结果取决于G蛋白的性质;信号的时间传递;以及成骨细胞的表型状态。要更清楚地了解促钙剂（如PTH）如何在骨中引起其复杂作用，需要在体内直接研究这些问题。在本研究中，我们将评估Gs和Gi信号在成骨细胞中介导合成代谢骨骼反应的作用。在一种方法中，称为RASSL的新型G蛋白偶联受体将靶向转基因小鼠中的成骨细胞。RASSLs激活特定的G蛋白途径，以响应合成激动剂的施用。Gs-和Gi RASSLs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，Gs和Gi功能将分别通过cre介导的功能性Gs-α等位基因的切除和通过百日咳毒素的催化亚基的靶向表达在体内成骨细胞中被消融。我们将确定消融这些信号通路对正常骨骼稳态和PTH合成代谢反应的影响。将进行机制研究，以评估G蛋白信号对成骨细胞增殖和凋亡的影响，在体内和骨髓基质细胞（BMSCs）分离的转基因小鼠。G蛋白信号与最近被证明对骨形成至关重要的两种途径-LRP/经典Wnt途径和最近鉴定的RSK 2/ATF 4途径-的融合将在BMSC中进行探索。本研究拟：1）探讨成骨细胞Gs和Gi信号在成年小鼠骨骼稳态调节中的作用。我们将确定成骨细胞在不同分化阶段的调节性间歇性Gs和Gi信号传导的影响;确定Gs和Gi信号传导的条件性敲除的骨骼效应;并评估Gs和Gi信号传导的操纵引起这些效应的机制;和2）确定Gs和Gi信号传导对PTH合成代谢反应的贡献以及这些效应的机制。这些研究为阐明G蛋白信号在成骨细胞不同分化阶段调控骨形成和骨吸收提供了新的思路。它们还可能提供G蛋白信号与骨中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点。 说明：我们将探讨骨形成细胞中特定信号的激活如何导致骨量增加。研究结果可能会为治疗骨质疏松症带来新的方法。