G PROTEIN SIGNALING IN OSTEOBLASTS

外在因素，如激素、生长因子和机械应变对骨骼产生影响。 通过对成骨细胞的作用进行生长和重塑。因此，人们对如何定义 特定的细胞内信号通路介导了这些因子在控制成骨细胞功能中的作用。 G蛋白信号在许多骨骼刺激下发生，这种信号的结果是 取决于G蛋白的性质；信号的暂时传递；以及细胞的表型状态 成骨细胞。更清楚地了解促钙剂如甲状旁腺素是如何在 骨骼需要在活体环境中直接解决这些问题的研究。在目前的提案中，我们 将评估成骨细胞中Gs和Gi信号在调节合成代谢骨骼反应中的作用。合而为一 新的G蛋白偶联受体RASSLs将以转基因方式靶向成骨细胞 老鼠。RASSLs在给予合成激动剂后激活特定的G蛋白通路。 Gs-和GI RASSLs的激活将使我们能够剖析这些通路在骨骼反应中的作用。在……里面 第二种方法，Gs和GI功能将在体内通过cre介导的切除成骨细胞来消融 功能Gs-α等位基因和百日咳毒素催化亚单位的靶向表达。 我们将确定消融这些信号通路对正常骨骼动态平衡的影响 对甲状旁腺素的合成代谢反应。将进行机制研究以评估G蛋白的作用 成骨细胞增殖和凋亡信号在体内和分离的骨髓基质细胞中的表达 来自转基因小鼠。G蛋白信号的会聚与最近显示的两条途径 骨形成的关键--LRP/规范的WNT通路和新近发现的RSK2/ATF4 途径-将在骨髓间充质干细胞中探索。我们建议：1)评估成骨细胞Gs和GI信号在 成年小鼠骨骼动态平衡的调节。我们将确定受监管的、间歇性的 成骨细胞分化不同阶段的GS和GI信号转导；决定成骨细胞的骨骼效应 有条件地敲除Gs和Gi信号；并评估Gs和Gi信号的操纵机制 GI信号引起这些效应；2)确定Gs和GI信号对合成代谢的贡献 对甲状旁腺素的反应及其作用机制。这些研究将为防治艾滋病提供新的线索。 不同分化阶段成骨细胞中G蛋白信号转导的骨形成和骨吸收。 它们还可能在G蛋白信号和骨骼中的合成代谢效应之间提供新的联系，从而识别 治疗骨质疏松症的新靶点。 Layer描述：我们将探索骨形成细胞中特定信号的激活如何导致 骨量增加。这一结果可能会带来治疗骨质疏松症的新方法。

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.