Genetic Analysis of Second Messengers in PTH Signaling in Bone

了解PTH对骨的合成代谢作用的机制是重要的，因为PTH 代表了第一种可用于治疗骨质疏松症的合成代谢剂， PTH的合成代谢作用将允许开发更有效的合成代谢剂。我们的目标是 使用体内模型来确定负责这些信号传导的特定“第二信使”途径的作用。 PTH的各种作用，总之，导致骨量增加。对多重性的理解， 以不同方式导致骨骼增加的特定途径将使下一代理性成为可能 合成代谢剂我们也想了解这些机制，以更好地了解PTH的作用， 和PTHrP在正常生理和疾病中的作用。PTH和PTHrP刺激骨形成和骨形成 通过活化成骨细胞谱系细胞中的PTH/PTHrP受体（PTHR 1）的吸收。的 PTHR 1激活几种异源三聚体G蛋白，其中Gs和Gq/11是最好的特征。我们将 使用两种遗传模型，允许分离这些下游介质在体内的作用。一 该模型使用了一种“敲入”小鼠，其中正常的PTHR 1基因已经发生突变，以选择性地破坏 通过Gq/11途径激活磷脂酶C，而不影响Gs的激活。另一个模型是 条件性敲除，其中在早期成骨细胞中有活性的osterix启动子驱动ere的表达 重组酶以可被四环素衍生物抑制的方式（“tet-off”）。这里是用来 通过与Gsa floxed交配来消除出生后成骨细胞谱系早期细胞中Gsa的表达 小鼠和给予多西环素不同时间。受体激活的三种模型（连续 通过微泵输注或低钙饮食升高PTH，以及每天注射一次PTH） 确定PTHR 1对成骨细胞的各种作用中不同途径的作用 脉目标1。PLC信号在骨中PTHR 1作用中的作用。间歇性和 目的1.通过连续给予PTH，研究PTHR 1在骨组织中的活化作用。 Gs信号在成骨细胞系细胞中的作用。成骨细胞Gsa缺失小鼠的比较 与暴露于PTH水平连续或间歇升高的相同小鼠相比， 对PTHR 1激活的反应需要Gsalpha

Understanding the mechanisms of the anabolic action of PTH on bone is important both because PTH represents the first anabolic agent useful to treat osteoporosis and because a molecular understanding of PTH's anabolic action will allow the development of even more effective anabolic agents. Our goal here is to use in vivo models to establish the roles of specific "second messenger" pathways responsible for the various actions of PTH that, in sum, result in an increase in bone mass. Understanding of the multiple, specific pathways leading in varying ways to increased bone will make possible the next rational generation of anabolic agents. We also want to understand these mechanisms to understand better the roles of PTH and PTHrP in normal physiology and disease. PTH and PTHrP stimulate both bone formation and bone resorption through activation of the PTH/PTHrP receptor (PTHR1) in cells of the osteoblast lineage. The PTHR1 activates several heterotrimeric G proteins, with Gs and Gq/11 being the best characterized. We will use two genetic models that allow the separation of the actions of these downstream mediators in vivo. One model uses a "knock-in" mouse in which the normal PTHR1 gene has been mutated to selectively disrupt the activation of phospholipase C by the Gq/11 pathway without affecting activation of Gs. The other model is a conditional knockout in which the osterix promoter, active in early osteoblasts, drives the expression of ere recombinase in a way that can be suppressed by tetracycline derivatives ("tet-off"). This ere is used to ablate expression of Gsa postnatally in early cells of the osteoblast lineage through mating with a Gsa floxed mouse and administration of doxycycline for various times. Three models of receptor activation (continuous elevation of PTH through minipump infusion or low calcium diet, and once daily injection of PTH) will be used to determine the roles of distinct pathways in the variety of actions of the PTHR1 on cells of the osteoblast lineage. Aim 1. Role of PLC signaling in actions of the PTHR1 in bone. Models of intermittent and continuous PTH administration will be used to determine the role of PTHR1 activation of PLC in bone.Aim 2. Role of Gs signaling in cells of the osteoblast lineage. Comparison of mice missing Gsa in osteoblastic cells with the same mice exposed to continuous or intermittent elevation of PTH levels should allow identification of the responses to activation of the PTHR1 that require Gsalpha