PTH Signaling through LRP6

通过 LRP6 的 PTH 信号传导

基本信息

批准号：
7633917
负责人：
Mei Wan
金额：
$ 41万
依托单位：
JOHNS HOPKINS UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2009
资助国家：
美国
起止时间：
2009-09-09 至 2014-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): PTH is a primary regulator of calcium homeostasis and bone metabolism, and its signaling system has served as a major target for the development of novel anabolic therapeutic approaches for osteoporosis. However, the exact mechanisms by which PTH exerts its actions in bone are not fully understood. Despite the progress having been made in determining the PTH downstream signals in osteoblasts, novel signaling components may exist to bridge some major gaps in our understanding of the bone anabolic effects of PTH. We have characterized a novel PTH signaling pathway in osteoblasts. Our preliminary data show that binding of PTH to its receptor PTH1R induced association of LRP6, a coreceptor of Wnt, with PTH1R. The formation of the ternary complex containing PTH, PTH1R and LRP6 promoted rapid LRP6 phosphorylation, which resulted in the recruitment of axin to LRP6, and stabilization of 2-catenin. Activation of PKA is essential for PTH-induced 2-catenin stabilization, but not for Wnt signaling. Our demonstration of that the LRP6 coreceptor mediates PTH- activated 2-catenin signaling in osteoblasts suggests for the first time that LRP6 is the component of PTH/PTH1R complex. Importantly, in vivo studies confirmed that PTH treatment led to phosphorylation of LRP6 and an increase in amount of 2-catenin in osteoblasts with a concurrent increase in bone formation in rat. Therefore, we hypothesize that PTH-induced phosphorylation of LRP6, which is induced through activation of PKA, is required for PTH anabolic effect on bone. The objective of this proposal is to characterize the mechanisms of the LRP6 activation in response to PTH stimulation in osteoblasts and examine the role of LRP6 in PTH bone anabolic action in vivo. The proposal is organized into three aims. In aim I, the PKA phosphorylation sites within LRP6 will be characterized, and the role of PKA-phosphorylated LRP6 in activation of LRP6-2-catenin signaling in osteoblasts will be determined. In aim II, the requirement of LRP6 in mediating PTH-stimulated osteoblast activities in primary calvarial preosteoblasts and bone marrow stromal cells will be defined. In aim III, the requirement of LRP6 in PTH bone anabolic action in vivo will be examined using a mouse model of OC- Cre-mediated conditional deletion of LRP6. PUBLIC HEALTH RELEVANCE: The mechanisms responsible for anabolic actions of PTH on bone are not completely understood. This proposal will characterize how LRP6, a coreceptor for Wnt, is activated in osteoblasts upon PTH stimulation and the role of LRP6 in PTH bone anabolic action.

描述（由申请人提供）：PTH是钙稳态和骨代谢的主要调节剂，其信号系统已成为开发骨质疏松症新型合成代谢治疗方法的主要靶标。然而，PTH 在骨中发挥作用的确切机制尚不完全清楚。尽管在确定成骨细胞中 PTH 下游信号方面已经取得了进展，但新的信号成分可能存在，以弥补我们对 PTH 骨合成代谢作用的理解中的一些主要差距。我们在成骨细胞中描述了一种新的 PTH 信号通路。我们的初步数据表明，PTH 与其受体 PTH1R 的结合诱导了 LRP6（Wnt 的共同受体）与 PTH1R 的结合。含有 PTH、PTH1R 和 LRP6 的三元复合物的形成促进了 LRP6 的快速磷酸化，从而导致轴蛋白募集到 LRP6，并稳定 2-连环蛋白。 PKA 的激活对于 PTH 诱导的 2-连环蛋白稳定至关重要，但对于 Wnt 信号转导则不然。我们证明 LRP6 辅助受体介导成骨细胞中 PTH 激活的 2-连环蛋白信号传导，这首次表明 LRP6 是 PTH/PTH1R 复合物的组成部分。重要的是，体内研究证实，PTH 治疗导致大鼠成骨细胞中 LRP6 磷酸化和 2-连环蛋白含量增加，同时骨形成增加。因此，我们假设 PTH 诱导的 LRP6 磷酸化（通过激活 PKA 诱导）是 PTH 对骨合成代谢作用所必需的。本提案的目的是表征成骨细胞中 LRP6 响应 PTH 刺激而激活的机制，并检查 LRP6 在体内 PTH 骨合成代谢作用中的作用。该提案分为三个目标。在目标 I 中，将表征 LRP6 内的 PKA 磷酸化位点，并确定 PKA 磷酸化的 LRP6 在成骨细胞中 LRP6-2-连环蛋白信号传导激活中的作用。在目标 II 中，将定义 LRP6 在介导原代颅骨前成骨细胞和骨髓基质细胞中 PTH 刺激的成骨细胞活性中的需求。在目标 III 中，将使用 OC-Cre 介导的 LRP6 条件性缺失的小鼠模型来检查 LRP6 在体内 PTH 骨合成代谢作用中的需求。公众健康相关性：PTH 对骨骼的合成代谢作用的机制尚不完全清楚。该提案将描述 LRP6（Wnt 的辅助受体）如何在 PTH 刺激下在成骨细胞中被激活，以及 LRP6 在 PTH 骨合成代谢作用中的作用。