PTH1R REGULATION IN BONE BIOLOGY USING A MOUSE MODEL

使用小鼠模型研究骨生物学中的 PTH1R 调节

• 批准号: 6736473
• 负责人: ABDUL B ABOU-SAMRA
• 金额: $ 40.34万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-15 至 2008-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6736473
• 关键词: biological models; bone development; cartilage development; cell differentiation; chondrocytes; enzyme linked immunosorbent assay; genetically modified animals; hormone receptor; in situ hybridization; laboratory mouse; model design /development; osteoblasts; parathyroid hormones; phosphorylation; physiologic bone resorption; receptor expression

DESCRIPTION (provided by applicant): Activation of the parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (the PTH/PTHrP receptor or PTH1R) by its cognate ligands, PTH or PTHrP, initiates two parallel processes: 1) stimulation of intracellular second messengers leading to biologic effects on mineral ion homeostasis and bone cell development, differentiation, and maturation; and 2) phosphorylation of PTH1R, internalization of the receptor - ligand complexes and desensitization of the biologic responses mediated by this receptor. The physiological role of PTH1R phosphorylation, internalization and desensitization is not known. We have recently mapped the phosphorylation sites on PTH1R and developed a phosphorylation-deficient (pd) PTH1R, which is defective in ligand-stimulated internalization. Using homologous recombination techniques we have "knocked in" the mutant pdPTH1R to replace the normal PTH1R in ES cell lines and have already developed homozygous knock-in (pd/pd) mice. The pd/pd mice are fertile, viable, and normocalcemic. However, these mice have low PTH and low phosphate levels. In addition, these mice showed prolonged and exaggerated cAMP response to PTH injection. One intriguing puzzle in PTH biology is to understand how intermittent PTH administration promotes bone formation whereas continuous PTH administration promotes bone resorption. In Specific Aim 1 we propose to develop a knock in mouse model expressing the pdPTH1R to understand the role of PTH1R phosphorylation, internalization and desensitization in bone development, differentiation and maturation and in the anabolic effects of intermittent PTH administration in vivo. In Specific Aim 2 we shall examine the bone and cartilage phenotype of the pdPTH1R knock in mouse to assess the hypothesis that phosphorylation and internalization of the PTH1R is important for the regulation of bone and chondrocytic cell development, differentiation and maturation. In Specific Aim 3 we shall use this model to examine the hypothesis that PTH1R phosphorylation and internalization play an important role for the expression of the anabolic actions of intermittent PTH administration. Achievement of the goals of this project will increase our understanding of how phosphorylation and internalization of the PTH/PTHrP receptor affects the expression of PTH actions in bone (formation and resorption); this is essential to understand bone diseases and design new therapeutic agents targeted for their prevention and reversal.

描述（由申请人提供）：甲状旁腺激素（PTH）/PTH相关肽（PTHrP）受体（PTH/PTHrP受体或PTH1R）通过其同源配体PTH或PTHrP激活，启动两个并行过程：1）刺激细胞内第二信使，导致对矿物质离子稳态和骨细胞发育、分化的生物效应， 和成熟； 2) PTH1R 的磷酸化、受体-配体复合物的内化以及该受体介导的生物反应的脱敏。 PTH1R 磷酸化、内化和脱敏的生理作用尚不清楚。我们最近绘制了 PTH1R 上的磷酸化位点，并开发了磷酸化缺陷（pd）PTH1R，其在配体刺激的内化中存在缺陷。使用同源重组技术，我们“敲入”突变的pdPTH1R以取代ES细胞系中的正常PTH1R，并且已经开发出纯合敲入(pd/pd)小鼠。 pd/pd 小鼠具有生育能力、可存活且血钙正常。然而，这些小鼠的 PTH 和磷酸盐水平较低。此外，这些小鼠对 PTH 注射表现出延长且过度的 cAMP 反应。 PTH 生物学中一个有趣的难题是了解间歇性 PTH 给药如何促进骨形成，而连续 PTH 给药如何促进骨吸收。在具体目标 1 中，我们建议开发表达 pdPTH1R 的小鼠模型，以了解 PTH1R 磷酸化、内化和脱敏在骨发育、分化和成熟以及体内间歇性 PTH 给药的合成代谢作用中的作用。在具体目标 2 中，我们将检查 pdPTH1R 敲入小鼠的骨和软骨表型，以评估 PTH1R 的磷酸化和内化对于骨和软骨细胞发育、分化和成熟的调节很重要的假设。在具体目标 3 中，我们将使用该模型来检验以下假设：PTH1R 磷酸化和内化对于间歇性 PTH 给药的合成代谢作用的表达发挥重要作用。该项目目标的实现将增加我们对 PTH/PTHrP 受体的磷酸化和内化如何影响骨中 PTH 作用表达（形成和吸收）的理解；这对于了解骨病和设计预防和逆转骨病的新治疗药物至关重要。