Regulation of the PTH/PTHrP Receptor

PTH/PTHrP 受体的调节

• 批准号: 7062732
• 负责人: ABDUL B ABOU-SAMRA
• 金额: $ 30.19万
• 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: 2004-12-01 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7062732
• 关键词: G protein; antireceptor antibody; biological signal transduction; cell line; fluorescence microscopy; genetically modified animals; green fluorescent proteins; hormone receptor; hormone regulation /control mechanism; laboratory mouse; osteoblasts; parathyroid hormone related protein; parathyroid hormones; phosphorylation; protein kinase; receptor binding; receptor sensitivity; transfection

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. We shall use the pdPTH1R knock in mouse model to understand the role of PTH1R phosphorylation, internalization and desensitization in calcium homeostasis in different physiological condition (Specific Aim 1). We shall also use in vitro cell line models to dissect the molecules involved in PTH1R phosphorylation and internalization (Specific Aim 2). Three naturally-occurring constitutively-active PTH1R mutants provide a unique opportunity to study the molecular mechanism of receptor regulation. The difference in their basal activity and agonist simulation may reflect intrinsic differences in phosphorylation and internalization. Understanding how these mutants are regulated will shed light into the molecular mechanisms of receptor phosphorylation, internalization and desensitization (Specific Aim 3). PTH analogs with unique binding and signaling properties, developed in Project I, will be tested for selective effects on internalization and desensitization. Identification of analogs which differentiate receptor activation from receptor internalization will provide a unique tool to understand the molecular mechanisms of receptor internalization and desensitization (Specific Aim 4).

甲状旁腺激素（PTH）/PTH相关肽（PTHrP）受体的激活（PTH/PTHrP受体或PTH 1 R）通过其同源配体PTH或PTHrP启动两个平行过程：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、分化和成熟的生物效应;和2）PTH 1 R的磷酸化、受体-配体复合物的内化和由该受体介导的生物反应的脱敏。PTH 1 R磷酸化、内化和脱敏的生理作用尚不清楚。我们最近绘制了PTH 1 R上的磷酸化位点，并开发了一种磷酸化缺陷型（PD）PTH 1 R，它在配体刺激的内化中有缺陷。使用同源重组技术，我们已经“敲入”突变型pdPTH 1 R以取代正常的PTH 1 R。我们将使用pdPTH 1 R敲除小鼠模型来了解PTH 1 R磷酸化、内化和脱敏在不同生理条件下钙稳态中的作用（具体目标1）。我们还将使用体外细胞系模型来剖析参与PTH 1 R磷酸化和内化的分子（具体目标2）。三种天然存在的组成型激活的PTH 1 R突变体为研究受体的分子机制提供了独特的机会。 调控它们的基础活性和激动剂模拟的差异可能反映了磷酸化和内化的内在差异。了解这些突变体是如何被调节的，将有助于了解受体磷酸化、内化和脱敏的分子机制（具体目标3）。在项目I中开发的具有独特结合和信号传导特性的PTH类似物将被测试对内化和脱敏的选择性作用。识别区分受体激活与受体内化的类似物将为理解受体内化和脱敏的分子机制提供独特的工具（具体目标4）。