Role of ATF-4 in the Anabolic Actions of PTH on Bone

ATF-4 在 PTH 对骨的合成代谢作用中的作用

• 批准号: 7258603
• 负责人: Guozhi Xiao
• 金额: $ 28.66万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-17 至 2012-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7258603
• 关键词: Affect; Amino Acids; Binding; Cultured Cells; Data; Foundations; Fracture; Gene Deletion; Gene Expression; Goals; Hormone Responsive; In Vitro; Mediating; Metabolic Bone Diseases; Molecular; Mus; Osteoblasts; Osteogenesis; Osteoporosis; Parathyroid Hormones; Phosphorylation; Phosphorylation Site; Protein Overexpression; Public Health; Rattus; Research; Risk; Role; Signal Transduction; Solid; Testing; Transgenes; Transgenic Mice; activating transcription factor 4; bone; bone strength; human PTH protein; improved; in vivo; mutant; novel; promoter; protein protein interaction; therapeutic target

DESCRIPTION (provided by applicant): Osteoporosis is a major public health problem that affects more than 10 million people in the US and results in 1.5 million fractures annually. Intermittent administration of parathyroid hormone (PTH) is the most effective current treatment for osteoporosis. PTH improves bone mass and bone microarchitecture, increases bone strength, and reduces the risk for fractures. However, the molecular mechanism underlying the anabolic actions of PTH on bone formation remains poorly understood. Gene deletion studies showed that activating transcription factor 4 (ATF4) is a critical factor for bone formation. The findings from our preliminary studies strongly suggest that PTH controls osteoblast-specific gene expression and bone formation, at least in part, through ATF4. The long-term goal of this project is to understand how PTH signals regulate osteoblast activity in bone formation. Our hypotheses are: i) PTH activates ATF4 by promoting its phosphorylation and protein-protein interactions with Runx2, and ii) ATF4 mediates the anabolic actions of PTH on bone. To test these hypotheses, we will pursue the following Specific Aims: Aim 1. Determine the mechanism used by PTH to regulate ATF4 and Runx2 transcriptional activity. To accomplish this aim: i) we will identify the PTH responsive phosphorylation sites in ATF4 and assess the functional significance of PTH-induced phosphorylation in ATF4 in cultured cells; ii) We will define the regions/amino acid residues within ATF4 and Runx2 that mediate the ATF4-Runx2 interactions; and iii) we will determine whether PTH signals increase ATF4-Runx2 binding and if these interactions are necessary for PTH actions in osteoblasts in vitro. Aim 2. Establish whether the anabolic actions of PTH require ATF4. We will determine if ATF4 is required for the anabolic actions of PTH in vivo using the ATF4-deficient mice and transgenic mice overexpressing ATF4 in osteoblasts. Aim 3. Determine whether ATF4-Runx2 interactions are required for normal and PTH-induced bone formation in vivo. This project will explore a novel mechanism to explain the anabolic actions of PTH and define new potential therapeutic targets for improved treatment of osteoporosis and other metabolic bone diseases.

描述(由申请人提供)：骨质疏松症是一个主要的公共健康问题，在美国有1000多万人受到影响，每年导致150万人骨折。间歇性甲状旁腺激素(PTH)是目前治疗骨质疏松症最有效的方法。甲状旁腺素改善骨量和骨微结构，增加骨骼强度，降低骨折风险。然而，甲状旁腺激素对骨形成的合成代谢作用的分子机制仍然知之甚少。基因缺失研究表明，激活转录因子4(ATF4)是骨形成的关键因素。我们的初步研究结果有力地表明，甲状旁腺素至少部分地通过ATF4调控成骨细胞特异性基因的表达和骨形成。该项目的长期目标是了解甲状旁腺激素信号如何调节成骨细胞在骨形成中的活动。我们的假设是：1)PTH通过促进ATF4的磷酸化和与Runx2的蛋白质-蛋白质相互作用来激活ATF4；2)ATF4介导了PTH对骨的合成代谢作用。为了验证这些假说，我们将追求以下具体目标：目的1.确定PTH调节ATF4和Runx2转录活性的机制。为了实现这一目标：i)我们将确定ATF4中PTH响应的磷酸化位点，并评估PTH诱导的ATF4在培养细胞中的功能意义；ii)我们将确定ATF4和Runx2中介导ATF4-Runx2相互作用的区域/氨基酸残基；以及iii)我们将确定PTH信号是否增加了ATF4-Runx2的结合，以及这些相互作用是否对体外培养的成骨细胞的PTH作用是必要的。目的2.确定甲状旁腺素的合成代谢作用是否需要ATF4。我们将使用ATF4缺陷小鼠和在成骨细胞中过度表达ATF4的转基因小鼠来确定在体内PTH的合成代谢活动是否需要ATF4。目的3.确定体内正常和甲状旁腺激素诱导的骨形成是否需要ATF4-Runx2相互作用。该项目将探索一种新的机制来解释甲状旁腺素的合成代谢作用，并为改善骨质疏松症和其他代谢性骨疾病的治疗确定新的潜在治疗靶点。