EBP50 REGULATION OF PTH RECEPTOR IN BONE AND KIDNEY

该项目的长期目标是阐明甲状旁腺激素受体的细胞机制 （PTH1R）作用。PTH1R通过其对细胞外钙和磷酸盐稳态的作用来调节细胞外钙和磷酸盐稳态。 肾和骨头像其他G蛋白偶联受体一样，PTH1R表现出一个周期性的过程， 激活、脱敏、内化和重新敏感。受体脱敏提供了一种 保护细胞免受过度刺激的机制，而再敏化则保护细胞免受 长期不活动和激素抵抗。然而，与大多数其他受体不同，PTH1R表现出 相当大的细胞和组织特异性差异，其激活。这些差异不能归因于 选择性剪接受体形式、受体丰度或G蛋白可用性。最近的证据表明 胞质衔接蛋白ezrin结合蛋白50 kD（EBP 50）可能有助于细胞特异性 PTH1R信号传导和内化。拟议研究的中心目标是检查相互作用 和EBP 50对PTH 1R循环的所有方面的调节活性。四个具体目标是为了测试 EBP 50调节PTH1R的配体特异性反应的统一假设。目标1将 表征EBP 50对细胞特异性PTH1R活化的作用。目标2将描述EBP 50对 PTH1R脱敏。目的3将确定参与PTH1R的EBP 50的结构决定因素 内化目的4将确定EBP 50对PTH1R再循环的影响。计划中的研究采用 一系列细胞生物学、生物化学和分子生物学技术，将应用于特定的 肾和骨细胞是PTH作用的主要靶点。初步数据提供临时数据 支持并确定大部分拟议工作的可行性。计划中的研究将产生新的和 关于PTH1R调节细胞外钙的机制和作用的重要信息 体内平衡这些结果将为PTH1R的启动和终止提供更好的理解 行动上结果可能提示导致PTH抵抗的其他病理生理机制， 带来新的治疗机会。

The long-term goal of this project is to elucidate the cellular mechanisms of parathyroid hormone receptor (PTH1R) action. The PTH1R regulates extracellular calcium and phosphate homeostasis by its actions on kidney and bone. Like other G protein-coupled receptors, the PTH1R exhibits a cyclical process of activation, desensitization, internalization, and resensitization. Receptor desensitization provides a mechanism to protect cells against excessive stimulation, while resensitization guards cells against prolonged inactivity and hormone resistance. Unlike most other receptors, however, the PTH1R exhibits considerable cell- and tissue-specific differences in its activation. These differences cannot be ascribed to alternatively spliced receptor forms, receptor abundance, or G protein availability. Recent evidence suggests that the cytoplasmic adaptor protein ezrin-binding protein 50 kD (EBP50) may contribute to cell-specific PTH1R signaling and internalization. The central goal of the proposed studies is to examine the interaction and modulatory activity of EBP50 on all aspects of PTH1R cycling. Four specific aims are developed to test the unifying hypothesis that EBP50 regulates ligand-specific responses of the PTH1R. Aim 1 will characterize the effects of EBP50 on cell-specific PTH1R activation. Aim 2 will describe EBP50 effects on PTH1R desensitization. Aim 3 will identify structural determinants of EBP50 that are involved in PTH1R internalization. Aim 4 will determine the effects of EBP50 on PTH1R recycling. The planned studies employ an array of cell biological, biochemical, and molecular biological techniques that will be applied to specific kidney and bone cells that are the primary targets of PTH action. Preliminary data provide provisional support and establish the feasibility for much of the proposed work. The planned studies will yield novel and important information on the mechanism and role by which the PTH1R regulates extracellular calcium homeostasis. The results will provide greater understanding of the initiation and termination of PTH1R action. The outcomes may suggest additional pathophysiological mechanisms causing PTH resistance and lead to new treatment opportunities.