VITAMIN D-REGULATED EXOCYTOSIS IN OSTEOBLASTS

成骨细胞中维生素 D 调节的胞吐作用

• 批准号: 6905073
• 负责人: LAURA P ZANELLO
• 金额: $ 21.08万
• 依托单位: UNIVERSITY OF CALIFORNIA RIVERSIDE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2008-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6905073
• 关键词: 1,25 dihydroxycholecalciferol; biological signal transduction; chloride channels; confocal scanning microscopy; exocytosis; gene induction /repression; genetically modified animals; hormone regulation /control mechanism; immunocytochemistry; laboratory mouse; osteoblasts; osteogenesis; protein localization; vitamin D receptors; voltage /patch clamp; voltage gated channel

DESCRIPTION (provided by applicant): The steroid 1alpha,25(OH)2 vitamin D3 (1,25D) is a systemic hormone with bone anabolic effects. 1,25D promotes the synthesis of bone matrix and its mineralization by acting on osteoblasts. This occurs via interaction with the vitamin D receptor (VDR) and modulation of gene transcription. In addition, 1,25D acts rapidly (sec-min) at the plasma membrane level, where it activates cytoplasmic signaling pathways and ion channel functions. I recently demonstrated that 1,25D-potentiation of chloride currents is coupled to a stimulation of secretion of matrix proteins in osteoblasts expressing a functional VDR. However, the precise molecular mechanisms of these 1,25D effects remain only partially understood. The long-term goal of this proposal is to elucidate 1,25D non-genomic mechanisms of bone formation in osteoblasts. My working hypothesis, which I propose as a new investigator, is that signal transduction triggered by 1,25D acting at a membrane-associated VDR leads to a non-genomic rapid exocytotic response, which is coupled to chloride channel activation in osteoblasts. This explains in part the anabolic effects of the hormone in bone. The first specific aim of this proposal investigates two parallel signal transduction pathways recruited by a membrane-associated VDR in osteoblasts: a) Galpha q/cAMP/PKA/CI- channel phosphorylation/exocytosis, and b) Galpha q/PLC/IP3/calcium/exocytosis. The second specific aim studies the osteoblastic CIC-3 gene, its protein product, and coupling to exocytosis. This will be studied in osteoblasts obtained from VDR WT and KO mice, the latter expressing a rachitic phenotype. Although the primary focus of this proposal is on basic research, the objective is to identify molecular targets in the treatment of bone pathologies characterized by decreased bone mass and mineralization. This typifies skeletal diseases such as osteoporosis and osteomalacia, respectively. Osteoporosis in particular affects a large sector of the aging American population and constitutes a significant economic burden.

说明(申请人提供)：类固醇1α，25(OH)2维生素D3(1，25D)是一种具有骨合成代谢作用的全身性激素。1，25D通过作用于成骨细胞促进骨基质的合成和矿化。这是通过与维生素D受体(VDR)的相互作用和基因转录的调节来实现的。此外，1，25D在质膜水平上作用迅速(秒-分钟)，激活细胞质信号通路和离子通道功能。我最近证明，在表达功能性VDR的成骨细胞中，氯电流的1，25D-增强与刺激基质蛋白的分泌有关。然而，这些1，25D效应的确切分子机制仍然只有部分了解。这项建议的长期目标是阐明成骨细胞骨形成的1，25D非基因组机制。我作为一名新的研究者提出了我的工作假设，即1，25D作用于膜相关的VDR所触发的信号转导导致了非基因组的快速胞吐反应，这与成骨细胞中氯通道的激活有关。这在一定程度上解释了骨骼中激素的合成代谢作用。这项建议的第一个具体目的是研究成骨细胞中膜相关VDR所招募的两条平行的信号转导途径：a)Galpha Q/cAMP/PKA/CI通道磷酸化/胞吐作用；b)Galpha Q/PLC/IP3/钙/胞吐作用。第二个特定目的是研究成骨细胞CIC-3基因及其蛋白产物与胞吐作用的偶联。这将在从VDR WT和KO小鼠获得的成骨细胞中进行研究，后者表现为脊椎病表型。虽然这项建议的主要重点是基础研究，但目标是确定治疗以骨量减少和矿化为特征的骨病理的分子靶点。这分别代表了骨质疏松症和骨软化症等骨骼疾病。骨质疏松症尤其影响到美国老龄化人口的很大一部分，并构成重大的经济负担。