VIT D AND ESTROGEN RECEPTOR COACTIVATORS IN OSTEOBLASTS

骨质疏松症是一种以骨量减少为特征的代谢性骨骼疾病。 和骨组织的微结构恶化，最终导致 增加骨骼的脆性，增加骨折的风险。两个原则 与骨质疏松症有密切联系的类固醇激素 过程是雌激素(E2)和1α，25-二羟基维生素D3 (1，25(OH)2D3)。雌二醇和1，25(OH)2D3的生物学效应为 由核受体(分别为内质网和视黄醇受体)介导 它们作为配体激活的转录因子控制 特定基因或基因网络在骨细胞中的表达。 然而，这些受体影响的确切机制 转录过程在很大程度上是未知的。在预赛中 研究发现，我们已经分离到一种新的人类cdna克隆，它编码一种 62,000 Da的核蛋白选择性地与几个 核受体，包括VDR和ER。重要的是 该克隆在VDR反应基因表达中的共表达 系统显著增强了L，25(OH)2D3-/VdR介导的转录。 该克隆被命名为NCOA-62，即核受体 分子质量为62,000 Da的助激活剂。这样做的长期目标是 建议了解VDR-和ER-的分子机制。 在骨细胞中介导的基因表达，在短期内，这 研究建议侧重于确定NCOA-62的功能作用 维生素D和雌激素调节转录。我们的假设 声明NCoA-62是一种桥蛋白，它是一种重要的 启动子结合受体和 转录预起始复合体。为了检验这一假设，我们 提出四个具体目标：1.确定NCoA62是否参与 在内质网介导的哺乳动物细胞转录中2.鉴定蛋白质 对NCoA62共激活子活性重要的结构域3.检查 NCOA-62在1，25(OH)2D3-和E_2介导中的重要性 成骨细胞系中的转录4.鉴定和表征 与NCoA62相互作用的成骨细胞核蛋白。 这些研究旨在提高我们对基本知识的理解 维生素D和雌激素依赖转录的机制 并确定其重要的功能成分 复杂的过程。通过对这一情结的了解 过程中，合理的治疗策略将在 治疗和预防衰弱的骨病，如 骨质疏松。

Osteoporosis is a metabolic bone disorder characterized by low bone mass and microstructural deterioration of bone tissue, culminating in increased bone fragility and increased risk of fracture. Two principle steroid hormones which have strong links to the osteoporotic disease process are estrogen (E2) and 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3). The biological effects of E2 and 1,25(OH)2D3 are mediated through nuclear receptors (the ER and the VDR, respectively) which function as ligand activated transcription factors that control the expression of specific genes or gene networks in bone cells. However, the precise mechanisms through which these receptors influence the transcriptional process are largely unknown. In preliminary studies, we have isolated a novel, human cDNA clone that encodes a 62,000 Da nuclear protein that interacts selectively with several nuclear receptors, including the VDR and the ER. Importantly, coexpression of this cDNA clone in a VDR-responsive gene expression system dramatically augments l,25(OH)2D3-/VDR-mediated transcription. The clone has been designated as NCoA-62, for Nuclear Receptor CoActivator of 62,000 Da molecular mass. The long-term goal of this proposal is to understand the molecular mechanism of VDR- and ER- mediated gene expression in bone cells and in the short-term, this research proposal focuses on determining the functional role of NCoA-62 in vitamin D and estrogen regulated transcription. Our hypothesis states that NCoA-62 is a bridging protein that serves as an important communication link between the promoter-bound receptor and the transcription preinitiation complex. To test this hypothesis, we propose four specific aims that: 1. establish whether NCoA62 is involved in ER-mediated transcription in mammalian cells 2. identify the protein domains that are important for NCoA62 coactivator activity 3. examine the essentiality of NCoA-62 in 1,25(OH)2D3- and E2-mediated transcription in osteoblast cell lines 4. identify and characterize osteoblast nuclear proteins that interact with NCoA62. These studies are designed to improve our understanding of the basic mechanisms involved in vitamin D and estrogen dependent transcription in bone and to identify the important functional components of this complex process. Through an acquired understanding of this complex process, rational therapeutic strategies will be realized in the treatment and prevention of debilitating bone disorders such as osteoporosis.