VITAMIN D HORMONE--FUNCTION AND MECHANISM OF ACTION

描述(改编自申请人的摘要)：本申请的目的 建议是为了更好地了解主动的行为 维生素D的形式，1，25二羟基维生素D3[1，25(OH)2D3]，在体内和 在分子水平上。这项续期申请建议继续 钙结合蛋白的合成及其功能意义的相关研究 通过1，25(OH)2D3代表了在体内最显著的效应之一 1，25(OH)2D3已知。拟议的研究包括使用Calbindin-D28k 并将重点研究哺乳动物Calbindin-D28k在 肾单位远端小管对胰岛素分泌的调节作用 对细胞凋亡的保护作用。在上一批资助期内， 调查人员完成了Calbindin对 1，25(OH)2D3，他们发现它是适度转录的。为了获得 进一步深入了解1，25(OH)2D3作用的分子机制， 24(OH)酶基因的调节，该基因除了钙结合蛋白外， 1，25(OH)2D3在肠道和肾脏明显诱导， 检查过了。细胞类型特异性机制，1，25(OH)2D3和其他 激素和信号通路协同调节24(OH)酶将 审查，包括：1)对VDR和RXR的监管；2)对监管的影响 启动子中的区域；3)对DNA与转录结合的影响 各种因素。此外，与VDR相互作用的新型转录因子 介导24(OH)酶基因和骨桥蛋白基因的转录(用于 比较)将被识别和表征(候选是YY1、SRC-1、 和TAFII110)。配体的细胞类型和基因特异性要求 VDR介导的转录的独立调节将被研究。 还将进行与功能意义相关的实验 24(OH)ase，使用零突变小鼠，这将集中在建议的作用 维生素D代谢中的24(OH)酶。这很可能是一个增加的 结合对靶蛋白功能意义的理解 随着对细胞和基因特异性相互作用的了解不断加深 1，25(OH)2D3和VDR与其他激素和转录因子一起发挥作用 在阐明机制方面发挥着越来越重要的作用 1，25(OH)2D3介导其生物学效应及其异常调控 患有骨质疏松症等疾病 甲状旁腺功能。

DESCRIPTION (Adapted from the Applicant's Abstract): The object of this proposal is to obtain a better understanding of the actions of the active form of vitamin D, 1,25 dihydroxyvitamin D3 [1,25(OH)2D3], both in vivo and at the molecular level. This renewal application proposes to continue studies related to the functional significance of calbindin, whose synthesis by 1,25(OH)2D3 represents one of the most pronounced in vivo effects of 1,25(OH)2D3 known. Proposed studies include the use of calbindin-D28k knock-out mice and will focus on effects of mammalian calbindin-D28k in the nephron's distal tubule, on modulation of insulin secretion, and on protection against apoptotic cell death. In the previous grant period, the investigators completed the characterization of calbindin's response to 1,25(OH)2D3, which they found to be modestly transcriptional. To obtain further insight into the molecular mechanism of 1,25(OH)2D3 action, regulation of the 24(OH)ase gene, the gene in addition to calbindin which is markedly induced by 1,25(OH)2D3 in the intestine and kidney, will be examined. Cell type -specific mechanisms by which 1,25(OH)2D3 and other hormones and signaling pathways coordinately regulate 24(OH)ase will be examined, including: 1) regulation of VDR and RXR; 2) effects on regulatory regions in the promoter; and 3) effects on DNA binding to transcription factors. In addition, novel transcription factors that interact with VDR to mediate transcription of the 24(OH)ase gene and the osteopontin gene (for comparison) will be identified and characterized (candidates are YY1, SRC-1, and TAFII110). Cell type and gene -specific requirements of ligand independent modulation of VDR-mediated transcription will be examined. Experiments will also be done related to the functional significance of 24(OH)ase, using null mutant mice, which will focus on the proposed role of 24(OH)ase in vitamin D metabolism. It is likely that an increased understanding of the functional significance of target proteins, combined with increased understanding of cell- and gene- specific interactions of 1,25(OH)2D3 and VDR with other hormones and transcription factors, will play an increasingly important role in the elucidation of the mechanisms by which 1,25(OH)2D3 mediates its biological effect and how aberrant regulation may be involved in diseases such as osteoporosis and perturbations of parathyroid function.