Vitamin D Hormone: Function and Mechanism of Action

描述（由申请人提供）：本提案的目的是获得 更好地了解维生素D的作用，这是一个需要的主要因素 用于骨骼的发育和维持，以及用于维持 钙稳态本续期申请在具体目标I中建议， 继续研究钙结合蛋白的功能意义， 已知维生素D作用靶点。上一个补助金期间提供的研究 钙结合蛋白-D28 k对抗TNF诱导的细胞死亡的第一个证据 钙结合蛋白通过与成骨细胞结合， 抑制胱天蛋白酶3。这些发现，这具有重要的治疗作用， 影响，将继续。我们将确定钙结合蛋白-D28 k是否可以 防止糖皮质激素以及TNF诱导的骨细胞死亡 细胞我们将确定钙结合蛋白的哪个区域与胱天蛋白酶3结合， 钙结合蛋白是否可以抑制细胞远端部分的其他半胱天冬酶 死亡之路此外，我们将确定钙结合蛋白是否也可以通过以下方式发挥作用： 影响其他钙调节蛋白，包括最近发现的 顶端钙通道，ECaC，其共定位于与 钙结合蛋白除钙结合蛋白外，1，25（OH）2D 3的另一个已知的显著作用 肠和肾中24（OH）酶的合成增加。在具体目标2中， 为了进一步了解1，25（OH）2D 3的分子机理， 行动，研究开始在最后一个赠款期有关的条例， 24（OH）ase将继续使用。在初步研究中，我们注意到， 增强子结合蛋白β（C/EBP β）在肾脏中由1，25（OH）2D 3诱导 和成骨细胞，并能增强转录反应， 24（OH）酶转化为1，25（OH）2D 3。建议进行研究，以检查机制 参与通过C/EBP β调节VDR介导的24（OH）ase转录，如 以及C/EBPbeta在我们观察到的 PKA信号通路和1，25（OH）2D 3。这些研究将确定C/EBP β 作为一种新的1，25（OH）2D 3靶基因，并首次表明了它在 24（OH）ase转录中的C/EBP β。拟议的研究补充了 在上一个赠款期开始的研究涉及影响 24（OH）酶转录（YY 1，TFIIB，DRIP 205，CBP）和信号传导的影响 24（OH）ase转录和辅因子募集的途径。这项提议， 它结合了与理解功能相关的研究 目的蛋白的意义，与分子相关的研究 1，25（OH）2D 3的作用机制，将提供新的见解的机制 维生素D是通过什么途径介导其生物学效应的， 可能与骨质疏松症等疾病有关。

DESCRIPTION (provided by applicant): The object of this proposal is to obtain a better understanding of the actions of vitamin D, a principal factor required for the development and maintenance of bone, as well as for maintenance of calcium homeostasis. This renewal application proposes in Specific Aim I to continue studies related to the functional significance of calbindin, the first known target of vitamin D action. Studies in the previous grant period provided the first evidence that calbindin-D28k protects against TNF-induced cell death in osteoblasts and that calbindin protects against cell death by binding to and inhibiting caspase 3. These findings, which have important therapeutic implications, will be continued. We will determine whether calbindin-D28k can protect against glucocorticoid, as well as TNF-induced cell death in bone cells. We will determine which region of calbindin binds to caspase 3, and whether calbindin can inhibit other caspases in the distal portion of the cell death pathway. In addition, we will determine whether calbindin can also act by affecting other calcium regulatory proteins, including the recently identified apical calcium channel, ECaC, which is colocalized in the same cells as calbindin. Besides calbindin, the other known pronounced effect of 1,25(OH)2D3 in intestine and kidney is increased synthesis of 24(OH)ase. In Specific Aim 2, in order to obtain further insight into the molecular mechanism of 1,25(OH)2D3 action, studies begun in the last grant period related to the regulation of 24(OH)ase will be continued. In preliminary studies, we have noted that CCAATT enhancer binding protein beta (C/EBPbeta) is induced by 1,25(OH)2D3 in kidney and osteoblastic cells and can enhance the transcriptional response of 24(OH)ase to 1,25(OH)2D3. Studies are proposed to examine the mechanisms involved in modulation of VDR-mediated 24(OH)ase transcription by C/EBPbeta, as well as the role of C/EBPbeta in the cross-talk we have observed between the PKA signaling pathway and 1,25(OH)2D3. These studies would establish C/EBPbeta as a novel 1,25(OH)2D3 target gene and would indicate for the first time a role for C/EBPbeta in 24(OH)ase transcription. The proposed studies complement the studies begun in the previous grant period related to the factors that affect 24(OH)ase transcription (YY1, TFIIB, DRIP205, CBP) and the effect of signaling pathways on 24(OH)ase transcription and cofactor recruitment. This proposal, which combines studies related to an understanding of the functional significance of target proteins, with studies related to the molecular mechanism of 1,25(OH)2D3 action, will provide new insight into the mechanisms by which vitamin D mediates its biological effects and how aberrant regulation may be involved in diseases such as osteoporosis.