MECHANISM OF NON-GENOMIC ACTION OF VITAMIN D

描述(改编自调查员摘要)：不再有 似乎任何问题都表明维生素D的代谢物，1α，25- 二羟基维生素D3(1α，25-(OH)2D3，骨化三醇或CT)及其 代谢和合成类似物表现出非基因组作用。迅速地 新出现的证据表明，非基因组作用发挥着重要作用。 在控制导致许多疾病发生的机制方面的作用 由于钙稳态失调(如骨质疏松症)，细胞 生长(乳腺癌、牛皮癣)、细胞分化和免疫 回应(可能是艾滋病)。最近出现的非钙质、合成的 类似物带来了治疗使用的现实可能性 这些用于治疗上述疾病的合成药物。 1α，25的非基因组作用的最突出证据是- (哦)2D3是一种急性、一过性增加的刺激。 细胞内游离钙浓度([Ca~(2+)]i)及其伴随 肌醇多聚磷酸盐的生产。这些是第一批可衡量的 细胞暴露后一分钟内出现的症状 探员们。这些行为与膜(细胞表面)的行为非常相似。 受体-激动剂介导的机制。然而，精确的机制 维生素D类似物通过这种方式引起[钙]i的急剧变化 未知。申请者的最新数据表明，维生素D 受体(VDR)与质膜和内质的结合 网状结构(ER)。此外，内质网部分中的钙网织蛋白(CRT)是 VDR的特异性接受蛋白。因为这两层膜 构成主要部位的[Ca~(2+)]_i控制，相互作用 VDR和膜，以及相互作用在[Ca~(2+)]i中的作用 必须澄清控制措施。细胞生物学(转染法)的新进展 技术)，合成具有不同生物学特性的维生素D类似物 与钙通量测量相关的特性和技术 在活细胞中，以及在分离的膜泡中，现在 有可能对手头的问题进行逻辑上的调查。因此， 拟议研究的具体目标是：1)分析相互作用 VDR与ER的关系，以阐明VDR/CT的作用 内质网钙离子释放的相互作用及确定其功能 CRT在调节细胞内钙储存中的作用；以及2)研究 VDR与PM的相互作用，以阐明 这种相互作用在CT刺激的急性钙内流中的作用，并确定 VDR的PM特异性接受蛋白。

DESCRIPTION (Adapted from investigator's abstract): There no longer appears to be any question that the vitamin D metabolite, 1alpha,25- dihydroxyvitamin D3 (1alpha,25-(OH)2D3, calcitriol or CT), and its metabolic and synthetic analogs manifest nongenomic actions. Rapidly emerging evidence indicates that the nongenomic action plays important roles in controlling the mechanisms that underlie many diseases arising from disturbances in calcium homeostasis (e.g., osteoporosis), cell growth (breast carcinoma, psoriasis), cell differentiation and immune responses (possibly AIDS). The recent advent of noncalcemic, synthetic analogs has ushered in the realistic possibility of therapeutic use of these synthetic agents for the treatment of the above-mentioned diseases. The most prominent evidence for the nongenomic action of 1alpha,25- (OH)2D3 is stimulation of an acute, transient increase in the intracellular free calcium concentration ([Ca2+]I) and concomitant production of inositol polyphosphates. These are the first measurable manifestations that occur within one minute of cellular exposure to the agents. These actions closely resemble those of membrane (cell surface) receptor-agonist mediated mechanisms. However, the precise mechanisms by which vitamin D analogs induce the acute change in [Ca2+]I are unknown. The applicants' recent data demonstrate that the vitamin D receptor (VDR) binds to both plasma membrane (PM) and endoplasmic reticulum (ER). Furthermore, calreticulin (CRT) in the ER fraction is a specific acceptance protein for VDR. Since these two membranes constitute the major sites of [Ca2+]I control, the interaction between VDR and the membranes, and the role of the interaction in [Ca2+]I control must be clarified. Recent advances in cell biology (transfection technology), synthesis of vitamin D analogs with different biological properties and technologies related to the measurement of calcium fluxes in living cells, as well as in isolated membrane vesicles, make it now possible to logically investigate the problems at hand. Therefore, the Specific Aims of the proposed studies are to: 1) analyze the interaction of the VDR with the ER in order to elucidate the role of VDR/CT interaction on Ca2+ release from the ER and to determine the function of CRT in regulating intracellular Ca2+ stores; and 2) study the interaction of the VDR with the PM in order to elucidate the role of this interaction in acute Ca2+ influx stimulated by CT, and to identify a PM-specific acceptance protein for VDR.