TRANSCRIPTIONAL REGULATION OF ZINC HOMEOSTASIS

 描述(申请人提供)：锌是一种重要的营养物质，对人类健康有深远的影响，因为锌缺乏和过量都会导致一系列的病理变化。锌在生物系统中扮演着许多角色，因为锌是许多蛋白质功能所必需的，并且锌调节信号转导途径。详细了解锌的运输和动态平衡对于开发新的锌操作方法以促进人类健康至关重要。目前对动物体内锌稳态的理解存在很大差距，因为用于吸收、感觉和排泄锌的基本机制还没有被很好地理解。我们的长期目标是阐明动物如何感知锌水平，并协调促进锌稳态的反应。这一目标将通过使用哺乳动物细胞和遗传易驯化的模式生物线虫来分析锌调控的转录因子和目标基因来实现。了解蛋白质网络如何控制动物体内的锌稳态是医学研究的一个重要目标，因为这些信息可能会为锌生物异常引起的疾病带来新的治疗方法。我们的初步结果已经建立了用于锌生物学研究的强大的线虫模型系统，方法是开发允许操纵膳食锌的培养条件，建立测量锌含量和分布的分析方法，以及鉴定控制锌生物学的基因突变。这些结果支持三个创新假说。(1)HZA增强子介导多个基因的转录激活，以响应过量的锌。核受体NHR-33受高锌饮食的调节，并与HZA增强子结合，控制调节体内平衡的靶基因。(2)ZIP转运蛋白Y54G9A.4促进锌的吸收，并受低锌饮食的调节。(3)LZA增强子介导多种基因的转录激活，以响应缺锌。为了检验这些假设，我们提出了三个具体目标。目的1：研究核受体在锌稳态调节中的调控和进化保守性。目的2：筛选高锌饮食调控的靶基因并对其进行功能分析。目的：分析ZIP基因Y54G9A.4的功能和调控。鉴定LZA增强子在缺锌时调节转录的作用，并鉴定调节这一元件的蛋白质因子。这些实验建立在我们在前一个赠款时期取得的成就的基础上，该时期建立了用于锌生物学研究的线虫模型系统，并产生了创新的新假说。这项提议将把这些发现扩展到哺乳动物系统，并利用线虫强大的实验优势来阐明基因网络如何调节多细胞动物的锌稳态。几种常见的人类疾病，如阿尔茨海默病、中风和癌症，都与锌稳态异常有关，这些研究结果可能会为解决锌中毒的障碍提供新的治疗策略。

 DESCRIPTION (provided by applicant): Zinc is an essential nutrient that profoundly affects human health, as zinc deficiency and excess both result in a broad spectrum of pathologies. Zinc plays many roles in biological systems, since zinc is essential for the function of many proteins, and zinc modulates signal transduction pathways. A detailed understanding of zinc trafficking and homeostasis is critical for the development of new approaches for manipulating zinc to promote human health. There are major gaps in the current understanding of zinc homeostasis in animals, since fundamental mechanisms used to take up, sense, and excrete zinc are not well understood. Our long- term goal is to elucidate how animals sense zinc levels and coordinate a response that promotes zinc homeostasis. This goal will be addressed by analyzing zinc-regulated transcription factors and target genes using mammalian cells and the genetically tractable model organism C. elegans. Understanding how a network of proteins controls zinc homeostasis in an animal is an important objective of medical research, since the information may lead to new therapeutic approaches for diseases caused by abnormal zinc biology. Our preliminary results have established the powerful C. elegans model system for studies of zinc biology by the development of culture conditions that permit manipulation of dietary zinc, the establishment of assays that measure zinc content and distribution, and the identification of mutations in genes that control zinc biology. These results support three innovative hypotheses. (1) The HZA enhancer mediates transcriptional activation of multiple genes in response to excess zinc. The nuclear receptor NHR-33 is regulated by high dietary zinc and binds the HZA enhancer to control target genes that mediate homeostasis. (2) The ZIP transporter Y54G9A.4 promotes zinc uptake and is regulated by low dietary zinc. (3) The LZA enhancer mediates transcriptional activation of multiple genes in response to zinc deficiency. To test these hypotheses, we propose three specific aims. Aim 1: Characterize the regulation and evolutionary conservation of nuclear receptors in mediating zinc homeostasis. Aim 2: Identify and functionally analyze target genes regulated by high dietary zinc. Aim 3: Analyze the function and regulation of the ZIP gene Y54G9A.4. Characterize the LZA enhancer that mediates transcriptional regulation in response to zinc deficiency, and identify protein factors that regulae this element. These experiments build on our accomplishments in the previous grant period that established the C. elegans model system for studies of zinc biology and generated innovative new hypotheses. This proposal will extend these discoveries to mammalian systems and exploit the powerful experimental advantages of C. elegans to elucidate how a network of genes regulates zinc homeostasis in a multicellular animal. Several prevalent human diseases such as Alzheimer's disease, stroke and cancer have been associated with abnormalities of zinc homeostasis, and the results of these studies may suggest new therapeutic strategies for addressing disorders of zinc toxicity.