Dissecting the Regulation of Zinc-Homeostasis

描述（由申请人提供）：锌是来自所有生命领域的生物体所需要的300多种已知酶的必需营养素。人体缺锌可导致出生体重过低、免疫功能受损、心功能障碍和肠病性肢端皮炎。过量的锌会干扰其他非锌金属蛋白，并会引起神经元等细胞的氧化损伤，这可能会导致阿尔茨海默病。因此，细胞必须精确地调节锌的体内平衡，以确保它们有足够的锌来允许蛋白质发挥作用，同时尽量减少可能造成损害的过量锌。真核藻类莱茵衣藻（Chlamydomonas reinhardtii）可以在大范围的锌浓度下生存，并且含有在动物和植物中都保守的锌反应基因，为研究锌稳态调节提供了一个完美的模型系统。为了了解衣藻对锌缺乏或毒性的感知和反应，我提出了以下具体目标：1)鉴定对锌营养不同阶段有反应的基因，并区分转录和转录后机制的运作；2)鉴定与一个或多个关键锌反应靶点相关的锌反应元件（ZREs），并评估Crr1的作用，Crr1是一种已知的调节锌和铜反应基因的转录因子。3)利用经典的遗传方法鉴定营养锌信号转导的组成部分，可能包括调节因子和靶基因。对衣藻的研究已经为铁和铜的体内平衡机制提供了有价值的见解，而锌体内平衡调节的细节将有助于我们更广泛地了解细胞如何进化到利用金属辅助因子来执行生命的重要功能。公共卫生相关性：锌是一种必需的营养素，从细菌到人类都需要大量的锌。超过300种已知的酶需要锌，包括那些参与呼吸、转录和光合作用的酶。在这项工作中，锌感知和适应性反应机制将被揭示，以了解细胞如何识别和调整锌缺乏和毒性。

DESCRIPTION (provided by applicant): Zinc is an essential nutrient required in over 300 known enzymes by organisms from all domains of life. Zinc deficiency in humans can result in low birth weight, impaired immune function, cardiac dysfunction and acrodermatitus enteropathica. Excess zinc can interrupt other non-zinc metalloproteins and can induce oxidative damage in cells such as neurons, which potentially leads to Alzheimer's Disease. Thus, cells must precisely regulate zinc homeostasis to ensure that they have enough zinc to allow proteins to function while minimizing the amount of excess zinc that can cause damage. The eukaryotic alga Chlamydomonas reinhardtii provides a perfect model system to study the regulation of zinc homeostasis because it can survive under a wide range of zinc-concentrations and contains putative zinc-responsive genes that are conserved in both animals and plants. To understand how Chlamydomonas senses and responds to zinc deficiency or toxicity, I propose the following specific aims: 1) To identify genes that are responsive to distinct stages of zinc nutrition and distinguish the operation of transcriptional vs. post-transcriptional mechanisms, 2) to identify zinc-responsive elements (ZREs) associated with one or more key zinc-responsive targets and assess the role of Crr1, a transcription factor known to regulate both zinc- and copper-responsive genes, in zinc homeostasis and 3) to use a classical genetic approach to identify components of nutritional zinc signal transduction, potentially including regulators and target genes. Studies of Chlamydomonas have already provided valuable insight into the mechanisms of iron and copper homeostasis, and details of zinc-homeostasis regulation will contribute to our broader understanding of how, cells evolved to take advantage of metal cofactors to perform the vital functions of life. Public Health Relevance: Zinc is an essential nutrient required in abundance by organisms ranging from bacteria to humans. Zinc is required by over 300 known enzymes, including those involved in respiration, transcription and photosynthesis. In this work, mechanisms of zinc-sensing and adaptive response will be unraveled to understand how cells recognize and adjust to zinc deficiency and toxicity.