Zinc is a Novel Ligand of Nuclear Receptors

锌是人体必需的营养物质，必须严格控制，因为锌过量和缺乏都是如此。 有害的。复杂的锌稳态机制使动物能够感知并对失衡做出反应 在细胞水平上的锌。然而，对这些机制的理解仍然不完整。我们最近 在线虫中的发现为锌的稳态机制提出了新的模型 对人类生物学有重要影响的生物。线虫已被证明是一种理想的模式生物 锌生物学的研究归功于新的方法来处理介质中的饮食锌，新描述的金属- 相关的表型，以及蠕虫群落中常见的遗传操作。在这个系统中，我们发现 高锌激活(HZA)元素介导的多基因转录反应 对高锌饮食的反应。此外，我们发现了高锌激活的核受体(HIZR-1)，它 是锌稳态的主要调节者，因为hizr-1(Lf)突变体不能诱导锌反应基因和这些 突变株对锌毒性敏感。HIZR-1 DNA结合域(DBD)直接与HZA和HZA结合 HIZR-1配体结合域(LBD)直接与锌结合。HIZR-1对高锌饮食的反应 在细胞核内堆积。最有趣的是，一个嵌合的Gal4(DBD)：：HIZR-1(LBD)融合蛋白 人类细胞培养中锌的响应性。这些观察结果提出了两个令人兴奋的假设：(1)HIZR-1 对高水平的锌作出反应是因为配体中特定的半胱氨酸、组氨酸和/或酸性氨基酸- 结合结构域直接配位锌。(2)人体细胞的高锌稳态反应受以下因素的调节 HIZR-1的功能性人类同源基因。我将通过以下方式检验这些假设：(1)定义锌的作用机制 通过对HIZR-1配体结合域的结构-功能分析进行结合，以及，(2)确定人类 孤儿核受体通过在体外和体内直接结合锌来感觉高锌。这些研究将是 通过定义一种新的高锌传感器的作用机制并潜在地识别人类 高锌传感器对治疗人类锌稳态异常疾病的启示。的能力 动物能够感知饮食中锌的高低，并通过调节摄取、储存和排泄来做出反应是至关重要的 用来维持动态平衡。拟议的实验建立在我们令人兴奋的初步结果的基础上，这些结果产生了创新的 锌稳态机制的新假说。我将在蠕虫中直接测试这些假设 人类细胞。锌的异常堆积与几种人类疾病有关，研究结果可能表明 解决人类锌代谢障碍的新治疗策略。

Zinc is an essential human nutrient that must be tightly regulated, as both zinc excess and deficiency are deleterious. Sophisticated mechanisms of zinc homeostasis allow animals to sense and respond to imbalances in zinc at the cellular level. However, the understanding of these mechanisms remains incomplete. Our recent discoveries in the roundworm C. elegans have suggested new models for mechanisms of zinc homeostasis that have important implications for human biology. C. elegans has proven to be an ideal model organism for the study of zinc biology thanks to new methods in manipulating dietary zinc in media, newly described metal- related phenotypes, and genetic manipulations common in the worm community. In this system, we discovered that the High Zinc Activation (HZA) element mediates the transcriptional response of multiple genes in response to high dietary zinc. Further, we discovered the high zinc activated nuclear receptor (HIZR-1), which is the master regulator of zinc homeostasis, as hizr-1(lf) mutants fail to induce zinc response genes and these mutants are hypersensitive to zinc toxicity. The HIZR-1 DNA binding domain (DBD) directly binds the HZA and the HIZR-1 ligand-binding domain (LBD) directly binds zinc. HIZR-1 responds to high dietary zinc by accumulating in the nucleus. Most interestingly, a chimeric Gal4(DBD)::HIZR-1(LBD) fusion protein confers zinc responsiveness in human cell culture. These observations suggested two exciting hypotheses: (1) HIZR-1 responds to high levels of zinc because specific cysteine, histidine and/or acidic amino acids in the ligand- binding domain directly coordinate zinc. (2) The high zinc homeostasis response in human cells is regulated by a functional human ortholog of hizr-1. I will test these hypotheses by, (1) defining the mechanism of zinc binding by structure-function analysis of the HIZR-1 ligand binding domain, and, (2) determining if a human orphan nuclear receptor senses high zinc by directly binding zinc in vitro and in vivo. These studies will be impactful by defining the mechanism of action of a new high zinc sensor and potentially identifying a human high zinc sensor with implications for treating human diseases of abnormal zinc homeostasis. The ability of animals to sense high and low dietary zinc and respond by adjusting uptake, storage and excretion is critical for homeostasis. The proposed experiments build on our exciting preliminary results that generated innovative new hypotheses about mechanisms of zinc homeostasis. I will directly test these hypotheses in worms and human cells. Aberrant zinc accumulation is implicated in several human diseases, and the results may suggest new therapeutic strategies for addressing disorders of zinc metabolism in humans.