Molecular Coordination of Iron Homeostasis by microRNAs

描述(申请人提供)：铁代谢疾病在美国仍然是一个主要的健康问题。缺铁仍然是美国最常见的单一营养素缺乏症，在没有贫血的情况下，个人会因缺铁而产生负面健康后果，主要是由于骨骼肌铁代谢的改变。令人惊讶的是，人们对调节骨骼肌铁代谢的分子机制以及该组织中的变化如何影响铁的动态平衡知之甚少。我们实验室的长期研究目标是促进对铁代谢如何协调的理解，以及铁感应变化如何导致疾病的发展或预防。有证据表明，铁代谢相关基因的表达受ID的调控，但其分子机制尚不清楚。直到最近，被称为microRNAs(MiRNAs)的小调节RNA分子的作用才被确定为调节各种细胞过程的重要机制。我们对miRNA靶标的初步电子分析导致识别出编码与铁代谢有关的蛋白质的mRNAs。因此，我们的主要目标是确定miRNAs的表达在多大程度上受到ID的调控，并表征miRNA表达对参与铁代谢的潜在调控靶点的影响。我们将严格评估差异表达的miRNAs的靶标，并研究这些靶标在细胞铁代谢中的作用。中心假设是miRNA的表达是受ID调节的，表达的变化与表达靶标mRNAs的变化有关，从而导致细胞铁代谢的动态平衡调节。为了检验这一假设，这一提议包含两个具体目标。在目标1中，我们将使用断奶大鼠ID模型来评估和表征miRNA表达的铁依赖变化。在目标2中，我们将通过调节参与细胞铁稳态的蛋白质的表达来确定miRNAs在调节细胞铁代谢中的作用程度。将使用miRNA微阵列确定肝脏和骨骼肌中的microRNA表达谱，并使用qPCR进行验证。结合体内和体外研究，我们将识别和鉴定靶向mRNAs，并确定这些mRNAs在铁代谢中的作用。我们还将确定miRNA表达的变化在多大程度上是由于铁状态的变化与铁感应的变化。这项拟议的研究与根据患病率ID保持最佳健康有关，通过采用跨学科的方法来检查铁状态和细胞代谢之间的关系，我们将扩大我们对铁如何有助于维持最佳健康的理解。 公共卫生相关性：缺铁仍然是最常见的营养缺乏症，并与免疫功能受损、认知发育迟缓和骨骼肌工作能力下降等变化有关。该项目的重点是研究铁状态在多大程度上与microRNA表达的变化有关，这可能有助于缺铁的一些组织特异性影响。这项研究的结果将有助于我们理解协调细胞对缺铁反应的分子机制，并可能对理解在癌症和糖尿病等慢性疾病中观察到的铁代谢的变化有一定的意义。

DESCRIPTION (provided by applicant): Diseases of iron metabolism continue to be a major health concern in the United States. Iron deficiency remains the most common single nutrient deficiency in the US and individuals experience negative health consequences due to iron deficiency in the absence of anemia, primarily due to alterations in iron metabolism in skeletal muscle. Surprisingly little is known about the molecular mechanisms regulating iron metabolism in skeletal muscle and how alterations in this tissue affects iron homeostasis. The long-term research goal of our laboratory is to advance understanding of how iron metabolism coordinated, and how alterations in iron sensing can lead to the development or prevention of disease. There is evidence suggesting expression of genes involved in iron metabolism is regulated by ID, however, the molecular mechanisms remain poorly characterized. Only recently has the role of small regulatory RNA molecules called microRNAs (miRNAs) been identified as an important mechanism for regulating various cellular processes. Our preliminary in silico analysis of miRNA targets resulted in the identification of mRNAs encoding proteins involved in iron metabolism. Thus our primary objectives are to determine the extent to which expression of miRNAs is regulated in response to ID and to characterize the impact of miRNA expression on potential regulatory targets involved in iron metabolism. We will critically evaluate targets of differentially expressed miRNAs and examine the roles of these targets in cellular iron metabolism. The central hypothesis is that miRNA expression is regulated in response to ID and that changes in expression are associated with changes in the expression target mRNAs resulting in the homeostatic regulation of cellular iron metabolism. To test this hypothesis, this proposal encompasses two specific aims. In Aim 1 we will evaluate and characterize iron-dependent changes in miRNA expression using a weanling rat model of ID. In Aim 2 we will determine the extent to which miRNAs contribute to the regulation cellular iron metabolism through modulating the expression of proteins involved in cellular iron homeostasis. MicroRNA expression profiles in the liver and skeletal muscle will be determined using miRNA microarrays and validated using qPCR. Combining in vivo and in vitro studies, we will identify and characterize target mRNAs and determine the role of these mRNAs in iron metabolism. We will also determine the extent to which changes in miRNA expression are due to alterations in iron status versus alterations in iron sensing. The proposed research is relevant to the maintenance of optimal health in light of the prevalence ID, and by taking an interdisciplinary approach to examine the relationships between iron status and cellular metabolism, we will expand our understanding of how iron contributes to the maintenance of optimal health. PUBLIC HEALTH RELEVANCE: Iron deficiency continues to be the most common nutrient deficiency and is associated with alterations ranging from impairment in immune function, delayed cognitive development, and decreased capacity of work in skeletal muscle. The focus of this project is to examine the extent to which iron status is associated with alterations in microRNA expression that may contribute to some of the tissue-specific effects of iron deficiency. The results of this study will inform our understanding of the molecular mechanisms coordinating the cellular response to iron deficiency and may have implications in understanding alterations in iron metabolism observed in chronic diseases such as cancer and diabetes.