Molecular Coordination of Iron Homeostasis by microRNAs

描述（由申请人提供）：铁代谢疾病仍然是美国的主要健康问题。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，由于缺铁，个体会经历负面的健康后果，主要是由于骨骼肌中铁代谢的改变。令人惊讶的是，很少有人知道的分子机制，调节骨骼肌中的铁代谢，以及如何改变在这个组织影响铁稳态。我们实验室的长期研究目标是促进对铁代谢如何协调，以及铁传感的改变如何导致疾病的发展或预防的理解。有证据表明参与铁代谢的基因表达受ID调节，然而，其分子机制仍不清楚。直到最近，被称为microRNA（miRNAs）的小调控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靶点的初步计算机分析鉴定了编码铁代谢相关蛋白的mRNA。因此，我们的主要目标是确定在何种程度上的表达的miRNA的调节响应ID和表征的影响，miRNA的表达对潜在的调节靶点参与铁代谢。我们将严格评估差异表达的miRNA的靶点，并研究这些靶点在细胞铁代谢中的作用。核心假设是miRNA表达响应于ID而被调节，并且表达的变化与表达靶mRNA的变化相关，从而导致细胞铁代谢的稳态调节。为了验证这一假设，本提案包含两个具体目标。在目标1中，我们将评估和表征铁依赖性变化的miRNA表达的断奶大鼠模型的ID。在目标2中，我们将确定在何种程度上的miRNA有助于调节细胞铁代谢，通过调节蛋白质的表达参与细胞铁稳态。将使用miRNA微阵列测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，我们将识别和表征靶mRNA，并确定这些mRNA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改变与铁传感的改变。拟议的研究与维持最佳健康的患病率ID有关，并通过采取跨学科的方法来研究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：铁缺乏仍然是最常见的营养缺乏症，并与免疫功能受损，认知发育延迟和骨骼肌工作能力下降等变化有关。该项目的重点是检查铁状态与microRNA表达改变相关的程度，这可能有助于铁缺乏的一些组织特异性影响。这项研究的结果将为我们了解协调细胞对缺铁反应的分子机制提供信息，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改变产生影响。

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.