Regulation of Liver Growth and Function

 描述(申请人提供)：我们对饮食和营养素如何引起信号通路和机制的变化，从而启动肝脏基因表达的翻译控制的变化，从而导致发病机制的理解存在根本的差距。 脂肪肝的症状。这一差距的持续存在是一个重要问题，因为在填补这一差距之前，了解脂肪性肝病的病因并制定预防或逆转它的干预措施在很大程度上仍将无法实现。我们的长期目标是更好地了解肝脏中基因表达的翻译控制。本申请中提出的项目的目的是描述翻译控制机制和蛋白质表达模式的特征，这些机制和蛋白质表达模式因开始摄入高糖和饱和脂肪的饮食(即西方饮食)而经历急剧变化。我们的中心假设是，蛋白质表达的急剧变化是通过涉及eIF4F和43S预起始复合体功能的机制来调节的。这项拟议研究的基本原理是，了解饮食导致的这些机制的急剧变化有可能转化为更好地理解非酒精性脂肪性肝病的发病机制，这种疾病影响到大约三分之一的美国人口。在强大的、在某些情况下是新的初步发现的指导下，该假说将在开始食用西方饮食的小鼠的肝脏中进行验证，以追求以下三个特定目标：1)确定mTORC1信号和蛋白表达模式的差异；2)表征eIF4F组装和功能所涉及的启动因子的表达和共价修饰(即磷酸化和O-GlcNacylation)；以及3)评估eIF2的a亚基的磷酸化以及eIF2B的磷酸化和全球环境基金活性。在第一个目标下，我们将探索我们的初步数据所建议的一种新的机制，即Rheb和RAG介导的mTORC1输入，以发展对西方饮食如何影响这一激素和营养感知途径的理解。此外，我们实验室最近开发的一项技术将用于识别蛋白质表达模式的变异。在第二个目标下，我们将把我们最近发现的高血糖介导的4E-BP1和eIF4G的O-GlcN酰化作用扩展到它在调节eIF4F复合体的组装和功能中的作用。在第三个目标下，我们将依靠我们在组装43S预起始复合体的研究中的丰富经验，以了解依赖于perk和/或PKR的eIF2a磷酸化的相对作用，以及具有上游开放阅读框架的mRNAs中eIF2B活性的相应降低。这项拟议的研究具有重要意义，因为它有望促进和扩大我们对饮食和营养物质如何调节肝脏基因表达模式的变化，从而导致代谢失调的理解。最终，这些知识有可能为饮食咨询和药物干预预防或逆转脂肪性肝病的发展提供信息。

 DESCRIPTION (provided by applicant): There is a fundamental gap in our understanding of how diet and nutrients induce variation in signaling pathways and mechanisms to initiate alterations in translational control of hepatic gene expression that contribute to the pathogenesis of fatty liver disease. Continued existence of this gap represents an important problem because, until it is filled, understanding the etiology of fatty liver disease and developing interventions o prevent or reverse it will remain largely unfulfilled. Our long-term goal is to better understand te translational control of gene expression in the liver. The objective of the project proposed in thi application is to characterize translational control mechanisms and protein expression patterns that undergo acute variation in response to initiating consumption of a diet high in sugar and saturated fat (i.e. a Western diet). Our central hypothesis is that acute variation in protein expression in response to the diet is mediated through mechanisms involving the function of eIF4F and the 43S preinitiation complex. The rationale for the proposed research is that understanding diet-induced acute variation in these mechanisms has the potential to translate into better under-standing the pathogenesis of non-alcoholic fatty liver disease, a condition that affects about one-third of the US population. Guided by strong and in some cases novel preliminary findings, the hypothesis will be tested in the liver of mice following initiation of consumption of a Western diet by pursuing the following three specific aims: 1) Define variation in mTORC1 signaling and protein expression patterns; 2) Characterize expression and covalent modification (i.e. phosphorylation and O-GlcNAcylation) of initiation factors involved in assembly and function of eIF4F; and 3) Assess phosphorylation of the a-subunit of eIF2 as well as phosphorylation and GEF activity of eIF2B. Under the first aim, a novel mechanism suggested by our preliminary data for the Rheb- and Rag-mediated inputs to mTORC1 will be explored to develop an understanding of how the Western diet affects this hormone and nutrient sensing pathway. In addition, a recently developed technology that is now established in our laboratory will be used to identify variation in protein expression patterns. Under the second aim, we will extend our recent discovery of hyperglycemia-mediated O-GlcNAcylation of 4E-BP1 and eIF4G to studies on its role in regulating assembly and function of the eIF4F complex. Under the third aim, we will rely on our extensive experience in studies on assembly of the 43S preinitiation complex to gain an understanding of the relative roles of PERK and/or PKR-dependent phosphorylation of eIF2a and a corresponding reduction in eIF2B activity in protein expression from mRNAs with upstream open reading frames. The proposed research is significant because it is expected to advance and expand our understanding of how diet and nutrients can mediate variation in the patterns of gene expression in the liver leading to maladapted metabolism. Ultimately, such knowledge has the potential to inform development of both dietary counseling and pharmacologic intervention to prevent or reverse fatty liver disease.