N-acetylglutamate Synthase: Structure, Function & Defects

描述（由申请人提供）：这是一个竞争性修订申请，以回应复苏法基金通知编号NOT-OD-09- 058。本项目的目标是探索N-乙酰谷氨酸合酶（NAGS）的生物学、生物化学和病理生理学，NAGS是一种产生同源辅因子N-乙酰谷氨酸（NAG）的酶，NAG是尿素生成中必不可少的变构激活剂。此修订应用程序向父项目添加了两个新目标。1.开发NAGS缺陷基因敲除小鼠，表征其表型，并探索其作为条件性高氨血症模型的用途。2.通过比较N-氨甲酰谷氨酸（NCG）处理的koNAGS小鼠与野生型同窝小鼠的氮代谢，“分离”并研究体内尿素生成的调节，特别是在NAGS/CPSI水平。除了将在两年内完成的这些新目标外，该项目还将长期加强两个现有目标，即研究精氨酸对NAGS功能的影响以及NAGS缺乏症患者中天然突变的影响。在这个修订后的项目中，我们将开发、研究并向研究界提供一种新的“可滴定的高氨血症小鼠模型”。该敲除NAGS小鼠将用NCG拯救，并且在停用该辅因子类似物后将发展高氨血症。我们将确定用NCG拯救的NAGS“调节剥夺”koNAGS小鼠与自然调节的野生型同窝仔在NCG和非NCG下的氮平衡和代谢之间的体内差异。这些研究将使用基因表达和蛋白质谱的方法，并将允许第一次在体内“隔离”NAGS对尿素生成的调节作用。该项目将通过为我们组和其他研究高氨血症的研究者提供体内研究的新工具来提高母基金的速度和质量。此外，该项目对经济的贡献是通过使koNGAS小鼠模型提供给全国各地的研究人员，加强他们的研究和促进新的就业机会的创造。 公共卫生相关性：该项目致力于研究一种重要的基因和蛋白质（NAGS），该基因和蛋白质决定了我们从体内消除多少氮。了解这一点很重要，因为肝病的主要问题之一是无法消除有毒的氮（氨），这可能会毒害大脑。我们将研究一种不含NAGS的工程小鼠，以使我们更好地了解这个系统及其如何调节。该项目的结果可以允许开发针对氨水平升高的新治疗方法，以保护大脑免受其毒性影响。

DESCRIPTION (provided by applicant): This is a Competitive Revision Application in response to the Recovery Act Funds Notice Number NOT-OD-09- 058. The parent project over goal is to explore the biology, biochemistry and pathophysiology of N- acetylglutamate synthase (NAGS) is an enzyme that produces the cognate cofactor N-acetylglutamate (NAG), an essential allosteric activator in ureagenesis. This revision application adds two new aims to the parent project. 1. To develop a knockout mouse for NAGS deficiency, characterize its phenotype, and explore its use as a conditional hyperammonemia model. 2. To "isolate" and study the in vivo regulation of ureagenesis specifically at the level of NAGS/CPSI by comparing nitrogen metabolism in N-carbamylglutamate (NCG) treated koNAGS mouse vs. wild type littermates. In addition to these new aims to be completed in two years, this project will enhance in the long term two of the existing aims that study the arginine effects on NAGS function and the effect of naturally-occurring mutations in patients with NAGS deficiency. In this revised project, we will develop, study and make available to the research community a novel "titratable mouse model of hyperammonemia. This knockout NAGS mouse will be rescued with NCG and will develop hyperammonemia upon withdrawal of this cofactor analog. We will determine the in vivo differences between nitrogen balance and metabolism in the NAGS "regulation-deprived" koNAGS mice rescued with NCG vs. the naturally-regulated wild type littermates on and off NCG. These studies will use both gene expression and protein profiles methods and will allow for the first time to "isolate" in vivo the regulatory effects of NAGS on ureagenesis. This project will enhance the pace and quality of the parent grant by providing a new tool for in vivo investigations for our group and other investigators studying hyperammonemia. In addition, The contribution of this project to the economy is leveraged by making the koNGAS mouse model available to othr investigators across the country, enhancing their research and promoting new job creation. PUBLIC HEALTH RELEVANCE: This project is dedicated to the investigation of an important gene and protein (NAGS) that determined how much nitrogen we eliminate from our bodies. It is important to know this since one of the main problem in liver disease is the inability to eliminate toxic nitrogen (ammonia) which can poison the brain. We will study an engineered mouse that does not posses NAGS to allow us to better understand this system and how it is regulated. The results from this project could allow the development of new treatments for elevated ammonia levels to protect the brain from its toxic effects.