Signaling Pathways Influencing Liver Disease Phenotype in Antitrypsin Deficiency

描述（由申请人提供）：在α1抗胰蛋白酶缺乏症（ATD）的经典形式中，点突变导致肝分泌蛋白的错误折叠，而变体1抗胰蛋白酶Z （ATZ）以聚合物和聚集体的形式积聚在肝细胞的内质网中。肝纤维化和肝细胞癌在受影响的纯合子亚群中通过功能获得的“蛋白质毒性”机制发展。肝脏表型存在广泛的差异，约10%的人在婴儿期/幼儿期发病，另一个亚组在生命的第6 -7个十年中通过明显的年龄依赖过程发展为肝脏疾病。我们研究的中心假设有三个组成部分：1)肝脏表型的变异性是由遗传和环境修饰因子决定的；2)这些修饰剂的靶点是内质网的质量控制机制，内质网是细胞蛋白酶平衡调节网络的一部分；3)两种主要的蛋白酶机制是蛋白质降解途径，如蛋白酶体和自噬，以及旨在保护细胞免受蛋白质毒性影响的信号通路。在这项资助中，我们建议研究3种信号通路的作用，这些信号通路被认为是旨在预防肝损伤的蛋白酶抑制调节机制，包括胰岛素和nf - κ b信号通路以及G信号通路16的调节剂（RGS16）。该建议是基于初步结果，表明这3种途径在几种模型系统中以独特的方式被激活，包括哺乳动物细胞系和小鼠模型，诱导ATZ表达，以及一种新的秀丽隐杆线虫模型，通过快速基因工程和药物发现促进机制询问。我们将确定这些途径是如何被激活的，以及它们是如何影响ATD的肝脏表型的，方法是利用新的小鼠模型，对每种途径进行靶向破坏，以及通过影响这些途径的药理学策略。我们还将使用ips衍生的肝细胞系来确定ATD患者个体中这些通路的激活是否存在差异。

DESCRIPTION (provided by applicant): In the classical form of α1antitrypsin deficiency (ATD) a point mutation leads to misfolding of a hepatic secretory protein and the variant, 1antitrypsin Z (ATZ), accumulates in the ER of liver cells as polymers and aggregates. Liver fibrosis and hepatocellular carcinoma develops in a subgroup of affected homozygotes by a gain-of-function 'proteotoxic' mechanism. There is wide variability in the hepatic phenotype with ~10% affected in infancy/early childhood and another subgroup that develop liver disease in the 6th-7th decade of life by an apparent age-dependent process. The central hypothesis of our research has 3 components: 1) variability in hepatic phenotype is determined by genetic and environmental modifiers; 2) the targets of these modifiers are the quality control mechanisms of the ER, part of the cell's proteostasis regulatory network; 3) the 2 major types of protestasis mechanisms are protein degradation pathways, such as the proteasome and autophagy, and signaling pathways that are designed to protect cells from proteotoxicity. In this grant we propose investigation of the role of 3 signaling pathways that are putative proteostasis regulatory mechanisms designed to prevent liver damage, including the insulin and NFκB signaling pathways as well as the regulator of G signaling 16 (RGS16). The proposal is based on preliminary results showing that these 3 pathways are activated in unique ways in several model systems including mammalian cell line and mouse models with inducible expression of ATZ and a novel C. elegans model that facilitates mechanistic interrogation through rapid genetic engineering and drug discovery. We will determine how these pathways are activated and how they affect the hepatic phenotype of ATD by utilizing novel mouse models with targeted disruption of each pathway as well as by pharmacological strategies that influence the pathways. We will also determine whether there is variation in activation of these pathways among individual patients with ATD using iPS-derived hepatocyte cell lines.