Signaling Pathways Influencing Liver Disease Phenotype in Antitrypsin Deficiency

描述(申请人提供)：在经典形式的α1抗胰蛋白酶缺乏症(ATD)中，一个点突变导致肝脏分泌蛋白的错误折叠，变异体1抗胰蛋白酶Z(ATZ)以聚合物和聚集体的形式聚集在肝细胞的内质网中。肝纤维化和肝细胞癌发生在受影响的纯合子亚群中，是一种功能获得的“蛋白毒性”机制。肝脏表型有很大的差异性，约10%影响在婴儿期/幼儿期，另一个亚组在6-7岁时通过明显的年龄相关过程发展为肝病。我们研究的中心假设有3个部分：1)肝脏表型的可变性是由遗传和环境修饰物决定的；2)这些修饰物的靶标是内质网的质量控制机制，这是细胞蛋白质平衡调控网络的一部分；3)蛋白质稳定机制的两种主要类型是蛋白质降解途径，如蛋白酶体和自噬，以及旨在保护细胞免受蛋白毒性的信号通路。在这项资助中，我们建议研究3种信号通路的作用，这些信号通路是被认为是蛋白质稳定调节机制，旨在防止肝损伤，包括胰岛素和核因子κB信号通路以及G信号16调节因子(RGS16)。这一建议是基于初步结果，表明这三条途径在几个模型系统中以独特的方式激活，包括哺乳动物细胞系和ATZ诱导表达的小鼠模型，以及通过快速基因工程和药物发现促进机械性询问的新型线虫模型。我们将利用靶向阻断每个通路的新型小鼠模型以及通过影响这些通路的药物策略来确定这些通路是如何被激活的，以及它们是如何影响ATD的肝脏表型的。我们还将使用iPS来源的肝细胞系来确定这些通路在ATD患者个体中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.