A New E3 Ligase Implicated in Protein Quality Control and Neurodegeneration

7.项目摘要 背景和相关性：这项基础研究提案的目标是更好地了解 分子水平上的神经退行性疾病。其中最著名的例子是老年痴呆症， 帕金森氏病和亨廷顿氏病以及肌萎缩性侧索硬化症（ALS）。神经退行性疾病 是不可治愈的和衰弱的条件，随着患病率的增加，并且没有其致病机制 在足够详细地阐明后，我们能够为纠正性治疗干预提供一个基本原理， 非常有限。我们之前描述了一种新的神经退行性变小鼠模型， LISTER基因突变。与一个重要的生物学功能相一致，该基因在所有 从酵母菌到人类。因此，我们一直在利用各种模型来发现基因 功能以及这种功能的缺陷如何导致疾病。LISTER基因编码一种蛋白质， 作为E3泛素连接酶，命名为Listerin。最近，我们利用酵母发现了Listerin的功能， 这与哺乳动物神经退化中的作用一致：它在一种称为蛋白质的过程中发挥作用， 质量控制，从而使异常蛋白质成为降解的目标。具体来说，它的目标是蛋白质 由缺乏终止密码子的缺陷mRNA（"非终止蛋白"）编码。Listerin通过标记那些 具有泛素分子（泛素化）的异常蛋白质，其通常充当破坏信号。突变 导致这些有毒蛋白质的积累。通过拟议的研究，我们计划指定 李斯特蛋白介导的泛素化的特点，并扩大对疾病的发现。 目的/假设：我们的主要假设是：（a）李斯特蛋白通过以下方式控制蛋白质质量： 泛素化不终止多肽停滞在核糖体中，和（B）缺陷型李斯特蛋白介导的降解 导致蛋白质聚集体和内含物的形成，这是神经变性的标志。 具体目的是表征Listerin在不停止蛋白质降解中的功能， Listerin在蛋白质质量控制中的功能的保守程度，并研究这种缺陷如何影响Listerin的功能。 功能导致神经退行性变。我们的长期目标是帮助阐明分子机制 参与人类神经退行性疾病的发病机制。 研究设计：我们将使用生物化学和酵母分子遗传学来说明E3如何识别其基因。 特定的靶底物;哺乳动物组织培养和生物化学研究的调控不停 蛋白质降解的哺乳动物李斯特菌和生物化学和细胞生物学研究的后果， 蛋白质在细胞中不断积累。

7. PROJECT SUMMARY Background and relevance: The goal of this basic research proposal is to better understand the causes of neurodegenerative disorders at the molecular level. Among the best known examples are Alzheimer's, Parkinson's and Huntington's diseases, and Amyotrophic Lateral Sclerosis (ALS). Neurodegenerative diseases are incurable and debilitating conditions with increasing prevalence, and without their pathogenic mechanisms being elucidated in sufficient detail, our ability to generate a rationale for corrective therapeutic interventions is greatly limited. We had previously characterized a novel mouse model of neurodegeneration caused by mutation of the LISTER gene. Consistent with an important biological function, this gene is conserved in all organisms from yeast to humans. Accordingly, we have been utilizing various models to discover the gene function and how defects in this function may lead to the disease. The LISTER gene encodes a protein that acts as an E3 ubiquitin ligase, named Listerin. More recently, using yeast we discovered a function for Listerin that is consistent with a role in neurodegeneration in mammals: it functions in a process known as protein quality control whereby aberrant proteins are targeted for degradation. Specifically, its targets are proteins encoded by defective mRNA lacking stop codons ("non-stop proteins"). Listerin functions by tagging those aberrant proteins with molecules of ubiquitin (ubiquitination), which often acts as a destruction signal. Mutation of Listerin causes those toxic proteins to accumulate. With the proposed research we plan to specify the features of Listerin-mediated ubiquitination and expand the findings towards disease. Objective/Hypothesis: Our main hypotheses are that (a) Listerin acts in protein quality control by ubiquitinating non-stop polypeptides stalled in ribosomes, and (b) defective Listerin-mediated degradation leads to the formation of protein aggregates and inclusions, which are hallmarks of neurodegeneration. The Specific Aims are to characterize Listerin's function in non-stop protein degradation, to investigate the extent of conservation of Listerin's function in protein quality control, and to investigate how defects in this function lead to neurodegeneration. Our long-term objective is to help elucidate molecular mechanisms involved in the pathogenesis of human neurodegenerative disease. Study design: We will use biochemistry and yeast molecular genetics to specify how the E3 recognizes its specific target substrates; mammalian tissue culture and biochemistry to investigate the regulation of non-stop protein degradation by mammalian Listerin and biochemistry and cell biology to study the consequences of non-stop protein accumulation in cells.