Identifying and characterizing protein quality control mechanisms in the nucleus

描述(由申请人提供)：受损或错误折叠的蛋白质的积累可能会对细胞生理和生存能力产生毁灭性的影响。为了保护自己，细胞拥有许多蛋白质质量控制(PQC)系统，将这些异常蛋白质的持久性和有害影响降至最低。虽然细胞质、内质网和线粒体中有多种PQC系统的特征，但对细胞核如何管理异常蛋白知之甚少。但是，了解核生物学的这一基本方面很重要，因为许多与年龄相关的神经肌肉疾病(亨廷顿氏症、肯尼迪氏症、几种脊髓-小脑性共济失调)是由于核内异常蛋白的有毒积累造成的。因此，我们的长期目标是通过识别在细胞核中工作的PQC系统，表征这些系统如何识别和靶向异常蛋白，检查核PQC系统中的损伤是否是这些病理发生所必需的，以及确定异常核蛋白破坏导致毒性的特定核过程，来了解核正常情况下如何保护自己免受有毒异常蛋白的伤害。从我们对酿酒酵母的初步研究中，我们已经确定了第一个已知的作用于细胞核的PQC降解系统。这个核PQC系统的核心是San1，它是一种定位于核的泛素蛋白连接酶，针对泛素化和蛋白酶体降解的异常核蛋白。随着San1的发现，我们现在可以很好地探索核PQC降解系统如何识别其底物，以及它识别出这些底物中的异常情况。这笔赠款的具体目标是：(1)确定SAN1内负责底物靶向的区域。SAN1的突变将被用来识别对底物识别重要的顺式区域。(2)确定San1识别的异常蛋白的特征。对San1底物的突变将被用来确定San1靶向所需的区域。(3)鉴定和鉴定San1途径的其他成分。基因和生化方法的结合将被用来识别额外的San1途径组件。公共卫生相关性：许多与年龄相关的神经肌肉疾病(亨廷顿氏症、肯尼迪氏症、几种脊髓-小脑性共济失调和眼咽肌营养不良等)都是由于易聚集蛋白在细胞核内有毒堆积造成的。我们的目标是了解细胞核通常是如何保护自己免受有毒的易于聚集的蛋白的影响，以及为什么在这些和其他疾病中它无法做到这一点。

DESCRIPTION (provided by applicant): The accumulation of damaged or misfolded proteins can have devastating effects on cellular physiology and viability. To protect itself, the cell possesses numerous Protein Quality Control (PQC) systems that minimize the persistence and detrimental effects of these aberrant proteins. While a variety of PQC systems have been characterized in the cytoplasm, ER, and mitochondria, how the nucleus manages aberrant proteins is poorly understood. But, understanding this fundamental aspect of nuclear biology is important because many age-correlated neuromuscular disorders (Huntington's, Kennedy's, several spinal-cerebellar ataxias) result from toxic accumulation of aberrant proteins in the nucleus. Therefore, our long-term goals are to understand how the nucleus normally protects itself from toxic aberrant proteins by identifying PQC systems that operate in the nucleus, characterizing how these systems recognize and target aberrant proteins, examining if lesions in nuclear PQC systems are required for these pathologies to develop, and determining the specific nuclear processes that are disrupted by aberrant nuclear proteins to cause toxicity. From our initial studies in S. cerevisiae, we've identified the first-known PQC degradation system that acts in the nucleus. The central player of this nuclear PQC system is San1, a nuclear-localized ubiquitin- protein ligase that targets aberrant nuclear proteins for ubiquitination and proteasome degradation. With the discovery of San1, we're now well positioned to explore how a nuclear PQC degradation system recognizes its substrates, and what it recognizes as aberrant within those substrates. The specific aims for this grant are to: (1) Determine the regions within San1 responsible for substrate targeting. Mutagenesis of San1 will be used to identify in cis regions important for substrate recognition. (2) Determine the features of an aberrant protein recognized by San1. Mutagenesis of San1 substrates will be used to identify regions required for targeting by San1. (3) Identify & characterize additional components of the San1 pathway. A combination of genetic and biochemical approaches will be used to identify additional San1 pathway components. PUBLIC HEALTH RELEVANCE: Many age-correlated neuromuscular disorders (Huntington's, Kennedy's, several spinal-cerebellar ataxias, and oculopharyngeal muscular dystrophy to name a few) result from toxic accumulation of aggregation-prone proteins in the cell's nucleus. Our goals are to understand how the nucleus normally protects itself from toxic aggregation-prone proteins, and why it fails to do so in these and other diseases.