Praja2 and the regulation of Ataxin-1 clearance in vivo

描述（由申请人提供）： 脊髓小脑性共济失调1型（SCA 1）是一种成人发病的遗传性疾病，导致小脑浦肯野细胞变性，并在发病后10-30年死亡。患者首先表现出轻微的协调和平衡问题（共济失调）。SCA 1是由ATXN 1基因中的CAG重复突变引起的，该基因编码具有异常扩增的多聚谷氨酰胺（polyQ）序列的ATXN 1蛋白。随着神经退行性疾病的进展，其他大脑区域也会参与其中，并导致认知缺陷以及言语、吞咽和呼吸控制方面的问题。病理学的基本基础是浦肯野细胞正常功能的异常，影响RNA剪接和基因转录的调节。谷氨酰胺扩增的ATXN 1高度稳定，更耐降解。此外，ATXN 1中S776的磷酸化是一种翻译后修饰，已知会影响蛋白质水平。研究提出在这里检查ATXN 1清除调节小脑浦肯野细胞（PC），在SCA 1的病理学的主要网站的细胞机制。 Praja 2是一种E3泛素-蛋白连接酶，介导靶蛋白的多聚泛素化。初步观察表明，体内PC中Praja 2敲低导致ATXN 1蛋白水平异常升高。Praja 2在PC中高度表达，有趣的是，在SCA 1小鼠模型的小脑中显著下调，表明该途径可能在疾病中受到影响。这项修订后的提案将探索Praja 2对PC中ATXN 1清除的调节，以及这可能如何依赖于polyQ扩增和/或S776磷酸化状态。第一个目标将检查是否敲低Praja 2在体内调节小脑PC中的ATXN 1水平。该提案的第二个目的是检查Praja 2是否是ATXN 1的泛素蛋白连接酶。第三个目标将检查体内调节PC中的Praja 2水平是否影响动物模型中的SCA 1病理学。更好地了解ATXN 1清除在体内是如何调节的，可能为开发治疗SCA 1的长期目标提供可行的途径。

DESCRIPTION (provided by applicant): Spinocerebellar ataxia type 1 (SCA1) is an adult-onset, inherited disease that leads to degeneration of Purkinje cells of the cerebellum and culminates in death 10-30 years after disease onset. Patients first present with mild problems with coordination and balance (ataxia). SCA1 is caused by a CAG repeat mutation in the ATXN1 gene, encoding the ATXN1 protein with an abnormally expanded polyglutamine (polyQ) tract. As neurodegeneration progresses, other brain regions get involved and contribute to cognitive deficits as well as problems with speech, swallowing, and control of breathing. The fundamental basis of pathology is an aberration in the normal function of Purkinje cells affecting regulation of RNA splicing and gene transcription. Glutamine-expanded ATXN1 is highly stable and more resistant to degradation. Moreover, phosphorylation at S776 in ATXN1 is a post-translational modification known to influence protein levels. Studies are proposed here to examine the cellular mechanisms by which ATXN1 clearance is regulated in cerebellar Purkinje cells (PCs), a primary site of pathology in SCA1. Praja2 is an E3 ubiquitin-protein ligase that mediates polyubiquitination of target proteins. Preliminary observations show that Praja2 knockdown in PCs in vivo results in abnormally elevated levels of ATXN1 protein. Praja2 is highly expressed in PCs and, intriguingly, is significantly downregulated in cerebella of SCA1 mouse models, suggesting this pathway may be affected in disease. This revised proposal will explore Praja2 regulation of ATXN1 clearance in PCs and how that may be dependent on polyQ expansion and/or S776 phosphorylation status. The first aim will examine whether knocking down Praja2 modulates ATXN1 levels in cerebellar PCs in vivo. The second aim in this proposal is to examine whether Praja2 is a ubiquitin-protein ligase to ATXN1. The third aim will examine whether modulating Praja2 levels in PCs in vivo impacts SCA1 pathology in animal models. A better understanding of how ATXN1 clearance is regulated in vivo may provide feasible avenues for the long-term goal of developing a therapy to treat SCA1.