THE ROLE OF NUB1 IN PATHOGENESIS OF PARKINSON'S DISEASE

描述（由申请人提供）：帕金森病（PD）是一种常见的神经退行性疾病，其特征为多巴胺能神经元丢失和存在称为路易体（IB）的胞质内含物。据报道，家族性或散发性帕金森病患者的编码α-突触核蛋白、帕金蛋白或突触亲蛋白-1的基因发生突变。最近，α-突触核蛋白和synphilin-1都被证明是通过野生型帕金蛋白的E3泛素连接酶活性泛素化，但不是通过家族连锁突变帕金蛋白。此外，α-突触核蛋白，synphilin-1，和parkin的共表达导致在培养的细胞中形成LB样泛素阳性的胞质内含物。重要的是，parkin家族连锁突变破坏了泛素阳性包涵体的形成。这些观察结果表明，LB相关蛋白的泛素化缺陷参与了帕金森病的发病机制。NEDD 8是一种泛素样蛋白，以类似于泛素化的方式共价修饰靶蛋白。最近，我们发现了一种新的NEDD 8相互作用蛋白，NUB 1，其功能类似于分子伴侣，将NEDD 8招募到26 S蛋白酶体的S5 a亚基进行降解。除了NEDD 8，NUB 1通过其NEDDS结合位点与synphilin-1相互作用，这意味着NUB 1还将synphilin-1募集到26 S蛋白酶体的S5 a亚基。由于parkin与相同的亚基结合，我们假设NUB 1将synphilin-1募集到S5 a亚基，用于parkin的泛素化。此外，我们推测，synphilin-1的S5 a亚基的靶向不仅参与synphilin-1的泛素化，而且在LB形成。事实上，我们在帕金森病患者的大脑LB中检测到NUB 1，这表明NUB 1在LB形成或分解中发挥作用。为了验证这些假设，我们将追求3个目标，即定义1）NUB 1在synphilin-1靶向S5 a亚基中的作用，2）NUB 1在synphilin-1的泛素化中的作用，和3）NUB 1在synphilin-1形成胞质内含物中的作用。我们的研究结果将为NUB 1参与帕金森病的发病机制提供分子基础。此外，该结果将可能导致帕金森病新的诊断方法和治疗靶点的开发。

DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons and the presence of cytosolic inclusions, called Lewy bodies (IBs). Mutations in the gene encoding alpha-synuclein, parkin, or synphilin-1 have been reported in patients with familial or sporadic Parkinson's disease. Recently, both alpha-synuclein and synphilin-1 were shown to be ubiquitinated through the E3 ubiquitin ligase activity of wild-type parkin, but not by familial-linked mutant parkin. Moreover, the coexpression of alpha-synuclein, synphilin-1, and parkin resulted in the formation of LB-like ubiquitin-positive cytosolic inclusions in cultured cells. Importantly, familial-linked mutations in parkin disrupted the formation of the ubiquitin-positive inclusions. These observations indicate that defects in the ubiquitination of LB-associated proteins are involved in the pathogenesis of Parkinson's disease. NEDD8 is a ubiquitin-like protein that covalently modifies target proteins in a manner analogous to ubiquitination. Recently, we identified a novel NEDD8-interacting protein, NUB1, that functioned like a molecular chaperone to recruit NEDD8 to the S5a subunit of the 26S proteasome for degradation. In addition to NEDD8, NUB1 interacted with synphilin-1 through its NEDDS-binding site, implying that NUB1 also recruits synphilin-1 to the S5a subunit of the 26S proteasome. Because parkin binds to the same subunit, we hypothesize that NUB1 recruits synphilin-1 to the S5a subunit for its ubiquitination by parkin. Furthermore, we hypothesize that the targeting of synphilin-1 to the S5a subunit is involved not only in the ubiquitination of synphilin-1, but also in LB formation. Indeed, we detected NUB1 in the LBs of brains from patients with Parkinson's disease, suggesting that NUB1 plays a role in LB formation or its breakdown. To test these hypotheses, we will pursue 3 Aims, which are to define 1) the role of NUB1 in the targeting of synphilin-1 to the S5a subunit, 2) the role of NUB1 in the ubiquitination of synphilin-1, and 3) the role of NUB1 in the formation of cytosolic inclusions by synphilin-1. The outcome of our research proposed here will provide a molecular basis for the involvement of NUB1 in the pathogenesis of Parkinson's disease. Furthermore, the outcome will potentially lead to the development of new diagnostic methods and therapeutic targets for Parkinson's disease.