Siah-1 facilitates ubiquitination and degradation of synphilin-1
Siah-1 facilitates ubiquitination and degradation of synphilin-1
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DOI：
10.1074/jbc.m306347200
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发表时间：
2003-12-19
影响因子：
4.8
通讯作者：
Matsumoto, M
中科院分区：
文献类型：
--
作者：
Nagano, Y;Yamashita, H;Matsumoto, M
帕金森病是一种常见的神经退行性疾病，其特征在于多巴胺能神经元的损失和路易体的出现，路易体是高度富含泛素的细胞质内含物。Synphilin-1、α-突触核蛋白和Parkin代表路易体的主要组分，并参与帕金森病的发病机制。Synphilin-1是一种由帕金泛素化的α-突触核蛋白结合蛋白。最近，在synphilin-1基因的突变已报告在散发性帕金森病患者。虽然synphilin-1定位接近突触囊泡，其功能仍然未知。为了研究与synphilin-1相互作用的蛋白质，本研究进行了酵母双杂交筛选，并确定了一个新的相互作用蛋白，Siah-1泛素连接酶。Synphilin-1和Siah-1蛋白在中枢神经系统中内源性表达，并发现在大鼠脑匀浆中相互共免疫沉淀。共聚焦显微镜分析表明，这两种蛋白质在细胞中的共定位。发现Siah-1通过其底物结合结构域与synphilin-1的N末端相互作用，并通过其RING指结构域特异性泛素化synphilin-1。Siah-1通过泛素-蛋白酶体途径比Parkin更有效地促进synphilin-1降解。发现Siah-1不促进野生型或突变体α-突触核蛋白的泛素化和降解。Synphilin-1抑制高钾诱导的PC 12细胞多巴胺释放。发现Siah-1消除了synphilin-1对多巴胺释放的抑制作用。这些发现表明Siah-1可能在synphilin-1功能的调节中发挥作用。
Parkinson's disease is a common neurodegenerative disorder characterized by loss of dopaminergic neurons and appearance of Lewy bodies, cytoplasmic inclusions that are highly enriched with ubiquitin. Synphilin-1, alpha-synuclein, and Parkin represent the major components of Lewy bodies and are involved in the pathogenesis of Parkinson's disease. Synphilin-1 is an alpha-synuclein-binding protein that is ubiquitinated by Parkin. Recently, a mutation in the synphilin-1 gene has been reported in patients with sporadic Parkinson's disease. Although synphilin-1 localizes close to synaptic vesicles, its function remains unknown. To investigate the proteins that interact with synphilin-1, the present study performed a yeast two-hybrid screening and identified a novel interacting protein, Siah-1 ubiquitin ligase. Synphilin-1 and Siah-1 proteins were endogenously expressed in the central nervous system and were found to coimmunoprecipitate each other in rat brain homogenate. Confocal microscopic analysis revealed colocalization of both proteins in cells. Siah-1 was found to interact with the N terminus of synphilin-1 through its substrate-binding domain and to specifically ubiquitinate synphilin-1 via its RING finger domain. Siah-1 facilitated synphilin-1 degradation via the ubiquitin-proteasome pathway more efficiently than Parkin. Siah-1 was found to not facilitate ubiquitination and degradation of wild type or mutant alpha-synuclein. Synphilin-1 inhibited high K+-induced dopamine release from PC12 cells. Siah-1 was found to abrogate the inhibitory effects of synphilin-1 on dopamine release. Such findings suggest that Siah-1 might play a role in regulation of synphilin-1 function.