A study on the mechanism of α-synuclein deposition: Is a novel α-synuclein interacting protein involved in α-synucleinopathies?

α-突触核蛋白（α-Syn）在路易小体中的沉积是几种神经退行性疾病的病理标志，包括帕金森病和路易小体痴呆，α-Syn的异常沉积似乎与神经退行性变性有关。基于任何与α-Syn相互作用的蛋白都可能参与α-Syn沉积机制的假设，我们采用酵母双杂交筛选的方法寻找与α-Syn物理相互作用的蛋白。我们获得了一个与未知基因的部分cDNA相对应的阳性克隆。随后的人脑cDNA文库筛选和EST数据库搜索产生全长cDNA克隆。我们将该基因命名为α-突触核蛋白结合蛋白（α- synnuclein binding protein）。这个基因编码一种由463个氨基酸组成的蛋白质。Northern blot分析显示，αSNBP mRNA在包括脑在内的多个组织中均有表达。转染αSNBP的细胞Western blot分析显示，αSNBP以约60 kD的蛋白表达。共表达α-Syn和αSNBP的细胞可溶部分的共免疫沉淀分析表明这些蛋白结合。细胞的免疫荧光染色也提示这两种蛋白的共定位。用αSNBP特异性抗体对人脑标本进行免疫组化染色，发现αSNBP在神经元中有不同水平的表达。我们认为αSNBP是一种与α-Syn相互作用的新蛋白。关于αSNBP是否参与α-突触核蛋白病的神经病理的进一步研究正在进行中。

Deposition of α-synuclein (α-Syn) in Lewy bodies is a pathological hallmark of several neurodegerative disorders, including Parkinson's disease and dementia with Lewy bodies, and this abnormal deposition of α-Syn appears to be associated with neurodegeneration. Based on the hypothesis that any protein interacting with α-Syn may play a role in the mechanism of α-Syn deposition, we searched for proteins physically interacting with α-Syn, using yeast two-hybrid screening. We obtained one positive clone which corresponds to a partial cDNA of an unknown gene. Subsequent screening of a human brain cDNA library and EST data base searches yielded full-length cDNA clones. We named this novel gene αSNBP (α-synuclein binding protein). This gene encodes a protein consisting of 463 amino acids. Northern blot analysis showed that αSNBP mRNA is expressed in multiple tissues including brain. Western blot analysis of αSNBP-transfected cells showed that αSNBP is expressed as a protein of 〜60 kD. Co-immunoprecipitation analysis of a soluble fraction from cells co-expressing α-Syn and αSNBP indicated binding of these proteins. Immunofluorescence staining of the cells also suggested co-localization of the two proteins. Immunohistochemical staining of human brain specimens with a specific αSNBP antibody showed that αSNBP is expressed in neurons at variable levels.We conclude that αSNBP is a novel protein physically interacting with α-Syn. Further investigation concerning whether αSNBP is involved in the neuropathology of α-synucleinopathies is in progress.