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)在路易体的沉积是包括帕金森病和路易体痴呆在内的多种神经退行性疾病的病理特征，这种α-Syn的异常沉积似乎与神经退行性变有关。基于任何与α-SYN相互作用的蛋白质可能在α-SYN沉积机制中发挥作用的假设，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质。我们获得了一个阳性克隆，该克隆对应于一个未知基因的部分cdna。随后对人脑cDNA文库进行筛选和EST数据库搜索，得到了全长的cDNA克隆。我们将这个新基因命名为αSNBP(α-突触核蛋白结合蛋白)。该基因编码一种由463个氨基酸组成的蛋白质。Northern印迹分析表明，αSNBP基因在包括脑在内的多种组织中均有表达。对αSNBP转基因细胞的Western印迹分析表明，αSNBP以约60kD的蛋白质形式表达。共表达α-Syn和αSNBP的细胞的可溶性部分的免疫共沉淀分析表明这些蛋白是结合的。细胞的免疫荧光染色也表明这两种蛋白是共定位的。用αSNBP抗体对人脑标本进行免疫组织化学染色，结果表明αSNBP在神经元中有不同程度的表达，提示αSNBP是一种与α-SYN发生物理作用的新蛋白。关于αSNBP是否参与α-突触核病症的神经病理的进一步调查正在进行中。

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.