Kabuta Tomohiro, Setsuie Rieko, Mitsui Takeshi, Kinugawa Aiko, Sakurai Mikako, Aoki Shunsuke, Uchida Kenko, Wada Keiji
Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan.
Hum Mol Genet. 2008 May 15;17(10):1482-96. doi: 10.1093/hmg/ddn037. Epub 2008 Feb 4.
Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons. The I93M mutation in ubiquitin C-terminal hydrolase L1 (UCH-L1) is associated with familial PD, and we have previously shown that the I93M UCH-L1-transgenic mice exhibit dopaminergic cell loss. Over 90% of neurodegenerative diseases, including PD, occur sporadically. However, the molecular mechanisms underlying sporadic PD as well as PD associated with I93M UCH-L1 are largely unknown. UCH-L1 is abundant (1-5% of total soluble protein) in the brain and is a major target of oxidative/carbonyl damage associated with sporadic PD. As well, abnormal microtubule dynamics and tubulin polymerization are associated with several neurodegenerative diseases including frontotemporal dementia and parkinsonism linked to chromosome 17. Here we show that familial PD-associated mutant UCH-L1 and carbonyl-modified UCH-L1 display shared aberrant properties: compared with wild-type UCH-L1, they exhibit increased insolubility and elevated interactions with multiple proteins, which are characteristics of several neurodegenerative diseases-linked mutants. Circular dichroism analyses suggest similar structural changes in both UCH-L1 variants. We further report that one of the proteins interacting with UCH-L1 is tubulin, and that aberrant interaction of mutant or carbonyl-modified UCH-L1 with tubulin modulates tubulin polymerization. These findings may underlie the toxic gain of function by mutant UCH-L1 in familial PD. Our results also suggest that the carbonyl modification of UCH-L1 and subsequent abnormal interactions of carbonyl-modified UCH-L1 with multiple proteins, including tubulin, constitute one of the causes of sporadic PD.
帕金森病（PD）是一种以多巴胺能神经元丧失为特征的神经退行性疾病。泛素C末端水解酶L1（UCH-L1）中的I93M突变与家族性PD相关，并且我们之前已经表明I93M UCH-L1转基因小鼠表现出多巴胺能细胞丧失。超过90%的神经退行性疾病，包括PD，是散发性发生的。然而，散发性PD以及与I93M UCH-L1相关的PD的分子机制在很大程度上尚不清楚。UCH-L1在大脑中含量丰富（占总可溶性蛋白的1-5%），并且是与散发性PD相关的氧化/羰基损伤的主要靶点。同样，异常的微管动力学和微管蛋白聚合与包括17号染色体连锁的额颞叶痴呆和帕金森综合征在内的几种神经退行性疾病相关。在这里我们表明，家族性PD相关的突变型UCH-L1和羰基修饰的UCH-L1表现出共同的异常特性：与野生型UCH-L1相比，它们表现出增加的不溶性以及与多种蛋白质的相互作用增强，这是几种神经退行性疾病相关突变体的特征。圆二色性分析表明两种UCH-L1变体具有相似的结构变化。我们进一步报道，与UCH-L1相互作用的一种蛋白质是微管蛋白，并且突变型或羰基修饰的UCH-L1与微管蛋白的异常相互作用会调节微管蛋白聚合。这些发现可能是家族性PD中突变型UCH-L1功能毒性获得的基础。我们的结果还表明，UCH-L1的羰基修饰以及随后羰基修饰的UCH-L1与包括微管蛋白在内的多种蛋白质的异常相互作用是散发性PD的原因之一。
