Department of Neuropathology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
Acta Neuropathol. 2010 Aug;120(2):145-54. doi: 10.1007/s00401-010-0676-z. Epub 2010 Mar 26.
Abnormally modified alpha-synuclein is a pathological hallmark of Parkinson's disease and the other alpha-synucleinopathies. Since proteinase K (PK) treatment is known to enhance the immunoreactivity of abnormal alpha-synuclein, we immunohistochemically examined the brain of transgenic (Tg) mice expressing human mutant A53T alpha-synuclein using this retrieval method. PK treatment abolished the immunoreactivity of alpha-synuclein in abnormal inclusions as well as of endogenous alpha-synuclein in Tg mice, whereas PK-resistant alpha-synuclein was found in the presynaptic nerve terminals, especially in the hippocampus and temporal cortex. In human Lewy body disease, PK-resistant alpha-synuclein was deposited in Lewy bodies and Lewy neurites, as well as in the presynapses in distinct brain regions, including the hippocampus, temporal cortex and substantia nigra. Biochemical analysis revealed that PK-resistant alpha-synuclein was detected in the presynaptic fraction in Tg mice and human Lewy body disease. Although PK-resistant alpha-synuclein was found in the presynapse in Tg mice even at 1 week of age, it was not phosphorylated until at least 8 months of age. Moreover, PK-resistant alpha-synuclein in the presynapse was not phosphorylated in human Lewy body disease. These findings suggest that phosphorylation is not necessary to cause the conversion of soluble form to PK-resistant alpha-synuclein. Considering that native alpha-synuclein is a soluble protein localized to the presynaptic terminals, our findings suggest that PK-resistant alpha-synuclein may disturb the neurotransmission in alpha-synucleinopathies.
异常修饰的α-突触核蛋白是帕金森病和其他α-突触核蛋白病的病理标志。由于蛋白酶 K（PK）处理已知可增强异常α-突触核蛋白的免疫反应性，我们使用这种检索方法对表达人突变 A53Tα-突触核蛋白的转基因（Tg）小鼠的大脑进行了免疫组织化学检查。PK 处理消除了 Tg 小鼠中异常包涵体中α-突触核蛋白以及内源性α-突触核蛋白的免疫反应性，而 PK 抗性α-突触核蛋白存在于突触前神经末梢中，特别是在海马体和颞叶皮质中。在人类路易体病中，PK 抗性α-突触核蛋白沉积在路易体和路易神经元中，以及包括海马体、颞叶皮质和黑质在内的不同脑区的突触前部位。生化分析显示，PK 抗性α-突触核蛋白存在于 Tg 小鼠和人类路易体病的突触前部分。尽管在 Tg 小鼠中，PK 抗性α-突触核蛋白甚至在 1 周龄时就存在于突触前部位，但直到至少 8 月龄时才发生磷酸化。此外，在人类路易体病中，突触前的 PK 抗性α-突触核蛋白未发生磷酸化。这些发现表明磷酸化不是导致可溶性形式转化为 PK 抗性α-突触核蛋白的必要条件。考虑到天然α-突触核蛋白是一种定位于突触前末梢的可溶性蛋白，我们的发现表明 PK 抗性α-突触核蛋白可能会干扰α-突触核蛋白病中的神经传递。
