Dufty Brian M, Warner Lisa R, Hou Sheng T, Jiang Susan X, Gomez-Isla Teresa, Leenhouts Kristen M, Oxford Julia T, Feany Mel B, Masliah Eliezer, Rohn Troy T
Department of Biology, Boise State University, Boise, ID 83725, USA.
Am J Pathol. 2007 May;170(5):1725-38. doi: 10.2353/ajpath.2007.061232.
Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are both characterized pathologically by the presence of neuronal inclusions termed Lewy bodies (LBs). A common feature found in LBs are aggregates of alpha-synuclein (alpha-Syn), and although it is now recognized that alpha-Syn is the major building block for these toxic filaments, the mechanism of how this occurs remains unknown. In the present study, we demonstrate that proteolytic processing of alpha-Syn by the protease calpain I leads to the formation of aggregated high-molecular weight species and adoption of a beta-sheet structure. To determine whether calpain-cleavage of alpha-Syn occurs in PD and DLB, we designed site-directed calpain-cleavage antibodies to alpha-Syn and tested their utility in several animal model systems. Detection of calpain-cleaved alpha-Syn was evident in mouse models of cerebral ischemia and PD and in a Drosophila model of PD. In the human PD and DLB brain, calpain-cleaved alpha-Syn antibodies immunolabeled LBs and neurites in the substantia nigra. Moreover, calpain-cleaved alpha-Syn fragments identified within LBs colocalized with activated calpain in neurons of the PD and DLB brains. These findings suggest that calpain I may participate in the disease-linked aggregation of alpha-Syn in various alpha-synucleinopathies.
帕金森病（PD）和路易体痴呆（DLB）在病理上均以存在称为路易小体（LBs）的神经元内含物为特征。路易小体的一个共同特征是α-突触核蛋白（α-Syn）的聚集，尽管现在人们认识到α-Syn是这些毒性细丝的主要组成部分，但这种情况发生的机制仍然未知。在本研究中，我们证明蛋白酶钙蛋白酶I对α-Syn的蛋白水解加工导致形成聚集的高分子量物质并采用β-折叠结构。为了确定α-Syn的钙蛋白酶切割是否发生在PD和DLB中，我们设计了针对α-Syn的定点钙蛋白酶切割抗体，并在几种动物模型系统中测试了它们的效用。在脑缺血和PD的小鼠模型以及PD的果蝇模型中，钙蛋白酶切割的α-Syn的检测很明显。在人类PD和DLB大脑中，钙蛋白酶切割的α-Syn抗体免疫标记黑质中的路易小体和神经突。此外，在路易小体中鉴定出的钙蛋白酶切割的α-Syn片段与PD和DLB大脑神经元中的活化钙蛋白酶共定位。这些发现表明，钙蛋白酶I可能参与各种α-突触核蛋白病中与疾病相关的α-Syn聚集。
