Inhibition of calpain cleavage of huntingtin reduces toxicity - Accumulation of calpain/caspase fragments in the nucleus
Inhibition of calpain cleavage of huntingtin reduces toxicity - Accumulation of calpain/caspase fragments in the nucleus
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DOI：
10.1074/jbc.m401267200
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发表时间：
2004-05-07
影响因子：
4.8
通讯作者：
Ellerby, LM
中科院分区：
文献类型：
--
作者：
Gafni, J;Hermel, E;Ellerby, LM
亨廷顿氏病（HD）是一种神经退行性疾病，由亨廷顿蛋白（Htt） N端附近的聚谷氨酰胺（polyQ）束扩张引起。突变体Htt蛋白水解加工和异常钙信号可能在疾病进展和发病机制中起关键作用。最近的研究表明，钙蛋白酶可能参与Htt蛋白水解模式的增加和/或改变，导致HD纹状体中观察到的选择性毒性。在这里，我们确定了Htt中的两个钙蛋白酶裂解位点，并在体外细胞培养模型中表明，这些位点的突变使polyQ扩增的Htt对蛋白质水解和聚集的敏感性降低，从而降低毒性。此外，我们发现calpain和caspase衍生的Htt片段优先在细胞核中积累，而不需要进一步切割成更小的片段。Calpain家族成员Calpain -1、-5、-7和-10在HD组织培养和转基因小鼠模型中水平升高或被激活，表明它们可能在Htt蛋白水解和疾病病理中发挥关键作用。有趣的是，calpain- 1, -5， -7和-10定位于细胞质和细胞核，而活化形式的calpain-7和-10仅在细胞核中发现。这些结果支持钙蛋白酶衍生的Htt片段在HD中的作用，并提示钙蛋白酶的异常激活可能在HD发病机制中发挥作用。
Huntington's disease (HD) is a neurodegenerative disorder caused by a polyglutamine (polyQ) tract expansion near the N terminus of huntingtin (Htt). Proteolytic processing of mutant Htt and abnormal calcium signaling may play a critical role in disease progression and pathogenesis. Recent work indicates that calpains may participate in the increased and/or altered patterns of Htt proteolysis leading to the selective toxicity observed in HD striatum. Here, we identify two calpain cleavage sites in Htt and show that mutation of these sites renders the polyQ expanded Htt less susceptible to proteolysis and aggregation, resulting in decreased toxicity in an in vitro cell culture model. In addition, we found that calpain- and caspase-derived Htt fragments preferentially accumulate in the nucleus without the requirement of further cleavage into smaller fragments. Calpain family members, calpain- 1, -5, -7, and -10, have increased levels or are activated in HD tissue culture and transgenic mouse models, suggesting they may play a key role in Htt proteolysis and disease pathology. Interestingly, calpain- 1, -5, -7, and -10 localize to the cytoplasm and the nucleus, whereas the activated forms of calpain-7 and -10 are found only in the nucleus. These results support the role of calpain- derived Htt fragmentation in HD and suggest that aberrant activation of calpains may play a role in HD pathogenesis.