Degradation of amyotrophic lateral sclerosis-linked mutant Cu,Zn-superoxide dismutase proteins by macroautophagy and the proteasome
Degradation of amyotrophic lateral sclerosis-linked mutant Cu,Zn-superoxide dismutase proteins by macroautophagy and the proteasome
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DOI：
10.1074/jbc.m603337200
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发表时间：
2006-10-13
影响因子：
4.8
通讯作者：
Wada, Keiji
中科院分区：
文献类型：
--
作者：
Kabuta, Tomohiro;Suzuki, Yasuyuki;Wada, Keiji
在20%的肌萎缩侧索硬化症(FALS)家族病例中，铜锌超氧化物歧化酶(SOD1)基因突变的原因与此相似。越来越多的证据表明，突变的SOD1蛋白的毒性功能增强是该病的原因。也有研究表明，泛素-蛋白酶体途径在突变型SOD1的清除和毒性中起作用。在这项研究中，我们研究了野生型和突变型SOD1在神经细胞和非神经细胞中的降解途径。我们在这里提供了第一个证据，证明野生型和突变型SOD1可以被宏自噬和蛋白酶体降解。基于对这些降解途径的抑制剂的实验，宏自噬对突变的SOD1清除的贡献与蛋白酶体途径的贡献相当。通过细胞活性和细胞死亡的检测，我们观察到在突变SOD1单独表达不会引起毒性的条件下，巨型自噬抑制诱导突变型SOD1介导的细胞死亡，表明宏自噬降低了突变型SOD1蛋白的毒性。因此，我们认为宏自噬和蛋白酶体对于减少突变型SOD1介导的FALS的神经毒性都是重要的。抑制大自噬也增加了洗涤剂可溶和不可溶组分中SOD1的水平，这表明洗涤剂可溶和不可溶SOD1都被大自噬降解。这些发现可能对FALS的发病机制提供进一步的认识。
Mutations in the Cu, Zn-superoxide dismutase (SOD1) gene cause similar to 20% of familial cases of amyotrophic lateral sclerosis (fALS). Accumulating evidence indicates that a gain of toxic function of mutant SOD1 proteins is the cause of the disease. It has also been shown that the ubiquitin-proteasome pathway plays a role in the clearance and toxicity of mutant SOD1. In this study, we investigated the degradation pathways of wild-type and mutant SOD1 in neuronal and nonneuronal cells. We provide here the first evidence that wild-type and mutant SOD1 are degraded by macroautophagy as well as by the proteasome. Based on experiments with inhibitors of these degradation pathways, the contribution of macroautophagy to mutant SOD1 clearance is comparable with that of the proteasome pathway. Using assays that measure cell viability and cell death, we observed that under conditions where expression of mutant SOD1 alone does not induce toxicity, macroautophagy inhibition induced mutant SOD1-mediated cell death, indicating that macroautophagy reduces the toxicity of mutant SOD1 proteins. We therefore propose that both macroautophagy and the proteasome are important for the reduction of mutant SOD1-mediated neurotoxicity in fALS. Inhibition of macroautophagy also increased SOD1 levels in detergent-soluble and -insoluble fractions, suggesting that both detergent- soluble and -insoluble SOD1 are degraded by macroautophagy. These findings may provide further insights into the mechanisms of pathogenesis of fALS.