Proteasomes remain intact, but show early focal alteration in their composition in a mouse model of amyotrophic lateral sclerosis
Proteasomes remain intact, but show early focal alteration in their composition in a mouse model of amyotrophic lateral sclerosis
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DOI：
10.1111/j.1471-4159.2008.05317.x
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发表时间：
2008-06-01
影响因子：
4.7
通讯作者：
Durham, H. D.
中科院分区：
文献类型：
--
作者：
Kabashi, E.;Agar, J. N.;Durham, H. D.
在由铜/锌超氧化物歧化酶(SOD1)突变引起的肌萎缩侧索硬化症中，突变蛋白的溶解性和聚集性的改变意味着错误折叠蛋白的检测和分解途径的失败。我们之前的研究表明，在SOD1(G93A)转基因小鼠的腰髓中，蛋白酶体介导的蛋白分解活性早期降低，这是特别容易患病的组织。这项研究的目的是确定蛋白酶体结构是否存在潜在的异常。在有症状的小鼠腰髓[出生后45天(45天)和75天(75天)]，20S/26S蛋白酶体中含有正常水平的结构20Sα亚基；然而，用天然凝胶电泳法分离的蛋白酶体复合体对20S蛋白酶体核心结构亚基β3和具有胰凝乳蛋白酶样活性的亚基β5的免疫反应性降低。这发生在β5i免疫蛋白酶体亚单位增加之前。信使核糖核酸水平保持不变，没有发现突变的SOD1与蛋白酶体相关，这暗示了转录后机制。在疾病的后期阶段(P100)，激光捕获的运动神经元中也保留了mRNAs，其中多个20S蛋白相对于周围的神经纤维层减少。P75位不溶于洗涤剂的泛素化蛋白质的增加提供了进一步的证据，表明在运动神经元显著死亡之前，多种细胞类型的蛋白质质量控制机制受到压力。
In amyotrophic lateral sclerosis caused by mutations in Cu/Zn-superoxide dismutase (SOD1), altered solubility and aggregation of the mutant protein implicates failure of pathways for detecting and catabolizing misfolded proteins. Our previous studies demonstrated early reduction of proteasome-mediated proteolytic activity in lumbar spinal cord of SOD1(G93A) transgenic mice, tissue particularly vulnerable to disease. The purpose of this study was to identify any underlying abnormalities in proteasomal structure. In lumbar spinal cord of pre-symptomatic mice [postnatal day 45 (P45) and P75], normal levels of structural 20S alpha subunits were incorporated into 20S/26S proteasomes; however, proteasomal complexes separated by native gel electrophoresis showed decreased immunoreactivity with antibodies to beta 3, a structural subunit of the 20S proteasome core, and beta 5, the subunit with chymotrypsin-like activity. This occurred prior to increase in beta 5i immunoproteasomal subunit. mRNA levels were maintained and no association of mutant SOD1 with proteasomes was identified, implicating post-transcriptional mechanisms. mRNAs also were maintained in laser captured motor neurons at a later stage of disease (P100) in which multiple 20S proteins are reduced relative to the surrounding neuropil. Increase in detergent-insoluble, ubiquitinated proteins at P75 provided further evidence of stress on mechanisms of protein quality control in multiple cell types prior to significant motor neuron death.