The accumulation of toxic protein aggregates is thought to play a key role in a range of degenerative pathologies, but it remains unclear why aggregation of polypeptides into non-native assemblies is toxic and why cellular clearance pathways offer ineffective protection. We here study the A4V mutant of SOD1, which forms toxic aggregates in motor neurons of patients with familial amyotrophic lateral sclerosis (ALS). A comparison of the location of aggregation prone regions (APRs) and Hsp70 binding sites in the denatured state of SOD1 reveals that ALS-associated mutations promote exposure of the APRs more than the strongest Hsc/Hsp70 binding site that we could detect. Mutations designed to increase the exposure of this Hsp70 interaction site in the denatured state promote aggregation but also display an increased interaction with Hsp70 chaperones. Depending on the cell type, in vitro this resulted in cellular inclusion body formation or increased clearance, accompanied with a suppression of cytotoxicity. The latter was also observed in a zebrafish model in vivo. Our results suggest that the uncontrolled accumulation of toxic SOD1A4V aggregates results from insufficient detection by the cellular surveillance network.

中文翻译：

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暴露的Hsp70秘密结合位点决定了ALS相关的SOD1突变A4V的细胞毒性。

毒性蛋白聚集体的积累被认为在一系列退化性病理中起关键作用，但目前尚不清楚为什么多肽聚集到非天然组装物中是有毒的，以及为什么细胞清除途径不能提供有效的保护。我们在这里研究SOD1的A4V突变体，该突变体在家族性肌萎缩性侧索硬化症（ALS）患者的运动神经元中形成毒性聚集体。在SOD1变性状态下，倾向于聚合的区域（APR）和Hsp70结合位点的位置的比较显示，与ALS相关的突变比我们可以检测到的最强的Hsc / Hsp70结合位点更能促进APR的暴露。设计为增加变性状态下此Hsp70相互作用位点的暴露程度的突变会促进聚集，但也显示与Hsp70伴侣的相互作用增加。取决于细胞类型，在体外导致细胞包涵体的形成或清除率的增加，同时抑制细胞毒性。在体内的斑马鱼模型中也观察到后者。我们的结果表明，有毒的SOD1A4V聚集体的不受控制的积累是由细胞监控网络检测不到的结果。