Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease with no effective treatment available. An increasing number of genetic causes of ALS are being identified, but how these genetic defects lead to motor neuron degeneration and to which extent they affect common cellular pathways remains incompletely understood. To address these questions, we performed an interactomic analysis to identify binding partners of wild-type (WT) and ALS-associated mutant versions of ATXN2, C9orf72, FUS, OPTN, TDP-43 and UBQLN2 in neuronal cells. This analysis identified several known but also many novel binding partners of these proteins. Interactomes of WT and mutant ALS proteins were very similar except for OPTN and UBQLN2, in which mutations caused loss or gain of protein interactions. Several of the identified interactomes showed a high degree of overlap: shared binding partners of ATXN2, FUS and TDP-43 had roles in RNA metabolism; OPTN- and UBQLN2-interacting proteins were related to protein degradation and protein transport, and C9orf72 interactors function in mitochondria. To confirm that this overlap is important for ALS pathogenesis, we studied fragile X mental retardation protein (FMRP), one of the common interactors of ATXN2, FUS and TDP-43, in more detail in in vitro and in vivo model systems for FUS ALS. FMRP localized to mutant FUS-containing aggregates in spinal motor neurons and bound endogenous FUS in a direct and RNA-sensitive manner. Furthermore, defects in synaptic FMRP mRNA target expression, neuromuscular junction integrity, and motor behavior caused by mutant FUS in zebrafish embryos, could be rescued by exogenous FMRP expression. Together, these results show that interactomics analysis can provide crucial insight into ALS disease mechanisms and they link FMRP to motor neuron dysfunction caused by FUS mutations.

中文翻译：

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不同ALS相关蛋白的比较相互作用组学分析确定了会聚的分子途径。

肌萎缩性侧索硬化症（ALS）是一种破坏性神经病，尚无有效的治疗方法。越来越多的ALS遗传原因被发现，但是这些遗传缺陷如何导致运动神经元变性以及它们在多大程度上影响常见的细胞途径仍未完全了解。为解决这些问题，我们进行了相互作用组学分析，以鉴定神经元细胞中ATXN2，C9orf72，FUS，OPTN，TDP-43和UBQLN2的野生型（WT）和ALS相关突变体的结合伴侣。该分析鉴定了这些蛋白质的几种已知但也许多新颖的结合伴侣。除了OPTN和UBQLN2外，WT和突变ALS蛋白的相互作用组非常相似，在OPTN和UBQLN2中，突变导致蛋白相互作用的丧失或获得。几个已鉴定的相互作用组表现出高度重叠：ATXN2，FUS和TDP-43的共享结合伴侣在RNA代谢中起作用；与OPTN和UBQLN2相互作用的蛋白与蛋白降解和蛋白运输有关，并且C9orf72相互作用子在线粒体中起作用。为了确认这种重叠对于ALS发病机理很重要，我们在FUS ALS的体内和体外模型系统中研究了脆弱的X智力低下蛋白（FMRP）（ATXN2，FUS和TDP-43的常见相互作用物之一） 。FMRP定位于脊髓运动神经元中突变的含FUS的聚集体，并以直接且对RNA敏感的方式结合内源性FUS。此外，由斑马鱼胚胎中的突变FUS引起的突触FMRP mRNA目标表达，神经肌肉接头完整性和运动行为方面的缺陷，可以通过外源性FMRP表达来挽救。总之，这些结果表明，相互作用组学分析可以提供有关ALS疾病机制的重要见解，并将FMRP与FUS突变引起的运动神经元功能障碍联系起来。