Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, United States.
Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, United States.
Elife. 2020 Mar 2;9:e51685. doi: 10.7554/eLife.51685.
Disruption of nucleocytoplasmic transport is increasingly implicated in the pathogenesis of neurodegenerative diseases, including ALS caused by a hexanucleotide repeat expansion. However, the mechanism(s) remain unclear. Karyopherins, including importin β and its cargo adaptors, have been shown to co-precipitate with the arginine-containing dipeptide repeat proteins (R-DPRs), poly-glycine arginine (GR) and poly-proline arginine (PR), and are protective in genetic modifier screens. Here, we show that R-DPRs interact with importin β, disrupt its cargo loading, and inhibit nuclear import of importin β, importin α/β, and transportin cargoes in permeabilized mouse neurons and HeLa cells, in a manner that can be rescued by RNA. Although R-DPRs induce widespread protein aggregation in this in vitro system, transport disruption is not due to nucleocytoplasmic transport protein sequestration, nor blockade of the phenylalanine-glycine (FG)-rich nuclear pore complex. Our results support a model in which R-DPRs interfere with cargo loading on karyopherins.
核质转运的中断越来越多地与神经退行性疾病的发病机制有关，包括由六核苷酸重复扩展引起的 ALS。然而，其机制尚不清楚。亲核素，包括 importin β及其货物衔接蛋白，已被证明与含有精氨酸的二肽重复蛋白（R-DPRs）、聚甘氨酸精氨酸（GR）和聚脯氨酸精氨酸（PR）共沉淀，并在遗传修饰筛选中具有保护作用。在这里，我们表明 R-DPRs 与 importin β相互作用，破坏其货物加载，并抑制渗透的小鼠神经元和 HeLa 细胞中 importin β、importin α/β 和 transportin 货物的核输入，这种作用可以通过 RNA 挽救。尽管 R-DPRs 在这种体外系统中诱导广泛的蛋白质聚集，但转运中断不是由于核质转运蛋白的隔离，也不是由于阻断富含苯丙氨酸-甘氨酸（FG）的核孔复合物。我们的结果支持这样一种模型，即 R-DPRs 干扰亲核素上的货物加载。
