Importin β-superfamily nuclear import receptors (NIRs) mitigate mislocalization and aggregation of RNA-binding proteins (RBPs), like FUS and TDP-43, which are implicated in neurodegenerative diseases. NIRs potently disaggregate RBPs by recognizing their nuclear localization signal (NLS). However, disease-causing mutations in NLS compromise NIR binding and activity. Here, we define features that characterize the anti-aggregation activity of NIR and NLS. We find that high binding affinity between NIR and NLS, and optimal NLS location relative to the aggregating domain plays a role in determining NIR disaggregation activity. A designed FUS chimera (FUS_IBB), carrying the importin β binding (IBB) domain, is solubilized by importin β in vitro, translocated to the nucleus in cultured cells, and downregulates the expression of endogenous FUS. In this study, we posit that guiding the mutual recognition of NLSs and NIRs will aid the development of therapeutics, illustrated by the highly soluble FUS_IBB replacing the aggregation-prone endogenous FUS.

Importin β超家族核输入受体 （NIR） 可减轻 RNA 结合蛋白 （RBP） 的错误定位和聚集，如 FUS 和 TDP-43，这些蛋白与神经退行性疾病有关。NIR 通过识别 RBP 的核定位信号 （NLS） 来有效地分解 RBP。然而，NLS 中的致病突变会损害 NIR 结合和活性。在这里，我们定义了表征 NIR 和 NLS 抗聚集活性的特征。我们发现 NIR 和 NLS 之间的高结合亲和力以及相对于聚集结构域的最佳 NLS 位置在确定 NIR 解聚活性中起作用。携带 importin β binding （IBB） 结构域的设计 FUS 嵌合体 （FUS_IBB） 在体外被 importin β 溶解，转位到培养细胞的细胞核，并下调内源性 FUS 的表达。在这项研究中，我们假设指导 NLS 和 NIRs 的相互识别将有助于治疗药物的发展，高度可溶性的 FUS_IBB 取代了易聚集的内源性 FUS。