Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autónoma de Barcelona, Bellaterra 08193, Spain.
Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Cell Rep. 2020 Jan 28;30(4):1117-1128.e5. doi: 10.1016/j.celrep.2019.12.080.
Prion-like proteins form multivalent assemblies and phase separate into membraneless organelles. Heterogeneous ribonucleoprotein D-like (hnRNPDL) is a RNA-processing prion-like protein with three alternative splicing (AS) isoforms, which lack none, one, or both of its two disordered domains. It has been suggested that AS might regulate the assembly properties of RNA-processing proteins by controlling the incorporation of multivalent disordered regions in the isoforms. This, in turn, would modulate their activity in the downstream splicing program. Here, we demonstrate that AS controls the phase separation of hnRNPDL, as well as the size and dynamics of its nuclear complexes, its nucleus-cytoplasm shuttling, and amyloidogenicity. Mutation of the highly conserved D378 in the disordered C-terminal prion-like domain of hnRNPDL causes limb-girdle muscular dystrophy 1G. We show that D378H/N disease mutations impact hnRNPDL assembly properties, accelerating aggregation and dramatically reducing the protein solubility in the muscle of Drosophila, suggesting a genetic loss-of-function mechanism for this muscular disorder.
类朊蛋白形成多价组装体，并相分离成无膜细胞器。异质核糖核蛋白 D 样 (hnRNPDL) 是一种 RNA 加工类朊蛋白，具有三种选择性剪接 (AS) 异构体，它们缺乏两个无规卷曲结构域中的一个或两个。有人提出，AS 可能通过控制多价无规区域在异构体中的掺入来调节 RNA 加工蛋白的组装特性。这反过来又会调节它们在下游剪接程序中的活性。在这里，我们证明 AS 控制 hnRNPDL 的相分离，以及其核复合物的大小和动态、核质穿梭和淀粉样变。hnRNPDL 无规卷曲 C 端类朊结构域中高度保守的 D378 突变导致肢带型肌营养不良 1G。我们表明，D378H/N 疾病突变影响 hnRNPDL 的组装特性，加速聚集并显著降低果蝇肌肉中的蛋白质溶解度，这表明该肌肉疾病存在遗传功能丧失机制。
