Stress Induces Dynamic, Cytotoxicity-Antagonizing TDP-43 Nuclear Bodies via Paraspeckle LncRNA NEAT1-Mediated Liquid-Liquid Phase Separation

Despite the prominent role of TDP-43 in neurodegeneration, its physiological and pathological functions are not fully understood. Here, we report an unexpected role of TDP-43 in the formation of dynamic, reversible, liquid droplet-like nuclear bodies (NBs) in response to stress. Formation of NBs alleviates TDP-43-mediated cytotoxicity in mammalian cells and fly neurons. Super-resolution microscopy reveals distinct functions of the two RRMs in TDP-43 NB formation. TDP-43 NBs are partially colocalized with nuclear paraspeckles, whose scaffolding lncRNA NEAT1 is dramatically upregulated in stressed neurons. Moreover, increase of NEAT1 promotes TDP-43 liquid-liquid phase separation (LLPS) in vitro. Finally, we discover that the ALS-associated mutation D169G impairs the NEAT1-mediated TDP-43 LLPS and NB assembly, causing excessive cytoplasmic translocation of TDP-43 to form stress granules, which become phosphorylated TDP-43 cytoplasmic foci upon prolonged stress. Together, our findings suggest a stress-mitigating role and mechanism of TDP-43 NBs, whose dysfunction may be involved in ALS pathogenesis.

尽管TDP - 43在神经退行性变中具有重要作用，但其生理和病理功能尚未完全明确。在此，我们报道了TDP - 43在应对压力时，在动态、可逆的液滴样核体（NBs）形成过程中所起的一种意想不到的作用。核体的形成减轻了TDP - 43在哺乳动物细胞和果蝇神经元中介导的细胞毒性。超分辨率显微镜揭示了TDP - 43中两个RNA识别基序（RRMs）在核体形成中的不同功能。TDP - 43核体与核旁斑部分共定位，在受应激的神经元中，其支架长链非编码RNA NEAT1显著上调。此外，NEAT1的增加在体外促进了TDP - 43的液 - 液相分离（LLPS）。最后，我们发现与肌萎缩侧索硬化症（ALS）相关的突变D169G损害了NEAT1介导的TDP - 43液 - 液相分离和核体组装，导致TDP - 43过度向细胞质转位形成应激颗粒，在长时间应激时，这些应激颗粒会变成磷酸化的TDP - 43细胞质聚集体。总之，我们的研究结果表明了TDP - 43核体具有缓解应激的作用和机制，其功能障碍可能参与了ALS的发病机制。