State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, PR China; University of Chinese Academy of Sciences, Beijing, PR China.
State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, PR China.
J Biol Chem. 2024 Jul;300(7):107413. doi: 10.1016/j.jbc.2024.107413. Epub 2024 May 27.
Ataxin-2 (Atx2) is a polyglutamine (polyQ) tract-containing RNA-binding protein, while its polyQ expansion may cause protein aggregation that is implicated in the pathogenesis of neurodegenerative diseases such as spinocerebellar ataxia type 2 (SCA2). However, the molecular mechanism underlying how Atx2 aggregation contributes to the proteinopathies remains elusive. Here, we investigated the influence of Atx2 aggregation on the assembly and functionality of cellular processing bodies (P-bodies) by using biochemical and fluorescence imaging approaches. We have revealed that polyQ-expanded (PQE) Atx2 sequesters the DEAD-box RNA helicase (DDX6), an essential component of P-bodies, into aggregates or puncta via some RNA sequences. The N-terminal like-Sm (LSm) domain of Atx2 (residues 82-184) and the C-terminal helicase domain of DDX6 are responsible for the interaction and specific sequestration. Moreover, sequestration of DDX6 may aggravate pre-mRNA mis-splicing, and interfere with the assembly of cellular P-bodies, releasing the endoribonuclease MARF1 that promotes mRNA decay and translational repression. Rescuing the DDX6 protein level can recover the assembly and functionality of P-bodies, preventing targeted mRNA from degradation. This study provides a line of evidence for sequestration of the P-body components and impairment of the P-body homeostasis in dysregulating RNA metabolism, which is implicated in the disease pathologies and a potential therapeutic target.
Ataxin-2（Atx2）是一种含有多聚谷氨酰胺（polyQ）结构域的 RNA 结合蛋白，其 polyQ 扩展可能导致蛋白聚集，这与神经退行性疾病如脊髓小脑共济失调 2 型（SCA2）的发病机制有关。然而，Atx2 聚集如何导致蛋白病变的分子机制仍不清楚。在这里，我们通过生化和荧光成像方法研究了 Atx2 聚集对细胞处理体（P 体）的组装和功能的影响。我们已经揭示，多聚谷氨酰胺扩展（PQE）Atx2 通过一些 RNA 序列将 DEAD 盒 RNA 解旋酶（DDX6），P 体的必需成分，隔离到聚集体或斑点中。Atx2 的 N 端类似 Sm（LSm）结构域（残基 82-184）和 DDX6 的 C 端解旋酶结构域负责相互作用和特异性隔离。此外，DDX6 的隔离可能会加重前体 mRNA 的剪接错误，并干扰细胞 P 体的组装，释放出促进 mRNA 降解和翻译抑制的内切核糖核酸酶 MARF1。挽救 DDX6 蛋白水平可以恢复 P 体的组装和功能，防止靶向 mRNA 的降解。这项研究为 P 体成分的隔离以及 RNA 代谢失调导致 P 体平衡受损提供了证据，这与疾病病理学有关，也是一个潜在的治疗靶点。
