Notch signaling pathway activity, particularly fluctuations in the biologically active effector fragment NICD, is required for rapid and efficient dynamic regulation of proper fate decisions in stem cells. In this study, we identified NEDD4-binding protein 1 (N4BP1), which is highly expressed in the developing mouse cerebral cortex, as a negative modulator of Notch signaling dynamics in neural progenitor cells. Intriguingly, N4BP1 regulated NICD stability specifically after Notch1 S3 cleavage through ubiquitin-mediated degradation that depended on its RAM domain, not its PEST domain, as had been extensively and previously described. The CoCUN domain in N4BP1, particularly the “Phe-Pro” motif (862/863 amino acid), was indispensable for mediating NICD degradation. The Ring family E3 ligase Trim21 was, in contrast to other NEDD4 family members, required for N4BP1-regulated NICD degradation. Overexpression of N4BP1 in cortical neural progenitors promoted neural stem cell differentiation, whereas neural progenitor cells lacking N4BP1 were sensitized to Notch signaling, resulting in the maintenance of stem-like properties in neural progenitor cells and lower production of cortical neurons.

中文翻译：

---

N4BP1 介导新皮层发育过程中 RAM 结构域依赖性 Notch 信号转导


Notch 信号通路活性，尤其是生物活性效应片段 NICD 的波动，是干细胞中正确命运决策的快速有效动态调节所必需的。在这项研究中，我们确定了在发育中的小鼠大脑皮层中高度表达的 NEDD4 结合蛋白 1 （N4BP1） 是神经祖细胞中 Notch 信号动力学的负调节剂。有趣的是，N4BP1 在 Notch1 S3 切割后通过泛素介导的降解专门调节 NICD 稳定性，该降解取决于其 RAM 结构域，而不是其 PEST 结构域，正如先前广泛描述的那样。N4BP1 中的 CoCUN 结构域，特别是“Phe-Pro”基序（862/863 氨基酸），对于介导 NICD 降解是必不可少的。与其他 NEDD4 家族成员相比，Ring 家族 E3 连接酶 Trim21 是 N4BP1 调节的 NICD 降解所必需的。N4BP1 在皮质神经祖细胞中过表达促进了神经干细胞分化，而缺乏 N4BP1 的神经祖细胞对 Notch 信号敏感，导致神经祖细胞中干细胞样特性的维持和皮质神经元的产生降低。