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 在新皮质发育过程中介导 RAM 域依赖性缺口信号转导

Notch信号通路活性，特别是生物活性效应片段NICD的波动，是快速有效地动态调节干细胞正确命运决定所必需的。在这项研究中，我们发现了 NEDD4 结合蛋白 1 (N4BP1)，它在发育中的小鼠大脑皮层中高度表达，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 裂解后通过泛素介导的降解来调节 NICD 稳定性，这种降解取决于其 RAM 结构域，而不是其 PEST 结构域，正如之前广泛描述的那样。N4BP1 中的 CoCUN 结构域，特别是“Phe-Pro”基序（862/863 个氨基酸），对于介导 NICD 降解是不可或缺的。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。皮质神经祖细胞中 N4BP1 的过度表达促进神经干细胞分化，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产量的降低。