39.6: Notch信号传导在肠干细胞更新中的作用

Notch信号首先在黑腹果蝇中发现，它参与细胞谱系的分化。Notch信号通过控制Atonal同源基因1（Atoh1）的表达来调节肠干细胞（ISCs）的维持和分化。Atoh1 指导细胞分化为分泌细胞。

Notch 信号传导的激活需要细胞间的直接接触。当Notch配体与相邻细胞上的受体结合时，信号就会启动，也称为反式结合。相反，当配体与同一细胞的受体结合时，即顺式结合，信号受到抑制。在反式激活过程中，ADAM 蛋白酶裂解 Notch 受体的胞外区域，γ-分泌酶裂解胞内结构域，也称为 Notch 胞内结构域 (NICD)，该区域转移到细胞核中并激活毛状增强子分裂 (Hes) 。Hes 反过来又抑制 Atoh1 并阻止 Notch 受体细胞分化为分泌细胞。

在肠上皮组织损伤期间，潘氏细胞通过Notch信号去分化并替换受损细胞。肠道细胞中的 Notch 信号的失调会导致多种疾病。例如，Hes1 或 Atoh1 的突变可引起结直肠肿瘤。Notch 信号传导的减少与一种罕见的炎症性疾病（称为乳糜泻）有关，这种疾病在摄入麸质时会引起过敏反应。因此，针对Notch信号通路可以成为治疗某些肠道疾病的治疗策略。

在肠上皮细胞中，Notch 信号通路在 Wnt 信号传导的影响下调节细胞命运。

Notch 信号转导有助于维持肠隐窝中的肠道干细胞或 ISC 库。

在这里，Paneth 细胞上表达的 Notch 配体与 ISC 上的 Notch 受体相互作用并抑制其分化，使 ISC 能够在隐窝中维持其干细胞状态。

随着 ISC 开始分化，Notch 信号通路也决定了转运扩增 TA 细胞的命运，这些细胞分化为吸收性或分泌性细胞类型。

一些 TA 细胞表达高水平的 Notch 配体，并通过激活其 Notch 受体来阻止相邻细胞的分化。

表达 Notch 受体的 TA 细胞不断分裂并向上移动，远离 Wnt 信号，然后分化成吸收细胞。

相反，表达 Notch 配体的 TA 细胞停止分裂并分化为分泌细胞。

• Notch signaling – Regulates cell differentiation and renewal in organisms, discovered in Drosophila melanogaster.
• Atoh1 – A gene that directs cells to become secretory when stimulated by Notch signaling.
• Trans-binding – Activation of Notch signaling via direct cell-to-cell contact initiating the differentiation of cells.
• Cis-binding – An inhibitory process preventing Notch signaling activation when ligand binds to the receptor in the same cell.
• Hes1 – A gene activated by Notch signaling that inhibits Atoh1 and prevents differentiation into secretory cells.

• Define Notch signaling – Explain its function on cell differentiation and renewal (e.g., stem cell renewal).
• Contrast trans-binding vs cis-binding – Illustrate their respective effects on Notch signaling (e.g., activation vs inhibition).
• Explore Atoh1 and Hes1 – Describe their role in cell differentiation (e.g., secretory cells).
• Explain damage repair process – Detail how Paneth cells de-differentiate and replace damaged cells via Notch signaling.
• Apply in Context – Discuss Notch signaling pathway's relevance in disease manifestation and potential therapeutic strategies.

• What is Notch signaling and how does it regulate cell differentiation and renewal?
• How does trans-binding differ from cis-binding in the activation of Notch signaling?
• What are the roles of Atoh1 and Hes1 expressions in cellular differentiation?

• Students – Understand how the Notch signaling pathway contributes to our understanding of cellular differentiation process.
• Educators – Provides a detailed view of molecular signaling pathways and their roles in health and disease.
• Researchers – Provides a model for studying cellular differentiation and cell renewal, as well as disease mechanisms.
• Science Enthusiasts – Offers insights into how cell-to-cell signalling regulates complex processes in organisms.