Mammary Biology and Tumorigenesis Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Cell Biol. 2009 Nov 2;187(3):343-53. doi: 10.1083/jcb.200905105.
Nodal and Notch signaling pathways play essential roles in vertebrate development. Through a yeast two-hybrid screening, we identified Notch3 as a candidate binding partner of the Nodal coreceptor Cripto-1. Coimmunoprecipitation analysis confirmed the binding of Cripto-1 with all four mammalian Notch receptors. Deletion analyses revealed that the binding of Cripto-1 and Notch1 is mediated by the Cripto-1/FRL-1/Cryptic domain of Cripto-1 and the C-terminal region of epidermal growth factor-like repeats of Notch1. Binding of Cripto-1 to Notch1 occurred mainly in the endoplasmic reticulum-Golgi network. Cripto-1 expression resulted in the recruitment of Notch1 protein into lipid raft microdomains and enhancement of the furin-like protein convertase-mediated proteolytic maturation of Notch1 (S1 cleavage). Enhanced S1 cleavage resulted in the sensitization to ligand-induced activation of Notch signaling. In addition, knockdown of Cripto-1 expression in human and mouse embryonal carcinoma cells desensitized the ligand-induced Notch signaling activation. These results suggest a novel role of Cripto-1 in facilitating the posttranslational maturation of Notch receptors.
节点和 Notch 信号通路在脊椎动物发育中发挥着重要作用。通过酵母双杂交筛选，我们鉴定出 Notch3 是 Nodal 共受体 Cripto-1 的候选结合伴侣。共免疫沉淀分析证实了 Cripto-1 与所有四种哺乳动物 Notch 受体的结合。缺失分析表明，Cripto-1 与 Notch1 的结合是由 Cripto-1 的 Cripto-1/FRL-1/Cryptic 结构域和 Notch1 的表皮生长因子样重复的 C 末端区域介导的。Cripto-1 与 Notch1 的结合主要发生在内质网-高尔基体网络中。Cripto-1 的表达导致 Notch1 蛋白被招募到脂筏微域中，并增强了弗林蛋白酶样蛋白转化酶介导的 Notch1（S1 切割）的蛋白水解成熟。增强的 S1 切割导致对配体诱导的 Notch 信号激活的敏感性增加。此外，在人胚胎癌细胞和鼠胚胎癌细胞中敲低 Cripto-1 的表达会使配体诱导的 Notch 信号激活脱敏。这些结果表明 Cripto-1 在促进 Notch 受体的翻译后成熟中具有新的作用。
