Division of Haematology, Centre for Cancer Biology, SA Pathology, Adelaide, SA, Australia.
Cell Death Differ. 2011 Jul;18(7):1150-60. doi: 10.1038/cdd.2010.130. Epub 2010 Oct 22.
In the Drosophila wing, the Nedd4 ubiquitin ligases (E3s), dNedd4 and Su(dx), are important negative regulators of Notch signaling; they ubiquitinate Notch, promoting its endocytosis and turnover. Here, we show that Drosophila Nedd4 family interacting protein (dNdfip) interacts with the Drosophila Nedd4-like E3s. dNdfip expression dramatically enhances dNedd4 and Su(dx)-mediated wing phenotypes and further disrupts Notch signaling. dNdfip colocalizes with Notch in wing imaginal discs and with the late endosomal marker Rab7 in cultured cells. In addition, dNdfip expression in the wing leads to ectopic Notch signaling. Supporting this, expression of dNdfip suppressed Notch(+/-) wing phenotype and knockdown of dNdfip enhanced the Notch(+/-) wing phenotype. The increase in Notch activity by dNdfip is ligand independent as dNdfip expression also suppressed deltex RNAi and Serrate(+/-) wing phenotypes. The opposing effects of dNdfip expression on Notch signaling and its late endosomal localization support a model whereby dNdfip promotes localization of Notch to the limiting membrane of late endosomes allowing for activation, similar to the model previously shown with ectopic Deltex expression. When dNedd4 or Su(dx) are also present, dNdfip promotes their activity in Notch ubiquitination and internalization to the lysosomal lumen for degradation.
在果蝇翅膀中，Nedd4 泛素连接酶（E3s），dNedd4 和 Su(dx)，是 Notch 信号的重要负调控因子；它们泛素化 Notch，促进其内吞和周转。在这里，我们表明果蝇 Nedd4 家族相互作用蛋白（dNdfip）与果蝇 Nedd4 样 E3s 相互作用。dNdfip 的表达显著增强了 dNedd4 和 Su(dx)介导的翅膀表型，并进一步破坏了 Notch 信号。dNdfip 在翅膀的 imaginal 盘中和培养细胞中的晚期内体标记 Rab7 共定位。此外，dNdfip 在翅膀中的表达导致异位 Notch 信号。支持这一点，dNdfip 的表达抑制了 Notch(+/-)翅膀表型，而 dNdfip 的敲低增强了 Notch(+/-)翅膀表型。dNdfip 增加 Notch 活性与配体无关，因为 dNdfip 的表达也抑制了 deltex RNAi 和 Serrate(+/-)翅膀表型。dNdfip 对 Notch 信号的相反影响及其晚期内体定位支持这样一种模型，即 dNdfip 促进 Notch 定位到晚期内体的限制膜，从而允许激活，类似于先前用异位 Deltex 表达显示的模型。当 dNedd4 或 Su(dx)也存在时，dNdfip 促进它们在 Notch 泛素化和内化到溶酶体腔中进行降解的活性。
