Drosophila Epsin's role in Notch ligand cells requires three Epsin protein functions: the lipid binding function of the ENTH domain, a single Ubiquitin interaction motif, and a subset of the C-terminal protein binding modules.
Drosophila Epsin's role in Notch ligand cells requires three Epsin protein functions: the lipid binding function of the ENTH domain, a single Ubiquitin interaction motif, and a subset of the C-terminal protein binding modules.
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果蝇 Epsin 在 Notch 配体细胞中的作用需要三种 Epsin 蛋白功能：ENTH 结构域的脂质结合功能、单个泛素相互作用基序和 C 端蛋白结合模块的子集。
DOI：
10.1016/j.ydbio.2012.01.004
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发表时间：
2012
影响因子：
2.7
通讯作者：
Fischer,JaniceA
中科院分区：
文献类型：
--
作者：
Xie,Xuanhua;Cho,Bomsoo;Fischer,JaniceA
Epsin是一种内吞蛋白，其通过充分表征的基序结合网格蛋白、质膜、泛素以及多种其他内吞蛋白。虽然Epsin是一种普遍的内吞因子，但果蝇和小鼠的遗传分析表明，Epsin对于Notch受体的泛素化跨膜配体的内化是必需的，这是Notch激活所需的过程。Epsin的功能机制是复杂的和依赖于上下文的。因此，Epsin如何促进配体内吞作用并因此促进Notch信号传导尚不清楚，这也是Notch信号传导独特地依赖于Epsin的原因。在这里，通过产生含有表达各种不同Epsin缺失和取代变体的转基因的果蝇品系，我们测试了五种蛋白质或脂质相互作用模块中的每一种在两种配体Serrate和Delta的Notch激活中的作用。这项工作的五个主要结果影响了目前对Epsin在配体细胞中作用的认识。首先，我们发现两个UIM的缺失或突变破坏了Epsin在Notch信号传导中的功能，并且对Epsin活性的负面影响比去除任何其他模块类型更大。第二，Epsin的两个UIM中只有一个是必不可少的。第三，ENTH结构域的脂质结合功能仅为最大化Epsin活性所需。第四，尽管与网格蛋白、衔接蛋白复合物AP-2或内吞辅助蛋白相互作用的C-末端Epsin模块对于Epsin活性是共同必需的，但它们的功能是高度冗余的;最出乎意料的是发现Epsin的网格蛋白结合基序是不对称的。最后，我们发现来自配体Serrate或Delta的信号传导需要相同的Epsin模块。所有这些观察结果与其中Epsin在配体细胞中的基本功能是通过其他网格蛋白衔接子蛋白将泛素化Notch配体连接到网格蛋白包被的囊泡的模型一致。我们认为Epsin对Notch信号传导的特异性仅仅反映了其与质膜、泛素和结合网格蛋白的蛋白质相互作用的独特能力。
Epsin is an endocytic protein that binds Clathrin, the plasma membrane, Ubiquitin, and also a variety of other endocytic proteins through well-characterized motifs. Although Epsin is a general endocytic factor, genetic analysis in Drosophila and mice revealed that Epsin is essential specifically for internalization of ubiquitinated transmembrane ligands of the Notch receptor, a process required for Notch activation. Epsin's mechanism of function is complex and context-dependent. Consequently, how Epsin promotes ligand endocytosis and thus Notch signaling is unclear, as is why Notch signaling is uniquely dependent on Epsin. Here, by generating Drosophila lines containing transgenes that express a variety of different Epsin deletion and substitution variants, we tested each of the five protein or lipid interaction modules for a role in Notch activation by each of the two ligands, Serrate and Delta. There are five main results of this work that impact present thinking about the role of Epsin in ligand cells. First, we discovered that deletion or mutation of both UIMs destroyed Epsin's function in Notch signaling and had a greater negative impact on Epsin activity than removal of any other module type. Second, only one of Epsin's two UIMs was essential. Third, the lipid-binding function of the ENTH domain was required only for maximal Epsin activity. Fourth, although the C-terminal Epsin modules that interact with Clathrin, the adapter protein complex AP-2, or endocytic accessory proteins were necessary collectively for Epsin activity, their functions were highly redundant; most unexpected was the finding that Epsin's Clathrin binding motifs were dispensable. Finally, we found that signaling from either ligand, Serrate or Delta, required the same Epsin modules. All of these observations are consistent with a model where Epsin's essential function in ligand cells is to link ubiquitinated Notch ligands to Clathrin-coated vesicles through other Clathrin adapter proteins. We propose that Epsin's specificity for Notch signaling simply reflects its unique ability to interact with the plasma membrane, Ubiquitin, and proteins that bind Clathrin.