de Melker Annemieke A, van der Horst Gerda, Borst Jannie
Division of Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam.
J Cell Sci. 2004 Oct 1;117(Pt 21):5001-12. doi: 10.1242/jcs.01354. Epub 2004 Sep 21.
c-Cbl associates with the activated EGF receptor before endocytosis. We here reveal that the capacity of c-Cbl to promote receptor internalization depends on its ubiquitin ligase activity, which functionally connects the EGF receptor to Eps15, a mediator of clathrin-coated pit formation. EGF-induced phosphorylation of Eps15, as well as recruitment of Eps15 to the plasma membrane and its co-localization with the EGF receptor in endosomes required the ubiquitin ligase activity of c-Cbl. This suggested that ubiquitin provides a direct or indirect link between the receptor and Eps15. Indeed, EGF-induced redistribution of Eps15 to the plasma membrane and endosomes depended on its ubiquitin-interacting motif. Upon over-expression, the ubiquitin-interacting motif abrogated the capacity of c-Cbl to promote EGF receptor endocytosis and only allowed receptor internalization via a route that lacked Eps15. Our findings disclose a novel function for the c-Cbl ubiquitin ligase and identify ubiquitin as a module that directs the EGF receptor into an endocytic pathway involving Eps15.
在胞吞作用之前,c-Cbl与活化的表皮生长因子(EGF)受体结合。我们在此揭示,c-Cbl促进受体内化的能力取决于其泛素连接酶活性,该活性在功能上将EGF受体与Eps15相连,Eps15是网格蛋白包被小窝形成的介导因子。EGF诱导的Eps15磷酸化,以及Eps15募集到质膜并与内体中的EGF受体共定位,都需要c-Cbl的泛素连接酶活性。这表明泛素在受体与Eps15之间提供了直接或间接的联系。事实上,EGF诱导的Eps15重新分布到质膜和内体取决于其泛素相互作用基序。过表达时,泛素相互作用基序消除了c-Cbl促进EGF受体内化的能力,并且仅允许受体通过缺乏Eps15的途径进行内化。我们的研究结果揭示了c-Cbl泛素连接酶的一种新功能,并确定泛素是将EGF受体导向涉及Eps15的内吞途径的一个模块。