Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242.
Cold Spring Harb Perspect Biol. 2014 Jan 1;6(1):a016808. doi: 10.1101/cshperspect.a016808.
When ubiquitin (Ub) is attached to membrane proteins on the plasma membrane, it directs them through a series of sorting steps that culminate in their delivery to the lumen of the lysosome where they undergo complete proteolysis. Ubiquitin is recognized by a series of complexes that operate at a number of vesicle transport steps. Ubiquitin serves as a sorting signal for internalization at the plasma membrane and is the major signal for incorporation into intraluminal vesicles of multivesicular late endosomes. The sorting machineries that catalyze these steps can bind Ub via a variety of Ub-binding domains. At the same time, many of these complexes are themselves ubiquitinated, thus providing a plethora of potential mechanisms to regulate their activity. Here we provide an overview of how membrane proteins are selected for ubiquitination and deubiquitination within the endocytic pathway and how that ubiquitin signal is interpreted by endocytic sorting machineries.
当泛素（Ub）附着在质膜上的膜蛋白上时，它会引导它们经历一系列分拣步骤，最终将它们递送至溶酶体的腔中，在那里它们会经历完全的蛋白水解。泛素被一系列复合物识别，这些复合物在许多囊泡运输步骤中起作用。泛素是质膜内化的分拣信号，也是多泡体晚期内体的腔内含物中掺入的主要信号。催化这些步骤的分拣机制可以通过各种泛素结合域与 Ub 结合。同时，这些复合物中的许多本身也被泛素化，从而提供了大量潜在的机制来调节它们的活性。在这里，我们概述了膜蛋白如何在内吞途径中被选择进行泛素化和去泛素化，以及内吞分拣机制如何解释泛素信号。
