A deubiquitinating enzyme UBPY regulates the level of protein ubiquitination on endosomes
A deubiquitinating enzyme UBPY regulates the level of protein ubiquitination on endosomes
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DOI：
10.1111/j.1600-0854.2006.00452.x
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发表时间：
2006-08-01
期刊：
影响因子：
4.5
通讯作者：
Komada, Masayuki
中科院分区：
文献类型：
--
作者：
Mizuno, Emi;Kobayashi, Kaoru;Komada, Masayuki
内吞的细胞表面受体的单泛素化充当其从内体运输到溶酶体的分选信号。泛素化蛋白的分选通过E类液泡蛋白分选（Vps）蛋白的协同作用来执行。一些蛋白质在分类机器进行monoubiquitination，这表明他们的功能也受到泛素化。Hrs-STAM复合物是分选途径初始步骤所必需的E类Vps蛋白复合物，结合两种去泛素化酶UBPY和AMSH。在这里，我们研究了UBPY失活对蛋白质内体泛素化的影响。过表达无催化活性的UBPY突变体或通过RNA干扰耗尽UBPY导致形态异常的内体上泛素化蛋白的积累。电子显微镜显示它们是多泡内体的聚集体。在经历泛素化的分选机器蛋白中，Eps 15在UBPY失活的细胞中以升高的水平被单泛素化。UBPY也在体外去泛素化Eps 15，表明Eps 15是UBPY的细胞底物。此外，UBPY的失活引起Eps 15在内体聚集体上的积累。这些结果表明，UBPY调节内体上的蛋白质泛素化水平，这是维持细胞器形态所必需的。
Monoubiquitination of endocytosed cell surface receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. The sorting of ubiquitinated proteins is executed by concerted actions of class E vacuolar protein sorting (Vps) proteins. Some proteins in the sorting machinery undergo monoubiquitination, suggesting that their functions are also regulated by ubiquitination. The Hrs-STAM complex, a class E Vps protein complex essential for the initial step of the sorting pathway, binds two deubiquitinating enzymes, UBPY and AMSH. Here we examined the effects of inactivating UBPY on protein ubiquitination at endosomes. Overexpression of a catalytically inactive UBPY mutant or depletion of UBPY by RNA interference resulted in the accumulation of ubiquitinated proteins on morphologically aberrant endosomes. Electron microscopy showed that they are aggregates of multivesicular endosomes. Among the sorting machinery proteins that undergo ubiquitination, Eps15 was monoubiquitinated at an elevated level in UBPY-inactivated cells. UBPY also deubiquitinated Eps15 in vitro, suggesting that Eps15 is a cellular substrate for UBPY. Furthermore, inactivation of UBPY caused the accumulation of Eps15 on the endosomal aggregates. These results suggest that UBPY regulates the level of protein ubiquitination on endosomes, which is required for maintaining the morphology of the organelle.