Regulation of epidermal growth factor receptor down-regulation by UBPY-mediated deubiquitination at endosomes
Regulation of epidermal growth factor receptor down-regulation by UBPY-mediated deubiquitination at endosomes
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DOI：
10.1091/mbc.e05-06-0560
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发表时间：
2005-11-01
影响因子：
3.3
通讯作者：
Komada, M
中科院分区：
文献类型：
--
作者：
Mizuno, E;Iura, T;Komada, M
配体激活的受体酪氨酸激酶经历内吞作用，并通过内体转运到溶酶体进行降解。这种“受体下调”过程对于终止由激活的受体产生的细胞增殖信号至关重要。在此过程中，受体的泛素化作为其从内体运输到溶酶体的分选信号。在这里，我们描述了去泛素化酶UBPY/USP 8在下调表皮生长因子（EGF）受体（EGFR）中的作用。UBPY的过表达降低了EGFR的泛素化水平，并延迟了其在EGF刺激的细胞中的降解。体外免疫纯化的UBPY去泛素化EGFR。在EGF刺激的细胞中，UBPY经历泛素化并与EGFR结合。Hrs或SKD 1的显性负突变体（在泛素化受体的内体分选中发挥作用的蛋白质）的过度表达导致内源性UBPY在夸张的内体上积累。无催化活性的UBPY突变体明显定位于内体，当细胞用EGF刺激时，它与EGFR重叠。最后，通过RNA干扰消除内源性UBPY导致EGF激活的EGFR的泛素化升高和加速降解。我们的结论是，UBPY负调控率EGFR下调，通过去泛素化EGFR的内涵体。
Ligand-activated receptor tyrosine kinases undergo endocytosis and are transported via endosomes to lysosomes for degradation. This "receptor down-regulation" process is crucial to terminate the cell proliferation signals produced by activated receptors. During the process, ubiquitination of the receptors serves as a sorting signal for their trafficking from endosomes to lysosomes. Here, we describe the role of a deubiquitinating enzyme UBPY/USP8 in the down-regulation of epidermal growth factor (EGF) receptor (EGFR). Overexpression of UBPY reduced the ubiquitination level of EGFR and delayed its degradation in EGF-stimulated cells. Immunopurified UBPY deubiquitinated EGFR in vitro. In EGF-stimulated cells, UBPY underwent ubiquitination and bound to EGFR. Overexpression of Hrs or a dominant-negative mutant of SKD1, proteins that play roles in the endosomal sorting of ubiquitinated receptors, caused the accumulation of endogenous UBPY on exaggerated endosomes. A catalytically inactive UBPY mutant clearly localized on endosomes, where it overlapped with EGFR when cells were stimulated with EGF. Finally, depletion of endogenous UBPY by RNA interference resulted in elevated ubiquitination and accelerated degradation of EGF-activated EGFR. We conclude that UBPY negatively regulates the rate of EGFR down-regulation by deubiquitinating EGFR on endosomes.