Regulation of Epidermal Growth Factor Receptor Ubiquitination and Trafficking by the USP8.STAM Complex
Regulation of Epidermal Growth Factor Receptor Ubiquitination and Trafficking by the USP8.STAM Complex
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DOI：
10.1074/jbc.m109.016287
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发表时间：
2010-11-05
影响因子：
4.8
通讯作者：
Nash, Piers D.
中科院分区：
文献类型：
--
作者：
Berlin, Ilana;Schwartz, Heather;Nash, Piers D.
激活的受体复合体的可逆泛素化发出信号，表明它们在循环和降解之间进行分类，从而决定受体的命运。去泛素化酶泛素特异性蛋白水解酶8(USP8/UBPy)参与了表皮生长因子受体(EGFR)的调节，但其募集和活性的分子机制尚不清楚。在这里，我们研究了USP8在对抗配体诱导的泛素化和EGFR下调中的作用，并表征了对这一功能至关重要的蛋白质-蛋白质相互作用决定因素的子集。USP8的缺失加速了受体的周转，而肝细胞生长因子调节底物(HRS)的缺失挽救了这一表型，表明USP8通过HRS依赖的途径保护EGFR免于降解。USP8的催化失活会导致EGFR的高泛素化，并促进受体定位到以高泛素含量为标志的内体。这些表型需要USP8的中心区域，包含三个扩展的Arg-X-X-Lys(RXXK)基序，这些基序指定与ESCRT-0蛋白的SH3结构域(S)直接低亲和力相互作用，STAM1/2。USP8.STAM复合体关键影响受体泛素化状态，并调节EGFR阳性内体上的泛素动态。因此，USP8介导的去泛素化以一种依赖于RXXK基序的方式减缓了EGFR通过早期到循环的内体回路的进展。总体而言，这些发现表明USP8.STAM复合体作为一种保护机制，调节早期内体对EGFR在溶酶体降解和再循环途径之间的分选。
Reversible ubiquitination of activated receptor complexes signals their sorting between recycling and degradation and thereby dictates receptor fate. The deubiquitinating enzyme ubiquitin-specific protease 8 (USP8/UBPy) has been previously implicated in the regulation of the epidermal growth factor receptor (EGFR); however, the molecular mechanisms governing its recruitment and activity in this context remain unclear. Herein, we investigate the role of USP8 in countering ligand-induced ubiquitination and down-regulation of EGFR and characterize a subset of protein-protein interaction determinants critical for this function. USP8 depletion accelerates receptor turnover, whereas loss of hepatocyte growth factor-regulated substrate (Hrs) rescues this phenotype, indicating that USP8 protects EGFR from degradation via an Hrs-dependent pathway. Catalytic inactivation of USP8 incurs EGFR hyperubiquitination and promotes receptor localization to endosomes marked by high ubiquitin content. These phenotypes require the central region of USP8, containing three extended Arg-X-X-Lys (RXXK) motifs that specify direct low affinity interactions with the SH3 domain(s) of ESCRT-0 proteins, STAM1/2. The USP8.STAM complex critically impinges on receptor ubiquitination status and modulates ubiquitin dynamics on EGFR-positive endosomes. Consequently, USP8-mediated deubiquitination slows progression of EGFR past the early-to-recycling endosome circuit in a manner dependent upon the RXXK motifs. Collectively, these findings demonstrate a role for the USP8.STAM complex as a protective mechanism regulating early endosomal sorting of EGFR between pathways destined for lysosomal degradation and recycling.