SCAMP3 Negatively Regulates Epidermal Growth Factor Receptor Degradation and Promotes Receptor Recycling
SCAMP3 Negatively Regulates Epidermal Growth Factor Receptor Degradation and Promotes Receptor Recycling
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DOI：
10.1091/mbc.e08-09-0894
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发表时间：
2009-03-15
影响因子：
3.3
通讯作者：
Castle, J. David
中科院分区：
文献类型：
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作者：
Aoh, Quyen L.;Castle, Anna M.;Castle, J. David
表皮生长因子受体（EGFR）通过与多囊泡体（MVBs）中的运输所需的内体分选复合物（ESCRTs）发生泛素介导的相互作用而被靶向运往溶酶体进行降解。我们发现分泌载体膜蛋白SCAMP3部分定位于早期内体，并通过涉及其泛素化以及与ESCRTs相互作用的过程对EGFR降解进行负调控。SCAMP3是多单泛素化的，并且能够分别通过其PY和PSAP基序与Nedd4 HECT泛素连接酶以及ESCRT - I亚基Tsg101结合。SCAMP3还与ESCRT - 0亚基Hrs结合。通过抑制性RNA使HeLa细胞中的SCAMP3耗竭会加速EGFR和EGF的降解，同时抑制其再循环。相反，除非SCAMP3中可泛素化的赖氨酸、PY或PSAP基序发生突变，否则过表达会增强EGFR的再循环。值得注意的是，对SCAMP3和ESCRT亚基的双重耗竭表明，SCAMP3与ESCRTs具有并行的独特功能，可调节受体降解。由于通过免疫电子显微镜检测发现SCAMP3的耗竭似乎维持了含EGFR的MVBs的出现频率，所以这一功能可能影响受体从溶酶体前区室的运输。总之，我们的研究结果表明，SCAMP3、其泛素修饰以及它与ESCRTs的相互作用协同调节内体途径并影响受体下调的效率。
The epidermal growth factor receptor (EGFR) is targeted for lysosomal degradation by ubiquitin-mediated interactions with the ESCRTs (endosomal-sorting complexes required for transport) in multivesicular bodies (MVBs). We show that secretory carrier membrane protein, SCAMP3, localizes in part to early endosomes and negatively regulates EGFR degradation through processes that involve its ubiquitylation and interactions with ESCRTs. SCAMP3 is multimonoubiquitylated and is able to associate with Nedd4 HECT ubiquitin ligases and the ESCRT-I subunit Tsg101 via its PY and PSAP motifs, respectively. SCAMP3 also associates with the ESCRT-0 subunit Hrs. Depletion of SCAMP3 in HeLa cells by inhibitory RNA accelerated degradation of EGFR and EGF while inhibiting recycling. Conversely, overexpression enhanced EGFR recycling unless ubiquitylatable lysines, PY or PSAP motifs in SCAMP3 were mutated. Notably, dual depletions of SCAMP3 and ESCRT subunits suggest that SCAMP3 has a distinct function in parallel with the ESCRTs that regulates receptor degradation. This function may affect trafficking of receptors from prelysosomal compartments as SCAMP3 depletion appeared to sustain the incidence of EGFR-containing MVBs detected by immunoelectron microscopy. Together, our results suggest that SCAMP3, its modification with ubiquitin, and its interactions with ESCRTs coordinately regulate endosomal pathways and affect the efficiency of receptor down-regulation.