Hrs, a mammalian master molecule in vesicular transport and protein sorting, suppresses the degradation of ESCRT proteins signal transducing adaptor molecule 1 and 2
Hrs, a mammalian master molecule in vesicular transport and protein sorting, suppresses the degradation of ESCRT proteins signal transducing adaptor molecule 1 and 2
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DOI：
10.1074/jbc.m409969200
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发表时间：
2005-03-18
影响因子：
4.8
通讯作者：
Sugamura, K
中科院分区：
文献类型：
--
作者：
Kobayashi, H;Tanaka, N;Sugamura, K
细胞质和细胞表面蛋白的降解和分选是控制细胞功能的关键步骤。我们之前鉴定了三种哺乳动物 Vps（液泡蛋白分选）蛋白、Hrs（肝细胞生长因子调节的酪氨酸激酶底物）和信号转导接头分子 (STAM) 1 和 -2，它们在细胞因子/生长因子刺激下被酪氨酸磷酸化。 Hrs 和 STAM 均包含泛素相互作用基序，并通过形成复合物参与早期内涵体的囊泡运输。为了探索该复合物在哺乳动物细胞中的机制和细胞功能，我们建立了 Hrs 缺陷型成纤维细胞系 (hrs(-/-))；具有这种基因型的胚胎在子宫内死亡。在hrs(-/-)细胞中仅检测到痕量的STAM1和STAM2。引入野生型 Hrs 或具有完整 STAM 结合结构域 (Hrs-dFYVE) 的 Hrs 突变体完全恢复了 STAM1 和 STAM2 的表达，而没有 STAM 结合能力的突变体 (Hrs-dC2、Hrs-dM) 则无法表达 STAM。 Hrs 对 STAM 表达的调节控制独立于转录。有趣的是，STAM1 降解是由蛋白酶体介导的，并且部分依赖于 STAM1 的泛素相互作用基序。 hrs(-/-)细胞中恢复的Hrs表达不仅导致泛素化蛋白（包括胞质内囊泡）的积累，而且还恢复了早期内体中的STAM1水平，并消除了因Hrs缺失而导致的扩大的内体表型。这些结果表明 Hrs 是部分控制 STAM1 降解和泛素化蛋白积累的主分子。
The degradation and sorting of cytoplasmic and cell-surface proteins are crucial steps in the control of cellular functions. We previously identified three mammalian Vps (vacuolar protein sorting) proteins, Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate) and signal transducing adaptor molecule (STAM) 1 and -2, which are tyrosine-phosphorylated upon cytokine/ growth factor stimulation. Hrs and the STAMs each contain a ubiquitin-interacting motif and through formation of a complex are involved in the vesicle transport of early endosomes. To explore the mechanism and cellular function of this complex in mammalian cells, we established an Hrs-defective fibroblastoid cell line (hrs(-/-)); embryos with this genotype died in utero. In the hrs(-/-) cells only trace amounts of STAM1 and STAM2 were detected. Introduction of wild-type Hrs or an Hrs mutant with an intact STAM binding domain (Hrs-dFYVE) fully restored STAM1 and STAM2 expression, whereas mutants with no STAM binding ability (Hrs-dC2, Hrs-dM) failed to express the STAMs. This regulated control of STAM expression by Hrs was independent of transcription. Interestingly, STAM1 degradation was mediated by proteasomes and was partially dependent on the ubiquitin-interacting motif of STAM1. Revertant Hrs expression in hrs(-/-) cells not only led to the accumulation of ubiquitinated proteins, including intracytoplasmic vesicles, but also restored STAM1 levels in early endosomes and eliminated the enlarged endosome phenotype caused by the absence of Hrs. These results suggest that Hrs is a master molecule that controls in part the degradation of STAM1 and the accumulation of ubiquitinated proteins.