Ubiquitin-independent binding of Hrs mediates endosomal sorting of the interleukin-2 receptor β-chain
Ubiquitin-independent binding of Hrs mediates endosomal sorting of the interleukin-2 receptor β-chain
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DOI：
10.1242/jcs.024455
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发表时间：
2008-05
影响因子：
4
通讯作者：
Yuki Yamashita;K. Kojima;Tomonori Tsukahara;H. Agawa;Koichiro Yamada;Yuji Amano;Naoki Kurotori;N. Tanaka;K. Sugamura;T. Takeshita
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文献类型：
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作者：
Yuki Yamashita;K. Kojima;Tomonori Tsukahara;H. Agawa;Koichiro Yamada;Yuji Amano;Naoki Kurotori;N. Tanaka;K. Sugamura;T. Takeshita
一些证据表明，膜蛋白的泛素化作为内体分选到溶酶体或裂解空泡的信号。肝细胞生长因子调节的酪氨酸激酶底物（Hrs）通过其泛素相互作用基序结构域（UIM结构域）与泛素化的货物相互作用，并在内体分选中起重要的早期作用。在这里，我们表明，C-末端区域的Hrs，其中不包含UIM域，可以结合白细胞介素-2受体β（IL-2 R β）。我们在GST pull-down分析中发现细菌表达的IL-2 R β和Hrs之间存在直接相互作用，表明它们的结合不依赖于泛素。运输和降解测定显示，与野生型IL-2 R β类似，缺乏所有细胞质赖氨酸残基的IL-2 R β突变体从Hrs阳性早期内体分选到LAMP 1阳性晚期内体，导致受体降解。相比之下，缺乏Hrs结合区的IL-2 R β突变体通过早期内体，并被错误分选到转铁蛋白受体阳性的隔室。后一种突变体表现出减弱的降解。总之，这些结果表明，IL-2 R β从早期到晚期内体的精确分选是由Hrs介导的，Hrs是泛素依赖性机制的已知分选组分，其方式不依赖于UIM-泛素结合。
Several lines of evidence have revealed that ubiquitylation of membrane proteins serves as a signal for endosomal sorting into lysosomes or lytic vacuoles. The hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) interacts with ubiquitylated cargoes through its ubiquitin-interacting-motif domain (UIM domain), and plays an essential early role in endosomal sorting. Here, we show that the C-terminal region of Hrs, which does not contain the UIM domain, can bind to interleukin-2 receptor β (IL-2Rβ). We found a direct interaction between bacterially expressed IL-2Rβ and Hrs in GST pull-down assays, indicating that their binding is independent of ubiquitin. Trafficking and degradation assays revealed that, similarly to wild-type IL-2Rβ, an IL-2Rβ mutant lacking all the cytoplasmic lysine residues is sorted from Hrs-positive early endosomes to LAMP1-positive late endosomes, resulting in degradation of the receptor. By contrast, an IL-2Rβ mutant lacking the Hrs-binding region passes through early endosomes and is mis-sorted to compartments positive for the transferrin receptor. The latter mutant exhibits attenuated degradation. Taken together, these results indicate that precise sorting of IL-2Rβ from early to late endosomes is mediated by Hrs, a known sorting component of the ubiquitin-dependent machinery, in a manner that is independent of UIM-ubiquitin binding.