Lu Quan, Hope Lila Weiqiao, Brasch Michael, Reinhard Christoph, Cohen Stanley N
Department of Genetics, Program in Cancer Biology, Stanford University School of Medicine, Stanford, CA 94305-5120, USA.
Proc Natl Acad Sci U S A. 2003 Jun 24;100(13):7626-31. doi: 10.1073/pnas.0932599100. Epub 2003 Jun 11.
Down-regulation of mitogenic signaling in mammalian cells relies in part on endosomal trafficking of activated receptors into lysosomes, where the receptors are degraded. These events are mediated by ubiquitination of the endosomal cargo and its consequent sorting into multivesicular bodies that form at the surfaces of late endosomes. Tumor susceptibility gene 101 (tsg101) recently was found to be centrally involved in this process. Here we report that TSG101 interacts with hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), an early endosomal protein, and that disruption of this interaction impedes endosomal trafficking and endocytosis-mediated degradation of mitogenic receptors. TSG101/HRS interaction occurs between a ubiquitin-binding domain of TSG101 and two distinct proline-rich regions of HRS, and is modulated by a C-terminal TSG101 sequence that resembles a motif targeted in HRS. Mutational perturbation of TSG101/HRS interaction prevented delivery of epidermal growth factor receptor (EGFR) to late endosomes, resulted in the cellular accumulation of ubiquitinated EGFR in early endosomes, and inhibited ligand-induced down-regulation of EGFR. Our results reveal the TSG101 interaction with HRS as a crucial step in endocytic down-regulation of mitogenic signaling and suggest a role for this interaction in linking the functions of early and late endosomes.
哺乳动物细胞中有丝分裂信号的下调部分依赖于活化受体的内体运输至溶酶体，受体在溶酶体中被降解。这些过程由内体货物的泛素化介导，并随后被分选到在内体晚期表面形成的多泡体中。肿瘤易感基因101（tsg101）最近被发现在此过程中起核心作用。在此我们报告，TSG101与早期内体蛋白——肝细胞生长因子调节的酪氨酸激酶底物（HRS）相互作用，并且这种相互作用的破坏会阻碍内体运输以及有丝分裂受体的内吞介导降解。TSG101/HRS相互作用发生在TSG101的泛素结合结构域与HRS的两个不同的富含脯氨酸区域之间，并受TSG101的C末端序列调节，该序列类似于HRS中靶向的基序。TSG101/HRS相互作用的突变扰动阻止了表皮生长因子受体（EGFR）向晚期内体的转运，导致早期内体中泛素化EGFR的细胞积累，并抑制了配体诱导的EGFR下调。我们的结果揭示了TSG101与HRS的相互作用是有丝分裂信号内吞下调的关键步骤，并表明这种相互作用在连接早期和晚期内体功能中起作用。
