Takata H, Kato M, Denda K, Kitamura N
Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
Genes Cells. 2000 Jan;5(1):57-69. doi: 10.1046/j.1365-2443.2000.00303.x.
Hrs (hepatocyte growth factor (HGF)-regulated tyrosine kinase substrate) is an early endosomal protein that is rapidly tyrosine-phosphorylated in cells stimulated with growth factors. Hrs is thought to play a regulatory role in the endocytosis of growth factor/receptor complexes through early endosomes. In this study, we searched for Hrs-interacting molecules which may regulate the function of Hrs, using a yeast two-hybrid system.
We isolated a cDNA clone encoding a novel Src homology 3 (SH3)-containing protein, and named it 'Hrs binding protein' (Hbp). Hbp was co-immunoprecipitated with Hrs, and its intracellular localization was similar to that of Hrs. The association between Hbp and Hrs was mediated through the coiled coil motifs in Hbp and Hrs. Deletion mutants of Hbp lacking either the SH3 domain or the Hrs binding domain showed dominantly negative effects on the intracellular degradation of a growth factor and its receptor, but not on the internalization of growth factor/receptor complexes.
Hbp is thought to be closely associated with Hrs on early endosomes. Hbp, together with Hrs may play a regulatory role in the vesicular transport of growth factor/receptor complexes through early endosomes, for their degradation.
Hrs（肝细胞生长因子（HGF）调节的酪氨酸激酶底物）是一种早期内体蛋白，在生长因子刺激的细胞中会迅速发生酪氨酸磷酸化。Hrs被认为在生长因子/受体复合物通过早期内体的内吞作用中发挥调节作用。在本研究中，我们使用酵母双杂交系统寻找可能调节Hrs功能的与Hrs相互作用的分子。
我们分离出一个编码新型含Src同源3（SH3）结构域蛋白的cDNA克隆，并将其命名为“Hrs结合蛋白”（Hbp）。Hbp与Hrs进行了共免疫沉淀，其细胞内定位与Hrs相似。Hbp与Hrs之间的关联是通过Hbp和Hrs中的卷曲螺旋基序介导的。缺失SH3结构域或Hrs结合结构域的Hbp缺失突变体对生长因子及其受体的细胞内降解显示出显性负效应，但对生长因子/受体复合物的内化没有影响。
Hbp被认为与早期内体上的Hrs密切相关。Hbp与Hrs一起可能在生长因子/受体复合物通过早期内体的囊泡运输中发挥调节作用，以促进其降解。
