A hrs binding protein having a Src homology 3 domain is involved in intracellular degradation of growth factors and their receptors.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Takata
H
H
Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
Kato
M
M
Denda
K
K
Kitamura
N
N
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D000077214:Becaplermin; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary; D056827:Endosomal Sorting Complexes Required for Transport; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010750:Phosphoproteins / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; D056827:Endosomal Sorting Complexes Required for Transport; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; C491648:Stam protein, mouse; C491646:Stam2 protein, mouse; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D000077214:Becaplermin; D017228:Hepatocyte Growth Factor; D017479:Receptors, Platelet-Derived Growth Factor