CIN85 participates in Cbl-b-mediated down-regulation of receptor tyrosine kinases.
The Cbl family of ubiquitin ligases in mammals contains three members, Cbl, Cbl-b, and Cbl-3, that are involved in down-regulation of receptor tyrosine kinases (RTKs) by mediating receptor ubiquitination and degradation. More recently, a novel pathway has been identified whereby Cbl promotes internalization of EGF receptor via a CIN85/endophilin pathway that is functionally separable from the ubiquitin ligase activity of Cbl (1). Here we show that Cbl-b, but not Cbl-3, utilize the same mechanism to down-regulate multiple RTKs. CIN85 was shown to bind to the minimal binding domain identified in the carboxyl terminus of Cbl-b. Ligand-induced phosphorylation of Cbl-b further increased their interactions and led to a rapid and sustained recruitment of CIN85 in the complex with EGF or PDGF receptors. Inhibition of binding between CIN85 and Cbl-b was sufficient to impair Cbl-b-mediated internalization of EGF receptors, while being dispensable for Cbl-b-directed polyubiquitination of EGF receptors. Moreover, CIN85 and Cbl/Cbl-b were constitutively associated with activated PDGF, EGF, or c-Kit receptors in several tumor cell lines. Our data reveal a common pathway utilized by Cbl and Cbl-b that may have an important and redundant function in negative regulation of ligand-activated as well as oncogenically activated RTKs in vivo.
Pubmed ID: 12177062 RIS Download
3T3 Cells | Adaptor Proteins, Signal Transducing | Animals | CHO Cells | Carrier Proteins | Cell Line | Cell Line, Transformed | Cloning, Molecular | Cricetinae | Down-Regulation | Endocytosis | Epidermal Growth Factor | HeLa Cells | Humans | Ligands | Mice | Microscopy, Fluorescence | Models, Biological | Phosphoproteins | Phosphorylation | Platelet-Derived Growth Factor | Precipitin Tests | Protein Binding | Protein Structure, Tertiary | Proto-Oncogene Proteins c-cbl | Proto-Oncogene Proteins c-kit | Receptor Protein-Tyrosine Kinases | Time Factors | Transfection | Two-Hybrid System Techniques | Ubiquitin-Protein Ligases