Direct binding of Cbl to Tyr568 and Tyr936 of the stem cell factor receptor/c-Kit is required for ligand-induced ubiquitination, internalization and degradation

Biochem J. 2006 Oct 1;399(1):59-67. doi: 10.1042/BJ20060464.

Abstract

The ubiquitin E3 ligase Cbl has been shown to negatively regulate tyrosine kinase receptors, including the stem cell factor receptor/c-Kit. Impaired recruitment of Cbl to c-Kit results in a deregulated positive signalling that eventually can contribute to carcinogenesis. Here, we present results showing that Cbl is activated by the SFKs (Src family kinases) and recruited to c-Kit in order to trigger receptor ubiquitination. We demonstrate that phosphorylated Tyr568 and Tyr936 in c-Kit are involved in direct binding and activation of Cbl and that binding of the TKB domain (tyrosine kinase binding domain) of Cbl to c-Kit is specified by the presence of an isoleucine or leucine residue in position +3 to the phosphorylated tyrosine residue on c-Kit. Apart from the direct association between Cbl and c-Kit, we show that phosphorylation of Cbl by SFK members is required for activation of Cbl to occur. Moreover, we demonstrate that Cbl mediates monoubiquitination of c-Kit and that the receptor is subsequently targeted for lysosomal degradation. Taken together, our findings reveal novel insights into the mechanisms by which Cbl negatively regulates c-Kit-mediated signalling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Endocytosis*
  • Humans
  • Ligands
  • Mice
  • Mutation
  • Phosphorylation
  • Protein Binding
  • Protein Processing, Post-Translational*
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins c-cbl / metabolism*
  • Proto-Oncogene Proteins c-kit / chemistry*
  • Proto-Oncogene Proteins c-kit / metabolism*
  • Proto-Oncogene Proteins pp60(c-src) / metabolism
  • Signal Transduction
  • Swine
  • Tyrosine / metabolism*
  • Ubiquitin / metabolism*

Substances

  • Ligands
  • Ubiquitin
  • Tyrosine
  • Proto-Oncogene Proteins c-cbl
  • Proto-Oncogene Proteins c-kit
  • Proto-Oncogene Proteins pp60(c-src)