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Oligopeptide Competition Assay for Phosphorylation Site Determination
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Oligopeptide Competition Assay for Phosphorylation Site Determination

Published on: May 18, 2017

Src-catalyzed phosphorylation of c-Cbl leads to the interdependent ubiquitination of both proteins

M Yokouchi1, T Kondo, A Sanjay

  • 1Departments of Cell Biology, Orthopaedics, and Genetics, Yale University School of Medicine, New Haven, Connecticut 06511, USA.

The Journal of Biological Chemistry
|July 13, 2001
PubMed

Insights

The protooncogene c-Cbl acts as an E3 ubiquitin ligase, targeting the non-receptor tyrosine kinase c-Src for degradation. This process down-regulates Src activity and its downstream signaling pathways.

Area of Science:

  • Molecular Biology
  • Oncology
  • Biochemistry

Background:

  • The protooncogene c-Cbl functions as an E3 ubiquitin ligase for activated receptor tyrosine kinases.
  • Protooncogenes play critical roles in cell growth and differentiation, and their dysregulation can lead to cancer.

Purpose of the Study:

  • To investigate whether c-Cbl mediates the ubiquitination of the non-receptor tyrosine kinase c-Src.
  • To elucidate the mechanisms underlying c-Cbl's regulation of c-Src.
  • To determine the functional consequences of c-Cbl-mediated c-Src ubiquitination.

Main Methods:

  • In vitro ubiquitination assays.
  • Co-immunoprecipitation to study protein complex formation.
  • Western blotting to assess protein levels and phosphorylation.
  • Analysis of STAT3 activation.

Main Results:

  • c-Cbl mediates the ubiquitination of both c-Src and itself.
  • This process requires c-Cbl's RING finger domain, Src kinase activity, and tyrosine phosphorylation of c-Cbl.
  • c-Cbl forms a complex with UbcH7, which is modulated by Src activity.
  • c-Cbl reduces v-Src protein levels and suppresses v-Src-induced STAT3 activation.

Conclusions:

  • c-Cbl functions as a ubiquitin ligase for the non-receptor tyrosine kinase c-Src.
  • c-Cbl-mediated ubiquitination leads to the down-regulation of Src protein levels and activity.
  • This pathway represents a novel mechanism for regulating Src signaling and has implications for cancer research.

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