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Transmembrane phosphoprotein Cbp regulates the activities of Src-family tyrosine kinases

M Kawabuchi1, Y Satomi, T Takao

  • 1Division of Protein Metabolism, Institute for Protein Research, Osaka University, Suita, Japan.

Nature
|May 9, 2000
PubMed

Insights

A newly discovered protein, Cbp, facilitates the interaction between cytoplasmic Csk and membrane-associated Src-PTKs. This interaction is crucial for regulating cell growth and differentiation by controlling Src-PTK activity.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Src family of protein tyrosine kinases (Src-PTKs) regulate eukaryotic cell growth and differentiation.
  • Csk negatively controls Src-PTK activity by phosphorylating a specific tyrosine residue.
  • A localization gap exists between cytoplasmic Csk and membrane-associated Src-PTKs.

Purpose of the Study:

  • To investigate the mechanism of interaction between Csk and Src-PTKs.
  • To identify novel proteins involved in regulating Src-PTK activity.

Main Methods:

  • Protein interaction studies using SH2 domain binding assays.
  • Localization studies of Cbp in plasma membrane domains.
  • Analysis of Csk-mediated inhibition of c-Src in the presence of Cbp.

Main Results:

  • Identified Cbp, a transmembrane phosphoprotein, that binds to the SH2 domain of Csk.
  • Demonstrated Cbp's role in the membrane localization of Csk.
  • Showed Cbp mediates Csk-dependent inhibition of c-Src activity.
  • Localized Cbp to GM1 ganglioside-enriched membrane domains involved in signaling.

Conclusions:

  • Cbp is a novel component linking cytoplasmic Csk to membrane-associated Src-PTKs.
  • Cbp facilitates Csk's regulatory function on Src-PTKs.
  • Cbp plays a role in controlling Src-PTK activity within signaling-relevant membrane microdomains.

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