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Phosphorylation of GAP and GAP-associated proteins by transforming and mitogenic tyrosine kinases

C Ellis1, M Moran, F McCormick

  • 1Division of Molecular and Developmental Biology, Mount Sinai Hospital Research Institute, Toronto, Ontario, Canada.

Nature
|January 25, 1990
PubMed

Insights

Protein-tyrosine kinases use functional p21ras to signal cell growth. This study identifies GTPase-activating protein (GAP) and associated proteins as targets, linking tyrosine kinases to p21ras signaling in cell transformation.

Area of Science:

  • Cellular biology
  • Molecular oncology
  • Signal transduction

Background:

  • The precise mechanisms by which protein-tyrosine kinases drive cellular proliferation and malignant transformation remain unclear.
  • While antibodies against p21ras block tyrosine kinase effects, a direct biochemical link between these pathways has not been established.
  • The SH2 domain in tyrosine kinases regulates kinase activity, and its presence in p21ras GTPase-activating protein (GAP) suggests a potential interaction.

Purpose of the Study:

  • To investigate the biochemical link between tyrosine kinases and p21ras signaling.
  • To identify potential targets of tyrosine kinases involved in cell transformation.
  • To elucidate the role of SH2 domains in mediating protein-tyrosine kinase interactions.

Main Methods:

  • Microinjection of antibodies against p21ras.
  • Analysis of protein phosphorylation on tyrosine residues in transformed cells.
  • Co-precipitation assays to identify interacting proteins.
  • Use of inducible tyrosine kinase expression systems (v-src, v-fps).
  • Stimulation of fibroblasts with epidermal growth factor.

Main Results:

  • GTPase-activating protein (GAP), p62, and p190 were found to be phosphorylated on tyrosine in cells transformed by various tyrosine kinases.
  • This tyrosine phosphorylation correlated with cellular transformation induced by v-src and v-fps.
  • GAP, p62, and p190 also underwent rapid tyrosine phosphorylation in response to epidermal growth factor stimulation.
  • SH2 domains appear to mediate interactions of cytoplasmic proteins in signal transduction pathways.

Conclusions:

  • Tyrosine kinases may modulate p21ras function through the phosphorylation of GAP and its associated proteins.
  • GAP and its partners are implicated as targets for both oncogenic tyrosine kinases and normal growth factor receptors.
  • These findings provide a mechanism linking tyrosine kinase activity to p21ras signaling and cellular transformation, highlighting the role of SH2 domains in signal transduction.

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