Activation of phosphoinositide 3-kinase by interaction with Ras and by point mutation

EMBO J. 1996 May 15;15(10):2442-51.


We have reported previously that Ras interacts with the catalytic subunit of phosphoinositide 3-kinase (PI 3-kinase) in a GTP-dependent manner. The affinity of the interaction of Ras-GTP with p85alpha/p110alpha is shown here to be approximately 150 nM. The site of interaction on the p110alpha and beta isoforms of PI 3-kinase lies between amino acid residues 133 and 314. A point mutation in this region, K227E, blocks the GTP-dependent interaction of PI 3-kinase p110alpha with Ras in vitro and the ability of Ras to activate PI 3-kinase in intact cells. In addition, this mutation elevates the basal activity of PI 3-kinase in intact cells, suggesting a direct influence of the Ras binding site on the catalytic activity of PI 3-kinase. Using an in vitro reconstitution assay, it is shown that the interaction of Ras-GTP, but not Ras-GDP, with PI 3-kinase leads to an increase in its enzymatic activity. This stimulation is synergistic with the effect of tyrosine phosphopeptide binding to p85, particularly at suboptimal peptide concentrations. These data show that PI 3-kinase is regulated by a number of mechanisms, and that Ras contributes to the activation of this lipid kinase synergistically with tyrosine kinases.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Phosphatidylinositol 4-Kinase
  • Amino Acid Sequence
  • Animals
  • Cell Line, Transformed
  • Chlorocebus aethiops
  • Consensus Sequence
  • Enzyme Activation / drug effects
  • Enzyme Activation / genetics
  • Guanosine Triphosphate / metabolism
  • Isoenzymes / genetics
  • Isoenzymes / metabolism*
  • Liposomes
  • Molecular Sequence Data
  • Molecular Weight
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Point Mutation
  • Protein Binding
  • Proto-Oncogene Proteins p21(ras) / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Signal Transduction / drug effects
  • Signal Transduction / physiology


  • Isoenzymes
  • Liposomes
  • Recombinant Fusion Proteins
  • Guanosine Triphosphate
  • Phosphotransferases (Alcohol Group Acceptor)
  • 1-Phosphatidylinositol 4-Kinase
  • Proto-Oncogene Proteins p21(ras)