Early phosphoinositide 3-kinase activity is required for late activation of protein kinase Cepsilon in platelet-derived-growth-factor-stimulated cells: evidence for signalling across a large temporal gap

Biochem J. 2001 Sep 1;358(Pt 2):281-5. doi: 10.1042/0264-6021:3580281.


At least two signalling systems have the potential to contribute to the activation of protein kinase C (PKC) family members such as PKCepsilon. One of these is phosphoinositide 3-kinase (PI 3-kinase), whose lipid products activate PKCepsilon in vitro and in living cells. The recent observation that there are multiple waves of PI 3-kinase and PKCepsilon activity within the G(0)-to-S phase interval provides a new opportunity to investigate the relationship between these two signalling enzymes in vivo. We have assessed the relative importance of the early and late waves of PI 3-kinase activity for the corresponding waves of PKCepsilon activity. Blocking the first phase of PI 3-kinase activity inhibited both early and late activation of PKCepsilon. In contrast, the second wave of PI 3-kinase activity was dispensable for late activation of PKCepsilon. These findings suggested that early PI 3-kinase activation induced a stable change in PKCepsilon, which predisposed it to subsequent activation by lipid cofactors. Indeed, partial proteolysis of PKCepsilon indicated that early activation of PI 3-kinase led to a conformation change in PKCepsilon that persisted as the activity of PKCepsilon cycled. We propose a two-step hypothesis for the activation of PKCepsilon in vivo. One step is stable and depends on PI 3-kinase, whereas the other is transient and may depend on the availability of lipid cofactors. Finally, these studies reveal that PI 3-kinase and PKCepsilon are capable of communicating over a relatively long time interval and begin to elucidate the mechanism.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Enzyme Activation
  • Enzyme Stability
  • Humans
  • Isoenzymes / chemistry
  • Isoenzymes / metabolism*
  • Kinetics
  • Models, Biological
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation
  • Platelet-Derived Growth Factor / pharmacology*
  • Protein Conformation
  • Protein Kinase C / chemistry
  • Protein Kinase C / metabolism*
  • Protein Kinase C-epsilon
  • Signal Transduction*


  • Isoenzymes
  • Platelet-Derived Growth Factor
  • Phosphatidylinositol 3-Kinases
  • PRKCE protein, human
  • Protein Kinase C
  • Protein Kinase C-epsilon