The role of 3-phosphoinositide-dependent protein kinase 1 in activating AGC kinases defined in embryonic stem cells

Curr Biol. 2000 Apr 20;10(8):439-48. doi: 10.1016/s0960-9822(00)00441-3.

Abstract

Background: Protein kinase B (PKB), and the p70 and p90 ribosomal S6 kinases (p70 S6 kinase and p90 Rsk, respectively), are activated by phosphorylation of two residues, one in the 'T-loop' of the kinase domain and, the other, in the hydrophobic motif carboxy terminal to the kinase domain. The 3-phosphoinositide-dependent protein kinase 1 (PDK1) activates many AGC kinases in vitro by phosphorylating the T-loop residue, but whether PDK1 also phosphorylates the hydrophobic motif and whether all other AGC kinases are substrates for PDK1 is unknown.

Results: Mouse embryonic stem (ES) cells in which both copies of the PDK1 gene were disrupted were viable. In PDK1(-/-) ES cells, PKB, p70 S6 kinase and p90 Rsk were not activated by stimuli that induced strong activation in PDK1(+/+) cells. Other AGC kinases - namely, protein kinase A (PKA), the mitogen- and stress-activated protein kinase 1 (MSK1) and the AMP-activated protein kinase (AMPK) - had normal activity or were activated normally in PDK1(-/-) cells. The insulin-like growth factor 1 (IGF1) induced PKB phosphorylation at its hydrophobic motif, but not at its T-loop residue, in PDK1(-/-) cells. IGF1 did not induce phosphorylation of p70 S6 kinase at its hydrophobic motif in PDK1(-/-) cells.

Conclusions: PDK1 mediates activation of PKB, p70 S6 kinase and p90 Rsk in vivo, but is not rate-limiting for activation of PKA, MSK1 and AMPK. Another kinase phosphorylates PKB at its hydrophobic motif in PDK1(-/-) cells. PDK1 phosphorylates the hydrophobic motif of p70 S6 kinase either directly or by activation of another kinase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Phosphoinositide-Dependent Protein Kinases
  • AMP-Activated Protein Kinases
  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinases / chemistry
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinases / pharmacology
  • Cells, Cultured
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Enzyme Activation / drug effects
  • Enzyme Activation / radiation effects
  • Gene Deletion
  • Glycogen Synthase Kinase 3
  • Immunoblotting
  • Insulin-Like Growth Factor I / pharmacology
  • Mice
  • Multienzyme Complexes / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Serine-Threonine Kinases / pharmacology
  • Protein-Serine-Threonine Kinases / physiology*
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases / metabolism
  • Ribosomal Protein S6 Kinases, 90-kDa*
  • Stem Cells / enzymology*
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Multienzyme Complexes
  • Proto-Oncogene Proteins
  • Insulin-Like Growth Factor I
  • 3-Phosphoinositide-Dependent Protein Kinases
  • Pdpk1 protein, mouse
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases
  • Ribosomal Protein S6 Kinases, 90-kDa
  • mitogen and stress-activated protein kinase 1
  • Cyclic AMP-Dependent Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Glycogen Synthase Kinase 3
  • AMP-Activated Protein Kinases
  • Tetradecanoylphorbol Acetate