Further evidence that the inhibition of glycogen synthase kinase-3beta by IGF-1 is mediated by PDK1/PKB-induced phosphorylation of Ser-9 and not by dephosphorylation of Tyr-216

FEBS Lett. 1997 Oct 27;416(3):307-11. doi: 10.1016/s0014-5793(97)01235-0.

Abstract

293 cells were transfected with wild-type GSK3beta (WT-GSK3beta) or a mutant in which the PKB phosphorylation site (Ser-9) was altered to Ala (A9-GSK3beta). Upon stimulation with IGF-1 or insulin, WT-GSK3beta was inhibited 75% or 60%, respectively, whereas the activity of the A9-GSK3beta mutant was unaffected. Incubation of WT-GSK3beta with PP2A1 (a Ser/Thr-specific phosphatase) completely reversed the IGF-1- or insulin-induced inhibition. IGF-1 stimulation did not induce any tyrosine dephosphorylation of WT-GSK3beta or A9-GSK3beta. Coexpression of WT-GSK3beta in 293 cells with either PKB alpha (also known as AKT) or PDK1 (the 'upstream' activator of PKB) mimicked the IGF-1- or insulin-induced phosphorylation of Ser-9 and inactivation of GSK3beta.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Phosphoinositide-Dependent Protein Kinases
  • Alanine
  • Amino Acid Sequence
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors*
  • Calcium-Calmodulin-Dependent Protein Kinases / biosynthesis
  • Cell Line
  • Glycogen Synthase Kinase 3
  • Glycogen Synthase Kinases
  • Humans
  • Insulin / pharmacology
  • Insulin-Like Growth Factor I / pharmacology*
  • Isoenzymes / metabolism
  • Mutagenesis, Site-Directed
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation
  • Phosphoserine / metabolism
  • Phosphotyrosine / metabolism
  • Protein-Serine-Threonine Kinases / metabolism*
  • Recombinant Proteins / antagonists & inhibitors
  • Recombinant Proteins / biosynthesis
  • Serine*
  • Transfection
  • Tyrosine*

Substances

  • Insulin
  • Isoenzymes
  • Recombinant Proteins
  • Phosphoserine
  • Phosphotyrosine
  • Tyrosine
  • Serine
  • Insulin-Like Growth Factor I
  • Glycogen Synthase Kinases
  • 3-Phosphoinositide-Dependent Protein Kinases
  • PDPK1 protein, human
  • Protein-Serine-Threonine Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Glycogen Synthase Kinase 3
  • Phosphoprotein Phosphatases
  • Alanine