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Identification of 14-3-3zeta as a protein kinase B/Akt substrate.

Protein kinase B/Akt (PKB/Akt) is a member of the ACG kinase family, which also includes protein kinase C, that phosphorylates a number of 14-3-3-binding proteins. 14-3-3 protein regulation of protein kinase C activity is modulated by 14-3-3 phosphorylation. We examined the hypothesis that PKB/Akt interacts with and phosphorylates 14-3-3zeta, leading to modulation of dimerization. By glutathione S-transferase pull-down, Akt precipitated recombinant 14-3-3zeta and endogenous 14-3-3zeta from HEK293 cell lysates. Recombinant active PKB/Akt phosphorylated recombinant 14-3-3zeta in an in vitro kinase assay. Transfection of active PKB/Akt into HEK293 cells resulted in phosphorylation of 14-3-3zeta. Based on a motif search of 14-3-3zeta, a potential PKB/Akt phosphorylation site, Ser-58, was mutated to alanine. PKB/Akt was unable to phosphorylate this mutant protein. Incubation of 14-3-3zeta with recombinant active PKB/Akt resulted in phosphorylation of 45% of the protein, as determined by a pI shift on two-dimensional electrophoresis, but 14-3-3zeta dimerization was not altered. These data indicate that PKB/Akt phosphorylates Ser-58 on 14-3-3zeta both in vitro and in intact cells. The functional relevance of this phosphorylation remains to be determined.

Pubmed ID: 11956222


  • Powell DW
  • Rane MJ
  • Chen Q
  • Singh S
  • McLeish KR


The Journal of biological chemistry

Publication Data

June 14, 2002

Associated Grants


Mesh Terms

  • 14-3-3 Proteins
  • Amino Acid Motifs
  • Cell Line
  • Dimerization
  • Glutathione Transferase
  • Humans
  • Phosphorylation
  • Protein Binding
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-akt
  • Recombinant Fusion Proteins
  • Serine
  • Substrate Specificity
  • Tyrosine 3-Monooxygenase