Ser-64 and Ser-111 in PHAS-I are dispensable for insulin-stimulated dissociation from eIF4E

Gail Ferguson, Isabelle Mothe-Satney, John C Lawrence

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Insulin stimulates phosphorylation of multiple sites in the eIF4E-binding protein, PHAS-I, leading to dissociation of the PHAS-I.eIF4E complex and to an increase in cap-dependent translation. The Ser-64 and Ser-111 sites have been proposed to have key roles in controlling the association of PHAS-I and eIF4E. To determine whether the effects of insulin require these sites, we assessed the control of PHAS-I proteins having Ala-64 or Ala-111 mutations. The results indicate that phosphorylation of neither site is required for insulin to promote release of PHAS-I from eIF4E. Also, the mutation of Ser-111, which has been proposed to serve as a necessary priming site for the phosphorylation of other sites in PHAS-I, did not affect the phosphorylation of Thr-36/45, Ser-64, or Thr-69. Insulin promoted the release of eIF4E from PHAS-II, a PHAS isoform that lacks the Ser-111 site, but it was without effect on the amount of eIF4E bound to the third isoform, PHAS-III. The results demonstrate that contrary to widely accepted models, Ser-64 and Ser-111 are not required for the control of PHAS-I binding to eIF4E in cells, implicating phosphorylation of the Thr sites in dissociation of the PHAS-I.eIF4E complex. The findings also indicate that PHAS-II, but not PHAS-III, contributes to the control of protein synthesis by insulin.

Original languageEnglish
Pages (from-to)47459-65
Number of pages7
JournalJournal of Biological Chemistry
Volume278
Issue number48
DOIs
Publication statusPublished - 28 Nov 2003

Keywords

  • Adaptor Proteins, Signal Transducing
  • Alanine/chemistry
  • Binding Sites
  • Carrier Proteins/chemistry
  • Cell Line
  • DNA, Complementary/metabolism
  • Eukaryotic Initiation Factor-4E/chemistry
  • Eukaryotic Initiation Factors/chemistry
  • Genetic Vectors
  • Humans
  • Insulin/metabolism
  • Mutation
  • Phosphoproteins/chemistry
  • Phosphorylation
  • Precipitin Tests
  • Protein Binding
  • Protein Biosynthesis
  • Protein Isoforms
  • Protein Structure, Tertiary
  • Serine/chemistry
  • Sirolimus/pharmacology
  • Threonine/chemistry
  • Transfection

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