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Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells

Published on: May 1, 2020

The Drosophila protein kinase LK6 is regulated by ERK and phosphorylates the eukaryotic initiation factor eIF4E in

Josep L Parra-Palau1, Gert C Scheper, Daniel E Harper

  • 1Division of Molecular Physiology, Faculty of Life Sciences, University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK.

The Biochemical Journal
|October 19, 2004
PubMed

Insights

Drosophila LK6 kinase phosphorylates eukaryotic initiation factor 4E (eIF4E), essential for cell growth. LK6 is activated by the ERK signaling pathway, not p38 MAPK, demonstrating its role in eIF4E regulation.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Drosophila melanogaster research

Background:

  • Phosphorylation of eukaryotic initiation factor 4E (eIF4E) is crucial for cell growth and development in Drosophila.
  • LK6 is the Drosophila homolog of mammalian MAP kinase-signal-integrating kinases (Mnk1/2), which phosphorylate eIF4E.
  • Mammalian Mnk1 is activated by ERK and p38 MAPK pathways, while Mnk2 selectively binds ERK.

Purpose of the Study:

  • To investigate the function of Drosophila LK6 in phosphorylating eIF4E.
  • To determine the signaling pathways that regulate LK6 activity in Drosophila.
  • To confirm LK6's role in eIF4E phosphorylation in vivo.

Main Methods:

  • In vitro kinase assays using LK6 and Drosophila eIF4E.
  • Analysis of LK6 binding to ERK and p38 MAPK homologues in mammalian and Drosophila cells.
  • RNA interference (RNAi) to assess the effect of LK6 depletion on eIF4E phosphorylation.
  • Stimulation of signaling pathways (ERK, p38 MAPK) to observe effects on eIF4E phosphorylation.

Main Results:

  • Drosophila LK6 phosphorylates eIF4E at the physiological site in vitro.
  • LK6 binds to the ERK homologue Rolled in Drosophila cells, but not the p38 MAPK homologue.
  • Activation of the ERK pathway increases endogenous eIF4E phosphorylation in Drosophila cells, while p38 MAPK activation does not.
  • RNAi-mediated knockdown of LK6 significantly reduces eIF4E phosphorylation in Drosophila cells.
  • LK6 binds ERK in mammalian cells, requiring an intact binding motif, and increases eIF4E phosphorylation.

Conclusions:

  • Drosophila LK6 binds to and is activated by the ERK signaling pathway.
  • LK6 is the primary kinase responsible for phosphorylating eIF4E in Drosophila.
  • This study elucidates a key regulatory mechanism for eIF4E phosphorylation in Drosophila, linking ERK signaling to eIF4E function via LK6.

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