Related Experiment Video

Updated: May 30, 2025

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

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Small-molecule modulators of B56-PP2A restore 4E-BP function to suppress eIF4E-dependent translation in cancer cells

Michelle A Lum1,2, Kayla A Jonas1,2, Shreya Parmar1,2

  • 1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska, USA.

The Journal of Clinical Investigation
|January 27, 2025
PubMed

Insights

Small-molecule activators of PP2A (SMAPs) restore translational control in tumors by activating 4E-BP1. This approach shows potential for cancer therapy and overcoming resistance to existing treatments.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Biochemistry

Background:

  • Dysregulated eukaryotic initiation factor 4E (eIF4E)-dependent translation drives tumorigenesis and therapy resistance.
  • eIF4E-binding proteins (4E-BPs) are key negative regulators of eIF4E translation, often inactivated in cancer.
  • Protein phosphatase 2A (PP2A) has been implicated in 4E-BP1 regulation.

Purpose of the Study:

  • To investigate the role of B56-PP2A phosphatases in regulating 4E-BP proteins.
  • To explore the therapeutic potential of activating B56-PP2A for restoring translational control in tumors.
  • To assess the efficacy of small-molecule activators of PP2A (SMAPs) in cancer models.

Main Methods:

  • Treatment with biased small-molecule activators of PP2A (SMAPs).
  • Analysis of 4E-BP1/2 phosphorylation and transcriptional regulation.
  • Cap-binding assays, coimmunoprecipitation, and cap-dependent translation assays.
  • Assessment of apoptosis and potentiation of existing cancer therapies.

Main Results:

  • SMAP treatment induced PP2A-dependent hypophosphorylation of 4E-BP1/2, identifying B56-PP2As as 4E-BP phosphatases.
  • SMAPs triggered 4E-BP1 transcriptional upregulation via a B56-PP2A→TFE3/TFEB→ATF4 signaling axis.
  • B56-PP2A activation inhibited eIF4F complex assembly and cap-dependent translation.
  • SMAPs promoted 4E-BP1-dependent apoptosis in tumor cells and enhanced the efficacy of ERK or mTOR inhibitors.

Conclusions:

  • B56-PP2A activation orchestrates a tumor-repressive program involving 4E-BP1 transcriptional induction and activation.
  • SMAPs demonstrate potential as a novel cancer therapeutic strategy.
  • PP2A activators may offer a means to overcome resistance to therapies targeting eIF4E-dependent translation.
Keywords:
Cell biologyOncologyPhosphoprotein phosphatasesSignal transductionTranslation

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