Related Experiment Video

Updated: May 15, 2025

A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
10:17

A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors

Published on: April 29, 2022

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Molecular mechanism of PP2A/B55α phosphatase inhibition by IER5

Ruili Cao1, Daniel T D Jones1, Li Pan2

  • 1Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.

Cell Chemical Biology
|April 10, 2025
PubMed

Insights

The IER5 protein inhibits PP2A/B55α phosphatase activity, crucial for cell differentiation. This study reveals the structural basis of this inhibition, offering targets for new therapies.

Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Protein phosphatase 2A (PP2A) are vital serine/threonine phosphatases.
  • PP2A activity is regulated by associated proteins like IER5.
  • Dysregulation of PP2A is implicated in various diseases.

Purpose of the Study:

  • To determine the structural basis of PP2A/B55α inhibition by IER5.
  • To investigate the role of IER5 in regulating PP2A/B55α activity in cellular differentiation.
  • To explore IER5 as a potential target for modulating PP2A/B55α function.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to determine the structure of the PP2A/B55α-IER5 complex.
  • Biochemical assays to measure PP2A/B55α phosphatase activity.
  • Site-directed mutagenesis and co-immunoprecipitation to study protein interactions.
  • Cellular assays in keratinocytes to assess the role of IER5 in differentiation.

Main Results:

  • The cryo-EM structure reveals IER5-N50 occludes a key surface on B55α, inhibiting substrate recruitment.
  • IER5-N50 inhibits PP2A/B55α-catalyzed dephosphorylation of pTau.
  • Mutations disrupting the IER5-PP2A/B55α interface impair their interaction.
  • IER5 is essential for KRT1 expression, a keratinocyte differentiation marker.
  • IER5-N50 homology to SERTA domain proteins was identified.

Conclusions:

  • IER5 directly inhibits PP2A/B55α nuclear activity by blocking substrate binding.
  • IER5 plays a critical role in keratinocyte differentiation.
  • The findings provide a molecular understanding of IER5-mediated PP2A/B55α inhibition.
  • This work lays the groundwork for developing selective PP2A/B55α modulators.
Keywords:
AlphafoldFoldseekKRT1cryoelectron microscopyimmediate early response genesnuclear localizationprotein phosphatase 2Astructure prediction

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