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Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during

P Turowski1, A Fernandez, B Favre

  • 1Friedrich Miescher-Institut, Basel, Switzerland.

The Journal of Cell Biology
|April 1, 1995
PubMed

Insights

Protein phosphatase 2A (PP2A) core subunits shuttle between the cytoplasm and nucleus, with nuclear concentration changing during the cell cycle. Differential methylation of PP2Ac regulates its localization and nuclear PP2A holoenzymes undergo conformational changes.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Protein phosphatase 2A (PP2A) is crucial for regulating diverse cellular processes.
  • The precise control mechanisms governing PP2A holoenzyme activation and deactivation are not fully understood.
  • The catalytic (PP2Ac) and regulatory (PR65) subunits form the core of all PP2A holoenzymes.

Purpose of the Study:

  • To investigate the cellular localization and cell cycle-dependent behavior of PP2A core subunits.
  • To explore the potential role of PP2Ac methylation in regulating its subcellular distribution.
  • To examine conformational changes in nuclear PP2A holoenzymes during the cell cycle.

Main Methods:

  • Utilized monospecific and affinity-purified antibodies for quantitative immunofluorescence.
  • Analyzed synchronized cells to track changes in PP2A subunit localization throughout the cell cycle.
  • Investigated differential methylation patterns of PP2Ac.

Main Results:

  • PP2A core subunits (PP2Ac and PR65) are ubiquitously present in both cytoplasm and nucleus.
  • The nucleus exhibits a twofold higher concentration of PP2A core subunits compared to the cytoplasm.
  • Significant alterations in the nuclear-to-cytoplasmic ratio of PP2Ac occur during the cell cycle, linked to differential methylation and conformational changes in nuclear holoenzymes.

Conclusions:

  • PP2A localization and activity are dynamically regulated during the cell cycle, involving differential PP2Ac methylation and nuclear holoenzyme conformational shifts.
  • PP2A is lost from the nucleus during mitosis, with distinct behavior compared to protein phosphatase 1.
  • These findings provide insights into the cell cycle-specific regulation of PP2A-mediated dephosphorylation events.

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