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Updated: Jul 10, 2026

Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes
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Expression of I2PP2A, an inhibitor of protein phosphatase 2A, induces c-Jun and AP-1 activity

S W Al-Murrani1, J R Woodgett, Z Damuni

  • 1Department of Cellular and Molecular Physiology H166, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Centre, P.O. Box 850, Hershey, PA 17033, USA.

The Biochemical Journal
|July 7, 1999
PubMed

Insights

Transient expression of I2PP2A, a protein phosphatase 2A inhibitor, increased c-Jun levels and DNA binding. Protein phosphatase 2A catalytic subunit (PP2AC) decreased c-Jun, suggesting PP2A regulates c-Jun phosphorylation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Protein phosphatase 2A (PP2A) is a key regulator of cellular processes.
  • The proto-oncogene c-Jun is involved in cell proliferation and differentiation.
  • PP2A's role in regulating c-Jun activity and phosphorylation is not fully understood.

Purpose of the Study:

  • To investigate the effect of I2PP2A and PP2AC on c-Jun concentration, DNA binding, and transcriptional activity.
  • To explore the role of c-Jun phosphorylation at Ser63 and Ser73 in mediating these effects.

Main Methods:

  • Transient expression of I2PP2A and PP2AC in HEK-293 cells.
  • Western blotting to assess c-Jun concentration and phosphorylation status (phospho-Ser63 and Ser73).
  • Densitometric analysis to quantify protein levels and phosphorylation.

Main Results:

  • I2PP2A expression increased c-Jun concentration and DNA binding.
  • PP2AC expression decreased c-Jun concentration and DNA binding.
  • I2PP2A enhanced activator protein-1 transcriptional activity, an effect reduced by PP2AC.
  • Changes in c-Jun phosphorylation at Ser63 correlated with these effects.

Conclusions:

  • I2PP2A acts as a functional inhibitor of PP2A in intact cells.
  • PP2A regulates c-Jun concentration, DNA binding, and transcriptional activity.
  • PP2A may exhibit site selectivity in phosphorylating c-Jun.

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