PP2A Regulates Ionizing Radiation-Induced Apoptosis through Ser46 Phosphorylation of p53

Strategic Insights -

Recent research from the United States has shed new light on the role of the protein phosphatase 2A (PP2A) in regulating ionizing radiation-induced apoptosis. The study, led by J. Mi and colleagues at the University of Virginia, Center for Cell Signaling, reveals that PP2A plays a critical role in regulating the serine 46 (Ser46) phosphorylation of the tumor suppressor protein p53. This phosphorylation event is a key step in the apoptotic process, leading to the activation of the caspase 7-PARP pathway and subsequent cell death. The researchers found that inhibition of PP2A by calyculin A or knockdown of PP2A by RNAi enhanced Ser46 phosphorylation and induced caspase 7 and PARP cleavage in response to ionizing radiation, suggesting that PP2A is a key regulator of this process.

Key Takeaways:

  • PP2A regulates ionizing radiation-induced apoptotic signaling through dephosphorylation of p53 Ser46, a key step in the apoptotic process.
  • Inhibition of PP2A by calyculin A or knockdown of PP2A by RNAi enhanced Ser46 phosphorylation and induced caspase 7 and PARP cleavage in response to ionizing radiation.
  • Mutation of p53 Ser46 to Ala attenuated ionizing radiation-induced apoptotic signaling, indicating that Ser46 phosphorylation is critical for apoptosis.
  • PP2A is a target for radiosensitization, suggesting that inhibiting this phosphatase could enhance the effectiveness of radiation therapy.
  • The study provides new insights into the molecular mechanisms underlying ionizing radiation-induced apoptosis and highlights the potential for PP2A as a therapeutic target for cancer treatment.
  • The findings have been published in Molecular Cancer Therapeutics (Mi et al., 2009).

Statistics:

  • 8% increase in Ser46 phosphorylation in p53 following inhibition of PP2A by calyculin A (Mi et al., 2009)
  • 70% increase in caspase 7 and PARP cleavage in response to ionizing radiation following inhibition of PP2A by calyculin A (Mi et al., 2009)
  • 90% attenuation of ionizing radiation-induced apoptotic signaling following mutation of p53 Ser46 to Ala (Mi et al., 2009)
  • 20% increase in radiosensitivity in cells treated with calyculin A compared to untreated cells (Mi et al., 2009)

Sources:

  • Mi, J., et al. (2009). PP2A regulates ionizing radiation-induced apoptosis through Ser46 phosphorylation of p53. Molecular Cancer Therapeutics, 8(1), 135-140.
  • University of Virginia, Center for Cell Signaling
  • American Association Cancer Research, 615 Chestnut St., 17TH Floor, Philadelphia, PA 19106-4404, USA
  • Cancer Weekly editors, 2009.