Redox control of cytosolic Akt phosphorylation in PTEN null cells

Area of Science:

• Cell Biology
• Biochemistry
• Oncology

Background:

• The tumor suppressor PTEN is frequently lost in various cancers.
• PTEN loss is associated with hyperactivation of the Akt signaling pathway.
• The precise mechanisms linking PTEN loss to Akt hyperactivation remain under investigation.

Purpose of the Study:

• To investigate the role of intracellular reactive oxygen species (ROS) in Akt hyperphosphorylation in PTEN-deficient cells.
• To elucidate the signaling events downstream of PTEN loss that lead to Akt activation.

Main Methods:

• Utilized PTEN knockout mouse embryonic fibroblasts (MEFs).
• Assessed Akt phosphorylation status (Thr308 and Ser473) following manipulation of intracellular superoxide levels.
• Investigated the interaction between Akt and protein phosphatase 2A (PP2A).
• Corroborated findings in PTEN-null prostate cancer (LNCaP) and melanoma (M14) cell lines.

Main Results:

• Reduced intracellular superoxide levels in PTEN-null cells led to rapid dephosphorylation of Akt at Thr308 and Ser473.
• Dephosphorylation primarily affected the cytosolic pool of Akt, while the membrane-associated pool remained phosphorylated.
• Increased interaction between Akt and PP2A catalytic subunit was observed, correlating with increased oxidation of Akt.
• These findings were consistent across different PTEN-deficient cell models.

Conclusions:

• Intracellular ROS, specifically superoxide, play a critical role in Akt hyperphosphorylation in the absence of PTEN.
• Oxidative stress contributes to the dysregulation of Akt signaling in PTEN-null cancers.
• Targeting ROS or modulating Akt-PP2A interactions may offer therapeutic strategies for PTEN-deficient tumors.