14-3-3 Proteins regulate Akt Thr308 phosphorylation in intestinal epithelial cells

Area of Science:

• Cell Biology
• Molecular Biology
• Gastroenterology

Background:

• Akt activation is crucial for epithelial cell functions, including proliferation, differentiation, survival, and death.
• Phosphorylation of Akt at Thr308 by phosphoinositide-dependent kinase 1 (PDK1) is essential for its activity, but the regulatory mechanisms are not fully understood.

Purpose of the Study:

• To investigate the role of 14-3-3 proteins in regulating Akt Thr308 phosphorylation during intestinal inflammation.
• To elucidate the molecular mechanisms by which 14-3-3 proteins control Akt activation in intestinal epithelial cells.

Main Methods:

• Treatment of intestinal epithelial cells with interferon-gamma (IFNγ) and tumor necrosis factor-alpha (TNFα).
• Investigation of protein degradation pathways, including autophagy.
• Assessment of Akt phosphorylation and activation.
• Use of the chemical inhibitor BV02 to block 14-3-3 protein function.

Main Results:

• IFNγ and TNFα treatment induce the degradation of 14-3-3η, a PDK1 inhibitor, in intestinal epithelial cells.
• 14-3-3ζ association with raptor triggers autophagy, leading to 14-3-3η degradation.
• Inhibition of 14-3-3 function with BV02 results in uncontrolled Akt activation, nuclear Akt accumulation, and intestinal epithelial cell death.

Conclusions:

• 14-3-3 proteins are critical regulators of Akt activation at Thr308 during intestinal inflammation.
• The 14-3-3/raptor/autophagy pathway controls PDK1 inhibitor levels, thereby modulating Akt activity.
• These findings establish a novel link between 14-3-3 proteins, Akt signaling, and the balance of cell survival and apoptosis in the intestinal epithelium during inflammation.