Does phosphorylation of eukaryotic elongation factor eEF2 regulate protein synthesis in ischemic preconditioning?

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Ischemia/reperfusion (I/R) injury impairs protein synthesis in the brain.
• Ischemic preconditioning (IP) can attenuate this inhibition.
• The role of eukaryotic elongation factor 2 (eEF2) phosphorylation in I/R-induced translation inhibition is unclear.

Purpose of the Study:

• To investigate the relationship between eEF2 phosphorylation and protein synthesis rates during I/R and oxidative stress.
• To determine if acquired ischemic tolerance (IT) affects eEF2 phosphorylation and protein synthesis.

Main Methods:

• Wistar rats were subjected to sublethal ischemia followed by lethal ischemia to induce IT.
• Protein synthesis rates and eEF2 phosphorylation levels were measured in brain tissue (cortex and hippocampus) after I/R.
• eEF2 phosphorylation was also assessed in vitro using H2O2-treated cells to model oxidative stress.

Main Results:

• eEF2 was dephosphorylated (activated) during transient cerebral ischemia and oxidative stress, yet protein synthesis was inhibited.
• Following reperfusion, protein synthesis remained low in rats without IT, despite varying eEF2 phosphorylation levels.
• In rats with IT, protein synthesis recovered, but eEF2 phosphorylation increased, further suggesting a lack of correlation.

Conclusions:

• eEF2 phosphorylation status does not directly correlate with protein synthesis rates during I/R or oxidative stress.
• Mechanisms other than eEF2 phosphorylation likely regulate translation during cerebral I/R and IT.