Calcium-regulated proteolysis of eEF1A.

Area of Science:

• Plant molecular biology
• Protein biochemistry
• Cell signaling

Background:

• Eukaryotic elongation factor 1alpha (eEF1A) is a crucial protein involved in translation.
• eEF1A can be post-translationally modified by phosphorylglycerylethanolamine (PGE).
• Calcium ions (Ca2+) are important second messengers in cellular signaling.

Purpose of the Study:

• To investigate the role of calcium in the regulation of eEF1A stability.
• To determine if the PGE modification affects eEF1A degradation.
• To explore the relationship between eEF1A proteolysis, calcium, and lipid signaling.

Main Methods:

• Utilized [(14)C]ethanolamine labeling to track eEF1A modification and degradation in carrot microsomes.
• Assessed the effect of calcium (CaCl2) and EGTA on [(14)C]ethanolamine-labeled eEF1A ([(14)C]et-eEF1A) stability.
• Investigated the impact of phospholipase C, D, and A(2) treatments on eEF1A degradation.
• Examined the influence of pH on Ca(2+)-dependent eEF1A proteolysis.

Main Results:

• Calcium addition (1 mM CaCl2) significantly decreased [(14)C]et-eEF1A recovery, an effect blocked by EGTA.
• Recombinant eEF1A, lacking PGE modification, was also degraded in a Ca(2+)-regulated manner.
• Phospholipase C and D treatment reduced [(14)C]et-eEF1A levels, while phospholipase A(2) did not.
• eEF1A proteolysis was pH-sensitive, requiring higher Ca(2+) concentrations at lower pH.

Conclusions:

• eEF1A degradation is regulated by calcium in plant microsomes.
• The PGE modification is not essential for Ca(2+)-induced proteolysis but aids in quantification.
• Lipid hydrolysis by certain phospholipases, but not all, affects eEF1A stability.
• eEF1A is a potential downstream target in Ca(2+) and lipid-mediated signal transduction.