Methionine Misacylation of tRNA on CaMKII in Response to ER Stress

Abstract

Methionine mistranslation is a recently discovered phenomenon that cells deliberately incorporate methionine residues at selected positions in proteins. Met-mistranslation is regulated by reactive oxygen species (ROS) and has been proposed to serve as an adaptive mechanism for oxidative stress response. CaMKII is a multifunctional protein that is necessary for Ca2+ homeostasis in cells. Recent evidence showed that CaMKII could be alternatively activated by ROS through methionine oxidation. Here we show that CaMKII activity could be regulated through methionine mistranslation triggered by Ca2+ stress in mammalian cells. For the first time we found that Ca2+ overload induced Met-mistranslation on CaMKII indicated by mass spectrometry. Mutant CaMKII proteins with extra Met residues have different kinase activity and autophosphorylation level from wild type CaMKII. In addition, mutant CaMKII (V208M) translocated into endoplasmic reticulum (ER) indicated by immunofluorescent staining. Furthermore, mammalian cells with mutant CaMKII has high level of cell apoptosis measured by TUNEL assay. In conclusion, our study provided additional evidence that Met-mistranslation of CaMKII protein could be used as a novel adaptive mechanism in response to ER stress upon elevated intracellular Ca2+ level in diverse disease processes.