Posttranslational arginylation enzyme Ate1 regulates cell death through a mitochondrial‐dependent pathway

Abstract

Arginyltransferase1 (Ate1) is an evolutionarily conserved enzyme that mediates posttranslational addition of one extra arginine to a protein substrate in a process called arginylation. Recent evidence suggests that Ate1 is essential for normal stress response. The level of Ate1 and total arginylation activity appear to increase follow acute stress and leads to cell death. Vice versa, the removal or reduction of this enzyme minimized cellular sensitivity to high doses of common cellular stressors such as oxidants, radiations, heavy metal, and high temperature. All these evidence suggest that Ate1 is a master regulator of cell death/growth. However, how does Ate1 accomplish this role remain unknown. In this study, we found that Ate1 regulates cell death in a mitochondrial‐dependent manner. By using S.cerevisiae, which contains a conserved Ate1 gene, we found that during acute stress, Ate1 is highly recruited to mitochondria. By using recombinant Ate1 that is bound to cell membrane, we found that the ability of locating to mitochondria is essential for Ate1‐mediated cell death. By screening of dozens of other players with known roles in cell death, we discovered that Ate1‐mediated cell death appears to be independent of the pan‐caspase in yeast, the mitochondrial membrane potential, or the ubiquitin‐proteasome system in general. Instead, the Ate1‐mediated cell death is dependent on the integrity of the mitochondrial pore complex and the existence of apoptosis‐inducing factor (AIF), a mitochondrial protein that is often released into cytosol during mitochondrial stress. Consistently, the Ate1‐mediated cell death can be at least partially blocked by the over‐expression of mammalian pro‐survival protein bcl2, which is known to block the formation of mitochondrial permeability transition pore. Finally, in mammalian cells, where the intrinsic and extrinsic cell‐death pathways are well‐separated, we found that the absence of Ate1 only has impacts on intrinsic pathway that is mainly mediated by mitochondria, but has little effects on cell‐death triggered by death receptors such as TNF‐R.In summary, our study has discovered a novel cell death mechanism that is regulated by a posttranslational modification enzyme.Support or Funding InformationNIGNMS R01 GM107333DoD (CDMRP), Idea Award, PC140622This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.