Electrochemical measurements reveal reactive oxygen species in stress granules

ABSTRACT Stress granules (SGs) are membraneless organelles that assemble in the cytoplasm to organize cellular contents and promote rapid adaptation during stress. To understand how SGs contribute to physiological functions, we used electrochemical measurements to detect electroactive species in SGs. With amperometry, we discovered that reactive oxygen species (ROS) are encapsulated inside arseniteinduced SGs, and H 2 O 2 is the main species. The release kinetics of H 2 O 2 from single SGs and the number of H 2 O 2 molecules were quantified. The discovery that SGs contain ROS implicates them as communicators of the cellular stresses rather than a simple end-point. This may explain how SGs regulate cellular metabolism and stress responses. This may also help better understand their cytoprotective functions in pathological conditions associated with SGs such as neurodegenerative diseases, cancers and viral infections.