Measurement of the Glutathione Redox Potentials in Membraneless Organelles

Glutathione (GSH) is essential for cellular redox regulation; however, the redox potential (EGSH) of the nucleus and membraneless organelles (MLOs) remains poorly understood. Here, we use the Grx1-roGFP2 sensor to measure the EGSH of the nucleus and several MLOs such as the nucleoli, stress granules, p-bodies, paraspeckles, and Cajal bodies. Unlike suggested by previous findings, we found that nuclear EGSH is stable throughout the cell cycle and identical to the cytosolic EGSH, and the EGSH of MLOs mirrors their surrounding environment. These findings challenge existing paradigms and provide novel insights into redox homeostasis across subcellular compartments.