A conserved cysteine-based redox mechanism sustains TFEB/HLH-30 activity under persistent stress

Mammalian TFEB and TFE3, as well as their ortholog in C. elegans HLH-30, play an important role in mediating cellular response to a variety of stress conditions, including nutrient deprivation, oxidative stress and pathogen infection. In this study we identify a novel mechanism of TFEB/HLH-30 regulation through a cysteine-mediated redox switch. Under stress conditions, TFEB-C212 undergoes oxidation, allowing the formation of intermolecular disulfide bonds that result in TFEB oligomerization. TFEB oligomers display increased resistance to mTORC1-mediated inactivation and are more stable under prolonged stress conditions. Mutation of the only cysteine residue present in HLH-30 (C284) significantly reduced its activity, resulting in developmental defects and increased pathogen susceptibility. Therefore, cysteine oxidation represents a new type of TFEB post-translational modification that functions as a molecular switch to link changes in redox balance with expression of TFEB/HLH-30 target genes.