High-content screening identifies mTORC1-independent TFEB activators that promote protective autophagy

Transcription factor EB (TFEB) is a master regulator of the autophagy-lysosome pathway. It becomes active upon nuclear translocation and induces the expression of genes involved in autophagy and lysosomal function. Mechanistic target of rapamycin complex 1 (mTORC1) inhibition typically triggers this process; however, chronic mTORC1 suppression often induces adverse metabolic and proliferative effects, necessitating the identification of mTORC1-independent mechanisms driving TFEB nuclear translocation. Therefore, this study aimed to identify pharmacological activators of TFEB nuclear translocation that function independently of mTORC1 inhibition. In this study, we developed a high-content screening assay to quantify TFEB nuclear translocation in HeLa cells and screened a library of 560 approved compounds. We identified two compounds, NSC-319726 and ML-SA1, that promoted TFEB nuclear translocation without reducing p70S6K phosphorylation, supporting an mTORC1-independent mechanism. Both compounds significantly increased LC3-II accumulation and the signal intensity of an autolysosomal marker, indicating enhanced autophagic flux. Functionally, these compounds protected the cells against staurosporine-induced apoptosis and hydrogen peroxide-induced oxidative stress. Notably, pre-treatment conferred significantly greater protection than co-treatment, suggesting that TFEB-mediated transcriptional remodeling is necessary for maximal cytoprotection. Overall, these findings highlight the potential of high-content phenotypic screening to identify mTORC1-independent TFEB activators and suggest NSC-319726 and ML-SA1 as pharmacological inducers of protective autophagy in vitro.