Lysine-specific demethylase 1 (LSD1) is a well characterized transcriptional regulator functioning on the chromatin to remove mono- and di-methyl groups from lysine 4 or lysine 9 of histone 3 (H3K4 or H3K9). LSD1 also has non-transcriptional activities via targeting non-histone substrates that participate in diverse biological processes. In this report, we determined that LSD1 negatively regulates autophagy in skeletal muscle cells by promoting PTEN degradation in a transcription-independent mechanism. In C2C12 cells, LSD1 inhibition or depletion significantly induced the initiation of autophagy; and autophagy resulted from LSD1 inhibition is associated with AKT/mTORC1 inactivation. Notably, the proteins of PTEN, a prominent repressive AKT modulator, are stabilized by LSD1 inhibition despite a decrease of its mRNA levels. Further data demonstrated that LSD1 interacts with PTEN protein and enhances its ubiquitination and degradation. Together, our findings identify a novel biological function of LSD1 in autophagy, mediated by regulating the stability of PTEN and the activity of AKT/mTORC1. (C) 2019 Elsevier Inc. All rights reserved.