PQ-loop repeat-containing 2 (PQLC2) regulates mTORC1 lysosomal localization and autophagic flux

PQ-loop repeat-containing 2 (PQLC2) is a lysosomal transporter for cationic amino acid that plays a critical role in regulating intracellular amino acid levels. However, its role in lysosomal biogenesis and autophagy remains poorly understood. Here, we investigate the impact of PQLC2 loss on lysosomal function and autophagic flux using PQLC2 knockdown and knockout cell models. PQLC2-deficient cells exhibited enhanced nuclear translocation of transcription factor EB (TFEB), a key regulator of lysosome, accompanied by increased expression of TFEB-lysosomal and autophagy target genes. In addition, genes related to mechanistic target of rapamycin complex 1 (mTORC1), a negative regulator of TFEB, were destabilized, leading to reduced lysosomal recruitment and impaired mTORC1 signaling. Loss of PQLC2 also resulted in lysosomal dysfunction, including defective lysosomal acidification, decreased cathepsin activity, and lysosomal enlargement. Furthermore, autophagosome maturation and autophagic flux were disrupted in PQLC2-deficient cells, as evidenced by p62 accumulation and decreased LC3-II levels. Collectively, our results highlight that PQLC2 is essential for regulating mTORC1-dependent lysosomal function and autophagy, underscoring its potential role in maintaining cellular homeostasis.