Cellular lysosomal capacity is tightly controlled to match catabolic demands and sustain lysosomal signaling pathways. Here, we report that cells can adjust their lysosomal capacity in response to varying autophagy loads. Manipulating the number of mitochondria targeted for mitophagy leads to a proportional upregulation of transcription factor EB (TFEB)-mediated lysosome adaptation programs. This quantitative control is exerted through Rag GTPase-driven mTORC1 suppression. GATOR1 is selectively recruited to lysosomes containing autophagic cargo, initiating local Rag GTPase-dependent suppression of mTORC1 activities. This mitophagy-induced mTORC1 suppression leads to TFEB activation and dephosphorylation of TOS-motif-containing substrates (S6K and 4EBP) under nutrient-rich conditions. This phenomenon similarly occurs during aggrephagy. These findings suggest that autophagic cargo-harboring lysosomes exhibit consistently low mTORC1 activity. Lysosomes can, therefore, sense the magnitude of autophagy loads and quantitatively translate this signal into TFEB activation to support self-regulated homeostasis.
Hsieh et al. (Wed,) studied this question.