J Biol Chem. 2022 Feb 17. pii: S0021-9258(22)00184-3. [Epub ahead of print]
101744
The mammalian target of rapamycin complex 1 (mTORC1) signaling pathway is activated by intracellular nutritional sufficiency and extracellular growth signals. It has been reported that mTORC1 acts as a hub that integrates these inputs to orchestrate a number of cellular responses, including translation, nucleotide synthesis, lipid synthesis, and lysosome biogenesis. However, little is known about specific control of mTORC1 signaling downstream of this complex. Here, we demonstrate that Ragulator, a heteropentameric protein complex required for mTORC1 activation in response to amino acids, is critical for inhibiting the nuclear translocation of transcription factor EB (TFEB). We established a unique RAW264.7 clone that lacked Ragulator but retained total mTORC1 activity. In a nutrition-sufficient state, the nuclear translocation of TFEB was markedly enhanced in the clone despite total mTORC1 kinase activity. In addition, as a cellular phenotype, the number of lysosomes was increased by ten-fold in the Ragulator-deficient clone compared to that of control cells. These findings indicate that mTORC1 essentially requires the Ragulator complex for regulating the subcellular distribution of TFEB. Our findings also suggest that other scaffold proteins may be associated with mTORC1 for the specific regulation of downstream signaling.
Keywords: Ragulator; lysosome; mammalian target of rapamycin (mTOR); nuclear translocation; scaffold protein; transcription factor EB