Rags connect mTOR and autophagy

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The mechanistic target of rapamycin (mTOR) pathway regulates protein synthesis and cell growth.
• Nutrient availability, particularly amino acids, is a key activator of mTOR signaling.
• Lysosomes are increasingly recognized as central hubs in cellular signaling pathways.

Purpose of the Study:

• To investigate the role of lysosomes in amino acid-mediated mTOR activation.
• To characterize a novel cytoplasmic compartment linking mTOR and autophagy.
• To elucidate the function of Rag GTPases in mTOR localization and activation.

Main Methods:

• Co-immunoprecipitation assays to detect protein-protein interactions.
• Confocal microscopy to visualize subcellular localization of mTOR and lysosomes.
• Genetic manipulation of Rag GTPases to assess their role in mTOR signaling.

Main Results:

• mTOR physically associates with lysosomes, a process mediated by Rag GTPases and the Ragulator complex.
• A novel compartment, the TOR-autophagy spatial coupling compartment (TASCC), forms in oncogenic Ras-induced senescent cells.
• TASCC formation facilitates the coordinated activation of mTOR and autophagy, requiring active Rag proteins.

Conclusions:

• Lysosomes are critical platforms for amino acid-mediated mTOR activation.
• The TASCC represents a novel mechanism for coupling anabolic (mTOR) and catabolic (autophagy) processes.
• Rag GTPases are essential for both lysosomal recruitment of mTOR and TASCC formation, impacting protein synthesis.