Redundant electrostatic interactions between GATOR1 and the Rag GTPase heterodimer drive efficient amino acid sensing...

Area of Science:

• Cellular biology
• Molecular mechanisms of nutrient sensing
• Signal transduction pathways

Background:

• Cellular growth and proliferation depend on nutrient availability.
• The mechanistic target of the rapamycin complex 1 (mTORC1) pathway coordinates nutrient sensing with cell growth.
• mTORC1 is regulated by Rag and Rheb GTPases, with RagA-RagC controlling mTORC1 localization and nucleotide loading.

Purpose of the Study:

• To functionally characterize the interaction between GATOR1 and RagC.
• To elucidate the biological relevance of the Depdc5-RagC interface in mTORC1 regulation.
• To understand how GATOR1 regulates Rag GTPase heterodimer nucleotide loading states.

Main Methods:

• Structure-function analysis
• Enzymatic kinetic measurements
• Cell-based signaling assays
• Cryo-electron microscopy (cryo-EM) structural analysis

Main Results:

• Identified a critical electrostatic interaction between Depdc5 (GATOR1 subunit) and RagC.
• This interaction involves Arg-1407 on Depdc5 and negatively charged residues on RagC.
• Disrupting this interaction impairs GATOR1's GTPase-activating protein (GAP) activity and cellular response to amino acid withdrawal.

Conclusions:

• GATOR1's regulation of the Rag GTPase heterodimer is mediated by a specific Depdc5-RagC interaction.
• This interaction is crucial for coordinating cellular behavior with amino acid availability.
• The findings provide new insights into the precise control of mTORC1 signaling by nutrient sensors.