Nutrient control of TORC1, a cell-cycle regulator

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The target of rapamycin (TOR) protein kinase is central to cellular functions like protein synthesis, growth, and proliferation.
• TOR signaling, particularly mammalian TOR complex 1 (mTORC1), is influenced by hormones, growth factors, and intracellular amino acids.
• Dysregulation of TOR signaling is linked to various human diseases.

Purpose of the Study:

• To elucidate the mechanism of amino acid-induced activation of mTORC1 signaling.
• To investigate the role of protein kinase MAP4K3 and Rag GTPases in this activation process.
• To explore the function of mTORC1 in cell cycle progression beyond the G1/S transition.

Main Methods:

• Investigated the molecular mechanisms underlying amino acid sensing by mTORC1.
• Utilized genetic and biochemical approaches to study MAP4K3 and Rag GTPases.
• Analyzed cell cycle progression in yeast and mammalian cells under various conditions.

Main Results:

• Identified MAP4K3 and Rag GTPases as key components in the amino acid-mediated activation of mTORC1.
• Demonstrated that mTORC1 controls not only the G1/S transition but also G2/M progression.
• Observed contrasting roles of mTORC1 in G2/M progression between yeast and mammalian cells.

Conclusions:

• Amino acid signaling to mTORC1 involves MAP4K3 and Rag GTPases.
• mTORC1 plays a broader role in cell cycle control, impacting G2/M progression.
• The precise mechanisms by which mTORC1 regulates G2/M differ between species, highlighting conserved and divergent pathways.