The Vam6 GEF controls TORC1 by activating the EGO complex.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The target of rapamycin complex 1 (TORC1) is a crucial regulator of eukaryotic cell growth.
• TORC1 activity is influenced by hormones and nutrients, and its dysregulation is linked to cancer.
• The EGO complex (EGOC) is involved in TORC1 regulation.

Purpose of the Study:

• To investigate the role of the yeast Rag GTPase homolog Gtr1 in TORC1 activation.
• To elucidate the regulatory mechanism of Gtr1 by the guanine nucleotide exchange factor Vam6.

Main Methods:

• Yeast genetics and molecular biology techniques.
• Analysis of protein-protein interactions between Gtr1 and TORC1.
• Assessment of TORC1 activity under different nutrient conditions and Gtr1 nucleotide-binding states.

Main Results:

• Gtr1 interacts with and activates TORC1 in an amino-acid-dependent manner.
• Constitutively active Gtr1 (Gtr1(GTP)) enhances TORC1 activity and confers resistance to leucine deprivation.
• GDP-bound Gtr1 (Gtr1(GDP)) leads to low TORC1 activity.
• Vam6 regulates the nucleotide-binding status of Gtr1, thereby controlling TORC1 function.

Conclusions:

• Gtr1 is a key component linking the EGO complex to TORC1 signaling.
• Vam6 acts as a guanine nucleotide exchange factor for Gtr1, modulating TORC1 activity.
• This pathway is essential for nutrient sensing and cell growth regulation in yeast.