TOR complex 2-Ypk1 signaling regulates actin polarization via reactive oxygen species

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• The mechanistic target of rapamycin complex 2 (mTORC2) pathway is crucial for cell structure and function.
• mTORC2's role in regulating the actin cytoskeleton, particularly in cancer cell motility, is of significant interest.
• The precise mechanisms by which mTORC2 influences the actin cytoskeleton remain largely unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms by which mTORC2 signaling regulates actin cytoskeletal organization.
• To investigate the role of reactive oxygen species (ROS) in mTORC2-mediated actin polarization.
• To identify key proteins and pathways downstream of mTORC2 involved in actin regulation.

Main Methods:

• Budding yeast model system (Saccharomyces cerevisiae).
• Genetic analysis of TORC2, Ypk1, Fpk1, Pkc1, and related signaling components.
• Measurement of reactive oxygen species (ROS) levels.
• Analysis of actin polarization and cytoskeletal organization.
• Investigation of protein localization and interactions.

Main Results:

• TORC2-Ypk1 signaling regulates actin polarization by controlling ROS accumulation.
• Both vacuole-associated ROS (via Fpk1 and sphingolipids) and mitochondria-mediated ROS (via Tpk3) are regulated by TORC2-Ypk1.
• The protein kinase C (Pkc1)/MAPK cascade acts downstream of Ypk1 to modulate ROS levels, partly through cyclin C degradation.
• Ypk1 controls Pkc1 activity via Rom2 localization, which is dependent on Fpk1 and sphingolipids.

Conclusions:

• TORC2/Ypk1 signaling, Fpk1, sphingolipids, Pkc1, and ROS are interconnected regulators of the actin cytoskeleton.
• ROS plays a significant role in mTORC2-dependent regulation of actin dynamics.
• These findings provide insights into potential therapeutic targets for cancer by understanding mTORC2's role in cell motility.