OTUB1 protein suppresses mTOR complex 1 (mTORC1) activity by deubiquitinating the mTORC1 inhibitor DEPTOR

Area of Science:

• Cellular signaling and metabolism
• Molecular biology and protein regulation

Background:

• Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) regulates cell growth and metabolism.
• DEPTOR is an endogenous inhibitor of mTORC1 and mTORC2, and its abundance controls mTOR signaling.
• Mechanisms regulating DEPTOR stability were previously unknown.

Purpose of the Study:

• To investigate the mechanisms regulating DEPTOR stability.
• To identify proteins that interact with and modify DEPTOR.
• To understand the role of OTUB1 in DEPTOR regulation and its impact on mTORC1 signaling.

Main Methods:

• In vitro deubiquitination assays to assess OTUB1 activity on DEPTOR.
• Co-immunoprecipitation to confirm direct interaction between OTUB1 and DEPTOR.
• Amino acid treatment to study the regulation of OTUB1-DEPTOR interaction.
• Analysis of mTORC1 activation, autophagy, cell proliferation, and cell size.

Main Results:

• OTU domain-containing ubiquitin aldehyde-binding protein 1 (OTUB1) specifically deubiquitinates DEPTOR.
• OTUB1 directly interacts with DEPTOR, stabilizing it via a non-canonical, deubiquitinase activity-independent mechanism.
• OTUB1 suppresses amino acid-induced mTORC1 activation in a DEPTOR-dependent manner, impacting cellular processes.

Conclusions:

• OTUB1 stabilizes the mTORC1 inhibitor DEPTOR through a novel mechanism.
• This OTUB1-DEPTOR interaction regulates cellular autophagy, proliferation, and size.
• Findings provide insights into mTOR signaling in diseases like cancer and suggest potential therapeutic targets.