Adenovirus overrides cellular checkpoints for protein translation

Area of Science:

• Molecular Biology
• Virology
• Cancer Research

Background:

• Mammalian target of rapamycin (mTOR) regulates protein translation and cellular replication.
• Deregulation of mTOR signaling is implicated in human cancers, making it a key therapeutic target.
• The precise mechanisms of mTOR activation, particularly in response to viral infections, remain incompletely understood.

Purpose of the Study:

• To investigate the mechanisms of mTOR activation during adenovirus infection in quiescent cells.
• To identify viral factors responsible for aberrant mTOR activation.
• To explore parallels between viral replication strategies and cancer cell pathways concerning mTOR.

Main Methods:

• Utilized adenovirus as a tool to study mTOR activation in primary quiescent cells.
• Analyzed the roles of viral proteins E4-ORF1 and E4-ORF4 in mTOR pathway modulation.
• Investigated the interaction of viral proteins with host cell signaling pathways like PI3-kinase and PP2A.

Main Results:

• Adenovirus infection activates mTOR independently of nutrient or growth factor signals.
• Viral proteins E4-ORF1 and E4-ORF4 were identified as key activators of mTOR.
• E4-ORF1 activates mTOR by mimicking growth factor signaling via PI3-kinase activation.
• E4-ORF4 activates mTOR by interacting with and relocalizing protein phosphatase 2A (PP2A), substituting for glucose-mediated activation.

Conclusions:

• Adenovirus employs specific viral proteins to inappropriately activate mTOR, facilitating viral replication.
• These viral strategies highlight functional similarities between virus-infected cells and tumor cells regarding mTOR pathway manipulation.
• Understanding these viral mechanisms provides novel insights into targeting mTOR in cancer therapy.