Mammalian Atg8 proteins and the autophagy factor IRGM control mTOR and TFEB at a regulatory node critical for...

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Autophagy is a fundamental cellular process for maintaining homeostasis in mammalian cells.
• TFEB is a key transcriptional activator regulating lysosomal biogenesis and cellular waste removal.
• The interplay between autophagy and lysosomal pathways is critical for cellular health.

Purpose of the Study:

• To elucidate the role of mammalian Atg8 proteins (mAtg8s) and IRGM in regulating TFEB.
• To investigate the molecular mechanisms linking autophagy regulators to lysosomal biogenesis control.
• To determine the involvement of IRGM and mAtg8s in cellular responses to starvation and infection.

Main Methods:

• Co-immunoprecipitation assays to study protein interactions.
• Western blotting and qPCR to analyze protein and gene expression.
• Gene deletion studies to assess the function of mAtg8s and GABARAPs.
• Cellular infection models (Mycobacterium tuberculosis, HIV) to study TFEB activation.

Main Results:

• IRGM directly interacts with TFEB, promoting its nuclear translocation.
• GABARAP, an mAtg8 partner, also interacts with TFEB.
• Deletion of mAtg8s or GABARAPs impairs transcriptional responses to starvation and downregulates TFEB targets.
• IRGM and GABARAPs counteract mTOR's negative regulation of TFEB.
• TFEB activation during M. tuberculosis and HIV infection is IRGM-dependent.

Conclusions:

• IRGM and mAtg8s form a regulatory loop connecting the autophagosomal pathway with TFEB-mediated lysosomal biogenesis.
• This pathway ensures coordinated activation of autophagy and lysosomal systems.
• The findings highlight a novel mechanism for integrating cellular stress responses and lysosomal function.