IRGM links autoimmunity to autophagy

Area of Science:

• Immunology
• Genetics
• Cell Biology

Background:

• Interferon (IFN) response dysregulation is implicated in autoimmune disease pathogenesis.
• The precise mechanism of IRGM's protective role in autoimmunity is unclear.
• IRGM is a known genetic risk factor for multiple autoimmune conditions.

Purpose of the Study:

• To elucidate the mechanism by which IRGM suppresses the type I interferon response.
• To investigate the role of IRGM in regulating nucleic acid sensor pathways and mitochondrial homeostasis in the context of autoimmunity.

Main Methods:

• Investigated the impact of IRGM depletion on CGAS-STING1, DDX58/RIG-I-MAVS, and TLR3-TICAM1/TRIF signaling pathways.
• Utilized SQSTM1/p62-dependent selective autophagy and mitophagy to assess IRGM's suppressive functions.
• Analyzed the upregulation of IFN-responsive genes and the accumulation of danger-associated molecular patterns (DAMPs).

Main Results:

• IRGM acts as a master suppressor of the interferon response.
• IRGM depletion leads to constitutive activation of key nucleic acid sensor pathways (CGAS-STING1, DDX58/RIG-I-MAVS, TLR3-TICAM1/TRIF).
• IRGM mediates autophagy of nucleic acid sensors and mitophagy of damaged mitochondria, preventing DAMPs and ROS accumulation.

Conclusions:

• IRGM employs a dual mechanism involving autophagy and mitophagy to suppress aberrant interferon activation.
• IRGM deficiency creates a cycle of increased nucleic acid sensors and DAMPs, promoting autoimmune conditions.
• Understanding IRGM's function offers potential therapeutic targets for autoimmune diseases.