Deficiency for SAMHD1 activates MDA5 in a cGAS/STING-dependent manner

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Defects in nucleic acid metabolizing enzymes can activate cGAS/STING or RLR signaling, leading to type I interferonopathies.
• Tonic type I interferon signaling is crucial for priming nucleic acid sensing pathways.

Purpose of the Study:

• To investigate the role of SAMHD1 deficiency and chronic DNA damage in innate immune priming and disease pathogenesis.
• To elucidate the interplay between cGAS/STING, MDA5/MAVS, and tonic interferon signaling in the context of DNA damage.

Main Methods:

• Utilized SAMHD1-deficient mice, crossed with p53-deficient or DNA mismatch repair-deficient backgrounds.
• Assessed tumor-free survival and type I interferon levels.
• Investigated the involvement of cGAS/STING and MDA5/MAVS pathways in interferon responses.

Main Results:

• Low-level chronic DNA damage in SAMHD1-deficient mice reduced tumor-free survival in a p53-dependent manner.
• Increased DNA damage did not elevate type I interferon levels.
• Chronic interferon response was mediated by MDA5/MAVS but required cGAS/STING pathway priming.

Conclusions:

• cGAS/STING pathway acts upstream of tonic interferon signaling in SAMHD1-deficient mice.
• Highlights the critical role of cGAS/STING in both physiological and pathophysiological innate immune priming.
• SAMHD1 deficiency and chronic DNA damage create a unique inflammatory environment impacting immune responses.