USP21 Deubiquitinase Regulates AIM2 Inflammasome Activation

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Innate immune sensing of cytosolic DNA by absent in melanoma 2 (AIM2) is crucial for inflammatory responses.
• Dysregulated AIM2 activity is linked to autoinflammatory diseases, necessitating tight control over AIM2 inflammasome activation.

Purpose of the Study:

• To investigate the role of ubiquitination and deubiquitination in regulating AIM2 inflammasome activation.
• To identify specific enzymes involved in the post-translational modification of AIM2.

Main Methods:

• Studied ubiquitination and deubiquitination of AIM2 in human macrophage cells.
• Utilized techniques to assess AIM2 protein stability, DNA-binding ability, and inflammasome complex formation.
• Depleted USP21 to evaluate its impact on AIM2 function.

Main Results:

• AIM2 undergoes constitutive ubiquitination and proteasomal degradation in resting macrophages.
• USP21 binds to AIM2 upon DNA stimulation, leading to deubiquitination and increased protein stability.
• USP21-mediated deubiquitination is essential for AIM2-ASC complex assembly, but not for AIM2 DNA binding.

Conclusions:

• Ubiquitination and deubiquitination are critical regulatory events for AIM2 inflammasome activation.
• USP21 plays a dual role in controlling AIM2 by regulating its stability and promoting inflammasome assembly.
• Fine-tuning of AIM2 by the ubiquitin system is vital for preventing aberrant inflammatory responses.