Loss-of-function CARD8 mutation causes NLRP3 inflammasome activation and Crohn's disease

Area of Science:

• Immunology
• Genetics
• Gastroenterology

Background:

• The NLRP3 inflammasome plays a role in inflammatory diseases.
• CARD8 is a known inhibitor of the NLRP3 inflammasome.

Purpose of the Study:

• To investigate the role of a CARD8 mutation in Crohn's disease (CD).
• To understand the mechanism by which the CARD8 mutation affects NLRP3 inflammasome activity.

Main Methods:

• Whole exome sequencing and PCR to identify the CARD8 mutation (V44I in T60 isoform).
• Measurement of serum and monocyte IL-1β levels.
• Immunoblotting to assess CARD8-NLRP3 interactions and inflammasome regulation.
• Inflammasome activation studies to evaluate CARD8's effect on NLRP3 deubiquitination and phosphorylation.

Main Results:

• Affected individuals with the CARD8 V44I mutation showed increased IL-1β levels.
• Mutated CARD8 failed to inhibit NLRP3 inflammasome oligomerization and exerted a dominant-negative effect.
• Intact CARD8 prevented NLRP3 deubiquitination and serine dephosphorylation, a function lost in the mutated form.
• CD in this kindred was resistant to anti-TNF-α therapy but responsive to IL-1β inhibitors.

Conclusions:

• A specific CARD8 mutation contributes to Crohn's disease pathogenesis through NLRP3 inflammasome dysregulation.
• The findings highlight the importance of the CARD8-NLRP3 interaction in intestinal inflammation.
• IL-1β inhibition represents a potential therapeutic strategy for anti-TNF-α-resistant CD associated with CARD8 mutations.