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

• Published in: The Journal of clinical investigation 2018-05, Vol.128 (5), p.1793-1806
• Main Authors: Mao, Liming, Kitani, Atsushi, Similuk, Morgan, Oler, Andrew J, Albenberg, Lindsey, Kelsen, Judith, Aktay, Atiye, Quezado, Martha, Yao, Michael, Montgomery-Recht, Kim, Fuss, Ivan J, Strober, Warren
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Biomedical research; CARD Signaling Adaptor Proteins - genetics; CARD Signaling Adaptor Proteins - immunology; Care and treatment; Caspases; Crohn Disease - genetics; Crohn Disease - immunology; Crohn Disease - pathology; Crohn's disease; Dephosphorylation; Development and progression; Female; Gene mutation; Genetic aspects; Health aspects; HEK293 Cells; Humans; Inflammasomes; Inflammasomes - genetics; Inflammasomes - immunology; Inflammatory bowel disease; Interleukin-1beta - genetics; Interleukin-1beta - immunology; Kinases; Loss of Function Mutation; Male; Missense mutation; Monocytes; Monocytes - immunology; Monocytes - pathology; Mutation; Mutation, Missense; Neoplasm Proteins - genetics; Neoplasm Proteins - immunology; NLR Family, Pyrin Domain-Containing 3 Protein - genetics; NLR Family, Pyrin Domain-Containing 3 Protein - immunology; Oligomerization; Phosphorylation - genetics; Phosphorylation - immunology; Protein Isoforms - genetics; Protein Isoforms - immunology; Rodents; Serine; Serum levels; Tumor necrosis factor-α; Ubiquitination - genetics; Ubiquitination - immunology; Whole Genome Sequencing
• ISSN: 0021-9738; 1558-8238; 1558-8238
• DOI: 10.1172/jci98642

In these studies, we evaluated the contribution of the NLRP3 inflammasome to Crohn's disease (CD) in a kindred containing individuals having a missense mutation in CARD8, a protein known to inhibit this inflammasome. Whole exome sequencing and PCR studies identified the affected individuals as having a V44I mutation in a single allele of the T60 isoform of CARD8. The serum levels of IL-1β in the affected individuals were increased compared with those in healthy controls, and their peripheral monocytes produced increased amounts of IL-1β when stimulated by NLRP3 activators. Immunoblot studies probing the basis of these findings showed that mutated T60 CARD8 failed to downregulate the NLRP3 inflammasome because it did not bind to NLRP3 and inhibit its oligomerization. In addition, these studies showed that mutated T60 CARD8 exerted a dominant-negative effect by its capacity to bind to and form oligomers with unmutated T60 or T48 CARD8 that impeded their binding to NLRP3. Finally, inflammasome activation studies revealed that intact but not mutated CARD8 prevented NLRP3 deubiquitination and serine dephosphorylation. CD due to a CARD8 mutation was not effectively treated by anti-TNF-α, but did respond to IL-1β inhibitors. Thus, patients with anti-TNF-α-resistant CD may respond to this treatment option.