Loss-of-function CARD8 mutation causes NLRP3 inflammasome activation and Crohn’s disease
Liming Mao, … , Ivan J. Fuss, Warren Strober
Liming Mao, … , Ivan J. Fuss, Warren Strober
Published February 6, 2018
Citation Information: J Clin Invest. 2018;128(5):1793-1806. https://doi.org/10.1172/JCI98642.
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Research Article Gastroenterology

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

Abstract

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.

Authors

Liming Mao, Atsushi Kitani, Morgan Similuk, Andrew J. Oler, Lindsey Albenberg, Judith Kelsen, Atiye Aktay, Martha Quezado, Michael Yao, Kim Montgomery-Recht, Ivan J. Fuss, Warren Strober

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Figure 1

A kindred with family members bearing a CARD8 mutation and CD-like intestinal inflammation.

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A kindred with family members bearing a CARD8 mutation and CD-like intes...
(A) A kindred containing 3 members bearing a CARD8 mutation. In all 3 members of the kindred, the proband (Pt), his mother (Pt M), and his maternal aunt (Pt Aunt), the mutation occurred in association with a CD-like intestinal inflammation. (B) Macroscopic examination of the colon exhibited scattered areas of superficial erythema and ulceration having a lenticular pattern especially evident in the rectosigmoid region. n = 3/group. (C–I) Biopsies from the terminal ileum and colon. (C) Index patient colon. Colitis with epithelial erosive changes and inflammation, significant crypt and goblet cell loss with regenerative changes. Features consistent with GvHD. (D) Index patient colon. Colitis with rare residual gland showing goblet cell loss, repair changes, and rare apoptotic bodies (arrow). (E) Index patient terminal ileum. Ileitis with focal erosion, villi loss, lymphocytic infiltrates, severe crypt drop-out, and repair changes. (F) Index patient terminal ileum. Chronic active ileitis with regenerative changes and poorly formed granulomas including giant cells. (G) Index patient terminal ileum. Poorly formed granuloma (arrow) with giant cells. Adjacent glands with repair/regenerative changes. (H) Aunt terminal ileum. Transmural lymphocyte infiltration with well-formed granuloma present. (I) Aunt terminal ileum. Well-formed granuloma (arrow). n = 3/group. Original magnification, ×4 (C, E, H); ×10 (F, I); ×20 (D, G). Parts G and I show higher magnification of boxed areas in F and H, respectively. (J) Anakinra therapy resulted in rapid clinical improvement marked by decreased fecal calprotectin levels. Data are representative of 3 independent experiments. (K) Whole exome sequencing revealed a CARD8 V44I mutation in 1 allele of chromosome 19 (see sequencing data in the text). The mutation site of V44I was present on the CARD8 T60 isoform, but not the “canonical” T48 isoform.