Deficiency of the NF-κB Inhibitor Caspase Activating and Recruitment Domain 8 in Patients with Rheumatoid Arthritis Is Associated with Disease Severity

Abstract

Caspase activating and recruitment domain 8 (CARD8) potently inhibits NF-κB signaling, which plays a key role in inflammation, and may contribute to avoid a pathologic activation of NF-κB; however, the transcriptional mechanisms regulating CARD8 expression and the relevance of this protein in inflammatory diseases are poorly understood. We found a NF-κB-binding element within the human CARD8 promoter that was required for transcriptional activity in response to TNF-α and the p65 subunit of NF-κB. Moreover, TNF-α and overexpression of p65 induced the formation of NF-κB-CARD8 promoter complexes. Thus, CARD8 may control NF-κB activation through a regulatory loop. To study the relevance of CARD8 in chronic inflammatory disorders, we functionally characterized a deleterious polymorphism (p.C10X) and studied its association with rheumatoid arthritis (RA). Transfection of cell lines with the allelic variants of CARD8 revealed that full-length (CARD8-L) but not truncated (CARD8-S) protein inhibits NF-κB transcriptional activity, and abrogates the binding of NF-κB to its consensus site. Furthermore, in contrast to the full-length protein, CARD8-S did not modify the expression of NF-κB target genes (cIAP, A1), in response to TNF-α. We analyzed the p.C10X polymorphism in 200 patients with RA, and found that homozygous carriers of the CARD8-S allele have higher disease activity score (p = 0.014), more extra-articular manifestations (p = 0.03), and a lower probability of clinical remission (p = 0.03) than the CARD8-L allele carriers. Overall, our findings provide molecular insight into the expression of CARD8 by NF-κB, and suggest that a deleterious polymorphism of CARD8 may help predict the severity of RA.

Functional genetic screen of human diversity reveals that a methionine salvage enzyme regulates inflammatory cell death

“…Lymphoblastoid cell lines (LCLs), collected and genotyped as part of the HapMap Project (23), were assayed for pyroptosis and other quantitative phenotypes of host response. Previously, we used Hi-HOST to show that a known nonsense mutation in the CARD8 gene, a reported caspase-1 inhibitor (24) associated with severity of rheumatoid arthritis (25), modulates cell death in response to S. typhimurium (18). In the report presented here, Hi-HOST was used as a true discovery tool to uncover variation altering expression of apoptotic protease activating factor 1 (APAF1)-interacting protein (APIP; National Center for Biotechnology Information gene 51074), a gene previously not known to regulate pyroptosis or be associated with phenotypic variation.…”

CARD8 rs2043211 Polymorphism is Associated with Gout in a Chinese Male Population

“…NALP3 inflammasome contains NALP3, apoptosis-associated speck (ASC)-like protein and caspase activation and recruitment domain 8 (CARD8) [11,12]. Recent studies suggest that CARD8 functional mutations contribute to the development of autoinflammatory diseases including inflammatory bowel disease, rheumatoid arthritis, and Alzheimer's disease [13,14,15,16,17]. CARD8 is a component of innate immunity involved in the suppression of NF-κB (nuclear factor κB) activation [13,16].…”

A Truncated Variant of ASCC1, a Novel Inhibitor of NF-κB, Is Associated with Disease Severity in Patients with Rheumatoid Arthritis

“…The RIPK3 SNP rs146886719 introduces a stop codon at position 422, within the proline-rich region, but main- tains the protein kinase domain. The CARD8 SNP rs2043211 codes for a protein of only 10 aa from the N terminus and has been previously associated with disease severity in RA patients (17). Finally, ASCC1 SNP rs11000217 introduces a stop codon at amino acid position 78 (p.S78*) that deletes all predicted domains of the protein (Fig.…”

“…Previous work has also identified variants of MYD88 and TNFRSF11A that promote constitutive activation of NF-kB (15,16). Our group has previously described that a truncating variant that abrogates the capacity of CARD8 to inhibit the NF-kB transcriptional activity is associated with disease severity in RA patients (17).…”