Deficiency of the NF-kappaB inhibitor caspase activating and recruitment domain 8 in patients with rheumatoid arthritis is associated with disease severity.
Caspase activating and recruitment domain 8 (CARD8) potently inhibits NF-kappaB signaling, which plays a key role in inflammation, and may contribute to avoid a pathologic activation of NF-kappaB; however, the transcriptional mechanisms regulating CARD8 expression and the relevance of this protein in inflammatory diseases are poorly understood. We found a NF-kappaB-binding element within the human CARD8 promoter that was required for transcriptional activity in response to TNF-alpha and the p65 subunit of NF-kappaB. Moreover, TNF-alpha and overexpression of p65 induced the formation of NF-kappaB-CARD8 promoter complexes. Thus, CARD8 may control NF-kappaB 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-kappaB transcriptional activity, and abrogates the binding of NF-kappaB to its consensus site. Furthermore, in contrast to the full-length protein, CARD8-S did not modify the expression of NF-kappaB target genes (cIAP, A1), in response to TNF-alpha. 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-kappaB, and suggest that a deleterious polymorphism of CARD8 may help predict the severity of RA.
Fontalba
Ana
A
Unidad de Genetica Molecular, Hospital Universitario Marques de Valdecilla, Santander, Spain.
Martinez-Taboada
Victor
V
Gutierrez
Olga
O
Pipaon
Carlos
C
Benito
Natividad
N
Balsa
Alejandro
A
Blanco
Ricardo
R
Fernandez-Luna
Jose L
JL
D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011110:Polymorphism, Genetic / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000235:genetics
D053468:CARD Signaling Adaptor Proteins; C455623:CARD8 protein, human; D016328:NF-kappa B; D009363:Neoplasm Proteins