Nod2, a Nod1/Apaf-1 family member that is restricted to monocytes and activates NF-kappaB.
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Apaf-1 and Nod1 are members of a protein family, each of which contains a caspase recruitment domain (CARD) linked to a nucleotide-binding domain, which regulate apoptosis and/or NF-kappaB activation. Nod2, a third member of the family, was identified. Nod2 is composed of two N-terminal CARDs, a nucleotide-binding domain, and multiple C-terminal leucine-rich repeats. Although Nod1 and Apaf-1 were broadly expressed in tissues, the expression of Nod2 was highly restricted to monocytes. Nod2 induced nuclear factor kappaB (NF-kappaB) activation, which required IKKgamma and was inhibited by dominant negative mutants of IkappaBalpha, IKKalpha, IKKbeta, and IKKgamma. Nod2 interacted with the serine-threonine kinase RICK via a homophilic CARD-CARD interaction. Furthermore, NF-kappaB activity induced by Nod2 correlated with its ability to interact with RICK and was specifically inhibited by a truncated mutant form of RICK containing its CARD. The identification of Nod2 defines a subfamily of Apaf-1-like proteins that function through RICK to activate a NF-kappaB signaling pathway. (+info)
The NOD: a signaling module that regulates apoptosis and host defense against pathogens.
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Nods, a growing family of proteins containing a nucleotide-binding oligomerization domain (NOD), are involved in the regulation of programmed cell death (PCD) and immune responses. Members of the family include Apaf-1, Ced-4, Nod1, Nod2, and the cytosolic products of plant disease resistance genes. The NOD module is homologous to the ATP-binding cassette (ABC) found in a large number of proteins with diverse biological function. The centrally located NOD promotes activation of effector molecules through self-association and induced proximity of binding partners. The C-terminal domain of Nods serves as a sensor for intracellular ligands, whereas the N-terminal domain mediates binding to dowstream effector molecules and activation of diverse signaling pathways. Thus, Nods activate, through the NOD module, diverse signaling pathways involved in the elimination of cells via PCD and the host defense against pathogens. (+info)
Evidence for a NOD2-independent susceptibility locus for inflammatory bowel disease on chromosome 16p.
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Heritable predisposition to inflammatory bowel disease (IBD) has been demonstrated by epidemiological and genetic analysis. Linkage of IBD to broad regions of chromosome 16 has been established by analysis of multiple populations. NOD2, located on proximal 16q, was recently identified as an IBD gene. As the linkage regions on chromosome 16 are large, we have investigated the possibility that NOD2 is not the only IBD gene located on this chromosome. A high-density experiment using 39 microsatellite markers was performed to identify additional regions of association, and to indicate areas of interest for further investigation. A triple-peaked configuration of the linkage curve with peak logarithm of odds (lod) scores of 2.7, 3.2, and 3.1 was observed on proximal 16p, proximal 16q, and central 16q, respectively. The cohort was stratified by coding individuals carrying the NOD2 single nucleotide polymorphism (SNP)8 and SNP13 "unknown." Significance at the central peak, corresponding to the genomic location of NOD2, then decreased from 3.2 to 1.2. The maximal lod scores on the proximal p-arm (lod = 2.1) and central q-arm (lod = 2.6) changed only moderately. An exploratory association analysis (TRANSMIT) yielded a strong lead at D16S3068 (P = 0.00028). The region around this marker was further investigated by using anonymous SNPs. An associated haplotype containing three SNPs was identified (peak significance P = 0.00027, IBD phenotype). On stratification based on NOD2 genotype, this significance increased to P = 0.0001. These results confirm the importance of NOD2 and provide evidence for a second IBD gene located on chromosome 16p. (+info)
CARD15/NOD2 mutational analysis and genotype-phenotype correlation in 612 patients with inflammatory bowel disease.
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CARD15/NOD2 encodes a protein involved in bacterial recognition by monocytes. Mutations in CARD15 have recently been found in patients with Crohn disease (CD), a chronic inflammatory condition of the digestive tract. Here, we report the mutational analyses of CARD15 in 453 patients with CD, including 166 sporadic and 287 familial cases, 159 patients with ulcerative colitis (UC), and 103 healthy control subjects. Of 67 sequence variations identified, 9 had an allele frequency >5% in patients with CD. Six of them were considered to be polymorphisms, and three (R702W, G908R, and 1007fs) were confirmed to be independently associated with susceptibility to CD. Also considered as potential disease-causing mutations (DCMs) were 27 rare additional mutations. The three main variants (R702W, G908R, and 1007fs) represented 32%, 18%, and 31%, respectively, of the total CD mutations, whereas the total of the 27 rare mutations represented 19% of DCMs. Altogether, 93% of the mutations were located in the distal third of the gene. No mutations were found to be associated with UC. In contrast, 50% of patients with CD carried at least one DCM, including 17% who had a double mutation. This observation confirmed the gene-dosage effect in CD. The patients with double-dose mutations were characterized by a younger age at onset (16.9 years vs. 19.8 years; P=.01), a more frequent stricturing phenotype (53% vs. 28%; P=.00003; odds ratio 2.92), and a less frequent colonic involvement (43% vs. 62%; P=.003; odds ratio 0.44) than were seen in those patients who had no mutation. The severity of the disease and extraintestinal manifestations were not different for any of the CARD15 genotypes. The proportion of familial and sporadic cases and the proportion of patients with smoking habits were similar in the groups of patients with CD with or without mutation. These findings provide tools for a DNA-based test of susceptibility and for genetic counseling in inflammatory bowel disease. (+info)
CARD15 genetic variation in a Quebec population: prevalence, genotype-phenotype relationship, and haplotype structure.
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The caspase recruitment domain gene (CARD15) was recently identified as the underlying gene associated with the IBD1 locus that confers susceptibility to Crohn disease (CD). CARD15 is related to the NOD1/Apaf-1 family of apoptosis regulators, and three sequence variants (Arg702Trp, Gly908Arg, and Leu1007fsinsC) in the gene were demonstrated to be associated with CD. We collected a cohort of 231 patients with CD and 71 healthy control individuals from the Canadian province of Quebec, to determine the prevalence of these sequence variants in an independent population. Clinical records of all patients were systematically reviewed, and detailed phenotypic information was obtained. All patient DNA samples were genotyped for the three variants, thus enabling an analysis of genotype-phenotype correlations. In this cohort, 45.0% of patients with CD carried at least one variant in the CARD15 gene, compared with 9.0% of control individuals (P<10-7). Allele frequencies of Arg702Trp, Gly908Arg, and Leu1007fsinsC were 12.9%, 5.2%, and 10.3% in patients with CD, compared with 4.2%, 0.7%, and 0.7% in control individuals, respectively. Importantly, CARD15 mutants were seen with equal frequency in patients with familial and sporadic CD. Analysis of the relationship between genotype and phenotype convincingly demonstrates that CARD15 variants are significantly associated with ileal disease involvement, as opposed to strictly colonic disease (P<.001). Moreover, we were able to determine the haplotype structure surrounding this disease gene by genotyping 45 single-nucleotide polymorphisms (SNPs) in a 177-kb region that contained the CARD15 gene. This structure helps clarify the history of these causal mutations. Finally, this analysis shows that CARD15 involvement with CD is detectable by use of publicly available SNPs alone. (+info)
Role of NOD2 variants in spondylarthritis.
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OBJECTIVE: To investigate the role of the gene NOD2 in susceptibility to, and clinical manifestations of, ankylosing spondylitis (AS). METHODS: A case-control study of NOD2 polymorphisms known to be associated with Crohn's disease (CD) (Pro(268)Ser, Arg(702)Trp, Gly(908)Arg, and Leu(1007)fsinsC) was performed in 229 cases of primary AS with no diagnosed inflammatory bowel disease (IBD), 197 cases of AS associated with IBD (referred to as colitic spondylarthritis; comprising 78 with CD and 119 with ulcerative colitis [UC]), and 229 ethnically matched, healthy controls. Associations between NOD2 polymorphisms and several clinical features of AS, including disease severity assessed by questionnaire and age at spondylarthritis onset, were also investigated. Exclusion linkage mapping of chromosome 16 was performed in a separate group of 185 multicase families with AS. RESULTS: An association was identified between Gly(908)Arg and UC spondylarthritis (P = 0.016, odds ratio [OR] 4.6, 95% confidence interval [95% CI] 1.3-16), and a nonsignificant trend with a similar magnitude was observed in association with CD spondylarthritis (P = 0.08, OR 3.9, 95% CI 0.8-18). The Pro(268)Ser variant was inversely associated with UC spondylarthritis (P = 0.003, OR 0.55, 95% CI 0.37-0.82), but not with CD spondylarthritis. No association was demonstrated between NOD2 variants and primary AS, or between other variants of NOD2 and either UC or CD spondylarthritis. Carriage of the Pro(268)Ser polymorphism was associated with greater disease activity as measured by the Bath Ankylosing Spondylitis Disease Activity Index (P = 0.002). Although patients with CD had a younger age at spondylarthritis onset than did those with UC (22.4 years versus 26.4 years; P = 0.01), no association was noted between the NOD2 variants linked with CD and age at spondylarthritis onset. In primary AS, the presence of a gene with a magnitude of association >2.0 was excluded (exclusion logarithm of odds score less than -2.0), and no association was observed with the microsatellite D16S3136. CONCLUSION: NOD2 variants do not significantly affect the risk of developing primary AS, but may influence susceptibility to, and clinical manifestations of, colitic spondylarthritis. (+info)
Induction of Nod2 in myelomonocytic and intestinal epithelial cells via nuclear factor-kappa B activation.
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Nod2, a member of the Apaf1/Nod protein family, confers responsiveness to bacterial products and activates NF-kappaB, a transcription factor that plays a central role in innate immunity. Recently, genetic variation in Nod2 has been associated with susceptibility to Crohn's disease. Here, we report that expression of Nod2 is induced upon differentiation of CD34(+) hematopoietic progenitor cells into granulocyte or monocyte/macrophages. In peripheral blood cells, the highest levels of Nod2 were observed in CD14(+) (monocytes), CD15(+) (granulocytes), and CD40(+)/CD86(+) (dendritic cells) cell populations. Notably, stimulation of myeloblastic and epithelial cells with bacterial lipopolysaccharide or TNFalpha resulted in up-regulation of Nod2. A search for consensus sites within the Nod2 promoter revealed a NF-kappaB binding element that was required for transcriptional activity in response to TNFalpha. Moreover, ectopic expression of p65 induced transactivation, whereas that of dominant-negative IkappaBalpha blocked the transcriptional activity of the Nod2 promoter. Upon stimulation with TNFalpha or lipopolysaccharide, both p50 and p65 subunits of NF-kappaB were bound to the Nod2 promoter. Thus, Nod2 expression is enhanced by proinflammatory cytokines and bacterial components via NF-kappaB, a mechanism that may contribute to the amplification of the innate immune response and susceptibility to inflammatory disease. (+info)
The CARD15 2936insC mutation and TLR4 896 A>G polymorphism in African Americans and risk of preterm premature rupture of membranes (PPROM).
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Infection is believed to be a leading cause of preterm premature rupture of membranes (PPROM). The bacterial cell wall component, lipopolysaccharide (LPS), is thought to initiate tissue responses leading to PPROM in the setting of Gram negative infection. LPS is recognized by the innate immune system, including the proteins encoded by the CARD15 and TLR4 genes. A recently described mutation (2936insC) in CARD15 and a polymorphism in TLR4 896 A>G impair responses to LPS. The objective of this study was to determine if African Americans, who have a higher incidence of PPROM than Caucasians, have different frequencies of the mutant CARD15 allele and the TLR4 hyporesponsive variant, and if risk of PPROM is influenced by fetal carriage of these alleles. The allele frequencies for the CARD15 mutation and the TLR4 896G variant in African Americans were similar to those reported for Caucasians. There was no association between the TLR4 alleles examined and PPROM. However, the CARD15 mutation was only detected in controls and not in PPROM cases. We conclude that the CARD15 mutation and hyporesponsive TLR4 allele do not contribute to ethnic variation in the incidence of PPROM. (+info)