A common functional variant of endoplasmic reticulum aminopeptidase 2 (ERAP2) that reduces major histocompatibility complex class I expression is not associated with ankylosing spondylitis

Association of the genetic variants in the endoplasmic reticulum aminopeptidase 2 gene with ankylosing spondylitis susceptibility

BACKGROUND

Genetic polymorphisms in the endoplasmic reticulum aminopeptidase gene ERAP2 has been attributed with the etiopathogenesis of ankylosing spondylitis (AS). Here we assessed the association of ERAP2 gene single nucleotide polymorphisms (SNPs) with AS predisposition in Iranian patients and determined their effect on the inflammatory state of the patients.

METHODS

For genotyping of rs2548538, rs2287988, and rs17408150 SNPs using a real-time allelic discrimination approach, DNA was extracted from the whole blood of 250 AS patients and 250 healthy individuals. RNA of the peripheral blood mononuclear cells was separated, cDNA was synthesized, and transcriptional levels of cytokines, including interleukin (IL)-17A, IL-23, IL-10, and transforming growth factor-β, were measured. Enzyme-linked immunosorbent assay was used to measure the serum concentration on the cytokines.

RESULTS

Three ERAP2 gene SNPs were not associated significantly with AS risk. Nonetheless, rs2287988 and rs17408150 SNPs showed statistically significant association with susceptibility to the disease in those AS patients who were positive for human leukocyte antigen (HLA)-B27. Transcriptional level and serum concentration of IL-17A and IL-23 were higher, but those of IL-10 were lower in both AS patients and the HLA-B27-positive patient group relative to the control group. Nevertheless, ERAP2 gene SNPs in the HLA-B27-positive AS patients did not affect the transcription level and serum concentration of cytokines.

CONCLUSIONS

ERAP2 gene rs2287988 and rs17408150 SNPs are associated with susceptibility to AS, but they are probably not determining the levels of IL-17A, IL-23, and IL-10 in this disease.

Lack of Associations between Endoplasmic Reticulum Aminopeptidase 2 Gene Polymorphisms and Ankylosing Spondylitis: A Meta-analysis with Trial Sequential Analysis

Background: Endoplasmic reticulum aminopeptidase 2 (ERAP2) gene is reported to be associated with inflammation-related diseases. Several studies have investigated the associations of ERAP2 gene polymorphisms and susceptibility to ankylosing spondylitis (AS). However, the findings of those studies were inconsistent. The aim of this study was to elucidate the associations by a meta-analysis with trial sequential analysis (TSA).Methods: Online databases of PubMed, Web of Science, EMBASE, Cochrane Library, Wanfang, and CNKI were searched to identify eligible studies on the associations of ERAP2 gene polymorphisms and AS. Study quality was judged based on the Newcastle-Ottawa scale (NOS). Strengths of associations were presented by P-value, odds ratios (ORs), and 95% confidence intervals (95%CIs). TSA was employed to evaluate the information size and statistical power.Results: A total of six studies encompassing 2774 AS patients and 4119 disease-free controls were eligible for this meta-analysis. Five studies reported rs2248374 polymorphism and three studies reported rs2549782 polymorphism. The pooled data suggested that the two polymorphisms were not significantly associated with AS susceptibility: rs2248374, A vs. G, OR = 0.94, 95%CI 0.86-1.02, P = .14; rs2549782, T vs. G, OR = 1.03, 95%CI 0.95-1.12, P = .45. TSA indicated that the sample sizes appeared to be inadequate to obtain a positive outcome.Conclusion: The present findings of this study do not support any evidence on the associations of rs2248374 and rs2549782 polymorphisms in the ERAP2 gene and susceptibility to AS. Additional well-designed and large-sample studies in diverse ethnicities are encouraged to validate the current findings.

Endoplasmic reticulum aminopeptidase 2 gene single nucleotide polymorphisms in association with susceptibility to ankylosing spondylitis in an Iranian population

BACKGROUND

Ankylosing spondylitis (AS) is a chronic autoimmune disease, in which genetic polymorphisms are critically important in establishing inflammatory state. Endoplasmic reticulum aminopeptidase (ERAP) 2 gene has been implied to be involved in AS etiopathogenesis. The current study evaluated the association of ERAP2 gene single nucleotide polymorphisms (SNPs) with susceptibility to AS in an Iranian population.

METHODS

Two hundred and forty AS patients and 240 healthy individuals were recruited. DNA extraction was performed from whole blood samples and RNA content was isolated from peripheral blood mononuclear cells (PBMCs). Real-time allelic discrimination approach was exerted to genotype all subjects for rs2910686, rs2248374, and rs2549782 SNPs. After cDNA synthesis, mRNA expression of cytokines was determined. Enzyme-linked immunosorbent assay (ELISA) was exerted to evaluate the cytokine levels in serum of participants.

RESULTS

None of the SNPs were associated with AS risk in the whole population. However, allele and heterozygote genotype of rs2910686 SNP were associated significantly with higher risk of AS in Human leukocyte antigen (HLA)-B27 positive group. mRNA expression and serum concentrations of interleukin (IL)-17A, IL-23, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α was increased in AS patients compared with controls. Nonetheless, mRNA expression and serum levels of cytokines was not significantly different among HLA-B27 positive AS patients with different three genotypes for rs2910686 SNP.

CONCLUSIONS

AlthoughERAP2 gene rs2910686 polymorphism was significantly associated with increased risk of AS susceptibility, it might not be involved in regulation of the inflammatory cytokines during AS pathogenesis.

Influence of ERAP1 and ERAP2 gene polymorphisms on disease susceptibility in different populations

The endoplasmic reticulum aminopeptidases (ERAPs), ERAP1 and ERAP2, makes a role in shaping the HLA class I peptidome by trimming peptides to the optimal size in MHC-class I-mediated antigen presentation and educating the immune system to differentiate between self-derived and foreign antigens. Association studies have shown that genetic variations in ERAP1 and ERAP2 genes increase susceptibility to autoimmune diseases, infectious diseases, and cancers. Both ERAP1 and ERAP2 genes exhibit diverse polymorphisms in different populations, which may influence their susceptibly to the aforementioned diseases. In this article, we review the distribution of ERAP1 and ERAP2 gene polymorphisms in various populations; discuss the risk or protective influence of these gene polymorphisms in autoimmune diseases, infectious diseases, and cancers; and highlight how ERAP genetic variations can influence disease associations.

Molecular impact of selective NFKB1 and NFKB2 signaling on DLBCL phenotype

Diffuse large B-cell lymphoma (DLBCL) has been categorized into two molecular subtypes that have prognostic significance, namely germinal center B-cell like (GCB) and activated B-cell like (ABC). Although ABC-DLBCL has been associated with NF-κB activation, the relationships between activation of specific NF-κB signals and DLBCL phenotype remain unclear. Application of novel gene expression classifiers identified two new DLBCL categories characterized by selective p100 (NF-κB2) and p105 (NF-κB1) signaling. Interestingly, our molecular studies showed that p105 signaling is predominantly associated with GCB subtype and histone mutations. Conversely, most tumors with p100 signaling displayed ABC phenotype and harbored ABC-associated mutations in genes such as MYD88 and PIM1. In vitro, MYD88 L265P mutation promoted p100 signaling through TAK1/IKKα and GSK3/Fbxw7a pathways, suggesting a novel role for this protein as an upstream regulator of p100. p100 signaling was engaged during activation of normal B cells, suggesting p100's role in ABC phenotype development. Additionally, silencing p100 in ABC-DLBCL cells resulted in a GCB-like phenotype, with suppression of Blimp, IRF4 and XBP1 and upregulation of BCL6, whereas introduction of p52 or p100 into GC cells resulted in differentiation toward an ABC-like phenotype. Together, these findings identify specific roles for p100 and p105 signaling in defining DLBCL molecular subtypes and posit MYD88/p100 signaling as a regulator for B-cell activation.

New insights toward the pathogenesis of ankylosing spondylitis; genetic variations and epigenetic modifications

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, characterized by typically an axial arthritis. AS is the prototype of a group of disorders called spondyloarthropathies, which is believed to have common clinical manifestations and genetic predisposition. To date, the exact etiology of AS remains unclear. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused through environmental factors have been extensively surveyed with respect to the pathogenesis of AS, resulted in important advances. This review article focuses on the recent advances in the field of AS research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with AS. HLA genes most significantly linked with AS susceptibility include HLA-B27 and its subtypes. Numerous non-HLA genes such as those in ubiquitination, aminopeptidases and MHC class I presentation molecules like ERAP-1 were also reported. Moreover, epigenetic modifications occurred in AS has been summarized. Taken together, the findings presented in this review attempt to explain the circumstance by which both genetic variations and epigenetic modifications are involved in triggering and development of AS. Nonetheless, several unanswered dark sides continue to clog our exhaustive understanding of AS. Future researches in the field of epigenetics should be carried out to extend our vision of AS etiopathogenesis.

Endoplasmic reticulum aminopeptidase 1 and rheumatic disease: functional variation

PURPOSE OF REVIEW

To review the recent developments in our understanding of endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) function in relation to its role in major histocompatibility complex (MHC) class I peptide presentation and human leukocyte antigen (HLA) class I-associated diseases.

RECENT FINDINGS

ERAP1 polymorphisms exhibiting loss-of-function have been associated with protection from AS. The aminopeptidase function of ERAP1 optimizes peptides for binding and presentation by MHC class I. Most of the studies have revealed reduced MHC class I expression in situations of reduced ERAP1 function. Under these circumstances, the presented peptides are often N-terminally extended, and cell surface complexes are unstable and fall apart more readily. In contrast, peptides presented by HLA-B*27 : 05 when ERAP1 is silenced are frequently extended on the C-terminus. Recent work has emphasized on the importance of assessing the function of allotypes encoded by ERAP1 haplotypes, rather than effects of single amino acid substitutions. The allotypes found in a series of AS patients were poorer at restoring HLA-B27 expression than allotypes found in unaffected controls, which may seem contrary to the genetic data linking loss-of-function to protection.

SUMMARY

More work is needed to understand how ERAP1 variants associated with risk and protection influence the quality and quantity of peptides available for binding to HLA class I molecules in the ER. Moreover, we need to determine allele-specific effects of ERAP1 variants in the context of HLA-B*51 and HLA-Cw*6, which are associated with Behçet's disease and psoriasis, respectively.

Endoplasmic reticulum aminopeptidases in the pathogenesis of ankylosing spondylitis

There has been significant progress in our understanding of the pathogenesis of AS. The advent of genome-wide association studies has increased the known loci associated with AS to more than 40. The endoplasmic reticulum resident aminopeptidases (ERAP) 1 and 2 were identified in this manner and are of particular interest. There appears to be a genetic as well as a functional interaction of ERAP1 and 2 with HLA-B27 based on the known functions of these molecules. Recent studies on the structure, immunological effects and the peptide-trimming properties of ERAP 1 and 2 have helped to provide insight into their pathogenic potential in AS. In this review, we explore the role of ERAP 1 and 2 in the pathogenesis of AS.

ERAP1 and ankylosing spondylitis

The strong genetic association of ERAP1 (endoplasmic reticulum aminopeptidase 1) with ankylosing spondylitis (AS), which is restricted to HLA-B27 positive cases, has profound pathogenetic implications. ERAP1 is involved in trimming peptides to optimal length for binding to HLA class 1 molecules, thereby not only affecting the stability and processing of HLA-B27 but also influencing the peptide repertoire presented to the immune system. This could have secondary effects on specific adaptive or autoimmune responses in AS. However, it appears increasingly likely that the pathogenic effect of ERAP1 may be mediated through effects on innate immunity, such as altering the interaction between HLA-B27 and immune receptors such as the killer immunoglobulin-like receptors (KIR) found on a range of innate immune cells or via the endoplasmic reticulum unfolded protein response. ERAP1 variants associated with reduced endopeptidase activity appear to be protective against AS, raising the possibility that ERAP1 inhibition could represent a future treatment strategy.

Genetics of ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that affects the spine and sacroiliac joints. It causes significant disability and is associated with a number of other features including peripheral arthritis, anterior uveitis, psoriasis and inflammatory bowel disease (IBD). Significant progress has been made in the genetics of AS have in the last five years, leading to new treatments in trial, and major leaps in understanding of the aetiopathogenesis of the disease.

Identification of multiple risk variants for ankylosing spondylitis through high-density genotyping of immune-related loci

Ankylosing spondylitis is a common, highly heritable inflammatory arthritis affecting primarily the spine and pelvis. In addition to HLA-B*27 alleles, 12 loci have previously been identified that are associated with ankylosing spondylitis in populations of European ancestry, and 2 associated loci have been identified in Asians. In this study, we used the Illumina Immunochip microarray to perform a case-control association study involving 10,619 individuals with ankylosing spondylitis (cases) and 15,145 controls. We identified 13 new risk loci and 12 additional ankylosing spondylitis-associated haplotypes at 11 loci. Two ankylosing spondylitis-associated regions have now been identified encoding four aminopeptidases that are involved in peptide processing before major histocompatibility complex (MHC) class I presentation. Protective variants at two of these loci are associated both with reduced aminopeptidase function and with MHC class I cell surface expression.

A common single nucleotide polymorphism in endoplasmic reticulum aminopeptidase 2 induces a specificity switch that leads to altered antigen processing

Endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2) cooperate to trim antigenic peptide precursors for loading onto MHC class I molecules and help regulate the adaptive immune response. Common coding single nucleotide polymorphisms in ERAP1 and ERAP2 have been linked with predisposition to human diseases ranging from viral and bacterial infections to autoimmunity and cancer. It has been hypothesized that altered Ag processing by these enzymes is a causal link to disease etiology, but the molecular mechanisms are obscure. We report in this article that the common ERAP2 single nucleotide polymorphism rs2549782 that codes for amino acid variation N392K leads to alterations in both the activity and the specificity of the enzyme. Specifically, the 392N allele excises hydrophobic N-terminal residues from epitope precursors up to 165-fold faster compared with the 392K allele, although both alleles are very similar in excising positively charged N-terminal amino acids. These effects are primarily due to changes in the catalytic turnover rate (k(cat)) and not in the affinity for the substrate. X-ray crystallographic analysis of the ERAP2 392K allele suggests that the polymorphism interferes with the stabilization of the N terminus of the peptide both directly and indirectly through interactions with key residues participating in catalysis. This specificity switch allows the 392N allele of ERAP2 to supplement ERAP1 activity for the removal of hydrophobic N-terminal residues. Our results provide mechanistic insight to the association of this ERAP2 polymorphism with disease and support the idea that polymorphic variation in Ag processing enzymes constitutes a component of immune response variability in humans.