ERAP1 Research Articles

Evaluation of ERAP1 gene single nucleotide polymorphisms in immunomodulation of pro-inflammatory and anti-inflammatory cytokines profile in ankylosing spondylitis

BackgroundAnkylosing spondylitis (AS) is a prototype of chronic inflammatory arthritis termed seronegative spondyloarthropathies that typically affects the joints. Among the non-Human leukocyte antigen (HLA) loci, the strongest association has been observed with Endoplasmic reticulum aminopeptidase 1 (ERAP1) gene single nucleotide polymorphisms (SNPs). Moreover, the effect of ERAP1 gene SNPs on the pro-inflammatory and anti-inflammatory cytokines in AS disease has still been poorly elucidated. In this study, we aimed to determine the association of ERAP1 gene SNPs (rs30187 and rs2287987) with AS risk as well as their effect on the mRNA expression of pro-inflammatory and anti-inflammatory cytokines, with emphasis on the immunoregulation of the IL-17/IL-23 pathway, in an Iranian population. MethodsWe performed Single specific primer (SSP)-PCR for genotyping of 160 AS patients and 160 healthy controls. After isolation of peripheral blood mononuclear cells (PBMCs), total RNA of PBMCs was isolated, complementary DNA (cDNA) was synthesized, and quantitative analyses of mRNA expression of cytokines were performed by Real-time PCR for 40 HLA-B27 positive AS patients and 40 healthy individuals as controls. ResultsIt was seen that T allele of rs30187 (OR = 1.54, 95% CI = 1.07–2.22, P = 0.017) and C allele of rs2287987 (OR 1.50, 95% CI 1.05–2.14, P = 0.024) were associated with the risk of AS. Both of these alleles were associated more strongly in the HLA-B27 positive AS patients. There was a significant overexpression of mRNAs of pro-inflammatory (IL-17A, IL-17F, IL-23, TNF-α and IFN-γ), while downregulation of anti-inflammatory cytokines (IL-10 and TGF-β) in PBMCs from 40 HLA-B27 positive AS patients in comparison to controls. AS patients with rs30187 SNP TT genotype expressed mRNA of IL-17A, IL-17F, and IL-23 significantly higher than patents with CT and CC genotypes for this SNP. ConclusionsThis study represented the association of ERAP1 gene rs30187 and rs2287987 polymorphism with the risk of AS. Additionally, it appears that rs30187 polymorphism may be involved in the immunomodulation of the IL-17/IL-23 pathway in the AS disease.

Sex-specific differences in endoplasmic reticulum aminopeptidase 1 modulation influence blood pressure and renin-angiotensin system responses.

Salt sensitivity of blood pressure (SSBP) and hypertension are common, but the underlying mechanisms remain unclear. Endoplasmic reticulum aminopeptidase 1 (ERAP1) degrades angiotensin II (ANGII). We hypothesized that decreasing ERAP1 increases BP via ANGII-mediated effects on aldosterone (ALDO) production and/or renovascular function. Compared with WT littermate mice, ERAP1-deficient (ERAP1+/-) mice had increased tissue ANGII, systolic and diastolic BP, and SSBP, indicating that ERAP1 deficiency leads to volume expansion. However, the mechanisms underlying the volume expansion differed according to sex. Male ERAP1+/- mice had increased ALDO levels and normal renovascular responses to volume expansion (decreased resistive and pulsatility indices and increased glomerular volume). In contrast, female ERAP1+/- mice had normal ALDO levels but lacked normal renovascular responses. In humans, ERAP1 rs30187, a loss-of-function gene variant that reduces ANGII degradation in vitro, is associated with hypertension. In our cohort from the Hypertensive Pathotype (HyperPATH) Consortium, there was a significant dose-response association between rs30187 risk alleles and systolic and diastolic BP as well as renal plasma flow in men, but not in women. Thus, lowering ERAP1 led to volume expansion and increased BP. In males, the volume expansion was due to elevated ALDO with normal renovascular function, whereas in females the volume expansion was due to impaired renovascular function with normal ALDO levels.

Substantial Influence of ERAP2 on the HLA-B*40:02 Peptidome: Implications for HLA-B*27-Negative Ankylosing Spondylitis

HLA-B*40:02 is one of a few major histocompatibility complex class I (MHC-I) molecules associated with ankylosing spondylitis (AS) independently of HLA-B*27. The endoplasmic reticulum aminopeptidase 2 (ERAP2), an enzyme that process MHC-I ligands and preferentially trims N-terminal basic residues, is also a risk factor for this disease. Like HLA-B*27 and other AS-associated MHC-I molecules, HLA-B*40:02 binds a relatively high percentage of peptides with ERAP2-susceptible residues. In this study, the effects of ERAP2 depletion on the HLA-B*40:02 peptidome were analyzed. ERAP2 protein expression was knocked out by CRISPR in the transfectant cell line C1R-B*40:02, and the differences between the peptidomes from the wild-type and ERAP2-KO cells were determined by label-free quantitative comparisons. The qualitative changes dependent on ERAP2 affected about 5% of the peptidome, but quantitative changes in peptide amounts were much more substantial, reflecting a significant influence of this enzyme on the generation/destruction balance of HLA-B*40:02 ligands. As in HLA-B*27, a major effect was on the frequencies of N-terminal residues. In this position, basic and small residues were increased, and aliphatic/aromatic ones decreased in the ERAP2 knockout. Other peptide positions were also affected. Because most of the non-B*27 MHC-I molecules associated with AS risk bind a relatively high percentage of peptides with N-terminal basic residues, we hypothesize that the non-epistatic association of ERAP2 with AS might be related to the processing of peptides with these residues, thus affecting the peptidomes of AS-associated MHC-I molecules.

The Pathogenesis of Ankylosing Spondylitis: an Update.

Ankylosing spondyloarthritis (AS) is a chronic inflammatory disease that involves the axial joints and entheses. Extra-spinal manifestations such as anterior uveitis, psoriasis, and colitis also occur frequently. This review on the pathogenesis of AS includes an update on the recent discoveries within the field. HLA-B*27 is still considered of major importance in the pathogenesis, and it has recently been shown to profoundly affect the gut microbiome and its metabolites and the handling of bacteria during infection. Biochemical and biophysical properties of HLA-B*27 influence its ability to misfold, to induce an endoplasmic reticulum stress response, and to promote autophagy/unfolded protein responses (UPR). HLA-B*27 free heavy chains may induce inflammation through T cells, NK cells, and myeloid cells. Induction of UPR genes results in release of tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-23, and interferon-γ and increase in T helper (Th) 17 cells. Several other HLA-B and non-B molecules have been associated with AS, although their role in the pathogenesis is unknown. Genotypes of endoplasmic reticulum aminopeptidases (ERAP) 1 and 2 have been associated with alterations in the antigenic pool expressed by HLA-B*27 molecules. In the gut, innate immune cells type 3 (ILC3) influence T cell expression of IL-17 and IL-22. Gamma-delta (γ/δ) T cells are induced by IL-23 to produce IL-17. IL-7 induces mucosa-associated invariant T (MAIT) cells to produce IL-17. Besides the microbiome, zonulin may be important through its effects on the permeability of tight junctions in the intestinal epithelial barrier.

Redundancy and Complementarity between ERAP1 and ERAP2 Revealed by their Effects on the Behcet's Disease-associated HLA-B*51 Peptidome*[S

The endoplasmic reticulum aminopeptidases ERAP1 and ERAP2 trim peptides to be loaded onto HLA molecules, including the main risk factor for Behçet's disease HLA-B*51. ERAP1 is also a risk factor among HLA-B*51-positive individuals, whereas no association is known with ERAP2. This study addressed the mutual relationships between both enzymes in the processing of an HLA-bound peptidome, interrogating their differential association with Behçet's disease. CRISPR/Cas9 was used to generate knock outs of ERAP1, ERAP2 or both from transfectant 721.221-HLA-B*51:01 cells. The surface expression of HLA-B*51 was reduced in all cases. The effects of depleting each or both enzymes on the B*51:01 peptidome were analyzed by quantitative label-free mass spectrometry. Substantial quantitative alterations of peptide length, subpeptidome balance, N-terminal residue usage, affinity and presentation of noncanonical ligands were observed. These effects were often different in the presence or absence of the other enzyme, revealing their mutual dependence. In the absence of ERAP1, ERAP2 showed similar and significant processing of B*51:01 ligands, indicating functional redundancy. The high overlap between the peptidomes of wildtype and double KO cells indicates that a large majority of B*51:01 ligands are present in the ER even in the absence of ERAP1/ERAP2. These results indicate that both enzymes have distinct, but complementary and partially redundant effects on the B*51:01 peptidome, leading to its optimization and maximal surface expression. The distinct effects of both enzymes on the HLA-B*51 peptidome provide a basis for their differential association with Behçet's disease and suggest a pathogenetic role of the B*51:01 peptidome.

Inhibitors of ER Aminopeptidase 1 and 2: From Design to Clinical Application.

Endoplasmic Reticulum aminopeptidase 1 and 2 are two homologous enzymes that help generate peptide ligands for presentation by Major Histocompatibility Class I molecules. Their enzymatic activity influences the antigenic peptide repertoire and indirectly controls adaptive immune responses. Accumulating evidence suggests that these two enzymes are tractable targets for the regulation of immune responses with possible applications ranging from cancer immunotherapy to treating inflammatory autoimmune diseases. Here, we review the state-of-the-art in the development of inhibitors of ERAP1 and ERAP2 as well as their potential and limitations for clinical applications.

ERAP1 promotes Hedgehog-dependent tumorigenesis by controlling USP47-mediated degradation of \u03b2TrCP

The Hedgehog (Hh) pathway is essential for embryonic development and tissue homeostasis. Aberrant Hh signaling may occur in a wide range of human cancers, such as medulloblastoma, the most common brain malignancy in childhood. Here, we identify endoplasmic reticulum aminopeptidase 1 (ERAP1), a key regulator of innate and adaptive antitumor immune responses, as a previously unknown player in the Hh signaling pathway. We demonstrate that ERAP1 binds the deubiquitylase enzyme USP47, displaces the USP47-associated βTrCP, the substrate-receptor subunit of the SCFβTrCP ubiquitin ligase, and promotes βTrCP degradation. These events result in the modulation of Gli transcription factors, the final effectors of the Hh pathway, and the enhancement of Hh activity. Remarkably, genetic or pharmacological inhibition of ERAP1 suppresses Hh-dependent tumor growth in vitro and in vivo. Our findings unveil an unexpected role for ERAP1 in cancer and indicate ERAP1 as a promising therapeutic target for Hh-driven tumors.

Endoplasmic Reticulum Associated Aminopeptidase 2 (ERAP2) Is Released in the Secretome of Activated MDMs and Reduces in vitro HIV-1 Infection.

Background: Haplotype-specific alternative splicing of the endoplasmic reticulum (ER) aminopeptidase type 2 (ERAP2) gene results in either full-length (FL, haplotype A) or alternatively spliced (AS, haplotype B) mRNA. HapA/HapA homozygous (HomoA) subjects show a reduced susceptibility to HIV-1 infection, probably secondary to the modulation of the antigen processing/presenting machinery. ERAP1 was recently shown to be secreted from the plasma membrane in response to activation; we investigated whether ERAP2 can be released as well and if the secreted form of this enzyme retains its antiviral function.Methods: Human monocyte derived macrophages (MDMs) were differentiated from peripheral blood mononuclear cells (PBMCs) isolated from 6 HomoA healthy controls and stimulated with IFNγ and LPS. ERAP2-FL secretion was evaluated by mass spectrometry. PBMCs (14 HomoA and 16 HomoB) and CD8-depleted PBMCs (CD8−PBMCs) (4 HomoA and 4 HomoB) were in vitro HIV-infected in the absence/presence of recombinant human ERAP2-FL (rhERAP2) protein; p24 viral antigen quantification was used to assess viral replication. IFNγ and CD69 mRNA expression, as well as the percentage of perforin-producing CD8+ T Lymphocytes, were analyzed 3 and 7-days post in vitro HIV-1-infection, respectively. The effect of rhERAP2 addition in cell cultures on T cell apoptosis, proliferation, activation, and maturation was evaluated as well on 24 h-stimulated PBMCs.Results: ERAP2 can be secreted from human MDMs in response to IFNγ/LPS stimulation. Notably, the addition of rhERAP2 to PBMC and CD8−PBMC cultures resulted in the reduction of viral replication, though these differences were statistically significant only in PBMCs (p < 0.05 in both HomoA and HomoB). This protective effect was associated with an increase in IFNγ and CD69 mRNA expression and in the percentage of perforin-expressing CD107+CD8+ cells. RhERAP2 addition also resulted in an increase in CD8+ activated lymphocyte (CD25+HLA−DRII+) and Effector Memory/Terminally differentiated CD8+ T cells ratio.Conclusions: This is the first report providing evidence for the release of ERAP2 in the secretome of immunocompetent cells. Data herein also indicate that exogenous ERAP2-FL exerts its protective function against HIV-1 infection, even in HomoB subjects who do not genetically produce it. Presumably, this defensive extracellular feature is only partially dependent on immune system modulation.

HPV Epitope Processing Differences Correlate with ERAP1 Allotype and Extent of CD8+ T-cell Tumor Infiltration in OPSCC.

Presence of tumor-infiltrating lymphocytes (TIL) predicts survival in many cancer types. In HPV-driven cancers, cervical and oropharyngeal squamous cell carcinomas (CSCC and OPSCC, respectively), numbers of infiltrating T cells, particularly CD8+ T cells, and presentation of HPV E6/E7 epitopes are associated with improved prognosis. Endoplasmic reticulum aminopeptidase 1 (ERAP1) regulates the presented peptide repertoire, trimming peptide precursors prior to MHC I loading. ERAP1 is polymorphic, and allotypic variation of ERAP1 enzyme activity has an impact on the presented peptide repertoire. Individual SNPs are associated with incidence and outcome in a number of diseases, including CSCC. Here, we highlight the requirement for ERAP1 in the generation of HPV E6/E7 epitopes and show that the functional activity of ERAP1 allotype combinations identified in OPSCC correlate with tumor-infiltrating CD8+ T-cell (CD8)/TIL (CD8/TIL) status of the tumor. Functional analyses revealed that ERAP1 allotype combinations associated with CD8/TILlow tumors have a reduced capacity to generate both a model antigen SIINFEHL and the HPV-16 E782-90 epitope LLMGTLGIV from N-terminally extended precursor peptides. In contrast, ERAP1 allotypes from CD8/TILhigh tumors generated the epitopes efficiently. These data reveal that ERAP1 function correlates with CD8/TIL numbers and, by implication, prognosis, suggesting that the presentation of HPV-16 epitopes at the cell surface, resulting in an anti-HPV T-cell response, may depend on the ERAP1 allotype combinations expressed within an individual.

Editing the immunopeptidome of melanoma cells using a potent inhibitor of endoplasmic reticulum aminopeptidase 1 (ERAP1).

The efficacy of cancer immunotherapy, including treatment with immune-checkpoint inhibitors, often is limited by ineffective presentation of antigenic peptides that elicit T-cell-mediated anti-tumor cytotoxic responses. Manipulation of antigen presentation pathways is an emerging approach for enhancing the immunogenicity of tumors in immunotherapy settings. ER aminopeptidase 1 (ERAP1) is an intracellular enzyme that trims peptides as part of the system that generates peptides for binding to MHC class I molecules (MHC-I). We hypothesized that pharmacological inhibition of ERAP1 in cells could regulate the cellular immunopeptidome. To test this hypothesis, we treated A375 melanoma cells with a recently developed potent ERAP1 inhibitor and analyzed the presented MHC-I peptide repertoire by isolating MHC-I, eluting bound peptides, and identifying them using capillary chromatography and tandem mass spectrometry (LC-MS/MS). Although the inhibitor did not reduce cell-surface MHC-I expression, it induced qualitative and quantitative changes in the presented peptidomes. Specifically, inhibitor treatment altered presentation of about half of the total 3204 identified peptides, including about one third of the peptides predicted to bind tightly to MHC-I. Inhibitor treatment altered the length distribution of eluted peptides without change in the basic binding motifs. Surprisingly, inhibitor treatment enhanced the average predicted MHC-I binding affinity, by reducing presentation of sub-optimal long peptides and increasing presentation of many high-affinity 9-12mers, suggesting that baseline ERAP1 activity in this cell line is destructive for many potential epitopes. Our results suggest that chemical inhibition of ERAP1 may be a viable approach for manipulating the immunopeptidome of cancer.

The rs75862629 minor allele in the endoplasmic reticulum aminopeptidases intergenic region affects human leucocyte antigen B27 expression and protects from ankylosing spondylitis in Sardinia.

HLA-B27 and the endoplasmic reticulum aminopeptidase 1 (ERAP1) and ERAP2 genes are predisposing factors for AS. A single nucleotide polymorphism (SNP) in the ERAP2 promoter (rs75862629) coordinates the transcription of both ERAP genes. We investigated whether this SNP associates with AS and whether it affects the expression of the two major HLA-B27 alleles present in Sardinia, the AS-associated B*2705 and the non-AS-associated B*2709. Four SNPs in the ERAP region were genotyped in HLA-B*2705-positive patients with AS (n = 145), B27-positive healthy subjects (n = 126) and B27-negative controls (n = 250) and the allele and haplotype frequencies were derived. The expression of ERAP1 and ERAP2 mRNAs in 36 HLA-B27-positive B lymphoblastoid cell lines was measured by quantitative PCR. An electrophoretic mobility shift assay was performed to search for a nuclear factor binding the DNA sequence encompassing rs75862629. The expression of HLA-B27 molecules related to the SNP at rs75862629 was determined by flow cytometry. The minor allele G at rs75862629 was found significantly increased in B27 healthy individuals, both B*2705 and B*2709, compared with B*2705-positive patients with AS and B27-negative controls. The electrophoretic mobility shift assay indicated the lack of binding of a transcription factor as the cause of the observed reduction in the ERAP2 concomitant with a higher ERAP1 expression. Of note, this occurs with a different cell surface expression of the HLA-B*2705 and HLA-B*2709 molecules. SNP rs75862629, by modulating simultaneously the expression of ERAP1 and ERAP2, provides protection from AS in HLA-B27-positive subjects in Sardinia. This has a functional impact on HLA-B27 expression and likely on disease onset.

From the Editor’s desk…: June 2019

From the Editor’s desk…: June 2019

Association Study of Single Nucleotide Polymorphisms of Endoplasmic Reticulum Aminopeptidase 1 and 2 Genes in Iranian Women with Preeclampsia

Endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and 2) are involved in blood pressure regulation and single nucleotide polymorphisms (SNPs) of these genes have been linked to preeclampsia. This study intended to assess the association of ERAP1 and 2 genes polymorphism with Iranian preeclamptic women. In this case-control study, 148 preeclamptic and 133 pregnant women were selected from the Kosar Hospital, Qazvin, Iran, during 2013-2015. In order to genotype the subjects for rs28096, rs30187, rs26653, rs3734016, rs34750 and rs2549782, rs17408150 for ERAP1 and 2 genes, respectively, Real-Time PCR allelic discrimination approach was exploited. Neither allelic nor genotype frequencies of all seven polymorphisms were significantly different between two groups. Though, ACGACTT and GTCAGGA haplotypes were related with decreased (P=0.0079, OR=0.559, 95% CI: 0.363-0.861 and P=0.02, OR=0.417, 95% CI: 0.194-0.896, respectively), but ACGACGT and GTGACTT haplotypes were associated with an increased (P=0.00082, OR=3.657, 95% CI: 1.630-8.206 and P=0.02, OR=2.401, 95% CI: 1.119-5.151, respectively) risk of preeclampsia. Moreover, some positions were detected to be in linkage disequilibrium. Ongoing investigation resulted differently from before performed studies considering the role of ERAP1 and ERAP2 gene polymorphisms in predisposing women to preeclampsia, emphasizing on the genetic structure differences among various racial populations.

Behçet's Disease: An Overview of Etiopathogenesis.

Behçet's disease (BD) is a systemic inflammatory disease with a chronic, relapsing-remitting course of unknown etiology hallmarked predominantly by mucocutaneous lesions and ocular involvement. BD shares some common features with autoimmune and autoinflammatory diseases and spondyloarthropathies (MHC-I-opathies). It is related to more than one pathogenic pathway triggered by environmental factors such as infectious agents in genetically predisposed subjects. The interplay between genetic background and immune system is linked to the BD presentation. Genetic factors have been investigated extensively, and several recent genome-wide association studies have confirmed HLA-B*51 to be the strongest genetic susceptibility factor. However, new non-HLA susceptibility genes have been identified. Genetic variations in the genes encoding the cytokines could affect their function and be associated with disease susceptibility. Infectious agents such as Streptococcus sanguinis or the differences in salivary or gut microbiome composition can be considered to trigger the innate-derived inflammation, which is, subsequently, sustained by adaptive immune responses. Altered trimming of microbial and/or endogenous peptides by endoplasmic reticulum aminopeptidase 1 (ERAP1), presented by HLA-B*51, may play a key role in BD pathogenesis causing an alteration in T cell balance with downregulation of Tregs and expansion of Th1 and Th17. The activity of neutrophils is increased and there is an intense neutrophil infiltration in the early stage of inflammation in organs affected by the disease. Association with HLA-B*51 and increased IL-17 response seems to have an important role in neutrophil activity. In this paper, we provide an overview of the most recent advances on BD etiopathogenesis.

Association of ERAP2 gene variants with risk of pre-eclampsia among Iranian women.

To determine the association between ERAP2 rs2549782 and rs17408150 polymorphisms and pre-eclampsia among Iranian women. A retrospective case-control study comparing 319 women with pre-eclampsia and 291 normotensive pregnant Iranian women between January and August 2016. Pre-eclampsia was diagnosed by the International Society for the Study of Hypertension in Pregnancy's criteria. Demographic data were collected by oral interview. Genotyping was done by allele-specific PCR. Data were analyzed using SPSS v. 16. The frequency of the rs2549782TT genotype was 31.0% and 27.5% among cases and controls, respectively (P=0.006). There was no difference in the frequency of the T allele between groups (P>0.05). Regarding the rs17408150 polymorphism, a high portion of women with pre-eclampsia was homozygous for the AA genotype (P<0.001). The frequency of the A allele was 32.5% and 25.05% among cases and controls, respectively (P=0.004). The combined haplotype of the rs2549782A and rs17408150G alleles was associated with increased risk of pre-eclampsia (P=0.031). ERAP2 gene polymorphisms were associated with the risk of pre-eclampsia in an Iranian population. The results provide further evidence of the role of ERAP2 in the pathophysiology of this disease.

SAT-057 Endoplasmic Reticulum Aminopeptidase-1 Is a Novel Regulator of the Renin-Angiotensin-Aldosterone System and Blood Pressure Homeostasis

Endoplasmic Reticulum Aminopeptidase-1 (ERAP1) has been proposed to metabolize angiotensin II (ANGII), an effector molecule of the renin-ANGII-aldosterone (ALDO) system (RAAS) and key regulator of volume and blood pressure (BP) homeostasis. ERAP1 plays an important role in immune function as it cleaves cytokine cell surface receptors and HLA binding precursors thereby modulating their inclusion into major histocompatibility complex-I (MHC). Indeed, absence of ERAP1 in vivo shows MHC-I peptide presentation defects and decreased T regulatory cells in mice. However, the interaction between ERAP1 and RAAS remains unclear. We hypothesized that ERAP1 mediates the interaction between BP homeostasis and cardiorenal disease. We studied ERAP1 deficient heterozygous (ERAP1+/-) mice; a mouse with a phenotype likely more equivalent to what would be seen in human subjects, i.e. reduced, not absent, ERAP1. We observed that ERAP1+/- mice had 45% lower ERAP1 levels by western blot analyses in heart and kidney as compared to wild-type (WT) littermate control mice maintained on regular rodent chow (n= 10 of each type, p=0.029). We measured ANGII tissue levels by LC/MS and show increased levels in heart, kidney and aortas from ERAP1+/- as compared to WT control mice (P<0.05). On regular rodent chow, urinary 24 hr ALDO levels were increased in ERAP1+/- compared to WT mice (7.11 ±0.82 [WT, n=10] vs 9.92 ±0.88 ng/dL [ERAP1+/-, n=8], p=0.03) while plasma renin activity (PRA) were not significantly different between the two mouse types (65.3±3.2 [WT, n=10] vs 66.16±2.3 ng/ml*h [ERAP1+/-, n=8]). We also evaluated BP by tail cuff on mice maintained on regular rodent chow and showed increased systolic BP in ERAP1+/- as compared to WT mice, (122.8±0.8 [ERAP1, n=9] vs. 110.2±1.6 mmHg [WT, n=12], p=0.003). We then studied the effects of salt intake on BP in these mice. ERAP1+/- mice had increased salt sensitivity of BP, defined as systolic BP on high, 1.6% Na+ diet minus systolic BP on low, 0.03% Na+ diet, when compared to WT mice (SSBP: 8.5±2.3 [ERAP1, n=15] vs -0.2 ±1.6 mmHg [WT, n=15], p=0.0043). Similar results were obtained using continuous intraarterial BP monitoring by telemetry in freely moving mice (SSBP by telemetry: 6.8±1.2 [ERAP1, n=3] vs 0.4±0.7 mmHg [WT, n=2], p<0.001). We then studied renal hemodynamics using 2D and Color-Doppler imaging and showed that ERAP1+/- mice have increased peak-systolic velocity (PSV) and end-diastolic velocity (EDV) compared to WT mice on regular mouse chow (PSV: 412.6±38.6 [WT, n=4] vs 570.2±27.7 mm/s [ERAP1+/-, n=3] p=0.027; EDV: 127.9±9.8 [WT, n=4] vs 191.0±16.3 mm/s [ERAP1+/-, n=6], p=0.02). In conclusion, ERAP1 deficiency is associated with SSBP, likely secondary both to increased ALDO and altered renovascular function.

Increased Endoplasmic Reticulum Amino Peptidase‐1 in Sickle Cell Disease: Role of Hypoxia

Sickle cell disease (SCD) is a genetic disorder caused by a single amino acid substitution in the β‐globin gene that results in hemoglobin polymerization, deformed erythrocytes and endothelial cell activation leading to chronic inflammation, anemia, hypoxemia and vaso‐occlusive crisis (VOC). These events contribute to the development of acute and often severe and debilitating, painful episodes in patients with SCD through unclear mechanisms. In SCD, chronic hypoxia and subacute inflammation contribute to endothelial cell activation that is associated with increased inflammatory cytokine markers such as endothelin‐1 (ET‐1), tumor necrosis factor‐α (TNFα), and TNFα receptor‐1 (TNFR1). Endoplasmic Reticulum Aminopeptidase‐1 (ERAP1) is a ubiquitously expressed zinc‐metallopeptidase involved in regulating immune function and inflammation that cleaves cytokine cell surface receptors such as TNFR1 and plays an important role in the pathophysiology of ankylosing spondylitis. However, the relationship between ERAP1 and SCD is, to the best of our knowledge, unexplored. We first studied the effects of deoxygenation (5% O2) on ERAP1 mRNA expression levels by qRT‐PCR in the human endothelial cell line, EA.hy926. We observed a 3‐fold increase in the expression of ERAP1 after 4 hrs of hypoxia (p&lt;0.05, n=4) and 4‐fold increase after 8 hrs of hypoxia (p&lt;0.05, n=4); events that were associated with a 3.5‐fold increase in the hypoxia‐inducible factor 1‐α mRNA levels at these time points. Consistent with these results, activation of EA.hy926 cells with agonist such as angiotensin II was likewise associated with increased ERAP1 mRNA (p&lt;0.05, n=4). We then studied two sickle transgenic knockout mouse models expressing human sickle hemoglobin, the βSAntilles and Berkeley (BERK) mice. We observed significant increases in ERAP1 mRNA levels (n=7 each; p&lt;0.01) in kidneys from sickle transgenic mice when compared to control transgenic knockout mice expressing human hemoglobin A (HbA). In addition, and as previously documented in other sickle mouse models, our sickle mice had increased circulating TNFα by ELISA as compared to HbA mice (p&lt;0.05, n=6–10 of each mouse type). In conclusion, increases in ERAP1 levels represent a novel target in SCD that is likely secondary to hypoxia and activated endothelial cells.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endoplasmic reticulum aminopeptidase 1 polymorphism Ile276Met is associated with atopic dermatitis and affects the generation of an HLA-C associated antigenic epitope in vitro.

Atopic dermatitis (AD) is a common inflammatory skin disease of complex aetiology, with interactions between susceptibility genes and environmental factors. We have previously described a protective effect of the KIR2DS1 gene encoding the natural killer cell receptor, whose ligands are HLA-C molecules. Here, we found an association of HLA-C*05:01 allele with AD. KIR-HLA-C interactions are affected by peptides presented by HLA-C. The generation of these peptides is strongly influenced by endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2). Expression and activity of ERAP molecules depend on the polymorphisms of their genes. Possible associations of several single nucleotide polymorphisms (SNPs) in the ERAP1 and ERAP2 genes with susceptibility to AD. Peripheral blood DNA isolation from 318 patients and 549 controls. PCR-SSO or PCR-SSP for HLA-C typing; TaqMan Genotyping Assay for ERAP typing. Only one SNP in the ERAP1 gene, rs26618T>C, causing the amino acid change Ile276Met, had an association with AD. To gain insight on the functional role of this SNP, we produced recombinant variants differing only at position 276 (Ile or Met) and tested their aminopeptidase activity against a N-terminally extended precursor LIVDRPVTLV of the HLA-C*05:01 epitope IVDRPVTLV. Both ERAP1 variants were able to efficiently generate the epitope, although the 276Ile allotype was able to do this about 50% faster. Furthermore, both variants were quite inefficient in further degradation of the mature epitope. Finally, we found that the effect of 276Met on susceptibility to AD was seen only in KIR2DS1-negative individuals, not protected by this KIR. Associations of HLA-C*05:01 allele and rs26618T>C (Ile276Met) ERAP1 polymorphism with AD, and a significant difference between these two ERAP1 variants in their ability to generate an epitope for the HLA-C*05:01 molecule was found.

MiRNA deregulation can contribute to breakdown of MHC I class antigen processing and presenting machinery in breast cancer cells

Background: To attack tumors, cytotoxic CD8+ T cells need to recognize tumor antigen peptides loaded onto major histocompatibility complex (MHC) class I molecules. Antigen processing and presentation is multistep process that includes proteasome-dependent and independent cleavage of cytosolic proteins, transport of derived peptides into the endoplasmic reticulum (ER) by transporters associated with antigen processing (TAPs), peptide trimming by ER aminopeptidases (ERAPs), peptide loading onto MHC molecules with the help of calnexin, calreticulin, protein disulfide-isomerase A3 and tapasin, movement of vesicles with MHC-peptide complex via the Golgi apparatus to the cell surface. Being one of the main immune escape pathways, defects in this machinery are frequently observed in various tumors and correlate with tumor grade and aggressiveness. This research aims to identify how the tumor-related abnormalities in microRNA (miRNA) expression pattern can disrupt antigen processing and presentation in breast cancer cells.

Distribution of rs17482078 and rs27044 ERAP1 polymorphisms in a group of Italian Behçet's syndrome patients: a preliminary case-control study.

The Endoplasmic reticulum aminopeptidase protein 1 (ERAP1) trims N-terminal amino acids from epitope precursors for Major Histocompatibility Complex class I presentation. Genome-wide association studies demonstrated that ERAP1 gene single nucleotide polymorphisms (SNPs) are associated with Behçet's syndrome (BS). This study was conducted on the two most consistently BS-associated ERAP1 polymorphisms, rs17482078 (NG_027839.1:g.35983G>A) and rs27044 (NG_027839.1:g.35997C>G) to analyse their distribution in 55 Italian BS patients and 65 ethnically matched controls (healthy controls, HC) and to test their association with BS risk. SNPs were detected by isolation, amplification of genomic DNA and direct sequencing. SNPs functional effects were predicted by bioinformatics software. The odds ratio (OR) with 95% confidence intervals was calculated to assess the strength of BS association for genotypes and alleles, also validated by logistic regression (LR). LR was used to test the association between both SNPs and patients HLA genetic data. Bonferroni correction was also applied. Comparing patients and controls, we found a significant higher frequency of rs17482078 A allele (32.73% BS vs 17.69% HC, p = 0.007) and AA genotype (18.18% BS vs 0% HC; p = 0.0003) and rs27044 G allele (63.64% BS vs 46.92% HC; p = 0.0096) in BS group after Bonferroni correction. No association was found between HLA-B*51 and both ERAP1 SNPs. Although preliminary, our data show a stronger association of rs17482078 with BS compared to rs27044 by means of case-control genetic analysis and bioinformatics prediction of protein structure change. A larger series of patients and controls is required to confirm our preliminary findings.