ERAP2 Antibody

What is ERAP2 and what is its primary function in the immune system?

ERAP2 (Endoplasmic Reticulum Aminopeptidase 2), also known as LRAP (Leukocyte-derived arginine aminopeptidase), is an intracellular enzyme localized in the endoplasmic reticulum that plays a central role in the antigen processing pathway. Its primary function is peptide trimming, a critical step required for generating most HLA class I-binding peptides. ERAP2 customizes longer precursor peptides to fit the correct length (typically 8-10 amino acids) required for presentation on MHC class I molecules . It preferentially hydrolyzes the basic residues Arg and Lys, complementing the activity of the homologous ERAP1 . This peptide processing is essential for initiating immune responses to infected cells, as it enables CD8+ T lymphocytes and natural killer cells to recognize presented antigens .

How do ERAP2 polymorphisms influence disease susceptibility?

The ERAP2 gene is highly polymorphic, with specific single nucleotide variants (SNVs) demonstrating significant associations with both disease susceptibility and protection. Research has revealed an intriguing evolutionary balance where specific ERAP2 polymorphisms show opposing effects on different conditions:

These polymorphisms have been maintained through balancing selection throughout human evolution, likely reflecting trade-offs between protection against infectious diseases and increased risk of autoimmune disorders .

What are the optimal conditions for detecting ERAP2 by Western blot using antibodies?

For optimal Western blot detection of ERAP2, researchers should consider the following methodology:

• Sample preparation: Use cell lysates from appropriate human or rat tissues/cell lines (A549, HeLa, HepG2 have demonstrated good expression) .

• Running conditions: Since ERAP2 has a high molecular weight (calculated: 105-110 kDa; observed: 110-120 kDa due to glycosylation), use lower percentage gels (8-10% acrylamide) with adequate running time .

• Antibody selection and dilution:

  • For monoclonal antibodies like 67477-1-Ig, use at 1:1000-1:5000 dilution

  • For rabbit recombinant monoclonal antibodies like EPR26475-10, optimal concentrations may vary by application

• Detection system: Standard HRP-conjugated secondary antibodies with ECL detection systems are effective .

• Controls: Include positive controls like A549 or HeLa cell lysates which consistently express ERAP2. Negative controls should include secondary antibody-only lanes .

It's important to note that the apparent molecular weight of ERAP2 (110-120 kDa) is slightly higher than calculated (105-110 kDa) due to post-translational modifications, particularly glycosylation .

How can researchers quantify ERAP2 protein levels in clinical samples?

Quantification of ERAP2 in clinical samples, particularly serum, can be achieved using enzyme-linked immunosorbent assay (ELISA). Based on published methodologies:

• Sample collection: For serum analysis, collect 6 ml of venous blood in tubes with clot activator. Allow 30 minutes for clotting at room temperature, then centrifuge at 1500 RPM for 10 minutes, aliquot and store at -70°C until analysis .

• ELISA procedure: Commercial ELISA kits (e.g., Human Endoplasmic Reticulum Aminopeptidase 2 test) with detection ranges of 0.312-20 ng/mL and sensitivity <0.16 ng/mL have been successfully employed . Undiluted serum samples (100 μl) can be measured at 450 nm wavelength using a microplate reader.

• Clinical interpretation: Based on ROC analysis for rheumatoid arthritis patients:

  • ERAP2 levels >3.47 ng/mL indicate middle phase RA (AUC = 0.7729)

  • ERAP2 levels >6.22 ng/mL indicate severe phase RA (AUC = 0.7547)

  • ERAP2 levels >5.85 ng/mL most reliably indicate severe RA (AUC = 0.8810, LR = 12.13)

These thresholds demonstrate the potential of ERAP2 as a biomarker for disease severity, particularly in rheumatoid arthritis patients .

How can researchers investigate the interaction between ERAP1 and ERAP2 using immunological techniques?

Investigating ERAP1-ERAP2 heterodimer formation requires sophisticated immunological approaches:

• Co-immunoprecipitation (Co-IP):

  • Use anti-ERAP2 antibodies for immunoprecipitation followed by Western blot probing for ERAP1, or vice versa

  • Selection of antibodies is critical; use those that recognize epitopes not involved in the heterodimer interface

  • IP buffers should maintain native protein conformation (avoid harsh detergents)

• Proximity Ligation Assay (PLA):

  • This technique can visualize protein-protein interactions in situ

  • Requires antibodies raised in different species (e.g., mouse anti-ERAP2 and rabbit anti-ERAP1)

  • Primary antibodies are detected by species-specific secondary antibodies conjugated with complementary oligonucleotides

• Mass spectrometry approaches:

  • Immunoprecipitated complexes can be analyzed by mass spectrometry to identify interaction partners and their stoichiometry

  • Cross-linking mass spectrometry (XL-MS) can provide structural information about the heterodimer interface

Studies have confirmed that ERAP1-ERAP2 heterodimers demonstrate distinct peptide-trimming activities compared to homodimers, potentially explaining some of the synergistic genetic effects observed in disease associations .

What methodologies can be used to assess the impact of ERAP2 polymorphisms on peptide processing efficiency?

Researchers investigating the functional consequences of ERAP2 polymorphisms on peptide processing can employ several methodological approaches:

• In vitro peptide trimming assays:

  • Express recombinant ERAP2 variants (e.g., those encoded by rs2549794 or rs2248374 alleles)

  • Incubate with fluorogenic peptide substrates

  • Measure trimming efficiency through fluorescence intensity changes or HPLC analysis of reaction products

  • Compare kinetic parameters (Km, Vmax) between variants

• Cellular peptide presentation models:

  • Use CRISPR/Cas9 to generate ERAP2 knockout cell lines

  • Reconstitute with different ERAP2 variants

  • Isolate and analyze the MHC-I-bound peptidome using immunoprecipitation and mass spectrometry

  • Compare peptide length distributions and N-terminal characteristics

• Mendelian randomization (MR) approach:

  • Identify independent cis SNPs associated with ERAP2 expression

  • Use expression QTLs (eQTLs) and protein QTLs (pQTLs) as genetic instruments

  • Perform conditional analysis to identify SNP effects independent of haplotype

  • This approach has revealed that rs2549794 has effects on ERAP2 expression beyond the haplotype-tagging SNP rs2248374

Recent research using these methodologies has demonstrated that alleles associated with decreased ERAP2 expression show opposing effects on infectious disease susceptibility and autoimmune conditions, supporting the hypothesis of balancing selection at this locus .

How can researchers address cross-reactivity issues when using ERAP2 antibodies?

Cross-reactivity is a significant concern when working with ERAP2 antibodies due to the structural similarity with ERAP1 (approximately 50% sequence identity). To address this:

• Antibody validation steps:

  • Test antibodies on ERAP2 knockout or knockdown samples

  • Compare against recombinant ERAP1 and ERAP2 proteins

  • Perform peptide competition assays with the immunizing peptide

• Epitope selection considerations:

  • Select antibodies that target regions with minimal homology between ERAP1 and ERAP2

  • Target unique post-translational modifications if present

  • Verify specificity using bioinformatic tools before purchase

• Experimental controls:

  • Include ERAP2-deficient samples (approximately 25% of individuals homozygous for the ERAP2 haplotype B lack protein expression)

  • Compare multiple ERAP2 antibodies targeting different epitopes

  • Include samples with known ERAP2 genotypes (AA, AB, and BB) as demonstrated in validation studies

Researchers can specifically identify validated ERAP2 antibodies that have been shown not to cross-react with ERAP1 through careful literature review and specialized validation data provided by manufacturers .

How should researchers interpret variations in ERAP2 expression levels between different tissue types?

Interpreting tissue-specific variations in ERAP2 expression requires careful consideration of multiple factors:

• Baseline expression considerations:

  • ERAP2 expression varies naturally between tissues

  • Kidney tissue shows consistently high expression and can serve as a positive control for immunohistochemistry

  • Expression may be induced or suppressed by inflammatory stimuli or interferon signaling

• Methodological normalization:

  • Always normalize ERAP2 expression to appropriate housekeeping genes

  • Consider using multiple reference genes for more robust normalization

  • When comparing across tissues, use tissue-specific reference genes

• Genetic factors affecting expression:

  • The rs2248374 G allele (haplotype B) is associated with nonsense-mediated decay and reduced expression

  • Approximately 25% of the population is homozygous for this allele and may show naturally reduced expression

  • Other cis-regulatory variants may affect tissue-specific expression independently

• Interpretation framework:

  • Compare results to reference datasets like GTEx for tissue-specific expression patterns

  • Consider disease context—ERAP2 expression may be altered in inflammatory or autoimmune conditions

  • Correlate with relevant clinical parameters when analyzing patient samples

How might ERAP2 antibodies be applied in developing novel therapeutic approaches for autoimmune diseases?

ERAP2 antibodies could facilitate development of therapeutic strategies for autoimmune diseases through several research approaches:

• Target validation and mechanism studies:

  • Use antibodies to map structural determinants of ERAP2 function in disease models

  • Identify specific ERAP2 conformations or interactions that correlate with pathology

  • Explore potential for allosteric inhibition by monitoring conformational changes

• Development of potential diagnostics:

  • ERAP2 serum levels show promise as biomarkers for disease severity in rheumatoid arthritis, with levels >5.85 ng/mL indicating severe disease (AUC = 0.8810)

  • Antibody-based assays could stratify patients for personalized treatment approaches

  • Longitudinal monitoring could assess therapeutic response

• Small molecule inhibitor development:

  • Antibodies can be used to validate ERAP2 inhibition in cellular models

  • Competitive binding assays with therapeutic candidates can map binding sites

  • Conformation-specific antibodies could monitor target engagement

• Therapeutic antibody engineering:

  • Develop antibodies that selectively inhibit ERAP2 trimming of disease-relevant peptides

  • Engineer cell-penetrating antibodies targeting intracellular ERAP2

  • Create bispecific antibodies linking ERAP2 to degradation machinery

Given the opposing effects of ERAP2 on autoimmunity and infection susceptibility, therapeutic targeting would require careful consideration of the potential increased risk of infections in treated patients .

What are the methodological considerations for investigating the role of ERAP2 in cancer immunosurveillance?

Investigating ERAP2's role in cancer immunosurveillance requires sophisticated methodological approaches:

• Tumor immunopeptidome analysis:

  • Use ERAP2 antibodies to immunoprecipitate ERAP2 from tumor samples

  • Compare ERAP2 expression levels between tumor and matched normal tissues

  • Isolate MHC-I complexes from tumors with different ERAP2 expression profiles

  • Analyze bound peptides by mass spectrometry to identify ERAP2-dependent tumor antigens

• Genetic manipulation in cancer models:

  • Create ERAP2 knockout or overexpression cancer cell lines using CRISPR/Cas9

  • Confirm alterations using validated ERAP2 antibodies by Western blot and immunofluorescence

  • Assess changes in MHC-I peptide presentation and T-cell recognition

  • Evaluate tumor growth and immune infiltration in immunocompetent models

• Clinical sample correlation studies:

  • Quantify ERAP2 expression in tumor microarrays using standardized immunohistochemistry protocols

  • Correlate with immune cell infiltration, patient outcomes, and response to immunotherapy

  • Stratify analyses based on patient HLA types and ERAP2 polymorphisms

  • Integrate with genomic data to identify potential synergistic mutations

• Therapeutic targeting assessment:

  • Develop methods to selectively modulate ERAP2 in tumors

  • Monitor changes in antigen presentation using ERAP2 antibodies

  • Evaluate combination approaches with checkpoint inhibitors

  • Assess potential synergy with ERAP1-targeting approaches

Recent evidence suggests that defects in ERAP2 expression may cause improper antigen processing, potentially enabling tumor escape from immune surveillance, making this an important area for future cancer immunotherapy research .