OR4E2 Antibody

What is OR4E2 and what applications are OR4E2 antibodies validated for?

OR4E2 (Olfactory Receptor Family 4 Subfamily E Member 2) is a G-protein coupled receptor belonging to the olfactory receptor family. It functions in olfactory transduction pathways and has been shown to respond to amyl acetate as an agonist . The protein has a calculated molecular weight of approximately 35 kDa, though it is often observed at 72 kDa in experimental conditions .

Commercial OR4E2 antibodies have been validated primarily for:

• Immunofluorescence (IF): Typically at dilutions of 1:200-1:1000

• Immunocytochemistry (ICC): Recommended dilutions similar to IF

• ELISA: Often at much higher dilutions (1:20000)

• Western Blot (WB): Less commonly validated

The most consistently validated application across different vendors is immunofluorescence, with demonstrated reactivity in cell lines such as A549 .

What species reactivity should I expect from commercially available OR4E2 antibodies?

Species reactivity varies by antibody source, but the most common pattern includes:

When selecting an antibody for cross-species applications, verify the validation data for each specific species. Some antibodies show broader cross-reactivity (like ABIN2791735), which may be advantageous for comparative studies, but validation quality may vary across species .

What is the recommended storage and handling protocol for OR4E2 antibodies?

Most OR4E2 antibodies share similar storage requirements:

• Long-term storage: -20°C for up to one year

• Short-term/frequent use: 4°C for up to one month

• Formulation: Typically supplied in PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide

• Concentration: Generally 0.5-1 mg/ml, though exact concentration varies by lot

Critical handling considerations:

• Avoid repeated freeze-thaw cycles which can degrade antibody performance

• Some vendors recommend storage at -80°C for enhanced stability

• Aliquoting upon receipt is strongly advised for antibodies that will be used multiple times

• Take precautions when handling solutions containing sodium azide, as it is a hazardous substance

What is the optimal protocol for immunofluorescence detection of OR4E2?

Based on validated experimental protocols, the following approach is recommended for immunofluorescence with OR4E2 antibodies:

Sample preparation:

• Fix cells using 4% paraformaldehyde in PBS (15 minutes at room temperature)

• Permeabilize with 0.2% Triton X-100 in PBS (10 minutes)

• Block using 5% normal serum in PBS (1 hour at room temperature)

Antibody incubation:

• Primary antibody: Use OR4E2 antibody at 1:200-1:500 dilution in blocking buffer (overnight at 4°C)

• Wash 3× with PBS (5 minutes each)

• Secondary antibody: Use appropriate fluorophore-conjugated anti-rabbit IgG at 1:500-1:1000 (1 hour at room temperature)

• Wash 3× with PBS (5 minutes each)

• Counterstain nuclei with DAPI and mount

Validated application:
Immunofluorescence analysis of A549 cells using OR4E2 antibody shows specific staining that can be blocked with synthesized peptide, confirming specificity .

For optimal results, include a peptide blocking control where available, as this has been demonstrated to effectively validate specificity in immunofluorescence applications .

How should I design experiments to validate OR4E2 antibody specificity?

Rigorous validation of OR4E2 antibody specificity is essential due to the high sequence similarity among olfactory receptors. A comprehensive validation strategy includes:

Competition assays:

• Preincubate antibody with immunizing peptide (where available) before application

• Example: The documented blocking experiment with OR4E2 antibody A17549 on A549 cells shows complete signal elimination when the antibody is preincubated with the synthesized peptide

Genetic approaches:

• Overexpression of tagged OR4E2 in a heterologous system

• siRNA or CRISPR-based knockout/knockdown of OR4E2

• Compare signal in tissues/cells known to express OR4E2 versus those that don't

Multiple antibody approach:

• Use antibodies targeting different epitopes of OR4E2 (e.g., N-terminal vs. C-terminal)

• Most commercial OR4E2 antibodies target C-terminal regions (amino acids 228-277)

• Compare staining patterns between antibodies

Cross-reactivity assessment:

• Test antibody on closely related olfactory receptors or in systems where OR4E2 is not expressed

• Consider testing in species where the immunogen sequence differs significantly

For complete validation, document all controls and validation experiments, as recommended by antibody validation initiatives in the field.

What controls are essential when studying OR4E2 genetic variants?

When studying OR4E2 genetic variants, controlling for multiple factors is crucial given the high genetic variability in the odorant receptor repertoire :

Essential controls:

• Allele-specific considerations:

  • OR4E2 has known pseudogene alleles affecting the MAYDRY domain in approximately 30% of the population

  • Design experiments to account for this genetic variation in your sample population

  • Include positive controls with known functional alleles

• Expression controls:

  • Surface expression of OR4E2 variants should be assessed, though research shows that relative surface expression does not necessarily correlate with functional potency or efficacy

  • Use Rho-tag antibody staining and FACS analysis to quantify surface expression

• Functional validation:

  • When studying receptor function, include dose-response curves with known agonists (e.g., amyl acetate)

  • Compare responses across different alleles using normalized response metrics

  • Include vector-only controls to establish baseline response

• Genetic background:

  • Whenever possible, study variants in the same genetic background to minimize confounding factors

  • Consider using CRISPR-engineered cell lines with specific OR4E2 variants

The research data shows that even single amino acid changes can significantly alter receptor function without completely abolishing it, highlighting the importance of thorough functional characterization .

How does OR4E2 genetic variability affect antibody binding and experimental outcomes?

OR4E2 exhibits significant genetic variability that can impact antibody-based detection:

Critical genetic variations:

• The human genome contains approximately 800 odorant receptor genes with high genetic variability

• OR4E2 specifically has pseudogene alleles in approximately 30% of the population

• The MAYDRY domain (a highly conserved region in G-protein coupled receptors) is affected in these pseudogene variants

Impact on antibody binding:

• Antibodies targeting regions with genetic variations may show differential binding

• Most commercial OR4E2 antibodies target the C-terminal region (amino acids 228-277) , which may overlap with variable regions

• Variants affecting protein folding may mask epitopes even if the sequence is conserved

Experimental strategies:

• Sequence OR4E2 in your experimental system to identify relevant variants

• If studying populations, consider using antibodies targeting highly conserved regions

• For variant-specific detection, custom antibodies against specific alleles may be required

• Use multiple detection methods (e.g., RNA-based plus protein-based) to validate findings

The 1000 Genomes Project data revealed functional differences in dose-response for odorant receptors, including OR4E2, highlighting the importance of considering genetic variation in experimental design and interpretation .

What explains the discrepancy between calculated (35 kDa) and observed (72 kDa) molecular weights for OR4E2?

The significant difference between the calculated molecular weight of OR4E2 (35,466 Da) and the observed molecular weight in experimental conditions (72 kDa) can be attributed to several factors :

Post-translational modifications:

• Glycosylation: G-protein coupled receptors, including olfactory receptors, often contain N-glycosylation sites that can substantially increase apparent molecular weight

• Phosphorylation: Multiple phosphorylation events, particularly on serine and threonine residues, can affect migration patterns

• Ubiquitination: Can add approximately 8.5 kDa per ubiquitin molecule

Technical considerations:

• SDS-binding anomalies: Hydrophobic membrane proteins like OR4E2 may bind SDS irregularly, affecting migration

• Incomplete denaturation: Residual secondary structure can cause proteins to migrate more slowly

• Protein-detergent complexes: Incomplete removal of membrane lipids can increase apparent size

Experimental approach:

• Validate using recombinant OR4E2 with known molecular weight as a standard

• Treatment with PNGase F or other deglycosylating enzymes to assess glycosylation contribution

• Phosphatase treatment to remove phosphate groups

• Use multiple gel systems (Tris-glycine versus Tris-tricine) to confirm observations

This discrepancy is common among membrane proteins and does not necessarily indicate antibody non-specificity.

How can I optimize OR4E2 detection in tissues with low expression levels?

Detecting OR4E2 in tissues with low expression levels requires specialized approaches:

Signal amplification methods:

• Tyramide Signal Amplification (TSA):

  • Can increase sensitivity 10-100 fold over conventional methods

  • Optimal for immunohistochemistry and immunofluorescence

  • Protocol adjustment: Use primary antibody at 1:1000-1:2000, followed by HRP-conjugated secondary and tyramide amplification

• Proximity Ligation Assay (PLA):

  • Allows single-molecule detection

  • Particularly useful when studying protein-protein interactions involving OR4E2

  • Generates punctate signals that can be quantified

Sample enrichment strategies:

• Subcellular fractionation:

  • Isolate membrane fractions to concentrate OR4E2 protein

  • Reduces background from cytosolic proteins

• Cell sorting:

  • For heterogeneous tissues, consider FACS to enrich OR4E2-expressing cells

  • Can be combined with reporter systems in model organisms

Protocol optimization:

• Extended primary antibody incubation (48-72 hours at 4°C)

• Reduced washing stringency (use TBS instead of TBST)

• Use of high-sensitivity detection substrates for enzymatic methods

• Signal averaging through increased exposure times or multiple image acquisition

Complementary approaches:

• Combine protein detection with mRNA detection (e.g., RNAscope plus immunofluorescence)

• Use single-cell approaches for heterogeneous tissues

• Consider mass spectrometry-based approaches for unbiased detection

What are common causes of false positives/negatives when detecting OR4E2?

Common causes of false positives:

• Cross-reactivity with related olfactory receptors:

  • The human genome contains approximately 800 odorant receptor genes with sequence similarities

  • Validate using peptide competition assays as demonstrated with the Boster antibody

  • Consider testing in systems lacking OR4E2 expression

• Non-specific binding of secondary antibodies:

  • Always include a secondary-only control

  • Pre-adsorb secondary antibodies against tissue from the same species as the primary

• Endogenous peroxidase/phosphatase activity:

  • Use appropriate blocking steps (e.g., 0.3% H₂O₂ for HRP-based detection)

  • Include enzyme inhibitors in blocking solutions

Common causes of false negatives:

• Epitope masking:

  • If the antibody target (e.g., amino acids 228-277) is hidden in the protein's tertiary structure

  • Try different antigen retrieval methods (heat-induced versus proteolytic)

  • Consider using denaturing conditions for applications like Western blot

• Low expression levels:

  • OR4E2 may be expressed at low levels in non-olfactory tissues

  • Use signal amplification methods as described in section 3.3

  • Consider enrichment of membrane fractions

• Genetic variations:

  • Approximately 30% of the population carries pseudogene alleles of OR4E2

  • Sequence variation may affect antibody binding

  • Consider using multiple antibodies targeting different epitopes

• Preservation/fixation artifacts:

  • G-protein coupled receptors are sensitive to fixation conditions

  • Compare results across different fixation methods (4% PFA, methanol, acetone)

  • Adjust fixation time based on tissue type

How should I approach contradictory results between OR4E2 protein expression and gene expression data?

When facing discrepancies between protein and mRNA expression data for OR4E2, consider these methodological approaches:

Systematic validation strategy:

• Evaluate technical factors:

  • Antibody specificity: Confirm using peptide competition as demonstrated for OR4E2 antibodies

  • Primer specificity: Validate RNA detection methods against highly similar olfactory receptor sequences

  • Tissue preparation: Different preservation methods may affect protein versus RNA detection differently

• Consider biological factors:

  • Post-transcriptional regulation: OR4E2 mRNA may be subject to regulatory mechanisms affecting translation

  • Protein half-life: OR4E2 protein may be more/less stable than its mRNA

  • Genetic variations: Pseudogene alleles (present in ~30% of the population) may produce mRNA but not functional protein

• Reconciliation approaches:

  • Single-cell analysis: Correlate mRNA and protein levels at the single-cell level

  • Time-course studies: Examine whether there's a temporal offset between mRNA and protein expression

  • Inhibitor studies: Use translation inhibitors to establish relationship between transcription and protein accumulation

Case-specific strategies:

If mRNA is detected without protein:

• Test multiple antibodies targeting different epitopes

• Use more sensitive protein detection methods (see section 3.3)

• Consider whether post-translational regulation prevents protein accumulation

If protein is detected without mRNA:

• Examine protein half-life (may persist after mRNA degradation)

• Validate RNA detection methods, especially for low-abundance transcripts

• Consider cross-reactivity with related proteins

When designing experiments to resolve contradictions, include positive controls with known OR4E2 expression and negative controls where neither protein nor mRNA should be present.

What considerations are important when using OR4E2 antibodies for co-localization studies?

Co-localization studies involving OR4E2 require careful experimental design due to the protein's membrane localization and the specificity challenges of olfactory receptor antibodies:

Technical considerations:

• Antibody compatibility:

  • When combining OR4E2 antibodies with antibodies against other targets, ensure they're raised in different host species

  • Most commercial OR4E2 antibodies are rabbit polyclonal , limiting co-staining options

  • Consider using directly conjugated antibodies to reduce cross-reactivity

• Sequential staining protocol:

  • For same-species antibodies, use a sequential staining protocol:

    1. First primary antibody → fluorophore-conjugated Fab fragment secondary

    2. Blocking with excess unlabeled Fab fragments

    3. Second primary antibody → differently labeled secondary antibody

• Optical considerations:

  • Use spectral unmixing for fluorophores with overlapping emission spectra

  • Account for the thin membrane distribution of OR4E2 when analyzing co-localization

  • Z-stack imaging is essential for accurate co-localization assessment of membrane proteins

Validation approaches:

• Controls for each antibody separately

  • Individual staining to establish baseline patterns

  • Peptide competition controls for each antibody independently

• Proximity validation

  • Complement antibody co-localization with proximity ligation assays

  • Consider FRET-based approaches for confirmed interactions

• Orthogonal confirmation

  • Validate key findings with tagged protein expression

  • Use biochemical fractionation to confirm co-localization in the same subcellular compartment

When interpreting results, set clear criteria for what constitutes meaningful co-localization, considering the resolution limits of your imaging system relative to the subcellular structures being examined.

How does fixation method affect OR4E2 antibody performance in different applications?

The choice of fixation method significantly impacts OR4E2 detection due to its membrane protein nature and complex tertiary structure:

Comparative analysis of fixation methods:

Application-specific recommendations:

• For immunofluorescence in cell culture:

  • Validated results have been obtained with paraformaldehyde fixation for A549 cells

  • Recommended protocol: 4% PFA for 15 minutes at room temperature followed by 0.2% Triton X-100 permeabilization

• For tissue immunohistochemistry:

  • Consider testing both frozen and FFPE approaches

  • For FFPE sections, heat-mediated antigen retrieval (citrate buffer pH 6.0 or EDTA buffer pH 9.0) may be necessary

  • Extended primary antibody incubation (overnight at 4°C) often improves signal

• For biochemical applications:

  • Direct lysis in SDS-PAGE sample buffer may better preserve epitopes than chemical fixation

  • For co-immunoprecipitation, milder detergents (CHAPS, digitonin) may better preserve protein-protein interactions

When optimizing fixation conditions, balance epitope preservation against structural integrity needs. Systematic comparison of multiple fixation methods is recommended when establishing a new application for OR4E2 antibodies.

How can OR4E2 antibodies be used to study the relationship between genetic variation and functional outcomes?

OR4E2 exhibits significant genetic variation that affects receptor function, making it an excellent model for structure-function studies:

Research approaches:

• Genetic-functional correlation studies:

  • Approximately 30% of the population carries pseudogene alleles affecting the MAYDRY domain of OR4E2

  • Design experiments to correlate genetic variants with:

    • Receptor trafficking (using surface labeling)

    • Ligand binding (using competitive binding assays)

    • Signal transduction (using calcium imaging or luciferase reporter assays)

• Structural impact assessment:

  • Use antibodies targeting different epitopes to assess how variants affect protein conformation

  • Compare antibody accessibility across variants to identify structural changes

  • Combine with computational modeling to predict impact of mutations

Methodological framework:

• Genetic screening to identify variants in study populations

• Functional characterization using in vitro expression systems

• Antibody-based detection to assess expression and localization

• Correlation of antibody binding patterns with functional outcomes

Example application:
Studies have shown that OR4E2 variants respond differently to amyl acetate, a known agonist. Researchers could use OR4E2 antibodies to determine whether these functional differences correlate with changes in protein expression, trafficking, or structural conformation .

This approach provides a powerful model for studying how genetic variation influences sensory perception at the molecular level.

What methodological approaches can resolve contradictory findings in OR4E2 research?

When faced with contradictory findings in OR4E2 research, systematic methodological approaches can help resolve discrepancies:

Antibody validation framework:

• Cross-validation with multiple antibodies:

  • Use antibodies targeting different epitopes (N-terminal vs C-terminal)

  • Compare results from multiple vendors with different validation approaches

  • Document epitope locations relative to known functional domains (e.g., MAYDRY domain)

• Orthogonal detection methods:

  • Complement antibody-based detection with mass spectrometry

  • Use CRISPR/Cas9-based tagging of endogenous OR4E2

  • Compare protein results with mRNA detection methods

Functional verification:

• Heterologous expression systems:

  • Express OR4E2 variants in controlled cellular backgrounds

  • Use antibodies to confirm expression and localization

  • Correlate with functional responses to known agonists like amyl acetate

• Dose-response relationships:

  • Examine the relationship between protein levels (quantified by antibodies) and functional responses

  • Control for genetic variations that might affect antibody binding

Resolution strategy for specific contradictions:

For contradictory cellular localization findings:

• Compare fixation and permeabilization methods

• Use subcellular fractionation followed by Western blotting

• Complement with live-cell imaging of tagged receptors

For contradictory expression pattern findings:

• Consider tissue-specific post-translational modifications

• Examine genetic variants in study populations

• Control for cross-reactivity with related olfactory receptors