EPHA2/EPHA5 (Ab-594) Antibody

What is the EPHA2/EPHA5 (Ab-594) antibody and what epitope does it recognize?

The EPHA2/EPHA5 (Ab-594) antibody is a polyclonal antibody raised in rabbits against a synthetic non-phosphopeptide derived from human EPHA2 around the phosphorylation site of tyrosine 594 . The antibody specifically recognizes the tyrosine 594 region in the juxtamembrane segment of the EPHA2 receptor, which is a critical site for receptor activation and downstream signaling. This site plays a key role in EphA2's functions in cell migration, adhesion, and proliferation . The antibody is affinity-purified using epitope-specific immunogen chromatography to ensure specificity .

What experimental applications is the EPHA2/EPHA5 (Ab-594) antibody validated for?

The antibody has been validated for several experimental applications:

The antibody can be particularly useful in studying EPHA2 phosphorylation dynamics in cancer models, as demonstrated in studies examining EPHA2's role in tumor progression .

What is the specificity of the EPHA2/EPHA5 (Ab-594) antibody?

The antibody detects endogenous levels of total EPHA2 protein with high specificity . It was designed to recognize the region around tyrosine 594, which is a key phosphorylation site involved in EphA2 signaling. In phosphorylation studies, research has shown that Tyr594 phosphorylation is involved in the recruitment of signaling molecules that regulate cell migration and invasion . The antibody has been validated against human and mouse samples, making it suitable for comparative studies across these species .

How does sample preparation affect the detection of EPHA2 using this antibody?

Proper sample preparation is critical for optimal detection:

• For cell lysates, use lysis buffers containing phosphatase inhibitors if studying phosphorylation states

• Sample heating time and temperature are critical - excessive heating can disrupt epitope recognition

• For tissue samples, optimized fixation protocols (4% paraformaldehyde for 15-20 minutes at room temperature) help preserve epitope integrity while maintaining tissue architecture

• When performing immunoprecipitation, cells should be incubated briefly at 37°C after antibody binding at 4°C to allow for receptor internalization dynamics to be captured accurately

How can the EPHA2/EPHA5 (Ab-594) antibody be used to investigate EphA2 phosphorylation dynamics?

To investigate EphA2 phosphorylation dynamics:

• Time course experiments: Stimulate cells with ephrin-A1 ligand (either soluble ephrin-A1-Fc or membrane-bound ephrin-A1) and collect samples at different time points (5, 15, 30, 60 minutes). Research has shown that EphA2 phosphorylation on Tyr594 occurs in a time-dependent manner after ligand binding .

• Comparative analysis with other phosphorylation sites: Researchers can examine multiple phosphorylation sites (Tyr588, Tyr594, Tyr772) simultaneously to build a complete profile of EphA2 activation states. Studies have shown that different tyrosine residues in EphA2 have distinct functions in receptor signaling .

• Quantitative assessment: Use quantitative phospho-proteomics in combination with immunoprecipitation using the Ab-594 antibody to identify the stoichiometry of phosphorylation and temporal dynamics .

For example, researchers have demonstrated that LMW-HA (low molecular weight hyaluronan) stimulation leads to time-dependent phosphorylation of EphA2 on Tyr594, which can be blocked by Src kinase inhibitor PP2, revealing a mechanism of EphA2 transactivation in angiogenesis .

What role does Tyr594 phosphorylation play in EphA2 signaling pathways and how can it be studied using this antibody?

Tyr594 phosphorylation plays multiple critical roles in EphA2 signaling:

Methodological approach to study this phosphorylation site:

• Use EPHA2/EPHA5 (Ab-594) antibody in combination with phospho-specific antibodies targeting Tyr594

• Implement site-directed mutagenesis (Y594F) to create phosphorylation-deficient mutants

• Compare signaling outcomes between wild-type and mutant receptors using phosphoproteomics

• Perform co-immunoprecipitation experiments to identify binding partners specific to phosphorylated Tyr594

Studies have shown that phosphorylation at this site is critical for proper vascular assembly of endothelial cells on Matrigel, indicating its importance in angiogenesis .

How can researchers validate the specificity of results obtained with the EPHA2/EPHA5 (Ab-594) antibody?

Validation approaches include:

• Genetic knockdown/knockout controls: Generate EPHA2 knockdown or knockout cell lines using siRNA, shRNA, or CRISPR-Cas9 technology. The absence of signal in these lines confirms antibody specificity .

• Peptide competition assays: Pre-incubate the antibody with the immunizing peptide before application to samples. This should abolish specific binding .

• Multiple antibody approach: Use alternative antibodies targeting different epitopes of EPHA2 for cross-validation .

• Phosphatase treatment: For phosphorylation studies, treat one set of samples with lambda phosphatase to remove phosphorylation; this should eliminate binding of phospho-specific antibodies but not total EPHA2 antibodies .

• Heterologous expression systems: Overexpress wild-type EPHA2 and Y594F mutants in cells with low endogenous EPHA2 (like BEAS-2B cells) to confirm specificity to this residue .

Research has demonstrated that validation through these approaches ensures reliable results when studying complex signaling mechanisms involving EphA2 .

How can the EPHA2/EPHA5 (Ab-594) antibody be used to investigate EphA2's role in cancer metastasis?

To investigate EphA2's role in cancer metastasis:

• In vitro migration and invasion assays:

  • Compare EphA2 phosphorylation status at Tyr594 between highly metastatic and less metastatic cell lines

  • Correlate phosphorylation levels with invasive potential in transwell assays

  • Manipulate EphA2 signaling through ligand stimulation or inhibition while monitoring Tyr594 phosphorylation

• Mechanistic studies:

  • Use the antibody to examine how Tyr594 phosphorylation affects interaction with other proteins involved in metastasis

  • Research has shown that EphA2 phosphorylation affects its interaction with Src, cortactin, and p130Cas, which are involved in cell motility and invasion

• Clinical correlation:

  • Analyze patient samples for EphA2 Tyr594 phosphorylation status

  • Correlate with clinical outcomes and metastatic potential

  • Studies have shown that EphA2 expression is significantly higher in metastatic lesions compared to primary tumors

Research demonstrates that G391R mutation in EPHA2 in lung squamous cell carcinoma leads to constitutive activation with increased phosphorylation of Src, cortactin, and p130Cas, resulting in 40% increased invasiveness compared to wild-type cells .

What considerations should be taken when using this antibody to analyze the conformational changes in EphA2 following phosphorylation?

When studying conformational changes:

Research has revealed that accumulation of negative charges (mimicking phosphorylation) induces cooperative changes in the EphA2 intracellular region from more closed to more extended conformations .

What are the optimal conditions for using the EPHA2/EPHA5 (Ab-594) antibody in co-immunoprecipitation experiments?

For optimal co-immunoprecipitation results:

• Buffer composition:

  • Use lysis buffers containing 1% NP-40 or 0.5% Triton X-100

  • Include phosphatase inhibitors (sodium orthovanadate, sodium fluoride, β-glycerophosphate)

  • Add protease inhibitor cocktail to prevent protein degradation

  • Buffer should contain 150mM NaCl and 50mM Tris-HCl (pH 7.4)

• Experimental procedure:

  • Incubate cells with antibody (10 μg/mL) for 20 minutes at 4°C followed by 5 minutes at 37°C

  • For ligand-induced studies, include ephrin-A1-Fc (5 μg/mL) during incubation

  • Use Protein G Sepharose beads coated with anti-EphA2 antibody (0.8 μg/sample) for immunoprecipitation

  • Incubate overnight at 4°C for optimal protein-antibody complex formation

• Washing conditions:

  • Perform 3-5 washes with buffer containing reduced detergent concentration

  • Maintain cold temperature throughout to preserve protein-protein interactions

Studies have successfully used these conditions to identify novel EphA2 interaction partners like PATJ (Pals1-associated tight junction protein), which is recruited to EphA2 in a time-dependent manner following ligand stimulation .

How should researchers optimize Western blot protocols for detecting EPHA2 with the Ab-594 antibody?

For optimal Western blot results:

• Sample preparation:

  • Lyse cells in RIPA buffer containing phosphatase and protease inhibitors

  • Sonicate briefly to shear DNA and reduce sample viscosity

  • Heat samples at 95°C for 5 minutes in Laemmli buffer containing β-mercaptoethanol

• Gel electrophoresis and transfer conditions:

  • Use 7.5% or 4-12% gradient gels due to the large size of EPHA2 (110 kDa)

  • Transfer proteins to PVDF membrane at 30V overnight at 4°C for high-molecular-weight proteins

  • Verify transfer efficiency with reversible protein stains

• Antibody incubation:

  • Block membranes in 5% BSA in TBST for 1 hour at room temperature

  • Dilute primary antibody 1:500 - 1:3000 in 5% BSA/TBST

  • Incubate overnight at 4°C with gentle agitation

  • Wash 3-5 times with TBST before applying HRP-conjugated secondary antibody

• Detection optimization:

  • Use enhanced chemiluminescence with exposure times ranging from 30 seconds to 5 minutes

  • For phosphorylation-specific detection, enhanced sensitivity reagents may be necessary

Research has successfully used these conditions to detect EphA2 phosphorylation in studies examining its role in tumor progression and metastasis .

What experimental design should be used to study the effects of EPHA2/EPHA5 (Ab-594) antibody on tumor growth and metastasis?

A comprehensive experimental design should include:

• In vitro studies:

  • Cell viability assays in multiple cancer cell lines with varying EphA2 expression levels

  • Dose-response experiments (0.1-10 μg/ml) to determine optimal concentration

  • Soft agar colony formation assays to assess anchorage-independent growth

  • Tube formation assays on Matrigel to evaluate angiogenic potential

• Animal models:

  • Orthotopic tumor models (as used with MEDI-547, an antibody-drug conjugate targeting EphA2)

  • Comparison of tumor growth inhibition between antibody treatment and controls

  • Assessment of metastatic burden through bioluminescence imaging or ex vivo analysis

  • Histological examination of tumor tissues for proliferation and apoptosis markers

• Mechanistic validation:

  • Analysis of EphA2 degradation and internalization following antibody binding

  • Evaluation of downstream signaling pathways using phospho-specific antibodies

  • Comparison with effects of known EphA2 ligands (ephrin-A1)

Research has shown that EphA2-targeting antibodies can induce receptor phosphorylation and subsequent degradation, resulting in inhibition of malignant behavior in tumor cells . In mouse orthotopic models, EphA2-targeting antibody-drug conjugates have demonstrated 86-88% growth inhibition with reduced distant metastasis compared to controls .

How can researchers investigate the cross-talk between EPHA2 and other receptor tyrosine kinases using this antibody?

To investigate receptor cross-talk:

• Co-immunoprecipitation studies:

  • Immunoprecipitate EPHA2 using the Ab-594 antibody followed by immunoblotting for other RTKs

  • Reverse co-IP to confirm interaction

  • Include conditions of ligand stimulation for both receptors

• Proximity ligation assays (PLA):

  • Use the Ab-594 antibody in combination with antibodies against other RTKs

  • Quantify interaction signals under different cellular conditions

  • Compare results between normal and cancer cells

• Signaling pathway analysis:

  • Monitor phosphorylation of shared downstream targets

  • Use specific inhibitors of each RTK to dissect pathway contributions

  • Implement phosphoproteomic approaches to capture global signaling changes

• Functional studies:

  • Knockdown each receptor individually and in combination

  • Compare effects on cell proliferation, migration, and invasion

  • Assess the impact on therapeutic resistance

Research has identified important cross-talk between EPHA2 and EGFR, where combination targeting shows enhanced anti-tumor effects. Studies have demonstrated that a bispecific anti-EGFR/EPHA2 antibody very effectively suppresses tumor growth compared to anti-EGFR therapy alone, suggesting potential for overcoming resistance mechanisms .

What are common technical challenges when using the EPHA2/EPHA5 (Ab-594) antibody and how can they be addressed?

Research utilizing anti-EphA2 antibodies has shown that optimizing these conditions is critical for reliable detection of EphA2 expression and phosphorylation states in experimental systems .

How can researchers distinguish between ligand-dependent and ligand-independent EPHA2 activation when using this antibody?

To distinguish between activation mechanisms:

• Experimental design:

  • Compare conditions with and without ephrin ligands

  • Include ephrin-A1-Fc as positive control for ligand-dependent activation

  • Use serum-starved cells to minimize background activation

• Specific controls:

  • Include EphA2 mutants defective in ligand binding (mutations in the ligand-binding domain)

  • Use soluble EphA2 extracellular domain to sequester ligands

  • Compare phosphorylation patterns between ligand-stimulated and growth factor-stimulated conditions

• Readouts to examine:

  • Analyze differential phosphorylation patterns (Tyr594 phosphorylation occurs in both mechanisms)

  • Monitor receptor internalization (more pronounced in ligand-dependent activation)

  • Examine downstream effector activation (different pathways can be activated)

Research has shown that EphA2 can be transactivated through CD44-mediated Src activation in the absence of ephrin ligands, leading to phosphorylation at Tyr594. This mechanism was confirmed using the Src inhibitor PP2, which blocked both ligand-dependent and ligand-independent phosphorylation of EphA2 .

What considerations should be taken when using this antibody for multi-color immunofluorescence studies?

For successful multi-color immunofluorescence:

• Antibody compatibility:

  • Select primary antibodies raised in different host species to avoid cross-reactivity

  • When using multiple rabbit antibodies, consider sequential staining with HRP-conjugated secondaries and tyramide signal amplification

• Fixation and antigen retrieval:

  • Optimize fixation protocol for all target antigens (4% PFA for 15 minutes works well for EPHA2)

  • Test different antigen retrieval methods if required (citrate buffer pH 6.0 or Tris-EDTA pH 9.0)

• Controls for specificity:

  • Include single-stain controls to assess bleed-through

  • Use isotype controls matched to each primary antibody

  • Include absorption controls with immunizing peptides

• Signal detection optimization:

  • Balance signal intensities between channels

  • Use spectral unmixing for closely overlapping fluorophores

  • Consider using Zenon Alexa Fluor labeling kits for direct antibody labeling

Researchers have successfully used immunofluorescence to study EphA2 internalization dynamics following antibody binding, capturing the formation of EphA2-positive vesicles over time (0, 30, 60, and 90 minutes after temperature shift to 37°C) .

How can researchers measure binding affinity and kinetics of the EPHA2/EPHA5 (Ab-594) antibody to its target?

To measure binding parameters:

• Surface Plasmon Resonance (SPR):

  • Immobilize purified recombinant EphA2 protein on sensor chip

  • Flow antibody at varying concentrations (0.1-100 nM)

  • Calculate association (ka) and dissociation (kd) rate constants

  • Determine equilibrium dissociation constant (KD)

• Bio-Layer Interferometry (BLI):

  • Load biotinylated EphA2 onto streptavidin sensors

  • Measure real-time binding kinetics

  • Analyze data using appropriate association/dissociation models

• Flow cytometry-based approach:

  • Incubate cells expressing EphA2 with varying antibody concentrations

  • Plot Mean Fluorescence Intensity (MFI) against antibody concentration

  • Fit data to saturation binding curve to determine apparent Kd

• Competition assays:

  • Perform competition between antibody and natural ligand (ephrin-A1)

  • Determine IC50 values for competitive displacement

Studies have determined apparent Kd values for anti-EphA2 antibodies on cell lines like MiaPaCa2 using flow cytometry-based methods. High-affinity antibodies typically show Kd values in the single-digit nanomolar range .

How might the EPHA2/EPHA5 (Ab-594) antibody contribute to developing targeted cancer therapies?

This antibody could advance cancer therapeutics through:

• Target validation:

  • Confirming the role of Tyr594 phosphorylation in tumor progression

  • Identifying patient populations with phospho-specific EphA2 activation

• Therapeutic antibody development:

  • Serving as a starting point for humanized antibody development

  • Guiding epitope selection for antibody-drug conjugates

• Combination therapy design:

  • Identifying synergistic pathway interactions

  • Monitoring treatment response based on EphA2 phosphorylation status

• Biomarker development:

  • Correlating Tyr594 phosphorylation with clinical outcomes

  • Predicting response to EphA2-targeted therapies

Research has already demonstrated that EphA2-targeting antibody-drug conjugates, such as MEDI-547, show significant anti-tumor effects in endometrial cancer models, with 86-88% growth inhibition and reduced distant metastasis . Additionally, bispecific antibodies targeting both EGFR and EphA2 have shown enhanced efficacy compared to single-target approaches .

What emerging technologies could enhance the utility of this antibody in studying EPHA2 biology?

Emerging technologies include:

• Single-cell analysis:

  • Combining the antibody with mass cytometry (CyTOF) for high-dimensional analysis

  • Correlating EphA2 phosphorylation with cellular phenotypes at single-cell resolution

• Live-cell imaging:

  • Developing non-perturbing Fab fragments for dynamic studies

  • Implementing FRET-based biosensors to monitor EphA2 activation in real-time

• Spatial transcriptomics and proteomics:

  • Correlating EphA2 phosphorylation with spatial gene expression patterns

  • Mapping EphA2 signaling networks within the tumor microenvironment

• CRISPR-based screening:

  • Identifying genes that modulate EphA2 phosphorylation at Tyr594

  • Discovery of novel regulatory mechanisms

• Structural biology approaches:

  • Cryo-EM studies of antibody-bound EphA2 to visualize conformational changes

  • Hydrogen-deuterium exchange mass spectrometry to map binding interfaces