EPHA6 Antibody

What is EPHA6 and what are its main biological functions?

EPHA6, also known as EHK-2 and HEK12, belongs to the Eph receptor family which binds members of the ephrin ligand family. It functions as a receptor tyrosine kinase that plays crucial roles in:

• Neural development including axon guidance, neuron-target interactions, and synaptic functions

• Learning and memory formation (genetic inhibition of EPHA6 in mice produces specific behavioral deficits)

• Cancer progression and metastasis in several tumor types

• Angiogenesis (tumor and developmental)

EPHA6 is highly expressed in the brain and testis, with reduction in EPHA6 detected in hypospadias, a common defect affecting the growth and closure of external genitalia. The receptor binds promiscuously to GPI-anchored ephrin-A family ligands (ephrin-A1, A2, A3, A4, and A5) residing on adjacent cells, leading to contact-dependent bidirectional signaling .

How do EPHA6 antibodies vary in their specificity and applications?

EPHA6 antibodies differ significantly in their target epitopes, host species, and validated applications:

When selecting an EPHA6 antibody, researchers should consider:

• Experimental application (IHC, WB, ELISA, etc.)

• Target species compatibility

• Epitope location (extracellular vs intracellular domains)

• Potential cross-reactivity with other Eph family members

What are the key structural features of EPHA6 protein?

EPHA6 shares the characteristic domain organization of Eph receptors:

• Extracellular region:

  • Globular domain (ephrin binding domain)

  • Cysteine-rich domain

  • Two fibronectin type III domains

• Transmembrane region

• Cytoplasmic region:

  • Juxtamembrane motif with two tyrosine residues (major autophosphorylation sites)

  • Kinase domain

  • Conserved sterile alpha motif (SAM) in the carboxy tail with one conserved tyrosine residue

The calculated molecular weight of EPHA6 is 116 kDa, and the protein catalyzes the reaction: ATP + [protein]-L-tyrosine = ADP + [protein]-L-tyrosine phosphate . The sterile alpha motif (SAM) domain of EPHA6 can bind to both SAMD5 and SHIP2/Odin SAM domains, unlike some other Eph receptors that exhibit more restricted binding specificity .

What are the optimal conditions for immunohistochemistry using EPHA6 antibodies?

For optimal immunohistochemistry with EPHA6 antibodies, consider the following methodology:

Antigen Retrieval:

• For formalin-fixed, paraffin-embedded tissues: Use TE buffer pH 9.0 (preferred) or citrate buffer pH 6.0 as alternatives

• Apply high pressure (10 min) for optimal epitope exposure

Dilution Range:

• For polyclonal antibody 20211-1-AP: 1:20-1:200 (optimal dilution is sample-dependent)

• For anti-EPHA6 extracellular antibody: 1:200

• For ab113239: 10 μg/ml

Protocol Elements:

• Dewax sections with xylene and rehydrate in descending alcohol series (100%, 95%, 70%)

• Block endogenous peroxidase with 0.3% hydrogen peroxide (30 min at 37°C)

• Perform antigen retrieval

• Block with normal goat serum (1:20) for 30 min at 37°C

• Incubate with primary antibody (overnight at 4°C recommended)

• Apply appropriate secondary antibody and detection system

Positive Control Tissues:

• Mouse brain tissue (cerebellum)

• Human testis

The validation gallery for specific antibodies should be consulted for reference images and expected staining patterns in different tissues .

How can I validate the specificity of an EPHA6 antibody in my experimental system?

Validating EPHA6 antibody specificity requires a multi-faceted approach:

• Positive and negative control tissues:

  • Positive controls: Brain tissue (especially cerebellum), testis

  • Negative controls: Tissues with minimal EPHA6 expression (based on literature)

• Antibody validation techniques:

  • Western blot analysis: Confirm single band at ~116 kDa in brain membrane preparations

  • Peptide competition: Pre-incubate antibody with immunizing peptide to block specific binding

  • Genetic controls: Use EPHA6 knockout tissues or cells (if available) or EPHA6 siRNA knockdown samples

  • Cross-reactivity assessment: Test against recombinant proteins of related Eph receptors

• Expression correlation:

  • Compare protein detection with mRNA expression using RT-qPCR

  • Primer design for EPHA6 validation:
    Forward: 5′-TTGGAGAAGTCTGTAGTGGG-3′
    Reverse: 5′-CTTCTTTGCCGATCCATGTG-3′

  • Use GAPDH as control:
    Forward: 5′-CTGACTTCAACAGCGACACC-3′
    Reverse: 5′-TGCTGTAGCCAAATTCGTTGT-3′

• Application-specific controls:

  • For IHC: Include secondary antibody-only control

  • For cell surface detection in flow cytometry: Use matched isotype control antibody

Thermal shift assays can also help determine binding specificity by measuring protein denaturation curves fitted to the Boltzmann sigmoid equation to obtain melting temperature (Tm) .

What are the best methods for detecting EPHA6 expression in various cancer types?

Multiple complementary approaches are recommended for comprehensive EPHA6 detection in cancer tissues:

1. Immunohistochemistry (IHC):

• Fixed tissues: Use antibodies validated for FFPE sections (e.g., 20211-1-AP at 1:20-1:200 dilution)

• Frozen sections: Anti-EphA6 extracellular antibody (AER-016) at 1:200 dilution followed by fluorescent secondary antibody

• Evaluate cellular localization patterns (membrane, cytoplasmic, nuclear)

2. mRNA Expression Analysis:

• RT-qPCR using validated EPHA6 primers:
  Forward: 5′-TTGGAGAAGTCTGTAGTGGG-3′
  Reverse: 5′-CTTCTTTGCCGATCCATGTG-3′

• Use GAPDH as normalizing control

• Calculate relative expression using the 2^-ΔΔCq method

3. Western Blot Analysis:

• Brain membrane preparations serve as positive controls

• Human cancer cell lines (PC-3M, LNCaP prostate cancer cells) can be used as reference materials

• Expected molecular weight: 116 kDa

4. Bioinformatic Analysis:

• Utilize public datasets from REMBRANDT and TCGA

• Extract Z-scored expression values from cBioPortal

• Divide patients into tertiles based on mRNA expression levels

• Evaluate correlation with clinical parameters using statistical tools like R software

What is the evidence linking EPHA6 to cancer progression and metastasis?

Substantial evidence connects EPHA6 to cancer progression across multiple tumor types:

Prostate Cancer:

• EPHA6 is consistently overexpressed in prostate cancer lymph node metastatic cell lines

• Immunohistochemistry shows strong EPHA6 expression in primary prostate cancer tissues compared to minimal detection in adjacent non-tumor tissues

• EPHA6 knockdown significantly decreases cancer cell invasion and extracellular matrix degradation in vitro

• In vivo studies demonstrate reduced incidence of metastases to local draining lymph nodes and lungs in EPHA6 knockdown models

• EPHA6 expression positively correlates with vascular invasion, neural invasion, PSA level, and TNM staging in clinical samples

Breast Cancer:

• RT-qPCR and IHC analyses show increased EPHA6 expression in breast cancer tissues compared to adjacent normal tissues

• EPHA6 overexpression correlates with clinicopathological parameters in breast cancer patients

Glioma:

• EPHA6 physically interacts with BMP type I receptor ALK-2

• This interaction sensitizes glioma-initiating cells to specific therapeutic approaches

Mechanism of Action:

• EPHA6 promotes angiogenesis through:

  • Enhanced tube formation of endothelial cells in vitro

  • Increased microvascular density in tumor tissues

• Genome-wide expression analysis in EPHA6 knockdown cells identified differentially regulated genes including PIK3IPA, AKT1, and EIF5A2

These findings identify EPHA6 as a potential novel metastasis gene that positively correlates with cancer progression across multiple types, suggesting its value as a possible therapeutic target in metastatic disease .

How does EPHA6 expression correlate with clinical outcomes in cancer patients?

EPHA6 expression demonstrates significant correlations with multiple clinical parameters and outcomes:

Prostate Cancer:

• EPHA6 mRNA expression is significantly higher in 112 prostate cancer tumor samples compared to benign tissues from 58 benign prostate hyperplasia patients

• Positive correlations exist between EPHA6 expression and:

  • Vascular invasion (p < 0.01)

  • Neural invasion (p < 0.01)

  • PSA levels (p < 0.01)

  • TNM staging (p < 0.01)

• Interestingly, no significant correlation was found with Gleason scores, possibly because the samples started from Gleason 6, representing already aggressive disease

Cancer Survival Analysis:

• Patient datasets from TCGA Pan-Cancer clinical data reveal:

  • Patients can be divided into tertiles based on EPHA6 mRNA expression levels

  • Differences in survival outcomes can be evaluated using log-rank tests

  • Z-scored expression values provide standardized comparison across datasets

Uveal Melanoma:

These clinical correlations suggest EPHA6 could serve as both a prognostic biomarker and potential therapeutic target. Research methods for such correlation studies typically involve:

• Immunohistochemical scoring of tissue microarrays

• RNA expression analysis using RT-qPCR

• Statistical correlation with clinical parameters using multivariate analysis

• Kaplan-Meier survival curves stratified by expression levels

How does EPHA6 interact with other signaling pathways in cancer and neural contexts?

EPHA6 exhibits significant crosstalk with multiple signaling pathways:

Cancer Signaling Pathways:

• BMP Signaling: EPHA6 physically interacts with BMP type I receptor ALK-2 through coimmunoprecipitation experiments

  • This interaction is reduced in the presence of LDN193189 (ALK-2 inhibitor)

  • ALK-2 kinase activity supports binding to EPHA6, correlating with cooperative effects in causing apoptosis

• Downstream Effectors: Genome-wide gene expression analysis in EPHA6 knockdown cells identified differentially regulated genes:

  • PIK3IPA (PI3K pathway component)

  • AKT1 (key survival pathway mediator)

  • EIF5A2 (translation factor implicated in cancer progression)

Structural Interaction Mechanisms:

• EPHA6 SAM domain can bind to both SAMD5 and SHIP2/Odin SAM domains

• Specific residues are critical for these interactions:

  • Mutations affecting the EPHA6 R1014 position disrupt SHIP2 binding

  • The sterile alpha motif (SAM) interactions provide distinct downstream signaling specificity

Ephrin-Based Signaling:

• EPHA6 binds promiscuously to GPI-anchored ephrin-A family ligands:

  • ephrin-A1, ephrin-A2, ephrin-A3, ephrin-A4, and ephrin-A5

• Only membrane-bound or Fc-clustered ligands activate the receptor

• Soluble monomeric ligands bind but don't induce receptor autophosphorylation

• This leads to bidirectional signaling: forward (into EPHA6-expressing cell) and reverse (into ephrin-expressing cell)

Understanding these pathway interactions is crucial for developing targeted therapeutic strategies and explaining the tissue-specific functions of EPHA6 in both neural development and cancer progression .

How can kinase-dead EPHA6 mutants be used to dissect signaling mechanisms?

Kinase-dead (KD) EPHA6 mutants provide powerful tools for distinguishing kinase-dependent and kinase-independent functions:

Construction of Kinase-Dead Mutants:

• EPHA6 K757R mutant can be constructed using mutagenesis primers: 5′-GTTGCCATTAGAACTTTGAAA-3′

• This design is based on corresponding kinase-dead mutants in other Eph receptors:

  • EPHA8 K666M

  • EPHA3 K653R

• Mutants should be confirmed by Sanger sequencing analysis

Experimental Applications:

• Comparative signaling studies:

  • Express wild-type EPHA6 (EPHA6-WT) and kinase-dead (EPHA6-KD) in cellular models using adenoviral vectors

  • Compare downstream phosphorylation events to identify kinase-dependent pathways

  • Assess protein-protein interactions that persist in kinase-dead mutants

• Structure-function analysis:

  • Mutations in the conserved regions can be introduced to determine which domains are essential for specific interactions

  • Cancer-associated mutations (e.g., EphA6 R1014Q) can be studied to understand their functional implications

• Dominant-negative approaches:

  • Overexpress kinase-dead mutants to compete with endogenous EPHA6

  • Assess whether kinase-dead mutants retain the ability to bind:

    • Ephrin ligands (extracellular interactions)

    • Intracellular signaling adaptors (kinase-independent functions)

• Thermal shift assays:

  • Use to determine binding of nucleotides and kinase inhibitors to wild-type versus kinase-dead proteins

  • Measure protein denaturation curves fitted to the Boltzmann sigmoid equation

  • Compare melting temperatures (Tm) between variants

The juxtaposition of wild-type and kinase-dead mutants reveals which cellular responses require EPHA6 catalytic activity versus those that depend merely on protein-protein interactions, providing crucial insight into the diverse functions of this receptor in different cellular contexts .

What are the current challenges in developing specific detection systems for EPHA6 versus other Eph family members?

Developing highly specific detection systems for EPHA6 faces several significant challenges:

Structural Homology Challenges:

• High sequence homology between Eph family members (especially within A or B subfamilies)

• Conserved domains (kinase domain, SAM domain) show particular similarity

• Cross-reactivity testing shows ~20-30% cross-reactivity between human and mouse EPHA6 antibodies

Epitope Selection Strategies:

• Target unique regions:

  • Focus on the most divergent regions between EPHA6 and other Eph receptors

  • Extracellular domain contains more unique sequences than intracellular domains

  • Peptide (C)KEHEQLTYSSTRSK (amino acids 482-495) has been successfully used for specific antibody generation

• Validation requirements:

  • Test against recombinant proteins of related Eph receptors

  • Include positive controls (brain tissue) and negative controls

  • Perform peptide competition assays to confirm specificity

Application-Specific Considerations:

Methodological Recommendations:

• Use multiple antibodies targeting different epitopes to confirm results

• Combine protein and mRNA detection methods

• Include appropriate genetic controls (siRNA knockdown or CRISPR knockout)

• Cross-reference findings with genomic databases to identify potential variants

These challenges necessitate rigorous validation strategies when studying EPHA6, particularly in contexts where multiple Eph receptors may be co-expressed, such as neural tissues and various cancer types .

How can researchers effectively study the role of EPHA6 in neural development and learning?

Investigating EPHA6's neural functions requires specialized experimental approaches:

In Vivo Models:

• Genetic knockout/knockdown models:

  • EPHA6-deficient mice show specific behavioral deficits in learning and memory tests

  • Reduced memory of the consequences of training context observed

  • Region-specific conditional knockouts can isolate functions in hippocampus versus cortex

• Temporal control systems:

  • Inducible Cre-lox systems allow developmental stage-specific deletion

  • Viral vector-mediated expression in specific brain regions

  • Optogenetic tools can be combined for temporal precision in activation studies

Behavioral Assays:

• Learning and memory tests specifically affected by EPHA6 deficiency:

  • Context fear conditioning

  • Spatial memory tasks (Morris water maze, radial arm maze)

  • Novel object recognition

Molecular and Cellular Approaches:

• Slice electrophysiology:

  • Long-term potentiation (LTP) and long-term depression (LTD) measurements

  • Paired-pulse facilitation for presynaptic function assessment

  • Field recordings from hippocampal CA1 region

• High-resolution imaging:

  • Dendritic spine morphology analysis (Golgi staining or fluorescent reporters)

  • Super-resolution microscopy of synaptic structures

  • Live imaging of EPHA6-GFP fusion proteins in developing neurons

• Molecular interaction studies:

  • Co-immunoprecipitation with post-synaptic density proteins

  • Proximity ligation assays to detect protein interactions in situ

  • FRET/FLIM for real-time interaction measurements

Experimental Design Considerations:

• Compare homozygous and heterozygous models to assess dose-dependency

• Include sex as biological variable (differences may exist)

• Control for developmental compensation in constitutive knockout models

• Use multiple antibodies for confirmation (e.g., extracellular domain antibody AER-016 at 1:200 dilution for immunohistochemistry)

The combination of these approaches can elucidate the mechanistic basis of EPHA6's effects on learning and memory, potentially identifying novel therapeutic targets for cognitive disorders .

What evidence exists for EPHA6 as a therapeutic target, and what approaches show promise?

Emerging evidence supports EPHA6 as a promising therapeutic target in multiple disease contexts:

Cancer Therapeutic Potential:

• Prostate Cancer: EPHA6 knockdown reduces:

  • Tumor cell invasion and matrix degradation in vitro

  • Metastasis to lymph nodes and lungs in vivo

  • Angiogenesis through decreased endothelial tube formation

• Glioma: EPHA6 interaction with ALK-2 sensitizes glioma-initiating cells to specific therapeutic approaches

  • This interaction is reduced by LDN193189 (ALK-2 inhibitor)

  • Suggests combination therapy potential

Neurological Applications:

• Neural Regeneration: EPHA6 signaling pathways are inhibitory for developing axons

  • Blocking these pathways enhances regeneration following spinal cord and brain injury

  • Renders EPHA6 an appealing drug target for regenerative approaches

• Cognitive Enhancement: Given EPHA6's role in learning and memory:

  • Modulating EPHA6 function might address cognitive deficits

  • Mice deficient in EPHA6 show reduced memory of training context consequences

Therapeutic Approach Options:

Validation Methodologies:

• Structure-based design informed by SAM domain interaction studies

• Thermal shift assays to assess binding of potential inhibitors

• Functional testing in relevant cell models:

  • Angiogenesis assays (tube formation)

  • Neural regeneration models

  • Cancer cell invasion studies