Phospho-EPHA2/EPHA5 (Tyr594) Antibody

Introduction to Phospho-EPHA2/EPHA5 (Tyr594) Antibody

Phospho-EPHA2/EPHA5 (Tyr594) Antibody is a specialized immunoreagent designed to detect EPHA2 and EPHA5 proteins specifically when phosphorylated at the tyrosine 594 position. This antibody represents an essential tool for researchers investigating the functional roles of these receptor tyrosine kinases in various biological contexts . The antibody's high specificity allows for precise detection of the phosphorylation state of EPHA2/EPHA5, enabling detailed studies of signaling pathways in both normal developmental processes and pathological conditions.

The antibody is typically derived from rabbit hosts and is available in both polyclonal and unconjugated forms, as well as with various conjugates for different detection methods . Its specificity is centered around recognizing the amino acid sequence H-T-Y(p)-E-D, where Y(p) represents the phosphorylated tyrosine at position 594 . This specific recognition capability makes the antibody valuable for monitoring the activation state of EPHA2/EPHA5 receptors in experimental settings.

Biological Significance of EPHA2/EPHA5 Phosphorylation

The phosphorylation of tyrosine 594 in EPHA2 and EPHA5 represents a critical regulatory event in the function of these receptors. This post-translational modification has been identified in various tumor cell lines, indicating its potential role in oncogenesis and tumor progression . Research has demonstrated that phosphorylated Tyr594, along with Tyr588, creates binding sites for guanine nucleotide exchange factors Vav2 and Vav3, which are involved in regulating cell migration processes . This phosphorylation-dependent interaction highlights the importance of detecting the specific phosphorylation state for understanding the mechanistic details of EPHA2/EPHA5 signaling in both normal and pathological conditions.

Physical and Chemical Properties

Phospho-EPHA2/EPHA5 (Tyr594) antibodies are typically provided in liquid formulation with stabilizing components. The concentration is generally standardized at 1 mg/mL, suspended in phosphate-buffered saline (PBS) containing 50% glycerol and 0.02% sodium azide at pH 7.4 . Some variants may use slightly different buffer compositions, such as 0.01M sodium phosphate, 0.25M NaCl, pH 7.6, with 5mg/ml bovine serum albumin and 0.02% sodium azide . The molecular weight of the target protein EPHA2 is reported as 110 kDa or 135 kDa, depending on the source and specific conditions of analysis .

Available Formats and Conjugates

The antibody is available in multiple formats to accommodate various experimental needs. The primary forms include:

1. Unconjugated antibody for standard applications

2. Conjugated versions with various fluorophores for direct fluorescence detection

For fluorescently conjugated variants, the following options are typically available with their respective excitation and emission wavelengths:

This range of conjugation options allows researchers to select the appropriate variant for their specific experimental setup and detection equipment .

Reactivity and Specificity

Phospho-EPHA2/EPHA5 (Tyr594) antibodies are designed to detect endogenous levels of EPHA2 and EPHA5 proteins only when phosphorylated at tyrosine residue 594 . The reactivity profile typically includes human and mouse samples, making these antibodies suitable for comparative studies across these species . Some versions may show restricted reactivity, with certain products being specified for transfected-only detection in human samples .

The high specificity is achieved through the use of synthetic peptides containing the phosphorylated tyrosine residue as immunogens. These peptides typically correspond to amino acid sequences surrounding the Tyr594 position (H-T-Y(p)-E-D) derived from human EPHA2/EPHA5 proteins . This targeted approach ensures that the antibody binds selectively to the phosphorylated form of the protein, allowing for precise monitoring of the activation state.

Role in the Ephrin Receptor Subfamily

EPHA2 and EPHA5 belong to the ephrin receptor subfamily of the protein tyrosine kinase family . These receptors are part of a larger system that includes multiple EPH receptors (A and B classes) and their ephrin ligands, forming one of the largest receptor tyrosine kinase families in the human genome. The EPH-ephrin system operates through contact-dependent cell-cell communication, where membrane-bound ephrin ligands on one cell activate EPH receptors on adjacent cells .

This bidirectional signaling system plays crucial roles in establishing tissue boundaries, cell positioning, and morphological development. The highly conserved nature of these receptors across species highlights their fundamental importance in developmental processes and cellular functions .

Physiological Functions

EPHA2 and EPHA5 are involved in various physiological processes, with particularly prominent roles in the development and function of the nervous system . These receptors mediate axon guidance, neuronal migration, and synaptogenesis during neural development. They participate in establishing topographic maps in the visual system and contribute to the formation of neuronal circuits.

Beyond the nervous system, EPHA2 has been implicated in vascular development, angiogenesis, and epithelial tissue homeostasis. It plays a role in maintaining the integrity of epithelial barriers and regulating cell adhesion and migration in various tissues . The phosphorylation status of tyrosine residues, including Tyr594, is critical for the proper functioning of these receptors in their diverse physiological contexts.

Implication in Developmental Processes and Disease

EPHA2 overexpression has been observed in numerous cancer types, including breast, prostate, lung, and colorectal cancers . This overexpression often correlates with tumor aggressiveness and poor patient prognosis. Interestingly, the functional consequences of EPHA2 in cancer appear to be context-dependent, with evidence supporting both tumor-promoting and tumor-suppressive roles depending on the tissue type and cellular environment.

The phosphorylation of tyrosine residues, including Tyr594, has been identified in several tumor cell lines . These phosphorylation events create docking sites for downstream signaling molecules, potentially contributing to cancer cell migration, invasion, and metastasis. The specific role of Tyr594 phosphorylation in providing binding sites for Vav2 and Vav3 guanine nucleotide exchange factors highlights its importance in regulating cytoskeletal dynamics and cell mobility .

Experimental Techniques

Phospho-EPHA2/EPHA5 (Tyr594) antibodies are versatile tools applicable across multiple experimental techniques. The most common applications include:

1. Western Blotting (WB): For detecting and quantifying phosphorylated EPHA2/EPHA5 in protein lysates

2. Enzyme-Linked Immunosorbent Assay (ELISA): For quantitative analysis in solution-based assays

3. Immunohistochemistry (IHC): For examining phosphorylation patterns in tissue sections

4. Immunocytochemistry (ICC): For visualizing subcellular localization in cultured cells

These diverse applications make the antibody valuable for both basic research and translational studies investigating the role of EPHA2/EPHA5 signaling in development and disease.

Recommended Protocols and Dilutions

For optimal results, specific dilution ratios are recommended for different applications:

These dilution guidelines should be considered starting points, with optimization recommended for specific experimental conditions, sample types, and detection methods. For Western blotting, the expected molecular weight of the detected band is approximately 110-135 kDa, depending on the specific conditions and post-translational modifications .

Technical Considerations

When working with Phospho-EPHA2/EPHA5 (Tyr594) antibodies, several technical considerations can help ensure reliable and reproducible results:

1. Phosphorylation-specific antibodies are sensitive to sample preparation methods, particularly phosphatase activity in lysates. Using appropriate phosphatase inhibitors during sample preparation is crucial.

2. Some products are specified for detecting only transfected levels of the phosphorylated protein, which may limit their utility for detecting endogenous phosphorylation in certain contexts .

3. For fluorescently conjugated variants, minimizing exposure to light is essential to prevent photobleaching and loss of signal intensity.

4. Validation with appropriate positive and negative controls is recommended, particularly when first establishing the assay or when working with new tissue types or experimental conditions.

Signaling Pathways Associated with Tyr594 Phosphorylation

The phosphorylation of Tyr594 in EPHA2 represents a critical event in the activation and downstream signaling of this receptor tyrosine kinase. Upon binding of ephrin ligands, EPHA2 undergoes autophosphorylation at multiple tyrosine residues, including Tyr594, initiating a cascade of downstream signaling events . This phosphorylation creates specific docking sites for proteins containing Src homology 2 (SH2) or phosphotyrosine-binding (PTB) domains, enabling the assembly of multiprotein signaling complexes.

The specific phosphorylation at Tyr594 has been shown to create binding sites for guanine nucleotide exchange factors (GEFs), particularly Vav2 and Vav3 . These GEFs catalyze the exchange of GDP for GTP on Rho family GTPases, including Rac1, RhoA, and Cdc42, which are master regulators of cytoskeletal dynamics and cell motility.

Role in Tumor Cell Lines

Phosphorylation of Tyr594 has been identified in several tumor cell lines, suggesting its involvement in cancer-related signaling pathways . This phosphorylation event may contribute to the altered cell-cell communication and dysregulated cell migration observed in cancer progression. The availability of phospho-specific antibodies targeting this residue enables researchers to investigate how this specific modification correlates with cancer phenotypes, potentially identifying new therapeutic targets or prognostic markers.

Studies have demonstrated that EPHA2 is frequently overexpressed in various cancer types, and its phosphorylation status can influence tumor behavior . The ability to specifically detect phosphorylation at Tyr594 provides researchers with a tool to dissect the complex and sometimes contradictory roles of EPHA2 in tumor development and progression.

Connection to Cell Migration via Vav2/Vav3

One of the most well-characterized functions of Tyr594 phosphorylation is its role in regulating cell migration through interaction with Vav2 and Vav3 . These GEFs, when recruited to phosphorylated EPHA2, activate Rho family GTPases, leading to changes in the actin cytoskeleton that drive cell movement. This mechanism has implications for both normal developmental processes, such as neuronal migration and vascular development, and pathological conditions, particularly cancer metastasis.

The specific detection of Tyr594 phosphorylation using phospho-specific antibodies allows researchers to monitor this critical regulatory event in various experimental models, contributing to our understanding of both normal cellular functions and disease mechanisms. This knowledge may ultimately inform the development of targeted therapies aimed at modulating EPHA2 signaling in cancer and other diseases.

Performance Considerations

When selecting a Phospho-EPHA2/EPHA5 (Tyr594) antibody, several performance factors should be considered:

1. Sensitivity: Some products are optimized for detecting transfected levels of the protein, while others can detect endogenous phosphorylation levels .

2. Application compatibility: Different antibodies may perform optimally in specific applications, such as Western blotting, ELISA, or immunohistochemistry .

3. Species cross-reactivity: While most products react with human and mouse samples, the exact cross-reactivity profile may vary between manufacturers .

4. Conjugation options: For direct detection methods, the availability of conjugated variants with appropriate fluorophores may be a determining factor .

These considerations highlight the importance of selecting the appropriate antibody based on the specific experimental design and research questions being addressed.

Potential Research Applications

The availability of specific antibodies against phosphorylated Tyr594 in EPHA2/EPHA5 opens up numerous research possibilities:

1. Investigating the correlation between Tyr594 phosphorylation and cancer progression, potentially identifying new prognostic markers or therapeutic targets.

2. Exploring the dynamic regulation of EPHA2/EPHA5 phosphorylation during developmental processes, particularly in the nervous system.

3. Examining the interplay between EPHA2/EPHA5 and other signaling pathways in both normal and pathological contexts.

4. Developing high-throughput screening methods for compounds that modulate EPHA2/EPHA5 phosphorylation, potentially leading to new therapeutic approaches.

Future Perspectives

As research on receptor tyrosine kinases continues to advance, several areas present promising avenues for future investigation:

1. Development of more sensitive and specific detection methods for phosphorylated EPHA2/EPHA5, including improved antibodies and novel biosensors.

2. Integration of phospho-specific detection with spatial and temporal resolution in living systems, allowing for real-time monitoring of signaling events.

3. Comprehensive characterization of the phosphorylation-dependent interactome of EPHA2/EPHA5, identifying novel binding partners and signaling nodes.

4. Translation of basic research findings into clinical applications, potentially using phospho-EPHA2/EPHA5 detection as a diagnostic or prognostic tool in cancer and other diseases.