Phospho-CDH5 (Y731) Antibody

What is VE-cadherin (CDH5) and its phosphorylated form at Y731?

VE-cadherin (Vascular Endothelial cadherin, also known as CDH5) is a calcium-dependent cell adhesion protein predominantly expressed in endothelial tissues and brain. It functions as a critical component in maintaining vascular integrity by forming adherens junctions between endothelial cells. The protein is a single-pass type I membrane protein located at cell-cell boundaries and cell-matrix boundaries .

Phosphorylation at tyrosine 731 (Y731) is a key post-translational modification of VE-cadherin that regulates its function in vascular permeability. This specific phosphorylation site is involved in coupling β-catenin to VE-cadherin and plays a crucial role in endothelial barrier function . Phosphorylation at this residue can be induced by various stimuli, including vascular endothelial growth factor (VEGF) and inflammatory cytokines.

What are the primary applications for Phospho-CDH5 (Y731) antibodies?

Phospho-CDH5 (Y731) antibodies have several validated research applications:

These applications help researchers investigate the phosphorylation status of VE-cadherin in various experimental settings, particularly in studies related to vascular permeability, angiogenesis, and endothelial cell function .

What species reactivity can be expected with commercial Phospho-CDH5 (Y731) antibodies?

Based on the product information from multiple suppliers, Phospho-CDH5 (Y731) antibodies typically show reactivity against:

When selecting an antibody for your research, it's critical to verify species reactivity in the product documentation, as this varies between manufacturers and specific antibody clones .

How should Phospho-CDH5 (Y731) antibodies be stored and handled to maintain optimal activity?

Proper storage and handling are crucial for maintaining antibody performance:

• Store at -20°C for long-term storage (up to one year)

• For frequent use and short-term storage (up to one month), store at 4°C

• Most Phospho-CDH5 (Y731) antibodies are supplied in a storage buffer containing:

  • PBS (pH 7.2-7.4)

  • 50% glycerol (to prevent freeze-thaw damage)

  • 0.02% sodium azide (as a preservative)

  • Sometimes includes BSA (0.5%) as a stabilizer

To preserve antibody activity:

• Avoid repeated freeze-thaw cycles by aliquoting the antibody upon receipt

• When thawing, allow the antibody to reach room temperature gradually

• Briefly centrifuge the vial before opening to collect all liquid at the bottom

• Handle using sterile technique and avoid contamination

What controls should be included when using Phospho-CDH5 (Y731) antibodies in experiments?

Rigorous experimental design requires appropriate controls:

Positive Controls:

• Lysates from endothelial cells treated with agents known to induce VE-cadherin phosphorylation (e.g., VEGF, histamine, thrombin)

• Recombinant phosphorylated VE-cadherin protein (if available)

• Tissues with known expression of phosphorylated VE-cadherin (e.g., endothelial tissues under inflammatory conditions)

Negative Controls:

• Lysates from cells treated with phosphatase inhibitors

• Non-endothelial cell lines that don't express VE-cadherin

• Samples pre-treated with lambda phosphatase to remove phosphorylation

Antibody Validation Controls:

• Blocking peptide competition assay using the immunogenic phosphopeptide

• Antibody omission control (all reagents except primary antibody)

• Isotype control (irrelevant rabbit IgG at the same concentration)

• Phosphorylation-specific controls (comparison with total VE-cadherin antibody)

What sample preparation protocols optimize detection of phosphorylated VE-cadherin?

Phosphorylation-specific detection requires specialized sample preparation:

For Western Blot:

• Include phosphatase inhibitors (e.g., sodium orthovanadate, sodium fluoride) in all lysis and wash buffers

• Use fresh tissue/cells when possible; flash-freeze samples if storage is necessary

• Maintain cold temperature throughout sample preparation

• Consider enrichment strategies for phosphoproteins if signal is weak

• Use a more sensitive detection method like ECL-plus or femto-sensitivity substrates

• Recommended dilution range: 1:500-1:2000

For Immunohistochemistry:

• Immediate fixation is crucial to preserve phosphorylation status

• Use phosphatase inhibitors in fixatives and wash buffers

• Consider antigen retrieval methods specific for phospho-epitopes

• Optimize blocking solutions to reduce background

• Recommended dilution range: 1:50-1:300

What factors might contribute to false negative results when using Phospho-CDH5 (Y731) antibodies?

Several factors can lead to false negative results when detecting phosphorylated VE-cadherin:

• Sample-related issues:

  • Rapid dephosphorylation during sample preparation (insufficient phosphatase inhibitors)

  • Improper storage leading to protein degradation

  • Inadequate antigen retrieval in fixed tissues

  • Masking of the phospho-epitope by protein-protein interactions

• Technical issues:

  • Suboptimal antibody concentration

  • Buffer incompatibility

  • Inadequate incubation time/temperature

  • Secondary antibody mismatch or degradation

  • Detection system sensitivity limitations

• Biological factors:

  • Y731 phosphorylation may be transient or at low levels under normal conditions

  • Context-dependent phosphorylation (requires specific stimuli)

  • Cell type-specific regulation of VE-cadherin phosphorylation

Methodological solutions:

• Validate phosphorylation status with multiple antibodies or techniques

• Use positive controls with known phosphorylation status

• Consider phosphatase treatment of duplicate samples as controls

• Test different lysis conditions and detection methods

How can researchers distinguish between specific and non-specific binding when using these antibodies?

Distinguishing specific from non-specific binding is crucial for accurate data interpretation:

Validation approaches:

• Peptide competition assay: Pre-incubate the antibody with the phosphorylated immunogenic peptide; specific signals should disappear

• Phosphatase treatment: Treat duplicate samples with lambda phosphatase; phospho-specific signals should be eliminated

• Knockdown/knockout validation: Use CDH5 knockdown or knockout samples as negative controls

• Signal correlation: Compare staining/band patterns with total VE-cadherin antibody; patterns should be consistent but not identical

• Cross-reactivity testing: Test the antibody against known structurally similar phosphoproteins

Signal assessment criteria:

• Specific signal should appear at the expected molecular weight (~87-120 kDa for VE-cadherin)

• In tissues, staining should localize to cell-cell junctions in endothelial cells

• Signal should increase under conditions known to enhance Y731 phosphorylation

• Background staining should be minimal at recommended dilutions

How can researchers quantify changes in VE-cadherin phosphorylation at Y731?

Accurate quantification of phosphorylation changes requires rigorous methodology:

Western Blot quantification:

• Use a dual detection approach with anti-phospho-VE-cadherin (Y731) and anti-total VE-cadherin antibodies

• Express results as a ratio of phosphorylated to total protein

• Include loading controls (β-actin, GAPDH) for normalization

• Use standard curves with recombinant proteins if absolute quantification is needed

• Perform densitometric analysis with appropriate software (ImageJ, Image Lab)

ELISA-based quantification:

• Commercial or custom sandwich ELISA with capture antibody against total VE-cadherin and detection antibody against phospho-Y731

• Standard curves using recombinant phosphorylated proteins

• Normalization to total protein content

Immunofluorescence quantification:

• Use appropriate image analysis software to measure fluorescence intensity

• Co-staining with endothelial markers (CD31, von Willebrand factor)

• Ratio measurement of phospho-specific to total protein signal

• Z-stack imaging to capture the complete junctional signal

How does phosphorylation at Y731 functionally impact VE-cadherin's role in endothelial barrier function?

The Y731 phosphorylation site on VE-cadherin plays a crucial role in regulating vascular permeability and barrier function:

Molecular mechanisms:

• Phosphorylation at Y731 is involved in coupling β-catenin to VE-cadherin

• This phosphorylation can weaken adherens junctions by promoting VE-cadherin internalization

• Y731 phosphorylation can be induced by various permeability-increasing factors including VEGF, inflammatory cytokines, and homocysteine

• Phosphorylation at this site modulates the interaction between VE-cadherin and cytoskeletal components

Experimental approaches to study functional impacts:

• Endothelial permeability assays: Measure transendothelial electrical resistance (TEER) or macromolecule passage while monitoring Y731 phosphorylation

• Phosphomimetic mutations: Create Y731E (mimics phosphorylation) or Y731F (prevents phosphorylation) to assess functional consequences

• Live-cell imaging: Monitor VE-cadherin internalization and junction remodeling in relation to Y731 phosphorylation status

• In vivo models: Assess vascular leakage in animal models while monitoring Y731 phosphorylation

What is the relationship between VE-cadherin Y731 phosphorylation and disease pathophysiology?

VE-cadherin phosphorylation at Y731 has been implicated in several pathological conditions:

Vascular hyperpermeability disorders:

• Increased Y731 phosphorylation occurs in inflammatory conditions and contributes to vascular leakage

• Studies indicate homocysteine increases phosphorylation of Y731 on VE-cadherin, which may contribute to cardiovascular diseases

Cancer and angiogenesis:

• VE-cadherin phosphorylation status affects tumor angiogenesis and metastasis

• Research indicates connections between EGFR mutations and CDH5 expression in lung cancer

• VE-cadherin phosphorylation may influence tumor cell extravasation and metastatic potential

Methodological approaches to study disease connections:

• Analyze phospho-Y731 levels in patient samples compared to controls

• Correlate phosphorylation status with disease progression or severity

• Use relevant disease models to track phosphorylation changes over time

• Test therapeutic interventions targeting the kinases responsible for Y731 phosphorylation

What emerging techniques are enhancing detection and functional analysis of phosphorylated VE-cadherin?

Advanced technologies are expanding our ability to study VE-cadherin phosphorylation:

Emerging detection methods:

• Proximity ligation assay (PLA): Allows in situ detection of phosphorylated proteins with enhanced specificity and sensitivity

• Mass spectrometry-based phosphoproteomics: Enables unbiased identification of multiple phosphorylation sites and their relative abundance

• Super-resolution microscopy: Provides nanoscale visualization of phosphorylated VE-cadherin at cell-cell junctions

• FRET/FLIM-based biosensors: Allows real-time monitoring of phosphorylation events in living cells

Functional analysis innovations:

• CRISPR/Cas9 genome editing: Creation of phospho-deficient or phospho-mimetic mutations in endogenous VE-cadherin

• Microfluidic vascular models: Allows assessment of phosphorylation under controlled flow conditions

• Intravital microscopy: Enables real-time visualization of vascular permeability in relation to phosphorylation status in vivo

• Phospho-specific nanobodies: Offers new tools for tracking and potentially inhibiting specific phosphorylation events

These advanced approaches are expanding our understanding of how Y731 phosphorylation regulates VE-cadherin function in health and disease contexts .

How should researchers design experiments to study the kinases responsible for VE-cadherin Y731 phosphorylation?

To identify and characterize kinases that phosphorylate VE-cadherin at Y731:

Experimental design strategy:

• Kinase inhibitor screening:

  • Treat endothelial cells with a panel of selective kinase inhibitors

  • Monitor Y731 phosphorylation by Western blot using phospho-specific antibodies

  • Focus on tyrosine kinases (Src family kinases, VEGFR2, etc.)

• Genetic approaches:

  • siRNA/shRNA knockdown of candidate kinases

  • CRISPR/Cas9 knockout of specific kinases

  • Overexpression of constitutively active or dominant-negative kinase mutants

• In vitro kinase assays:

  • Recombinant kinases with VE-cadherin cytoplasmic domain as substrate

  • Detection of phosphorylation using phospho-Y731 antibodies

  • Mass spectrometry confirmation of site-specific phosphorylation

• Phosphorylation dynamics:

  • Time-course analysis after stimulus application (VEGF, thrombin, etc.)

  • Correlation between kinase activation and Y731 phosphorylation

  • Use phospho-specific antibodies against both the kinase and VE-cadherin Y731

What methodological approaches can reveal cross-talk between VE-cadherin phosphorylation and other signaling pathways?

Understanding the integration of VE-cadherin phosphorylation with other signaling pathways requires specialized approaches:

Multi-pathway analysis methods:

• Multiplexed immunoassays:

  • Simultaneous detection of phosphorylated VE-cadherin and components of related pathways

  • Correlation analysis between phosphorylation events

  • Time-course studies to establish causality and feedback loops

• Interactome analysis:

  • Immunoprecipitation of phosphorylated VE-cadherin followed by mass spectrometry

  • Identification of phosphorylation-dependent binding partners

  • Comparison of interactome in phosphorylated vs. non-phosphorylated states

• Systems biology approaches:

  • Phosphoproteomics analysis after modulating VE-cadherin phosphorylation

  • Computational modeling of signaling networks

  • Perturbation studies to validate model predictions

Research suggests connections between:

• EGFR signaling and CDH5 expression in lung cancer cells

• PI3K recruitment to phosphorylated VE-cadherin for osteoclast function

• β-catenin coupling to VE-cadherin regulated by Y731 phosphorylation

These approaches can reveal how VE-cadherin phosphorylation integrates with broader cellular signaling networks.

How can researchers effectively validate novel compounds targeting VE-cadherin phosphorylation?

For researchers developing or validating compounds that modulate VE-cadherin phosphorylation:

Comprehensive validation workflow:

• In vitro target engagement:

  • Biochemical assays with purified kinases/phosphatases

  • Cellular thermal shift assay (CETSA) to confirm compound binding

  • Dose-response analysis of Y731 phosphorylation using phospho-specific antibodies

• Cellular functional assays:

  • Endothelial barrier function (TEER, permeability assays)

  • VE-cadherin internalization and trafficking

  • Adherens junction assembly/disassembly dynamics

  • Endothelial cell migration and tube formation

• Specificity profiling:

  • Phosphoproteomic analysis to assess off-target effects

  • Comparison with genetic manipulation (siRNA, CRISPR) of the target

  • Counter-screening against related kinases/phosphatases

• Translational models:

  • Ex vivo tissue models (vessel explants)

  • In vivo vascular permeability assays

  • Disease-specific models (inflammation, tumor vasculature)