Phospho-PECAM1 (Y713) Antibody

What is Phospho-PECAM1 (Y713) antibody and what does it detect?

Phospho-PECAM1 (Y713) antibody specifically recognizes CD31/PECAM1 protein only when phosphorylated at tyrosine 713. CD31 (Platelet Endothelial Cell Adhesion Molecule-1 or PECAM-1) is a 130 kDa transmembrane glycoprotein belonging to the immunoglobulin superfamily of cell adhesion molecules. This antibody is typically generated using a synthetic peptide corresponding to the human PECAM-1 sequence around the phosphorylation site of Tyr713, usually within the amino acid range 686-735 .

Which cell types express PECAM1 and where is it phosphorylated?

PECAM1 is expressed by circulating platelets, monocytes, neutrophils, some T cells, and endothelial cells. It is primarily localized at the intercellular junctions of confluent endothelial cell monolayers. PECAM1 undergoes phosphorylation on several residues including Tyr713. This phosphorylation occurs under various stimuli such as mechanical stress, oxidative stress, and is often mediated by Src family kinases. In endothelial cells specifically, the kinase Fyn mediates mechanical force-induced (stretch or pull) tyrosine phosphorylation .

What is the functional significance of Y713 phosphorylation in PECAM1?

Phosphorylation at Tyr713 is part of a sequential phosphorylation cascade in PECAM1. Upon cellular activation, Ser-729 is phosphorylated first, which initiates the dissociation of the membrane-interaction segment (residues 709-729) from the cell membrane. This structural change allows the sequential phosphorylation of Tyr-713 and Tyr-690. The phosphorylation status at Y713 has been shown to inversely correlate with neutrophil distance from vessel walls, suggesting its active role during extravasation processes. This phosphorylation mediates associations with SH2 domain-containing binding partners such as PI3-kinase, SHIP, PLCγ, and SHP-2, allowing PECAM1 to serve as a scaffold for various signaling molecules .

What applications is the Phospho-PECAM1 (Y713) antibody validated for?

The commercially available Phospho-PECAM1 (Y713) antibodies have been validated for multiple applications with specific recommended dilutions:

It's important to validate the antibody in your specific experimental system, as reactivity and optimal dilutions may vary between manufacturers and experimental conditions .

How should I design controls when using Phospho-PECAM1 (Y713) antibody?

When designing experiments with Phospho-PECAM1 (Y713) antibody, include the following controls:

• Positive control: Lysates from cells known to express phosphorylated PECAM1, such as activated endothelial cells (HUVEC), NIH-3T3, or PC12 cells that have been subjected to mechanical stress or oxidative stress

• Negative control:

  • Untreated cells showing basal phosphorylation levels

  • Cells treated with phosphatase to remove phosphorylation

  • PECAM1 knockout or knockdown samples

  • Samples pre-treated with phosphorylation inhibitors specific to Src-family kinases

• Antibody controls:

  • Primary antibody omission

  • Isotype control (rabbit IgG)

  • Blocking with the immunizing peptide when available

• Specificity validation: Compare staining patterns with total PECAM1 antibody to confirm localization patterns .

What is the best sample preparation method to preserve phosphorylation at Y713?

Preserving phosphorylation status is critical when working with phospho-specific antibodies. Follow these recommendations:

• Cell/tissue collection: Work quickly and keep samples cold throughout processing

• Lysis buffer components:

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

  • Add protease inhibitors to prevent protein degradation

  • Use a buffer containing 1% NP-40 or Triton X-100, 150 mM NaCl, 50 mM Tris-HCl (pH 7.4)

• Fixation for IHC/IF:

  • Use 4% paraformaldehyde fixation

  • Avoid harsh permeabilization methods

• Storage: Aliquot samples and store at -80°C to avoid freeze-thaw cycles

• Phosphorylation induction: For positive controls, stimulate cells with peroxide, mechanical stress, or specific growth factors .

How can Phospho-PECAM1 (Y713) antibody be used to study leukocyte transendothelial migration?

Leukocyte transendothelial migration (TEM) is a crucial process during inflammation where PECAM1 plays a significant role. Advanced methodologies using Phospho-PECAM1 (Y713) antibody include:

• In vitro transmigration assays: Use Phospho-PECAM1 (Y713) antibody to monitor phosphorylation status during TEM in Transwell systems with endothelial monolayers

• Live cell imaging: Combine antibody staining with time-lapse microscopy to correlate PECAM1 phosphorylation with leukocyte migration dynamics

• Comparative studies: Research has shown that phosphorylation level of CD31 (pY713) inversely correlates with neutrophil distance from the vessel wall, with increased pY713 when cells are close to the blood vessel wall. Compare wild-type and PECAM1 knockout models to assess this relationship

• Mechanistic analysis: Use the antibody in combination with PECAM1 mutants (Y713F) to determine the specific contribution of this phosphorylation site to TEM

• Signaling cascade investigation: Employ the antibody in biochemical assays to identify binding partners that associate with phosphorylated Y713 during TEM .

Studies using Phospho-PECAM1 (Y713) antibody have revealed that CD31 signaling promotes the detachment of neutrophils from the outer components of the vessel wall after extravasation, which is crucial for timely migration to inflammatory sites .

What experimental approaches can reveal the relationship between mechanical forces and PECAM1 Y713 phosphorylation?

PECAM1 functions as a mechanosensor in endothelial cells, with phosphorylation at Y713 playing a role in mechanotransduction. Advanced experimental approaches include:

• Fluid shear stress systems: Apply defined laminar or oscillatory flow to endothelial cells and monitor Y713 phosphorylation over time

• Cell stretching devices: Use flexible membrane systems to apply mechanical stretch to cells while monitoring phosphorylation changes

• Atomic force microscopy (AFM): Combine AFM with phospho-specific immunostaining to correlate local mechanical forces with Y713 phosphorylation

• FRET-based biosensors: Develop tension sensors incorporating PECAM1 to monitor conformational changes upon mechanical stimulation in real-time

• Electric Cell-substrate Impedance Sensing (ECIS): Use ECIS to measure PECAM1-mediated endothelial cell barrier function in response to stimuli like thrombin, while simultaneously monitoring Y713 phosphorylation status .

Research has demonstrated that in endothelial cells, the kinase Fyn mediates mechanical force-induced (stretch or pull) tyrosine phosphorylation of PECAM1, making this a critical area for investigation in vascular mechanobiology .

How can contradictory results in PECAM1 Y713 phosphorylation studies be reconciled?

Researchers sometimes encounter contradictory results when studying PECAM1 Y713 phosphorylation. Several methodological approaches can help reconcile these discrepancies:

• Temporal analysis: Perform detailed time-course experiments, as Y713 phosphorylation may be transient or biphasic

• Cell-type specificity: Compare phosphorylation patterns across different cell types (platelets vs. endothelial cells vs. leukocytes) under identical conditions

• Stimulation conditions: Systematically vary the type, duration, and intensity of stimuli (mechanical vs. biochemical vs. oxidative)

• Microenvironment factors: Consider the influence of extracellular matrix components, cell density, and neighboring cell types

• Antibody validation: Cross-validate results using multiple antibody clones or alternative detection methods like mass spectrometry

• Phosphatase activity: Monitor the activity of phosphatases that may counterregulate Y713 phosphorylation

• Data normalization: Standardize quantification methods against total PECAM1 levels .

How can PECAM1-containing nanodiscs be used to study Y713 phosphorylation?

Nanodiscs represent an advanced approach for studying membrane proteins like PECAM1 in a native-like lipid environment. The application of this technology to study Y713 phosphorylation includes:

• Nanodisc preparation: Purify PECAM1 from platelets and assemble it into phospholipid nanodiscs using membrane scaffold proteins like MSP1D1

• Structural integrity validation: Confirm that PECAM1-containing nanodiscs retain both extracellular and cytoplasmic domains using domain-specific antibodies

• Phosphorylation studies: Investigate how Y713 phosphorylation affects:

  • Homophilic binding between PECAM1 molecules

  • Interaction with binding partners

  • Conformational changes in the protein

• Binding affinity regulation: Examine how engagement of membrane-proximal Ig domain 6 modulates the binding affinity of PECAM1 and whether this regulation involves Y713 phosphorylation

• Single-molecule studies: Use techniques like total internal reflection fluorescence (TIRF) microscopy to study individual PECAM1 molecules and their phosphorylation-dependent interactions .

Studies have shown that PECAM1-containing nanodiscs retain their ability to bind homophilically to PECAM1-expressing cells and exhibit regulatable adhesive interactions that can be modulated by ligands that bind membrane-proximal Ig Domain 6 .

What are the technical challenges in detecting PECAM1 Y713 phosphorylation in complex samples?

Detecting phosphorylation at specific residues like Y713 in PECAM1 presents several technical challenges that researchers should address:

• Signal-to-noise ratio: The phosphorylation signal may be weak relative to background, especially in heterogeneous tissue samples

• Phosphorylation dynamics: Y713 phosphorylation can be transient, requiring precise timing for sample collection

• Cross-reactivity: Antibodies may recognize similar phosphorylation motifs in other proteins, necessitating thorough validation

• Sample preparation: Improper sample handling can lead to rapid dephosphorylation by endogenous phosphatases

• Antibody specificity: Batch-to-batch variation in antibody production can affect specificity and sensitivity

Advanced approaches to overcome these challenges include:

• Phosphopeptide enrichment: Use titanium dioxide or immobilized metal affinity chromatography before mass spectrometry analysis

• Proximity ligation assays: Detect interactions between total PECAM1 and phosphorylated Y713 with higher sensitivity

• Multiplexed analysis: Simultaneously detect multiple phosphorylation sites (Y686, Y713, S729) to understand the phosphorylation sequence

• Super-resolution microscopy: Visualize the spatial distribution of phosphorylated PECAM1 at the nanoscale level .

How does PECAM1 Y713 phosphorylation contribute to vascular inflammatory disorders?

PECAM1 Y713 phosphorylation plays a significant role in vascular inflammatory processes, with implications for various pathological conditions:

• Atherosclerosis: PECAM1 has been shown to induce susceptibility to atherosclerosis. The phosphorylation at Y713 may influence:

  • Endothelial barrier function

  • Monocyte recruitment to atherosclerotic plaques

  • Inflammatory signaling cascades

• Ischemia-reperfusion injury: Y713 phosphorylation status affects:

  • Neutrophil extravasation dynamics

  • Endothelial cell survival

  • Vascular permeability

• Thrombosis: In platelets, PECAM1 functions largely as an inhibitory receptor. Y713 phosphorylation contributes to:

  • Negative regulation of platelet activation

  • Control of thrombus formation

  • Modulation of integrin signaling

• Angiogenesis: PECAM1 modulates endothelial cell migration and angiogenesis, with Y713 phosphorylation potentially regulating:

  • Tip cell selection

  • Vessel stabilization

  • Endothelial cell-cell contact formation .

How can quantitative analysis of PECAM1 Y713 phosphorylation improve experimental reproducibility?

Achieving reproducible quantification of PECAM1 Y713 phosphorylation requires standardized methodologies:

• Standardized phosphorylation index: Calculate the ratio of phospho-Y713 signal to total PECAM1 to normalize for expression level variations

• Digital image analysis: Use software tools for unbiased quantification of immunofluorescence intensity and localization

• Calibration standards: Include known quantities of phosphorylated and non-phosphorylated peptides as internal standards

• Multi-laboratory validation: Establish standardized protocols across different research groups using the same antibody lots and controls

• Reporting guidelines: Implement comprehensive reporting of experimental conditions, including:

• Data repository: Contribute to and utilize shared databases of phosphorylation data to enable meta-analyses .

By implementing these standardized approaches, researchers can significantly improve the reproducibility and comparability of PECAM1 Y713 phosphorylation studies across different experimental systems and laboratories.