Phospho-CD44 (S706) Antibody

What is the specificity of Phospho-CD44 (S706) Antibody and how is it validated?

The Phospho-CD44 (S706) Antibody specifically detects endogenous levels of CD44 protein only when phosphorylated at the serine 706 residue. According to validation data, its specificity is confirmed through multiple methodologies:

• Western Blot validation: Tests against NIH/3T3 cells treated with PMA (250ng/ml for 5 minutes) to demonstrate specificity for the phosphorylated form .

• Phospho-ELISA validation: Comparative analysis using immunogen phosphopeptide versus non-phosphopeptide, showing selective recognition of the phosphorylated form .

• Blocking peptide experiments: To confirm epitope specificity, where signal is abolished when the antibody is pre-incubated with phosphorylated peptide .

The antibody is generated using synthetic peptides corresponding to the region surrounding S706 of human CD44 (typically amino acids 681-730), ensuring targeted recognition of this specific phosphorylation site .

What are the optimal applications and dilution recommendations for Phospho-CD44 (S706) Antibody?

The antibody has been validated for several experimental applications with specific dilution recommendations:

The optimal working dilution should be determined by each researcher through preliminary experiments, as results may vary depending on sample type, experimental conditions, and detection methods .

How should Phospho-CD44 (S706) Antibody be stored and handled to maintain activity?

Proper storage and handling are crucial for maintaining antibody performance:

• Long-term storage: Store at -20°C for up to one year from receipt date .

• Short-term/frequent use: Store at 4°C for up to one month .

• Avoid repeated freeze-thaw cycles: Aliquot upon receipt to minimize degradation .

• Formulation: Typically supplied in PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide as preservative .

• Safety note: Contains sodium azide, which should be handled according to laboratory safety protocols as it is considered hazardous .

What is the biological significance of CD44 phosphorylation at S706?

CD44 phosphorylation at S706 plays several important roles in cellular signaling and function:

• Regulation of signaling pathways: The phosphorylation status at S706 affects CD44's participation in multiple signaling cascades, including the CD44/PAK1/AKT axis .

• Dephosphorylation dynamics: Activation of PKC results in the dephosphorylation of S706 (which is constitutively phosphorylated), while inducing phosphorylation at S672 .

• Cancer relevance: Phosphorylation modifications of CD44 are implicated in resistance mechanisms to targeted therapies in cancer, particularly in lung cancer treatment resistance .

• Cytoskeletal interactions: Phosphorylation status influences CD44's interaction with the cytoskeleton through ERM (ezrin-radixin-moesin) proteins, affecting cell adhesion and migration behaviors .

How can Phospho-CD44 (S706) Antibody be used to study resistance mechanisms in cancer treatment?

Phospho-CD44 (S706) Antibody serves as a critical tool for investigating treatment resistance mechanisms:

• Phosphoproteomic analysis: In studies of lung cancer resistance to FGFR1 inhibitors, phosphoproteomic mass-spectrometry using phospho-specific antibodies identified the CD44/PAK1/AKT signaling axis as a common resistance mechanism .

• Experimental approach:

  • Compare phosphorylation levels between sensitive and resistant cell lines

  • Monitor changes in CD44 phosphorylation before and after treatment with targeted therapies

  • Correlate phosphorylation patterns with treatment outcomes

  • Use in combination with inhibitors of CD44, PAK1, or AKT to assess pathway interactions

• Clinical correlation: Strong CD44 expression was significantly correlated with AKT activation in squamous cell lung cancer patients, suggesting this antibody can help identify patients who might benefit from combination therapies targeting both pathways .

What role does phosphorylation of CD44 at S706 play in the CD44/PAK1/AKT signaling axis?

The phosphorylation status of CD44 at S706 significantly impacts signaling through the CD44/PAK1/AKT axis:

• Pathway activation: Phosphorylation at S706 represents a key regulatory mechanism in this pathway, with phosphoproteomic analysis revealing its importance in determining downstream signaling outcomes .

• Resistance mechanism: In lung cancer cells resistant to FGFR1 inhibition, activation of the CD44/PAK1/AKT pathway was identified as a common mechanism across multiple types of resistance (intrinsic, pharmacologically induced, and mutationally induced) .

• Therapeutic implications: Co-inhibition strategies targeting CD44/FGFR1, PAK1/FGFR1, or AKT/FGFR1 showed synergistic effects in sensitizing resistant lung cancer cells to FGFR1 inhibition, demonstrating the functional importance of this pathway .

How does CD44 phosphorylation status affect its interaction with other signaling molecules?

CD44 phosphorylation regulates its interactions with numerous signaling partners:

• ERM protein interactions: Phosphorylation of CD44 affects its association with ezrin-radixin-moesin (ERM) proteins, which in turn regulates CD44's interactions with cytoskeletal elements and subsequent signaling pathways .

• Wnt pathway connections: CD44 functions as a positive regulator of Wnt pathway activation by associating with LRP6. While all CD44 isoforms can associate with LRP6, some variants (like CD44v6) may promote higher levels of Wnt activity .

• c-Met signaling: CD44v6 is required for c-Met activation upon HGF stimulation, with the intracellular domain of CD44 facilitating downstream signaling through interactions with ERM proteins that enable association with GRB2 and SOS .

• Receptor recycling: CD44 phosphorylation status may influence the internalization and recycling of activated receptors like c-Met, which affects sustained signaling during processes like cell migration and branching .

What methodological considerations are important when designing experiments to study CD44 phosphorylation dynamics?

When investigating CD44 phosphorylation dynamics, researchers should consider:

• Selection of appropriate controls:

  • Include both phosphorylated and non-phosphorylated peptide controls in ELISA and Western blot applications

  • Use stimulants known to affect CD44 phosphorylation (e.g., PMA treatment of NIH/3T3 cells) as positive controls

• Sample preparation techniques:

  • Use phosphatase inhibitors during cell/tissue lysis to preserve phosphorylation status

  • Standardize protein extraction and quantification methods across experimental groups

  • Consider subcellular fractionation to assess compartment-specific phosphorylation patterns

• Quantification approaches:

  • Employ spike-in standards for accurate comparison between different conditions

  • For phosphoproteomic studies, use titanium dioxide enrichment for GPome analysis (primarily serine and threonine phosphopeptides) and tyrosine antibodies for pYome analysis

  • Ensure normal distribution of log values in data analysis

• Validation strategies:

  • Confirm findings using multiple antibodies targeting different epitopes

  • Employ complementary techniques (Western blot, mass spectrometry, ELISA)

  • Use genetic approaches (mutation of S706 to non-phosphorylatable residue) to validate functional significance

How can researchers integrate Phospho-CD44 (S706) Antibody studies with investigation of other post-translational modifications of CD44?

CD44 undergoes multiple post-translational modifications that may interact with phosphorylation events:

• Integrated analysis approach:

  • Assess glycosylation status alongside phosphorylation: CD44 is both N-glycosylated and O-glycosylated, which may affect accessibility of phosphorylation sites

  • Investigate chondroitin sulfate modifications: CD44 contains chondroitin sulfate glycans with varying degrees of sulfation that may influence protease accessibility to cleavage sites

  • Examine proteolytic processing: CD44 is cleaved in the extracellular matrix by specific proteinases (possibly MMPs) in several cell lines and tumors

• Technical considerations:

  • Use antibodies that specifically recognize the phosphorylated form (S706) independently of other modifications

  • Design experiments to sequentially assess different modifications on the same samples

  • Consider mass spectrometry approaches that can simultaneously detect multiple modifications

• Functional correlation:

  • Assess how phosphorylation at S706 correlates with other CD44 modifications in different cellular contexts

  • Investigate whether certain modifications are prerequisites for others

  • Determine how combinations of modifications affect CD44's protein interactions and signaling outcomes

What are common issues when using Phospho-CD44 (S706) Antibody in Western blot applications and how can they be resolved?

Researchers may encounter these challenges when using the antibody in Western blot experiments:

How should results be interpreted when examining CD44 phosphorylation in different experimental contexts?

Interpretation of CD44 phosphorylation data requires careful consideration:

• Baseline phosphorylation levels: S706 is constitutively phosphorylated in many cell types, with dephosphorylation occurring upon PKC activation .

• Isoform considerations: CD44 exists in multiple splice variants (standard and variable exon variants), which may show different phosphorylation patterns or accessibility of the S706 site .

• Pathway activation markers: When studying signaling, assess additional pathway components (PAK1, AKT) to confirm functional consequences of phosphorylation changes .

• Subcellular localization: Consider that phosphorylation may affect CD44's distribution between membrane microdomains (lipid rafts) and other cellular compartments .

• Cross-validation: Combine antibody-based detection with mass spectrometry or other approaches to verify phosphorylation status changes.

How is Phospho-CD44 (S706) being utilized in studies of treatment resistance in cancer?

Recent research has highlighted important applications in cancer treatment resistance:

• Biomarker development: Phospho-CD44 (S706) status is being investigated as a potential biomarker for predicting response to targeted therapies, particularly FGFR1 inhibitors in lung cancer .

• Resistance mechanism characterization: Phosphoproteomic studies have identified the CD44/PAK1/AKT signaling axis, involving phosphorylated CD44, as a common resistance mechanism across different types of treatment resistance .

• Combination therapy rationale: Research demonstrates that co-inhibition of AKT/FGFR1, CD44/FGFR1, or PAK1/FGFR1 can synergistically sensitize resistant cancer cells to treatment, providing rationale for combination therapies .

• Patient stratification approach: Strong correlation between CD44 expression and AKT activation in squamous cell lung cancer patients suggests potential for using phospho-CD44 status to stratify patients for appropriate treatment regimens .

What insights does phosphorylation at S706 provide into CD44's roles in Wnt signaling pathways?

Emerging research highlights connections between CD44 phosphorylation and Wnt signaling:

• Regulatory mechanisms: Phosphorylation of CD44 may influence its ability to function as a positive regulator of Wnt pathway activation through association with LRP6 .

• Isoform-specific effects: While all CD44 isoforms appear capable of associating with LRP6, certain variants like CD44v6 may be associated with higher levels of Wnt activity, with phosphorylation potentially playing a regulatory role .

• Structural coordination: The extracellular domain of CD44 interacts with LRP6, while the intracellular domain interacts with and coordinates protein complexes with downstream Wnt pathway targets through cytoskeletal arrangement, which may be regulated by phosphorylation status .

• Clinical relevance: Given that CD44 variant isoform expression correlates with tumor progression in colorectal cancer and high Wnt activity, understanding how phosphorylation regulates these interactions has significant therapeutic implications .