Phospho-KIT (Tyr936) Antibody

Basic Research Questions

• What is the biological significance of KIT phosphorylation at Tyr936?

  Phosphorylation at tyrosine 936 plays a critical role in signaling pathways involved in cell growth, survival, and differentiation. This specific phosphorylation site is particularly important for the interaction with adapter proteins GRB2 and GRB7, which facilitate downstream signaling . Dysregulation of phosphorylation at this site has been associated with various diseases, including cancer, diabetes, and neurodegenerative disorders, making it a key target for research and therapeutic development .

• What applications are suitable for Phospho-KIT (Tyr936) antibodies?

  Phospho-KIT (Tyr936) antibodies have been validated for multiple applications including:

  • Western Blot (WB): Typically used at dilutions of 1:500-1:2000

  • Immunohistochemistry (IHC): Recommended dilutions range from 1:100-1:300

  • Immunofluorescence (IF): Optimal at dilutions of 1:50-200

  • ELISA: Effective at approximately 1:5000 dilution

  The antibody shows reactivity with human and mouse samples, making it versatile for comparative studies across these species .

• How should Phospho-KIT (Tyr936) antibodies be stored to maintain reactivity?

  For optimal performance, store the antibody at -20°C for up to 1 year from the date of receipt, and avoid repeat freeze-thaw cycles. For short-term storage and frequent use, keeping the antibody at 4°C for up to one month is acceptable . The antibody is typically provided in a formulation containing PBS, 50% Glycerol, 0.5% BSA, and 0.02% Sodium Azide, which helps maintain stability .

Advanced Research Questions

• How can I verify the specificity of Phospho-KIT (Tyr936) antibody in my experimental system?

  Verifying specificity is crucial due to documented challenges with phospho-specific antibodies. Recommended validation approaches include:

  1. Peptide competition assay: Pre-incubate the antibody with a synthesized phosphopeptide corresponding to the target site. A significant reduction in signal when using the blocked antibody confirms specificity, as demonstrated in published immunohistochemistry and western blot validation studies .

  2. Phosphatase treatment: Treat your samples with a universal phosphatase (e.g., alkaline phosphatase) and compare with untreated controls. A genuine phospho-specific antibody should show diminished signal after phosphatase treatment .

  3. Mutant controls: When possible, use Y936F mutant samples as negative controls. Some antibodies may still bind to the non-phosphorylatable mutant, indicating potential cross-reactivity with the unphosphorylated form .

  4. Stimulation/inhibition experiments: Treat cells with known activators (e.g., EGF) or inhibitors of the pathway to modulate phosphorylation states and confirm antibody responsiveness .

• What are the recommended normalization strategies for Phospho-KIT (Tyr936) detection in cell-based assays?

  For accurate quantification, particularly in cell-based ELISA formats, consider these normalization methods:

  1. Housekeeping protein normalization: Use anti-GAPDH antibody as an internal positive control to normalize target absorbance values across samples.

  2. Cell density normalization: After colorimetric measurement, use Crystal Violet whole-cell staining to determine cell density and adjust for plating differences.

  3. Total protein normalization: Use anti-KIT antibody (non-phospho-specific) to normalize phosphorylated target values to total KIT expression levels .

  The choice of normalization method should be determined by your specific experimental design and research question.

• How does SCF stimulation affect KIT phosphorylation at Tyr936 and what are the implications for experimental design?

  Stem Cell Factor (SCF) binding to KIT enhances autophosphorylation, including at Tyr936. When designing experiments:

  1. Consider that some antibodies like 4C9 do not inhibit SCF binding to c-Kit, as demonstrated by competitive ELISA .

  2. The response to SCF stimulation can vary significantly between cell lines. For example, SCF-mediated c-Kit phosphorylation is observed in GIST-T1 cells but shows variable responses in some SCLC cell lines like NCI-H526 and NCI-H1048 .

  3. Time-course experiments are essential, as 4C9 antibody has been shown to dramatically decrease total c-Kit levels in a time-dependent manner in GIST cell lines but not in all SCLC cell lines .

  These differential responses highlight the importance of cell-specific validation when studying KIT signaling pathways.

• What are the technical considerations for using Phospho-KIT (Tyr936) antibody in multiplex phosphorylation analysis?

  When incorporating Phospho-KIT (Tyr936) detection into multiplex studies:

  1. Antibody cross-reactivity: Ensure compatibility with other phospho-specific antibodies in your panel. Be aware that post-translational modifications near Tyr936, such as phosphorylation at Thr304 or methylation at Leu309, may influence antibody binding .

  2. Signal normalization: In mass spectrometry-based phosphoproteomics, Tyr936 phosphorylation can be used as part of broader kinase activity analysis frameworks, such as the Integrated Inferred Kinase Activity (INKA) analysis .

  3. Experimental design: When integrating antibody-based detection with MS-based phosphoproteomics, consider that enrichment methods (e.g., pY antibody-based versus metal affinity-based) can affect the relative abundance of phosphotyrosine sites detected .

• How does Phospho-KIT (Tyr936) status correlate with response to KIT inhibitors in research models?

  The relationship between Tyr936 phosphorylation and inhibitor response is complex:

  1. In antibody-drug conjugate (ADC) studies targeting c-Kit for small cell lung cancer treatment, researchers observed that antibody binding to c-Kit could affect total c-Kit levels through potential ubiquitination-dependent degradation, rather than directly inhibiting phosphorylation .

  2. For experimental design, it's crucial to include appropriate controls when assessing inhibitor efficacy:

     • Positive controls with known pathway activators (e.g., SCF, EGF)

     • Time-course analyses to capture both rapid and delayed phosphorylation changes

     • Parallel assessment of multiple phosphorylation sites on KIT (not just Tyr936)

     • Evaluation of downstream signaling molecules (e.g., ERK, Akt)

  3. The phosphorylation status at Tyr936 may serve as one of several biomarkers for predicting response to KIT inhibitors, but should be evaluated alongside other phosphorylation sites and total KIT expression.

• What are the advantages and limitations of Cell-Based ELISA versus traditional Western Blot for Phospho-KIT (Tyr936) detection?

  Advantages of Cell-Based ELISA:

  • Higher throughput capability for screening multiple conditions

  • Lysate-free workflow that preserves cellular context

  • Quantitative results with lower sample requirements

  • Ability to incorporate multiple normalization strategies in a single assay

  • Sensitivity to detect phosphorylation in samples with >5000 cells

  Limitations of Cell-Based ELISA:

  • Primarily qualitative rather than absolutely quantitative

  • Potential for non-specific binding in complex cellular environments

  • Limited ability to distinguish isoforms or verify antibody specificity by molecular weight

  When to choose Western Blot:

  • When verification of target protein molecular weight is necessary (92 and 145 kDa for KIT)

  • When analyzing specific cell compartments through fractionation

  • When detecting multiple phosphorylation sites simultaneously

  • For confirming antibody specificity through peptide competition

• How can Phospho-KIT (Tyr936) analysis be integrated into broader phosphoproteomics workflows?

  For comprehensive signaling pathway analysis:

  1. Targeted phosphoproteomic approaches: PTMScan® Direct Tyrosine Kinases Service and similar approaches allow for targeted screening and quantification of defined sets of phosphorylation sites, including KIT Tyr936, within the broader tyrosine kinase network .

  2. Data integration frameworks: Consider integrating antibody-based detection with mass spectrometry data using frameworks like INKA (Integrative Inferred Kinase Activity), which combines kinase-centric and substrate-centric information to rank kinase activities .

  3. Experimental design considerations:

     • Include samples with known KIT activation states as positive controls

     • Consider time-course experiments to capture dynamic phosphorylation changes

     • When possible, complement with inhibitor studies to validate pathway connections

     • Integrate phosphorylation data with other -omics approaches (transcriptomics, proteomics) for a more comprehensive view of cellular signaling

  This integrated approach provides a more comprehensive understanding of KIT signaling in the context of the broader cellular phosphorylation network.

Frequently Asked Questions (FAQs) for Researchers Using Phospho-KIT (Tyr936) Antibody

Basic Research Questions

• What is the biological significance of KIT phosphorylation at Tyr936?

  Phosphorylation at tyrosine 936 plays a critical role in signaling pathways involved in cell growth, survival, and differentiation. This specific phosphorylation site is particularly important for the interaction with adapter proteins GRB2 and GRB7, which facilitate downstream signaling . Dysregulation of phosphorylation at this site has been associated with various diseases, including cancer, diabetes, and neurodegenerative disorders, making it a key target for research and therapeutic development .

• What applications are suitable for Phospho-KIT (Tyr936) antibodies?

  Phospho-KIT (Tyr936) antibodies have been validated for multiple applications including:

  • Western Blot (WB): Typically used at dilutions of 1:500-1:2000

  • Immunohistochemistry (IHC): Recommended dilutions range from 1:100-1:300

  • Immunofluorescence (IF): Optimal at dilutions of 1:50-200

  • ELISA: Effective at approximately 1:5000 dilution

  The antibody shows reactivity with human and mouse samples, making it versatile for comparative studies across these species .

• How should Phospho-KIT (Tyr936) antibodies be stored to maintain reactivity?

  For optimal performance, store the antibody at -20°C for up to 1 year from the date of receipt, and avoid repeat freeze-thaw cycles. For short-term storage and frequent use, keeping the antibody at 4°C for up to one month is acceptable . The antibody is typically provided in a formulation containing PBS, 50% Glycerol, 0.5% BSA, and 0.02% Sodium Azide, which helps maintain stability .

Advanced Research Questions

• How can I verify the specificity of Phospho-KIT (Tyr936) antibody in my experimental system?

  Verifying specificity is crucial due to documented challenges with phospho-specific antibodies. Recommended validation approaches include:

  1. Peptide competition assay: Pre-incubate the antibody with a synthesized phosphopeptide corresponding to the target site. A significant reduction in signal when using the blocked antibody confirms specificity, as demonstrated in published immunohistochemistry and western blot validation studies .

  2. Phosphatase treatment: Treat your samples with a universal phosphatase (e.g., alkaline phosphatase) and compare with untreated controls. A genuine phospho-specific antibody should show diminished signal after phosphatase treatment .

  3. Mutant controls: When possible, use Y936F mutant samples as negative controls. Some antibodies may still bind to the non-phosphorylatable mutant, indicating potential cross-reactivity with the unphosphorylated form .

  4. Stimulation/inhibition experiments: Treat cells with known activators (e.g., EGF) or inhibitors of the pathway to modulate phosphorylation states and confirm antibody responsiveness .

• What are the recommended normalization strategies for Phospho-KIT (Tyr936) detection in cell-based assays?

  For accurate quantification, particularly in cell-based ELISA formats, consider these normalization methods:

  1. Housekeeping protein normalization: Use anti-GAPDH antibody as an internal positive control to normalize target absorbance values across samples.

  2. Cell density normalization: After colorimetric measurement, use Crystal Violet whole-cell staining to determine cell density and adjust for plating differences.

  3. Total protein normalization: Use anti-KIT antibody (non-phospho-specific) to normalize phosphorylated target values to total KIT expression levels .

  The choice of normalization method should be determined by your specific experimental design and research question.

• How does SCF stimulation affect KIT phosphorylation at Tyr936 and what are the implications for experimental design?

  Stem Cell Factor (SCF) binding to KIT enhances autophosphorylation, including at Tyr936. When designing experiments:

  1. Consider that some antibodies like 4C9 do not inhibit SCF binding to c-Kit, as demonstrated by competitive ELISA .

  2. The response to SCF stimulation can vary significantly between cell lines. For example, SCF-mediated c-Kit phosphorylation is observed in GIST-T1 cells but shows variable responses in some SCLC cell lines like NCI-H526 and NCI-H1048 .

  3. Time-course experiments are essential, as 4C9 antibody has been shown to dramatically decrease total c-Kit levels in a time-dependent manner in GIST cell lines but not in all SCLC cell lines .

  These differential responses highlight the importance of cell-specific validation when studying KIT signaling pathways.

• What are the technical considerations for using Phospho-KIT (Tyr936) antibody in multiplex phosphorylation analysis?

  When incorporating Phospho-KIT (Tyr936) detection into multiplex studies:

  1. Antibody cross-reactivity: Ensure compatibility with other phospho-specific antibodies in your panel. Be aware that post-translational modifications near Tyr936, such as phosphorylation at Thr304 or methylation at Leu309, may influence antibody binding .

  2. Signal normalization: In mass spectrometry-based phosphoproteomics, Tyr936 phosphorylation can be used as part of broader kinase activity analysis frameworks, such as the Integrated Inferred Kinase Activity (INKA) analysis .

  3. Experimental design: When integrating antibody-based detection with MS-based phosphoproteomics, consider that enrichment methods (e.g., pY antibody-based versus metal affinity-based) can affect the relative abundance of phosphotyrosine sites detected .

• How does Phospho-KIT (Tyr936) status correlate with response to KIT inhibitors in research models?

  The relationship between Tyr936 phosphorylation and inhibitor response is complex:

  1. In antibody-drug conjugate (ADC) studies targeting c-Kit for small cell lung cancer treatment, researchers observed that antibody binding to c-Kit could affect total c-Kit levels through potential ubiquitination-dependent degradation, rather than directly inhibiting phosphorylation .

  2. For experimental design, it's crucial to include appropriate controls when assessing inhibitor efficacy:

     • Positive controls with known pathway activators (e.g., SCF, EGF)

     • Time-course analyses to capture both rapid and delayed phosphorylation changes

     • Parallel assessment of multiple phosphorylation sites on KIT (not just Tyr936)

     • Evaluation of downstream signaling molecules (e.g., ERK, Akt)

  3. The phosphorylation status at Tyr936 may serve as one of several biomarkers for predicting response to KIT inhibitors, but should be evaluated alongside other phosphorylation sites and total KIT expression.

• What are the advantages and limitations of Cell-Based ELISA versus traditional Western Blot for Phospho-KIT (Tyr936) detection?

  Advantages of Cell-Based ELISA:

  • Higher throughput capability for screening multiple conditions

  • Lysate-free workflow that preserves cellular context

  • Quantitative results with lower sample requirements

  • Ability to incorporate multiple normalization strategies in a single assay

  • Sensitivity to detect phosphorylation in samples with >5000 cells

  Limitations of Cell-Based ELISA:

  • Primarily qualitative rather than absolutely quantitative

  • Potential for non-specific binding in complex cellular environments

  • Limited ability to distinguish isoforms or verify antibody specificity by molecular weight

  When to choose Western Blot:

  • When verification of target protein molecular weight is necessary (92 and 145 kDa for KIT)

  • When analyzing specific cell compartments through fractionation

  • When detecting multiple phosphorylation sites simultaneously

  • For confirming antibody specificity through peptide competition

• How can Phospho-KIT (Tyr936) analysis be integrated into broader phosphoproteomics workflows?

  For comprehensive signaling pathway analysis:

  1. Targeted phosphoproteomic approaches: PTMScan® Direct Tyrosine Kinases Service and similar approaches allow for targeted screening and quantification of defined sets of phosphorylation sites, including KIT Tyr936, within the broader tyrosine kinase network .

  2. Data integration frameworks: Consider integrating antibody-based detection with mass spectrometry data using frameworks like INKA (Integrative Inferred Kinase Activity), which combines kinase-centric and substrate-centric information to rank kinase activities .

  3. Experimental design considerations:

     • Include samples with known KIT activation states as positive controls

     • Consider time-course experiments to capture dynamic phosphorylation changes

     • When possible, complement with inhibitor studies to validate pathway connections

     • Integrate phosphorylation data with other -omics approaches (transcriptomics, proteomics) for a more comprehensive view of cellular signaling

  This integrated approach provides a more comprehensive understanding of KIT signaling in the context of the broader cellular phosphorylation network.