Phospho-DAPK3 (T265) Antibody

What is DAPK3 and what is the significance of its phosphorylation at T265?

DAPK3 (Death-associated protein kinase 3), also known as ZIPK (Zipper-interacting protein kinase), is a serine/threonine kinase involved in various cellular processes including apoptosis, autophagy, and immune responses. It functions as a critical regulator in cancer biology, particularly in tumor immune surveillance pathways . The protein contains multiple functional domains that facilitate its involvement in diverse cellular mechanisms.

Phosphorylation of DAPK3 at threonine 265 (T265) represents a key post-translational modification that regulates its kinase activity and cellular functions. This specific phosphorylation site appears to be critical for DAPK3's role in signaling pathways related to immune responses and cancer suppression . Research has identified DAPK3 as an essential component of the STING pathway for cytosolic DNA sensing, where it coordinates post-translational modifications of STING and drives tumor-intrinsic innate immunity .

What detection methods are available for studying Phospho-DAPK3 (T265)?

Multiple detection methods have been validated for Phospho-DAPK3 (T265) analysis:

• Western Blot (WB): Antibodies against Phospho-DAPK3 (T265) can be used at dilutions of 1:500-1:2000 to detect the phosphorylated protein in cellular lysates . This technique provides semi-quantitative assessment of phosphorylation status across different experimental conditions.

• Immunohistochemistry (IHC): Phospho-DAPK3 (T265) antibodies can be applied at dilutions of 1:100-1:300 for tissue section analysis, allowing spatial visualization of phosphorylated DAPK3 in tissue contexts .

• Immunofluorescence (IF): Using dilutions of 1:200-1:1000, researchers can examine subcellular localization and quantify phosphorylated DAPK3 at the single-cell level .

• ELISA: For quantitative analysis, ELISA applications typically use a 1:10000 dilution of the antibody, providing sensitive detection of phosphorylated DAPK3 in complex samples .

• Cell-Based Colorimetric ELISA: Specialized kits have been developed for detecting Phospho-DAPK3 (T265) in intact cells, maintaining cellular context during analysis .

• Mass Spectrometry: For unbiased detection, TMT-labeling-based mass spectrometry enables comprehensive phospho-proteomic profiling to identify phosphorylated DAPK3 alongside other phosphoproteins .

What is the specificity of Phospho-DAPK3 (T265) antibodies?

Phospho-DAPK3 (T265) antibodies are engineered to selectively recognize DAPK3 protein only when phosphorylated at threonine 265. These antibodies are generated using synthetic phospho-peptides corresponding to the amino acid sequence surrounding the T265 phosphorylation site in human DAPK3 .

According to product specifications, these antibodies "detect endogenous levels of DAPK3 protein only when phosphorylated at T265" . The antibodies are raised against synthetic phospho-peptides corresponding to the exact phosphorylation site region and do not cross-react with other phosphorylation sites .

To ensure specificity, the antibodies undergo affinity purification using epitope-specific immunogens . This process enhances their ability to distinguish between phosphorylated and non-phosphorylated forms of DAPK3, which is essential for studying phosphorylation-dependent functions.

What are the recommended applications and dilutions for Phospho-DAPK3 (T265) antibodies?

Based on validated protocols, the following applications and dilutions are recommended for optimal results:

Western blot analysis has been successfully demonstrated using 40μg of whole cell lysate from various cell lines, indicating robust detection across multiple experimental systems . Researchers should optimize these recommended dilutions for their specific experimental conditions.

In which species does the Phospho-DAPK3 (T265) antibody show reactivity?

Phospho-DAPK3 (T265) antibodies demonstrate reliable cross-species reactivity across three major research organisms:

• Human (Accession No. O43293)

• Mouse (Accession No. O54784)

• Rat (Accession No. O88764)

This multi-species reactivity is particularly valuable for translational research, as it allows consistent experimental approaches across human samples and animal models. According to validation data, no significant cross-reactivity is measured among different phosphorylated sites or species outside these three organisms .

The conservation of this phosphorylation site across species suggests its functional importance in DAPK3 regulation across evolutionary boundaries, making it a relevant target for comparative studies.

How does DAPK3 phosphorylation influence its function in tumor immunity?

DAPK3 plays a pivotal role in tumor immunity through regulation of the STING pathway of cytosolic DNA sensing. Research has identified DAPK3 as a "previously unrecognized driver of anti-tumor immunity" with significant implications for cancer immunotherapy .

The functional consequences of DAPK3 phosphorylation (including T265) in tumor immunity are multifaceted:

• Immunosurveillance Regulation: Loss of DAPK3 expression or kinase activity significantly impairs STING activation and interferon-β (IFN-β) stimulated gene induction, demonstrating that DAPK3 phosphorylation status directly impacts immune surveillance mechanisms .

• Tumor Growth and Immune Cell Infiltration: DAPK3 deficiency in IFN-β-producing tumors leads to rapid tumor growth and reduced infiltration of CD103+CD8α+DCs and cytotoxic lymphocytes, ultimately attenuating responses to cancer chemo-immunotherapy .

• STING Pathway Coordination: DAPK3 coordinates critical post-translational modifications of STING through multiple mechanisms:

  • In unstimulated cells, DAPK3 inhibits STING K48-linked poly-ubiquitination and proteasome-mediated degradation

  • After cGAMP stimulation, DAPK3 facilitates STING K63-linked poly-ubiquitination and STING-TBK1 interaction

Functional DAPK3 kinase activity, which depends on proper phosphorylation, is essential for STING-driven IRF3 activation and IFN-β induction, connecting phosphorylation status to immunological outcomes .

What is the role of DAPK3 in STING pathway regulation and how does phosphorylation affect this function?

DAPK3 serves as a master regulator of the STING pathway through multiple coordinated mechanisms that depend on its phosphorylation state:

• Protein Stability Regulation: DAPK3 maintains steady-state STING protein levels in specific cell types (HUVEC, MCA205, L929), but this effect is cell-type dependent and not observed in BMDM or B16F10 cells . This regulation appears to involve phosphorylation-dependent interactions that protect STING from degradation.

• Differential Ubiquitination Control:

  • DAPK3 inhibits STING K48-linked poly-ubiquitination in unstimulated cells, preventing proteasomal degradation

  • Following cGAMP stimulation, DAPK3 facilitates STING K63-linked poly-ubiquitination, which promotes STING-TBK1 interaction

• Downstream Signaling Activation: Functional DAPK3 kinase activity, which depends on its phosphorylation status, is required for:

  • STING-driven IRF3 activation

  • IFN-β gene induction

  • cGAMP-induced STING K63-linked poly-ubiquitination

• Pleiotropic Regulation: DAPK3 regulates not only STING but also NFκB activation induced by TLR3 and TLR4, which occurs independently of TBK1 , suggesting broader phosphorylation-dependent regulatory functions.

Notably, expression of kinase-dead DAPK3 in DAPK3-depleted cells restored STING protein expression but not responsiveness to STING agonists, confirming that phosphorylation-dependent DAPK3 kinase activity is essential for functional STING pathway activation beyond protein stabilization .

How can phospho-proteomics be utilized to identify DAPK3 targets?

Comprehensive phospho-proteomic approaches provide powerful tools for identifying DAPK3 substrates and understanding its regulatory network. Based on published research, the following methodological framework can be implemented:

• Experimental Design:

  • Generate cellular models with DAPK3 knockdown (shDAPK3) alongside relevant controls (shControl)

  • Include parallel knockdown of known pathway components (e.g., shTBK1) for comparative analysis

  • Stimulate cells with appropriate agonists (e.g., 2′,3′-cGAMP for STING pathway)

• Mass Spectrometry Analysis:

  • Implement tandem mass tag (TMT)-labeling-based mass spectrometry

  • Quantify phosphorylated peptides across experimental conditions

  • Prioritize phospho-proteins by identifying hypo-phosphorylation in DAPK3-depleted samples

• Sequence Motif Analysis:

  • Focus on phospho-sites demonstrating the DAPK3 consensus sequence (R/K-X-X-S/T)

  • Compare with other kinase consensus sequences (e.g., IKK consensus sequence S-X-X-X-S/T)

  • Identify overlapping and distinct targets

• Pathway Analysis:

  • Apply Ingenuity Pathway Analysis (IPA) to DAPK3-specific phosphorylation clusters

  • Identify enriched signaling pathways and biological processes

  • Validate key targets through independent approaches

Through this approach, researchers identified 196 phospho-sites in 165 proteins showing hypo-phosphorylation at the DAPK3 consensus sequence, revealing enrichment of regulatory kinases (ERL/MAPK, mTOR, SAPK/JNK), innate immune response genes, Rho signaling, actin remodeling, and autophagy pathways .

What experimental considerations are important when analyzing DAPK3 phosphorylation in different cell types?

When studying DAPK3 phosphorylation across different cellular contexts, researchers should account for several critical factors:

• Cell Type-Specific Expression and Function:

  • DAPK3 effects on STING stability vary dramatically between cell types (present in HUVEC and MCA205, absent in BMDM and B16F10)

  • Baseline DAPK3 expression levels should be quantified in each cell system

  • Cell-specific interaction partners may alter DAPK3 phosphorylation and function

• Experimental Controls:

  • Include both phosphorylated and non-phosphorylated DAPK3 standards

  • Implement phosphatase-treated samples as negative controls

  • Use stimulation conditions known to enhance T265 phosphorylation as positive controls

  • Validate with DAPK3 knockdown/knockout systems

• Detection Method Selection:

  • For abundant DAPK3 expression: Western blotting provides reliable detection

  • For low-abundance systems: Consider ELISA or Cell-Based Colorimetric ELISA

  • For spatial information: Implement immunofluorescence or immunohistochemistry

  • For unbiased phosphosite mapping: Utilize mass spectrometry approaches

• Statistical Analysis:

  • Apply appropriate statistical methods for analyzing phosphorylation data

  • For expression comparisons, consider Welch's t-test for samples with unequal variance

  • Present data with median values and interquartile ranges (IQR) between 25th and 75th percentiles

  • Ensure adequate sample sizes to detect biologically meaningful differences

• Stimulation Protocols:

  • Optimize stimulation timing for each cell type (kinetics may vary)

  • Consider pathway-specific stimuli (e.g., cGAMP for STING pathway)

  • Account for feedback mechanisms that may alter phosphorylation dynamics

These considerations ensure robust and reproducible analysis of DAPK3 phosphorylation across diverse experimental systems.

How can researchers validate the specificity of phospho-DAPK3 antibodies in their experimental systems?

Rigorous validation of phospho-DAPK3 (T265) antibody specificity is crucial for generating reliable data. Researchers should implement the following comprehensive validation strategy:

• Peptide Competition Assays:

  • Pre-incubate the antibody with the phosphorylated peptide immunogen

  • This should abolish specific signal while non-specific binding will remain

  • Include non-phosphorylated peptide controls to confirm phospho-specificity

• Phosphatase Treatment:

  • Treat biological samples with lambda phosphatase

  • This should eliminate detection by the phospho-specific antibody

  • Total DAPK3 detection should remain unaffected, serving as an internal control

• Genetic Validation:

  • Implement DAPK3 knockdown or knockout models

  • All specific signals should be absent in DAPK3-depleted samples

  • Re-expression of wild-type DAPK3 should restore detection

• Phospho-site Mutants:

  • Generate T265A (non-phosphorylatable) mutants

  • These should show no reactivity with the phospho-specific antibody

  • T265D/E phosphomimetic mutants can serve as positive controls

• Stimulation/Inhibition Experiments:

  • Treat cells with stimuli known to induce DAPK3 phosphorylation

  • Apply kinase inhibitors to reduce phosphorylation

  • Confirm expected signal modulation

• Orthogonal Detection Methods:

  • Validate findings using multiple techniques (WB, IF, IHC, ELISA, mass spectrometry)

  • Consistent results across platforms strengthen confidence in antibody specificity

• Cross-reactivity Assessment:

  • Test for reactivity with similar phosphorylation sites

  • Confirm absence of signal in non-target tissues/species

• Functional Validation:

  • Correlate phospho-DAPK3 detection with functional outcomes

  • Example: Expression of kinase-dead DAPK3 in DAPK3-depleted cells restored STING protein levels but not responsiveness to STING agonists

Through systematic implementation of these validation approaches, researchers can ensure that their observations truly represent Phospho-DAPK3 (T265) rather than non-specific signals or artifacts.

What role does DAPK3 phosphorylation play in cancer biology beyond immune regulation?

DAPK3 phosphorylation contributes to multiple cancer-related processes beyond its established role in immune regulation:

• Cytoskeletal Regulation and Cell Migration:

  • DAPK3 promotes actin reorganization and actomyosin contraction by controlling the phosphorylation of myosin-regulatory light chain

  • These mechanisms impact cell migration, focal adhesion regulation, and stress fiber bundling

  • DAPK3 can attenuate myosin light chain phosphatase activity, affecting cellular contractility

• Genomic Stability:

  • Loss of myosin phosphatase function, which is regulated by DAPK3, has been linked to cancer cell nuclear dysmorphia and genomic instability

  • This suggests DAPK3 phosphorylation status may influence chromosomal stability and DNA repair mechanisms

• Prognostic Significance:

  • Although DAPK3 expression is often reduced in colon cancer, high expression correlates with greater lymphatic invasion

  • Combined expression patterns of ULK1 and DAPK3 correlate with favorable survival outcomes in gastric cancer patients

• Autophagic Regulation:

  • DAPK3 phosphorylation status affects autophagic cell death pathways

  • This mechanism may contribute to tumor suppression through elimination of damaged cells

These diverse functions highlight the importance of precisely measuring DAPK3 phosphorylation at T265 and other sites to understand its context-dependent roles in cancer biology.

How can multiplexed approaches be used to study DAPK3 phosphorylation in complex biological systems?

Multiplexed technologies offer powerful solutions for studying DAPK3 phosphorylation in complex biological contexts:

• Multiplexed Random Peptide Library Screening:

  • Enables efficient identification of phosphorylation-specific antibodies

  • Can screen >800 peptides and dozens of antibodies simultaneously

  • Accelerates development of detection reagents for specific phospho-sites like T265

• Time-Resolved Fluorometry Technology:

  • Allows rapid screening of antibodies in 96-well plate format

  • Successfully identified p(S/T)F antibody that detects phosphorylated FKD peptide

  • Can be miniaturized to 1,536-well format for high-throughput screening

• TR-FRET (Time-Resolved Fluorescence Resonance Energy Transfer):

  • Provides robust assays for detecting phosphorylation events

  • Enables screening of compound libraries for modulators of DAPK3 phosphorylation

  • Minimizes background interference through time-resolved detection

• Phospho-Flow Cytometry:

  • Allows simultaneous detection of multiple phospho-proteins in single cells

  • Can correlate DAPK3 phosphorylation with cell type and activation state

  • Particularly useful for heterogeneous samples like tumor biopsies

• Multiplex Western Blotting:

  • Enables detection of total and phospho-DAPK3 alongside other pathway components

  • Provides comprehensive pathway analysis from limited sample material

  • Reduces technical variability compared to separate blots

• Cell-Based Colorimetric ELISA Multiplexing:

  • Measures phosphorylated proteins and relative total proteins simultaneously

  • Allows for normalization and more accurate quantification

  • Adaptable to high-throughput screening platforms

These multiplexed approaches enhance the efficiency, reproducibility, and biological relevance of DAPK3 phosphorylation studies in complex experimental systems.

What are appropriate statistical methods for analyzing DAPK3 phosphorylation data across experimental conditions?

Robust statistical analysis is essential for interpreting DAPK3 phosphorylation data. Based on published methodologies, the following approaches are recommended:

Implementing these statistical approaches ensures rigorous interpretation of DAPK3 phosphorylation data across experimental conditions.