PTK2 (Ab-843) Antibody

What is PTK2/FAK and what role does the S843 phosphorylation site play in cellular signaling?

PTK2 (Protein Tyrosine Kinase 2), also known as FAK (Focal Adhesion Kinase), is a 119.2 kDa cytoplasmic protein tyrosine kinase concentrated in focal adhesions between cells growing in the presence of extracellular matrix. While PTK2 has multiple phosphorylation sites, the S843 site represents a specific serine phosphorylation site distinct from the well-characterized Y397 autophosphorylation site .

The S843 phosphorylation plays a regulatory role in FAK function that differs from tyrosine phosphorylation sites. Unlike tyrosine phosphorylation that often directly affects catalytic activity, serine phosphorylation at S843 may modulate protein-protein interactions or subcellular localization of FAK, potentially affecting downstream signaling pathways . Monitoring S843 phosphorylation status provides insights into alternative regulatory mechanisms of FAK beyond its canonical tyrosine kinase activity.

How should I validate the specificity of a PTK2 (Ab-843) antibody before experimental use?

A rigorous validation strategy for PTK2 (Ab-843) antibody should include:

• Phosphatase treatment control: Treat cell lysates with phosphatase (like CIP as shown in R&D Systems' validation data) to remove phosphorylation and confirm signal loss on Western blot .

• Positive control stimulation: Use pervanadate treatment of cells (as demonstrated with HUVEC cells) to enhance phosphorylation levels for clearer detection .

• Multi-technique validation: Confirm specificity across different techniques (Western blot, immunofluorescence, etc.) using the same cellular models.

• Knockout/knockdown controls: Compare antibody signal in wild-type versus PTK2-depleted samples to verify specificity.

• Peptide competition assay: Pre-incubate antibody with phosphorylated and non-phosphorylated peptides to demonstrate phospho-specific binding.

What are the recommended experimental conditions for Western blot detection using PTK2 (Ab-843) antibody?

For optimal Western blot detection with PTK2 (Ab-843) antibody:

• Sample preparation: When studying phosphorylated proteins, rapid sample processing is essential. Use phosphatase inhibitors (sodium orthovanadate, sodium fluoride) in lysis buffers to preserve phosphorylation status .

• Protein loading: Load 20-50 μg of total protein per lane for cell lysates.

• Antibody dilution: Start with 0.5-1 μg/mL for Western blot as recommended by R&D Systems , then optimize as needed.

• Membrane type: PVDF membranes generally provide better results for phospho-specific antibodies .

• Blocking conditions: Use 5% BSA in TBST rather than milk, as milk contains phosphoproteins that may interfere with phospho-specific antibody binding.

• Detection system: HRP-conjugated secondary antibodies with enhanced chemiluminescence provide good sensitivity for phospho-protein detection .

How does S843 phosphorylation relate to other PTK2 phosphorylation sites in experimental models?

PTK2 contains multiple phosphorylation sites with distinct functions:

When investigating S843 phosphorylation, researchers should consider:

• Temporal relationship: Determine whether S843 phosphorylation precedes or follows tyrosine phosphorylation events using time-course experiments.

• Pathway integration: S843 phosphorylation may interact with or antagonize other phosphorylation sites. Design experiments with site-specific phospho-antibodies for multiple sites simultaneously.

• Functional consequence: Use phospho-mimetic (S843D/E) and phospho-deficient (S843A) mutations to assess functional consequences of this modification independently of other sites .

What experimental approaches can distinguish between direct and indirect effects of S843 phosphorylation on PTK2 function?

To distinguish direct from indirect effects of S843 phosphorylation:

• In vitro kinase assays: Compare kinase activity of wild-type versus S843A (phospho-deficient) and S843D/E (phospho-mimetic) PTK2 using purified recombinant proteins.

• Proximity labeling: Use BioID or APEX2 fused to wild-type versus S843 mutant PTK2 to identify differential protein interactions dependent on phosphorylation status.

• FRET-based sensors: Develop conformational biosensors to detect structural changes induced by S843 phosphorylation in living cells.

• Pharmacological approach: Use specific kinase inhibitors like PF573228 (FAK inhibitor) in combination with signaling pathway modulators to dissect the role of S843 phosphorylation in different contexts .

• Mutational analysis combined with phospho-proteomic profiling: Compare phosphorylation patterns in cells expressing wild-type versus S843 mutant PTK2 to identify downstream signaling events dependent on this site.

How can I optimize immunofluorescence protocols using PTK2 (Ab-843) antibody for subcellular localization studies?

For high-resolution subcellular localization studies with PTK2 (Ab-843) antibody:

• Fixation method optimization:

  • Test both paraformaldehyde (preserves structure) and methanol (better for phospho-epitope access) fixation

  • For phospho-epitopes, short fixation times (10 minutes) often yield better results

• Permeabilization conditions:

  • Use 0.1-0.3% Triton X-100 for adequate antibody access to intracellular phospho-epitopes

  • Consider saponin (0.1%) for gentler permeabilization that better preserves phospho-epitopes

• Signal amplification:

  • Implement tyramide signal amplification for weak phospho-specific signals

  • Consider using quantum dots as secondary antibody conjugates for improved signal-to-noise ratio

• Co-staining optimization:

  • Use focal adhesion markers (paxillin, vinculin) to correlate S843 phosphorylation with adhesion structure dynamics

  • Include cytoskeletal markers (F-actin) to relate S843 phosphorylation to cytoskeletal organization

• Confocal settings:

  • Use narrow bandpass filters to reduce channel bleed-through

  • Employ Airyscan or STED microscopy for super-resolution imaging of focal adhesion structures

• Quantification approaches:

  • Implement automated image analysis for quantifying phospho-S843 intensity at focal adhesions versus cytoplasmic regions

  • Use line-scan analysis to measure phospho-S843 gradient across focal adhesion structures

What experimental design effectively demonstrates the functional significance of S843 phosphorylation in cell migration models?

A comprehensive experimental design would include:

• Genetic manipulation:

  • Generate stable cell lines expressing wild-type PTK2, phospho-deficient (S843A), and phospho-mimetic (S843D/E) mutants in PTK2-null background

  • Use inducible expression systems to control timing of expression

• Migration assays:

  • Wound healing assay with time-lapse microscopy

  • Single-cell tracking for detailed migration parameters (velocity, directionality, persistence)

  • 3D migration assays in collagen matrices to assess matrix-dependent migration

• Focal adhesion dynamics:

  • Express fluorescently-tagged paxillin to visualize focal adhesion turnover

  • Quantify adhesion formation/disassembly rates using TIRF microscopy

  • Correlate S843 phosphorylation with adhesion lifetime using dual-color imaging

• Molecular mechanism:

  • Perform phospho-proteomics to identify differential phosphorylation events downstream of S843

  • Use proximity labeling to identify S843-dependent protein interactions

  • Measure RhoGTPase activity using FRET-based biosensors in cells with different S843 mutations

• Physiological relevance:

  • Extend findings to 3D organoid models or in vivo using CRISPR-edited cell lines

  • Correlate S843 phosphorylation with functional outcomes in tissue-specific contexts

How should I design experiments to investigate the relationship between PTK2 S843 phosphorylation and the UPS/autophagy pathways?

Based on research showing PTK2's involvement in UPS (Ubiquitin Proteasome System) and autophagy , a systematic investigation would include:

• Temporal dynamics:

  • Time-course analysis of S843 phosphorylation in response to proteasome inhibitors (MG132, lactacystin) and autophagy modulators

  • Compare with other PTK2 phosphorylation sites (Y397, Y576, Y861) to determine sequence of events

• Pathway crosstalk:

  • Investigate S843 phosphorylation in TBK1-SQSTM1 pathway manipulation (as suggested by search result #4)

  • Use PTK2 inhibitors (PF573228) in combination with pathway-specific modulators to dissect signaling hierarchy

• Protein-protein interactions:

  • Perform co-immunoprecipitation with phospho-S843-specific antibody to identify unique binding partners

  • Compare interactome of wild-type versus S843A/D mutants using mass spectrometry

  • Investigate direct interactions with autophagy machinery components

• Functional readouts:

  • Measure UPS activity using reporter substrates (GFP-degron)

  • Assess autophagy flux using LC3 conversion and p62/SQSTM1 degradation assays

  • Correlate S843 phosphorylation status with poly-ubiquitinated protein levels

• Integration with other PTK2 functions:

  • Determine whether S843 phosphorylation affects PTK2's canonical roles in adhesion and migration simultaneously with UPS/autophagy regulation

What are common technical challenges when working with phospho-specific antibodies like PTK2 (Ab-843) and how can they be overcome?

Common challenges with phospho-specific antibodies include:

• Low signal intensity:

  • Enhance phosphorylation using phosphatase inhibitors (pervanadate, calyculin A)

  • Use signal amplification methods (HRP-polymer detection systems)

  • Concentrate proteins using immunoprecipitation before Western blotting

• High background signal:

  • Optimize blocking (use 5% BSA instead of milk)

  • Increase washing stringency (0.1% to 0.3% Tween-20)

  • Try alternative secondary antibodies or detection systems

• Cross-reactivity issues:

  • Perform peptide competition assays with phospho and non-phospho peptides

  • Include knockout/knockdown controls in every experiment

  • Use orthogonal methods to confirm phosphorylation (mass spectrometry)

• Antibody batch variability:

  • Validate each new antibody lot against previous lots

  • Maintain consistent positive controls across experiments

  • Consider preparing your own reference standards for long-term projects

• Sample handling issues:

  • Process samples rapidly and maintain cold temperature throughout

  • Use phosphatase inhibitor cocktails in all buffers

  • Consider stabilizing phosphorylation by crosslinking before cell lysis

How can I integrate PTK2 (Ab-843) antibody data with other research techniques for comprehensive phosphorylation analysis?

To build a complete picture of PTK2 phosphorylation biology:

• Multi-omics integration:

  • Combine antibody-based detection with phospho-proteomics mass spectrometry

  • Correlate phosphorylation data with transcriptomics to identify feedback mechanisms

  • Integrate with metabolomics to link phosphorylation to metabolic changes

• Spatial and temporal resolution:

  • Use phospho-specific antibodies in time-course experiments alongside live-cell biosensors

  • Combine fixed-cell immunofluorescence with dynamic biosensor imaging

  • Implement multiplexed imaging to detect multiple phosphorylation sites simultaneously

• Functional correlation:

  • Pair phosphorylation detection with activity-based protein profiling

  • Link phosphorylation status to protein-protein interaction maps

  • Correlate with functional assays (migration, adhesion, survival)

• Data analysis approaches:

  • Implement machine learning to identify patterns in multi-parameter phosphorylation data

  • Use principal component analysis to distinguish major modes of regulation

  • Develop computational models integrating phosphorylation with protein function

How might S843 phosphorylation of PTK2 influence its interaction with the MET-PTPRK signaling axis in Wnt pathway regulation?

Recent research suggests PTK2/FAK may function within complex signaling networks involving MET (hepatocyte growth factor receptor) and PTPRK (protein tyrosine phosphatase receptor type K) in regulating pathways like Wnt signaling . To investigate this:

• Protein interaction studies:

  • Perform co-immunoprecipitation experiments with S843 phospho-specific antibodies to identify differential binding to MET or PTPRK

  • Use proximity ligation assays to visualize interactions between phospho-S843 PTK2 and MET/PTPRK in situ

• Signaling pathway analysis:

  • Monitor S843 phosphorylation in response to HGF stimulation and PTPRK activity modulation

  • Assess how S843 phosphorylation status affects downstream Wnt pathway components like ZNRF3 and RNF43

• Phosphorylation dynamics:

  • Determine whether S843 phosphorylation is regulated by MET kinase activity (directly or indirectly)

  • Investigate if PTPRK can dephosphorylate S843 directly using in vitro phosphatase assays

• Functional outcomes:

  • Measure Wnt pathway activity using TOPFlash reporter assays in cells expressing wild-type versus S843 mutant PTK2

  • Assess β-catenin stabilization and nuclear translocation in relation to S843 phosphorylation status

• Therapeutic implications:

  • Test how FAK inhibitors affect this signaling network in cancer models

  • Investigate potential combinatorial approaches targeting both MET and FAK pathways

What role might PTK2 S843 phosphorylation play in neurodegenerative conditions like ALS based on its involvement in UPS and autophagy regulation?

Given PTK2's role in UPS impairment and neuronal toxicity in TARDBP proteinopathies , investigating S843 phosphorylation in this context could involve:

• Neuropathological analysis:

  • Examine S843 phosphorylation in post-mortem tissues from ALS patients versus controls

  • Correlate with markers of proteinopathy (TDP-43 aggregates, ubiquitin inclusions)

• Cellular models:

  • Generate neuronal models expressing wild-type versus S843 mutant PTK2

  • Assess impact on TDP-43 aggregation, UPS function, and neuronal survival

  • Monitor autophagy flux using standard markers (LC3, p62/SQSTM1)

• Mechanism investigation:

  • Determine if S843 phosphorylation affects PTK2's interaction with TBK1-SQSTM1 pathway components

  • Investigate whether S843 phosphorylation influences PTK2's regulation of the autophagy machinery

• Therapeutic exploration:

  • Test whether modulating S843 phosphorylation using small molecules affects neuronal survival

  • Examine if phosphorylation status correlates with response to autophagy-enhancing compounds

• In vivo models:

  • Generate knock-in mouse models with S843A or S843D mutations

  • Cross with ALS model mice (SOD1^G93A, TDP-43 transgenic) to assess disease modification

  • Perform behavioral, electrophysiological, and biochemical analyses to determine functional impact