STK39 (Ab-325) Antibody

What is STK39 and what functional significance does phosphorylation at Ser325 have?

STK39 (Serine/Threonine Kinase 39), also known as SPAK (STE20/SPS1-related proline-alanine-rich kinase), is a member of the Ste20-like serine/threonine kinase family. STK39 is composed of a short N-terminal proline and alanine repeats (PAPA box), a kinase catalytic domain, and a C-terminal regulatory domain .

Functionally, STK39 plays critical roles in:

• Ion homeostasis by regulating cation chloride cotransporters

• Modulation of renal salt transport and blood pressure

• Cellular stress response pathways, particularly in response to hypotonic stress

• Activation of the p38 MAP kinase pathway

Phosphorylation at Ser325 is a key regulatory modification that indicates STK39 activation. According to the search results, phosphorylated STK39 at Ser325 can be detected by specific antibodies designed to recognize this post-translational modification . This phosphorylation site appears to be particularly important for STK39 function, as demonstrated in research examining WNK1-induced phosphorylation of OXSR1 on S325, a known target of WNK1 activity .

For optimal performance, the following storage and handling recommendations should be followed:

• Store at -20°C for long-term storage (up to one year)

• For frequent use and short-term storage, keep at 4°C for up to one month

• Avoid repeated freeze/thaw cycles as they can degrade antibody performance

• The antibody is typically supplied in liquid form in PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide

• Some formulations include phosphate buffered saline without Mg2+ and Ca2+, pH 7.4, with 150mM NaCl and 50% glycerol

Proper aliquoting upon receipt can minimize freeze/thaw cycles and extend antibody shelf life.

What are the optimal validation methods for confirming STK39 (Ab-325) Antibody specificity?

To properly validate STK39 (Ab-325) Antibody specificity, researchers should consider implementing the following strategies:

• Peptide competition assays: Pre-incubate the antibody with the immunizing phosphopeptide before application. The search results indicate this approach has been used for validation, where the right-hand panel in immunohistochemical analysis represented a negative control with antibody pre-incubated with the immunizing peptide .

• Knockdown/knockout controls: Using siRNA or CRISPR/Cas9 to deplete STK39 can confirm signal specificity. The search results mention depletion of STK39 in experimental contexts .

• Phosphatase treatment: Treating samples with phosphatases should eliminate the signal if the antibody is truly phospho-specific.

• Stimulation experiments: Using treatments known to induce STK39 phosphorylation (such as hypotonic stress) should increase the signal.

• Parallel detection with multiple antibodies: Compare results with other validated STK39 antibodies targeting different epitopes.

Research data shows that immunohistochemical analysis of paraffin-embedded human brain tissue using Anti-STK39 (phospho Ser325) Antibody can demonstrate specificity when compared with peptide-blocked controls .

How does STK39 phosphorylation at Ser325 relate to cancer progression mechanisms?

Research has indicated important roles for STK39 in cancer progression, particularly in breast cancer metastasis:

• Metastatic promotion: STK39 has been identified as enhancing the stability of SNAI1, a key transcription factor in epithelial-mesenchymal transition (EMT) .

• Mechanism of action: STK39 interacts with and phosphorylates SNAI1 at T203, which is critical for its nuclear retention .

• Functional consequences:

  • STK39 inhibition markedly impairs the EMT phenotype

  • Decreases tumor cell migration, invasion, and metastasis both in vitro and in vivo

  • These effects were rescued by ectopic SNAI1 expression

• Therapeutic implications: Depletion of STK39 dramatically enhanced sensitivity to chemotherapeutic agents, highlighting the STK39-SNAI1 signaling axis as a promising therapeutic target for treatments of metastatic breast cancer .

When studying these mechanisms, phospho-specific antibodies like STK39 (Ab-325) Antibody can help track the activation status of STK39 during cancer progression and in response to potential therapeutic interventions.

What is the relationship between WNK1, OXSR1, and STK39 phosphorylation in cellular signaling pathways?

The WNK1-OXSR1-STK39 pathway represents an important signaling cascade with roles in multiple cellular processes:

• Phosphorylation cascade:

  • WNK1 phosphorylates OXSR1 at S325

  • OXSR1 and STK39 (SPAK) function downstream of WNK1

  • WNK463 (WNKi), a selective WNK inhibitor, blocks CCL21-induced phosphorylation of OXSR1 on S325

• Functional relevance in T cell migration:

  • WNK1, OXSR1, STK39, and ion influx through SLC12A2 are required for CCL21-induced migration of T cells

  • Live cell imaging showed WNK1, OXSR1, and SLC12A2 are enriched at the leading edge of migrating T cells

  • The pathway regulates actin polymerization and membrane dynamics during cell migration

• B cell immune responses:

  • WNK1 kinase is essential in B cells for T-dependent antibody responses

  • WNK1 signals through OXSR1 and STK39, with STK39-T243A mutations preventing phosphorylation and activation by WNK1

  • This pathway affects LFA-1-mediated adhesion in B cells

Understanding these pathways is critical when designing experiments targeting STK39 phosphorylation, as interventions at different points in the cascade may have distinct effects on STK39 phosphorylation status at Ser325.

What are the optimal protocols for using STK39 (Ab-325) Antibody in Western blot analysis?

For optimal Western blot performance with STK39 (Ab-325) Antibody:

Sample preparation:

• Use appropriate lysis buffers containing phosphatase inhibitors to preserve phosphorylation status

• Process samples quickly and keep them cold to minimize dephosphorylation

• The expected molecular weight of STK39 is approximately 59-62 kDa

Western blot protocol:

• Separate proteins using SDS-PAGE (10% gel recommended)

• Transfer to PVDF or nitrocellulose membrane

• Block with 5% BSA in TBST (recommended over milk for phospho-antibodies)

• Dilute antibody 1:500-1:1000 in blocking buffer

• Incubate overnight at 4°C

• Wash with TBST (3-5 times)

• Incubate with appropriate secondary antibody (anti-rabbit IgG conjugated to HRP is suitable)

• Develop using ECL or other detection methods

Positive controls:
Various cell lines can be used as positive controls, including:

• Jurkat cells

• MCF-7 cells

• SH-SY5Y cells

• HEK-293T cells

• HepG2 cells

• Rat brain tissue

What are the best practices for immunohistochemistry with STK39 (Ab-325) Antibody?

For immunohistochemistry applications using STK39 (Ab-325) Antibody:

Tissue preparation:

• Paraffin-embedded or frozen sections can be used

• For paraffin sections, antigen retrieval is critical (citrate buffer pH 6.0 recommended)

• Human brain tissue has been successfully used for validation

IHC protocol:

• Deparaffinize and rehydrate sections (if using paraffin-embedded tissues)

• Perform antigen retrieval

• Block endogenous peroxidase activity (3% H₂O₂ in methanol)

• Block non-specific binding (1% BSA in PBS recommended)

• Dilute antibody 1:100-1:300 in blocking buffer

• Incubate overnight at 4°C

• Wash with PBS (3-5 times)

• Apply appropriate secondary antibody

• Develop with DAB or other suitable substrate

• Counterstain, dehydrate, and mount

Controls:

• Negative control: Pre-incubate the antibody with immunizing peptide

• Positive control: Human brain tissue has shown positive staining

Validation data from immunohistochemical analysis of paraffin-embedded human brain using Anti-STK39 (phospho Ser325) Antibody has been reported, with appropriate negative controls where the antibody was pre-incubated with the immunizing peptide .

How can researchers troubleshoot non-specific binding when using STK39 (Ab-325) Antibody?

When encountering non-specific binding issues with STK39 (Ab-325) Antibody, consider these troubleshooting approaches:

• Optimize blocking conditions:

  • Try different blocking agents (BSA, normal serum, commercial blockers)

  • Increase blocking time (2 hours or longer)

  • Use 0.1-0.3% Tween-20 in washing buffers to reduce background

• Adjust antibody concentration:

  • Titrate the antibody to find optimal concentration

  • Start with manufacturer's recommended dilution and adjust as needed

  • For Western blot: try 1:1000-1:2000 dilutions

  • For IHC: try 1:100-1:300 dilutions

• Implement additional controls:

  • Use peptide competition assays to confirm specificity

  • Include phosphatase-treated samples as negative controls

  • Use tissues or cells known to be negative for STK39 expression

• Modify incubation conditions:

  • Reduce incubation temperature (4°C overnight instead of room temperature)

  • Use gentle agitation during antibody incubation

  • Consider adding 0.1% Triton X-100 to antibody diluent to improve penetration

• Purification methods matter:

  • The antibody's purification method can affect specificity

  • STK39 (Ab-325) Antibody is typically purified from rabbit serum by antigen affinity chromatography using the immunizing phospho peptide or by Protein A purification

How should experiments be designed to study the role of STK39 phosphorylation in cancer progression?

When investigating STK39's role in cancer progression through phosphorylation at Ser325:

Experimental design recommendations:

• Cell model selection:

  • Use established cancer cell lines with known STK39 expression

  • Consider paired normal/cancer cell lines from the same tissue type

  • Breast cancer cell lines are particularly relevant based on STK39's role in breast cancer metastasis

• Manipulation strategies:

  • siRNA or shRNA knockdown of STK39

  • CRISPR/Cas9-mediated knockout

  • Overexpression of wild-type STK39 and phospho-mutants (S325A, S325D/E)

  • Use of STK39 inhibitors

• Functional assays:

  • Migration and invasion assays (Boyden chamber, wound healing)

  • EMT marker analysis (E-cadherin, N-cadherin, Vimentin, SNAI1)

  • Drug sensitivity assays (as STK39 depletion enhances chemosensitivity)

  • In vivo metastasis models

• Monitoring STK39 phosphorylation:

  • Use STK39 (Ab-325) Antibody to track phosphorylation status

  • Compare with total STK39 levels

  • Analyze correlation between phosphorylation status and:

    • Invasive capacity

    • EMT marker expression

    • Patient outcomes (in clinical samples)

• Pathway analysis:

  • Examine interaction with SNAI1 (co-IP, proximity ligation assay)

  • Analyze downstream targets of STK39 signaling

  • Study the relationship with WNK1 and OXSR1 in cancer context

Research has shown that STK39 enhances SNAI1 stability through phosphorylation, promoting breast cancer invasion and metastasis, and STK39 inhibition impairs EMT phenotype and tumor metastasis .

What methodological approaches are recommended for studying STK39 phosphorylation in immune cell function?

When investigating STK39 phosphorylation in immune cells:

Recommended methodological approaches:

• Immune cell isolation and culture:

  • Isolate primary T cells, B cells, or other immune populations

  • Maintain appropriate culture conditions to preserve signaling pathway integrity

  • Consider using CD4+ T cells, which have been successfully used in STK39 research

• Stimulation protocols:

  • For T cells: Stimulate with chemokines (e.g., CCL21)

  • For B cells: Use anti-IgM, CXCL13, or MnCl₂

  • Include time course analysis to capture phosphorylation dynamics

• Inhibitor studies:

  • Use WNK463 (WNKi) to block WNK1 activity upstream of STK39

  • Employ SLC12A2 inhibitors to study ion co-transporter involvement

  • Include appropriate vehicle controls

• Genetic manipulation:

  • Generate conditional knockout models (e.g., Wnk1 fl/fl, Oxsr1 fl/fl, Stk39 T243A/T243A)

  • Use tamoxifen-inducible Cre systems for temporal control

  • Create bone marrow chimeras to study cell-intrinsic effects

• Phosphorylation detection:

  • Western blot with STK39 (Ab-325) Antibody

  • Flow cytometry (for high-throughput single-cell analysis)

  • Immunofluorescence to assess subcellular localization of phosphorylated STK39

• Functional readouts:

  • T cell migration assays (Transwell, collagen matrix, live imaging)

  • B cell adhesion to ICAM-1

  • Antibody responses in vivo

  • Cytokine production

Recent research has demonstrated that WNK1, OXSR1, STK39, and ion influx through SLC12A2 are required for CCL21-induced migration of T cells , and that WNK1 kinase is essential in B cells for T-dependent antibody responses through OXSR1 and STK39 .

How can STK39 (Ab-325) Antibody be effectively used in multiplex imaging studies?

For multiplex imaging studies involving STK39 (Ab-325) Antibody:

Optimization strategies:

• Antibody panel design:

  • Ensure compatible host species to avoid cross-reactivity

  • STK39 (Ab-325) Antibody is typically a rabbit polyclonal antibody

  • Can be paired with mouse monoclonal antibodies against other targets

  • Consider antibodies against WNK1, OXSR1, and downstream targets for pathway analysis

• Fluorophore selection:

  • Choose fluorophores with minimal spectral overlap

  • Consider brightness relative to target abundance (STK39 pS325 may require brighter fluorophores)

  • Secondary antibody options include:

    • Goat Anti-Rabbit IgG H&L with various conjugates (FITC, AP, Biotin, HRP)

• Fixation and antigen retrieval protocols:

  • 4% paraformaldehyde fixation for 15 minutes at room temperature has been successful

  • Consider testing multiple fixation methods if signal is weak

  • For paraffin sections, optimize antigen retrieval conditions

• Sequential staining protocol:

  1. Block in 1% BSA in PBS for 20 minutes

  2. Permeabilize with 0.1% Tween20 in PBS for 15 minutes

  3. Apply primary antibodies overnight at 4°C

  4. Wash with PBS

  5. Apply appropriate secondary antibodies for 1 hour

  6. Wash thoroughly (0.1% Tween20 in PBS) before imaging

• Controls for multiplex imaging:

  • Single-color controls for spectral unmixing

  • Peptide competition controls for STK39 (Ab-325) Antibody

  • Phosphatase-treated controls

  • Secondary-only controls to assess background

Research has successfully used immunofluorescence to visualize phosphorylated STK39 along with other markers like CDC42 (leading edge marker) and CD44 (trailing edge marker) in migrating T cells .

How should researchers interpret differences in STK39 phosphorylation patterns between normal and diseased tissues?

When analyzing STK39 phosphorylation patterns in comparative studies:

Interpretation framework:

• Baseline expression considerations:

  • STK39 expression varies across tissues

  • Normalize phospho-STK39 signals to total STK39 levels

  • Consider cell-type specific expression within heterogeneous tissues

• Pattern analysis:

  • Assess both intensity and localization of phosphorylation

  • In cancer studies, compare tumor center vs. invasive front

  • In brain tissue, examine phosphorylation patterns in different cell types and regions

• Correlation with pathological features:

  • Correlate phosphorylation status with:

    • Disease stage/grade

    • Patient outcomes

    • Molecular subtypes

    • Treatment response

• Pathway context:

  • Examine concurrent changes in WNK1 and OXSR1 phosphorylation

  • Assess downstream effectors (ion transporters, cytoskeletal regulators)

  • Consider the activation status of parallel pathways

• Quantification approaches:

  • Use digital pathology tools for objective quantification

  • Consider H-score, Allred score, or percentage positive cells

  • For Western blot, use densitometry normalized to loading controls and total protein

Research has shown increased STK39 activity in breast cancer, where it promotes metastasis through SNAI1 stabilization . When interpreting such findings, consider whether phosphorylation changes reflect cause or consequence of disease progression.

What statistical approaches are recommended for analyzing STK39 phosphorylation data?

For robust statistical analysis of STK39 phosphorylation data:

Statistical methodology recommendations:

Recent research in T cell migration utilized these statistical approaches to establish significant relationships between STK39 pathway activity and functional outcomes .

What are the emerging therapeutic applications targeting STK39 phosphorylation?

Research on STK39 inhibition shows promising therapeutic potential:

Emerging therapeutic strategies:

• Cancer treatment applications:

  • STK39 inhibition impairs EMT phenotype and decreases tumor cell migration, invasion, and metastasis

  • Depletion of STK39 dramatically enhances sensitivity to chemotherapeutic agents

  • Targeting the STK39-SNAI1 signaling axis could be particularly relevant for metastatic breast cancer

• Hypertension management:

  • STK39 has been identified as a hypertension susceptibility gene

  • Modulating STK39 activity could affect blood pressure regulation through ion cotransporter activity

  • Could lead to novel antihypertensive approaches with different mechanism than current drugs

• Neurodegenerative disease implications:

  • STK39 has been implicated in Parkinson's disease risk

  • Phosphorylation status may influence neuronal function and survival

  • Could represent a novel target for neuroprotective strategies

• Targeting approaches:

  • Small molecule inhibitors of STK39 kinase activity

  • Disruption of protein-protein interactions (STK39-SNAI1)

  • Targeting upstream regulators like WNK1

  • Gene therapy approaches to modulate STK39 expression

• Monitoring treatment response:

  • STK39 (Ab-325) Antibody could serve as a biomarker for target engagement

  • Phosphorylation status might predict response to certain therapies

  • Sequential biopsies could track phosphorylation changes during treatment

The STK39-SNAI1 signaling axis has been highlighted as a promising therapeutic target for treatments of metastatic breast cancer , suggesting phosphorylation-specific targeting could be a valuable approach.

What technical advances are improving detection and quantification of STK39 phosphorylation?

Recent technological advances are enhancing our ability to study STK39 phosphorylation:

Technological advancements:

• Mass spectrometry approaches:

  • Phosphoproteomics can identify multiple phosphorylation sites simultaneously

  • Allows quantitative comparison across conditions

  • Can reveal novel phosphorylation sites on STK39

  • Enables phosphorylation stoichiometry calculations

• Single-cell techniques:

  • Single-cell Western blot for phospho-protein analysis

  • Mass cytometry (CyTOF) with phospho-specific antibodies

  • Single-cell RNA-seq to correlate transcriptional changes with pathway activation

• Advanced imaging methods:

  • Super-resolution microscopy (STORM, PALM, SIM) for detailed localization

  • Intravital imaging to track phosphorylation dynamics in vivo

  • Phospho-specific biosensors for real-time monitoring

  • Instant structured illumination microscopy has been applied in studying related pathways

• Computational approaches:

  • Machine learning algorithms for image analysis

  • Pathway modeling to predict phosphorylation dynamics

  • Integration of multi-omics data to contextualize phosphorylation events

• Antibody technology improvements:

  • Development of recombinant phospho-specific antibodies with improved specificity

  • Nanobodies and alternative binding proteins for improved tissue penetration

  • Directly conjugated primary antibodies for simplified multiplexing

These advances are enabling researchers to study STK39 phosphorylation with unprecedented detail, revealing new insights into its role in various biological processes and disease states.

What are the key research publications on STK39 phosphorylation at Ser325?

Based on the available search results, these are key publications relevant to STK39 phosphorylation at Ser325:

• Research demonstrating WNK1-induced phosphorylation of OXSR1 on S325, a known target of WNK1 activity

• Studies showing that WNK1, OXSR1, STK39, and ion influx through SLC12A2 are required for CCL21-induced migration of T cells

• Work demonstrating that STK39 promotes breast cancer invasion and metastasis through stabilization of SNAI1

• Research on B cell-intrinsic requirement for WNK1 kinase in T cell-dependent antibody responses, involving STK39

• Genome-wide association studies identifying STK39 as a hypertension susceptibility gene

• Research implicating STK39 in Parkinson's disease risk through meta-analysis of genome-wide association studies

For a complete literature review, researchers should consult PubMed, Google Scholar, and specialized databases for the most recent publications on STK39 phosphorylation.

Where can researchers find additional resources and tools for STK39 research?

Additional resources for STK39 research:

• Antibody resources:

  • Commercial suppliers offer various STK39 antibodies, including phospho-specific antibodies targeting Ser325

  • Validation data is available for many antibodies, including immunohistochemistry images

• Genetic tools:

  • Mouse models with conditional alleles of Wnk1 (Wnk1 fl)

  • Mouse models with deletion of exon 2 of Wnk1 (Wnk1−)

  • Mouse models with conditional allele of Oxsr1 (Oxsr1 fl)

  • Mouse models with an allele of Stk39 encoding STK39-T243A (Stk39 T243A)

• Protein information resources:

  • UniProt ID for human STK39: Q9UEW8

  • Gene ID (NCBI): 27347

  • Protein molecular weight: approximately 59-62 kDa

• Inhibitors and activators:

  • WNK463 (WNKi), a selective WNK inhibitor that affects STK39 phosphorylation

  • SLC12A2 inhibitors for studying downstream effects

• Experimental protocols:

  • Detailed protocols for immunohistochemistry using STK39 (Ab-325) Antibody

  • Methods for studying T cell migration involving STK39 phosphorylation

  • Approaches for investigating B cell function related to STK39