RPS6KA4 (Ab-568) Antibody

What is RPS6KA4 and what are its key biological functions?

RPS6KA4 (ribosomal protein S6 kinase, 90kDa, polypeptide 4) is a serine/threonine kinase belonging to the RSK family. It plays important regulatory roles in cell growth, movement, survival, and proliferation . The protein is also known by alternative names including MSK2, RSK-B, S6K-alpha-4, and Nuclear mitogen- and stress-activated protein kinase 2 . With a calculated molecular weight of approximately 86-90 kDa , RPS6KA4 functions through the MAPK/ERK pathway and has been implicated in various cellular processes including epigenetic regulation, cell adhesion, and tumor-driven GTPase pathways .

What applications has RPS6KA4 antibody been validated for?

RPS6KA4 antibodies have been validated for multiple research applications. For example, the 14581-1-AP antibody from Proteintech has been validated specifically for ELISA applications . Other commercially available antibodies like ab99411 have been validated for Western blotting (WB), immunoprecipitation (IP), and immunohistochemistry on paraffin-embedded tissues (IHC-P) . When designing experiments, researchers should verify the specific validations for their chosen antibody clone, as application suitability varies between manufacturers and clones.

What species reactivity has been confirmed for RPS6KA4 antibodies?

The species reactivity for RPS6KA4 antibodies varies by manufacturer and clone. From the available data, several antibodies show reactivity with:

When working with species not listed, validation experiments should be conducted due to the prediction of reactivity based on sequence homology, which may not always translate to functional cross-reactivity.

How should I design experiments to study RPS6KA4 in cancer research?

When designing experiments to study RPS6KA4 in cancer research, particularly hepatocellular carcinoma (HCC), consider these methodological approaches:

What positive controls should be used when working with RPS6KA4 antibodies?

When validating RPS6KA4 antibody specificity, appropriate positive controls should include:

• HCC cell lines known to express RPS6KA4, as this protein has been found overexpressed in hepatocellular carcinoma tissues .

• Recombinant RPS6KA4 protein standards, such as the C13 and N15-labeled recombinant protein expressed in HEK293 cells (e.g., PH312570) .

• For kinase activity assays, staurosporine can serve as a control inhibitor when setting up binding assays, as it's commonly used in LanthaScreen Eu Kinase Binding Assays for RPS6KA4 .

• Lysates from tissues with confirmed RPS6KA4 expression, such as liver cancer specimens with validated overexpression .

The inclusion of these controls will help establish the specificity and sensitivity of the antibody in your experimental system.

What is the optimal protocol for using RPS6KA4 antibodies in kinase binding assays?

For optimal kinase binding assays with RPS6KA4, the LanthaScreen Eu Kinase Binding Assay provides a well-established methodology:

• Prepare a kinase/antibody solution at 15 nM kinase and 6 nM antibody (3X the desired final assay concentration) .

• Calculate the required concentration using the formula:
  Stock kinase conc. (nM) = stock conc. (mg/mL) * 1,000,000,000 (nmol/mol) / kinase MW (grams/mol)

• For kinase volume calculation:
  Kinase volume needed (μL) = (total volume * desired concentration) / Stock kinase conc.

• Follow a sequential addition protocol:

  • Add 5 μL of each concentration of serially diluted compound to triplicate assay wells

  • Add 5 μL of kinase/antibody solution to all wells

  • Add 5 μL of tracer solution to all wells

• Incubate the plate at room temperature for 60 minutes before reading .

• For data analysis, divide the acceptor/tracer emission (665 nm) by the antibody/donor emission (615 nm) to calculate the emission ratio, and plot this against tracer concentration .

How should RPS6KA4 antibodies be stored and handled for optimal performance?

Proper storage and handling of RPS6KA4 antibodies is crucial for maintaining their performance. Based on product information from multiple suppliers:

How do I interpret discrepancies between RPS6KA4 expression data from different detection methods?

When facing discrepancies in RPS6KA4 expression data across different detection methods, consider these analytical approaches:

• Antibody epitope location: Check if different antibodies target different epitopes of RPS6KA4. For example, some antibodies like ab99411 target synthetic peptides within the 700 to C-terminus region , which might detect specific isoforms or post-translationally modified forms.

• Method sensitivity: Western blotting and mass spectrometry have different detection thresholds. MS standards for RPS6KA4 (such as C13 and N15-labeled recombinant proteins) can provide absolute quantification , while antibody-based methods may offer relative quantification.

• Phosphorylation status: As a kinase, RPS6KA4 function is regulated by phosphorylation. Certain antibodies may preferentially detect phosphorylated or non-phosphorylated forms, affecting your results based on the cellular context.

• Sample preparation variables: Different fixation methods for IHC or lysis buffers for WB can affect epitope accessibility. Test multiple preparation methods if results are inconsistent.

• Biological variation: RPS6KA4 overexpression in HCC has been correlated with T stage, pathological stage, and vascular invasion . Ensure your samples are properly stratified by these variables when comparing across methods.

What might cause high background when using RPS6KA4 antibodies in immunostaining?

High background in immunostaining experiments with RPS6KA4 antibodies can be attributed to several factors:

• Insufficient blocking: RPS6KA4 antibodies like the polyclonal variants may require optimized blocking conditions. Try different blocking agents including BSA, normal serum matching the secondary antibody host, or commercial blocking reagents.

• Antibody concentration: Polyclonal antibodies such as the 14581-1-AP and ab99411 may require careful titration . Start with manufacturer-recommended dilutions and adjust as needed.

• Cross-reactivity: RPS6KA4 belongs to the RSK family with several homologous members. Verify antibody specificity against related proteins (e.g., other RSK family members).

• Fixation issues: Overfixation can increase non-specific binding. Test different fixation protocols, particularly for formalin-fixed paraffin-embedded tissues when using IHC-P validated antibodies .

• Secondary antibody problems: Secondary antibody cross-reactivity can contribute to background. Include controls omitting primary antibody, and ensure secondary antibodies are appropriate for your tissue type.

• Endogenous peroxidase or phosphatase activity: When using enzymatic detection systems, properly quench endogenous activities in your samples.

How can RPS6KA4 antibodies be used to study its role in cancer progression?

RPS6KA4 antibodies can be employed in multiple advanced research strategies to investigate its role in cancer progression:

How does phosphorylation status affect RPS6KA4 detection with antibodies?

Phosphorylation status can significantly impact RPS6KA4 detection with antibodies through several mechanisms:

• Epitope masking: Phosphorylation events can alter protein conformation, potentially masking antibody epitopes. This is particularly relevant for antibodies targeting regions near phosphorylation sites in RPS6KA4.

• Functional states: As a kinase involved in the MAPK/ERK pathway , RPS6KA4 exists in both active (phosphorylated) and inactive states. Antibodies may preferentially detect one state over the other.

• Experimental considerations:

  • Include phosphatase inhibitors in lysis buffers when studying phosphorylated forms

  • Consider using phospho-specific antibodies alongside total RPS6KA4 antibodies

  • For kinase binding assays like the LanthaScreen Eu Kinase Binding Assay, the buffer composition (50mM HEPES pH 7.5, 10 mM MgCl2, 1 mM EGTA, 0.01% Brij-35) helps maintain kinase stability

• Validation strategies: When studying phosphorylation-dependent functions, validate antibody specificity by testing detection following treatment with phosphatase inhibitors versus phosphatases.

• Alternative approaches: For absolute quantification of phosphorylation states, consider using mass spectrometry with labeled standards like the RPS6KA4 MS Standard (C13 and N15-labeled recombinant protein) alongside antibody-based methods.

What are emerging applications for RPS6KA4 antibodies in precision medicine?

Emerging applications for RPS6KA4 antibodies in precision medicine include:

• Biomarker development: RPS6KA4 has demonstrated potential as an independent prognostic biomarker for HCC . Antibody-based detection methods could be standardized for clinical implementation.

• Patient stratification: Given the association between RPS6KA4 overexpression and clinical parameters such as T stage, pathological stage, AFP values, and vascular invasion , antibody-based assays could help stratify patients for personalized treatment approaches.

• Therapeutic monitoring: As targeted therapies against kinases continue to develop, RPS6KA4 antibodies may be useful for monitoring treatment efficacy by measuring changes in expression or activation status.

• Immunotherapy response prediction: The negative correlation between RPS6KA4 and immune cell infiltration suggests potential applications in predicting immunotherapy responses, which could be assessed using multiplexed immunohistochemistry panels including RPS6KA4 antibodies.

• Companion diagnostics: As the role of RPS6KA4 in cancer progression becomes better understood, antibody-based assays may serve as companion diagnostics for future targeted therapies aimed at this kinase or its pathway components.