RPS6KB2 (Ab-423) Antibody

What is RPS6KB2 (Ab-423) Antibody and what is its target?

RPS6KB2 (Ab-423) Antibody is a polyclonal antibody raised in rabbit that specifically recognizes the human p70 S6 Kinase β (RPS6KB2) protein around the phosphorylation site of serine 423, with the sequence motif P-V-S(p)-P-L. The antibody detects endogenous levels of total p70 S6 Kinase β protein . This kinase contains two non-identical kinase catalytic domains and phosphorylates the S6 ribosomal protein and eukaryotic translation initiation factor 4B (eIF4B), leading to increased protein synthesis and cell proliferation .

What applications is RPS6KB2 (Ab-423) Antibody validated for?

RPS6KB2 (Ab-423) Antibody has been validated for multiple applications:

• Western Blot (WB) at dilutions of 1:500-1:3000

• ELISA assays

• Immunohistochemistry (IHC) in some formulations

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

What is the recommended storage and handling protocol for RPS6KB2 (Ab-423) Antibody?

For optimal antibody performance:

• Store at -20°C or -80°C upon receipt

• Avoid repeated freeze-thaw cycles

• The antibody is typically supplied in phosphate buffered saline (without Mg²⁺ and Ca²⁺), pH 7.4, containing 150mM NaCl, 0.02% sodium azide and 50% glycerol

For long-term storage, aliquoting the antibody into smaller volumes is recommended to minimize freeze-thaw cycles that can degrade antibody quality .

How should I design a Western blot experiment using RPS6KB2 (Ab-423) Antibody?

For optimal Western blot results with RPS6KB2 (Ab-423) Antibody:

• Sample preparation: Extract proteins from cells of interest (validated in 293T, 3T3, HeLa, and K562 cell lines)

• Gel selection: Use 8% SDS-PAGE for optimal separation of the target protein (p70 S6 Kinase β has a molecular weight of ~53-60 kDa)

• Protein loading: Load 10-40 μg of total protein per lane

• Transfer conditions: Standard wet or semi-dry transfer protocols are suitable

• Blocking: Block membrane with 5% non-fat milk or BSA in TBST

• Primary antibody: Dilute antibody 1:500-1:3000 in blocking buffer and incubate overnight at 4°C

• Secondary antibody: Use anti-rabbit HRP-conjugated secondary antibody

• Detection: Use standard ECL detection methods

Control samples treated with phosphatase can serve as negative controls to confirm specificity of phosphorylation-dependent detection .

What cell types and experimental conditions are optimal for studying RPS6KB2 phosphorylation?

Based on published research using this antibody:

For studying phosphorylation dynamics, serum starvation followed by stimulation with growth factors (particularly FGF2) has been shown to effectively modulate RPS6KB2 activity .

How can I optimize immunohistochemistry protocols using RPS6KB2 (Ab-423) Antibody?

For IHC applications:

• Fixation: Use formalin-fixed, paraffin-embedded tissues

• Antigen retrieval: Heat-induced epitope retrieval in citrate buffer (pH 6.0)

• Blocking: 5-10% normal serum from secondary antibody host species

• Primary antibody dilution: 1:50-1:200 range (optimize empirically)

• Detection: Use a Vecstatin ABC Elite kit and DAB peroxidase substrate for visualization

• Counterstaining: Hematoxylin provides good nuclear contrast

Include appropriate positive controls (breast or melanoma tissues with known RPS6KB2 expression) and negative controls (omit primary antibody) .

What is the role of S6K2 phosphorylation at Ser423 in cellular signaling?

Serine 423 phosphorylation in S6K2 occurs in the autoinhibitory domain and plays a critical role in kinase regulation:

• Ser423 is one of three proline-directed serines (along with Ser410 and Ser417) in the autoinhibitory domain that regulate S6K2 activity in a MEK-dependent manner

• Phosphorylation of these autoinhibitory serines occurs prior to Thr388 activation

• These phosphorylation events help relieve autoinhibition, allowing for further phosphorylation at Thr388, which is crucial for full S6K2 activation

• Mutational analyses show that changing these serine residues affects S6K2 activity, confirming their regulatory importance

This phosphorylation site is part of a complex regulatory network that integrates inputs from multiple signaling pathways, including mTOR, PI3K, and MAPK cascades .

How does S6K2 differ functionally from S6K1, and why is this distinction important?

Despite structural similarities, S6K1 and S6K2 have important differences:

These differences suggest that S6K2 may have unique functions in certain cellular contexts, particularly in cancer cell survival and drug resistance mechanisms. Targeting S6K2 specifically (rather than both S6K isoforms) may provide therapeutic advantages in certain cancers, such as MAPK inhibitor-resistant NRAS-mutant melanomas .

What is the significance of S6K2 in cancer research and potential therapeutic applications?

S6K2 has emerged as an important cancer research target:

• Triple-negative breast cancer (TNBC): S6K2 is overexpressed in both ER-positive and triple-negative breast tumors compared to normal tissues. Silencing S6K2 enhances sensitivity of TNBC cells to chemotherapeutic drugs (cisplatin, doxorubicin) and TRAIL-induced apoptosis

• NRAS-mutant melanoma: Selectively silencing S6K2 while preserving S6K1 activity disrupts lipid metabolism, enhances fatty acid unsaturation, and triggers lethal lipid peroxidation in melanoma cells resistant to MAPK inhibition. Combining PPARα agonists with polyunsaturated fatty acids phenocopies S6K2 abrogation effects

• COVID-19 research: S6K (RPS6KB1) phosphorylation increased 3.5-fold at S418 in RAW264.7 macrophages following SPIKE protein treatment, suggesting potential involvement in COVID-19 pathogenesis

These findings position S6K2 as a promising therapeutic target, particularly in treatment-resistant cancers where conventional therapies fail .

How can I verify the specificity of RPS6KB2 (Ab-423) Antibody in my experiments?

To confirm antibody specificity:

• Peptide competition assay: Preincubate the antibody with the immunizing peptide (P-V-S(p)-P-L) before application. This should abolish specific signal

• Phosphatase treatment control: Treat lysate samples with alkaline phosphatase (as shown in search result 12) to remove phosphorylation and confirm phospho-specificity

• RPS6KB2 knockdown/knockout: Use siRNA to silence RPS6KB2 expression or CRISPR to generate knockout cells as negative controls

• Molecular weight verification: Confirm that the detected band runs at the expected molecular weight (~53-60 kDa)

• Positive control samples: Use cell lines known to express RPS6KB2, such as K562, HEK293, or breast cancer cell lines

Western blot analysis has shown signal at approximately 60 kDa in K562, rat brain, C6, and 3T3 cell lysates, which can serve as positive controls .

What are common pitfalls when using phospho-specific antibodies like RPS6KB2 (Ab-423) and how can they be avoided?

Common challenges and solutions:

• Loss of phosphorylation during sample preparation:

  • Add phosphatase inhibitors (sodium fluoride, sodium orthovanadate, etc.) to all buffers

  • Keep samples cold throughout preparation

  • Minimize processing time

• Non-specific binding:

  • Optimize blocking conditions (try both BSA and milk-based blockers)

  • Include detergents like Tween-20 in wash buffers

  • Titrate antibody concentration carefully

• Variability in phosphorylation status:

  • Standardize cell culture conditions and treatment times

  • Control harvesting conditions carefully

  • Include positive controls (e.g., growth factor-stimulated samples)

• Background issues in IHC:

  • Optimize antigen retrieval conditions

  • Include appropriate blocking of endogenous peroxidases

  • Test multiple antibody dilutions

• Storage-related antibody degradation:

  • Aliquot antibody to avoid freeze-thaw cycles

  • Store at recommended temperatures (-20°C or -80°C)

  • Check expiration dates and antibody performance periodically

How can I use RPS6KB2 (Ab-423) Antibody in co-immunoprecipitation studies?

For co-immunoprecipitation experiments:

• Lysate preparation:

  • Use non-denaturing lysis buffer (e.g., RIPA or IP lysis buffer)

  • Include protease and phosphatase inhibitors

  • Clear lysate by centrifugation (14,000g, 10 min, 4°C)

• Pre-clearing (optional):

  • Incubate lysate with Protein A/G beads for 1h at 4°C

  • Remove beads by centrifugation

• Immunoprecipitation:

  • Incubate 2-5 μg of RPS6KB2 (Ab-423) Antibody with 500-1000 μg lysate overnight at 4°C

  • Add Protein A beads (for rabbit antibodies) and incubate 2-4h

  • Wash beads 3-5 times with lysis buffer

• Analysis:

  • Elute proteins with SDS sample buffer

  • Analyze by Western blot for interacting proteins

This approach has successfully demonstrated interactions between S6K2 and proteins like hnRNPA1 following FGF2 stimulation, as described in the research literature .

How can I use the RPS6KB2 (Ab-423) Antibody in multi-color immunofluorescence studies?

For multi-color immunofluorescence:

• Sample preparation:

  • Fix cells or tissue sections (4% paraformaldehyde for cells, formalin for tissues)

  • Permeabilize with 0.1-0.5% Triton X-100

  • Block with 5-10% normal serum

• Primary antibody incubation:

  • Use RPS6KB2 (Ab-423) Antibody at 1:50-1:200 dilution

  • Co-incubate with other primary antibodies from different host species

  • Incubate overnight at 4°C

• Secondary antibody selection:

  • Choose anti-rabbit secondary antibody conjugated to your preferred fluorophore (e.g., Alexa Fluor 488)

  • Ensure secondary antibodies against other primaries have different fluorophores

  • Incubate 1-2 hours at room temperature

• Counterstaining and mounting:

  • Use DAPI for nuclear staining

  • Mount with anti-fade mounting medium

• Controls:

  • Include single-color controls for spectral compensation

  • Secondary-only controls to assess background

This technique can be used to simultaneously visualize RPS6KB2 localization alongside other proteins of interest, such as mTOR pathway components or translation factors .

What is the current understanding of S6K2's role in the mTOR signaling pathway and how can the antibody help elucidate this?

S6K2 functions within the mTOR signaling network:

• Pathway position: S6K2 acts downstream of mTOR complex 1 (mTORC1) in response to growth factors and nutrients

• Regulation: S6K2 activation requires phosphorylation at multiple sites, including Thr388 (mTOR-dependent) and Ser423 (MEK-dependent)

• Alternative pathway: Recent research indicates S6K2 may function in an alternative pathway regulated by MEAK7

• Substrates: S6K2 phosphorylates ribosomal protein S6 and potentially other targets like hnRNPA1

The RPS6KB2 (Ab-423) Antibody can be used to:

• Monitor S6K2 activation status in response to mTOR modulators

• Assess pathway activation in different cellular contexts

• Investigate cross-talk between mTOR and MAPK pathways

• Evaluate effects of novel therapeutic compounds targeting this pathway

Combined with phospho-specific antibodies targeting other pathway components (S6, 4EBP1, etc.), this antibody enables comprehensive mapping of mTOR signaling dynamics under various conditions.

How can cell-based ELISA be optimized for quantitative measurement of S6K2 phosphorylation?

For quantitative analysis of S6K2 phosphorylation using cell-based ELISA:

• Cell seeding optimization:

  • Seed approximately 20,000-30,000 adherent cells per well in 96-well plates

  • For suspension cells, coat plates with 10 μg/ml Poly-L-Lysine before seeding

  • Aim for 75-90% confluence at time of treatment

• Treatment conditions:

  • Include appropriate controls: untreated, positive control (e.g., serum stimulation)

  • Include inhibitor controls (rapamycin, MEK inhibitors) to demonstrate specificity

  • Use time-course treatments to capture phosphorylation dynamics

• Fixation and detection:

  • Fix cells with 4% formaldehyde for adherent cells (8% for suspension cells)

  • Block with appropriate buffer

  • Use RPS6KB2 (Ab-423) Antibody at 1:1000 dilution

  • Include anti-GAPDH antibody as internal control for normalization

• Analysis:

  • Calculate normalized OD values (target/GAPDH)

  • Generate standard curves if needed

  • Perform statistical analysis across replicate wells

This approach can detect S6K2 expression and phosphorylation changes in as few as 5,000 cells, making it suitable for high-throughput screening applications .