Phospho-RFWD2 (S387) Antibody

What is RFWD2/COP1 and why is its S387 phosphorylation site significant?

RFWD2 (also known as COP1, RNF200, or hCOP1) is an E3 ubiquitin-protein ligase that plays crucial roles in regulating cell proliferation and apoptosis. It contains a RING finger domain essential for ubiquitin transfer and WD repeat domains for substrate recognition . RFWD2 is overexpressed in numerous human cancers, including leukemia, lung cancer, breast cancer, renal cell carcinoma, and colorectal cancer, indicating its potential significance in oncogenesis .

The S387 phosphorylation site represents a key regulatory position that can modulate RFWD2's function as an E3 ubiquitin ligase. Phosphorylation at this site may alter its enzymatic activity, substrate specificity, or protein-protein interactions. Understanding this specific phosphorylation is critical for elucidating RFWD2's regulatory mechanisms in cellular processes including protein degradation pathways and cancer progression .

What are the main applications for Phospho-RFWD2 (S387) antibodies in research?

Phospho-RFWD2 (S387) antibodies have several key research applications:

• Western Blot (WB): Typically used at dilutions of 1:500-1:2000 to detect and quantify phosphorylated RFWD2 in cell or tissue lysates

• Enzyme-Linked Immunosorbent Assay (ELISA): Employed at approximately 1:5000 dilution for high-throughput quantification

• Cell-Based Colorimetric ELISA: Specialized assays for measuring relative protein levels and phosphorylation degrees in different cell types under various conditions

• Immunohistochemistry: For detection of phosphorylated RFWD2 in tissue sections, though this application requires specific validation

These antibodies enable researchers to investigate phosphorylation-dependent regulation of RFWD2 in various signaling pathways, particularly those relevant to cancer biology and protein degradation mechanisms.

For maximum stability and performance of Phospho-RFWD2 (S387) antibodies:

• Long-term storage: -20°C or -80°C in small aliquots

• Short-term storage (up to 2 weeks): 4°C

• Storage buffer typically contains: PBS with 50% glycerol, 0.5% BSA, and 0.02% sodium azide

• Critical handling note: Avoid repeated freeze-thaw cycles which can significantly degrade antibody performance

• Transport conditions: Typically shipped on blue ice

Most manufacturers recommend dividing the antibody into small working aliquots upon first thaw to minimize freeze-thaw damage. Always check the specific manufacturer's recommendations for your particular antibody.

How should I design experiments to validate the specificity of a Phospho-RFWD2 (S387) antibody?

A comprehensive validation approach should include:

• Peptide Competition Assay:

  • Pre-incubate antibody with the immunizing phosphopeptide

  • This should eliminate signal in subsequent applications if the antibody is specific

• Phosphatase Treatment Control:

  • Divide your sample into two portions

  • Treat one portion with lambda phosphatase

  • The signal should significantly decrease or disappear in the treated sample

• Genetic Approaches:

  • Use RFWD2 knockdown models via shRNA/siRNA approaches

  • Compare with controls to confirm signal specificity

  • Express S387A mutant (non-phosphorylatable) as a negative control

• Kinase Manipulation:

  • Identify and manipulate kinases that might phosphorylate S387

  • Monitor changes in antibody signal that correlate with expected phosphorylation status

Each validation approach provides complementary evidence for antibody specificity, strengthening the reliability of your research findings.

What is the recommended protocol for Western blotting with Phospho-RFWD2 (S387) antibodies?

Optimized Western Blot Protocol:

• Sample Preparation:

  • Include fresh phosphatase inhibitors in lysis buffer

  • For ubiquitination studies, consider pre-treating cells with proteasome inhibitors (e.g., MG132 for 12h)

• Electrophoresis and Transfer:

  • Separate proteins on standard SDS-PAGE gels

  • Transfer to PVDF membrane (preferred for phosphoproteins)

• Blocking:

  • Block with 5% BSA in TBST (not milk, which contains phosphoproteins)

  • Block for 1 hour at room temperature

• Primary Antibody Incubation:

  • Dilute antibody 1:500-1:2000 in blocking buffer

  • Incubate overnight at 4°C with gentle agitation

• Washing:

  • Wash 3-5 times with TBST, 5-10 minutes each

• Secondary Antibody Incubation:

  • Use appropriate HRP-conjugated secondary antibody (typically anti-rabbit IgG)

  • Incubate for 1 hour at room temperature

• Detection:

  • Develop using ECL or similar detection system

  • Expected molecular weight: ~80-111 kDa

• Controls:

  • Run parallel blot with total RFWD2 antibody for normalization

  • Include positive controls (cells with known RFWD2 phosphorylation)

This protocol may require optimization for your specific experimental conditions.

How can I use Phospho-RFWD2 (S387) antibodies in co-immunoprecipitation experiments?

Co-Immunoprecipitation Protocol:

• Cell Preparation:

  • Harvest cells at 70-80% confluency

  • Lyse in non-denaturing buffer containing phosphatase inhibitors

  • Clear lysate by centrifugation (14,000 rpm for 1 min)

• Pre-clearing:

  • Incubate lysate with protein A/G beads for 1 hour at 4°C

  • Remove beads by centrifugation

• Immunoprecipitation:

  • Add 2-5 μg of Phospho-RFWD2 (S387) antibody to pre-cleared lysate

  • Incubate overnight at 4°C with gentle rotation

  • Add protein A/G beads and incubate for additional 2-4 hours

  • Wash beads 3-5 times with lysis buffer

• Elution and Analysis:

  • Elute proteins by boiling in SDS sample buffer

  • Analyze by Western blot, probing for potential interaction partners

• Critical Controls:

  • IgG control immunoprecipitation

  • Input sample (5-10% of lysate used for IP)

  • Use of both phospho-specific and total RFWD2 antibodies to compare interactomes

Research indicates that RFWD2 interacts with proteins like TRIB2 and forms complexes that regulate proteasome-mediated degradation of substrates . Co-IP experiments can reveal whether these interactions are phosphorylation-dependent.

What are the advantages of using a Phospho-RFWD2 (S387) Cell-Based ELISA Kit compared to traditional Western blot?

Cell-Based ELISA kits measure the relative amount of phospho-specific or total protein directly in cultured cells, allowing simultaneous measurement and normalization to total protein levels . This approach is particularly valuable for screening compounds that affect RFWD2 phosphorylation or for time-course experiments requiring multiple sampling points.

How does RFWD2 phosphorylation affect its activity in the ubiquitin-proteasome pathway?

RFWD2 functions as an E3 ubiquitin ligase in the ubiquitin-proteasome system, targeting specific proteins for degradation. Research indicates that phosphorylation may serve as a regulatory mechanism affecting its function in several ways:

• Substrate Recognition:

  • Phosphorylation may alter RFWD2's ability to recognize and bind substrate proteins

  • Studies suggest RFWD2 targets proteins such as p27 and IκB-α for ubiquitination and degradation

• Complex Formation:

  • Research has demonstrated that RFWD2 can form complexes with proteins like TRIB2

  • These interactions affect proteasome-mediated degradation of RFWD2 substrates

  • The N-SH2 domain of Shp2 has been shown to interact with both FASN and COP1 (RFWD2), suggesting complex regulatory mechanisms

• Enzymatic Activity Regulation:

  • Phosphorylation at S387 may directly influence the E3 ligase activity of RFWD2

  • Similar to other E3 ligases, phosphorylation could serve as a molecular switch controlling activity

• Signal Integration:

  • RFWD2 phosphorylation potentially integrates signals from various kinase pathways

  • This allows for context-specific regulation of protein degradation

Experimental approaches to study these effects include in vitro ubiquitination assays, comparing the activity of wild-type RFWD2 with phosphomimetic (S387D/E) and phospho-dead (S387A) mutants, and mass spectrometry analysis to identify phosphorylation-dependent protein interactions .

What is known about the role of RFWD2 and its phosphorylation in cancer progression?

RFWD2 has significant implications in cancer biology, with phosphorylation potentially serving as a key regulatory mechanism:

• Expression Pattern:

  • RFWD2 is overexpressed in multiple human cancers including leukemia, lung cancer, breast cancer, renal cell carcinoma, and colorectal cancer

  • High expression levels correlate with adverse outcomes in some cancers

• Functional Impact:

  • RFWD2 knockdown significantly suppresses cell proliferation and induces apoptosis in hepatocellular carcinoma and other cancer cells

  • RFWD2-siRNA treatment can suppress liver cancer growth and reduce tumor mass in nude mice

  • RFWD2 can function as a tumor suppressor by negatively regulating ETV1 in colorectal cancer

• Mechanistic Studies:

  • In multiple myeloma, RFWD2 participates in cell cycle regulation, cell growth, and death processes

  • Flow cytometry studies demonstrate that targeting RFWD2 significantly affects apoptotic rates in cancer cells

  • Immunohistochemical analysis has been used to correlate RFWD2 expression with clinical parameters in cancer tissues

• Phosphorylation-Specific Effects:

  • While the general role of RFWD2 in cancer is increasingly understood, the specific impact of S387 phosphorylation remains an active area of investigation

  • Phospho-specific antibodies enable researchers to examine whether phosphorylation status correlates with cancer progression or treatment response

Further research using phospho-specific antibodies could elucidate whether S387 phosphorylation serves as a biomarker for cancer progression or a target for therapeutic intervention.

What experimental approaches can I use to study the kinases responsible for RFWD2 S387 phosphorylation?

To identify and characterize kinases that phosphorylate RFWD2 at S387:

• Bioinformatic Prediction:

  • Use phosphorylation site prediction tools (e.g., NetPhos, GPS, Scansite) to identify candidate kinases

  • Analyze the amino acid sequence context surrounding S387 for consensus motifs

• Kinase Inhibitor Screening:

  • Treat cells with panels of kinase inhibitors with known specificity profiles

  • Monitor S387 phosphorylation by Western blot using phospho-specific antibodies

  • A significant decrease in phosphorylation indicates potential kinase involvement

• In Vitro Kinase Assays:

  • Express recombinant RFWD2 or synthetic peptides containing the S387 site

  • Incubate with purified candidate kinases and ATP

  • Detect phosphorylation using phospho-specific antibodies or radioactive ATP

• Genetic Approaches:

  • Overexpress or knock down candidate kinases

  • Assess changes in S387 phosphorylation

  • Use phosphomimetic (S387D/E) or phospho-dead (S387A) mutants as controls

• Mass Spectrometry:

  • Perform immunoprecipitation with anti-RFWD2 antibody

  • Analyze co-precipitating proteins by mass spectrometry to identify associated kinases

  • Use quantitative phosphoproteomics to measure S387 phosphorylation changes after kinase manipulation

• Cellular Context Studies:

  • Stimulate specific signaling pathways known to activate candidate kinases

  • Monitor temporal correlation between kinase activation and S387 phosphorylation

Understanding the kinases responsible for S387 phosphorylation would provide insights into the upstream regulation of RFWD2 and potential therapeutic targets.

How can Phospho-RFWD2 (S387) antibodies be used in high-throughput drug screening?

Phospho-RFWD2 (S387) antibodies can be effectively implemented in drug discovery pipelines through several approaches:

• Cell-Based ELISA Screening:

  • Utilize 96-well format Cell-Based Colorimetric ELISA kits

  • Treat cells with compound libraries in multi-well plates

  • Quantify changes in S387 phosphorylation relative to total RFWD2

  • Screen throughput: hundreds to thousands of compounds

  • Data output: Normalized phosphorylation indices

• Automated Western Blot Platforms:

  • Employ capillary-based or microfluidic Western platforms

  • Process multiple samples simultaneously

  • Quantify phosphorylation/total protein ratios

  • Advantage: Confirms protein size and potential additional modifications

• Phospho-Specific Flow Cytometry:

  • Adapt phospho-RFWD2 antibodies for intracellular flow cytometry

  • Enable cell-by-cell analysis of phosphorylation status

  • Benefit: Can examine phosphorylation in specific cell populations

• Image-Based High-Content Screening:

  • Perform immunofluorescence with phospho-RFWD2 antibodies

  • Quantify signal intensity, subcellular localization, and morphological changes

  • Advantage: Provides spatial information on phosphorylation

• Multiplexed Assays:

  • Combine phospho-RFWD2 detection with other pathway markers

  • Analyze multiple endpoints simultaneously

  • Benefit: Contextualizes RFWD2 phosphorylation within broader signaling networks

• Validation Cascade:

  • Primary screen: Cell-Based ELISA for high throughput

  • Secondary validation: Western blot for hit confirmation

  • Tertiary analysis: Functional assays (ubiquitination, substrate degradation)

This multi-tiered approach enables efficient screening while ensuring biological relevance of identified compounds affecting RFWD2 phosphorylation.

What are common issues when using Phospho-RFWD2 (S387) antibodies and how can I resolve them?

For difficult samples, consider enriching for RFWD2 using immunoprecipitation with a total RFWD2 antibody before detection with the phospho-specific antibody.

How does sample preparation affect the detection of phosphorylated RFWD2?

Sample preparation is critical for preserving phosphorylation status and ensuring reliable detection:

• Cell/Tissue Harvesting:

  • Rapid harvesting minimizes phosphatase activity

  • Consider direct lysis in wells for adherent cells to prevent phosphorylation changes during processing

• Lysis Buffer Composition:

  • Must contain fresh phosphatase inhibitors (sodium fluoride, sodium orthovanadate, β-glycerophosphate)

  • For ubiquitination studies, include deubiquitinase inhibitors like N-ethylmaleimide

  • RIPA or NP-40 based buffers typically work well for phosphoprotein extraction

• Temperature Control:

  • Keep samples cold throughout preparation

  • Process quickly to minimize degradation and dephosphorylation

• Protein Quantification:

  • Use Bradford or BCA assays for accurate quantification

  • Load equal amounts of protein (typically 20-50 μg for Western blot)

• Denaturing Conditions:

  • Add SDS sample buffer with reducing agents

  • Heat at 95-100°C for 5 minutes for complete denaturation

  • Use fresh DTT or β-mercaptoethanol

• Special Treatment Considerations:

  • For proteasome-related studies, pre-treat cells with proteasome inhibitors (MG132 for 12h)

  • For phosphorylation studies, consider treatment with phosphatase inhibitors

  • For signaling pathway analysis, serum starve cells before stimulation

• Storage:

  • Avoid repeated freeze-thaw cycles

  • Store at -80°C in single-use aliquots

Proper sample preparation is particularly important for phosphorylation studies, as phospho-epitopes can be rapidly lost due to endogenous phosphatase activity.

What controls should I include when using Phospho-RFWD2 (S387) antibodies in my experiments?

A comprehensive set of controls ensures experimental validity and interpretable results:

• Positive Controls:

  • Cell lines known to express phosphorylated RFWD2

  • Cells treated with agents that enhance RFWD2 phosphorylation

  • Recombinant phosphorylated RFWD2 protein (if available)

• Negative Controls:

  • Phosphatase-treated samples

  • RFWD2 knockdown or knockout samples

  • Non-phosphorylatable mutant (S387A) expressing cells

• Specificity Controls:

  • Peptide competition assay using the immunizing phosphopeptide

  • Comparison with total RFWD2 antibody detection

  • IgG control for immunoprecipitation experiments

• Loading and Normalization Controls:

  • Housekeeping proteins (β-actin, GAPDH)

  • Total RFWD2 detection on parallel samples

  • For cell-based assays, whole-cell staining (e.g., crystal violet) for normalization

• Technical Controls:

  • Secondary antibody only (to check for non-specific binding)

  • Multiple technical replicates

  • Antibody titration to ensure optimal working concentration

• Biological Controls:

  • Multiple cell lines or tissue types

  • Time-course or dose-response relationships

  • Biological replicates to account for variability

Proper controls not only validate your findings but also help troubleshoot when experiments don't yield expected results.

How can I optimize immunocytochemistry and immunohistochemistry protocols for Phospho-RFWD2 (S387) detection?

While some Phospho-RFWD2 (S387) antibodies may not be explicitly validated for immunocytochemistry (ICC) or immunohistochemistry (IHC), these techniques can be optimized:

• Fixation Optimization:

  • Test different fixatives: 4% paraformaldehyde preserves protein epitopes

  • Fixation time: Typically 10-15 minutes at room temperature

  • Include phosphatase inhibitors in fixation and washing buffers

• Antigen Retrieval:

  • For paraffin sections: Heat-induced epitope retrieval (HIER)

  • Test different pH buffers (citrate buffer pH 6.0 or EDTA buffer pH 8.0)

  • Optimize retrieval time (typically 10-20 minutes)

• Blocking and Permeabilization:

  • Block with 5-10% normal serum from the same species as secondary antibody

  • Add 0.1-0.3% Triton X-100 for permeabilization in ICC

  • Include 0.1% BSA in blocking buffer to reduce non-specific binding

• Antibody Dilution:

  • Start with manufacturer's recommended dilution

  • If not provided, begin with 1:100-1:200 dilution and optimize

  • Incubate primary antibody overnight at 4°C

• Detection Systems:

  • For fluorescent detection: Use high-quality fluorophore-conjugated secondary antibodies

  • For chromogenic detection: Use polymer-based detection systems like Poly peroxidase anti-rabbit IgG

  • Include DAPI or hematoxylin counterstain for nuclear visualization

• Controls:

  • Include positive and negative tissue/cell controls

  • Use peptide competition controls

  • Compare with total RFWD2 staining pattern

• Analysis:

  • For quantification, use standardized scoring systems

  • For IHC, consider: <5% positive cells (negative), 5-25% (weak), 25-50% (moderate), >50% (strong)

  • For ICC, quantify signal intensity using appropriate imaging software

By systematically optimizing these parameters, researchers can develop reliable protocols for visualizing RFWD2 phosphorylation in tissues and cells.