Phospho-ESR1 (Ser102) Antibody

What is the Phospho-ESR1 (Ser102) antibody and what is its specificity?

The Phospho-ESR1 (Ser102) antibody is a rabbit polyclonal antibody that specifically recognizes the estrogen receptor alpha (ESR1) protein only when phosphorylated at serine 102. This antibody detects endogenous levels of ER Alpha protein specifically at this phosphorylation site within the amino acid range 71-120 . The antibody's specificity is achieved through its production against a synthesized peptide derived from human Estrogen Receptor-alpha around the phosphorylation site of Ser102, with subsequent purification using affinity-chromatography with the epitope-specific phosphopeptide . Non-phospho specific antibodies are removed during purification by chromatography using non-phosphopeptide .

What experimental applications is the Phospho-ESR1 (Ser102) antibody validated for?

The Phospho-ESR1 (Ser102) antibody has been validated for multiple research applications with specific recommended dilutions:

These applications enable researchers to detect and quantify phosphorylated ESR1 in various experimental contexts .

What are the optimal storage conditions for maintaining antibody activity?

For optimal preservation of antibody activity, the Phospho-ESR1 (Ser102) antibody should be stored at -20°C for up to one year from the date of receipt . It is formulated as a liquid in PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide, which helps maintain stability . Researchers should avoid repeated freeze-thaw cycles as these can degrade antibody quality and compromise experimental results .

How should I optimize IHC protocols when using Phospho-ESR1 (Ser102) antibody for breast cancer tissue samples?

When optimizing IHC protocols for breast cancer tissue samples with Phospho-ESR1 (Ser102) antibody, consider the following methodological approach:

• Antigen retrieval: Use heat-induced epitope retrieval (HIER) with citrate buffer (pH 6.0) or EDTA buffer (pH 9.0) to unmask antigens that may be crosslinked during fixation.

• Blocking: Implement a dual blocking strategy with both 5% normal serum and 1% BSA to minimize background staining, which is particularly important when studying phosphorylation states.

• Primary antibody incubation: Start with the middle of the recommended dilution range (1:200) and optimize from there based on signal-to-noise ratio. Incubate overnight at 4°C to enhance sensitivity.

• Controls: Always include a phosphatase-treated control section to validate phospho-specificity, particularly important when evaluating ESR1 phosphorylation status in relation to breast cancer progression .

• Signal amplification: For samples with potentially low phosphorylation levels, consider using a polymer-based detection system rather than the traditional avidin-biotin complex.

When analyzing results, remember that ESR1 can localize to different cellular compartments depending on its phosphorylation status; Ser102 phosphorylation may affect nuclear-cytoplasmic shuttling of the receptor .

What are the critical considerations when designing Western blot experiments to detect Phospho-ESR1 (Ser102)?

When designing Western blot experiments for Phospho-ESR1 (Ser102) detection, researchers should consider these critical methodological aspects:

• Sample preparation: Include phosphatase inhibitors (e.g., sodium orthovanadate, sodium fluoride, and β-glycerophosphate) in lysis buffers to preserve phosphorylation states.

• Loading controls: Use total ESR1 antibody on parallel blots rather than standard housekeeping proteins to calculate the phosphorylation ratio accurately.

• Gel percentage optimization: Use 8% acrylamide gels to achieve optimal separation of ESR1 isoforms (MW: ER-α is approximately 66 kDa).

• Transfer conditions: Implement wet transfer at lower voltage (30V) overnight at 4°C to ensure efficient transfer of larger proteins like ESR1.

• Antibody dilution: Begin with 1:750 dilution for Phospho-ESR1 (Ser102) antibody in 5% BSA (not milk, which contains phosphatases) in TBST .

• Visualization: For lower abundance phosphorylation events, consider using enhanced chemiluminescence with longer exposure times or more sensitive detection methods.

• Multiple isoform detection: Be aware that the antibody will detect both full-length ESR1 and potential splice variants, which may complicate band pattern interpretation .

How can Phospho-ESR1 (Ser102) antibody be utilized in studying the interaction between ESR1 and transcription factors like NFIB and YBX1?

The Phospho-ESR1 (Ser102) antibody can be instrumental in studying ESR1 interactions with transcription factors through several methodological approaches:

• Co-immunoprecipitation (Co-IP) with phosphorylation status assessment: Use the phospho-specific antibody to immunoprecipitate Ser102-phosphorylated ESR1 and probe for associated transcription factors like NFIB and YBX1. This can reveal whether phosphorylation at this specific site modulates these protein-protein interactions.

• Reverse Co-IP with phosphorylation detection: Immunoprecipitate NFIB or YBX1 and probe for phospho-ESR1 (Ser102) to determine if these factors preferentially interact with the phosphorylated form of the receptor.

• Chromatin immunoprecipitation (ChIP) sequential analysis: Perform ChIP using the Phospho-ESR1 (Ser102) antibody followed by re-ChIP with antibodies against NFIB or YBX1 to identify genomic loci where these factors co-localize with phosphorylated ESR1.

• Phosphorylation dynamics under different signaling conditions: Use the antibody to monitor how FGFR2 signaling affects ESR1 phosphorylation at Ser102 and correlate this with NFIB/YBX1 binding and transcriptional outcomes.

Recent research has shown that NFIB and YBX1 interact with the ESR1-FOXA1 complex and inhibit the transactivational potential of ESR1 . Understanding how Ser102 phosphorylation influences these interactions could provide insights into the mechanisms through which FGFR2 signaling modulates estrogen responsiveness in breast cancer cells .

What role does ESR1 Ser102 phosphorylation play in breast cancer, and how can this antibody help elucidate disease mechanisms?

ESR1 Ser102 phosphorylation plays a complex role in breast cancer biology that can be investigated using the Phospho-ESR1 (Ser102) antibody through several methodological approaches:

• Phosphorylation status across breast cancer subtypes: The antibody can be used in IHC studies of tumor microarrays to correlate Ser102 phosphorylation levels with clinical parameters, molecular subtypes, and patient outcomes.

• Kinase pathway identification: Combining the antibody with kinase inhibitor treatments can help identify which signaling pathways regulate Ser102 phosphorylation. Research suggests that cyclin A/CDK2 and CK1 may phosphorylate ESR1, potentially enhancing its transcriptional activity .

• Transcriptional consequences: By coupling ChIP-seq using the Phospho-ESR1 (Ser102) antibody with RNA-seq, researchers can map the genomic binding sites of specifically phosphorylated ESR1 and correlate this with gene expression changes.

• Interaction with ESR1 mutations: Recent proteomic profiling has revealed that ESR1 mutations enhance cyclin-dependent pathways in breast cancer . The antibody can help determine whether these mutations affect Ser102 phosphorylation levels and consequently alter downstream signaling.

• Metabolic regulation: Studies show that serine starvation can silence estrogen receptor signaling . The antibody can be used to investigate whether this metabolic stress affects Ser102 phosphorylation specifically.

Understanding the functional consequences of this specific post-translational modification may reveal new therapeutic vulnerabilities in ESR1-positive breast cancers .

How does ESR1 Ser102 phosphorylation differ from other phosphorylation sites on the receptor, and what techniques can be employed to study site-specific effects?

ESR1 contains multiple phosphorylation sites with distinct functional consequences. To study the site-specific effects of Ser102 phosphorylation compared to other sites:

• Comparative phosphorylation profiling: Use a panel of site-specific phospho-antibodies including Phospho-ESR1 (Ser102) to map phosphorylation patterns under various conditions. Unlike Ser118 (which when dephosphorylated by PPP5C inhibits transactivation activity), Ser102 phosphorylation has distinct regulatory mechanisms .

• Phospho-mimetic and phospho-deficient mutants: Generate S102E (phospho-mimetic) and S102A (phospho-deficient) ESR1 mutants and compare their activity to similar mutants of other phosphorylation sites (e.g., Ser118, Ser167) using reporter assays.

• Temporal dynamics analysis: Use the Phospho-ESR1 (Ser102) antibody in time-course experiments to determine if Ser102 phosphorylation occurs with different kinetics compared to other sites following estrogen stimulation or growth factor signaling.

• Kinase prediction and validation: Apply in silico kinase prediction tools to identify potential kinases for different ESR1 phosphorylation sites, then validate these predictions using kinase inhibitors and the Phospho-ESR1 (Ser102) antibody.

• Domain-specific functional impact: Investigate how Ser102 phosphorylation in the N-terminal domain affects receptor function differently from phosphorylation in other domains (e.g., DNA-binding domain, ligand-binding domain).

• Subcellular localization effects: Use immunofluorescence with the Phospho-ESR1 (Ser102) antibody to determine if this specific phosphorylation alters ESR1 localization differently than other phosphorylation events .

Understanding these site-specific effects is crucial as ESR1 phosphorylation at different residues may have cooperative, antagonistic, or independent functions in breast cancer progression .

What are the common technical challenges when working with Phospho-ESR1 (Ser102) antibody, and how can they be addressed?

Researchers frequently encounter several technical challenges when working with Phospho-ESR1 (Ser102) antibody that require systematic troubleshooting:

• High background in immunostaining:

  • Problem: Nonspecific binding leading to high background

  • Solution: Implement more stringent blocking with 5% BSA combined with 5% normal serum from the species of the secondary antibody, and increase washing duration/frequency with 0.1% Tween-20 in PBS .

• Weak or absent phospho-specific signal:

  • Problem: Loss of phosphorylation during sample processing

  • Solution: Add phosphatase inhibitors (10mM sodium fluoride, 1mM sodium orthovanadate) to all buffers and keep samples cold throughout processing .

• Contradictory results between techniques:

  • Problem: Discrepancies between WB and IHC results

  • Solution: Validate antibody specificity using phosphatase treatment controls for each technique separately, as fixation in IHC may affect epitope accessibility differently than denaturation in WB.

• Cross-reactivity concerns:

  • Problem: Potential cross-reactivity with other phosphorylated proteins

  • Solution: Verify specificity using knockout/knockdown systems or peptide competition assays with both phosphorylated and non-phosphorylated peptides .

• Quantification challenges:

  • Problem: Accurately quantifying relative phosphorylation levels

  • Solution: Always normalize phospho-signal to total ESR1 levels rather than housekeeping proteins, and use recombinant phosphorylated standards when possible.

• Fixation-sensitive epitopes in IHC/IF:

  • Problem: Fixation may mask the phospho-epitope

  • Solution: Test different fixation protocols (paraformaldehyde vs. methanol) and optimize antigen retrieval methods (citrate vs. EDTA buffers at varying pH) .

How can I validate antibody specificity for Phospho-ESR1 (Ser102) in my experimental system?

Validating the specificity of Phospho-ESR1 (Ser102) antibody requires a multi-faceted approach:

• Phosphatase treatment control: Divide your samples and treat half with lambda phosphatase before immunoblotting or immunostaining. The phospho-specific signal should disappear in treated samples while total ESR1 signal remains.

• Peptide competition assay: Pre-incubate the antibody with:

  • Phosphorylated peptide (should eliminate specific signal)

  • Non-phosphorylated peptide (should have minimal effect on specific signal)

  • Irrelevant phospho-peptide (should not affect specific signal)

• Genetic approaches:

  • Use CRISPR/Cas9 to generate S102A mutant cell lines where the signal should be absent

  • Use siRNA knockdown of ESR1 to confirm signal reduction parallels total ESR1 reduction

• Stimulation experiments: Treat cells with agents known to modulate ESR1 phosphorylation (e.g., estradiol, kinase inhibitors) and confirm expected changes in signal intensity.

• Cross-validation with other techniques: If possible, validate phosphorylation using mass spectrometry-based phosphoproteomics to confirm the presence and regulation of the Ser102 phosphorylation site.

• Positive controls: Include cell lines or tissue samples with known high levels of Ser102 phosphorylation; breast cancer cell lines treated with estrogen can serve as positive controls .

This comprehensive validation ensures that experimental findings truly reflect the biology of ESR1 Ser102 phosphorylation rather than technical artifacts.

How does ESR1 Ser102 phosphorylation interact with other post-translational modifications of the receptor?

ESR1 undergoes multiple post-translational modifications (PTMs) that may interact with Ser102 phosphorylation to create a complex regulatory code:

• PTM crosstalk analysis: To study the interplay between Ser102 phosphorylation and other modifications:

  • Use sequential immunoprecipitation with Phospho-ESR1 (Ser102) antibody followed by antibodies against other modifications (e.g., acetylation, methylation, ubiquitination)

  • Apply mass spectrometry to map the co-occurrence patterns of multiple PTMs on individual ESR1 molecules

• Functional interplay with ubiquitination: ESR1 is known to be ubiquitinated by multiple E3 ligases including STUB1/CHIP and regulated by LATS1 via DCAF1, leading to proteasomal degradation . Researchers should investigate whether Ser102 phosphorylation affects:

  • Ubiquitination rates by these ligases

  • Proteasomal degradation kinetics

  • Interaction with deubiquitinating enzymes like OTUB1

• Relationship with methylation and palmitoylation: ESR1 can be dimethylated by PRMT1 at Arg-260 (affecting cytoplasmic localization) and palmitoylated by ZDHHC7 and ZDHHC21 (required for plasma membrane targeting) . Methods to study their relationship with Ser102 phosphorylation include:

  • Site-directed mutagenesis of multiple modification sites

  • Enzyme inhibitor studies targeting specific modification pathways

  • Live-cell imaging of fluorescently tagged ESR1 variants

• Phosphorylation site interdependence: Investigate whether Ser102 phosphorylation influences other phosphorylation events (like Ser118) through:

  • Phospho-specific antibody arrays

  • In vitro kinase assays with pre-modified ESR1 substrates

  • Computational modeling of the ESR1 phosphorylation network

Understanding these interactions could reveal how the cell integrates multiple signals to fine-tune ESR1 activity in both normal physiology and cancer .

What role might Phospho-ESR1 (Ser102) play in resistance to endocrine therapies, and how can this be studied?

The potential role of ESR1 Ser102 phosphorylation in endocrine therapy resistance can be investigated through several methodological approaches:

• Clinical correlation studies: Use the Phospho-ESR1 (Ser102) antibody in IHC analysis of patient samples:

  • Compare phosphorylation levels between treatment-responsive and resistant tumors

  • Perform longitudinal analysis of matched pre-treatment and post-resistance tumor samples

  • Correlate phosphorylation status with progression-free survival on endocrine therapy

• In vitro resistance models: Develop and characterize endocrine-resistant cell lines:

  • Monitor changes in Ser102 phosphorylation during resistance development

  • Apply the antibody in ChIP-seq studies to identify altered binding patterns

  • Use CRISPR-Cas9 to generate S102A or S102E mutations and assess impact on resistance

• Signaling pathway integration: Investigate how altered signaling in resistant cells affects Ser102 phosphorylation:

  • Test whether cross-talk with growth factor signaling pathways (particularly FGFR2) affects this specific phosphorylation site

  • Examine if metabolic stress conditions like serine starvation, which has been shown to silence estrogen receptor signaling, alter Ser102 phosphorylation

  • Determine if ESR1 mutations found in resistant tumors show altered patterns of Ser102 phosphorylation

• Therapeutic targeting strategies: Evaluate therapeutic approaches targeting phosphorylation:

  • Screen kinase inhibitor libraries to identify drugs that modulate Ser102 phosphorylation

  • Test combination therapies targeting both ESR1 and the kinases responsible for Ser102 phosphorylation

  • Develop phosphorylation-state specific degraders (PROTACs) that selectively target phosphorylated ESR1

This research direction is particularly important as finding ways to overcome endocrine resistance remains a major clinical challenge in breast cancer treatment .

How can advanced imaging techniques be combined with Phospho-ESR1 (Ser102) antibody for dynamic studies of ESR1 signaling?

Integrating advanced imaging techniques with Phospho-ESR1 (Ser102) antibody can provide unprecedented insights into the spatiotemporal dynamics of ESR1 signaling:

• Super-resolution microscopy approaches:

  • Use Stimulated Emission Depletion (STED) or Structured Illumination Microscopy (SIM) with the phospho-specific antibody to visualize nanoscale distribution of phosphorylated ESR1 within nuclear structures

  • Combine with proximity ligation assay (PLA) to detect interactions between phosphorylated ESR1 and specific cofactors like FOXA1 at sub-diffraction resolution

• Live-cell phosphorylation sensors:

  • Develop FRET-based biosensors incorporating ESR1 and phospho-binding domains to monitor Ser102 phosphorylation in real-time

  • Use the phospho-antibody to validate these sensors in fixed cells at specific timepoints

• Correlative light and electron microscopy (CLEM):

  • Apply immunogold labeling with the Phospho-ESR1 (Ser102) antibody for electron microscopy

  • Correlate with fluorescence microscopy of the same sections to map phosphorylated ESR1 to specific ultrastructural features

• Lattice light-sheet microscopy:

  • For dynamic studies, develop cell lines expressing fluorescently tagged ESR1

  • Use the phospho-antibody on fixed timepoints to validate phosphorylation status during observed dynamic events

• Spatial transcriptomics correlation:

  • Combine immunofluorescence using the phospho-antibody with in situ sequencing to correlate Ser102 phosphorylation with local transcriptional activity

  • Apply this method to investigate how YBX1 and NFIB interaction with phosphorylated ESR1 affects spatial transcriptional patterns

These advanced imaging approaches can reveal how subcellular localization of phosphorylated ESR1 contributes to its diverse functions in the nucleus, cytoplasm, and membrane .

What bioinformatic approaches can help interpret data generated using Phospho-ESR1 (Ser102) antibody in multi-omics studies?

Integrating Phospho-ESR1 (Ser102) antibody data into multi-omics frameworks requires sophisticated bioinformatic approaches:

• Integrative phosphoproteomics analysis:

  • Develop computational pipelines to correlate Ser102 phosphorylation with global phosphoproteomic changes

  • Implement kinase activity inference algorithms to identify upstream regulators of Ser102 phosphorylation

  • Apply network analysis to position Ser102 phosphorylation within signaling cascades

• ChIP-seq data interpretation:

  • Use motif enrichment analysis on phospho-ESR1 binding sites to identify co-operating transcription factors

  • Apply differential binding analysis between total ESR1 and phospho-ESR1 ChIP-seq to identify phosphorylation-specific binding sites

  • Integrate with chromatin accessibility data (ATAC-seq) to determine how phosphorylation affects pioneer factor activity

• Multi-modal data integration:

  • Develop machine learning models that integrate phosphorylation status with gene expression and clinical outcomes

  • Use Bayesian network approaches to infer causal relationships between Ser102 phosphorylation and downstream molecular changes

  • Apply tensor factorization methods to identify patterns across phosphoproteomic, transcriptomic, and phenotypic data

• Single-cell multi-omics interpretation:

  • Develop computational methods to incorporate phospho-protein data from antibody-based techniques into single-cell analyses

  • Implement trajectory inference algorithms to map how Ser102 phosphorylation changes during cellular state transitions

• Structural biology integration:

  • Use molecular dynamics simulations to predict how Ser102 phosphorylation affects ESR1 conformation and protein-protein interactions

  • Apply these predictions to interpret experimental data on altered interactions with cofactors like NFIB and YBX1