PGR (Ab-190) Antibody

What is PGR (Ab-190) Antibody and what epitope does it recognize?

PGR (Ab-190) Antibody is a rabbit polyclonal antibody that specifically targets the human Progesterone Receptor. The antibody is generated against a synthetic peptide derived from human Progesterone Receptor. Different suppliers report slightly different target epitopes:

• Some sources indicate it targets amino acids 371-420 of the human Progesterone Receptor

• Other sources specify it recognizes the sequence around amino acids 188-192 (G-L-S-P-A)

This discrepancy may be due to different antibody lot preparations or specific vendor modifications. The antibody detects endogenous levels of total Progesterone Receptor protein in samples .

What applications is the PGR (Ab-190) Antibody validated for?

The antibody has been validated for multiple experimental applications:

Experimental validation confirms reactivity with human, mouse, and rat samples, making it versatile across multiple model systems .

What are the optimal storage and handling conditions for maintaining antibody activity?

For optimal performance and stability:

• Long-term storage: -20°C is recommended for preserving antibody activity over extended periods

• Short-term use: 4°C is suitable for temporary storage during active experimental periods

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

• Alternative formulations may include phosphate buffered saline (without Mg²⁺ and Ca²⁺), pH 7.4, 150mM NaCl, 0.02% sodium azide and 50% glycerol

To minimize freeze-thaw cycles that could affect antibody performance, aliquoting the stock solution upon first thaw is advisable.

How should I validate PGR (Ab-190) Antibody specificity in my experimental system?

A comprehensive validation strategy should include:

• Positive and negative controls:

  • Use cell lines with known PGR expression (e.g., T47D cells) as positive controls

  • Include PGR-negative cell lines or knockdown samples as negative controls

• Blocking peptide experiments:

  • Pre-incubate the antibody with excess immunizing peptide (G-L-S-P-A sequence)

  • Compare staining with and without blocking peptide to confirm specificity

• Cross-validation with other antibodies:

  • Compare results with other well-characterized PR antibodies such as clone 636, clone 16, or H-190

  • Look for consistent detection patterns across antibodies

• siRNA knockdown verification:

  • Perform PGR knockdown using siRNA targeting the 3'-UTR of PGR mRNA

  • Confirm reduction in signal corresponds with reduced protein expression

Research has demonstrated that antibody validation through multiple approaches is essential, as shown in studies comparing PR isoform specificity across different antibodies .

What are the recommended sample preparation protocols for different applications?

For Western Blotting:

• Prepare whole cell lysates in RIPA buffer with protease inhibitors

• Load 20-50 μg protein per lane

• Use 8% SDS-PAGE gels for optimal resolution of the ~99 kDa PR protein

• Transfer to PVDF membrane at 100V for 1 hour or 30V overnight

• Block with 5% non-fat milk in TBST for 1 hour at room temperature

• Incubate with primary antibody at 1:500-1:1000 dilution overnight at 4°C

For Immunofluorescence:

• Fix cells with 4% paraformaldehyde for 15 minutes

• Permeabilize with 0.1% Triton X-100 for 10 minutes

• Block with 10% serum for 45 minutes at 25°C

• Incubate with primary antibody at 1:100-1:200 dilution for 1 hour at 37°C

• Counterstain with DAPI for nuclear visualization

• Use appropriate fluorescently-labeled secondary antibodies (e.g., AlexaFluor594-conjugated goat anti-rabbit IgG)

For ChIP Assays:

• Cross-link protein-DNA complexes with 1% formaldehyde for 10 minutes

• Sonicate chromatin to 200-500 bp fragments

• Incubate chromatin with 2-5 μg antibody overnight at 4°C

• Capture immune complexes with protein A agarose beads

• Wash, elute, and reverse cross-links

• Purify DNA by phenol-chloroform extraction and ethanol precipitation

How can I differentiate between PRA and PRB isoforms using antibody-based approaches?

Distinguishing between PR isoforms requires careful experimental design:

• Western blotting for isoform identification:

  • PRA appears at ~90 kDa

  • PRB appears at ~118 kDa

  • PGR (Ab-190) Antibody recognizes both isoforms

  • Compare with isoform-specific antibodies like Ab-6 (PRB-specific)

• PR isoform-specific cell models:

  • Use T47D-YA (expressing PRA) and T47D-YB (expressing PRB) cell lines as controls

  • Consider MDA-MB-231/iPRAB cells which can inducibly express either PRA or PRB

• Quantification approaches:

  • Measure the PRA/PRB ratio via densitometry in Western blots

  • Note that measurement of PR isoforms by PCR can be problematic due to promoter and sequence overlap

  • Western blotting remains the most appropriate method to discriminate PR isoforms by molecular weight

Research has demonstrated that many commercial antibodies claimed to be isoform-specific may recognize both PRA and PRB in certain experimental conditions, emphasizing the importance of proper controls .

What considerations are important when using PGR (Ab-190) Antibody in ChIP-seq experiments?

For optimal ChIP-seq results with PGR (Ab-190) Antibody:

• Experimental design:

  • Use hormone-treated samples (e.g., 1 mg progesterone) for 1-2 hours to induce PR binding to chromatin

  • Include vehicle-treated controls to identify specific binding events

  • Consider cross-linking time optimization for best results

• Data analysis:

  • Use model-based analysis peak finding algorithms (e.g., MACS) to normalize immunoprecipitated chromatin against input DNA

  • Apply a false discovery rate of ≤5% and fold enrichment of ≥4.5 for high-confidence binding sites

  • Validate ChIP-seq results using ChIP-qPCR on selected target regions

• Biological insights:

  • PGR-B can bind more genomic sites (~13,407) compared to PGR-A (~6,552)

  • Most PGR-A binding sites are common to PGR-B, while PGR-B occupies many unique sites

  • PGR-B can regulate PGR-A expression by binding directly to its promoter region

These considerations can help identify genuine genome-wide binding sites for progesterone receptor in various experimental contexts.

How does phosphorylation at Ser190 impact PR function and antibody recognition?

Phosphorylation of PR at Ser190 has important functional implications:

• Functional significance:

  • Phosphorylation state affects PR transcriptional activity and target gene regulation

  • Phosphorylated PR isoforms can mediate opposing stem cell and cancer phenotypes

  • Phosphorylation modifies interactions with co-regulators and other transcription factors

• Detection considerations:

  • Phospho-specific antibodies (e.g., Anti-phospho-PGR pSer190) are available for detecting specifically phosphorylated PR

  • These recognize the phosphorylated epitope sequence (G-L-SP-P-A) where SP indicates phosphoserine

  • The PGR (Ab-190) Antibody may have differential affinity for phosphorylated versus non-phosphorylated forms

• Experimental approaches:

  • Use lambda phosphatase treatment as a control to confirm phosphorylation-dependent signals

  • Compare results with phospho-specific and total PR antibodies

  • Consider cell treatment conditions that alter phosphorylation status (kinase inhibitors, phosphatase inhibitors)

When investigating phosphorylation-dependent PR functions, researchers should carefully select antibodies that specifically recognize the phosphorylation state of interest.

How can I address weak or non-specific signals in Western blotting experiments?

When facing weak or non-specific signals:

• For weak signals:

  • Increase antibody concentration (try 1:250 dilution)

  • Extend primary antibody incubation time to overnight at 4°C

  • Increase protein loading (50-100 μg)

  • Use enhanced chemiluminescence detection systems

  • Consider using signal amplification methods

• For non-specific binding:

  • Increase blocking time (2-3 hours) with 5% BSA instead of milk

  • Increase washing time and number of washes (5× 5 minutes with TBST)

  • Pre-absorb antibody with non-specific proteins

  • Optimize secondary antibody dilution (1:5000-1:10000)

  • Try using 0.05% Tween-20 instead of 0.1% in wash buffers

• Sample preparation optimization:

  • Include phosphatase inhibitors in lysis buffer to preserve phosphorylation state

  • Use fresh samples or properly stored frozen samples

  • Consider nuclear extraction for enrichment of nuclear receptors like PR

Methodical troubleshooting of each parameter will help identify the source of the problem and improve experimental outcomes.

What are the key considerations for developing quantitative assays using PGR (Ab-190) Antibody?

For developing reliable quantitative assays:

• Standard curve establishment:

  • Use recombinant PR protein or cell lysates with known PR expression levels

  • Create a dilution series covering the expected range of expression

  • Analyze linearity and determine the dynamic range of detection

• Normalization strategies:

  • Use housekeeping proteins (e.g., β-actin, GAPDH) for Western blot normalization

  • For IHC/IF, consider cell count-based normalization or tissue-specific controls

  • For ChIP-qPCR, normalize to input DNA and use non-target regions as controls

• Validation of quantitative measurements:

  • Include positive controls with known PR expression levels (e.g., T47D cells)

  • Use PR-negative cell lines as negative controls

  • Compare results with other quantitative methods (e.g., RT-qPCR for mRNA expression)

• Technical considerations:

  • Maintain consistent experimental conditions across all samples

  • Perform technical replicates (minimum triplicate) for statistical validity

  • Use appropriate statistical tests to analyze differences between samples

Establishing robust quantitative assays requires careful validation and strict adherence to standardized protocols to ensure reproducibility.

How are PGR antibodies being used in emerging antibody-based therapeutic applications?

Recent advances in antibody-based therapeutics include:

• Site-specific antibody-drug conjugates (ADCs):

  • Similar technologies to those used in developing PSMA-targeting ADCs like ARX517 could potentially be applied to PR-targeting approaches

  • These employ stable conjugation chemistries and non-cleavable linkers for improved pharmacokinetics

  • The principles of target selection and validation are translatable to other nuclear receptor targets

• Relevant research approaches:

  • Antibody engineering to improve target specificity and reduce off-target effects

  • Exploration of tumor-specific delivery mechanisms

  • Development of companion diagnostics based on PR expression status

• Translational considerations:

  • Understanding PR isoform expression patterns in different cancer types

  • Correlating PR phosphorylation status with treatment response

  • Addressing potential resistance mechanisms

While direct therapeutic applications of PR antibodies remain exploratory, the rapidly evolving field of targeted therapies provides valuable insights for future development.

How does the biophysical characterization of antibodies inform their research applications?

Understanding antibody biophysical properties is increasingly important:

• Developability parameters:

  • Recent research has mapped 40 sequence-based and 46 structure-based developability parameters (DPs) across millions of antibody sequences

  • Structure-based DPs show lower interdependency compared to sequence-based DPs

  • These parameters influence antibody stability, specificity, and performance in various applications

• Application to research antibodies:

  • Antibody engineering can enhance specificity and reduce cross-reactivity

  • Improved understanding of structure-function relationships can guide application-specific optimization

  • Machine learning approaches can help predict antibody performance in different applications

• Future directions:

  • Integration of computational prediction with experimental validation

  • Development of application-specific antibody variants

  • Improved antibody design based on biophysical principles

Advances in biophysical characterization of antibodies are enabling more rational selection and optimization of research reagents like the PGR (Ab-190) Antibody for specific experimental needs.

What novel genomic applications are being developed for PR-targeting antibodies?

Emerging genomic applications include:

• CUT&RUN and CUT&Tag technologies:

  • These new chromatin profiling methods offer advantages over traditional ChIP-seq

  • They require fewer cells and provide improved signal-to-noise ratio

  • PR antibodies can be adapted for these techniques with appropriate optimization

• Single-cell applications:

  • Advances in single-cell technologies allow examination of PR binding heterogeneity

  • Integration with single-cell transcriptomics can link PR binding to gene expression at single-cell resolution

  • Enables study of cell-specific PR functions in heterogeneous tissues

• Long-read sequencing integration:

  • Combining PR ChIP with long-read sequencing technologies

  • Allows examination of PR binding in relation to chromatin architecture

  • Provides insights into 3D genome organization at PR binding sites

These advanced genomic applications represent the cutting edge of PR research and offer new opportunities for understanding PR biology at unprecedented resolution.

How can PR binding data be integrated with other genomic datasets?

Integrative analysis approaches include:

• Multi-omics integration frameworks:

  • Combine PR ChIP-seq data with RNA-seq to correlate binding with transcriptional outcomes

  • Integrate with histone modification ChIP-seq to understand chromatin context of PR binding

  • Correlate with ATAC-seq to analyze chromatin accessibility at PR binding sites

• Methodological considerations:

  • Use consistent experimental conditions across datasets

  • Apply appropriate normalization methods for cross-platform comparisons

  • Implement computational workflows that account for different data types

• Biological insights:

  • PR-A and PR-B isoforms show distinct but overlapping genome-wide binding patterns

  • PR-B can regulate PGR-A expression by binding to its promoter

  • Integration reveals PR isoform-specific gene networks that regulate distinct cellular functions

This integrated approach provides a systems-level understanding of PR function beyond what can be achieved with individual techniques.

What are the methodological considerations for comparing results across different PR antibodies?

When comparing results from different antibodies:

• Epitope mapping and overlap:

  • Different PR antibodies recognize distinct epitopes (e.g., Ab-190 region vs. other regions)

  • Epitope accessibility may vary depending on PR conformation or interaction partners

  • Consider potential epitope masking in different experimental contexts

• Standardization approaches:

  • Use consistent positive and negative controls across antibodies

  • Apply standardized protocols for each application

  • Perform side-by-side comparisons under identical conditions

• Validation for specific applications:

  • Not all PR antibodies perform equally across different applications

  • Validate each antibody for the specific application of interest

  • Studies have shown differences in isoform specificity between antibodies that should be accounted for

Methodical comparison and validation ensure reliable interpretation of results across different antibody reagents.