PAQR5 Antibody

What is PAQR5 and what are its key biological functions?

PAQR5 (Progestin and adipoQ receptor family member 5), also known as membrane progestin receptor gamma (mPR gamma), functions as a plasma membrane progesterone (P4) receptor coupled to G proteins. Research indicates that PAQR5 likely acts through a G(i)-mediated pathway and may play significant roles in:

• Oocyte maturation processes

• Renal physiology and kidney function

• Immune cell interaction in various tissues

• Cancer progression and suppression

Studies have demonstrated that progesterone signaling through membrane receptors like PAQR5 differs functionally from classical nuclear progesterone receptors, providing distinct cellular responses to hormonal stimulation .

How is PAQR5 expressed in normal versus pathological tissues?

PAQR5 shows tissue-specific expression patterns with notable differences between normal and pathological conditions:

• Normal kidney tissue: PAQR5 is predominantly expressed in normal kidney compared to other organs

• Kidney cancer: Significantly downregulated in kidney clear cell carcinoma (KIRC)

• Other cancers: Expression varies by cancer type:

  • Overexpressed in liver hepatocellular carcinoma, cholangiocarcinoma, and breast invasive carcinoma

  • Downregulated in glioblastoma multiforme, esophageal carcinoma, colon adenocarcinoma, lung cancers, prostate adenocarcinoma, thyroid carcinoma, and rectal adenocarcinoma

Comparative analysis in KIRC shows PAQR5 has high accuracy in distinguishing between tumor and normal tissue (AUC = 0.962, CI = 0.941–0.984) .

What applications are PAQR5 antibodies suitable for?

Commercial PAQR5 antibodies have been validated for multiple laboratory applications:

When performing Western blot analysis, researchers should note the observed molecular weight of PAQR5 is approximately 72 kDa, which differs from the calculated molecular weight of approximately 38 kDa, suggesting potential post-translational modifications .

What are the optimal sample preparation protocols for detecting PAQR5 in kidney tissues?

For optimal detection of PAQR5 in kidney tissues, particularly in studies comparing normal versus diseased states, the following methodology has proven effective:

For Western blotting:

• Load 40 μg total protein per well for PAQR5 detection

• Use 10% SDS-PAGE gels for optimal separation

• After electrophoretic separation, transfer to PVDF membrane

• Block membranes for 45 min at room temperature with 5% nonfat milk in TBS containing 0.1% Tween-20

• Incubate with primary anti-PAQR5 antibody (1:500 dilution) at 4°C overnight

• Normalize band densities to β-actin for accurate quantification

For immunohistochemistry:

• Prepare 3-μm-thick paraffin-embedded tissue sections

• For antigen retrieval, use Tris-EDTA, pH 9.0

• Incubate with rabbit polyclonal antibody against PAQR5 (1:200 dilution) for 2 hours at 37°C

• Follow with secondary antibody incubation (1:200) at room temperature for 45-60 minutes

• Visualize with 3,3-diaminobenzidine and counterstain nuclei with hematoxylin

How can researchers address potential cross-reactivity issues with PAQR5 antibodies?

Cross-reactivity is a critical concern when working with antibodies against membrane proteins like PAQR5. To ensure specificity:

• Validation across multiple species: Confirm antibody specificity in your target species. While many commercial PAQR5 antibodies react with human, mouse, and rat samples, cross-reactivity with other species (e.g., canine) should be empirically tested .

• Negative controls: Include appropriate negative controls:

  • Tissues known to lack PAQR5 expression

  • Secondary antibody-only controls

  • Blocking peptide competition assays using the specific immunogenic peptide (available from some vendors)

• Multiple antibody validation: When feasible, use antibodies targeting different epitopes of PAQR5:

  • Some antibodies target N-terminal regions (aa 1-100)

  • Others target central/C-terminal regions (aa 281-330)

• Complementary approaches: Confirm protein expression with mRNA analysis methods (qPCR, RNA-seq) to corroborate antibody-based detection .

What are the key considerations for quantitative analysis of PAQR5 expression in western blotting?

For accurate quantitative analysis of PAQR5 expression:

• Protein loading optimization:

  • For PAQR5 detection, 40 μg total protein per well is recommended

  • Adjust loading based on tissue/cell type and expression level

  • Always run a protein gradient to establish the linear detection range

• Reference protein selection:

  • β-actin is commonly used for normalization of PAQR5 expression

  • Consider alternative housekeeping proteins (GAPDH, tubulin) if β-actin expression varies under your experimental conditions

• Detection systems:

  • Chemiluminescence with ECL provides good sensitivity (e.g., Advansta ECL Bright)

  • Digital imaging systems (e.g., ChemiDoc MP) allow precise quantification

  • Use ImageLab software or similar for band intensity measurement

• Technical replication:

  • Perform at least three independent experiments

  • Include technical replicates within each experiment

  • Report both biological and technical variability in results

How does PAQR5 expression correlate with immune cell infiltration in tumor microenvironments?

Research on PAQR5 in kidney clear cell carcinoma has revealed significant correlations between PAQR5 expression and immune cell infiltration:

• Positive correlations: PAQR5 expression positively correlates with infiltration of:

  • B cells

  • Neutrophils

  • Macrophages

  • Dendritic cells (DCs)

• Negative correlations: PAQR5 expression negatively correlates with:

  • FOXP3+ Treg cells infiltration

  • Immune checkpoint molecules including PD-1, CTLA4, and LAG3

These findings suggest PAQR5 may influence the tumor immune microenvironment, potentially affecting immunotherapy response. Researchers investigating this relationship should consider:

• Employing multiparameter flow cytometry or multiplex immunohistochemistry to simultaneously assess PAQR5 expression and immune cell markers

• Using bioinformatic tools like TIMER and GEPIA for correlative analysis with immune cell gene signatures

• Validating in silico findings with functional assays to establish causality between PAQR5 and immune responses

What mechanisms regulate PAQR5 expression in renal tissues, and how can researchers study these pathways?

Multiple mechanisms appear to regulate PAQR5 expression in renal tissues:

1. Epigenetic regulation:

• DNA methylation of the PAQR5 promoter is significantly higher in kidney cancer tissues than in normal kidney tissues

• Methylation correlates with tumor stage and cancer grade

2. TGFβ1-mediated suppression:

• TGFB1 expression is negatively correlated with PAQR5 expression in kidney cancer

• TGFβ1 treatment significantly suppresses PAQR5 expression in human cancer cells

3. Fibrosis-associated downregulation:

• In the unilateral ureteral obstruction (UUO) rat model, decreased PAQR5 expression is observed in obstructed kidneys

• This suggests mechanical stress or inflammatory signals may regulate PAQR5

To study these regulatory mechanisms, researchers should consider:

• For epigenetic regulation: Employ bisulfite sequencing, methylation-specific PCR, or pyrosequencing to analyze PAQR5 promoter methylation

• For TGFβ1 pathway: Use reporter assays with PAQR5 promoter constructs to test direct transcriptional regulation

• For signaling pathways: Investigate connections between PAQR5 and JAK/STAT, VHL/HIF, and PI3K/AKT/mTOR pathways, as PAQR5 expression negatively correlates with STAT1/2/3/4/5A, HIF-1α, and mTOR

How can PAQR5 antibodies be utilized in prognostic and predictive biomarker development for kidney cancer?

PAQR5 shows significant potential as a prognostic biomarker in kidney cancer:

For biomarker development using PAQR5 antibodies, researchers should:

• Standardize detection methods:

  • Establish reproducible IHC scoring systems with digital pathology quantification

  • Develop tissue microarray-based high-throughput screening approaches

  • Consider multiplex staining approaches to assess PAQR5 alongside other markers

• Validate across patient cohorts:

  • Test in independent patient populations

  • Stratify by clinical parameters (stage, grade, treatment)

  • Correlate with standard clinical markers

• Explore functional relationships:

  • Investigate connections between PAQR5 expression and response to specific therapies

  • Test whether PAQR5 status can predict response to immunotherapy given its correlation with immune infiltrates

  • Determine whether measuring PAQR5 adds value beyond existing risk stratification methods

What are potential solutions for weak or nonspecific PAQR5 antibody signals in Western blotting?

When encountering weak or nonspecific signals:

• Antibody concentration optimization:

  • Try a range of dilutions; recommended starting range is 1:500-2000

  • Increase primary antibody concentration and/or incubation time if signal is weak

  • Decrease concentration if background is high

• Protein extraction optimization:

  • For membrane proteins like PAQR5, use extraction buffers containing appropriate detergents

  • Consider membrane-enriched fractionation to concentrate target protein

  • Avoid repeated freeze-thaw cycles of protein samples

• Blocking optimization:

  • Try different blocking agents (BSA vs. nonfat milk)

  • Adjust blocking time (30-60 minutes typically sufficient)

  • Use the same protein for antibody diluent as for blocking

• Band size discrepancy resolution:

  • Note that PAQR5's observed molecular weight (72 kDa) differs from calculated weight (38 kDa)

  • This may reflect post-translational modifications or alternative splicing

  • Consider deglycosylation treatments to confirm glycosylation status

  • Use positive control samples with confirmed PAQR5 expression

How should researchers interpret conflicting PAQR5 antibody results between different detection methods?

When faced with conflicting results between methods (e.g., IHC vs. WB):

• Epitope accessibility differences:

  • Fixation in IHC may mask certain epitopes

  • Denaturation in WB may expose epitopes hidden in native conformation

  • Solution: Use antibodies raised against different epitopes (N-terminal vs. C-terminal)

• Expression level threshold differences:

  • Western blotting may detect lower expression levels than IHC

  • Solution: Perform titration experiments to determine detection limits for each method

• Cross-validation approaches:

  • Complement antibody-based detection with mRNA analysis (qPCR, RNA-seq)

  • Consider knockout/knockdown validation to confirm specificity

  • Apply multiple antibodies targeting different epitopes of PAQR5

• Sample preparation considerations:

  • For membrane proteins like PAQR5, different extraction methods may yield varying results

  • Optimize sample preparation for each specific application

  • Consider native vs. denaturing conditions based on antibody epitope recognition

What emerging technologies could enhance PAQR5 detection and functional analysis?

Several cutting-edge approaches show promise for advancing PAQR5 research:

• Proximity ligation assays (PLA):

  • Allows visualization of protein-protein interactions involving PAQR5

  • Could help map progesterone signaling networks through membrane receptors

  • Enables study of PAQR5 interactions with G proteins and downstream effectors

• CRISPR-Cas9 gene editing:

  • Generation of PAQR5 knockout cell lines for functional validation

  • Creation of tagged PAQR5 variants for live-cell imaging

  • Domain-specific mutations to map functional regions

• Single-cell technologies:

  • Single-cell RNA-seq to identify PAQR5-expressing cell populations

  • CyTOF or spectral flow cytometry for high-dimensional protein analysis

  • Spatial transcriptomics to map PAQR5 expression in tissue context

• Advanced imaging techniques:

  • Super-resolution microscopy for subcellular localization

  • FRET-based assays to study PAQR5 activation dynamics

  • Correlative light and electron microscopy for ultrastructural analysis

How can researchers differentiate between the functions of PAQR5 and other membrane progesterone receptors?

Distinguishing PAQR5 from other membrane progesterone receptors requires specialized approaches:

• Selective pharmacological tools:

  • Identify PAQR5-specific agonists and antagonists

  • Design peptide inhibitors based on structural predictions

  • Employ siRNA or antisense oligonucleotides for selective knockdown

• Receptor expression systems:

  • Heterologous expression of individual receptors in cell lines lacking endogenous expression

  • Creation of chimeric receptors to identify functional domains

  • CRISPR-mediated tagging for receptor-specific tracking

• Comparative signaling analysis:

  • Phosphoproteomic analysis of downstream signaling

  • cAMP/calcium measurements to distinguish G-protein coupling specificity

  • Receptor internalization and trafficking studies

• Cross-species comparative studies:

  • Leverage evolutionary differences in receptor structure and function

  • Use model organisms with simplified progesterone receptor systems

  • Employ sequence homology and structural modeling to predict functional differences