PAQR4 Antibody

What is PAQR4 and why is it important in research?

PAQR4 (Progestin and AdipoQ Receptor Family Member IV) is a member of the PAQR family that primarily localizes to the Golgi apparatus, unlike other family members such as AdipoR1/2 which function as plasma membrane receptors . PAQR4 has emerged as a critical regulator in multiple biological processes including metabolism and cancer development . Recent research has revealed its important roles in:

• Regulation of ceramide metabolism and systemic metabolic health

• Chemoresistance in non-small cell lung cancer (NSCLC)

• Adipocyte function and adipose tissue maintenance

• Tumor progression in multiple cancer types

This multifaceted role makes PAQR4 an important research target for understanding both metabolic disorders and cancer biology.

What types of PAQR4 antibodies are available for research?

Based on current commercial and research offerings, several types of PAQR4 antibodies are available:

Most commercially available PAQR4 antibodies are rabbit polyclonal antibodies that have been validated for western blot applications .

How stable are PAQR4 antibodies and what are the optimal storage conditions?

PAQR4 antibodies require specific storage conditions to maintain their activity and specificity:

• Short-term storage (up to 1 week): 2-8°C

• Long-term storage: -20°C

• Avoiding freeze-thaw cycles is critical for maintaining antibody integrity

• Most PAQR4 antibodies are supplied in buffer solutions containing preservatives such as sodium azide (0.02-0.09%) and stabilizers like glycerol (40-50%)

The stability of properly stored antibodies is typically maintained for at least 6-12 months from the date of receipt, with activity loss rates of less than 5% within the expiration date under appropriate storage conditions .

What are the optimal dilutions and conditions for using PAQR4 antibodies in Western blotting?

For Western blotting applications with PAQR4 antibodies, the following conditions are recommended:

• Dilution ranges: 1:500-1:1000 for most PAQR4 polyclonal antibodies

• Expected molecular weight: 28-29 kDa (273 amino acids)

• Positive controls: HeLa cells and mouse liver tissue have been validated

• Sample preparation: Standard protein extraction protocols are suitable, with care taken to preserve Golgi proteins where PAQR4 is primarily localized

• Blocking conditions: Standard blocking solutions (5% non-fat milk or BSA in TBST) are typically effective

• Detection: Both standard chemiluminescence and fluorescence-based detection systems are compatible

It's important to note that optimal working dilutions should be determined experimentally by each investigator, as they may vary depending on the specific experimental conditions and sample types .

How can researchers validate the specificity of PAQR4 antibodies?

Validating antibody specificity is crucial for ensuring reliable research results. For PAQR4 antibodies, several validation approaches are recommended:

• Positive and negative control samples:

  • Use cell lines with known PAQR4 expression (e.g., HeLa cells, A549, H1299, H1650, H1975, H358, GLC-82, and SPC-A1 for positive controls)

  • Include PAQR4 knockdown samples as negative controls

• PAQR4 knockdown/knockout validation:

  • Several publications have utilized PAQR4 knockdown models to validate antibody specificity

  • Stable knockdown cell lines (as described in the literature) can serve as excellent negative controls

• Cross-reactivity testing:

  • Check for cross-reactivity with other PAQR family members, particularly with the closely related AdipoR1/2

  • Consider the predicted reactivity information provided by manufacturers (e.g., Cow: 100%, Dog: 100%, Goat: 93%, Guinea Pig: 100%, Human: 100%, Mouse: 100%, Rabbit: 93%, Rat: 100%)

• Peptide competition assays:

  • Using the immunogen peptide (when available) to compete with endogenous PAQR4 for antibody binding

What methodologies are effective for detecting PAQR4 expression in tissue samples?

Based on published research and manufacturer recommendations, several techniques have been validated for detecting PAQR4 in tissue samples:

• Immunohistochemistry (IHC):

  • Has been successfully used to detect PAQR4 in NSCLC and noncancerous control lung tissues using tissue microarrays

  • Can differentiate between lung adenocarcinoma and lung squamous cell carcinoma samples

  • Requires appropriate antigen retrieval methods (typically citrate buffer, pH 6.0)

• Western blotting:

  • Most widely validated application for PAQR4 antibodies

  • Effective for comparing expression levels between different tissue types

  • Expected band at approximately 28-29 kDa

• Real-time RT-PCR:

  • Complementary approach to validate protein expression findings

  • Has been used to verify PAQR4 knockdown efficiency in research studies

• Immunofluorescence (IF):

  • Can be used to confirm the subcellular localization of PAQR4 to the Golgi apparatus

  • Requires co-staining with Golgi markers for accurate localization

How does PAQR4 contribute to chemoresistance in cancer, and how can PAQR4 antibodies help study this mechanism?

PAQR4 has been identified as a key factor in chemoresistance, particularly in non-small cell lung cancer (NSCLC). Research findings reveal:

• PAQR4-Nrf2-Keap1 interaction mechanism:

  • PAQR4 physically interacts with Nrf2 in NSCLC cells, blocking the interaction between Nrf2 and Keap1

  • This prevents Nrf2 degradation through the Keap1-mediated ubiquitination process

  • PAQR4 knockdown enhances cancer cell sensitivity to chemotherapy both in vitro and in xenograft models in vivo

• Research methodologies using PAQR4 antibodies:

  • Co-immunoprecipitation (co-IP) with PAQR4 antibodies to identify protein interactions

  • Western blotting to monitor PAQR4 expression in cisplatin-resistant vs. sensitive cell lines

  • Immunohistochemistry of xenograft tumors to correlate PAQR4 expression with proliferation markers (Ki67) and apoptosis markers (Cleaved Caspase 3)

• Experimental findings:

  • Increased cisplatin (DDP), Carboplatin (CBP), or Etoposide (ETO) induced cellular apoptosis was observed in PAQR4 knockdown cells

  • PAQR4 is upregulated in cisplatin-resistant A549 (A549/DDP) and SPC-A1 (SPC-A1/DDP) cell lines

  • Knockdown of PAQR4 in resistant cell lines inhibited cellular viability

These findings suggest PAQR4 antibodies are valuable tools for studying chemoresistance mechanisms and potentially developing targeted therapies for chemoresistant cancers.

What is the relationship between PAQR4 and ceramide metabolism, and how can researchers study this interaction?

Recent research has uncovered a critical role for PAQR4 in ceramide metabolism, which contrasts with the function of its related family members AdipoR1/2:

• PAQR4's effect on ceramide levels:

  • Unlike AdipoR1/2 that lower ceramide levels, PAQR4 increases multiple ceramide species in adipose tissues

  • Most pronounced increases are observed in very long-chain ceramides (C24:1 and C24:0) and more moderate increases in long-chain C16:0 ceramide

  • PAQR4 also increases multiple species of dihydroceramides, hexosylceramides, sphingomyelin, and lactosylceramides

• Mechanistic insights:

  • PAQR4 regulates ceramide levels by mediating the stability of ceramide synthases (CERS2 and CERS5)

  • PAQR4 enhances CERS protein stability through inhibition of its lysosomal translocation and degradation

  • CERS2 has a relatively short half-life (~4 h) that is extended by PAQR4

  • CERS5 has a relatively long half-life (>24 h) but its levels are also increased by PAQR4

• Research methodologies:

  • Lipidomic analysis of tissue samples from PAQR4 overexpression or knockout models

  • Cycloheximide (CHX) chase assays to measure protein stability

  • "Pulse-chasing" with CERS2-HaloTag to track protein degradation

  • Lysosomal inhibitors (bafilomycin A1) and proteasome inhibitors (MG132) to determine degradation pathways

These findings suggest that PAQR4 antibodies can be valuable tools for studying the relationship between PAQR4 and ceramide metabolism, potentially leading to new therapeutic approaches for metabolic disorders.

How can PAQR4 antibodies be used to study its role in adipose tissue function and metabolic health?

PAQR4 has been identified as a critical regulator of adipose tissue function and whole-body metabolic health. Researchers can use PAQR4 antibodies to investigate:

• Adipose tissue-specific expression patterns:

  • Immunohistochemistry with PAQR4 antibodies can be used to compare expression in different adipose depots (e.g., gWAT vs. sWAT)

  • Western blotting to quantify expression levels in models of metabolic disease

• Mechanisms of PAQR4 action in adipocytes:

  • Co-immunoprecipitation to identify adipocyte-specific interaction partners

  • Subcellular fractionation combined with western blotting to determine localization in adipocytes

  • PAQR4 antibodies can help track changes in protein expression during adipocyte differentiation or in response to metabolic stressors

• In vivo models:

  • Research has utilized inducible adipocyte-specific PAQR4 expression models (Paqr4^ad) and inducible adipocyte-specific knockout models (Paqr4 iAKO)

  • PAQR4 antibodies can be used to validate these models and study the metabolic consequences of altered PAQR4 expression

• Therapeutic implications:

  • PAQR4 antibodies can help evaluate the efficacy of interventions targeting the PAQR4-ceramide axis

  • For example, studies have shown that blocking de novo ceramide biosynthesis rescues PAQR4-induced metabolic defects

These applications highlight the value of PAQR4 antibodies in understanding the complex relationship between PAQR4, adipose tissue function, and metabolic health.

What are common challenges when working with PAQR4 antibodies and how can they be overcome?

Researchers may encounter several challenges when working with PAQR4 antibodies, including:

• Specificity issues:

  • Challenge: Cross-reactivity with other PAQR family members, particularly AdipoR1/2, which share sequence similarity with PAQR4

  • Solution: Use antibodies targeting unique regions of PAQR4; validate with knockout/knockdown controls; consider using epitope-tagged PAQR4 constructs in overexpression studies

• Sensitivity limitations:

  • Challenge: Detecting endogenous PAQR4 which may be expressed at low levels in some tissues

  • Solution: Optimize protein loading; use enhanced chemiluminescence detection systems; consider employing signal amplification methods; use positive control samples with known high PAQR4 expression (e.g., NSCLC cell lines)

• Background signal:

  • Challenge: High background in immunohistochemistry or western blot applications

  • Solution: Optimize blocking conditions; increase washing steps; titrate antibody concentration; use higher quality secondary antibodies; consider alternative detection systems

• Reproducibility issues:

  • Challenge: Variability between experiments or antibody lots

  • Solution: Maintain consistent experimental conditions; use internal controls; consider pooling antibody lots for long-term studies; standardize sample preparation methods

• Detecting Golgi-localized PAQR4:

  • Challenge: Preserving Golgi structure in sample preparation

  • Solution: Use gentle lysis conditions; consider using subcellular fractionation to enrich for Golgi membranes; use appropriate fixation conditions for immunocytochemistry

How should researchers design experiments to study PAQR4's interactions with other proteins?

To effectively study PAQR4's protein interactions, researchers should consider the following experimental design principles:

• Co-immunoprecipitation (co-IP) approaches:

  • Use PAQR4 antibodies for pull-down experiments to identify interaction partners

  • Consider the directionality of the interaction (i.e., also perform reverse co-IP)

  • Include appropriate controls (IgG control, PAQR4 knockout/knockdown samples)

  • For known interactions (e.g., PAQR4-Nrf2), optimize buffer conditions to preserve the interaction

• GST-pulldown assays:

  • Have been successfully used to study PAQR4 interactions

  • Require recombinant GST-tagged PAQR4 or its potential interaction partners

  • Can help determine if interactions are direct or indirect

• Proximity ligation assays (PLA):

  • Can detect protein-protein interactions in situ

  • Requires high-quality antibodies against both PAQR4 and its potential interaction partners

  • Particularly useful for confirming interactions in their native cellular context

• Subcellular localization studies:

  • Given PAQR4's Golgi localization, co-localization studies with potential interaction partners can provide supporting evidence for interactions

  • Use confocal microscopy with appropriate Golgi markers

  • Consider live-cell imaging with fluorescently tagged proteins

• Functional validation of interactions:

  • Validate the functional significance of identified interactions (e.g., PAQR4-CERS2/5 or PAQR4-Nrf2)

  • Design experiments to test if disrupting the interaction affects downstream processes (e.g., ceramide production or chemoresistance)

What considerations should be made when using PAQR4 antibodies across different species?

PAQR4 is evolutionarily conserved across species, but researchers should consider several factors when using PAQR4 antibodies across different model organisms:

• Sequence homology and epitope conservation:

  • Check the antibody immunogen sequence against the target species' PAQR4 sequence

  • Many PAQR4 antibodies show high predicted reactivity across species (Cow: 100%, Dog: 100%, Goat: 93%, Guinea Pig: 100%, Human: 100%, Mouse: 100%, Rabbit: 93%, Rat: 100%)

  • The C-terminal region used in some antibodies shows particularly high conservation

• Validation in target species:

  • Even with high sequence homology, empirical validation in each species is essential

  • Use positive control samples from the target species

  • Consider species-specific optimization of experimental conditions

• Species-specific expression patterns:

  • PAQR4 expression levels and patterns may vary between species

  • Consider tissue-specific expression differences when planning experiments

  • Mouse models have shown PAQR4 expression in adipose tissue that is functionally significant

• Alternative splicing considerations:

  • Check if the target species has known PAQR4 splice variants

  • Ensure the antibody epitope is present in all relevant splice variants

  • Consider using multiple antibodies targeting different regions if splice variants are a concern

• Secondary antibody compatibility:

  • Ensure secondary antibodies are appropriate for the primary antibody host species

  • Consider potential cross-reactivity issues in tissue samples containing endogenous immunoglobulins