cxadr Antibody

Basic Research Questions

• What is CXADR and why is it important for antibody-based research?

  CXADR (Coxsackievirus and Adenovirus Receptor) is a 40-46 kDa transmembrane glycoprotein belonging to the immunoglobulin superfamily. While initially identified as an entry receptor for coxsackie B virus and adenovirus 2 and 5, recent research has revealed its function as a human IgG Fc receptor. This multifunctional protein is present in epithelial tight junctions and other tissues, playing roles in transepithelial migration of lymphocytes, neurite outgrowth, synaptic function, cardiomyocyte function, and spermatogenesis .

  Its expression pattern varies across tissues, with highest expression observed in:

  • Pancreas

  • Brain

  • Heart

  • Small intestine

  • Testis

  • Prostate

  CXADR's recently discovered function as an Fc receptor has significant implications for antibody-based research, as it binds specifically to human and rabbit IgG with an estimated affinity of approximately 1nM .

• Which applications can CXADR antibodies be used for?

  CXADR antibodies have been validated for multiple research applications:

  Application	Validated Antibody Types	Notes
  Western Blot (WB)	Polyclonal, Monoclonal	Observed at ~46-55 kDa
  Flow Cytometry (FCM)	Conjugated, Unconjugated	Multiple fluorophore options available
  Immunohistochemistry (IHC)	Polyclonal, Monoclonal	Both paraffin and frozen sections
  Immunocytochemistry (ICC)	Polyclonal, Monoclonal	Fixed and permeabilized cells
  Immunofluorescence (IF)	Fluorophore-conjugated	For tissue and cell imaging
  ELISA	Various formats	For protein quantification

  When selecting an antibody for specific applications, consider epitope accessibility, which may vary depending on fixation methods and protein conformation .

• What types of CXADR antibodies are available for researchers?

  Various formats of anti-CXADR antibodies are available:

  • Host species: Rabbit, mouse, human, chimeric

  • Clonality: Monoclonal (e.g., clone S382), polyclonal

  • Format:

    • Unconjugated

    • Conjugated (PE, PerCP, APC, FITC, Cy3, DyLight488)

    • Biotinylated

  • Applications: Different antibodies optimized for WB, FCM, IHC, ICC, IF, ELISA

  • Species reactivity: Human, mouse, rat, with variable cross-reactivity

  • Target region: Some antibodies target specific domains or the C-terminus

• How do I validate the specificity of a CXADR antibody?

  Methodological approach to validate CXADR antibodies:

  1. Positive controls: Use cell lines with known CXADR expression (e.g., BxPC-3 cells, DU-145 prostate cancer cells)

  2. Negative controls: Use CXADR knockout cells or tissues

  3. Blocking peptide: Test with the immunizing peptide to confirm specificity

  4. Multiple detection methods: Compare results across techniques (WB, IHC, FCM)

  5. siRNA knockdown: Confirm reduction in signal intensity follows CXADR knockdown

  6. Cross-species reactivity: Test on samples from different species to confirm expected pattern

  Important consideration: Due to CXADR's Fc-binding properties, include appropriate controls to rule out non-specific binding .

Advanced Research Questions

• How does CXADR's newly discovered Fc receptor function affect antibody-based experiments?

  The identification of CXADR as an Fc receptor for human and rabbit IgG has significant implications for research:

  • Potential false positives: CXADR can bind human and rabbit IgG antibodies directly through their Fc portion, not just through antigen recognition

  • Specificity controls: When using human or rabbit antibodies in tissues expressing CXADR, additional controls are essential

  • Interference with detection: CXADR binding is competitive with anti-Fc binding secondary antibodies, but not with anti-Fab secondary antibodies

  • Species specificity: CXADR does not bind mouse, rat, donkey, or goat IgG, making these better options for certain experiments

  • FcBlock effectiveness: Binding of IgG to CXADR is inhibited by FcBlock, which can be used as a methodological control

  Recommended methodology: When studying CXADR in tissues, consider using:

  • F(ab')₂ fragments instead of whole IgG

  • Mouse or rat IgG antibodies (which don't bind CXADR)

  • FcBlock pre-treatment as a control condition

• What approaches are effective for evaluating CXADR expression in cancer research?

  CXADR is expressed in various cancer types and has therapeutic relevance:

  • Flow cytometry: For quantitative assessment of cell surface expression using antibodies like ch6G10A

  • Tissue microarrays: CXADR is highly expressed in neuroendocrine lung cancers, prostate cancer, and brain tumors

  • Western blotting: For total protein quantification using antibodies like 11777-1-AP (1:1000-1:4000 dilution)

  • Orthotopic xenograft models: For evaluating therapeutic targeting of CXADR in vivo

  Research finding: Anti-CXADR antibody 6G10A significantly inhibits the growth of cancer xenografts expressing CXADR through both antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) .

• How can I distinguish between different CXADR isoforms using antibodies?

  CXADR exists in multiple isoforms, including membrane-bound and soluble forms:

  • Domain-specific antibodies: Select antibodies targeting specific domains present or absent in isoforms

  • Western blotting: Distinguish isoforms by molecular weight differences

    • Full-length CXADR: ~46-55 kDa

    • CXADR2 (alternative splice variant): Differs in C-terminal 15 amino acids

    • Soluble forms: Lower molecular weight

  • Epitope mapping: Use antibodies targeting different epitopes to identify isoform-specific regions

  • RT-PCR validation: Confirm antibody results with transcript analysis

  Methodological note: When studying isoforms, combine protein and transcript-level analyses for conclusive identification.

• What considerations should be made when developing therapeutic anti-CXADR antibodies?

  Developing therapeutic anti-CXADR antibodies requires several considerations:

  • Target specificity: Chimeric antibodies like ch6G10A show high specificity and potent anti-tumor activity

  • Mechanism of action: Effective antibodies work through ADCC and CDC mechanisms

  • Expression profiling: CXADR is expressed in normal tissues including heart, so tissue cross-reactivity studies are essential

  • Species differences: Human and mouse CXADR share 90% amino acid sequence identity, but functional differences exist

  • Toxicity assessment: Evaluate cardiac effects due to CXADR expression in cardiomyocytes

  • Functional impact: Consider CXADR's multiple physiological roles when targeting it therapeutically

  Research finding: Mouse-human chimeric anti-CXADR antibody (ch6G10A) demonstrates significant anti-tumor activity against CAR-expressing cancer cells both in vitro and in vivo .

Methodological Questions

• What are the optimal conditions for Western blotting detection of CXADR?

  Optimized Western blotting protocol for CXADR detection:

  Parameter	Recommended Condition	Notes
  Sample preparation	RIPA buffer with protease inhibitors	Preserves membrane protein integrity
  Protein amount	20-50 μg per lane	Dependent on expression level
  Gel percentage	10-12% SDS-PAGE	For optimal resolution of 40-55 kDa
  Transfer	Wet transfer at 100V for 60-90 min	PVDF membrane recommended
  Blocking	5% non-fat milk in TBST (1 hour, RT)	BSA for phospho-detection
  Primary antibody	1:1000-1:4000 dilution (e.g., 11777-1-AP)	Overnight at 4°C
  Secondary antibody	HRP-conjugated, 1:5000-1:10000	1 hour at room temperature
  Expected band size	46-55 kDa	Glycosylation may affect migration

  Troubleshooting tip: If non-specific bands appear when using rabbit antibodies, this may be due to CXADR's Fc-binding property. Use mouse antibodies or F(ab')₂ fragments to avoid this issue .

• How should flow cytometry experiments be designed for CXADR detection?

  Methodological approach for flow cytometry analysis of CXADR:

  1. Cell preparation:

     • Live cells: Use gentle enzymatic dissociation (avoid trypsin)

     • Fixed cells: 2-4% paraformaldehyde, 10 min at RT

  2. Antibody selection:

     • Direct conjugates: PE- or APC-conjugated anti-CXADR for single-step staining

     • Unconjugated: Follow with fluorophore-conjugated secondary antibody

  3. Staining protocol:

     • Block with 1-5% BSA in PBS, add 10% serum matching secondary host

     • Primary antibody: 1-10 μg/mL, 30-60 min at 4°C

     • Wash 2-3 times with PBS/0.1% BSA

     • Secondary antibody (if needed): 30 min at 4°C

  4. Controls:

     • Isotype control (matched to primary antibody)

     • FMO (Fluorescence Minus One) control

     • CXADR-positive and negative cell lines

     • FcBlock treatment control (especially for human/rabbit antibodies)

  Important note: Due to CXADR's location in tight junctions, some epitopes may be inaccessible in intact cells. Consider gentle permeabilization if studying total rather than surface CXADR .

• What are the best methods for immunoprecipitating CXADR for interaction studies?

  Optimized immunoprecipitation protocol for CXADR:

  1. Lysis buffer selection:

     • For membrane proteins: 1% NP-40 or 0.5% Triton X-100 in TBS with protease inhibitors

     • For tight junction complexes: Include 150-300 mM NaCl to preserve interactions

  2. Antibody selection:

     • Avoid human or rabbit antibodies unless using F(ab')₂ fragments (due to Fc binding)

     • Use mouse monoclonal antibodies (don't bind CXADR's Fc domain)

  3. Immunoprecipitation approaches:

     • Direct coupling to beads (recommended): Reduces IgG contamination

     • Traditional IP: Pre-clear lysate with protein A/G alone first

  4. Elution considerations:

     • Mild: Non-denaturing elution with competing peptide

     • Strong: Boiling in SDS sample buffer

  5. Verification:

     • Immunoblot CXADR (~46-55 kDa band)

     • Mass spectrometry for complex identification

  Critical note: When studying CXADR's interaction with IgG, use mouse antibodies for immunoprecipitation to avoid interference with the Fc receptor function being studied .

• How can I optimize immunohistochemical detection of CXADR in different tissues?

  Tissue-specific optimization for CXADR immunohistochemistry:

  Tissue Type	Fixation Method	Antigen Retrieval	Recommended Antibody	Special Considerations
  Heart	10% NBF, 24h	Citrate buffer, pH 6.0	Rabbit polyclonal	Focus on intercalated discs
  Brain	4% PFA, 24-48h	EDTA buffer, pH 8.0	Mouse monoclonal	Background can be high
  Epithelial tissues	10% NBF, 24h	Citrate buffer, pH 6.0	Rabbit polyclonal	Look for tight junction staining
  Testis	Bouin's, 6-12h	Tris-EDTA, pH 9.0	Rabbit polyclonal	High background common
  Tumors	10% NBF, 24h	Citrate buffer, pH 6.0	Mouse monoclonal	Compare with normal tissue

  Methodological tips:

  • Block with 10% serum from species of secondary antibody

  • Include 0.1-0.3% Triton X-100 for intracellular epitopes

  • Use tyramide signal amplification for low expression

  • For dual staining with junction proteins, use mouse anti-CXADR with rabbit antibodies against other proteins

  • When using rabbit anti-CXADR, be aware of potential Fc binding artifacts