CBR1 Antibody

What is CBR1 and why is it significant for research?

Carbonyl reductase 1 (CBR1) is an enzyme encoded by the CBR1 gene mapped to chromosome 21q22.12 in humans. It belongs to the short-chain dehydrogenases/reductases (SDR) family and functions as an NADPH-dependent oxidoreductase with broad specificity for carbonyl compounds, including quinones, prostaglandins, and various xenobiotics . The significance of CBR1 in research stems from its role in drug metabolism, particularly in the reduction of carbonyl-containing drugs, and its potential implications in disease processes. The protein has a calculated molecular weight of approximately 97 kDa, though it is often observed at around 30-36 kDa in experimental conditions .

It's crucial to note that the abbreviation "CBR1" can also refer to cannabinoid receptor 1, which has different structure and functions. Cannabinoid receptor 1 is being extensively investigated due to its potential role in glucose and lipid metabolism as evidenced by its expression in hepatic cells and lipid tissue . This distinction is important when selecting antibodies for specific research applications.

What types of CBR1 antibodies are available for research applications?

Based on current research tools, there are several types of CBR1 antibodies available:

• Polyclonal antibodies: These are commonly used for CBR1 detection across multiple species. For example, rabbit anti-CBR1 polyclonal antibodies like the Picoband® antibody are effective for detecting human, mouse, and rat CBR1 .

• Monoclonal antibodies: These offer higher specificity for particular epitopes. Though less common for carbonyl reductase 1, monoclonal antibodies have been developed for cannabinoid receptor 1, demonstrating high specificity with an affinity constant (Kaff) of 7.85 × 10^8 M/L .

The choice between polyclonal and monoclonal antibodies depends on the research application, with polyclonals offering broader epitope recognition and monoclonals providing higher specificity for defined epitopes.

How can I verify the specificity of my CBR1 antibody?

Verifying antibody specificity is critical for obtaining reliable research data. For CBR1 antibodies, consider these methodological approaches:

• Western blot validation: Run samples from various cell lines or tissues known to express CBR1 alongside negative controls. For example, validation studies have successfully detected CBR1 in human cell lines (SW620, SK-OV-3, 293T, Hela, MCF-7, SH-SY5Y) and tissue lysates (rat testis, mouse liver) .

• Cross-reactivity testing: Test your antibody against recombinant human CBR3, which shares structural similarity with CBR1. Quality antibodies should show no cross-reactivity with CBR3, as demonstrated in published validation studies .

• Immunohistochemistry with appropriate controls: Include positive controls (tissues known to express CBR1) and negative controls (antibody diluent without primary antibody) to confirm specific staining .

• Flow cytometry validation: Compare staining patterns between cells expressing CBR1 and appropriate isotype controls to distinguish specific from non-specific binding .

What are the validated applications for CBR1 antibodies?

CBR1 antibodies have been validated for multiple experimental applications, each requiring specific optimization parameters:

These applications have been successfully demonstrated using rabbit anti-CBR1 antibodies across human, mouse, and rat samples .

What is the recommended Western blot protocol for optimal CBR1 detection?

For optimal CBR1 detection by Western blot, follow this evidence-based protocol:

• Sample preparation: Load 30 μg of protein per lane under reducing conditions .

• Electrophoresis conditions: Use 5-20% SDS-PAGE gel at 70V (stacking gel) followed by 90V (resolving gel) for 2-3 hours .

• Transfer parameters: Transfer proteins to a nitrocellulose membrane at 150 mA for 50-90 minutes .

• Blocking conditions: Block with 5% non-fat milk in TBS for 1.5 hours at room temperature .

• Primary antibody incubation: Incubate with rabbit anti-CBR1 antibody at 0.5 μg/mL overnight at 4°C .

• Washing steps: Wash with TBS-0.1% Tween three times, 5 minutes each .

• Secondary antibody: Incubate with goat anti-rabbit IgG-HRP at 1:5000 dilution for 1.5 hours at room temperature .

• Detection: Develop using an enhanced chemiluminescent detection system .

Look for a specific band at approximately 30-36 kDa, which represents CBR1 .

How should immunohistochemistry protocols be optimized for CBR1 detection in tissue sections?

For effective immunohistochemical detection of CBR1 in tissue sections:

• Antigen retrieval: Perform heat-mediated antigen retrieval in EDTA buffer (pH 8.0). This step is critical for unmasking epitopes after formalin fixation .

• Blocking: Block non-specific binding with 10% goat serum .

• Primary antibody incubation: Apply rabbit anti-CBR1 antibody at 2 μg/mL and incubate overnight at 4°C for optimal sensitivity .

• Secondary antibody: Use peroxidase-conjugated goat anti-rabbit IgG and incubate for 30 minutes at 37°C .

• Visualization: Develop with DAB (3,3'-diaminobenzidine) as the chromogen .

This protocol has been validated in multiple tissue types including human breast cancer, liver cancer, lung cancer, rectal cancer, and normal kidney tissues from mouse and rat .

How can I quantify CBR1 protein levels in tissue or cell samples?

For accurate quantification of CBR1 protein levels:

• Western blot quantification: Use recombinant CBR1 protein to generate a standard curve for direct extrapolation of CBR1 levels. Published methods have established a linear detection range of 0.05-0.30 μg (r² > 0.85) with a coefficient of variation of 9.5%. The limit of quantification is typically around 0.02 μg, with a detection limit of 0.01 μg .

• Band intensity analysis: Quantify band intensity values (pixels per square millimeter) using imaging software such as Quantity One with a gel documentation system .

• Normalization: Always normalize CBR1 expression to housekeeping proteins such as β-actin to account for loading variations .

• Quality control: Include recombinant CBR1 of known concentration in each experiment to verify consistency across blots .

What are common pitfalls in CBR1 antibody experiments and how can they be addressed?

Several methodological challenges can arise when working with CBR1 antibodies:

• Cross-reactivity with CBR3: Some antibodies may cross-react with CBR3 due to structural similarities. Validate specificity by testing against recombinant CBR3 protein .

• Variable expression across tissues: CBR1 expression varies significantly across tissue types and disease states. Always include positive control samples with known CBR1 expression .

• Background in immunohistochemistry: High background can mask specific staining. Optimize blocking conditions (10% goat serum has shown good results) and include isotype controls .

• Detection in flow cytometry: Cell fixation and permeabilization can affect epitope accessibility. For intracellular CBR1 detection, use 4% paraformaldehyde for fixation followed by permeabilization buffer treatment .

• Storage and handling: Antibody performance can deteriorate with improper storage. Store lyophilized antibodies at -20°C and reconstituted antibodies at 4°C for short-term (one month) or aliquoted at -20°C for long-term (six months) storage. Avoid repeated freeze-thaw cycles .

How do genetic variations affect CBR1 expression and antibody detection?

Genetic variations can significantly impact CBR1 expression levels and potentially influence antibody detection:

• Ethnic variations: Studies have documented variations in hepatic expression of CBR1 between different ethnic groups. When designing experiments, consider potential ethnic differences in your sample population .

• Alternative splicing: The CBR1 gene has alternatively spliced transcript variants. Antibodies targeting specific regions might miss certain splice variants .

• Post-translational modifications: These can affect epitope accessibility. Consider using antibodies that target conserved regions less affected by post-translational modifications .

• Single nucleotide polymorphisms (SNPs): CBR1 polymorphisms can affect enzyme activity and potentially epitope structure. In pharmacogenetic studies, genotyping samples alongside protein detection provides more comprehensive data .

How is CBR1 involved in cancer research and drug metabolism?

CBR1 plays significant roles in cancer research and drug metabolism:

• Anthracycline metabolism: CBR1 metabolizes anthracycline chemotherapeutics like doxorubicin to less active alcohols, potentially affecting treatment efficacy .

• Expression in cancer tissues: CBR1 expression has been detected in various cancers including breast, liver, lung, and rectal cancers, suggesting potential roles in cancer biology .

• Drug resistance mechanisms: Altered CBR1 expression may contribute to drug resistance patterns. Quantitative analysis of CBR1 in tumor samples can provide insights into treatment response .

• Biomarker potential: CBR1 expression patterns may serve as potential biomarkers for certain cancer types or treatment response predictors .

What are emerging applications of CBR1 antibodies beyond traditional Western blot and IHC?

Research with CBR1 antibodies is expanding beyond traditional applications:

• Flow cytometry: CBR1 antibodies have been validated for flow cytometric analysis, allowing quantification of CBR1 expression at the single-cell level. This technique has been successfully applied to cell lines such as U87 .

• Live cell imaging: Using appropriate fluorophore-conjugated CBR1 antibodies for real-time visualization of CBR1 dynamics in living cells.

• Chromatin immunoprecipitation (ChIP): Investigating transcriptional regulation of CBR1 through protein-DNA interaction studies.

• Immunoprecipitation-mass spectrometry: Identifying novel CBR1 binding partners to elucidate broader functional networks.

• Tissue microarray analysis: High-throughput screening of CBR1 expression across large sample collections to identify clinically relevant patterns.

How do CBR1 expression patterns differ between normal and disease states?

Understanding differential CBR1 expression has important implications for disease research:

• Cancer tissues: Immunohistochemical analyses have revealed CBR1 expression in various cancer tissues including breast, liver, lung, and rectal cancers . The pattern and intensity of expression may differ from normal tissues.

• Metabolic conditions: Research on cannabinoid receptor 1 (a different protein sharing the CBR1 abbreviation) has shown expression in HL-7702 cells and lipid tissue, suggesting potential roles in glucose and lipid metabolism disorders .

• Drug-induced changes: Treatment with certain pharmaceuticals may alter CBR1 expression levels as part of adaptive responses.

• Tissue-specific expression: Normal expression patterns vary across tissues, with detection in kidney tissues of both mouse and rat models suggesting conserved physiological roles .

What are the current best practices for CBR1 antibody selection and validation?

Based on current research methodologies, these best practices will ensure reliable CBR1 antibody experiments:

• Antibody selection criteria:

  • Choose antibodies validated for your specific application (WB, IHC, IF, Flow)

  • Select antibodies raised against relevant species (human, mouse, rat as needed)

  • Consider polyclonal antibodies for broader epitope recognition or monoclonal for higher specificity

• Comprehensive validation:

  • Perform Western blot validation with positive and negative controls

  • Verify absence of cross-reactivity with closely related proteins (especially CBR3)

  • Include appropriate isotype controls in all experiments

  • Validate across multiple cell lines/tissues when possible

• Experimental design considerations:

  • Include standardized recombinant protein for quantification

  • Optimize protocols for each specific application

  • Document and report all experimental conditions in publications