cis4 Antibody

What is Carbonic Anhydrase IV and what tissues commonly express it?

Carbonic Anhydrase IV (CA4) is a membrane-bound isoform of the carbonic anhydrase enzyme family that catalyzes the reversible hydration of carbon dioxide. It is prominently expressed in several human tissues including lung, brain (particularly cerebellum), kidney, and colon. Immunohistochemical studies have demonstrated localization primarily to cell membranes, with specific staining observed in epithelial cells of mucosal glands in human colon tissue. Western blot analyses have detected CA4 at approximately 33 kDa under reducing conditions in brain and lung tissue lysates, while Simple Western™ analysis revealed a band at approximately 40 kDa in lung and kidney tissue lysates . This tissue distribution pattern makes CA4 antibodies particularly valuable for studying pH regulation and ion transport in these tissues.

What are the recommended applications for CA4 antibody detection?

CA4 antibody can be effectively utilized across multiple experimental platforms:

For all applications, optimal dilutions should be determined experimentally for each laboratory's specific conditions .

How should researchers validate CA4 antibody specificity?

Antibody validation requires multiple complementary approaches. First, perform positive control experiments with tissues known to express CA4 (lung, kidney, brain). Western blots should show specific bands at the expected molecular weight (~33-40 kDa depending on the detection method). For immunohistochemistry, membranous staining patterns in epithelial cells provide evidence of specificity. Additionally, researchers should include negative controls such as isotype controls and tissues/cell lines with minimal CA4 expression. For definitive validation, consider using siRNA knockdown or CRISPR-Cas9 edited cells lacking CA4 expression. The detection of CA4 across multiple experimental platforms (Western blot, Simple Western™, and immunohistochemistry) with consistent results strengthens validation .

What factors affect CA4 antibody detection in Western blotting experiments?

Several technical factors can significantly impact CA4 detection in Western blotting:

• Sample preparation: CA4 is a membrane-bound protein, making efficient extraction critical. Use detergent-based lysis buffers (containing 1-2% Triton X-100 or NP-40) to properly solubilize membrane proteins.

• Reducing conditions: CA4 antibody detection works optimally under reducing conditions using Immunoblot Buffer Group 1, which maintains appropriate protein conformation for epitope recognition .

• Molecular weight variations: CA4 can appear at different molecular weights (~33 kDa in traditional Western blot vs. ~40 kDa in Simple Western™) due to post-translational modifications or differences in the detection systems. This variation is normal and should be considered when interpreting results .

• Tissue specificity: Expression levels vary significantly between tissues, with highest detection typically observed in lung and kidney samples, requiring optimization of protein loading amounts based on the source tissue.

How can researchers optimize immunohistochemical detection of CA4?

For optimal immunohistochemical detection of CA4:

• Epitope retrieval: Heat-induced epitope retrieval using basic pH buffer (VisUCyte Antigen Retrieval Reagent-Basic) is critical for exposing the CA4 epitope in formalin-fixed, paraffin-embedded tissues .

• Antibody concentration: Begin with 3 μg/mL concentration for overnight incubation at 4°C or 1 hour at room temperature, then optimize based on signal-to-noise ratio .

• Detection system: Polymer-based detection systems (such as Anti-Goat IgG VisUCyte™ HRP Polymer) provide superior sensitivity compared to traditional avidin-biotin methods .

• Counterstaining: Use light hematoxylin counterstaining to avoid obscuring the DAB (brown) signal that localizes to cell membranes.

• Controls: Include positive control tissues (colon, lung) where CA4 expression has been well-documented. For negative controls, omit primary antibody or use non-immune IgG at equivalent concentration.

What are the challenges in studying CA4 in lung tissue compared to other organs?

Studying CA4 in lung tissue presents unique challenges:

• Cell type heterogeneity: Lung tissue contains numerous cell types, making interpretation of CA4 expression patterns complex. Flow cytometry with cell-specific markers or single-cell RNA sequencing might be necessary to determine exact cellular distribution.

• Background autofluorescence: Lung tissue exhibits high autofluorescence, especially in immunofluorescence applications. Consider using Sudan Black B treatment or spectral unmixing to reduce background.

• Disease-state variation: CA4 expression may be altered in pathological conditions like lung carcinoma. A549 human lung carcinoma cells show detectable but different expression levels compared to normal lung tissue, requiring careful experimental design when comparing normal versus diseased states .

• Tissue processing: The alveolar architecture of lung tissue is delicate and can be disrupted during processing, potentially affecting membrane protein localization. Gentle handling and optimized fixation protocols are essential.

How can CA4 antibody be used to study pH regulation in epithelial cells?

CA4 plays a crucial role in pH regulation by catalyzing the conversion between CO₂ and bicarbonate. To investigate this function:

• Ciliary motility studies: Research has demonstrated that CA4 affects ciliary motility in human nasal epithelial cells through pH regulation. Combine CA4 antibody staining with ciliary beat frequency measurements under different CO₂/HCO₃⁻ conditions to correlate CA4 expression with functional outcomes .

• Knockdown experiments: Use siRNA targeting CA4 alongside antibody detection to confirm specificity and correlate expression levels with functional changes in pH regulation.

• Live cell imaging: Combine CA4 immunocytochemistry with pH-sensitive fluorescent probes (like BCECF) to visualize the spatial relationship between CA4 localization and pH microdomains near cell membranes.

• Inhibitor studies: Apply carbonic anhydrase inhibitors (e.g., acetazolamide) while monitoring pH changes and compare results with CA4 antibody staining patterns to establish structure-function relationships.

What is the relationship between CA4 and CIS protein signaling pathways?

Although CA4 (Carbonic Anhydrase IV) and CIS (Cytokine-Inducible SH2 protein) are distinct molecules, their signaling pathways may intersect in certain physiological contexts:

• Inflammatory microenvironments: CIS regulates STAT3, STAT5, and STAT6 phosphorylation in T cells, controlling TH2 and TH9 differentiation which can influence airway inflammation . CA4, being expressed in lung tissue, may have altered expression or function in these inflammatory environments.

• pH-dependent immune responses: CA4's role in pH regulation may indirectly affect immune cell function, as acidic microenvironments can modulate T cell responses. Researchers can use CA4 antibody in combination with CIS detection to investigate potential functional relationships in inflammatory lung conditions.

• STAT signaling: While CIS directly regulates STAT signaling , CA4's involvement in pH homeostasis might indirectly affect STAT activation through pH-sensitive signaling pathways. Dual immunostaining experiments could reveal spatial relationships between these proteins in relevant tissues.

• Therapeutic targeting: Understanding both pathways could inform therapeutic strategies for airway diseases. CIS-deficient mice develop spontaneous airway inflammation , and CA4 function in lung epithelium may contribute to disease pathology through different mechanisms.

What are common causes of non-specific binding with CA4 antibody?

Non-specific binding can compromise experimental results. Common causes and solutions include:

• Suboptimal blocking: Use 5% BSA or 5% non-fat dry milk in TBS-T for Western blots and 10% normal serum from the species of the secondary antibody for immunohistochemistry.

• Secondary antibody cross-reactivity: Pre-adsorb secondary antibodies against tissue proteins or use highly cross-adsorbed secondary antibodies.

• Endogenous peroxidase activity: For IHC applications, quench endogenous peroxidase with 0.3% H₂O₂ in methanol before antibody incubation.

• Endogenous biotin: If using biotin-based detection systems, block endogenous biotin with avidin/biotin blocking kit.

• Fixation artifacts: Overfixation can cause epitope masking; optimize fixation time and perform proper antigen retrieval for FFPE tissues.

• Antibody concentration: Excessive antibody concentration increases background; titrate to determine optimal concentration showing specific signal with minimal background.

How should researchers assess batch-to-batch variability in CA4 antibody performance?

Batch-to-batch variability can significantly impact experimental reproducibility. Implement these quality control measures:

• Reference sample testing: Maintain a consistent positive control sample (e.g., normal human lung tissue lysate) and test each new antibody batch against it using the same protocol.

• Quantitative comparison: Perform quantitative analysis of signal intensity and band pattern in Western blots or staining intensity in IHC across batches.

• Epitope mapping: If inconsistencies arise, determine if the recognition epitope (Ala19-Lys283 of human CA4) is equally accessible across batches .

• Documentation: Maintain detailed records of antibody lot numbers, experimental conditions, and quantitative performance metrics for longitudinal quality control.

• Manufacturer validation data: Request and compare manufacturer's batch-specific quality control data when available.

How can CA4 antibody be incorporated into multiplexed imaging systems?

Multiplexed imaging enables simultaneous visualization of multiple targets. For CA4 antibody integration:

• Spectral compatibility: Carefully select fluorophores for CA4 antibody that are spectrally distinct from other targets in your panel, considering tissue autofluorescence characteristics.

• Sequential staining protocols: For co-localization studies with challenging antibody combinations, consider sequential staining protocols with intermediate fixation steps.

• Tyramide signal amplification: For low-abundance detection, implement tyramide signal amplification which allows antibody stripping and re-probing while preserving the amplified CA4 signal.

• Mass cytometry adaptation: For highly multiplexed approaches, CA4 antibody can be metal-conjugated for mass cytometry (CyTOF) analysis, enabling simultaneous detection of dozens of proteins.

• Imaging mass cytometry: Combining antibody detection with laser ablation inductively coupled plasma mass spectrometry enables subcellular spatial resolution of CA4 alongside numerous other markers.

What considerations are important when studying protein-protein interactions involving CA4?

Investigating CA4's interaction partners requires specialized approaches:

• Antibody interference: The binding of CA4 antibody may sterically hinder protein-protein interactions. Consider epitope mapping and use antibodies targeting non-interactive domains.

• Membrane protein challenges: As a membrane-bound protein, CA4 requires detergent-based approaches for co-immunoprecipitation, which can disrupt weak or transient interactions. Consider mild detergents like digitonin or CHAPS.

• Crosslinking strategies: Implement chemical crosslinking prior to cell lysis to stabilize transient interactions before immunoprecipitation with CA4 antibody.

• Micropattern techniques: Adapt the two-hybrid antibody micropattern assay (described for MHC proteins ) for CA4 to study cell surface protein interactions under controlled conditions.

• Proximity labeling: Consider BioID or APEX2 proximity labeling approaches, where CA4 fusion proteins can biotinylate proximal proteins, followed by streptavidin pulldown and mass spectrometry.