ZBP1 Antibody

What is ZBP1 and why is it important in immunological research?

ZBP1, also known as DAI (DNA-dependent Activator of IFN-regulatory factors) or DLM-1, functions as a cytoplasmic sensor that detects viral nucleic acids and initiates innate immune responses. Its significance in immunological research stems from its multifaceted roles:

ZBP1 serves as a critical mediator in several cell death pathways, including necroptosis, apoptosis, and pyroptosis during viral infections. Recent studies have identified Z-RNA generated during influenza virus infection as a natural ligand for ZBP1 . Beyond viral sensing, ZBP1 also promotes inflammatory responses downstream of TLR3/TLR4, demonstrating its broader involvement in immunity . During SARS-CoV-2 infection, ZBP1 contributes significantly to inflammatory signaling and necroptosis activation, affecting disease pathogenesis . Understanding ZBP1's diverse functions provides crucial insights into host-virus interactions, inflammatory diseases, and potential therapeutic targets.

What molecular weight(s) should I expect when detecting ZBP1 with Western blot?

When detecting ZBP1 via Western blot, researchers should anticipate multiple bands representing various isoforms:

• The calculated molecular weight of ZBP1 is approximately 46 kDa

• Observed molecular weights typically range between 42-68 kDa

• Specific isoforms have been documented at approximately 42 kDa, 45 kDa, 55 kDa, and 58 kDa

• Additional bands around 68 kDa have been reported by some researchers

These multiple bands represent either different isoforms or degradation products of ZBP1. Their specificity can be verified through ZBP1 siRNA knockdown experiments, as all bands should be downregulated following treatment . When performing Western blotting, utilizing appropriate positive controls such as 293T cells transfected with ZBP1 or mouse spleen lysate can help confirm band identity .

Optimizing Western blot protocols for ZBP1 detection requires attention to several critical parameters:

Sample Preparation:

• Use appropriate positive controls such as 293T cells transfected with ZBP1 or mouse spleen tissue

• Consider stimulating cells with poly(dA.dT)·poly(dT.dA) to upregulate ZBP1 expression for easier detection

• For comprehensive analysis, include both unstimulated and stimulated samples to observe expression changes

Gel Electrophoresis and Transfer:

• Use 8-10% polyacrylamide gels to adequately resolve the multiple ZBP1 isoforms (42-68 kDa)

• Include molecular weight markers spanning the 40-70 kDa range to accurately identify bands

• Optimize transfer conditions for proteins in this molecular weight range

Antibody Incubation:

• Start with a 1:1000 dilution for primary antibody and adjust based on signal strength

• For rabbit polyclonal antibodies like CAB13899, a dilution range of 1:2000-1:6000 is recommended

• Extend primary antibody incubation to overnight at 4°C for stronger signals

• Use appropriate secondary antibodies (anti-rabbit IgG for rabbit polyclonals, anti-mouse IgG for mouse monoclonals)

Controls and Validation:

• Include ZBP1 knockout cells or siRNA-treated cells as negative controls

• The multiple bands observed likely represent isoforms or degradation products of ZBP1, as they are downregulated upon ZBP1 siRNA treatment

• Include stimulated samples (e.g., with viral components or TLR ligands) as positive controls

By implementing these optimizations, researchers can achieve more consistent and specific detection of ZBP1 across its various isoforms.

How can I distinguish between different ZBP1 isoforms using antibody-based techniques?

Distinguishing between different ZBP1 isoforms requires strategic approaches:

Gel Electrophoresis Optimization:

• Use lower percentage gels (6-8%) or gradient gels (4-15%) to better separate the multiple ZBP1 isoforms ranging from 42-68 kDa

• Extended run times can improve separation of closely migrating bands

Strategic Antibody Selection:

• Choose antibodies targeting different epitopes: Select antibodies recognizing N-terminal vs. C-terminal regions

• Antibodies like CAB13899 (targeting amino acids 1-170) and anti-ZBP1 mAb Zippy-1 (targeting amino acids 1-411) recognize different regions of ZBP1

• Compare detection patterns between antibodies to identify isoform-specific recognition

Validation Approaches:

• Perform peptide competition assays with specific peptides representing unique regions of each isoform

• Use cells transfected with individual ZBP1 isoform constructs as positive controls

• Include ZBP1 knockout or knockdown samples to confirm band specificity

Multiple isoforms of ZBP1 have been detected at molecular weights of approximately 42 kDa, 45 kDa, 55 kDa, 58 kDa, and 68 kDa . Their expression patterns may vary depending on cell type and stimulation conditions. For comprehensive isoform analysis, combining protein detection with RNA expression analysis may provide additional insights into isoform-specific functions.

What are the best experimental controls when studying ZBP1 activation in viral infection models?

When studying ZBP1 activation in viral infection models, comprehensive controls are essential for reliable interpretation:

Genetic Controls:

• ZBP1 knockout (Zbp1^-/-) cells/animals: Essential negative controls that confirm ZBP1-specific effects

• ZBP1 reconstituted cells: Reintroducing ZBP1 into knockout cells confirms phenotype rescue

• Varying ZBP1 expression levels: Low vs. high ZBP1 expression can produce different kinetics of inflammatory complex formation

Viral Controls:

• Inactivated virus: Distinguishes between effects requiring viral replication vs. mere presence

• Viral mutants: Viruses lacking specific components (like VP22 in PRV) help identify viral factors interacting with ZBP1

• Viral dose titration: Different multiplicities of infection reveal threshold-dependent effects

Stimulation Controls:

• Synthetic nucleic acid stimulants: Poly(I:C) (TLR3 agonist), poly(dA.dT) (DNA sensor agonist)

• Time course experiments: Critical for capturing the dynamic nature of ZBP1 activation

• TLR agonists: LPS (TLR4) can be used to study ZBP1's role in TRIF-dependent pathways

Readout Controls:

• Include markers for different cell death pathways (necroptosis, apoptosis, pyroptosis)

• In SARS-CoV-2 infection studies, measurement of MLKL phosphorylation, PARP1 cleavage, and Caspase3 cleavage provided evidence of ZBP1's role in necroptosis

• Measure both protein expression/modification and functional outcomes (cytokine production, cell death)

In vivo studies should include appropriate controls such as the Ad5-hACE2 mouse model used for SARS-CoV-2 infection, where both wild-type and Zbp1^-/- mice can be compared .

How does ZBP1 contribute to SARS-CoV-2 pathogenesis?

ZBP1 plays a significant role in SARS-CoV-2 pathogenesis through multiple mechanisms:

Regulation of Inflammatory Signaling:

• RNA-seq analysis revealed upregulation of ZBP1 during SARS-CoV-2 infection

• ZBP1 depletion through CRISPR-Cas9-mediated knockout significantly reduced the transcriptional levels of proinflammatory cytokines and chemokines, including IL-1β, CCL2, and CXCL2

• In mouse models, ZBP1 depletion significantly reduced expression of IL-6, CXCL10, CCL2, and CCL4 in lung tissue following SARS-CoV-2 infection

Cell Death Pathway Activation:

• ZBP1 depletion reduced SARS-CoV-2-induced MLKL phosphorylation, indicating its role in necroptosis activation

• PI and Annexin V staining showed that ZBP1 depletion reduced virus-triggered cell death

• Western blot analysis revealed that ZBP1 depletion reduced cleavage of PARP1 and Caspase3, markers of cell death

In Vivo Pathological Effects:

• Histological analysis demonstrated that ZBP1 depletion alleviated SARS-CoV-2-induced immune cell infiltration and alveolar septa expansion in lungs

• Immunohistochemistry revealed decreased recruitment of macrophages (CD68+), neutrophils (MPO+), and T cells (CD3+) in the lungs of Zbp1^-/- mice infected with SARS-CoV-2

• Both CD4+ and CD8+ T cell infiltration was reduced in ZBP1-depleted mice, with CD8+ T cell infiltration showing more pronounced reduction

Interestingly, while ZBP1 significantly impacts inflammatory and cell death responses, its depletion did not affect SARS-CoV-2 viral load or replication . This suggests that ZBP1-targeting strategies might potentially reduce pathological inflammation without compromising viral clearance mechanisms.

How does ZBP1 interact with the NLRP3 inflammasome?

ZBP1 has emerged as an important regulator of NLRP3 inflammasome activation:

Activation Mechanisms:

• ZBP1 contributes to SARS-CoV-2-triggered inflammatory signaling and processing of IL-1β, a key inflammasome-dependent cytokine

• ZBP1 depletion significantly reduced release of the matured form of IL-1β (P17) during SARS-CoV-2 infection

• The ZBP1-RIPK3 pathway appears central to inflammasome activation during viral infections

Viral Regulation:

• Pseudorabies virus (PRV) VP22, a viral virulence factor, interacts with ZBP1 and suppresses ZBP1-mediated activation of the NLRP3 inflammasome

• In Zbp1^+/+ bone marrow-derived macrophages (BMDMs), IL-1β levels were significantly higher upon infection with PRV lacking VP22 compared to viruses containing intact VP22, indicating that VP22 suppresses ZBP1-mediated inflammasome activation

• These differences in IL-1β induction between viruses were significantly reduced in Zbp1^-/- BMDMs, confirming ZBP1 dependency

Signaling Pathway Integration:

• ZBP1 appears to function as a critical link between viral sensing and inflammasome activation

• The ZBP1-RIPK3 axis is crucial for promoting inflammatory cytokine release during viral infections

• ZBP1-mediated inflammasome activation contributes to host defense mechanisms, as evidenced by distinct survival patterns in Zbp1^+/+ versus Zbp1^-/- mice infected with different viruses

These findings highlight the dual role of ZBP1 in both protecting against viral infection through inflammasome activation and potentially contributing to immunopathology when this activation becomes excessive. Understanding the precise regulation of ZBP1-mediated inflammasome activation could provide targets for therapeutic intervention in viral diseases.

How does ZBP1 influence immune cell infiltration in cancer models?

ZBP1 demonstrates significant associations with immune infiltration in cancer models, particularly in clear cell renal cell carcinoma (ccRCC):

Correlation with Immune Cell Populations:

• ZBP1 expression showed strong positive correlation with infiltrating levels of T cells (R = 0.704, p < 0.001) and cytotoxic cells (R = 0.613, p < 0.001) in ccRCC

• In contrast, ZBP1 expression negatively correlated with infiltration of mast cells (R = −0.166, p < 0.001) and Th17 cells (R = −0.264, p < 0.001)

• These differential associations suggest ZBP1 may play a role in shaping the immune microenvironment in tumors

Relationship with Immune Checkpoint Molecules:

• ZBP1 expression positively correlated with multiple immune checkpoint genes in ccRCC, including LAG3, TIGIT, CTLA-4, HAVCR2, SIGLEC15, CD274 (PD-L1), PDCD1 (PD-1), and PDCD1LG2 (PD-L2)

• This association suggests potential implications for immunotherapy response and resistance mechanisms

Clinical Correlations:

• TCGA data analysis revealed that high ZBP1 expression was associated with pathologic T stage (p = 0.008), pathologic stage (p = 0.003), and histologic grade in ccRCC

• These associations suggest ZBP1 may serve as a prognostic biomarker in cancer

The involvement of ZBP1 in both immune cell recruitment and immune checkpoint regulation presents interesting opportunities for cancer research. Understanding how ZBP1 influences the balance between pro- and anti-tumor immune responses could potentially inform immunotherapeutic strategies. Further research is needed to determine whether ZBP1 directly influences immune cell recruitment or whether its expression is simply a marker of certain immune microenvironments.

How does ZBP1 contribute to TLR3/TLR4-mediated inflammatory responses?

ZBP1 plays a significant role in promoting inflammatory responses downstream of TLR3/TLR4 signaling:

Inflammatory Complex Formation:

• ZBP1 promotes the recruitment of RIPK1 to the TLR3/4 adaptor TRIF in a dose-dependent manner

• In ZBP1-deficient macrophages, the binding of RIPK1 to TRAM (TRIF-related adaptor molecule) was delayed following LPS stimulation, supporting a role for ZBP1 in promoting RIPK1 recruitment to TRIF

• ZBP1 deficiency delayed RIPK1 S321 phosphorylation and recruitment of TRAF3, TBK1, and NEMO to RIPK1 in response to both LPS and poly(I:C)

Visualization of Complex Formation:

• Immunofluorescence studies demonstrated that as early as 10 minutes after LPS treatment, TRIF puncta were detectable in wild-type macrophages

• After 30 minutes of LPS treatment, nearly 80% of TRIF puncta colocalized with RIPK1 puncta

• ZBP1 deficiency did not affect TRIF puncta formation but dramatically decreased the colocalization of TRIF- and RIPK1-positive puncta, further supporting the role of ZBP1 in recruiting RIPK1 to TRIF

Timing and Magnitude Effects:

• The level of ZBP1 expression modulates the timing of inflammatory complex formation

• Reconstitution of Zbp1^-/- cells with low levels of ZBP1 accelerated complex formation compared to Zbp1^-/- cells, with inflammatory complex component recruitment occurring at 20 minutes post-stimulation versus 40 minutes in ZBP1-deficient cells

• High levels of ZBP1 enhanced inflammatory complex formation further, with binding of TRAM, TRAF3, TBK1, and NEMO detectable as early as 5 minutes after LPS stimulation

These findings demonstrate that ZBP1 acts as a crucial modulator of TLR3/TLR4-mediated inflammatory responses by regulating the assembly and activation kinetics of signaling complexes. The dose-dependent effect of ZBP1 on complex formation suggests that its expression levels may serve as a rheostat for inflammatory responses.

What are the optimal conditions for immunohistochemistry with ZBP1 antibodies?

Optimizing immunohistochemistry (IHC) with ZBP1 antibodies requires attention to several key parameters:

Antigen Retrieval:

• TE buffer pH 9.0 is the primary recommended antigen retrieval method for ZBP1 IHC

• Alternatively, citrate buffer pH 6.0 may be used for antigen retrieval

• Complete antigen retrieval is critical for detecting ZBP1, which can be present in multiple cellular compartments

Antibody Selection and Dilution:

• For IHC applications, a recommended dilution range of 1:50-1:500 should be tested

• Antibody 13285-1-AP has been validated for human liver cancer tissue and human colon cancer tissue in IHC applications

• Titrate antibody concentration based on tissue type and fixation method

Positive Controls:

• Human liver cancer tissue and human colon cancer tissue serve as positive controls for ZBP1 IHC

• Include known positive samples alongside experimental tissues

Visualization Systems:

• Choose detection systems appropriate for the primary antibody host species

• For rabbit antibodies (such as 13285-1-AP), anti-rabbit secondary antibodies conjugated to HRP or biotin-streptavidin systems are suitable

Counterstaining:

• Nuclear counterstains help distinguish cytoplasmic from nuclear ZBP1 localization

• ZBP1 has been reported to localize in the cytoplasm, cytosol, and nucleus

Validation Approaches:

• Include ZBP1 knockout or knockdown tissues as negative controls where possible

• Consider dual immunofluorescence with other markers to confirm cellular identity and subcellular localization

• Compare IHC results with RNA-seq or qRT-PCR data when available

These recommendations provide a starting point for ZBP1 IHC optimization, but protocol adjustments may be necessary based on specific tissue types, fixation methods, and experimental questions.

How can I design co-immunoprecipitation experiments to study ZBP1's interaction partners?

Designing effective co-immunoprecipitation (Co-IP) experiments to study ZBP1's interaction partners requires careful consideration of several factors:

Antibody Selection:

• Choose antibodies with validated specificity for ZBP1 in IP applications

• Anti-ZBP1 mAb (Zippy-1) has been validated for immunoprecipitation

• Consider using antibodies targeting different epitopes of ZBP1 to avoid potential interference with protein-protein interactions

Lysis and Buffer Conditions:

• Use lysis buffers that preserve protein-protein interactions (e.g., NP-40 or CHAPS-based buffers)

• Include protease and phosphatase inhibitors to prevent degradation and preserve post-translational modifications

• Consider the cellular compartments where interactions occur - ZBP1 has been reported in cytoplasm, cytosol, and nucleus

Stimulation Conditions:

• For studying virus-related interactions, consider time course experiments after viral infection

• LPS or poly(I:C) stimulation enhances formation of ZBP1-containing complexes

• From research findings, ZBP1-RIPK1 interaction kinetics vary with stimulation time and ZBP1 expression levels

Controls:

• Include isotype control antibodies for non-specific binding assessment

• Use ZBP1-deficient cells as negative controls

• For reverse Co-IP validation, perform reciprocal experiments (e.g., IP with anti-RIPK1 and blot for ZBP1)

Identifying Novel Interactions:

• Consider sequential immunoprecipitation for complex purification

• Mass spectrometry analysis of immunoprecipitated complexes can identify novel binding partners

• Validate interactions using multiple techniques (proximity ligation assay, FRET, BiFC)

Specific Interaction Examples:

• ZBP1-RIPK1: Research shows ZBP1 promotes RIPK1 recruitment to TRIF-containing complexes

• ZBP1-RIPK3: Critical for necroptosis initiation during viral infections

• ZBP1-VP22: Viral protein VP22 interacts with ZBP1 to suppress NLRP3 inflammasome activation

When analyzing results, consider that the timing of complex formation is critical - the search results indicate that ZBP1 levels modulate the kinetics of inflammatory complex assembly, with high ZBP1 levels accelerating complex formation to as early as 5 minutes after stimulation .