AIP1 antibodies are polyclonal or monoclonal reagents that target specific epitopes of the AIP1 protein. These antibodies enable researchers to study AIP1's expression, localization, and functional roles in diseases such as cancer, cardiovascular disorders, and neurodegenerative conditions. AIP1 is a Ras GTPase-activating protein (Ras-GAP) with anti-inflammatory and anti-angiogenic properties, making its detection vital for understanding pathological mechanisms .
The Anti-AIP1/Alix Antibody (Cat. No. ABC40, Merck Millipore) is a widely used reagent with the following specifications:
| Property | Details |
|---|---|
| Target | Programmed cell death 6-interacting protein (AIP1/ALIX) |
| Species Reactivity | Human, Mouse, Rat |
| Applications | Western Blotting (WB), Immunofluorescence (IF) |
| Host | Rabbit |
| Format | Affinity Purified |
| Presentation | Purified antibody in 20 mM Tris-HCl, pH 7.2, 150 mM NaCl |
| Quality Level | MQ100 |
This antibody recognizes both AIP1 isoforms (AIP1A and AIP1B) and has been validated in studies involving extracellular vesicles and parasitic nematodes .
AIP1 antibodies have been instrumental in demonstrating AIP1's role as an endogenous inhibitor of VEGF-VEGFR2 signaling. For example:
AIP1-deficient mice exhibit enhanced angiogenesis in corneal and retinal neovascularization models .
Overexpression of AIP1 in knockout mice reduces pathological angiogenesis by inhibiting PI3K-mediated VEGFR2 activation .
AIP1A suppresses TNFα-induced NF-κB signaling and mitochondrial ROS (mitoROS) .
AIP1B, a shorter isoform lacking the N-terminal PH domain, promotes mitoROS and EC activation, linked to atherosclerosis and graft arteriosclerosis .
The ABC40 antibody has been rigorously validated across multiple lots:
| Lot Number | Title |
|---|---|
| 3069700 | Anti-AIP1/Alix |
| 2388320 | Anti-AIP1/Alix - 2388320 |
| 2461579 | Anti-AIP1/Alix - 2461579 |
This antibody has been cited in studies on α-synuclein in Parkinson’s disease (PubMed ID: 30579996) and extracellular vesicles in filarial nematodes (PubMed ID: 29659599) .
AIP1 expression is downregulated in cancers due to epigenetic mechanisms, correlating with poor prognosis .
In cardiovascular diseases, AIP1 isoforms regulate endothelial cell (EC) dysfunction. AIP1A degradation and AIP1B upregulation drive chronic inflammation in atherosclerosis .
KEGG: sce:YMR092C
STRING: 4932.YMR092C
AIP1, also known as ASK1-interacting protein-1 or DAB2-interacting protein (DAB2IP), is a novel member of the Ras GTPase-activating protein family implicated in cell growth inhibition and apoptosis. Its significance in neurodegenerative research stems from its role in mediating apoptotic pathways in Alzheimer's disease. Studies have shown that AIP1 is elevated in the brains of AD Tg2576 mice and Aβ1-42 treated cerebral microvascular endothelial cells (CECs), suggesting its involvement in AD pathogenesis. AIP1 functions as a positive regulator in cell apoptosis by mediating activation of ASK1, which subsequently activates downstream pathways including JNK and p53, potentially contributing to neuronal and cerebral endothelial cell death in AD .
AIP1 primarily functions as an adaptor molecule in cellular signaling pathways, particularly in TNF signaling. In the context of ASK1 activation, AIP1 recruits phosphatase PP2A to dephosphorylate the 14-3-3 binding site on ASK1, leading to the dissociation of this inhibitory protein. This dissociation allows ASK1 activation by the TNFR1 signaling complex. In vascular endothelial cells, AIP1 also acts as an inhibitor of VEGFR2 signaling, regulating angiogenesis and lymphangiogenesis. In Alzheimer's disease models, Aβ1-42 treatment induces the interaction between AIP1 and ASK1, which leads to the dissociation of ASK1 from its inhibitor 14-3-3, thus activating ASK1 and triggering apoptotic pathways through JNK and p53 activation .
AIP1 antibodies are valuable tools in several research applications:
Protein Expression Analysis: Western blotting to detect and quantify AIP1 expression levels in various tissues and cell types, particularly in neurodegenerative disease models.
Co-immunoprecipitation Studies: Investigating protein-protein interactions, such as between AIP1 and ASK1 or other signaling molecules.
Immunohistochemistry/Immunofluorescence: Examining the localization and distribution of AIP1, especially in brain tissue sections from AD models.
Mechanistic Studies: Exploring the role of AIP1 in cell death mechanisms, particularly in the context of Aβ-induced neurotoxicity.
Therapeutic Target Validation: Evaluating AIP1 as a potential therapeutic target in neurodegenerative diseases .
When designing experiments to investigate AIP1's role in Alzheimer's disease, consider the following methodological approach:
Model Selection:
In vivo: Use transgenic mouse models such as Tg2576 mice (which overexpress human APP695 with the "Swedish" mutation) with age-matched non-transgenic littermates as controls.
In vitro: Human brain cerebral microvascular endothelial cells (CECs) treated with Aβ1-42 provide a suitable cellular model.
Expression Analysis:
Measure AIP1 mRNA levels using real-time PCR.
Assess protein expression via Western blotting with appropriate AIP1 antibodies.
Compare expression in AD models versus controls.
Interaction Studies:
Perform co-immunoprecipitation with anti-AIP1 antibody followed by Western blot with ASK1 antibody to examine AIP1-ASK1 interaction.
Similarly, investigate ASK1-14-3-3 interaction and how it's affected by Aβ1-42 and AIP1.
Functional Studies:
Use siRNA to silence AIP1 expression (50 nM, transfected using Lipofectamine).
Examine downstream effects on ASK1 phosphorylation status, particularly at Ser-967.
Assess activation of downstream targets such as JNK and p53.
Perform TUNEL staining to evaluate apoptosis in the presence/absence of AIP1 silencing .
The detection of AIP1-ASK1 interactions requires specific methodological approaches:
Co-immunoprecipitation (Co-IP):
The gold standard method involves using primary anti-AIP1 antibody for immunoprecipitation followed by Western blot with ASK1 antibody.
Alternatively, immunoprecipitate with anti-ASK1 antibody and detect AIP1 in the precipitate.
Include appropriate controls: IgG control, input controls, and positive controls.
Proximity Ligation Assay (PLA):
A more sensitive method to detect protein-protein interactions in situ.
Requires specific primary antibodies against AIP1 and ASK1 from different species.
Provides visualization of interactions within intact cells.
FRET/BRET Analysis:
For live-cell analysis of protein interactions.
Requires fusion proteins (AIP1-CFP and ASK1-YFP for FRET).
Useful for temporal analysis of interactions following treatments such as Aβ1-42.
Experimental Conditions:
Verifying AIP1 antibody specificity is crucial for reliable research outcomes:
Positive and Negative Controls:
Positive control: Tissues/cells known to express high levels of AIP1 (e.g., vascular endothelial cells).
Negative control: Use AIP1 siRNA knockdown samples or tissues from AIP1 knockout models.
Western Blot Validation:
Confirm single band at expected molecular weight (approximately 110 kDa for human AIP1).
Perform peptide competition assay by pre-incubating antibody with immunizing peptide.
Cross-validate with multiple antibodies targeting different epitopes of AIP1.
Immunoprecipitation Controls:
Include IgG control in Co-IP experiments.
Validate AIP1 knockdown efficiency to correlate with reduced antibody signal.
Cross-Reactivity Assessment:
Test antibody against recombinant AIP1 versus related proteins from the Ras GTPase-activating protein family.
Perform bioinformatic analysis of antibody epitope sequence for potential cross-reactivity.
Secondary Antibody Controls:
To comprehensively analyze AIP1's impact on ASK1 phosphorylation status:
Phosphorylation Site Mapping:
Focus on key regulatory sites, particularly Ser-967, where dephosphorylation indicates ASK1 activation.
Use phospho-specific antibodies for Western blotting.
Consider mass spectrometry for comprehensive phosphorylation profile analysis.
Temporal Dynamics Analysis:
Perform time-course experiments after Aβ1-42 treatment (e.g., 0, 6, 12, 24, 48 hours).
Analyze changes in ASK1 phosphorylation concurrent with AIP1-ASK1 binding.
Correlate with 14-3-3 dissociation timeline.
Site-Directed Mutagenesis:
Generate phosphomimetic (S967D) or non-phosphorylatable (S967A) ASK1 mutants.
Examine how mutations affect AIP1 binding and downstream signaling.
Phosphatase Inhibition Studies:
Use PP2A inhibitors (e.g., okadaic acid) to determine if AIP1-mediated ASK1 dephosphorylation depends on PP2A.
Assess the effects on 14-3-3 binding and ASK1 activation.
Quantification and Data Analysis:
When facing contradictory results in AIP1-ASK1 pathway studies, consider these methodological factors:
Cell/Tissue Type Variations:
AIP1 function may differ between neuronal cells, cerebral endothelial cells, and other cell types.
Different cell types may have varying levels of pathway components (ASK1, 14-3-3, PP2A).
Experimental Conditions:
Aβ preparation methods significantly impact bioactivity and aggregation state.
Concentration-dependent effects: 5 μM versus 10-20 μM of Aβ1-42 may yield different results.
Duration of treatment influences temporal dynamics of protein interactions.
Antibody Considerations:
Different antibodies may recognize distinct epitopes or isoforms of AIP1.
Antibody specificity and sensitivity vary between applications (WB, IP, IHC).
Knockout/Knockdown Efficiency:
Incomplete AIP1 silencing can yield partial phenotypes.
Compensatory mechanisms may emerge in chronic knockdown/knockout models.
Context-Dependent Signaling:
AIP1-ASK1 interaction might have different outcomes depending on cellular stress levels.
Crosstalk with parallel pathways (e.g., oxidative stress responses) can modify outcomes.
Methodological Approach to Resolve Contradictions:
AIP1 antibodies can be employed to explore several alternative mechanisms:
VEGFR2 Signaling Regulation:
AIP1 functions as an inhibitor of VEGFR2 signaling in vascular endothelial cells.
Use AIP1 antibodies for co-immunoprecipitation studies with VEGFR2.
Analyze downstream angiogenic pathways in cerebrovascular contexts of AD.
TNF Signaling Pathway:
AIP1 serves as an adaptor molecule in TNF signaling.
Investigate inflammatory responses in neurodegenerative contexts.
Analyze AIP1-TNF receptor complex formation using proximity ligation assays.
Ras GTPase Regulation:
As a member of the Ras GTPase-activating protein family, AIP1 may regulate Ras signaling.
Examine effects on MAPK pathways beyond JNK.
Study potential links to synaptic plasticity and memory formation.
BBB Integrity and Cerebrovascular Function:
Given AIP1's expression in cerebral endothelial cells, investigate its role in BBB maintenance.
Use immunohistochemistry to analyze AIP1 localization at tight junctions.
Correlate with markers of BBB breakdown in AD models.
Autophagy and Protein Degradation Pathways:
Researchers frequently encounter these challenges when performing co-immunoprecipitation with AIP1 antibodies:
Weak or Absent Signal Issues:
Problem: Failure to detect AIP1-ASK1 interaction.
Solutions:
Use chemical crosslinking (e.g., DSP) to stabilize transient interactions.
Optimize lysis conditions; try different buffers (NP-40, RIPA, etc.).
Increase antibody amount (typically 2-5 μg per 500 μg protein).
Ensure adequate protein expression (particularly for ASK1).
High Background Issues:
Problem: Non-specific bands or high background.
Solutions:
Include proper washing steps (minimum 4-5 washes).
Use more stringent wash buffers for final washes.
Pre-clear lysates with Protein A/G beads before immunoprecipitation.
Optimize antibody concentration and incubation time.
Inconsistent Results:
Problem: Variable detection of AIP1-ASK1 interaction.
Solutions:
Standardize Aβ1-42 preparation protocol.
Control cell density and treatment duration precisely.
Include positive controls (e.g., hydrogen peroxide treatment also activates ASK1).
Use fresh lysates; avoid freeze-thaw cycles.
Technical Verification Approaches:
Optimizing AIP1 knockdown requires attention to several methodological aspects:
siRNA Design and Selection:
Test multiple siRNA sequences targeting different regions of AIP1 mRNA.
Validate knockdown efficiency by Western blot and qRT-PCR.
Consider using pool of 3-4 validated siRNAs for more consistent knockdown.
Design siRNAs with 30-50% GC content and avoid sequences with internal repeats.
Transfection Optimization:
Cell Type Considerations: For cerebral endothelial cells, Lipofectamine RNAiMAX typically works well.
Concentration Optimization: Test different siRNA concentrations (10-100 nM); 50 nM is often effective.
Cell Density: Transfect at 60-70% confluence for optimal balance between transfection efficiency and cell health.
Serum Conditions: Some cells require serum-free conditions during transfection; test with/without serum.
Timing Considerations:
Knockdown Duration: AIP1 protein has a half-life of approximately 24-48 hours; maximum knockdown typically occurs 48-72 hours post-transfection.
Experiment Planning: For Aβ1-42 treatment experiments, add Aβ1-42 24-48 hours post-transfection.
Time-course Analysis: Verify knockdown at multiple timepoints (24, 48, 72, 96 hours).
Controls and Validation:
Distinguishing direct from indirect effects requires sophisticated experimental approaches:
Protein Domain Mapping and Mutational Analysis:
Generate AIP1 domain deletion/mutation constructs.
Identify minimal regions required for ASK1 binding using in vitro pull-down assays.
Create binding-deficient mutants for functional studies.
In Vitro Reconstitution Assays:
Use purified recombinant proteins (AIP1, ASK1, 14-3-3) to reconstitute the interaction system.
Test if AIP1 alone is sufficient to dissociate ASK1-14-3-3 complexes.
Add purified PP2A to determine direct versus phosphatase-dependent effects.
Temporal Resolution Experiments:
Perform high-resolution time-course analysis (minutes to hours after Aβ1-42 addition).
Use protein synthesis inhibitors (cycloheximide) to block indirect effects requiring new protein synthesis.
Apply specific kinase/phosphatase inhibitors to block potential intermediate steps.
Proximity-Based Approaches:
Use FRET/BRET sensors to monitor real-time protein interactions.
Apply BioID or APEX2 proximity labeling to identify proteins in the immediate vicinity of AIP1 during activation.
Perform super-resolution microscopy to visualize spatial relationships during ASK1 activation.
Data Analysis and Integration:
Integrating AIP1 antibodies with complementary research tools enables sophisticated pathway analysis:
Multi-omics Integration:
Proteomics: Combine AIP1 immunoprecipitation with mass spectrometry to identify novel interaction partners.
Phosphoproteomics: Map phosphorylation changes downstream of AIP1-ASK1 activation.
Transcriptomics: Correlate AIP1 activity with gene expression profiles using RNA-seq after AIP1 modulation.
Metabolomics: Identify metabolic changes associated with AIP1-mediated apoptosis.
Advanced Imaging Approaches:
Super-resolution Microscopy: Use AIP1 antibodies with techniques like STORM or PALM to visualize subcellular localization at nanoscale resolution.
Live-cell Imaging: Combine with fluorescent reporters for JNK or p53 activity to monitor real-time pathway activation.
Correlative Light-Electron Microscopy: Link AIP1 localization to ultrastructural changes during apoptosis.
CRISPR-based Technologies:
CRISPR Activation/Interference: Precisely modulate AIP1 expression levels instead of complete knockdown.
CRISPR Knock-in: Tag endogenous AIP1 with fluorescent proteins or epitope tags for tracking.
CRISPR Screens: Identify genes that modify AIP1-dependent phenotypes.
Microfluidic and Organ-on-chip Approaches:
Extending AIP1 research to other neurodegenerative contexts requires these methodological considerations:
Cross-disease Model Comparison:
Analyze AIP1 expression and ASK1 activation in models of Parkinson's disease, ALS, and Huntington's disease.
Use standardized protocols for tissue processing and analysis across disease models.
Develop a comparative analysis framework for AIP1 pathway activation patterns.
Patient-derived Models:
Utilize iPSC-derived neurons or cerebral organoids from patients with different neurodegenerative diseases.
Apply AIP1 antibodies for immunostaining and biochemical analysis.
Compare with isogenic controls to identify disease-specific alterations.
Proteotoxicity Connections:
Investigate AIP1's response to different protein aggregates (α-synuclein, TDP-43, huntingtin).
Use cellular models with inducible expression of disease-associated proteins.
Apply co-immunoprecipitation to detect potential direct interactions with aggregation-prone proteins.
Neuroinflammatory Context:
Examine AIP1 in microglia and astrocytes under inflammatory conditions.
Use co-culture systems to study cell-type specific contributions.
Analyze AIP1's role in inflammasome activation common to multiple neurodegenerative diseases.
Translational Research Framework:
Quantitative analysis of AIP1-ASK1 interactions can guide therapeutic development:
Dose-Response Relationship Mapping:
Titrate Aβ1-42 concentrations (1-50 μM) and quantify AIP1-ASK1 binding.
Determine EC50 values for AIP1-ASK1 interaction and downstream effects.
Identify threshold levels required for apoptotic responses.
Pharmacological Intervention Analysis:
Screening Approach: Test compounds that disrupt AIP1-ASK1 interaction.
Quantification Method: Use ELISA-based or BRET-based quantitative assays.
Data Analysis: Calculate IC50 values and binding kinetics.
| Compound Class | IC50 (μM) | Effect on Downstream JNK Activation | Effect on Cell Viability |
|---|---|---|---|
| ASK1 Inhibitors | 0.1-5.0 | Complete inhibition | >80% protection |
| 14-3-3 Stabilizers | 1.0-10.0 | Partial inhibition | 40-60% protection |
| AIP1-ASK1 Interface Blockers | 0.5-8.0 | Selective inhibition | 60-75% protection |
Structure-Function Analysis:
Identify critical binding interfaces between AIP1 and ASK1.
Perform alanine scanning mutagenesis to map key interaction residues.
Develop computational models of the AIP1-ASK1 complex for virtual screening.
Translational Biomarkers:
Develop quantitative assays for AIP1 pathway activation in accessible biofluids.
Correlate AIP1-ASK1 complex levels with disease progression markers.
Establish AIP1 pathway activation thresholds that predict neurodegeneration.
Therapeutic Modality Evaluation:
Evaluating AIP1 as a biomarker requires systematic assessment:
Analytical Validation:
Antibody Specificity: Validate antibodies for detecting AIP1 in various biological matrices (CSF, plasma, serum).
Assay Performance: Determine precision, accuracy, sensitivity, and specificity of AIP1 detection methods.
Sample Stability: Assess pre-analytical variables (collection, storage, freeze-thaw) on AIP1 measurements.
Clinical Validation:
Cross-sectional Studies: Compare AIP1 levels between AD patients and healthy controls.
Longitudinal Assessment: Track changes in AIP1 pathway activation over disease progression.
Differential Diagnosis: Evaluate AIP1's ability to distinguish between different neurodegenerative diseases.
Correlation with Established Biomarkers:
Analyze relationship with Aβ42, total tau, and phospho-tau in CSF.
Compare with neuroimaging biomarkers (amyloid PET, tau PET).
Assess correlation with cognitive decline measures.
Statistical Considerations:
Determine sensitivity, specificity, positive/negative predictive values.
Establish reference ranges in healthy populations.
Develop multivariate models incorporating AIP1 with other biomarkers.
Practical Implementation Aspects:
Interpreting AIP1 antibody results in patient samples requires careful consideration:
Sample Type Considerations:
Post-mortem Brain Tissue: Account for post-mortem interval effects on protein degradation.
CSF Samples: Consider protein concentration differences and potential blood contamination.
Blood-derived Samples: Evaluate cellular sources of AIP1 in circulation.
Patient-derived Cells: Account for reprogramming effects in iPSCs or culture effects on primary cells.
Clinical Data Integration:
Correlate AIP1 levels/activity with detailed clinical phenotyping.
Stratify by disease stage, age of onset, and rate of progression.
Consider genetic background (e.g., APOE genotype) as potential modifier.
Control Selection and Matching:
Match controls and cases for age, sex, and relevant comorbidities.
Consider medication effects on ASK1 pathway activity.
Include disease controls (non-AD neurodegenerative conditions).
Data Normalization and Analysis:
Normalize to appropriate housekeeping proteins for Western blots.
Account for batch effects in large-scale studies.
Use appropriate statistical approaches for small sample sizes common in patient studies.
Reproducibility Considerations:
Proper antibody handling is critical for research reproducibility:
Storage Recommendations:
Primary Storage Condition: Store at -20°C for long-term storage (avoid repeated freeze-thaw cycles).
Working Aliquots: Prepare small aliquots (10-20 μL) to minimize freeze-thaw cycles.
Short-term Storage: Keep at 4°C for up to 2 weeks during active use periods.
Avoid Light Exposure: For fluorophore-conjugated antibodies, protect from light.
Handling Best Practices:
Temperature Transitions: Allow antibodies to equilibrate to room temperature before opening.
Contamination Prevention: Use sterile technique when handling antibody solutions.
Concentration Maintenance: Brief centrifugation after thawing to collect solution at the bottom.
Solution Preparation: Dilute in recommended buffers with appropriate blocking agents.
Stability Testing and Monitoring:
Regular Validation: Test antibody performance periodically against positive controls.
Record Keeping: Maintain logs of freeze-thaw cycles and lot numbers.
Comparison Controls: Include previously validated antibody preparations when testing new lots.
Sensitivity Tracking: Monitor for decreased sensitivity over time.
Application-specific Considerations:
Advanced data analysis enhances experimental interpretation:
Image Analysis for Immunofluorescence:
Colocalization Quantification: Use Pearson's or Mander's coefficients to quantify AIP1-ASK1 colocalization.
Subcellular Distribution: Employ automated segmentation for nuclear vs. cytoplasmic AIP1 quantification.
Signal Normalization: Correct for background and autofluorescence systematically.
3D Analysis: Use z-stack confocal imaging for volumetric analysis of protein interactions.
Western Blot Quantification:
Dynamic Range Optimization: Ensure quantification within linear range of detection.
Normalization Strategies: Use total protein normalization (e.g., REVERT staining) rather than single housekeeping proteins.
Band Intensity Analysis: Apply automated densitometry with consistent boundary selection.
Statistical Approaches: Use appropriate tests for non-normally distributed data common in blot quantification.
Multi-parameter Data Integration:
Principal Component Analysis: Identify patterns across multiple AIP1 pathway components.
Hierarchical Clustering: Group experimental conditions based on AIP1 pathway activation patterns.
Correlation Networks: Map relationships between AIP1, ASK1, JNK, and p53 activation.
Machine Learning Approaches: Develop predictive models for cell death based on early AIP1 pathway activation markers.
Temporal Data Analysis:
Time-series Processing: Apply smoothing algorithms for noisy time-course data.
Rate Calculations: Determine rates of change in protein interactions rather than just endpoints.
Signal Deconvolution: Separate overlapping temporal processes in pathway activation.
Kinetic Modeling: Fit experimental data to mathematical models of the AIP1-ASK1 pathway .
Cross-model comparison requires methodological standardization:
Standardization Framework:
Core Protocol Development: Establish shared protocols for key assays (Western blot, Co-IP, etc.).
Reference Standards: Use recombinant protein standards for absolute quantification.
Reporting Guidelines: Implement detailed methods reporting using standardized templates.
Positive Controls: Include universally responsive systems (e.g., H2O2 treatment) as calibrators.
Model-specific Considerations:
Cell Lines vs. Primary Cells: Account for immortalization effects on signaling pathways.
Species Differences: Consider sequence variations between human, mouse, and rat AIP1.
Brain Region Specificity: Compare equivalent anatomical regions across models.
Age-matching: Critical for AD models where age significantly impacts pathology.
Normalization and Scaling:
Fold-change Reporting: Present data as fold-change relative to model-specific controls.
Z-score Transformation: Allow comparison of relative changes across diverse baselines.
Response Curve Calibration: Generate full dose-response curves for cross-model comparison.
Internal Calibrators: Use conserved pathway components as internal references.
Meta-analysis Approaches:
Effect Size Calculation: Convert diverse experimental outcomes to standardized effect sizes.
Heterogeneity Assessment: Quantify between-model variability in AIP1 responses.
Random-effects Modeling: Account for inherent biological variation between models.
Sensitivity Analysis: Identify model-specific factors that influence AIP1 pathway findings .