WIPI2 Antibody

What is WIPI2 and why is it important in autophagy research?

WIPI2 (WD Repeat Domain Phosphoinositide Interacting 2) is a critical component of the autophagy machinery that controls intracellular degradation processes. It functions as a key PtdIns3P effector required for recruiting the ATG12-ATG5-ATG16L1 complex, which facilitates LC3 lipidation and autophagosome biogenesis during nonselective macroautophagy . The protein has a molecular weight of approximately 49 kDa and is the mammalian homologue of the yeast ATG18 gene .

WIPI2 binds to the omegasome, a phosphatidylinositol 3-phosphate (PI3P) rich domain of the endoplasmic reticulum from which mature autophagosomes develop . Recent research has revealed WIPI2's involvement in selective autophagy pathways, including mitophagy and xenophagy, making it a crucial target for studying various cellular degradation mechanisms .

What applications are most reliable for WIPI2 antibody detection?

Based on extensive validation data, WIPI2 antibodies have demonstrated reliable performance in the following applications:

For optimal results in immunohistochemistry, antigen retrieval with TE buffer pH 9.0 is recommended, though citrate buffer pH 6.0 may be used as an alternative . Each antibody should be titrated in the specific experimental system to obtain optimal results, as performance can be sample-dependent .

How can I validate the specificity of my WIPI2 antibody?

A multi-step validation approach is recommended:

• Positive and negative controls: Use cell lines known to express WIPI2 (such as HeLa or RAW 264.7) as positive controls. WIPI2 knockout cell lines (using CRISPR-Cas9) serve as excellent negative controls .

• siRNA knockdown verification: Transfect cells with siRNA against WIPI2 (si WIPI2) for 72 hours to reduce endogenous WIPI2 expression, then confirm reduced antibody signal in Western blot or immunofluorescence .

• Molecular weight confirmation: Verify that your antibody detects a band at the expected molecular weight of 49 kDa in Western blotting .

• Cross-reactivity assessment: If using the antibody across species, verify cross-reactivity with the target species. Many WIPI2 antibodies have been validated with human and mouse samples .

• Functional validation: Test antibody performance in autophagy induction conditions (e.g., starvation in EBSS) to observe expected translocation to autophagosomal structures .

How does WIPI2 regulate mitophagy and what methods can be used to study this interaction?

WIPI2 plays a critical regulatory role in PINK1-PRKN/parkin-mediated mitophagy through multiple mechanisms:

• Recruitment to damaged mitochondria: Upon mitochondrial depolarization (e.g., using CCCP or oligomycin/antimycin A), WIPI2 is recruited to damaged mitochondria .

• VCP complex interaction: WIPI2 binds to and promotes AAA-ATPase VCP/p97 (valosin containing protein) translocation to damaged mitochondria. The VCP-UFD1-NPLOC4 complex then extracts and delivers ubiquitinated outer mitochondrial membrane (OMM) proteins to the 26S proteasome for degradation .

• OMM protein degradation: WIPI2 depletion impairs the degradation of OMM proteins like MFN2 and TOMM20, as well as inner mitochondrial membrane proteins such as TIMM23 and MT-CO2 .

Methodological approaches to study WIPI2 in mitophagy:

What is the role of WIPI2 in cancer research and what methodologies are most effective?

Research has revealed significant implications of WIPI2 in cancer biology, particularly in colorectal cancer:

• Expression analysis: Gene expression profiling data shows that WIPI2 is significantly more expressed in colorectal cancer tissues than in normal tissues .

• Prognostic value: High WIPI2 expression predicts poor prognosis for colorectal cancer patients, as demonstrated by Cox proportional risk regression models (HR>1.9) .

• Cell proliferation impact: Knockdown of WIPI2 expression inhibits the growth and proliferation of HCT116 and HT29 colorectal cancer cell lines .

• Ferroptosis regulation: WIPI2 potentially regulates cancer cell ferroptosis, as knockdown decreases ACSL4 expression and increases GPX4 expression .

Recommended methodological approaches:

• Expression analysis in patient samples:

  • TCGA database analysis comparing tumor vs. normal tissues

  • Immunohistochemistry of WIPI2 in tissue microarrays

  • Correlation with clinical outcomes using Kaplan-Meier survival analysis

• Functional studies in cell lines:

  • siRNA-mediated knockdown of WIPI2 (72h transfection recommended)

  • Cell viability assays (e.g., after treatment with ferroptosis inducers like Erastin)

  • Western blot analysis of ferroptosis markers (ACSL4, GPX4)

  • Colony formation assays to assess long-term proliferation effects

• Mechanistic investigations:

  • Analysis of autophagy and ferroptosis pathway proteins

  • Measurement of lipid peroxidation (e.g., BODIPY-C11 staining)

  • Assessment of cellular iron levels and ROS production

How can I investigate WIPI2's interactions with the ULK1 complex?

Recent research has identified interactions between WIPI2 and the ULK1 complex that are critical for autophagosome formation. To investigate these interactions:

• Co-immunoprecipitation approaches:

  • Immunopurify endogenous WIPI2 from cells (e.g., HEK293A) and probe for ULK1 and ATG13

  • Use HEK293A WIPI2 KO cells rescued with GFP-WIPI2b WT or mutants (e.g., RERE mutant that abolishes ATG16L1 binding)

  • Pre-treat cells with crosslinking agents like dithiobis(succinimidyl propionate)/Lomat's reagent (DSP) at 0.5 mM in PBS for 30 min on ice before lysis

• Protein domain analysis:

  • Use GFP-WIPI2b constructs with specific mutations (e.g., R108E/R125E) to disrupt ATG16L1 binding

  • Compare ULK1 binding between wild-type and mutant WIPI2 constructs

  • Analyze whether ULK1 interaction increases when WIPI2's binding to ATG16L1 is abolished

• Functional assays:

  • Assess autophagosome formation in cells expressing WIPI2 mutants

  • Monitor LC3 lipidation (LC3-I to LC3-II conversion) by Western blot

  • Evaluate the recruitment of ATG16L1 complex to phagophores

What are the optimal conditions for immunoprecipitation of WIPI2?

Successful immunoprecipitation of WIPI2 requires specific considerations:

• Crosslinking recommendations:

  • Pre-treat cells with dithiobis(succinimidyl propionate)/Lomat's reagent (DSP) at 0.5 mM in PBS for 30 min on ice

  • This stabilizes protein-protein interactions before cell lysis

• Lysis conditions:

  • Use 1% Triton TNTE buffer for cell lysis

  • Alternative: For GFP-tagged WIPI2, protein complexes can be pulled down using GFP-Trap beads (ChromoTek)

• Immunoprecipitation approaches:

  • For endogenous WIPI2: Use specific antibodies plus protein A beads

  • For tagged WIPI2: Use either GFP-Trap beads or anti-FLAG M2 affinity gel (for FLAG-tagged constructs)

• Experimental conditions:

  • Compare fed cells vs. cells starved for 1 hr in Earle's balanced salt solution (EBSS) to identify starvation-dependent interactions

  • For mitophagy studies, treat cells with mitophagy inducers (CCCP or oligomycin/antimycin A) before immunoprecipitation

What controls should be included when studying WIPI2 in knockout or knockdown experiments?

When conducting WIPI2 knockout or knockdown experiments, include these essential controls:

• Knockdown validation controls:

  • Verify WIPI2 reduction by Western blot (protein level) and qRT-PCR (mRNA level)

  • Use multiple siRNA sequences targeting different regions of WIPI2 to rule out off-target effects

  • Include a non-targeting siRNA control (siNC) treated with the same transfection reagent

• Knockout validation controls:

  • Confirm complete knockout by Western blot and genomic DNA sequencing of the targeted region

  • Use multiple guide RNAs targeting different exons of WIPI2

  • Include wild-type cells subjected to the same CRISPR-Cas9 procedure but with non-targeting guides

• Rescue experiments:

  • Re-express WIPI2 in knockout cells to restore function and confirm phenotype specificity

  • Use both wild-type WIPI2 and functional mutants (e.g., RERE mutant) for mechanistic insights

• Functional controls:

  • For autophagy studies: Monitor LC3 lipidation (known to be impaired in WIPI2 KO cells)

  • For mitophagy studies: Assess degradation of mitochondrial markers (OMM and IMM proteins)

  • For cancer cell studies: Include cell viability and proliferation assays

How can I optimize WIPI2 detection in immunofluorescence studies?

For optimal detection of WIPI2 by immunofluorescence:

• Fixation methods:

  • 4% paraformaldehyde (10-15 minutes at room temperature) works well for most applications

  • For better detection of membrane-associated WIPI2, methanol fixation (-20°C for 5 minutes) may provide clearer results

• Antibody optimization:

  • Start with recommended dilutions (typically 1:200-1:800) and optimize for your specific system

  • Incubate primary antibodies overnight at 4°C for best results

  • For co-staining experiments, carefully select compatible secondary antibodies to avoid cross-reactivity

• Signal enhancement strategies:

  • Use tyramide signal amplification for weak signals

  • Consider detergent concentration in permeabilization step (0.1-0.3% Triton X-100)

  • Optimize blocking conditions (3-5% BSA or normal serum from secondary antibody host species)

• Autophagy induction conditions:

  • Starve cells in EBSS for 1-2 hours to induce autophagy and enhance WIPI2 puncta formation

  • For mitophagy studies, treat with CCCP (10-20 μM) for 3-6 hours

  • Include bafilomycin A1 treatment to prevent autophagosome-lysosome fusion and accumulate visible structures

How is WIPI2 implicated in neurodegenerative diseases?

WIPI2 plays a significant role in neurodegenerative diseases through its function in mitophagy:

• Parkinson's disease connection:

  • WIPI2 participates in PINK1-PRKN-mediated mitophagy, which is impaired in Parkinson's disease

  • WIPI2 promotes VCP recruitment to damaged mitochondria, facilitating mitochondrial quality control

  • Defective mitophagy is associated with accumulation of damaged mitochondria in neurons

• Alzheimer's disease implications:

  • Mitophagy is impaired in Alzheimer's disease

  • WIPI2 is a critical positive upstream regulator of mitophagy that could be targeted therapeutically

• Research approaches:

  • Study WIPI2 expression and function in patient-derived neurons or brain tissue

  • Assess mitophagy flux in neuronal models with altered WIPI2 expression

  • Investigate WIPI2 interaction with disease-associated proteins

  • Develop genetic or pharmacological approaches to upregulate WIPI2 for therapeutic applications

What is the relationship between WIPI2 and ferroptosis in cancer research?

Recent studies have revealed important connections between WIPI2 and ferroptosis, particularly in colorectal cancer:

• Regulatory relationship:

  • WIPI2 knockdown decreases ACSL4 expression and increases GPX4 expression, suggesting that WIPI2 positively regulates ferroptosis in colorectal cancer cells

  • Erastin (a ferroptosis inducer) treatment enhances WIPI2 expression while decreasing GPX4 expression

• Functional impact:

  • WIPI2 knockdown cells show increased resistance to Erastin-induced growth inhibition

  • This suggests Erastin induces colorectal cancer ferroptosis through the WIPI2/GPX4 pathway

• Methodological approaches for investigation:

  • Compare the effects of ferroptosis inducers between WIPI2 wildtype and knockdown/knockout cells

  • Measure lipid peroxidation levels using C11-BODIPY or MDA assays

  • Assess iron metabolism through ferritin and transferrin receptor expression

  • Analyze rescue experiments with ferroptosis inhibitors (Ferrostatin-1, Liproxstatin-1)

  • Examine the expression correlation between WIPI2 and ferroptosis markers in patient samples

How can WIPI2 antibodies be used to investigate bacterial infection responses?

WIPI2 is involved in xenophagy (selective autophagy targeting pathogens), making it relevant for infectious disease research:

• Salmonella infection model:

  • WIPI2 isoform 4 binds to the membrane surrounding Salmonella and recruits the ATG12-5-16L1 complex

  • This initiates LC3 conjugation, autophagosomal membrane formation, and engulfment of Salmonella

• Experimental approaches:

  • Infect mammalian cell cultures with Salmonella Typhimurium SL 1344 at appropriate MOI (e.g., 100 for HeLa cells, 25 for MEF cell lines)

  • Centrifuge at 2000 × g for 10 min at room temperature and incubate at 37°C for 20 min

  • Replace medium with fresh medium containing gentamicin (50 μg/ml) and incubate at 37°C for 1 hr

  • Use immunofluorescence to visualize WIPI2 recruitment to bacteria

  • Perform colony-forming unit assays to assess bacterial clearance

• Analysis methods:

  • Quantify colocalization of WIPI2 with bacterial markers

  • Compare xenophagy efficiency between WIPI2 wildtype and knockout cells

  • Assess the requirement for different WIPI2 domains/isoforms in bacterial targeting

How should I design experiments to investigate the differential roles of WIPI2 isoforms?

WIPI2 has multiple splice isoforms (WIPI2a-f) with potentially distinct functions:

• Isoform-specific experimental design:

  • Generate WIPI2 knockout cells as a clean background

  • Create rescue constructs expressing specific isoforms (particularly WIPI2b, the most studied isoform)

  • Use mutagenesis to introduce specific mutations (e.g., RERE mutant that abolishes ATG16L1 binding)

• Functional assays to compare isoforms:

  • Assess autophagosome formation efficiency

  • Measure LC3 lipidation levels by Western blot

  • Evaluate mitochondrial recruitment during mitophagy

  • Quantify bacterial clearance in infection models

• Protein interaction analysis:

  • Compare binding partners between isoforms using immunoprecipitation followed by mass spectrometry

  • Assess ULK1 complex binding to different isoforms

  • Evaluate membrane localization patterns by fractionation and microscopy

• Domain-specific functions:

  • Create chimeric constructs exchanging domains between isoforms

  • Use point mutations to disrupt specific functions (PtdIns3P binding, protein-protein interactions)

  • Assess the impact on autophagy, mitophagy, and xenophagy processes

What methodological approaches can resolve contradictory findings about WIPI2 in cell death pathways?

Research has revealed seemingly contradictory roles of WIPI2 in different cell death pathways:

• Comprehensive cell death profiling:

  • Compare multiple cell death inducers in the same cellular model

  • WIPI2 KO cells show resistance to mitochondrial damage-induced death but increased sensitivity to amino acid starvation (EBSS)-induced death

  • Use multiple cell death assays (Annexin V/PI, TUNEL, LDH release, caspase activation)

• Context-dependent analysis:

  • Examine WIPI2 function across different cell types (cancer vs. normal)

  • Compare acute vs. chronic knockdown/knockout effects

  • Assess the impact of cellular energetic state and nutrient availability

• Pathway intersection analysis:

  • Investigate crosstalk between autophagy, apoptosis, and ferroptosis pathways

  • Determine whether WIPI2's role in mitophagy affects cell fate decisions

  • Use specific inhibitors of each pathway to dissect mechanisms

• Temporal dynamics assessment:

  • Employ inducible knockdown/knockout systems to control timing of WIPI2 depletion

  • Monitor cell death progression over time with live-cell imaging

  • Use pulse-chase experiments to track protein degradation kinetics

What are the best approaches for studying WIPI2 post-translational modifications?

Post-translational modifications of WIPI2 may regulate its function in autophagy and selective autophagy pathways:

• PTM identification strategies:

  • Immunoprecipitate WIPI2 followed by mass spectrometry analysis

  • Use phospho-specific antibodies to detect known phosphorylation sites

  • Employ protein mobility shift assays to detect modifications

• Functional analysis of PTMs:

  • Generate phosphomimetic (S/T to D/E) and phospho-deficient (S/T to A) mutants

  • Assess the impact on WIPI2 localization, protein interactions, and autophagy/mitophagy functions

  • Compare PTM patterns under different autophagy-inducing conditions

• Regulatory enzyme identification:

  • Use pharmacological inhibitors or genetic approaches to identify kinases or other enzymes responsible for WIPI2 modifications

  • Verify direct modification using in vitro kinase assays

  • Assess enzyme-WIPI2 interactions by co-immunoprecipitation

• PTM crosstalk analysis:

  • Investigate how multiple modifications on WIPI2 interact functionally

  • Determine whether PTMs affect WIPI2's interaction with the ULK1 complex or ATG16L1

  • Assess the impact on WIPI2's binding to PtdIns3P and membrane recruitment