Fbxw4 Antibody

What is FBXW4 and what biological processes is it involved in?

FBXW4 (F-box and WD repeat domain containing 4) is a protein that functions within the ubiquitin-proteasome pathway, recognizing phosphorylated proteins and promoting their ubiquitination and degradation . It belongs to the F-box/WD-40 gene family, characterized by an approximately 40 amino acid F-box motif and WD-40 protein-protein binding domains . FBXW4 serves as a variable component in SCF (Skp1-Cullin-F-box) ubiquitin ligase complexes, where it plays a critical role in determining substrate specificity .

The protein is particularly significant in developmental biology, as it is involved in key signaling pathways crucial for normal limb development . FBXW4 is believed to participate in Wnt signaling, which regulates cell fate determination, cell migration, and organogenesis . In mice, FBXW4 is essential for maintaining the apical ectodermal ridge of developing limb buds, with disruption resulting in digit abnormalities . The gene is also known as SHFM3, as mutations are associated with split-hand/foot malformation type 3 in humans .

What are the typical applications for FBXW4 antibodies in research?

FBXW4 antibodies are primarily employed in several fundamental protein detection techniques:

Western blotting is the most widely validated application, allowing researchers to detect FBXW4 protein (calculated MW ~46 kDa, though sometimes observed at ~50 kDa) in tissue extracts . The technique enables quantification of FBXW4 expression across different experimental conditions, providing insights into its regulation and potential involvement in disease states.

Immunohistochemistry and immunofluorescence complement protein quantification by revealing the spatial distribution of FBXW4 within tissues and cells, respectively. These applications are particularly valuable for developmental studies examining FBXW4's role in limb formation and other morphogenic processes .

How should FBXW4 antibodies be stored and handled to maintain optimal activity?

Proper storage and handling of FBXW4 antibodies are critical for maintaining their specificity and sensitivity. Most commercial FBXW4 antibodies are supplied in a PBS buffer with 0.02% sodium azide and 50% glycerol (pH 7.3) . This formulation enables storage at -20°C while preventing freeze-thaw damage.

Storage recommendations:

• Store at -20°C for long-term preservation

• Avoid repeated freeze-thaw cycles which can degrade antibody performance

• Most antibodies remain stable for at least one year after shipment when properly stored

• Aliquoting is generally unnecessary for the glycerol-containing formulations

When handling FBXW4 antibodies for experiments:

• Thaw aliquots completely before use and mix gently

• Keep on ice during experimental procedures

• Return to -20°C promptly after use

• Follow manufacturer's recommendations for specific antibody preparations

Note that some FBXW4 antibody preparations may contain bovine serum albumin (BSA) as a stabilizer, which should be considered when designing blocking strategies for immunodetection experiments .

What controls should be included when using FBXW4 antibodies for Western blotting?

Rigorous experimental design with appropriate controls is essential for generating reliable data with FBXW4 antibodies. The following controls should be incorporated:

Positive tissue controls: Mouse brain, liver, and lung tissues have been validated as positive controls for FBXW4 expression . Western blot analysis of mouse brain extracts using FBXW4 antibody (1:1000 dilution) has shown specific detection of the target protein . Additionally, human samples can be used when working with human-reactive antibodies .

Loading controls: Include housekeeping proteins (β-actin, GAPDH, or tubulin) to normalize for loading variations and ensure equal protein amounts across lanes.

Molecular weight marker: Always run a molecular weight marker to confirm the detected band corresponds to the expected size of FBXW4 (calculated MW of 46 kDa, though observed at 50 kDa in some reports) .

Antibody controls:

• Primary antibody omission control to detect non-specific binding of secondary antibody

• Secondary antibody-only control to assess background

• If possible, include a knockdown/knockout sample to verify antibody specificity

Protocol optimization considerations:

• Test a range of antibody dilutions (1:500-1:2000 for WB) to determine optimal signal-to-noise ratio

• Optimize blocking conditions to minimize background (typically 3% nonfat dry milk in TBST)

• Consider enhanced chemiluminescence (ECL) detection systems for optimal sensitivity

How can researchers validate the specificity of FBXW4 antibodies for their particular experimental system?

Validating antibody specificity is crucial before proceeding with extensive experiments. For FBXW4 antibodies, consider these validation approaches:

Multiple antibody validation: When possible, use multiple antibodies targeting different epitopes of FBXW4. The search results indicate various antibodies have been developed using different immunogens:

• Recombinant fusion protein containing amino acids 143-412 of human FBXW4 (NP_071322.1)

• FBXW4 fusion protein Ag1047

• N-terminal region specific antibodies

Genetic approaches:

• siRNA or shRNA knockdown of FBXW4 should reduce or eliminate the signal if the antibody is specific

• CRISPR/Cas9-mediated knockout validation provides definitive confirmation of specificity

• Overexpression of tagged FBXW4 should produce an additional band at the expected molecular weight plus the tag size

Immunoprecipitation-mass spectrometry: Perform IP with the FBXW4 antibody followed by mass spectrometric analysis to confirm capture of the target protein.

Tissue expression profiling: Compare detected expression patterns with known FBXW4 expression profiles (brain, kidney, lung, and liver) . Consistency with established patterns supports antibody specificity.

Species cross-reactivity assessment: Test the antibody against samples from different species if cross-reactivity is claimed. Available antibodies show reactivity with human and mouse samples, with some potentially reactive with rabbit, rat, bovine, dog, guinea pig, and horse samples .

What are the optimal sample preparation methods for detecting FBXW4 in different tissue types?

Effective sample preparation is critical for reliable FBXW4 detection across different applications:

For Western blotting:

• Use fresh tissue samples or flash-frozen tissues stored at -80°C

• Homogenize tissues in RIPA buffer supplemented with protease inhibitors and phosphatase inhibitors (particularly important given FBXW4's role in phosphoprotein recognition)

• Include 1% SDS in lysis buffer to ensure complete solubilization of membrane-associated proteins

• Centrifuge lysates at high speed (>10,000 × g) to remove insoluble debris

• Quantify protein concentration using Bradford or BCA assay

• Load 25 μg protein per lane for standard detection

• Use reducing conditions with β-mercaptoethanol or DTT in sample buffer

For immunohistochemistry:

• Fix tissues in 10% neutral buffered formalin

• For FBXW4 detection in human pancreas tissue, antigen retrieval with TE buffer pH 9.0 is recommended

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

• Block endogenous peroxidase activity with hydrogen peroxide treatment

• Use protein blocking solution to minimize non-specific binding

• Follow with primary antibody incubation at dilutions between 1:50-1:500

For immunofluorescence:

• Fix cells with 4% paraformaldehyde

• Permeabilize with 0.1% Triton X-100

• Block with appropriate serum/BSA solution

• Apply primary antibody at manufacturer's recommended dilution

• Include nuclear counterstain (DAPI) and cytoskeletal markers for co-localization studies

How does FBXW4 function in the ubiquitin-proteasome pathway, and what experimental approaches can investigate its substrates?

FBXW4 functions as a substrate recognition component of SCF (Skp1-Cullin-F-box) ubiquitin ligase complexes, recognizing and binding to phosphorylated proteins to promote their ubiquitination and subsequent degradation . This positions FBXW4 as a key regulator of protein turnover in developmental pathways, particularly those involved in limb development.

Experimental approaches to identify FBXW4 substrates:

• Immunoprecipitation-mass spectrometry:

  • Perform co-immunoprecipitation using FBXW4 antibodies

  • Analyze by LC-MS/MS to identify interacting proteins

  • Validate interactions using reciprocal co-IPs with antibodies against identified proteins

• Proximity-based labeling:

  • Generate BioID or TurboID fusion constructs with FBXW4

  • Identify nearby proteins through streptavidin pulldown and MS analysis

  • Filter results for potential substrates based on domain characteristics and phosphorylation status

• Ubiquitination assays:

  • Express tagged ubiquitin and potential substrates

  • Immunoprecipitate under denaturing conditions

  • Detect ubiquitinated forms using FBXW4 and substrate antibodies

  • Perform in vitro ubiquitination assays with purified components

• Degradation kinetics:

  • Treat cells with protein synthesis inhibitor cycloheximide

  • Monitor potential substrate degradation in presence/absence of FBXW4

  • Compare protein half-lives between wild-type and FBXW4 knockout/knockdown cells

• Phosphorylation-dependent binding:

  • Generate phospho-deficient mutants of candidate substrates

  • Assess FBXW4 binding through co-IP experiments

  • Use phosphatase treatments to confirm phosphorylation-dependence

What is the relationship between FBXW4 mutations and split-hand/foot malformation, and how can antibodies help investigate this connection?

FBXW4 (also known as SHFM3) has been implicated in split-hand/foot malformation type 3 (SHFM3), a developmental disorder characterized by the absence of central digits, underdeveloped or absent metacarpal/metatarsal bones, and syndactyly . This phenotype is observed in both humans with FBXW4 mutations and in mouse models with disrupted FBXW4 expression.

Research approaches using FBXW4 antibodies to investigate this relationship:

• Comparative expression analysis:

  • Use Western blotting with FBXW4 antibodies to compare protein expression in normal and affected tissues

  • Quantify expression levels in different developmental stages to identify critical periods

  • Analyze protein expression in patient-derived samples versus controls

• Developmental immunohistochemistry:

  • Perform IHC on developing limb tissues at various stages

  • Map FBXW4 expression patterns in the apical ectodermal ridge

  • Compare wild-type and mutant tissue architecture and FBXW4 localization

• Analysis of signaling pathway alterations:

  • Investigate Wnt signaling components in normal and SHFM3 tissues

  • Use co-immunoprecipitation with FBXW4 antibodies to identify altered protein interactions

  • Perform phospho-specific Western blots to assess downstream signaling changes

• iPSC-derived model systems:

  • Generate iPSCs from SHFM3 patients and differentiate into limb bud-like organoids

  • Use FBXW4 antibodies to track protein expression and localization during differentiation

  • Perform rescue experiments with wild-type FBXW4 expression

• Automated high-content imaging:

  • Immunofluorescence with FBXW4 antibodies in developmental model systems

  • Quantify protein levels, subcellular localization, and co-localization with pathway components

  • Track changes throughout developmental processes with single-cell resolution

What role does FBXW4 play in Wnt signaling, and how can researchers study this interaction?

FBXW4 is believed to participate in Wnt signaling, a critical pathway in embryonic development, tissue homeostasis, and disease . The precise mechanism of FBXW4's involvement remains an active area of research, with antibody-based techniques playing a central role in elucidating these interactions.

Research strategies to investigate FBXW4-Wnt signaling connections:

• Co-localization studies:

  • Perform dual immunofluorescence with FBXW4 antibodies and key Wnt pathway components

  • Use confocal microscopy to assess subcellular co-localization

  • Quantify co-localization using Pearson's correlation coefficient and Mander's overlap coefficient

• Wnt pathway activation analysis:

  • Treat cells with Wnt ligands and assess FBXW4 expression/localization changes

  • Use Western blotting with FBXW4 antibodies to quantify protein level changes

  • Compare wild-type and FBXW4-depleted cells for differences in Wnt response

• Protein-protein interaction mapping:

  • Perform co-immunoprecipitation with FBXW4 antibodies following Wnt stimulation

  • Analyze interactions with β-catenin and other Wnt pathway components

  • Use proximity ligation assays to visualize and quantify interactions in situ

• Reporter assays:

  • Utilize TOPFlash/FOPFlash reporter systems to measure Wnt pathway activation

  • Compare reporter activity in cells with normal, reduced, or enhanced FBXW4 expression

  • Correlate changes with FBXW4 protein levels measured by Western blotting

• Substrate degradation analysis:

  • Identify potential Wnt pathway proteins targeted by FBXW4 for degradation

  • Monitor half-lives of candidates in presence/absence of FBXW4

  • Use ubiquitination assays to confirm direct targeting

What are common issues when using FBXW4 antibodies in Western blotting, and how can they be resolved?

Researchers may encounter several technical challenges when using FBXW4 antibodies in Western blotting. Here are common issues and their solutions:

High background/non-specific bands:

• Increase blocking strength (try 5% nonfat dry milk or BSA in TBST)

• Optimize primary antibody dilution (test range from 1:500-1:2000)

• Increase washing duration and frequency (4-5 times, 5-10 minutes each)

• Try alternative blocking agents (casein, commercial blockers)

• Include 0.1% Tween-20 in all buffers to reduce non-specific binding

Weak or no signal:

• Ensure adequate protein loading (25 μg per lane minimum)

• Reduce antibody dilution (try 1:200-1:500)

• Extend primary antibody incubation time (overnight at 4°C)

• Use more sensitive detection systems (enhanced ECL solutions)

• Check sample preparation (ensure complete lysis and protein solubilization)

• Extend exposure time (up to 90 seconds has been effective)

Multiple bands/band at unexpected size:

• FBXW4 calculated MW is 46 kDa, but observed MW is often around 50 kDa

• Post-translational modifications (phosphorylation, ubiquitination) can cause shifts

• Degradation products may appear as lower molecular weight bands

• Different isoforms may be detected simultaneously

• Include phosphatase treatment controls to assess phosphorylation contribution

Inconsistent results between experiments:

• Standardize tissue/cell lysis procedures

• Use consistent protein quantification methods

• Prepare fresh samples when possible

• Aliquot antibodies to avoid repeated freeze-thaw cycles

• Standardize transfer conditions and blocking protocols

How can researchers optimize FBXW4 immunohistochemistry protocols for different tissue types?

Optimizing IHC protocols for FBXW4 detection requires careful consideration of tissue-specific factors:

Antigen retrieval optimization:

• For human pancreatic tissue, TE buffer pH 9.0 is recommended

• Alternative approach: citrate buffer pH 6.0

• Test both heat-induced epitope retrieval (HIER) and enzymatic retrieval methods

• Optimize retrieval time and temperature based on tissue type

Antibody dilution titration:

• Start with manufacturer's recommended range (1:50-1:500 for IHC)

• Prepare a dilution series and process identical sections simultaneously

• Select dilution providing optimal signal-to-noise ratio

• Consider sensitivity differences between chromogenic and fluorescent detection

Tissue-specific considerations:

• Fixed vs. frozen sections: For frozen sections, shorter fixation and no antigen retrieval

• Highly pigmented tissues: Include peroxidase blocking step (3% H₂O₂)

• Tissues with high endogenous biotin: Block with avidin/biotin when using biotin-based detection

• High-background tissues: Extend blocking time and consider adding 10% serum from secondary antibody species

Detection system selection:

• Polymer-HRP systems offer higher sensitivity than traditional ABC methods

• TSA (tyramide signal amplification) for very low abundance targets

• DAB chromogen for brightfield or fluorophores for multi-color co-localization studies

• Automated IHC platforms can improve consistency across experiments

Validation approaches:

• Include positive control tissues (brain, kidney, lung, liver)

• Use negative controls (primary antibody omission, non-relevant isotype controls)

• Compare multiple FBXW4 antibodies targeting different epitopes

• Correlate IHC results with Western blot data from the same tissues

What approaches can resolve contradictory results when comparing different FBXW4 antibodies?

Researchers occasionally encounter contradictory results when using different antibodies against the same target. For FBXW4, consider these systematic troubleshooting approaches:

Epitope mapping and antibody characteristics:

• Compare the immunogens used to generate each antibody:

  • Amino acids 143-412 of human FBXW4

  • FBXW4 fusion protein Ag1047

  • N-terminal region specific antibodies

• Antibodies recognizing different epitopes may yield different results due to:

  • Epitope masking in protein complexes

  • Isoform-specific detection

  • Post-translational modifications affecting epitope availability

Validation experiments:

• Side-by-side Western blot comparison:

  • Run identical samples with each antibody

  • Compare band patterns, sizes, and intensities

  • Look for consistency with predicted molecular weight (46 kDa)

• Knockout/knockdown controls:

  • Test all antibodies against FBXW4-depleted samples

  • Truly specific antibodies should show reduced/absent signal

• Overexpression validation:

  • Express tagged FBXW4 and probe with both tag-specific and FBXW4 antibodies

  • Compare detection patterns and sensitivity

• Immunoprecipitation-mass spectrometry:

  • Perform IP with each antibody separately

  • Analyze precipitates by MS to confirm target capture

  • Compare off-target binding profiles

Reconciliation strategies:

• Determine which antibody has the most thorough validation data

• Consider using antibody combinations for critical experiments

• Correlate antibody results with orthogonal techniques (qPCR, CRISPR screens)

• Be transparent about discrepancies in publications and explain methodology choices

How is FBXW4 research contributing to our understanding of developmental disorders, and what novel techniques can advance this field?

FBXW4 research is providing critical insights into developmental disorders, particularly split-hand/foot malformation type 3 (SHFM3) . As a component of SCF ubiquitin ligase complexes, FBXW4 regulates the degradation of key developmental proteins, making it a crucial node in signaling networks governing limb morphogenesis.

Current research contributions:

• Identification of FBXW4's role in maintaining the apical ectodermal ridge during limb development

• Association between chromosomal rearrangements affecting FBXW4 and congenital limb abnormalities

• Links between FBXW4 and Wnt signaling pathways in morphogenesis

Novel techniques advancing FBXW4 developmental research:

• Single-cell analyses:

  • scRNA-seq to map FBXW4 expression in developing tissues with cellular resolution

  • Correlate with protein expression using index sorting and antibody-based detection

  • Construct developmental trajectories incorporating FBXW4 activity

• 3D organoid models:

  • Generate limb bud organoids from control and patient-derived iPSCs

  • Use FBXW4 antibodies for immunofluorescence analysis of protein distribution

  • Test pharmacological interventions to rescue developmental defects

• CRISPR-based approaches:

  • Create precise genomic modifications mimicking human SHFM3 mutations

  • Engineer tagged endogenous FBXW4 for live imaging studies

  • Perform CRISPR screens to identify genetic interactors of FBXW4

• Advanced microscopy:

  • Light-sheet microscopy of developing structures with FBXW4 immunolabeling

  • Super-resolution imaging to visualize FBXW4-containing protein complexes

  • Intravital imaging of FBXW4 dynamics in developmental models

• Proteomics and interactomics:

  • Quantitative proteomics across developmental timepoints

  • Analysis of the FBXW4 interactome under normal and pathological conditions

  • Identification of substrates and binding partners in tissue-specific contexts

What are the considerations for using FBXW4 antibodies in multiplex immunofluorescence studies?

Multiplex immunofluorescence enables simultaneous detection of multiple proteins in single samples, providing valuable insights into co-expression and interaction patterns. When incorporating FBXW4 antibodies into multiplex studies, consider these technical aspects:

Antibody selection and validation:

• Choose FBXW4 antibodies with demonstrated specificity in immunofluorescence applications

• Validate antibodies individually before multiplexing

• Test for cross-reactivity with other primary antibodies in the panel

• Select antibodies raised in different host species to enable distinct secondary detection

Panel design considerations:

• Select fluorophores with minimal spectral overlap

• Consider FBXW4's subcellular localization when choosing other targets

• Include markers for relevant compartments (nucleus, cytoskeleton, etc.)

• Incorporate pathway-specific markers based on FBXW4's known functions in Wnt signaling

Technical optimization:

• Sequential staining approaches:

  • Apply antibodies in order of sensitivity (weakest signal first)

  • Consider tyramide signal amplification for FBXW4 if expression is low

  • Include thorough washing between sequential applications

• Multiplexed detection methods:

  • Traditional fluorophore-conjugated secondaries

  • Directly conjugated primary antibodies

  • Zenon labeling technology for antibodies of the same species

  • Spectral unmixing for overlapping fluorophores

• Controls for multiplex studies:

  • Single-stain controls for each antibody

  • Fluorescence minus one (FMO) controls

  • Absorption controls to verify antibody specificity in the multiplex context

Data analysis approaches:

• Use automated image analysis software for colocalization quantification

• Apply machine learning algorithms to identify spatial patterns

• Implement neighborhood analysis to study FBXW4's relationship with other proteins

• Consider single-cell analysis to account for heterogeneity

How can researchers integrate FBXW4 antibody-based techniques with genomic and transcriptomic approaches for comprehensive pathway analysis?

Integrating protein-level studies using FBXW4 antibodies with genomic and transcriptomic data provides a comprehensive understanding of FBXW4's functional role in developmental and disease contexts. This multi-omics approach can reveal regulatory networks and causal relationships not apparent with single-method analyses.

Integration strategies:

• Correlative multi-omics:

  • Perform RNA-seq and Western blotting/IHC with FBXW4 antibodies on matched samples

  • Correlate FBXW4 protein levels with transcriptional changes in related pathways

  • Identify discordance between mRNA and protein levels indicating post-transcriptional regulation

• ChIP-seq and antibody-based protein detection:

  • Use ChIP-seq to identify genomic regions affected by FBXW4-regulated transcription factors

  • Validate protein-level changes using FBXW4 antibodies in Western blotting or IHC

  • Connect FBXW4's ubiquitination activity to transcriptional regulation

• CRISPR screens with protein-level validation:

  • Conduct genome-wide or targeted CRISPR screens for FBXW4-related phenotypes

  • Validate hits using FBXW4 antibodies to assess protein interaction or expression changes

  • Build regulatory networks incorporating genetic and protein-level data

• Spatial transcriptomics with protein co-detection:

  • Combine spatial transcriptomics with immunofluorescence using FBXW4 antibodies

  • Map spatial relationships between FBXW4 protein expression and transcriptional signatures

  • Identify tissue microenvironments with coordinated FBXW4 activity

• Temporal multi-omics in developmental models:

  • Track FBXW4 expression across developmental timepoints using antibody techniques

  • Parallel RNA-seq and proteomic analyses at matched timepoints

  • Construct temporal maps of FBXW4-dependent developmental processes

Analytical frameworks:

• Use systems biology approaches to integrate protein, transcript, and genomic data

• Apply pathway enrichment analyses incorporating FBXW4 protein interaction data

• Develop predictive models of FBXW4 activity based on multi-omic signatures

• Implement machine learning algorithms to identify patterns across data types