VPS27 Antibody

What is VPS27 and what is its functional significance in cellular processes?

VPS27 (also known as HGS or Hrs in mammals) is a key component of the ESCRT-0 complex that initiates the sorting of ubiquitinated membrane proteins into multivesicular bodies (MVBs) for lysosomal degradation. VPS27 contains several functional domains including a VHS domain, FYVE zinc finger domain, UIM (ubiquitin-interacting motif), and clathrin-binding domains that enable it to recognize ubiquitinated cargo and recruit subsequent ESCRT complexes . This protein serves as an essential mediator in the endosomal sorting pathway by binding to ubiquitinated membrane proteins and phosphatidylinositol 3-phosphate (PI3P) on endosomal membranes simultaneously, thus initiating the MVB sorting process .

How does VPS27 differ across species, and which model organisms are commonly used for VPS27 research?

VPS27 exhibits notable structural and functional conservation across eukaryotes while maintaining species-specific variations. In yeast (Saccharomyces cerevisiae), it's known as VPS27 with alternative names including DID7, GRD11, and SSV17 . In Schizosaccharomyces pombe (fission yeast), it's called sst4 . In mammals, the homolog is known as HGS (Hepatocyte growth factor-regulated tyrosine kinase substrate) or Hrs . Common model organisms for VPS27 research include yeasts (S. cerevisiae, S. pombe), Drosophila melanogaster, and various mammalian cell lines (human, mouse, rat) . Each model system offers distinct advantages: yeast provides genetic tractability, Drosophila enables developmental studies, and mammalian systems allow investigation of disease-relevant pathways and protein interactions.

What are the known interacting partners of VPS27 and how do these interactions contribute to ESCRT-mediated sorting?

VPS27/HGS forms the ESCRT-0 complex primarily through interaction with STAM (Signal Transducing Adaptor Molecule) . This heterodimeric complex recognizes ubiquitinated cargo proteins and initiates the ESCRT-mediated sorting pathway. VPS27 also interacts with:

• Clathrin - through its clathrin-binding motif to stabilize protein clusters on endosomal membranes

• ESCRT-I components (particularly TSG101) - to recruit subsequent ESCRT machinery

• Phosphatidylinositol 3-phosphate (PI3P) - through its FYVE domain to facilitate endosomal membrane binding

• Ubiquitinated cargo proteins - via its UIM domains

These interactions create a coordinated protein network that enables the sequential recruitment of ESCRT-I, ESCRT-II, and ESCRT-III complexes, ultimately leading to cargo sequestration and intraluminal vesicle formation .

What criteria should be considered when selecting an appropriate VPS27/HGS antibody for specific research applications?

When selecting a VPS27/HGS antibody, researchers should consider:

• Target species specificity: Ensure the antibody recognizes your species of interest. Available antibodies target human, mouse, rat, Drosophila, and various yeast species including S. cerevisiae and S. pombe .

• Application compatibility: Verify the antibody has been validated for your intended applications (Western blot, immunohistochemistry, immunofluorescence, etc.) .

• Epitope location: Consider where the antibody binds on VPS27/HGS, particularly if studying specific domains or if post-translational modifications might interfere with antibody binding.

• Antibody format: Determine whether native antibodies or those conjugated to fluorophores (FITC, Cy3, APC) or enzymes are more appropriate for your experimental design .

• Clonality: Polyclonal antibodies provide higher sensitivity but potentially lower specificity compared to monoclonals. Most available VPS27 antibodies appear to be polyclonal .

• Validation data: Review existing literature, manufacturer data, and independent validation resources to confirm antibody performance in conditions similar to your planned experiments.

How should researchers validate a VPS27 antibody before using it in critical experiments?

A rigorous validation protocol for VPS27 antibodies should include:

• Positive and negative controls:

  • Positive: Cells/tissues known to express VPS27/HGS

  • Negative: VPS27/HGS knockout samples or siRNA-depleted cells

• Molecular weight verification: Confirm the detected band matches the expected molecular weight (approximately 70 kDa for human HGS) .

• Peptide competition assay: Pre-incubate the antibody with the immunizing peptide to confirm specificity.

• Orthogonal detection methods: Compare results with different antibodies targeting distinct epitopes of VPS27/HGS.

• Cross-reactivity assessment: Test potential cross-reactivity with closely related proteins, particularly STAM1 and STAM2 .

• Immunoprecipitation validation: For co-IP studies, verify the antibody can efficiently immunoprecipitate native VPS27/HGS.

• Cellular localization pattern: Confirm the expected endosomal localization pattern in immunofluorescence applications.

What are the advantages and limitations of using polyclonal versus monoclonal antibodies for VPS27 detection?

Most commercially available VPS27/HGS antibodies are polyclonal, which provides good sensitivity for detecting this protein in various applications, though some monoclonal options like the STAM2 antibody (which doesn't cross-react with STAM1) demonstrate the specificity advantages of monoclonals .

What are the optimal conditions for using VPS27 antibodies in Western blot applications?

For optimal Western blot detection of VPS27/HGS:

• Sample preparation:

  • Use RIPA or NP-40 buffer with protease inhibitors

  • Include phosphatase inhibitors if studying phosphorylated forms

  • Sonicate briefly to shear DNA and reduce sample viscosity

• Gel separation:

  • 8-10% SDS-PAGE for optimal resolution of HGS (~70 kDa)

  • Consider gradient gels (4-15%) when analyzing both VPS27/HGS and binding partners

• Transfer conditions:

  • Wet transfer at 100V for 1 hour or 30V overnight

  • Use PVDF membrane for higher protein binding capacity

  • Methanol concentration of 10-15% in transfer buffer

• Blocking and antibody incubation:

  • Block with 5% non-fat dry milk in TBST (avoid BSA unless specified by manufacturer)

  • Primary antibody dilution typically 1:500-1:2000 (optimize based on specific antibody)

  • Incubate overnight at 4°C for maximum sensitivity

  • Secondary antibody incubation at 1:5000-1:10000 for 1 hour at room temperature

• Detection considerations:

  • Enhanced chemiluminescence (ECL) for standard detection

  • Consider fluorescent secondary antibodies for multi-protein co-detection and quantification

How can VPS27 antibodies be effectively used in immunofluorescence to study endosomal localization?

For optimal immunofluorescence detection of VPS27/HGS:

• Fixation method:

  • 4% paraformaldehyde (PFA) for 15 minutes at room temperature preserves structure

  • Avoid methanol fixation which can disrupt membrane structures

• Permeabilization:

  • 0.1% Triton X-100 for 5-10 minutes

  • Alternative: 0.1% saponin (maintains better membrane structure)

• Blocking and antibody incubation:

  • Block with 5% normal serum (goat or donkey) with 0.1% Triton X-100

  • Primary antibody dilution typically 1:100-1:500 (optimize for each antibody)

  • Incubate overnight at 4°C in humidified chamber

  • Secondary antibody incubation for 1 hour at room temperature

• Co-localization markers:

  • Early endosome marker: EEA1

  • Late endosome marker: Rab7

  • MVB/ESCRT pathway markers: TSG101, HRS, STAM2

• Image acquisition:

  • Confocal microscopy recommended for precise localization

  • Z-stack acquisition for complete visualization of endosomal structures

  • Consider super-resolution techniques (STED, STORM) for detailed co-localization studies

• Controls:

  • Secondary-only control to assess background

  • Cells depleted of VPS27/HGS (siRNA or CRISPR) as negative control

What are recommended protocols for immunoprecipitation of VPS27 and its interacting partners?

For effective immunoprecipitation of VPS27/HGS complexes:

• Lysis conditions:

  • Use mild lysis buffer (25 mM Tris-HCl pH 7.4, 150 mM NaCl, 1 mM EDTA, 1% NP-40, 5% glycerol)

  • Include protease and phosphatase inhibitor cocktails

  • Maintain samples at 4°C throughout processing

• Pre-clearing:

  • Pre-clear lysate with Protein A/G beads (30 minutes at 4°C) to reduce non-specific binding

  • Remove beads by centrifugation before adding antibody

• Antibody binding:

  • Use 2-5 μg antibody per 500 μg protein lysate

  • Incubate overnight at 4°C with gentle rotation

  • Add 30-50 μl protein A/G beads and incubate for additional 2-4 hours

• Washing:

  • Perform 4-5 washes with lysis buffer

  • Consider including one higher stringency wash (250-300 mM NaCl)

  • Final wash with PBS to remove detergent

• Elution options:

  • Denaturing: Boil in 2X SDS-PAGE sample buffer

  • Non-denaturing: Peptide competition or mild acid elution (for preserving activity)

• Validation approaches:

  • Immunoblot for VPS27/HGS to confirm successful IP

  • Probe for known interacting partners (STAM1/2, TSG101)

  • Mass spectrometry for unbiased interaction profiling

What are common issues when working with VPS27 antibodies and how can they be resolved?

How should researchers interpret changes in VPS27 localization or expression patterns in response to experimental manipulations?

When analyzing VPS27/HGS localization or expression changes:

• Endosomal clustering interpretation:

  • Increased clustering often indicates enhanced endosomal sorting activity

  • Distinguish between endosomal enlargement (often seen with Rab5-Q79L expression) versus increased endosome number

  • Quantify changes using parameters like puncta size, number, and intensity

• Expression level changes:

  • Normalize to appropriate housekeeping proteins (β-actin, GAPDH, tubulin)

  • Consider post-translational modifications that might affect antibody recognition

  • Verify with qRT-PCR for transcriptional effects versus post-transcriptional regulation

• Response to perturbations:

  • Growth factor stimulation typically causes transient VPS27/HGS phosphorylation and activity changes

  • PI3K inhibitors may reduce endosomal localization due to decreased PI3P levels

  • Proteasome inhibitors might increase ubiquitinated cargo and alter VPS27/HGS distribution

• Colocalization analysis:

  • Use proper controls for threshold setting

  • Calculate Pearson's or Mander's coefficients for quantitative assessment

  • Consider dynamic processes when interpreting static images

• Cell type considerations:

  • Expression levels vary considerably between cell types

  • Some tissues show specialized functions (e.g., neurons, immune cells)

  • Compare within same cell type whenever possible

How can conflicting antibody data be reconciled when studying VPS27 function across different experimental systems?

When facing conflicting VPS27/HGS antibody data:

• Antibody validation comparison:

  • Review epitope locations - different domains may show different accessibility

  • Compare antibody documentation for specificity testing

  • Test multiple antibodies on the same samples

• Experimental system differences:

  • Cell type-specific post-translational modifications

  • Expression level variations between systems

  • Interacting proteins that might mask epitopes

• Technical resolution approaches:

  • Use orthogonal detection methods (mass spectrometry, tagged constructs)

  • Conduct parallel knockdown/knockout controls in each system

  • Standardize sample preparation methods across systems

• Results interpretation:

  • Consider the possibility that conflicting results reflect actual biological differences

  • Evaluate which antibody detection most closely matches other functional data

  • When publishing, document all antibody information and preparation methods

How can VPS27 antibodies be used to investigate the dynamics of ESCRT-0 assembly in live cells?

Advanced live-cell imaging approaches with VPS27 antibodies include:

• Antibody fragment techniques:

  • Generate Fab fragments or single-chain variable fragments (scFv) from validated VPS27 antibodies

  • Label fragments with bright, photostable fluorophores (Alexa Fluor 647, JF646)

  • Deliver into cells via microinjection or cell-penetrating peptide conjugation

• Super-resolution compatible systems:

  • Use antibody conjugates optimized for STORM, PALM, or STED microscopy

  • Combine with photoactivatable/photoconvertible fluorescent protein-tagged ESCRT components

  • Implement lattice light sheet microscopy for reduced phototoxicity during extended imaging

• Multi-color tracking:

  • Combine VPS27 detection with STAM and ESCRT-I component labeling

  • Implement spectral unmixing to resolve closely emitting fluorophores

  • Use differential labeling strategies (HaloTag, SNAP-tag) for orthogonal detection

• Quantitative analysis approaches:

  • Track individual endosomes using particle tracking algorithms

  • Measure dwell times of VPS27 and subsequent ESCRT components

  • Determine order of assembly through pulse-chase labeling

• Correlative light-electron microscopy (CLEM):

  • Visualize fluorescently labeled VPS27 by light microscopy

  • Process same sample for electron microscopy to resolve ultrastructural details

  • Determine precise localization within endosomal membrane subdomains

What are current approaches for studying VPS27 post-translational modifications and their functional consequences?

Advanced techniques for investigating VPS27/HGS post-translational modifications include:

• Phosphorylation analysis:

  • Use phospho-specific antibodies targeting known sites (Tyr334, Ser270)

  • Implement phosphatase treatments as controls

  • Combine with mass spectrometry to identify novel phosphorylation sites

  • Create phosphomimetic mutants (S→D, Y→E) and phosphodeficient mutants (S→A, Y→F)

• Ubiquitination studies:

  • Use denaturing immunoprecipitation to preserve ubiquitin modifications

  • Analyze with ubiquitin chain-specific antibodies (K48, K63)

  • Implement tandem ubiquitin binding entities (TUBEs) for enrichment

  • Apply ubiquitin remnant profiling by mass spectrometry

• SUMOylation detection:

  • Perform SUMO-IP followed by VPS27 detection

  • Use SUMO-interacting motif (SIM) pulldowns

  • Apply INCA (in-cell SUMO-1 activation assay) for dynamic studies

• Computational prediction integration:

  • Use PTM prediction algorithms to identify potential modification sites

  • Create a comprehensive PTM map using proteomic data

  • Model structural consequences of modifications

How can researchers investigate the role of VPS27 in disease models and therapeutic development?

Advanced approaches for studying VPS27/HGS in disease contexts:

• Neurodegenerative disease models:

  • Analyze VPS27/HGS interactions with disease-associated proteins (Tau, α-synuclein, Huntingtin)

  • Quantify changes in VPS27/HGS expression and localization in patient-derived samples

  • Implement VPS27/HGS overexpression or knockdown in neuronal models to assess effects on protein aggregation

• Cancer research applications:

  • Study VPS27/HGS role in receptor tyrosine kinase (RTK) degradation

  • Examine correlation between VPS27/HGS expression and tumor progression/metastasis

  • Target VPS27/HGS-dependent pathways to modulate growth factor signaling

• Infectious disease relevance:

  • Investigate viral hijacking of ESCRT machinery requiring VPS27/HGS

  • Study bacterial evasion of degradative pathways via VPS27/HGS manipulation

  • Develop antibodies targeting pathogen-VPS27 interaction sites

• Therapeutic screening approaches:

  • Develop high-content screening assays monitoring VPS27/HGS-dependent cargo sorting

  • Create split-reporter systems to detect VPS27/ESCRT complex formation

  • Implement PROTAC (Proteolysis Targeting Chimera) strategies targeting VPS27/HGS for degradation

• Biomarker development:

  • Assess VPS27/HGS as diagnostic/prognostic markers in disease contexts

  • Evaluate extracellular vesicle composition changes upon VPS27/HGS modulation

  • Develop sensitive detection methods for VPS27/HGS modifications in patient samples

How are new antibody engineering technologies enhancing VPS27 research capabilities?

Recent technological advances in antibody engineering applicable to VPS27 research include:

• Nanobodies and single-domain antibodies:

  • Small size (15 kDa) allows access to sterically restricted epitopes

  • Enhanced penetration into cellular compartments

  • Stability under various buffer conditions

  • Direct expression in cells as intrabodies

• Bispecific antibody formats:

  • Simultaneous targeting of VPS27/HGS and interacting partners

  • Creation of forced proximity systems to study protein interactions

  • Recruitment of effector molecules to VPS27-positive structures

• Proximity labeling antibody conjugates:

  • Antibodies linked to promiscuous biotin ligases (TurboID, APEX2)

  • Enables mapping of the local VPS27 interactome in intact cells

  • Temporal control through inducible systems

• Optogenetic antibody systems:

  • Light-activatable binding domains fused to anti-VPS27 antibody fragments

  • Allows precise temporal and spatial control of VPS27 function

  • Integration with live-cell imaging for direct cause-effect assessment

• Degradation-inducing antibodies:

  • TRIM-Away adaptation for acute VPS27 depletion

  • Antibody-PROTAC conjugates for targeted degradation

  • Advantages over genetic approaches for studying essential proteins

What are the most significant recent discoveries about VPS27 function that researchers should consider when designing experiments?

Recent significant findings about VPS27/HGS with experimental implications:

• Non-canonical functions beyond ESCRT-0:

  • VPS27/HGS involvement in autophagy regulation

  • Nuclear translocation and potential transcriptional roles

  • Cytoskeletal interaction beyond endosomal functions

  • Experimental implication: Include multiple cellular compartments in analysis

• Tissue-specific functions and isoforms:

  • Differential expression patterns across tissues

  • Specialized functions in polarized cells

  • Isoform-specific interactions

  • Experimental implication: Verify isoform expression in your model system

• Regulatory mechanisms:

  • Complex phosphorylation patterns affecting activity

  • Ubiquitination-dependent regulation beyond substrate recognition

  • Interaction with lipid microdomains

  • Experimental implication: Consider lipid composition in reconstitution systems

• Disease connections:

  • Links to neurodegenerative pathways

  • Altered expression in various cancers

  • Involvement in viral budding processes

  • Experimental implication: Include disease-relevant stressors in experimental design

• Methodological advances:

  • Super-resolution visualization of ESCRT-0 assembly

  • Cryo-EM structures of VPS27 complexes

  • Phase separation properties of ESCRT components

  • Experimental implication: Consider higher-resolution approaches for mechanistic studies

How can integrative multi-omics approaches be combined with VPS27 antibody techniques to gain systems-level insights?

Advanced multi-omics integration strategies for VPS27 research:

• Comprehensive interactome mapping:

  • Immunoprecipitation coupled to mass spectrometry (IP-MS)

  • Proximity labeling approaches (BioID, APEX) centered on VPS27

  • Yeast two-hybrid and mammalian two-hybrid screening

  • Integration with public protein interaction databases

• Functional genomics combinations:

  • CRISPR screens for synthetic lethality with VPS27 perturbation

  • Transcriptomics after acute vs. chronic VPS27 depletion

  • Correlation of genetic dependencies with VPS27 expression levels

  • Integration of human genetic variation data

• Structural biology integration:

  • Antibody epitope mapping with hydrogen-deuterium exchange MS

  • Negative-stain EM of immunocomplexes

  • Cryo-EM structure determination using antibody fragments as fiducial markers

  • Computational modeling constrained by crosslinking-MS data

• Single-cell approaches:

  • Single-cell proteomics with VPS27 antibody-based sorting

  • Spatial transcriptomics combined with VPS27 protein mapping

  • Multi-parameter imaging with machine learning analysis

  • Correlation of cellular heterogeneity with endosomal phenotypes

• Translational data integration:

  • Patient sample analysis for VPS27 expression/modifications

  • Correlation with clinical parameters and outcomes

  • Drug response profiling in relation to VPS27 status

  • Development of companion diagnostics based on VPS27 pathway activity