SH3GL3 Antibody

What is SH3GL3 and what is its significance in research?

SH3GL3 (SH3-domain GRB2-like 3), also known as Endophilin-A3, is a member of the endophilin family containing both SH3 (Src homology 3) and BAR (Bin-amphiphysin-Rvs) structural domains. It is primarily expressed in brain and testis tissues and plays crucial roles in endocytosis, signal transduction, and regulation of synaptic vesicles .

The protein contains a C-terminal SH3 domain that drives protein-protein interactions through binding to proline-rich ligands, and an N-terminal BAR domain involved in sensing and inducing membrane curvature . This structural arrangement enables SH3GL3 to recruit other proteins to membranes with high curvature during endocytic processes .

Research significance includes:

• Role in clathrin-independent endocytosis of CD166/ALCAM

• Potential involvement in neurodegenerative disorders, particularly Huntington's disease

• Contribution to vascular lumen maintenance during development

What molecular characteristics define SH3GL3 protein and how can they affect antibody selection?

SH3GL3 has several key molecular characteristics that researchers should consider when selecting antibodies:

When selecting antibodies, researchers should verify which epitope is targeted and whether the antibody has been validated against other endophilin family members to ensure specificity .

What are the common applications for SH3GL3 antibodies in research?

SH3GL3 antibodies are utilized across multiple experimental platforms:

When designing experiments, researchers should validate each antibody for their specific application and sample type, as performance can vary significantly between tissue sources and experimental conditions .

How can researchers distinguish between SH3GL3 and other endophilin family members?

Distinguishing between SH3GL3 (Endophilin-A3) and related endophilin family members (SH3GL1/Endophilin-A1 and SH3GL2/Endophilin-A2) requires careful experimental design:

• Antibody specificity validation: Select antibodies specifically tested against all three endophilin family members. Some manufacturers provide dot blot data showing non-cross-reactivity with SH3GL1 and SH3GL2 .

• Tissue-specific expression patterns:

  • SH3GL3 (Endophilin-A3): Primarily brain and testis

  • SH3GL2 (Endophilin-A1): Predominantly brain

  • SH3GL1 (Endophilin-A2): Broader distribution including pancreas, placenta, prostate, testis, and uterus

• Molecular verification techniques:

  • Recombinant protein dot blots with all three proteins

  • siRNA knockdown or CRISPR knockout controls

  • Western blotting with careful molecular weight discrimination

• Immunohistochemical validation: Perform parallel staining with antibodies against each endophilin family member on serial sections to observe distinct distribution patterns.

When publishing results, clearly document which validation methods were employed to confirm specificity for SH3GL3 over other family members .

What experimental design considerations are important when studying SH3GL3's role in neurodegenerative diseases?

When investigating SH3GL3 in neurodegenerative contexts, particularly Huntington's disease where SH3GL3 interaction with huntingtin has been documented , several experimental design factors are critical:

• Tissue processing optimization:

  • Post-mortem interval standardization

  • Fixation protocol optimization to preserve SH3GL3 epitopes

  • Antigen retrieval methods specifically suited for neurodegenerative disease tissues

• Aggregate-specific considerations:

  • SH3GL3 promotes formation of insoluble polyglutamine-containing aggregates in Huntington's disease

  • Use detergent-resistant fraction analysis to assess SH3GL3 incorporation into aggregates

  • Consider sequential extraction protocols to isolate different protein fractions

• Interaction assessment techniques:

  • Co-immunoprecipitation with huntingtin or other disease-associated proteins

  • Proximity ligation assays to visualize protein interactions in situ

  • FRET/BRET assays for real-time interaction monitoring

• Domain-specific analysis:

  • The C-terminal SH3 domain of SH3GL3 and the proline-rich region in huntingtin exon 1 are essential for interaction

  • Generate domain-specific constructs to map interaction interfaces

• Comprehensive controls:

  • Age-matched control tissues

  • Disease stage stratification

  • Verification across multiple patient samples

This multilayered approach helps elucidate whether SH3GL3 contributes to disease pathogenesis or represents a compensatory response .

How can SH3GL3 antibodies be employed in studies of clathrin-independent endocytosis?

SH3GL3 has been implicated in clathrin-independent endocytic pathways, particularly in the internalization of CD166/ALCAM (Activated Leukocyte Cell Adhesion Molecule) . Researchers can leverage SH3GL3 antibodies to investigate these processes through:

• Co-localization studies:

  • Dual immunofluorescence labeling with SH3GL3 antibodies and markers of clathrin-independent endocytosis

  • Super-resolution microscopy to resolve spatial relationships at endocytic sites

  • Live-cell imaging with fluorescently tagged SH3GL3 and endocytic cargo

• Functional intervention approaches:

  • Antibody-mediated inhibition in semi-permeabilized cell systems

  • Correlation of SH3GL3 knockdown/knockout with changes in clathrin-independent cargo internalization

  • Rescue experiments with wildtype vs. mutant SH3GL3

• Biochemical fractionation:

  • Isolation of endocytic intermediates using density gradient centrifugation

  • Immunoisolation of SH3GL3-positive vesicles followed by proteomic analysis

  • Tracking cargo progression through endocytic compartments using antibody-based detection

• Temporal dynamics assessment:

  • Antibody pulse-chase experiments to track SH3GL3 recruitment timing

  • Synchronized endocytosis assays with temporal fixation and immunostaining

  • Correlation with membrane curvature sensors

These approaches can help delineate the specific role of SH3GL3 in alternative endocytic pathways and its functional relationship with other regulators like Galectin-8 .

What are the optimal protocols for using SH3GL3 antibodies in Western blot applications?

Based on the compiled data from multiple sources, the following optimized Western blot protocol for SH3GL3 detection is recommended:

Sample Preparation:

• Extract proteins from tissues (preferably brain or testis) or cells using RIPA buffer with protease inhibitors

• For challenging samples, consider using stronger lysis buffers containing sodium deoxycholate

SDS-PAGE:

• Load 20-50 μg protein per lane

• Use 12% SDS-PAGE gels for optimal separation in the 39-40 kDa range

• Always include reducing conditions (β-mercaptoethanol or DTT)

Transfer and Blocking:

• Transfer to PVDF or nitrocellulose membrane at 100V for 60-90 minutes

• Block with 5% non-fat dry milk in TBST for 1 hour at room temperature

Antibody Incubation:

Detection:

• Use enhanced chemiluminescence (ECL) reagents

• Typical exposure times range from 30 seconds to 3 minutes

• Expected molecular weight: 39-40 kDa

Critical Controls:

• Positive control: Brain or testis lysate

• Negative control: SH3GL3 knockout/knockdown sample if available

• Loading control: β-actin, GAPDH, or vinculin

This protocol has been validated across multiple sources and should provide specific detection of SH3GL3 in various sample types .

What immunohistochemistry protocols yield optimal SH3GL3 detection in tissue sections?

For immunohistochemical detection of SH3GL3 in tissue sections, the following optimized protocol synthesizes best practices from multiple sources:

Tissue Processing:

• Fix tissues in 10% neutral buffered formalin for 24-48 hours

• Process and embed in paraffin following standard procedures

• Cut sections at 4-5 μm thickness

Antigen Retrieval:

• Heat-mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes

• Allow slides to cool slowly to room temperature (~20 minutes)

Staining Protocol:

• Deparaffinization and Rehydration:

  • Xylene: 3 changes, 5 minutes each

  • 100% ethanol: 2 changes, 3 minutes each

  • 95%, 80%, 70% ethanol: 3 minutes each

  • Distilled water: 5 minutes

• Blocking and Antibody Incubation:

  Step	Conditions	Notes
  Peroxidase block	3% H₂O₂, 10 minutes	Reduces endogenous peroxidase activity
  Protein block	5-10% normal goat serum, 1 hour	Reduces non-specific binding
  Primary antibody	1:100-1:1000 dilution, overnight at 4°C	Optimal dilution requires titration
  Wash	PBS or TBS, 3 × 5 minutes	Thorough washing is essential
  Detection system	Polymer detection system (e.g., Bond™ Polymer Refine)	Enhances sensitivity over traditional ABC methods
  Counterstain	Hematoxylin, 30-60 seconds	Provides nuclear contrast

• Post-Staining:

  • Dehydrate through graded alcohols

  • Clear in xylene

  • Mount with permanent mounting medium

Validation Controls:

• Positive control: Human cerebrum or testis tissue

• Negative control: Primary antibody omission

• Specificity control: Pre-absorption with immunizing peptide when available

This protocol has been shown to produce specific staining of SH3GL3 in various tissues, with particularly strong signal in brain tissues where SH3GL3 is highly expressed .

How should researchers troubleshoot cross-reactivity issues with SH3GL3 antibodies?

Cross-reactivity is a significant concern when working with SH3GL3 antibodies due to homology with other endophilin family members. A systematic troubleshooting approach includes:

Diagnostic Steps:

• Identify potential cross-reactivity:

  • Compare band patterns between wild-type and SH3GL3 knockout samples

  • Look for unexpected bands in Western blots or staining patterns in immunohistochemistry

  • Check for signal in tissues not known to express SH3GL3 (e.g., liver, kidney)

• Evaluate antibody documentation:

  • Review specificity testing data from manufacturer

  • Examine immunogen sequence for homology with other proteins

  • Check whether the antibody has been validated against other endophilin family members

Troubleshooting Strategies:

• Antibody optimization:

  Issue	Solution	Rationale
  Multiple bands in Western blot	Increase antibody dilution (1:2000-1:5000)	Reduces non-specific binding
  High background in IHC	Extend blocking time to 2 hours	Minimizes non-specific antibody interactions
  Cross-reactivity with other endophilins	Try antibodies targeting unique regions of SH3GL3	Reduces shared epitope recognition

• Protocol modifications:

  • Increase washing duration and frequency

  • Test alternative blocking reagents (BSA vs. normal serum vs. commercial blockers)

  • Reduce primary antibody incubation temperature (4°C vs. room temperature)

  • Add 0.1% Tween-20 to antibody diluent to reduce non-specific binding

• Validation approaches:

  • Perform peptide competition assays with the immunizing peptide

  • Test multiple antibodies targeting different SH3GL3 epitopes

  • Include SH3GL3 siRNA/shRNA knockdown controls

  • Use dot blots with recombinant SH3GL1, SH3GL2, and SH3GL3 proteins

By systematically applying these troubleshooting steps, researchers can significantly improve specificity when using SH3GL3 antibodies across different applications .

How can researchers design experiments to study SH3GL3's role in endocytosis?

Investigating SH3GL3's function in endocytic processes requires a multi-faceted experimental design:

Functional Perturbation Approaches:

• Genetic manipulation:

  • CRISPR-Cas9 knockout of SH3GL3

  • siRNA/shRNA knockdown for partial depletion

  • Expression of dominant-negative mutants (e.g., SH3 domain deletions)

  • Domain-specific mutations to separate membrane-binding and protein-interaction functions

• Cargo-specific endocytosis assays:

  • CD166/ALCAM internalization tracking (identified SH3GL3-dependent cargo)

  • Fluorescently-labeled endocytic markers (transferrin, dextran, cholera toxin B)

  • Biotinylation-based endocytosis assays for surface protein internalization

  • Antibody feeding assays for receptor trafficking

Mechanistic Analysis:

• Membrane dynamics assessment:

  • Live-cell imaging with fluorescently tagged SH3GL3

  • Membrane tension measurements during endocytosis

  • Correlation with BAR domain curvature sensors

  • Liposome tubulation assays with purified SH3GL3

• Interaction mapping:

  Method	Application	Outcome Measure
  Co-immunoprecipitation	Protein complex isolation	Identification of SH3GL3 partners during endocytosis
  Proximity ligation assay	In situ interaction visualization	Spatial distribution of SH3GL3 complexes
  FRET/BRET	Real-time interaction dynamics	Temporal coordination of SH3GL3 recruitment
  Split-GFP complementation	Verification of direct interactions	Binary confirmation of protein pairing

• Ultrastructural analysis:

  • Immunogold electron microscopy for precise localization

  • Correlative light-electron microscopy to link dynamic events with ultrastructure

  • High-pressure freezing/freeze substitution to capture transient intermediates

This comprehensive approach enables researchers to dissect both the functional requirement for SH3GL3 in endocytosis and the underlying mechanisms through which it operates .

What controls should be included when using SH3GL3 antibodies in co-immunoprecipitation experiments?

Co-immunoprecipitation (co-IP) experiments with SH3GL3 antibodies require rigorous controls to ensure valid interpretation of protein interactions:

Essential Controls:

• Input control:

  • Reserve 5-10% of pre-IP lysate

  • Confirms presence of both SH3GL3 and potential interacting proteins

  • Allows quantification of IP efficiency

• Antibody controls:

  Control Type	Implementation	Purpose
  Isotype control	Matching non-specific IgG from same species	Identifies non-specific binding to antibody or beads
  Pre-immune serum	If using custom antibodies	Establishes baseline before immunization
  Blocking peptide	Pre-incubate antibody with immunizing peptide	Confirms binding specificity

• Sample controls:

  • SH3GL3 knockout/knockdown lysates to confirm antibody specificity

  • Cells lacking the putative interacting protein

  • Treatment conditions that should modify the interaction (if known)

• Technical controls:

  • "Beads only" control without primary antibody

  • Reverse IP with antibody against the interacting protein

  • DNase/RNase treatment to eliminate nucleic acid-mediated associations

Validation Strategy:
When studying specific interactions (e.g., SH3GL3-huntingtin as in ):

• Perform parallel IPs with antibodies against both proteins

• Include conditions that should strengthen or weaken the interaction:

  • Examine HD brain extracts with different polyQ repeat lengths

  • Compare wild-type vs. proline-rich region mutants of huntingtin

• Test interaction domain specificity using truncation constructs:

  • SH3GL3 lacking the SH3 domain should show reduced huntingtin binding

  • Huntingtin fragments without the proline-rich region should show reduced binding

This comprehensive control strategy ensures that detected interactions represent genuine biological phenomena rather than experimental artifacts .

How can researchers quantitatively analyze SH3GL3 expression in different tissues or experimental conditions?

Quantitative analysis of SH3GL3 expression requires rigorous methodologies to ensure accurate and reproducible measurements:

Western Blot Quantification:

• Sample preparation standardization:

  • Consistent protein extraction methods across all samples

  • Accurate protein quantification (BCA or Bradford assay)

  • Equal loading (20-50 μg total protein)

• Technical considerations:

  • Include recombinant SH3GL3 standards for absolute quantification

  • Use housekeeping proteins (β-actin, GAPDH) as loading controls

  • Perform in technical triplicates

• Densitometric analysis:

  • Use linear range of detection for quantification

  • Normalize SH3GL3 signal to loading control

  • Apply statistical testing appropriate for experimental design

Immunohistochemical Quantification:

• Standardized image acquisition:

  • Consistent exposure settings across all samples

  • Multiple fields per sample (≥5) to account for heterogeneity

  • Blinded analysis to prevent bias

• Quantification approaches:

  Method	Application	Metrics
  Cell counting	Cell-specific expression	Percentage of SH3GL3-positive cells
  Intensity measurement	Expression level variation	Mean optical density, integrated density
  Area measurement	Expression distribution	Percentage area above threshold

• Data normalization and analysis:

  • Background subtraction

  • Internal reference standards on each slide

  • Statistical comparison between experimental groups

mRNA Quantification (complementary approach):

• qRT-PCR with SH3GL3-specific primers

• RNA-seq analysis for transcriptome-wide context

• Single-cell RNA-seq for cell-type specific expression patterns

Integrated Multi-omics Analysis:
For comprehensive understanding, correlate:

• Protein expression (Western blot, IHC, mass spectrometry)

• mRNA levels (qPCR, RNA-seq)

• Protein localization (immunofluorescence)

• Function (endocytosis assays)

This integrated approach provides robust quantitative assessment of SH3GL3 expression across experimental conditions or tissue types, enabling meaningful comparisons and correlation with functional outcomes .

How can SH3GL3 antibodies be used to investigate the protein's role in neurodegenerative diseases?

SH3GL3 has been implicated in neurodegenerative processes, particularly in Huntington's disease . Researchers can leverage antibodies to investigate these connections through several sophisticated approaches:

Pathological Aggregate Studies:

• Aggregate composition analysis:

  • Co-localization of SH3GL3 with inclusion bodies

  • Sequential extraction protocols to isolate insoluble fractions

  • Quantification of SH3GL3 incorporation into aggregates at different disease stages

• Interaction with disease proteins:

  • Co-immunoprecipitation with huntingtin containing different polyQ repeat lengths

  • Analysis of SH3 domain-dependent binding to the proline-rich region of huntingtin

  • Proximity ligation assays to visualize interactions in situ

Mechanistic Investigations:

• Pathway analysis:

  • Phosphorylation status of SH3GL3 in disease states

  • Impact on endocytic trafficking of neuronal receptors

  • Effects on synaptic vesicle recycling

• Functional consequences:

  Approach	Implementation	Outcome Measure
  Protein misfolding	Thioflavin T assays with/without SH3GL3	Aggregation kinetics modification
  Cellular toxicity	Cell viability with SH3GL3 manipulation	Neuroprotective/toxic effects
  Synaptic function	Electrophysiology with SH3GL3 perturbation	Synaptic transmission alterations

Translational Applications:

• Biomarker development:

  • SH3GL3 levels or post-translational modifications in CSF

  • Correlation with disease progression markers

  • Predictive value for symptom onset in presymptomatic individuals

• Therapeutic target validation:

  • Disruption of pathological interactions

  • Rescue of endocytic defects

  • Modification of aggregate formation

These approaches can help determine whether SH3GL3 represents a disease modifier, potential therapeutic target, or biomarker for neurodegenerative conditions like Huntington's disease .

What role does SH3GL3 play in vascular development, and how can researchers investigate this function?

SH3GL3 has been implicated in vascular development, particularly in maintaining dorsal aorta lumen integrity in zebrafish embryos . To investigate this function:

Developmental Analysis:

• Temporal-spatial expression profiling:

  • Whole-mount immunostaining in developing vasculature

  • Time-course analysis of SH3GL3 expression during vascular formation

  • Co-localization with vascular markers (e.g., VEGFR2, VE-cadherin)

• Loss-of-function studies:

  • Morpholino knockdown in zebrafish (as in )

  • CRISPR-Cas9 knockout/mutation models

  • Temporal control using heat-shock or drug-inducible systems

Mechanistic Pathways:

• Signaling integration:

  • Interaction with epidermal growth factor receptor (EGFR)

  • Connection to phosphatidylinositol 3-kinase (PI3K) pathway

  • Synergistic effects with Cbl-interacting protein of 85K (Cin85)

• Cellular processes:

  Process	Assessment Method	Relevance
  Endothelial cell junction formation	VE-cadherin localization	Vascular integrity
  Cell shape regulation	F-actin cytoskeleton analysis	Lumen formation
  Membrane trafficking	Endocytic vesicle tracking	Cell polarity establishment

Functional Assessment:

• Vascular phenotyping:

  • In vivo imaging of vessel lumen dynamics

  • Vessel perfusion and permeability assays

  • Quantitative measurement of lumen diameter changes

• Rescue experiments:

  • Structure-function analysis through domain-specific mutations

  • Pathway-specific rescue with constitutively active downstream effectors

  • Combined knockdown with synergistic partners (e.g., Cin85)

These approaches can illuminate SH3GL3's role in vascular development and potentially identify new therapeutic targets for vascular disorders .

How can researchers investigate SH3GL3's tissue-specific functions and expression patterns?

SH3GL3 exhibits tissue-specific expression, predominantly in brain and testis . Investigating these specialized functions requires tailored approaches:

Expression Profiling:

• Multi-level analysis:

  • Transcriptomic profiling across tissues (bulk RNA-seq)

  • Protein-level confirmation (Western blot, IHC)

  • Single-cell resolution (scRNA-seq, multiplex immunofluorescence)

• Developmental trajectory:

  • Expression changes during organ development

  • Correlation with tissue-specific differentiation markers

  • Response to physiological challenges or disease states

Cell Type-Specific Functions:

• Isolation strategies:

  Tissue	Isolation Method	Application
  Brain	Fluorescence-activated cell sorting (FACS)	Neuronal vs. glial expression
  Testis	Sedimentation velocity cell separation	Stage-specific spermatogenic cells
  Blood vessels	Laser capture microdissection	Arterial vs. venous endothelium

• Conditional genetic approaches:

  • Cell type-specific Cre driver lines for conditional knockout

  • Tissue-specific promoters for overexpression studies

  • Inducible systems for temporal control

Functional Assessment:

• Tissue-relevant assays:

  • Neuronal: Electrophysiology, synaptic vesicle recycling, neurite outgrowth

  • Testicular: Spermatogenesis, acrosome formation, sperm motility

  • Vascular: Lumen formation, endothelial barrier function, angiogenesis

• Protein interaction networks:

  • Tissue-specific interactome mapping

  • Comparison of binding partners across tissues

  • Identification of tissue-restricted co-factors

• Pathological relevance:

  • Analysis in tissue-specific disease models

  • Correlation with clinical samples from relevant disorders

  • Potential as tissue-specific biomarker

This comprehensive approach can elucidate how SH3GL3 functions are tailored to specific cellular contexts, potentially revealing novel therapeutic targets for tissue-specific disorders .