ATG17 Antibody

What is ATG17 and what is its role in autophagy?

ATG17 is an autophagy-related protein that plays a crucial role in the formation and regulation of autophagosomes. In yeast, ATG17 functions in cooperation with ATG1 and ATG13 to form a complex that is required for proper autophagosome formation. This complex formation is regulated by Tor signaling and is essential for normal autophagy . ATG17 specifically regulates the magnitude of the autophagic response, influencing both the number and size of autophagosomes formed during starvation-induced autophagy . Disruption of ATG17 results in the formation of reduced numbers of small autophagosomes, leading to defects in peroxisome degradation and partial impairment of autophagy .

How does ATG17 interact with other autophagy proteins?

ATG17 interacts with both ATG1 and ATG13 through specific coiled-coil domains. Yeast two-hybrid analyses have confirmed direct interactions between ATG17 and ATG1, between ATG17 and ATG13, and self-interactions of ATG17 . Interestingly, these interactions do not significantly depend on the presence of other autophagy proteins. Affinity isolation experiments using protein A-tagged ATG17 have demonstrated that ATG17 preferentially interacts with less phosphorylated forms of ATG13, which is consistent with findings that partially dephosphorylated ATG13 has a higher affinity for ATG1 . The first and third coiled-coil regions (CC1 and CC3) of ATG17 are particularly important for mediating these interactions, as deletion of either region severely impairs binding to ATG1 and ATG13 .

What are the specific domains in ATG17 important for antibody generation?

For generating effective antibodies against ATG17, researchers typically target specific domains that are unique to the protein and highly immunogenic. Based on published research, antibodies have been successfully generated using recombinant His6-tagged ATG17 and against amino acid residues 150-417 of the ATG17 ORF fused to a maltose-binding protein tag . These regions likely contain immunogenic epitopes that produce specific antibodies. When designing custom antibodies against ATG17, avoiding regions involved in protein-protein interactions (such as the coiled-coil domains CC1 and CC3) might be beneficial to ensure the antibody can recognize the native protein in its complexed form.

What are the optimal methods for immunoprecipitation using ATG17 antibodies?

For effective immunoprecipitation of ATG17 and its interaction partners, the following protocol has shown success in research settings:

• Prepare cell lysates in a buffer containing 50 mM Tris-HCl (pH 7.5), 150 mM NaCl, 1 mM EDTA, 0.5% Nonidet P-40, and protease inhibitors.

• Incubate lysates with anti-ATG17 antibody at 4°C for 2-3 hours.

• Add protein G-Sepharose and continue incubation for an additional 1-2 hours.

• Wash the immunoprecipitates 3-5 times with lysis buffer.

• Elute bound proteins by boiling in SDS sample buffer.

• Separate proteins by SDS-PAGE for subsequent immunoblotting with antibodies against potential interaction partners such as ATG1 and ATG13 .

This approach has been successfully used to demonstrate the interactions between ATG17 and both ATG1 and ATG13, particularly detecting the less phosphorylated forms of ATG13 that preferentially associate with ATG17 .

How can ATG17 antibodies be used to study autophagy dynamics during starvation?

ATG17 antibodies are valuable tools for monitoring changes in autophagy dynamics during nutrient starvation. A comprehensive experimental approach includes:

• Time-course analysis: Collect samples at different time points after shifting cells to starvation medium.

• Subcellular fractionation: Separate cellular components to track ATG17 translocation between cytosol and membrane fractions.

• Immunoblotting: Use ATG17 antibodies to detect changes in protein expression, localization, and potential post-translational modifications.

• Co-immunoprecipitation: Combine ATG17 antibodies with antibodies against ATG1 and ATG13 to track complex formation under different nutritional conditions.

• Microscopy: Employ immunofluorescence with ATG17 antibodies to visualize its recruitment to pre-autophagosomal structures.

Studies have shown that during starvation, ATG17 localizes to pre-autophagosomal structures and participates in the formation of autophagosomes, making these approaches particularly informative for studying the early steps of autophagy induction .

What controls should be included when using ATG17 antibodies in immunoblotting experiments?

When using ATG17 antibodies for immunoblotting, the following controls are essential for ensuring reliable and interpretable results:

These controls are particularly important because ATG17 often exists in complex with other proteins and may undergo post-translational modifications during autophagy induction, potentially affecting antibody recognition .

How can ATG17 antibodies be used to investigate the structural changes in the ATG1-ATG13-ATG17 complex during autophagy initiation?

To investigate structural changes in the ATG1-ATG13-ATG17 complex during autophagy initiation, researchers can employ a combination of techniques using ATG17 antibodies:

• Sequential immunoprecipitation: First precipitate with ATG17 antibodies, followed by elution and a second precipitation with ATG1 or ATG13 antibodies to isolate specific subcomplexes.

• Cross-linking coupled with immunoprecipitation: Treat cells with cross-linking agents before lysis and immunoprecipitation with ATG17 antibodies to capture transient interactions.

• Hydrogen-deuterium exchange mass spectrometry: Combine with ATG17 immunoprecipitation to identify regions of conformational change upon complex formation.

• FRET analysis: Use fluorescently-labeled ATG17 antibodies (for cell-free systems) to detect proximity changes between complex components.

• Protein footprinting: Compare antibody epitope accessibility in different nutritional states to identify structural rearrangements.

Research has shown that ATG17 preferentially interacts with less phosphorylated forms of ATG13, which occurs during starvation conditions when TOR is inhibited . This suggests that structural rearrangements in the complex are critical for autophagy induction, making these approaches valuable for understanding the molecular mechanisms involved.

What are the approaches for investigating ATG17 phosphorylation status using phospho-specific antibodies?

Investigating ATG17 phosphorylation requires specialized approaches:

• Development of phospho-specific antibodies: Generate antibodies that specifically recognize phosphorylated residues in ATG17, targeting predicted phosphorylation sites based on consensus sequences for known kinases.

• Phosphorylation site mapping: Combine immunoprecipitation using general ATG17 antibodies with mass spectrometry to identify phosphorylation sites, which can guide the development of phospho-specific antibodies.

• Phosphatase treatment controls: Compare immunoblots of samples with and without phosphatase treatment to confirm phosphorylation-dependent signals.

• Kinase inhibitor studies: Treat cells with inhibitors of candidate kinases (e.g., TOR, PKA) before immunoprecipitation and blotting with both general and phospho-specific ATG17 antibodies.

• Phosphomimetic mutant analysis: Compare antibody recognition of wild-type ATG17 versus phosphomimetic (S/T to D/E) and phospho-dead (S/T to A) mutants.

While specific phosphorylation sites on ATG17 have not been extensively characterized in the provided search results, the interaction of ATG17 with less phosphorylated forms of ATG13 suggests that phosphorylation plays a regulatory role in the ATG1-ATG13-ATG17 complex .

How can ATG17 antibodies be used to distinguish between different types of autophagy?

ATG17 antibodies can be valuable tools for distinguishing between different types of autophagy, as ATG17 has been shown to function primarily in nonspecific (starvation-induced) autophagy rather than selective types:

• Comparative analysis: Analyze ATG17 localization in cells undergoing different types of autophagy (e.g., starvation-induced, mitophagy, pexophagy) through immunofluorescence or subcellular fractionation followed by immunoblotting.

• Co-localization studies: Combine ATG17 antibodies with markers for specific cargo (e.g., mitochondria, peroxisomes) to assess selective autophagy processes.

• Time-course experiments: Monitor ATG17 recruitment during different autophagy paradigms, as timing may differ between selective and non-selective processes.

• Genetic background manipulation: Compare ATG17 localization and complex formation in wild-type cells versus cells deficient in selective autophagy receptors.

Research has demonstrated that ATG17 is particularly important for non-selective autophagy induced by starvation, with atg17Δ mutants showing defects in peroxisome degradation and forming a reduced number of small autophagosomes . This suggests that ATG17 may be specifically involved in regulating the magnitude of the autophagic response rather than cargo selection.

What are common issues when using ATG17 antibodies and how can they be resolved?

When troubleshooting ATG17 antibody applications, it's crucial to remember that ATG17 interacts with ATG1 and ATG13 via specific coiled-coil domains . Antibodies targeting these interaction regions may interfere with complex formation, potentially affecting experimental outcomes.

How can the specificity of ATG17 antibodies be validated in knockout/knockdown models?

Validating ATG17 antibody specificity using genetic models is a critical step in ensuring reliable experimental results:

• Complete knockout validation: Test the antibody in atg17Δ null mutant cells, which should show no signal in immunoblotting or immunofluorescence . This provides the most stringent validation of antibody specificity.

• Knockdown validation: In systems where complete knockout is not feasible, use siRNA or shRNA to reduce ATG17 expression and confirm proportional reduction in antibody signal.

• Rescue experiments: Reintroduce ATG17 expression in knockout cells and verify restored antibody detection. This can be accomplished using transgenic Atg17-GFP expression systems, which have been shown to restore viability in Atg17-null mutant animals .

• Epitope mapping: Express truncated versions of ATG17 (e.g., constructs lacking specific coiled-coil domains) and determine which regions are recognized by the antibody .

• Cross-species reactivity: Test the antibody across related species to confirm epitope conservation and specificity.

Research has demonstrated the effectiveness of these validation approaches, particularly the use of atg17Δ null mutants as negative controls for antibody specificity testing .

What methods can be used to optimize immunofluorescence protocols for detecting endogenous ATG17?

Optimizing immunofluorescence protocols for endogenous ATG17 detection requires careful attention to several factors:

• Fixation optimization:

  • Test multiple fixation methods (e.g., 4% paraformaldehyde, methanol, acetone)

  • Determine optimal fixation duration (typically 10-20 minutes)

  • Consider dual fixation approaches for preserving both protein epitopes and cellular architecture

• Permeabilization refinement:

  • Compare different detergents (Triton X-100, saponin, digitonin)

  • Optimize concentration and incubation time

  • Consider the subcellular localization of ATG17 when selecting permeabilization methods

• Antibody conditions:

  • Determine optimal antibody dilution through titration

  • Test extended incubation times (overnight at 4°C versus 1-2 hours at room temperature)

  • Evaluate signal enhancement methods (tyramide signal amplification, secondary antibody selection)

• Background reduction:

  • Increase blocking time and concentration

  • Use bovine serum albumin, normal serum, or commercial blocking reagents

  • Include detergents in washing buffers

• Controls and validation:

  • Include atg17Δ cells as negative controls

  • Use GFP-ATG17 expressing cells as positive controls

  • Perform peptide competition assays

Research has shown that ATG17 localizes to pre-autophagosomal structures during starvation, making it important to optimize protocols for detecting both diffuse cytosolic and punctate localization patterns .

How can ATG17 antibodies be used in proximity labeling experiments to identify novel interaction partners?

Proximity labeling combined with ATG17 antibodies offers powerful approaches for identifying transient or context-dependent interaction partners:

• BioID/TurboID approach:

  • Generate expression constructs for ATG17 fused to biotin ligase (BioID2 or TurboID)

  • After expression and biotin supplementation, use streptavidin pulldown to isolate proximity-labeled proteins

  • Confirm specific interactions using co-immunoprecipitation with ATG17 antibodies

• APEX2 proximity labeling:

  • Express ATG17-APEX2 fusion proteins

  • After brief treatment with biotin-phenol and H₂O₂, isolate biotinylated proteins

  • Validate findings using standard immunoprecipitation with ATG17 antibodies

• Split-BioID system:

  • Fuse ATG17 to one half of a split biotin ligase

  • Fuse candidate interactors to the complementary half

  • Reconstitution of functional biotin ligase indicates protein-protein interaction

  • Confirm with standard antibody-based methods

• Temporal analysis:

  • Perform proximity labeling at different time points during autophagy induction

  • Use ATG17 antibodies to confirm changing interaction profiles

• Subcellular targeting:

  • Direct proximity labeling to specific subcellular compartments where ATG17 functions

  • Compare interactome differences between cytosolic and membrane-associated fractions

These approaches can build upon known interactions between ATG17 and proteins like ATG1 and ATG13 , potentially revealing additional components of the autophagy initiation complex or regulatory proteins that interact transiently during specific phases of autophagy.

What are the considerations for using ATG17 antibodies in super-resolution microscopy studies?

Super-resolution microscopy with ATG17 antibodies requires specific considerations to achieve optimal results:

• Antibody selection and validation:

  • Choose high-affinity, monospecific antibodies

  • Validate specificity using atg17Δ cells as negative controls

  • Consider direct fluorophore conjugation to primary antibodies to minimize displacement error

• Sample preparation optimization:

  • Use thin samples (≤10 μm) for optimal optical performance

  • Test different fixation/permeabilization protocols to preserve nanoscale structures

  • Consider expansion microscopy for improved resolution of dense structures

• Fluorophore selection:

  • For STORM/PALM: Choose photoswitchable fluorophores (Alexa Fluor 647, mEos)

  • For STED: Select fluorophores with good depletion characteristics (ATTO 647N, Abberior STAR RED)

  • For SIM: Use bright, photostable fluorophores with minimal bleedthrough

• Multicolor imaging considerations:

  • Co-label with markers for autophagic structures (LC3/ATG8, WIPI2)

  • Use spectral unmixing for closely emitting fluorophores

  • Consider sequential imaging to minimize crosstalk

• Controls and analysis:

  • Include fiducial markers for drift correction

  • Perform cluster analysis to quantify ATG17 distribution

  • Use correlation analysis to quantify colocalization with other autophagy proteins

These approaches can provide new insights into the organization of the ATG1-ATG13-ATG17 complex and its role in autophagosome formation, particularly given ATG17's function in regulating autophagosome size and number .

How can ATG17 antibodies be integrated into multiplexed proteomic workflows to study autophagy dynamics?

Integrating ATG17 antibodies into multiplexed proteomic workflows can provide comprehensive insights into autophagy regulation:

• Sequential immunoprecipitation workflows:

  • First round: Immunoprecipitate with ATG17 antibodies

  • Elute under mild conditions

  • Second round: Immunoprecipitate with antibodies against other complex components

  • This approach enables isolation of specific subcomplexes containing ATG17

• Mass spectrometry-based approaches:

  • Immunoprecipitate with ATG17 antibodies under different conditions (fed, starved)

  • Perform quantitative proteomics (TMT, iTRAQ, SILAC) to identify condition-dependent interactions

  • Analyze post-translational modifications on ATG17 and interacting partners

• Antibody-based multiplexed arrays:

  • Develop reverse-phase protein arrays with ATG17 antibodies

  • Profile multiple autophagy components simultaneously across conditions

  • Quantify phosphorylation status using phospho-specific antibodies

• Single-cell analysis integration:

  • Combine ATG17 antibody-based flow cytometry with single-cell proteomics

  • Correlate ATG17 levels/modification state with cellular phenotypes

  • Identify cell-to-cell variability in autophagy responses

• Spatial proteomics approaches:

  • Use imaging mass cytometry with ATG17 antibodies

  • Map spatial relationships between ATG17 and other autophagy components

  • Correlate with functional autophagic structures

These integrated approaches can build upon the known interactions between ATG17 and proteins like ATG1 and ATG13 , potentially revealing dynamic changes in complex composition during different phases of autophagy.