Biological Description

Specificity GABARAP Antibody (Rabbit mAb) [P12P16] detects endogenous levels of total GABARAP protein.
Background GABARAP, gamma-aminobutyric acid receptor-associated protein, belongs to the ATG8 family of ubiquitin-like modifiers, sitting within the GABARAP/GATE-16 subfamily that is functionally distinct from the LC3 subfamily also encoded by ATG8 orthologs. While LC3 proteins drive elongation of the growing phagophore membrane during autophagosome formation, GABARAP subfamily members act at a later stage, supporting autophagosome maturation rather than initial membrane expansion. GABARAP performs this maturation function through direct, LC3-interacting-region-dependent binding to receptor proteins displayed on cargo destined for degradation, and this receptor-based recognition mechanism extends beyond bulk cytoplasmic autophagy into organelle-selective clearance. In reticulophagy, the selective autophagic turnover of the endoplasmic reticulum, GABARAP engages the ER-resident receptor TEX264, a single-pass transmembrane protein whose C-terminal cytosolic region carries a single LC3-interacting motif; the ATG8-containing isolation membrane cradles a tubular segment of TEX264-positive ER at three-way junctions, forming a synapse of two juxtaposed membranes held together by trans interaction between TEX264 and ATG8-family proteins including GABARAP, and expansion of the isolation membrane extends this ER capture in a zipper-like process until membrane fission closes the autophagosome around the captured ER fragment. Beyond its role in membrane trafficking, GABARAP functions as a membrane-localized signaling scaffold independent of autophagy: it recruits a CUL3 RING ubiquitin ligase complex built from the substrate adaptors KBTBD6 and KBTBD7, which engage GABARAP preferentially over other ATG8 family members through dedicated ATG8-interacting motifs, and this GABARAP-anchored complex ubiquitylates TIAM1, a RAC1-specific guanine nucleotide exchange factor, targeting it for proteasomal degradation. Binding to GABARAP is required for this ubiquitylation event to proceed, meaning GABARAP does not merely tether the ligase complex to membranes but is mechanistically necessary for TIAM1 turnover itself; depleting KBTBD6 and KBTBD7 increases TIAM1 abundance, elevates RAC1 activity, alters actin cytoskeletal morphology, reduces focal adhesions, and enhances invasive cell behavior, directly linking GABARAP-scaffolded ubiquitin ligase activity to spatial restriction of RAC1-driven cytoskeletal signaling and cell motility. Through these two mechanistically distinct roles, membrane-remodeling receptor engagement during ER-phagy and ubiquitin ligase scaffolding during RAC1 pathway regulation, GABARAP functions as a dual-purpose ATG8 protein positioned at the interface of organelle quality control and localized signal transduction, making it a relevant target for researchers studying selective autophagy substrate specificity as well as spatially restricted small GTPase signaling in cell migration and proliferation.

Usage Information

Application WB, IHC Dilution
WB IHC
1:1000 1:100 - 1:250
Reactivity Human
Source Rabbit Monoclonal Antibody MW 14 kDa
Storage Buffer PBS, pH 7.2+50% Glycerol+0.05% BSA+0.01% NaN3
Storage
(from the date of receipt)
-20°C (avoid freeze-thaw cycles), 2 years
WB
Experimental Protocol:
 
Sample preparation
1. Tissue: Lyse the tissue sample by adding an appropriate volume of ice-cold Tris-Triton Lysis Buffer (containing Protease Inhibitor Cocktail),and homogenize the tissue at a low temperature or lyse it by sonication on ice, then incubate on ice for 30 minutes.
2. Adherent cell: Aspirate the culture medium and wash the cells with ice-cold PBS twice. Lyse the cells by adding an appropriate volume of Tris-Triton Lysis Buffer (containing Protease Inhibitor Cocktail) , sonicate to lyse the cells, and incubate on ice for 30 minutes.
3. Suspension cell: Transfer the culture medium to a pre-cooled centrifuge tube. Centrifuge and aspirate the supernatant. Wash the cells with ice-cold PBS twice. Lyse the cells by adding an appropriate volume of Tris-Triton Lysis Buffer (containing Protease Inhibitor Cocktail) , sonicate to lyse the cells, and incubate on ice for 30 minutes.
4. Place the lysate into a pre-cooled microcentrifuge tube. Centrifuge at 4°C for 15 min. Collect the supernatant;
5. Remove a small volume of lysate to determine the protein concentration;
6. Combine the lysate with protein loading buffer. Boil 20 µL sample under 95-100°C for 5 min. Centrifuge for 5 min after cool down on ice.
 
Electrophoretic separation
1. According to the concentration of extracted protein, load appropriate amount of protein sample and marker onto SDS-PAGE gels for electrophoresis. Recommended separating gel (lower gel) concentration: 10%. Reference Table for Selecting SDS-PAGE Separation Gel Concentrations
2. Power up 80V for 30 minutes. Then the power supply is adjusted (110 V~150 V), the Marker is observed, and the electrophoresis can be stopped when the indicator band of the predyed protein Marker where the protein is located is properly separated. (Note that the current should not be too large when electrophoresis, too large current (more than 150 mA) will cause the temperature to rise, affecting the result of running glue. If high currents cannot be avoided, an ice bath can be used to cool the bath.)
 
Transfer membrane
1. Take out the converter, soak the clip and consumables in the pre-cooled converter;
2. Activate PVDF membrane with methanol for 1 min and rinse with transfer buffer;
3. Install it in the order of "black edge of clip - sponge - filter paper - filter paper - glue -PVDF membrane - filter paper - filter paper - sponge - white edge of clip";
4. The protein was electrotransferred to PVDF membrane. ( 0.22 µm PVDF membrane is recommended )Reference Table for Selecting PVDF Membrane Pore Size Specifications
Recommended conditions for wet transfer: 200 mA, 60 min.
( Note that the transfer conditions can be adjusted according to the protein size. For high-molecular-weight proteins, a higher current and longer transfer time are recommended. However, ensure that the transfer tank remains at a low temperature to prevent gel melting.)
 
Block
1. After electrotransfer, wash the film with TBST at room temperature for 5 minutes;
2. Incubate the film in the blocking solution for 1 hour at room temperature;
3. Wash the film with TBST for 3 times, 5 minutes each time.
 
Antibody incubation
1. Use primary antibody dilution buffer to prepare the primary antibody working liquid (recommended dilution ratio for primary antibody 1:1000), gently shake and incubate with the film at 4°C overnight;
2. Wash the film with TBST 3 times, 5 minutes each time;
3. Add the secondary antibody to the blocking solution and incubate with the film gently at room temperature for 1 hour;
4. After incubation, wash the film with TBST 3 times for 5 minutes each time.
 
Antibody staining
1. Add the prepared ECL luminescent substrate (or select other color developing substrate according to the second antibody) and mix evenly;
2. Incubate with the film for 1 minute, remove excess substrate (keep the film moist), wrap with plastic film, and expose in the imaging system.
IHC
Experimental Protocol:
 
Deparaffinization/Rehydration
1. Deparaffinize/hydrate sections:
2. Incubate sections in three washes of xylene for 5 min each.
3. Incubate sections in two washes of 100% ethanol for 10 min each.
4. Incubate sections in two washes of 95% ethanol for 10 min each.
5. Wash sections two times in dH2O for 5 min each.
6.Antigen retrieval: For Citrate: Heat slides in a microwave submersed in 1X citrate unmasking solution until boiling is initiated; continue with 10 min at a sub-boiling temperature (95°-98°C). Cool slides on bench top for 30 min.
 
Staining
1. Wash sections in dH2O three times for 5 min each.
2. Incubate sections in 3% hydrogen peroxide for 10 min.
3. Wash sections in dH2O two times for 5 min each.
4. Wash sections in wash buffer for 5 min.
5. Block each section with 100–400 µl of blocking solution for 1 hr at room temperature.
6. Remove blocking solution and add 100–400 µl primary antibody diluent in to each section. Incubate overnight at 4°C.
7. Remove antibody solution and wash sections with wash buffer three times for 5 min each.
8. Cover section with 1–3 drops HRPas needed. Incubate in a humidified chamber for 30 min at room temperature.
9. Wash sections three times with wash buffer for 5 min each.
10. Add DAB Chromogen Concentrate to DAB Diluent and mix well before use.
11. Apply 100–400 µl DAB to each section and monitor closely. 1–10 min generally provides an acceptable staining intensity.
12. Immerse slides in dH2O.
13. If desired, counterstain sections with hematoxylin.
14. Wash sections in dH2O two times for 5 min each.
15. Dehydrate sections: Incubate sections in 95% ethanol two times for 10 sec each; Repeat in 100% ethanol, incubating sections two times for 10 sec each; Repeat in xylene, incubating sections two times for 10 sec each.
16. Mount sections with coverslips and mounting medium.
 

References

  • https://pubmed.ncbi.nlm.nih.gov/31006538/
  • https://pubmed.ncbi.nlm.nih.gov/25684205/

Application Data

WB

Validated by Selleck

  • F3963-wb
    Lane 1: 293T, Lane 2: 293T (human GABARAP transfected)