Evaluation of LC3-II Release via Extracellular Vesicles in Relation to the Accumulation of Intracellular LC3-positive Vesicles
October 18th, 2024
Here, we present the methodology for concisely assessing autophagosome marker LC3-II levels in extracellular vesicles (EVs) by immunoblotting. Analysis for LC3-II levels in EVs, autolysosome formation, and omegasome formation suggests the new role of STX6 in the release of LC3-II-positive EVs when autophagosome-lysosome fusion is inhibited.
Our research focuses on progressive neurodegenerative diseases characterized by the accumulation of the nuclear protein TDP-43 in the cytoplasm, such as ALS or FTLD-TDP. We aim to understand how TDP-43 pathologies spread through the brain in a prion-like manner. We previously found that the release of TDP-43 via extracellular vesicles is mediated by the dysregulation of autophagy.
Progranulin of the of FTLD-TDP facilitates this process. The next challenge is to clarify how autophagy regulates the production and release of extracellular vesicles containing TDP-43, which could lead to the discovery of therapeutic targets for ALS or FTLD-TDP. To begin, take the cultured HeLa cells, count them using a cell counter, and seed one times ten to the power of six cells on a six-centimeter plate containing a culture medium.
Incubate the cells at 37 degrees Celsius with 5%carbon dioxide and controlled humidity for 24 hours. Next, prepare a 20-micromolar siRNA solution. Mix 100 microliters of reduced serum medium and three microliters of siRNA in a low-retention tube to prepare Solution A.Then, mix 100 microliters of reduced serum medium and five microliters of transfection reagent in a low-retention tube to prepare Solution B.After that, mix Solution A and Solution B, then incubate the mixture at room temperature for five minutes.
Now add the mixture of Solutions A and B to the medium used for culturing HeLa cells and incubate for 24 hours. On the next day, wash the cells with PBS and expose the cells to 500 microliters of 0.25%trypsin and one millimolar EDTA solution at 37 degrees Celsius with 5%carbon dioxide and controlled humidity for five minutes. Next, add 2.5 milliliters of the culture medium to the cells and using a Pasteur transfer pipette with a 20-microliter pipette tip attached, prepare a single-cell suspension.
After counting the cells, seed one times ten to the power of six cells on a ten-centimeter plate and incubate, as demonstrated earlier. At the end of the incubation, prepare the culture medium containing either vehicle or 100 nanomolar bafilomycin A1.Then expose the cells to the medium containing either vehicle or 100 nanomolar bafilomycin A1 and incubate for 24 hours. The following day, collect all the culture medium from the 10-centimeter plate.
Transfer the collected medium into a 15-milliliter tube and centrifuge it at 3, 000 G for 10 minutes at four degrees Celsius to remove cell debris. To isolate the P1 extracellular vesicle fraction, transfer the supernatant after centrifugation at 3, 000 G into a centrifugation tube. Centrifuge the tube at 20, 000 G at four degrees Celsius for one hour.
For the isolation of the P2 extracellular vesicle fraction, transfer the supernatant after centrifugation at 20, 000 G into an ultra-centrifuge tube. Centrifuge it at 110, 000 G at four degrees Celsius for one hour. After wiping off the excess moisture inside the tube with a laboratory wipe, resuspend the remaining pellets in the centrifugation tube in 50 microliters of two-time sample buffer to prepare the P1 extracellular vesicle fraction.
Then remove the supernatant by decanting. Wipe off the excess moisture inside the tube with a laboratory wipe and resuspend the remaining pellets in the ultracentrifugation tube in 50 microliters of two-time sample buffer to prepare the P2 extracellular vesicle fraction. Incubate the P1 and P2 extracellular vesicle fractions at 100 degrees Celsius on a heat block for 10 minutes.
After transferring the culture medium from the 10-centimeter plate into a 15-milliliter tube, wash the cells in the 10-centimeter dish with PBS. Then expose the cells to two milliliters of 0.25%trypsin and one millimolar EDTA solution at 37 degrees Celsius with 5%carbon dioxide and controlled humidity for five minutes. Add eight milliliters of growth medium to the cells.
Using a Pasteur transfer pipette with a 200-microliter pipette tip attached, pipette the cells to prepare a single-cell suspension. Transfer the cell suspension into a 15-milliliter tube and centrifuge it at 1, 000 G for 10 minutes at four degrees Celsius. Then remove the supernatant using an aspirator.
Add PBS to the cell pellet and centrifuge at 1, 000 G for five minutes at four degrees Celsius. After removing the PBS, sonicate the cell pellet in one milliliter of A68 buffer containing 1%sarcosil. Mix 300 microliters of the cell lysate with 100 microliters of four-time sample buffer.
Incubate the mixture at 100 degrees Celsius on a heat block for 10 minutes to prepare the cell fraction.
Overview
This study investigates the role of TDP-43 in neurodegenerative diseases and its release via extracellular vesicles (EVs). The research highlights the involvement of autophagy in regulating TDP-43 release, potentially leading to therapeutic targets for ALS and FTLD-TDP.
Key Study Components
Area of Science
- Neuroscience
- Cell Biology
- Neurodegenerative Diseases
Background
- TDP-43 is a nuclear protein associated with neurodegenerative diseases.
- ALS and FTLD-TDP are characterized by TDP-43 accumulation in the cytoplasm.
- Understanding TDP-43 pathology may reveal mechanisms of disease spread.
- Extracellular vesicles play a role in TDP-43 release.
Purpose of Study
- To clarify how autophagy regulates the production and release of TDP-43-containing EVs.
- To explore potential therapeutic targets for ALS and FTLD-TDP.
- To investigate the role of progranulin in TDP-43 release.
Methods Used
- Cell culture of HeLa cells.
- Counting cells using a cell counter.
- Seeding cells in culture medium for experimentation.
- Immunoblotting to assess autophagosome marker levels.
Main Results
- Identification of STX6's role in LC3-II-positive EV release.
- Analysis of autophagosome-lysosome fusion inhibition effects.
- Evidence of autophagy dysregulation in TDP-43 release.
- Progranulin's facilitation of TDP-43 release via EVs.
Conclusions
- Autophagy is crucial for the regulation of TDP-43 release.
- Targeting autophagy may provide new therapeutic avenues for ALS and FTLD-TDP.
- Further research is needed to fully understand the mechanisms involved.
Frequently Asked Questions
Executive Industry Relevance
Quantitative evaluation of LC3-II release via extracellular vesicles (EVs) provides a mechanistic window into autophagy-dependent protein trafficking, a process implicated in neurodegenerative disease progression. This protocol enables biopharma teams to interrogate the molecular determinants of pathological protein dissemination, supporting target validation and risk-adjusted advancement in neurodegeneration portfolios. The approach strengthens predictive confidence at the intersection of autophagy modulation and EV-mediated biomarker release.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables functional assessment of autophagy-related genes in EV-mediated protein export.
- Supports mechanistic de-risking by isolating the impact of candidate targets such as STX6 on LC3-II trafficking.
- Facilitates hypothesis-driven interrogation of disease-relevant pathways in neurodegeneration.
Screening & Assay Development
- Provides a reproducible immunoblot-based workflow for quantifying LC3-II in cellular and EV fractions.
- Establishes assay controls using bafilomycin A1 to benchmark autophagosome-lysosome fusion inhibition.
- Enables standardization of EV isolation and marker quantification for downstream screening applications.
Translational & Preclinical Research
- Aligns with translational biomarker strategies by quantifying EV-associated LC3-II under disease-relevant perturbations.
- Supports continuity from mechanistic discovery to preclinical validation of autophagy-modulating interventions.
- Provides a platform for evaluating the extracellular dissemination of pathological proteins in neurodegenerative models.
Pipeline & Workflow Integration
This protocol integrates into the discovery-to-preclinical continuum by enabling quantitative, mechanistic readouts of autophagy and EV biology.
- Discovery Biology: Supports null hypothesis testing for target genes regulating LC3-II export via EVs.
- Screening: Delivers standardized, quantitative immunoblot outputs for comparative analysis across conditions.
- Analytics: Enables measurement of LC3-II and TSG101 as orthogonal markers for pathway and vesicle specificity.
- Translational Research: Bridges mechanistic findings to disease-relevant models of protein aggregation and spread.
- Enterprise Reuse: Offers a modular workflow adaptable to diverse autophagy and EV research programs.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation for autophagy and EV pathways.
- Operational Value: Standardizes EV isolation and LC3-II quantification for reproducible, scalable studies.
- Strategic Value: Informs go/no-go decisions for neurodegeneration targets by clarifying mechanistic roles in protein dissemination.
- Portfolio Impact: Enables risk-adjusted prioritization of autophagy-modulating candidates in neurodegenerative disease pipelines.
Implementation Considerations
- Requires expertise in cell culture, siRNA transfection, and immunoblotting techniques.
- Demands access to high-speed and ultracentrifugation infrastructure for EV isolation.
- Necessitates rigorous cross-team standardization of sample preparation and marker quantification.
- Adaptable to various cell models but may require optimization for primary or disease-relevant systems.
- Interpretation of LC3-II and TSG101 outputs must consider pathway specificity and experimental controls.
