Author interview: Sourav Dasadhikari is a researcher at TIFR- Hyderabad, studying protein aggregation in Alzheimer’s under the supervision of Prof. Kanchan Garai, using advanced single-molecule fluorescence techniques.
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Lab: Prof. Kanchan Garai, Tata Institute of Fundamental Research- Hyderabad
Research Summary: Our study using single-molecule techniques shows ApoE isoforms (E2, E3, E4) inhibit Aβ42 fibril elongation differently, with ApoE4 being the least effective, impacting Alzheimer’s amyloid buildup.
What was the core problem you aimed to solve with this research?
ApoE-ε4 is the strongest genetic risk factor for late-onset Alzheimer’s disease, linked to increased amyloid-β (Aβ) buildup. However, how ApoE isoforms (E2, E3, E4) influence Aβ aggregation and clearance at the molecular level remains unclear. This is critical because ApoE4 accelerates amyloid deposition, while ApoE3 and ApoE2 may offer protection by either inhibiting aggregation or potentially aiding microglia (brain immune cells) in plaque clearance—or both. Our goal was to quantify how ApoE isoforms affect Aβ42 fibril growth, focusing on microscopic processes like elongation and secondary nucleation (a monomer-dependent, fibril-catalyzed process that generates more toxic oligomeric and fibrillar aggregates), which are crucial to Alzheimer’s pathology.
How did you go about solving this problem?
First, we built an in-house Total Internal Reflection Fluorescence Microscope (TIRFM) that is considerably more sensitive than those that are available commercially. It enabled us to observe the growth of single fibrils of Aβ42 fibril growth in real time and test how lipidated ApoE2, E3, and E4 affect elongation and secondary nucleation. Then, we used an array of homebuilt single molecule techniques such as superresolution microscopy and single-molecule photobleaching assay to map ApoE binding to the fibrils. The application of high-resolution and highly sensitive homebuilt techniques enabled us to examine the isoform-specific impacts on fibril dynamics, providing key insights into how ApoE modulates Aβ aggregation.
This work offers an exciting opportunity to explore strategies for controlling the apoE-Aβ interaction, a key determinant of Alzheimer’s disease. – Prof. Kanchan Garai.
How would you explain your research outcomes (Key findings) to the non-scientific community?
Imagine Aβ42 as a sticky protein that forms fibrils and plaques in the brains of Alzheimer’s patients. ApoE acts like a protective agent, slowing the growth of these plaques. We found that ApoE3 and ApoE2 are better protectors, about 4–5 times more efficient than ApoE4. This explains why people with ApoE4 end up having more plaques in their brains. Furthermore, ApoE3 binds more tightly to the fibrils, and we believe that the microglia—the brain cleanup cells—might be able to sense these ApoE3-bound fibrils and clean them up from the sites of accumulation. However, this idea is still under investigation.
What are the potential implications of your findings for the field and society?
Our study suggests that ApoE4’s weaker ability to bind and inhibit Aβ42 fibril growth contributes to greater amyloid buildup, whereas ApoE3 and ApoE2 offer better protection by more effectively slowing down this process. This insight opens the door to developing therapies that mimic the behavior of ApoE3 and ApoE2 to slow down Alzheimer’s progression. The single-molecule techniques we have established can be employed to test these therapeutic approaches.
What was the exciting moment during your research?
A thrilling moment was when the videos recorded in our TIRF microscope first showed ApoE3 drastically slowing down fibril growth compared to ApoE4—fibrils with ApoE3 barely grew, while ApoE4 ones extended much faster. After months of optimizing imaging conditions and tracking hundreds of fibrils, seeing these clear isoform-specific differences was incredibly exciting. Another highlight was the TIRFM and STORM images showing ApoE3 clustering at fibril ends, providing visual proof of its stronger binding and helping explain why ApoE4 fails to prevent Alzheimer’s buildup as effectively.
Paper reference: Dasadhikari, S., Ghosh, S., Pal, S. et al. A single fibril study reveals that ApoE inhibits the elongation of Aβ42 fibrils in an isoform-dependent manner. Commun Chem 8, 133 (2025). https://doi.org/10.1038/s42004-025-01524-z. https://www.nature.com/articles/s42004-025-01524-z
