Work done in the lab of Prof. Samrat Mukhopadhyay at the Indian Institute of Science, Education and Research (IISER), Mohali.
About author
Aishwarya is a native of Rampur, Uttar Pradesh. She was a graduate student in the lab of Prof. Samrat Mukhopadhyay at the Indian Institute of Science, Education and Research (IISER), Mohali. Recently, she defended her Ph.D. thesis and nowPostdoc with Prof. Janin Lautenschlaege at The Cambridge Institute for Medical Research, Cambridge University. She is particularly interested in studying the mechanism of protein misfolding and aggregation in neurodegenerative disorders. In her free time, she likes to do gardening, listen to music and watch movies.
Interview
How would you explain your research outcomes to the non-scientific community?
Proteins are the essential constituents of all living organisms which keep the cells under constant surveillance. The phenomenal diversity of cellular functions performed by these proteins is in turn dictated by their specific three-dimensional structure. However, acquiring this correctly folded conformation in a highly crowded cellular environment is highly error-prone and can often give rise to incorrectly folded proteins/misfolded proteins. Such protein misfolding is also a common feature in several aging and neurodegenerative disorders, for instance, Alzheimer’s, Parkinson’s, Huntington’s, prion diseases, and so forth. This good to evil transformation of protein from its functional native state to the misfolded disease-causing state can be imagined as the split personality of the character in the novel The Strange Case of Dr. Jekyll and Mr. Hyde.
The misfolding is often also assisted by multiple binding partners like nucleic acids, proteins, salts, and so forth. Also, there is increasing evidence of the presence of unrelated/multiple proteins in these amyloid-like aggregates which indicates cross-interaction between multiple proteins. Therefore, the central idea behind these projects was to decode the molecular mechanism of the protein misfolding as well as to identify the factors which promote such events.
We elucidated a novel mechanism by which a pathological variant of the prion protein retaining only the N-terminal intrinsically disordered region (IDR) misfolds and forms amyloid-like aggregates. At higher concentrations, the protein undergoes spontaneous biomolecular condensation/liquid-liquid phase separation (LLPS) to form liquid-like protein-rich condensates. The addition of certain cofactors like nucleic acids promoted phase separation at physiological protein concentrations. We also characterized different features that regulate prion condensation. The N-terminal IDR and the sequence-specific bias of the prion protein promote its LLPS. These condensates are highly dynamic and reversible i.e., they respond to various external factors like temperature, pH, etc. However, upon aging, these condensates are no longer reversible and exhibit solid-like behavior. Our study showed that these protein-rich droplets might act as the center for the growth and maturation of amyloid-like fibrils which are a common occurrence in prion diseases.
In another study, we also demonstrate the heterotypic phase separation of native prion protein (Fl-PrP) with another protein namely α-synuclein which occurs at much lower protein concentrations. Domain-specific electrostatic interactions between the N-terminal of Fl-PrP and C-terminal of α-synuclein facilitate their condensation whereas the addition of RNA in a certain ratio resulted in their dissolution. These heterotypic condensates upon aging also demonstrate similar liquid-to-solid transition indicating a central role of such phase transition pathways in the onset of neurodegenerative disorders.
How do these findings contribute to your research area?
Our study finds broad implications in both functional and pathological aspects of the prion protein. The N-terminal IDR of the prion protein promotes its phase separation as well as its cross-interaction with α-synuclein. These findings may have implications for the clustering of the membrane-anchored cellular prion protein at the cell surface to facilitate signal transductions. On the other hand, our study also demonstrates liquid-liquid phase separation as one of the potential pathways in promoting misfolding and aggregation of the prion protein which correlates with the onset/progression of neurodegenerative disorders.
“Our study demonstrates liquid-liquid phase separation as one of the potential pathways in promoting misfolding and aggregation of the prion protein which correlates with the onset/progression of neurodegenerative disorders.”
What was the exciting moment during your research?
There were numerous occasions when we felt the thrill, but our eureka moment was the one where we realized our hypothesis is indeed true and we observed beautiful liquid-like droplets of the prion protein. Seeing is believing! From there, it was onwards and upwards.
What do you hope to do next?
After my Ph.D. I look forward to pursuing post-doctoral studies in the field of biomolecular condensation. I hope to gain more insights into understanding the role of phase separation in cellular function and neurodegenerative disorders.
Where do you seek scientific inspiration from?
There is no straight answer to this question as there have been numerous instances as well as a lot of people I have been inspired from. I seek my scientific inspiration from my Ph.D. advisor and my colleagues. Every single person who is persistent, hardworking, and has a never-say-die attitude is my source of inspiration. The unpredictability and continuous excitement during my experiments drive me more curious. As scientists, we should never stop seeking inspiration because I believe it is everywhere.
How do you intend to help Indian science improve?
Indian science has largely expanded in the past few years and there is an increasing excitement toward academia. The future of our science lies in the hands of our younger generation. Therefore, providing them with the right guidance and direction is very important. I have plans to open my research lab in India if given the opportunity, but I also plan to participate in teaching activities and outreach programs to spread more awareness and motivate younger students to nurture their scientific aspirations.
Reference
- Agarwal A, Rai SK, Avni A, & Mukhopadhyay S. An intrinsically disordered pathological prion variant Y145Stop converts into self-seeding amyloids via liquid-liquid phase separation. Proc. Natl. Acad. Sci. U. S. A. 118, e2100968118 (2021).
- Agarwal A, Arora L, Rai S.K, Avni, A, & Mukhopadhyay S. Spatiotemporal Modulations in Heterotypic Condensates of Prion and α-Synuclein Control Phase Transitions and Amyloid Conversion. Nat. Commun. 13, 1154 (2022).
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