Several hypotheses have been proposed on the mechanisms responsible for the death of neuronal cells in Parkinson’s Disease (PD). In this thesis (Mechanisms of membrane disruption by alpha-synuclein aggregates) a more detailed understanding is obtained on one of the possible mechanisms involved in PD-related cell death: αS-induced membrane damage. ‘Membrane model systems comprised of phospholipids were used here to mimic cellular membranes,’ says Himanshu Chaudhary. ‘Using spectroscopy and microscopy techniques, we were able to follow aggregation processes in real-time.’
A characteristic feature of PD is the appearance of fibrillar aggregates mainly containing fibrillar α-synuclein (αS) but also containing other proteins and even lipids. In the past, most of the research on αS-induced membrane damage has been performed on model membranes, consisting of 100% negatively charged phospholipids.
‘Physiological membranes contain much less charged lipids,’ Himanshu Chaudhary says. ‘The first step in this project was to prepare in vitro lipid membranes of more physiologically relevant mixtures.’
Previously, intermediate structures found during fibrillization, such as oligomers, were shown to damage membranes of selective composition. However, it is found that the process of fibrillization itself could disrupt the membrane integrity as well. Furthermore, fibrillization on the membranes could remodel giant unilamellar vesicles to tabulate or adopt polyhedral shapes.
‘Although we showed that fibrillization processes play an important role in membrane damage, we cannot rule out the role of oligomer in membrane disruption’ says Himanshu.
To investigate further, the effect of purified oligomers on supported lipid bilayers (SLBs) was probed. Himanshu et al observed that with pre-existing defects, the addition of oligomers resulted in extraction of lipids, which leads to fractal-like damage patterns. Some of the findings have been published in FEBS Letters, while other articles are still in the process of peer-review in leading journals.
In summary, as a member of the Nanobiophysics group, Himanshu endeavored to understand the mechanisms by which αS-aggregation or αS-aggregates can damage membranes in in vitro experiments. Himanshu concludes: ‘In case fibrillization is the prevailing toxicity mechanism, the inhibition of fibrillization processes would be the key therapeutic target.’
During his thesis work Himanshu learned to work with various microscopy techniques, almost from scratch. Himanshu adds: ‘Also the interplay of physico-chemical properties in complex membrane systems was new to me. Actually building systems to encapsulate proteins in vesicles and study their interaction with different intermediates formed during aggregation pathway, gave me insights into understanding the pathological mechanism of PD.’
As a next step in his career, Himanshu prefers an academic position but also options in industry appeal to him.
Social commitment will anyway remain a central theme in his life. ‘As a member of the academic social organisation “AADHAAR”, we are active in many rural development projects in India, to empower people using the benefits of technology. This help is often of a practical nature, like installing computers and opening libraries in rural areas’.