Structural insight of MODAG-005 on 𝛼-Synuclein aggregates as a novel PET tracer
by Myeongkyu Kim
Date of Examination:2023-12-21
Date of issue:2024-11-15
Advisor:Prof. Dr. Christian Griesinger
Referee:Prof. Dr. Markus Zweckstetter
Referee:Prof. Dr. Tiago Fleming Outeiro
Persistent Address:
http://dx.doi.org/10.53846/goediss-10855
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Abstract
English
Neurodegenerative disorders, including Parkinson's disease (PD) and related synucleinopathies, are characterized by the accumulation of pathological protein aggregates in the brain. Among the key proteins implicated in these diseases is α -synuclein (αSyn), an intrinsically disordered protein (IDP) known to play a crucial role in synaptic function and neurotransmitter regulation. Positron emission tomography (PET) imaging holds promise as a non-invasive and sensitive tool for early detection and monitoring of αSyn pathology, facilitating improved patient care, treatment evaluation and therapeutic development. This research focuses on the development of a novel PET tracer targeting αSyn aggregates to enable in-vivo visualization and quantification of pathological burden. The study begins with the rational design and synthesis of a series of potential radioligands with high affinity and specificity for αSyn aggregates. The candidate PET tracer, MODAG-005 was assessed through in-vitro binding assays, utilizing recombinant αSyn and post-mortem brain tissue samples from individuals with confirmed synucleinopathies. The tracer's binding site, which exhibited the most favorable profiles, was further investigated using Nuclear Magnetic Resonance (NMR) and Cryo-electron microscopy (Cryo-EM). Furthermore, a significant discovery was made concerning the tracer's behavior, revealing its capability to bind to two distinct sites depending on the preparation protocol. Specifically, when the tracer was administered at during aggregation stage, it exhibited a preference for binding within the cavity of lipidic α-Syn aggregates. In contrast, when administered at after aggregation stage, the tracer showed a specific binding to an external site on the aggregates, specifically near F94. Moreover, through continuous observation following tracer administration it was discovered that the external binding mode/pose is thermodynamically unstable, causing MODAG-005 to migrate into the internal cavity over time. This observation provides valuable insights into the temporal dynamics of the tracer's interactions and may have implications for its practical applications as a reliable and effective tool in various research and diagnostic contexts. In conclusion, understanding the binding site of MODAG-005 to lipidic αSyn aggregates depending on the treatment timing supports the development of a highly specific and sensitive PET tracer for αSyn imaging. This represents a significant step towards enhancing our understanding and diagnosing synucleinopathies. The successful translation of such a tracer into clinical practice could revolutionize the management of neurodegenerative disorders by enabling early and accurate diagnosis, facilitating patient stratification in clinical trials, and ultimately aiding the development of disease-modifying treatments.
Keywords: Alpha synuclein; PET tracer; NMR; Cryo-EM; MD simulation
