Towards a high-resolution picture of the stability of protein deposits and its modulation in neurodegenerative diseases: visualizing the invisible by fluorine NMR dynamics

• Applicant: Nasrollah Rezaei-Ghaleh, Ph.D.
• Subject Area: Structural Biology ; Biophysics
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 327959918

Neurodegenerative diseases such as Alzheimer’s disease (AD) are characterized by the presence of protein deposits in brains. In recent years, several lines of evidence suggest that variation in disease phenotype is rooted in the molecular properties of protein deposits. Molecular stability of protein deposits is widely believed to control the prion-like spreading of protein aggregation in the brain and the consequent progressive course of neurodegenerative pathology. In this project started in June 2017, I have employed high-pressure Nuclear Magnetic Resonance (NMR) spectroscopy in combination with molecular dynamic simulation and studied the thermodynamic stability of amyloid-beta (Ab) fibrils, the main constituent of senile plaques in the brains of AD patients. I first developed an integrative approach to study atomic-scale motions in disordered proteins, which provided a detailed picture of Ab dynamics at ambient pressure as a reference. I also developed an oxygen-NMR method, which enables disentangling the effect of pressure on viscosity from its specific effects on the dynamics of Ab and other proteins. The hitherto collected results, (i) unambiguously demonstrate that the early-onset AD-related mutations modify the stability of Ab aggregates, (ii) reveal how stability of Ab aggregates changes over the course of aggregation, and (iii) propose mechanistic roles for the N- and C-terminal residues of Ab during aggregation. Further progress towards providing a high-resolution picture of Ab aggregation is however hindered by the inherent properties of the standard nuclei such as 15N currently employed in the project. In the proposed renewal of the project, we will attempt to overcome these restrictions by shifting from conventional nuclei to 19F spins and exploiting the unique advantages of fluorine NMR. In particular, through combining fluorine and paramagnetic NMR, the exchange between Ab monomers and aggregates can be brought into a proper NMR-accessible regime. Furthermore, we will benefit our recently developed NMR-singlet method enabling selective access to the six glycine residues of Ab and utilize them as additional probes of Ab aggregation. Through integrating various complementary probes, the proposed project enables capturing the otherwise in-accessible exchange processes and promises an atomic resolution picture of Ab aggregation. The mechanistic insights provided by this project will open new avenues to inhibit toxic aggregation of Ab and control the pathological course of AD.

• DFG Programme: Research Grants