Many high-resolution structures of the cross-ß core of amyloid ¿brils have been solved using solid-state NMR and cryo-electron microscopy in recent years. However, most ¿brils important in neurodegenerative diseases, as for example a-synuclein (aSyn) ¿brils found in in Lewy body dementia (LBD) and other synucleinopathies, have sizable intrinsically disordered regions (IDRs) surrounding their ordered cross-ß ¿bril core. These IDRs are part of the ¿bril surface, where they can interact with ¿bril-speci¿c binders and be important for ¿bril toxicity. Therefore, determining the residual structure and dynamics of these IDRs, how they interact with other cellular components, and how they relate to ¿bril toxicity is the next logical step in the LBD and Alzheimer’s disease related dementia (ADRD) ¿eld. The goal of this proposal is to determine the conformational ensemble and dynamics of the IDRs from aSyn ¿brils important in LBD, ADRD and other synucleinopathies. The N and especially the C-terminus of aSyn are intrinsically disordered in the ¿bril. These IDRs are binding sites for ¿bril-speci¿c interactors such as the co-chaperone DNAJB1. Our central hypothesis is that a speci¿c ¿bril core structure (polymorph) will determine the residual structure and dynamics of these IDRs and consequently the interaction with ¿brils-speci¿c binders. The rationale of this research is that only complete molecular models of amyloid ¿brils that include their IDRs will allow us to determine polymorph-speci¿c binding partners, which can explain the di¿erence between LBD and other synucleinopathies. These complete molecular models will not only point to natural interactors, but also to disease-speci¿c biomarkers and therapeutics for LBD as well as ADRD and other synucleinopathies. We will use a combination of solid-state NMR, EPR, and molecular dynamics simulations to test our hypothesis using three speci¿c aims. Aim 1 is to determine the change in residual structure and dynamics of IDRs upon ¿bril formation. Based on the known core structure and our conformational ensemble of the IDRs, we will create a model of the entire ¿bril. Aim 2 is to determine the e¿ect of ¿bril polymorphs on residual structure and dynamics of IDRs. We will show to what degree a speci¿c cross-ß core determines the conformational ensemble of its adjacent IDRs and determine the cytotoxicity of di¿erent aSyn polymorphs and chimeras. Aim 3 is to determine the e¿ect of the ¿bril core on aSyn-DNAJB1 interaction. Here, our hypothesis is that ¿bril formation increases the accessibility of the DNAJB1 binding site and that some ¿bril cores found in LBD and other synucleinopathies do this better than others. These aims will (i) determine the changes in the IDRs outside the ¿bril core upon ¿bril formation and result in a whole ¿bril model. We will (ii) learn how speci¿c cross-ß core structures found in LBD and other synucleinopathies change the conformational ensemble and dynamics of the IDRs, and (iii) we will understand how these changes in¿uence the interaction of speci¿c binders, in our case DNAJB1. Together these advances will facilitate the development of new approaches to diagnose and treat LBD and ADRD.
