Structural Biology of Alpha-Synuclein in Lewy Body Dementia

Washington University, Saint Louis MO

Investigators

Linked publications, trials & patents

Abstract

Abstract Parkinson disease (PD) is defined pathologically by the accumulation of alpha-synuclein (Asyn) fibrils in neuronal cytoplasmic and neuritic inclusions known as Lewy bodies and Lewy neurites. The role of Asyn in the pathogenesis of PD is supported by the identification of dominant mutations in the gene encoding Asyn (SNCA) in rare familial versions of PD. Dementia occurs frequently in PD. It sometimes begins at approximately the same time as motor symptoms (often referred to as Dementia with Lewy bodies or DLB), or up to 20 years after motor symptoms begin (PD with dementia or PDD). The term Lewy body dementia (LBD) encompasses this spectrum of clinical presentations and is associated with widespread deposition of Asyn fibrils throughout the brain, particularly neocortex. Multiple therapeutic approaches targeting Asyn accumulation are being pursued. A further priority is to develop a Positron Emission Tomography (PET) imaging agent to quantify the deposition of Asyn in living individuals, as a biomarker for target engagement and disease progression. Understanding Asyn fibril structure in LBD can guide the development of Asyn-targeted therapies and imaging agents. In this project, we will use a combination of solid-state NMR (SSNMR) and cryo- electron microscopy (cryo-EM) to determine atomic resolution structures of Asyn fibrils in LBD. We developed multiple complimentary approaches to isolate fibrils from tissue and grow them in the presence of labeled monomeric Asyn protein for SSNMR and cryo-EM studies, enabling more comprehensive analysis of structure. We will analyze and compare structures of Asyn fibrils isolated from multiple subgroups of LBD autopsy cases defined by early versus late onset of dementia, as well as the presence or absence of co-occurring amyloid β accumulation, and determine whether structural variations relate to disease phenotype. To promote the translation of these structural studies we will utilize SSNMR and cryo-EM to determine the structural features of binding sites for leading PET imaging ligand candidates, which can guide further optimization of PET ligands. Finally, we will utilize Asyn fibrils derived from LBD tissue to seed accumulation of Asyn fibrils in cell culture and mouse models. We will utilize SSNMR, cryo-EM and cryo-electron tomography to analyze Asyn fibril structure in these model systems, which will guide future studies of disease mechanisms, PET ligand development and therapeutic development.