Solid-state NMR studies of α-synuclein fibril structure

Lewy bodies are intracytoplasmic aggregates that are the major pathological feature of Parkinson’s disease (PD). Their primary protein component, α-synuclein (α- syn), adopts an amyloidogenic fibrillar form in Lewy bodies. In recent years research has slowly started to unravel clear pathological links between this fibrillar protein and PD disease progression. While great progress is being made, it has become evident that the structures of different α-syn fibril forms are closely linked to their pathogenicity, and the lack of structural details have hindered our understanding of PD. Here, I present the first 3D structure of α-syn fibrils determined through solid- state NMR spectroscopy experiments validated with X-ray fiber diffraction and electron microscopy mass per-length measurements. The fibril form presented here is shown to be pathologically active in neuronal cell culture. Further, the structure is validated by comparison of the structure to three of the early-onset PD mutants, A30P, E46K, and A53T, and show that the changes in the SSNMR spectra induced by the mutation are consistent with the structural features present in the fibril, most notably the E46K mutant disrupting a stabilizing salt-bridge within the fibril core. Additionally, I show that non- native cysteine mutants of T33C, V48C, T59C, A85C, and Q99C further validate the structure. The results and studies presented here establish the first structure of α-syn fibrils and provide the experimental and computational basis for greatly increasing our understanding of PD, amyloid fibril structure, and advancing the techniques available for structural studies via SSNMR spectroscopy