Cryo-EM structure of amyloid fibril formed by α-synuclein familial A53E mutation

Synucleinopathies, including Parkinsons disease (PD), dementia with Lewy bodies (DLB), and multiple systems atrophy (MSA) have the same hallmark pathologic feature of misfolded -synuclein protein accumulation in the brain. PD patients who carry -syn hereditary mutations tend to have an earlier onset and more severe clinical symptoms and pathology than sporadic PD patients who carry wild-type (WT) -syn. Therefore, revealing the structural effect of -syn hereditary mutations on the wild-type fibril structure can help us understand synucleinopathies structural basis. Here, we present a 3.38 [A] cryo-electron microscopy structure of -synuclein fibrils containing the hereditary A53E mutation. The A53E fibril is symmetrically composed of two protofilaments, as are many other synucleopathic structures - including WT. Interestingly, the interface between the protofilaments in A53E has significantly less buried surface area than all other documented fibril structures of -syn and its other mutants. The A53E fibril also exhibits slower formation/growth in in vitro fibrillation experiment compared to other mutants. This implies that the structural differences - both in the protofilament and between each protofilament of A53E - change the aggregation mechanism, or in the least, its kinetics of formation. These differences influence the molecular characteristics of each fibril mutant and likely plays a macro-scale role in progressing one clinical pathology over another.