Structural and functional landscape of α-synuclein fibril conformations amplified from cerebrospinal fluid

Abstract

Lewy body dementias are pathologically defined by the deposition of α-synuclein fibrils into inclusions throughout the brain. Cerebrospinal fluid (CSF) from cases harbors circulating α-synuclein-fibril seeds, and parental α-synuclein fibrils can template core structure into amplified fibrils. Using cryo-electron microscopy, we identify six novel α-synuclein fibril assemblies amplified from ten CSF samples (3.8 Å to 2.9 Å nominal resolutions). Fibrils are classified based on two types of filament interaction, two types of β-sheet stacking, and two types of hydrophobic pocket. CSF-amplified fibril products have one, two, or three distinct assemblies each. Six of ten samples share a common fibril assembly. Within this classification, the fibrils have distinct profiles in amyloid dye binding, and dramatically different potencies in both seeding new inclusions in neurons and evoked microglial pro-inflammatory responses. However, no single structural feature predicts functional phenotypes. Our results highlight CSF as a valuable resource to identify novel α-synuclein assemblies potentially important in disease.

Structures of α-synuclein filaments from human brains with Lewy pathology

“…Filament assemblies amplified in vitro have also been shown to differ in their seeding behaviour in vivo ( 44 , 45 ). However, known structures of seeded α-synuclein aggregates are different from those of the seeds ( 46 – 49 ). Unlike for Lewy body diseases, two filament types have been observed in MSA, each of which is made of two different protofilaments ( 6 ).…”

Ultrastructures of α-Synuclein Filaments in Synucleinopathy Brains and Experimental Models

“…As in the study described earlier, the majority of amplified α-syn filaments were identical to spontaneous recombinant α-syn filaments, and several other filaments identified at low percentages did not show the Lewy fold. The structures of α-syn filaments formed in other SAA studies also differed from those of brain-derived filaments [ 113 - 116 ]. More recently, it has been demonstrated that α-syn in serum from patients with synucleinopathy can be amplified by SAA after immunoprecipitation [ 117 ].…”

“…The structures of α-syn filaments formed in other SAA studies also differed from those of brain-derived filaments. [113][114][115][116] More recently, it has been demonstrated that α-syn in serum from patients with synucleinopathy can be amplified by SAA after immunoprecipitation. 117 The ultrastructures of SAA products differed from those of brain-derived filaments, such as straight or twisted protofilaments in MSA-derived products and twisted or bundled filaments in LBD-derived products.…”

Distinct biological activity of Lewy body α-Synuclein strain in mice

“…Despite the clear in uence of bril structure on αSyn in vitro and in vivo pathological activity with respect to seeding potency, inclusion morphology, cell tropism, and biophysical signatures, attempts to generate recombinant brils that faithfully recapitulate the properties of brain-derived αSyn aggregates have been met with limited success. Furthermore, even though brain-derived αSyn aggregates can template the brillization of recombinant αSyn, as observed in seeded aggregation assays or protein misfolding cyclic ampli cation-based strategies using brain lysates or cerebrospinal uid, brils generated in this manner remain conformationally and functionally distinct from brain-derived αSyn aggregates [27][28][29][30][31] .…”