The effect of truncation on prion-like properties of α-synuclein

Abstract

Increasing evidence suggests that α-synuclein (αS) aggregates in brains of individuals with Parkinson's disease and dementia with Lewy bodies can spread in a prion-like manner. Although the initial αS nuclei are pivotal in determining αS fibril polymorphs and resulting phenotypes, it is not clear how the initial fibril seeds are generated. Previous studies have shown that αS truncation might have an important role in αS aggregation. However, little is known about how this truncation influences αS's propagation properties. In the present study, we generated αS fibrils from a series of truncated human αS constructs, characterized their structures and conformational stabilities, and investigated their ability to convert the conformation of full-length αS , in cultured cells, and in WT mice. We show that both C- and N-terminal truncations of human αS induce fibril polymorphs and exhibit different cross-seeding activities. N-terminally 10- or 30-residue-truncated human αS fibrils induced more abundant αS pathologies than WT fibrils in mice, whereas other truncated fibrils induced less abundant pathologies. Biochemical analyses of these truncated fibrils revealed that N-terminal 10- or 30-residue truncations of human αS change the fibril conformation in a manner that increases their structural compatibility with WT mouse αS fibrils and reduces their stability. C-terminally 20-residue-truncated fibrils displayed enhanced seeding activity Our findings imply that truncation of αS can influence its prion-like pathogenicity, resulting in phenotypic diversity of α-synucleinopathies.

The making of a Lewy body: the role of alpha-synuclein post-fibrillization modifications in regulating the formation and the maturation of pathological inclusions.

“…However, the role of the C-terminal truncations in regulating α-syn aggregation has been studied almost exclusively in the context of its impact on the aggregation of monomeric α-syn, with an emphasis on truncation as potentially the primary trigger of α-syn aggregation, seeding and LB formation 27,29 . This working hypothesis is based on the consistent observation that Cterminal truncations dramatically increase the propensity of monomeric α-syn to aggregate in vitro [46][47][48][49][50][51] and that fibrils derived from C-terminal truncated α-syn fragments seed the aggregation of full-length α-syn in vitro 17,50,52 and in vivo 35,45,50,52,53 . To the best of our knowledge, the present work is the first attempt to dissect the role of post-fibrillization Cterminal cleavage of α-syn in the seeding, fibril formation and the evolution and maturation of LB-like aggregates in neurons.…”

“…,45,[48][49][50][51][52] and in cellular and animal models34,36,37,39,[41][42][43]45,[50][51][52][53] of α-synucleinopathies have consistently shown that C-terminal truncations accelerate α-syn aggregation and pathology formation.Furthermore, α-syn aggregates derived from C-terminally truncated variants of α-syn retain the ability to seed the aggregation of full-length α-syn. These observations led us to the hypothesis that C-terminal cleavage is one of the primary triggers for initiating α-syn aggregation in vivo.…”

Carboxy‐terminal truncations of mouse α‐synuclein alter aggregation and prion‐like seeding

“…One mechanism by which αsyn may gain toxic aggregation properties is through post‐translational modifications common in disease including phosphorylation, ubiquitination, and truncation . Carboxy‐truncation (C‐truncation) of αsyn is one modification that has been shown in vitro and in cultured cells to increase the propensity of monomeric αsyn to spontaneously aggregate and also to modulate the prion‐like seeding activity of the fibrils . Recent characterization of αsyn fibrils through the use of cryo‐electron microscopy and other techniques suggests that C‐terminal truncation modifications can greatly alter αsyn fibril structure ; consequent alterations in prion‐like seeding as a result of these modifications may be important in explaining strain‐like diversity in fibril structure and seeding capacity isolated from LBs .…”

“…Additionally, recent works have suggested that PFFs when introduced to healthy neurons are quickly trafficked for lysosomal processing where extensive truncation of exposed C‐terminal regions on the PFFs can readily occur ; this indicates that initial seeding events in a neuron likely involve truncated αsyn fibrils. Indeed, various truncated forms of human αsyn have been recently investigated and it has been found that seeding activity can increase or decrease depending on the specific truncation . Herein, a subset of the most common C‐truncated forms of αsyn is investigated with mouse αsyn for compatibility with NTG mouse‐based models of prion‐like seeding to further characterize how C‐truncation affects induction of pathology.…”

Mechanisms of strain diversity of disease-associated in-register parallel β-sheet amyloids and implications about prion strains

“…Those findings suggested existence of two mutually exclusive aggregation paths of αSyn amyloid formation. Cross-seeding experiments also proved the contribution of the N-terminal- and the C-terminal-side regions to efficient propagation and strain-specific properties of Syn amyloids, as demonstrated by in vitro fibril formation and in vivo inoculation experiments with various human-mouse chimeric αSyn [45], or with N- and C-terminally truncated mutant αSyn [46]. Not only cross-seeding efficiencies between αSyn molecules, strain-specific structures of αSyn amyloids can also affect interactions with other proteins.…”