Role of α-Synuclein Regions in Nucleation and Elongation of Amyloid Fiber Assembly

Abstract

α-Synuclein is an intrinsically disordered protein whose aggregation in the form of amyloid fibers is directly implicated in Parkinson's disease and other neurological disorders. α-Synuclein is composed of three different regions. The central region (61−95), called NAC, is responsible for protein fibrillation. The N-terminal region (1−61) has some helical propensity and can be divided into H1 (1−31) and H2 (32−61), while the highly acidic C-terminal region (96−140) is completely disordered. It has been postulated that the acidic character of the C-terminus, as well as the interaction between the soluble N-and C-terminal parts, protects the NAC region from fibrillation. In consequence, N-and C-terminal deletions increase α-synuclein fibrillation. Both N-and C-terminal truncations are common in synucleinopathies, but despite their clinical relevance, to date, there are no systematic and exhaustive studies that quantify the effect of these truncations in fiber nucleation and elongation. In this work, we measured both nucleation and fibrillation elongation kinetics in order to study the influence of N-and C-terminal deletions, including the simultaneous deletion of several regions, in α-synuclein fibrillation. We also tested whether the fibrillation prone mutation A53T had an additional effect when combined with truncations. Furthermore, our cross-seeding experiments showed that the deletions studied induce changes in fiber morphology. Our results unravel then the role of the different α-synuclein regions and the A53T mutation in the nucleation and elongation of amyloid fibers.

Prion-like C-Terminal Domain of TDP-43 and α-Synuclein Interact Synergistically to Generate Neurotoxic Hybrid Fibrils

“…αS is a 140 amino acid protein containing three regions; lipid binding N-terminal domain (NTD), an aggregation-prone non-amyloid component (NAC) middle region, and an intrinsically disordered, charged C-terminal domain (CTD). NAC and a part of NTD are the primary regions responsible for aggregation, while CTD seems to play an inhibitory role for this process [28,29]. On the other hand, TDP-43 is a 414 amino acid containing ribonucloprotein protein with an N-terminal domain, two RNA recognition motifs (RRMs), and a disordered prion-like C-terminal domain (PrLD) containing low complexity sequences [30].…”

Truncation-Driven Lateral Association of α-Synuclein Hinders Amyloid Clearance by the Hsp70-Based Disaggregase

“…α-Syn C-terminal truncation enhances aggregation in vitro [ 16 , 17 , 46 , 47 ] and in vivo [ 48 , 49 , 50 ]. The protective role proposed for the charges at the C-terminus via long-range intramolecular interactions is lost upon truncation, which favors aggregation [ 18 , 51 , 52 , 53 , 54 ]. C-terminal charges also seem to play an important role after fibril formation, generating an interfibrillar electrostatic repulsion.…”

“…Although it has been shown that truncation strongly influences α-syn aggregation and prion-like pathogenicity [ 14 , 17 , 18 ], very little is known about the effect of this PTM on aggregate clearance. α-Syn fibrils and oligomers are disassembled by the human disaggregase, a chaperone system composed of three proteins: Hsc70 (a constitutively expressed member of the Hsp70 family), DnaJB1 (a representative of the class B Hsp40 or J-protein family) and Apg2 (a nucleotide exchange factor of the Hsp110 family) [ 19 , 20 ].…”

Implementing Complementary Approaches to Shape the Mechanism of α-Synuclein Oligomerization as a Model of Amyloid Aggregation

“…α-syn can be divided into three different domains ( Figure 1 A): an N-terminal amphipathic region (residues 1–60) which presents five conserved lysine-rich repeats, the central non-amyloid-β component (NAC) domain (residues 61–95) which forms the core of α-syn amyloid fibrils, and the unstructured C-terminal acidic region (residues 96–140) [ 12 ]. While the first 37 residues of the N-terminal region and the C-terminal domain hinder nucleation, the second portion of the N-terminal domain favors it [ 13 ]. The structure of α-syn is highly dependent on environmental factors and the complexation state.…”