Looking Beyond the Core: The Role of Flanking Regions in the Aggregation of Amyloidogenic Peptides and Proteins

• Published in: Frontiers in neuroscience Vol. 14; p. 611285
• Main Authors: Ulamec, Sabine M, Brockwell, David J, Radford, Sheena E
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 01-12-2020; Frontiers Media S.A
• Subjects: aggregation; Alzheimer's disease; amyloid; Amyloidogenesis; Amyotrophic lateral sclerosis; Disease; Electron microscopy; Fibrils; flanking region; fuzzy coat; Kinetics; Movement disorders; Mutation; Neurodegenerative diseases; Neuroscience; Neurotoxicity; NMR; Nuclear magnetic resonance; Parkinson's disease; Peptides; Protein folding; Ribonucleic acid; RNA; Roles; Synuclein; Tau; Tau protein; synuclein; amyloid; flanking region; Orb2; TDP-43; fuzzy coat; Tau; aggregation
• ISSN: 1662-4548; 1662-453X; 1662-453X
• DOI: 10.3389/fnins.2020.611285

Amyloid proteins are involved in many neurodegenerative disorders such as Alzheimer's disease [Tau, Amyloid β (Aβ)], Parkinson's disease [alpha-synuclein (αSyn)], and amyotrophic lateral sclerosis (TDP-43). Driven by the early observation of the presence of ordered structure within amyloid fibrils and the potential to develop inhibitors of their formation, a major goal of the amyloid field has been to elucidate the structure of the amyloid fold at atomic resolution. This has now been achieved for a wide variety of sequences using solid-state NMR, microcrystallography, X-ray fiber diffraction and cryo-electron microscopy. These studies, together with
methods able to predict aggregation-prone regions (APRs) in protein sequences, have provided a wealth of information about the ordered fibril cores that comprise the amyloid fold. Structural and kinetic analyses have also shown that amyloidogenic proteins often contain less well-ordered sequences outside of the amyloid core (termed here as flanking regions) that modulate function, toxicity and/or aggregation rates. These flanking regions, which often form a dynamically disordered "fuzzy coat" around the fibril core, have been shown to play key parts in the physiological roles of functional amyloids, including the binding of RNA and in phase separation. They are also the mediators of chaperone binding and membrane binding/disruption in toxic amyloid assemblies. Here, we review the role of flanking regions in different proteins spanning both functional amyloid and amyloid in disease, in the context of their role in aggregation, toxicity and cellular (dys)function. Understanding the properties of these regions could provide new opportunities to target disease-related aggregation without disturbing critical biological functions.