The Contrasting Effect of Macromolecular Crowding on Amyloid Fibril Formation

Abstract

BackgroundAmyloid fibrils associated with neurodegenerative diseases can be considered biologically relevant failures of cellular quality control mechanisms. It is known that in vivo human Tau protein, human prion protein, and human copper, zinc superoxide dismutase (SOD1) have the tendency to form fibril deposits in a variety of tissues and they are associated with different neurodegenerative diseases, while rabbit prion protein and hen egg white lysozyme do not readily form fibrils and are unlikely to cause neurodegenerative diseases. In this study, we have investigated the contrasting effect of macromolecular crowding on fibril formation of different proteins.Methodology/Principal FindingsAs revealed by assays based on thioflavin T binding and turbidity, human Tau fragments, when phosphorylated by glycogen synthase kinase-3β, do not form filaments in the absence of a crowding agent but do form fibrils in the presence of a crowding agent, and the presence of a strong crowding agent dramatically promotes amyloid fibril formation of human prion protein and its two pathogenic mutants E196K and D178N. Such an enhancing effect of macromolecular crowding on fibril formation is also observed for a pathological human SOD1 mutant A4V. On the other hand, rabbit prion protein and hen lysozyme do not form amyloid fibrils when a crowding agent at 300 g/l is used but do form fibrils in the absence of a crowding agent. Furthermore, aggregation of these two proteins is remarkably inhibited by Ficoll 70 and dextran 70 at 200 g/l.Conclusions/SignificanceWe suggest that proteins associated with neurodegenerative diseases are more likely to form amyloid fibrils under crowded conditions than in dilute solutions. By contrast, some of the proteins that are not neurodegenerative disease-associated are unlikely to misfold in crowded physiological environments. A possible explanation for the contrasting effect of macromolecular crowding on these two sets of proteins (amyloidogenic proteins and non-amyloidogenic proteins) has been proposed.

Amyloid-like Fibril Formation by Trypsin in Aqueous Ethanol. Inhibition of Fibrillation by PEG

“…conditions, PEGs can facilitate or inhibit protein aggregation [21,22]. PEG treatment after traumatic brain injury reduces the accumulation of -amyloid precursor protein in degenerating axons [23].…”

Recent progress in prion and prion-like protein aggregation

“…3, prion protein is a GPI-anchored cell surface protein and the conversion of PrP from a normal soluble conformation PrP C to its pathogenic conformation PrP Sc is dramatically accelerated by crowded physiological environment containing high concentrations of polysaccharides and collagen. Our data suggested that prion-like proteins associated with neurodegenerative diseases are more inclined to form amyloid fibrils in crowded physiological environments than in dilute solutions [64,66,67]. The 'driving power' for fibrillization of prion-like proteins involves both the formation of an intermolecular or intramolecular disulfide bond and non-covalent interactions such as electrostatic interactions, hydrogen bonds, and hydrophobic interactions, which could be enhanced by crowded physiological environments [66].…”

“…It is known that in vivo human prion protein and its pathogenic mutants, human Tau protein and its pathogenic mutants, and human SOD1 pathogenic mutants have the tendency to form amyloid deposits in many different kinds of tissue and they are associated with different kinds of neurodegenerative diseases [64]. However, it is hard to distinguish the factors that affect prion-like protein aggregation in vivo because of the interaction network between proteins and proteins, proteins and nucleic acids, and so on.…”

“…However, it is hard to distinguish the factors that affect prion-like protein aggregation in vivo because of the interaction network between proteins and proteins, proteins and nucleic acids, and so on. Therefore, it is necessary to imitate crowded physiological environments where prion-like protein aggregation takes place by the addition of macromolecular crowding agents in vitro [64][65][66][67]. In macromolecular crowding environments, choosing the right crowders is the key event.…”

A review on the salt bridge ASP177-ARG163 (O–N) of wild-type rabbit prion protein

“…A number of previous studies showed that a few animals such as rabbits exhibit low susceptibility to be infected by the PrP Sc (Vorberg et al, 2003;Khan et al, 2010;Barlow & Rennie, 1976;Fernandez-Funez et al, 2009;Korth et al, 1997;Courageot et al, 2008;Vilette et al, 2001;Nisbet et al, 2010;Wen et al, 2010aWen et al, & 2010bZhou et al, 2011;Ma et al, 2012). Now experimental structural data for rabbit PrP C (RaPrP C ) is available from the Protein Data Bank (PDB bank: http://www.rcsb.org/).…”