title: Small liposomes accelerate the fibrillation of amyloid β (1-40).
abstract: The deposition of amyloid β (Aβ) peptides is a pathological hallmark of Alzheimer disease. Aβ peptides were previously considered to interact specifically with ganglioside-containing membranes. Several studies have suggested that Aβ peptides also bind to phosphatidylcholine membranes, which lead to deformation of membranes and fibrillation of Aβ. Moreover, the role of membrane curvature, one type of deformation produced by binding of proteins to a membrane, in the binding and fibrillation of Aβ remains unclear. To clearly understand the relationship between the binding, consequent membrane deformation, and fibrillation of Aβ, we examined the amyloid fibrillation of Aβ-(1-40) in the presence of liposomes of various sizes. Membrane curvature increased with a decrease in the size of the liposomes. We used liposomes made of 1,2-dioleoyl-sn-glycero-3-phosphocholine to eliminate electrostatic effects. The results obtained showed that liposomes of smaller sizes (≤50 nm) significantly accelerated the nucleation step, thereby shortening the lag time of fibrillation. On the other hand, liposomes of larger sizes decreased the amount of fibrils but did not notably affect the lag time. The morphologies of fibrils, which were monitored by total internal reflection fluorescence microscopy, atomic force microscopy, and transmission electron microscopy, revealed that the length of Aβ-(1-40) fibrils became shorter and the amount of amorphous aggregates became larger as liposomes increased in size. These results suggest that the curvature of membranes coupled with an increase in water-accessible hydrophobic regions is important for binding and concentrating Aβ monomers, leading to amyloid nucleation. Furthermore, amyloid fibrillation on membranes may compete with non-productive binding to produce amorphous aggregates.
authors.affiliation: From the Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
authors.forename: Mayu S
authors.initials: MS
authors.lastname: Terakawa
authors.affiliation: From the Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yagi
authors.affiliation: From the Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Adachi
authors.affiliation: From the Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Lee
authors.affiliation: From the Institute for Protein Research, Osaka University, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan ygoto@protein.osaka-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Goto
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D018625:Microscopy, Atomic Force; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D066329:Protein Aggregates / Q000235:genetics*; D011485:Protein Binding; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D008051:Lipid Bilayers; D008081:Liposomes; D010446:Peptide Fragments; D066329:Protein Aggregates; C078592:amyloid beta-protein (1-40)
keywords: Amyloid; Amyloid Fibrils; Amyloid-β (AB); Lipid; Membrane; Protein Aggregation; Supersaturation