title: Amyloidogenic Mutation Promotes Fibril Formation of the N-terminal Apolipoprotein A-I on Lipid Membranes.
abstract: The N-terminal amino acid 1-83 fragment of apolipoprotein A-I (apoA-I) has a strong propensity to form amyloid fibrils at physiological neutral pH. Because apoA-I has an ability to bind to lipid membranes, we examined the effects of the lipid environment on fibril-forming properties of the N-terminal fragment of apoA-I variants. Thioflavin T fluorescence assay as well as fluorescence and transmission microscopies revealed that upon lipid binding, fibril formation by apoA-I 1-83 is strongly inhibited, whereas the G26R mutant still retains the ability to form fibrils. Such distinct effects of lipid binding on fibril formation were also observed for the amyloidogenic prone region-containing peptides, apoA-I 8-33 and 8-33/G26R. This amyloidogenic region shifts from random coil to α-helical structure upon lipid binding. The G26R mutation appears to prevent this helix transition because lower helical propensity and more solvent-exposed conformation of the G26R variant upon lipid binding were observed in the apoA-I 1-83 fragment and 8-33 peptide. With a partially α-helical conformation induced by the presence of 2,2,2-trifluoroethanol, fibril formation by apoA-I 1-83 was strongly inhibited, whereas the G26R variant can form amyloid fibrils. These findings suggest a new possible pathway for amyloid fibril formation by the N-terminal fragment of apoA-I variants: the amyloidogenic mutations partially destabilize the α-helical structure formed upon association with lipid membranes, resulting in physiologically relevant conformations that allow fibril formation.
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Mizuguchi
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Fuka
authors.initials: F
authors.lastname: Ogata
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Shiho
authors.initials: S
authors.lastname: Mikawa
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Tsuji
authors.affiliation: Research Center for Stem Cell Engineering (SCRC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Baba
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Shigenaga
authors.affiliation: Graduate School of Environmental and Life Science, Okayama University, Okayama 700-8530, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Shimanouchi
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Okuhira
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Otaka
authors.affiliation: Institute of Biomedical Sciences, Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78-1 Shomachi, Tokushima 770-8505, Japan. Electronic address: hsaito@tokushima-u.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Saito
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000235:genetics; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics; D052160:Benzothiazoles; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005456:Fluorescent Dyes; D015870:Gene Expression; D006801:Humans; D009154:Mutation; D010713:Phosphatidylcholines / Q000737:chemistry*; D011485:Protein Binding; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics; D013329:Structure-Activity Relationship; D013844:Thiazoles; D014270:Trifluoroethanol / Q000737:chemistry; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D000682:Amyloid; D016632:Apolipoprotein A-I; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D010713:Phosphatidylcholines; D011993:Recombinant Fusion Proteins; D013844:Thiazoles; D053835:Unilamellar Liposomes; C009462:thioflavin T; D014270:Trifluoroethanol
keywords: amyloid; apoA-I; apolipoprotein; fibril; helix; lipid bilayer; membrane