title: Aβ(39-42) modulates Aβ oligomerization but not fibril formation.
abstract: Recently, certain C-terminal fragments (CTFs) of Aβ42 have been shown to be effective inhibitors of Aβ42 toxicity. Here, we examine the interactions between the shortest CTF in the original series, Aβ(39-42), and full-length Aβ. Mass spectrometry results indicate that Aβ(39-42) binds directly to Aβ monomers and to the n = 2, 4, and 6 oligomers. The Aβ42:Aβ(39-42) complex is further probed using molecular dynamics simulations. Although the CTF was expected to bind to the hydrophobic C-terminus of Aβ42, the simulations show that Aβ(39-42) binds at several locations on Aβ42, including the C-terminus, other hydrophobic regions, and preferentially in the N-terminus. Ion mobility-mass spectrometry (IM-MS) and electron microscopy experiments indicate that Aβ(39-42) disrupts the early assembly of full-length Aβ. Specifically, the ion-mobility results show that Aβ(39-42) prevents the formation of large decamer/dodecamer Aβ42 species and, moreover, can remove these structures from solution. At the same time, thioflavin T fluorescence and electron microscopy results show that the CTF does not inhibit fibril formation, lending strong support to the hypothesis that oligomers and not amyloid fibrils are the Aβ form responsible for toxicity. The results emphasize the role of small, soluble assemblies in Aβ-induced toxicity and suggest that Aβ(39-42) inhibits Aβ-induced toxicity by a unique mechanism, modulating early assembly into nontoxic hetero-oligomers, without preventing fibril formation.
authors: Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States.
authors: Megan Murray
authors: MM
authors: Gessel
authors: Chun
authors: C
authors: Wu
authors: Huiyuan
authors: H
authors: Li
authors: Gal
authors: G
authors: Bitan
authors: Joan-Emma
authors: JE
authors: Shea
authors: Michael T
authors: MT
authors: Bowers
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000737:chemistry*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D000818:Animals; D052160:Benzothiazoles; D006801:Humans; D008856:Microscopy, Fluorescence; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D016716:PC12 Cells; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D055503:Protein Multimerization; D051381:Rats; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization; D013844:Thiazoles
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D052160:Benzothiazoles; D010446:Peptide Fragments; D013844:Thiazoles; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); C538897:amyloid beta-protein (40-42); C009462:thioflavin T