Unique molecular signatures of Alzheimer's disease amyloid [beta] peptide mutations and deletion during aggregate/oligomer/fibril formation

• Published in: Journal of neuroscience research 2015-03, Vol.93 (3), p.410
• Main Authors: Poduslo, Joseph F, Howell, Kyle G
• Format: Article
• Language: English
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.23507

The formation of amyloid [beta] (A[beta]) peptide aggregates, oligomers, and fibrils is a dynamic process; however, the kinetics of their formation is not well understood. This study compares the time course of aggregate/fibril formation by transmission electron microscopy (TEM) analyses with that of oligomer/fibril formation by Western blot analysis under native and denaturing conditions. Efforts to deaggregate/defibrillate these peptides by using hexafluoroisopropanol, ammonium hydroxide, or dimethylsulfoxide did not change the nondenaturing polyacrylamide gel electrophoresis (PAGE) footprints or drive the peptides to a monomeric species. Regardless of the pretreatment protocol, TEM analyses reveal that all A[beta] peptides (A[beta]40, A[beta]42, A[beta]39E22[Delta] [Osaka], A[beta]40E22G [Arctic], A[beta]40E22Q [Dutch], and A[beta]40A2T [Icelandic]) immediately formed nonfibrillar, amorphous aggregates when first placed into solution with the Osaka mutation, quickly forming early-stage fibrils. The extent of fibril formation for other A[beta] peptides is time dependent, with the Arctic mutation forming fibrils at 1 hr, the Dutch and Icelandic at 4 hr, A[beta]42 at 8 hr, and A[beta]40 at 24 hr. In contrast, nondenaturing PAGE revealed unique footprints for the different A[beta] species. The rapidity of aggregate formation and the rapid transition to fibrils, particularly for the Osaka deletion, suggest an important role for aggregates/fibrils of A[beta] in the development of neuronal degeneration. © 2014 Wiley Periodicals, Inc.