Small Amphipathic Molecules Modulate Secondary Structure and Amyloid Fibril-forming Kinetics of Alzheimer Disease Peptide Aβ1–42

Abstract

Background: A␤ aggregation may be modulated by small lipid-like molecules. Results: Activators induced ␤-structure and rapid aggregation, whereas inhibitors induced ␣-helical structure and small A␤ oligomers. Conclusion: Small lipid-like molecules modulate A␤ secondary structure and self-association at stoichiometric levels. Significance: Understanding the role of small molecules and lipids in Alzheimer disease is crucial for the development of effective therapeutic targets.

Stabilization of Nontoxic Aβ-Oligomers: Insights into the Mechanism of Action of Hydroxyquinolines in Alzheimer's Disease

“…The effect of PBT2 on the aggregation of A␤1-42 was measured using a continuous ThT fluorescence assay described previously (McColl et al, 2009;Ryan et al, 2012Ryan et al, , 2013a. PBT2/CQ was prepared as a 1 mM stock in DMSO, and diluted into PBS containing ThT (10 M) to a final concentration of 10 M. A␤1-42 was added to a final concentration of 5 M, and the plate was incubated at 37°C, with shaking every 7 min, for 3 s, before the measurement of the ThT fluorescence intensity (444 nm excitation and 485 nm emission), using a Flexstation 3 Plate reader.…”

“…To address this, we initially took advantage of inherent UV absorbance of the 8-HQ molecules, which provide an excellent tool to monitor the association of these compounds with A␤. Analyzing the absorbance unique to a species in solution, such as PBT2 or CQ, is a powerful tool to measure direct interactions, as exemplified by studies investigating the interaction of 7-nitrobenz-2-oxa-1,3-diazol-4-yl aminolabeled phospholipids with apoC-II (Mok et al, 2011;Ryan et al, 2011), or the interaction of Alexa-488 labeled DNA with Klenow fragment (Bailey et al, 2009). PBT2 and CQ are particularly suited to this approach because they have a low molecular mass and do not sediment effectively in the aqueous-based buffer systems of the experiment.…”

“…This theory has been supported by the finding of SDS-stable dimers in human brain tissue, which affect LTP (Shankar et al, 2008), and the observation that levels of a 56 kDa oligomer (labeled A␤ 56*) correlate with the severity of cognitive dysfunction (Lesné et al, 2006). There are many different methods for generating toxic oligomers in vitro (for review, see Benilova et al, 2012), which lead to a corresponding array of numerous oligomeric forms of A␤, with little evidence of which in vitro configurations actually exist in vivo, or are specific to disease pathogenesis (for reviews, see Hayden and Teplow, 2013;Ryan et al, 2013b). Despite this uncertainty, assays of these oligomers and development of antibodies targeting the A␤ peptide have been a major theme in the recent efforts to develop a therapy for AD (Imbimbo et al, 2012;Tayeb et al, 2013).…”

Mechanism of protein phosphatase-2Aregulating phosphorylation of amyloid precursor proteosome and Aβ generation

“…PP-2A is a protein phosphatase widely present and conservative in cells, which can catalyze in vivo dephosphorylation of the phosphorylated site of the substrate (15). A number of reports have demonstrated that the activity of PP-2A in AD patients was decreasing (16).…”

The Role of Lipid in Misfolding and Amyloid Fibril Formation by Apolipoprotein C-II

“…Interestingly, a parallel study using the same compound library with amyloid-β peptides displayed a quite different pattern of activators and inhibitors. This indicates that the pattern of activation and inhibition observed with apoC-II is specifi c to this protein, and should not be generalised to other amyloidforming proteins (Ryan et al 2012 ).…”