Alzheimer's Amyloid beta: Lipid membrane interactions, detected in real-time

There are strong implications that Amyloid beta (Aβ) peptide causes neurotoxicity in Alzheimer's disease (AD) through (i) pore formation, (ii) the disruption of ionic channels that could affect calcium homeostasis, and (iii) receptor binding. The actual mechanism(s) remains unclear. In this study, we utilised cell-sized model membranes to observe the stability of lipid vesicles, in real-time, in the presence of Aβ-peptides. Using fluorescence-labelled Aβ-peptides, we imaged the localisation of pre-fibrillar Aβ species on the membrane surface, whereas mature fibrils hardly co-localised with the membrane surface. Further, we investigated the interaction of different oligomeric species of the Aβ peptide with lipid vesicles, observing membrane stability in terms of fluctuations and morphological changes. We observed a few different membrane morphological changes, with oligomeric species inducing a higher level of membrane instability. Interestingly, gramicidin A, a pore-forming peptide, did not induce any membrane transformations. We propose that this membrane transformation may be a different toxicity mechanism, from the proposed pore-formation hypothesis. This `toxicity' mechanism may aid in real-time observation of these morphological understanding the mechanisms behind Aβ-induced neuro-toxicity in Alzheimer's.