AbstractsChemistry

Alzheimer’s disease (AD) is a neurodegenerative disorder which major risk factor is age. Current drugs only offer symptomatic alleviation in AD, thus a disease-modifying treatment is urgent. The amyloid-β (Aβ) protein aggregation is strongly associated with AD. Aggregates of Aβ are deposited in the form of amyloid plaques in the brains of AD patients. Aβ monomer self-assembles into intermediate oligomeric species that evolve into protofibrils, that finally aggregate into amyloid fibrils, the main component of amyloid plaques. The soluble Aβ oligomers have been posed as the main causative agents of the neurotoxicity and cognitive decline observed in AD. However, the heterogeneity of the aggregation process together with the dynamic and transient nature of Aβ oligomers, makes it very diffcult to characterize each of the aggregates formed and thus to establish the specific features that make them responsible for the neurotoxicity observed. Pulse-labelling hydrogen deuterium exchange experiments analyzed by electrospray mass spectrometry (PL-HDX-ESI-MS) allow the detection, characterization, and quantification of the species formed during aggregation on the basis of structural differences among them. We applied this strategy to study the aggregation of three Aβ variants: Aβ40, the peptide most abundantly produced, Aβ42, the variant most linked to neurotoxicity in AD, and the muta¬tion E22Δ-Aβ42, a peptide that was first described to form oligomers but not amyloid fibrils although later reports showed that it indeed formed amyloid fibrils. The application of this strategy allowed detection of three species for Aβ40 and Aβ42: Early aggregates (EA), Protofibrils (PF) and Fibrils (F). In the case of E22Δ-Aβ42 we detected two species, PFE22Δ-Aβ42 and FE22Δ-Aβ42. These experiments imply that different species populate Aβ aggregation and that important structural rearrangements occur during this process. Having been able to “dissect” the different species populating Aβ aggregation, we then aimed at assigning the contribution of each species to neurotoxicity. To this end, in parallel experiments we assessed cell viability by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in primary neural cultures. We found that protofibrillar species were the aggregates that most correlated with the neurotoxicity observed.; L’agregació de la proteïna beta-amiloide (βA) està associada amb la malaltia d’Alzheimer (MA). Tanmateix, l’heterogeneïtat del procés d’agregació fa molt difícil la caracterització de les diferents espècies conformant el procés, dificultant, per tant, la identificació de trets comuns explicant la neurotoxicitat d’aquests agregats. Els experiments de bescanvi protó/protó deuteri amb marcatge de pols analitzats per espectrometria de masses (PL-HDX-ESI-MS, de l’anglès Pulse-labelling hydrogen deuterium exchange electrospray mass spectrometry) possibiliten la detecció, caracterització i quantificació de les espècies formades durant l’agregació. Vam aplicar aquesta metodologia a l’estudi de l’agregació…