Aβ dimers differ from monomers in structural propensity, aggregation paths and population of synaptotoxic assemblies

Abstract

Dimers of Aβ (amyloid β-protein) are believed to play an important role in Alzheimer's disease. In the absence of sufficient brain-derived dimers, we studied one of the only possible dimers that could be produced in vivo, [Aβ](DiY) (dityrosine cross-linked Aβ). For comparison, we used the Aβ monomer and a design dimer cross-linked by replacement of Ser²⁶ with cystine [AβS26C]₂. We showed that similar to monomers, unaggregated dimers lack appreciable structure and fail to alter long-term potentiation. Importantly, dimers exhibit subtly different structural propensities from monomers and each other, and can self-associate to form larger assemblies. Although [Aβ](DiY) and [AβS26C]₂ have distinct aggregation pathways, they both populate bioactive soluble assemblies for longer durations than Aβ monomers. Our results indicate that the link between Aβ dimers and Alzheimer's disease results from the ability of dimers to further assemble and form synaptotoxic assemblies that persist for long periods of time.

Targeted Magnetic Nanoparticles for Remote Magnetothermal Disruption of Amyloid‐β Aggregates

“…Fractions (0.5 mL) were collected and Aβ monomer containing fractions were pooled. The concentration of Aβ in the pooled sample was determined by measuring the absorbance at 275 nm (ε = 1361 M −1 cm −1 ) [ 57 ] in a quartz cuvette (Starna Cells, Atascadero, CA) and using a SpectraMax M2 cuvette reader (Molecular Devices, Sunnyvale, CA). Peptide solution was diluted to 20 × 10 −6 M , and 200 µL aliquots were prepared in low protein binding tubes (Eppendorf, Hauppauge, NY).…”

Soluble Aβ oligomers impair hippocampal LTP by disrupting glutamatergic/GABAergic balance

“…Peptide mass and purity (>99%) were confirmed by electrospray/ion trap mass spectrometry and reverse phase HPLC. Oxidatively cross-linked Aβ(1–40)S26C dimer ([Aβ 40 S26C] 2 ) was prepared as described previously (O’Nuallain et al, 2010; O’Malley et al, 2014). Following oxidation the [Aβ 40 S26C] 2 was treated with 7 M guanidinium HCl to remove aggregates and dimer isolated using a Superdex 75 10/30 HR column (GE Healthcare Biosciences, Pittsburgh, PA) eluted in 20 mM sodium phosphate, pH 7.4.…”

“…The peak fraction of [Aβ 40 S26C] 2 was collected, the concentration determined (ɛ 275 = 2272 M −1 cm −1 ) and the sample diluted to 20 µM in elution buffer. [Aβ 40 S26C] 2 readily assembles to form kinetically trapped protofibrillar assemblies under quiescent conditions (O’Nuallain et al, 2010; O’Malley et al, 2014); thus aliquots (120 μl) of the diluted sample were incubated in the wells of a black polystyrene, 96-well plate (Fisher Scientific) at 37°C for 5 days until a maximal ThT fluorescence was attained. Thereafter, material from 40 wells was pooled, gently mixed and aliquoted into 50 μl lots and stored at −80°C until required.…”

The impact of luteinizing hormone and testosterone on beta amyloid (Aβ) accumulation: Animal and human clinical studies

“…The current focus is on non-fibrillar, soluble, aggregates as the toxic species of Aβ [reviewed in (Walsh and Teplow, 2012), (O'Malley et al, 2014)]. These Aβ oligomers have been shown to be neurotoxic, inhibit synapse and memory formation in vivo (Walsh and Teplow, 2012), (O'Malley et al, 2014), and correlate well with the severity of neurodegeneration in AD (McLean et al, 1999), . The mechanism(s) by which Aβ induces neurotoxicity is not completely understood.…”