Search

Amyloid β oligomers (AβOs) accumulate early in Alzheimer's disease (AD) and experimentally cause memory dysfunction and the major pathologies associated with AD, for example, tau abnormalities, synapse loss, oxidative damage, and cognitive dysfunction. In order to develop the most effective AβO‐targeting diagnostics and therapeutics, the AβO structures contributing to AD‐associated toxicity must be elucidated. Here, we investigate the structural properties and pathogenic relevance of AβOs stabilized by the bifunctional crosslinker 1,5‐difluoro‐2,4‐dinitrobenzene (DFDNB). We find that DFDNB stabilizes synthetic Aβ in a soluble oligomeric conformation. With DFDNB, solutions of Aβ that would otherwise convert to large aggregates instead yield solutions of stable AβOs, predominantly in the 50–300 kDa range, that are maintained for at least 12 days at 37°C. Structures were determined by biochemical and native top–down mass spectrometry analyses. Assayed in neuronal cultures and i.c.v.‐injected mice, the DFDNB‐stabilized AβOs were found to induce tau hyperphosphorylation, inhibit choline acetyltransferase, and provoke neuroinflammation. Most interestingly, DFDNB crosslinking was found to stabilize an AβO conformation particularly potent in inducing memory dysfunction in mice. Taken together, these data support the utility of DFDNB crosslinking as a tool for stabilizing pathogenic AβOs in structure‐function studies. The structures of amyloid beta oligomers (AβOs) most germane to the pathogenesis of Alzheimer's disease (AD) are ill‐defined. Here, we demonstrate the utility of the crosslinker 1,5‐difluoro‐2,4‐dinitrobenzene (DFDNB) as a tool for AβO stabilization in structure–function studies. We find that DFDNB‐linked AβOs are detergent‐insensitive and remain in a soluble conformation with time and with increased concentration. Importantly, DFDNB stabilization does not alter the ability of AβOs to invoke potent responses than in multiple AD‐relevant pathogenic assays. [ABSTRACT FROM AUTHOR]

Inflammatory activation precedes and correlates with accumulating τ lesions in Alzheimer's disease and tauopathies. However, the relationship between neuroinflammation and etiology of pathologic τ remains elusive. To evaluate whether inflammatory signaling may promote or accelerate neurofibrillary tangle pathology, we explored the effect of recombinant adeno-associated virus (rAAV)-mediated overexpression of a master inflammatory cytokine, IFN-γ, on κ phosphorylation. In initial studies in primary neuroglial cultures, rAAV-mediated expression of IFN-γ did not alter endogenous κ production or paired helical filament κ phosphorylation. Next, we tested the effect of rAAV-mediated expression of IFN-γ in the brains of 2 mouse models of tauopathy: JNPL3 and rTg4510. In both models, IFN-γ increased 1) signal transducer and activator of transcription 1 levels and gliosis, and 2) hyperphosphorylation and conformational alterations of soluble κ compared with control cohorts. However, sarkosyl-insoluble phosphorylated κ levels and ubiquitin staining were unaltered in the IFN-γ cohorts. Notably, IFN-γ-induced κ hyperphosphorylation was associated with release of the inhibitory effect of glycogen synthase kinase 3β function by decreasing Ser9 phosphorylation. Our data suggest that type II IFN signaling can promote κ phosphorylation by modulating cellular kinase activity, though this is insufficient in accelerating neuritic tangle pathology. [ABSTRACT FROM AUTHOR]