Atomic view of an amyloid dodecamer exhibiting selective cellular toxic vulnerability in acute brain slices

Abstract

Atomic structures of amyloid oligomers that capture the neurodegenerative disease pathology are essential to understand disease-state causes and finding cures. Here we investigate the G6W mutation of the cytotoxic, hexameric amyloid model KV11. The mutation results into an asymmetric dodecamer composed of a pair of 30 twisted antiparallel β-sheets. The complete break between adjacent β-strands is unprecedented among amyloid fibril crystal structures and supports that our structure is an oligomer. The poor shape complementarity between mated sheets reveals an interior channel for binding lipids, suggesting that the toxicity may be due to a perturbation of lipid transport rather than a direct disruption of membrane integrity. Viability assays on mouse suprachiasmatic nucleus, anterior hypothalamus, and cerebral cortex demonstrated selective regional vulnerability consistent with Alzheimer's disease. Neuropeptides released from the brain slices may provide clues to how G6W initiates cellular injury.

Potential Protective Function of Aβ42 Monomer on Tauopathies

“…Coronal brain slices with a 500 μM thickness, containing the suprachiasmatic nucleus (SCN) and the surrounding anterior hypothalamus (AH), were prepared immediately after lights-on. Tissue slices were maintained at 37 °C and supplied with 95% O 2 /5% CO 2 in an interface brain slice chamber constantly perfused with Earl’s balanced salt solution (EBSS, MP Biomedicals, LLC, Solon, OH), supplemented with dextrose anhydrous and sodium bicarbonate (pH 7.4), at a rate of approximately 20 mL/h, as described . Approximately 1 h after preparation, tissue slices were transferred to small-volume, static wells maintained within the perfusion chambers.…”

“…Finally, it is noteworthy that the acute toxicity of Aβ 42 seen here is much less than when similar tissue slices were exposed for 4 h to KVKVLWDVIEV (G6W), an 11-residue mutant segment of αB crystallin. 34 The G6W peptide was shown to self-assemble into a novel dodecameric structure and is currently the most structurally sophisticated model of amyloid oligomers published. This suggests that neither Aβ 42 nor Tau PHF43 is exceedingly toxic to hypothalamic brain tissue upon initial exposure.…”

“…Tissue slices were maintained at 37 °C and supplied with 95% O 2 /5% CO 2 in an interface brain slice chamber constantly perfused with Earl's balanced salt solution (EBSS, MP Biomedicals, LLC, Solon, OH), supplemented with dextrose anhydrous and sodium bicarbonate (pH 7.4), at a rate of approximately 20 mL/h, as described. 34 Approximately 1 h after preparation, tissue slices were transferred to small-volume, static wells maintained within the perfusion chambers. 200 mL of EBSS (control) or EBSS supplemented with Aβ 42 , Tau PHF43 , or Aβ 42 + Tau PHF43 peptides was added into the static wells to slightly submerge the tissue slices.…”

Ex vivo comparative investigation of suprachiasmatic nucleus excitotoxic resiliency

“…For example, we have performed similar experiments exposing SCN and cortex slices to amyloid oligomers for 4 h during the daytime, followed by 2 of post-exposure perfusion prior to fixation and found significant increases in cell death and damage. 48 Third, we did not parse our analyses to investigate subregions within the cortex or SCN. As illustrated in Figure 1, our ROIs encompassed the entire coronal aspect of the SCN and included all cortical sublayers contained in our histological sections.…”

Elucidating the Oligomerization and Cellular Interactions of a Trimer Derived from Aβ through Fluorescence and Mass Spectrometric Studies

“…Aβ aggregates to form toxic oligomers and the fibrils that make up the characteristic plaques observed in the brains from those with Alzheimer’s disease . These oligomers are thought to be the main synaptotoxic species but have proven difficult to study as they are inherently heterogeneous and metastable with a high propensity to form fibrils. − Trimers of Aβ 42 are among the most toxic oligomers and are implicated in neuronal cell death. ,− …”