Biology subjects

Roberts, K. F.

Publications and source records attributed to Roberts, K. F..

2 recordsLinked to original sources

bioRxiv2025

Post-translational modifications distinguish amyloid-β isoform patterns extracted from vascular deposits and parenchymal plaques

Deposition of amyloid-{beta} (A{beta}) aggregates is a core pathological hallmark of both cerebral amyloid angiopathy (CAA) and extracellular parenchymal plaques in Alzheimers disease (AD). While both disease processes share progressive, decades-long deposition of fibrillar A{beta} peptide, they differ in isoform composition. We hypothesized that post-translational modifications (PTMs) on A{beta} would also differ between CAA and parenchymal plaques. Using Lys-N enzymatic digestion followed by quantitative mass spectrometry, we profiled A{beta} isoforms and N-terminus PTMs (aspartic acid isomerization and pyroglutamate formation) across CAA severity and compared them to parenchymal plaque A{beta} in AD. Moderate to severe CAA primarily featured intact N-terminus (A{beta}1-x) ([~]95%) with minimal N-truncated species (A{beta}2-x, A{beta}3pGlu-x, A{beta}4-x), whereas parenchymal plaques displayed diverse N-terminus truncations and PTMs. Increasing CAA severity correlated with a shift from longer, hydrophobic C-terminal isoforms (A{beta}41, A{beta}42, A{beta}43) to shorter, less hydrophobic C-terminal isoforms (A{beta}37, A{beta}38, A{beta}39, A{beta}40). Importantly, moderate and severe CAA displayed minimal isomerization of Asp-1 and Asp-7 residues, which correlated significantly (r > 0.9) with shorter C-terminal isoforms (A{beta}37, A{beta}38, A{beta}39, A{beta}40). These patterns suggest distinct A{beta} aggregation mechanisms in CAA versus parenchymal plaques. We propose that the intact N-terminus found in CAA with limited Asp isomerization is due to its inclusion within the protofibril structure (less disordered and inaccessible to PTMs), unlike the parenchymal plaques, where the N-terminus is more disordered and accessible to PTMs. These biochemical differences may reflect distinct protofibril architectures with potential implications for biomarker development for early CAA detection and therapeutic targeting of vascular and parenchymal A{beta}.

neuroscience↗

bioRxiv2020

Cobalt(III) Schiff Base complexes stabilize non-fibrillar amyloid-β aggregates with reduced toxicity

The aggregation of A{beta} is believed to be foundational to the pathogenesis of Alzheimers disease (AD). In vitro aggregation kinetics have been shown to correlate with rates of disease progression in both AD patients and animal models, thus proving to be a useful metric for testing A{beta}-targeted therapeutics. Here we present evidence of Cobalt(III) Schiff base complex (Co(III)-sb) modulation of A{beta} aggregation kinetics by a variety of complementary techniques. These include Thioflavin T (ThT) fluorescence, circular dichroism (CD) spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM). Our data was fitted to kinetic rate laws using a mathematical model developed by Knowles et al. in order to extract mechanistic information about the effect of Co(III)-sb on aggregation kinetics. Our analysis revealed that Co(III)-sb significantly decreases the kinetic parameter k+, and significantly increases the polymerization rate kn, suggesting that Co(III)-sb causes A{beta} to rapidly form stable oligomeric species that are unable to elongate into mature fibrils. This result was corroborated by TEM and AFM of A{beta} aggregates in vitro. We also demonstrate that A{beta} aggregate mixtures produced in the presence of Co(III)-sb exhibit decreased cytotoxicity compared to untreated samples. Statement of SignificanceAmyloid-{beta} is thought to be a key mediator in the pathology of Alzheimers disease, yet its precise mechanisms of toxicity are poorly understood. The interaction of A{beta} with endogenous metal ions via its N terminal Histidine residues has been shown to alter the peptides aggregation and toxicity. As such, metal-based complexes have been developed both as therapeutic agents as well as tools for investigating the role of metal binding in the pathogenesis of AD. This work expands on our previous studies developing Cobalt(III) Schiff base complexes as amyloid inhibitors. Here we demonstrate effective inhibition of aggregation by various complementary modalities. Additionally we show that Co(III)-sb reduces the toxicity of A{beta} aggregates to cells in culture.

neuroscience↗