Loading...
Modeling tauopathies in vitro with diverse aggregation inducing techniques
Ingham, David Jon
Ingham, David Jon
Citations
Altmetric:
Abstract
The microtubule-associated protein tau promotes the stabilization of the axonal cytoskeleton in neurons. In several neurodegenerative diseases, such as Alzheimer’s disease, Pick’s disease, corticobasal degeneration, chronic traumatic encephalopathy, and progressive supranuclear palsy, tau has been found to dissociate from microtubules leading to the formation of pathological aggregates that display an amyloid fibril-like structure. Recent structural studies have shown that the tau filaments isolated from different neurodegenerative disorders have structurally distinct fibril cores that are specific to the disease, or groups of diseases. These “strains” of tau fibrils appear to propagate between neurons in a prion-like fashion that maintains their initial template structure. In addition, the strains isolated from diseased tissue appear to have structures that are different from those made by the most commonly used in vitro modeling inducer molecule, heparin. The structural differences among strains in different diseases and, potentially, in vitro induced tau fibrils may contribute to recent failures in clinical trials of compounds designed to target tau pathology. Unfortunately, isolating authentic tau filaments from diseased brain tissue is not practical due to the large amount of protein required to conduct high-throughput drug screening, and studies aimed at characterizing tau aggregation dynamics and understanding the effects of disease related mutations. This body of work encompasses two studies that highlight the importance of developing disease relevant in vitro tau aggregation model systems. The first shows how different in vitro tau aggregation inducer molecules can have significant effects on how tau interacts with different classes of aggregation inhibitors. We identified an isoquinoline compound (ANTC-15) isolated from the fungus Aspergillus nidulans that is able to both inhibit filaments induced by arachidonic acid (ARA) and also disassemble pre-formed ARA-fibrils. When compared to a phenothiazine tau aggregation inhibitor currently in clinical trials, LMTX (LMTM, or TRx0237), ANTC-15 and LMTX were found to have opposing inducer-specific activities against ARA and heparin in vitro induced tau filaments. These findings may help explain the disappointing results in translating potent pre-clinical inhibitor candidates to successful clinical treatments. The second study highlights how different inducer molecules can have fundamental disparities to how disease related mutations effect the aggregation dynamics of tau. Using three different classes of tau aggregation inducer molecules we characterized disease relevant mutations in tau’s PGGG motifs at positions P301S, P332S, and P364S. When comparing these mutations to wild type tau, we found that depending on the type of inducer molecule used we saw fundamental differences in total aggregation, aggregation kinetics, immunoreactivity, and filament morphology. These data support the hypothesis that different tau aggregation inducer molecules make different polymorphs and perhaps structurally distinct strains. The impact of using non-disease relevant induced filaments for research studies may lead to significant set-backs to research of tau-based pathology. Moving forward, we must prioritize identifying disease relevant aggregation inducer molecules, methods for propagating tau fibril folds from authentic filaments with high fidelity and reproducibility, or co-factor free systems that convert monomeric tau to disease relevant structures. Chapter 4 discusses some preliminary data, techniques, and protocols for A) comparing synthetic filaments using a range of different inducer molecules, B) in vitro seeding assays using authentic filaments isolated from Alzheimer’s disease and progressive supranuclear palsy brain tissue, C) a technique for mechanically inducing co-factor free aggregates of a 3R tau isoform. The importance of furthering our fundamental understanding of how tau aggregates in disease and how we can best reproduce disease relevant structures in vitro is not to be underestimated. It is likely to have a critical impact on the future of treatment discovery and development of this devastating set of neurological disorders.
Description
Date
2021-12-31
Journal Title
Journal ISSN
Volume Title
Publisher
University of Kansas
Collections
Research Projects
Organizational Units
Journal Issue
Keywords
Molecular biology, Biochemistry, Neurosciences, aggregation, Alzheimer's, inducer, inhibitor, neurodegeneration, tau