Abstract
Dementia is the leading cause of death in the UK, and there is no cure. One of the hallmarks of Alzheimer’s disease, the most common cause of dementia, is the presence of neurofibrillary tangles: intracellular, insoluble aggregates of the microtubule associated protein tau. Tau mutations, such as P301L, are sufficient to cause frontotemporal dementia (FTD) and the accumulation of pathological tau species in the brain correlates with cognitive decline. In disease, tau is hyperphosphorylated which promotes aggregation and downstream neuronal dysfunction and loss.A previous study showed that the flavonoid (-)-epicatechin (EC) inhibited tau phosphorylation and possibly aggregation in rTg4510 mice overexpressing the tauP301L mutant. This study aimed to determine whether the inhibition of tau phosphorylation could be replicated at a neuronal specific level with the aim of identifying potential mechanisms of action and functional consequences.
A neuronal model of tauopathy was developed using adeno-associated viral transduction of eGFP-tagged human tau constructs (wild-type and P301L) under the control of a neuronal-specific promoter in mouse primary cortical neurons. In this model, mutant tau was more phosphorylated at Ser262, a phospho-epitope associated with disease, and EC was able to inhibit phosphorylation at Ser262. Investigation of GSK3β kinase suggested that EC-mediated inhibition of tau phosphorylation was independent of inhibition of GSK3β.
To better understand the mechanisms of action of tau in this model a proteomics approach was adopted. Using affinity-purification mass spectrometry, the tau interactome was identified. This revealed differential association of wild-type and mutant tauP301L with proteins involved in translation, proteasomal degradation and synaptic calcium signalling. To establish the impact of mutant tau on neuronal function, micro-electrode arrays were used to assess neural network activity in these cultures. Primary cortical neurons formed connected and active networks within two weeks and neurons overexpressing tauP301L exhibited increased basal excitability.
Therefore, this study confirmed that EC inhibits tau phosphorylation at a neuronal level. Characterisation of this novel model of tauopathy identified several pathological phenotypes that could be used to investigate the ability of EC to alleviate tau toxicity while contributing to the understanding of tau mechanisms of action.
| Date of Award | 26 Jul 2023 |
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| Original language | English |
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| Supervisor | Jody Mason (Supervisor), Robert Williams (Supervisor) & Jonathan Brown (Supervisor) |