Analysis of Filamentous Tau Protein Associated with Neurodegenerative Diseases and Its Interactions with Human Neuronal Cells

Dementia and neurodegenerative diseases are posing an increasing health risk to the public, especially in the elderly. Among the most common neurodegenerative diseases are tauopathies, such as Alzheimer's Disease. Tauopathies are a diverse group of disorders that present with neuronal loss and pathological intracellular inclusions of tau protein. Human tau protein is a natively unstructured protein that regulates assembly and spacing in microtubules but can misfold and aggregate into filaments and form the aforementioned intracellular inclusions in tauopathies. Different diseases are associated with a distinct conformational tau fold. Tau monomers can be recruited to existing fibrils in a template-based prion-like manner, resulting in tau pathology spread from the point of origin in the brain to other regions, where it induces neurodegeneration that can lead to dementia, cognitive and motor deficits and, ultimately, death. The cause of tau misfolding and the mode of transportation of pathological tau through neuronal tissue is still unknown, as is how exactly it induces cell death. The goal of this PhD thesis was to gain new insights into tau mediated neurodegeneration.
In chapter 2 the aggregation of tau protein induced by a non-mammalian prion protein is shown, both with recombinant human tau in vitro and in a transgenic mouse model expressing human tau, demonstrating the possibility of inter-species cross-seeding.
Chapter 3 describes the development of a human neuronal cell model for the study of tau-related neurodegenerative diseases. SH-SY5Y human neuroblastoma cells were differentiated into mature neurons and characterised by immunofluorescent labelling of general and cell type specific neuronal markers.
In chapter 4 the uptake of tau seeds into the newly developed cellular model is demonstrated, showing cell specific tau seed localisation and the impact of tau seeds on various cellular components.
Chapter 5 documents the attempt to develop a detergent-free approach to extract and isolate filamentous tau from homogenised brain tissue for analysis in transmission electron microscopy using immuno-targeting and magnetic trapping.