Tau protein is an intrinsically disordered protein expressed predominantly in the central nervous system. It has countless functions in neurons, namely microtubule regulation, signal transduction, fast axonal transport regulation, and others.
Tau filaments are aggregated polymers of misregulated tau protein, present in the neurons of people suffering from neurodegenerative diseases, namely Alzheimer’s disease. Aggregation and accumulation of tau is toxic to the neurons, but the underlying mechanisms of tau pathology are not understood well [1].
The structure of tau filaments remained unknown until recently. Advances in helical reconstruction finally allowed reconstruction of tau filaments from different diseases, and it was revealed, that the structure of tau filaments differs between neurodegenerative diseases [2].
Previously, anionic co-factors were used to induce tau filament assembly in vitro. Heparin-induced tau filaments, commonly used for the study of aggregation inhibitors, were found to have a completely different structure than that of pathological tau filaments [3]. Due to that, new in vitro models of tau filaments replicating pathological tau filaments are needed to study the mechanism of aggregation and its inhibition.
Our goal is to understand what are the factors causing and influencing tau aggregation and to prepare recombinant in vitro tau filaments replicating the known disease folds. We have prepared in vitro tau protein filaments from the longest isoform of tau (2N4R) without the use of aggregation co-factors. Filaments were prepared in different buffer conditions, as we were interested in impact of the solvent ions on morphology of the filament. Prepared filaments were studied using atomic force microscopy, negative stain electron microscopy, and cryo-electron microscopy. Here we present our preliminary results of the ongoing structural analysis of the filaments, and discuss the morphological differences of prepared filaments.
This work has received funding from European Union Excellence Hub program (101087124). We acknowledge CEITEC CryoEM CF and Nanobiotechnology CF of CIISB, Instruct-CZ Centre, supported by MEYS CR (LM2023042) ) and European Regional Development Fund-Project „UP CIISB“ (No. CZ.02.1.01/0.0/0.0/18_046/0015974).