Characterisation of the biophysical and cellular properties of Tau35, a disease‐associated tau fragment

Abstract

AbstractBackgroundTauopathies are characterised by the accumulation of intracellular tau aggregates in the brain. Tau inclusions contain various of truncated tau species, but the potential detrimental effects of these tau fragments are not well established. Tau35 is a C‐terminal fragment of wild‐type human tau, identified in tauopathy brain. We showed that minimal expression of Tau35 in transgenic mice recapitulates key features of tauopathy, including cognitive and motor dysfunction.MethodWe used small angle X‐ray scattering (SAXS), circular dichroism (CD), and transmission electron microscopy (TEM) to characterise the conformations of recombinant or aggregated Tau35 and full‐length (2N4R) tau. Tau assembly kinetics was monitored using Thioflavin T (ThT) and quantified. To assess cellular effects of tau, differentiated SH‐SY5Y cells (dSH) and mouse primary cortical neurons were exposed to Cy5‐labelled oligomeric tau and examined by immunofluorescence, western blots and live dead assay.ResultSAXS analysis showed that both Tau35 and 2N4R tau display characteristics of intrinsically disordered monomeric proteins, with Tau35 exhibiting more restricted motions. ThT kinetics indicated that Tau35 is more prone to beta‐sheet formation and this was confirmed by CD and TEM analysis. Rapid uptake of aggregated Tau35 and 2N4R tau was observed by both dSH and mouse neurons. Internalised tau accumulates with time. However no significant cell death were observed with dSH.ConclusionOur results demonstrate that Tau35, a fragment associated with human tauopathy, exhibits increased aggregation and rapid uptake into neuronal cells, which likely impacts on tau propagation.