In-vitro propagation of pathological tau filaments related to Alzheimer’s Disease

Abstract

Alzheimer's Disease (AD) is one of the devastating neurodegenerative diseases that affects more than 5.5 million people every year. In AD, hyperphosphorylated tau proteins self-propagate into aggregated paired helical filaments that mature into neurofibrillary tangles, which are hallmarks of AD and other neurodegenerative diseases known as tauopathies. Such toxic amyloid filaments tend to propagate across cells and thus are key therapeutic targets. Recent cryo-EM structures have revealed that tau adopts distinct filament conformations in the brain that are specific to Alzheimer's disease and these conformations are unable to be recapitulated in in-vitro experiments with recombinant wild-type tau proteins. Given the high abundance of tau posttranslational modifications (PTMs), particularly phosphorylation in pathological tau aggregates, it is likely that phosphorylation influences tau filament propagation and structures. Therefore, I generated hyperphosphorylated tau proteins from a eukaryotic baculovirus expression system in insect cells in order to characterize the effects of this PTM on tau aggregation. I characterized whether E.coli-derived unmodified tau and insect cell-derived phosphorylated tau could propagate into AD-like fibrils using AD tau seeds. Here I present the validation of phosphorylated tau proteins followed by assessment of fibril formation by kinetic assays, negative stain, and immuno-electron microscopy. The kinetic experiments indicates that phosphorylation on tau slows the aggregation process. The transmission electron microscopy reveals that seeding recombinant tau with AD brain homogenate causes the tau protein to adopt structures that appear similar to the AD paired helical filament conformation of tau.

Exploring the effectiveness and safety profile of TAU protein antibodies as potential therapies for alzheimer's disease: a comprehensive review

“…When TAU protein is altered abnormally in Alzheimer's disease (AD), it becomes hyperphosphorylated and separates from microtubules, aggregating into insoluble straight filaments (SFs) and paired helical filaments (PHFs and PHFs) [17]. Within neurons, these aggregated TAU proteins build up to create what are called neurofibrillary tangles (NFTs) [18].…”