Tau seeding in a HEK cell model is influenced by aggregation inducers and cellular chaperones

Abstract

The tau protein is a microtubule associated protein whose misfolding and subsequent aggregation have been associated with a group of neurodegenerative diseases known as tauopathies. Studying tau in a lab setting has been crucial for the advancement of knowledge and technology used to treat people afflicted with tauopathies. The use of recombinant tau aggregates has and continues to playan important role in these advancements. Recombinant tau can be induced to aggregate using a variety of different inducers, however our lab focuses on heparin, polyphosphate, and arachidonic acid. Here, we explore the ways in which these three different inducers influence the ability of their resulting aggregates to seed tau aggregation in a HEK cell model. Additionally, we reveal structural differences existing between aggregates generated with different inducers that may dictate their abilities to seed cellular aggregation. Our findings reinforce the importance of structure in relation to tau templating and spread, and may inform studies on tau strains. They also give us insight into how commonly used aggregation inducers may affect experimental outcomes. We also used recombinant tau aggregates in cellular seeding assays to explore the effects that certain cellular components, specifically chaperone proteins, have on tau aggregation. One chaperone in particular, DNAJA2, is known to have inhibitory effects on tau aggregation in vitro and has increased expression in mild cognitive impairment and Alzheimer’s disease. Given this information, we focused on establishing a cell line capable of overexpressing this chaperone, as well as analyzing the ability of tau to seed in cells where DNAJA2 is knocked down. Our results indicate that a decrease in DNAJA2 expression in cells leads to an increase in cells positive for tau aggregates.