Quantification and Analysis of Tau Protein Effects on Microtubule Dynamics in Mammalian (LLC-PK1) Cells

Abstract

Overall, we found that multiple biophysical properties of tau protein affect MT dynamics in LLC-PK1 cells; various isoforms exhibit differential effects. 2N4R tau exhibits MT tip avoidance (~200 nm) during growth that is lost for 0N4R tau. 2N4R and 0N4R tau phenocopy MTAs to make MTs less dynamic via different processes. We propose 2N4R tau has at least two binding sites, one of higher and one of lower affinity, resulting in KD=0.31 µM that preferentially associates with GDP-tubulin lattice to enable growing tip avoidance. 0N4R tau loses access to higher but retains lower affinity binding, resulting in KD=3.2 µM. Uniquely, 0N4R P301L tau does not bind to MTs (KD>>10 µM), indicating loss of both higher and lower affinity binding, perhaps due to induced conformation changes. Possible implications for tauopathies include the decreased ability of 0N4R P301L tau to bind to MTs, which may promote disease-associated progression toward tau oligomerization.