Fig. 5: The microtubule-targeting drug Epothilone D increases MT polymer, normalizes the interaction of TauC3 with microtubules, and modulates the transport of APP-vesicles in the presence of overexpressed human tau.
A Effect of EpoD on the percentage of tubulin polymerized in PC12 cell processes. The average constants for association (avg k*on) and dissociation rate (avg koff) are shown in the middle and on the right. The rate constants are displayed relative to the carrier control (0.01% DMSO). Mean ± SEM (n = 15–24). B Effect of EpoD on the association (k*on) and dissociation rate constants (koff) of the tau-MT interaction in processes of PC12 cells. Rate constants are indicated relative to PAGFP-tau (Tau) in the presence of the carrier control (0.01% DMSO). Mean ± SEM (n = 7–13). C Effect of EpoD on the transport of mobile APP-vesicles. mCherry-tagged Tau or TauC3 was co-expressed with eGFP-tagged APP and vesicle mobility was determined using an autoregressive motion algorithm. The velocity, processivity, and state changes are shown in the scatter plots. Each point represents an average value for a respective cell (mean ± SEM of n = 19–25 cells with 532–624 trajectories). D a, a’, a” Time series under physiological conditions: Tau (blue) interacts dynamically with microtubules by kiss-and-hop. Due to the high dynamics of the interaction of tau with microtubules, it does not stand in the way of kinesin-driven vesicle transport. D b, b’, b” Time series after caspase-3 cleavage of tau in senescent neurons. TauC3 (red) shows less dynamics in its interaction with microtubules, which can create a temporary roadblock to vesicle movement causing a change in direction. This leads to a reduced processivity of the movement. D c, c’, c” Time series after treatment with Epothilone D. EpoD modulates the structure of microtubules, resulting in increased dynamics of the TauC3-MT interaction, similar to full-length tau. However, EpoD also reduces the processivity of APP-vesicle transport in the presence of overexpressed human tau. All transfected or transduced tau constructs are based on the human tau sequence. Treatment with EpoD or carrier control was done 1 h before imaging. Statistically significant differences determined by one-way ANOVA (A) or two-way ANOVA (B, C) and post hoc Fischer LSD are indicated. *p < 0.05; **p < 0.01; ***p < 0.001.
