Fig. 1: Caspase-3-cleaved tau (TauC3) is present in mice and patients and shows decreased dynamics of its microtubule (MT) interaction.
A Immunoblots from lysates of hippocampal brain tissue from young (2 months (M)) and aged mice (27 M) showing caspase-3-cleaved tau (TauC3), total tau (Tau5) and GAPDH as loading control. Molecular mass standards are indicated. The relative amounts of TauC3/GAPDH, Tau5/GAPDH, and TauC3/Tau5 are shown below (mean ± SEM; n = 9). B Immunoblots from lysates of the human temporal neocortex from healthy controls (con) and AD patients (AD) showing TauC3 and total tau (panTau). Molecular mass standards are indicated. The relative amounts of TauC3/Coomassie, panTau/Coomassie and TauC3/panTau with respect to the Braak stage are shown below (mean ± SEM; n = 6 (con) and n = 7 (AD)). C Schematic representation of the expressed tau constructs. The MT-binding repeat regions (RR1–RR4) are indicated by yellow boxes, the pseudorepeat region in orange and the N-terminal PAGFP-fusion in green. Adult-specific exons in the N-terminus of tau (N1, N2) are shown in dark gray. Immunoblots of PC12 lysates after transfection with the respective tau constructs are displayed below, which shows the specific detection of the shorter tau construct with the TauC3 antibody. Molecular mass standards are given. D A schematic representation of an FDAP experiment is shown on the left. Representative time-lapse micrographs of fluorescence decay after photoactivation (FDAP) in an axon-like process are shown on the right. A 6 µm long segment (white box) in the middle of a process was photoactivated and the fluorescence decay over time within this region was monitored. E FDAP diagrams after photoactivation of PAGFP-Tau (Tau) and PAGFP-TauC3 (TauC3)-expressing cells. Mean ± SEM of 16 (Tau) and 15 (TauC3) cells is shown. Scatter plots of the effective diffusion constants (Deff) (F), and association (k*on) and dissociation rate constants (koff) (G) (mean ± SEM, n = 16 (Tau) and n = 15 (TauC3)). A schematic representation indicating k*on and koff of the MT-Tau interaction is shown in G. Statistically significant differences between samples determined by an unpaired Student’s t test are indicated. *p < 0.05; **p < 0.01; ***p < 0.001.
