Figure 5.

Hsp70 counteracts the ability of K18 ΔK280 tau aggregates to permeabilize lipid vesicles. (a) Schematic of the membrane disruption assay. Single Cal520 filled vesicles are immobilized onto a glass cover slide. The addition of agents, which are able to disrupt the membrane of the vesicles, leads to an influx of Ca²⁺ ions from the buffer into these vesicles. The resulting increase of fluorescence intensity in each vesicle is detected on a TIRF microscope. (b,c) Hsp70 neutralizes the ability of K18 ΔK280 tau oligomers to impair lipid membranes. To test the effect of tau species—present at different times of the aggregation reaction—on membranes, either 10 nM monomeric tau, oligomeric tau, or Hsp70-tau oligomer complexes were added to the lipid vesicles. Membrane disruption was measured by an increase of fluorescence intensity in each vesicle. Ionomycin was used as a positive control to normalize the data (100% Ca²⁺ influx). N = 4, error are s.e.m. (b) Representative images (N = 4). Scale bar 5 μm. (c) Data from four independent experiments. Statistical test: One-way ANOVA; ****p ≤ 0.0001.