Fig. 2

IAPP accelerates tau fibrillization in vitro. a ThT fluorescence assay of tau fibrillization in the presence of different concentrations of IAPP monomers or scrambled peptide (n = 3 independent experiments. The mean ThT fluorescence are shown). b Representative images of transmission electron microscopy (TEM) for IAPP PFFs, Tau PFFs, and IAPP-tau PFFs. Scale bar, 200 nm. c PK digestion assay. Tau PFFs or IAPP-tau PFFs were incubated with increasing concentrations of PK (0 to 1.5 mg/ml) and analyzed by Coomassie blue staining (left). Quantification represents the ratio of remaining protein to total PFFs (right). Data are means ± SEM (n = 3 independent experiments). d Tau PFFs and IAPP-tau PFFs induce tau aggregation in HEK293 cells stably expressing YFP-tagged tau RD. Scale bars, 20 μm. e The percentage of cells with tau inclusions induced by tau PFFs and IAPP-tau PFFs. Data are presented as means ± SEM. One-way ANOVA followed by Tukey’s post hoc test (n = 10 slices from 3 independent experiments). ***P < 0.001. f, g Cells transduced with tau PFFs and IAPP-tau PFFs were sequentially extracted with 1% Triton X-100 (TX-100) (TX soluble) and 2% SDS (TX insoluble). Lysates were subjected to Western blot to show the presence of tau in different fractions (n = 4 independent samples). Data are presented as means ± SEM. One-way ANOVA followed by Tukey’s post hoc test. **P < 0.01, ***P < 0.001. DAPI, 4′,6-diamidino-2-phenylindole