Fig. 6

ISAD1 and ISAD1rev induce the formation of large Tau high-n oligomers, measured by DLS and pelleting assay. A Samples for DLS measurements were prepared with 10 μM Tau^RDΔK, 2.5 μM heparin, and 20 μM ThS. The peptides were added in a concentration of 100 μM. All samples were incubated for 24 h. DLS was performed by 25 °C with an equilibration time of 2 min and 3 measurements within 15 runs. The average of the results is shown as a volume graph. Tau^RDΔK monomer shows a hydrodynamic size of < 10 nm (blue curve). When Tau is incubated with heparin, larger aggregates (PHF-like fibrils) with a size between 15 and 100 nm are formed (red curve). In the presence of ISAD1 and ISAD1rev, even larger high-n oligomers are formed, with a size of 1500–5000 nm (black and green curve), but without β-structure. B In general, fibrillization of monomeric Tau to fibrils is a multistep process that involves the formation of various aggregates, including protofibrillar oligomers. In the presence of ISAD1 peptides, Tau forms non-toxic clump-shaped high molecular oligomers. C Western blot of SDS-gels showing proteins in pellets (P) and supernatant (S) when 10 μM Tau was incubated with 100 μM peptide ISAD1 or ISAD1rev. After 24 h of Tau fibrillization, samples were centrifuged and the supernatant was separated from the pellet. The western blot was detected by the antibody K9JA. Tau^RDΔK fibrils resolved on SDS-gels show fractions in the supernatant (S) and pellet (P) after centrifugation (lanes 1,2). Due to the high molecular oligomers which are formed in the presence of the D-peptides, there are only apparent in the pellet (lanes 3–6). D The quantification of the western blot was performed using ImageJ. The intensity of protein amount in supernatant and pellet of the fibrils was set as 100%. There is a difference between the Tau fibrils and D-peptide-treated supernatant and pellet fractions