Supplementary Figure 4: Extended data from Fig. 2. SFRP1 interacts with Aβ and reduces the time-dependent formation of the less harmful Aβ1-42 protofibrils.

A, B) Western blot analysis of Aβ or SFRP1 interaction with BSA, Heparin, SFRP1 or Aβ after microplate-based solid-phase protein-protein binding assay as indicated in the panels. Note that Aβ seems to bind more efficiently to SFRP1 than to BSA. C) Examples of transmission electron microscopic images showing the conformation of Aβ1-42 and SFRP1 alone or in combination, after incubation at 37°C for the indicated times. Note that SFRP1 favors the oligomeric (red arrows) vs proto-fibrillary (black arrows) form of Aβ1-42, which are instead prevalent when Aβ1-42 peptides are incubated alone. SFRP1 alone also tends to form aggregates. D) Dot blot analysis of samples with different concentrations of Aβ1-42 and SFRP1 alone or in combination at 0 or 24 hr of incubation at 37°C. Membranes were probed to detect the presence and relative abundance of Aβ1-42 fibril/protofibril forms (OC antibody) and low molecular weight amyloid oligomers (A11 conformation antibody) as well as control anti- SFRP1 and Aβ1-42 (6E10) antibodies. Note that Aβ1-42 fibril/protofibril forms increases with time (compare time 0h with 24h) but their relative abundance is decreased in the presence of SFRP1. Note that the A11 antibody recognizes also SFRP1. Scale bar 80 nm. These experiments were repeated three times obtaining similar results.