Figure 5.

Fragmented Species Trigger Cell Lysis

(A) A lactate dehydrogenase (LDH) assay was used to detect lysis of HEK293 cells after incubation with either intact aggregated tau (column 1), the fragmented species (column 2), the buffer alone (column 3), or proteasome holoenzyme alone (column 4). Cells were tested for levels of lysis after incubation with fibrils treated with free RP (column 5) or with free RP alone as a control (column 6).

(B) Aggregation buffers and tau fibrils are not toxic to cells. Monomers (column 1) or fibrils (column 2–4) at 1-, 10-, and 100-fold (10× and 100×) of the incubation concentration in (A) were incubated with the cells. Several controls including sodium chloride-sodium phosphate-EDTA (SSPE) buffer alone (column 5), SSPE buffer containing heparin (column 6), the pellet (containing tau fibrils, column 7), or the supernatant fraction (containing soluble aggregates and monomers, column 8) after centrifugation (STAR Methods) were also tested for cell lysis. As a positive control (column 9), fibrils were sonicated briefly and centrifuged to separate insoluble fibrils so that the supernatant could be added to cells at the same calculated concentration.

Error bars represent SD of measurements from the mean of three independent experiments (n = 3).