TY - JOUR AU - Kaniyappan, Senthilvelrajan AU - Tepper, Katharina AU - Biernat, Jacek AU - Chandupatla, Ram Reddy AU - Hübschmann, Sabrina AU - Irsen, Stephan AU - Bicher, Sandra AU - Klatt, Christoph AU - Mandelkow, Eva-Maria AU - Mandelkow, Eckhard PY - 2020 DA - 2020/07/16 TI - FRET-based Tau seeding assay does not represent prion-like templated assembly of Tau filaments JO - Molecular Neurodegeneration SP - 39 VL - 15 IS - 1 AB - Tau aggregation into amyloid fibers based on the cross-beta structure is a hallmark of several Tauopathies, including Alzheimer Disease (AD). Trans-cellular propagation of Tau with pathological conformation has been suggested as a key disease mechanism. This is thought to cause the spreading of Tau pathology in AD by templated conversion of naive Tau in recipient cells into a pathological state, followed by assembly of pathological Tau fibers, similar to the mechanism of nucleated polymerization proposed for prion pathogenesis. In cell cultures, the process is often monitored by a FRET assay where the recipient cell expresses the Tau repeat domain (TauRD) with a pro-aggregant mutation, fused to GFP-based FRET pairs. Since the size of the reporter GFP (barrel of ~ 3 nm × 4 nm) is ~ 7 times larger than the β-strand distance (0.47 nm), this points to a potential steric clash. Hence, we investigated the influence of the GFP tag on TauFL or TauRD aggregation. Using biophysical methods (light scattering, atomic force microscopy (AFM), and scanning-transmission electron microscopy (STEM)), we found that the assembly of TauRD-GFP was severely inhibited and incompatible with that of Alzheimer filaments. These observations argue against the hypothesis that the propagation of Tau pathology in AD is caused by the prion-like templated aggregation of Tau protein, transmitted via cell-to-cell spreading of Tau. Thus, even though the observed local increase of FRET in recipient cells may be a valid hallmark of a pathological reaction, our data argue that it is caused by a process distinct from assembly of TauRD filaments. SN - 1750-1326 UR - https://doi.org/10.1186/s13024-020-00389-1 DO - 10.1186/s13024-020-00389-1 ID - Kaniyappan2020 ER -