Biophysical properties of a tau seed

Abstract

Pathogenesis of tauopathies involves conversion of tau monomer into pathological tau conformers that serve as templates to recruit native tau into growing assemblies. Small soluble tau seeds have been proposed to drive pathological tau assembly in vitro, in cells and in vivo. We have previously described the isolation of monomeric pathogenic tau seeds derived from recombinant samples and tauopathy tissues but in-depth biophysical characterization of these species has not been done. Here we describe a chromatographic method to isolate recombinant soluble tau seeds derived from heparin treatment. We used biochemical and biophysical approaches to show that the seeds are predominantly monomeric and have the capacity to nucleate aggregation of inert forms of tau in vitro and in cells. Finally, we used crosslinking mass spectrometry to identify the topological changes in tau as it converts from an inert state to a pathogenic seed. Future studies will reveal the relationship between soluble seeds and structural polymorphs derived from tauopathies to help diagnose and develop therapeutics targeting specific tauopathies.

DnaJC7 binds natively folded structural elements in tau to inhibit amyloid formation

“…Taken together, DnaJC7 binds full-length tau with nanomolar affinity and pathogenic mutations in full-length tau decrease affinity to levels similar to WT and P301L tauRD. Consistent with this idea, we also measured binding of DnaJC7 for a recombinant tau monomer seed 41 and found that it binds weakly with 15.5 ± 2.2 µM affinity (Supplementary Fig. 3a ).…”

Seed-competent tau monomer initiates pathology in a tauopathy mouse model

“…Another study is consistent with this idea ( 18 ), although this concept is not widely accepted. We have recently developed methods to create M s from M i using recombinant protein ( 16 , 19 , 20 ), and we have also isolated it from human tauopathies ( 16 , 17 ). Intriguingly, M s adopts multiple seed-competent conformational states that serve as templates to create defined tau prion “strains” ( 17 ), which are tau species that faithfully replicate their structure in vivo , and produce defined patterns of neuropathology ( 5 , 6 , 21 ).…”

“…Intriguingly, M s adopts multiple seed-competent conformational states that serve as templates to create defined tau prion “strains” ( 17 ), which are tau species that faithfully replicate their structure in vivo , and produce defined patterns of neuropathology ( 5 , 6 , 21 ). We have proposed that a critical conformational change from M i to M s represents the first step in the aggregation process ( 16 ), that M s encodes strains ( 17 ), and we have also reported methods to produce M s in vitro ( 20 ). However, it is unknown whether M s precedes or follows the formation of large assemblies in vivo —a critical question for the origin of tauopathies.…”

Interaction kinetics reveal distinct properties of conformational ensembles of three‐repeat and four‐repeat tau proteins

“…Higher exposition of tau RD was detected by XL-MS also by the group of Joachimiak, where they reported decrease in number of crosslink identifications upon converting tau from an inert state to a pathogenic seed state [45].…”

“…This is in line with the recent findings observed by XL-MS that interactions/local folding in the C-terminal domain and between I1/I2 and R2 are present in an inert tau monomer and absent in a seed competent tau monomer, leaving the aggregationprone sequences in MTBR unshielded. Short incubation of inert tau monomer with heparin and subsequent separation has disrupted these interactions and produced seed competent conformation of tau monomer [45].…”