Selective Detection of Misfolded Tau From Postmortem Alzheimer’s Disease Brains

Abstract

Tau aggregates are present in multiple neurodegenerative diseases known as “tauopathies,” including Alzheimer’s disease, Pick’s disease, progressive supranuclear palsy, and corticobasal degeneration. Such misfolded tau aggregates are therefore potential sources for selective detection and biomarker discovery. Six human tau isoforms present in brain tissues and both 3R and 4R isoforms have been observed in the neuronal inclusions. To develop selective markers for AD and related rare tauopathies, we first used an engineered tau protein fragment 4RCF as the substrate for ultrasensitive real-time quaking-induced conversion analyses (RT-QuIC). We showed that misfolded tau from diseased AD and other tauopathy brains were able to seed recombinant 4RCF substrate. We further expanded to use six individual recombinant tau isoforms as substrates to amplify misfolded tau seeds from AD brains. We demonstrated, for the first time to our knowledge, that misfolded tau from the postmortem AD brain tissues was able to specifically seed all six full-length human tau isoforms. Our results demonstrated that RT-QuIC analysis can discriminate AD and other tauopathies from non-AD normal controls. We further uncovered that 3R-tau isoforms displayed significantly faster aggregation kinetics than their 4R-tau counterparts under conditions of both no seeding and seeding with AD brain homogenates. In summary, our work offers potential new avenues of misfolded tau detection as potential biomarkers for diagnosis of AD and related tauopathies and provides new insights into isoform-specific human tau aggregation.

Sequence-Dependent Conformational Properties of PGGG Motif in Tau Repeats: Insights from Molecular Dynamics Simulations of Narrow Pick Filament

“…Through our experimental study, we demonstrated that the E264G mutation (R1R3-GG) favors fibril formation, whereas the G326E mutation (R1R3-EE) forms disordered aggregates. Understanding the conformations of 3R isoforms could pave way to tune PiD specific ligands, which might help in the detection of Tau conformations similar to bithiophene-vinylene-benzothiazole (bTVBT4), which can detect the AD fold but not the PiD fold. − With Tau pathogenesis suggested to occur on the surface of MT, the results described in this work share insights on the sequence-specific conformation of Tau protein paving the way to probe pathogenesis at a monomeric level. , Thus, our study exemplifies the importance of NH6 peptides, owing to their ability to tune the conformational properties of the PGGG motif and thus influence the VQ6 peptide downstream to it. The NH6 peptide also plays a significant role in understanding Tau–MT interactions, which might help in building therapeutics targeting the inter-repeat regions.…”

Codon-optimized TDP-43 mediates neurodegeneration in a Drosophila model of ALS/FTLD

“…Protein misfolding is one of the salient features of neurodegenerative diseases. Hyperphosphorylated and aggregated forms of Tau protein are found in the brains of patients with Alzheimer’s Disease ( Wu et al, 2022 ). Similarly misfolded and aggregated Alpha-Synuclein deposits are found in individuals with Parkison’s Disease and in Dementia with Lewy Bodies ( Sanderson et al, 2020 ).…”

Site-Specific Phospho-Tau Aggregation-Based Biomarker Discovery for AD Diagnosis and Differentiation

“…Therefore, identification of p-tau198 or other promising candidates for general MCI diagnosis may have significant impact on clinical practice for much needed early AD biomarker development. Because of relatively small size of our cohorts, it will be interesting and important to further develop such biomarkers with a significantly large case number of clinical cohorts and with AD patient plasma samples in the future, incorporating ultrasensitive detection methods such as Single Molecular Array (Simoa) or Meso Scale Discovery Multi-Array technologies (MSD). , It will also be interesting to compare the sensitivity of different ultrasensitive detection methods, for example, misfolded protein-based amplification RT-QuIC technology − versus p-tau aggregation-based Simoa tests.…”