Million-fold sensitivity enhancement in proteopathic seed amplification assays for biospecimens by Hofmeister ion comparisons

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 46; pp. 23029 - 23039
• Main Authors: Metrick, Michael A., Ferreira, Natalia do Carmo, Saijo, Eri, Hughson, Andrew G., Kraus, Allison, Orrú, Christina, Miller, Michael W., Zanusso, Gianluigi, Ghetti, Bernardino, Vendruscolo, Michele, Caughey, Byron
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 12.11.2019
• Series: From the Cover
• Subjects: Aggregates; alpha-Synuclein - chemistry; alpha-Synuclein - metabolism; Alzheimer Disease - diagnosis; Alzheimer Disease - metabolism; Alzheimer's disease; Amplification; Anions; Anions - chemistry; Assaying; Biological Sciences; Biomarkers; Biomarkers - chemistry; Biomarkers - metabolism; Chronic wasting disease; Creutzfeldt-Jakob Syndrome - diagnosis; Creutzfeldt-Jakob Syndrome - metabolism; Diagnostic systems; Diagnostic Techniques and Procedures; Environmental effects; Folding; Humans; Kinetics; Neurodegenerative diseases; Paralysis; Physical Sciences; PNAS Plus; Polymerization; Prion Diseases - diagnosis; Prion Diseases - metabolism; Prion protein; Prion Proteins - chemistry; Prion Proteins - metabolism; Prions; Progressive supranuclear palsy; Protein Aggregates; Protein folding; Proteins; Salts; Seeds; Sensitivity analysis; Sensitivity enhancement; Synuclein; Tau protein; tau Proteins - chemistry; tau Proteins - metabolism; Transmissible spongiform encephalopathy; ion hydration; tau; Hofmeister series; protein misfolding; RT-QuIC
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1909322116

Recent work with prion diseases and synucleinopathies indicates that accurate diagnostic methods for protein-folding diseases can be based on the ultrasensitive, amplified measurement of pathological aggregates in biospecimens. A better understanding of the physicochemical factors that control the seeded polymerization of such aggregates, and their amplification in vitro, should allow improvements in existing assay platforms, as well as the development of new assays for other proteopathic aggregates. Here, we systematically investigated the effects of the ionic environment on the polymerization of tau, α-synuclein, and the prion protein (PrP) induced by aggregates in biospecimens.We screened salts of the Hofmeister series, a relative ordering of strongly and weakly hydrated salts that tend to precipitate or solubilize proteins. We found that sensitivities of tau-based assays for Alzheimer’s seeds and PrP-based assays for prions were best in weakly hydrated anions. In contrast, we saw an inverse trend with different tau-based assays, improving detection sensitivity for progressive supranuclear palsy seeds by ≈10⁶. Hofmeister analysis also improved detection of sporadic Creutzfeldt–Jakob disease prions in human nasal brushings and chronic wasting disease prions in deer-ear homogenates. Our results demonstrate strong and divergent influences of ionic environments on the amplification and detection of proteopathic seeds as biomarkers for protein-folding diseases.