Defining the Protein Seeds of Neurodegeneration using Real-Time Quaking-Induced Conversion Assays.

Matteo Manca,Allison Kraus

doi:10.3390/biom10091233

Abstract

Neurodegenerative diseases are characterized by the accumulation of disease-related misfolded proteins. It is now widely understood that the characteristic self-amplifying (i.e., seeding) capacity once only attributed to the prions of transmissible spongiform encephalopathy diseases is a feature of other misfolded proteins of neurodegenerative diseases, including tau, Aβ, and αSynuclein (αSyn). Ultrasensitive diagnostic assays, known as real-time quaking-induced conversion (RT-QuIC) assays, exploit these seeding capabilities in order to exponentially amplify protein seeds from various biospecimens. To date, RT-QuIC assays have been developed for the detection of protein seeds related to known prion diseases of mammals, the αSyn aggregates of Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy, and the tau aggregates of Alzheimer’s disease, chronic traumatic encephalopathy, and other tauopathies including progressive supranuclear palsy. Application of these assays to premortem human biospecimens shows promise for diagnosis of neurodegenerative disease and is an area of active investigation. RT-QuIC assays are also powerful experimental tools that can be used to dissect seeding networks within and between tissues and to evaluate how protein seed distribution and quantity correlate to disease-related outcomes in a host. As well, RT-QuIC application may help characterize molecular pathways influencing protein seed accumulation, transmission, and clearance. In this review we discuss the application of RT-QuIC assays as diagnostic, experimental, and structural tools for detection and discrimination of PrP prions, tau, and αSyn protein seeds.

Highlights

Neurodegenerative diseases are complex, multifactorial, heterogenous diseases identified by the accumulation of misfolded proteins in the brain
Targeting the characteristic misfolded proteins as biomarkers provides a biochemical definition of disease to aid definitive diagnosis as well as to help elucidate mechanisms associated with disease processes
Regardless, this is reminiscent of the observed seed selectivity with different prion and tau real-time quaking-induced conversion (RT-QuIC) assays

Summary

Introduction

Neurodegenerative diseases are complex, multifactorial, heterogenous diseases identified by the accumulation of misfolded proteins in the brain. The K12 RT-QuIC demonstrates similar sensitivity to that of the AD RT-QuIC, and is able to detect both 3R seeds, in the case of PiD cases, and 3R/4R tau seeds of AD, CTE, and PART [71] Both the 4R and K12 RT-QuIC assays are capable of discriminating templating subtypes of disease-specific seeds using readouts of ThT amplitudes and fibrillar assay products. Cases examined in this study were clinically diagnosed, with neuropathological confirmation of select AD and DLB cases where autopsy tissue was available These seed amplification assays indicate that αSyn seeds can be detected with incredible sensitivity and specificity and can be done so reproducibly. Larger cohorts of pre- and postmortem peripheral biospecimens will be revealing as to how readily αSyn RT-QuIC assays can be applied to peripheral tissues

Application of RT-QuIC Assays to Understand Characteristics of Protein Seeds

Defining Protein Seed Distributions and Networks

Seeding Activity Assessments of Prion Propagation and Transmission

The Networks of Tau and αSyn Seeds

Findings

Conclusions