# Monomeric α-Synuclein Real-Time Induced Conversion: A New Approach to the Diagnostics of Neurodegenerative Synucleinopathies with Weak RT-QuIC Responses

## TL;DR

A new diagnostic method for neurodegenerative diseases like Parkinson's uses purified α-synuclein to detect protein aggregates in body fluids, improving early diagnosis accuracy.

## Contribution

A three-step purification protocol produces high-purity α-synuclein, enhancing RT-QuIC sensitivity for synucleinopathies with weak responses.

## Key findings

- High-purity recombinant α-synuclein improves RT-QuIC sensitivity and specificity.
- Extended incubation times enable detection of weak RT-QuIC responses in multiple-system atrophy subtypes.
- Optimized RT-QuIC components allow accurate diagnosis of synucleinopathies.

## Abstract

Neurodegenerative disorders classified as synucleinopathies (Parkinson’s
disease, dementia with Lewy bodies, and multiple-system atrophy) are
characterized by the accumulation of aberrant α-synuclein aggregates in
neurons and glial cells. These diseases manifest clinically several years after
the initial formation of pathological protein aggregates in the brain, making
early and accurate diagnosis challenging. In recent years, a new method, which
is based on real-time quaking-induced conversion (RT-QuIC) of α-synuclein,
has been developed and validated. This technology holds great promise as a
powerful diagnostic tool for the early and precise identification of
synucleinopathies, potentially opening new horizons in the study of
neurodegenerative diseases. RT-QuIC detects misfolded α-synuclein
aggregates in human physiological fluids by introducing an excess of
recombinant α-synuclein, which undergoes conformational conversion in an
exponential, prion-like manner. The production of high-quality recombinant
α-synuclein is a critical step in the effective application of this
method, as protein purity significantly affects the sensitivity and specificity
of the assay — key factors in its diagnostic utility. Using a three-step
chromatographic purification protocol, we produced recombinant monomeric
α-synuclein with a purity exceeding 97% from the periplasmic fraction of
bacterial cells. While higher purity increases the assay duration, it also
reduces the background signal and permits extended incubation times, which are
essential for reliably detecting synucleinopathies with weak RT-QuIC responses,
such as the cerebellar subtype of multiple-system atrophy. The data presented
support the conclusion that optimized components of the RT-QuIC system will
enable an accurate diagnosis of neurodegenerative synucleinopathies.