A nanobody-based reporter reveals the entrance of human α-synuclein into the cell cytoplasm

hαSyn is a small protein of 140 amino acids that is enriched in the presynaptic endings of neurons. Under normal physiological conditions, hαSyn is typically found as a monomer, and its exact function is still under debate. However, it has regularly been proposed that arrangements of hαSyn monomers into small-to-intermediate oligomeric or larger insoluble assemblies might be the essence of its pathogenic activity. Besides, recent controversial evidence suggests that toxic forms of hαSyn can be transmitted from cell-to-cell in a prion-like fashion. Unfortunately, there are several assumptions, unknown molecular steps, and contradictory observations around the toxic transmission of hαSyn.
Therefore, the development of new tools that can reliably detect and track hαSyn in vitro or in vivo is an essential goal for deciphering the molecular mechanisms of hαSyn associated neurodegeneration disorders.

The laboratory of Dr. Felipe Opazo from the center for Biostructural Imaging of Neurodegeneration (BIN) of the UMG, together with several other laboratories, including those of MBExC members Rizzoli and Griesinger, developed the first biosensor for the transmission of hαSyn, based on single-domain antibodies from alpacas (known as nanobodies). This molecular sensor was engineered in cultured human cells and was termed Fluorescent Reporter for human αSyn (FluoReSyn). The characterization and validation of FluoReSyn were recently published in the journal Nature Communications.

Different than current methods detecting total hαSyn, the authors demonstrated that FluoReSyn could accurately identify the hαSyn variants that are able to enter the cell cytoplasm from patients' cerebrospinal fluid (CSF) samples.
The method presented in this publication has an enormous potential to be further optimized and eventually to be used as a diagnostic tool for αSyn associated neurodegenerative disorders.