ENHANCEMENT OF α-SYNUCLEIN TOXICITY BY STRESS-INDUCED POST-TRANSLATIONAL MODIFICATIONS

Parkinson´s disease (PD) is a debilitating and incurable neurodegenerative disease that affects more than 1% of the population above 60 years-old and belongs to the group of pathologies known as Synucleinopathies, whose main common feature is the cytosolic presence of amyloid aggregates of α Synuclein (aSyn), an intrinsically disordered, single domain protein. Its gain of toxic function has been largely linked to PD development and progress. However, the identity of aSyn toxic species remains elusive. Several genetic alterations in its coding gene, SNCA, have been reported in familiar dominant forms of PD. However, their penetrance is very minor among patients, while oxidative stress and aging remain the main general risk factors within all neurodegenerative diseases. In this context, several oxidative stress related post-translational modifications (PTMs) could act as modulators of aSyn´s structural features and its physiopathology, and, therefore, may be responsible of triggering aSyn´s pathological role towards neurons and/or glial cells.
We explored a series of oxidative modifications on recombinant aSyn induced by a photo-tunable method based on Ru complex photosensitizer that promote selectively Tyr-residues oxidation through a radical mechanism. This method has been adapted to generate both covalent oligomers and nitrated monomers of aSyn. We isolated and characterized these proteins variants by mass spectrometry to quantitate the degree of modification, the PTMs positions and exposure of Tyr residues under different conformational states, highlighting its impact on aSyn´s susceptibility. Initial biochemical and cytotoxicity characterization of modified species, as well as their effect on amyloid aggregation and membrane binding of aSyn are presented suggesting a mechanism that triggers early stages of molecular pathology leading to PD.
This work was supported by grants PICT2014-2019, PICT2016-3776 ANPCyT, M217 UNLP, PIP2014-0618 CONICET (Argentina), and grant SFB860 DFG (Germany). LJFL acknowledges support from Alexander von Humboldt Foundation, and EG from CONICET and from Bunge & Born-Max Planck Society-Williams Foundations.