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ACCEPTED MANUSCRIPT<br />

cysteines at positions 106, 53 or 46 had no impact on the mitochondrial localization of<br />

DJ-1 upon oxidative stress.<br />

What might be the function of mitochondrial DJ-1? Isolated mitochondria<br />

from DJ-1 knockout mice showed a twofold increase in hydrogen peroxide<br />

accompanied by a reduction in mitochondrial aconitase activity, indicating a deficit in<br />

scavenging mitochondrial ROS [253]. By employing recombinant DJ-1 and mass<br />

spectrometry analysis, Andres-Mateos et al. demonstrated that DJ-1 is an atypical<br />

peroxiredoxin-like peroxidase and that cysteine 106 is the principal target for sulfinic<br />

acid formation.<br />

Of note, DJ-1 could not compensate for the mitochondrial alterations observed<br />

in parkin- or PINK1-deficient cells, neither in the Drosophila model nor in cultured<br />

human cells, suggesting that it does not function within PINK1/parkin pathway [134,<br />

213].<br />

2.4. α-Synuclein<br />

Three missense mutations (A53T, A30P, E46K) as well as genomic<br />

duplication and triplication of the gene encoding α-synuclein have been identified in<br />

ACCEPTED MANUSCRIPT<br />

rare cases of familial PD [254-260]. α-Synuclein is the major component of Lewy<br />

bodies, therefore providing the most obvious link between sporadic and familial PD<br />

[1]. Despite enormous efforts, little is known about the physiological function of α-<br />

synuclein and its mechanism of toxicity. α-Synuclein is a 140 amino acid protein<br />

which is abundantly expressed in the central nervous system. Its enrichment in<br />

presynaptic terminals and its association with vesicles suggests a role in synaptic<br />

dynamics (rev. in [261, 262]). α-Synuclein is a natively unfolded or intrinsically<br />

disordered protein with considerable conformational plasticity (rev. in [263-265]).<br />

33

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