DJ-1 gene deletion reveals that DJ-1 is an atypical peroxiredoxin-like peroxidase.

Parkinson's disease (PD) is a common neurodegenerative movement disorder. Whereas the majority of PD cases are sporadic, rare genetic defects have been linked to this prevalent movement disorder. Mutations in DJ-1 are associated with autosomal recessive early-onset PD. The exact biochemical function of DJ-1 has remained elusive. Here we report the generation of DJ-1 knockout (KO) mice by targeted deletion of exon 2 and exon 3. There is no observable degeneration of the central dopaminergic pathways, and the mice are anatomically and behaviorally similar to WT mice. Fluorescent Amplex red measurements of H(2)O(2) indicate that isolated mitochondria from young and old DJ-1 KO mice have a 2-fold increase in H(2)O(2). DJ-1 KO mice of 2-3 months of age have a 60% reduction in mitochondrial aconitase activity without compromising other mitochondrial processes. At an early age there are no differences in antioxidant enzymes, but in older mice there is an up-regulation of mitochondrial manganese superoxide dismutase and glutathione peroxidase and a 2-fold increase in mitochondrial glutathione peroxidase activity. Mutational analysis and mass spectrometry reveal that DJ-1 is an atypical peroxiredoxin-like peroxidase that scavenges H(2)O(2) through oxidation of Cys-106. In vivo there is an increase of DJ-1 oxidized at Cys-106 after 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine intoxication of WT mice. Taken together these data indicate that the DJ-1 KO mice have a deficit in scavenging mitochondrial H(2)O(2) due to the physiological function of DJ-1 as an atypical peroxiredoxin-like peroxidase.

Metabolism of 3-nitrotyrosine induces apoptotic death in dopaminergic cells.

Intrastriatal injection of 3-nitrotyrosine, which is a biomarker for nitrating oxidants, provokes dopaminergic neuronal death in rats by unknown mechanisms. Herein, we show that extracellular 3-nitrotyrosine is transported via the l-aromatic amino acid transporter in nondopaminergic NT2 cells, whereas in dopaminergic PC12 cells, it is transported by both the l-aromatic amino acid and the dopamine transporters. In both cell lines, 3-nitrotyrosine is a substrate for tyrosine tubulin ligase, resulting in its incorporation into the C terminus of alpha-tubulin. In NT2 cells, incorporation of 3-nitrotyrosine into alpha-tubulin induces a progressive, reversible reorganization of the microtubule architecture. In PC12 cells, 3-nitrotyrosine decreases intracellular dopamine levels and is metabolized by the concerted action of the aromatic amino acid decarboxylase and monoamine oxidase. Intracellular levels of 133 micromol of 3-nitrotyrosine per mole of tyrosine did not alter NT2 viability but induced PC12 apoptosis. The cell death was reversed by caspases and aromatic amino acid decarboxylase and monoamine oxidase inhibitors. 3-Nitrotyrosine induced loss of tyrosine hydroxylase-positive primary rat neurons, which was also prevented by an aromatic amino acid decarboxylase inhibitor. These findings provide a novel mechanism by which products generated by reactive nitrogen species induce dopaminergic neuron death and thus may contribute to the selective neurodegeneration in Parkinson's disease.