5-S-cysteinyldopamine neurotoxicity: Influence on the expression of α-synuclein and ERp57 in cellular and animal models of Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disorder whose etiology is still unclear in spite of extensive investigations. It has been hypothesized that 5-S-cysteinyldopamine (CysDA), a catechol-thioether metabolite of dopamine (DA), could be an endogenous parkinsonian neurotoxin. To gain further insight into its role in the neurodegenerative process, both CD1 mice and SH-SY5Y neuroblastoma cells were treated with CysDA, and the data were compared with those obtained by the use of 6-hydroxydopamine, a well-known parkinsonian mimetic. Intrastriatal injection of CysDA in CD1 mice caused a long-lasting depletion of DA, providing evidence of in vivo neurotoxicity of CysDA. Both in mice and in SH-SY5Y cells, CysDA treatment induced extensive oxidative stress, as evidenced by protein carbonylation and glutathione depletion, and affected the expression of two proteins, α-synuclein (α-Syn) and ERp57, whose levels are modulated by oxidative insult. Real-time PCR experiments support these findings, indicating an upregulation of both ERp57 and α-Syn expression. α-Syn aggregation was also found to be modulated by CysDA treatment. The present work provides a solid background sustaining the hypothesis that CysDA is involved in parkinsonian neurodegeneration by inducing extensive oxidative stress and protein aggregation.

ERp57/PDIA3 binds specific DNA fragments in a melanoma cell line.

ERp57/PDIA3 is a ubiquitously expressed disulfide isomerase protein, which acts in concert with calreticulin and calnexin in the folding of glycoproteins destined to the plasma membrane or to be secreted. Its canonical compartment is the endoplasmic reticulum, where it acts as a chaperone and redox catalyst, but non canonical locations have been described as well, and ERp57 has been found associated with DNA and nuclear proteins. In previous work performed in HeLa cells, ERp57 has been demonstrated to bind specific DNA sequences involved in the stress response. The direct interaction with the DNA sequences identified as ERp57-targeted regions in HeLa cells has now been confirmed in a melanoma cell line. Furthermore, the ERp57 silencing, achieved by RNA interference, has produced a significant down-regulation of the expression of target genes. The possible involvement of other proteins in complex with ERp57 has been studied by an in vitro biotin-streptavidin based binding assay and the interacting protein APE/Ref-1 has been also assessed for its direct association with the ERp57 target regions. In conclusion, nuclear ERp57 interacts in vivo with DNA fragments in melanoma cells and is potentially involved in the transcriptional regulation of its target genes.