Role of ERp57 in the regulation of gene expression and its involvement in neurodegeneration

Parkinson disease (PD) is a progressive neurodegenerative disorder characterized by a progressive and selective loss of dopaminergic neurons in the Substantia nigra. Recent studies indicate that 5-S-cysteinyldopamine (CysDA), a catechol-thioether metabolite of dopamine (DA), is strongly neurotoxic and may contribute to the onset and progression of this disease (1). To better understand CysDA contribution to neurodegeneration, it has been evaluated the modulation of the expression, aggregation and cellular localization of proteins known to be involved in the oxidative stress response. In particular, we focused our study on alpha-Synuclein (a-Syn), a protein considered the PD “hallmark” and on ERp57, an endoplasmic reticulum thiol oxidoreductase, known to be implicated in neurodegenerative disease (2). To achieve these goals, both CD1 mice and SH-SY5Y neuroblastoma cells were treated with CysDA and the data were compared to those obtained by the use of 6-hydroxydopamine (6-OHDA), a well known parkinsonian mimetic. Intrastriatal injection of CysDA in CD1 mice caused a long-lasting depletion of DA, without affecting serotonergic or noradrenergic systems, providing in vivo evidence of CysDA specific neurotoxicity at dopaminergic system level. Both in CD1 mice and in SH-SY5Y cells, CysDA treatment induced extensive oxidative stress, as evidenced by protein carbonylation and Glutathione (GSH) depletion. Moreover, CysDA treatment induced in CD1 mice an increase of α-Syn aggregated forms in the prefrontal cortex with respect to the striatum and hippocampus. These data are in agreement with previous findings which indicate that α-Syn is overexpressed in the prefrontal cortex in cognitive impairment (3). Conversely, ERp57 protein increase was observed in the striatum after CysDA treatment, the other brain regions were slightly affected. To assess α-Syn and ERp57 protein levels, aggregation and their cellular distribution, cytoplasm and nuclei fractions were obtained from SH-SY5Y cells treated with CysDA at different times. In the cytosol, α-Syn dimeric forms increased with incubation time, up to 24 hours, whereas the monomeric form was overexpressed within 8 hours, and decreased in prolonged incubations. In the nuclei, only the monomeric form was present. Concerning ERp57, the protein level was increased up to 24 hours in the cytosol, whereas in the nuclei it was transiently increased within 3 hours. Gene expression analyses have demonstrated that α-Syn and ERp57 mRNAs increased at 6 and 3 hours, respectively from neurotoxins administration. The overall data suggest that CysDA exerts neurotoxic effects similar to 6-OHDA, supporting the hypothesis that it may be an endogenous parkinsonian mimetic, able to induce α-Syn overexpression and aggregation and ERp57 upregulation. 1. Mosca et al (2006) Neurochem Int. 49:262 2.Coe et al (2010) Int J Biochem Cell Biol 42:796 3.Ferrer et al (2009) Progr Neurobiol 88:89