γ-glutamylcysteine ethyl ester protection of proteins from Aβ(1-42)-mediated oxidative stress in neuronal cell culture: A proteomics approach

Protein oxidation mediated by amyloid β-peptide (1-42) (Aβ[1-42]) has been proposed to play a central role in the pathogenesis of Alzheimer's disease (AD), a neurodegenerative disorder associated with aging and the loss of cognitive function. The specific mechanism by which Aβ(1-42), the primary component of the senile plaque and a pathologic hallmark of AD, contributes to the oxidative damage evident in AD brain is unknown. Moreover, the specific proteins that are vulnerable to oxidative damage induced by Aβ(1-42) are unknown. Identification of such proteins could contribute to our understanding of not only the role of Aβ(1-42) in the pathogenesis of AD, but also provide insight into the mechanisms of neurodegeneration at the protein level in AD. We report the proteomic identification of two proteins found to be oxidized significantly in neuronal cultures treated with Aβ(1-42): 14-3-3ζ and glyceraldehyde-3-phosphate dehydrogenase. We also report that pretreatment of neuronal cultures with γ-glutamylcysteine ethyl ester, a compound that supplies the limiting substrate for the synthesis of glutathione and results in the upregulation of glutathione in neuronal cultures, protects both proteins against Aβ(1-42)-mediated protein oxidation.