摘要：Protein S -nitrosylation modulates important cellular processes, including neurotransmission, vasodilation, proliferation, and apoptosis in various cell types. We have previously reported that protein disulfide isomerase (PDI) is S -nitrosylated in brains of patients with sporadic neurodegenerative diseases. This modification inhibits PDI enzymatic activity and consequently leads to the accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) lumen. Here, we describe S -nitrosylation of additional ER pathways that affect the unfolded protein response (UPR) in cell-based models of Parkinson’s disease (PD). We demonstrate that nitric oxide (NO) can S -nitrosylate the ER stress sensors IRE1α and PERK. While S -nitrosylation of IRE1α inhibited its ribonuclease activity, S -nitrosylation of PERK activated its kinase activity and downstream phosphorylation/inactivation or eIF2α. Site-directed mutagenesis of IRE1α(Cys931) prevented S -nitrosylation and inhibition of its ribonuclease activity, indicating that Cys931 is the predominant site of S -nitrosylation. Importantly, cells overexpressing mutant IRE1α(C931S) were resistant to NO-induced damage. Our findings show that nitrosative stress leads to dysfunctional ER stress signaling, thus contributing to neuronal cell death.
