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Regulation of the unfolded protein response via S-nitrosylation of sensors of endoplasmic reticulum stress.

ABSTRACT: 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.

SUBMITTER: Nakato R

PROVIDER: S-EPMC4597200 | biostudies-other | 2015 Oct

REPOSITORIES: biostudies-other

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Project description:Background Glioblastoma (GBM; grade IV glioma) is characterized by a very short overall survival time and extremely low 5-year survival rates. We intend to promote experimental and clinical research on rationale and scientifically driven drug repurposing. This may represent a safe and often inexpensive way to propose novel pharmacological approaches to GBM. Our precedent work describes the role of chlorpromazine (CPZ) in hindering malignant features of GBM. Here, we investigate in greater detail the molecular mechanisms at the basis of the effect of CPZ on GBM cells. Methods We employed proteomics platforms, i.e., activity-based protein profiling plus mass spectrometry, to identify potential cellular targets of the drug. Then, by means of established molecular and cellular biology techniques, we assessed the effects of this drug on GBM cell metabolic and survival pathways. Results The experimental output indicated as putative targets of CPZ several of factors implicated in endoplasmic reticulum (ER) stress, with consequent unfolded protein response (UPR). Such a perturbation culminated in a noticeable reactive oxygen species generation and intense autophagic response that resulted in cytotoxic and abortive effects for six GBM cell lines, three of which growing as neurospheres, while it appeared cytoprotective for the RPE-1 human non-cancer neuro-ectodermal cell line. Conclusions This discrepancy could be central in explaining the lethal effects of the drug on GBM cells and the relatively scarce cytotoxicity toward normal tissues attributed to this compound. The data presented here offer support to the multicenter phase II clinical trial we have undertaken, which consists of the addition of CPZ to first-line treatment of GBM patients carrying a hypo- or un-methylated MGMT gene, i.e. those characterized by intrinsic resistance to temozolomide. Supplementary Information The online version contains supplementary material available at 10.1186/s13046-021-02144-w.

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Regulation of the unfolded protein response via S-nitrosylation of sensors of endoplasmic reticulum stress.

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