Discovery of a Compound That Inhibits IRE1α S-Nitrosylation and Preserves the Endoplasmic Reticulum Stress Response under Nitrosative Stress

Inositol-requiring enzyme 1 alpha (IRE1 alpha) is a sensor of endoplasmic reticulum (ER) stress and drives ER stress response pathways. Activated IRE1 alpha exhibits RNase activity and cleaves mRNA encoding X-box binding protein 1, a transcription factor that induces the expression of genes that maintain ER proteostasis for cell survival. Previously, we showed that IRE1 alpha undergoes S-nitrosylation, a post-translational modification induced by nitric oxide (NO), resulting in reduced RNase activity. Therefore, S-nitrosylation of IRE1 alpha compromises the response to ER stress, making cells more vulnerable. We conducted virtual screening and cell-based validation experiments to identify compounds that inhibit the S-nitrosylation of IRE1 alpha by targeting nitrosylated cysteine residues. We ultimately identified a compound (1ACTA) that selectively inhibits the S-nitrosylation of IRE1 alpha and prevents the NO-induced reduction of RNase activity. Furthermore, 1ACTA reduces the rate of NO-induced cell death. Our research identified S-nitrosylation as a novel target for drug development for IRE1 alpha and provides a suitable screening strategy.