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

Inositol-requiring enzyme 1α (IRE1α) is a sensor of endoplasmic reticulum (ER) stress and drives ER stress response pathways. Activated IRE1α 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 IRE1α undergoes -nitrosylation, a post-translational modification induced by nitric oxide (NO), resulting in reduced RNase activity. Therefore, -nitrosylation of IRE1α 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 -nitrosylation of IRE1α by targeting nitrosylated cysteine residues. We ultimately identified a compound (1ACTA) that selectively inhibits the -nitrosylation of IRE1α and prevents the NO-induced reduction of RNase activity. Furthermore, 1ACTA reduces the rate of NO-induced cell death. Our research identified -nitrosylation as a novel target for drug development for IRE1α and provides a suitable screening strategy.