ERN1 (also called IRE1α) is a serine/threonine kinase and endoribonuclease that functions as a critical sensor of endoplasmic reticulum (ER) stress through the unfolded protein response (UPR) 12. In unstressed cells, ERN1's luminal domain remains inactive through binding to the ER chaperone BiP; accumulation of misfolded proteins triggers BiP release, allowing ERN1 homodimerization, autophosphorylation, and endoribonuclease activation 3. ERN1 specifically cleaves 26 nucleotides from XBP1 mRNA, generating a spliced transcript encoding a transcriptional activator that upregulates UPR target genes to restore ER homeostasis 4. Prolonged ER stress can shift ERN1 signaling toward apoptosis induction 1. ERN1 dysfunction is implicated in multiple diseases. In neurodegeneration, sustained ERN1 activation contributes to Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis pathology through chr17 protein misfolding 5. In type 1 diabetes, genetic variants affecting insulin mRNA recognition by ERN1 influence disease susceptibility through altered mRNA decay rates 6. In prostate cancer, ERN1 inhibition reduces tumor growth and enhances anti-tumor immunity by reprogramming the tumor microenvironment 7. These findings establish ERN1 as both a fundamental stress-response regulator and a promising therapeutic target across diverse pathologies.