The endoplasmic reticulum (ER) is responsible for properly folding and processing secreted and transmembrane proteins. Any factors that disrupt this function may cause an accumulation of misfolded and unfolded proteins in the ER, a condition known as ER stress. Upon ER stress a signaling network called the Unfolded Protein Response (UPR) will be initiated to eliminate this stress and restore ER homeostasis. In case of failure however, the UPR promotes apoptosis. ER stress play role in many chronic diseases like diabetes, neurodegeneration and cancer. Researchers have to measure mRNA or protein expression in order to study ER stress or UPR.

Signosis has developed a luciferase reporter stable cell line with ERSE (ER stress response element) that can be easily used to monitor ER stress in the cell. Under conditions of ER stress, ER stress-responsive proteins bind to the ERSE, resulting in the transcriptional induction of luciferase gene.