XBP1

By Natalia Gurule, PhD

Inositol-requiring protein 1/IRE1 alpha (also called Endoplasmic Reticulum to Nucleus Signaling 1/ERN1; predicted mol wt 110 kDa) is a serine-threonine protein kinase/endoribonuclease which plays a highly critical role in unfolded protein response/UPR signaling, a mechanism by which eukaryotic cells sense and deal with ER stress. The latter triggers growth arrest and apoptosis in cells with misfolded proteins.

During cellular stress the protein folding capacity of the ER is diminished. In order to maintain homeostasis and ensure proper protein folding cells activate the unfolded protein response (UPR), a signaling network consisting of sensors and effectors to enhance the chaperone activity of the cell, increase degradation of accumulated proteins, and/or trigger apoptosis.  Inositol-requiring enzyme 1 (IRE1), an ER-transmembrane protein, is an essential component of the UPR pathway important for sensing and responding to ER stress.