Inositol-requiring enzyme 1 (IRE1), also known as endoplasmic reticulum to nucleus signaling 1 (ERN1), is a resident transmembrane ER protein with both kinase and endonuclease domains. Both yeast (IRE1) and mammalian (IRE1α) homologs are involved in the degradation of misfolded proteins, as part of the unfolded protein response (UPR). IRE1 (yeast) is involved in the endonucleolytic cleavage of HAC1 mRNA, whereas IRE1α (human) catalyzes the splicing of X-box binding protein (XBP) 1 mRNA. XBP1 mRNA splicing triggers upregulation of genes involved in the ERAD pathway, induction of XBP1 expression and the synthesis of ER chaperones.
Under normal conditions, IRE1 is maintained in an inactive state due to the binding of B-cell immunoglobulin binding protein (BiP) to its luminal domain. However, the accumulation of unfolded proteins within the ER induces ER stress, causing BiP to detach from IRE1. Following BiP detachment, IRE1 undergoes dimerization and autophosphorylation through the actions of IRE1 kinase domains. Activation of IRE1 endonuclease and kinase domains may also occur by direct binding of unfolded proteins to IRE1.View all products for IRE1 »