Serine/threonine-protein kinase and endoribonuclease that acts as a key sensor for the endoplasmic reticulum unfolded protein response (UPR) (PubMed:11175748, PubMed:11779464, PubMed:12637535, PubMed:21317875, PubMed:28128204, PubMed:30118681, PubMed:9637683). In unstressed cells, the endoplasmic reticulum luminal domain is maintained in its inactive monomeric state by binding to the endoplasmic reticulum chaperone HSPA5/BiP (PubMed:21317875). Accumulation of misfolded proteins in the endoplasmic reticulum causes release of HSPA5/BiP, allowing the luminal domain to homodimerize, promoting autophosphorylation of the kinase domain and subsequent activation of the endoribonuclease activity (PubMed:21317875). The endoribonuclease activity is specific for XBP1 mRNA and excises 26 nucleotides from XBP1 mRNA (PubMed:11779464, PubMed:21317875, PubMed:24508390). The resulting spliced transcript of XBP1 encodes a transcriptional activator protein that up-regulates expression of UPR target genes (PubMed:11779464, PubMed:21317875, PubMed:24508390). Acts as an upstream signal for ER stress-induced GORASP2-mediated unconventional (ER/Golgi-independent) trafficking of CFTR to cell membrane by modulating the expression and localization of SEC16A (PubMed:21884936, PubMed:28067262).
Autophosphorylated following homodimerization. Autophosphorylation promotes activation of the endoribonuclease domain (PubMed:12637535, PubMed:21317875, PubMed:28128204, PubMed:9637683). In response to ER stress, phosphorylated at Ser-724, Ser-729 and possibly Ser-726; phosphorylation promotes oligomerization and endoribonuclease activity (PubMed:30118681). Dephosphorylated at Ser-724, Ser-729 and possibly Ser-726 by RPAP2 to abort failed ER-stress adaptation and trigger apoptosis (PubMed:30118681).
ADP-ribosylated by PARP16 upon ER stress, which increases both kinase and endonuclease activities.
Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.
Ubiquitously expressed. High levels observed in pancreatic tissue.
IRE1, ERN1, Serine/threonine-protein kinase/endoribonuclease IRE1, Endoplasmic reticulum-to-nucleus signaling 1, Inositol-requiring protein 1, Ire1-alpha, hIRE1p, IRE1a
Proteins
Oncology
109735Da
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