ERN1
Description
The ERN1 (endoplasmic reticulum to nucleus signaling 1) is a protein-coding gene located on chromosome 17.
The serine/threonine-protein kinase/endoribonuclease inositol-requiring enzyme 1 α (IRE1α) is an enzyme that in humans is encoded by the ERN1 gene.
== Function == The protein encoded by this gene is the ER to nucleus signalling 1 protein, a human homologue of the yeast Ire1 gene product. This protein possesses intrinsic kinase activity and an endoribonuclease activity and it is important in altering gene expression as a response to endoplasmic reticulum-based stress signals (mainly the unfolded protein response). Two alternatively spliced transcript variants encoding different isoforms have been found for this gene.
== Signaling == IRE1α possesses two functional enzymatic domains, an endonuclease and a trans-autophosphorylation kinase domain. Upon activation, IRE1α oligomerizes and carries out an unconventional RNA splicing activity, removing an intron from the X-box binding protein 1 (XBP1) mRNA, and allowing it to become translated into a functional transcription factor, XBP1s. XBP1s upregulates ER chaperones and endoplasmic reticulum associated degradation (ERAD) genes that facilitate recovery from ER stress.
== Clinical significance == As IRE1α is a primary sensor for unfolded protein response, its disruption could be linked with neurodegenerative diseases, by which the accumulation of intracellular toxic proteins serves as one of the key pathogenic mechanisms. IRE1 signalling is considered to be pathogenic in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.
== Interactions == ERN1 has been shown to interact with Heat shock protein 90kDa alpha (cytosolic), member A1.
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:9637683, PubMed:30118681). 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:24508390, PubMed:21317875). The resulting spliced transcript of XBP1 encodes a transcriptional activator protein that up-regulates expression of UPR target genes (PubMed:11779464, PubMed:24508390, PubMed:21317875). 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). {ECO:0000269|PubMed:11175748, ECO:0000269|PubMed:11779464, ECO:0000269|PubMed:12637535, ECO:0000269|PubMed:21317875, ECO:0000269|PubMed:21884936, ECO:0000269|PubMed:28067262, ECO:0000269|PubMed:28128204, ECO:0000269|PubMed:30118681, ECO:0000269|PubMed:9637683, ECO:0000305|PubMed:24508390}
ERN1 is also known as IRE1, IRE1P, IRE1a, hIRE1p.
