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Gene Review

ERN1  -  endoplasmic reticulum to nucleus signaling 1

Homo sapiens

Synonyms: Endoplasmic reticulum-to-nucleus signaling 1, IRE1, IRE1P, IRE1a, Inositol-requiring protein 1, ...
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Disease relevance of ERN1


High impact information on ERN1

  • Dominant-negative TRAF2 inhibited activation of JNK by IRE1 [4].
  • Coupling of stress in the ER to activation of JNK protein kinases by transmembrane protein kinase IRE1 [4].
  • In mammalian cells, two homologs, Ire1 alpha and Ire1 beta, are implicated in signaling the UPR [5].
  • These mutants were used to demonstrate that the RNase activity is required for UPR activation by IRE1 alpha and IRE1 beta [5].
  • XBP1 is required for the terminal differentiation of B lymphocytes into plasma cells, and IRE1 also participates in this differentiation event [6].

Biological context of ERN1

  • Collectively, these results suggest that the IRE1/XBP-1 pathway is required for efficient protein folding, maturation, and degradation in the ER and imply the existence of subsets of UPR target genes as defined by their dependence on XBP-1 [7].
  • A study in this issue of the JCI reveals, quite unexpectedly, that IRE1 is also required early in B lymphocyte development for the induction of the machinery that mediates Ig gene rearrangement [6].
  • Silencing of IRE-1 and JNK inhibition downregulated Nox-4 expression and subsequently prevented the UPR-dependent cell death induced by 7-Kchol [8].
  • The fast type (IRE1) (relative mobility 1.05) had a heterozygote frequency of 1/3,780, and the slow type (IRE2) (relative mobility of 0.94) had a heterozygote frequency of 1/8,500 [9].
  • When accumulation of misfolded protein becomes toxic, apoptosis is triggered, potentially with IRE1 involved in signaling via caspase-12 [10].

Anatomical context of ERN1

  • The mechanisms involve prolonged stress of the endoplasmic reticulum (ER) leading to the activation of the two main branches of the unfolded protein response (UPR), including the Ire1/XBP-1/GRP78/Bip and PERK/eIF2alpha arms [11].
  • Mammalian homologs of yeast IRE1, which activate chaperone genes in response to ER stress, also activated JNK, and IRE1alpha-/- fibroblasts were impaired in JNK activation by ER stress [4].
  • These responses are mediated by a transmembrane kinase/ribonuclease, IRE1, which transduces the signal from the ER lumen to the cytosol [12].
  • IRE1alpha-null MEFs, a cell line with a defective IRE1-XBP1 pathway, show elevated levels of HCV IRES-mediated translation [13].
  • Therefore, HCV may suppress the IRE1-XBP1 pathway to not only promote HCV expression but also to contribute to the persistence of the virus in infected hepatocytes [13].

Associations of ERN1 with chemical compounds

  • Furthermore, the 7-Kchol activating pathway included an early triggering of endoplasmic reticulum stress, as assessed by transient intracellular Ca(2+) oscillations, and the induction of the expression of the cell death effector CHOP and of GRP78/Bip chaperone via the activation of IRE-1, all hallmarks of the unfolded protein response (UPR) [8].
  • Finally, the luminal portion of Ire1p (Ire=high inositol-requiring), thought to convey the sensing function of this transmembrane kinase and endoribonuclease, was shown to contain repeats similar to those in beta-propeller proteins [14].
  • In contrast, chronic exposure of beta cells to high glucose causes ER stress and hyperactivation of IRE1, leading to the suppression of insulin gene expression [15].
  • Manganese superoxide dismutase is induced by endoplasmic reticulum stress through IRE1-mediated nuclear factor (NF)-kappaB and AP-1 activation [16].
  • DKO mice responded abnormally to tunicamycin-induced ER stress in the liver, with extensive tissue damage and decreased expression of the IRE1 substrate X-box-binding protein 1 and its target genes [17].

Other interactions of ERN1

  • HCV NS4B activated the IRE1 pathway, as indicated by splicing of X box-binding protein (Xbp-1) mRNA [18].
  • We demonstrate that HCV NS4B could induce activating transcription factor (ATF6) and inositol-requiring enzyme 1 (IRE1), to favor the HCV subreplicon and HCV viral replication [18].
  • Thus, we provide a missing link in the ER stress-induced apoptosis-signaling pathway, one which connects the stress sensor molecule IRE1 and the activation of caspase-12 [19].
  • Activation signal of nuclear factor-kappa B in response to endoplasmic reticulum stress is transduced via IRE1 and tumor necrosis factor receptor-associated factor 2 [12].
  • With an approach combining semi-quantitative RT-PCR and immunoblotting using phospho-specific antibodies, we show that the IRE-1 pathway is activated upon early ischaemia and, in a second phase, upon early reperfusion [20].

Analytical, diagnostic and therapeutic context of ERN1

  • Although PERK and IRE1 are activated in the initial hours of reperfusion, total PERK decreases, ATF6 is not activated, and there is delayed appearance of UPR-induced mRNAs [21].
  • Although ER stress-responsive genes often are up-regulated by ATF6, IRE1 and XBP1, which are ER stress-related transcription factors/transducers, the overexpression of neither molecule affected the levels of MnSOD mRNA and protein [16].


  1. Activation of hepatitis B virus S promoter by a cell type-restricted IRE1-dependent pathway induced by endoplasmic reticulum stress. Huang, Z.M., Tan, T., Yoshida, H., Mori, K., Ma, Y., Yen, T.S. Mol. Cell. Biol. (2005) [Pubmed]
  2. Proteasome inhibitors disrupt the unfolded protein response in myeloma cells. Lee, A.H., Iwakoshi, N.N., Anderson, K.C., Glimcher, L.H. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  3. ER stress, hypoxia tolerance and tumor progression. Koumenis, C. Curr. Mol. Med. (2006) [Pubmed]
  4. Coupling of stress in the ER to activation of JNK protein kinases by transmembrane protein kinase IRE1. Urano, F., Wang, X., Bertolotti, A., Zhang, Y., Chung, P., Harding, H.P., Ron, D. Science (2000) [Pubmed]
  5. The endoribonuclease activity of mammalian IRE1 autoregulates its mRNA and is required for the unfolded protein response. Tirasophon, W., Lee, K., Callaghan, B., Welihinda, A., Kaufman, R.J. Genes Dev. (2000) [Pubmed]
  6. Birth pangs: the stressful origins of lymphocytes. Pillai, S. J. Clin. Invest. (2005) [Pubmed]
  7. XBP-1 regulates a subset of endoplasmic reticulum resident chaperone genes in the unfolded protein response. Lee, A.H., Iwakoshi, N.N., Glimcher, L.H. Mol. Cell. Biol. (2003) [Pubmed]
  8. NAD(P)H oxidase Nox-4 mediates 7-ketocholesterol-induced endoplasmic reticulum stress and apoptosis in human aortic smooth muscle cells. Pedruzzi, E., Guichard, C., Ollivier, V., Driss, F., Fay, M., Prunet, C., Marie, J.C., Pouzet, C., Samadi, M., Elbim, C., O'dowd, Y., Bens, M., Vandewalle, A., Gougerot-Pocidalo, M.A., Lizard, G., Ogier-Denis, E. Mol. Cell. Biol. (2004) [Pubmed]
  9. Purification and structural study of two albumin variants in an Irish population. Sakamoto, Y., Davis, E., Madison, J., Watkins, S., McLaughlin, H., Leahy, D.T., Putnam, F.W. Clin. Chim. Acta (1991) [Pubmed]
  10. Endoplasmic reticulum quality control and apoptosis. Groenendyk, J., Michalak, M. Acta Biochim. Pol. (2005) [Pubmed]
  11. Dihydroxyphenylethanol induces apoptosis by activating serine/threonine protein phosphatase PP2A and promotes the endoplasmic reticulum stress response in human colon carcinoma cells. Guichard, C., Pedruzzi, E., Fay, M., Marie, J.C., Braut-Boucher, F., Daniel, F., Grodet, A., Gougerot-Pocidalo, M.A., Chastre, E., Kotelevets, L., Lizard, G., Vandewalle, A., Driss, F., Ogier-Denis, E. Carcinogenesis (2006) [Pubmed]
  12. Activation signal of nuclear factor-kappa B in response to endoplasmic reticulum stress is transduced via IRE1 and tumor necrosis factor receptor-associated factor 2. Kaneko, M., Niinuma, Y., Nomura, Y. Biol. Pharm. Bull. (2003) [Pubmed]
  13. Hepatitis C virus suppresses the IRE1-XBP1 pathway of the unfolded protein response. Tardif, K.D., Mori, K., Kaufman, R.J., Siddiqui, A. J. Biol. Chem. (2004) [Pubmed]
  14. Proteins of the endoplasmic-reticulum-associated degradation pathway: domain detection and function prediction. Ponting, C.P. Biochem. J. (2000) [Pubmed]
  15. Regulation of insulin biosynthesis in pancreatic beta cells by an endoplasmic reticulum-resident protein kinase IRE1. Lipson, K.L., Fonseca, S.G., Ishigaki, S., Nguyen, L.X., Foss, E., Bortell, R., Rossini, A.A., Urano, F. Cell metabolism. (2006) [Pubmed]
  16. Manganese superoxide dismutase is induced by endoplasmic reticulum stress through IRE1-mediated nuclear factor (NF)-kappaB and AP-1 activation. Kaneko, M., Takahashi, T., Niinuma, Y., Nomura, Y. Biol. Pharm. Bull. (2004) [Pubmed]
  17. Proapoptotic BAX and BAK modulate the unfolded protein response by a direct interaction with IRE1alpha. Hetz, C., Bernasconi, P., Fisher, J., Lee, A.H., Bassik, M.C., Antonsson, B., Brandt, G.S., Iwakoshi, N.N., Schinzel, A., Glimcher, L.H., Korsmeyer, S.J. Science (2006) [Pubmed]
  18. Hepatitis C virus non-structural protein NS4B can modulate an unfolded protein response. Zheng, Y., Gao, B., Ye, L., Kong, L., Jing, W., Yang, X., Wu, Z., Ye, L. J. Microbiol. (2005) [Pubmed]
  19. Activation of caspase-12, an endoplastic reticulum (ER) resident caspase, through tumor necrosis factor receptor-associated factor 2-dependent mechanism in response to the ER stress. Yoneda, T., Imaizumi, K., Oono, K., Yui, D., Gomi, F., Katayama, T., Tohyama, M. J. Biol. Chem. (2001) [Pubmed]
  20. Distinct endoplasmic reticulum stress responses are triggered during human liver transplantation. Emadali, A., Nguyên, D.T., Rochon, C., Tzimas, G.N., Metrakos, P.P., Chevet, E. J. Pathol. (2005) [Pubmed]
  21. Cerebral ischemia and the unfolded protein response. DeGracia, D.J., Montie, H.L. J. Neurochem. (2004) [Pubmed]
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