GO:1990332 Ire1 complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990332 Ire1 complex is a type-I transmembrane protein complex in the endoplasmic reticulum (ER) consisting of an IRE1-IRE1 dimer that forms in response to ER unfolded protein accumulation.
• The dimeric Ire1 complex has endoribonuclease (RNase) activity and cleaves a single phosphodiester bond in each of two RNA hairpins to remove an intron from HAC1 (yeast) or XBP1 (mammals) mRNA.
• IRE1 is the most conserved of the three canonical UPR sensors (IRE1, PERK, ATF6) and is the only one with intrinsic RNase activity.
• IRE1 activation is regulated by chaperones such as Hsp90/p-Cdc37 and by redox-sensitive proteins such as thioredoxin-1.
• Dysregulated IRE1 signaling is implicated in cancer, neurodegeneration, and metabolic disease, making it a therapeutic target.
• CRISPR knockout, point-mutation, knock-in, and overexpression models are essential for dissecting IRE1 function and identifying synthetic lethal interactions.
Description
The Ire1 complex (GO:1990332) is a type-I transmembrane protein complex located in the endoplasmic reticulum (ER) that forms an IRE1-IRE1 dimer in response to the accumulation of unfolded proteins in the ER. This dimeric complex possesses endoribonuclease (RNase) activity and evokes the unfolded protein response (UPR) by cleaving an intron of the mRNA coding for the transcription factor HAC1 in yeast or XBP1 in mammals. The complex cleaves a single phosphodiester bond in each of two RNA hairpins with non-specific base-paired stems and loops of consensus sequence CNCNNGN, removing an intervening intron from the target transcript. As the most evolutionarily conserved UPR sensor, IRE1 is central to cellular proteostasis and stress adaptation. Researchers study the Ire1 complex to understand how cells cope with ER stress, how this pathway contributes to diseases such as cancer and neurodegeneration, and how it can be targeted therapeutically. The complex is also a model for studying membrane-bound RNase mechanisms and RNA substrate recognition.
Ire1 complex At A Glance
| GO ID | GO:1990332 |
|---|---|
| GO term | Ire1 complex |
| Ontology | cellular_component |
| Synonym | ER-bound kinase/endoribonuclease (RNase), inositol-requiring enzyme-1, ERN1 complex, Ire1 complex dimer, Ire1 complex homodimer, Ire1 complex homooligomer, IRE1 dimer |
| Major function | Endoribonuclease activity that cleaves HAC1/XBP1 mRNA to activate the unfolded protein response |
| Location | Endoplasmic reticulum membrane |
| Subunits | IRE1-IRE1 homodimer |
| Substrate | HAC1 mRNA (yeast) or XBP1 mRNA (mammals) |
| Consensus sequence | CNCNNGN in RNA hairpin loops |
What Is GO:1990332?
The Ire1 complex is a type-I transmembrane protein complex in the endoplasmic reticulum (ER) consisting of an IRE1-IRE1 dimer that forms when unfolded proteins accumulate in the ER. The dimeric complex has endoribonuclease (RNase) activity and activates the unfolded protein response (UPR) by cleaving an intron from the mRNA encoding the transcription factor HAC1 in yeast or XBP1 in mammals. It cleaves a single phosphodiester bond in each of two RNA hairpins with non-specific base-paired stems and loops of consensus sequence CNCNNGN, where N is any base, to remove an intervening intron from the target transcript.
Why Is Ire1 complex Important in Cell Biology?
The Ire1 complex is the most conserved branch of the unfolded protein response and serves as a primary sensor of ER stress, linking protein-folding homeostasis to gene expression, autophagy, and apoptosis. Its endoribonuclease activity is unique among UPR sensors and is essential for splicing XBP1 mRNA to produce a potent transcription factor that upregulates chaperones, lipid biosynthesis, and ER-associated degradation components. Dysregulation of IRE1 signaling contributes to cancer progression, neurodegeneration, and metabolic disorders, and the complex is a target for chemical degraders and inhibitors. Understanding its structure, regulation, and substrates is therefore critical for both basic cell biology and therapeutic development.
• Central to the unfolded protein response (UPR) and ER proteostasis.
• Only UPR sensor with intrinsic endoribonuclease activity, making it a unique drug target.
• Regulates XBP1 splicing, which controls genes for chaperones, lipid synthesis, and ERAD.
• Implicated in cancer cell survival and chemoresistance, with synthetic lethal interactions with mRNA quality control complexes.
• Linked to neurodegeneration, including Parkinson disease, through redox regulation by thioredoxin-1 and Hsp90/p-Cdc37.
• Targeted by chemically induced degradation via VHL-recruiting chimeras, demonstrating therapeutic potential.
• Involved in ER stress-induced cell death mechanisms, relevant to ischemia and degenerative diseases.
• Regulated by the ribosome-associated complex, connecting translation to IRE1 activation.
• Contributes to ER homeostasis in neurons, with WDR45 mutations affecting neuronal survival.
• Plays a role in thermotolerance and grain quality in rice, showing agricultural relevance.
Core Biology of the Ire1 Complex
Activation by ER Stress
In simple terms: When unfolded proteins build up in the ER, IRE1 molecules pair up and switch on.
The Ire1 complex forms when unfolded proteins accumulate in the ER lumen. IRE1, a type-I transmembrane protein, undergoes dimerization and higher-order oligomerization, which activates its endoribonuclease domain. This activation is the first step in the UPR and is conserved from yeast to humans. The ribosome-associated complex has been shown to play a role in activating the IRE1 branch of the UPR.
Endoribonuclease Cleavage of HAC1/XBP1 mRNA
In simple terms: The active Ire1 complex cuts a specific intron out of a messenger RNA, allowing a stress-response protein to be made.
The dimeric Ire1 complex cleaves a single phosphodiester bond in each of two RNA hairpins within the HAC1 (yeast) or XBP1 (mammals) mRNA. The hairpins have non-specific base-paired stems and loops of consensus sequence CNCNNGN, where N is any base. This cleavage removes an intervening intron, and subsequent ligation by tRNA ligase produces a spliced mRNA encoding a functional transcription factor. The spliced XBP1 protein then upregulates genes involved in protein folding, ERAD, and lipid synthesis.
Structural Organization of the Ire1 Dimer
In simple terms: IRE1 proteins join together in the ER membrane to form the active complex.
The Ire1 complex is a homodimer of IRE1 proteins, each containing an N-terminal ER luminal domain, a transmembrane domain, and a cytosolic kinase and endoribonuclease domain. Dimerization is driven by ER stress and is required for RNase activity. The complex can further oligomerize into higher-order structures that enhance signaling. The kinase domain is not essential for RNase activity but regulates it through conformational changes.
Regulation by Chaperones and Redox State
In simple terms: Helper proteins and the cell's redox balance can turn IRE1 activity up or down.
IRE1 activation is modulated by chaperones such as Hsp90 and its co-chaperone p-Cdc37; thioredoxin-1 inhibits IRE1 activation by targeting the Hsp90/p-Cdc37 complex in Parkinson disease models. This redox-sensitive regulation links ER stress to oxidative stress. Additionally, the ribosome-associated complex contributes to IRE1 activation, connecting translation efficiency to UPR signaling.
Downstream Signaling and Cell Fate
In simple terms: Once active, the Ire1 complex can help cells survive or, if stress is severe, trigger cell death.
Activated IRE1 signals through XBP1 splicing to promote adaptation and survival, but prolonged activation can lead to apoptosis via mechanisms involving ER stress-induced cell death pathways. IRE1 also degrades select mRNAs through regulated IRE1-dependent decay (RIDD), reducing the load of proteins entering the ER. The balance between adaptive and pro-death signaling determines cell fate and is relevant to diseases such as cancer and neurodegeneration.
Key Genes Involved in GO:1990332 Ire1 complex
The following genes and proteins are central to the structure, regulation, and function of the Ire1 complex.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ERN1 (IRE1) | Core transmembrane kinase/endoribonuclease that forms the Ire1 complex | Primary target for knockout, point mutation, and degradation studies |
| XBP1 | Transcription factor produced by IRE1-mediated mRNA splicing | Key readout of IRE1 activity; knockout models show UPR defects |
| HAC1 | Yeast transcription factor activated by Ire1-mediated splicing | Model for studying IRE1 RNase mechanism |
| HSP90AA1 | Chaperone that regulates IRE1 activation | Target for modulating IRE1 in disease models |
| CDC37 | Co-chaperone that partners with Hsp90 to regulate IRE1 | Phosphorylated form (p-Cdc37) involved in IRE1 inhibition |
| TXN | Thioredoxin-1 inhibits IRE1 by targeting Hsp90/p-Cdc37 | Redox regulation of IRE1 in Parkinson disease |
| WDR45 | Regulates ER homeostasis and neuronal survival | Mutations cause neurodegeneration with ER stress |
| RAC (ribosome-associated complex) | Activates IRE1 branch of UPR | Links translation to UPR signaling |
| MTOR | Coordinates autophagy and apoptosis in chondrocytes | Cross-talk with ER stress in osteoarthritis |
| VHL | E3 ligase used for targeted degradation of IRE1 | Chemically induced degradation of IRE1 |
| ATF6 | Parallel UPR sensor | Comparative studies of UPR branches |
| EIF2AK3 (PERK) | Parallel UPR sensor | Comparative studies of UPR branches |
| CASP3 | Executioner caspase in ER stress-induced apoptosis | Downstream cell death readout |
| BECN1 | Autophagy regulator cross-talking with ER stress | MTORC1 coordination in disease |
| MAP1LC3B | Autophagosome marker | Autophagy flux measurement |
| ERN2 (IRE2) | Paralog of IRE1 in some organisms | Functional redundancy studies |
| SEC61 | ER translocon component | ER stress induction models |
| CALR | ER chaperone and calcium-binding protein | ER stress marker |
How Is Ire1 complex Regulated?
IRE1 activity is regulated at multiple levels. Chaperones such as Hsp90 and its co-chaperone p-Cdc37 modulate IRE1 activation, and thioredoxin-1 inhibits IRE1 by targeting this chaperone complex in Parkinson disease models. The ribosome-associated complex also contributes to IRE1 activation, linking translation status to UPR signaling. Additionally, mTORC1 coordinates autophagy and apoptosis signaling in chondrocytes, providing cross-talk between ER stress and metabolic pathways. Chemically induced degradation using VHL-recruiting chimeras demonstrates that IRE1 protein levels can be pharmacologically controlled.
Ire1 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ERN1 (IRE1) | Cancer, neurodegeneration | Knockout and point-mutation cell lines; xenograft models |
| XBP1 | Cancer, plasma cell differentiation | Knockout and knock-in reporter models |
| TXN | Parkinson disease | Overexpression and knockout neuronal cells |
| WDR45 | Neurodegeneration with brain iron accumulation | Knockout neurons and mouse models |
| MTOR | Osteoarthritis | Chondrocyte-specific knockout and overexpression |
Cancer
IRE1 signaling supports cancer cell survival under ER stress, and synthetic lethality screens have identified mRNA quality control complexes as vulnerabilities in cancer cells with dysregulated UPR. Targeting IRE1 with chemical degraders may offer a therapeutic strategy.
Neurodegeneration
IRE1 activation is implicated in Parkinson disease, where thioredoxin-1 inhibits IRE1 by targeting the Hsp90/p-Cdc37 chaperone complex. WDR45 mutations cause neurodegeneration through dysregulation of ER homeostasis and neuronal death. ER stress-induced cell death mechanisms contribute to neuronal loss.
Metabolic and Musculoskeletal Disorders
MTORC1 coordinates autophagy and apoptosis in articular chondrocytes in osteoarthritic temporomandibular joint, linking ER stress to cartilage degeneration. IRE1 signaling also affects metabolic tissues, though specific mechanisms vary.
Plant Stress and Agriculture
A natural gene on-off system confers field thermotolerance for grain quality and yield in rice, involving ER stress-related pathways. This highlights the conserved importance of IRE1-like signaling beyond mammals.
From Ire1 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does IRE1 kinase activity regulate RNase function? | Point-mutation knock-in of kinase-dead IRE1 |
| What is the effect of IRE1 loss on XBP1 splicing? | CRISPR knockout of ERN1 in cell lines |
| Can IRE1 be degraded pharmacologically? | Knock-in of VHL-recruiting degron tag or chemical degrader treatment |
| How does IRE1 activation affect neuronal survival? | Overexpression of wild-type vs. mutant IRE1 in neurons |
| What genes are synthetic lethal with IRE1 loss? | CRISPR library screening in cancer cell lines |
| How does IRE1 signaling cross-talk with autophagy? | Knockout of ERN1 combined with autophagy reporters |
How to Study the Ire1 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| RT-PCR for XBP1 splicing | Ratio of spliced to unspliced XBP1 mRNA | Assessing IRE1 RNase activity |
| RNA-seq | Global transcriptome changes | Identifying UPR target genes and RIDD substrates |
| Ribo-seq | Translation efficiency | Measuring XBP1 mRNA translation |
| Western blot | Protein levels and phosphorylation | Detecting IRE1 activation and XBP1s |
| Co-immunoprecipitation | Protein-protein interactions | Identifying Hsp90/p-Cdc37 binding |
| Fluorescence microscopy | Subcellular localization and dimerization | Visualizing Ire1 complex formation |
| CRISPR library screening | Gene essentiality and synthetic lethality | Finding combination targets in cancer |
| Chemical degrader assays | IRE1 protein degradation | Testing VHL-recruiting chimeras |
RNA-Based Methods for IRE1 Activity
XBP1 splicing can be measured by RT-PCR followed by restriction fragment length polymorphism or sequencing. RNA-seq can quantify global changes in gene expression and identify RIDD targets. Ribo-seq can assess translation efficiency of XBP1 and other mRNAs.
Protein and Proteomic Approaches
Western blotting for phosphorylated IRE1, total IRE1, and XBP1s protein is standard. Co-immunoprecipitation can identify interacting partners such as Hsp90 and p-Cdc37. Mass spectrometry-based proteomics can map the IRE1 interactome and post-translational modifications.
Imaging and Cellular Assays
Fluorescence microscopy with tagged IRE1 can visualize dimerization and oligomerization in live cells. ER stress reporters such as GFP-XBP1 splicing reporters enable high-throughput screening. Apoptosis and autophagy can be monitored by flow cytometry and LC3B puncta formation.
Genetic and Chemical Perturbation
CRISPR knockout, point mutation, and knock-in models allow precise dissection of IRE1 domains. Chemical degraders and inhibitors provide temporal control of IRE1 activity. Synthetic lethality screens with CRISPR libraries can identify combination targets.
How CRISPR Can Be Used to Study GO:1990332 Ire1 complex
Knockout
CRISPR knockout of ERN1 (IRE1) eliminates the Ire1 complex, abolishing XBP1 splicing and UPR signaling. This is used to study loss-of-function phenotypes in cancer, neurodegeneration, and metabolic disease models.
Point Mutation
Point mutations in the kinase or RNase domains of IRE1 can dissect domain-specific functions. For example, kinase-dead mutants reveal whether kinase activity is required for RNase activation. Point mutations in the RNase domain can abolish XBP1 splicing without affecting dimerization.
Knock-in
Knock-in of epitope tags (e.g., HA, FLAG) or fluorescent proteins into the endogenous ERN1 locus enables real-time imaging and proteomic analysis of the Ire1 complex. Knock-in of degron tags allows conditional degradation.
Overexpression
Overexpression of wild-type or mutant IRE1 in cell lines can amplify signaling and facilitate biochemical studies. It is used to test the effect of disease-associated mutations on IRE1 function.
How EDITGENE Supports Ire1 complex Research
Researchers studying Ire1 complex-related genes often need to determine whether a candidate gene is causally involved in ER stress signaling, XBP1 splicing, or disease progression. EDITGENE provides comprehensive CRISPR-based services to create precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for Ire1 complex research.
Frequently Asked Questions About Ire1 complex
What is the Ire1 complex?
The Ire1 complex (GO:1990332) is a type-I transmembrane protein complex in the ER consisting of an IRE1-IRE1 dimer that activates the unfolded protein response by cleaving HAC1/XBP1 mRNA.
What genes are involved in the Ire1 complex?
The core gene is ERN1 (IRE1), with downstream targets XBP1 and HAC1, and regulators such as HSP90AA1, CDC37, and TXN.
What is the function of GO:1990332?
It has endoribonuclease activity that cleaves a single phosphodiester bond in each of two RNA hairpins to remove an intron from HAC1/XBP1 mRNA, activating the UPR.
Where is the Ire1 complex located?
It is located in the endoplasmic reticulum membrane.
How is the Ire1 complex activated?
It forms dimers in response to accumulation of unfolded proteins in the ER, and is regulated by chaperones such as Hsp90/p-Cdc37 and thioredoxin-1.
What diseases are associated with Ire1 complex dysfunction?
Cancer, neurodegeneration (e.g., Parkinson disease), and metabolic disorders such as osteoarthritis.
What is the difference between IRE1 and PERK?
IRE1 has intrinsic endoribonuclease activity for XBP1 splicing, while PERK phosphorylates eIF2α to attenuate translation; both are UPR sensors.
How can I study Ire1 complex activity in the lab?
Common methods include XBP1 splicing RT-PCR, RNA-seq, Ribo-seq, Western blot for phosphorylated IRE1, and fluorescence microscopy.
Can CRISPR be used to model Ire1 complex mutations?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect IRE1 function.
What are the therapeutic strategies targeting the Ire1 complex?
Chemical degraders such as VHL-recruiting chimeras and small-molecule inhibitors are being developed to modulate IRE1 activity.
Conclusion
The Ire1 complex (GO:1990332) is a central ER stress sensor with unique endoribonuclease activity that controls the unfolded protein response through XBP1 splicing. Its dysregulation is linked to cancer, neurodegeneration, and metabolic diseases, making it a high-value target for basic and translational research. CRISPR-based models and advanced screening methods are essential for dissecting its mechanism and identifying therapeutic opportunities.
References
- 1. Zeng X et al.. 2023. Thioredoxin-1 inhibits the activation of IRE1 by targeting Hsp90/p-Cdc37 chaperone complex in Parkinson disease.. Ageing Res Rev 90:102000 PMID: 37437766
- 2. Sano R et al.. 2013. ER stress-induced cell death mechanisms.. Biochim Biophys Acta 1833(12):3460-3470 PMID: 23850759
- 3. Li W et al.. 2025. A natural gene on-off system confers field thermotolerance for grain quality and yield in rice.. Cell 188(14):3661-3678.e21 PMID: 40311617
- 4. Yang H et al.. 2020. MTORC1 coordinates the autophagy and apoptosis signaling in articular chondrocytes in osteoarthritic temporomandibular joint.. Autophagy 16(2):271-288 PMID: 31007149
- 5. Prindle V et al.. 2025. Synthetic lethality of mRNA quality control complexes in cancer.. Nature 638(8052):1095-1103 PMID: 39910291
- 6. Wu IH et al.. 2021. A role for the ribosome-associated complex in activation of the IRE1 branch of UPR.. Cell Rep 35(10):109217 PMID: 34107246
- 7. Wan H et al.. 2020. WDR45 contributes to neurodegeneration through regulation of ER homeostasis and neuronal death.. Autophagy 16(3):531-547 PMID: 31204559
- 8. Du J et al.. 2025. Chemically-induced degradation of the endoplasmic-reticulum stress sensor IRE1 by a VHL-recruiting chimera.. Nat Commun 16(1):11445 PMID: 41381506
