Mus musculus
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA116837 | ENA |
REPOSITORIES: ENA
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Project description:Signaling cascades during adipogenesis culminate in the expression of two essential adipogenic factors, PPARγ and C/EBPα. Here we demonstrate that the IRE1α-XBP1 pathway, the most conserved branch of the unfolded protein response (UPR), is indispensable for adipogenesis. Indeed, XBP1-deficient mouse embryonic fibroblasts and 3T3-L1 cells with XBP1 or IRE1α knockdown exhibit profound defects in adipogenesis. Intriguingly, C/EBPβ, a key early adipogenic factor, induces Xbp1 expression by directly binding to its proximal promoter region. Subsequently, XBP1 binds to the promoter of Cebpa and activates its gene expression. The posttranscriptional splicing of Xbp1 mRNA by IRE1α is required as only the spliced form of XBP1 (XBP1s) rescues the adipogenic defect exhibited by XBP1-deficient cells. Taken together, our data show that the IRE1α-XBP1 pathway plays a key role in adipocyte differentiation by acting as a critical regulator of the morphological and functional transformations during adipogenesis.
2009-04-25 | GSE15771 | GEO
Project description:Signaling cascades during adipogenesis culminate in the expression of two essential adipogenic factors, PPARγ and C/EBPα. Here we demonstrate that the IRE1α-XBP1 pathway, the most conserved branch of the unfolded protein response (UPR), is indispensable for adipogenesis. Indeed, XBP1-deficient mouse embryonic fibroblasts and 3T3-L1 cells with XBP1 or IRE1α knockdown exhibit profound defects in adipogenesis. Intriguingly, C/EBPβ, a key early adipogenic factor, induces Xbp1 expression by directly binding to its proximal promoter region. Subsequently, XBP1 binds to the promoter of Cebpa and activates its gene expression. The posttranscriptional splicing of Xbp1 mRNA by IRE1α is required as only the spliced form of XBP1 (XBP1s) rescues the adipogenic defect exhibited by XBP1-deficient cells. Taken together, our data show that the IRE1α-XBP1 pathway plays a key role in adipocyte differentiation by acting as a critical regulator of the morphological and functional transformations during adipogenesis. The Xbp1 deficient MEFs are subjected to adipogenesis using standard drug induction. The cells are collected at day 0 and day 3. Total RNA are extracted from the cells and used for one channel microarray analysis. Expression levels on day 3 are compared to that on day 0.
2010-06-19 | E-GEOD-15771 | biostudies-arrayexpress
Project description:Background/Aims: Cholestatic liver diseases (CLD) are the leading indication for pediatric liver transplantation. Increased intrahepatic bile acid concentrations cause endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) is activated to maintain homeostasis. UPR dysregulation, including the inositol-requiring enzyme 1α/X-box protein 1 (IRE1α/XBP1) pathway, is associated with several adult liver diseases. We evaluated hepatic UPR expression in pediatric patients with end-stage CLD and hypothesize that an inability to appropriately activate the hepatic IRE1α/XBP1 pathway is associated with the pathogenesis of CLD. Methods: We evaluated 34 human liver explants. Cohorts included: pediatric CLD (Alagille, ALGS, and progressive familial intrahepatic cholestasis, PFIC), pediatric non-cholestatic liver disease controls (autoimmune hepatitis, AIH), adult CLD, and normal controls. We performed RNA-seq, quantitative PCR, and western blotting to measure expression differences of the hepatic UPR and other signaling pathways. Results: Metascape pathway analysis demonstrated that the KEGG ‘protein processing in ER’ pathway was downregulated in pediatric CLD compared to normal controls. Pediatric CLD had decreased hepatic IRE1α/XBP1 pathway gene expression and decreased protein expression of p-IRE1α compared to normal controls. These CLD changes were not disease-specific to ALGS or PFIC. IRE1α/XBP1 pathway gene expression was decreased in pediatric CLD compared to AIH disease controls. Conclusion: Pediatric CLD explants have decreased gene and protein expression of the protective IRE1α/XBP1 pathway and down-regulated KEGG protein processing in the ER pathways. IRE1α/XBP1 pathway expression differences occur when compared to both normal and non-cholestatic disease controls. Attenuated expression of the IRE1α/XBP1 pathway is associated with cholestatic diseases and could be targeted to treat pediatric CLD.
2022-06-23 | GSE206364 | GEO
Project description:The IRE1α-XBP1 arm of the unfolded protein response (UPR) maintains endoplasmic reticulum (ER) homeostasis, but also controls UPR-independent processes such as cytokine production and lipid metabolism. Yet, the physiological consequences of IRE1α-XBP1 activation in immune cells remain largely unexplored. Here, we report that leukocyte-intrinsic IRE1α-XBP1 signaling drives prostaglandin biosynthesis and pain. Transcriptomic analyses revealed that induction of prostaglandin-endoperoxide synthase 2 (Ptgs2/Cox-2) and prostaglandin E synthase (Ptges/mPGES-1) was compromised in IRE1α-deficient myeloid cells undergoing ER stress or stimulated via pattern recognition receptors. Inducible biosynthesis of prostaglandins, including PGE2, was markedly decreased in myeloid cells lacking IRE1α or XBP1, but not altered in the absence of the two other ER stress sensors PERK and ATF6. Mechanistically, IRE1α-activated XBP1 bound to and directly induced the expression of human PTGS2 and PTGES to enable PGE2 generation. Mice selectively lacking IRE1α-XBP1 in leukocytes, or treated with pharmacological IRE1α inhibitors, failed to induce PGE2 upon challenge with inflammatory stimuli and demonstrated reduced behavioral pain responses in PGE2-dependent models of pain. Our study uncovers an unexpected role for IRE1α-XBP1 as a key mediator of prostaglandin biosynthesis and indicates that targeting this pathway may represent an alternative approach to control pain.
2020-05-16 | GSE131404 | GEO
Project description:Endoplasmic Reticulum (ER) stress is a hallmark of various diseases, which is dealt with through the activation of an adaptive signaling pathway named the Unfolded Protein Response (UPR). This response is mediated by three ER-resident sensors and the most evolutionary conserved, IRE1α signals through its cytosolic kinase and endoribonuclease (RNase) activities. IRE1α RNase activity can either catalyze the initial step of XBP1 mRNA unconventional splicing or degrade a number of RNAs through Regulated IRE1-Dependent Decay (RIDD). The balance between these two activities plays an instrumental role in cells’ life and death decisions upon ER stress. Until now, the biochemical and biological outputs of IRE1α RNase activity have been well documented, however, the precise mechanisms controlling whether IRE1 signaling is adaptive or pro-death (terminal) remain unclear. This prompted us to further investigate those mechanisms and we hypothesized that XBP1 mRNA splicing and RIDD activity could be co-regulated by the IRE1α RNase regulatory network. We showed that a key nexus in this pathway is the tRNA ligase RtcB which, together with IRE1α, is responsible for XBP1 mRNA splicing. We demonstrated that RtcB is tyrosine phosphorylated by c-Abl and dephosphorylated by PTP1B. Moreover, we identified RtcB Y306 as a key residue which, when phosphorylated, perturbs RtcB interaction with IRE1α, thereby attenuating XBP1 mRNA splicing and favoring RIDD. Our results demonstrate that the IRE1α RNase regulatory network is dynamically fine-tuned by tyrosine kinases and phosphatases upon various stresses and that the nature of the stress determines cell adaptive or death outputs.
2022-02-21 | PXD023433 | Pride
Project description:The IRE1α-XBP1s signaling branch of the unfolded protein response is a well-characterized survival pathway that allows cells to adapt to and resolve endoplasmic reticulum stress. Recent data has broadened our understanding of IRE1α-XBP1s signaling beyond a stress response and revealed a physiological mechanism required for the differentiation and maturation of a wide variety of cell types. Here we provide evidence that the IRE1α-XBP1s signaling pathway is required for the proliferation and maturation of basal keratinocytes in the mouse tongue and esophageal epithelium. Mice with conditional targeted deletion of either IRE1α or XBP1 in keratin 14 expressing basal keratinocytes displayed severe thinning of the lingual and esophageal mucosa that rendered them unable to eat. In IRE1α null epithelium harvested at an earlier timepoint, genes regulating cell proliferation, cell-cell adhesion, and keratinization were significantly downregulated; indirect immunofluorescence revealed fewer proliferating basal keratinocytes, downregulation of E-Cadherin, and thinning of the loricrin-positive granular and cornified layers. The number of Tp63 positive basal keratinocytes was reduced in the absence of IRE1α, and expression of the Wnt pathway transcription factor LEF1, which is required for the proliferation of lingual transit amplifying cells, was also significantly downregulated at the transcript and protein level. Together these results reveal an essential role for IRE1α-XBP1s in the maintenance of the stratified squamous epithelial tissue of the tongue and esophagus.
2022-09-30 | GSE205488 | GEO
Project description:The unfolded protein response (UPR) preserves endoplasmic reticulum proteostasis through coordinated signaling pathways, including the IRE1α-XBP1 axis, which promotes adaptive transcriptional programs via non-canonical XBP1 mRNA splicing. However, upstream mechanisms regulating this pathway remain incompletely defined. Here, we apply CRASP-Seq, a scalable RNA-coupled CRISPR screening platform, to systematically identify regulators of XBP1 splicing. We uncover the U2 snRNP auxiliary factor RBM39 as a critical positive regulator of this process. Perturbation of RBM39 or U2 snRNP components induces alternative splicing of ERN1, leading to exon-18 skipping and the production of an unstable transcript subject to nonsense-mediated decay, as well as a truncated IRE1α isoform that acts in a dominant-negative manner to suppress XBP1 splicing. Mechanistically, we show that heat shock reduces RBM39 functional activity and promotes ERN1 exon-18 skipping, thereby attenuating IRE1α–XBP1 signaling. Functionally, hyperactivation of this pathway is detrimental under proteotoxic stress, suggesting that exon-18 skipping serves as a stress-adaptive mechanism to limit UPR output. Together, our findings reveal a previously unrecognized regulatory axis linking the canonical splicing machinery to UPR signaling and establish alternative splicing of ERN1 as a key modulator of cellular stress responses.
2026-04-27 | GSE312841 | GEO
Project description:The unfolded protein response (UPR) preserves endoplasmic reticulum proteostasis through coordinated signaling pathways, including the IRE1α-XBP1 axis, which promotes adaptive transcriptional programs via non-canonical XBP1 mRNA splicing. However, upstream mechanisms regulating this pathway remain incompletely defined. Here, we apply CRASP-Seq, a scalable RNA-coupled CRISPR screening platform, to systematically identify regulators of XBP1 splicing. We uncover the U2 snRNP auxiliary factor RBM39 as a critical positive regulator of this process. Perturbation of RBM39 or U2 snRNP components induces alternative splicing of ERN1, leading to exon-18 skipping and the production of an unstable transcript subject to nonsense-mediated decay, as well as a truncated IRE1α isoform that acts in a dominant-negative manner to suppress XBP1 splicing. Mechanistically, we show that heat shock reduces RBM39 functional activity and promotes ERN1 exon-18 skipping, thereby attenuating IRE1α–XBP1 signaling. Functionally, hyperactivation of this pathway is detrimental under proteotoxic stress, suggesting that exon-18 skipping serves as a stress-adaptive mechanism to limit UPR output. Together, our findings reveal a previously unrecognized regulatory axis linking the canonical splicing machinery to UPR signaling and establish alternative splicing of ERN1 as a key modulator of cellular stress responses.
2026-04-27 | GSE312839 | GEO
Project description:The unfolded protein response (UPR) preserves endoplasmic reticulum proteostasis through coordinated signaling pathways, including the IRE1α-XBP1 axis, which promotes adaptive transcriptional programs via non-canonical XBP1 mRNA splicing. However, upstream mechanisms regulating this pathway remain incompletely defined. Here, we apply CRASP-Seq, a scalable RNA-coupled CRISPR screening platform, to systematically identify regulators of XBP1 splicing. We uncover the U2 snRNP auxiliary factor RBM39 as a critical positive regulator of this process. Perturbation of RBM39 or U2 snRNP components induces alternative splicing of ERN1, leading to exon-18 skipping and the production of an unstable transcript subject to nonsense-mediated decay, as well as a truncated IRE1α isoform that acts in a dominant-negative manner to suppress XBP1 splicing. Mechanistically, we show that heat shock reduces RBM39 functional activity and promotes ERN1 exon-18 skipping, thereby attenuating IRE1α–XBP1 signaling. Functionally, hyperactivation of this pathway is detrimental under proteotoxic stress, suggesting that exon-18 skipping serves as a stress-adaptive mechanism to limit UPR output. Together, our findings reveal a previously unrecognized regulatory axis linking the canonical splicing machinery to UPR signaling and establish alternative splicing of ERN1 as a key modulator of cellular stress responses.
2026-04-27 | GSE312847 | GEO
Project description:The unfolded protein response (UPR) preserves endoplasmic reticulum proteostasis through coordinated signaling pathways, including the IRE1α-XBP1 axis, which promotes adaptive transcriptional programs via non-canonical XBP1 mRNA splicing. However, upstream mechanisms regulating this pathway remain incompletely defined. Here, we apply CRASP-Seq, a scalable RNA-coupled CRISPR screening platform, to systematically identify regulators of XBP1 splicing. We uncover the U2 snRNP auxiliary factor RBM39 as a critical positive regulator of this process. Perturbation of RBM39 or U2 snRNP components induces alternative splicing of ERN1, leading to exon-18 skipping and the production of an unstable transcript subject to nonsense-mediated decay, as well as a truncated IRE1α isoform that acts in a dominant-negative manner to suppress XBP1 splicing. Mechanistically, we show that heat shock reduces RBM39 functional activity and promotes ERN1 exon-18 skipping, thereby attenuating IRE1α–XBP1 signaling. Functionally, hyperactivation of this pathway is detrimental under proteotoxic stress, suggesting that exon-18 skipping serves as a stress-adaptive mechanism to limit UPR output. Together, our findings reveal a previously unrecognized regulatory axis linking the canonical splicing machinery to UPR signaling and establish alternative splicing of ERN1 as a key modulator of cellular stress responses.
2026-04-27 | GSE312843 | GEO