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The IRE1α-XBP1 Pathway of the Unfolded Protein Response is Required for Adipogenesis

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE15771 | GEO | 2009/04/25

SECONDARY ACCESSION(S): PRJNA116837

REPOSITORIES: GEO

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The IRE1Î±-XBP1 Pathway of the Unfolded Protein Response is Required for Adipogenesis

Project description:Signaling cascades during adipogenesis culminate in the expression of two essential adipogenic factors, PPARÎ³ and C/EBPÎ±. Here we demonstrate that the IRE1Î±-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 IRE1Î± knockdown exhibit profound defects in adipogenesis. Intriguingly, C/EBPÎ², 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 IRE1Î± 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 IRE1Î±-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

IRE1α-XBP1 signaling in leukocytes controls prostaglandin biosynthesis and pain

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2020-05-16 | GSE131404 | GEO

INS1 cells expressing either WT IRE1α, I642G IRE1α, N906A IRE1α, or spliced XBP1 treated with dox and 1NMPP1

Project description:Transcriptional profiling of INS1 cells expressing either WT IRE1α, I642G IRE1α, N906A IRE1α, or spliced XBP1 comparing 1μg/mL dox and 5μM 1NMPP1 treated vs control.

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IRE1α-XBP1 controls T cell function in ovarian cancer by regulating mitochondrial activity

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2018-10-18 | GSE118430 | GEO

The IRE1α/XBP1 pathway expression is impaired in pediatric cholestatic liver disease explants

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

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Project description:The IRE1α-XBP1 arm of the unfolded protein response (UPR) has emerged as a central orchestrator of malignant progression and immunosuppression in various cancer types. Yet the role of this pathway in non-small cell lung cancer (NSCLC) has remained largely unexplored. Using an RNA-seq based computational XBP1s detection method applied to TCGA datasets, we uncovered that expression of the IRE1a-generated XBP1s mRNA isoform predicts poor survival in NSCLC patients. Ablation of IRE1a in malignant cells delayed tumor progression and extended survival in an XBP1-dependent fashion in mouse models of NSCLC. This protective effect was accompanied by marked alterations in both lymphoid and myeloid intratumoral cell subsets that elicited durable adaptive anti-cancer immunity. Mechanistically, cancer cell-intrinsic IRE1α activation sustained mPGES-1 expression, enabling production of the immunosuppressive lipid mediator PGE2 in the tumor microenvironment (TME). Accordingly, restoring mPGES-1 expression in IRE1αKO cancer cells rescued normal tumor progression. By identifying the dominant transcriptional networks controlled by IRE1α in mouse lung tumors, we further developed a new gene signature that predicted immune cell infiltration and overall survival in human NSCLC. Hence, our study unveils a key immunoregulatory role for cancer cell-intrinsic IRE1α activation and suggests that targeting this pathway may help enhance anti-tumor immunity in NSCLC.

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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.

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CARM1 determines endoplasmic reticulum stress response by controlling XBP1 in ovarian cancer [RNA-seq]

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