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. All arrays are hybed pairwise with treated hybed against untreated
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.
Project description:Cancer cells exploit adaptive responses such as endoplasmic reticulum (ER) stress to support their survival. ER stress response is mediated in part by the ER-localized transmembrane sensor IRE1α endoribonuclease and its substrate XBP1 to regulate XBP1 target gene expression. However, the mechanism that controls the IRE1α/XBP1 pathway remains poorly understood. CARM1 is an oncogene that is often overexpressed in a number of cancer types including ovarian cancer. Here we report that CARM1 determines ER stress response by controlling the IRE1α/XBP1 pathway. Genome-wide profiling revealed that CARM1 regulates XBP1 target gene expression during ER stress response. CARM1 directly interacts with XBP1. Inhibition of the IRE1α/XBP1 pathway was effective in ovarian cancer in a CARM1-dependent manner both in vitro and in vivo in orthotopic and patient-derived xenograft models. In addition, IRE1α inhibitor B-I09 synergizes with immune checkpoint blockade anti-PD1 antibody in an immunocompetent CARM1-expressing ovarian cancer model.
Project description:Cancer cells exploit adaptive responses such as endoplasmic reticulum (ER) stress to support their survival. ER stress response is mediated in part by the ER-localized transmembrane sensor IRE1α endoribonuclease and its substrate XBP1 to regulate XBP1 target gene expression. However, the mechanism that controls the IRE1α/XBP1 pathway remains poorly understood. CARM1 is an oncogene that is often overexpressed in a number of cancer types including ovarian cancer. Here we report that CARM1 determines ER stress response by controlling the IRE1α/XBP1 pathway. Genome-wide profiling revealed that CARM1 regulates XBP1 target gene expression during ER stress response. CARM1 directly interacts with XBP1. Inhibition of the IRE1α/XBP1 pathway was effective in ovarian cancer in a CARM1-dependent manner both in vitro and in vivo in orthotopic and patient-derived xenograft models. In addition, IRE1α inhibitor B-I09 synergizes with immune checkpoint blockade anti-PD1 antibody in an immunocompetent CARM1-expressing ovarian cancer model.
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.
Project description:We developed a bioinformatics approach called the Read-Split-Walk (RSW) pipeline, and evaluated it using two Ire1α heterozygous and two Ire1α-null samples. The 26nt non-canonical splice site in Xbp1 was detected as the top hit by our RSW pipeline in heterozygous samples but not in the negative control Ire1α knockout samples. We compared the Xbp1 results from our approach with results using the alignment program BWA, STAR, Exonerate and the Unix “grep” command. We then applied our RSW pipeline to RNA-Seq data from the SKBR3 human breast cancer cell line. RSW reported a large number of non-canonical spliced regions for 108 genes in chromosome 17, which were identified by an independent study.