Whole lung transcriptome from lung epithelial IRE1α knockout mice
Ontology highlight
ABSTRACT: This experiment sought to characterize the whole lung transcriptional changes induced by loss of IRE1a function in the lung epithelium. Mice were Shh(Cre/+) IRE1a(fl/fl) on the C57BL/6 background, and had loss of IRE1a function in the epithelium based on XBP1 splicing activity. Lungs from uninjured mice were harvested, flash-frozen, homogenized, and RNA isolated by Trizol extraction.
Project description:This experiment sought to characterize the epithelial-specific transcriptional response in the bleomycin model of lung fibrosis, and the contribution of IRE1a and the TGFb-activating integrin avb6 to this response. "Ribotag" mice were crossed to ShhCre mice, both on the C57BL/6 background to generate experimental cohorts. Mice used for the experiment conditionally expressed HA-tagged ribosomal protein Rpl22 in the epithelium. Mice were exposed to intranasal bleomycin (3 U/kg) on day 1 and subsequently treated with the IRE1a kinase inhibitor KIRA8 (50 mg/kg daily), or the anti-integrin beta6 antibody 3G9 (10 mg/kg on day 1 and day 4). Treatment controls were either drug vehicle (3% ethanol, 7% Tween80, and 90% saline) or the inert antibody Axum8 in saline). Lungs were harvested on day 7 after bleomycin exposure, flash-frozen, and later homogenized under native conditions with cycloheximide. An aliquot of the “input” homogenate was removed and total RNA purified by Qiagen RNeasy Mini and is representative of the whole-lung transcriptome/translatome. The remaining homogenate was subjected to immunoprecipitation of HA-tagged polysomes, followed by RNA purification by Qiagen RNeasy Micro, and is representative of the lung epithelial transcriptome/translatome.
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.
Project description:IRE1a and XBP1 are key regulators of the unfolded protein response (UPR). XBP1 ablation causes profound hypolipidemia in mice, and triggers feedback activation of its upstream enzyme IRE1a, instigating regulated IRE1-dependent decay (RIDD), an mRNA degradation mechanism dependent on IRE1a's endoribonuclease activity. Comprehensive microarray analysis of XBP1 and/or IRE1a deficient liver identified genes involved in lipogenesis and lipoprotein metabolism as RIDD substrates, which might contribute to the suppression of plasma lipid levels by activated IRE1a. To identify RIDD substrate mRNAs and direct XBP1 targets in the liver, we performed a comprehensive comparative microarray analysis of three groups of RNA samples: WT and XBP1 deficient mice, WT and IRE1a deficient mice untreated or injected with tunicamycin, and XBP1 deficient mice injected with luciferase or IRE1a siRNA.
Project description:IRE1a and XBP1 are key regulators of the unfolded protein response (UPR). XBP1 ablation causes profound hypolipidemia in mice, and triggers feedback activation of its upstream enzyme IRE1a, instigating regulated IRE1-dependent decay (RIDD), an mRNA degradation mechanism dependent on IRE1a's endoribonuclease activity. Comprehensive microarray analysis of XBP1 and/or IRE1a deficient liver identified genes involved in lipogenesis and lipoprotein metabolism as RIDD substrates, which might contribute to the suppression of plasma lipid levels by activated IRE1a.
Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed over 6 million individuals worldwide and continues to spread in countries where vaccines are not yet widely available, or its citizens are hesitant to become vaccinated. Therefore, it is critical to unravel the molecular mechanisms that allow SARS-CoV-2 and other coronaviruses to infect and overtake the host machinery of human cells. Coronavirus replication triggers endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR), a key host cell pathway widely believed essential for viral replication. We examined the master UPR sensor IRE1a kinase/RNase and its downstream transcription factor effector XBP1s, which is processed through an IRE1a-mediated mRNA splicing event, in human lung-derived cells infected with betacoronaviruses. We found human respiratory coronavirus OC43 (HCoV-OC43), Middle East respiratory syndrome coronavirus (MERS-CoV), and murine coronavirus (MHV) all induce ER stress and strongly trigger the kinase and RNase activities of IRE1a as well as XBP1 splicing. In contrast, SARS-CoV-2 only partially activates IRE1a through autophosphorylation, but its RNase activity fails to splice XBP1. Moreover, while IRE1a was dispensable for replication in human cells for all coronaviruses tested, it was required for maximal expression of genes associated with several key cellular functions, including the interferon signaling pathway, during SARS-CoV-2 infection. Our data suggest that SARS-CoV-2 actively inhibits the RNase of autophosphorylated IRE1a, perhaps as a strategy to eliminate detection by the host immune system.
Project description:IRE1a is a critical modulator of the unfolded protein response. Its RNAse activity generates the mature transcript for the XBP1 transcription factor and also degrades other ER associated mRNAs in a process termed Regulated IRE1a Dependent mRNA Decay or RIDD. To determine if IRE1a is critical in the response to oncogenic Ras we used ShRNA to knockdown Ire1a or Xbp1 in primary mouse epidermal keratinocytes transduced with a v-HRAS retrovirus.
Project description:The purpose of the study was to examine the role of the IRE1a-XBP1 pathway during Th2 lymphocyte activation and differentiation. In vitro Th2 cells were treated with 4μ8c, a drug that specifically inhibits IRE1a endonuclease activity, and transcriptomes were compared.
Project description:Group 3 innate lymphoid cells (ILC3s) are key players in intestinal homeostasis. Endoplasmic reticulum (ER) stress is linked to inflammatory bowel disease (IBD). Herein, we used cell culture, novel mouse models, and human specimens to examine if ER stress in ILC3s impacts IBD pathophysiology. We show that mouse intestinal ILC3s exhibited a 24h-rhythmic expression pattern of the master ER stress response regulator, IRE1α-XBP1. Proinflammatory cytokine IL-23 selectively stimulated IRE1α-XBP1 in mouse ILC3s through mitochondrial reactive oxygen species (mtROS). IRE1α-XBP1 was activated in ILC3s of mice exposed to experimental colitis and in inflamed human IBD specimens. Mice with Ire1α deletion in ILC3s (Ire1αΔRorc) showed reduced expression of ER stress response and cytokine genes including Il22 in ILC3s and were highly vulnerable to infections and colitis. Administration of IL-22 counteracted their colitis susceptibility. In human ILC3s, IRE1 inhibitors suppressed cytokine production, which was upregulated by an IRE1 activator. Moreover, the frequencies of intestinal XBP1s+ ILC3s in Crohn’s disease patients before administration of ustekinumab, an anti-IL-12/IL-23 antibody, positively correlated with response to treatment. We demonstrate that a non-canonical mtROS-IRE1α-XBP1 pathway augments cytokine production by ILC3s and identify XBP1+ ILC3s as a potential biomarker for predicting response to anti-IL-23 therapies in IBD. Group 3 innate lymphoid cells (ILC3s) have recently emerged as important regulators and potential drug targets for IBD. However, the response of ILC3s to environmental stimuli during intestinal inflammation remains elusive. IRE1a-XBP1 serves as the regulatory hub of the unfolded protein response (UPR) that plays a vital role in intestinal inflammation.
Project description:The inositol-requiring enzyme-1a (IRE1a), through its key effector transcription factor X-box binding protein-1 (XBP1), regulates cell fate and malignancy in a tissue and cell-specific manner. Here, we define the transcriptional perturbations associated with induction of XBP1 (encoded by the XBP1S gene generated by IRE1a) eficiency in patient derived human AML cells. Beyond its classical role in activating genes involved in restoring cellular proteostasis during the unfolded protein response (UPR), our transcriptome analysis reveal XBP1-dependent regulation of genes involved in diverse biological processes required for HSC homeostasis and acute myeloid leukemia (AML) development.
Project description:During mammalian cell growth and differentiation, the unfolded protein response (UPR) homeostatically adjusts endoplasmic reticulum (ER) protein-folding capacity to match changing cellular secretory demands. However, under high/chronic ER stress conditions the UPR triggers apoptosis. This dichotomy is promoted in part by differential activation levels of the ER transmembrane kinase/endoribonuclease (RNase) IRE1a. IRE1a kinase auto-phosphorylation operates as a rheostat to control downstream RNase-induced outputs that either sustain adaptive ER protein-folding or cause apoptosis. We have previously shown that IRE1a’s RNase activity can be activated or fully inactivated by ATP-competitive kinase inhibitors. Here we developed a new class of ATP-competitive kinase inhibitors that partially antagonize the RNase of IRE1a at full occupancy. An atomic level resolution co-crystal structure shows that these small molecule partial antagonists—which we named ‘PAIR’s for (Partial Antagonists of IRE1a RNase)—occupy the ATP-binding site of IRE1a and partially displace a helix (helix aC) in the kinase domain that forms part of a dimeric interface. In insulin-producing beta cells, PAIRs permit adaptive XBP1 mRNA splicing, while quelling destructive/terminal outputs from extra-XBP1 mRNA endonucleolytic decay, thus preventing apoptosis. Preservation of XBP1 splicing by PAIRs permits B lymphocytes to differentiate into immunoglobulin-producing plasma cells. In summary, we propose that an intermediate RNase-inhibitory “sweet spot,” achieved by PAIR-bound IRE1a, may capture a structural conformation naturally available to IRE1a that could represent a desirable therapeutic state for drugging this master UPR sensor/effector.