Project description:The unfolded protein response (UPR) has emerged as important signaling pathway mediating anti-viral defenses to Respiratory Syncytial Virus (RSV) infection. In this study, we examine how Inositol Requiring Enzyme (IREa X-Box Binding Protein spliced (XBP1s) arm of the Unfolded Protein Response (UPR) pathway controls the innate response integrating RNA-seq and Cleavage Under Targets and Release Using Nuclease (CUT&RUN) analyses. XBP1s binds to ~4.2 K high-confidence genomic binding sites. Surprisingly these map to only a small subset of IL10/cytokine genes. We further find that that RSV infection enhances XBP1s occupancy on 786 genomic sites enriched in AP1/Fra-1, RELA and SP1 binding sites controlling a core subset of cytokine regulatory factors genes including IFN response factor 1 (IRF1), CSF2, NFKB1A and DUSP10. Selective IRF1 knockdown experiments demonstrates its requirement in control of type I and -III IFNs and IFN-stimulated genes (ISGs) indicating these genes are indirectly regulated through IRF1 transactivation. We conclude that RSV modulates the XBP1 binding complex to the IRF1 epromoter, providing novel insight into how the IRE1-XBP1s pathway potentiates airway mucosal anti-viral responses.
Project description:Epithelial mesenchymal plasticity (EMP) is a complex cellular reprogramming event that plays a major role in tissue homeostasis to infections and injury. Recently we elucidated a mechanism wherein the unfolded protein response (UPR) triggers EMP through the inositol-requiring protein 1 (IRE1α)–X-box-binding protein 1 (XBP1) axis, enhancing glucose shunting to protein N glycosylation producing ER stress. To better the genomic targets for the IRE1-XBP1 pathway that activate compensatory metabolic changes in EMP, we systematically identified the genomic XBP1 targets using Cleavage Under Targets and Release Using Nuclease (CUT&RUN) of a FLAG-epitope tagged XBP1 in RSV infection. CUT&RUN identified 7,086 enriched binding sites mapped to 4,827 genes; of these XBP1 binds to 2,119 sites within 1 kb of the transcription start sites. Interestingly, XBP1 binds to 322 superenhancers associated with RHO GTPase signaling that were associated with largely inert gene expression. By contrast, XBP1 binds to proximal promoters inducing coordinate mRNA expression of hexosamine biosynthetic enzymes encoding sequential steps in UDP-GlcNAc biosynthesis through AGCTCA motifs. We demonstrate that IRE1-XBP1 signaling is necessary and sufficient to activate core HBP enzymatic pathway by recruiting transcriptional elongation-competent phospho-Ser2 CTD modified RNA Pol II (pSer-PolII).
Project description:Analysis of Xbp1s overexpression in liver after 24 hr indution or 48 hr induction in LIXs mouse. As a control, WT mice after 2 hr refeed and 24 hr fast without refeed are used for analysis of postprandial gene expression. This microarray study was used to screen for target genes activated by Xbp1s in liver. Results provide important information for the role of Xbp1s during postprandial. Total RNA obtained from liver tissues from mice on Dox200 chow diet for 24 hr or 48 hr. Mice were fasted for 6 hr before sacrifice for liver.
Project description:The physiological role of the spliced form of X-box-binding protein 1 (XBP1s), a key transcription factor of the endoplasmic reticulum (ER) stress response, in adipose tissue remains largely unknown. Here we show that overexpression of XBP1s promotes adiponectin multimerization in adipocytes, thereby regulating systemic glucose homeostasis. Ectopic expression of XBP1s in adipocytes improves glucose tolerance and insulin sensitivity in both lean and obese (ob/ob) mice. The beneficial effect of adipocyte XBP1s on glucose homeostasis is associated with elevated serum levels of HMW adiponectin and indeed, is adiponectin dependent. Mechanistically, XBP1s promotes adiponectin multimerization rather than activating its transcription likely through a direct regulation of the expression of several ER-chaperones involved in adiponectin maturation, including Grp78, Pdia6, ERp44 and DsbA-L. Thus, we conclude that XBP1s is an important regulator of adiponectin multimerization, which may lead to a new therapeutic approach for the treatment of type 2 diabetes and hypoadiponectinemia. Epididymal adipose tissue from wild type and XBP1-overexpressing mice was subjected to gene expression profiling.
Project description:Analysis of Xbp1s overexpression in liver after 24 hr indution or 48 hr induction in LIXs mouse. As a control, WT mice after 2 hr refeed and 24 hr fast without refeed are used for analysis of postprandial gene expression. This microarray study was used to screen for target genes activated by Xbp1s in liver. Results provide important information for the role of Xbp1s during postprandial.
Project description:The unfolded protein response (UPR), as its name implies, safeguards secretory pathway proteostasis. The most ancient arm of the UPR, the IRE1-activated, XBP1s-mediated transcriptional response, has roles in secretory pathway maturation beyond resolving proteostatic stress. Understanding the consequences of XBP1s’ transcriptional output for cellular processes is critical for elucidating mechanistic connections between XBP1s and development, immunity, and disease. Here, we show that a key functional consequence of XBP1s activation is a cell type-dependent shift in the distribution of N-glycan structures on endogenous membrane and secreted proteomes. XBP1s activity decreases sialylation of tri- and tetra-antennary N-glycans in the HEK293 membrane proteome and secretome, while substantially increasing the population of high mannose N-glycans only in the secretome. Related, but distinctive, signatures in the HEK293 N-glycome are observed when the entire UPR is activated in a stress-dependent manner using thapsigargin. In HeLa cells, stress-independent XBP1s activation increases the population of cell surface high mannose N-glycans and tetra-antennary N-glycans. mRNA profiling experiments suggest that the XBP1s-mediated remodeling of the N-glycome may re-flect a coordinated consequence of transcriptional resculpting of the N-glycan maturation pathway by XBP1s. The discovery of XBP1s-induced N-glycan structural remodeling on a glycome-wide scale suggests that XBP1s is a master regulator of N-glycan maturation. Moreover, because the sugars on cell surface proteins or on those proteins secreted from an XBP1s-activated cell can be molecularly distinct from those of an unactivated cell, these findings reveal a potential new mechanism for translating intracellular stress signaling pathways into al-tered interactions with the extracellular environment.
Project description:We previously reported that XBP1s, an essential transcription factor downstream of IL-15 and AKT signaling, controls cell survival and effector functions of human natural killer (NK) cells. However, the precise mechanisms remain unknown. In this study, by using XBP1 conditional knock-out mice, we found that XBP1s is critical for IL-15-mediated NK cell survival but not proliferation in vitro and in vivo. Mechanistically, XBP1s regulates homeostatic NK cell survival through targeting PIM-2, a critical anti-apoptotic gene, which in turn stabilizes XBP1s protein by phosphorylating it at Thr58. In addition, XBP1s enhances the effector functions and anti-tumor immunity of NK cells by recruiting T-bet to the promoter region of Ifng. Collectively, our findings identify a previously unknown mechanism by which IL-15–XBP1s signaling regulates the survival and effector functions of NK cells.
Project description:The unfolded protein response (UPR) maintains endoplasmic reticulum (ER) proteostasis through the activation of transcription factors such as XBP1s and ATF6. The functional consequences of these transcription factors for ER proteostasis remain poorly defined. Here, we describe methodology that enables orthogonal, small molecule-mediated activation of the UPR-associated transcription factors XBP1s and/or ATF6 in the same cell independent of stress. We employ transcriptomics and quantitative proteomics to evaluate ER proteostasis network remodeling owing to the XBP1s and/or ATF6 transcriptional programs. Furthermore, we demonstrate that the three ER proteostasis environments accessible by activating XBP1s and/or ATF6 differentially influence the folding, trafficking, and degradation of destabilized ER client proteins without globally affecting the endogenous proteome. Our data reveal how the ER proteostasis network is remodeled by the XBP1s and/or ATF6 transcriptional programs at the molecular level and demonstrate the potential for selectively restoring aberrant ER proteostasis of pathologic, destabilized proteins through arm-selective UPR-activation. The unfolded protein response adapts endoplasmic reticulum (ER) proteostasis via stress-responsive transcription factors including XBP1s and ATF6. Here, R. Luke Wiseman and colleagues implement technology for the orthogonal, ligand-dependent activation of XBP1s and/or ATF6 in a single cell. They characterize how XBP1s and/or ATF6 activation impacts ER proteostasis pathway composition and function. Adapted ER environments influence the proteostasis of destabilized protein variants without affecting the endogenous proteome. The work informs the development of proteostasis environment-adapting therapeutics for protein misfolding-related diseases. In order to activate both XBP1s and ATF6 in the same cell, we incorporated DHFR.ATF6 and tet-inducible XBP1s into a HEK293T-REx cell line stably expressing the tet-repressor. Selection of a single colony resulted in the HEK293DAX cell line in which XBP1s is induced by doxycycline and DHFR.ATF6 is activated by trimethoprim (TMP; TMP-dependent DHFR.ATF6 activation in HEK293DAX cells will henceforth be referred to as ATF6 activation for simplicity). HEK293DAX cells were treated for 12 h with vehicle, 1 ?g/mL dox, 10 ?M TMP, or both in biological triplicate. Cells were harvested and RNA was extracted using the RNeasy Mini Kit (Qiagen). Genomic DNA was removed by on-column digestion using the RNase-free DNase Set (Qiagen). Data from HEK293DYG cells showed no significant overlap in the ligand-treated transcriptomes obtained from the control HEK293DYG cells.
Project description:The physiological role of the spliced form of X-box-binding protein 1 (XBP1s), a key transcription factor of the endoplasmic reticulum (ER) stress response, in adipose tissue remains largely unknown. Here we show that overexpression of XBP1s promotes adiponectin multimerization in adipocytes, thereby regulating systemic glucose homeostasis. Ectopic expression of XBP1s in adipocytes improves glucose tolerance and insulin sensitivity in both lean and obese (ob/ob) mice. The beneficial effect of adipocyte XBP1s on glucose homeostasis is associated with elevated serum levels of HMW adiponectin and indeed, is adiponectin dependent. Mechanistically, XBP1s promotes adiponectin multimerization rather than activating its transcription likely through a direct regulation of the expression of several ER-chaperones involved in adiponectin maturation, including Grp78, Pdia6, ERp44 and DsbA-L. Thus, we conclude that XBP1s is an important regulator of adiponectin multimerization, which may lead to a new therapeutic approach for the treatment of type 2 diabetes and hypoadiponectinemia.