Project description:To understand the mechanistic basis by which inositol-requiring enzyme 1 (IRE1) is involved in luminal breast cancer malignancy, we analyzed the transcriptomic signature that IRE1 regulates in breast cancer. We suppressed the activity of IRE1 RNase in luminal breast cancer SUM52 line by adenoviral-based over-expression of the IRE1 dominant-negative K599A or K907A, and then performed RNA-sequencing (RNA-seq) analysis with IRE1 dominant-negative and control SUM52 cells. Through the RNA-seq analysis, we identified 98 genes that were commonly upregulated (65 genes) or downregulated (33 genes) in K599A-expressing SUM52 (SUM52-K599A) or K907A-expressing SUM52 (SUM52-K907A) cells.
Project description:Dysregulation of inositol-requiring enzyme 1 (IRE1), the primary transducer of Unfolded Protein Response (UPR), has been observed in tumor initiation and progression, but the underlying mechanism remains to be further elucidated. In this study, we identified that the IRE1 gene is frequently amplified and over-expressed in aggressive luminal B breast cancer cells and that IRE1 upregulation is significantly associated with worse overall survival of patients with breast cancer. IRE1 processes and mediates degradation of a subset of tumor suppressor microRNAs (miRNAs), including miR-3607, miR-374a, and miR-96, via a mechanism called Regulated IRE1-Dependent Decay (RIDD). IRE1-dependent degradation of tumor suppressor miR-3607 leads to elevation of RAS oncogene GTPase RAB3B in breast cancer cells. Inhibition of IRE1 endoribonuclease activity with the pharmacological compound 4μ8C or genetic approaches effectively suppresses luminal breast cancer cell proliferation and aggressive cancer phenotypes. Our work revealed the IRE1-RIDD-miRNAs pathway that promotes malignancy of luminal breast cancer.
Project description:We measured steady-state mRNA levels by microarray hybridization, comparing WT, (delta)ire1, (delta)gcn4, and (delta)gcn2 cells treated with 2 mM DTT for 30 min (by which time the UPR is qualitatively complete) to untreated samples of the same genotype. WT cells were taken as a positive control for UPR induction, and (delta)ire1 cells as a negative control. Fold change in expression of a given gene was computed as the ratio of mRNA level in the treated sample to the level in an untreated sample of the same genotype. Values reported here are the log2 fold change. Keywords = unfolded protein response Keywords = UPR Keywords = ire1 Keywords = gcn4 Keywords = gcn2
Project description:Membrane integrity at the endoplasmic reticulum (ER) is tightly regulated and its disturbance is implicated in metabolic diseases. Using an engineered sensor that activates the unfolded protein response (UPR) exclusively when normal ER membrane lipid composition is compromised, we identified pathways beyond lipid metabolism that are necessary to maintain ER integrity in yeast and in C. elegans. To systematically validate yeast mutants that disrupt ER membrane homeostasis, we identified a lipid bilayer stress (LBS) sensor in the UPR transducer protein Ire1, located at the interface of the amphipathic and transmembrane helices. Furthermore, transcriptome and chromatin immunoprecipitation (ChIP) analyses pinpoint the UPR as a broad-spectrum compensatory response wherein LBS and proteotoxic stress deploy divergent transcriptional UPR programs. Together, these findings reveal the UPR program as the sum of two independent stress responses, an insight that could be exploited for future therapeutic intervention.
Project description:The unfolded protein response (UPR) aims to restore ER homeostasis under conditions of high protein folding load, a function primarily serving secretory cells. Additional, non-canonical UPR functions have recently been unraveled in immune cells. We addressed the function of the inositol-requiring-enzyme 1 (IRE1) signaling branch of the UPR in NK cells in homeostasis and microbial challenge. Cell-intrinsic compound deficiency (DKO) of IRE1 and its downstream transcription factor XBP1 in NKp46 + NK cells, did not affect basal NK cell homeostasis, or overall outcome of viral MCMV infection. However, mixed bone marrow chimeras revealed a competitive advantage in the proliferation of IRE1 sufficient Ly49H + NK cells after viral infection. CITE-Seq analysis confirmed strong induction of IRE1 early upon infection, concomitant with the activation of a canonical UPR signature. Therefore, we conclude that cell-intrinsic IRE1/XBP1 activation is required for NK cell proliferation early upon viral infection, as part of a canonical UPR response.
Project description:The unfolded protein response (UPR) aims to restore ER homeostasis under conditions of high protein folding load, a function primarily serving secretory cells. Additional, non-canonical UPR functions have recently been unraveled in immune cells. We addressed the function of the inositol-requiring-enzyme 1 (IRE1) signaling branch of the UPR in NK cells in homeostasis and microbial challenge. Cell-intrinsic compound deficiency (DKO) of IRE1 and its downstream transcription factor XBP1 in NKp46 + NK cells, did not affect basal NK cell homeostasis, or overall outcome of viral MCMV infection. However, mixed bone marrow chimeras revealed a competitive advantage in the proliferation of IRE1 sufficient Ly49H + NK cells after viral infection. CITE-Seq analysis confirmed strong induction of IRE1 early upon infection, concomitant with the activation of a canonical UPR signature. Therefore, we conclude that cell-intrinsic IRE1/XBP1 activation is required for NK cell proliferation early upon viral infection, as part of a canonical UPR response.
Project description:We measured steady-state mRNA levels by microarray hybridization, comparing WT, (delta)ire1, (delta)gcn4, and (delta)gcn2 cells treated with 2 mM DTT for 30 min (by which time the UPR is qualitatively complete) to untreated samples of the same genotype. WT cells were taken as a positive control for UPR induction, and (delta)ire1 cells as a negative control. Fold change in expression of a given gene was computed as the ratio of mRNA level in the treated sample to the level in an untreated sample of the same genotype. Values reported here are the log2 fold change. Keywords = unfolded protein response Keywords = UPR Keywords = ire1 Keywords = gcn4 Keywords = gcn2 Keywords: parallel sample
Project description:The unfolded protein response (UPR) allows the endoplasmic reticulum (ER) to recover from the accumulation of misfolded proteins, in part by increasing its folding capacity. IRE1 promotes this remodeling by detecting misfolded ER proteins and activating a transcription factor, XBP-1, through endonucleolytic cleavage of its mRNA. We found that IRE1 independently mediated the rapid degradation of a specific subset of mRNAs. The arrays deposited here show the effects of depletion of IRE1 and XBP-1 on UPR induction in S2 cells. We have characterized the IRE1-dependent repressive branch of this response. Keywords: stress response, RNAi, DTT
Project description:The ubiquitous ribosome-associated complex (RAC) is a chaperone that spans ribosomes, making contacts near both the polypeptide exit tunnel and the decoding center, a position prime for sensing and coordinating translation and folding. Loss of RAC is known to result in growth defects and sensitization to translational and osmotic stresses. However, the physiological substrates of RAC and the mechanism(s) by which RAC is involved in responding to specific stresses in higher eukaryotes remain obscure. Data presented here uncover an essential function of mammalian RAC in the unfolded protein response (UPR). Knockdown of RAC sensitizes mammalian cells to ER stress and selectively interferes with IRE1 branch activation. Higher-order oligomerization of the IRE1α kinase/endoribonuclease depends upon RAC. These results reveal a surveillance function for RAC in the UPR: modulating IRE1α clustering as required for endonuclease activation and splicing of the substrate Xbp1 mRNA.
Project description:The role of the unfolded protein response (UPR) in the cellular innate response to RSV infection is not fully understood. To better the genomic targets for the IRE1-XBP1 pathway, RNA seq was conducted on RSV-infected small airway cells in the absence or presence of RSV infection and in the absence or presence of a selective IRE1a RNAse inhibitor. We identified expression changes in ~3.2K genes; of these, 279 required IRE1 and were enriched in IL-10 signaling and cytokine signaling pathways. These data indicate that IRE1a-XBP1s regulates genes important in epithelial mesenchymal transition, hexosamine biosynthesis and anti-viral signaling.