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Slaine PD, Kleer M, Duguay BA, Pringle ES, Kadijk E, Ying S, Balgi A, Roberge M, McCormick C, Khaperskyy DA. Thiopurines activate an antiviral unfolded protein response that blocks influenza A virus glycoprotein accumulation. J Virol 2021; 95:JVI. [PMID: 33762409 DOI: 10.1128/JVI.00453-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Influenza A viruses (IAVs) utilize host shutoff mechanisms to limit antiviral gene expression and redirect translation machinery to the synthesis of viral proteins. Previously, we showed that IAV replication is sensitive to protein synthesis inhibitors that block translation initiation and induce formation of cytoplasmic condensates of untranslated messenger ribonucleoprotein complexes called stress granules (SGs). In this study, using an image-based high-content screen, we identified two thiopurines, 6-thioguanine (6-TG) and 6-thioguanosine (6-TGo), that triggered SG formation in IAV-infected cells and blocked IAV replication in a dose-dependent manner without eliciting SG formation in uninfected cells. 6-TG and 6-TGo selectively disrupted the synthesis and maturation of IAV glycoproteins hemagglutinin (HA) and neuraminidase (NA) without affecting the levels of the viral RNAs that encode them. By contrast, these thiopurines had minimal effect on other IAV proteins or the global host protein synthesis. Disruption of IAV glycoprotein accumulation by 6-TG and 6-TGo correlated with activation of unfolded protein response (UPR) sensors activating transcription factor-6 (ATF6), inositol requiring enzyme-1 (IRE1) and PKR-like endoplasmic reticulum kinase (PERK), leading to downstream UPR gene expression. Treatment of infected cells with the chemical chaperone 4-phenylbutyric acid diminished thiopurine-induced UPR activation and partially restored the processing and accumulation of HA and NA. By contrast, chemical inhibition of the integrated stress response downstream of PERK restored accumulation of NA monomers but did not restore processing of viral glycoproteins. Genetic deletion of PERK enhanced the antiviral effect of 6-TG without causing overt cytotoxicity, suggesting that while UPR activation correlates with diminished viral glycoprotein accumulation, PERK could limit the antiviral effects of drug-induced ER stress. Taken together, these data indicate that 6-TG and 6-TGo are effective host-targeted antivirals that trigger the UPR and selectively disrupt accumulation of viral glycoproteins.IMPORTANCESecreted and transmembrane proteins are synthesized in the endoplasmic reticulum (ER), where they are folded and modified prior to transport. Many viruses rely on the ER for the synthesis and processing of viral glycoproteins that will ultimately be incorporated into viral envelopes. Viral burden on the ER can trigger the unfolded protein response (UPR). Much remains to be learned about how viruses co-opt the UPR to ensure efficient synthesis of viral glycoproteins. Here, we show that two FDA-approved thiopurine drugs, 6-TG and 6-TGo, induce the UPR, which represents a previously unrecognized effect of these drugs on cell physiology. This thiopurine-mediated UPR activation blocks influenza virus replication by impeding viral glycoprotein accumulation. Our findings suggest that 6-TG and 6-TGo may have broad antiviral effect against enveloped viruses that require precise tuning of the UPR to support viral glycoprotein synthesis.
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Bae J, Hideshima T, Zhang GL, Zhou J, Keskin DB, Munshi NC, Anderson KC. Identification and characterization of HLA-A24-specific XBP1, CD138 (Syndecan-1) and CS1 (SLAMF7) peptides inducing antigens-specific memory cytotoxic T lymphocytes targeting multiple myeloma. Leukemia 2018; 32:752-764. [PMID: 29089645 PMCID: PMC5953209 DOI: 10.1038/leu.2017.316] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 09/17/2017] [Accepted: 10/03/2017] [Indexed: 12/27/2022]
Abstract
X-box binding protein 1 (XBP1), CD138 (Syndecan-1) and CS1 (SLAMF7) are highly expressed antigens in cancers including multiple myeloma (MM). Here, we identify and characterize immunogenic HLA-A24 peptides derived from these antigens for potential vaccination therapy of HLA-A24+ patients with MM. The identified immunogenic HLA-A24-specific XBP1 unspliced (UN)185-193 (I S P W I L A V L), XBP1 spliced (SP)223-231 (V Y P E G P S S L), CD138265-273 (I F A V C L V G F) and CS1240-248 (L F V L G L F L W) peptides induced antigen-specific CTL with anti-MM activity in an HLA-A24 restricted manner. Furthermore, a cocktail containing the four HLA-A24 peptides evoked MM-specific CTL with distinct phenotypic profiles (CD28, CD40L, 41BB, CD38, CD69) and anti-tumor activities, evidenced by perforin upregulation, CD107a degranulation (cytotoxicity) and Th1-type cytokines (IFN-γ/IL-2/TNF-α) production in response to HLA-A24+ MM cells. The multipeptide-specific CTL included antigen-specific memory CD8+ T cells expressing both T-cell activation (CD38, CD69) and immune checkpoints antigens (CTLA, PD-1, LAG-3, TIM-3). These results provide the framework for a multipeptide vaccination therapy to induce tumor-specific CTL in HLA-A24-positive patients with myeloma and other cancers expressing these antigens.
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Affiliation(s)
- Jooeun Bae
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Teru Hideshima
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | | | - Jun Zhou
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Derin B. Keskin
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
| | - Nikhil C. Munshi
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
- VA Boston Healthcare System, Boston, Massachusetts, USA
| | - Kenneth C. Anderson
- Dana-Farber Cancer Institute, Boston, Massachusetts, USA
- Harvard Medical School, Boston, Massachusetts, USA
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Maiers JL, Kostallari E, Mushref M, de Assuncao TM, Li H, Huebert RC, Cao S, Malhi H, Shah VH, Shah VH. The unfolded protein response mediates fibrogenesis and collagen I secretion through regulating TANGO1 in mice. Hepatology 2017; 65:983-998. [PMID: 28039913 PMCID: PMC5319908 DOI: 10.1002/hep.28921] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 09/21/2016] [Accepted: 10/26/2016] [Indexed: 12/14/2022]
Abstract
UNLABELLED Fibrogenesis encompasses the deposition of matrix proteins, such as collagen I, by hepatic stellate cells (HSCs) that culminates in cirrhosis. Fibrogenic signals drive transcription of procollagen I, which enters the endoplasmic reticulum (ER), is trafficked through the secretory pathway, and released to generate extracellular matrix. Alternatively, disruption of procollagen I ER export could activate the unfolded protein response (UPR) and drive HSC apoptosis. Using a small interfering RNA screen, we identified Transport and Golgi organization 1 (TANGO1) as a potential participant in collagen I secretion. We investigated the role of TANGO1 in procollagen I secretion in HSCs and liver fibrogenesis. Depletion of TANGO1 in HSCs blocked collagen I secretion without affecting other matrix proteins. Disruption of secretion led to procollagen I retention within the ER, induction of the UPR, and HSC apoptosis. In wild-type (WT) HSCs, both TANGO1 and the UPR were induced by transforming growth factor β (TGFβ). As the UPR up-regulates proteins involved in secretion, we studied whether TANGO1 was a target of the UPR. We found that UPR signaling is responsible for up-regulating TANGO1 in response to TGFβ, and this mechanism is mediated by the transcription factor X-box binding protein 1 (XBP1). In vivo, murine and human cirrhotic tissue displayed increased TANGO1 messenger RNA levels. Finally, TANGO1+/- mice displayed less hepatic fibrosis compared to WT mice in two separate murine models: CCl4 and bile duct ligation. CONCLUSION Loss of TANGO1 leads to procollagen I retention in the ER, which promotes UPR-mediated HSC apoptosis. TANGO1 regulation during HSC activation occurs through a UPR-dependent mechanism that requires the transcription factor, XBP1. Finally, TANGO1 is critical for fibrogenesis through mediating HSC homeostasis. The work reveals a unique role for TANGO1 and the UPR in facilitating collagen I secretion and fibrogenesis. (Hepatology 2017;65:983-998).
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Vijay H. Shah
- Division of Gastroenterology and Hepatology; Mayo Clinic; Rochester MN
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Yue S, Zhu J, Zhang M, Li C, Zhou X, Zhou M, Ke M, Busuttil RW, Ying QL, Kupiec-Weglinski JW, Xia Q, Ke B. The myeloid heat shock transcription factor 1/β-catenin axis regulates NLR family, pyrin domain-containing 3 inflammasome activation in mouse liver ischemia/reperfusion injury. Hepatology 2016; 64:1683-1698. [PMID: 27474884 PMCID: PMC5074868 DOI: 10.1002/hep.28739] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 06/08/2016] [Accepted: 07/12/2016] [Indexed: 12/18/2022]
Abstract
UNLABELLED Heat shock transcription factor 1 (HSF1) has been implicated in the differential regulation of cell stress and disease states. β-catenin activation is essential for immune homeostasis. However, little is known about the role of macrophage HSF1-β-catenin signaling in the regulation of NLRP3 inflammasome activation during ischemia/reperfusion (I/R) injury (IRI) in the liver. This study investigated the functions and molecular mechanisms by which HSF1-β-catenin signaling influenced NLRP3-mediated innate immune response in vivo and in vitro. Using a mouse model of IR-induced liver inflammatory injury, we found that mice with a myeloid-specific HSF1 knockout (HSF1M-KO ) displayed exacerbated liver damage based on their increased serum alanine aminotransferase levels, intrahepatic macrophage/neutrophil trafficking, and proinflammatory interleukin (IL)-1β levels compared to the HSF1-proficient (HSF1FL/FL ) controls. Disruption of myeloid HSF1 markedly increased transcription factor X-box-binding protein (XBP1), NLR family, pyrin domain-containing 3 (NLRP3), and cleaved caspase-1 expression, which was accompanied by reduced β-catenin activity. Knockdown of XBP1 in HSF1-deficient livers using a XBP1 small interfering RNA ameliorated hepatocellular functions and reduced NLRP3/cleaved caspase-1 and IL-1β protein levels. In parallel in vitro studies, HSF1 overexpression increased β-catenin (Ser552) phosphorylation and decreased reactive oxygen species (ROS) production in bone-marrow-derived macrophages. However, myeloid HSF1 ablation inhibited β-catenin, but promoted XBP1. Furthermore, myeloid β-catenin deletion increased XBP1 messenger RNA splicing, whereas a CRISPR/CRISPR-associated protein 9-mediated XBP1 knockout diminished NLRP3/caspase-1. CONCLUSION The myeloid HSF1-β-catenin axis controlled NLRP3 activation by modulating the XBP1 signaling pathway. HSF1 activation promoted β-catenin, which, in turn, inhibited XBP1, leading to NLRP3 inactivation and reduced I/R-induced liver injury. These findings demonstrated that HSF1/β-catenin signaling is a novel regulator of innate immunity in liver inflammatory injury and implied the therapeutic potential for management of sterile liver inflammation in transplant recipients. (Hepatology 2016;64:1683-1698).
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Affiliation(s)
- Shi Yue
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Jianjun Zhu
- Department of Liver Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Ming Zhang
- Department of Liver Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Changyong Li
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Xingliang Zhou
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, Department of Stem Cell Biology & Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Min Zhou
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Michael Ke
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Ronald W. Busuttil
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Qi-Long Ying
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, Department of Stem Cell Biology & Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Jerzy W. Kupiec-Weglinski
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Qiang Xia
- Department of Liver Surgery, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Bibo Ke
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA.
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Ying Z, Zhai R, McLean NA, Johnston JM, Misra V, Verge VM. The Unfolded Protein Response and Cholesterol Biosynthesis Link Luman/CREB3 to Regenerative Axon Growth in Sensory Neurons. J Neurosci 2015; 35:14557-70. [PMID: 26511246 DOI: 10.1523/JNEUROSCI.0012-15.2015] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We recently revealed that the axon endoplasmic reticulum resident transcription factor Luman/CREB3 (herein called Luman) serves as a unique retrograde injury signal in regulation of the intrinsic elongating form of sensory axon regeneration. Here, evidence supports that Luman contributes to axonal regeneration through regulation of the unfolded protein response (UPR) and cholesterol biosynthesis in adult rat sensory neurons. One day sciatic nerve crush injury triggered a robust increase in UPR-associated mRNA and protein expression in both neuronal cell bodies and the injured axons. Knockdown of Luman expression in 1 d injury-conditioned neurons by siRNA attenuated axonal outgrowth to 48% of control injured neurons and was concomitant with reduced UPR- and cholesterol biosynthesis-associated gene expression. UPR PCR-array analysis coupled with qRT-PCR identified and confirmed that four transcripts involved in cholesterol regulation were downregulated >2-fold by the Luman siRNA treatment of the injury-conditioned neurons. Further, the Luman siRNA-attenuated outgrowth could be significantly rescued by either cholesterol supplementation or 2 ng/ml of the UPR inducer tunicamycin, an amount determined to elevate the depressed UPR gene expression to a level equivalent of that observed with crush injury. Using these approaches, outgrowth increased significantly to 74% or 69% that of injury-conditioned controls, respectively. The identification of Luman as a regulator of the injury-induced UPR and cholesterol at levels that benefit the intrinsic ability of axotomized adult rat sensory neurons to undergo axonal regeneration reveals new therapeutic targets to bolster nerve repair.
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Bi K, Nishihara K, Machleidt T, Hermanson S, Wang J, Sakamuru S, Huang R, Xia M. Identification of known drugs targeting the endoplasmic reticulum stress response. Anal Bioanal Chem 2015; 407:5343-51. [PMID: 25925857 DOI: 10.1007/s00216-015-8694-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 04/03/2015] [Accepted: 04/10/2015] [Indexed: 02/07/2023]
Abstract
The endoplasmic reticulum (ER), a multifunctional organelle, plays a central role in cellular signaling, development, and stress response. Dysregulation of ER homeostasis has been associated with human diseases, such as cancer, inflammation, and diabetes. A broad spectrum of stressful stimuli including hypoxia as well as a variety of pharmacological agents can lead to the ER stress response. In this study, we have developed a stable ER stress reporter cell line that stably expresses a β-lactamase reporter gene under the control of the ER stress response element (ESRE) present in the glucose-regulated protein, 78 kDa (GRP78) gene promoter. This assay has been optimized and miniaturized into a 1536-well plate format. In order to identify clinically used drugs that induce ER stress response, we screened approximately 2800 drugs from the NIH Chemical Genomics Center Pharmaceutical Collection (NPC library) using a quantitative high-throughput screening (qHTS) platform. From this study, we have identified several known ER stress inducers, such as 17-AAG (via HSP90 inhibition), as well as several novel ER stress inducers such as AMI-193 and spiperone. The confirmed drugs were further studied for their effects on the phosphorylation of eukaryotic initiation factor 2α (eIF2α), the X-box-binding protein (XBP1) splicing, and GRP78 gene expression. These results suggest that the ER stress inducers identified from the NPC library using the qHTS approach could shed new lights on the potential therapeutic targets of these drugs.
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Zhang Y, Chen G, Liu Z, Tian S, Zhang J, Carey CD, Murphy KM, Storkus WJ, Falo LD, You Z. Genetic vaccines to potentiate the effective CD103+ dendritic cell-mediated cross-priming of antitumor immunity. J Immunol 2015; 194:5937-47. [PMID: 25972487 PMCID: PMC4458448 DOI: 10.4049/jimmunol.1500089] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 04/16/2015] [Indexed: 12/24/2022]
Abstract
The development of effective cancer vaccines remains an urgent, but as yet unmet, clinical need. This deficiency is in part due to an incomplete understanding of how to best invoke dendritic cells (DC) that are crucial for the induction of tumor-specific CD8(+) T cells capable of mediating durable protective immunity. In this regard, elevated expression of the transcription factor X box-binding protein 1 (XBP1) in DC appears to play a decisive role in promoting the ability of DC to cross-present Ags to CD8(+) T cells in the therapeutic setting. Delivery of DNA vaccines encoding XBP1 and tumor Ag to skin DC resulted in increased IFN-α production by plasmacytoid DC (pDC) from skin/tumor draining lymph nodes and the cross-priming of Ag-specific CD8(+) T cell responses associated with therapeutic benefit. Antitumor protection was dependent on cross-presenting Batf3(+) DC, pDC, and CD8(+) T cells. CD103(+) DC from the skin/tumor draining lymph nodes of the immunized mice appeared responsible for activation of Ag-specific naive CD8(+) T cells, but were dependent on pDC for optimal effectiveness. Similarly, human XBP1 improved the capacity of human blood- and skin-derived DC to activate human T cells. These data support an important intrinsic role for XBP1 in DC for effective cross-priming and orchestration of Batf3(+) DC-pDC interactions, thereby enabling effective vaccine induction of protective antitumor immunity.
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Affiliation(s)
- Yi Zhang
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Guo Chen
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Zuqiang Liu
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Shenghe Tian
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Jiying Zhang
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Cara D Carey
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Kenneth M Murphy
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110; Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO 63110
| | - Walter J Storkus
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213
| | - Louis D Falo
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213
| | - Zhaoyang You
- Department of Dermatology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213
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Guiliano DB, Fussell H, Lenart I, Tsao E, Nesbeth D, Fletcher AJ, Campbell EC, Yousaf N, Williams S, Santos S, Cameron A, Towers GJ, Kellam P, Hebert DN, Gould K, Powis SJ, Antoniou AN. Endoplasmic reticulum degradation-enhancing α-mannosidase-like protein 1 targets misfolded HLA-B27 dimers for endoplasmic reticulum-associated degradation. Arthritis Rheumatol 2014; 66:2976-88. [PMID: 25132672 PMCID: PMC4399817 DOI: 10.1002/art.38809] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 07/29/2014] [Indexed: 12/29/2022]
Abstract
OBJECTIVE HLA-B27 forms misfolded heavy chain dimers, which may predispose individuals to inflammatory arthritis by inducing endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). This study was undertaken to define the role of the UPR-induced ER-associated degradation (ERAD) pathway in the disposal of HLA-B27 dimeric conformers. METHODS HeLa cell lines expressing only 2 copies of a carboxy-terminally Sv5-tagged HLA-B27 were generated. The ER stress-induced protein ER degradation-enhancing α-mannosidase-like protein 1 (EDEM1) was overexpressed by transfection, and dimer levels were monitored by immunoblotting. EDEM1, the UPR-associated transcription factor X-box binding protein 1 (XBP-1), the E3 ubiquitin ligase hydroxymethylglutaryl-coenzyme A reductase degradation 1 (HRD1), and the degradation-associated proteins derlin 1 and derlin 2 were inhibited using either short hairpin RNA or dominant-negative mutants. The UPR-associated ERAD of HLA-B27 was confirmed using ER stress-inducing pharamacologic agents in kinetic and pulse chase assays. RESULTS We demonstrated that UPR-induced machinery can target HLA-B27 dimers and that dimer formation can be controlled by alterations to expression levels of components of the UPR-induced ERAD pathway. HLA-B27 dimers and misfolded major histocompatibility complex class I monomeric molecules bound to EDEM1 were detected, and overexpression of EDEM1 led to inhibition of HLA-B27 dimer formation. EDEM1 inhibition resulted in up-regulation of HLA-B27 dimers, while UPR-induced ERAD of dimers was prevented in the absence of EDEM1. HLA-B27 dimer formation was also enhanced in the absence of XBP-1, HRD1, and derlins 1 and 2. CONCLUSION The present findings indicate that the UPR ERAD pathway can dispose of HLA-B27 dimers, thus presenting a potential novel therapeutic target for modulation of HLA-B27-associated inflammatory disease.
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Affiliation(s)
- David B. Guiliano
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
- School of Health, Sport and Bioscience, University of East London, London, E15 4LZ
| | - Helen Fussell
- Histocompatibility and Immunogenetics Department, NHS Blood and Transplant, Colindale Blood Centre, Colindale Avenue, London, NW9 5BG
| | - Izabela Lenart
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | - Edward Tsao
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | - Darren Nesbeth
- The Advanced Centre for Biochemical Engineering, University College London, Gower Street, London, WC1E 7JE
| | - Adam J. Fletcher
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | | | - Nasim Yousaf
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | - Sarah Williams
- School of Medicine, University of St. Andrews, Fife, Scotland, KY16 9TF
| | - Susana Santos
- INEB-Instituto de Engenharia Biomedica, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal
| | - Amy Cameron
- School of Medicine, University of St. Andrews, Fife, Scotland, KY16 9TF
| | - Greg J. Towers
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | - Paul Kellam
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
| | - Daniel N. Hebert
- Biochemistry and Molecular Biology, 701 N. Pleasant St. LGRT 1228, University of Massachusetts, Amherst, MA 01003
| | - Keith Gould
- Wright-Fleming Institute, Imperial College London, London, England, W2 1PG
| | - Simon J. Powis
- School of Medicine, University of St. Andrews, Fife, Scotland, KY16 9TF
| | - Antony N. Antoniou
- Division of Infection and Immunity/Centre of Rheumatology, Rayne Building, 5 University Street, University College London, London, WC1E 6JF
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Sone M, Zeng X, Larese J, Ryoo HD. A modified UPR stress sensing system reveals a novel tissue distribution of IRE1/ XBP1 activity during normal Drosophila development. Cell Stress Chaperones 2013; 18:307-19. [PMID: 23160805 PMCID: PMC3631089 DOI: 10.1007/s12192-012-0383-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 10/24/2012] [Accepted: 10/30/2012] [Indexed: 12/20/2022] Open
Abstract
Eukaryotic cells respond to stress caused by the accumulation of unfolded/misfolded proteins in the endoplasmic reticulum by activating the intracellular signaling pathways referred to as the unfolded protein response (UPR). In metazoans, UPR consists of three parallel branches, each characterized by its stress sensor protein, IRE1, ATF6, and PERK, respectively. In Drosophila, IRE1/XBP1 pathway is considered to function as a major branch of UPR; however, its physiological roles during the normal development and homeostasis remain poorly understood. To visualize IRE1/XBP1 activity in fly tissues under normal physiological conditions, we modified previously reported XBP1 stress sensing systems (Souid et al., Dev Genes Evol 217: 159-167, 2007; Ryoo et al., EMBO J 26: 242-252, 2007), based on the recent reports regarding the unconventional splicing of XBP1/HAC1 mRNA (Aragon et al., Nature 457: 736-740, 2009; Yanagitani et al., Mol Cell 34: 191-200, 2009; Science 331: 586-589, 2011). The improved XBP1 stress sensing system allowed us to detect new IRE1/XBP1 activities in the brain, gut, Malpighian tubules, and trachea of third instar larvae and in the adult male reproductive organ. Specifically, in the larval brain, IRE1/XBP1 activity was detected exclusively in glia, although previous reports have largely focused on IRE1/XBP1 activity in neurons. Unexpected glial IRE1/XBP1 activity may provide us with novel insights into the brain homeostasis regulated by the UPR.
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Affiliation(s)
- Michio Sone
- Department of Cell Biology, New York University School of Medicine, 560 First Avenue, New York, NY 10016 USA
| | - Xiaomei Zeng
- Department of Cell Biology, New York University School of Medicine, 560 First Avenue, New York, NY 10016 USA
| | - Joseph Larese
- Department of Cell Biology, New York University School of Medicine, 560 First Avenue, New York, NY 10016 USA
| | - Hyung Don Ryoo
- Department of Cell Biology, New York University School of Medicine, 560 First Avenue, New York, NY 10016 USA
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Margariti A, Li H, Chen T, Martin D, Vizcay-Barrena G, Alam S, Karamariti E, Xiao Q, Zampetaki A, Zhang Z, Wang W, Jiang Z, Gao C, Ma B, Chen YG, Cockerill G, Hu Y, Xu Q, Zeng L. XBP1 mRNA splicing triggers an autophagic response in endothelial cells through BECLIN-1 transcriptional activation. J Biol Chem 2013; 288:859-72. [PMID: 23184933 PMCID: PMC3543035 DOI: 10.1074/jbc.m112.412783] [Citation(s) in RCA: 204] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 11/13/2012] [Indexed: 11/06/2022] Open
Abstract
Sustained activation of X-box-binding protein 1 (XBP1) results in endothelial cell (EC) apoptosis and atherosclerosis development. The present study provides evidence that XBP1 mRNA splicing triggered an autophagic response in ECs by inducing autophagic vesicle formation and markers of autophagy BECLIN-1 and microtubule-associated protein 1 light chain 3β (LC3-βII). Endostatin activated autophagic gene expression through XBP1 mRNA splicing in an inositol-requiring enzyme 1α (IRE1α)-dependent manner. Knockdown of XBP1 or IRE1α by shRNA in ECs ablated endostatin-induced autophagosome formation. Importantly, data from arterial vessels from XBP1 EC conditional knock-out (XBP1eko) mice demonstrated that XBP1 deficiency in ECs reduced the basal level of LC3β expression and ablated response to endostatin. Chromatin immunoprecipitation assays further revealed that the spliced XBP1 isoform bound directly to the BECLIN-1 promoter at the region from nt -537 to -755. BECLIN-1 deficiency in ECs abolished the XBP1-induced autophagy response, whereas spliced XBP1 did not induce transcriptional activation of a truncated BECLIN-1 promoter. These results suggest that XBP1 mRNA splicing triggers an autophagic signal pathway through transcriptional regulation of BECLIN-1.
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Affiliation(s)
- Andriana Margariti
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Hongling Li
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Ting Chen
- the Department of Cardiology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China
| | - Daniel Martin
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Gema Vizcay-Barrena
- the Centre for Ultrastructural Imaging, King's College London, Guy's Campus, London WC2R 2LS, United Kingdom
| | - Saydul Alam
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Eirini Karamariti
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Qingzhong Xiao
- the Centre for Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London EC1M 6BQ, United Kingdom
| | - Anna Zampetaki
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Zhongyi Zhang
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Wen Wang
- the School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Zhixin Jiang
- the Centre Laboratory, 305th Hospital of the People's Liberation Army, Beijing 100017, China
| | - Chan Gao
- the State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China, and
| | - Benyu Ma
- the State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China, and
| | - Ye-Guang Chen
- the State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China, and
| | - Gillian Cockerill
- the Department of Cardiovascular Science, St. George's University of London, London SW17 0RE, United Kingdom
| | - Yanhua Hu
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Qingbo Xu
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Lingfang Zeng
- From the Cardiovascular Division, King's College London BHF Centre, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
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Wang FM, Galson DL, Roodman GD, Ouyang H. Resveratrol triggers the pro-apoptotic endoplasmic reticulum stress response and represses pro-survival XBP1 signaling in human multiple myeloma cells. Exp Hematol 2011; 39:999-1006. [PMID: 21723843 PMCID: PMC3261654 DOI: 10.1016/j.exphem.2011.06.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/27/2011] [Accepted: 06/21/2011] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Resveratrol, trans-3, 4', 5,-trihydroxystilbene, suppresses multiple myeloma (MM). The endoplasmic reticulum (ER) stress response component inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 (XBP1) axis is essential for MM pathogenesis. We investigated the molecular action of resveratrol on IRE1α/XBP1 axis in human MM cells. MATERIALS AND METHODS Human MM cell lines ANBL-6, OPM2, and MM.1S were utilized to determine the molecular signaling events following treatment with resveratrol. The stimulation of IRE1α/XBP1 axis was analyzed by Western blot and reverse transcription polymerase chain reaction. The effect of resveratrol on the transcriptional activity of spliced XBP1 was assessed by luciferase assays. Chromatin immunoprecipitation was performed to determine the effects of resveratrol on the DNA binding activity of XBP1 in MM cells. RESULTS Resveratrol activated IRE1α as evidenced by XBP1 messenger RNA splicing and phosphorylation of both IRE1α and its downstream kinase c-Jun N-terminal kinase in MM cells. These responses were associated with resveratrol-induced cytotoxicity of MM cells. Resveratrol selectively suppressed the transcriptional activity of XBP1s while it stimulated gene expression of the molecules that are regulated by the non-IRE1/XBP1 axis of the ER stress response. Luciferase assays indicated that resveratrol suppressed the transcriptional activity of XBP1s through sirtuin 1, a downstream molecular target of resveratrol. Chromatin immunoprecipitation studies revealed that resveratrol decreased the DNA binding capacity of XBP1 and increased the enrichment of sirtuin 1 at the XBP1 binding region in the XBP1 promoter. CONCLUSIONS Resveratrol exerts its chemotherapeutic effect on human MM cells through mechanisms involving the impairment of the pro-survival XBP1 signaling and the activation of pro-apoptotic ER stress response.
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Affiliation(s)
- Feng-Ming Wang
- Division of Hematology & Oncology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- The State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
| | - Deborah L. Galson
- Division of Hematology & Oncology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - G. David Roodman
- Division of Hematology & Oncology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hongjiao Ouyang
- Division of Hematology & Oncology, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Comprehensive Care, Restorative Dentistry, and Endodontics, School of Dental Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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12
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Xue Z, He Y, Ye K, Gu Z, Mao Y, Qi L. A conserved structural determinant located at the interdomain region of mammalian inositol-requiring enzyme 1alpha. J Biol Chem 2011; 286:30859-30866. [PMID: 21757700 PMCID: PMC3162446 DOI: 10.1074/jbc.m111.273714] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Revised: 07/07/2011] [Indexed: 01/17/2023] Open
Abstract
Inositol-requiring enzyme 1α (IRE1α), an endoplasmic reticulum-resident sensor for mammalian unfolded protein response, is a bifunctional enzyme containing kinase and RNase domains critical for trans-autophosphorylation and Xbp1 mRNA splicing, respectively, in response to endoplasmic reticulum stress. However, the amino acid residues important for its function and activation remain largely unexplored. Here, through analysis of IRE1α mutants associated with human somatic cancers, we have identified a highly conserved proline residue at position 830 (Pro(830)) that is critical for its structural integrity and hence, the activation of both kinase and RNase domains. Structural analysis revealed that Pro(830) may form a highly conserved structural linker with adjacent tryptophan and tyrosine residues at positions 833 and 945 (Trp(833) and Tyr(945)), thereby bridging the kinase and RNase domains. Indeed, mutation of Pro(830) to leucine (P830L) completely abolished the kinase and RNase activities, significantly decreased protein stability, and prevented oligomerization of IRE1α upon ER stress; similar observations were made for mutations of Trp(833) to alanine (W833A) and to a lesser extent for Y945A. Our finding may facilitate the identification of small molecules to compromise IRE1α function specifically.
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Affiliation(s)
- Zhen Xue
- Graduate Program in Nutrition, Cornell University, Ithaca, New York 14853; Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853
| | - Yin He
- Graduate Program in Genetics and Development, Cornell University, Ithaca, New York 14853
| | - Kaixiong Ye
- Graduate Program in Nutrition, Cornell University, Ithaca, New York 14853; Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853
| | - Zhenglong Gu
- Graduate Program in Nutrition, Cornell University, Ithaca, New York 14853; Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853; Graduate Program in Genetics and Development, Cornell University, Ithaca, New York 14853
| | - Yuxin Mao
- Weill Institute of Molecular and Cell Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Ling Qi
- Graduate Program in Nutrition, Cornell University, Ithaca, New York 14853; Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853; Graduate Program in Genetics and Development, Cornell University, Ithaca, New York 14853.
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Martinon F, Chen X, Lee AH, Glimcher LH. TLR activation of the transcription factor XBP1 regulates innate immune responses in macrophages. Nat Immunol 2010; 11:411-8. [PMID: 20351694 PMCID: PMC3113706 DOI: 10.1038/ni.1857] [Citation(s) in RCA: 754] [Impact Index Per Article: 53.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 02/22/2010] [Indexed: 02/06/2023]
Abstract
Sensors of pathogens, such as Toll-like receptors (TLRs), detect microbes to activate transcriptional programs that orchestrate adaptive responses to specific insults. Here we report that TLR4 and TLR2 specifically activated the endoplasmic reticulum (ER) stress sensor kinase IRE1alpha and its downstream target, the transcription factor XBP1. Previously described ER-stress target genes of XBP1 were not induced by TLR signaling. Instead, TLR-activated XBP1 was required for optimal and sustained production of proinflammatory cytokines in macrophages. Consistent with that finding, activation of IRE1alpha by ER stress acted in synergy with TLR activation for cytokine production. Moreover, XBP1 deficiency resulted in a much greater bacterial burden in mice infected with the TLR2-activating human intracellular pathogen Francisella tularensis. Our findings identify an unsuspected critical function for XBP1 in mammalian host defenses.
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Affiliation(s)
- Fabio Martinon
- Dept. of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Ave, Boston, MA 02115, USA
| | - Xi Chen
- Dept. of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Ave, Boston, MA 02115, USA
| | - Ann-Hwee Lee
- Dept. of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Ave, Boston, MA 02115, USA
- Dept of Medicine, MIT and Harvard, Harvard Medical School, 651 Huntington Ave, Boston, MA 02115, USA
| | - Laurie H. Glimcher
- Dept. of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Ave, Boston, MA 02115, USA
- Dept of Medicine, MIT and Harvard, Harvard Medical School, 651 Huntington Ave, Boston, MA 02115, USA
- Ragon Institute of MGH, MIT and Harvard, Harvard Medical School, 651 Huntington Ave, Boston, MA 02115, USA
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Sha H, He Y, Chen H, Wang C, Zenno A, Shi H, Yang X, Zhang X, Qi L. The IRE1alpha- XBP1 pathway of the unfolded protein response is required for adipogenesis. Cell Metab 2009; 9:556-64. [PMID: 19490910 PMCID: PMC2963107 DOI: 10.1016/j.cmet.2009.04.009] [Citation(s) in RCA: 210] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 04/02/2009] [Accepted: 04/28/2009] [Indexed: 11/29/2022]
Abstract
Signaling cascades during adipogenesis culminate in the expression of two essential adipogenic factors, PPARgamma and C/EBPalpha. Here we demonstrate that the IRE1alpha-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 IRE1alpha knockdown exhibit profound defects in adipogenesis. Intriguingly, C/EBPbeta, 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 IRE1alpha 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 IRE1alpha-XBP1 pathway plays a key role in adipocyte differentiation by acting as a critical regulator of the morphological and functional transformations during adipogenesis.
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Affiliation(s)
- Haibo Sha
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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Schwartz R, Engel I, Fallahi-Sichani M, Petrie HT, Murre C. Gene expression patterns define novel roles for E47 in cell cycle progression, cytokine-mediated signaling, and T lineage development. Proc Natl Acad Sci U S A 2006; 103:9976-81. [PMID: 16782810 PMCID: PMC1502564 DOI: 10.1073/pnas.0603728103] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Indexed: 11/18/2022] Open
Abstract
In maturing T lineage cells, the helix-loop-helix protein E47 has been shown to enforce a critical proliferation and developmental checkpoint commonly referred to as beta selection. To examine how E47 regulates cellular expansion and developmental progression, we have used an E2A-deficient lymphoma cell line and DNA microarray analysis to identify immediate E47 target genes. Hierarchical cluster analysis of gene expression patterns revealed that E47 coordinately regulates the expression of genes involved in cell survival, cell cycle progression, lipid metabolism, stress response, and lymphoid maturation. These include Plcgamma2, Cdk6, CD25, Tox, Gadd45a, Gadd45b, Gfi1, Gfi1b, Socs1, Socs3, Id2, Eto2, and Xbp1. We propose a regulatory network linking Janus kinase (JAK)/signal transducer and activator of transcription (STAT)-mediated signaling, E47, and suppressor of cytokine signaling (SOCS) proteins in a common pathway. Finally, we suggest that the aberrant activation of Cdk6 in E47-deficient T lineage cells contributes to the development of lymphoid malignancy.
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Affiliation(s)
- Ruth Schwartz
- *Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0377; and
| | - Isaac Engel
- *Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0377; and
| | | | - Howard T. Petrie
- Scripps/Florida Research Institute, 5353 Parkside Drive, RF-1, Jupiter, FL 33458
| | - Cornelis Murre
- *Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0377; and
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