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López-Collazo E, del Fresno C. Endotoxin tolerance and trained immunity: breaking down immunological memory barriers. Front Immunol 2024; 15:1393283. [PMID: 38742111 PMCID: PMC11089161 DOI: 10.3389/fimmu.2024.1393283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 04/09/2024] [Indexed: 05/16/2024] Open
Abstract
For decades, innate immune cells were considered unsophisticated first responders, lacking the adaptive memory of their T and B cell counterparts. However, mounting evidence demonstrates the surprising complexity of innate immunity. Beyond quickly deploying specialized cells and initiating inflammation, two fascinating phenomena - endotoxin tolerance (ET) and trained immunity (TI) - have emerged. ET, characterized by reduced inflammatory response upon repeated exposure, protects against excessive inflammation. Conversely, TI leads to an enhanced response after initial priming, allowing the innate system to mount stronger defences against subsequent challenges. Although seemingly distinct, these phenomena may share underlying mechanisms and functional implications, blurring the lines between them. This review will delve into ET and TI, dissecting their similarities, differences, and the remaining questions that warrant further investigation.
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Affiliation(s)
- Eduardo López-Collazo
- The Innate Immune Response Group, Hospital la Paz Institute for Health Research (IdiPAZ), La Paz University Hospital, Madrid, Spain
- Tumour Immunology Laboratory, IdiPAZ, La Paz University Hospital, Madrid, Spain
- Centro de Investigación Biomédica en Red (CIBER), Respiratory Diseases (CIBRES), Madrid, Spain
| | - Carlos del Fresno
- The Innate Immune Response Group, Hospital la Paz Institute for Health Research (IdiPAZ), La Paz University Hospital, Madrid, Spain
- Immunomodulation Laboratory, IdiPAZ, La Paz University Hospital, Madrid, Spain
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2
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Lee FFY, Alper S. Alternative pre-mRNA splicing as a mechanism for terminating Toll-like Receptor signaling. Front Immunol 2022; 13:1023567. [PMID: 36531997 PMCID: PMC9755862 DOI: 10.3389/fimmu.2022.1023567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 11/11/2022] [Indexed: 12/03/2022] Open
Abstract
While inflammation induced by Toll-like receptor (TLR) signaling is required to combat infection, persistent inflammation can damage host tissues and contribute to a myriad of acute and chronic inflammatory disorders. Thus, it is essential not only that TLR signaling be activated in the presence of pathogens but that TLR signaling is ultimately terminated. One mechanism that limits persistent TLR signaling is alternative pre-mRNA splicing. In addition to encoding the canonical mRNAs that produce proteins that promote inflammation, many genes in the TLR signaling pathway also encode alternative mRNAs that produce proteins that are dominant negative inhibitors of signaling. Many of these negative regulators are induced by immune challenge, so production of these alternative isoforms represents a negative feedback loop that limits persistent inflammation. While these alternative splicing events have been investigated on a gene by gene basis, there has been limited systemic analysis of this mechanism that terminates TLR signaling. Here we review what is known about the production of negatively acting alternative isoforms in the TLR signaling pathway including how these inhibitors function, how they are produced, and what role they may play in inflammatory disease.
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Affiliation(s)
- Frank Fang Yao Lee
- Department of Immunology and Genomic Medicine and Center for Genes, Environment, and Health, National Jewish Health, Denver, CO, United States,Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz, CO, United States
| | - Scott Alper
- Department of Immunology and Genomic Medicine and Center for Genes, Environment, and Health, National Jewish Health, Denver, CO, United States,Department of Immunology and Microbiology, University of Colorado School of Medicine, Anschutz, CO, United States,*Correspondence: Scott Alper,
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3
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Li N, Li Y, Han X, Zhang J, Han J, Jiang X, Wang W, Xu Y, Xu Y, Fu Y, Si S. LXR agonist inhibits inflammation through regulating MyD88 mRNA alternative splicing. Front Pharmacol 2022; 13:973612. [PMID: 36313296 PMCID: PMC9614042 DOI: 10.3389/fphar.2022.973612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 09/22/2022] [Indexed: 12/02/2022] Open
Abstract
Liver X receptors (LXRs) are important regulators of cholesterol metabolism and inflammatory responses. LXR agonists exhibit potently anti-inflammatory effects in macrophages, which make them beneficial to anti-atherogenic therapy. In addition to transrepressive regulation by SUMOylation, LXRs can inhibit inflammation by various mechanisms through affecting multiple targets. In this study, we found that the classic LXR agonist T0901317 mediated numerous genes containing alternative splice sites, including myeloid differentiation factor 88 (MyD88), that contribute to inflammatory inhibition in RAW264.7 macrophages. Furthermore, T0901317 increased level of alternative splice short form of MyD88 mRNA by down-regulating expression of splicing factor SF3A1, leading to nuclear factor κB-mediated inhibition of inflammation. In conclusion, our results suggest for the first time that the LXR agonist T0901317 inhibits lipopolysaccharide-induced inflammation through regulating MyD88 mRNA alternative splicing involved in TLR4 signaling pathway.
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Affiliation(s)
- Ni Li
- State Key Laboratory of Bioactive Substances and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing, China
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- *Correspondence: Ni Li, ; Yu Fu, ; Shuyi Si,
| | - Yan Li
- College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang, Hebei
| | - Xiaowan Han
- State Key Laboratory of Bioactive Substances and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing, China
| | - Jing Zhang
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Jiangxue Han
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xinhai Jiang
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Weizhi Wang
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yang Xu
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yanni Xu
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yu Fu
- College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang, Hebei
- *Correspondence: Ni Li, ; Yu Fu, ; Shuyi Si,
| | - Shuyi Si
- NHC Key Laboratory of Biotechnology of Antibiotics, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
- *Correspondence: Ni Li, ; Yu Fu, ; Shuyi Si,
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4
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Chen Y, Cao B, Zheng W, Sun Y, Xu T. eIF3k inhibits NF-κB signaling by targeting MyD88 for ATG5-mediated autophagic degradation in teleost fish. J Biol Chem 2022; 298:101730. [PMID: 35176284 PMCID: PMC8914388 DOI: 10.1016/j.jbc.2022.101730] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 02/02/2022] [Accepted: 02/08/2022] [Indexed: 12/18/2022] Open
Abstract
Optimal activation of NF-κB signaling is crucial for the initiation of inflammatory responses and eliminating invading bacteria. Bacteria have likewise evolved the ability to evade immunity; however, mechanisms by which bacteria dysregulate host NF-κB signaling are unclear. In this study, we identify eukaryotic translation initiation factor eIF3k, a nonessential member of the eIF3 translation initiation complex, as a suppressor of the NF-κB pathway. Mechanistically, we show that eIF3k expression induced by Vibrio harveyi enhances E3 ligase Nrdp1-mediated K27-linked ubiquitination of MyD88, an upstream regulator of NF-κB pathway activation. Furthermore, we show that eIF3k acts as a bridge linking ubiquitin-tagged MyD88 and ATG5, an important mediator of autophagy. We demonstrate that the MyD88-eIF3k-ATG5 complex is transported to the autophagosome for degradation, and that innate immune signaling is subsequently terminated and does not attack invading V. harveyi. Therefore, our study identifies eIF3k as a specific inhibitor of the MyD88-dependent NF-κB pathway and suggests that eIF3k may act as a selective autophagic receptor that synergizes with ATG5 to promote the autophagic degradation of MyD88, which helps V. harveyi to evade innate immunity. We conclude that V. harveyi can manipulate a host's autophagy process to evade immunity in fish and also provide a new perspective on mammalian resistance to bacterial invasion.
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Affiliation(s)
- Ya Chen
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Baolan Cao
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Weiwei Zheng
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Yuena Sun
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China; Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, Shanghai, China; National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai, China
| | - Tianjun Xu
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China; Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, Shanghai, China; National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai, China.
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5
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Yu L, Zhang L, Yang H, Gui G, Liu Y, Xiao Y. Identification and characterization of the myeloid differentiation factor 88 gene in yellow catfish. 3 Biotech 2018; 8:430. [PMID: 30305999 PMCID: PMC6163110 DOI: 10.1007/s13205-018-1448-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 09/24/2018] [Indexed: 10/28/2022] Open
Abstract
Myeloid differentiation factor 88 (MyD88) is an important adapter protein of the innate immune system, but it has never before been reported in yellow catfish (Pelteobagrus fulvidraco). In this study, we cloned and characterized the yellow catfish MyD88 gene. The gene was 1230 bp in length and contained an 876-bp open reading frame which encodes a polypeptide of 291 amino acid residues. The theoretical molecular mass and isoelectric point of this polypeptide were 33.4341 kDa and 5.17, respectively. Furthermore, bioinformatic and phylogenetic analyses grouped yellow catfish MyD88 with MyD88 of other fish. We found that the deduced amino acid sequence showed that the conserved N-terminal death domain and the C-terminal typical Toll/interleukin-1 receptor domain were very similar to those of other fish. Moreover, reverse transcription PCR showed that yellow catfish MyD88 is ubiquitously expressed in all tissues examined, with highest expression levels observed in the spleen and lowest levels in the intestine. Importantly, MyD88 was shown to be significantly up-regulated in the intestines after 30-day dietary supplement of Clostridium butyricum. Collectively, these results indicate that yellow catfish MyD88 has a conserved structure and is probably an important component of innate immunity in yellow catfish. This study is the first to identify and characterize MyD88 in yellow catfish, thereby providing a reference for further research into the yellow catfish innate immune system.
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Affiliation(s)
- Lintian Yu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, 611130 China
- Guangxi Agricultural Vocational College, Nanning, 530007 Guangxi China
| | - Long Zhang
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, 611130 China
- Institute of Ecology, China West Normal University, Nanchong, 637009 China
| | - Hua Yang
- Institute of Quality Standards for Agro-Products, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021 China
| | - Guohong Gui
- Institute of Quality Standards for Agro-Products, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021 China
| | - Yiping Liu
- Farm Animal Genetic Resources Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, 611130 China
| | - Yingping Xiao
- Institute of Quality Standards for Agro-Products, Zhejiang Academy of Agricultural Sciences, Hangzhou, 310021 China
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6
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Blumhagen RZ, Hedin BR, Malcolm KC, Burnham EL, Moss M, Abraham E, Huie TJ, Nick JA, Fingerlin TE, Alper S. Alternative pre-mRNA splicing of Toll-like receptor signaling components in peripheral blood mononuclear cells from patients with ARDS. Am J Physiol Lung Cell Mol Physiol 2017; 313:L930-L939. [PMID: 28775099 DOI: 10.1152/ajplung.00247.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/28/2017] [Accepted: 07/30/2017] [Indexed: 12/14/2022] Open
Abstract
A key physiological feature of acute respiratory distress syndrome (ARDS) is inflammation. Toll-like receptor (TLR) signaling is required to combat the infection that underlies many ARDS cases but also contributes to pathological inflammation. Several TLR signaling pathway genes encoding positive effectors of inflammation also produce alternatively spliced mRNAs encoding negative regulators of inflammation. An imbalance between these isoforms could contribute to pathological inflammation and disease severity. To determine whether splicing in TLR pathways is altered in patients with ARDS, we monitored alternative splicing of MyD88 and IRAK1, two genes that function in multiple TLR pathways. The MyD88 and IRAK1 genes produce long proinflammatory mRNAs (MyD88L and IRAK1) and shorter anti-inflammatory mRNAs (MyD88S and IRAK1c). We quantified mRNA encoding inflammatory cytokines and MyD88 and IRAK1 isoforms in peripheral blood mononuclear cells (PBMCs) from 104 patients with ARDS and 30 healthy control subjects. We found that MyD88 pre-mRNA splicing is altered in patients with ARDS in a proinflammatory direction. We also observed altered MyD88 isoform levels in a second critically ill patient cohort, suggesting that these changes may not be unique to ARDS. Early in ARDS, PBMC IRAK1c levels were associated with patient survival. Despite the similarities in MyD88 and IRAK1 alternative splicing observed in previous in vitro studies, there were differences in how MyD88 and IRAK1 alternative splicing was altered in patients with ARDS. We conclude that pre-mRNA splicing of TLR signaling genes is altered in patients with ARDS, and further investigation of altered splicing may lead to novel prognostic and therapeutic approaches.
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Affiliation(s)
- Rachel Z Blumhagen
- Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado.,Department of Biomedical Research, National Jewish Health, Denver, Colorado
| | - Brenna R Hedin
- Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado.,Department of Biomedical Research, National Jewish Health, Denver, Colorado
| | - Kenneth C Malcolm
- Department of Medicine, National Jewish Health, Denver, Colorado.,Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Ellen L Burnham
- Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Marc Moss
- Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Edward Abraham
- Office of the Dean, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Tristan J Huie
- Department of Medicine, National Jewish Health, Denver, Colorado.,Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Jerry A Nick
- Department of Medicine, National Jewish Health, Denver, Colorado.,Division of Pulmonary Science and Critical Care Medicine, Department of Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado
| | - Tasha E Fingerlin
- Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado.,Department of Biomedical Research, National Jewish Health, Denver, Colorado.,Department of Biostatistics and Bioinformatics, Colorado School of Public Health, Aurora, Colorado
| | - Scott Alper
- Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado; .,Department of Biomedical Research, National Jewish Health, Denver, Colorado.,Program in Mucosal Inflammation and Immunity, National Jewish Health, Denver, Colorado; and.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado
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7
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Niu S, Shi X, Zhang J, Chai L, Xiao X. Cloning, Characterization, and Expression Analysis of MyD88 in Rana dybowskii. Appl Biochem Biotechnol 2016; 179:294-306. [DOI: 10.1007/s12010-016-1994-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/19/2016] [Indexed: 11/28/2022]
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8
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O’Connor BP, Danhorn T, De Arras L, Flatley BR, Marcus RA, Farias-Hesson E, Leach SM, Alper S. Regulation of toll-like receptor signaling by the SF3a mRNA splicing complex. PLoS Genet 2015; 11:e1004932. [PMID: 25658809 PMCID: PMC4450051 DOI: 10.1371/journal.pgen.1004932] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 12/02/2014] [Indexed: 12/31/2022] Open
Abstract
The innate immune response plays a key role in fighting infection by activating inflammation and stimulating the adaptive immune response. However, chronic activation of innate immunity can contribute to the pathogenesis of many diseases with an inflammatory component. Thus, various negatively acting factors turn off innate immunity subsequent to its activation to ensure that inflammation is self-limiting and to prevent inflammatory disease. These negatively acting pathways include the production of inhibitory acting alternate proteins encoded by alternative mRNA splice forms of genes in Toll-like receptor (TLR) signaling pathways. We previously found that the SF3a mRNA splicing complex was required for a robust innate immune response; SF3a acts to promote inflammation in part by inhibiting the production of a negatively acting splice form of the TLR signaling adaptor MyD88. Here we inhibit SF3a1 using RNAi and subsequently perform an RNAseq study to identify the full complement of genes and splicing events regulated by SF3a in murine macrophages. Surprisingly, in macrophages, SF3a has significant preference for mRNA splicing events within innate immune signaling pathways compared with other biological pathways, thereby affecting the splicing of specific genes in the TLR signaling pathway to modulate the innate immune response. Within minutes after we are exposed to pathogens, our bodies react with a rapid response known as the “innate immune response.” This arm of the immune response regulates the process of inflammation, in which various immune cells are recruited to sites of infection and are activated to produce a host of antimicrobial compounds. This response is critical to fight infection. However, this response, if it is activated too strongly or if it becomes chronic, can do damage and can contribute to numerous very common diseases ranging from atherosclerosis to asthma to cancer. Thus it is essential that this response be tightly regulated, turned on when we have an infection, and turned off when not needed. We are investigating a mechanism that helps turn off this response, to ensure that inflammation is limited to prevent inflammatory disease. This mechanism involves the production of alternate forms of RNAs and proteins that control inflammation. We have discovered that a protein known as SF3a1 can regulate the expression of these alternate inhibitory RNA forms and are investigating how to use this knowledge to better control inflammation.
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Affiliation(s)
- Brian P. O’Connor
- Department of Pediatrics, National Jewish Health, Denver, Colorado, United States of America
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
| | - Thomas Danhorn
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Lesly De Arras
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Brenna R. Flatley
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
| | - Roland A. Marcus
- Department of Pediatrics, National Jewish Health, Denver, Colorado, United States of America
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Eveline Farias-Hesson
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Sonia M. Leach
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
| | - Scott Alper
- Integrated Center for Genes, Environment and Health, National Jewish Health, Denver, Colorado, United States of America
- Department of Biomedical Research, National Jewish Health, Denver, Colorado, United States of America
- Department of Immunology and Microbiology, University of Colorado, Aurora, Colorado, United States of America
- * E-mail:
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9
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Du J, Nicolaes GA, Kruijswijk D, Versloot M, van der Poll T, van 't Veer C. The structure function of the death domain of human IRAK-M. Cell Commun Signal 2014; 12:77. [PMID: 25481771 PMCID: PMC4273448 DOI: 10.1186/s12964-014-0077-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 11/21/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND IRAK-M is an inhibitor of Toll-like receptor signaling that acts by re-directing IRAK-4 activity to TAK1 independent NF-κB activation and by inhibition of IRAK-1/IRAK-2 activity. IRAK-M is expressed in monocytes/macrophages and lung epithelial cells. Lack of IRAK-M in mice greatly improves the resistance to nosocomial pneumonia and lung tumors, which entices IRAK-M as a potential therapeutic target. IRAK-M consists of an N-terminal death domain (DD), a dysfunctional kinase domain and unstructured C-terminal domain. Little is known however on IRAK-M's structure-function relationships. RESULTS Since death domains provide the important interactions of IRAK-1, IRAK-2 and IRAK-4 molecules, we generated a 3D structure model of the human IRAK-M-DD (residues C5-G119) to guide mutagenesis studies and predict protein-protein interaction points. First we identified the DD residues involved in the endogenous capacity of IRAK-M to activate NF-κB that is displayed upon overexpression in 293T cells. W74 and R97, at distinct interfaces of the IRAK-M-DD, were crucial for this endogenous NF-κB activating capacity, as well as the C-terminal domain (S445-E596) of IRAK-M. Resulting anti-inflammatory A20 and pro-inflammatory IL-8 transcription in 293T cells was W74 dependent, while IL-8 protein expression was dependent on R97 and the TRAF6 binding motif at P478. The IRAK-M-DD W74 and R97 binding interfaces are predicted to interact with opposite sides of IRAK-4-DD's. Secondly we identified DD residues important for the inhibitory action of IRAK-M by stable overexpression of mutants in THP-1 macrophages and H292 lung epithelial cells. IRAK-M inhibited TLR2/4-mediated cytokine production in macrophages in a manner that is largely dependent on W74. R97 was not involved in inhibition of TNF production but was engaged in IL-6 down-regulation by IRAK-M. Protein-interactive residues D19-A23, located in between W74 and R97, were also observed to be crucial for inhibition of TLR2/4 mediated cytokine induction in macrophages. Remarkably, IRAK-M inhibited TLR5 mediated IL-8 production by lung epithelial cells independent of W74 and R97, but dependent on D19-A23 and R70, two surface-exposed regions that harbor predicted IRAK-2-DD interaction points of IRAK-M. CONCLUSION IRAK-M employs alternate residues of its DD to inhibit the different inflammatory mediators induced by varying TLRs and cells.
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10
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Cubillos-Zapata C, Hernández-Jiménez E, Toledano V, Esteban-Burgos L, Fernández-Ruíz I, Gómez-Piña V, Del Fresno C, Siliceo M, Prieto-Chinchiña P, Pérez de Diego R, Boscá L, Fresno M, Arnalich F, López-Collazo E. NFκB2/p100 is a key factor for endotoxin tolerance in human monocytes: a demonstration using primary human monocytes from patients with sepsis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2014; 193:4195-202. [PMID: 25225662 DOI: 10.4049/jimmunol.1400721] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endotoxin tolerance (ET) is a state of reduced responsiveness to endotoxin stimulation after a primary bacterial insult. This phenomenon has been described in several pathologies, including sepsis, in which an endotoxin challenge results in reduced cytokine production. In this study, we show that the NFκ L chain enhancer of activated B cells 2 (NFκB2)/p100 was overexpressed and accumulated in a well-established in vitro human monocyte model of ET. The p100 accumulation in these cells inversely correlated with the inflammatory response after LPS stimulation. Knocking down NFκB2/p100 using small interfering RNA in human monocytes further indicated that p100 expression is a crucial factor in the progression of ET. The monocytes derived from patients with sepsis had high levels of p100, and a downregulation of NFκB2/p100 in these septic monocytes reversed their ET status.
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Affiliation(s)
- Carolina Cubillos-Zapata
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Enrique Hernández-Jiménez
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Víctor Toledano
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Laura Esteban-Burgos
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Irene Fernández-Ruíz
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Vanesa Gómez-Piña
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Carlos Del Fresno
- Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain
| | - María Siliceo
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Patricia Prieto-Chinchiña
- Instituto de Investigaciones Biomédicas Alberto Sols (Centro Mixto Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), 28046 Madrid, Spain
| | - Rebeca Pérez de Diego
- Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Laboratory of Immunogenetics of Diseases, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; and
| | - Lisardo Boscá
- Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Instituto de Investigaciones Biomédicas Alberto Sols (Centro Mixto Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), 28046 Madrid, Spain
| | - Manuel Fresno
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Francisco Arnalich
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain
| | - Eduardo López-Collazo
- Tumor Immunology Laboratory, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain; Innate Immunity Group, IdiPAZ, La Paz Hospital, 28046 Madrid, Spain;
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11
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De Arras L, Laws R, Leach SM, Pontis K, Freedman JH, Schwartz DA, Alper S. Comparative genomics RNAi screen identifies Eftud2 as a novel regulator of innate immunity. Genetics 2014; 197:485-96. [PMID: 24361939 PMCID: PMC4063909 DOI: 10.1534/genetics.113.160499] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 12/15/2013] [Indexed: 01/08/2023] Open
Abstract
The extent of the innate immune response is regulated by many positively and negatively acting signaling proteins. This allows for proper activation of innate immunity to fight infection while ensuring that the response is limited to prevent unwanted complications. Thus mutations in innate immune regulators can lead to immune dysfunction or to inflammatory diseases such as arthritis or atherosclerosis. To identify novel innate immune regulators that could affect infectious or inflammatory disease, we have taken a comparative genomics RNAi screening approach in which we inhibit orthologous genes in the nematode Caenorhabditis elegans and murine macrophages, expecting that genes with evolutionarily conserved function also will regulate innate immunity in humans. Here we report the results of an RNAi screen of approximately half of the C. elegans genome, which led to the identification of many candidate genes that regulate innate immunity in C. elegans and mouse macrophages. One of these novel conserved regulators of innate immunity is the mRNA splicing regulator Eftud2, which we show controls the alternate splicing of the MyD88 innate immunity signaling adaptor to modulate the extent of the innate immune response.
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Affiliation(s)
- Lesly De Arras
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Rebecca Laws
- Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts 02118
| | - Sonia M Leach
- Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Kyle Pontis
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
| | - Jonathan H Freedman
- Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Durham, North Carolina 27709
| | - David A Schwartz
- Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206 Department of Medicine, University of Colorado, Aurora, Colorado 80045
| | - Scott Alper
- Integrated Department of Immunology, National Jewish Health and University of Colorado, Denver, Colorado 80206 Integrated Center for Genes, Environment and Health, National Jewish Health and University of Colorado, Denver, Colorado 80206
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López-Collazo E, del Fresno C. Pathophysiology of endotoxin tolerance: mechanisms and clinical consequences. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2013; 17:242. [PMID: 24229432 PMCID: PMC4059412 DOI: 10.1186/cc13110] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Endotoxin tolerance was first described in a study that exposed animals to a sublethal dose of bacterial endotoxin. The animals subsequently survived a lethal injection of endotoxin. This refractory state is associated with the innate immune system and, in particular, with monocytes and macrophages, which act as the main participants. Several mechanisms are involved in the control of endotoxin tolerance; however, a full understanding of this phenomenon remains elusive. A number of recent reports indicate that clinical examples of endotoxin tolerance include not only sepsis but also diseases such as cystic fibrosis and acute coronary syndrome. In these pathologies, the risk of new infections correlates with a refractory state. This review integrates the molecular basis and clinical implications of endotoxin tolerance in various pathologies.
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De Arras L, Alper S. Limiting of the innate immune response by SF3A-dependent control of MyD88 alternative mRNA splicing. PLoS Genet 2013; 9:e1003855. [PMID: 24204290 PMCID: PMC3812059 DOI: 10.1371/journal.pgen.1003855] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 08/20/2013] [Indexed: 12/16/2022] Open
Abstract
Controlling infectious disease without inducing unwanted inflammatory disease requires proper regulation of the innate immune response. Thus, innate immunity needs to be activated when needed during an infection, but must be limited to prevent damage. To accomplish this, negative regulators of innate immunity limit the response. Here we investigate one such negative regulator encoded by an alternative splice form of MyD88. MyD88 mRNA exists in two alternative splice forms: MyD88L, a long form that encodes a protein that activates innate immunity by transducing Toll-like receptor (TLR) signals; and a short form that encodes a different protein, MyD88S, that inhibits the response. We find that MyD88S levels regulate the extent of inflammatory cytokine production in murine macrophages. MyD88S mRNA levels are regulated by the SF3A and SF3B mRNA splicing complexes, and these mRNA splicing complexes function with TLR signaling to regulate MyD88S production. Thus, the SF3A mRNA splicing complex controls production of a negative regulator of TLR signaling that limits the extent of innate immune activation.
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Affiliation(s)
- Lesly De Arras
- Integrated Department of Immunology and Integrated Center for Genes, Environment, and Health, National Jewish Health and University of Colorado School of Medicine, Denver, Colorado, United States of America
| | - Scott Alper
- Integrated Department of Immunology and Integrated Center for Genes, Environment, and Health, National Jewish Health and University of Colorado School of Medicine, Denver, Colorado, United States of America
- * E-mail:
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Avbelj M, Horvat S, Jerala R. The Role of Intermediary Domain of MyD88 in Cell Activation and Therapeutic Inhibition of TLRs. THE JOURNAL OF IMMUNOLOGY 2011; 187:2394-404. [DOI: 10.4049/jimmunol.1100515] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Abstract
The stimulation of TLR4 by LPS activates two distinct signaling pathways leading to the expression of diverse inflammatory genes. Intensive studies over the past decade have revealed the components involved in these signaling pathways, however, more recently the focus has shifted somewhat towards the components that regulate these pathways. Several regulatory mechanisms, including localisation of components, splice variants and inhibitory molecules will be discussed in this review.
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Affiliation(s)
- Anne F McGettrick
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
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