1
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She L, Alanazi HH, Xu Y, Yu Y, Gao Y, Guo S, Xiong Q, Jiang H, Mo K, Wang J, Chupp DP, Zan H, Xu Z, Sun Y, Xiong N, Zhang N, Xie Z, Jiang W, Zhang X, Liu Y, Li XD. Direct activation of toll-like receptor 4 signaling in group 2 innate lymphoid cells contributes to inflammatory responses of allergic diseases. iScience 2024; 27:111240. [PMID: 39563895 PMCID: PMC11574794 DOI: 10.1016/j.isci.2024.111240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 07/04/2024] [Accepted: 10/21/2024] [Indexed: 11/21/2024] Open
Abstract
Group 2 innate lymphoid cells (ILC2s) are key players in type 2 immunity, but whether they can be directly activated by microbial ligands remain uncertain. In this study, we observed a positive correlation between blood endotoxin (LPS) levels and circulating ILC2s in allergic patients. In vitro, LPS robustly induced ILC2 proliferation and production of type 2 effector cytokines. RNA-seq revealed a type 2 immune-responsive profile in LPS-stimulated ILC2s. Notably, ILC2s lost their LPS-mediated growth and activation capacity when treated with TLR4 receptor antagonists and inhibitors of the NF-κB and JAK pathways, though this effect was not observed with IL-33 receptor blocking antibodies. Genetically, ILC2s from TLR4 knockout (KO) mice, but not from ST2 KO mice, were unresponsive to LPS. Collectively, these findings suggest a direct, non-canonical activation mechanism of ILC2s via the LPS-TLR4-NF-κB/JAK signaling axis.
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Affiliation(s)
- Li She
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Hamad H Alanazi
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
- Department of Clinical Laboratory Sciences, College of Applied Medical Sciences at Al-Qurayyat, Jouf University, Aldwally Road, Al-Qurayyat 77454, Saudi Arabia
| | - Yimin Xu
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Yuxuan Yu
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Yuzhang Gao
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Shuting Guo
- Sino-French Hoffmann Institute, School of Basic Medical Sciences, Guangzhou Medical University, 1 Xinzao Road, Guangzhou, Guangdong 511495, China
| | - Qingquan Xiong
- Sino-French Hoffmann Institute, School of Basic Medical Sciences, Guangzhou Medical University, 1 Xinzao Road, Guangzhou, Guangdong 511495, China
| | - Hui Jiang
- Department of Gynecology, The Fifth Affiliated Hospital, Guangzhou Medical University, 621 Gangwan Road, Guangzhou, Guangdong 510700, China
| | - Kexin Mo
- Department of Gynecology, The Fifth Affiliated Hospital, Guangzhou Medical University, 621 Gangwan Road, Guangzhou, Guangdong 510700, China
| | - Jingwei Wang
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Daniel P Chupp
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Hong Zan
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Zhenming Xu
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Yilun Sun
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Na Xiong
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Nu Zhang
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
| | - Zhihai Xie
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Weihong Jiang
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Xin Zhang
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Yong Liu
- Department of Otolaryngology-Head and Neck Surgery, Clinical Research Center for Pharyngolaryngeal Diseases and Voice Disorders, Otolaryngology Major Disease Research Key Laboratory of Hunan Province, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China
| | - Xiao-Dong Li
- Department of Microbiology, Immunology and Molecular Genetics, Long School of Medicine, University of Texas Health San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
- Sino-French Hoffmann Institute, School of Basic Medical Sciences, Guangzhou Medical University, 1 Xinzao Road, Guangzhou, Guangdong 511495, China
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2
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Murray BO, Flores C, Williams C, Flusberg DA, Marr EE, Kwiatkowska KM, Charest JL, Isenberg BC, Rohn JL. Recurrent Urinary Tract Infection: A Mystery in Search of Better Model Systems. Front Cell Infect Microbiol 2021; 11:691210. [PMID: 34123879 PMCID: PMC8188986 DOI: 10.3389/fcimb.2021.691210] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 05/04/2021] [Indexed: 12/12/2022] Open
Abstract
Urinary tract infections (UTIs) are among the most common infectious diseases worldwide but are significantly understudied. Uropathogenic E. coli (UPEC) accounts for a significant proportion of UTI, but a large number of other species can infect the urinary tract, each of which will have unique host-pathogen interactions with the bladder environment. Given the substantial economic burden of UTI and its increasing antibiotic resistance, there is an urgent need to better understand UTI pathophysiology - especially its tendency to relapse and recur. Most models developed to date use murine infection; few human-relevant models exist. Of these, the majority of in vitro UTI models have utilized cells in static culture, but UTI needs to be studied in the context of the unique aspects of the bladder's biophysical environment (e.g., tissue architecture, urine, fluid flow, and stretch). In this review, we summarize the complexities of recurrent UTI, critically assess current infection models and discuss potential improvements. More advanced human cell-based in vitro models have the potential to enable a better understanding of the etiology of UTI disease and to provide a complementary platform alongside animals for drug screening and the search for better treatments.
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Affiliation(s)
- Benjamin O. Murray
- Centre for Urological Biology, Department of Renal Medicine, University College London, London, United Kingdom
| | - Carlos Flores
- Centre for Urological Biology, Department of Renal Medicine, University College London, London, United Kingdom
| | - Corin Williams
- Department of Bioengineering, Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Deborah A. Flusberg
- Department of Bioengineering, Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Elizabeth E. Marr
- Department of Bioengineering, Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Karolina M. Kwiatkowska
- Centre for Urological Biology, Department of Renal Medicine, University College London, London, United Kingdom
| | - Joseph L. Charest
- Department of Bioengineering, Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Brett C. Isenberg
- Department of Bioengineering, Charles Stark Draper Laboratory, Inc., Cambridge, MA, United States
| | - Jennifer L. Rohn
- Centre for Urological Biology, Department of Renal Medicine, University College London, London, United Kingdom
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3
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Mousavi S, Bereswill S, Heimesaat MM. Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections. Curr Top Microbiol Immunol 2021; 431:233-263. [PMID: 33620654 DOI: 10.1007/978-3-030-65481-8_9] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.
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Affiliation(s)
- Soraya Mousavi
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany
| | - Stefan Bereswill
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany
| | - Markus M Heimesaat
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany.
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4
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Anderson JA, Loes AN, Waddell GL, Harms MJ. Tracing the evolution of novel features of human Toll-like receptor 4. Protein Sci 2019; 28:1350-1358. [PMID: 31075178 PMCID: PMC6566505 DOI: 10.1002/pro.3644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/07/2019] [Accepted: 05/08/2019] [Indexed: 12/13/2022]
Abstract
Toll-like receptor 4 (TLR4) is a critical innate immune protein that activates inflammation in response to extracellular cues. Much of the work to understand how the protein works in humans has been done using mouse models. Although human and mouse TLR4 have many shared features, they have also diverged significantly since their last common ancestor, acquiring 277 sequence differences. Functional differences include the extent of ligand-independent activation, whether lipid IVa acts as an antagonist or agonist, and the relative species cross-compatibility of their MD-2 cofactor. We set out to understand the evolutionary origins for these functional differences between human and mouse TLR4. Using a combination of phylogenetics, ancestral sequence reconstruction, and functional characterization, we found that evolutionary changes to the human TLR4, rather than changes to the mouse TLR4, were largely responsible for these functional changes. Human TLR4 repressed ancestral ligand-independent activity and gained antagonism to lipid IVa. Additionally, mutations to the human TLR4 cofactor MD-2 led to lineage-specific incompatibility between human and opossum TLR4 complex members. These results were surprising, as mouse TLR4 has acquired many more mutations than human TLR4 since their last common ancestor. Our work has polarized this set of transitions and sets up work to study the mechanistic underpinnings for the evolution of new functions in TLR4.
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Affiliation(s)
- Jeremy A. Anderson
- Institute for Molecular Biology, University of OregonEugeneOregon97403
- Department of Chemistry and BiochemistryUniversity of OregonEugeneOregon97403
| | - Andrea N. Loes
- Institute for Molecular Biology, University of OregonEugeneOregon97403
- Department of Chemistry and BiochemistryUniversity of OregonEugeneOregon97403
| | - Grace L. Waddell
- Institute for Molecular Biology, University of OregonEugeneOregon97403
- Department of Chemistry and BiochemistryUniversity of OregonEugeneOregon97403
| | - Michael J. Harms
- Institute for Molecular Biology, University of OregonEugeneOregon97403
- Department of Chemistry and BiochemistryUniversity of OregonEugeneOregon97403
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5
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A Thermodynamic Funnel Drives Bacterial Lipopolysaccharide Transfer in the TLR4 Pathway. Structure 2018; 26:1151-1161.e4. [DOI: 10.1016/j.str.2018.04.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 12/29/2017] [Accepted: 04/10/2018] [Indexed: 12/21/2022]
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6
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Abstract
In humans and other mammals, recognition of endotoxins—abundant surface lipopolysaccharides (LPS) of Gram-negative bacteria—provides a potent stimulus for induction of inflammation and mobilization of host defenses. The structurally unique lipid A region of LPS is the principal determinant of this pro-inflammatory activity. This region of LPS is normally buried within the bacterial outer membrane and aggregates of purified LPS, making even more remarkable its picomolar potency and the ability of discrete variations in lipid A structure to markedly alter the pro-inflammatory activity of LPS. Two recognition systems—MD-2/TLR4 and “LPS-sensing” cytosolic caspases—together confer LPS responsiveness at the host cell surface, within endosomes, and at sites physically accessible to the cytosol. Understanding how the lipid A of LPS is delivered and recognized at these diverse sites is crucial to understanding how the magnitude and character of the inflammatory responses are regulated.
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Affiliation(s)
- Jerrold Weiss
- Inflammation Program and Departments of Internal Medicine and Microbiology, University of Iowa, Iowa City, Iowa, USA.,Veterans Affairs Medical Center, Iowa City, Iowa, USA
| | - Jason Barker
- Inflammation Program and Departments of Internal Medicine and Microbiology, University of Iowa, Iowa City, Iowa, USA.,Veterans Affairs Medical Center, Iowa City, Iowa, USA
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7
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Loes AN, Bridgham JT, Harms MJ. Coevolution of the Toll-Like Receptor 4 Complex with Calgranulins and Lipopolysaccharide. Front Immunol 2018. [PMID: 29515592 PMCID: PMC5826337 DOI: 10.3389/fimmu.2018.00304] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Toll-like receptor 4 (TLR4) induces inflammation in response to both pathogen- and host-derived molecules. Lipopolysaccharide (LPS) recognition by TLR4 has been shown to occur across the amniotes, but endogenous signaling through TLR4 has not been validated outside of placental mammals. To determine whether endogenous danger signaling is also shared across amniotes, we studied the evolution of TLR4-activation by the calgranulin proteins (S100A8, S100A9, and S100A12), a clade of host molecules that potently activate TLR4 in placental mammals. We performed phylogenetic and syntenic analysis and found MRP-126—a gene in birds and reptiles—is likely orthologous to the mammalian calgranulins. We then used an ex vivo TLR4 activation assay to establish that calgranulin pro-inflammatory activity is not specific to placental mammals, but is also exhibited by representative marsupial and sauropsid species. This activity is strongly dependent on the cofactors CD14 and MD-2 for all species studied, suggesting a conserved mode of activation across the amniotes. Ortholog complementation experiments between the calgranulins, TLR4, CD14, and MD-2 revealed extensive lineage specific-coevolution and multi-way interactions between components that are necessary for the activation of NF-κB signaling by calgranulins and LPS. Our work demonstrates that calgranulin activation of TLR4 evolved at least ~320 million years ago and has been conserved in the amniote innate immune system.
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Affiliation(s)
- Andrea N Loes
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, United States.,Institute of Molecular Biology, University of Oregon, Eugene, OR, United States
| | - Jamie T Bridgham
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR, United States
| | - Michael J Harms
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR, United States.,Institute of Molecular Biology, University of Oregon, Eugene, OR, United States
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8
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Al-Anazi MR, Nazir N, Abdo AA, Sanai FM, Alkahtani S, Alarifi S, Alkahtane AA, Al-Yahya H, Ali D, Alessia MS, Al-Ahdal MN, Al-Qahtani AA. Genetic variations of NOD2 and MD2 genes in hepatitis B virus infection. Saudi J Biol Sci 2016; 26:270-280. [PMID: 31485165 PMCID: PMC6717085 DOI: 10.1016/j.sjbs.2016.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 11/09/2016] [Accepted: 11/09/2016] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVES Nucleotide oligomerization domain 2 (NOD2) and myeloid differentiation protein 2 (MD-2) have crucial roles in the innate immune system. NOD2 is a member of the NOD-like receptor (NLR) family of pattern recognition receptors (PRRs), while MD-2 is a co-receptor for Toll-like receptor 4 (TLR4), which comprises another group of PRRs. Genetic variations in the NOD2 and MD-2 genes may be susceptibility factors to viral pathogens including hepatitis B virus (HBV). We investigated whether polymorphisms at NOD2 (rs2066845 and rs2066844) or at MD-2 (rs6472812 and rs11466004) were associated with susceptibility to HBV infection and advancement to related liver complications in a Saudi Arabian population. Methods: A total of 786 HBV-infected patients and 600 healthy uninfected controls were analyzed in the present study. HBV-infected patients were categorized into three groups based on the clinical stage of the infection: inactive HBV carriers, active HBV carriers, and patients with liver cirrhosis + hepatocellular carcinoma (HCC). Results: All four SNPs were significantly associated with susceptibility to HBV infection although none of the SNPs tested in NOD2 and MD-2 were significantly associated with persistence of HBV infection. We found that HBV-infected patients that were homozygous CC for rs2066845 in the NOD2 gene were at a significantly increased risk of progression to HBV-related liver complications (Odds Ratio = 7.443 and P = 0.044). Furthermore, haplotype analysis found that the rs2066844-rs2066845 C-G and T-G haplotypes at the NOD2 gene and four rs6472812-rs11466004 haplotypes (G-C, G-T, A-C, and A-T) at the MD-2 gene were significantly associated with HBV infection in the affected cohort compared to those found in our control group. Conclusion: We found that the single nucleotide polymorphisms rs2066844 and rs2066845 at NOD2 and rs6472812 and rs11466004 at MD-2 were associated with susceptibility to HBV infection in a Saudi population.
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Affiliation(s)
- Mashael R Al-Anazi
- Department of Infection and Immunity, Research Center, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Nyla Nazir
- Department of Infection and Immunity, Research Center, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia
| | - Ayman A Abdo
- Section of Gastroenterology, Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.,Liver Disease Research Center, King Saud University, Riyadh, Saudi Arabia
| | - Faisal M Sanai
- Gastroenterology Unit, Department of Medicine, King Abdulaziz Medical City, Jeddah, Saudi Arabia.,Liver Disease Research Center, King Saud University, Riyadh, Saudi Arabia
| | - Saad Alkahtani
- Department of Zoology, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Saud Alarifi
- Department of Zoology, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Abdullah A Alkahtane
- Department of Zoology, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Hamad Al-Yahya
- Department of Zoology, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Daoud Ali
- Department of Zoology, Science College, King Saud University, Riyadh, Saudi Arabia
| | - Mohammed S Alessia
- Department of Biology, Science College, AI-Imam Muhammad Ibn Saud Islamic University, Riyadh, Saudi Arabia
| | - Mohammed N Al-Ahdal
- Department of Infection and Immunity, Research Center, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia.,Department of Microbiology and Immunology, Alfaisal University School of Medicine, Riyadh, Saudi Arabia
| | - Ahmed A Al-Qahtani
- Department of Infection and Immunity, Research Center, King Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia.,Department of Microbiology and Immunology, Alfaisal University School of Medicine, Riyadh, Saudi Arabia
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9
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Vašl J, Oblak A, Peternelj TT, Klett J, Martín-Santamaría S, Gioannini TL, Weiss JP, Jerala R. Molecular Basis of the Functional Differences between Soluble Human Versus Murine MD-2: Role of Val135 in Transfer of Lipopolysaccharide from CD14 to MD-2. THE JOURNAL OF IMMUNOLOGY 2016; 196:2309-18. [PMID: 26826249 DOI: 10.4049/jimmunol.1502074] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 12/26/2015] [Indexed: 11/19/2022]
Abstract
Myeloid differentiation factor 2 (MD-2) is an extracellular protein, associated with the ectodomain of TLR4, that plays a critical role in the recognition of bacterial LPS. Despite high overall structural and functional similarity, human (h) and murine (m) MD-2 exhibit several species-related differences. hMD-2 is capable of binding LPS in the absence of TLR4, whereas mMD-2 supports LPS responsiveness only when mMD-2 and mTLR4 are coexpressed in the same cell. Previously, charged residues at the edge of the LPS binding pocket have been attributed to this difference. In this study, site-directed mutagenesis was used to explore the hydrophobic residues within the MD-2 binding pocket as the source of functional differences between hMD-2 and mMD-2. Whereas decreased hydrophobicity of residues 61 and 63 in the hMD-2 binding pocket retained the characteristics of wild-type hMD-2, a relatively minor change of valine to alanine at position 135 completely abolished the binding of LPS to the hMD-2 mutant. The mutant, however, retained the LPS binding in complex with TLR4 and also cell activation, resulting in a murine-like phenotype. These results were supported by the molecular dynamics simulation. We propose that the residue at position 135 of MD-2 governs the dynamics of the binding pocket and its ability to accommodate lipid A, which is allosterically affected by bound TLR4.
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Affiliation(s)
- Jožica Vašl
- Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia
| | - Alja Oblak
- Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia
| | - Tina T Peternelj
- Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia
| | - Javier Klett
- Center for Biological Research, Superior Council for Scientific Research, 28040 Madrid, Spain
| | | | - Theresa L Gioannini
- Inflammation Program, Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52241; Veterans Affairs Medical Center, Iowa City, IA 52246; and
| | - Jerrold P Weiss
- Inflammation Program, Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52241
| | - Roman Jerala
- Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia; Excellent Nuclear Magnetic Resonance-Future Innovation for Sustainable Technologies Center of Excellence, 1000 Ljubljana, Slovenia
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10
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Paramo T, Tomasio SM, Irvine KL, Bryant CE, Bond PJ. Energetics of Endotoxin Recognition in the Toll-Like Receptor 4 Innate Immune Response. Sci Rep 2015; 5:17997. [PMID: 26647780 PMCID: PMC4673606 DOI: 10.1038/srep17997] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/12/2015] [Indexed: 01/08/2023] Open
Abstract
Bacterial outer membrane lipopolysaccharide (LPS) potently stimulates the mammalian innate immune system, and can lead to sepsis, the primary cause of death from infections. LPS is sensed by Toll-like receptor 4 (TLR4) in complex with its lipid-binding coreceptor MD-2, but subtle structural variations in LPS can profoundly modulate the response. To better understand the mechanism of LPS-induced stimulation and bacterial evasion, we have calculated the binding affinity to MD-2 of agonistic and antagonistic LPS variants including lipid A, lipid IVa, and synthetic antagonist Eritoran, and provide evidence that the coreceptor is a molecular switch that undergoes ligand-induced conformational changes to appropriately activate or inhibit the receptor complex. The plasticity of the coreceptor binding cavity is shown to be essential for distinguishing between ligands, whilst similar calculations for a model bacterial LPS bilayer reveal the "membrane-like" nature of the protein cavity. The ability to predict the activity of LPS variants should facilitate the rational design of TLR4 therapeutics.
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Affiliation(s)
- Teresa Paramo
- Unilever Centre for Molecular Science Informatics, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Susana M. Tomasio
- Unilever Centre for Molecular Science Informatics, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
- Current Address: Cresset Biomolecular Discovery, New Cambridge House, Bassingbourn Road, Litlington SG8 0SS, UK
| | - Kate L. Irvine
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - Clare E. Bryant
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK
| | - Peter J. Bond
- Bioinformatics Institute (A*STAR), 30 Biopolis Str, #07-01 Matrix, Singapore 138671
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, 117543 Singapore
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11
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Manček-Keber M, Jerala R. Postulates for validating TLR4 agonists. Eur J Immunol 2015; 45:356-70. [DOI: 10.1002/eji.201444462] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 10/20/2014] [Accepted: 12/01/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Mateja Manček-Keber
- Department of Biotechnology; National Institute of Chemistry; Ljubljana Slovenia
- EN-FIST Centre of Excellence; Ljubljana Slovenia
| | - Roman Jerala
- Department of Biotechnology; National Institute of Chemistry; Ljubljana Slovenia
- EN-FIST Centre of Excellence; Ljubljana Slovenia
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12
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Human coagulation factor X-adenovirus type 5 complexes poorly stimulate an innate immune response in human mononuclear phagocytes. J Virol 2014; 89:2884-91. [PMID: 25540380 DOI: 10.1128/jvi.03576-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
UNLABELLED One of the first lines of host defense against many viruses in vertebrates is the innate immune system, which detects pathogen-associated molecular patterns (PAMPs) using pathogen recognition receptors (PRR). The dynamic interactions between pathogens and hosts create, in some cases, species-specific relationships. Recently, it was shown that murine factor X (mFX)-armored human adenovirus (HAd) stimulated a mFX-Toll-like receptor 4 (TLR4)-associated response in mouse macrophages in vitro and in vivo. Given the importance of studies using animals to better understand host-pathogen interactions, we asked if human FX (hFX)-armored HAd type 5 (HAd5) was capable of activating innate immune sensors in primary human mononuclear phagocytes. To this end, we assayed human mononuclear phagocytes for their ability to be stimulated by hFX-armored HAd5 via a TLR/NF-κB pathway, in particular, a TLR4 pathway. In our hands, we found no significant interaction, activation, or maturation of human mononuclear phagocytes caused by the presence of hFX-armored HAd5. IMPORTANCE Animals, and mice in particular, are often used as informative and powerful surrogates for how pathogens interact with natural host systems. When possible, extended and targeted studies in the natural host can then be performed. Our data will help us understand the differences in preclinical testing in mice and clinical use in humans in order to improve treatment for HAd diseases and Ad vector effectiveness.
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Species-specific activation of TLR4 by hypoacylated endotoxins governed by residues 82 and 122 of MD-2. PLoS One 2014; 9:e107520. [PMID: 25203747 PMCID: PMC4159346 DOI: 10.1371/journal.pone.0107520] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 08/19/2014] [Indexed: 11/20/2022] Open
Abstract
The Toll-like receptor 4/MD-2 receptor complex recognizes endotoxin, a Gram-negative bacterial cell envelope component. Recognition of the most potent hexaacylated form of endotoxin is mediated by the sixth acyl chain that protrudes from the MD-2 hydrophobic pocket and bridges TLR4/MD-2 to the neighboring TLR4 ectodomain, driving receptor dimerization via hydrophobic interactions. In hypoacylated endotoxins all acyl chains could be accommodated within the binding pocket of the human hMD-2. Nevertheless, tetra- and pentaacylated endotoxins activate the TLR4/MD-2 receptor of several species. We observed that amino acid residues 82 and 122, located at the entrance to the endotoxin binding site of MD-2, have major influence on the species-specific endotoxin recognition. We show that substitution of hMD-2 residue V82 with an amino acid residue with a bulkier hydrophobic side chain enables activation of TLR4/MD-2 by pentaacylated and tetraacylated endotoxins. Interaction of the lipid A phosphate group with the amino acid residue 122 of MD-2 facilitates the appropriate positioning of the hypoacylated endotoxin. Moreover, mouse TLR4 contributes to the agonistic effect of pentaacylated msbB endotoxin. We propose a molecular model that explains how the molecular differences between the murine or equine MD-2, which both have sufficiently large hydrophobic pockets to accommodate all five or four acyl chains, influence the positioning of endotoxin so that one of the acyl chains remains outside the pocket and enables hydrophobic interactions with TLR4, leading to receptor activation.
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14
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The molecular mechanism of species-specific recognition of lipopolysaccharides by the MD-2/TLR4 receptor complex. Mol Immunol 2014; 63:134-42. [PMID: 25037631 DOI: 10.1016/j.molimm.2014.06.034] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/20/2014] [Accepted: 06/25/2014] [Indexed: 01/17/2023]
Abstract
Lipid A, a component of bacterial lipopolysaccharide, is a conserved microbe-associated molecular pattern that activates the MD-2/TLR4 receptor complex. Nevertheless, bacteria produce lipid A molecules of considerable structural diversity. The human MD-2/TLR4 receptor most efficiently recognizes hexaacylated bisphosphorylated lipid A produced by enterobacteria, but in some animal species the immune response can be elicited also by alternative lipid A varieties, such as tetraacylated lipid IVa or pentaacylated lipid A of Rhodobacter spheroides. Several crystal structures revealed that hexaacylated lipid A and tetraacylated lipid IVa activate the murine MD-2/TLR4 in a similar manner, but failed to explain the antagonistic vs. agonistic activity of lipid IVa in the human vs. equine receptor, respectively. Targeted mutagenesis studies of the receptor complex revealed intricate combination of electrostatic and hydrophobic interactions primarily within the MD-2 co-receptor, but with a contribution of TLR4 as well, that contribute to species-specific recognition of lipid A. We will review current knowledge regarding lipid A diversity and species-specific activation of the MD-2/TLR4 receptor complex in different species (e.g. human, mouse or equine) by lipid A varieties.
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15
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Vaure C, Liu Y. A comparative review of toll-like receptor 4 expression and functionality in different animal species. Front Immunol 2014; 5:316. [PMID: 25071777 PMCID: PMC4090903 DOI: 10.3389/fimmu.2014.00316] [Citation(s) in RCA: 573] [Impact Index Per Article: 57.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 06/23/2014] [Indexed: 01/16/2023] Open
Abstract
Toll-like receptors (TLRs) belong to the pattern recognition receptor (PRR) family, a key component of the innate immune system. TLRs detect invading pathogens and initiate an immediate immune response to them, followed by a long-lasting adaptive immune response. Activation of TLRs leads to the synthesis of pro-inflammatory cytokines and chemokines and the expression of co-stimulatory molecules. TLR4 specifically recognizes bacterial lipopolysaccharide, along with several other components of pathogens and endogenous molecules produced during abnormal situations, such as tissue damage. Evolution across species can lead to substantial diversity in the TLR4’s affinity and specificity to its ligands, the TLR4 gene and cellular expression patterns and tissue distribution. Consequently, TLR4 functions vary across different species. In recent years, the use of synthetic TLR agonists as adjuvants has emerged as a realistic therapeutic goal, notably for the development of vaccines against poorly immunogenic targets. Given that an adjuvanted vaccine must be assessed in pre-clinical animal models before being tested in humans, the extent to which an animal model represents and predicts the human condition is of particular importance. This review focuses on the current knowledge on the critical points of divergence between human and the mammalian species commonly used in vaccine research and development (non-human primate, mouse, rat, rabbit, swine, and dog), in terms of molecular, cellular, and functional properties of TLR4.
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Affiliation(s)
- Céline Vaure
- Research Department, Sanofi Pasteur , Marcy L'Etoile , France
| | - Yuanqing Liu
- Research Department, Sanofi Pasteur , Marcy L'Etoile , France
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16
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Zähringer U, Ittig S, Lindner B, Moll H, Schombel U, Gisch N, Cornelis GR. NMR-based structural analysis of the complete rough-type lipopolysaccharide isolated from Capnocytophaga canimorsus. J Biol Chem 2014; 289:23963-76. [PMID: 24993825 DOI: 10.1074/jbc.m114.571489] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We here describe the NMR analysis of an intact lipopolysaccharide (LPS, endotoxin) in water with 1,2-dihexanoyl-sn-glycero-3-phosphocholine as detergent. When HPLC-purified rough-type LPS of Capnocytophaga canimorsus was prepared, (13)C,(15)N labeling could be avoided. The intact LPS was analyzed by homonuclear ((1)H) and heteronuclear ((1)H,(13)C, and (1)H,(31)P) correlated one- and two-dimensional NMR techniques as well as by mass spectrometry. It consists of a penta-acylated lipid A with an α-linked phosphoethanolamine attached to C-1 of GlcN (I) in the hybrid backbone, lacking the 4'-phosphate. The hydrophilic core oligosaccharide was found to be a complex hexasaccharide with two mannose (Man) and one each of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo), Gal, GalN, and l-rhamnose residues. Position 4 of Kdo is substituted by phosphoethanolamine, also present in position 6 of the branched Man(I) residue. This rough-type LPS is exceptional in that all three negative phosphate residues are "masked" by positively charged ethanolamine substituents, leading to an overall zero net charge, which has so far not been observed for any other LPS. In biological assays, the corresponding isolated lipid A was found to be endotoxically almost inactive. By contrast, the intact rough-type LPS described here expressed a 20,000-fold increased endotoxicity, indicating that the core oligosaccharide significantly contributes to the endotoxic potency of the whole rough-type C. canimorsus LPS molecule. Based on these findings, the strict view that lipid A alone represents the toxic center of LPS needs to be reassessed.
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Affiliation(s)
- Ulrich Zähringer
- From the Division of Immunochemistry/Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 4a, 23845 Borstel, Germany,
| | - Simon Ittig
- Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland, and
| | - Buko Lindner
- From the Division of Immunochemistry/Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 4a, 23845 Borstel, Germany
| | - Hermann Moll
- From the Division of Immunochemistry/Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 4a, 23845 Borstel, Germany
| | - Ursula Schombel
- From the Division of Immunochemistry/Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 4a, 23845 Borstel, Germany
| | - Nicolas Gisch
- From the Division of Immunochemistry/Bioanalytical Chemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 4a, 23845 Borstel, Germany
| | - Guy R Cornelis
- Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland, and the Department of Biology, University of Namur, B5000 Namur, Belgium
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17
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Tan Y, Kagan JC. A cross-disciplinary perspective on the innate immune responses to bacterial lipopolysaccharide. Mol Cell 2014; 54:212-23. [PMID: 24766885 DOI: 10.1016/j.molcel.2014.03.012] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The study of innate immunity to bacteria has focused heavily on the mechanisms by which mammalian cells detect lipopolysaccharide (LPS), the conserved surface component of Gram-negative bacteria. While Toll-like receptor 4 (TLR4) is responsible for all the host transcriptional responses to LPS, recent discoveries have revealed the existence of several TLR4-independent responses to LPS. These discoveries not only broaden our view of the means by which mammalian cells interact with bacteria, but they also highlight new selective pressures that may have promoted the evolution of bacterial immune evasion strategies. In this review, we highlight past and recent discoveries on host LPS sensing mechanisms and discuss bacterial countermeasures that promote infection. By looking at both sides of the host-pathogen interaction equation, we hope to provide comprehensive insights into host defense mechanisms and bacterial pathogenesis.
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Affiliation(s)
- Yunhao Tan
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Jonathan C Kagan
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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18
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Chan M, Hayashi T, Mathewson RD, Nour A, Hayashi Y, Yao S, Tawatao RI, Crain B, Tsigelny IF, Kouznetsova VL, Messer K, Pu M, Corr M, Carson DA, Cottam HB. Identification of substituted pyrimido[5,4-b]indoles as selective Toll-like receptor 4 ligands. J Med Chem 2013; 56:4206-23. [PMID: 23656327 PMCID: PMC3722616 DOI: 10.1021/jm301694x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
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A cell-based
high-throughput screen to identify small molecular
weight stimulators of the innate immune system revealed substituted
pyrimido[5,4-b]indoles as potent NFκB activators.
The most potent hit compound selectively stimulated Toll-like receptor
4 (TLR4) in human and mouse cells. Synthetic modifications of the
pyrimido[5,4-b]indole scaffold at the carboxamide,
N-3, and N-5 positions revealed differential TLR4 dependent production
of NFκB and type I interferon associated cytokines, IL-6 and
interferon γ-induced protein 10 (IP-10) respectively. Specifically,
a subset of compounds bearing phenyl and substituted phenyl carboxamides
induced lower IL-6 release while maintaining higher IP-10 production,
skewing toward the type I interferon pathway. Substitution at N-5
with short alkyl substituents reduced the cytotoxicity of the leading
hit compound. Computational studies supported that active compounds
appeared to bind primarily to MD-2 in the TLR4/MD-2 complex. These
small molecules, which stimulate innate immune cells with minimal
toxicity, could potentially be used as adjuvants or immune modulators.
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Affiliation(s)
- Michael Chan
- Moores Cancer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0695, USA
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Teghanemt A, Weiss JP, Gioannini TL. Radioiodination of an endotoxin·MD-2 complex generates a novel sensitive, high-affinity ligand for TLR4. Innate Immun 2013; 19:545-60. [PMID: 23439691 DOI: 10.1177/1753425913475688] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A purified complex of metabolically labeled [(3)H]lipooligosaccharide (LOS) and recombinant human myeloid differentiation factor 2 (MD-2), [(3)H]LOS·MD-2, has been used to demonstrate pM affinity binding interactions with soluble TLR4 ectodomain (TLR4ecd). For measurement of the binding parameters of membrane-bound TLR4, we took advantage of the stability of endotoxin·MD-2 and tyrosine(s) present on the surface of MD-2 to radioiodinate LOS·MD-2. Radioiodinated LOS·MD-2 generated a reagent with an estimated 1:1 molar ratio of [(125)I] to sMD-2 with 20-fold higher specific radioactivity and TLR4-activating properties comparable to metabolically-labeled LOS·MD-2. LOS·MD-2[(125)I] and [(3)H]LOS·MD-2 have similar affinities for soluble (FLAG) TLR4ecd and for membrane-bound TLR4 in HEK293T/TLR4 cells. In a similar dose-dependent manner, sMD-2 and LOS·MD-2 inhibit LOS·MD-2[(125)I] binding to TLR4 indicating the pM affinity binding of LOS·MD-2[(125)I] is agonist-independent. LOS·MD-2[(125)I] allowed measurement of low levels of cell-surface human or murine TLR4 expressed by stable cell lines (2000-3000 sites/cell) and quantitatively measures low levels of 'MD-2-free' TLR4 (est. 250 molecules/cell) in cells co-expressing TLR4 and MD-2. Occupation of 50-100 TLR4/cell by LOS·MD-2 is sufficient to trigger measurable TLR4-dependent cell activation. LOS·MD-2[(125)I] provides a powerful reagent to measure quantitatively functional human and murine cell-surface TLR4, including in cells where surface TLR4 is potentially functionally significant but not detectable by other methods.
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Affiliation(s)
- Athmane Teghanemt
- 1Inflammation Program, Department of Internal Medicine, Roy A. and Lucille J. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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Bowen WS, Gandhapudi SK, Kolb JP, Mitchell TC. Immunopharmacology of Lipid A Mimetics. ADVANCES IN PHARMACOLOGY 2013; 66:81-128. [DOI: 10.1016/b978-0-12-404717-4.00003-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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21
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Structural basis of species-specific endotoxin sensing by innate immune receptor TLR4/MD-2. Proc Natl Acad Sci U S A 2012; 109:7421-6. [PMID: 22532668 DOI: 10.1073/pnas.1201193109] [Citation(s) in RCA: 260] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lipopolysaccharide (LPS), also known as endotoxin, activates the innate immune response through toll-like receptor 4 (TLR4) and its coreceptor, MD-2. MD-2 has a unique hydrophobic cavity that directly binds to lipid A, the active center of LPS. Tetraacylated lipid IVa, a synthetic lipid A precursor, acts as a weak agonist to mouse TLR4/MD-2, but as an antagonist to human TLR4/MD-2. However, it remains unclear as to how LPS and lipid IVa show agonistic or antagonistic activities in a species-specific manner. The present study reports the crystal structures of mouse TLR4/MD-2/LPS and TLR4/MD-2/lipid IVa complexes at 2.5 and 2.7 Å resolutions, respectively. Mouse TLR4/MD-2/LPS exhibited an agonistic "m"-shaped 2:2:2 complex similar to the human TLR4/MD-2/LPS complex. Mouse TLR4/MD-2/lipid IVa complex also showed an agonistic structural feature, exhibiting architecture similar to the 2:2:2 complex. Remarkably, lipid IVa in the mouse TLR4/MD-2 complex occupied nearly the same space as LPS, although lipid IVa lacked the two acyl chains. Human MD-2 binds lipid IVa in an antagonistic manner completely differently from the way mouse MD-2 does. Together, the results provide structural evidence of the agonistic property of lipid IVa on mouse TLR4/MD-2 and deepen understanding of the ligand binding and dimerization mechanism by the structurally diverse LPS variants.
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22
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Crystal structure of soluble MD-1 and its interaction with lipid IVa. Proc Natl Acad Sci U S A 2010; 107:10990-5. [PMID: 20534476 DOI: 10.1073/pnas.1004153107] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Lipopolysaccharide (LPS) of Gram-negative bacteria is a common pathogen-associated molecular pattern (PAMP) that induces potent innate immune responses. The host immune response against LPS is triggered by myeloid differentiation factor 2 (MD-2) in association with Toll-like receptor 4 (TLR4) on the cell surface. The MD-2/TLR4-mediated LPS response is regulated by the evolutionarily related complex of MD-1 and Toll-like receptor homolog RP105. Here, we report crystallographic and biophysical data that demonstrate a previously unidentified direct interaction of MD-1 with LPS. The crystal structure of chicken MD-1 (cMD-1) at 2.0 A resolution exhibits a beta-cup-like fold, similar to MD-2, that encloses a hydrophobic cavity between the two beta-sheets. A lipid-like moiety was observed inside the cavity, suggesting the possibility of a direct MD-1/LPS interaction. LPS was subsequently identified as an MD-1 ligand by native gel electrophoresis and gel filtration analyses. The crystal structure of cMD-1 with lipid IVa, an LPS precursor, at 2.4 A resolution revealed that the lipid inserts into the deep hydrophobic cavity of the beta-cup-like structure, but with some important differences compared with MD-2. These findings suggest that soluble MD-1 alone, in addition to its complex with RP105, can regulate host LPS sensitivity.
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23
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Prohinar P, Rallabhandi P, Weiss JP, Gioannini TL. Expression of functional D299G.T399I polymorphic variant of TLR4 depends more on coexpression of MD-2 than does wild-type TLR4. THE JOURNAL OF IMMUNOLOGY 2010; 184:4362-7. [PMID: 20212095 DOI: 10.4049/jimmunol.0903142] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Two missense variants (D299G and T399I) of TLR4 are cosegregated in individuals of European descent and, in a number of test systems, result in reduced responsiveness to endotoxin. How these changes within the ectodomain (ecd) of TLR4 affect TLR4 function is unclear. For both wild-type and D299G.T399I TLR4, we used endotoxinCD14 and endotoxinMD-2 complexes of high specific radioactivity to measure: 1) interaction of recombinant MD-2TLR4 with endotoxinCD14 and TLR4 with endotoxinMD-2; 2) expression of functional MD-2TLR4 and TLR4; and 3) MD-2TLR4 and TLR4-dependent cellular endotoxin responsiveness. Both wild-type and D299G.T399I TLR4(ecd) demonstrated high affinity (K(d) approximately 200 pM) interaction of endotoxinCD14 with MD-2TLR4(ecd) and endotoxinMD-2 with TLR4(ecd). However, levels of functional TLR4 were reduced up to 2-fold when D299G.T399I TLR4 was coexpressed with MD-2 and >10-fold when expressed without MD-2, paralleling differences in cellular endotoxin responsiveness. The dramatic effect of the D299G.T399I haplotype on expression of functional TLR4 without MD-2 suggests that cells expressing TLR4 without MD-2 are most affected by these polymorphisms.
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Affiliation(s)
- Polonca Prohinar
- Department of Internal Medicine, Roy A and Lucille J Carver College of Medicine, University of Iowa, Iowa City, IA 52240, USA
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