1
|
Jastrab JB, Kagan JC. Strategies of bacterial detection by inflammasomes. Cell Chem Biol 2024; 31:835-850. [PMID: 38636521 PMCID: PMC11103797 DOI: 10.1016/j.chembiol.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/09/2024] [Accepted: 03/26/2024] [Indexed: 04/20/2024]
Abstract
Mammalian innate immunity is regulated by pattern-recognition receptors (PRRs) and guard proteins, which use distinct strategies to detect infections. PRRs detect bacterial molecules directly, whereas guards detect host cell manipulations by microbial virulence factors. Despite sensing infection through different mechanisms, both classes of innate immune sensors can activate the inflammasome, an immune complex that can mediate cell death and inflammation. Inflammasome-mediated immune responses are crucial for host defense against many bacterial pathogens and prevent invasion by non-pathogenic organisms. In this review, we discuss the mechanisms by which inflammasomes are stimulated by PRRs and guards during bacterial infection, and the strategies used by virulent bacteria to evade inflammasome-mediated immunity.
Collapse
Affiliation(s)
- Jordan B Jastrab
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Division of Infectious Diseases, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Jonathan C Kagan
- Division of Gastroenterology, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
2
|
Chou WC, Jha S, Linhoff MW, Ting JPY. The NLR gene family: from discovery to present day. Nat Rev Immunol 2023; 23:635-654. [PMID: 36973360 PMCID: PMC11171412 DOI: 10.1038/s41577-023-00849-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2023] [Indexed: 03/29/2023]
Abstract
The mammalian NLR gene family was first reported over 20 years ago, although several genes that were later grouped into the family were already known at that time. Although it is widely known that NLRs include inflammasome receptors and/or sensors that promote the maturation of caspase 1, IL-1β, IL-18 and gasdermin D to drive inflammation and cell death, the other functions of NLR family members are less well appreciated by the scientific community. Examples include MHC class II transactivator (CIITA), a master transcriptional activator of MHC class II genes, which was the first mammalian NBD-LRR-containing protein to be identified, and NLRC5, which regulates the expression of MHC class I genes. Other NLRs govern key inflammatory signalling pathways or interferon responses, and several NLR family members serve as negative regulators of innate immune responses. Multiple NLRs regulate the balance of cell death, cell survival, autophagy, mitophagy and even cellular metabolism. Perhaps the least discussed group of NLRs are those with functions in the mammalian reproductive system. The focus of this Review is to provide a synopsis of the NLR family, including both the intensively studied and the underappreciated members. We focus on the function, structure and disease relevance of NLRs and highlight issues that have received less attention in the NLR field. We hope this may serve as an impetus for future research on the conventional and non-conventional roles of NLRs within and beyond the immune system.
Collapse
Affiliation(s)
- Wei-Chun Chou
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sushmita Jha
- Department of Bioscience and Bioengineering, Indian Institute of Technology Jodhpur, Jodhpur, India
| | - Michael W Linhoff
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Jenny P-Y Ting
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| |
Collapse
|
3
|
Ouyang W, Xie T, Fang H, Frucht DM. Development of a New Cell-Based AP-1 Gene Reporter Potency Assay for Anti-Anthrax Toxin Therapeutics. Toxins (Basel) 2023; 15:528. [PMID: 37755954 PMCID: PMC10538138 DOI: 10.3390/toxins15090528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/18/2023] [Accepted: 08/24/2023] [Indexed: 09/28/2023] Open
Abstract
Anthrax toxin is a critical virulence factor of Bacillus anthracis. The toxin comprises protective antigen (PA) and two enzymatic moieties, edema factor (EF) and lethal factor (LF), forming bipartite lethal toxin (LT) and edema toxin (ET). PA binds cellular surface receptors and is required for intracellular translocation of the enzymatic moieties. For this reason, anti-PA antibodies have been developed as therapeutics for prophylaxis and treatment of human anthrax infection. Assays described publicly for the control of anti-PA antibody potency quantify inhibition of LT-mediated cell death or the ET-induced increase in c-AMP levels. These assays do not fully reflect and/or capture the pathological functions of anthrax toxin in humans. Herein, we report the development of a cell-based gene reporter potency assay for anti-PA antibodies based on the rapid LT-induced degradation of c-Jun protein, a pathogenic effect that occurs in human cells. This new assay was developed by transducing Hepa1c1c7 cells with an AP-1 reporter lentiviral construct and has been qualified for specificity, accuracy, repeatability, intermediate precision, and linearity. This assay not only serves as a bioassay for LT activity, but has applications for characterization and quality control of anti-PA therapeutic antibodies or other products that target the AP-1 signaling pathway.
Collapse
Affiliation(s)
- Weiming Ouyang
- Division of Biotechnology Review and Research II, Office of Biotechnology Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA; (T.X.); (H.F.)
| | | | | | - David M. Frucht
- Division of Biotechnology Review and Research II, Office of Biotechnology Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993, USA; (T.X.); (H.F.)
| |
Collapse
|
4
|
Andreev I, Laidlaw KME, Giovanetti SM, Urtecho G, Shriner D, Bloom JS, MacDonald C, Sadhu MJ. Discovery of a rapidly evolving yeast defense factor, KTD1, against the secreted killer toxin K28. Proc Natl Acad Sci U S A 2023; 120:e2217194120. [PMID: 36800387 PMCID: PMC9974470 DOI: 10.1073/pnas.2217194120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 12/09/2022] [Indexed: 02/18/2023] Open
Abstract
Secreted protein toxins are widely used weapons in conflicts between organisms. Elucidating how organisms genetically adapt to defend themselves against these toxins is fundamental to understanding the coevolutionary dynamics of competing organisms. Within yeast communities, "killer" toxins are secreted to kill nearby sensitive yeast, providing a fitness advantage in competitive growth environments. Natural yeast isolates vary in their sensitivity to these toxins, but to date, no polymorphic genetic factors contributing to defense have been identified. We investigated the variation in resistance to the killer toxin K28 across diverse natural isolates of the Saccharomyces cerevisiae population. Using large-scale linkage mapping, we discovered a novel defense factor, which we named KTD1. We identified many KTD1 alleles, which provided different levels of K28 resistance. KTD1 is a member of the DUP240 gene family of unknown function, which is rapidly evolving in a region spanning its two encoded transmembrane helices. We found that this domain is critical to KTD1's protective ability. Our findings implicate KTD1 as a key polymorphic factor in the defense against K28 toxin.
Collapse
Affiliation(s)
- Ilya Andreev
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, NIH, Bethesda, MD20892
| | - Kamilla M. E. Laidlaw
- Biology Department, University of York, YorkYO10 5DD, UK
- York Biomedical Research Institute, University of York, YorkYO10 5NG, UK
| | - Simone M. Giovanetti
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, NIH, Bethesda, MD20892
| | - Guillaume Urtecho
- Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, CA90095
| | - Daniel Shriner
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, NIH, Bethesda, MD20892
| | - Joshua S. Bloom
- Department of Human Genetics, University of California, Los Angeles, CA90095
- Department of Biological Chemistry, University of California, Los Angeles, CA90095
- HHMI, University of California, Los Angeles, CA90095
- Institute for Quantitative and Computational Biology, University of California, Los Angeles, CA90095
- Department of Computational Medicine, University of California, Los Angeles, CA90095
| | - Chris MacDonald
- Biology Department, University of York, YorkYO10 5DD, UK
- York Biomedical Research Institute, University of York, YorkYO10 5NG, UK
| | - Meru J. Sadhu
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, NIH, Bethesda, MD20892
| |
Collapse
|
5
|
Protein folding stress potentiates NLRP1 and CARD8 inflammasome activation. Cell Rep 2023; 42:111965. [PMID: 36649711 PMCID: PMC10042216 DOI: 10.1016/j.celrep.2022.111965] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 08/25/2022] [Accepted: 12/21/2022] [Indexed: 01/18/2023] Open
Abstract
NLRP1 and CARD8 are related pattern-recognition receptors (PRRs) that detect intracellular danger signals and form inflammasomes. Both undergo autoproteolysis, generating N-terminal (NT) and C-terminal (CT) fragments. The proteasome-mediated degradation of the NT releases the CT from autoinhibition, but the stimuli that trigger NT degradation have not been fully elucidated. Here, we show that several distinct agents that interfere with protein folding, including aminopeptidase inhibitors, chaperone inhibitors, and inducers of the unfolded protein response, accelerate NT degradation. However, these agents alone do not trigger inflammasome formation because the released CT fragments are physically sequestered by the serine dipeptidase DPP9. We show that DPP9-binding ligands must also be present to disrupt these complexes and allow the CT fragments to oligomerize into inflammasomes. Overall, these results indicate that NLRP1 and CARD8 detect a specific perturbation that induces both protein folding stress and DPP9 ligand accumulation.
Collapse
|
6
|
Mi L, Min X, Chai Y, Zhang J, Chen X. NLRP1 Inflammasomes: A Potential Target for the Treatment of Several Types of Brain Injury. Front Immunol 2022; 13:863774. [PMID: 35707533 PMCID: PMC9189285 DOI: 10.3389/fimmu.2022.863774] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 04/28/2022] [Indexed: 12/28/2022] Open
Abstract
NOD-like receptor (NLR) family pyrin domain-containing 1 (NLRP1) is a member of the NLR family. The NLRP1 inflammasome consists of the NLRP1 protein, the adaptor protein apoptosis-associated speck-like protein containing a CARD domain, and the effector molecule pro-caspase-1. When stimulated, the inflammasome initiates the cleavage of pro-caspase-1 and converts it into its active form, caspase-1; then, caspase-1 facilitates the cleavage of the proinflammatory cytokines interleukin-1β and interleukin-18 into their active and secreted forms. In addition, caspase-1 also mediates the cleavage of gasdermin D, which leads to pyroptosis, an inflammatory form of cell death. Pathological events that damage the brain and result in neuropathological conditions can generally be described as brain injury. Neuroinflammation, especially that driven by NLRP1, plays a considerable role in the pathophysiology of brain injury, such as early brain injury (EBI) of subarachnoid hemorrhage, ischemic brain injury during stroke, and traumatic brain injury (TBI). In this article, a thorough overview of NLRP1 is presented, including its structure, mechanism of activation, and role in neuroinflammation. We also present recent studies on NLRP1 as a target for the treatment of EBI, ischemic brain injury, TBI, and other types of brain injury, thus highlighting the perspective of NLRP1 as an effective mediator of catastrophic brain injury.
Collapse
Affiliation(s)
- Liang Mi
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Neurological Institute, Key Laboratory of Posttrauma Neurorepair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Key Laboratory of Injuries, Variations and Regeneration of Nervous System, Tianjin, China
| | - Xiaobin Min
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
- Baodi Clinical College, Tianjin Medical University, Tianjin, China
| | - Yan Chai
- Tianjin Neurological Institute, Key Laboratory of Posttrauma Neurorepair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Key Laboratory of Injuries, Variations and Regeneration of Nervous System, Tianjin, China
| | - Jianning Zhang
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Neurological Institute, Key Laboratory of Posttrauma Neurorepair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Key Laboratory of Injuries, Variations and Regeneration of Nervous System, Tianjin, China
| | - Xin Chen
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
- Tianjin Neurological Institute, Key Laboratory of Posttrauma Neurorepair and Regeneration in Central Nervous System, Ministry of Education, Tianjin Key Laboratory of Injuries, Variations and Regeneration of Nervous System, Tianjin, China
- *Correspondence: Xin Chen,
| |
Collapse
|
7
|
Zhang KJ, Wu Q, Jiang SM, Ding L, Liu CX, Xu M, Wang Y, Zhou Y, Li L. Pyroptosis: A New Frontier in Kidney Diseases. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:6686617. [PMID: 34007404 PMCID: PMC8102120 DOI: 10.1155/2021/6686617] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/31/2021] [Accepted: 04/20/2021] [Indexed: 12/18/2022]
Abstract
Pyroptosis is a pattern of programmed cell death that significantly differs from apoptosis and autophagy in terms of cell morphology and function. The process of pyroptosis is characterized predominantly by the formation of gasdermin protein family-mediated membrane perforation, cell collapse, and the release of inflammatory factors, including IL-1β and IL-18. In recent years, with the rise of pyroptosis research, scholars have devoted time to study the mechanism of pyroptosis in kidney-related diseases. Pyroptosis is probably involved in kidney diseases through two pathways: the caspase-1-mediated canonical pathway and the caspase-4/5/11-mediated noncanonical pathway. In addition, some scholars have identified targets for the treatment of kidney-related diseases from the viewpoint of pyroptosis and developed corresponding medicines, which may become a recommendation for prognosis, targeted treatment, and clinical diagnosis of kidney diseases. This paper focuses on the up-to-date advances in the field of pyroptosis, especially on the key pathogenic role of pyroptosis in the development and progression of kidney diseases. It presents a more in-depth understanding of the pathogenesis of kidney diseases and introduces novel therapeutic targets for the prevention and clinical treatment of kidney diseases.
Collapse
Affiliation(s)
- Ke-jia Zhang
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, Xuzhou 221009, China
| | - Qi Wu
- Department of Physiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Shi-min Jiang
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Lei Ding
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Chao-xia Liu
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Ming Xu
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Ying Wang
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
| | - Yao Zhou
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, Xuzhou 221009, China
| | - Li Li
- Department of Pathophysiology, Xuzhou Medical University, Xuzhou 221009, China
- Laboratory of Clinical and Experimental Pathology, Xuzhou Medical University, Xuzhou 221009, China
| |
Collapse
|
8
|
Zhang S, Zhang Y, Gan L, Wei F, Chai B, A Aljaafreh AAH, Liu X, Duan X, Jiang J, Wang X, He M, Huang X, Cai H, Chen T, Chen H. Progesterone Suppresses Neisseria gonorrhoeae-Induced Inflammation Through Inhibition of NLRP3 Inflammasome Pathway in THP-1 Cells and Murine Models. Front Microbiol 2021; 12:570093. [PMID: 33633700 PMCID: PMC7900005 DOI: 10.3389/fmicb.2021.570093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Accepted: 01/15/2021] [Indexed: 01/01/2023] Open
Abstract
Asymptomatic/subclinical gonococcal infections in females continue to be prevalent within the general population, thus emerging as a global health problem. However, the reasons for these clinical manifestations are unknown. Our group had previously found out that in females, asymptomatic gonococcal infections correlate with higher serum progesterone (P4) levels and lower IL-1β levels in cervical secretions. We used murine infection model and THP-1 cells to determine whether P4 exerts anti-inflammatory effects on gonococcal infections. In the murine infection model, P4 (1 mg/day) inhibited the inflammatory effects induced by gonococcal infections which led to decreased neutrophil infiltration, reduced polymorphonuclear neutrophils (PMNs) numbers, IL-1β, TNF-α, and IL-6 levels in vaginal secretions. In addition, P4 down-regulated the mRNA and protein levels of NLRP3, associated with lower mRNA levels of pro-IL-1β, repressed caspase-1 activity in genital tissues and THP-1 cells. Moreover, P4 suppressed the phosphorylation levels of NF-κB and attenuated Neisseria gonorrhoeae (N. gonorrhoeae, gonococci or GC)-induced ROS generation. This is consistent with the two signals required for activation of the NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome. In conclusion, our result shows that P4 suppresses the gonococci induced-inflammation, especially through the NLRP3 inflammasome pathway, and partially explains the pathogenesis of asymptomatic GC infection in women.
Collapse
Affiliation(s)
- Song Zhang
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yingmiao Zhang
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China.,Department of Clinical Laboratory, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Tchnology, Wuhan, China
| | - Lu Gan
- Department of Dermatology, Zhongnan Hospital, Wuhan University, Wuhan, China
| | - Fen Wei
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Bao Chai
- Department of Dermatology, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China.,Department of Dermatology, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, China
| | - Amaneh Abdel Hafez A Aljaafreh
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xinxin Liu
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiaoru Duan
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jian Jiang
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xin Wang
- Department of Dermatology, Affiliated Hospital of Nantong University, Nantong, China
| | - Mengwen He
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xian Huang
- Department of Dermatology, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China
| | - Huahua Cai
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Tie Chen
- Department of Clinical Immunology, Tongji Hospital, Tongji Medical College, Huazhong University of Sciences and Technology, Wuhan, China
| | - Hongxiang Chen
- Department of Dermatology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Dermatology, The 6th Affiliated Hospital of Shenzhen University Health Science Center, Shenzhen, China.,Department of Dermatology, Huazhong University of Science and Technology Union Shenzhen Hospital, Shenzhen, China
| |
Collapse
|
9
|
Wang Y, Zhu J, Cao Y, Shen J, Yu L. Insight Into Inflammasome Signaling: Implications for Toxoplasma gondii Infection. Front Immunol 2020; 11:583193. [PMID: 33391259 PMCID: PMC7772217 DOI: 10.3389/fimmu.2020.583193] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 11/17/2020] [Indexed: 12/19/2022] Open
Abstract
Inflammasomes are multimeric protein complexes regulating the innate immune response to invading pathogens or stress stimuli. Recent studies have reported that nucleotide-binding leucine-rich repeat-containing (NLRs) proteins and DNA sensor absent in melanoma 2 (AIM2) serve as inflammasome sentinels, whose stimulation leads to the proteolytic activation of caspase-1, proinflammatory cytokine secretion, and pyroptotic cell death. Toxoplasma gondii, an obligate intracellular parasite of phylum Apicomplexans, is reportedly involved in NLRP1, NLRP3 and AIM2 inflammasomes activation; however, mechanistic evidence regarding the activation of these complexes is preliminary. This review describes the current understanding of inflammasome signaling in rodent and human models of T. gondii infection.
Collapse
Affiliation(s)
- Yang Wang
- Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Microbiology and Parasitology, Anhui Provincial Laboratory of Zoonoses of High Institutions, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Jinjin Zhu
- Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Microbiology and Parasitology, Anhui Provincial Laboratory of Zoonoses of High Institutions, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Yuanyuan Cao
- Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Microbiology and Parasitology, Anhui Provincial Laboratory of Zoonoses of High Institutions, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Jilong Shen
- Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Microbiology and Parasitology, Anhui Provincial Laboratory of Zoonoses of High Institutions, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Li Yu
- Department of Microbiology and Parasitology, Anhui Provincial Laboratory of Microbiology and Parasitology, Anhui Provincial Laboratory of Zoonoses of High Institutions, School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| |
Collapse
|
10
|
Robinson KS, Teo DET, Tan KS, Toh GA, Ong HH, Lim CK, Lay K, Au BV, Lew TS, Chu JJH, Chow VTK, Wang DY, Zhong FL, Reversade B. Enteroviral 3C protease activates the human NLRP1 inflammasome in airway epithelia. Science 2020; 370:eaay2002. [PMID: 33093214 DOI: 10.1126/science.aay2002] [Citation(s) in RCA: 137] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 02/11/2020] [Accepted: 10/08/2020] [Indexed: 12/17/2023]
Abstract
Immune sensor proteins are critical to the function of the human innate immune system. The full repertoire of cognate triggers for human immune sensors is not fully understood. Here, we report that human NACHT, LRR, and PYD domains-containing protein 1 (NLRP1) is activated by 3C proteases (3Cpros) of enteroviruses, such as human rhinovirus (HRV). 3Cpros directly cleave human NLRP1 at a single site between Glu130 and Gly131 This cleavage triggers N-glycine-mediated degradation of the autoinhibitory NLRP1 N-terminal fragment via the cullinZER1/ZYG11B complex, which liberates the activating C-terminal fragment. Infection of primary human airway epithelial cells by live human HRV triggers NLRP1-dependent inflammasome activation and interleukin-18 secretion. Our findings establish 3Cpros as a pathogen-derived trigger for the human NLRP1 inflammasome and suggest that NLRP1 may contribute to inflammatory diseases of the airway.
Collapse
Affiliation(s)
- Kim S Robinson
- Skin Research Institute of Singapore (SRIS), 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore
- Institute of Medical Biology, Agency of Science, Technological and Research, 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore
| | - Daniel Eng Thiam Teo
- Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, 308232, Singapore
| | - Kai Sen Tan
- Department of Otolaryngology, Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - Gee Ann Toh
- Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, 308232, Singapore
| | - Hsiao Hui Ong
- Department of Otolaryngology, Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - Chrissie Kaishi Lim
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
| | - Kenneth Lay
- Institute of Medical Biology, Agency of Science, Technological and Research, 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore
- Genome Institute of Singapore, 60 Biopolis Street, 138672, Singapore
| | - Bijin Veonice Au
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
| | - Tian Sheng Lew
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - Justin Jang Hann Chu
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - Vincent Tak Kwong Chow
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - De Yun Wang
- Department of Otolaryngology, Infectious Diseases Translational Research Programme, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
| | - Franklin L Zhong
- Skin Research Institute of Singapore (SRIS), 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore.
- Institute of Medical Biology, Agency of Science, Technological and Research, 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, 11 Mandalay Road, 308232, Singapore
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
| | - Bruno Reversade
- Institute of Medical Biology, Agency of Science, Technological and Research, 8A Biomedical Grove, #06-06 Immunos, 138648, Singapore.
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore
- Genome Institute of Singapore, 60 Biopolis Street, 138672, Singapore
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, 117597, Singapore
- The Medical Genetics Department, Koç University School of Medicine, 34010 Istanbul, Turkey
| |
Collapse
|
11
|
Chui AJ, Griswold AR, Taabazuing CY, Orth EL, Gai K, Rao SD, Ball DP, Hsiao JC, Bachovchin DA. Activation of the CARD8 Inflammasome Requires a Disordered Region. Cell Rep 2020; 33:108264. [PMID: 33053349 PMCID: PMC7594595 DOI: 10.1016/j.celrep.2020.108264] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 06/25/2020] [Accepted: 09/22/2020] [Indexed: 12/23/2022] Open
Abstract
Several cytosolic pattern-recognition receptors (PRRs) form multiprotein complexes called canonical inflammasomes in response to intracellular danger signals. Canonical inflammasomes recruit and activate caspase-1 (CASP1), which in turn cleaves and activates inflammatory cytokines and gasdermin D (GSDMD), inducing pyroptotic cell death. Inhibitors of the dipeptidyl peptidases DPP8 and DPP9 (DPP8/9) activate both the human NLRP1 and CARD8 inflammasomes. NLRP1 and CARD8 have different N-terminal regions but have similar C-terminal regions that undergo autoproteolysis to generate two non-covalently associated fragments. Here, we show that DPP8/9 inhibition activates a proteasomal degradation pathway that targets disordered and misfolded proteins for destruction. CARD8’s N terminus contains a disordered region of ~160 amino acids that is recognized and destroyed by this degradation pathway, thereby freeing its C-terminal fragment to activate CASP1 and induce pyroptosis. Thus, CARD8 serves as an alarm to signal the activation of a degradation pathway for disordered and misfolded proteins. Inflammasomes are multiprotein complexes that detect intracellular danger signals and stimulate powerful immune responses. DPP8/9 inhibitors activate the CARD8 inflammasome through an unknown mechanism. Here, Chui et al. show that DPP8/9 inhibitors induce the degradation of many disordered and misfolded proteins. CARD8 has an N-terminal disordered region that is degraded upon DPP8/9 inhibition, triggering inflammasome formation.
Collapse
Affiliation(s)
- Ashley J Chui
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Andrew R Griswold
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065, USA
| | - Cornelius Y Taabazuing
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Elizabeth L Orth
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Kuo Gai
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Sahana D Rao
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Daniel P Ball
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Jeffrey C Hsiao
- Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Daniel A Bachovchin
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
| |
Collapse
|
12
|
Johnson DC, Okondo MC, Orth EL, Rao SD, Huang HC, Ball DP, Bachovchin DA. DPP8/9 inhibitors activate the CARD8 inflammasome in resting lymphocytes. Cell Death Dis 2020; 11:628. [PMID: 32796818 PMCID: PMC7428001 DOI: 10.1038/s41419-020-02865-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/28/2020] [Accepted: 07/29/2020] [Indexed: 02/07/2023]
Abstract
Canonical inflammasomes are innate immune signaling platforms that are formed in response to intracellular pathogen-associated signals and trigger caspase-1-dependent pyroptosis. Inflammasome formation and signaling is thought to mainly occur in myeloid cells, and in particular monocytes and macrophages. Here we show that small molecule inhibitors of dipeptidyl peptidases 8 and 9 (DPP8/9), which activate the related CARD8 and NLRP1 inflammasomes, also activate pyroptosis in human and rodent resting lymphocytes. We found that both CD4+ and CD8+ T cells were particularly sensitive to these inhibitors, although the sensitivity of T cells, like macrophages, varied considerably between species. In human T cells, we show that CARD8 mediates DPP8/9 inhibitor-induced pyroptosis. Intriguingly, although activated human T cells express the key proteins known to be required for CARD8-mediated pyroptosis, these cells were completely resistant to DPP8/9 inhibitors. Overall, these data show that resting lymphoid cells can activate at least one inflammasome, revealing additional cell types and states poised to undergo rapid pyroptotic cell death in response to danger-associated signals.
Collapse
Affiliation(s)
- Darren C Johnson
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Marian C Okondo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Elizabeth L Orth
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Sahana D Rao
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Hsin-Che Huang
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Daniel P Ball
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Daniel A Bachovchin
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA. .,Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA. .,Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
| |
Collapse
|
13
|
Szpirer C. Rat models of human diseases and related phenotypes: a systematic inventory of the causative genes. J Biomed Sci 2020; 27:84. [PMID: 32741357 PMCID: PMC7395987 DOI: 10.1186/s12929-020-00673-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/09/2020] [Indexed: 12/13/2022] Open
Abstract
The laboratory rat has been used for a long time as the model of choice in several biomedical disciplines. Numerous inbred strains have been isolated, displaying a wide range of phenotypes and providing many models of human traits and diseases. Rat genome mapping and genomics was considerably developed in the last decades. The availability of these resources has stimulated numerous studies aimed at discovering causal disease genes by positional identification. Numerous rat genes have now been identified that underlie monogenic or complex diseases and remarkably, these results have been translated to the human in a significant proportion of cases, leading to the identification of novel human disease susceptibility genes, helping in studying the mechanisms underlying the pathological abnormalities and also suggesting new therapeutic approaches. In addition, reverse genetic tools have been developed. Several genome-editing methods were introduced to generate targeted mutations in genes the function of which could be clarified in this manner [generally these are knockout mutations]. Furthermore, even when the human gene causing a disease had been identified without resorting to a rat model, mutated rat strains (in particular KO strains) were created to analyze the gene function and the disease pathogenesis. Today, over 350 rat genes have been identified as underlying diseases or playing a key role in critical biological processes that are altered in diseases, thereby providing a rich resource of disease models. This article is an update of the progress made in this research and provides the reader with an inventory of these disease genes, a significant number of which have similar effects in rat and humans.
Collapse
Affiliation(s)
- Claude Szpirer
- Université Libre de Bruxelles, B-6041, Gosselies, Belgium.
- , Waterloo, Belgium.
| |
Collapse
|
14
|
Wang J, Chai J. Molecular actions of NLR immune receptors in plants and animals. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1303-1316. [DOI: 10.1007/s11427-019-1687-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/21/2020] [Indexed: 12/11/2022]
|
15
|
Taabazuing CY, Griswold AR, Bachovchin DA. The NLRP1 and CARD8 inflammasomes. Immunol Rev 2020; 297:13-25. [PMID: 32558991 PMCID: PMC7483925 DOI: 10.1111/imr.12884] [Citation(s) in RCA: 104] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/06/2020] [Accepted: 05/14/2020] [Indexed: 12/28/2022]
Abstract
Inflammasomes are multiprotein complexes that activate inflammatory cytokines and induce pyroptosis in response to intracellular danger-associated signals. NLRP1 and CARD8 are related germline-encoded pattern recognition receptors that form inflammasomes, but their activation mechanisms and biological purposes have not yet been fully established. Both NLRP1 and CARD8 undergo post-translational autoproteolysis to generate two non-covalently associated polypeptide chains. NLRP1 and CARD8 activators induce the proteasome-mediated destruction of the N-terminal fragment, liberating the C-terminal fragment to form an inflammasome. Here, we review the danger-associated stimuli that have been reported to activate NLRP1 and/or CARD8, including anthrax lethal toxin, Toxoplasma gondii, Shigella flexneri and the small molecule DPP8/9 inhibitor Val-boroPro, focusing on recent mechanistic insights and highlighting unresolved questions. In addition, we discuss the recently identified disease-associated mutations in NLRP1 and CARD8, the potential role that DPP9's protein structure plays in inflammasome regulation, and the emerging link between NLRP1 and metabolism. Finally, we summarize all of this latest research and consider the possible biological purposes of these enigmatic inflammasomes.
Collapse
Affiliation(s)
| | - Andrew R Griswold
- Weill Cornell, Rockefeller, Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY, USA.,Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Daniel A Bachovchin
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.,Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, USA.,Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| |
Collapse
|
16
|
Tupik JD, Nagai-Singer MA, Allen IC. To protect or adversely affect? The dichotomous role of the NLRP1 inflammasome in human disease. Mol Aspects Med 2020; 76:100858. [PMID: 32359693 DOI: 10.1016/j.mam.2020.100858] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 03/23/2020] [Accepted: 04/11/2020] [Indexed: 01/06/2023]
Abstract
NLRP1 is an inflammasome forming pattern recognition receptor (PRR). When activated by pathogen- and damage- associated molecular patterns (PAMPS/DAMPS), NLRP1 inflammasome formation leads to inflammation through the production of proinflammatory cytokines IL-18 and IL-1β. As with other inflammasome forming NLR family members, NLRP1 also regulates cell death processes, termed pyroptosis. The domain structure of NLRP1 differs between mice and humans, making it possible for the function of the inflammasome to differ between species and adds complexity to the study of this NLR family member. In humans, mutations in both coding and non-coding regions of the NLRP1 gene are linked to a variety of diseases. Likewise, interruption of NLRP1 inhibitors or changes in the prevalence of NLRP1 activators can also impact disease pathobiology. Adding to its complexity, the NLRP1 inflammasome plays a dichotomous role in human diseases, functioning to either attenuate or augment miscellaneous biological processes in a tissue specific manner. For example, NLRP1 plays a protective role in the gastrointestinal tract by modulating the microbiome composition; however, it augments neurological disorders, cardio-pulmonary diseases, and cancer through promoting inflammation. Thus, it is critical that the role of NLRP1 in each of these disease processes be robustly defined. In this review, we summarize the current research landscape to provide a better understanding of the mechanisms associated with NLRP1 function and dysfunction in human disease pathobiology. We propose that a better understanding of these mechanisms will ultimately result in improved insight into immune system dysfunction and therapeutic strategies targeting inflammasome function in multiple human diseases.
Collapse
Affiliation(s)
- Juselyn D Tupik
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA
| | - Margaret A Nagai-Singer
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA
| | - Irving C Allen
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA; Department of Basic Science Education, Virginia Tech Carilion School of Medicine, Roanoke, VA, USA.
| |
Collapse
|
17
|
Chen X, Ran D, Zeng L, Xin M. Immunoassay of cooked wild rat meat by ELISA with a highly specific antibody targeting rat heat-resistant proteins. FOOD AGR IMMUNOL 2020. [DOI: 10.1080/09540105.2020.1740180] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Xiangmei Chen
- Department of Food Science and Technology, Foshan University, Guangdong, People’s Republic of China
| | - Di Ran
- Department of Food Science and Technology, Foshan University, Guangdong, People’s Republic of China
| | - Lin Zeng
- Department of Food Science and Technology, Foshan University, Guangdong, People’s Republic of China
| | - Meiguo Xin
- Department of Food Science and Technology, Foshan University, Guangdong, People’s Republic of China
| |
Collapse
|
18
|
Fox D, Mathur A, Xue Y, Liu Y, Tan WH, Feng S, Pandey A, Ngo C, Hayward JA, Atmosukarto II, Price JD, Johnson MD, Jessberger N, Robertson AAB, Burgio G, Tscharke DC, Fox EM, Leyton DL, Kaakoush NO, Märtlbauer E, Leppla SH, Man SM. Bacillus cereus non-haemolytic enterotoxin activates the NLRP3 inflammasome. Nat Commun 2020; 11:760. [PMID: 32029733 PMCID: PMC7005308 DOI: 10.1038/s41467-020-14534-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Accepted: 01/14/2020] [Indexed: 02/07/2023] Open
Abstract
Inflammasomes are important for host defence against pathogens and homeostasis with commensal microbes. Here, we show non-haemolytic enterotoxin (NHE) from the neglected human foodborne pathogen Bacillus cereus is an activator of the NLRP3 inflammasome and pyroptosis. NHE is a non-redundant toxin to haemolysin BL (HBL) despite having a similar mechanism of action. Via a putative transmembrane region, subunit C of NHE initiates binding to the plasma membrane, leading to the recruitment of subunit B and subunit A, thus forming a tripartite lytic pore that is permissive to efflux of potassium. NHE mediates killing of cells from multiple lineages and hosts, highlighting a versatile functional repertoire in different host species. These data indicate that NHE and HBL operate synergistically to induce inflammation and show that multiple virulence factors from the same pathogen with conserved function and mechanism of action can be exploited for sensing by a single inflammasome.
Collapse
Affiliation(s)
- Daniel Fox
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Anukriti Mathur
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Yansong Xue
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Yunqi Liu
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Wei Hong Tan
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Shouya Feng
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Abhimanu Pandey
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Chinh Ngo
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Jenni A Hayward
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Ines I Atmosukarto
- Lipotek Pty Ltd. The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Jason D Price
- Lipotek Pty Ltd. The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Matthew D Johnson
- Research School of Biology, The Australian National University, Canberra, Australia
| | - Nadja Jessberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
| | - Avril A B Robertson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Gaetan Burgio
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - David C Tscharke
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
| | - Edward M Fox
- Department of Applied Sciences, Northumbria University, Newcastle Upon Tyne, UK
| | - Denisse L Leyton
- Research School of Biology, The Australian National University, Canberra, Australia.,Medical School, The Australian National University, Canberra, Australia
| | - Nadeem O Kaakoush
- School of Medical Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Si Ming Man
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia.
| |
Collapse
|
19
|
Vrentas CE, Boggiatto PM, Olsen SC, Leppla SH, Moayeri M. Characterization of the NLRP1 inflammasome response in bovine species. Innate Immun 2019; 26:301-311. [PMID: 31711335 PMCID: PMC7251794 DOI: 10.1177/1753425919886649] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Inflammasomes act as sensors of infection or damage to initiate immune responses.
While extensively studied in rodents, understanding of livestock inflammasomes
is limited. The NLRP1 inflammasome sensor in rodents is activated by
Toxoplasma gondii, Bacillus anthracis
lethal toxin (LT), and potentially other zoonotic pathogens. LT activates NLRP1
by N-terminal proteolysis, inducing macrophage pyroptosis and a pro-inflammatory
cytokine response. In contrast, NLRP1 in macrophages from humans and certain
rodent strains is resistant to LT cleavage, and pyroptosis is not induced.
Evolution of NLRP1 sequences towards those leading to pyroptosis is of interest
in understanding innate immune responses in different hosts. We characterized
NLRP1 in cattle (Bos taurus) and American bison (Bison
bison). Bovine NLRP1 is not cleaved by LT, and cattle and bison
macrophages do not undergo toxin-induced pyroptosis. Additionally, we found a
predicted Nlrp1 splicing isoform in cattle macrophages lacking
the N-terminal domain. Resistance to LT in bovine and human NLRP1 correlates
with evolutionary sequence similarity to rodents. Consistent with LT-resistant
rodents, bovine macrophages undergo a slower non-pyroptotic death in the
presence of LPS and LT. Overall, our findings support the model that NLRP1
activation by LT requires N-terminal cleavage, and provide novel information on
mechanisms underlying immune response diversity.
Collapse
Affiliation(s)
- Catherine E Vrentas
- Infectious Bacterial Diseases Unit, National Animal Disease
Center, Agricultural Research Service, US Department of Agriculture, Ames,
USA
- Catherine E Vrentas, Infectious Bacterial
Diseases Unit, National Animal Disease Center, Agricultural Research Service, US
Department of Agriculture, Ames, IA 50010, USA.
| | - Paola M Boggiatto
- Infectious Bacterial Diseases Unit, National Animal Disease
Center, Agricultural Research Service, US Department of Agriculture, Ames,
USA
| | - Steven C Olsen
- Infectious Bacterial Diseases Unit, National Animal Disease
Center, Agricultural Research Service, US Department of Agriculture, Ames,
USA
| | - Stephen H Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy
and Infectious Diseases, National Institutes of Health, Bethesda, USA
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy
and Infectious Diseases, National Institutes of Health, Bethesda, USA
| |
Collapse
|
20
|
Gai K, Okondo MC, Rao SD, Chui AJ, Ball DP, Johnson DC, Bachovchin DA. DPP8/9 inhibitors are universal activators of functional NLRP1 alleles. Cell Death Dis 2019; 10:587. [PMID: 31383852 PMCID: PMC6683174 DOI: 10.1038/s41419-019-1817-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/08/2019] [Accepted: 07/12/2019] [Indexed: 12/20/2022]
Abstract
Intracellular pathogenic structures or activities stimulate the formation of inflammasomes, which recruit and activate caspase-1 and trigger an inflammatory form of cell death called pyroptosis. The well-characterized mammalian inflammasome sensor proteins all detect one specific type of signal, for example double-stranded DNA or bacterial flagellin. Remarkably, NLRP1 was the first protein discovered to form an inflammasome, but the pathogenic signal that NLRP1 detects has not yet been identified. NLRP1 is highly polymorphic, even among inbred rodent strains, and it has been suggested that these diverse NLRP1 alleles may have evolved to detect entirely different stimuli. Intriguingly, inhibitors of the serine proteases DPP8 and DPP9 (DPP8/9) were recently shown to activate human NLRP1, its homolog CARD8, and several mouse NLRP1 alleles. Here, we show now that DPP8/9 inhibitors activate all functional rodent NLRP1 alleles, indicating that DPP8/9 inhibition induces a signal detected by all NLRP1 proteins. Moreover, we discovered that the NLRP1 allele sensitivities to DPP8/9 inhibitor-induced and Toxoplasma gondii-induced pyroptosis are strikingly similar, suggesting that DPP8/9 inhibition phenocopies a key activity of T. gondii. Overall, this work indicates that the highly polymorphic NLRP1 inflammasome indeed senses a specific signal like the other mammalian inflammasomes.
Collapse
Affiliation(s)
- Kuo Gai
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Marian C Okondo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Sahana D Rao
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Ashley J Chui
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Daniel P Ball
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Darren C Johnson
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
| | - Daniel A Bachovchin
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA. .,Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA. .,Pharmacology Program of the Weill Cornell Graduate School of Medical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
| |
Collapse
|
21
|
Xu H, Shi J, Gao H, Liu Y, Yang Z, Shao F, Dong N. The N-end rule ubiquitin ligase UBR2 mediates NLRP1B inflammasome activation by anthrax lethal toxin. EMBO J 2019; 38:e101996. [PMID: 31268597 PMCID: PMC6600268 DOI: 10.15252/embj.2019101996] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 11/09/2022] Open
Abstract
Anthrax lethal toxin (LT) is known to induce NLRP1B inflammasome activation and pyroptotic cell death in macrophages from certain mouse strains in its metalloprotease activity-dependent manner, but the underlying mechanism is unknown. Here, we establish a simple but robust cell system bearing dual-fluorescence reporters for LT-induced ASC specks formation and pyroptotic lysis. A genome-wide siRNA screen and a CRISPR-Cas9 knockout screen were applied to this system for identifying genes involved in LT-induced inflammasome activation. UBR2, an E3 ubiquitin ligase of the N-end rule degradation pathway, was found to be required for LT-induced NLRP1B inflammasome activation. LT is known to cleave NLRP1B after Lys44. The cleaved NLRP1B, bearing an N-terminal leucine, was targeted by UBR2-mediated ubiquitination and degradation. UBR2 partnered with an E2 ubiquitin-conjugating enzyme UBE2O in this process. NLRP1B underwent constitutive autocleavage before the C-terminal CARD domain. UBR2-mediated degradation of LT-cleaved NLRP1B thus triggered release of the noncovalent-bound CARD domain for subsequent caspase-1 activation. Our study illustrates a unique mode of inflammasome activation in cytosolic defense against bacterial insults.
Collapse
Affiliation(s)
- Hao Xu
- National Institute of Biological SciencesBeijingChina
- Present address:
Molecular Pathogenesis ProgramThe Kimmel Center for Biology and Medicine of the Skirball InstituteNew York University School of MedicineNew YorkNYUSA
| | - Jianjin Shi
- National Institute of Biological SciencesBeijingChina
- Present address:
Department of BiologyStanford UniversityStanfordCAUSA
| | - Hang Gao
- State Key Laboratory of Animal NutritionCollege of Animal Science and TechnologyChina Agricultural UniversityBeijingChina
| | - Ying Liu
- State Key Laboratory of Animal NutritionCollege of Animal Science and TechnologyChina Agricultural UniversityBeijingChina
| | - Zhenxiao Yang
- National Institute of Biological SciencesBeijingChina
| | - Feng Shao
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Na Dong
- National Institute of Biological SciencesBeijingChina
- State Key Laboratory of Animal NutritionCollege of Animal Science and TechnologyChina Agricultural UniversityBeijingChina
| |
Collapse
|
22
|
Wang Y, Cirelli KM, Barros PDC, Sangaré LO, Butty V, Hassan MA, Pesavento P, Mete A, Saeij JPJ. Three Toxoplasma gondii Dense Granule Proteins Are Required for Induction of Lewis Rat Macrophage Pyroptosis. mBio 2019; 10:e02388-18. [PMID: 30622189 PMCID: PMC6325250 DOI: 10.1128/mbio.02388-18] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 11/28/2018] [Indexed: 11/20/2022] Open
Abstract
Upon invasion of Lewis rat macrophages, Toxoplasma rapidly induces programmed cell death (pyroptosis), which prevents Toxoplasma replication, possibly explaining the resistance of the Lewis rat to Toxoplasma Using a chemical mutagenesis screen, we identified Toxoplasma mutants that no longer induced pyroptosis. Whole-genome sequencing led to the identification of three Toxoplasma parasitophorous vacuole-localized dense granule proteins, GRA35, GRA42, and GRA43, that are individually required for induction of Lewis rat macrophage pyroptosis. Macrophage infection with Δgra35, Δgra42, and Δgra43 parasites led to greatly reduced cell death rates and enhanced parasite replication. Lewis rat macrophages infected with parasites containing a single, double, or triple deletion of these GRAs showed similar levels of cell viability, suggesting that the three GRAs function in the same pathway. Deletion of GRA42 or GRA43 resulted in GRA35 (and other GRAs) being retained inside the parasitophorous vacuole instead of being localized to the parasitophorous vacuole membrane. Despite having greatly enhanced replication in Lewis rat macrophages in vitro, Δgra35, Δgra42, and Δgra43 parasites did not establish a chronic infection in Lewis rats. Toxoplasma did not induce F344 rat macrophage pyroptosis, but F344 rats infected with Δgra35, Δgra42, and Δgra43 parasites had reduced cyst numbers. Thus, these GRAs determined parasite in vivo fitness in F344 rats. Overall, our data suggest that these three Toxoplasma dense granule proteins play a critical role in establishing a chronic infection in vivo, independently of their role in mediating macrophage pyroptosis, likely due to their importance in regulating protein localization to the parasitophorous vacuole membrane.IMPORTANCE Inflammasomes are major components of the innate immune system and are responsible for detecting various microbial and environmental danger signals. Upon invasion of Lewis rat macrophages, the parasite rapidly activates the NLRP1 inflammasome, resulting in pyroptosis and elimination of the parasite's replication niche. The work reported here revealed that Toxoplasma GRA35, GRA42, and GRA43 are required for induction of Lewis rat macrophage pyroptosis. GRA42 and GRA43 mediate the correct localization of other GRAs, including GRA35, to the parasitophorous vacuole membrane. These three GRAs were also found to be important for parasite in vivo fitness in a Toxoplasma-susceptible rat strain, independently of their role in NLRP1 inflammasome activation, suggesting that they perform other important functions. Thus, this study identified three GRAs that mediate the induction of Lewis rat macrophage pyroptosis and are required for pathogenesis of the parasite.
Collapse
Affiliation(s)
- Yifan Wang
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Kimberly M Cirelli
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Patricio D C Barros
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Lamba Omar Sangaré
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Vincent Butty
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Musa A Hassan
- College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
- The Roslin Institute, The University of Edinburgh, Edinburgh, United Kingdom
- Center for Tropical Livestock Health and Genetics, The University of Edinburgh, Edinburgh, United Kingdom
| | - Patricia Pesavento
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Asli Mete
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Jeroen P J Saeij
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| |
Collapse
|
23
|
Structural Biology of NOD-Like Receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1172:119-141. [DOI: 10.1007/978-981-13-9367-9_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
24
|
Okondo MC, Rao SD, Taabazuing CY, Chui AJ, Poplawski SE, Johnson DC, Bachovchin DA. Inhibition of Dpp8/9 Activates the Nlrp1b Inflammasome. Cell Chem Biol 2018; 25:262-267.e5. [PMID: 29396289 DOI: 10.1016/j.chembiol.2017.12.013] [Citation(s) in RCA: 139] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 12/13/2017] [Accepted: 12/22/2017] [Indexed: 12/26/2022]
Abstract
Val-boroPro (PT-100, Talabostat) induces powerful anti-tumor immune responses in syngeneic cancer models, but its mechanism of action has not yet been established. Val-boroPro is a non-selective inhibitor of post-proline-cleaving serine proteases, and the inhibition of the highly related cytosolic serine proteases Dpp8 and Dpp9 (Dpp8/9) by Val-boroPro was recently demonstrated to trigger an immunostimulatory form of programmed cell death known as pyroptosis selectively in monocytes and macrophages. Here we show that Dpp8/9 inhibition activates the inflammasome sensor protein Nlrp1b, which in turn activates pro-caspase-1 to mediate pyroptosis. This work reveals a previously unrecognized mechanism for activating an innate immune pattern recognition receptor and suggests that Dpp8/9 serve as an intracellular checkpoint to restrain Nlrp1b and the innate immune system.
Collapse
Affiliation(s)
- Marian C Okondo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Sahana D Rao
- Tri-institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Cornelius Y Taabazuing
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Ashley J Chui
- Tri-institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Sarah E Poplawski
- Department of Developmental, Chemical, & Molecular Biology, Tufts University Sackler School of Graduate Biomedical Sciences, Boston, MA 02111, USA
| | - Darren C Johnson
- Tri-institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Daniel A Bachovchin
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA; Tri-institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
| |
Collapse
|
25
|
Turk BE. Exceptionally Selective Substrate Targeting by the Metalloprotease Anthrax Lethal Factor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1111:189-203. [PMID: 30267305 DOI: 10.1007/5584_2018_273] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The zinc-dependent metalloprotease anthrax lethal factor (LF) is the enzymatic component of a toxin thought to have a major role in Bacillus anthracis infections. Like many bacterial toxins, LF is a secreted protein that functions within host cells. LF is a highly selective protease that cleaves a limited number of substrates in a site-specific manner, thereby impacting host signal transduction pathways. The major substrates of LF are mitogen-activated protein kinase kinases (MKKs), which lie in the middle of three-component phosphorylation cascades mediating numerous functions in a variety of cells and tissues. How LF targets its limited substrate repertoire has been an active area of investigation. LF recognizes a specific sequence motif surrounding the scissile bonds of substrate proteins. X-ray crystallography of the protease in complex with peptide substrates has revealed the structural basis of selectivity for the LF cleavage site motif. In addition to having interactions proximal to the cleavage site, LF binds directly to a more distal region in its substrates through a so-called exosite interaction. This exosite has been mapped to a surface within a non-catalytic domain of LF with previously unknown function. A putative LF-binding site has likewise been identified on the catalytic domains of MKKs. Here we review our current state of understanding of LF-substrate interactions and discuss the implications for the design and discovery of inhibitors that may have utility as anthrax therapeutics.
Collapse
Affiliation(s)
- Benjamin E Turk
- Department of Pharmacology, Yale School of Medicine, New Haven, CT, USA.
| |
Collapse
|
26
|
Ranson N, Kunde D, Eri R. Regulation and Sensing of Inflammasomes and Their Impact on Intestinal Health. Int J Mol Sci 2017; 18:ijms18112379. [PMID: 29120406 PMCID: PMC5713348 DOI: 10.3390/ijms18112379] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 11/02/2017] [Accepted: 11/06/2017] [Indexed: 12/20/2022] Open
Abstract
Pattern recognition receptors such as nucleotide-binding oligomerization domain (NOD)-containing protein receptors (NLRs) and the pyrin and hematopoitic interferon-inducible nuclear protein (HIN) domain (PYHIN) receptors initiate the inflammatory response following cell stress or pathogenic challenge. When activated, some of these receptors oligomerize to form the structural backbone of a signalling platform known as an inflammasome. Inflammasomes promote the activation of caspase-1 and the maturation of the proinflammatory cytokines, interleukin (IL)-1β and IL-18. The gut dysregulation of the inflammasome complex is thought to be a contributing factor in the development of inflammatory bowel diseases (IBD), such as ulcerative colitis (UC) and Crohn's disease (CD). The importance of inflammasomes to intestinal health has been emphasized by various inflammasome-deficient mice in dextran sulphate sodium (DSS) models of intestinal inflammation and by the identification of novel potential candidate genes in population-based human studies. In this review, we summarise the most recent findings with regard to the formation, sensing, and regulation of the inflammasome complex and highlight their importance in maintaining intestinal health.
Collapse
Affiliation(s)
- Nicole Ranson
- School of Health Sciences, University of Tasmania, Launceston, Tasmania 7250, Australia.
| | - Dale Kunde
- School of Health Sciences, University of Tasmania, Launceston, Tasmania 7250, Australia.
| | - Rajaraman Eri
- School of Health Sciences, University of Tasmania, Launceston, Tasmania 7250, Australia.
| |
Collapse
|
27
|
Yu CH, Moecking J, Geyer M, Masters SL. Mechanisms of NLRP1-Mediated Autoinflammatory Disease in Humans and Mice. J Mol Biol 2017; 430:142-152. [PMID: 28733143 DOI: 10.1016/j.jmb.2017.07.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 07/06/2017] [Accepted: 07/14/2017] [Indexed: 01/25/2023]
Abstract
NLRP1 was the first NOD-like receptor described to form an inflammasome, recruiting ASC to activate caspase-1, which processes interleukin-1β and interleukin-18 to their active form. A wealth of new genetic information has now redefined our understanding of this innate immune sensor. Specifically, rare loss-of-function variants in the N-terminal pyrin domain indicate that this part of NLRP1 is autoinhibitory and normally acts to prevent a familial autoinflammatory skin disease associated with cancer. In the absence of a ligand to trigger human NLRP1, these mutations have now confirmed the requirement of NLRP1 autolytic cleavage within the FIIND domain, which had previously been implicated in NLRP1 activation. Autolytic cleavage generates a C-terminal fragment of NLRP1 containing the CARD domain which then forms an ASC-dependent inflammasome. The CARD domain as an inflammasome linker is consistent with the observation that under some conditions, particularly for mouse NLRP1, caspase-1 can be engaged directly, and although it is no longer processed, it is still capable of producing mature IL-1β. Additional rare variants in a linker region between the LRR and FIIND domains of NLRP1 also cause autoinflammatory disease in both humans and mice. This new genetic information is likely to provide for more mechanistic insight in the years to come, contributing to our understanding of how NLRP1 functions as an innate immune sensor of infection and predisposes to autoimmune or autoinflammatory diseases.
Collapse
Affiliation(s)
- Chien-Hsiung Yu
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3010, Australia.
| | - Jonas Moecking
- Department of Structural Immunology, Institute of Innate Immunity, University of Bonn, 53127 Bonn, Germany
| | - Matthias Geyer
- Department of Structural Immunology, Institute of Innate Immunity, University of Bonn, 53127 Bonn, Germany
| | - Seth L Masters
- Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, VIC 3010, Australia
| |
Collapse
|
28
|
Abstract
The inflammasome is a large multimeric protein complex comprising an effector protein that demonstrates specificity for a variety of activators or ligands; an adaptor molecule; and procaspase-1, which is converted to caspase-1 upon inflammasome activation. Inflammasomes are expressed primarily by myeloid cells and are located within the cell. The macromolecular inflammasome structure can be visualized by cryo-electron microscopy. This complex has been found to play a role in a variety of disease models in mice, and several have been genetically linked to human diseases. In most cases, the effector protein is a member of the NLR (nucleotide-binding domain leucine-rich repeat-containing) or NOD (nucleotide oligomerization domain)-like receptor protein family. However, other effectors have also been described, with the most notable being AIM-2 (absent in melanoma 2), which recognizes DNA to elicit inflammasome function. This review will focus on the role of the inflammasome in myeloid cells and its role in health and disease.
Collapse
|
29
|
Li W, Li MF, Zhao PP, Qiao JL, Xu KL, Zeng LY. [Effects of allogeneic hematopoietic stem cell transplantation in combination with infusion of endothelial progenitor cells on bone marrow inflammatory injury]. ZHONGHUA XUE YE XUE ZA ZHI = ZHONGHUA XUEYEXUE ZAZHI 2017; 38:318-324. [PMID: 28468094 PMCID: PMC7342716 DOI: 10.3760/cma.j.issn.0253-2727.2017.04.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Indexed: 11/27/2022]
Abstract
Objective: To explore effects of allogeneic hematopoietic stem cell transplantation (HSCT) in combination with infusion of endothelial progenitor cells (EPC) on bone marrow inflammatory injury. Methods: 6-8 weeks BALB/c (H-2K(d)) mice after lethal dose of irradiation (TBI) were subjected to allogeneic bone marrow transplantation (BMT group) or co-transplantation of EPC (EPC group) . Samples of bone marrow cells of mice in each group on days 7,14,21,28 after transplantation were obtained to detect EPC cultural and cell chimeric rates by flow cytometer. Mice were sacrificed on days 7, 14, 21 and 28 post HSCT to analyze bone marrow pathology by H&E staining, the infiltration of macrophages and neutrophils by Western blot, validation expression levels of inflammatory complexes nlrp1、nlrp6 and its downstream molecules casepase-1 by Q-PCR and Western blot. Results: Cell chimeric rate on day 7 after transplantation in EPC group[ (91.65±2.77) %] was significantly higher than in BMT group[ (83.69±1.26) %]. Alleviated osteomyelitis injury and inflammatory cell infiltration in EPC group were observed when compared with BMT mice. Also significant reductions of the levels of nlrp1、nlrp6、casepase-1 transcription complexes in EPC mice were noted when compared with BMT ones. Conclusion: Co-transplantation of HSC and EPC could alleviate inflammatory cell infiltration and activation of the complex to promote the repair of bone marrow.
Collapse
Affiliation(s)
- W Li
- Blood Diseases Institute, Xuzhou Medical University, Xuzhou 221002, China
| | | | | | | | | | | |
Collapse
|
30
|
NLRP1 promotes tumor growth by enhancing inflammasome activation and suppressing apoptosis in metastatic melanoma. Oncogene 2017; 36:3820-3830. [PMID: 28263976 PMCID: PMC5501746 DOI: 10.1038/onc.2017.26] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Revised: 11/13/2016] [Accepted: 01/11/2017] [Indexed: 02/06/2023]
Abstract
Inflammasomes are mediators of inflammation, and constitutively activated NLRP3 inflammasomes have been linked to IL-1β-mediated tumorigenesis in human melanoma. Whereas NLRP3 regulation of caspase-1 activation requires the adaptor protein ASC, caspase-1 activation by another danger-signaling sensor NLRP1 does not require ASC because NLRP1 contains a C-terminal CARD domain that facilitates direct caspase-1 activation via CARD-CARD interaction. We hypothesized that NLRP1 has additional biological activities besides IL-1β maturation and investigated its role in melanoma tumorigenesis. NLRP1 expression in melanoma was confirmed by analysis of 216 melanoma tumors and 13 human melanoma cell lines. Unlike monocytic THP-1 cells with prominent nuclear localization of NLRP1, melanoma cells expressed NLRP1 mainly in the cytoplasm. Knocking down NLRP1 revealed a tumor promoting property of NLRP1 both in vitro and in vivo. Mechanistic studies showed that caspase-1 activity, IL-1β production, IL-1β secretion, and NF-kB activity were reduced by knocking down of NLRP1 in human metastatic melanoma cell lines 1205Lu and HS294T, indicating that NLRP1 inflammasomes are active in metastatic melanoma. However, unlike previous reports showing that NLRP1 enhances pyroptosis in macrophages, NLRP1 in melanoma behaved differently in the context of cell death. Knocking down NLRP1 increased caspase-2, -9, and -3/7 activities and promoted apoptosis in human melanoma cells. Immunoprecipitation revealed interaction of NLRP1 with CARD-containing caspase-2 and -9, whereas NLRP3 lacking a CARD motif did not interact with the caspases. Consistent with these findings, NLRP1 activation but not NLRP3 activation reduced caspase-2, -9, and -3/7 activities and provided protection against apoptosis in human melanoma cells, suggesting a suppressive role of NLRP1 in caspase-3/7 activation and apoptosis via interaction with caspase-2 and -9. In summary, we showed that NLRP1 promotes melanoma growth by enhancing inflammasome activation and suppressing apoptotic pathways. Our study demonstrates a tumor-promoting role of NLRP1 in cancer cells.
Collapse
|
31
|
Animal Models for the Pathogenesis, Treatment, and Prevention of Infection by Bacillus anthracis. Microbiol Spectr 2016; 3:TBS-0001-2012. [PMID: 26104551 DOI: 10.1128/microbiolspec.tbs-0001-2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
This article reviews the characteristics of the major animal models utilized for studies on Bacillus anthracis and highlights their contributions to understanding the pathogenesis and host responses to anthrax and its treatment and prevention. Advantages and drawbacks associated with each model, to include the major models (murine, guinea pig, rabbit, nonhuman primate, and rat), and other less frequently utilized models, are discussed. Although the three principal forms of anthrax are addressed, the main focus of this review is on models for inhalational anthrax. The selection of an animal model for study is often not straightforward and is dependent on the specific aims of the research or test. No single animal species provides complete equivalence to humans; however, each species, when used appropriately, can contribute to a more complete understanding of anthrax and its etiologic agent.
Collapse
|
32
|
Zhao Y, Shao F. Diverse mechanisms for inflammasome sensing of cytosolic bacteria and bacterial virulence. Curr Opin Microbiol 2016; 29:37-42. [DOI: 10.1016/j.mib.2015.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 10/15/2015] [Accepted: 10/18/2015] [Indexed: 12/15/2022]
|
33
|
do Vale A, Cabanes D, Sousa S. Bacterial Toxins as Pathogen Weapons Against Phagocytes. Front Microbiol 2016; 7:42. [PMID: 26870008 PMCID: PMC4734073 DOI: 10.3389/fmicb.2016.00042] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/11/2016] [Indexed: 12/31/2022] Open
Abstract
Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favor microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signaling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.
Collapse
Affiliation(s)
- Ana do Vale
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Fish Immunology and Vaccinology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| | - Didier Cabanes
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Molecular Microbiology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| | - Sandra Sousa
- Host Interaction and Response, Instituto de Investigação e Inovação em Saúde, Universidade do PortoPorto, Portugal; Group of Molecular Microbiology, Instituto de Biologia Molecular e Celular, Universidade do PortoPorto, Portugal
| |
Collapse
|
34
|
Abstract
Inflammasomes are cytosolic protein complexes that serve as platforms for the recruitment and activation of the pro-inflammatory CASPASE-1 protease. CASPASE-1 activation leads to processing and maturation of the cytokines interleukin-1β and interleukin-18 and a lytic form of cell death termed pyroptosis. Inflammasome assembly is initiated by cytosolic sensors in response to microbial infections. Many of these sensors, including NLRP1 (NLR family, pyrin domain containing 1), are described to form an inflammasome, but until recently, the mechanism of inflammasome activation and its physiological functions in host defense have remained unclear. In the last few years, important advances in our understanding of NLRP1 biology have been achieved. In this review, we discuss the activation of NLRP1 by various stimuli, including Bacillus anthracis lethal toxin, Toxoplasma gondii, muramyl dipeptide, and host intracellular ATP depletion. The role NLRP1 plays in pathogen recognition and resistance during infection is also discussed, as is the regulation of NLRP1 by host and viral proteins. We conclude by discussing the unexpected differences in the mechanism of NLRP1 inflammasome activation, as compared to the activation of other inflammasomes, such as the NAIP (NLR family, apoptosis inhibitory protein)/NLRC4 inflammasomes.
Collapse
Affiliation(s)
- Joseph Chavarría-Smith
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | | |
Collapse
|
35
|
Greaney AJ, Leppla SH, Moayeri M. Bacterial Exotoxins and the Inflammasome. Front Immunol 2015; 6:570. [PMID: 26617605 PMCID: PMC4639612 DOI: 10.3389/fimmu.2015.00570] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 10/26/2015] [Indexed: 11/24/2022] Open
Abstract
The inflammasomes are intracellular protein complexes that play an important role in innate immune sensing. Activation of inflammasomes leads to activation of caspase-1 and maturation and secretion of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18. In certain myeloid cells, this activation can also lead to an inflammatory cell death (pyroptosis). Inflammasome sensor proteins have evolved to detect a range of microbial ligands and bacterial exotoxins either through direct interaction or by detection of host cell changes elicited by these effectors. Bacterial exotoxins activate the inflammasomes through diverse processes, including direct sensor cleavage, modulation of ion fluxes through plasma membrane pore formation, and perturbation of various host cell functions. In this review, we summarize the findings on some of the bacterial exotoxins that activate the inflammasomes.
Collapse
Affiliation(s)
- Allison J Greaney
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD , USA
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD , USA
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD , USA
| |
Collapse
|
36
|
Activation of the NLRP1b inflammasome independently of ASC-mediated caspase-1 autoproteolysis and speck formation. Nat Commun 2015; 5:3209. [PMID: 24492532 PMCID: PMC3926011 DOI: 10.1038/ncomms4209] [Citation(s) in RCA: 169] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 01/07/2014] [Indexed: 01/03/2023] Open
Abstract
Despite its clinical importance in infection and autoimmunity, the activation mechanisms of the NLRP1b inflammasome remain enigmatic. Here we show that deletion of the inflammasome adaptor ASC in BALB/c mice and in C57BL/6 macrophages expressing a functional NLRP1b prevents anthrax lethal toxin (LeTx)-induced caspase-1 autoproteolysis and speck formation. However, ASC−/− macrophages undergo normal LeTx-induced pyroptosis and secrete significant amounts of interleukin (IL)-1β. In contrast, ASC is critical for caspase-1 autoproteolysis and IL-1β secretion by the NLRC4, NLRP3 and AIM2 inflammasomes. Notably, LeTx-induced inflammasome activation is associated with caspase-1 ubiquitination, which is unaffected in ASC-deficient cells. In vivo, ASC-deficient mice challenged with LeTx produce significant levels of IL-1β, IL-18 and HMGB1 in circulation, although caspase-1 autoproteolysis is abolished. As a result, ASC−/− mice are sensitive to rapid LeTx-induced lethality. Together, these results demonstrate that ASC-driven caspase-1 autoprocessing and speck formation are dispensable for the activation of caspase-1 and the NLRP1b inflammasome. The NLRP1b inflammasome activation may lead to pyroptosis and secretion of the inflammatory cytokines IL-1ß and IL-18 but the mechanisms behind these processes are not fully understood. Here, the authors show that they can occur independently of the inflammasome adaptor ASC and without caspase-1 autoprocessing.
Collapse
|
37
|
Abstract
Anthrax is caused by the spore-forming, gram-positive bacterium Bacillus anthracis. The bacterium's major virulence factors are (a) the anthrax toxins and (b) an antiphagocytic polyglutamic capsule. These are encoded by two large plasmids, the former by pXO1 and the latter by pXO2. The expression of both is controlled by the bicarbonate-responsive transcriptional regulator, AtxA. The anthrax toxins are three polypeptides-protective antigen (PA), lethal factor (LF), and edema factor (EF)-that come together in binary combinations to form lethal toxin and edema toxin. PA binds to cellular receptors to translocate LF (a protease) and EF (an adenylate cyclase) into cells. The toxins alter cell signaling pathways in the host to interfere with innate immune responses in early stages of infection and to induce vascular collapse at late stages. This review focuses on the role of anthrax toxins in pathogenesis. Other virulence determinants, as well as vaccines and therapeutics, are briefly discussed.
Collapse
Affiliation(s)
- Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Catherine Vrentas
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Andrei P Pomerantsev
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| | - Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892; , , , ,
| |
Collapse
|
38
|
Robbins GR, Wen H, Ting JPY. Inflammasomes and metabolic disorders: old genes in modern diseases. Mol Cell 2014; 54:297-308. [PMID: 24766894 DOI: 10.1016/j.molcel.2014.03.029] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Modern medical and hygienic practices have greatly improved human health and longevity; however, increased human life span occurs concomitantly with the emergence of metabolic and age-related diseases. Studies over the past decade have strongly linked host inflammatory responses to the etiology of several metabolic diseases including atherosclerosis, type 2 diabetes (T2D), obesity, and gout. A common immunological factor to these diseases is the activation of the inflammasome and release of proinflammatory cytokines that promote disease progression. Here we review the molecular mechanism(s) of inflammasome activation in response to metabolic damage-associated molecular patterns (DAMPs) and discuss potential targets for therapeutic intervention.
Collapse
Affiliation(s)
- Gregory R Robbins
- The Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Haitao Wen
- The Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Surgery, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jenny P-Y Ting
- The Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| |
Collapse
|
39
|
Distinct regions of NLRP1B are required to respond to anthrax lethal toxin and metabolic inhibition. Infect Immun 2014; 82:3697-703. [PMID: 24935976 DOI: 10.1128/iai.02167-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pattern recognition receptors monitor for signs of infection or cellular dysfunction and respond to these events by initiating an immune response. NLRP1B is a receptor that upon activation recruits multiple copies of procaspase-1, which promotes cytokine processing and a proinflammatory form of cell death termed pyroptosis. NLRP1B detects anthrax lethal toxin when the toxin cleaves an amino-terminal fragment from the protein. In addition, NLRP1B is activated when cells are deprived of glucose or treated with metabolic inhibitors, but the mechanism by which the resulting reduction in cytosolic ATP is sensed by NLRP1B is unknown. Here, we addressed whether these two activating signals of NLRP1B converge on a common sensing system. We show that an NLRP1B mutant lacking the amino-terminal region exhibits some spontaneous activity and fails to be further activated by lethal toxin. This mutant was still activated in cells depleted of ATP, however, indicating that the amino-terminal region is not the sole sensing domain of NLRP1B. Mutagenesis of the leucine-rich repeat domain of NLRP1B provided evidence that this domain is involved in autoinhibition of the receptor, but none of the mutants tested was specifically defective at sensing activating signals. Comparison of two alleles of NLRP1B that differed in their response to metabolic inhibitors, but not to lethal toxin, led to the finding that a repeated sequence in the function to find domain (FIIND) that arose from exon duplication facilitated detection of ATP depletion. These results suggest that distinct regions of NLRP1B detect activating signals.
Collapse
|
40
|
Cavailles P, Flori P, Papapietro O, Bisanz C, Lagrange D, Pilloux L, Massera C, Cristinelli S, Jublot D, Bastien O, Loeuillet C, Aldebert D, Touquet B, Fournié GJ, Cesbron-Delauw MF. A highly conserved Toxo1 haplotype directs resistance to toxoplasmosis and its associated caspase-1 dependent killing of parasite and host macrophage. PLoS Pathog 2014; 10:e1004005. [PMID: 24699513 PMCID: PMC3974857 DOI: 10.1371/journal.ppat.1004005] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 01/22/2014] [Indexed: 02/03/2023] Open
Abstract
Natural immunity or resistance to pathogens most often relies on the genetic make-up of the host. In a LEW rat model of refractoriness to toxoplasmosis, we previously identified on chromosome 10 the Toxo1 locus that directs toxoplasmosis outcome and controls parasite spreading by a macrophage-dependent mechanism. Now, we narrowed down Toxo1 to a 891 kb interval containing 29 genes syntenic to human 17p13 region. Strikingly, Toxo1 is included in a haplotype block strictly conserved among all refractory rat strains. The sequencing of Toxo1 in nine rat strains (5 refractory and 4 susceptible) revealed resistant-restricted conserved polymorphisms displaying a distribution gradient that peaks at the bottom border of Toxo1, and highlighting the NOD-like receptor, Nlrp1a, as a major candidate. The Nlrp1 inflammasome is known to trigger, upon pathogen intracellular sensing, pyroptosis programmed-cell death involving caspase-1 activation and cleavage of IL-1β. Functional studies demonstrated that the Toxo1-dependent refractoriness in vivo correlated with both the ability of macrophages to restrict T. gondii growth and a T. gondii-induced death of intracellular parasites and its host macrophages. The parasite-induced cell death of infected macrophages bearing the LEW-Toxo1 alleles was found to exhibit pyroptosis-like features with ROS production, the activation of caspase-1 and IL1-β secretion. The pharmacological inactivation of caspase-1 using YVAD and Z-VAD inhibitors prevented the death of both intravacuolar parasites and host non-permissive macrophages but failed to restore parasite proliferation. These findings demonstrated that the Toxo1-dependent response of rat macrophages to T. gondii infection may trigger two pathways leading to the control of parasite proliferation and the death of parasites and host macrophages. The NOD-like receptor NLRP1a/Caspase-1 pathway is the best candidate to mediate the parasite-induced cell death. These data represent new insights towards the identification of a major pathway of innate resistance to toxoplasmosis and the prediction of individual resistance. Toxoplasmosis is a ubiquitous parasitic infection causing a wide spectrum of diseases. It is usually asymptomatic but can lead to severe ocular and neurological disorders. The host factors that determine natural resistance to toxoplasmosis are yet poorly characterized. Among the animal models to study susceptibility to toxoplasmosis, rats develop like humans a subclinical chronic infection. The finding of a total resistance in the LEW rat strain has allowed genetic studies leading to the identification of Toxo1, a unique locus that controls the outcome of toxoplasmosis. In this report, a panel of recombinant inbred rat strains was used to genetically reduce the Toxo1 locus, on chromosome 10, to a limited region containing 29 genes. This locus is highly conserved among five resistant, by comparison to four susceptible, rat strains, indicating that refractoriness to toxoplasmosis could be predicted. The Toxo1-controlled refractoriness depends on the ability of macrophages to restrict parasite proliferation and the rapid death of both T. gondii and host macrophages in vitro. The NOD-like receptor NLRP1a/Caspase-1 pathway is the best candidate to mediate the parasite-induced cell death. Our data represent new insights towards the identification of a major pathway of innate immunity that protects from toxoplasmosis.
Collapse
Affiliation(s)
- Pierre Cavailles
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Pierre Flori
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- GIMAP, EA 3064, Saint-Etienne, France
| | - Olivier Papapietro
- UMR Inserm, U1043, Toulouse, France
- Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Cordelia Bisanz
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Dominique Lagrange
- UMR Inserm, U1043, Toulouse, France
- Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Ludovic Pilloux
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Céline Massera
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Sara Cristinelli
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Delphine Jublot
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Olivier Bastien
- UMR 5168, CNRS/INRA, Université Joseph Fourier, CEA, Grenoble, France
| | - Corinne Loeuillet
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Delphine Aldebert
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Bastien Touquet
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
| | - Gilbert J. Fournié
- UMR Inserm, U1043, Toulouse, France
- Université de Toulouse, UPS, Centre de Physiopathologie de Toulouse Purpan (CPTP), Toulouse, France
| | - Marie France Cesbron-Delauw
- UMR 5163, Centre National de la Recherche Scientifique (CNRS), Grenoble, France
- Université Grenoble 1, Grenoble, France
- * E-mail:
| |
Collapse
|
41
|
Liu S, Moayeri M, Leppla SH. Anthrax lethal and edema toxins in anthrax pathogenesis. Trends Microbiol 2014; 22:317-25. [PMID: 24684968 DOI: 10.1016/j.tim.2014.02.012] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/23/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
Abstract
The pathophysiological effects resulting from many bacterial diseases are caused by exotoxins released by the bacteria. Bacillus anthracis, a spore-forming bacterium, is such a pathogen, causing anthrax through a combination of bacterial infection and toxemia. B. anthracis causes natural infection in humans and animals and has been a top bioterrorism concern since the 2001 anthrax attacks in the USA. The exotoxins secreted by B. anthracis use capillary morphogenesis protein 2 (CMG2) as the major toxin receptor and play essential roles in pathogenesis during the entire course of the disease. This review focuses on the activities of anthrax toxins and their roles in initial and late stages of anthrax infection.
Collapse
Affiliation(s)
- Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| |
Collapse
|
42
|
Cirelli KM, Gorfu G, Hassan MA, Printz M, Crown D, Leppla SH, Grigg ME, Saeij JPJ, Moayeri M. Inflammasome sensor NLRP1 controls rat macrophage susceptibility to Toxoplasma gondii. PLoS Pathog 2014; 10:e1003927. [PMID: 24626226 PMCID: PMC3953412 DOI: 10.1371/journal.ppat.1003927] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 12/21/2013] [Indexed: 12/22/2022] Open
Abstract
Toxoplasma gondii is an intracellular parasite that infects a wide range of warm-blooded species. Rats vary in their susceptibility to this parasite. The Toxo1 locus conferring Toxoplasma resistance in rats was previously mapped to a region of chromosome 10 containing Nlrp1. This gene encodes an inflammasome sensor controlling macrophage sensitivity to anthrax lethal toxin (LT) induced rapid cell death (pyroptosis). We show here that rat strain differences in Toxoplasma infected macrophage sensitivity to pyroptosis, IL-1β/IL-18 processing, and inhibition of parasite proliferation are perfectly correlated with NLRP1 sequence, while inversely correlated with sensitivity to anthrax LT-induced cell death. Using recombinant inbred rats, SNP analyses and whole transcriptome gene expression studies, we narrowed the candidate genes for control of Toxoplasma-mediated rat macrophage pyroptosis to four genes, one of which was Nlrp1. Knockdown of Nlrp1 in pyroptosis-sensitive macrophages resulted in higher parasite replication and protection from cell death. Reciprocally, overexpression of the NLRP1 variant from Toxoplasma-sensitive macrophages in pyroptosis-resistant cells led to sensitization of these resistant macrophages. Our findings reveal Toxoplasma as a novel activator of the NLRP1 inflammasome in rat macrophages. Inflammasomes are multiprotein complexes that are a major component of the innate immune system. They contain “sensor” proteins that are responsible for detecting various microbial and environmental danger signals and function by activating caspase-1, an enzyme that mediates cleavage and release of the pro-inflammatory cytokines, IL-1β and IL-18. Toxoplasma gondii is a highly successful protozoan parasite capable of infecting a wide range of host species that have variable levels of resistance. Rat strains have been previously shown to vary in their susceptibility to this parasite. We report here that rat macrophages from different inbred strains also vary in sensitivity to Toxoplasma induced lysis. We find that NLRP1, an inflammasome sensor whose only known agonist is anthrax LT, is also activated by Toxoplasma infection. In rats there is a perfect correlation between NLRP1 sequence and macrophage sensitivity to Toxoplasma-induced rapid cell death, inhibition of parasite proliferation, and IL-1β/IL-18 processing. Nlrp1 genes from sensitive rat macrophages can confer sensitivity to this rapid cell death when expressed in Toxoplasma resistant rat macrophages. Our findings suggest Toxoplasma is a new activator of the NLRP1 inflammasome.
Collapse
Affiliation(s)
- Kimberly M. Cirelli
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
| | - Gezahegn Gorfu
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Musa A. Hassan
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
| | - Morton Printz
- Department of Pharmacology, University of California-San Diego, La Jolla, California, United States of America
| | - Devorah Crown
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
| | - Michael E. Grigg
- Molecular Parasitology Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
- * E-mail: (MEG); (JPJS); (MM)
| | - Jeroen P. J. Saeij
- Massachusetts Institute of Technology, Department of Biology, Cambridge, Massachusetts, United States of America
- * E-mail: (MEG); (JPJS); (MM)
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, NIAID, NIH, Bethesda, Maryland, United States of America
- * E-mail: (MEG); (JPJS); (MM)
| |
Collapse
|
43
|
Abstract
Induction of immunity that limits Toxoplasma gondii infection in mice is critically dependent on the activation of the innate immune response. In this study, we investigated the role of cytoplasmic nucleotide-binding domain and leucine-rich repeat containing a pyrin domain (NLRP) inflammasome sensors during acute toxoplasmosis in mice. We show that in vitro Toxoplasma infection of murine bone marrow-derived macrophages activates the NLRP3 inflammasome, resulting in the rapid production and cleavage of interleukin-1β (IL-1β), with no measurable cleavage of IL-18 and no pyroptosis. Paradoxically, Toxoplasma-infected mice produced large quantities of IL-18 but had no measurable IL-1β in their serum. Infection of mice deficient in NLRP3, caspase-1/11, IL-1R, or the inflammasome adaptor protein ASC led to decreased levels of circulating IL-18, increased parasite replication, and death. Interestingly, mice deficient in NLRP1 also displayed increased parasite loads and acute mortality. Using mice deficient in IL-18 and IL-18R, we show that this cytokine plays an important role in limiting parasite replication to promote murine survival. Our findings reveal T. gondii as a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis. Inflammasomes are multiprotein complexes that are a major component of the innate immune system. They contain “sensor” proteins that are responsible for detecting various microbial and environmental danger signals and function by activating caspase-1, an enzyme that mediates cleavage and release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18. Toxoplasma gondii is a highly successful protozoan parasite capable of infecting a wide range of host species that have variable levels of resistance. We report here that T. gondii is a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis. Using mice deficient in IL-18 and IL-18R, we show that the IL-18 cytokine plays a pivotal role by limiting parasite replication to promote murine survival.
Collapse
|
44
|
Maier NK, Crown D, Liu J, Leppla SH, Moayeri M. Arsenic trioxide and other arsenical compounds inhibit the NLRP1, NLRP3, and NAIP5/NLRC4 inflammasomes. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2014; 192:763-70. [PMID: 24337744 PMCID: PMC3884817 DOI: 10.4049/jimmunol.1301434] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inflammasomes are large cytoplasmic multiprotein complexes that activate caspase-1 in response to diverse intracellular danger signals. Inflammasome components termed nucleotide-binding oligomerization domain-like receptor (NLR) proteins act as sensors for pathogen-associated molecular patterns, stress, or danger stimuli. We discovered that arsenicals, including arsenic trioxide and sodium arsenite, inhibited activation of the NLRP1, NLRP3, and NAIP5/NLRC4 inflammasomes by their respective activating signals, anthrax lethal toxin, nigericin, and flagellin. These compounds prevented the autoproteolytic activation of caspase-1 and the processing and secretion of IL-1β from macrophages. Inhibition was independent of protein synthesis induction, proteasome-mediated protein breakdown, or kinase signaling pathways. Arsenic trioxide and sodium arsenite did not directly modify or inhibit the activity of preactivated recombinant caspase-1. Rather, they induced a cellular state inhibitory to both the autoproteolytic and substrate cleavage activities of caspase-1, which was reversed by the reactive oxygen species scavenger N-acetylcysteine but not by reducing agents or NO pathway inhibitors. Arsenicals provided protection against NLRP1-dependent anthrax lethal toxin-mediated cell death and prevented NLRP3-dependent neutrophil recruitment in a monosodium urate crystal inflammatory murine peritonitis model. These findings suggest a novel role in inhibition of the innate immune response for arsenical compounds that have been used as therapeutics for a few hundred years.
Collapse
Affiliation(s)
- Nolan K. Maier
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Devorah Crown
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Jie Liu
- Center for Molecular Medicine, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
45
|
Jin HS, Park JK, Jo EK. Toll-like Receptors and NOD-like Receptors in Innate Immune Defense during Pathogenic Infection. ACTA ACUST UNITED AC 2014. [DOI: 10.4167/jbv.2014.44.3.215] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Hyo Sun Jin
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, Korea
| | - Jeong-Kyu Park
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon, Korea
| | - Eun-Kyeong Jo
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, Korea
| |
Collapse
|
46
|
Williams JD, Khan AR, Cardinale SC, Butler MM, Bowlin TL, Peet NP. Small molecule inhibitors of anthrax lethal factor toxin. Bioorg Med Chem 2013; 22:419-34. [PMID: 24290062 DOI: 10.1016/j.bmc.2013.11.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/29/2013] [Accepted: 11/05/2013] [Indexed: 10/26/2022]
Abstract
This manuscript describes the preparation of new small molecule inhibitors of Bacillus anthracis lethal factor. Our starting point was the symmetrical, bis-quinolinyl compound 1 (NSC 12155). Optimization of one half of this molecule led to new LF inhibitors that were desymmetrized to afford more drug-like compounds.
Collapse
Affiliation(s)
- John D Williams
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States
| | - Atiyya R Khan
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States
| | - Steven C Cardinale
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States
| | - Michelle M Butler
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States
| | - Terry L Bowlin
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States
| | - Norton P Peet
- Microbiotix, Inc., Department of Medicinal Chemistry, One Innovation Drive, Worcester, MA 01605, United States; Microbiotix, Inc., Department of Molecular Biology, One Innovation Drive, Worcester, MA 01605, United States.
| |
Collapse
|
47
|
Abstract
The obligate intracellular parasite Toxoplasma gondii is able to infect nearly all nucleated cell types of warm-blooded animals. This is achieved through the injection of hundreds of parasite effectors into the host cell cytosol, allowing the parasite to establish a vacuolar niche for growth, replication, and persistence. Here we show that Toxoplasma infection actives an inflammasome response in mice and rats, an innate immune sensing system designed to survey the host cytosol for foreign components leading to inflammation and cell death. Oral infection with Toxoplasma triggers an inflammasome response that is protective to the host, limiting parasite load and dissemination. Toxoplasma infection is sufficient to generate an inflammasome response in germfree animals. Interleukin 1β (IL-1β) secretion by macrophage requires the effector caspases 1 and 11, the adapter ASC, and NLRP1, the sensor previously described to initiate the inflammasome response to Bacillus anthracis lethal factor. The allele of NLRP1b derived from 129 mice is sufficient to enhance the B6 bone marrow-derived macrophage (BMDM) inflammasome response to Toxoplasma independent of the lethal factor proteolysis site. Moreover, N-terminal processing of NLRP1b, the only mechanism of activation known to date, is not observed in response to Toxoplasma infection. Cumulatively, these data indicate that NLRP1 is an innate immune sensor for Toxoplasma infection, activated via a novel mechanism that corresponds to a host-protective innate immune response to the parasite.
Collapse
|
48
|
Leysath CE, Phillips DD, Crown D, Fattah RJ, Moayeri M, Leppla SH. Anthrax edema factor toxicity is strongly mediated by the N-end rule. PLoS One 2013; 8:e74474. [PMID: 24015319 PMCID: PMC3755998 DOI: 10.1371/journal.pone.0074474] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/30/2013] [Indexed: 11/29/2022] Open
Abstract
Anthrax edema factor (EF) is a calmodulin-dependent adenylate cyclase that converts adenosine triphosphate (ATP) into 3’–5’-cyclic adenosine monophosphate (cAMP), contributing to the establishment of Bacillus anthracis infections and the resulting pathophysiology. We show that EF adenylate cyclase toxin activity is strongly mediated by the N-end rule, and thus is dependent on the identity of the N-terminal amino acid. EF variants having different N-terminal residues varied by more than 100-fold in potency in cultured cells and mice. EF variants having unfavorable, destabilizing N-terminal residues showed much greater activity in cells when the E1 ubiquitin ligase was inactivated or when proteasome inhibitors were present. Taken together, these results show that EF is uniquely affected by ubiquitination and/or proteasomal degradation.
Collapse
Affiliation(s)
- Clinton E. Leysath
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Damilola D. Phillips
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Devorah Crown
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rasem J. Fattah
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| |
Collapse
|
49
|
Key tissue targets responsible for anthrax-toxin-induced lethality. Nature 2013; 501:63-8. [PMID: 23995686 DOI: 10.1038/nature12510] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/31/2013] [Indexed: 02/01/2023]
Abstract
Bacillus anthracis, the causative agent of anthrax disease, is lethal owing to the actions of two exotoxins: anthrax lethal toxin (LT) and oedema toxin (ET). The key tissue targets responsible for the lethal effects of these toxins are unknown. Here we generated cell-type-specific anthrax toxin receptor capillary morphogenesis protein-2 (CMG2)-null mice and cell-type-specific CMG2-expressing mice and challenged them with the toxins. Our results show that lethality induced by LT and ET occurs through damage to distinct cell types; whereas targeting cardiomyocytes and vascular smooth muscle cells is required for LT-induced mortality, ET-induced lethality occurs mainly through its action in hepatocytes. Notably, and in contradiction to what has been previously postulated, targeting of endothelial cells by either toxin does not seem to contribute significantly to lethality. Our findings demonstrate that B. anthracis has evolved to use LT and ET to induce host lethality by coordinately damaging two distinct vital systems.
Collapse
|
50
|
Direct proteolytic cleavage of NLRP1B is necessary and sufficient for inflammasome activation by anthrax lethal factor. PLoS Pathog 2013; 9:e1003452. [PMID: 23818853 PMCID: PMC3688554 DOI: 10.1371/journal.ppat.1003452] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 05/08/2013] [Indexed: 01/24/2023] Open
Abstract
Inflammasomes are multimeric protein complexes that respond to infection by recruitment and activation of the Caspase-1 (CASP1) protease. Activated CASP1 initiates immune defense by processing inflammatory cytokines and by causing a rapid and lytic cell death called pyroptosis. Inflammasome formation is orchestrated by members of the nucleotide-binding domain and leucine-rich repeat (NLR) or AIM2-like receptor (ALR) protein families. Certain NLRs and ALRs have been shown to function as direct receptors for specific microbial ligands, such as flagellin or DNA, but the molecular mechanism responsible for activation of most NLRs is still poorly understood. Here we determine the mechanism of activation of the NLRP1B inflammasome in mice. NLRP1B, and its ortholog in rats, is activated by the lethal factor (LF) protease that is a key virulence factor secreted by Bacillus anthracis, the causative agent of anthrax. LF was recently shown to cleave mouse and rat NLRP1 directly. However, it is unclear if cleavage is sufficient for NLRP1 activation. Indeed, other LF-induced cellular events have been suggested to play a role in NLRP1B activation. Surprisingly, we show that direct cleavage of NLRP1B is sufficient to induce inflammasome activation in the absence of LF. Our results therefore rule out the need for other LF-dependent cellular effects in activation of NLRP1B. We therefore propose that NLRP1 functions primarily as a sensor of protease activity and thus could conceivably detect a broader spectrum of pathogens than just B. anthracis. By adding proteolytic cleavage to the previously established ligand-receptor mechanism of NLR activation, our results illustrate the remarkable flexibility with which the NLR architecture can be deployed for the purpose of pathogen-detection and host defense. Recognition of pathogens by the innate immune system is necessary for initiating an appropriate immune response. The innate immune system must distinguish pathogens from abundant harmless microbes present within the host and the environment, and scale the response appropriately. It has been proposed that the host can respond specifically to pathogens by monitoring common virulence-associated activities, previously termed “patterns of pathogenesis,” that are used by pathogens to survive and replicate within their hosts. For example, pathogens can manipulate host functions by delivering toxins into host cells. In response, the host encodes dedicated cytosolic sensors to detect these toxins, but the molecular basis for how the sensors recognize the toxins is poorly understood. Here we define the molecular mechanism by which a mouse sensor, NLRP1B, directly recognizes the activity of a bacterial toxin, lethal factor. Lethal factor is a protease secreted by Bacillus anthracis, the causative agent of anthrax. We show that anthrax lethal factor cleaves NLRP1B and this cleavage event is both necessary and sufficient for the activation of this sensor. Our findings raise the possibility that NLRP1B could sense the activity of other proteases encoded by diverse pathogens.
Collapse
|