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Feng Shao - One of the best experts on this subject based on the ideXlab platform.
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sequence determinants of specific pattern recognition of bacterial ligands by the naip nlrc4 inflammasome
Cell discovery, 2018Co-Authors: Jingyi Yang, Maohua Zhong, Dihan Zhou, Ejuan Zhang, Yaoming Li, Yue Zhao, Yi Yang, Peng Li, Mengji Lu, Feng ShaoAbstract:The NLR apoptosis inhibitory proteins (NAIPs) function as specific cytosolic receptors for bacterial ligands to form the NAIP–NLRC4 inflammasome for anti-bacterial defenses. In mice, NAIP5/6 and NAIP2 recognize bacteria Flagellin and the rod protein of the type III secretion system (T3SS), respectively. However, molecular mechanism for specific ligand pattern-recognition by the NAIPs is largely unknown. Here, through extensive domain swapping and truncation analyses, three structural domains, the pre-BIR, BIR1, and HD1, in NAIP2 and NAIP5 are identified, that are important for specific recognition of their respective ligand(s). The three domains are sufficient to confer the ligand specificity for NAIP2. Asp-18, Arg-108, and Arg-667, respectively, in the pre-BIR, BIR1 and HD1 of NAIP2 are further identified, each of which is essential for efficient binding to the rod protein. To our surprise, we find that the C-terminal leucine-rich repeat domain is dispensable for NAIP2 recognition of the T3SS rod protein, but is required for NAIP5 binding to Flagellin. At the ligand side, we discover that the C-terminal 35 residues in Flagellin are crucial for binding to NAIP5. Among the 35 residues, three critical residues are identified, which determine Flagellin recognition by NAIP5 and subsequent inflammasome activation. The differences in the three amino-acid residues among Flagellins from various pathogenic and commensal bacterial species correlate well with whether they are susceptible to NAIP5-mediated immune detection. Taken together, our studies identify critical sequence and amino-acid determinants in both NAIP receptors and the bacterial ligand Flagellin that are important for the specificity of the pattern-recognition.
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the nlrc4 inflammasome receptors for bacterial Flagellin and type iii secretion apparatus
Nature, 2011Co-Authors: Yue Zhao, Jieling Yang, Yinan Gong, Qiuhe Lu, Hao Xu, Feng ShaoAbstract:The inflammasomes are multiprotein complexes involved in innate immunity, and induce an immune response to pathogenic microbes by activating the caspase 1 protease. Two groups now report that the intracellular receptors known as NAIPs (NLR family, apoptosis inhibitory proteins), previously thought to have an auxiliary role in recognizing microbial proteins, are in fact central to the process. Eric Kofoed and Russell Vance, and Feng Shao and colleagues, show that different members of the NAIP family bind to different bacterial ligands, including bacterial Flagellin and a conserved bacterial type III secretion system rod protein. Inflammasomes are large cytoplasmic complexes that sense microbial infections/danger molecules and induce caspase-1 activation-dependent cytokine production and macrophage inflammatory death1,2. The inflammasome assembled by the NOD-like receptor (NLR) protein NLRC4 responds to bacterial Flagellin and a conserved type III secretion system (TTSS) rod component3,4,5. How the NLRC4 inflammasome detects the two bacterial products and the molecular mechanism of NLRC4 inflammasome activation are not understood. Here we show that NAIP5, a BIR-domain NLR protein required for Legionella pneumophila replication in mouse macrophages6, is a universal component of the Flagellin–NLRC4 pathway. NAIP5 directly and specifically interacted with Flagellin, which determined the inflammasome-stimulation activities of different bacterial Flagellins. NAIP5 engagement by Flagellin promoted a physical NAIP5–NLRC4 association, rendering full reconstitution of a Flagellin-responsive NLRC4 inflammasome in non-macrophage cells. The related NAIP2 functioned analogously to NAIP5, serving as a specific inflammasome receptor for TTSS rod proteins such as Salmonella PrgJ and Burkholderia BsaK. Genetic analysis of Chromobacterium violaceum infection revealed that the TTSS needle protein CprI can stimulate NLRC4 inflammasome activation in human macrophages. Similarly, CprI is specifically recognized by human NAIP, the sole NAIP family member in human. The finding that NAIP proteins are inflammasome receptors for bacterial Flagellin and TTSS apparatus components further predicts that the remaining NAIP family members may recognize other unidentified microbial products to activate NLRC4 inflammasome-mediated innate immunity.
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the nlrc4 inflammasome receptors for bacterial Flagellin and type iii secretion apparatus
Nature, 2011Co-Authors: Yue Zhao, Jieling Yang, Yinan Gong, Jianjin Shi, Liping Liu, Feng ShaoAbstract:Inflammasomes are large cytoplasmic complexes that sense microbial infections/danger molecules and induce caspase-1 activation-dependent cytokine production and macrophage inflammatory death. The inflammasome assembled by the NOD-like receptor (NLR) protein NLRC4 responds to bacterial Flagellin and a conserved type III secretion system (TTSS) rod component. How the NLRC4 inflammasome detects the two bacterial products and the molecular mechanism of NLRC4 inflammasome activation are not understood. Here we show that NAIP5, a BIR-domain NLR protein required for Legionella pneumophila replication in mouse macrophages, is a universal component of the Flagellin-NLRC4 pathway. NAIP5 directly and specifically interacted with Flagellin, which determined the inflammasome-stimulation activities of different bacterial Flagellins. NAIP5 engagement by Flagellin promoted a physical NAIP5-NLRC4 association, rendering full reconstitution of a Flagellin-responsive NLRC4 inflammasome in non-macrophage cells. The related NAIP2 functioned analogously to NAIP5, serving as a specific inflammasome receptor for TTSS rod proteins such as Salmonella PrgJ and Burkholderia BsaK. Genetic analysis of Chromobacterium violaceum infection revealed that the TTSS needle protein CprI can stimulate NLRC4 inflammasome activation in human macrophages. Similarly, CprI is specifically recognized by human NAIP, the sole NAIP family member in human. The finding that NAIP proteins are inflammasome receptors for bacterial Flagellin and TTSS apparatus components further predicts that the remaining NAIP family members may recognize other unidentified microbial products to activate NLRC4 inflammasome-mediated innate immunity.
Andrew T Gewirtz - One of the best experts on this subject based on the ideXlab platform.
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Flagellin elicited adaptive immunity suppresses flagellated microbiota and vaccinates against chronic inflammatory diseases
Nature Communications, 2019Co-Authors: Hao Q Tran, Andrew T Gewirtz, Ruth E Ley, Benoit ChassaingAbstract:Alterations in gut microbiota composition are associated with metabolic syndrome and chronic inflammatory diseases such as inflammatory bowel disease. One feature of inflammation-associated gut microbiotas is enrichment of motile bacteria, which can facilitate microbiota encroachment into the mucosa and activate pro-inflammatory gene expression. Here, we set out to investigate whether elicitation of mucosal anti-Flagellin antibodies by direct administration of purified Flagellin might serve as a general vaccine against subsequent development of chronic gut inflammation. We show, in mice, that repeated injection of Flagellin elicits increases in fecal anti-Flagellin IgA and alterations in microbiota composition, reduces fecal Flagellin concentration, prevents microbiota encroachment, protects against IL-10 deficiency-induced colitis, and ameliorates diet-induced obesity. Flagellin's impact on the microbiota is B-lymphocyte dependent and, in humans, obese subjects exhibit increased levels of fecal Flagellin and reduced levels of fecal Flagellin-specific IgA, relative to normal weight subjects. Thus, administration of Flagellin, and perhaps other pathobiont antigens, may confer some protection against chronic inflammatory diseases.
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humoral immune response to Flagellin requires t cells and activation of innate immunity
Journal of Immunology, 2006Co-Authors: Catherine J Sanders, Daniel A Moore, Ifor R Williams, Andrew T GewirtzAbstract:Bacterial Flagellin, the primary structural component of flagella, is a dominant target of humoral immunity upon infection by enteric pathogens and in Crohn's disease. To better understand how such responses may be regulated, we sought to define, in mice, basic mechanisms that regulate generation of Flagellin-specific Igs. We observed that, in response to i.p. injection with Flagellin, generation of Flagellin-specific Ig required activation of innate immunity in that these responses were ablated in MyD88-deficient mice and that Flagellin from Helicobacter pylori, which is known not to activate TLR5, also did not elicit Abs. Mice lacking alphabeta T cells (TCRbeta(null)) were completely deficient in their ability to make Flagellin Abs in various contexts indicating that, in contrast to common belief, generation of Flagellin-specific Ig is absolutely T cell dependent. In contrast to Ab responses to whole flagella (H serotyping), responses to Flagellin monomers displayed only moderate serospecificity. Whereas neither oral nor rectal administration of Flagellin elicited a strong serum Ab response, induction of colitis with dextran sodium sulfate resulted in a MyD88-dependent serum Ab response to endogenous Flagellin, suggesting that, in an inflammatory milieu, TLR signaling promotes acquisition of Abs to intestinal Flagellin. Thus, acquisition of a humoral immune response to Flagellin requires activation of innate immunity, is T cell dependent, and can originate from Flagellin in the intestinal tract in inflammatory conditions in the intestine.
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helicobacter pylori Flagellin evades toll like receptor 5 mediated innate immunity
The Journal of Infectious Diseases, 2004Co-Authors: Andrew T Gewirtz, Sean Lyons, Uma Krishna, Dawn A Israel, Richard M PeekAbstract:Helicobacter pylori colonizes the human stomach for decades unless pharmacologically eradicated. We hypothesized that this flagellated pathogen escapes immune clearance, in part, by avoiding detection by the Flagellin receptor Toll-like receptor 5 (TLR5). In contrast to other gram-negative microbes, H. pylori did not release Flagellin. Furthermore, recombinant H. pylori Flagellin (FlaA) was significantly less potent (1000-fold) than Salmonella typhimurium Flagellin in activating TLR5-mediated interleukin (IL)-8 secretion. TLR5 can mediate Flagellin-induced IL-8 secretion via p38 mitogen-activated protein kinase signaling; however, compared with potent induction by S. typhimurium Flagellin, H. pylori FlaA-dependent p38 activation was substantially attenuated. In addition, disruption of H. pylori flaA decreased motility but had no effect on H. pylori-induced IL-8 secretion, which indicates that H. pylori Flagellin plays no role in activating epithelial orchestration of inflammation. We conclude that H. pylori evades TLR5-mediated detection, which may contribute to its long-term persistence in individual hosts.
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cutting edge bacterial Flagellin activates basolaterally expressed tlr5 to induce epithelial proinflammatory gene expression
Journal of Immunology, 2001Co-Authors: Andrew T Gewirtz, Tony A Navas, Sean Lyons, Paul J Godowski, James L MadaraAbstract:Flagellin, the structural component of bacterial flagella, is secreted by pathogenic and commensal bacteria. Flagellin activates proinflammatory gene expression in intestinal epithelia. However, only Flagellin that contacts basolateral epithelial surfaces is proinflammatory; apical Flagellin has no effect. Pathogenic Salmonella , but not commensal Escherichia coli , translocate Flagellin across epithelia, thus activating epithelial proinflammatory gene expression. Investigating how epithelia detect Flagellin revealed that cell surface expression of Toll-like receptor 5 (TLR5) conferred NF-κB gene expression in response to Flagellin. The response depended on both extracellular leucine-rich repeats and intracellular Toll/IL-1R homology region of TLR5 as well as the adaptor protein MyD88. Furthermore, immunolocalization and cell surface-selective biotinylation revealed that TLR5 is expressed exclusively on the basolateral surface of intestinal epithelia, thus providing a molecular basis for the polarity of this innate immune response. Thus, detection of Flagellin by basolateral TLR5 mediates epithelial-driven inflammatory responses to Salmonella .
Andrew F Bent - One of the best experts on this subject based on the ideXlab platform.
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rice osfls2 mediated perception of bacterial Flagellins is evaded by xanthomonas oryzae pvs oryzae and oryzicola
Molecular Plant, 2015Co-Authors: Shanzhi Wang, Zhe Sun, Huiqin Wang, Lijuan Liu, Jun Yang, Min Zhang, Shiyong Zhang, Zejian Guo, Andrew F Bent, Wenxian SunAbstract:Abstract Bacterial Flagellins are often recognized by the receptor kinase Flagellin SENSITIVE2 (FLS2) and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize Flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting flg22 peptide and in vitro purified Acidovorax avenae ( Aa ) Flagellin in an expression level-dependent manner, but does not recognize purified Flagellins or derivative flg22 Xo peptides of Xanthomonas oryzae pvs. oryzae ( Xoo ) and oryzicola ( Xoc ). Consistently, the flg22 peptide and purified Aa Flagellin, but not Xoo/Xoc Flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of Flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa Flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different flg22 sequences. In addition, post-translational modification of Xoc Flagellin was altered by deletion of glycosyltransferase-encoding rbfC , but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of Flagellin-encoding fliC from Xoo / Xoc blocked swimming motility but also did not significantly alter Xoo / Xoc virulence. These results suggest that Xoo / Xoc carry flg22-region amino acid changes that allow motility while evading the ancient Flagellin detection system in rice, which retains recognition capacity for other bacterial pathogens.
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within species Flagellin polymorphism in xanthomonas campestris pv campestris and its impact on elicitation of arabidopsis Flagellin sensing2 dependent defenses
The Plant Cell, 2006Co-Authors: Mark F Dunning, Christine Pfund, Rebecca Weingarten, Andrew F BentAbstract:Bacterial Flagellins have been portrayed as a relatively invariant pathogen-associated molecular pattern. We have found within-species, within-pathovar variation for defense-eliciting activity of Flagellins among Xanthomonas campestris pv campestris (Xcc) strains. Arabidopsis thaliana Flagellin SENSING2 (FLS2), a transmembrane leucine-rich repeat kinase, confers Flagellin responsiveness. The flg22 region was the only Xcc Flagellin region responsible for detectable elicitation of Arabidopsis defense responses. A Val-43/Asp polymorphism determined the eliciting/noneliciting nature of Xcc Flagellins (structural gene fliC). Arabidopsis detected Flagellins carrying Asp-43 or Asn-43 but not Val-43 or Ala-43, and it responded minimally for Glu-43. Wild-type Xcc strains carrying nonrecognized Flagellin were more virulent than those carrying a recognized Flagellin when infiltrated into Arabidopsis leaf mesophyll, but this correlation was misleading. Isogenic Xcc fliC gene replacement strains expressing eliciting or noneliciting Flagellins grew similarly, both in leaf mesophyll and in hydathode/vascular colonization assays. The plant FLS2 genotype also had no detectable effect on disease outcome when previously untreated plants were infected by Xcc. However, resistance against Xcc was enhanced if FLS2-dependent responses were elicited 1 d before Xcc infection. Prior immunization was not required for FLS2-dependent restriction of Pseudomonas syringae pv tomato. We conclude that plant immune systems do not uniformly detect all Flagellins of a particular pathogen species and that Xcc can evade Arabidopsis FLS2-mediated defenses unless the FLS2 system has been activated by previous infections.
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Flagellin is not a major defense elicitor in ralstonia solanacearum cells or extracts applied to arabidopsis thaliana
Molecular Plant-microbe Interactions, 2004Co-Authors: Christine Pfund, Mark F Dunning, Julie Tanskersten, Jose M Alonso, Joseph R Ecker, Caitilyn Allen, Andrew F BentAbstract:The phytopathogenic bacterium Ralstonia solanacearum requires motility for full virulence, and its Flagellin is a candidate pathogen-associated molecular pattern that may elicit plant defenses. Boiled extracts from R. solanacearum contained a strong elicitor of defense-associated responses. However, R. solanacearum Flagellin is not this elicitor, because extracts from wild-type bacteria and fliC or flhDC mutants defective in Flagellin production all elicited similar plant responses. Equally important, live R. solanacearum caused similar disease on Arabidopsis ecotype Col-0, regardless of the presence of Flagellin in the bacterium or the FLS2-mediated Flagellin recognition system in the plant. Unlike the previously studied flg22 Flagellin peptide, a peptide based on the corresponding conserved N-terminal segment of R. solanacearum, Flagellin did not elicit any response from Arabidopsis seedlings. Thus recognition of Flagellin plays no readily apparent role in this pathosystem. Flagellin also was not the primary elicitor of responses in tobacco. The primary eliciting activity in boiled R. solanacearum extracts applied to Arabidopsis was attributable to one or more proteins other than Flagellin, including species purifying at approximately 5 to 10 kDa and also at larger molecular masses, possibly due to aggregation. Production of this eliciting activity did not require hrpB (positive regulator of type III secretion), pehR (positive regulator of polygalacturonase production and motility), gspM (general secretion pathway), or phcA (LysR-type global virulence regulator). Wild-type R. solanacearum was virulent on Arabidopsis despite the presence of this elicitor in pathogen extracts.
Ken F. Jarrell - One of the best experts on this subject based on the ideXlab platform.
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identification of genes involved in the assembly and attachment of a novel Flagellin n linked tetrasaccharide important for motility in the archaeon methanococcus maripaludis
Molecular Microbiology, 2009Co-Authors: David J Vandyke, John F Kelly, Susan M Logan, Shino Mizuno, Shin-ichi Aizawa, John Wu, Ken F. JarrellAbstract:Summary Recently, the Flagellin proteins of Methanococcus maripaludis were found to harbour an N-linked tetrasaccharide composed of N-acetylgalactosamine, di-acetylated glucuronic acid, an acetylated and acetamidino-modified mannuronic acid linked to threonine, and a novel terminal sugar [(5S)-2-acetamido-2,4-dideoxy-5-O-methyl-α-L-erythro-hexos-5-ulo-1,5-pyranose]. To identify genes involved in the assembly and attachment of this glycan, in-frame deletions were constructed in putative glycan assembly genes. Successful deletion of genes encoding three glycosyltransferases and an oligosaccharyltransferase (Stt3p homologue) resulted in Flagellins of decreased molecular masses as evidenced by immunoblotting, indicating partial or completely absent glycan structures. Deletion of the oligosaccharyltransferase or the glycosyltransferase responsible for the transfer of the second sugar in the chain resulted in Flagellins that were not assembled into flagella filaments, as evidenced by electron microscopy. Deletions of the glycosyltransferases responsible for the addition of the third and terminal sugars in the glycan were confirmed by mass spectrometry analysis of purified Flagellins from these mutants. Although flagellated, these mutants had decreased motility as evidenced by semi-swarm plate analysis with the presence of each additional sugar improving movement capabilities.
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identification of a putative acetyltransferase gene mmp0350 which affects proper assembly of both flagella and pili in the archaeon methanococcus maripaludis
Journal of Bacteriology, 2008Co-Authors: David J Vandyke, Masaomi Kanbe, Sandy Y. M. Ng, Bonnie Chaban, Shin-ichi Aizawa, John Wu, Ken F. JarrellAbstract:Glycosylation is a posttranslational modification utilized in all three domains of life. Compared to eukaryotic and bacterial systems, knowledge of the archaeal processes involved in glycosylation is limited. Recently, Methanococcus voltae Flagellin proteins were found to have an N-linked trisaccharide necessary for proper flagellum assembly. Current analysis by mass spectrometry of Methanococcus maripaludis Flagellin proteins also indicated the attachment of an N-glycan containing acetylated sugars. To identify genes involved in sugar biosynthesis in M. maripaludis, a putative acetyltransferase was targeted for in-frame deletion. Deletion of this gene (MMP0350) resulted in a Flagellin molecular mass shift to a size comparable to that expected for underglycosylated or completely nonglycoslyated Flagellins, as determined by immunoblotting. Assembled flagellar filaments were not observed by electron microscopy. Interestingly, the deletion also resulted in defective pilus anchoring. Mutant cells with a deletion of MMP0350 had very few, if any, pili attached to the cell surface compared to a nonflagellated but piliated strain. However, pili were obtained from culture supernatants of this strain, indicating that the defect was not in pilus assembly but in stable attachment to the cell surface. Complementation of MMP0350 on a plasmid restored pilus attachment, but it was unable to restore flagellation, likely because the mutant ceased to make detectable Flagellin. These findings represent the first report of a biosynthetic gene involved in Flagellin glycosylation in archaea. Also, it is the first gene to be associated with pili, linking flagellum and pilus structure and assembly through posttranslational modifications.
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cleavage of preFlagellins by an aspartic acid signal peptidase is essential for flagellation in the archaeon methanococcus voltae
Molecular Microbiology, 2003Co-Authors: Sonia L Bardy, Ken F. JarrellAbstract:The differences between archaeal and bacterial flagella are becoming more apparent as research on the archaeal structure progresses. One crucial difference is the presence of a leader peptide on archaeal preFlagellins, which is removed from the Flagellin prior to its incorporation into the flagellar filament. The enzyme responsible for the removal of the Flagellin leader peptide was identified as FlaK. FlaK of Methanococcus voltae retains its preFlagellin peptidase activity when expressed in Escherichia coli and used in an in vitro assay. Homologous recombination of an integration vector into the chromosomal copy of flaK resulted in a non-motile, non-flagellated phenotype. The Flagellins of the mutant had larger molecular weights than their wild-type counterparts, as expected if they retained their 11- to 12-amino-acid leader peptide. Membranes of the flaK mutant were unable to process preFlagellin in the in vitro assay. Site-directed mutagenesis demonstrated that two aspartic acid residues conserved with ones in type IV prepilin peptidases were necessary for proper recognition or processing of the preFlagellin. As bacterial Flagellins lack a leader peptide and a peptidase is not required for export and assembly, the requirement for FlaK further emphasizes the similarity archaeal flagella have with type IV pili, rather than with bacterial flagella.
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the archaeal flagellum a different kind of prokaryotic motility structure
Fems Microbiology Reviews, 2001Co-Authors: Nikhil A Thomas, Sonia L Bardy, Ken F. JarrellAbstract:The archaeal flagellum is a unique motility apparatus distinct in composition and likely in assembly from the bacterial flagellum. Gene families comprised of multiple Flagellin genes co-transcribed with a number of conserved, archaeal-specific accessory genes have been identified in several archaea. However, no homologues of any bacterial genes involved in flagella structure have yet been identified in any archaeon, including those archaea in which the complete genome sequence has been published. Archaeal Flagellins possess a highly conserved hydrophobic N-terminal sequence that is similar to that of type IV pilins and clearly unlike that of bacterial Flagellins. Also unlike bacterial Flagellins but similar to type IV pilins, archaeal Flagellins are initially synthesized with a short leader peptide that is cleaved by a membrane-located peptidase. With recent advances in genetic transfer systems in archaea, knockouts have been reported in several genes involved in flagellation in different archaea. In addition, techniques to isolate flagella with attached hook and anchoring structures have been developed. Analysis of these preparations is under way to identify minor structural components of archaeal flagella. This and the continued isolation and characterization of flagella mutants should lead to significant advances in our knowledge of the composition and assembly of archaeal flagella.
Yue Zhao - One of the best experts on this subject based on the ideXlab platform.
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sequence determinants of specific pattern recognition of bacterial ligands by the naip nlrc4 inflammasome
Cell discovery, 2018Co-Authors: Jingyi Yang, Maohua Zhong, Dihan Zhou, Ejuan Zhang, Yaoming Li, Yue Zhao, Yi Yang, Peng Li, Mengji Lu, Feng ShaoAbstract:The NLR apoptosis inhibitory proteins (NAIPs) function as specific cytosolic receptors for bacterial ligands to form the NAIP–NLRC4 inflammasome for anti-bacterial defenses. In mice, NAIP5/6 and NAIP2 recognize bacteria Flagellin and the rod protein of the type III secretion system (T3SS), respectively. However, molecular mechanism for specific ligand pattern-recognition by the NAIPs is largely unknown. Here, through extensive domain swapping and truncation analyses, three structural domains, the pre-BIR, BIR1, and HD1, in NAIP2 and NAIP5 are identified, that are important for specific recognition of their respective ligand(s). The three domains are sufficient to confer the ligand specificity for NAIP2. Asp-18, Arg-108, and Arg-667, respectively, in the pre-BIR, BIR1 and HD1 of NAIP2 are further identified, each of which is essential for efficient binding to the rod protein. To our surprise, we find that the C-terminal leucine-rich repeat domain is dispensable for NAIP2 recognition of the T3SS rod protein, but is required for NAIP5 binding to Flagellin. At the ligand side, we discover that the C-terminal 35 residues in Flagellin are crucial for binding to NAIP5. Among the 35 residues, three critical residues are identified, which determine Flagellin recognition by NAIP5 and subsequent inflammasome activation. The differences in the three amino-acid residues among Flagellins from various pathogenic and commensal bacterial species correlate well with whether they are susceptible to NAIP5-mediated immune detection. Taken together, our studies identify critical sequence and amino-acid determinants in both NAIP receptors and the bacterial ligand Flagellin that are important for the specificity of the pattern-recognition.
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the nlrc4 inflammasome receptors for bacterial Flagellin and type iii secretion apparatus
Nature, 2011Co-Authors: Yue Zhao, Jieling Yang, Yinan Gong, Qiuhe Lu, Hao Xu, Feng ShaoAbstract:The inflammasomes are multiprotein complexes involved in innate immunity, and induce an immune response to pathogenic microbes by activating the caspase 1 protease. Two groups now report that the intracellular receptors known as NAIPs (NLR family, apoptosis inhibitory proteins), previously thought to have an auxiliary role in recognizing microbial proteins, are in fact central to the process. Eric Kofoed and Russell Vance, and Feng Shao and colleagues, show that different members of the NAIP family bind to different bacterial ligands, including bacterial Flagellin and a conserved bacterial type III secretion system rod protein. Inflammasomes are large cytoplasmic complexes that sense microbial infections/danger molecules and induce caspase-1 activation-dependent cytokine production and macrophage inflammatory death1,2. The inflammasome assembled by the NOD-like receptor (NLR) protein NLRC4 responds to bacterial Flagellin and a conserved type III secretion system (TTSS) rod component3,4,5. How the NLRC4 inflammasome detects the two bacterial products and the molecular mechanism of NLRC4 inflammasome activation are not understood. Here we show that NAIP5, a BIR-domain NLR protein required for Legionella pneumophila replication in mouse macrophages6, is a universal component of the Flagellin–NLRC4 pathway. NAIP5 directly and specifically interacted with Flagellin, which determined the inflammasome-stimulation activities of different bacterial Flagellins. NAIP5 engagement by Flagellin promoted a physical NAIP5–NLRC4 association, rendering full reconstitution of a Flagellin-responsive NLRC4 inflammasome in non-macrophage cells. The related NAIP2 functioned analogously to NAIP5, serving as a specific inflammasome receptor for TTSS rod proteins such as Salmonella PrgJ and Burkholderia BsaK. Genetic analysis of Chromobacterium violaceum infection revealed that the TTSS needle protein CprI can stimulate NLRC4 inflammasome activation in human macrophages. Similarly, CprI is specifically recognized by human NAIP, the sole NAIP family member in human. The finding that NAIP proteins are inflammasome receptors for bacterial Flagellin and TTSS apparatus components further predicts that the remaining NAIP family members may recognize other unidentified microbial products to activate NLRC4 inflammasome-mediated innate immunity.
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the nlrc4 inflammasome receptors for bacterial Flagellin and type iii secretion apparatus
Nature, 2011Co-Authors: Yue Zhao, Jieling Yang, Yinan Gong, Jianjin Shi, Liping Liu, Feng ShaoAbstract:Inflammasomes are large cytoplasmic complexes that sense microbial infections/danger molecules and induce caspase-1 activation-dependent cytokine production and macrophage inflammatory death. The inflammasome assembled by the NOD-like receptor (NLR) protein NLRC4 responds to bacterial Flagellin and a conserved type III secretion system (TTSS) rod component. How the NLRC4 inflammasome detects the two bacterial products and the molecular mechanism of NLRC4 inflammasome activation are not understood. Here we show that NAIP5, a BIR-domain NLR protein required for Legionella pneumophila replication in mouse macrophages, is a universal component of the Flagellin-NLRC4 pathway. NAIP5 directly and specifically interacted with Flagellin, which determined the inflammasome-stimulation activities of different bacterial Flagellins. NAIP5 engagement by Flagellin promoted a physical NAIP5-NLRC4 association, rendering full reconstitution of a Flagellin-responsive NLRC4 inflammasome in non-macrophage cells. The related NAIP2 functioned analogously to NAIP5, serving as a specific inflammasome receptor for TTSS rod proteins such as Salmonella PrgJ and Burkholderia BsaK. Genetic analysis of Chromobacterium violaceum infection revealed that the TTSS needle protein CprI can stimulate NLRC4 inflammasome activation in human macrophages. Similarly, CprI is specifically recognized by human NAIP, the sole NAIP family member in human. The finding that NAIP proteins are inflammasome receptors for bacterial Flagellin and TTSS apparatus components further predicts that the remaining NAIP family members may recognize other unidentified microbial products to activate NLRC4 inflammasome-mediated innate immunity.