RESUMEN
Inflammasomes are supramolecular complexes that form in the cytosol in response to pathogen-associated and damage-associated stimuli, as well as other danger signals that perturb cellular homoeostasis, resulting in host defence responses in the form of cytokine release and programmed cell death (pyroptosis). Inflammasome activity is closely associated with numerous human disorders, including rare genetic syndromes of autoinflammation, cardiovascular diseases, neurodegeneration and cancer. In recent years, a range of inflammasome components and their functions have been discovered, contributing to our knowledge of the overall machinery. Here, we review the latest advances in inflammasome biology from the perspective of structural and mechanistic studies. We focus on the most well-studied components of the canonical inflammasome - NAIP-NLRC4, NLRP3, NLRP1, CARD8 and caspase-1 - as well as caspase-4, caspase-5 and caspase-11 of the noncanonical inflammasome, and the inflammasome effectors GSDMD and NINJ1. These structural studies reveal important insights into how inflammasomes are assembled and regulated, and how they elicit the release of IL-1 family cytokines and induce membrane rupture in pyroptosis.
Asunto(s)
Inflamasomas , Piroptosis , Inflamasomas/inmunología , Inflamasomas/metabolismo , Humanos , Piroptosis/inmunología , Animales , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas Adaptadoras de Señalización CARD/genética , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/genética , Proteínas de Unión a Fosfato/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/inmunología , Caspasas/metabolismo , Caspasas/inmunología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Péptidos y Proteínas de Señalización Intracelular/inmunología , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas NLR/metabolismo , Proteínas de Unión al Calcio/metabolismo , Proteínas de Unión al Calcio/inmunología , GasderminasRESUMEN
Salmonella enterica serovar Typhimurium is a Gram-negative pathogen that uses two distinct type III secretion systems (T3SSs), termed Salmonella pathogenicity island (SPI)-1 and SPI-2, to deliver virulence factors into the host cell. The SPI-1 T3SS enables Salmonella to invade host cells, while the SPI-2 T3SS facilitates Salmonella's intracellular survival. In mice, a family of cytosolic immune sensors, including NAIP1, NAIP2, and NAIP5/6, recognizes the SPI-1 T3SS needle, inner rod, and flagellin proteins, respectively. Ligand recognition triggers assembly of the NAIP/NLRC4 inflammasome, which mediates caspase-1 activation, IL-1 family cytokine secretion, and pyroptosis of infected cells. In contrast to mice, humans encode a single NAIP that broadly recognizes all three ligands. The role of NAIP/NLRC4 or other inflammasomes during Salmonella infection of human macrophages is unclear. We find that although the NAIP/NLRC4 inflammasome is essential for detecting T3SS ligands in human macrophages, it is partially required for responses to infection, as Salmonella also activated the NLRP3 and CASP4/5 inflammasomes. Importantly, we demonstrate that combinatorial NAIP/NLRC4 and NLRP3 inflammasome activation restricts Salmonella replication in human macrophages. In contrast to SPI-1, the SPI-2 T3SS inner rod is not sensed by human or murine NAIPs, which is thought to allow Salmonella to evade host recognition and replicate intracellularly. Intriguingly, we find that human NAIP detects the SPI-2 T3SS needle protein. Critically, in the absence of both flagellin and the SPI-1 T3SS, the NAIP/NLRC4 inflammasome still controlled intracellular Salmonella burden. These findings reveal that recognition of Salmonella SPI-1 and SPI-2 T3SSs and engagement of both the NAIP/NLRC4 and NLRP3 inflammasomes control Salmonella infection in human macrophages.
Asunto(s)
Inflamasomas/inmunología , Macrófagos/inmunología , Macrófagos/microbiología , Infecciones por Salmonella/inmunología , Sistemas de Secreción Tipo III/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas de Unión al Calcio/inmunología , Humanos , Proteína con Dominio Pirina 3 de la Familia NLR/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Salmonella typhimurium/inmunología , Salmonella typhimurium/patogenicidad , VirulenciaRESUMEN
Inflammasomes are cytosolic multi-protein complexes that detect infection or cellular damage and activate the Caspase-1 (CASP1) protease. The NAIP5/NLRC4 inflammasome detects bacterial flagellin and is essential for resistance to the flagellated intracellular bacterium Legionella pneumophila. The effectors required downstream of NAIP5/NLRC4 to restrict bacterial replication remain unclear. Upon NAIP5/NLRC4 activation, CASP1 cleaves and activates the pore-forming protein Gasdermin-D (GSDMD) and the effector caspase-7 (CASP7). However, Casp1-/- (and Casp1/11-/-) mice are only partially susceptible to L. pneumophila and do not phenocopy Nlrc4-/-mice, because NAIP5/NLRC4 also activates CASP8 for restriction of L. pneumophila infection. Here we show that CASP8 promotes the activation of CASP7 and that Casp7/1/11-/- and Casp8/1/11-/- mice recapitulate the full susceptibility of Nlrc4-/- mice. Gsdmd-/- mice exhibit only mild susceptibility to L. pneumophila, but Gsdmd-/-Casp7-/- mice are as susceptible as the Nlrc4-/- mice. These results demonstrate that GSDMD and CASP7 are the key substrates downstream of NAIP5/NLRC4/CASP1/8 required for resistance to L. pneumophila.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas de Unión al Calcio/inmunología , Caspasa 1/inmunología , Caspasa 7/inmunología , Caspasa 8/inmunología , Inflamasomas/inmunología , Legionella pneumophila/inmunología , Enfermedad de los Legionarios/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Animales , Proteínas Reguladoras de la Apoptosis/genética , Proteínas de Unión al Calcio/genética , Caspasa 1/genética , Caspasa 7/genética , Caspasa 8/genética , Inflamasomas/genética , Péptidos y Proteínas de Señalización Intracelular , Enfermedad de los Legionarios/genética , Enfermedad de los Legionarios/patología , Ratones , Ratones Noqueados , Proteína Inhibidora de la Apoptosis Neuronal/genética , Proteínas de Unión a FosfatoRESUMEN
Robust innate immune detection of rapidly evolving pathogens is critical for host defense. Nucleotide-binding domain leucine-rich repeat (NLR) proteins function as cytosolic innate immune sensors in plants and animals. However, the structural basis for ligand-induced NLR activation has so far remained unknown. NAIP5 (NLR family, apoptosis inhibitory protein 5) binds the bacterial protein flagellin and assembles with NLRC4 to form a multiprotein complex called an inflammasome. Here we report the cryo-electron microscopy structure of the assembled ~1.4-megadalton flagellin-NAIP5-NLRC4 inflammasome, revealing how a ligand activates an NLR. Six distinct NAIP5 domains contact multiple conserved regions of flagellin, prying NAIP5 into an open and active conformation. We show that innate immune recognition of multiple ligand surfaces is a generalizable strategy that limits pathogen evolution and immune escape.
Asunto(s)
Flagelina/inmunología , Interacciones Huésped-Patógeno/inmunología , Inflamasomas/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Animales , Proteínas Reguladoras de la Apoptosis/química , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Reguladoras de la Apoptosis/ultraestructura , Proteínas de Unión al Calcio/química , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/ultraestructura , Microscopía por Crioelectrón , Flagelina/química , Flagelina/ultraestructura , Células HEK293 , Humanos , Inmunidad Innata , Inflamasomas/química , Inflamasomas/ultraestructura , Legionella pneumophila , Ratones , Mutación , Proteína Inhibidora de la Apoptosis Neuronal/química , Proteína Inhibidora de la Apoptosis Neuronal/genética , Dominios ProteicosRESUMEN
Myeloid cells assemble inflammasomes in response to infection or cell damage; cytosolic sensors activate pro-caspase-1, indirectly for the most part, via the adaptors ASC and NLRC4. This leads to secretion of proinflammatory cytokines and pyroptosis. To explore complex formation under physiological conditions, we generated an alpaca single domain antibody, VHHASC, which specifically recognizes the CARD of human ASC via its type II interface. VHHASC not only impairs ASC(CARD) interactions in vitro, but also inhibits inflammasome activation in response to NLRP3, AIM2, and NAIP triggers when expressed in living cells, highlighting a role of ASC in all three types of inflammasomes. VHHASC leaves the Pyrin domain of ASC functional and stabilizes a filamentous intermediate of inflammasome activation. Incorporation of VHHASC-EGFP into these structures allowed the visualization of endogenous ASC(PYD) filaments for the first time. These data revealed that cross-linking of ASC(PYD) filaments via ASC(CARD) mediates the assembly of ASC foci.
Asunto(s)
Proteínas del Citoesqueleto/inmunología , Inflamasomas/inmunología , Monocitos/inmunología , Anticuerpos de Cadena Única/farmacología , Células A549 , Proteínas Adaptadoras de Señalización CARD , Proteínas de Unión al ADN/inmunología , Femenino , Humanos , Masculino , Proteína con Dominio Pirina 3 de la Familia NLR/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Anticuerpos de Cadena Única/inmunologíaRESUMEN
NLRs (nucleotide-binding domain [NBD] leucine-rich repeat [LRR]-containing proteins) exhibit diverse functions in innate and adaptive immunity. NAIPs (NLR family, apoptosis inhibitory proteins) are NLRs that appear to function as cytosolic immunoreceptors for specific bacterial proteins, including flagellin and the inner rod and needle proteins of bacterial type III secretion systems (T3SSs). Despite strong biochemical evidence implicating NAIPs in specific detection of bacterial ligands, genetic evidence has been lacking. Here we report the use of CRISPR/Cas9 to generate Naip1(-/-) and Naip2(-/-) mice, as well as Naip1-6(Δ/Δ) mice lacking all functional Naip genes. By challenging Naip1(-/-) or Naip2(-/-) mice with specific bacterial ligands in vivo, we demonstrate that Naip1 is uniquely required to detect T3SS needle protein and Naip2 is uniquely required to detect T3SS inner rod protein, but neither Naip1 nor Naip2 is required for detection of flagellin. Previously generated Naip5(-/-) mice retain some residual responsiveness to flagellin in vivo, whereas Naip1-6(Δ/Δ) mice fail to respond to cytosolic flagellin, consistent with previous biochemical data implicating NAIP6 in flagellin detection. Our results provide genetic evidence that specific NAIP proteins function to detect specific bacterial proteins in vivo.
Asunto(s)
Bacterias/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Sistemas de Secreción Tipo III/inmunología , Animales , Bacterias/genética , Flagelina/genética , Flagelina/inmunología , Ratones , Ratones Noqueados , Proteína Inhibidora de la Apoptosis Neuronal/genética , Sistemas de Secreción Tipo III/genéticaRESUMEN
Biochemical studies suggest that the NAIP family of NLR proteins are cytosolic innate receptors that directly recognize bacterial ligands and trigger NLRC4 inflammasome activation. In this study, we generated Naip5(-/-), Naip1(-/-), and Naip2(-/-) mice and showed that bone marrow macrophages derived from these knockout mice are specifically deficient in detecting bacterial flagellin, the type III secretion system needle, and the rod protein, respectively. Naip1(-/-), Naip2(-/-), and Naip5(-/-) mice also resist lethal inflammasome activation by the corresponding ligand. Furthermore, infections performed in the Naip-deficient macrophages have helped to define the major signal in Legionella pneumophila, Salmonella Typhimurium and Shigella flexneri that is detected by the NAIP/NLRC4 inflammasome. Using an engineered S. Typhimurium infection model, we demonstrate the critical role of NAIPs in clearing bacterial infection and protecting mice from bacterial virulence-induced lethality. These results provide definitive genetic evidence for the important physiological function of NAIPs in antibacterial defense and inflammatory damage-induced lethality in mice.
Asunto(s)
Células de la Médula Ósea/inmunología , Bacterias Gramnegativas , Infecciones por Bacterias Gramnegativas/inmunología , Inflamasomas/inmunología , Macrófagos/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Factores de Virulencia/inmunología , Animales , Bacterias Gramnegativas/inmunología , Bacterias Gramnegativas/patogenicidad , Inflamasomas/genética , Ratones , Ratones Noqueados , Proteína Inhibidora de la Apoptosis Neuronal/genética , Factores de Virulencia/genéticaRESUMEN
Murine NLR family, apoptosis inhibitory protein (Naip)1, Naip2, and Naip5/6 are host sensors that detect the cytosolic presence of needle and rod proteins from bacterial type III secretion systems and flagellin, respectively. Previous studies using human-derived macrophage-like cell lines indicate that human macrophages sense the cytosolic needle protein, but not bacterial flagellin. In this study, we show that primary human macrophages readily sense cytosolic flagellin. Infection of primary human macrophages with Salmonella elicits robust cell death and IL-1ß secretion that is dependent on flagellin. We show that flagellin detection requires a full-length isoform of human Naip. This full-length Naip isoform is robustly expressed in primary macrophages from healthy human donors, but it is drastically reduced in monocytic tumor cells, THP-1, and U937, rendering them insensitive to cytosolic flagellin. However, ectopic expression of full-length Naip rescues the ability of U937 cells to sense flagellin. In conclusion, human Naip functions to activate the inflammasome in response to flagellin, similar to murine Naip5/6.
Asunto(s)
Sistemas de Secreción Bacterianos/inmunología , Flagelina/inmunología , Inflamasomas/inmunología , Macrófagos/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Células Cultivadas , Humanos , Interleucina-1beta/inmunología , Interleucina-1beta/metabolismo , Proteína Inhibidora de la Apoptosis Neuronal/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/inmunología , Salmonella/inmunología , Infecciones por Salmonella/inmunología , Células U937RESUMEN
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-1ß 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.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Infecciones/inmunología , Inflamasomas/metabolismo , Proteínas Adaptadoras Transductoras de Señales/inmunología , Animales , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Interacciones Huésped-Patógeno , Humanos , Inmunidad Activa , Inflamasomas/inmunología , Proteínas NLR , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismoRESUMEN
Lower respiratory tract infections (LRTIs) are a persistent and pervasive public health problem worldwide. Pneumonia and other LRTIs will be among the leading causes of death in adults, and pneumonia is the single largest cause of death in children. LRTIs are also an important cause of acute lung injury and acute exacerbations of chronic obstructive pulmonary disease. Because innate immunity is the first line of defense against pathogens, understanding the role of innate immunity in the pulmonary system is of paramount importance. Pattern recognition molecules (PRMs) that recognize microbial-associated molecular patterns are an integral component of the innate immune system and are located in both cell membranes and cytosol. Toll-like receptors and nucleotide-binding oligomerization domain-like receptors (NLRs) are the major sensors at the forefront of pathogen recognition. Although Toll-like receptors have been extensively studied in host immunity, NLRs have diverse and important roles in immune and inflammatory responses, ranging from antimicrobial properties to adaptive immune responses. The lung contains NLR-expressing immune cells such as leukocytes and nonimmune cells such as epithelial cells that are in constant and close contact with invading microbes. This pulmonary perspective addresses our current understanding of the structure and function of NLR family members, highlighting advances and gaps in knowledge, with a specific focus on immune responses in the respiratory tract during bacterial infection. Further advances in exploring cellular and molecular responses to bacterial pathogens are critical to develop improved strategies to treat and prevent devastating infectious diseases of the lung.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/inmunología , Infecciones Bacterianas/inmunología , Receptores Citoplasmáticos y Nucleares/inmunología , Infecciones del Sistema Respiratorio/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas de Unión al Calcio/inmunología , Proteínas Portadoras/inmunología , Humanos , Inflamasomas/inmunología , Proteína con Dominio Pirina 3 de la Familia NLR , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Adaptadora de Señalización NOD1/inmunología , Proteína Adaptadora de Señalización NOD2/inmunologíaRESUMEN
A major function of a subfamily of NLR (nucleotide-binding domain, leucine-rich repeat containing, or NOD-like receptor) proteins is in inflammasome activation, which has been implicated in a multitude of disease models and human diseases. This work will highlight key progress in understanding the mechanisms that activate the best-studied NLRs (NLRP3, NLRC4, NAIP, and NLRP1) and in uncovering inflammasome NLRs.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteínas de Unión al Calcio/metabolismo , Proteínas Portadoras/metabolismo , Inflamasomas/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Proteínas Adaptadoras Transductoras de Señales/inmunología , Animales , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas de Unión al Calcio/inmunología , Proteínas Portadoras/inmunología , Caspasa 1/metabolismo , Activación Enzimática , Humanos , Ratones , Proteína con Dominio Pirina 3 de la Familia NLR , Proteínas NLR , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Receptores Citoplasmáticos y Nucleares/inmunología , Transducción de SeñalRESUMEN
Infection of macrophages by bacterial pathogens can trigger Toll-like receptor (TLR) activation as well as Nod-like receptors (NLRs) leading to inflammasome formation and cell death dependent on caspase-1 (pyroptosis). Complicating the study of inflammasome activation is priming. Here, we develop a priming-free NLRC4 inflammasome activation system to address the necessity and role of priming in pyroptotic cell death and damage-associated molecular pattern (DAMP) release. We find pyroptosis is not dependent on priming and when priming is re-introduced pyroptosis is unaffected. Cells undergoing unprimed pyroptosis appear to be independent of mitochondrial involvement and do not produce inflammatory cytokines, nitrous oxide (NO), or reactive oxygen species (ROS). Nevertheless, they undergo an explosive cell death releasing a chemotactic isoform of the DAMP high mobility group protein box 1 (HMGB1). Importantly, priming through surface TLRs but not endosomal TLRs during pyroptosis leads to the release of a new TLR4-agonist cysteine redox isoform of HMGB1. These results show that pyroptosis is dominant to priming signals and indicates that metabolic changes triggered by priming can affect how cell death is perceived by the immune system.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas de Unión al Calcio/metabolismo , Caspasa 1/metabolismo , Proteína HMGB1/metabolismo , Macrófagos/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Receptores Toll-Like/metabolismo , Acetilación , Secuencia de Aminoácidos , Animales , Apoptosis , Proteínas Reguladoras de la Apoptosis/agonistas , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Bacterianas/metabolismo , Proteínas de Unión al Calcio/agonistas , Proteínas de Unión al Calcio/inmunología , Muerte Celular , Línea Celular , Expresión Génica , Proteína HMGB1/análisis , Interacciones Huésped-Patógeno , Inflamasomas/inmunología , Inflamasomas/metabolismo , Activación de Macrófagos/fisiología , Macrófagos/microbiología , Macrófagos/fisiología , Ratones , Datos de Secuencia Molecular , Proteína Inhibidora de la Apoptosis Neuronal/agonistas , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Isoformas de Proteínas/metabolismo , Transducción de Señal , Receptores Toll-Like/inmunologíaRESUMEN
Pseudomonas aeruginosa is an opportunistic pathogen involved in nosocomial infections. Flagellin is a P. aeruginosa virulence factor involved in host response to this pathogen. We examined the role of flagellin in P. aeruginosa-induced mucus secretion. Using a mouse model of pulmonary infection we showed that PAK, a wild type strain of P. aeruginosa, induced airway mucus secretion and mucin muc5ac expression at higher levels than its flagellin-deficient mutant (ΔFliC). PAK induced expression of MUC5AC and MUC2 in both human airway epithelial NCI-H292 cell line and in primary epithelial cells. In contrast, ΔFliC infection had lower to no effect on MUC5AC and MUC2 expressions. A purified P. aeruginosa flagellin induced MUC5AC expression in parallel to IL-8 secretion in NCI-H292 cells. Accordingly, ΔFliC mutant stimulated IL-8 secretion at significantly lower levels compared to PAK. Incubation of NCI-H292 cells with exogenous IL-8 induced MUC5AC expression and pre-incubation of these cells with an anti-IL-8 antibody abrogated flagellin-mediated MUC5AC expression. Silencing of TLR5 and Naip, siRNA inhibited both flagellin-induced MUC5AC expression and IL-8 secretion. Finally, inhibition of ERK abolished the expression of both PAK- and flagellin-induced MUC5AC. We conclude that: (i) flagellin is crucial in P. aeruginosa-induced mucus hyper-secretion through TLR5 and Naip pathways; (ii) this process is mediated by ERK and amplified by IL-8. Our findings help understand the mechanisms involved in mucus secretion during pulmonary infectious disease induced by P. aeruginosa, such as in cystic fibrosis.
Asunto(s)
Flagelina/metabolismo , Moco/metabolismo , Infecciones por Pseudomonas/metabolismo , Pseudomonas aeruginosa/metabolismo , Mucosa Respiratoria/metabolismo , Transducción de Señal , Animales , Línea Celular , Femenino , Flagelina/inmunología , Regulación de la Expresión Génica/inmunología , Humanos , Interleucina-8/biosíntesis , Interleucina-8/inmunología , Ratones , Mucina 5AC/biosíntesis , Mucina 5AC/inmunología , Mucina 2/biosíntesis , Mucina 2/inmunología , Moco/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Infecciones por Pseudomonas/inmunología , Pseudomonas aeruginosa/inmunología , Pseudomonas aeruginosa/patogenicidad , Mucosa Respiratoria/inmunología , Mucosa Respiratoria/microbiología , Receptor Toll-Like 5/inmunología , Receptor Toll-Like 5/metabolismoRESUMEN
The innate immune system of mammals encodes several families of immune detector proteins that monitor the cytosol for signs of pathogen invasion. One important but poorly understood family of cytosolic immunosurveillance proteins is the NLR (nucleotide-binding domain, leucine-rich repeat containing) proteins. Recent work has demonstrated that one subfamily of NLRs, the NAIPs (NLR family, apoptosis inhibitory proteins), are activated by specific interaction with bacterial ligands, such as flagellin. NAIP activation leads to assembly of a large multiprotein complex called the inflammasome, which initiates innate immune responses by activation of the Caspase-1 protease. NAIPs therefore appear to detect pathogen molecules via a simple and direct receptor-ligand mechanism. Interestingly, other NLR family members appear to detect pathogens indirectly, perhaps by responding to host cell "stress" caused by the pathogen. Thus, the NLR family may have evolved surprisingly diverse mechanisms for detecting pathogens.
Asunto(s)
Proteínas Bacterianas/inmunología , Citosol/microbiología , Inmunidad Innata , Inflamasomas/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Bacterias/inmunología , Bacterias/metabolismo , Infecciones Bacterianas/inmunología , Infecciones Bacterianas/metabolismo , Infecciones Bacterianas/microbiología , Proteínas Bacterianas/metabolismo , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Citosol/inmunología , Citosol/metabolismo , Flagelina/inmunología , Flagelina/metabolismo , Interacciones Huésped-Patógeno , Humanos , Inflamasomas/metabolismo , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Estructura Terciaria de Proteína , Especificidad por SustratoRESUMEN
The inflammasome is an emerging new pathway in innate immune defense against microbial infection or endogenous danger signals. The inflammasome stimulates activation of inflammatory caspases, mainly caspase-1. Caspase-1 activation is responsible for processing and secretion of IL-1ß and IL-18 as well as for inducing macrophage pyroptotic death. Assembly of the large cytoplasmic inflammasome complex is thought to be mediated by members of NOD-like receptor (NLR) family. While functions of most of the NLR proteins remain to be defined, several NLR proteins including NLRC4 have been shown to assemble distinct inflammasome complexes. These inflammasome pathways, particularly the NLRC4 inflammasome, play a critical role in sensing and restricting diverse types of bacterial infections. Here we review recent advances in defining the exact bacterial ligands and the ligand-binding receptors involved in NLRC4 inflammasome activation. Implications of the discovery of the NAIP family of inflammasome receptors for bacterial flagellin and type III secretion apparatus on future inflammasome and bacterial infection studies are also discussed.
Asunto(s)
Infecciones Bacterianas/metabolismo , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Animales , Bacterias/inmunología , Infecciones Bacterianas/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Caspasa 1/metabolismo , Flagelina/inmunología , Flagelina/metabolismo , Humanos , Inmunidad Innata/inmunología , Macrófagos/inmunología , Macrófagos/metabolismo , Macrófagos/microbiología , Proteína Inhibidora de la Apoptosis Neuronal/inmunologíaRESUMEN
Synergy between intracellular and extracellular sensing mechanisms of the innate immune system improves adaptive immune responses to cancer vaccines and clearance of tumors.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Vacunas contra el Cáncer/inmunología , Neoplasias/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Receptores Toll-Like/inmunología , Receptores Toll-Like/metabolismo , Animales , Femenino , MasculinoRESUMEN
Toll-like receptor (TLR) ligands are increasingly being used as adjuvants in cancer vaccine trials to harness innate immunity and prime effective antitumor immune responses. Despite some success, enhancing tumor antigen presentation, promoting a protective antitumor response, and overcoming the immunosuppressive tumor microenvironment pose considerable challenges that necessitate further improvements in vaccine design. Here, we show that expression of the TLR ligand flagellin within tumor cells constitutes an effective antitumor vaccination strategy that relies on simultaneous engagement of TLR5 and the Nod-like receptors (NLRs) NLRC4/NAIP5 (neuronal apoptosis inhibitory protein 5) by flagellin along with associative recognition of tumor antigen for optimal antigen presentation to T cells. Although TLR5 signaling was critical for mediating rapid macrophage-dependent clearance of flagellin-expressing tumor cells in vivo, TLR5 and NLRC4/NAIP5 were equally important for priming antitumor CD4(+) and CD8(+) T cells and suppressing tumor growth. Vaccination with irradiated flagellin-expressing tumor cells prevented tumor development, and disrupting flagellin recognition by TLR5 or NLRC4/NAIP5 impaired protective immunization against an existing or subsequent tumor. Our findings delineate a new strategy to induce anticancer immune responses consisting of introducing microbial structures with dual TLR and NLR stimulatory activity into tumor cells. This ensures recognition of tumor-derived antigen within the inflammatory context of microbial recognition and additionally activates both the phagocytic and the cytosolic pathways of innate immune defense against the tumor.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Vacunas contra el Cáncer/inmunología , Neoplasias/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Receptores Toll-Like/inmunología , Receptores Toll-Like/metabolismo , Animales , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD8-positivos/metabolismo , Línea Celular Tumoral , Femenino , Flagelina/genética , Flagelina/metabolismo , Activación de Linfocitos/fisiología , Masculino , Ratones , Ratones Endogámicos C57BLAsunto(s)
Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Vacunas contra el Cáncer/inmunología , Neoplasias/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/metabolismo , Receptores Toll-Like/inmunología , Receptores Toll-Like/metabolismo , Animales , Femenino , MasculinoAsunto(s)
Antígenos Bacterianos/inmunología , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas Reguladoras de la Apoptosis/metabolismo , Bacterias/inmunología , Sistemas de Secreción Bacterianos/inmunología , Proteínas Adaptadoras de Señalización CARD/inmunología , Proteínas Adaptadoras de Señalización CARD/metabolismo , Proteínas de Unión al Calcio/inmunología , Proteínas de Unión al Calcio/metabolismo , Flagelina/inmunología , Inmunidad Innata/inmunología , Inflamasomas/inmunología , Proteína Inhibidora de la Apoptosis Neuronal/inmunología , Animales , HumanosRESUMEN
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.