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Nigericin, an ionophore derived from Streptomyces hygroscopicus, is arguably the most commonly used tool compound to study the NLRP3 inflammasome. Recent findings, however, showed that nigericin also activates the NLRP1 inflammasome in human keratinocytes. In this study, we resolve the mechanistic basis of nigericin-driven NLRP1 inflammasome activation. In multiple nonhematopoietic cell types, nigericin rapidly and specifically inhibits the elongation stage of the ribosome cycle by depleting cytosolic potassium ions. This activates the ribotoxic stress response (RSR) sensor kinase ZAKα, p38, and JNK, as well as the hyperphosphorylation of the NLRP1 linker domain. As a result, nigericin-induced pyroptosis in human keratinocytes is blocked by extracellular potassium supplementation, ZAKα knockout, or pharmacologic inhibitors of ZAKα and p38 kinase activities. By surveying a panel of ionophores, we show that electroneutrality of ion movement is essential to activate ZAKα-driven RSR and a greater extent of K+ depletion is necessary to activate ZAKα-NLRP1 than NLRP3. These findings resolve the mechanism by which nigericin activates NLRP1 in nonhematopoietic cell types and demonstrate an unexpected connection between RSR, perturbations of potassium ion flux, and innate immunity.
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Inflamasomas , Proteína con Dominio Pirina 3 de la Familia NLR , Humanos , Inflamasomas/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Nigericina/farmacología , Potasio/metabolismo , Inmunidad Innata , Ionóforos , Proteínas NLRRESUMEN
Cholesterol is important for membrane integrity and cell signaling, and dysregulation of the distribution of cellular cholesterol is associated with numerous diseases, including neurodegenerative disorders. While regulated transport of a specific pool of cholesterol, known as "accessible cholesterol", contributes to the maintenance of cellular cholesterol distribution and homeostasis, tools to monitor accessible cholesterol in live cells remain limited. Here, we engineer a highly sensitive accessible cholesterol biosensor by taking advantage of the cholesterol-sensing element (the GRAM domain) of an evolutionarily conserved lipid transfer protein, GRAMD1b. Using this cholesterol biosensor, which we call GRAM-W, we successfully visualize in real time the distribution of accessible cholesterol in many different cell types, including human keratinocytes and iPSC-derived neurons, and show differential dependencies on cholesterol biosynthesis and uptake for maintaining levels of accessible cholesterol. Furthermore, we combine GRAM-W with a dimerization-dependent fluorescent protein (ddFP) and establish a strategy for the ultrasensitive detection of accessible plasma membrane cholesterol. These tools will allow us to obtain important insights into the molecular mechanisms by which the distribution of cellular cholesterol is regulated.
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Técnicas Biosensibles , Colesterol , Humanos , Membrana Celular/metabolismo , Colesterol/metabolismo , Transporte Biológico , HomeostasisRESUMEN
Human airway and corneal epithelial cells, which are critically altered during chronic infections mediated by Pseudomonas aeruginosa, specifically express the inflammasome sensor NLRP1. Here, together with a companion study, we report that the NLRP1 inflammasome detects exotoxin A (EXOA), a ribotoxin released by P. aeruginosa type 2 secretion system (T2SS), during chronic infection. Mechanistically, EXOA-driven eukaryotic elongation factor 2 (EEF2) ribosylation and covalent inactivation promote ribotoxic stress and subsequent NLRP1 inflammasome activation, a process shared with other EEF2-inactivating toxins, diphtheria toxin and cholix toxin. Biochemically, irreversible EEF2 inactivation triggers ribosome stress-associated kinases ZAKα- and P38-dependent NLRP1 phosphorylation and subsequent proteasome-driven functional degradation. Finally, cystic fibrosis cells from patients exhibit exacerbated P38 activity and hypersensitivity to EXOA-induced ribotoxic stress-dependent NLRP1 inflammasome activation, a process inhibited by the use of ZAKα inhibitors. Altogether, our results show the importance of P. aeruginosa virulence factor EXOA at promoting NLRP1-dependent epithelial damage and identify ZAKα as a critical sensor of virulence-inactivated EEF2.
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Fibrosis Quística , Eucariontes , Humanos , Factor 2 de Elongación Peptídica , Inflamasomas , Citoplasma , Proteínas NLRRESUMEN
The ZAKα-driven ribotoxic stress response (RSR) is activated by ribosome stalling and/or collisions. Recent work demonstrates that RSR also plays a role in innate immunity by activating the human NLRP1 inflammasome. Here, we report that ZAKα and NLRP1 sense bacterial exotoxins that target ribosome elongation factors. One such toxin, diphtheria toxin (DT), the causative agent for human diphtheria, triggers RSR-dependent inflammasome activation in primary human keratinocytes. This process requires iron-mediated DT production in the bacteria, as well as diphthamide synthesis and ZAKα/p38-driven NLRP1 phosphorylation in host cells. NLRP1 deletion abrogates IL-1ß and IL-18 secretion by DT-intoxicated keratinocytes, while ZAKα deletion or inhibition additionally limits both pyroptotic and inflammasome-independent non-pyroptotic cell death. Consequently, pharmacologic inhibition of ZAKα is more effective than caspase-1 inhibition at protecting the epidermal barrier in a 3D skin model of cutaneous diphtheria. In summary, these findings implicate ZAKα-driven RSR and the NLRP1 inflammasome in antibacterial immunity and might explain certain aspects of diphtheria pathogenesis.
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Toxina Diftérica , Difteria , Humanos , Toxina Diftérica/toxicidad , Inflamasomas , Piroptosis , Inmunidad Innata , Proteínas NLRRESUMEN
Upon detecting pathogens or cell stress, several NOD-like receptors (NLRs) form inflammasome complexes with the adapter ASC and caspase-1, inducing gasdermin D (GSDMD)-dependent cell death and maturation and release of IL-1ß and IL-18. The triggers and activation mechanisms of several inflammasome-forming sensors are not well understood. Here we show that mitochondrial damage activates the NLRP10 inflammasome, leading to ASC speck formation and caspase-1-dependent cytokine release. While the AIM2 inflammasome can also sense mitochondrial demise by detecting mitochondrial DNA (mtDNA) in the cytosol, NLRP10 monitors mitochondrial integrity in an mtDNA-independent manner, suggesting the recognition of distinct molecular entities displayed by the damaged organelles. NLRP10 is highly expressed in differentiated human keratinocytes, in which it can also assemble an inflammasome. Our study shows that this inflammasome surveils mitochondrial integrity. These findings might also lead to a better understanding of mitochondria-linked inflammatory diseases.
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Citocinas , Inflamasomas , Humanos , Inflamasomas/metabolismo , Caspasa 1/metabolismo , Citocinas/metabolismo , Muerte Celular , ADN Mitocondrial/genética , Interleucina-1beta/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismoRESUMEN
Nucleotide-binding oligomerization domain (NBD), leucine-rich repeat (LRR) containing protein family (NLRs) are intracellular pattern recognition receptors that mediate innate immunity against infections. The endothelium is the first line of defense against blood-borne pathogens, but it is unclear which NLRs control endothelial cell (EC) intrinsic immunity. Here, we demonstrate that human ECs simultaneously activate NLRP1 and CARD8 inflammasomes in response to DPP8/9 inhibitor Val-boro-Pro (VbP). Enterovirus Coxsackie virus B3 (CVB3)-the most common cause of viral myocarditis-predominantly activates CARD8 in ECs in a manner that requires viral 2A and 3C protease cleavage at CARD8 p.G38 and proteasome function. Genetic deletion of CARD8 in ECs and human embryonic stem cell-derived cardiomyocytes (HCMs) attenuates CVB3-induced pyroptosis, inflammation, and viral propagation. Furthermore, using a stratified endothelial-cardiomyocyte co-culture system, we demonstrate that deleting CARD8 in ECs reduces CVB3 infection of the underlying cardiomyocytes. Our study uncovers the unique role of CARD8 inflammasome in endothelium-intrinsic anti-viral immunity.
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Sistema Cardiovascular , Inflamasomas , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Adaptadoras de Señalización CARD/metabolismo , Sistema Cardiovascular/metabolismo , Humanos , Inflamasomas/metabolismo , Leucina , Proteínas de Neoplasias/metabolismo , Nucleótidos , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteasas ViralesRESUMEN
Dipeptidyl peptidase 9 (DPP9) is a direct inhibitor of NLRP1, but how it affects inflammasome regulation in vivo is not yet established. Here, we report three families with immune-associated defects, poor growth, pancytopenia, and skin pigmentation abnormalities that segregate with biallelic DPP9 rare variants. Using patient-derived primary cells and biochemical assays, these variants were shown to behave as hypomorphic or knockout alleles that failed to repress NLRP1. The removal of a single copy of Nlrp1a/b/c, Asc, Gsdmd, or Il-1r, but not Il-18, was sufficient to rescue the lethality of Dpp9 mutant neonates in mice. Similarly, dpp9 deficiency was partially rescued by the inactivation of asc, an obligate downstream adapter of the NLRP1 inflammasome, in zebrafish. These experiments suggest that the deleterious consequences of DPP9 deficiency were mostly driven by the aberrant activation of the canonical NLRP1 inflammasome and IL-1ß signaling. Collectively, our results delineate a Mendelian disorder of DPP9 deficiency driven by increased NLRP1 activity as demonstrated in patient cells and in two animal models of the disease.
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Proteínas Reguladoras de la Apoptosis , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas , Inflamasomas , Animales , Ratones , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/genética , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/metabolismo , Inflamasomas/metabolismo , Interleucina-1/metabolismo , Proteínas NLR/genética , Pez CebraRESUMEN
Cell asked LGBTQ+ scientists around the world about how their identity shapes their experiences in STEM. Here we share six unique perspectives of researchers highlighting how their area of expertise, research focus, institutions, and geographical location have played a role in this regard. We thank them for sharing their voices and continued efforts toward making science more inclusive.
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Investigadores , HumanosRESUMEN
Human NLRP1 (NACHT, LRR, and PYD domain-containing protein 1) is an innate immune sensor predominantly expressed in the skin and airway epithelium. Here, we report that human NLRP1 senses the ultraviolet B (UVB)- and toxin-induced ribotoxic stress response (RSR). Biochemically, RSR leads to the direct hyperphosphorylation of a human-specific disordered linker region of NLRP1 (NLRP1DR) by MAP3K20/ZAKα kinase and its downstream effector, p38. Mutating a single ZAKα phosphorylation site in NLRP1DR abrogates UVB- and ribotoxin-driven pyroptosis in human keratinocytes. Moreover, fusing NLRP1DR to CARD8, which is insensitive to RSR by itself, creates a minimal inflammasome sensor for UVB and ribotoxins. These results provide insight into UVB sensing by human skin keratinocytes, identify several ribotoxins as NLRP1 agonists, and establish inflammasome-driven pyroptosis as an integral component of the RSR.
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Inflamasomas , Quinasas Quinasa Quinasa PAM , Proteínas NLR , Piroptosis , Ribosomas , Estrés Fisiológico , Anisomicina/toxicidad , Proteínas Adaptadoras de Señalización CARD/metabolismo , Humanos , Inflamasomas/efectos de los fármacos , Inflamasomas/metabolismo , Inflamasomas/efectos de la radiación , Queratinocitos/efectos de los fármacos , Queratinocitos/metabolismo , Queratinocitos/efectos de la radiación , Quinasas Quinasa Quinasa PAM/metabolismo , Mutación , Proteínas NLR/genética , Proteínas NLR/metabolismo , Proteínas de Neoplasias/metabolismo , Fosforilación/efectos de los fármacos , Fosforilación/efectos de la radiación , Piroptosis/efectos de los fármacos , Piroptosis/efectos de la radiación , Ribosomas/efectos de los fármacos , Ribosomas/efectos de la radiación , Rayos UltravioletaRESUMEN
ABSTRACTMelioidosis is a serious infectious disease endemic in Southeast Asia, Northern Australia and has been increasingly reported in other tropical and subtropical regions in the world. Percutaneous inoculation through cuts and wounds on the skin is one of the major modes of natural transmission. Despite cuts in skin being a major route of entry, very little is known about how the causative bacterium Burkholderia pseudomallei initiates an infection at the skin and the disease manifestation at the skin known as cutaneous melioidosis. One key issue is the lack of suitable and relevant infection models. Employing an in vitro 2D keratinocyte cell culture, a 3D skin equivalent fibroblast-keratinocyte co-culture and ex vivo organ culture from human skin, we developed infection models utilizing surrogate model organism Burkholderia thailandensis to investigate Burkholderia-skin interactions. Collectively, these models show that the bacterial infection was largely limited at the wound's edge. Infection impedes wound closure, triggers inflammasome activation and cellular extrusion in the keratinocytes as a potential way to control bacterial infectious load at the skin. However, extensive infection over time could result in the epidermal layer being sloughed off, potentially contributing to formation of skin lesions.
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Burkholderia pseudomallei/fisiología , Burkholderia/fisiología , Epidermis/microbiología , Inflamasomas/metabolismo , Queratinocitos/microbiología , Melioidosis/microbiología , Piel/microbiología , Heridas y Lesiones/microbiología , Células Cultivadas , Epidermis/metabolismo , Humanos , Queratinocitos/metabolismo , Melioidosis/metabolismo , Melioidosis/patología , Modelos Biológicos , Piel/metabolismo , Piel/patología , Heridas y Lesiones/metabolismo , Heridas y Lesiones/patologíaRESUMEN
Mito-SEPs are small open reading frame-encoded peptides that localize to the mitochondria to regulate metabolism. Motivated by an intriguing negative association between mito-SEPs and inflammation, here we screen for mito-SEPs that modify inflammatory outcomes and report a mito-SEP named "Modulator of cytochrome C oxidase during Inflammation" (MOCCI) that is upregulated during inflammation and infection to promote host-protective resolution. MOCCI, a paralog of the NDUFA4 subunit of cytochrome C oxidase (Complex IV), replaces NDUFA4 in Complex IV during inflammation to lower mitochondrial membrane potential and reduce ROS production, leading to cyto-protection and dampened immune response. The MOCCI transcript also generates miR-147b, which targets the NDUFA4 mRNA with similar immune dampening effects as MOCCI, but simultaneously enhances RIG-I/MDA-5-mediated viral immunity. Our work uncovers a dual-component pleiotropic regulation of host inflammation and immunity by MOCCI (C15ORF48) for safeguarding the host during infection and inflammation.
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Complejo IV de Transporte de Electrones/genética , Pleiotropía Genética/inmunología , Inflamación/inmunología , MicroARNs/metabolismo , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Línea Celular , Complejo IV de Transporte de Electrones/metabolismo , Técnicas de Inactivación de Genes , Humanos , Inflamación/genética , Inflamación/patología , Potencial de la Membrana Mitocondrial/inmunología , MicroARNs/genética , Mitocondrias/inmunología , Mitocondrias/patología , Cultivo Primario de Células , Especies Reactivas de Oxígeno/metabolismo , Regulación hacia Arriba/inmunologíaRESUMEN
INTRODUCTION: Adipose tissue and adipocytes are primary regulators of insulin sensitivity and energy homeostasis. Defects in insulin sensitivity of the adipocytes predispose the body to insulin resistance (IR) that could lead to diabetes. However, the mechanisms mediating adipocyte IR remain elusive, which emphasizes the need to develop experimental models that can validate the insulin signaling pathways and discover new mechanisms in the search for novel therapeutics. Currently in vitro adipose organ-chip devices show superior cell function over conventional cell culture. However, none of these models represent disease states. Only when these in vitro models can represent both healthy and disease states, they can be useful for developing therapeutics. Here, we establish an organ-on-chip model of insulin-resistant adipocytes, as well as characterization in terms of insulin signaling pathway and lipid metabolism. METHODS: We differentiated, maintained, and induced insulin resistance into primary adipocytes in a microfluidic organ-on-chip. We then characterized IR by looking at the insulin signaling pathway and lipid metabolism, and validated by studying a diabetic drug, rosiglitazone. RESULTS: We confirmed the presence of insulin resistance through reduction of Akt phosphorylation, Glut4 expression, Glut4 translocation and glucose uptake. We also confirmed defects of disrupted insulin signaling through reduction of lipid accumulation from fatty acid uptake and elevation of glycerol secretion. Testing with rosiglitazone showed a significant improvement in insulin sensitivity and fatty acid metabolism as suggested by previous reports. CONCLUSIONS: The adipose-chip exhibited key characteristics of IR and can serve as model to study diabetes and facilitate discovery of novel therapeutics.
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Nucleotide-binding domain, leucine-rich repeat receptors (NLRs) mediate innate immunity by forming inflammasomes. Activation of the NLR protein NLRP1 requires autocleavage within its function-to-find domain (FIIND)1-7. In resting cells, the dipeptidyl peptidases DPP8 and DPP9 interact with the FIIND of NLRP1 and suppress spontaneous NLRP1 activation8,9; however, the mechanisms through which this occurs remain unknown. Here we present structural and biochemical evidence that full-length rat NLRP1 (rNLRP1) and rat DPP9 (rDPP9) form a 2:1 complex that contains an autoinhibited rNLRP1 molecule and an active UPA-CARD fragment of rNLRP1. The ZU5 domain is required not only for autoinhibition of rNLRP1 but also for assembly of the 2:1 complex. Formation of the complex prevents UPA-mediated higher-order oligomerization of UPA-CARD fragments and strengthens ZU5-mediated NLRP1 autoinhibition. Structure-guided biochemical and functional assays show that both NLRP1 binding and enzymatic activity are required for DPP9 to suppress NLRP1 in human cells. Together, our data reveal the mechanism of DPP9-mediated inhibition of NLRP1 and shed light on the activation of the NLRP1 inflammasome.
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Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/química , Proteínas NLR/química , Animales , Proteínas Adaptadoras de Señalización CARD , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intracelular , Proteínas del Tejido Nervioso , Unión Proteica , Dominios Proteicos , Estructura Secundaria de Proteína , RatasRESUMEN
Nod-like receptor (NLR) proteins activate pyroptotic cell death and IL-1 driven inflammation by assembling and activating the inflammasome complex. Closely related sensor proteins NLRP1 and CARD8 undergo unique auto-proteolysis-dependent activation and are implicated in auto-inflammatory diseases; however, their mechanisms of activation are not understood. Here we report the structural basis of how the activating domains (FIINDUPA-CARD) of NLRP1 and CARD8 self-oligomerize to assemble distinct inflammasome complexes. Recombinant FIINDUPA-CARD of NLRP1 forms a two-layered filament, with an inner core of oligomerized CARD surrounded by an outer ring of FIINDUPA. Biochemically, self-assembled NLRP1-CARD filaments are sufficient to drive ASC speck formation in cultured human cells-a process that is greatly enhanced by NLRP1-FIINDUPA which forms oligomers in vitro. The cryo-EM structures of NLRP1-CARD and CARD8-CARD filaments, solved here at 3.7 Å, uncover unique structural features that enable NLRP1 and CARD8 to discriminate between ASC and pro-caspase-1. In summary, our findings provide structural insight into the mechanisms of activation for human NLRP1 and CARD8 and reveal how highly specific signaling can be achieved by heterotypic CARD interactions within the inflammasome complexes.
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Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteínas Adaptadoras de Señalización CARD/metabolismo , Inflamasomas/química , Inflamasomas/metabolismo , Proteínas de Neoplasias/metabolismo , Proteínas Adaptadoras Transductoras de Señales/química , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Reguladoras de la Apoptosis/química , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Adaptadoras de Señalización CARD/genética , Caspasa 1/metabolismo , Microscopía por Crioelectrón , Células HEK293 , Humanos , Inflamasomas/genética , Inflamación , Simulación del Acoplamiento Molecular , Mutación , Proteínas NLR , Proteínas de Neoplasias/química , Proteínas de Neoplasias/genética , Transducción de SeñalRESUMEN
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.
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Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Cisteína Endopeptidasas/metabolismo , Inmunidad Innata , Inflamasomas/metabolismo , Mucosa Respiratoria/virología , Rhinovirus/enzimología , Proteínas Virales/metabolismo , Proteasas Virales 3C , Proteínas Adaptadoras Transductoras de Señales/química , Proteínas Reguladoras de la Apoptosis/química , Proteínas de Ciclo Celular/metabolismo , Proteínas Cullin/metabolismo , Glutamina/química , Glutamina/metabolismo , Glicina/química , Glicina/metabolismo , Células HEK293 , Células HeLa , Humanos , Interleucina-18/metabolismo , Proteínas NLR , ProteolisisRESUMEN
Juvenile-onset recurrent respiratory papillomatosis (JRRP) is a rare and debilitating childhood disease that presents with recurrent growth of papillomas in the upper airway. Two common human papillomaviruses (HPVs), HPV-6 and -11, are implicated in most cases, but it is still not understood why only a small proportion of children develop JRRP following exposure to these common viruses. We report 2 siblings with a syndromic form of JRRP associated with mild dermatologic abnormalities. Whole-exome sequencing of the patients revealed a private homozygous mutation in NLRP1, encoding Nucleotide-Binding Domain Leucine-Rich Repeat Family Pyrin Domain-Containing 1. We find the NLRP1 mutant allele to be gain of function (GOF) for inflammasome activation, as demonstrated by the induction of inflammasome complex oligomerization and IL-1ß secretion in an overexpression system. Moreover, patient-derived keratinocytes secrete elevated levels of IL-1ß at baseline. Finally, both patients displayed elevated levels of inflammasome-induced cytokines in the serum. Six NLRP1 GOF mutations have previously been described to underlie 3 allelic Mendelian diseases with differing phenotypes and modes of inheritance. Our results demonstrate that an autosomal recessive, syndromic form of JRRP can be associated with an NLRP1 GOF mutation.
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Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Reguladoras de la Apoptosis/genética , Mutación con Ganancia de Función , Homocigoto , Infecciones por Papillomavirus/genética , Infecciones por Papillomavirus/patología , Infecciones del Sistema Respiratorio/genética , Infecciones del Sistema Respiratorio/patología , Preescolar , Citocinas/metabolismo , Femenino , Humanos , Lactante , Inflamasomas , Queratinocitos/citología , Queratinocitos/inmunología , Queratinocitos/metabolismo , Masculino , Proteínas NLR , Linaje , Hermanos , SíndromeRESUMEN
Rett syndrome (RTT) is a childhood neurodevelopmental disorder caused by mutations in MECP2. To study the molecular mechanisms underlying RTT, four sublines of H1 hESCs were generated, carrying a hemizygous knockout or mutant allele of MECP2. Exons 3 and 4 of MECP2 were targeted using the CRISPR/Cas9 nuclease system.
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Células Madre Embrionarias/citología , Edición Génica , Proteína 2 de Unión a Metil-CpG/genética , Sistemas CRISPR-Cas/genética , Diferenciación Celular , Línea Celular , Células Madre Embrionarias/metabolismo , Exones , Humanos , Cariotipo , Síndrome de Rett/genética , Síndrome de Rett/patologíaRESUMEN
Signals arising from bacterial infections are detected by pathogen recognition receptors (PRRs) and are transduced by specialized adapter proteins in mammalian cells. The Receptor-interacting-serine/threonine-protein kinase 2 (RIPK2 or RIP2) is such an adapter protein that is critical for signal propagation of the Nucleotide-binding-oligomerization-domain-containing proteins 1/2 (NOD1 and NOD2). Dysregulation of this signaling pathway leads to defects in bacterial detection and in some cases autoimmune diseases. Here, we show that the Caspase-activation-and-recruitment-domain (CARD) of RIP2 (RIP2-CARD) forms oligomeric structures upon stimulation by either NOD1-CARD or NOD2-2CARD. We reconstitute this complex, termed the RIPosome in vitro and solve the cryo-EM filament structure of the active RIP2-CARD complex at 4.1 Å resolution. The structure suggests potential mechanisms by which CARD domains from NOD1 and NOD2 initiate the oligomerization process of RIP2-CARD. Together with structure guided mutagenesis experiments at the CARD-CARD interfaces, we demonstrate molecular mechanisms how RIP2 is activated and self-propagating such signal.
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Proteína Serina-Treonina Quinasa 2 de Interacción con Receptor/química , Proteína Serina-Treonina Quinasa 2 de Interacción con Receptor/metabolismo , Transducción de Señal , Secuencia de Aminoácidos , Proteínas Adaptadoras de Señalización CARD/química , Proteínas Adaptadoras de Señalización CARD/metabolismo , Microscopía por Crioelectrón , Células HEK293 , Humanos , Modelos Moleculares , Unión Proteica , Dominios Proteicos , Multimerización de Proteína , Proteína Serina-Treonina Quinasa 2 de Interacción con Receptor/ultraestructura , Proteínas Recombinantes/metabolismo , Relación Estructura-ActividadRESUMEN
The inflammasome is a critical molecular complex that activates interleukin-1 driven inflammation in response to pathogen- and danger-associated signals. Germline mutations in the inflammasome sensor NLRP1 cause Mendelian systemic autoimmunity and skin cancer susceptibility, but its endogenous regulation remains less understood. Here we use a proteomics screen to uncover dipeptidyl dipeptidase DPP9 as a novel interacting partner with human NLRP1 and a related inflammasome regulator, CARD8. DPP9 functions as an endogenous inhibitor of NLRP1 inflammasome in diverse primary cell types from human and mice. DPP8/9 inhibition via small molecule drugs and CRISPR/Cas9-mediated genetic deletion specifically activate the human NLRP1 inflammasome, leading to ASC speck formation, pyroptotic cell death, and secretion of cleaved interleukin-1ß. Mechanistically, DPP9 interacts with a unique autoproteolytic domain (Function to Find Domain (FIIND)) found in NLRP1 and CARD8. This scaffolding function of DPP9 and its catalytic activity act synergistically to maintain NLRP1 in its inactive state and repress downstream inflammasome activation. We further identified a single patient-derived germline missense mutation in the NLRP1 FIIND domain that abrogates DPP9 binding, leading to inflammasome hyperactivation seen in the Mendelian autoinflammatory disease Autoinflammation with Arthritis and Dyskeratosis. These results unite recent findings on the regulation of murine Nlrp1b by Dpp8/9 and uncover a new regulatory mechanism for the NLRP1 inflammasome in primary human cells. Our results further suggest that DPP9 could be a multifunctional inflammasome regulator involved in human autoinflammatory diseases.
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Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Reguladoras de la Apoptosis/metabolismo , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/metabolismo , Inflamasomas/metabolismo , Proteínas Adaptadoras Transductoras de Señales/antagonistas & inhibidores , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Reguladoras de la Apoptosis/antagonistas & inhibidores , Proteínas Reguladoras de la Apoptosis/genética , Ácidos Borónicos/farmacología , Proteínas Adaptadoras de Señalización CARD/metabolismo , Dipéptidos/farmacología , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/antagonistas & inhibidores , Inhibidores Enzimáticos/farmacología , Mutación de Línea Germinal , Células HEK293 , Humanos , Inflamación/genética , Mutación Missense , Proteínas NLR , Proteínas de Neoplasias/metabolismo , Unión Proteica , Dominios ProteicosRESUMEN
Calcium/calmodulin-dependent protein kinase II (CAMK2) plays fundamental roles in synaptic plasticity that underlies learning and memory. Here, we describe a new recessive neurodevelopmental syndrome with global developmental delay, seizures and intellectual disability. Using linkage analysis and exome sequencing, we found that this disease maps to chromosome 5q31.1-q34 and is caused by a biallelic germline mutation in CAMK2A. The missense mutation, p.His477Tyr is located in the CAMK2A association domain that is critical for its function and localization. Biochemically, the p.His477Tyr mutant is defective in self-oligomerization and unable to assemble into the multimeric holoenzyme.In vivo, CAMK2AH477Y failed to rescue neuronal defects in C. elegans lacking unc-43, the ortholog of human CAMK2A. In vitro, neurons derived from patient iPSCs displayed profound synaptic defects. Together, our data demonstrate that a recessive germline mutation in CAMK2A leads to neurodevelopmental defects in humans and suggest that dysfunctional CAMK2 paralogs may contribute to other neurological disorders.