The Yersinia Type III secretion effector YopM Is an E3 ubiquitin ligase that induced necrotic cell death by targeting NLRP3.
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ABSTRACT:
SUBMITTER: Wei C
PROVIDER: S-EPMC5260993 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Type III effectors are virulence factors of Gram-negative bacterial pathogens delivered directly into host cells by the type III secretion nanomachine where they manipulate host cell processes such as the innate immunity and gene expression. Here, we show that the novel type III effector XopL from the model plant pathogen Xanthomonas campestris pv. vesicatoria exhibits E3 ubiquitin ligase activity in vitro and in planta, induces plant cell death and subverts plant immunity. E3 ligase activity is associated with the C-terminal region of XopL, which specifically interacts with plant E2 ubiquitin conjugating enzymes and mediates formation of predominantly K11-linked polyubiquitin chains. The crystal structure of the XopL C-terminal domain revealed a single domain with a novel fold, termed XL-box, not present in any previously characterized E3 ligase. Mutation of amino acids in the central cavity of the XL-box disrupts E3 ligase activity and prevents XopL-induced plant cell death. The lack of cysteine residues in the XL-box suggests the absence of thioester-linked ubiquitin-E3 ligase intermediates and a non-catalytic mechanism for XopL-mediated ubiquitination. The crystal structure of the N-terminal region of XopL confirmed the presence of a leucine-rich repeat (LRR) domain, which may serve as a protein-protein interaction module for ubiquitination target recognition. While the E3 ligase activity is required to provoke plant cell death, suppression of PAMP responses solely depends on the N-terminal LRR domain. Taken together, the unique structural fold of the E3 ubiquitin ligase domain within the Xanthomonas XopL is unprecedented and highlights the variation in bacterial pathogen effectors mimicking this eukaryote-specific activity.
| S-EPMC3554608 | biostudies-literature
Project description:Type III secretion systems (T3SS) are central virulence factors for many pathogenic Gram-negative bacteria, and secreted T3SS effectors can block key aspects of host cell signaling. To counter this, innate immune responses can also sense some T3SS components to initiate anti-bacterial mechanisms. The Yersinia pestis T3SS is particularly effective and sophisticated in manipulating the production of pro-inflammatory cytokines IL-1β and IL-18, which are typically processed into their mature forms by active caspase-1 following inflammasome formation. Some effectors, like Y. pestis YopM, may block inflammasome activation. Here we show that YopM prevents Y. pestis induced activation of the Pyrin inflammasome induced by the RhoA-inhibiting effector YopE, which is a GTPase activating protein. YopM blocks YopE-induced Pyrin-mediated caspase-1 dependent IL-1β/IL-18 production and cell death. We also detected YopM in a complex with Pyrin and kinases RSK1 and PKN1, putative negative regulators of Pyrin. In contrast to wild-type mice, Pyrin deficient mice were also highly susceptible to an attenuated Y. pestis strain lacking YopM, emphasizing the importance of inhibition of Pyrin in vivo. A complex interplay between the Y. pestis T3SS and IL-1β/IL-18 production is evident, involving at least four inflammasome pathways. The secreted effector YopJ triggers caspase-8- dependent IL-1β activation, even when YopM is present. Additionally, the presence of the T3SS needle/translocon activates NLRP3 and NLRC4-dependent IL-1β generation, which is blocked by YopK, but not by YopM. Taken together, the data suggest YopM specificity for obstructing the Pyrin pathway, as the effector does not appear to block Y. pestis-induced NLRP3, NLRC4 or caspase-8 dependent caspase-1 processing. Thus, we identify Y. pestis YopM as a microbial inhibitor of the Pyrin inflammasome. The fact that so many of the Y. pestis T3SS components are participating in regulation of IL-1β/IL-18 release suggests that these effects are essential for maximal control of innate immunity during plague.
| S-EPMC5135138 | biostudies-literature
Project description:The NLRP3 inflammasome has an important function in inflammation by promoting the processing of pro-IL-1? and pro-IL-18 to their mature bioactive forms, and by inducing cell death via pyroptosis. Here we show a critical function of the E3 ubiquitin ligase Pellino2 in facilitating activation of the NLRP3 inflammasome. Pellino2-deficient mice and myeloid cells have impaired activation of NLRP3 in response to toll-like receptor priming, NLRP3 stimuli and bacterial challenge. These functions of Pellino2 in the NLRP3 pathway are dependent on Pellino2 FHA and RING-like domains, with Pellino2 promoting the ubiquitination of NLRP3 during the priming phase of activation. We also identify a negative function of IRAK1 in the NLRP3 inflammasome, and describe a counter-regulatory relationship between IRAK1 and Pellino2. Our findings reveal a Pellino2-mediated regulatory signaling system that controls activation of the NLRP3 inflammasome.
| S-EPMC5908787 | biostudies-literature
Project description:Microbial pathogens of both plants and animals employ virulence factors that suppress the host immune response. The tomato pathogen Pseudomonas syringae injects the AvrPtoB type III effector protein into the plant cell to suppress programmed cell death (PCD) associated with plant immunity. AvrPtoB also inhibits PCD in yeast, indicating that AvrPtoB manipulates a conserved component of eukaryotic PCD. To identify host targets of AvrPtoB, we performed a yeast two-hybrid screen and identified tomato ubiquitin (Ub) as a strong AvrPtoB interactor. AvrPtoB is ubiquitinated in vitro and exhibits E3 Ub ligase activity in the presence of recombinant E1 activating enzyme and specific E2 Ub-conjugating enzymes. The C terminus of AvrPtoB is sufficient for both anti-PCD and E3 Ub ligase activities, suggesting the two functions are associated. Indeed, mutation of AvrPtoB lysine residues in the C terminus, between K512 and K529, disrupts AvrPtoB-Ub interactions, decreases AvrPtoB-mediated anti-PCD activity, and abrogates P. syringae pathogenesis of susceptible tomato plants. Remarkably, quantitative decreases in AvrPtoB anti-PCD activity are correlated with decreases in AvrPtoB ubiquitination and E3 Ub ligase activity. Overall, these data reveal a unique bacterial pathogenesis strategy, where AvrPtoB manipulates the host Ub system and requires intrinsic E3 Ub ligase activity to suppress plant immunity.
| S-EPMC1413779 | biostudies-literature
Project description:Plant immunity is tightly controlled by a complex and dynamic regulatory network, which ensures optimal activation upon detection of potential pathogens. Accordingly, each component of this network is a potential target for manipulation by pathogens. Here, we report that RipAC, a type III-secreted effector from the bacterial pathogen Ralstonia solanacearum, targets the plant E3 ubiquitin ligase PUB4 to inhibit pattern-triggered immunity (PTI). PUB4 plays a positive role in PTI by regulating the homeostasis of the central immune kinase BIK1. Before PAMP perception, PUB4 promotes the degradation of non-activated BIK1, while, after PAMP perception, PUB4 contributes to the accumulation of activated BIK1. RipAC leads to BIK1 degradation, which correlates with its PTI-inhibitory activity. RipAC causes a reduction in pathogen-associated molecular pattern (PAMP)-induced PUB4 accumulation and phosphorylation. Our results shed light on the role played by PUB4 in immune regulation, and illustrate an indirect targeting of the immune signalling hub BIK1 by a bacterial effector.
| S-SCDT-10_15252-EMBJ_2020107257 | biostudies-other
Project description:The NLRP3 inflammasome has a fundamental role in host defence against microbial pathogens and its deregulation may cause diverse inflammatory diseases. NLRP3 protein expression is a rate-limiting step for inflammasome activation, thus its expression must be tightly controlled to maintain immune homeostasis and avoid detrimental effects. However, how NLRP3 expression is regulated remains largely unknown. In this study, we identify E3 ubiquitin ligase TRIM31 as a feedback suppressor of NLRP3 inflammasome. TRIM31 directly binds to NLRP3, promotes K48-linked polyubiquitination and proteasomal degradation of NLRP3. Consequently, TRIM31 deficiency enhances NLRP3 inflammasome activation and aggravates alum-induced peritonitis in vivo. Furthermore, TRIM31 deficiency attenuates the severity of dextran sodium sulfate (DSS)-induced colitis, an inflammatory bowel diseases model in which NLRP3 possesses protective roles. Thus, our research describes a mechanism by which TRIM31 limits NLRP3 inflammasome activity under physiological conditions and suggests TRIM31 as a potential therapeutic target for the intervention of NLRP3 inflammasome related diseases.
| S-EPMC5155141 | biostudies-literature
Project description:Pathogenic Yersinia, including Y. pestis, the agent of plague in humans, and Y. pseudotuberculosis, the related enteric pathogen, deliver virulence effectors into host cells via a prototypical type III secretion system to promote pathogenesis. These effectors, termed Yersinia outer proteins (Yops), modulate multiple host signaling responses. Studies in Y. pestis and Y. pseudotuberculosis have shown that YopM suppresses infection-induced inflammasome activation; however, the underlying molecular mechanism is largely unknown. Here we show that YopM specifically restricts the pyrin inflammasome, which is triggered by the RhoA-inactivating enzymatic activities of YopE and YopT, in Y. pseudotuberculosis-infected macrophages. The attenuation of a yopM mutant is fully reversed in pyrin knockout mice, demonstrating that YopM inhibits pyrin to promote virulence. Mechanistically, YopM recruits and activates the host kinases PRK1 and PRK2 to negatively regulate pyrin by phosphorylation. These results show how a virulence factor can hijack host kinases to inhibit effector-triggered pyrin inflammasome activation.
| S-EPMC5025386 | biostudies-literature
Project description:Primary and secondary hypertension are major risk factors for cardiovascular disease, the leading cause of death worldwide. Elevated secretion of aldosterone resulting from primary aldosteronism (PA) is a key driver of secondary hypertension. Here, we report an unexpected role for the ubiquitin ligase Siah1 in adrenal gland development and PA. Siah1a-/- mice exhibit altered adrenal gland morphology, as reflected by a diminished X-zone, enlarged medulla, and dysregulated zonation of the glomerulosa as well as increased aldosterone levels and aldosterone target gene expression and reduced plasma potassium levels. Genes involved in catecholamine biosynthesis and cAMP signaling are upregulated in the adrenal glands of Siah1a-/- mice, while genes related to retinoic acid signaling and cholesterol biosynthesis are downregulated. Loss of Siah1 leads to increased expression of the Siah1 substrate PIAS1, an E3 SUMO protein ligase implicated in the suppression of LXR, a key regulator of cholesterol levels in the adrenal gland. In addition, SIAH1 sequence variants were identified in patients with PA; such variants impaired SIAH1 ubiquitin ligase activity, resulting in elevated PIAS1 expression. These data identify a role for the Siah1-PIAS1 axis in adrenal gland organization and function and point to possible therapeutic targets for hyperaldosteronism.
| S-EPMC5752272 | biostudies-literature
Project description:The dysregulation of NLRP3 inflammasome plays a critical role in pathogenesis of various human inflammatory diseases, thus NLRP3 inflammasome activation must be tightly controlled at multiple levels. However, the underlying mechanism regulating NLRP3 inflammasome activation remains unclear. Herein, the effects of Tripartite motif-containing protein 65 (TRIM65) on NLRP3 inflammasome activation and the underlying molecular mechanism were investigated in vitro and in vivo. Inhibition or deletion of Trim65 could significantly strengthen agonist induced NLRP3 inflammasome activation in THP-1 cells and BMDMs, indicated by increased caspase-1 activation and interleukin-1β secretion. However, TRIM65 had no effect on poly (dA: dT)-induced AIM2 inflammasome activation or flagellin-induced IPAF inflammasome activation. Mechanistically, immunoprecipitation assays demonstrated that TRIM65 binds to NACHT domain of NLRP3, promotes lys48- and lys63- linked ubiquitination of NLRP3 and restrains the NEK7-NLRP3 interaction, thereby inhibiting NLRP3 inflammasome assembly, caspase-1 activation, and IL-1β secretion. In vivo, three models of inflammatory diseases were used to confirm the suppression role of TRIM65 in NLRP3 inflammasome activation. TRIM65-deficient mice had a higher production of IL-1β induced by lipopolysaccharide in sera, and more IL-1β secretion and neutrophil migration in the ascites, and more severity of joint swelling and associated IL-1β production induced by monosodium urate, suggesting that TRIM65 deficiency was susceptible to inflammation. Therefore, the data elucidate a TRIM65-dependent negative regulation mechanism of NLRP3 inflammasome activation and provide potential therapeutic strategies for the treatment of NLRP3 inflammasome-related diseases.
| S-EPMC8427430 | biostudies-literature
Project description:Inflammasome assembly activates caspase-1 and initiates the inflammatory cell death program pyroptosis, which is protective against numerous pathogens. Consequently, several pathogens, including the plague causing bacterium Yersinia pestis, avoid activating this pathway to enhance their virulence. However, bacterial molecules that directly modulate the inflammasome have yet to be identified. Examining the contribution of Yersinia type III secretion effectors to caspase-1 activation, we identified the leucine-rich repeat effector YopM as a potent antagonist of both caspase-1 activity and activation. YopM directly binds caspase-1, which both inhibits caspase-1 activity and sequesters it to block formation of the mature inflammasome. Caspase-1 activation antagonizes Yersinia survival in vivo, and consequently YopM inhibition of caspase-1 is required for Yersinia pathogenesis. Thus, a bacterium obstructs pyroptosis utilizing a direct mechanism of caspase-1 inhibition that is distinct from known viral or host inhibitors.
| S-EPMC3703949 | biostudies-literature