Acetylation of MEK2 and IκB (IKK) activation loop residues by YopJ inhibits signaling

Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra, India
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2007; 103(49):18574-9. DOI: 10.1073/pnas.0608995103
Source: PubMed


To overcome host defenses, bacterial pathogens of the genus Yersinia inject specific effector proteins into colonized mammalian cells. One such virulence factor, YopJ, inhibits the host inflammatory response and induces apoptosis of immune cells by blocking multiple signaling pathways, including the MAPK and NF-kappaB pathways. In this study, we show that YopJ exerts its deleterious effects by catalyzing the acetylation of two serine residues in the activation loop of the MAP kinase kinase, MEK2. This covalent modification prevents the phosphorylation of these serine residues that is required for activation of MEK2 and downstream signal propagation. We also show that YopJ causes acetylation of a threonine residue in the activation loop of both the alpha and beta subunits of the NF-kappaB pathway kinase, IKK. These results establish a hitherto uncharacterized mode of action for bacterial toxins and suggest the possibility that serine/threonine acetylation may occur even under nonpathogenic conditions and may be a widespread protein modification regulating protein function in eukaryotic cells.

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Available from: Rohit Mittal, Nov 24, 2014
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    • "Thus, in order to establish successful infection, Yersinia is dependent on targeting multiple host signaling pathways to evade host immune defense and induce host cell death. For example, YopP/J functions as a deubiquitinating protease and acetyltransferase to inhibit both the host NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways, leading to a block in cytokine secretion and apoptosis of host macrophages [9-11]. Although discovery of Yop effector targets have begun to clarify mechanisms of Yersinia virulence, it is likely the case that additional host targets remain to be defined. "
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    ABSTRACT: The pathogenic Yersinia species exhibit a primarily extracellular lifestyle through manipulation of host signaling pathways that regulate proinflammatory gene expression and cytokine release. To identify host genes that are targeted by Yersinia during the infection process, we performed an RNA interference (RNAi) screen based on recovery of host NF-kappaB-mediated gene activation in response to TNF-alpha stimulation upon Y. enterocolitica infection. We screened shRNAs against 782 genes in the human kinome and 26 heat shock genes, and identified 19 genes that exhibited >=40% relative increase in NF-kappaB reporter gene activity. The identified genes function in multiple cellular processes including MAP and ERK signaling pathways, ion channel activity, and regulation of cell growth. Pre-treatment with small molecule inhibitors specific for the screen hits c-KIT and CKII recovered NF-kappaB gene activation and/or pro-inflammatory TNF-alpha cytokine release in multiple cell types, in response to either Y. enterocolitica or Y. pestis infection. We demonstrate that pathogenic Yersinia exploits c-KIT signaling in a T3SS-dependent manner to downregulate expression of transcription factors EGR1 and RelA/p65, and pro-inflammatory cytokines. This study is the first major functional genomics RNAi screen to elucidate virulence mechanisms of a pathogen that is primarily dependent on extracellular-directed immunomodulation of host signaling pathways for suppression of host immunity.
    Full-text · Article · Nov 2013 · BMC Microbiology
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    • "The yersiniae counteract the aforementioned inflammatory response when YopP/J acetylate I kappa B kinase (IKK) and MAPK kinases (MKKs), preventing their phosphorylation and subsequent activation. The disruption in these signaling events results in innate immune cells undergoing apoptosis (Orth, 2002; Mittal et al., 2006; Mukherjee et al., 2006). A more detailed description of Yersinia outer membrane protein J (YopJ) mechanisms of mollifying host defenses is discussed in a later section . "
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    ABSTRACT: Like other pathogenic bacteria, Yersinia and Aeromonas species have been continuously co-evolving with their respective hosts. Although the former is a bonafide human pathogen, the latter has gained notararity as an emerging disease-causing agent. In response to immune cell challenges, bacterial pathogens have developed diverse mechanism(s) enabling their survival, and, at times, dominance over various host immune defense systems. The bacterial type three secretion system (T3SS) is evolutionarily derived from flagellar subunits and serves as a vehicle by which microbes can directly inject/translocate anti-host factors/effector proteins into targeted host immune cells. A large number of Gram-negative bacterial pathogens possess a T3SS empowering them to disrupt host cell signaling, actin cytoskeleton re-arrangements, and even to induce host-cell apoptotic and pyroptotic pathways. All pathogenic yersiniae and most Aeromonas species possess a T3SS, but they also possess T2- and T6-secreted toxins/effector proteins. This review will focus on the mechanisms by which the T3SS effectors Yersinia outer membrane protein J (YopJ) and an Aeromonas hydrophila AexU protein, isolated from the diarrheal isolate SSU, mollify host immune system defenses. Additionally, the mechanisms that are associated with host cell apoptosis/pyroptosis by Aeromonas T2SS secreted Act, a cytotoxic enterotoxin, and Hemolysin co-regulated protein (Hcp), an A. hydrophila T6SS effector, will also be discussed.
    Full-text · Article · Oct 2013 · Frontiers in Cellular and Infection Microbiology
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    • "TcpB/Btp1 Mimics TIRAP, causing its degradation Sengupta et al., 2010; Radhakrishnan et al., 2009 E. coli TcpC Binds to MyD88 and negatively interferes with signalling Cirl et al., 2008 IRAKs Po. gingivalis LPS Induces expression of the inhibitory IRAK-M Domon et al., 2008 TRAF Y. pestis YopJ Prevents K63-polyubiquitination of TRAF6 Sweet et al., 2007; Zhou et al., 2005 Shig. flexneri OpsI Deamidates and inactivates the ubiquitin-conjugating enzyme Ubc13 Sanada et al., 2012 TAK/TAB Helicobacter pylori CagA Enhances the activity of TAK1 Lamb et al., 2009 E. coli NleE Methylates TAB2 and TAB3, thereby inhibiting the UBD binding ability Zhang et al., 2011b IKK complex Y. pseudotuberculosis YopJ Acetylates the activation loop of IKKa and IKKb, thereby preventing their phosphorylation-induced activation Mittal et al., 2006 Shig. flexneri IpaH9.8 "
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    ABSTRACT: The human body is constantly challenged by a variety of commensal and pathogenic microorganisms that trigger the immune system. Central in the first line of defense is the pattern-recognition receptor (PRR)-induced stimulation of the nuclear factor κB (NFκB) pathway, leading to NFκB activation. The subsequent production of pro-inflammatory cytokines and/or antimicrobial peptides results in recruitment of professional phagocytes and bacterial clearance. To overcome this, bacteria have developed mechanisms for targeted interference in every single step in the PRR-NFκB pathway to dampen host inflammatory responses. This review aims to briefly overview the PRR-NFκB pathway in relation to the immune response and give examples of the diverse bacterial evasion mechanisms including changes in the bacterial surface, decoy production and injection of effector molecules. Targeted regulation of inflammatory responses is needed and bacterial molecules developed for immune evasion could provide future anti-inflammatory agents.
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