Initial phospholipid-dependent Irgb6 targeting to<i>Toxoplasma gondii</i>vacuoles mediates host defense

Lee, Youngae; Yamada, Hiroshi; Pradipta, Ariel; Su, Ji Guo; Okamoto, Masaaki; Nagaoka, Hikaru; Takashima, Eizo; Standley, Daron M.; Sasai, Miwa; Takei, Kohji; Yamamoto, Masahiro

doi:10.26508/lsa.201900549

Cited by 26 publications

(70 citation statements)

References 77 publications

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“…However, p62-PV association was not inhibited by ROP5A but instead phenocopied the PV-association patterns of Irgb6 ( Fig 4D and 4E ). Irgb6 has recently been shown to be required for p62-PV association in IFNγ-stimulated cells, which is consistent with these observations [ 89 ]. The ROP18 [ 4 ] and ROP17 kinases [ 6 ] phosphorylate and inactivate Irga6 and Irgb6.…”

Section: Resultssupporting

confidence: 81%

“…The ROP5 locus consists of ROP5A , ROP5B and ROP5C genes, which differ in copy number between strains, and is under diversifying selection [ 3 , 9 , 12 , 13 , 81 , 85 ]. ROP5B and ROP5C isoforms of virulent strains bind to and prevent accumulation of effector IRGs on the parasite’s PVM, including Irga6 and Irgb6 [ 3 , 4 , 81 ], which are required for host resistance to primary infection [ 88 , 89 ]. In contrast, ROP5A lacks a defined host binding partner and function, but does promote virulence by an unknown mechanism that is sensitive to copy number.…”

Section: Resultsmentioning

confidence: 99%

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Naïve CD8 T cell IFNγ responses to a vacuolar antigen are regulated by an inflammasome-independent NLRP3 pathway and Toxoplasma gondii ROP5

et al. 2020

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Host resistance to Toxoplasma gondii relies on CD8 T cell IFNγ responses, which if modulated by the host or parasite could influence chronic infection and parasite transmission between hosts. Since host-parasite interactions that govern this response are not fully elucidated, we investigated requirements for eliciting naïve CD8 T cell IFNγ responses to a vacuolar resident antigen of T . gondii , TGD057. Naïve TGD057 antigen-specific CD8 T cells (T57) were isolated from transnuclear mice and responded to parasite-infected bone marrow-derived macrophages (BMDMs) in an antigen-dependent manner, first by producing IL-2 and then IFNγ. T57 IFNγ responses to TGD057 were independent of the parasite’s protein export machinery ASP5 and MYR1. Instead, host immunity pathways downstream of the regulatory Immunity-Related GTPases (IRG), including partial dependence on Guanylate-Binding Proteins, are required. Multiple T . gondii ROP5 isoforms and allele types, including ‘avirulent’ ROP5A from clade A and D parasite strains, were able to suppress CD8 T cell IFNγ responses to parasite-infected BMDMs. Phenotypic variance between clades B, C, D, F, and A strains suggest T57 IFNγ differentiation occurs independently of parasite virulence or any known IRG-ROP5 interaction. Consistent with this, removal of ROP5 is not enough to elicit maximal CD8 T cell IFNγ production to parasite-infected cells. Instead, macrophage expression of the pathogen sensors, NLRP3 and to a large extent NLRP1, were absolute requirements. Other members of the conventional inflammasome cascade are only partially required, as revealed by decreased but not abrogated T57 IFNγ responses to parasite-infected ASC, caspase-1/11, and gasdermin D deficient cells. Moreover, IFNγ production was only partially reduced in the absence of IL-12, IL-18 or IL-1R signaling. In summary, T . gondii effectors and host machinery that modulate parasitophorous vacuolar membranes, as well as NLR-dependent but inflammasome-independent pathways, determine the full commitment of CD8 T cells IFNγ responses to a vacuolar antigen.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Naïve CD8 T cell IFNγ responses to a vacuolar antigen are regulated by an inflammasome-independent NLRP3 pathway and Toxoplasma gondii ROP5

et al. 2020

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“…Because the two GRAs were not identified as components of the ROP5/18 complex from previous proteomic studies 27 , 28 , it is unlikely they directly bind to the IRGB6 on the PVM and inhibit its polymerization. A recent study suggested that IRGB6 recruitment is dependent on the recognition of specific phospholipids present on the PVM 88 . It is therefore also possible that the increased IRGB6 loading on the vacuole of Δ TGGT1_263560 or Δ TGGT1_269950 parasites is due to a change of PVM lipid composition.…”

Section: Discussionmentioning

confidence: 99%

Genome-wide screens identify Toxoplasma gondii determinants of parasite fitness in IFNγ-activated murine macrophages

et al. 2020

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Macrophages play an essential role in the early immune response against Toxoplasma and are the cell type preferentially infected by the parasite in vivo. Interferon gamma (IFNγ) elicits a variety of anti-Toxoplasma activities in macrophages. Using a genome-wide CRISPR screen we identify 353 Toxoplasma genes that determine parasite fitness in naїve or IFNγ-activated murine macrophages, seven of which are further confirmed. We show that one of these genes encodes dense granule protein GRA45, which has a chaperone-like domain, is critical for correct localization of GRAs into the PVM and secretion of GRA effectors into the host cytoplasm. Parasites lacking GRA45 are more susceptible to IFNγ-mediated growth inhibition and have reduced virulence in mice. Together, we identify and characterize an important chaperone-like GRA in Toxoplasma and provide a resource for the community to further explore the function of Toxoplasma genes that determine fitness in IFNγ-activated macrophages.

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“…Upon infection of murine cells with the avirulent ME49 and Prugniaud strains, the cytosolically abundant Irga6, Irgb10 and Irgb6 proteins (Martens et al, 2004; Martens & Howard, 2006) diffuse to the vacuolar membrane (Khaminets et al, 2010; Lee et al, 2020). IRGs loading at the PVM exhibits spatial hierarchy and cooperation (Hunn et al, 2008; Khaminets et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Toxoplasma gondii GRA60 is an effector protein that modulates host cell autonomous immunity and contributes to virulence

Nyonda

Hammoudi

et al. 2020

Cellular Microbiology

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Toxoplasma gondii infects virtually any nucleated cell and resides inside a non‐phagocytic vacuole surrounded by a parasitophorous vacuolar membrane (PVM). Pivotal to the restriction of T. gondii dissemination upon infection in murine cells is the recruitment of immunity regulated GTPases (IRGs) and guanylate binding proteins (GBPs) to the PVM that leads to pathogen elimination. The virulent T. gondii type I RH strain secretes a handful of effectors including the dense granule protein GRA7, the serine–threonine kinases ROP17 and ROP18, and a pseudo‐kinase ROP5, that synergistically inhibit the recruitment of IRGs to the PVM. Here, we characterise GRA60, a novel dense granule effector, which localises to the vacuolar space and PVM and contributes to virulence of RH in mice, suggesting a role in the subversion of host cell defence mechanisms. Members of the host cell IRG defence system Irgb10 and Irga6 are recruited to the PVM of RH parasites lacking GRA60 as observed previously for the avirulent RHΔrop5 mutant, with RH preventing such recruitment. Deletion of GRA60 in RHΔrop5 leads to a recruitment of IRGs comparable to the single knockouts. GRA60 therefore represents a novel parasite effector conferring resistance to IRGs in type I parasites, and found associated to ROP18, a member of the virulence complex.

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Initial phospholipid-dependent Irgb6 targeting toToxoplasma gondiivacuoles mediates host defense

Abstract: Irgb6 has a role in the cell-autonomous response against T. gondii and involves ubiquitination and breakdown of vacuoles via binding of a specific phospholipid on the parasitophorous vacuole membrane.

Cited by 26 publications

References 77 publications

Naïve CD8 T cell IFNγ responses to a vacuolar antigen are regulated by an inflammasome-independent NLRP3 pathway and Toxoplasma gondii ROP5

Naïve CD8 T cell IFNγ responses to a vacuolar antigen are regulated by an inflammasome-independent NLRP3 pathway and Toxoplasma gondii ROP5

Genome-wide screens identify Toxoplasma gondii determinants of parasite fitness in IFNγ-activated murine macrophages

Toxoplasma gondii GRA60 is an effector protein that modulates host cell autonomous immunity and contributes to virulence

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