Ehrlichia moonlighting effectors and interkingdom interactions with the mononuclear phagocyte

Dunphy, Paige S.; Luo, Tian; McBride, Jere W.

doi:10.1016/j.micinf.2013.09.011

Cited by 29 publications

(23 citation statements)

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“…To date, the molecular mechanisms by which Ehrlichia enters and modulates host cells are not well understood (4,(6)(7)(8), but our findings regarding Wnt pathways are consistent with previous reports that described some characteristics of cellular signaling upon internalization of ehrlichiae (43,44). E. chaffeensis enters the monocyte through lipid raft-caveola-mediated endocytosis, where it can reside within a cytoplasmic vacuole that resembles an early endosome, preventing lysosomal fusion and protecting it from killing (44).…”

Section: Discussionsupporting

confidence: 91%

Ehrlichia chaffeensis Exploits Canonical and Noncanonical Host Wnt Signaling Pathways To Stimulate Phagocytosis and Promote Intracellular Survival

et al. 2016

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Ehrlichia chaffeensis invades and survives in phagocytes by modulating host cell processes and evading innate defenses, but the mechanisms are not fully defined. Recently we have determined that E. chaffeensis tandem repeat proteins (TRPs) are type 1 secreted effectors involved in functionally diverse interactions with host targets, including components of the evolutionarily conserved Wnt signaling pathways. In this study, we demonstrated that induction of host canonical and noncanonical Wnt pathways by E. chaffeensis TRP effectors stimulates phagocytosis and promotes intracellular survival. After E. chaffeensis infection, canonical and noncanonical Wnt signalings were significantly stimulated during early stages of infection (1 to 3 h) which coincided with dephosphorylation and nuclear translocation of ␤-catenin, a major canonical Wnt signal transducer, and NFATC1, a noncanonical Wnt transcription factor. In total, the expression of ϳ44% of Wnt signaling target genes was altered during infec- Ehrlichia chaffeensis is an obligately intracellular bacterium responsible for the emerging life-threatening human zoonosis human monocytotropic ehrlichiosis (HME) (1). E. chaffeensis selectively infects mononuclear phagocytes and resides in early-endosome-like membrane-bound vacuoles (1). The mechanisms by which E. chaffeensis enters host cells, establishes persistent infection, and avoids host defenses are not completely understood but occur through functionally relevant host-pathogen interactions involving secreted ehrlichial tandem repeat protein (TRP) effectors that are posttranslationally modified by ubiquitin (Ub) and the small ubiquitin-like modifier (SUMO) (2-5). E. chaffeensis TRPs interact with a diverse group of human proteins associated with major cellular processes, including transcription, translation, protein trafficking, cell signaling, cytoskeleton organization, and apoptosis, indicating that they play a role in manipulating these important cellular processes to facilitate infection (6-8).E. chaffeensis TRPs were first recognized as antigens that elicit strong protective antibody responses during infection that are directed at continuous species-specific epitopes in tandem repeat regions (9-12). Subsequently, our understanding of the functional role of TRPs as effectors in pathobiology has been advanced through studies that have defined specific TRP-host protein and DNA interactions (4, 13). Notably, E. chaffeensis TRP120 and TRP32 interact with numerous host proteins and genes associated with the canonical and noncanonical Wnt signaling pathways. One of TRP32-interacting targets, deleted-in-azoospermia-associated protein 2 (DAZAP2), is a highly conserved protein that modulates gene transcription driven by Wnt/␤-catenin signaling effector T-cell factors (TCFs), and knockdown of host DAZAP2 by small interfering RNA (siRNA) reduced the E. chaffeensis load in infected cells (7,14). Several other TRP120-interacting host proteins, such as AT-rich interactive domain 1B (ARID1B), lysine (K)-specific demethylase...

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Section: Discussionsupporting

confidence: 91%

Ehrlichia chaffeensis Exploits Canonical and Noncanonical Host Wnt Signaling Pathways To Stimulate Phagocytosis and Promote Intracellular Survival

et al. 2016

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“…Indeed, our current study and previous publications showed virB6-4, the largest and most downstream gene in the virB6 operon (EHF_0445, APH_0377, MC1_00820) is consistently disrupted by Himar1 transposon without affecting Ehrlichia, Anaplasma, or Rickettsia growth in mammalian host cells (Felsheim et al, 2006;Lamason et al, 2018). Despite extensive arrays of in vitro functions proposed for TRP120 (former gp120) for E. chaffeensis infection of macrophages (Yu et al, 2000;Luo et al, 2011;Zhu et al, 2011;Dunphy et al, 2013Dunphy et al, , 2014, the gene encoding HF strain TRP120 homolog had the insertion near 5 ′ end, implicating this gene is dispensable for Ehrlichia HF infection of macrophages. TRP120 appears to be an abundantly produced protein in E. chaffeensis (Yu et al, 2000), TRP mutant of HF obtained in our study would help elucidate in vivo or other functions of TRP120 in the future.…”

Section: Discussionsupporting

confidence: 47%

Discovery of in vivo Virulence Genes of Obligatory Intracellular Bacteria by Random Mutagenesis

Bekebrede

Lin

Teymournejad

et al. 2020

Front. Cell. Infect. Microbiol.

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Ehrlichia spp. are emerging tick-borne obligatory intracellular bacteria that cause febrile and sometimes fatal diseases with abnormal blood cell counts and signs of hepatitis. Ehrlichia HF strain provides an excellent mouse disease model of fatal human ehrlichiosis. We recently obtained and established stable culture of Ehrlichia HF strain in DH82 canine macrophage cell line, and obtained its whole genome sequence and annotation. To identify genes required for in vivo virulence of Ehrlichia, we constructed random insertional HF strain mutants by using Himar1 transposon-based mutagenesis procedure. Of total 158 insertional mutants isolated via antibiotic selection in DH82 cells, 74 insertions were in the coding regions of 55 distinct protein-coding genes, including TRP120 and multicopy genes, such as p28/omp-1, virB2, and virB6. Among 84 insertions mapped within the non-coding regions, seven are located in the putative promoter region since they were within 50 bp upstream of the seven distinct genes. Using limited dilution methods, nine stable clonal mutants that had no apparent defect for multiplication in DH82 cells, were obtained. Mouse virulence of seven mutant clones was similar to that of wild-type HF strain, whereas two mutant clones showed significantly retarded growth in blood, livers, and spleens, and the mice inoculated with them lived longer than mice inoculated with wild-type. The two clones contained mutations in genes encoding a conserved hypothetical protein and a staphylococcal superantigen-like domain protein, respectively, and both genes are conserved among Ehrlichia spp., but lack homology to other bacterial genes. Inflammatory cytokine mRNA levels in the liver of mice infected with the two mutants were significantly diminished than those infected with HF strain wild-type, except IL-1β and IL-12 p40 in one clone. Thus, we identified two Ehrlichia virulence genes responsible for in vivo infection, but not for infection and growth in macrophages.Keywords: Ehrlichia HF strain, Himar1 transposon mutagenesis, mouse virulence, inflammatory cytokines, staphylococcal superantigen-like domain, obligatory intracellular bacteria IMPORTANCE Ehrlichiosis, a sometimes deadly febrile disease in man and animal, is caused by infection with Gram-negative obligatory intracellular bacteria, Ehrlichia. Ehrlichia species lack typical pathogen-associate molecular patterns (PAMPs), such as lipopolysaccharide, peptidoglycan, pili, and flagella, yet they induce acute and/or chronic inflammatory cytokines in infected animals.Bekebrede et al. In vivo Virulence Genes of EhrlichiaStudies to identify virulence factors and PAMPs of Ehrlichia species are hampered by the limitation to applicable genetic tools and small laboratory animal models. Mouse infection with Ehrlichia HF strain provides an excellent model for fatal human ehrlichiosis, as the HF strain is highly virulent in laboratory mice. However, due to inability to culture the HF stain, the use of this model has been limited. As we have succeeded in culturing and who...

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“…lar trafficking and cytoskeletal organization, and apoptosis (4,5). Most recently, E. chaffeensis via the TRP120 effector was shown to activate Wnt and Notch signaling pathways to promote intracellular survival (6,7).…”

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confidence: 99%

Ehrlichia chaffeensis TRP120 Moonlights as a HECT E3 Ligase Involved in Self- and Host Ubiquitination To Influence Protein Interactions and Stability for Intracellular Survival

et al. 2017

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Ehrlichia chaffeensis secretes tandem repeat protein (TRP) effectors that are involved in a diverse array of host cell interactions, some of which directly activate cell signaling pathways and reprogram host gene transcription to promote survival in the mononuclear phagocyte. However, the molecular details of these effectorhost interactions and roles in pathobiology are incompletely understood. In this study, we determined that the E. chaffeensis effector TRP120 is posttranslationally modified by ubiquitin (Ub) and that ubiquitination occurs through intrinsic and host-mediated HECT ligase activity. A functional HECT E3 ligase domain with a conserved catalytic site was identified in the C-terminal region of TRP120, and TRP120 autoubiquitination occurred in vitro in the presence of host UbcH5b/c E2 enzymes. TRP120 ubiquitination sites were mapped using a high-density microfluidic peptide array and confirmed by ectopic expression of TRP120 lysine mutants in cells. Moreover, we determined that the HECT E3 ubiquitin ligase, Nedd4L, interacts with TRP120 during infection and also mediates TRP120 ubiquitination. Nedd4L knockdown resulted in the reduction of TRP120-Ub, decreased ehrlichial infection, and reduced recruitment of a known TRP120-interacting host protein, PCGF5, to ehrlichial inclusions. TRP120-mediated PCGF5 polyubiquitination was associated with a reduction in PCGF5 levels. Inhibition of ubiquitination with small molecules also significantly decreased ehrlichial infection, indicating that the Ub pathway is critical for ehrlichial intracellular replication and survival. The current study identified a novel E. chaffeensis ubiquitin ligase and revealed an important role for the ubiquitin pathway in effector-host interactions and pathogen-mediated host protein stability in order to promote intracellular survival.

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Ehrlichia moonlighting effectors and interkingdom interactions with the mononuclear phagocyte

Cited by 29 publications

References 64 publications

Ehrlichia chaffeensis Exploits Canonical and Noncanonical Host Wnt Signaling Pathways To Stimulate Phagocytosis and Promote Intracellular Survival

Ehrlichia chaffeensis Exploits Canonical and Noncanonical Host Wnt Signaling Pathways To Stimulate Phagocytosis and Promote Intracellular Survival

Discovery of in vivo Virulence Genes of Obligatory Intracellular Bacteria by Random Mutagenesis

Ehrlichia chaffeensis TRP120 Moonlights as a HECT E3 Ligase Involved in Self- and Host Ubiquitination To Influence Protein Interactions and Stability for Intracellular Survival

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