Rapid Activation of Protein Tyrosine Kinase and Phospholipase C-γ2 and Increase in Cytosolic Free Calcium Are Required by<i>Ehrlichia chaffeensis</i>for Internalization and Growth in THP-1 Cells

Lin, Mingqun; Zhu, Michael X.; Rikihisa, Yasuko

doi:10.1128/iai.70.2.889-898.2002

Cited by 56 publications

(76 citation statements)

References 59 publications

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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: 81%

“…A Ca 2ϩ increase was detected in THP-1 cells infected with E. chaffeensis or treated with beads coated with a mixture of TRP32, TRP47, and TRP120. Consistent with a previous study (43), a rapid increase of Ca 2ϩ was detected to about 80 s after cell-free E. chaffeensis was added. Similarly, TRP-coated beads also caused a rapid increase of Ca 2ϩ to about 60 s, although the Ca 2ϩ concentration was lower than that stimulated by Ehrlichia.…”

Section: Gene Activity Analysis Of the Wnt Signaling Pathway In E Chsupporting

confidence: 79%

“…Intracellular Ca 2ϩ release was measured in THP-1 cells using an acetoxymethyl (AM) ester derivative of fluo-3 (fluo-3/AM) (PromoKine, Heidelberg, Germany) as previously described (43). Fluo-3-preloaded cells were treated with cell-free E. chaffeensis (MOI ϭ ϳ50), TRP-coated beads (50 beads/cell), or a control (cell-free uninfected THP-1 or thioredoxin-coated beads) and mixed briefly.…”

Section: Methodsmentioning

confidence: 99%

“…chaffeensis binding and entry are known to involve one or more glycosylphosphatidylinositol (GPI)-anchored proteins associated with caveolae at the cell surface, inducing receptormediated phagocytosis that triggers Wnt signaling-like events, including transglutamination, tyrosine phosphorylation, phospholipase C␥2 (PLC-␥2) activation, inositol-(1,4,5)-trisphosphate (IP 3 ) production, and intracellular calcium release (43,44). In addition, multiple studies have shown the importance of E. chaffeensis TRP120 in ehrlichial binding and internalization (45,46); however, the specific cellular pathways exploited to mediate invasion and intracellular survival have not been defined.…”

mentioning

confidence: 99%

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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: 81%

Section: Gene Activity Analysis Of the Wnt Signaling Pathway In E Chsupporting

confidence: 79%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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

et al. 2016

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“…An influx of Ca 2ϩ , calmodulin, and activation of phospholipase C (PLC) are required for A. phagocytophila, N. risticii, and E. chaffeensis infection (28,35,44). The involvement of these signals in induction of IL-1␤, TNF-␣, and IL-6 mRNAs in PBLs and monocytes or in induction of IL-1␤ mRNA in neutrophils in response to A. phagocytophila was examined.…”

Section: Figmentioning

confidence: 99%

Roles of p38 Mitogen-Activated Protein Kinase, NF-κB, and Protein Kinase C in Proinflammatory Cytokine mRNA Expression by Human Peripheral Blood Leukocytes, Monocytes, and Neutrophils in Response toAnaplasma phagocytophila

Kim

Rikihisa

2002

Infect Immun

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Anaplasma phagocytophila, an obligately intracellular bacterium of granulocytes, causes human granulocytic ehrlichiosis. Within 2 h after addition of A. phagocytophila, interleukin-1␤ (IL-1␤), tumor necrosis factor alpha (TNF-␣), and IL-6 mRNAs are induced in human peripheral blood leukocytes (PBLs) or monocytes in vitro. However, neutrophils generate only IL-1␤ mRNA. In the present study, signaling pathways for induction of these three cytokines were examined. TNF-␣ and IL-6 mRNA expression by PBLs was inhibited with SB 203580 (a p38 mitogen-activated protein kinase [MAPK] inhibitor), MG-132 (a proteasome inhibitor), and SN-50 (an NF-B inhibitor). Activation of p38 MAPK and NF-B mRNAs in monocytes was detectable within 15 to 30 min after addition of A. phagocytophila. Expression of these two cytokine mRNAs in PBLs and monocytes was also dependent on protein kinase C (PKC), protein kinase A (PKA), and protein tyrosine kinase (PTK). IL-1␤ mRNA expression by neutrophils was not dependent on p38 MAPK, and p38 MAPK was not activated in neutrophils incubated with A. phagocytophila. IL-1␤ mRNA induction by PBLs, monocytes, and neutrophils was dependent on PKC and PKA. Neutrophil expression of IL-1␤ mRNA was dependent on transglutaminase, phospholipase C, and PTK, all of which are also required for internalization of A. phagocytophila. However, monocyte expression of IL-1␤ mRNA was less dependent on these enzymes. These results suggest that A. phagocytophila transduces different signals between its host neutrophils and monocytes for proinflammatory cytokine generation.

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Pathogenesis of Human Ehrlichioses

Saito

Walker

2015

Human Emerging and Re‐emerging Infections

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Rapid Activation of Protein Tyrosine Kinase and Phospholipase C-γ2 and Increase in Cytosolic Free Calcium Are Required byEhrlichia chaffeensisfor Internalization and Growth in THP-1 Cells

Cited by 56 publications

References 59 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

Roles of p38 Mitogen-Activated Protein Kinase, NF-κB, and Protein Kinase C in Proinflammatory Cytokine mRNA Expression by Human Peripheral Blood Leukocytes, Monocytes, and Neutrophils in Response toAnaplasma phagocytophila

Pathogenesis of Human Ehrlichioses

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