Cholera Toxin B-Subunit Prevents Activation and Proliferation of Human CD4+ T Cells by Activation of a Neutral Sphingomyelinase in Lipid Rafts

Rouquette-Jazdanian, Alexandre K.; Foussat, Arnaud; Lamy, Laurence; Pelassy, Claudette; Lagadec, Patricia; Breittmayer, Jean‐Philippe; Aussel, Claude

doi:10.4049/jimmunol.175.9.5637

Cited by 22 publications

(18 citation statements)

References 55 publications

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“…Several bacterial toxins exert their cellular effects by initial interaction with lipid rafts, as exemplified by cholera toxin, anthrax, and listeriolysin (1,18,38). Our data suggest that this may also be true for Hly-induced cell signaling, although this must be addressed in further detail.…”

Section: Discussionmentioning

confidence: 85%

Role of the Lipopolysaccharide-CD14 Complex for the Activity of Hemolysin from Uropathogenic Escherichia coli

et al. 2007

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Bacterial pathogens produce a variety of exotoxins, which often become associated with the bacterial outer membrane component lipopolysaccharide (LPS) during their secretion. LPS is a potent proinflammatory mediator; however, it is not known whether LPS contributes to cell signaling induced by those microbial components to which it is attached. This is partly due to the common view that LPS present in bacterial component preparations is an experimental artifact. The Escherichia coli exotoxin hemolysin (Hly) is a known inducer of proinflammatory signaling in epithelial cells, and the signal transduction pathway involves fluctuation of the intracellular-Ca 2؉ concentration. Since LPS is known to interact with Hly, we investigated whether it is required as a cofactor for the activity of Hly. We found that the LPS/Hly complex exploits the CD14/LPSbinding protein recognition system to bring Hly to the cell membrane, where intracellular-Ca 2؉ signaling is initiated via specific activation of the small GTPase RhoA. Hly-induced Ca 2؉ signaling was found to occur independently of the LPS receptor TLR4, suggesting that the role of LPS/CD14 is to deliver Hly to the cell membrane. In contrast, the cytolytic effect triggered by exposure of cells to high Hly concentrations occurs independently of LPS/CD14. Collectively, our data reveal a novel molecular mechanism for toxin delivery in bacterial pathogenesis, where LPS-associated microbial compounds are targeted to the host cell membrane as a consequence of their association with LPS.The exotoxin hemolysin (Hly) produced by uropathogenic Escherichia coli (UPEC) is an important virulence factor in extraintestinal infections, such as urinary tract infections, newborn meningitis, bacteremia, and septicemia (33). Hly exerts a cytolytic effect when present in high concentrations, while low, sublytic concentrations have been demonstrated to induce intracellular-Ca 2ϩ signaling in epithelial cells, leading to proinflammatory responses, such as production of interleukin-6 (IL-6) and . Hly is secreted from bacteria via the type I secretion pathway (26) and is found associated with bacterial outer membranes, in supernatants, and in outer membrane vesicles (5, 34). Hly forms high-molecular-weight complexes with lipopolysaccharide (LPS), and this interaction has been suggested to prevent aggregation and degradation of Hly as well as to promote an active conformation of the toxin (6, 12, 15). Whether there is also a molecular function of LPS in the Ca 2ϩ signaling and cytolytic activities of Hly remains unknown. Detailed information regarding the signal transduction pathway elicited by LPS does exist, however. LPS is a large amphipathic molecule composed of the acylated, hydrophobic lipid A component, the LPS core, and the O-antigen polysaccharide. Host recognition of LPS is a multistep process initiated by the binding of LPS by the LPS-binding protein (LBP). This interaction enhances the binding of LPS to the glycosylphosphatidylinositol-linked receptor CD14, whose protein structure conta...

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Section: Discussionmentioning

confidence: 85%

Role of the Lipopolysaccharide-CD14 Complex for the Activity of Hemolysin from Uropathogenic Escherichia coli

et al. 2007

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“…1F). Moreover, MV but not CTB caused ASM activation, and thus, though not directly analysed, ceramide accumulation measured in extracts of CTB exposed cells, may not be predominantly displayed at the cell surface [55]. Further suggesting that signalling pathways modulated by CTB ligation of GM1 and MV, though both causing ceramide accumulation, may substantially differ, CTB, but not MV exposure interfered with stimulated expression of early T cell activation markers CD25 and CD69 [26],[55],[56].…”

Section: Discussionmentioning

confidence: 92%

“…Unlike that by MV (Fig. 2), inhibition of CD4 T cell activation and proliferation after cholera toxin B (CTB) binding to and generating ceramides from rafts was strictly NSM–dependent and did not involve ASM [55]. Reasons for this discrepancy are unclear at present.…”

Section: Discussionmentioning

confidence: 93%

Induction of Membrane Ceramides: A Novel Strategy to Interfere with T Lymphocyte Cytoskeletal Reorganisation in Viral Immunosuppression

et al. 2009

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Silencing of T cell activation and function is a highly efficient strategy of immunosuppression induced by pathogens. By promoting formation of membrane microdomains essential for clustering of receptors and signalling platforms in the plasma membrane, ceramides accumulating as a result of membrane sphingomyelin breakdown are not only essential for assembly of signalling complexes and pathogen entry, but also act as signalling modulators, e. g. by regulating relay of phosphatidyl-inositol-3-kinase (PI3K) signalling. Their role in T lymphocyte functions has not been addressed as yet. We now show that measles virus (MV), which interacts with the surface of T cells and thereby efficiently interferes with stimulated dynamic reorganisation of their actin cytoskeleton, causes ceramide accumulation in human T cells in a neutral (NSM) and acid (ASM) sphingomyelinase–dependent manner. Ceramides induced by MV, but also bacterial sphingomyelinase, efficiently interfered with formation of membrane protrusions and T cell spreading and front/rear polarisation in response to β1 integrin ligation or αCD3/CD28 activation, and this was rescued upon pharmacological or genetic ablation of ASM/NSM activity. Moreover, membrane ceramide accumulation downmodulated chemokine-induced T cell motility on fibronectin. Altogether, these findings highlight an as yet unrecognised concept of pathogens able to cause membrane ceramide accumulation to target essential processes in T cell activation and function by preventing stimulated actin cytoskeletal dynamics.

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“…To determine whether this reflected an acquired global cellular defect or a property of the tolerized TCR complex, we investigated lipid-raft accumulation in dual-TCR cells at the point of T cell:APC contact. FACSsorted naive CD8 + CD44 lo and tolerant CD8 + CD44 hi dual-TCR T cells were incubated with peptide-pulsed E10 tumor cells as APCs, stained with labeled Cholera Toxin B-subunit (CTxB), which specifically binds the raft marker monosialoganglioside G M1 (Janes et al, 1999;Janes et al, 2000;Rouquette-Jazdanian et al, 2005), and lipid-raft aggregation was visualized by confocal microscopy of T cell:APC conjugates ( Figure 3A). Images of 40 conjugates from each group (240 total images) were graded for CTxB staining on a 0-5 scale, with 5 being most intense, and each set of 40 scores was averaged ( Figure 3B).…”

Section: Tolerant Tcr Complexes Selectively Exhibit Proximal Signalinmentioning

confidence: 99%

Peripheral CD8+ T Cell Tolerance to Self-Proteins Is Regulated Proximally at the T Cell Receptor

et al. 2008

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CD8(+) T cell tolerance, although essential for preventing autoimmunity, poses substantial obstacles to eliciting immune responses to tumor antigens, which are generally overexpressed normal proteins. Development of effective strategies to overcome tolerance for clinical applications would benefit from elucidation of the immunologic mechanism(s) regulating T cell tolerance to self. To examine how tolerance is maintained in vivo, we engineered dual-T cell receptor (TCR) transgenic mice in which CD8(+) T cells recognize two distinct antigens: a foreign viral-protein and a tolerizing self-tumor protein. Encounter with peripheral self-antigen rendered dual-TCR T cells tolerant to self, but these cells responded normally through the virus-specific TCR. Moreover, proliferation induced by virus rescued function of tolerized self-tumor-reactive TCR, restoring anti-tumor activity. These studies demonstrate that peripheral CD8(+) T cell tolerance to self-proteins can be regulated at the level of the self-reactive TCR complex rather than by central cellular inactivation and suggest an alternate strategy to enhance adoptive T cell immunotherapy.

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Cholera Toxin B-Subunit Prevents Activation and Proliferation of Human CD4+ T Cells by Activation of a Neutral Sphingomyelinase in Lipid Rafts

Cited by 22 publications

References 55 publications

Role of the Lipopolysaccharide-CD14 Complex for the Activity of Hemolysin from Uropathogenic Escherichia coli

Role of the Lipopolysaccharide-CD14 Complex for the Activity of Hemolysin from Uropathogenic Escherichia coli

Induction of Membrane Ceramides: A Novel Strategy to Interfere with T Lymphocyte Cytoskeletal Reorganisation in Viral Immunosuppression

Peripheral CD8+ T Cell Tolerance to Self-Proteins Is Regulated Proximally at the T Cell Receptor

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