A Novel Mode of Action for a Microbial-Derived Immunotoxin: The Cytolethal Distending Toxin Subunit B Exhibits Phosphatidylinositol 3,4,5-Triphosphate Phosphatase Activity

Shenker, Bruce J.; Dlakić, Mensur; Walker, Lisa M.; Besack, Dave; Jaffe, Eileen K.; Labelle, Ed; Boesze‐Battaglia, Kathleen

doi:10.4049/jimmunol.178.8.5099

Cited by 95 publications

(224 citation statements)

References 51 publications

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“…The absence of CDT receptor on infected host cells has been proposed as a protective mechanism against cytotoxicity allowing intracellular survival of S. Typhi, and thus persistence in infected host tissues (Spanò et al, 2008). While it is well-established that cellular toxicity is mediated by the nuclease function of CdtB, other studies suggest that phosphatidylinositol-3,4,5-triphosphate (PIP 3 ) phosphatase activity plays a role in cellular toxicity (Shenker et al, 2007). This is based in part on in silico comparative analysis of predicted amino acid sequences suggesting that several phosphatases involved in cell cycle regulation and signal transduction, including inositol phosphatases, contain a protein fold similar to Mg 2+ -dependent endonucleases including mammalian DNase I and bacterial CDT (Dlakić, 2000).…”

Section: Cdtmentioning

confidence: 99%

“…This is based in part on in silico comparative analysis of predicted amino acid sequences suggesting that several phosphatases involved in cell cycle regulation and signal transduction, including inositol phosphatases, contain a protein fold similar to Mg 2+ -dependent endonucleases including mammalian DNase I and bacterial CDT (Dlakić, 2000). Demonstration of PIP 3 phosphatase activity is more clearly seen when using human leukaemia T-cell lines with constitutively elevated PIP 3 levels because of mutations in SHIP1 and/or PTEN (Shenker et al, 2007). Therefore, an alternative mechanism of cellular toxicity might result from depletion of cell membrane PIP 3 and suppression of the protein kinase B (PKB)/Akt signalling pathway (Shenker et al, 2007).…”

Section: Cdtmentioning

confidence: 99%

“…Based on caspase activation patterns in this and other cell lines, and together with other experimental evidence, the major mechanism for CDT-induced apoptosis appears to be through the ATM-dependent intrinsic pathway ( (Wising et al, 2005). Based on their extreme susceptibility, lymphocytes have been proposed as the in vivo target of CDT, suggesting that immunomodulation is responsible for persistent bacterial colonization (Ge et al, 2005;Pratt et al, 2006;Shenker et al, 2007). Although CDT is a broad range genotoxin (Ge et al, 2005;Pratt et al, 2006;Shenker et al, 2007), it remains to be shown whether this apparent cell type specificity is in part attributable to inherent differences in cell surface receptor binding of CdtA and CdtC to host cell membrane based on: (i) host cell surface biomolecule chemical composition or density, (ii) intrinsic differences in CdtB uptake and nuclear translocation or (iii) variable target cell lineage DDR competence (Carette et al, 2009;Eshraghi et al, 2010).…”

mentioning

confidence: 99%

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Cytolethal distending toxin: a conserved bacterial genotoxin that blocks cell cycle progression, leading to apoptosis of a broad range of mammalian cell lineages

et al. 2011

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Cytolethal distending toxin (CDT) is a heterotrimeric AB-type genotoxin produced by several clinically important Gram-negative mucocutaneous bacterial pathogens. Irrespective of the bacterial species of origin, CDT causes characteristic and irreversible cell cycle arrest and apoptosis in a broad range of cultured mammalian cell lineages. The active subunit CdtB has structural homology with the phosphodiesterase family of enzymes including mammalian DNase I, and alone is necessary and sufficient to account for cellular toxicity. Indeed, mammalian cells treated with CDT initiate a DNA damage response similar to that elicited by ionizing radiationinduced DNA double strand breaks resulting in cell cycle arrest and apoptosis. The mechanism of CDT-induced apoptosis remains incompletely understood, but appears to involve both p53-dependent and -independent pathways. While epithelial, endothelial and fibroblast cell lines respond to CDT by undergoing arrest of cell cycle progression resulting in nuclear and cytoplasmic distension that precedes apoptotic cell death, cells of haematopoietic origin display rapid apoptosis following a brief period of cell cycle arrest. In this review, the ecology of pathogens producing CDT, the molecular biology of bacterial CDT and the molecular mechanisms of CDT-induced cytotoxicity are critically appraised. Understanding the contribution of a broadly conserved bacterial genotoxin that blocks progression of the mammalian cell cycle, ultimately causing cell death, should assist with elucidating disease mechanisms for these important pathogens. IntroductionJohnson and Lior's seminal observations in the 1980s identified a novel heat-labile toxin in culture filtrates obtained from certain Escherichia coli, Shigella dysenteriae and Campylobacter jejuni strains which caused distinctive and progressive cytoplasmic and nuclear enlargement of cultured mammalian cells, so called cytolethal distending toxin (CDT), and uncovered a novel paradigm amongst bacterial toxins and virulence mechanisms (Johnson & Lior, 1987, 1988a. It was not until many years later that Scott & Kaper (1994) identified the genes encoding CDT in E. coli, which set the stage for fundamental investigations into the ecology, biochemistry and molecular mechanisms of cellular toxicity associated with this novel bacterial toxin (Table 1). While a secreted protein cytotoxin was identified among Haemophilus (Haem.) ducreyi clinical isolates in the early 1990s by Purvén & Lagergård (1992), it was not until the late 1990s that this cytotoxin was conclusively shown to be encoded by a cdt gene cluster with homology to the previously identified E. coli genes (Cope et al., 1997). This discovery extended the range of niches where CDTproducing bacteria are found to include mucocutaneous surfaces of the genital tract in addition to the intestinal tract. At that time, Pérès et al. (1997) first reported that the mechanism of mammalian cell intoxication by E. coli CDT involved arrest of the cell cycle at the G2/M phase. Soon after, these observa...

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Section: Cdtmentioning

confidence: 99%

Section: Cdtmentioning

confidence: 99%

mentioning

confidence: 99%

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Cytolethal distending toxin: a conserved bacterial genotoxin that blocks cell cycle progression, leading to apoptosis of a broad range of mammalian cell lineages

et al. 2011

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“…CdtB shares a common tertiary structure with DNase I and phosphatidylinositol 3,4,5-triphosphate phosphatase enzymes and displays both activities in cell-free systems (9 -13). It is not currently known which activity is of greater importance, and this may depend on the specific toxin and/or the host target cell type (12,14). CdtB enzymatic activity induces cell cycle arrest predominantly at the G 2 /M transition, resulting in cellular distension and ultimately cell death (5,15,16).…”

mentioning

confidence: 99%

Cytolethal Distending Toxin Family Members Are Differentially Affected by Alterations in Host Glycans and Membrane Cholesterol

Eshraghi

Maldonado-Arocho

Gargi

et al. 2010

Journal of Biological Chemistry

109

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Cytolethal distending toxins (CDTs) 6 are members of a group of bacterial toxins and effectors called "cyclomodulins" that interfere with the eukaryotic cell cycle rather than inducing overt cytotoxicity (1, 2). Inhibiting cell cycle disrupts many of the normal functions of rapidly dividing eukaryotic cells, including lymphocytes and epithelial cells, which provide immunity and physical barriers to microbial pathogens (3-5). Thus, it is not surprising that cdt genes are found in a diverse group of Gram-negative pathogens that colonize different niches within the host. Although a growing body of evidence supports the importance of CDTs in bacterial virulence and host-pathogen interactions (6), the manner in which individual CDTs interact with and intoxicate host cells remains poorly understood.CDTs are AB 2 toxins, consisting of a hetero-trimeric complex of three proteins (CdtA, CdtB, and CdtC) at a 1:1:1 molar ratio (5,7,8). The current model is that CdtA and CdtC are the binding "B" moieties that collaborate to facilitate binding and entry of the catalytic "A" subunit, CdtB, into mammalian cells. CdtB shares a common tertiary structure with DNase I and phosphatidylinositol 3,4,5-triphosphate phosphatase enzymes and displays both activities in cell-free systems (9 -13). It is not currently known which activity is of greater importance, and this may depend on the specific toxin and/or the host target cell type (12,14). CdtB enzymatic activity induces cell cycle arrest predominantly at the G 2 /M transition, resulting in cellular distension and ultimately cell death (5,15,16).Consistent with their proposed roles as binding subunits, CdtA and/or CdtC increase the ability of CdtB to associate with host cells and greatly enhance intoxication (7,(17)(18)(19)(20)(21)(22)(23)(24)(25). The identification of ricin-like lectin domains in CdtA and CdtC from structural and biochemical data first suggested that these subunits may interact with carbohydrates on the cell surface (13,26,27). Consistent with this hypothesis, CDT produced by Escherichia coli (Ec-CDT) was reported to require N-linked glycoproteins for binding and subsequent intoxication of HeLa cells (23). Moreover, Ec-CDT bound fucose in vitro, and fucose-specific lectins blocked Ec-CDT-mediated cell cycle arrest, presumably by preventing binding of toxin to its receptor. These findings suggested that fucose might serve as a binding determinant for Ec-CDT. Similarly, host glycans were reported to support Aggregatibacter actinomycetemcomitans (Aa-CDT) intoxication. Specifically, Aa-CDT bound three glycosphingolipids, GM1, GM2, and GM3, and intoxication of human monocytic U937 cells was blocked by preincubation of toxin with liposomes that contained G M3 (24). In addition, the CdtA subunit of Aa-CDT bound to the glycoprotein thyroglobulin (19). However, the functional significance of this binding is * This work was supported, in whole or in part, by National Institutes of Health Grants T32DE007296 (to A. E.), F31AI061837 (to F. J. M.-A.), and AI59095 (to S. R. B. ...

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“…For example, cytolethal distending toxin subunit B (CdtB) is an immunotoxin produced by Actinobacillus actinomycetemcomitans that can hydrolyze PtdIns(3,4,5)P 3 to PtdIns(3,4)P 2 (50). Exposure to CdtB leads to cell cycle arrest and death by apoptosis, consistent with the down-regulation of proliferation observed upon overexpression of SHIP in leukemic cell lines (51).…”

Section: Lipid Phosphatases Are Exploited By Pathogensmentioning

confidence: 67%

Phosphoinositide Lipid Phosphatases: Natural Regulators of Phosphoinositide 3-Kinase Signaling in T Lymphocytes

Harris

Parry

Westwick

et al. 2008

Journal of Biological Chemistry

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The phosphoinositide 3-kinase signaling pathway has been implicated in a range of T lymphocyte cellular functions, particularly growth, proliferation, cytokine secretion, and survival. Dysregulation of phosphoinositide 3-kinase-dependent signaling and function in leukocytes, including B and T lymphocytes, has been implicated in many inflammatory and autoimmune diseases. As befits a pivotal signaling cascade, several mechanisms exist to ensure that the pathway is tightly regulated. This minireview focuses on two lipid phosphatases, viz. the 3 -phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10) and SHIP (Src homology 2 domain-containing inositol-5-phosphatase). We discuss their role in regulating T lymphocyte signaling as well their potential as future therapeutic targets.The PI3K 3 pathway plays a central role in regulating many biological processes, primarily via the generation of the potent second messenger PtdIns(3,4,5)P 3 , which acts as a docking site at the plasma membrane, recruiting and activating proteins containing pleckstrin homology (PH) domains (1). These downstream PI3K effectors include PDK-1 (3Ј-phosphoinositide-dependent kinase-1), which phosphorylates and activates the AGC protein kinases, including protein kinase B/Akt. Other kinases such as Tec family kinases can also interact directly with PtdIns(3,4,5)P 3 , as can GTPase-activating proteins and guanine nucleotide exchange factors as well as scaffolding proteins that nucleate the assembly of key signaling complexes (1, 2). PI3K and T LymphocytesT cells express all three class 1A PI3K isoforms (p110␣, p110␤, and p110␦), which are regulated by protein-tyrosine kinase-coupled receptors, as well as class 1B p110␥, which is activated by G protein-coupled receptors (GPCRs). The T cell antigen receptor (TCR), CD28 family co-stimulatory receptors, and cytokine receptors activate class 1A isoforms (3). Chemokines (by virtue of interacting with GPCRs), activate mainly class 1B PI3K (4). Use of pharmacological tools in leukemic human T cell lines first indicated a possible role for PI3K in T cell activation (5). Mice with a knock-in point mutation of p110␦ that abolishes kinase activity exhibit selective impairments in TCR signaling and reduced proliferation in vitro (6) and impaired function of CD4 ϩ CD25 ϩ Foxp3 ϩ T Reg cells (7). Interestingly, mice lacking both p110␥ and p110␦ show much more profound defects in thymocyte development and survival compared with mice lacking individual isoforms, indicating that these isoforms serve partially redundant functions in thymocytes (8, 9). Pathological consequences of combined p110␥␦ deficiency includes T cell lymphopenia, which leads to multiple-organ inflammation (10). Surprisingly, mice with T cellspecific loss of class 1A PI3K exhibit largely normal thymocyte development, and peripheral T cell numbers and subsets are unimpaired in young animals (11,12). In vitro proliferation of T cells from these mice in response to TCR ligation is abrogated, and there is complete loss of PI3K sig...

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A Novel Mode of Action for a Microbial-Derived Immunotoxin: The Cytolethal Distending Toxin Subunit B Exhibits Phosphatidylinositol 3,4,5-Triphosphate Phosphatase Activity

Cited by 95 publications

References 51 publications

Cytolethal distending toxin: a conserved bacterial genotoxin that blocks cell cycle progression, leading to apoptosis of a broad range of mammalian cell lineages

Cytolethal distending toxin: a conserved bacterial genotoxin that blocks cell cycle progression, leading to apoptosis of a broad range of mammalian cell lineages

Cytolethal Distending Toxin Family Members Are Differentially Affected by Alterations in Host Glycans and Membrane Cholesterol

Phosphoinositide Lipid Phosphatases: Natural Regulators of Phosphoinositide 3-Kinase Signaling in T Lymphocytes

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