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Dixon SD, Huynh MM, Tamilselvam B, Spiegelman LM, Son SB, Eshraghi A, Blanke SR, Bradley KA. Distinct Roles for CdtA and CdtC during Intoxication by Cytolethal Distending Toxins. PLoS One 2015; 10:e0143977. [PMID: 26618479 PMCID: PMC4664275 DOI: 10.1371/journal.pone.0143977] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 11/11/2015] [Indexed: 12/29/2022] Open
Abstract
Cytolethal distending toxins (CDTs) are heterotrimeric protein exotoxins produced by a diverse array of Gram-negative pathogens. The enzymatic subunit, CdtB, possesses DNase and phosphatidylinositol 3-4-5 trisphosphate phosphatase activities that induce host cell cycle arrest, cellular distension and apoptosis. To exert cyclomodulatory and cytotoxic effects CDTs must be taken up from the host cell surface and transported intracellularly in a manner that ultimately results in localization of CdtB to the nucleus. However, the molecular details and mechanism by which CDTs bind to host cells and exploit existing uptake and transport pathways to gain access to the nucleus are poorly understood. Here, we report that CdtA and CdtC subunits of CDTs derived from Haemophilus ducreyi (Hd-CDT) and enteropathogenic E. coli (Ec-CDT) are independently sufficient to support intoxication by their respective CdtB subunits. CdtA supported CdtB-mediated killing of T-cells and epithelial cells that was nearly as efficient as that observed with holotoxin. In contrast, the efficiency by which CdtC supported intoxication was dependent on the source of the toxin as well as the target cell type. Further, CdtC was found to alter the subcellular trafficking of Ec-CDT as determined by sensitivity to EGA, an inhibitor of endosomal trafficking, colocalization with markers of early and late endosomes, and the kinetics of DNA damage response. Finally, host cellular cholesterol was found to influence sensitivity to intoxication mediated by Ec-CdtA, revealing a role for cholesterol or cholesterol-rich membrane domains in intoxication mediated by this subunit. In summary, data presented here support a model in which CdtA and CdtC each bind distinct receptors on host cell surfaces that direct alternate intracellular uptake and/or trafficking pathways.
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Affiliation(s)
- Shandee D. Dixon
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Melanie M. Huynh
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Batcha Tamilselvam
- Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America
| | - Lindsey M. Spiegelman
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Sophia B. Son
- Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America
| | - Aria Eshraghi
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
| | - Steven R. Blanke
- Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America
| | - Kenneth A. Bradley
- Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Eshraghi A, Dixon SD, Tamilselvam B, Kim EJK, Gargi A, Kulik JC, Damoiseaux R, Blanke SR, Bradley KA. Cytolethal distending toxins require components of the ER-associated degradation pathway for host cell entry. PLoS Pathog 2014; 10:e1004295. [PMID: 25078082 PMCID: PMC4117610 DOI: 10.1371/journal.ppat.1004295] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 06/23/2014] [Indexed: 11/18/2022] Open
Abstract
Intracellular acting protein exotoxins produced by bacteria and plants are important molecular determinants that drive numerous human diseases. A subset of these toxins, the cytolethal distending toxins (CDTs), are encoded by several Gram-negative pathogens and have been proposed to enhance virulence by allowing evasion of the immune system. CDTs are trafficked in a retrograde manner from the cell surface through the Golgi apparatus and into the endoplasmic reticulum (ER) before ultimately reaching the host cell nucleus. However, the mechanism by which CDTs exit the ER is not known. Here we show that three central components of the host ER associated degradation (ERAD) machinery, Derlin-2 (Derl2), the E3 ubiquitin-protein ligase Hrd1, and the AAA ATPase p97, are required for intoxication by some CDTs. Complementation of Derl2-deficient cells with Derl2:Derl1 chimeras identified two previously uncharacterized functional domains in Derl2, the N-terminal 88 amino acids and the second ER-luminal loop, as required for intoxication by the CDT encoded by Haemophilus ducreyi (Hd-CDT). In contrast, two motifs required for Derlin-dependent retrotranslocation of ERAD substrates, a conserved WR motif and an SHP box that mediates interaction with the AAA ATPase p97, were found to be dispensable for Hd-CDT intoxication. Interestingly, this previously undescribed mechanism is shared with the plant toxin ricin. These data reveal a requirement for multiple components of the ERAD pathway for CDT intoxication and provide insight into a Derl2-dependent pathway exploited by retrograde trafficking toxins.
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Affiliation(s)
- Aria Eshraghi
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Shandee D. Dixon
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Batcha Tamilselvam
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Urbana, Illinois, United States of America
| | - Emily Jin-Kyung Kim
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Amandeep Gargi
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Urbana, Illinois, United States of America
| | - Julia C. Kulik
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Robert Damoiseaux
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Steven R. Blanke
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Urbana, Illinois, United States of America
| | - Kenneth A. Bradley
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Gargi A, Tamilselvam B, Powers B, Prouty MG, Lincecum T, Eshraghi A, Maldonado-Arocho FJ, Wilson BA, Bradley KA, Blanke SR. Cellular interactions of the cytolethal distending toxins from Escherichia coli and Haemophilus ducreyi. J Biol Chem 2013; 288:7492-7505. [PMID: 23306199 DOI: 10.1074/jbc.m112.448118] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The cytolethal distending toxins (CDTs) compose a subclass of intracellularly acting genotoxins produced by many Gram-negative pathogenic bacteria that disrupt the normal progression of the eukaryotic cell cycle. Here, the intoxication mechanisms of CDTs from Escherichia coli (Ec-CDT) and Haemophilus ducreyi (Hd-CDT), which share limited amino acid sequence homology, were directly compared. Ec-CDT and Hd-CDT shared comparable in vitro DNase activities of the CdtB subunits, saturable cell surface binding with comparable affinities, and the requirement for an intact Golgi complex to induce cell cycle arrest. In contrast, disruption of endosome acidification blocked Hd-CDT-mediated cell cycle arrest and toxin transport to the endoplasmic reticulum and nucleus, while having no effects on Ec-CDT. Phosphorylation of the histone protein H2AX, as well as nuclear localization, was inhibited for Hd-CdtB, but not Ec-CdtB, in cells expressing dominant negative Rab7 (T22N), suggesting that Hd-CDT, but not Ec-CDT, is trafficked through late endosomal vesicles. In support of this idea, significantly more Hd-CdtB than Ec-CdtB co-localized with Rab9, which is enriched in late endosomal compartments. Competitive binding studies suggested that Ec-CDT and Hd-CDT bind to discrete cell surface determinants. These results suggest that Ec-CDT and Hd-CDT are transported within cells by distinct pathways, possibly mediated by their interaction with different receptors at the cell surface.
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Affiliation(s)
- Amandeep Gargi
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801
| | - Batcha Tamilselvam
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801
| | - Brendan Powers
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801
| | - Michael G Prouty
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801
| | - Tommie Lincecum
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | - Aria Eshraghi
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, California 90095
| | | | - Brenda A Wilson
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801; Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801
| | - Kenneth A Bradley
- Department of Microbiology, Immunology, and Molecular Genetics, UCLA, Los Angeles, California 90095
| | - Steven R Blanke
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801; Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801.
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Pan X, Tamilselvam B, Hansen EJ, Daefler S. Modulation of iron homeostasis in macrophages by bacterial intracellular pathogens. BMC Microbiol 2010; 10:64. [PMID: 20184753 PMCID: PMC2838877 DOI: 10.1186/1471-2180-10-64] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Accepted: 02/25/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Intracellular bacterial pathogens depend on acquisition of iron for their success as pathogens. The host cell requires iron as an essential component for cellular functions that include innate immune defense mechanisms. The transferrin receptor TfR1 plays an important part for delivering iron to the host cell during infection. Its expression can be modulated by infection, but its essentiality for bacterial intracellular survival has not been directly investigated. RESULTS We identified two distinct iron-handling scenarios for two different bacterial pathogens. Francisella tularensis drives an active iron acquisition program via the TfR1 pathway program with induction of ferrireductase (Steap3), iron membrane transporter Dmt1, and iron regulatory proteins IRP1 and IRP2, which is associated with a sustained increase of the labile iron pool inside the macrophage. Expression of TfR1 is critical for Francisella's intracellular proliferation. This contrasts with infection of macrophages by wild-type Salmonella typhimurium, which does not require expression of TfR1 for successful intracellular survival. Macrophages infected with Salmonella lack significant induction of Dmt1, Steap3, and IRP1, and maintain their labile iron pool at normal levels. CONCLUSION The distinction between two different phenotypes of iron utilization by intracellular pathogens will allow further characterization and understanding of host-cell iron metabolism and its modulation by intracellular bacteria.
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Affiliation(s)
- Xin Pan
- Mount Sinai School of Medicine, One Gustave Levy Place, New York, NY 10570, USA
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Abstract
Francisella tularensis is a pathogen optimally adapted to efficiently invade its respective host cell and to proliferate intracellularly. We investigated the role of host cell membrane microdomains in the entry of F. tularensis subspecies holarctica vaccine strain (F. tularensis live vaccine strain) into murine macrophages. F. tularensis live vaccine strain recruits cholesterol-rich lipid domains ("lipid rafts") with caveolin-1 for successful entry into macrophages. Interference with lipid rafts through the depletion of plasma membrane cholesterol, through induction of raft internalization with choleratoxin, or through removal of raft-associated GPI-anchored proteins by treatment with phosphatidylinositol phospholipase C significantly inhibited entry of Francisella and its intracellular proliferation. Lipid raft-associated components such as cholesterol and caveolin-1 were incorporated into Francisella-containing vesicles during entry and the initial phase of intracellular trafficking inside the host cell. These findings demonstrate that Francisella requires cholesterol-rich membrane domains for entry into and proliferation inside macrophages.
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Tamilselvam B, Almeida RA, Dunlap JR, Oliver SP. Streptococcus uberis internalizes and persists in bovine mammary epithelial cells. Microb Pathog 2006; 40:279-85. [PMID: 16678381 DOI: 10.1016/j.micpath.2006.02.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Revised: 01/03/2006] [Accepted: 02/28/2006] [Indexed: 11/18/2022]
Abstract
Streptococcus uberis is one of the most important emerging bovine mastitis pathogens and chronic persistent intramammary infections (IMI) are often described. To define the ability of S. uberis to persist intracellularly, studies on time-dependent internalization and survival of S. uberis strains in bovine mammary epithelial cells were conducted. Two S. uberis strains (UT366 and UT888) and a Staphylococcus aureus strain used as positive control, all isolated from cows with clinical mastitis were cocultured with bovine mammary epithelial cells (MAC-T) and persistent survival in host epithelial cells for extended periods (120 h) studied. Of S. uberis strains tested, UT366 showed highest internalization values at 60 min of incubation whereas at 8 h of incubation the corresponding values for UT888 were the highest. Of both strains of S. uberis tested, UT366 seems to internalize bovine mammary cells more efficiently initially, however, during the first 8 h, UT888 seems to survive intracellularly better than UT366. Results showed that both S. uberis strains could survive intracellularly up to 120 h without apparent loss of host cells viability. S. aureus internalized more efficiently than all strains tested and host cell death was observed after 72 h of incubation. These results indicate that S. uberis can survive within mammary epithelial cells for extended time without apparent loss of host cells viability. Intracellular persistence of S. uberis may be associated with the spread of the infection to deeper tissues and development of persistent IMI.
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Affiliation(s)
- Batcha Tamilselvam
- Department of Animal Science, Institute of Agriculture, Food Safety Center of Excellence, The University of Tennessee, 60 McCord Hall, Knoxville, TN 37996, USA
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Srinivasan V, Nam HM, Nguyen LT, Tamilselvam B, Murinda SE, Oliver SP. Prevalence of Antimicrobial Resistance Genes inListeria monocytogenesIsolated from Dairy Farms. Foodborne Pathog Dis 2005; 2:201-11. [PMID: 16156701 DOI: 10.1089/fpd.2005.2.201] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Antimicrobial resistance of Listeria monocytogenes (n = 38) isolated from the four dairy farms to 15 antimicrobial agents was evaluated. All 38 L. monocytogenes isolates from the four farms evaluated were resistant to more than one antimicrobial in different combinations. All L. monocytogenes isolates evaluated were resistant to cephalosporin C (minimum inhibitory concentration [MIC] > or = 512 microg/mL), streptomycin (MIC > or = 32) and trimethoprim (MIC > or = 512). Most L. monocytogenes isolates were resistant to ampicillin (92%, MIC > or = 2), rifampicin (84%, MIC > or = 4), rifamycin (84%, MIC > or = 4), and florfenicol (66%, MIC > or = 32) and some were resistant to tetracycline (45%, MIC > or = 16), penicillin G (40%, MIC > or = 2) and chloramphenicol (32%, MIC > or = 32). All L. monocytogenes isolates were susceptible to amoxicillin, erythromycin, gentamicin, kanamycin and vancomycin. Susceptibility of L. monocytogenes to the antimicrobials evaluated was quite consistent among the dairy farms evaluated. However, some variability in antimicrobial susceptibility among dairy farms was noted. Nineteen of 38 L. monocytogenes isolates contained more than one antimicrobial resistance gene sequence. A high frequency of floR (66%) was found in L. monocytogenes followed by penA (37%), strA (34%), tetA (32%), and sulI (16%). Other tetracycline resistance genes (tetB, tetC, tetD, tetE, and tetG) and other antimicrobial resistance genes (cmlA, strB, aadA, sulI, vanA, vanB, ampC, ermB, ereA, and ereB) were not found in any of the L. monocytogenes isolates from the four dairy farms. Results of the present study demonstrated that L. monocytogenes isolated from the dairy farm environment were resistant to many antimicrobials and contained one or more antimicrobial resistance genes.
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Affiliation(s)
- V Srinivasan
- Food Safety Center of Excellence, University of Tennessee, 59 McCord Hall, Knoxville, TN 37996, USA
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