title: Distinct Roles for CdtA and CdtC during Intoxication by Cytolethal Distending Toxins.
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.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Shandee D
authors.initials: SD
authors.lastname: Dixon
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Huynh
authors.affiliation: Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America.
authors.forename: Batcha
authors.initials: B
authors.lastname: Tamilselvam
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Lindsey M
authors.initials: LM
authors.lastname: Spiegelman
authors.affiliation: Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America.
authors.forename: Sophia B
authors.initials: SB
authors.lastname: Son
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Aria
authors.initials: A
authors.lastname: Eshraghi
authors.affiliation: Department of Microbiology, Institute for Genomic Biology, University of Illinois Urbana, Urbana, Illinois, United States of America.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Blanke
authors.affiliation: 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.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Bradley
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D016466:CHO Cells; D002453:Cell Cycle; D002470:Cell Survival; D003412:Cricetulus; D054308:Enteropathogenic Escherichia coli / Q000378:metabolism / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology*; D006191:Haemophilus ducreyi / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D019169:Jurkat Cells; D021381:Protein Transport; D013601:T-Lymphocytes / Q000166:cytology*
chemical_list: D001427:Bacterial Toxins; C067044:cytolethal distending toxin