title: The Haemophilus ducreyi cytolethal distending toxin induces cell cycle arrest and apoptosis via the DNA damage checkpoint pathways.
abstract: The cytolethal distending toxins (CDTs) induce cell cycle arrest by a mechanism still not well characterized. We demonstrate that the effect of the Haemophilus ducreyi CDT (HdCDT) is cell type-specific: B cell lines underwent apoptosis, epithelial cells and keratinocytes arrested exclusively in G(2), whereas normal fibroblasts arrested both in G(1) and G(2). We studied normal keratinocytes and fibroblasts, which are relevant for understanding the pathogenicity of H. ducreyi. The response to HdCDT resembles the checkpoint response activated by ionizing radiation. Both responses were characterized by an early induction of the p53 gene and the cyclin-dependent kinase inhibitor p21 in fibroblasts, and activation of the chk2 kinase in epithelial cells. In the Ataxia Telangiectasia-mutated gene (ATM)-deficient lymphoblastoid cell lines, intoxication was significantly delayed compared with ATM wild type cells, and was associated with a slower kinetic of p53 stabilization, suggesting that the early response to HdCDT is ATM-dependent. Activation of ATM-dependent pathways was further confirmed by the ability of caffeine to partially override the HdCDT-mediated cell cycle arrest. Our data shed new light on the mechanism of action of this novel family of bacterial toxins, limiting the target candidates to DNA or molecules directly involved in activation of checkpoint responses.
authors.affiliation: Microbiology and Tumorbiology Center, Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm S-171 77, Sweden.
authors.forename: X
authors.initials: X
authors.lastname: Cortes-Bratti
authors.forename: C
authors.initials: C
authors.lastname: Karlsson
authors.forename: T
authors.initials: T
authors.lastname: Lagergård
authors.forename: M
authors.initials: M
authors.lastname: Thelestam
authors.forename: T
authors.initials: T
authors.lastname: Frisan
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D064007:Ataxia Telangiectasia Mutated Proteins; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001427:Bacterial Toxins / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002460:Cell Line; D004247:DNA / Q000032:analysis; D004249:DNA Damage; D004268:DNA-Binding Proteins; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006191:Haemophilus ducreyi / Q000472:pathogenicity*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins
chemical_list: D001427:Bacterial Toxins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C067044:cytolethal distending toxin; D002110:Caffeine; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases