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Mitotic block and delayed lethality in HeLa epithelial cells exposed to Escherichia coli BM2-1 producing cytotoxic necrotizing factor type 1

Abstract : The cytopathic effect (CPE) of Escherichia coli producing cytotoxic necrotizing factor type 1 (CNF1) was investigated by using a human epithelial cell (HeLa) model of infection with CNF1-producing E. coli BM2-1. This strain was shown to bind loosely, but massively, to HeLa cells. A 4-h interaction between bacteria and eukaryotic cells triggered the delayed appearance of a progressive dose-dependent CPE characterized by (i) intense swelling of cells accompanied by the formation of a dense network of actin stress fibers, (ii) inhibition of cell division due to a complete block in the G2 phase of the cell cycle, and (iii) nucleus swelling and chromatin fragmentation. These alterations resulted in cell death starting about 5 days after interaction. The absence of multinucleation clearly distinguished the CPE from the effect produced by cell-free culture supernatants of infected cells nor prevented by a CNF1-neutralizing antiserum. Pathogenicity was completely abolished after Tn5::phoA insertion mutagenesis in the cnf-1 structural gene but not restored by trans complementation with a recombinant plasmid containing intact cnf-1 and its promoter. These results suggest that a gene downstream of cnf-1, essential to the induction of the CPE, was affected by the mutation. On the other hand, transformation of the wild-type strain BM2-1 with the same recombinant plasmid leads to a significant increase in both CNF1 activity and CPE, demonstrating the direct contribution of CNF1 to the CPE. In conclusion, the pathogenicity of E. coli BM2-1 for HeLa cells results from a complex interaction involving cnf-1 and associated genes and possibly requiring a preliminary step of binding of bacterial organisms to target cells.
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Déposant : Frédéric Hérault <>
Soumis le : lundi 1 juin 2020 - 12:13:02
Dernière modification le : jeudi 12 novembre 2020 - 17:07:24
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Jean de Rycke, Philippe Mazars, Jean-Philippe Nougayrede, Christian Tasca, Michèle Boury, et al.. Mitotic block and delayed lethality in HeLa epithelial cells exposed to Escherichia coli BM2-1 producing cytotoxic necrotizing factor type 1. Infection and Immunity, American Society for Microbiology, 1996, 64 (5), pp.1694-1705. ⟨hal-02648871⟩

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