Mitotic block and delayed lethality in HeLa epithelial cells exposed to Escherichia coli BM2-1 producing cytotoxic necrotizing factor type 1.
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.
De Rycke
J
J
Laboratoire Associé de Microbiologie Moléculaire, Institut National de la Recherche Agronomique, Ecole Nationale Vétérinaire, Toulouse, France.
Mazars
P
P
Nougayrede
J P
JP
Tasca
C
C
Boury
M
M
Herault
F
F
Valette
A
A
Oswald
E
E
D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics / Q000633:toxicity*; D001483:Base Sequence; D016923:Cell Death / Q000187:drug effects; D002843:Chromatin / Q000187:drug effects; D003603:Cytotoxins / Q000096:biosynthesis / Q000235:genetics / Q000633:toxicity*; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology; D005798:Genes, Bacterial; D006367:HeLa Cells; D006460:Hemolysin Proteins / Q000633:toxicity; D006801:Humans; D008938:Mitosis / Q000187:drug effects; D008969:Molecular Sequence Data; D014774:Virulence / Q000235:genetics
D001427:Bacterial Toxins; D002843:Chromatin; D003603:Cytotoxins; D017931:DNA Primers; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C060296:cytotoxic necrotizing factor type 1; D004247:DNA