Increased levels of intracellular calcium are not required for the formation of attaching and effacing lesions by enteropathogenic and enterohemorrhagic Escherichia coli.
Elevated concentrations of intracellular calcium ([Ca]i) have been implicated as an important signalling event during attaching and effacing (A/E) lesion formation by enteropathogenic Escherichia coli (EPEC). The highly localized nature of the cytoskeletal and cell surface alterations occurring during A/E lesion formation suggests that there should be equally localized EPEC-induced signalling events. To analyze further the calcium responses to infection of HEp-2 cells by EPEC, we employed calcium-imaging fluorescence microscopy, which allows both temporal and spatial measurements of [Ca]i in live cells. Using this imaging technique, not only were we unable to detect any significant elevation in [Ca]i at sites of A/E EPEC adhesion, but, with several different classical EPEC and enterohemorrhagic E. coli (EHEC) strains and three different infection procedures, each of which resulted in extensive A/E bacterial adhesion, we were unable to detect any significant alterations in [Ca]i in infected cells compared to uninfected cells. In addition, chelation of intracellular free calcium with bis-(aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) did not, as previously reported, prevent A/E lesion formation. We conclude that increased [Ca]i are not required for A/E lesion formation by EPEC and EHEC.
Institute of Child Health, University of Birmingham, Birmingham B4 6NH, United Kingdom.
C
C
Bain
R
R
Keller
G K
GK
Collington
L R
LR
Trabulsi
S
S
Knutton
D002118:Calcium / Q000378:metabolism*; D004926:Escherichia coli / Q000502:physiology*; D006801:Humans; D014407:Tumor Cells, Cultured
D002118:Calcium