Escherichia coli-induced epithelial hyporesponsiveness to secretagogues is associated with altered CFTR localization.
Both pathogenic and commensal strains of Escherichia coli colonize the human intestinal tract. Pathogenic strains differ only in the expression of virulence factors, many of which comprise a type III secretion system (TTSS). Little is known regarding the effect of E. coli on the intestinal epithelial response to the secretagogues that drive ion secretion, despite its importance in causing clinically significant diarrhoea. Using Ussing chambers to measure electrogenic ion transport of T84 intestinal epithelial cell monolayers, we found that all strains of E. coli tested (pathogenic, commensal, probiotic and lab strain) significantly reduced cAMP-dependent ion secretion after 4-8 h exposure. Enteropathogenic E. coli mutants lacking a functional TTSS caused similar hyposecretion while not causing significant apoptosis (as shown by caspase-3 cleavage) or necrosis (lactate dehydrogenase release), as did the commensal strain F18, indicating that epithelial cell death was not the cause of hyposecretion. Enteropathogenic E. coli and the TTSS mutant significantly reduced cell surface expression of the apical anion channel, cystic fibrosis transmembrane conductance regulator, which is likely the mechanism behind the pathogen-induced hyposecretion. However, F18 did not cause cystic fibrosis transmembrane conductance regulator mislocalization and the commensal-induced mechanism remains unclear.
Department of Physiology and Pharmacology, Inflammation Research Group, University of Calgary, Calgary, AB T2N 4N1, Canada.
Christina L
CL
Ohland
Rebekah
R
DeVinney
Wallace K
WK
MacNaughton
D058947:Bacterial Secretion Systems; D016923:Cell Death; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005576:Colforsin / Q000031:analogs & derivatives / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D003967:Diarrhea / Q000382:microbiology; D054324:Enterohemorrhagic Escherichia coli / Q000187:drug effects / Q000472:pathogenicity; D054308:Enteropathogenic Escherichia coli / Q000187:drug effects / Q000472:pathogenicity*; D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology; D004927:Escherichia coli Infections / Q000378:metabolism* / Q000382:microbiology; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D021381:Protein Transport; D013997:Time Factors; D037521:Virulence Factors / Q000378:metabolism; D050994:Voltage-Dependent Anion Channels / Q000378:metabolism
D058947:Bacterial Secretion Systems; D037521:Virulence Factors; D050994:Voltage-Dependent Anion Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000242:Cyclic AMP