Differing roles of protein kinase C-ζ in disruption of tight junction barrier by enteropathogenic and enterohemorrhagic Escherichia coli

Abstract

Background & Aims: Enteropathogenic Escherichia coli and enterohemorrhagic E. coli harbor highly homologous pathogenicity islands yet show key differences in their mechanisms of action. Both disrupt host intestinal epithelial tight junctions, but the effects of enteropathogenic E. coli are more profound than those of enterohemorrhagic E. coli. The basis for this is not understood. The atypical protein kinase C isoform, protein kinase C-ζ, associates with and regulates the tight junction complex. The aim of this study was to compare the role of protein kinase C-ζ in the disruption of tight junctions after infection with enteropathogenic E. coli and enterohemorrhagic E. coli. Methods: Model intestinal epithelial monolayers infected by enteropathogenic E. coli or enterohemorrhagic E. coli were used for these studies. Results: Neither bisindolylmaleimide nor Gö6976, which block several protein kinase C isoforms but not protein kinase C-ζ, protected against the decrease in transepithelial electrical resistance after enteropathogenic E. coli infection. Rottlerin at concentrations that block novel and atypical isoforms, including protein kinase C-ζ, significantly attenuated the decrease in transepithelial electrical resistance. The specific inhibitory peptide, myristoylated protein kinase C-ζ pseudosubstrate, also significantly decreased the enteropathogenic E. coli-associated decrease in transepithelial electrical resistance and redistribution of tight junction proteins. In contrast to enteropathogenic E. coli, the level of protein kinase C-ζ enzyme activity stimulated by enterohemorrhagic E. coli was transient and minor, and protein kinase C-ζ inhibition had no effect on the decrease in transepithelial electrical resistance or the redistribution of occludin. Conclusions: The differential regulation of protein kinase C-ζ by enteropathogenic E. coli and enterohemorrhagic E. coli may in part explain the less profound effect of the latter on the barrier function of tight junctions.