EPEC-activated ERK1/2 participate in inflammatory response but not tight junction barrier disruption.
Enteropathogenic Escherichia coli (EPEC) alters many functions of the host intestinal epithelia. Inflammation is initiated by activation of nuclear factor (NF)-kappaB, and paracellular permeability is enhanced via a Ca2+- and myosin light-chain kinase (MLCK)-dependent pathway. The aims of this study were to identify signaling pathways by which EPEC triggers inflammation and to determine whether these pathways parallel or diverge from those that alter permeability. EPEC-induced phosphorylation and degradation of the primary inhibitor of NF-kappaB (IkappaBalpha) were tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta independent. In contrast to Salmonella typhimurium, EPEC-stimulated IkappaBalpha degradation and IL-8 expression did not require Ca2+. Instead, extracellular signal-regulated kinase (ERK)-1/2 was significantly and rapidly activated. ERK1/2 inhibitors attenuated IkappaBalpha degradation and IL-8 expression. Although ERK1/2 can activate MLCK, its inhibition had no impact on EPEC disruption of the tight junction barrier. In conclusion, EPEC-induced inflammation 1) is TNF-alpha and IL-1beta receptor independent, 2) utilizes pathways differently from S. typhimurium, 3) requires ERK1/2, and 4) employs signals that are distinct from those that alter permeability. This is the first time that EPEC-activated signaling cascades have been linked to independent functional consequences.
Savkovic
S D
SD
Department of Medicine, Section of Digestive and Liver Diseases, University of Illinois, West Side Veterans Affairs Medical Center, Chicago, Illinois 60612, USA.
Ramaswamy
A
A
Koutsouris
A
A
Hecht
G
G
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D017097:Electric Impedance; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000472:pathogenicity* / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins; D015151:Immunoblotting; D007249:Inflammation; D007375:Interleukin-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000382:microbiology* / Q000648:ultrastructure; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012486:Salmonella typhimurium / Q000502:physiology; D019108:Tight Junctions / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020672:I-kappa B Proteins; D007375:Interleukin-1; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium