I. Simonovic et al., Enteropathogenic Escherichia coli dephosphorylates and dissociates occludin from intestinal epithelial tight junctions, CELL MICROB, 2(4), 2000, pp. 305-315
Enteropathogenic Escherichia coli (EPEC) increases tight junction permeabil
ity in part by phosphorylating the 20 kDa myosin light chain (MLC20) that i
nduces cytoskeletal contraction. The impact of this enteric pathogen on spe
cific tight junction (TJ) proteins has not been investigated. We examined t
he effect of EPEC infection on occludin localization and phosphorylation in
intestinal epithelial cells. After infection by EPEC, a progressive shift
of occludin from a primarily TJ-associated domain to an intracellular compa
rtment occurred, as demonstrated by immunofluorescent staining. A reverse i
n the ratio of phosphorylated to dephosphorylated occludin accompanied this
morphological change. Eradication of EPEC with gentamicin resulted in the
normalization of occludin localization and phosphorylation. The serine/thre
onine phosphatase inhibitor, calyculin A, prevented these events. The EPEC-
associated decrease in transepithelial electrical resistance, a measure of
TJ barrier function, returned to baseline after gentamicin treatment. Non-p
athogenic E. coli, K-12, did not induce these changes. Transformation of K-
12 with the pathogenicity island of EPEC, however, conferred the phenotype
of wild-type EPEC. Deletion of specific EPEC genes encoding proteins involv
ed in EPEC type III secretion markedly attenuated these effects. These find
ings suggest that EPEC-induced alterations in occludin contribute to the pa
thophysiology associated with this infection.