Abstract
EPEC colonise the small bowel and cause diarrhoea by a mechanism that is unrelated to production of recognised enterotoxins or mucosal invasion. Intestinal ion transport is thought to be regulated by intracellular second messenger molecules which function through activation of their appropriate protein kinases. Since EPEC do not induce elevated levels of cyclic nucleotide second messengers, we considered the possibility that EPEC cause diarrhoea by a mechanism which involves an intracellular calcium second messenger. Cultured HEp-2 cells were used as a model of EPEC infection and levels of intracellular calcium determined fluorimetrically using the calcium indicator dye, Quin-2. HEp-2 cells infected with EPEC for 3 hours showed a 5-6 fold increase in calcium levels (280-320 nanomolar) compared to uninfected cells (55 nanomolar). Alteration in the phosphorylation state of proteins following infection of 32P treated HEp-2 cells with EPEC was analysed by autoradiography following electrophoresis. A protein band of Mr 21-23 kDa showed increased phosphorylation within 2 hours of infection; the same band was phosphorylated a) on treatment of cells with TPA, a potent secretagogue and activator of protein kinase C (PKC), and b) on addition of purified PKC to HEp-2 cell lysates. These results suggest that EPEC pathogenesis involves contact of bacteria with target cells, a calcium intracellular signal and phosphorylation of a critical host cell protein.
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Baldwin, T., Knutton, S., Williams, P. et al. ELEVATED CALCIUM LEVELS AND PROTEIN KINASE C ACTIVATION IN RESPONSE TO INFECTION BY ENTEROPATHCGENIC ESCIIERICHIA COLI (EPEC). Pediatr Res 26, 272 (1989). https://doi.org/10.1203/00006450-198909000-00055
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DOI: https://doi.org/10.1203/00006450-198909000-00055