Enteropathogenic E. coli- mediated Fast and Coordinated Ca ^²⁺ responses regulate NF-κB activation

Enteropathogenic Escherichia coli (EPEC) is a major bacterial enteropathogen causing diarrhea among children in developing countries. Here, we found that EPEC induced isolated Ca ²⁺ responses in epithelial cells, triggered by extracellular ATP (eATP). These responses were dependent on type III secretion (T3S) and down-regulated by the bacterial secreted protease EspC, consistent with eATP released by the T3S translocon. By performing high speed Ca ²⁺ imaging, we uncovered that at the onset of infection, low eATP levels triggered Ca ²⁺ -responses involving the whole cell but showing the small amplitude and fast kinetics usually associated with local Ca ²⁺ responses. The findings, supported by theoretical modeling, evocate a conceptual shift whereby low amounts of inositol 1, 4, 5-trisphosphate (IP ₃ ) induced by low eATP levels and subsequent moderate Ca ²⁺ release enable the fast coordination of IP ₃ receptor cluster activation throughout the cell. Importantly, these yet undescribed coordinated fast responses occurred over prolonged time periods and defined a cell state with dampened activation of the pro-inflammatory transcriptional activator NF-kB associated with a decrease in its Ca ²⁺ -dependent O-linked β-N-acetylglucosamine modification.