Caractérisation fonctionnelle des signaux calciques induits par Escherichia coli entéropathogène (EPEC) dans les cellules épithéliales

Enteropathogenic Escherichia coli (EPEC) manipulates host signaling pathways to colonize intestinal epithelial cells. This study investigates how EPEC alters epithelial calcium (Ca²˖) signaling and its downstream effects on inflammation and mitochondrial function.We found EPEC triggers distinct, transient Ca²˖ signals initiated by extracellular ATP (eATP), likely released via the Type III Secretion System (T3SS) translocon pore. Ca²˖ responses varied significantly in amplitude and occurred in a subset of infected cells, indicating precise T3SS regulation. Deletion of EspC—a bacterial protease that negatively regulates T3SS translocon—greatly increased the proportion of cells exhibiting frequent Ca²˖ signals. Additionally, we identified novel, brief (<10s) and low-amplitude global Ca²˖ transients, termed Coordinated Ca²˖ Responses from IP3R Clusters (CCRICs). Unlike conventional localized "puffs," these involved simultaneous activation of IP₃ receptor clusters driven by minimal IP₃ concentrations, validated through computational modeling and low-level eATP mimicking experiments.Low-dose eATP significantly delayed TNFα-induced NF-κB activation, reflected by slower IκBα degradation and reduced p65 phosphorylation. Correspondingly, NF-κB p65 exhibited lower O-GlcNAcylation upon TNFα stimulation with eATP compared to TNFα alone; chelating intracellular Ca²˖ with BAPTA-AM prevented this effect, suggesting that CCRICs modulate NF-κB activation through reduced O-GlcNAcylation.EPEC infection also caused marked mitochondrial fragmentation, but ectopic expression of the mitochondrial- targeting effector Map alone did not. However, Map expression altered Ca²˖ dynamics, resulting in fewer cytosolic Ca²˖ oscillations and slower return to baseline. These altered dynamics corresponded with reduced mitochondrial Ca²˖ uptake, lower amplitude mitochondrial Ca²˖ transients, and delayed decay, indicating impaired cytosolic-mitochondrial Ca²˖ coupling.Our findings uncover novel aspects of Ca²˖ signaling hijacked by EPEC to suppress inflammation and alter organelle function.