K+ efflux is required for histone H3 dephosphorylation by Listeria monocytogenes listeriolysin O and other pore-forming toxins.

Chromatin modification triggered by bacteria is a newly described mechanism by which pathogens impact host transcription. Listeria monocytogenes dephosphorylates histone H3 through the action of listeriolysin O (LLO); however, the underlying mechanism is unknown. Here we show that an unrelated pore-forming toxin, Aeromonas aerolysin, also provokes H3 dephosphorylation (dePH3). As reported for aerolysin, we show that LLO and related toxins induce a pore-dependent K(+) efflux and that this efflux is the signal required for dePH3. In addition, LLO-induced K(+) efflux activates caspase-1. However, we demonstrate that dePH3 is unlinked to this activation. Therefore, our study unveils K(+) efflux as an important signal leading to two independent events critical for infection, inflammasome activation and histone modification.