The Streptococcus pyogenesNAD⁺ glycohydrolase modulates epithelial cell PARylation and HMGB1 release

Streptococcus pyogenes uses the cytolysin streptolysin O (SLO) to translocate an enzyme, the S.pyogenesNAD⁺ glycohydrolase (SPN), into the host cell cytosol. However, the function of SPN in this compartment is not known. As a complication, many S.pyogenes strains express a SPN variant lacking NAD⁺ glycohydrolase (NADase) activity. Here, we show that SPN modifies several SLO- and NAD⁺-dependent host cell responses in patterns that correlate with NADase activity. SLO pore formation results in hyperactivation of the cellular enzyme poly-ADP-ribose polymerase-1 (PARP-1) and production of polymers of poly-ADP-ribose (PAR). However, while SPN NADase activity moderates PARP-1 activation and blocks accumulation of PAR, these processes continued unabated in the presence of NADase-inactive SPN. Temporal analyses revealed that while PAR production is initially independent of NADase activity, PAR rapidly disappears in the presence of NADase-active SPN, host cell ATP is depleted and the pro-inflammatory mediator high-mobility group box-1 (HMGB1) protein is released from the nucleus by a PARP-1-dependent mechanism. In contrast, HMGB1 is not released in response to NADase-inactive SPN and instead the cells release elevated levels of interleukin-8 and tumour necrosis factor-α. Thus, SPN and SLO combine to induce cellular responses subsequently influenced by the presence or absence of NADase activity.