Streptolysin S induces pronounced calcium-ion influx-dependent expression of immediate early genes encoding transcription factors.

Anginosus group streptococci (AGS) are opportunistic human pathogens of the oral cavity. The beta-hemolytic subgroup of Streptococcus anginosus subsp. anginosus secretes streptolysin S (SLS) and exhibits not only hemolytic activity but also cytotoxicity toward cultured human cell lines. However, the detailed mechanism of action of SLS and the cellular responses of host cells have not yet been fully clarified. To determine the pathogenic potential of SLS-producing beta-hemolytic S. anginosus subsp. anginosus, the SLS-dependent response induced in the human oral squamous cell carcinoma HSC-2 cells was investigated to determine the pathogenic potential of SLS-producing beta-hemolytic S. anginosus subsp. anginosus. This study revealed that the Ca(2+) influx and the expression of immediate early genes (IEGs) encoding transcription factors such as early growth responses (EGRs) and activator protein-1 (AP-1) were greatly increased in HSC-2 cells incubated with the culture supernatant of SLS-producing beta-hemolytic S. anginosus subsp. anginosus. Moreover, this SLS-dependent increase in expression was significantly suppressed by Ca(2+) chelation, except for jun. These results suggest that SLS caused Ca(2+) influx into the cells following greatly enhanced expression of IEG-encoding transcription factors. The results of this study may help in understanding the pathogenicity of SLS-producing AGS.