Serine/Threonine Phosphatase (SP-STP), Secreted from Streptococcus pyogenes, Is a Pro-apoptotic Protein*□S

Background: Eukaryote-type serine/threonine phosphatase (SP-STP) of group A Streptococcus (GAS) is essential for viru-lence, but its direct role in causing pathological effects in the host remains unknown. Results: SP-STP crosses two membrane barriers and causes apoptosis of human pharyngeal cells from within and without. Conclusion: SP-STP is a quintessential virulence-controlling factor. Significance: The study illustrates how GAS utilizes SP-STP to exploit host machinery for its own advantage. This investigation illustrates an important property of eukaryote-type serine/threonine phosphatase (SP-STP) of group A Streptococcus (GAS) in causing programmed cell death of human pharyngeal cells. The secretory nature of SP-STP, its elevated expression in the intracellular GAS, and the ability of wild-type GAS but not the GAS mutant devoid of SP-STP to cause apoptosis of the host cell both in vitro and in vivo suggest that GAS deploys SP-STP as an important virulence determi-nant to exploit host cell machinery for its own advantage during infection. The exogenously added SP-STP is able to enter th