Inhibition of chlamydial infectious activity due to P2X ₇R-dependent phospholipase D activation

Chlamydia trachomatis survives within host cells by inhibiting fusion between Chlamydia vacuoles and lysosomes. We show here that treatment of infected macrophages with ATP leads to killing of chlamydiae through ligation of the purinergic receptor, P2X₇R. Chlamydial killing required phospholipase D (PLD) activation, as PLD inhibition led to rescue of chlamydiae in ATP-treated macrophages. However, there was no PLD activation nor chlamydial killing in ATP-treated P2X₇R-deficient macrophages. P2X₇R ligation exerts its effects by promoting fusion between Chlamydia vacuoles and lysosomes. P2X₇R stimulation also resulted in macrophage death, but fusion with lysosomes preceded macrophage death and PLD inhibition did not prevent macrophage death. These results suggest that P2X₇R ligation leads to PLD activation, which is directly responsible for inhibition of infection.