Evaluation of ATM Kinase Inhibitor KU-55933 as Potential Anti-Toxoplasma gondii Agent

JONATHAN MUNERA LOPEZ; AGUSTINA GANUZA; SILVINA S. BOGADO; DANIELA MUÑOZ; DIEGO M. RUIZ; WILLIAM J. SULLIVAN JR.; SERGIO O. ANGEL; LAURA VANAGAS

Frontiers in Cellular and Infection Microbiology

Frontiers Editorial Office

Año: 2019 vol. 9

2235-2988

Toxoplasma gondii is an apicomplexan protozoan parasite with a complex life cyclecomposed of multiple stages that infect mammals and birds. Tachyzoites rapidly replicatewithin host cells to produce acute infection during which the parasite disseminatesto tissues and organs. Highly replicative cells are subject to Double Strand Breaks(DSBs) by replication fork collapse and ATM, a member of the phosphatidylinositol3-kinase (PI3K) family, is a key factor that initiates DNA repair and activates cell cyclecheckpoints. Here we demonstrate that the treatment of intracellular tachyzoites withthe PI3K inhibitor caffeine or ATM kinase-inhibitor KU-55933 affects parasite replicationrate in a dose-dependent manner. KU-55933 affects intracellular tachyzoite growth andinduces G1-phase arrest. Addition of KU-55933 to extracellular tachyzoites also leads toa significant reduction of tachyzoite replication upon infection of host cells. ATM kinasephosphorylates H2A.X (γH2AX) to promote DSB damage repair. The level of γH2AXincreases in tachyzoites treated with camptothecin (CPT), a drug that generates forkcollapse, but this increase was not observed when co-administered with KU-55933.These findings support that KU-55933 is affecting the Toxoplasma ATM-like kinase(TgATM). The combination of KU-55933 and other DNA damaging agents such as methylmethane sulfonate (MMS) and CPT produce a synergic effect, suggesting that TgATMkinase inhibition sensitizes the parasite to damaged DNA. By contrast, hydroxyurea (HU)did not further inhibit tachyzoite replication when combined with KU-55933.