Protein kinases of Toxoplasma gondii: functions and drug targets

Toxoplasma gondii is an important opportunistic parasite that infects almost all warm-blooded animals, causing congenital neurological and ocular diseases, especially in immunocompromised humans. The available therapeutic drugs are hypersensitive and toxic, and no vaccine is available to block the transmission of this parasite. Safer and more effective drugs are thus urgently needed to treat toxoplasmosis. Protein kinases (PKs) play crucial roles in the proliferation, differentiation, and pathogenesis of T. gondii. T. gondii calcium-dependent protein kinase 1 and cGMP-dependent protein kinase are associated with cell invasion; mitogen-activated protein kinase 1 and cAMP-dependent protein kinase are involved in stress response and conversion from tachyzoite to bradyzoite; casein kinase 1 and cdc2 cyclin-dependent kinase control cell cycle. Rhoptry kinases, the T. gondii-specific PKs, are involved in host manipulation. Because of their difference in structure and function from that of mammalian PKs, T. gondii PKs are promising drug targets. In this review, we describe the functions of T. gondii protein kinases and their inhibitors as potential drugs against T. gondii.