Identification of an interaction between calcium-dependent protein kinase 4 (EtCDPK4) and serine protease inhibitor (EtSerpin) in Eimeria tenella

BACKGROUND: Eimeria tenella is an obligate intracellular apicomplexan protozoan parasite that has a complex life-cycle. Calcium ions, through various calcium-dependent protein kinases (CDPKs), regulate key events in parasite growth and development, including protein secretion, movement, differentiation, and invasion of and escape from host cells. In this study, we identified proteins that interact with EtCDPK4 to lay a foundation for clarifying the role of CDPKs in calcium channels. METHODS: Eimeria tenella merozoites were collected to construct a yeast two-hybrid (Y2H) cDNA library. The Y2H system was used to identify proteins that interact with EtCDPK4. One of interacting proteins was confirmed using bimolecular fluorescence complementation and co-immunoprecipitation in vivo. Co-localization of proteins was performed using immunofluorescence assays. RESULTS: Eight proteins that interact with EtCDPK4 were identified using the Y2H system. One of the proteins, E. tenella serine protease inhibitor 1 (EtSerpin), was further confirmed. CONCLUSION: In this study, we screened for proteins that interact with EtCDPK4. An interaction between EtSerpin and EtCDPK4 was identified that may contribute to the invasion and development of E. tenella in host cells.