Identification, molecular characterization and subcellular localization of a Theileria annulata parasite protein secreted into the host cell cytoplasm.

Intracellular leucoproliferative Theileria are unique as eukaryotic organisms that transform the immune cells of their ruminant host. Theileria utilize the uncontrolled proliferation for rapid multiplication and distribution into host daughter cells. The equal distribution of the schizont into the daughter cells is thought to be accomplished by a tight association with the host cell mitotic apparatus. In this study, we describe a highly conserved novel 37 kD Theileria annulata protein (TaSE). TaSE was found to be localized inside the parasite, the parasite membrane and within the host cell cytoplasm. Moreover, it co-localized at distinct points with host cell microtubules, which was especially apparent during mitosis, where co-localization was found with the centromere, the mitotic spindle and the midbody. Association of TaSE with the host cell tubulin network was corroborated by coimmunoprecipitation and transient transfection experiments. This is the first description of a theilerial protein co-localizing and potentially interacting with a host cell protein. The distribution of TaSE during mitosis makes it a protein to consider as playing a potential role for parasite distribution into daughter host cells.